WorldWideScience

Sample records for maximum photosynthetic activity

  1. Effect of temperature and light intensity on growth and photosynthetic activity of Chlamydomonas Reinhardtii

    International Nuclear Information System (INIS)

    Alfonsel, M.; Fernandez Gonzalez, J.

    1986-01-01

    The effect of five temperatures (15, 20, 25, 30 and 35 0 C) and two levels of illumination on growth and photosynthetic activity of Chlamydomonas reinhardtii has been studied. The growth of the cultures was evaluated by optical density. Photosynthetic activity has been carried out studying either the assimilation rate of CO 2 labelled with C 14 or the oxygen evolution by means of polarographic measurements. The maximum photosynthetic rate has been obtained at 25 0 C for the lower lavel of illumination (2400 lux) and at 35 0 C for the higher one (13200 lux). These results suggest an interacton of temperature and illumination on photosynthetic activity. (author)

  2. The effect of nitrogen on the development and photosynthetic activity ...

    African Journals Online (AJOL)

    Whole plant net photosynthetic rates appeared to vary according to the units in which the activity is expressed. The optimum levels of photosynthetic activity differed with the stage of development, depending on the basis of expression. The form and concentration of nitrogen applied influenced morphological development ...

  3. Effect of Temperature and light intensity on growth and Photosynthetic Activity of Chlamydomonas reinhard II

    International Nuclear Information System (INIS)

    Alfonsel Jaen, M.; Fernandez Gonzalez, J.

    1985-01-01

    The effect of five temperatures (15,20,25,30 and 35 degree centigree) and two levels of illumination on growth and photosynthetic activity of Chlamydomonas reinhard II has been studied. The growth of the cultures was evaluated by optical density. Photosynthetic activity has been carried out studying either the assimilation rate of C0 2 labelled with C-14 or the oxygen evolution by means of polarographic measurements. The maximum photosynthetic rate has been obtained at 25 degree centigree for the lower level of illumination (2400 lux) and at 35 degree centigree for the higher one (13200 lux) and at 35 degree centigree for the higher ono (13200 lux). These results suggest an interaction of temperature and illumination on photosynthetic activity. (Author) 37 refs

  4. Dynamics of photosynthetic activity of cyanobacteria after gut ...

    African Journals Online (AJOL)

    African Journal of Biotechnology ... carp and goldfish, whereas there was a significant stimulation of photosynthetic activity of diatom and green algae following the depressed cyanobacteria during cultivation. The mainly stimulated eukaryotic algae species were Fragilariaceae and Scenedesmus obliquus by microscopy.

  5. Coral bleaching independent of photosynthetic activity.

    Science.gov (United States)

    Tolleter, Dimitri; Seneca, François O; DeNofrio, Jan C; Krediet, Cory J; Palumbi, Stephen R; Pringle, John R; Grossman, Arthur R

    2013-09-23

    The global decline of reef-building corals is due in part to the loss of algal symbionts, or "bleaching," during the increasingly frequent periods of high seawater temperatures. During bleaching, endosymbiotic dinoflagellate algae (Symbiodinium spp.) either are lost from the animal tissue or lose their photosynthetic pigments, resulting in host mortality if the Symbiodinium populations fail to recover. The >1,000 studies of the causes of heat-induced bleaching have focused overwhelmingly on the consequences of damage to algal photosynthetic processes, and the prevailing model for bleaching invokes a light-dependent generation of toxic reactive oxygen species (ROS) by heat-damaged chloroplasts as the primary trigger. However, the precise mechanisms of bleaching remain unknown, and there is evidence for involvement of multiple cellular processes. In this study, we asked the simple question of whether bleaching can be triggered by heat in the dark, in the absence of photosynthetically derived ROS. We used both the sea anemone model system Aiptasia and several species of reef-building corals to demonstrate that symbiont loss can occur rapidly during heat stress in complete darkness. Furthermore, we observed damage to the photosynthetic apparatus under these conditions in both Aiptasia endosymbionts and cultured Symbiodinium. These results do not directly contradict the view that light-stimulated ROS production is important in bleaching, but they do show that there must be another pathway leading to bleaching. Elucidation of this pathway should help to clarify bleaching mechanisms under the more usual conditions of heat stress in the light. Copyright © 2013 Elsevier Ltd. All rights reserved.

  6. Controls on seasonal patterns of maximum ecosystem carbon uptake and canopy-scale photosynthetic light response: contributions from both temperature and photoperiod.

    Science.gov (United States)

    Stoy, Paul C; Trowbridge, Amy M; Bauerle, William L

    2014-02-01

    Most models of photosynthetic activity assume that temperature is the dominant control over physiological processes. Recent studies have found, however, that photoperiod is a better descriptor than temperature of the seasonal variability of photosynthetic physiology at the leaf scale. Incorporating photoperiodic control into global models consequently improves their representation of the seasonality and magnitude of atmospheric CO2 concentration. The role of photoperiod versus that of temperature in controlling the seasonal variability of photosynthetic function at the canopy scale remains unexplored. We quantified the seasonal variability of ecosystem-level light response curves using nearly 400 site years of eddy covariance data from over eighty Free Fair-Use sites in the FLUXNET database. Model parameters describing maximum canopy CO2 uptake and the initial slope of the light response curve peaked after peak temperature in about 2/3 of site years examined, emphasizing the important role of temperature in controlling seasonal photosynthetic function. Akaike's Information Criterion analyses indicated that photoperiod should be included in models of seasonal parameter variability in over 90% of the site years investigated here, demonstrating that photoperiod also plays an important role in controlling seasonal photosynthetic function. We also performed a Granger causality analysis on both gross ecosystem productivity (GEP) and GEP normalized by photosynthetic photon flux density (GEP n ). While photoperiod Granger-caused GEP and GEP n in 99 and 92% of all site years, respectively, air temperature Granger-caused GEP in a mere 32% of site years but Granger-caused GEP n in 81% of all site years. Results demonstrate that incorporating photoperiod may be a logical step toward improving models of ecosystem carbon uptake, but not at the expense of including enzyme kinetic-based temperature constraints on canopy-scale photosynthesis.

  7. Hyperspectral estimation of corn fraction of photosynthetically active radiation

    International Nuclear Information System (INIS)

    Yang Fei; Zhang Bai; Song Kaishan

    2008-01-01

    Fraction of absorbed photosynthetically active radiation (FPAR) is one of the important variables in many productivity and biomass estimation models, this analyzed the effect of FPAR estimation with hyperspectral information, which could provide the scientific support on the improvement of FPAR estimation, remote sensing data validation, and the other ecological models. Based on the field experiment of corn, this paper analyzed the correlations between FPAR and spectral reflectance or the differential coefficient, and discussed the mechanism of FPAR estimation, studied corn FPAR estimation with reflectance, first differential coefficient, NDVI and RVI. The reflectance of visible bands showed much better correlations with FPAR than near-infrared bands. The correlation curve between FPAR and differential coefficient varied more frequently and greatly than the curve of FPAR and reflectance. Reflectance and differential coefficient both had good regressions with FPAR of the typical single band, with the maximum R2 of 0.791 and 0.882. In a word, differential coefficient and vegetation index were much effective than reflectance for corn FPAR estimating, and the stepwised regression of multibands differential coefficient showed the best regression with R2 of 0.944. 375 nm purpled band and 950 nm near-infraed band absorbed by water showed prodigious potential for FPAR estimating precision. On the whole, vegetation index and differential coefficient have good relationships with FPAR, and could be used for FAPR estimation. It would be effective of choosing right bands and excavating the hyperspectral data to improve FPAR estimating precision

  8. Conversion Efficiency of Photosynthetically Active Radiation Into Acacia mearnsii Biomass

    Directory of Open Access Journals (Sweden)

    Elder Eloy

    2018-02-01

    Full Text Available ABSTRACT The objective of this experiment was to determine the conversion efficiency of intercepted photosynthetically active radiation into biomass of Acacia mearnsii De Wild. seedlings. A forest species, plastic tubes (90 cm3, and 11 evaluation periods (up to 180 days after emergence were used in this study. The leaf area index (LAI, total dry biomass (BIO, global solar radiation (GSR, cumulative intercepted photosynthetically active radiation (PARic, and conversion efficiency of radiation (εb were determined using a pyranometer (LI200X, LICOR. The value of εb in BIO seedlings of Acacia mearnsii was 7.76 g MJ-1. LAI was directly related to the efficiency of PARic, and this influenced the development, production potential and accumulation of BIO. The value of GSR flow was 11.81 MJ m-2 day-1, while the value inside the greenhouse was 6.26 MJ m-2 day-1.

  9. A theoretical approach to photosynthetically active radiation silicon sensor

    International Nuclear Information System (INIS)

    Tamasi, M.J.L.; Martínez Bogado, M.G.

    2013-01-01

    This paper presents a theoretical approach for the development of low cost radiometers to measure photosynthetically active radiation (PAR). Two alternatives are considered: a) glass optical filters attached to a silicon sensor, and b) dielectric coating on a silicon sensor. The devices proposed are based on radiometers previously developed by the Argentine National Atomic Energy Commission. The objective of this work is to adapt these low cost radiometers to construct reliable instruments for measuring PAR. The transmittance of optical filters and sensor response have been analyzed for different dielectric materials, number of layers deposited, and incidence angles. Uncertainties in thickness of layer deposition were evaluated. - Highlights: • Design of radiometers to measure photosynthetically active radiation • The study has used a filter and a Si sensor to modify spectral response. • Dielectric multilayers on glass and silicon sensor • Spectral response related to different incidence angles, materials and spectra

  10. Photosynthetic activity, photoprotection and photoinhibition in intertidal microphytobenthos as studied in situ using variable chlorophyll fluorescence

    Science.gov (United States)

    Serôdio, João; Vieira, Sónia; Cruz, Sónia

    2008-06-01

    The photosynthetic activity of microphytobenthos biofilms was studied in situ on an intertidal mudflat of the Ria de Aveiro, Portugal. Time series of physical variables characterizing the microenvironment at the sediment photic zone (incident solar irradiance, temperature, salinity), photophysiological parameters and productive biomass of undisturbed microalgal assemblages were measured during daytime low-tide periods along one spring-neap tidal cycle, with the objective of (1) characterizing the short-term variability in photosynthetic activity in situ, (2) relating it with the changing environmental conditions and (3) with the operation of physiologically (xanthophyll cycle) and behaviorally (vertical migration) based photoprotective processes, and (4) assessing the occurrence of photoinhibition. Pulse Amplitude Modulated (PAM) fluorometry was applied to measure photosynthetic activity (the effective and maximum quantum yield of photosystem II, Δ F/ Fm' and Fv/ Fm; the photosynthesis index EFY; rapid light-response curves (RLC)), the photoprotective operation of the xanthophyll cycle and photoinhibition (non-photochemical quenching, NPQ; quantum efficiency of open RCs, Fv'/ Fm'), and vertical migration (productive biomass, Fo). The photosynthetic activity was found to be strongly affected by the cumulative light dose received during the morning low-tide periods. The fluorescence indices Δ F/ Fm', EFY, Fv'/ Fm' and RLC parameters were more depressed under high irradiances when clear sky was present during the morning low tide than when foggy conditions reduced the light dose received during a comparable period. Productive biomass exhibited maximum values in the first hours of the morning, followed by a steep decrease when irradiance reached moderate levels, due to the downward migration of the microalgae. This photophobic migratory response appeared to display a photoprotective role, allowing Δ F/ Fm' to remain near optimum values until irradiance reached

  11. Influence of stomatic aperture on photosynthetic activity of bean-seedlings leaves

    International Nuclear Information System (INIS)

    Suarez Moya, J.; Fernandez Gonzalez, J.

    1984-01-01

    The present paper contains the data of photosynthetic activity and stomatic aperture of bean-seedlings Ieaves, and the relations obtained with both results. It has been observed that the product of photosynthetic activity by the resistance; to transpiration measured by a promoter ia a constant, between some limits. (Author) 45 refs

  12. Seasonal photosynthetic activity in evergreen conifer leaves monitored with spectral reflectance

    Science.gov (United States)

    Wong, C. Y.; Gamon, J. A.

    2013-12-01

    Boreal evergreen conifers must maintain photosynthetic systems in environments where temperatures vary greatly across seasons from high temperatures in the summer to freezing levels in the winter. This involves seasonal downregulation and photoprotection during periods of extreme temperatures. To better understand this downregulation, seasonal dynamics of photosynthesis of lodgepole (Pinus contorta D.) and ponderosa pine (Pinus ponderosa D.) were monitored in Edmonton, Canada over two years. Spectral reflectance at the leaf and stand scales was measured weekly and the Photochemical Reflectance Index (PRI), often used as a proxy for chlorophyll and carotenoid pigment levels and photosynthetic light-use efficiency (LUE), was used to track the seasonal dynamics of photosynthetic activity. Additional physiological measurements included leaf pigment content, chlorophyll fluorescence, and gas exchange. All the metrics indicate large seasonal changes in photosynthetic activity, with a sharp transition from winter downregulation to active photosynthesis in the spring and a more gradual fall transition into winter. The PRI was a good indicator of several other variables including seasonally changing photosynthetic activity, chlorophyll fluorescence, photosynthetic LUE, and pigment pool sizes. Over the two-year cycle, PRI was primarily driven by changes in constitutive (chlorophyll:carotenoid) pigment levels correlated with seasonal photosynthetic activity, with a much smaller variation caused by diurnal changes in xanthophyll cycle activity (conversion between violaxanthin & zeaxanthin). Leaf and canopy scale PRI measurements exhibited parallel responses during the winter-spring transition. Together, our findings indicate that evergreen conifers photosynthetic system possesses a remarkable degree of resilience in response to large temperature changes across seasons, and that optical remote sensing can be used to observe the seasonal effects on photosynthesis and

  13. A cost-effective microbial fuel cell to detect and select for photosynthetic electrogenic activity in algae and cyanobacteria

    NARCIS (Netherlands)

    Luimstra, V.M.; Kennedy, S.J.; Güttler, J.; Wood, S.A.; Williams, D.E.; Packer, M.A.

    2014-01-01

    This work describes the development of an easily constructed, cost-effective photosynthetic microbial fuel cell design with highly reproducible electrochemical characteristics that can be used to screen algae and cyanobacteria for photosynthetic electrogenic activity. It is especially suitable for

  14. FEATURES OF PHYSIOLOGICAL AND PHOTOSYNTHETIC ACTIVITY OF MAIZE PLANTS AT USING NON-TRADITIONAL ORGANIC FERTILIZERS

    Directory of Open Access Journals (Sweden)

    A. Kojuhov

    2012-07-01

    Full Text Available The use of fertilizers in cultivation of crops is an objective necessity. However, their use has a negative impact on environment and especially on the soil polluting it with heavy metals. Organic fertilizers can significantly improve physical and chemical soil properties and increase its fertility. In connection with deficiency of manure particular interest represents using of waste as non-conventional fertilizers, in particular waste of alcohol production. Using of high-dose alcohol stillage stronger growth processes and number of leaves, which leads to an increase of maize photosynthetic activity and productivity. Maximum formation of green mass was observed in variant with a dose of making alcohol stillage 40 m3/ha during vegetation.

  15. Effect of maize seed laser irradiation on plant photosynthetic activity

    International Nuclear Information System (INIS)

    Antonov, M.; Stanev, V.; Velichkov, D.; Tsonev, Ts.

    1986-01-01

    Investigations were made with the two hybrids, H-708 and P x -20. The seeds were irradiated by a helium-neon quantum generator (L'vov-1 Electronica) with output power of 24 MW and 632.8 nm wave length. Once and twice irradiated seeds were sown on the 2nd, 5th and 10th day post irradiation. Changes in leaf area, chlorophyll content in the leaves, photosynthetic rate and its dependence on temperature and light, transpiration, stomatal resistance to CO 2 and total dry matter of the overground plant part were traced. Seed irradiation with laser rays did not affect the chlorophyll content of the leaves. The photosynthetic rate did not depend on the cultivar characteristics of the crop. Single and repeated irradiation of the hybrid H-708 in most case enhanced photosynthetic rate, but a similar effect was not observed in P x -20. Transpiration and CO 2 stomatal resistance were not equally affected by radiation. Laser rays enhanced the ability of the photosynthetic apparatus of the entire plants to use more efficiently high light intensities. The leaf area and the total plant dry matter increased in case of sowing on the 2nd and 5th day and a single irradiation and in case of sowing on the 5th and 10th day and twice repeated irradiations

  16. System to determine leaf photosynthetic activity by means of 14CO2

    International Nuclear Information System (INIS)

    Fernandez Gonzalez, J.

    1977-01-01

    A method to determine leaf photosynthetic activity is described. 14 CO 2 labeled air is produced from 14 CO 3 Ba and stored in a poliethylene balloon and supplied by means of an automatic dispenser to a perspex chamber inside of which is the leaf. (author) [es

  17. Solar PAR and UVR modify the community composition and photosynthetic activity of sea ice algae.

    Science.gov (United States)

    Enberg, Sara; Piiparinen, Jonna; Majaneva, Markus; Vähätalo, Anssi V; Autio, Riitta; Rintala, Janne-Markus

    2015-10-01

    The effects of increased photosynthetically active radiation (PAR) and ultraviolet radiation (UVR) on species diversity, biomass and photosynthetic activity were studied in fast ice algal communities. The experimental set-up consisted of nine 1.44 m(2) squares with three treatments: untreated with natural snow cover (UNT), snow-free (PAR + UVR) and snow-free ice covered with a UV screen (PAR). The total algal biomass, dominated by diatoms and dinoflagellates, increased in all treatments during the experiment. However, the smaller biomass growth in the top 10-cm layer of the PAR + UVR treatment compared with the PAR treatment indicated the negative effect of UVR. Scrippsiella complex (mainly Scrippsiella hangoei, Biecheleria baltica and Gymnodinium corollarium) showed UV sensitivity in the top 5-cm layer, whereas Heterocapsa arctica ssp. frigida and green algae showed sensitivity to both PAR and UVR. The photosynthetic activity was highest in the top 5-cm layer of the PAR treatment, where the biomass of the pennate diatom Nitzschia frigida increased, indicating the UV sensitivity of this species. This study shows that UVR is one of the controlling factors of algal communities in Baltic Sea ice, and that increased availability of PAR together with UVR exclusion can cause changes in algal biomass, photosynthetic activity and community composition. © FEMS 2015. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  18. Nitrogen fixation and diurnal changes of photosynthetic activity in Arctic soil crusts at different development stage

    Czech Academy of Sciences Publication Activity Database

    Pushkareva, E.; Kvíderová, Jana; Šimek, Miloslav; Elster, Josef

    2017-01-01

    Roč. 79, 1 March 2017 (2017), s. 21-30 ISSN 1164-5563 Institutional support: RVO:60077344 ; RVO:67985939 Keywords : Soil crust * Arctic * Photosynthetic activity Subject RIV: EH - Ecology, Behaviour; EH - Ecology, Behaviour (BC-A) OBOR OECD: Ecology; Ecology (BC-A) Impact factor: 2.445, year: 2016

  19. Estimation of absorbed photosynthetically active radiation and vegetation net production efficiency using satellite data

    International Nuclear Information System (INIS)

    Hanan, N.P.; Prince, S.D.; Begue, A.

    1995-01-01

    The amount of photosynthetically active radiation (PAR) absorbed by green vegetation is an important determinant of photosynthesis and growth. Methods for the estimation of fractional absorption of PAR (iff PAR ) for areas greater than 1 km 2 using satellite data are discussed, and are applied to sites in the Sahel that have a sparse herb layer and tree cover of less than 5%. Using harvest measurements of seasonal net production, net production efficiencies are calculated. Variation in estimates of seasonal PAR absorption (APAR) caused by the atmospheric correction method and relationship between surface reflectances and iff PAR is considered. The use of maximum value composites of satellite NDVI to reduce the effect of the atmosphere is shown to produce inaccurate APAR estimates. In this data set, however, atmospheric correction using average optical depths was found to give good approximations of the fully corrected data. A simulation of canopy radiative transfer using the SAIL model was used to derive a relationship between canopy NDVI and iff PAR . Seasonal APAR estimates assuming a 1:1 relationship between iff PAR and NDVI overestimated the SAIL modeled results by up to 260%. The use of a modified 1:1 relationship, where iff PAR was assumed to be linearly related to NDVI scaled between minimum (soil) and maximum (infinite canopy) values, underestimated the SAIL modeled results by up to 35%. Estimated net production efficiencies (ϵ n , dry matter per unit APAR) fell in the range 0.12–1.61 g MJ −1 for above ground production, and in the range 0.16–1.88 g MJ −1 for total production. Sites with lower rainfall had reduced efficiencies, probably caused by physiological constraints on photosynthesis during dry conditions. (author)

  20. Estimation of chromophoric dissolved organic matter (CDOM) and photosynthetic activity of estuarine phytoplankton using a multiple-fixed-wavelength spectral fluorometer.

    Science.gov (United States)

    Goldman, Emily A; Smith, Erik M; Richardson, Tammi L

    2013-03-15

    The utility of a multiple-fixed-wavelength spectral fluorometer, the Algae Online Analyser (AOA), as a means of quantifying chromophoric dissolved organic matter (CDOM) and phytoplankton photosynthetic activity was tested using algal cultures and natural communities from North Inlet estuary, South Carolina. Comparisons of AOA measurements of CDOM to those by spectrophotometry showed a significant linear relationship, but increasing amounts of background CDOM resulted in progressively higher over-estimates of chromophyte contributions to a simulated mixed algal community. Estimates of photosynthetic activity by the AOA at low irradiance (≈ 80 μmol quanta m(-2) s(-1)) agreed well with analogous values from the literature for the chlorophyte, Dunaliella tertiolecta, but were substantially lower than previous measurements of the maximum quantum efficiency of photosystem II (F(v)/F(m)) in Thalassiosira weissflogii (a diatom) and Rhodomonas salina (a cryptophyte). When cells were exposed to high irradiance (1500 μmol quanta m(-2) s(-1)), declines in photosynthetic activity with time measured by the AOA mirrored estimates of cellular fluorescence capacity using the herbicide 3'-(3, 4-dichlorophenyl)-1',1'-dimethyl urea (DCMU). The AOA shows promise as a tool for the continuous monitoring of phytoplankton community composition, CDOM, and the group-specific photosynthetic activity of aquatic ecosystems. Copyright © 2012 Elsevier Ltd. All rights reserved.

  1. Effect of Temperature and light intensity on growth and Photosynthetic Activity of Chlamydomonas reinhard II; Efecto de la temperatura e intensidad luminosa sobre el crecimiento y actividad fotosintetica del alga Chlamydomonas Reinhardt II

    Energy Technology Data Exchange (ETDEWEB)

    Alfonsel Jaen, M; Fernandez Gonzalez, J

    1985-07-01

    The effect of five temperatures (15,20,25,30 and 35 degree centigree) and two levels of illumination on growth and photosynthetic activity of Chlamydomonas reinhard II has been studied. The growth of the cultures was evaluated by optical density. Photosynthetic activity has been carried out studying either the assimilation rate of C0{sub 2} labelled with C-14 or the oxygen evolution by means of polarographic measurements. The maximum photosynthetic rate has been obtained at 25 degree centigree for the lower level of illumination (2400 lux) and at 35 degree centigree for the higher one (13200 lux) and at 35 degree centigree for the higher ono (13200 lux). These results suggest an interaction of temperature and illumination on photosynthetic activity. (Author) 37 refs.

  2. Characteristics of diurnal pattern of global photosynthetically-active ...

    African Journals Online (AJOL)

    A two year data (September 1992 August 1994) on photosynhetically-active radiation (PAR) measured at Ilorin (Lat.: 832´N. Long.:434´E) using LI-190SA quantum sensor are analysed both on daily and monthly mean diurnal bases. This was done with the aim of characterizing the diurnal pattern of this radiation at this ...

  3. Incorporating GOES Satellite Photosynthetically Active Radiation (PAR) Retrievals to Improve Biogenic Emission Estimates in Texas

    Science.gov (United States)

    Zhang, Rui; White, Andrew T.; Pour Biazar, Arastoo; McNider, Richard T.; Cohan, Daniel S.

    2018-01-01

    This study examines the influence of insolation and cloud retrieval products from the Geostationary Operational Environmental Satellite (GOES) system on biogenic emission estimates and ozone simulations in Texas. Compared to surface pyranometer observations, satellite-retrieved insolation and photosynthetically active radiation (PAR) values tend to systematically correct the overestimation of downwelling shortwave radiation in the Weather Research and Forecasting (WRF) model. The correlation coefficient increases from 0.93 to 0.97, and the normalized mean error decreases from 36% to 21%. The isoprene and monoterpene emissions estimated by the Model of Emissions of Gases and Aerosols from Nature are on average 20% and 5% less, respectively, when PAR from the direct satellite retrieval is used rather than the control WRF run. The reduction in biogenic emission rates using satellite PAR reduced the predicted maximum daily 8 h ozone concentration by up to 5.3 ppbV over the Dallas-Fort Worth (DFW) region on some days. However, episode average ozone response is less sensitive, with a 0.6 ppbV decrease near DFW and 0.3 ppbV increase over East Texas. The systematic overestimation of isoprene concentrations in a WRF control case is partially corrected by using satellite PAR, which observes more clouds than are simulated by WRF. Further, assimilation of GOES-derived cloud fields in WRF improved CAMx model performance for ground-level ozone over Texas. Additionally, it was found that using satellite PAR improved the model's ability to replicate the spatial pattern of satellite-derived formaldehyde columns and aircraft-observed vertical profiles of isoprene.

  4. Changes in growth, photosynthetic activities, biochemical parameters and amino acid profile of Thompson Seedless grapes (Vitis vinifera L.).

    Science.gov (United States)

    Somkuwar, R G; Bahetwar, Anita; Khan, I; Satisha, J; Ramteke, S D; Itroutwar, Prerna; Bhongale, Aarti; Oulkar, Dashrath

    2014-11-01

    The study on photosynthetic activity and biochemical parameters in Thompson Seedless grapes grafted on Dog Ridge rootstock and its impact on growth, yield and amino acid profile at various stages of berry development was conducted during the year 2012-2013. Leaf and berry samples from ten year old vines of Thompson Seedless were collected at different growth and berry developmental stages. The analysis showed difference in photosynthetic activity, biochemical parameters and amino acid status with the changes in berry development stage. Higher photosynthetic rate of 17.39 umol cm(-2) s(-1) was recorded during 3-4mm berry size and the lowest (10.08 umol cm(-2) s(-1)) was recorded during the veraison stage. The photosynthetic activity showed gradual decrease with the onset of harvest while the different biochemical parameters showed increase and decrease from one stage to another in both berry and leaves. Changes in photosynthetic activity and biochemical parameters thereby affected the growth, yield and amino acid content of the berry. Positive correlation of leaf area and photosynthetic rate was recorded during the period of study. Reducing sugar (352.25 mg g(-1)) and total carbohydrate (132.52 mg g(-1)) was more in berries as compared to leaf. Amino acid profile showed variations in different stages of berry development. Marked variations in photosynthetic as well as biochemical and amino acid content at various berry development stages was recorded and thereby its cumulative effect on the development of fruit quality.

  5. The photochemical reflectance index provides an optical indicator of spring photosynthetic activation in evergreen conifers.

    Science.gov (United States)

    Wong, Christopher Y S; Gamon, John A

    2015-04-01

    In evergreens, the seasonal down-regulation and reactivation of photosynthesis is largely invisible and difficult to assess with remote sensing. This invisible phenology may be changing as a result of climate change. To better understand the mechanism and timing of these hidden physiological transitions, we explored several assays and optical indicators of spring photosynthetic activation in conifers exposed to a boreal climate. The photochemical reflectance index (PRI), chlorophyll fluorescence, and leaf pigments for evergreen conifer seedlings were monitored over 1 yr of a boreal climate with the addition of gas exchange during the spring. PRI, electron transport rate, pigment levels, light-use efficiency and photosynthesis all exhibited striking seasonal changes, with varying kinetics and strengths of correlation, which were used to evaluate the mechanisms and timing of spring activation. PRI and pigment pools were closely timed with photosynthetic reactivation measured by gas exchange. The PRI provided a clear optical indicator of spring photosynthetic activation that was detectable at leaf and stand scales in conifers. We propose that PRI might provide a useful metric of effective growing season length amenable to remote sensing and could improve remote-sensing-driven models of carbon uptake in evergreen ecosystems. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

  6. Endosulfan induced changes in growth rate, pigment composition and photosynthetic activity of mosquito fern Azolla microphylla

    Directory of Open Access Journals (Sweden)

    Raja W.

    2012-11-01

    Full Text Available This paper is the first in a series reporting a study on the effects of different concentrations of insecticide, Endosulfan (0-600ppm was premeditated on 5th day after insecticide exposure with respect to growth rate, pigment composition and photosynthetic activity of Azolla microphylla under laboratory conditions which become non-target organism in the rice fields. Endosulfan inhibited the relative growth rate, pigment content and photosynthetic O2 evolution. Phycocyanin was main target followed by carotenoid and total chlorophyll. Significant increase in pigment, flavonoid and Anthocyanin was noticed after six days of treatment. In contrast to the photosynthetic activity, the rate of respiration in Azolla microphylla was increased significantly. Our results show that Endosulfan at normally recommended field rates and intervals are seldom deleterious to the beneficial and Eco friendly Azolla microphylla and their activities and thus in turn suppress plant growth and development. Phytotoxity of Azolla microphylla can be minimized by restrictions on application, timing, method and rate of application.

  7. Photosynthetic activity buffers ocean acidification in seagrass meadows

    Science.gov (United States)

    Hendriks, I. E.; Olsen, Y. S.; Ramajo, L.; Basso, L.; Steckbauer, A.; Moore, T. S.; Howard, J.; Duarte, C. M.

    2014-01-01

    Macrophytes growing in shallow coastal zones characterised by intense metabolic activity have the capacity to modify pH within their canopy and beyond. We observed diel pH changes in shallow (5-12 m) seagrass (Posidonia oceanica) meadows spanning 0.06 pH units in September to 0.24 units in June. The carbonate system (pH, DIC, and aragonite saturation state (ΩAr)) and O2 within the meadows displayed strong diel variability driven by primary productivity, and changes in chemistry were related to structural parameters of the meadow, in particular, the leaf surface area available for photosynthesis (LAI). LAI was positively correlated to mean, max and range pHNBS and max and range ΩAr. In June, vertical mixing (as Turbulent Kinetic Energy) influenced max and min ΩAr, while in September there was no effect of hydrodynamics on the carbonate system within the canopy. Max and range ΩAr within the meadow showed a positive trend with the calcium carbonate load of the leaves, pointing to a possible link between structural parameters, ΩAr and carbonate deposition. Calcifying organisms, e.g. epiphytes with carbonate skeletons, may benefit from the modification of the carbonate system by the meadow. There is, however, concern for the ability of seagrasses to provide modifications of similar importance in the future. The predicted decline of seagrass meadows may alter the scope for alteration of pH within a seagrass meadow and in the water column above the meadow, particularly if shoot density and biomass decline, on which LAI is based. Organisms associated with seagrass communities may therefore suffer from the loss of pH buffering capacity in degraded meadows.

  8. Effect of low-dose 60Co gamma irradiation on the photosynthetic activity of maize seedlings

    International Nuclear Information System (INIS)

    Turcsanyi, G.

    1979-01-01

    Photosynthesis investigations were carried out on maize seedlings treated with 1000 rad of 60 Co gamma irradiation prior to sowing. The aim of the work was to find out, to what degree the individual processes of photosynthesis are affected by small doses of irradiation. The increase in weight, the chlorophyll a, chlorophyll b and carotinoid content as well as the photosynthetic O 2 -evolution and 14 CO 2 -fixation of the seedlings were measured. The results indicate that, in contradiction to the data given in the literature, the occasional increase in weight caused by small-dose irradiation is not in connection with the membrane-bound part of the photosynthetic apparatus, but it is the consequence of the increased activity of the Calvin-cycle enzymes in the stroma of the chloroplasts. (author)

  9. Progress in Remote Sensing of Photosynthetic Activity over the Amazon Basin

    Science.gov (United States)

    Resende de Sousa, Celio Helder; Hilker, Thomas; Waring, Richard; Mendes De Moura, Yhasmin; Lyapustin, Alexei

    2017-01-01

    Although quantifying the massive exchange of carbon that takes place over the Amazon Basin remains a challenge, progress is being made as the remote sensing community moves from using traditional, reflectance-based vegetation indices, such as the Normalized Difference Vegetation Index (NDVI), to the more functional Photochemical Reflectance Index (PRI). This new index, together with satellite-derived estimates of canopy light interception and Sun-Induced Fluorescence (SIF), provide improved estimates of Gross Primary Production (GPP). This paper traces the development of these new approaches, compares the results of their analyses from multiple years of data acquired across the Amazon Basin and suggests further improvements in instrument design, data acquisition and processing. We demonstrated that our estimates of PRI are in generally good agreement with eddy-flux tower measurements of photosynthetic light use efficiency (epsilon) at four sites in the Amazon Basin: r(exp 2) values ranged from 0.37 to 0.51 for northern flux sites and to 0.78for southern flux sites. This is a significant advance over previous approaches seeking to establish a link between global-scale photosynthetic activity and remotely-sensed data. When combined with measurements of Sun-Induced Fluorescence (SIF), PRI provides realistic estimates of seasonal variation in photosynthesis over the Amazon that relate well to the wet and dry seasons. We anticipate that our findings will steer the development of improved approaches to estimate photosynthetic activity over the tropics.

  10. NOAA Climate Data Record (CDR) of Leaf Area Index (LAI) and Fraction of Absorbed Photosynthetically Active Radiation (FAPAR), Version 4

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset contains gridded daily Leaf Area Index (LAI) and Fraction of Absorbed Photosynthetically Active Radiation (FAPAR) derived from the NOAA Climate Data...

  11. Study the effect of insecticide dimethoate on photosynthetic pigments and photosynthetic activity of pigeon pea: Laser-induced chlorophyll fluorescence spectroscopy.

    Science.gov (United States)

    Pandey, Jitendra Kumar; Dubey, Gunjan; Gopal, R

    2015-10-01

    Pigeon pea is one of the most important legume crops in India and dimethoate is a widely used insecticide in various crop plants. We studied the effect of dimethoate on growth and photosynthetic activity of pigeon pea plants over a short and long term exposure. Plant growth parameters, photosynthetic pigment content and chlorophyll fluorescence response of pigeon pea (Cajanus cajan L.) plants treated with various concentrations of the insecticide dimethoate (10, 20, 40 and 80 ppm) have been compared for 30 days at regular intervals of 10 days each. Laser induced chlorophyll fluorescence spectra and fluorescence-induction kinetics (FIK) curve of dimethoate treated pigeon pea plants were recorded after 10, 20 and 30 days of treatment. Fluorescence intensity ratio at the two fluorescence maxima (F685/F730) was calculated by evaluating curve-fitted parameters. The variable chlorophyll fluorescence decrease ratio (Rfd) was determined from the FIK curves. Our study revealed that after 10 days of treatment, 10 ppm of dimethoate showed stimulatory response whereas 20, 40 and 80 ppm of dimethoate showed inhibitory response for growth and photosynthetic activity of pigeon pea plants, but after 20 and 30 days of treatment all the tested concentrations of dimethoate became inhibitory. This study clearly shows that dimethoate is highly toxic to the pigeon pea plant, even at very low concentration (10 ppm), if used for a prolonged duration. Our study may thus be helpful in determining the optimal dose of dimethoate in agricultural practices. Copyright © 2014 Elsevier B.V. All rights reserved.

  12. Effects of the pear tree canopy on photosynthetically active radiation availability

    International Nuclear Information System (INIS)

    Rossi, F.; Baldini, E.; Baraldi, R.

    1984-01-01

    The relationships existing between radiant energy and photosynthesis have been extensively investigated on the apple /2/ but not on the other fruit trees, pear included. In addition, such information resists generalization, owing to the remarkable differences underlying tree morphology and physiology of the different species; furthermore, some disagreement arises regarding the terminology and the units used to evaluate the amount of radiant energy useful for the photosynthetic process. In general this evaluation is based on the readouts of illuminance (symbol Ev; unit: lux), in agreement with the photopic curve (fig. 1:A), i.e. with the human eye sensibility to the visible radiation(light). However, the relative response of the chloroplasts to the radiant flux, although included within the same spectral wavebands as the photopic curve, follows a different model (fig.1:B), that is, it has two peaks in connection with the spectral wavelenghts of blue (440–490 nm), and, particularly, of red (620–700 nm). Therefore, according to a number of authors /3/6/8/11/, the correct evaluation of the photosynthetically active radiation should be made using sensors calibrated to measure the photosynthetic photon lux density (symbol: PPFD; unit: μE m -2 s -1 ), and provided with a relative spectral response similar to that of the leaves. (author)

  13. Use of in vivo chlorophyll fluorescence to estimate photosynthetic activity and biomass productivity in microalgae grown in different culture systems

    Directory of Open Access Journals (Sweden)

    Félix L Figueroa

    2013-11-01

    Full Text Available In vivo chlorophyll fluorescence associated to Photosystem II is being used to evaluate photosynthetic activity of microalgae grown in different types of photobioreactors; however, controversy on methodology is usual. Several recommendations on the use of chlorophyll fluorescence to estimate electron transport rate and productivity of microalgae grown in thin-layer cascade cultivators and methacrylate cylindrical vessels are included. Different methodologies related to the measure of photosynthetic activity in microalgae are discussed: (1 measurement of light absorption, (2 determination of electron transport rates versus irradiance and (3 use of simplified devices based on pulse amplitude modulated (PAM fluorescence as Junior PAM or Pocket PAM with optical fiber and optical head as measuring units, respectively. Data comparisons of in vivo chlorophyll fluorescence by using these devices and other PAM fluorometers as Water-PAM in the microalga Chlorella sp. (Chlorophyta are presented. Estimations of carbon production and productivity by transforming electron transport rate to gross photosynthetic rate (as oxygen evolution using reported oxygen produced per photons absorbed values and carbon photosynthetic yield based on reported oxygen/carbon ratio are also shown. The limitation of ETR as estimator of photosynthetic and biomass productivity is discussed. Low cost:quality PAMs can promote monitoring of chlorophyll fluorescence in algal biotechnology to estimate the photosynthetic activity and biomass productivity.

  14. Continuous high and low temperature induced a decrease of photosynthetic activity and changes in the diurnal fluctuations of organic acids in Opuntia streptacantha.

    Directory of Open Access Journals (Sweden)

    Zaida Zarely Ojeda-Pérez

    Full Text Available Opuntia plants grow naturally in areas where temperatures are extreme and highly variable in the day during the entire year. These plants survive through different adaptations to respond to adverse environmental conditions. Despite this capability, it is unknown how CAM photosynthetic activity and growth in Opuntia plantlets is affected by constant heat or cold. Therefore, the main objective of this research was to evaluate the short-term effect of high (40°C and low (4°C continuous temperatures on the photosynthetic efficiency, the organic acid content (malic acid and the relative growth rate (RGR in seven-month-old Opuntia streptacantha plantlets during 5, 10, and 15 days. Chlorophyll fluorescence analysis allowed us to determine that high temperatures negatively impact the photosynthetic efficiency of O. streptacantha plantlets, which exhibited the lowest values of maximum quantum efficiency of the photosystem II (Fv/Fm = 52%, Fv/F0 = 85%, operational quantum yield of PS (ΦPSII = 65% and relative electron transport rate (rETR = 65%, as well as highest values of basal fluorescence (F0 = 226% during 15 days of treatment. Similarly, low temperatures decreased Fv/Fm (16%, Fv/F0 (50%, ΦPSII and rETR (16%. High temperatures also decreased nocturnal acidification in approximately 34-50%, whereas low temperatures increased it by 30-36%. Additionally, both continuous temperatures affected drastically diurnal consumption of malic acid, which was related to a significant RGR inhibition, where the specific photosynthetic structure area component was the most affected. Our results allowed determining that, despite the high tolerance to extreme temperatures described for Opuntia plants, young individuals of O. streptacantha suffered photosynthetic impairment that led to the inhibition of their growth. Thus, the main findings reported in this study can help to predict the potential impact of climatic change on the establishment and survival of succulent

  15. Low-cost sensor integrators for measuring the transmissivity of complex canopies to photosynthetically active radiation

    International Nuclear Information System (INIS)

    Newman, S.M.

    1985-01-01

    A system has been designed, tested and evaluated for measuring the transmissivities of complex canopies to photosynthetically active radiation (PAR). The system consists of filtered silicon photocells in cosine corrected mounts with outputs integrated by the use of chemical coulometers. The reading accumulated by the coulometers was taken electronically by the use of microcomputers. The low-cost sensor integrators, which do not require batteries, performed as expected and proved ideal for the study of agroforestry systems in remote areas. Information on the PAR transmissivity of a temperate agroforestry system in the form of an intercropped orchard is also presented. (author)

  16. Efeito do hexazinone isolado e em mistura na eficiência fotossintética de Panicum maximum Effect of hexazinone applied alone and in combination on the photosynthetic efficiency of Panicum maximum

    Directory of Open Access Journals (Sweden)

    M. Girotto

    2012-06-01

    Full Text Available Esta pesquisa teve como objetivo avaliar a velocidade e intensidade de ação do hexazinone isolado e em mistura com outros inibidores do fotossistema II, através da eficiência fotossintética de Panicum maximum em pós-emergência. O ensaio foi constituído de seis tratamentos: hexazinone (250 g ha-1, tebuthiuron (1,0 kg ha-1, hexazinone + tebuthiuron (125 g ha-1 + 0,5 kg ha-1, diuron (2.400 g ha-1, hexazinone + diuron (125 + 1.200 g ha-1, metribuzin (1.440 g ha-1, hexazinone + metribuzin (125 + 720 g ha-1 e uma testemunha. O experimento foi instalado em delineamento inteiramente casualizado, com quatro repetições. Após a aplicação dos tratamentos, as plantas foram transportadas para casa de vegetação sob condições controladas de temperatura e umidade, onde ficaram durante o período experimental, sendo realizadas as seguintes avaliações: taxa de transporte de elétrons e análise visual de intoxicação. A avaliação com o fluorômetro foi realizada nos intervalos de 1, 2, 6, 24, 48, 72, 120 e 168 horas após a aplicação, e as avaliações visuais, aos três e sete dias após a aplicação. Os resultados demonstraram diferença nos tratamentos, enfatizando a aplicação do diuron, que reduziu lentamente o transporte de elétrons comparado com os outros herbicidas e, em mistura com hexazinone, apresentou efeito sinérgico. Verificou-se com o uso do fluorômetro a intoxicação antecipada em plantas de P. maximum após a aplicação de herbicidas inibidores do fotossistema II de forma isolada e em mistura.This work aimed to evaluate the speed and intensity of action of hexazinone applied alone and in combination with other photo-system II inhibitors on the photosynthetic efficiency of Panicum maximum in post-emergence. The assay consisted of six treatments: hexazinone (250 g ha-1, tebuthiuron (1.0 kg ha-1, hexazinone + tebuthiuron (125 g ha-1+ 0.5 kg ha-1, diuron (2,400 g ha-1, hexazinone + diuron (125 + 1,200 g ha-1, metribuzin

  17. Visualization of water usage and photosynthetic activity of street trees exposed to 2 ppm of SO2-A combined evaluation by cold neutron and chlorophyll fluorescence imaging

    International Nuclear Information System (INIS)

    Matsushima, U.; Kardjilov, N.; Hilger, A.; Manke, I.; Shono, H.; Herppich, W.B.

    2009-01-01

    Photosynthetic efficacy and auto-exhaust-fume resistance of street trees were evaluated by cold neutron radiography (CNR) with D 2 O tracer and chlorophyll fluorescence (CF) imaging. With these techniques, information on the responses of water usage and photosynthetic activity of plants exposed to simulate toxic auto-exhaust fumes (2 ppm SO 2 in air) were obtained. Branches of hibiscus trees were detached, placed into a tub with aerated water and used for the experiments after rooting. A CF image was taken before SO 2 was applied for 1 h. During the experiment, CNR and CF imaging were conduced. H 2 O and D 2 O in the plant container were exchanged every 30 min to observe water uptake. D 2 O tracer clearly showed water uptake into the hibiscus stem during each treatment. When the atmosphere was changed from simulated auto-exhaust fumes to normal air again, the amount of D 2 O and, hence, water uptake increased. CF imaging was well suited to evaluate the effects of SO 2 as simulated toxic auto-exhaust fumes on plants. The maximum photochemical efficiency (F v /F m ), a sensitive indicator of the efficacy and the integrity of plants' photosynthesis, immediately dropped by 30% after supplying the simulated auto-exhaust fumes. This indicates that toxic auto-exhaust fumes negatively affected the photosynthetic activity of hibiscus leaves. Simultaneous CNR and CF imaging successfully visualized variations of photosynthetic activity and water uptake in the sample. Thus, this combination method was effective to non-destructive analyze the physiological status of plants.

  18. High rates of solar radiation - an important natural stress factor of the photosynthetic activity of mountainous norway spruce stands

    International Nuclear Information System (INIS)

    Sprtova, M.; Marek, M.V.

    1996-01-01

    Photosynthetic activity can be regarded as the basis of biomass productivity and vitality of forest trees, respectively. Moreover, this activity is under the strong influence of environment. Excess of photosynthetically active radiation (PhAR) can be a harmful factor of environment which is the reason of photoinhibition. Photoinhibition is demonstrated by a decrease of photosynthetic rate. An analysis of the influence of PhAR excess on function of the assimilatory apparatus of Norway spruce during summer days was done. The strong influence of PhAR excess on values of parameters of photosynthesis reflecting changes in the level of quanta capture and electron transport chain was observed. The comprehensive description of the method of chlorophyll a is given. Excess of PhAR caused rapid changes of assimilatory apparatus function and thus this PhAR excess can be regarded as a significant stress of productional activity of Norway spruce stands under field conditions

  19. Evaluating Maximum Wind Energy Exploitation in Active Distribution Networks

    DEFF Research Database (Denmark)

    Siano, Pierluigi; Chen, Peiyuan; Chen, Zhe

    2010-01-01

    The increased spreading of distributed and renewable generation requires moving towards active management of distribution networks. In this paper, in order to evaluate maximum wind energy exploitation in active distribution networks, a method based on a multi-period optimal power flow (OPF......) analysis is proposed. Active network management schemes such as coordinated voltage control, energy curtailment and power factor control are integrated in the method in order to investigate their impacts on the maximization of wind energy exploitation. Some case studies, using real data from a Danish...... distribution system, confirmed the effectiveness of the proposed method in evaluating the optimal applications of active management schemes to increase wind energy harvesting without costly network reinforcement for the connection of wind generation....

  20. Temperature Effects on the Growth Rates and Photosynthetic Activities of Symbiodinium Cells

    Directory of Open Access Journals (Sweden)

    Widiastuti Karim

    2015-06-01

    Full Text Available Coral bleaching is caused by environmental stress and susceptibility to bleaching stress varies among types of coral. The physiological properties of the algal symbionts (Symbiodinium spp., especially extent of damage to PSII and its repair capacity, contribute importantly to this variability in stress susceptibility. The objective of the present study was to investigate the relationship between the growth rates and photosynthetic activities of six cultured strains of Symbiodinium spp. (clades A, B, C, D, and F at elevated temperature (33 °C. We also observed the recovery of photodamaged-PSII in the presence or absence of a chloroplast protein synthesis inhibitor (lincomycin. The growth rates and photochemical efficiencies of PSII (Fv/Fm decreased in parallel at high temperature in thermally sensitive strains, B-K100 (clade B followed by culture name and A-Y106, but not in thermally tolerant strains, F-K102 and D-K111. In strains A-KB8 and C-Y103, growth declined markedly at high temperature, but Fv/Fm decreased only slightly. These strains may reallocate energy from growth to the repair of damaged photosynthetic machineries or protection pathways. Alternatively, since recoveries of photo-damaged PSII at 33 °C were modest in strains A-KB8 and C-Y103, thermal stressing of other metabolic pathways may have reduced growth rates in these two strains. This possibility should be explored in future research efforts.

  1. Screening of photosynthetic pigments for herbicidal activity with a new computational molecular approach.

    Science.gov (United States)

    Krishnaraj, R Navanietha; Chandran, Saravanan; Pal, Parimal; Berchmans, Sheela

    2013-12-01

    There is an immense interest among the researchers to identify new herbicides which are effective against the herbs without affecting the environment. In this work, photosynthetic pigments are used as the ligands to predict their herbicidal activity. The enzyme 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase is a good target for the herbicides. Homology modeling of the target enzyme is done using Modeler 9.11 and the model is validated. Docking studies were performed with AutoDock Vina algorithm to predict the binding of the natural pigments such as β-carotene, chlorophyll a, chlorophyll b, phycoerythrin and phycocyanin to the target. β-carotene, phycoerythrin and phycocyanin have higher binding energies indicating the herbicidal activity of the pigments. This work reports a procedure to screen herbicides with computational molecular approach. These pigments will serve as potential bioherbicides in the future.

  2. Nitrate reductase and photosynthetic activities of wheat and their relationship with plant productivity under soil water deficit conditions (abstract)

    International Nuclear Information System (INIS)

    Ashraf, M.Y.; Sarwar, G.; Hussain, F.

    2005-01-01

    Experiments were conducted in lysimeters with wheat during two consecutive years. The first year experiment comprised of eight wheat genotypes with four water stress treatments, i.e. normal irrigation, pre-anthesis drought, post-anthesis drought and terminal drought, with four replications. The results showed that yield and yield parameters reduced with the severity of drought in all wheat lines. However, wheat lines Chakwal-86, DS-4 and Barani-83 had comparatively higher yield and yield components than others. The maximum reduction in all parameters was under terminal drought. The difference between pre- and post-anthesis drought was nonsignificant, particularly for grain yield. The second experiment was conducted with four wheat lines: two were tolerant (Chakwal-86 and DS-4) and two susceptible (Pavon and DS-17) under similar environments with same treatments to study the photosynthetic efficiency, nitrogen metabolism and their relationship with plant productivity (yield). The results showed that leaf area, transpiration, dry matter accumulation and nitrate reductase activity were reduced while diffusive resistance and total amino acids increased in all the wheat lines under water deficit conditions. The relationship between yield and leaf area, transpiration, dry matter accumulation and nitrate reductase activity was positive. The overall results showed that wheat lines Chakwal-86 and DS-4 showed better performance than others. (author)

  3. Far-red enrichment and photosynthetically active radiation level influence leaf senescence in field-grown sunflower

    International Nuclear Information System (INIS)

    Rousseaux, M.C.; Hall, A.J.; Sánchez, R.A.

    1996-01-01

    Basal leaves frequently senesce before anthesis in high population density crops. This paper evaluates the hypothesis that quantitative and qualitative changes in the light environment associated with a high leaf area index (LAI) trigger leaf senescence in sunflower (Helianthus annuus L.) canopies. Mean leaf duration (LD, time from achievement of maximum leaf area) of leaf 8 was significantly (P < 0.05) reduced from 51 to 19 days as crop population density was increased from 0.47 to 4.76 plants m−2. High compared to low plant population density was associated with earlier reduction in the photosynthetically active radiation (PAR) and red/far-red ratio (R/FR) reaching the target leaf. However the changes in R/FR preceded those in PAR. When the light environment of individual leaves of isolated plants growing under field conditions was manipulated using filters and FR-reflecting mirrors, LD was positively and linearly related with the mean daily PAR (MDR) received in the FR- (no FR enrichment) treatments. FR enrichment of light reaching the abaxial surface of the leaf significantly (P < 0.05) reduced LD by 9 days at intermediate PAR levels with respect to FR-controls, but did not affect LD at the maximum PAR used in these experiments. However, when light reaching both leaf surfaces was enriched with FR, LD (for leaves receiving maximum PAR) was 13 days shorter than that of the FR- control. These results show that basal leaf senescence in sunflower is enhanced both by a decrease in PAR and by a decrease in R/FR. (author)

  4. Transmittance of young Norway spruce stand canopy for photosynthetically active radiation during the growing season

    International Nuclear Information System (INIS)

    Markova, I.; Kubasek, J.

    2013-01-01

    Analysis of transmittance of young Norway spruce stand canopy for photosynthetically active radiation (PAR) was made at the study site of Bily Kriz (the Moravian-Silesian Beskids Mts., the Czech Republic) at different sky conditions during the growing season in 2010. For the description of PAR transmittance different phenological phases of the spruce stand development in clear and overcast days were chosen. The mean daily PAR transmittance of the spruce canopy was significantly higher in overcast days compared with clear ones. Diffuse PAR thus penetrated into lower parts of the canopy more efficiently than direct one. PAR transmittance of young Norway spruce stand canopy was different in individual phenological phases of the spruce stand canopy which was caused by changes in the stand structure during the growing season. Thus monitoring of transmittance of young Norway spruce stand canopy for PAR can help to describe the development of spruce stand canopy

  5. Photosynthetic water oxidation: binding and activation of substrate waters for O-O bond formation.

    Science.gov (United States)

    Vinyard, David J; Khan, Sahr; Brudvig, Gary W

    2015-01-01

    Photosynthetic water oxidation occurs at the oxygen-evolving complex (OEC) of Photosystem II (PSII). The OEC, which contains a Mn4CaO5 inorganic cluster ligated by oxides, waters and amino-acid residues, cycles through five redox intermediates known as S(i) states (i = 0-4). The electronic and structural properties of the transient S4 intermediate that forms the O-O bond are not well understood. In order to gain insight into how water is activated for O-O bond formation in the S4 intermediate, we have performed a detailed analysis of S-state dependent substrate water binding kinetics taking into consideration data from Mn coordination complexes. This analysis supports a model in which the substrate waters are both bound as terminal ligands and react via a water-nucleophile attack mechanism.

  6. Induced modifications on algae photosynthetic activity monitored by pump-and-probe technique

    Energy Technology Data Exchange (ETDEWEB)

    Barbini, R; Colao, F; Fantoni, R; Palucci, A; Ribezzo, S [ENEA, Centro Ricerche Frascati, Rome (Italy). Dip. Innovazione; Tarzillo, G; Carlozzi, P; Pelosi, E [CNR, Florence (Italy). Centro Studi Microorganismi Autotrofi

    1995-12-01

    The lidar fluorosensor system available at ENEA Frascati has been used for a series of laboratory measurements on brackish-water and marine phytoplankton grown in laboratory with the proper saline solution. The system, already used to measure the laser induced fluorescence spectra of different algae species and their detection limits, has been upgraded with a short pulse Nd:YAG laser and rearranged to test a new technique based on laser pump and probe excitation. Results of this new technique for remote monitoring of the in-vivo photosynthetic activity will be presented, as measured during a field campaign carried out in Florence during the Autumn 1993, where the effects of an actinic saturating light and different chemicals have also been checked.

  7. Antimycobacterial and Photosynthetic Electron Transport Inhibiting Activity of Ring-Substituted 4-Arylamino-7-Chloroquinolinium Chlorides

    Directory of Open Access Journals (Sweden)

    Alois Cizek

    2013-09-01

    Full Text Available In this study, a series of twenty-five ring-substituted 4-arylamino-7-chloroquinolinium chlorides were prepared and characterized. The compounds were tested for their activity related to inhibition of photosynthetic electron transport (PET in spinach (Spinacia oleracea L. chloroplasts and also primary in vitro screening of the synthesized compounds was performed against mycobacterial species. 4-[(2-Bromophenylamino]-7-chloroquinolinium chloride showed high biological activity against M. marinum, M. kansasii, M. smegmatis and 7-chloro-4-[(2-methylphenylamino]quinolinium chloride demonstrated noteworthy biological activity against M. smegmatis and M. avium subsp. paratuberculosis. The most effective compounds demonstrated quite low toxicity (LD50 > 20 μmol/L against the human monocytic leukemia THP-1 cell line within preliminary in vitro cytotoxicity screening. The tested compounds were found to inhibit PET in photosystem II. The PET-inhibiting activity expressed by IC50 value of the most active compound 7-chloro-4-[(3-trifluoromethylphenylamino]quinolinium chloride was 27 μmol/L and PET-inhibiting activity of ortho-substituted compounds was significantly lower than this of meta- and para-substituted ones. The structure-activity relationships are discussed for all compounds.

  8. Seasonal variations in the rate of photosynthetic activity and chemical composition of the seagrass Cymodocea nodosa (Ucr. Asch.

    Directory of Open Access Journals (Sweden)

    N. Zavodnik

    1998-12-01

    Full Text Available Temporal changes in biomass, rate of photosynthetic activity and chemical composition of the seagrass Cymodocea nodosa (Ucr. Asch., under the influence of various environmental factors, were followed in the Faborsa Bay, Northern Adriatic. Throughout the year the estimated average biomass was about 130 g dry wt m-2 with annual production of 80 g C m-2. In general, leaf length, biomass and production showed clear seasonality, with maximum values during the summer period (July-September and clear minima in winter. Net oxygen production was closely related to biomass, leaf length, chlorophyll concentration, water temperature and incident light intensity. No clear seasonality was observed in the chemical composition (protein, fats, total phosphorus of C. nodosa. Over the annual cycle, the range of measured variables was 10-16% for protein, 1.7-3.1% for fat, 0.3-0.8% for phosphorus, 1.6-2.6 for nitrogen in leaves, and 5-17% for protein, 0.9-3.2% for fat, 0.1-0.6% for phosphorus and 0.9-2.8 for nitrogen in roots.

  9. Influence of stomatic aperture on photosynthetic activity of bean-seedlings leaves; Influencia de la apertura estomatica sobre la actividad fotosintetica de las hojas de plantas de judias

    Energy Technology Data Exchange (ETDEWEB)

    Suarez Moya, J; Fernandez Gonzalez, J

    1984-07-01

    The present paper contains the data of photosynthetic activity and stomatic aperture of bean-seedlings Ieaves, and the relations obtained with both results. It has been observed that the product of photosynthetic activity by the resistance; to transpiration measured by a promoter ia a constant, between some limits. (Author) 45 refs.

  10. Characterization of Co-Cultivation of Cyanobacteria on Growth, Productions of Polysaccharides and Extracellular Proteins, Nitrogenase Activity, and Photosynthetic Activity.

    Science.gov (United States)

    Xue, Chuizhao; Wang, Libo; Wu, Tong; Zhang, Shiping; Tang, Tao; Wang, Liang; Zhao, Quanyu; Sun, Yuhan

    2017-01-01

    Cyanobacteria as biofertilizers are benefit to reduce the use of chemical fertilizers and reestablish the ecological system in soil. In general, several strains of cyanobacteria were involved in the biofertilizers. The co-cultivation of cyanobacteria were characterized on growth profile, production of polysaccharides and extracellular proteins, nitrogenase activity, and photosynthetic activity for three selected N 2 -fixing cyanobacteria, Anabaena cylindrica (B1611 and F243) and Nostoc sp. (F280). After eight-day culture, the highest dry weights were obtained in F280 pure culture and co-cultivation of B1611 and F280. Higher production of extracellular proteins and cell-bonding polysaccharides (CPS) were observed in co-cultivations compared with pure culture. The highest released polysaccharides (RPS) contents were obtained in pure culture of F280 and co-cultivation of F280 and F243. Galactose and glucose were major components of CPS and RPS in all samples. Trehalose was a specific component of RPS in F280 pure culture. Based on the monosaccharide contents of CPS and RPS, F280 was the dominant species in the related treatments of co-cultivation. The nitrogenase activities in all treatments exhibited a sharp rise at the late stage while a significant decrease existed when three cyanobacteria strains were mixed. Photosynthetic activities for all treatments were determined with rapid light curve, and the related parameters were estimated.

  11. Vegetative and reproductive plasticity of broccoli at three levels of incident photosynthetically active radiation

    International Nuclear Information System (INIS)

    Francescangeli, N.; Martí, H.R.; Sangiacomo, M.A.

    2007-01-01

    To study the effects of shading on the growth, development, dry matter partitioning, and plant architecture of broccoli, ‘Legacy’ hybrid plants were grown in pots in a greenhouse under black shading meshes to generate different levels of photosynthetically active radiation (PAR). The average incident PAR was 23 mol PPF m –2 d –1 under control conditions, 15.2 under a 35% mesh, and 6.7 under a 70% mesh. The air temperature was within the range 15-22°C. As shading increased so did the duration of the growth cycle and the leaf area (LA). Shading did not affect the number of leaves, although the upper ones were more erect. The stem length and the accumulated intercepted PAR (IPAR) were negatively related. Inflorescence diameter and commercial fresh weight decreased only with the 70% mesh. Shading did not affect stem dry weight (DW) but altered dry matter allocation in the root and spear. The DW of the leaves maintained an average 45.7% of the total DW despite the greater LA developed under shade. The net assimilation rate diminished with the reduction of IPAR, and the LA increased; the plant relative growth rate was therefore practically constant. With increased shading, the leaves and the stem became the dominant photosynthate sinks. The commercial fresh weight achieved with 15.2 mol photosynthetic photon flux (PPF) m –2 d –1 was equivalent to that obtained with 23 mol PPF m –2 d –1 , but the cycle was extended for 4.5 days. With 6.7 mol PPF m –2 d –1 , yield diminished because of the lower DW produced in a cycle extended by 15 days, and because more dry matter was allocated to the stem than to the spear. Based on these results, broccoli could be considered a shade-tolerant plant. (author) [es

  12. Seasonal and diel changes in photosynthetic activity of the snow algae Chlamydomonas nivalis (Chlorophyceae) from Svalbard determined by PAM fluorometry

    Czech Academy of Sciences Publication Activity Database

    Stibal, Marek; Elster, Josef; Šabacká, Marie; Kaštovská, Klára

    2007-01-01

    Roč. 59, - (2007), s. 265-273 ISSN 0168-6496 R&D Projects: GA AV ČR KJB6005409 Institutional research plan: CEZ:AV0Z60050516 Keywords : Chlamydomonas nivalis * photosynthetic activity * PAM fluorometry Subject RIV: EF - Botanics Impact factor: 3.039, year: 2007

  13. Photosynthetic pigments and peroxidase activity of Lepidium sativum L. during assisted Hg phytoextraction.

    Science.gov (United States)

    Smolinska, Beata; Leszczynska, Joanna

    2017-05-01

    The study was conducted to evaluate metabolic answer of Lepidium sativum L. on Hg, compost, and citric acid during assisted phytoextraction. The chlorophyll a and b contents, total carotenoids, and activity of peroxidase were determined in plants exposed to Hg and soil amendments. Hg accumulation in plant shoots was also investigated. The pot experiments were provided in soil artificially contaminated by Hg and/or supplemented with compost and citric acid. Hg concentration in plant shoots and soil substrates was determined by cold vapor atomic absorption spectroscopy (CV-AAS) method after acid mineralization. The plant photosynthetic pigments and peroxidase activity were measured by standard spectrophotometric methods. The study shows that L. sativum L. accumulated Hg in its aerial tissues. An increase in Hg accumulation was noticed when soil was supplemented with compost and citric acid. Increasing Hg concentration in plant shoots was correlated with enhanced activation of peroxidase activity and changes in total carotenoid concentration. Combined use of compost and citric acid also decreased the chlorophyll a and b contents in plant leaves. Presented study reveals that L. sativum L. is capable of tolerating Hg and its use during phytoextraction assisted by combined use of compost and citric acid lead to decreasing soil contamination by Hg.

  14. Foliar nitrogen and potassium applications improve photosynthetic activities and water relations in sunflower under moisture deficit condition

    International Nuclear Information System (INIS)

    Hussain, R.A.; Ahmad, R.

    2016-01-01

    This study investigated the influence of foliar supplementation of nitrogen (N) potassium (K) and their combination on photosynthetic activities, physiological indices and water relations of two sunflower (Helianthus annuus L.) hybrids Hysen-33 and LG-5551 under water deficit condition. Studies were conducted in a wire-house at Nuclear Institute for Agriculture and Biology, Faisalabad, Pakistan. Treatments were two water stress levels [100 (control) and 60% field capacity (water deficit)], six levels of foliar spray (no spray, water spray, 1% N, 1% K, 0.5% N + 0.5% K and 1% N + 1% K) and each treatment was replicated three times. Results showed that water stress reduced the photosynthetic activities: Pn (photosynthetic rate), E (rate of tanspiration) and gs (stomatal conductance) and water relations i.e., pie w (water potential), pie s (osmotic potential) and pie p (turgor potential) . Soil moisture deficit also significantly reduced the plant height, root length, fresh and dry matter which consequently affected the plant height stress tolerance index (PHSI), root length stress tolerance index (RLSI) and dry matter stress tolerance index (DMSI) in both sunflower hybrids. However, foliar supplementation with N and K or N+K improved the photosynthetic activities, water relations and physiological indices of both the sunflower hybrids. The findings of present study suggest that application of N+K is necessary to have high plant productivity. (author)

  15. Overexpression of plastidial thioredoxins f and m differentially alters photosynthetic activity and response to oxidative stress in tobacco plants

    Directory of Open Access Journals (Sweden)

    Pascal eREY

    2013-10-01

    Full Text Available Plants display a remarkable diversity of thioredoxins (Trxs, reductases controlling the thiol redox status of proteins. The physiological function of many of them remains elusive, particularly for plastidial Trxs f and m, which are presumed based on biochemical data to regulate photosynthetic reactions and carbon metabolism. Recent reports revealed that Trxs f and m participate in vivo in the control of starch metabolism and cyclic photosynthetic electron transfer around photosystem I, respectively. To further delineate their in planta function, we compared the photosynthetic characteristics, the level and/or activity of various Trx targets and the responses to oxidative stress in transplastomic tobacco plants overexpressing either Trx f or Trx m. We found that plants overexpressing Trx m specifically exhibit altered growth, reduced chlorophyll content, impaired photosynthetic linear electron transfer and decreased pools of glutathione and ascorbate. In both transplastomic lines, activities of two enzymes involved in carbon metabolism, NADP-malate dehydrogenase and NADP-glyceraldehyde-3-phosphate dehydrogenase are markedly and similarly altered. In contrast, plants overexpressing Trx m specifically display increased capacity for methionine sulfoxide reductases, enzymes repairing damaged proteins by regenerating methionine from oxidized methionine. Finally, we also observed that transplastomic plants exhibit distinct responses when exposed to oxidative stress conditions generated by methyl viologen or exposure to high light combined with low temperature, the plants overexpressing Trx m being notably more tolerant than Wt and those overexpressing Trx f. Altogether, these data indicate that Trxs f and m fulfill distinct physiological functions. They prompt us to propose that the m type is involved in key processes linking photosynthetic activity, redox homeostasis and antioxidant mechanisms in the chloroplast.

  16. Measurement and modelling of the photosynthetically active radiation transmitted in a canopy of maritime pine

    International Nuclear Information System (INIS)

    Hassika, P.; Berbigier, P.; Bonnefond, J.M.

    1997-01-01

    Modelling the photosynthesis of a forest requires the evaluation of the quantity of photosynthetically active radiation (PAR) absorbed by the crowns and the understorey. In this article a semi-empirical model, based on Beer's law is used to study PAR absorption and its seasonal variation. Our purpose was to confirm that the PAR and the solar radiation follow the same interception laws for both the direct and diffuse part, using correct values of needle transmission and reflection coefficients. The model developed took into account the direct and the diffuse radiation. The radiation rescattered by the crowns was neglected following an estimation using the Kubelka-Munk equations, which indicated that the term was small. The model was calibrated and tested from the measurements taken in a maritime pine forest during the summer and autumn of 1995. The comparison between the results of the model and the measurements was satisfactory for the direct radiation as well as for the diffuse radiation. In conclusion, although the measurement wavebands are different, the penetration of the PAR can be estimated using the same simple semi-empirical model already established for solar radiation. (author) [fr

  17. Photosynthetic activity of young Ricinus communis L. plants under conditions of flooded soil

    Directory of Open Access Journals (Sweden)

    Davi Silva Dalberto

    2017-03-01

    Full Text Available Soil flooding is a stress condition that causes changes in hydric relationships and in the metabolism of crops, thereby affecting their productivity. To evaluate the effects of soil flooding on the chlorophyll a fluorescence transient, as well as gas exchange and Ricinus communis growth, young plants of the ‘AL Guarany 2002’ and ‘IAC Guarani’ cultivars, grown in a greenhouse, were subjected to flood conditions by maintaining a layer of water 2-3 cm above the soil. The stressed plants showed drastic reduction in net CO2 assimilation and growth variables. There was, however, an increase in performance index (PIABS e PITOTAL at different moments of stress between the two cultivars. In general, R. communis plants possess mechanisms to protect the electron transport chain during a period of stress, without causing damage and reducing functionality. However, this is not enough to maintain photosynthetic activity owing to the decrease in stomatal conductance and intrinsic carboxylation efficiency, which affects biomass accumulation in stressed plants. In summary, this study found that the ‘AL Guarany 2002’ was found to be more sensitive to stress than the ‘IAC Guarani’ was.

  18. Estimating hourly variation in photosynthetically active radiation across the UK using MSG SEVIRI data

    International Nuclear Information System (INIS)

    Pankaew, P; Milton, E J; Dash, J

    2014-01-01

    The amount of photosynthetically active radiation (PAR) reaching the Earth's surface is a key input variable in most gross primary productivity models. However, poor representation of PAR due to large pixel size or limited temporal sampling is one of the main sources of uncertainty in such models. This paper presents a method to estimate PAR at up to 1 km spatial resolution at a regional to global scale. The method uses broadband radiance data (400–1100nm) and per-pixel estimates of relative cloud cover from a geostationary satellite to estimate the amount of PAR reaching the Earth's surface at high spatial and temporal resolution (1–2 km and hourly). The method was validated using data from 54 pyranometers located at sites across the UK. Hourly averaged PAR over the range 400–1400 μmol m −2 s −1 was estimated with a mean bias error = 5.01 μmol m −2 s −1 (R 2 = 0.87), providing a source of accurate data for high resolution models of gross primary productivity

  19. Remotely Assessing Fraction of Photosynthetically Active Radiation (FPAR for Wheat Canopies Based on Hyperspectral Vegetation Indexes

    Directory of Open Access Journals (Sweden)

    Changwei Tan

    2018-06-01

    Full Text Available Fraction of photosynthetically active radiation (FPAR, as an important index for evaluating yields and biomass production, is key to providing the guidance for crop management. However, the shortage of good hyperspectral data can frequently result in the hindrance of accurate and reliable FPAR assessment, especially for wheat. In the present research, aiming at developing a strategy for accurate FPAR assessment, the relationships between wheat canopy FPAR and vegetation indexes derived from concurrent ground-measured hyperspectral data were explored. FPAR revealed the most strongly correlation with normalized difference index (NDI, and scaled difference index (N*. Both NDI and N* revealed the increase as the increase of FPAR; however, NDI value presented the stagnation as FPAR value beyond 0.70. On the other hand, N* showed a decreasing tendency when FPAR value was higher than 0.70. This special relationship between FPAR and vegetation index could be employed to establish a piecewise FPAR assessment model with NDI as a regression variable during FPAR value lower than 0.70, or N* as the regression variable during FPAR value higher than 0.70. The model revealed higher assessment accuracy up to 16% when compared with FPAR assessment models based on a single vegetation index. In summary, it is feasible to apply NDI and N* for accomplishing wheat canopy FPAR assessment, and establish an FPAR assessment model to overcome the limitations from vegetation index saturation under the condition with high FPAR value.

  20. Energy transfer in light-adapted photosynthetic membranes: from active to saturated photosynthesis.

    Science.gov (United States)

    Fassioli, Francesca; Olaya-Castro, Alexandra; Scheuring, Simon; Sturgis, James N; Johnson, Neil F

    2009-11-04

    In bacterial photosynthesis light-harvesting complexes, LH2 and LH1 absorb sunlight energy and deliver it to reaction centers (RCs) with extraordinarily high efficiency. Submolecular resolution images have revealed that both the LH2:LH1 ratio, and the architecture of the photosynthetic membrane itself, adapt to light intensity. We investigate the functional implications of structural adaptations in the energy transfer performance in natural in vivo low- and high-light-adapted membrane architectures of Rhodospirillum photometricum. A model is presented to describe excitation migration across the full range of light intensities that cover states from active photosynthesis, where all RCs are available for charge separation, to saturated photosynthesis where all RCs are unavailable. Our study outlines three key findings. First, there is a critical light-energy density, below which the low-light adapted membrane is more efficient at absorbing photons and generating a charge separation at RCs, than the high-light-adapted membrane. Second, connectivity of core complexes is similar in both membranes, suggesting that, despite different growth conditions, a preferred transfer pathway is through core-core contacts. Third, there may be minimal subareas on the membrane which, containing the same LH2:LH1 ratio, behave as minimal functional units as far as excitation transfer efficiency is concerned.

  1. Photosynthetically active radiation and comparison of methods for its estimation in equatorial Singapore

    Science.gov (United States)

    Tan, Puay Yok; Ismail, Mirza Rifqi Bin

    2016-02-01

    Photosynthetically active radiation (PAR) is an important input variable for urban climate, crop modelling and ecosystem services studies. Despite its importance, only a few empirical studies have been conducted on PAR, its relationship to global solar radiation and sky conditions and its estimation in the tropics. We report in this study, the characterisation of PAR in Singapore through direct measurements and development of models for its estimation using input variables of global solar radiation ( H), photometric radiation ( L), clearness index ( k t ) and sky view factor (SVF). Daily PAR showed a good correlation with daily H and had a comparatively small seasonal variation in PAR due to Singapore's equatorial position. The ratio of PAR to H ( PAR/ H) showed a slight depression in midyear from May to August, which correlated well with seasonal patterns in rainfall over the study period. Hourly PAR/ H increased throughout the day. Three empirical models developed in this study were able to predict daily PAR satisfactorily, with the most accurate model being one which included both H and k t as independent variables. A regression model for estimation of PAR under shaded conditions using SVF produced satisfactory estimation of daily PAR but was prone to high mean percentage error at low PAR levels.

  2. Guard cell zeaxanthin tracks photosynthetically active radiation and stomatal apertures in Vicia faba leaves

    International Nuclear Information System (INIS)

    Srivastava, A.; Zeiger, E.

    1995-01-01

    Zeaxanthin, antheraxanthin and violaxanthin concentrations in guard cells from sonicated abaxial epidermal peels of Vicia faba were measured from dawn to dusk, and compared with concentrations in mesophyll tissue of the same leaves. Measured changes in guard cell zeaxanthin and violaxanthin concentrations indicate that guard cells operate the xanthophyll cycle throughout the day. Mesophyll tissue had no detectable zeaxanthin at dawn, whereas guard cells had 30–50 mmol mol −1 chlorophyll a+b. On a chlorophyll basis, maximal zeaxanthin levels were 3–4 fold higher in guard cells than in mesophyll cells. Zeaxanthin concentrations tracked levels of photosynthetically active radiation (PAR) in both mesophyll and guard cells. In the mesophyll, most of the zeaxanthin changes occurred in mid-morning and mid-afternoon. In guard cells, zeaxanthin concentrations changed nearly linearly with PAR in the early morning and late afternoon, and closely tracked PAR levels throughout the day. Guard cell zeaxanthin concentrations were also closely correlated with stomatal apertures. The close relationship between zeaxanthin concentrations and PAR levels in guard cells indicates that zeaxanthin is well suited to function as a molecular photosensor in stomatal movements. (author)

  3. Moderate Thermal Stress Causes Active and Immediate Expulsion of Photosynthetically Damaged Zooxanthellae (Symbiodinium from Corals.

    Directory of Open Access Journals (Sweden)

    Lisa Fujise

    Full Text Available The foundation of coral reef biology is the symbiosis between corals and zooxanthellae (dinoflagellate genus Symbiodinium. Recently, coral bleaching, which often results in mass mortality of corals and the collapse of coral reef ecosystems, has become an important issue around the world as coral reefs decrease in number year after year. To understand the mechanisms underlying coral bleaching, we maintained two species of scleractinian corals (Acroporidae in aquaria under non-thermal stress (27°C and moderate thermal stress conditions (30°C, and we compared the numbers and conditions of the expelled Symbiodinium from these corals. Under non-thermal stress conditions corals actively expel a degraded form of Symbiodinium, which are thought to be digested by their host coral. This response was also observed at 30°C. However, while the expulsion rates of Symbiodinium cells remained constant, the proportion of degraded cells significantly increased at 30°C. This result indicates that corals more actively digest and expel damaged Symbiodinium under thermal stress conditions, likely as a mechanism for coping with environmental change. However, the increase in digested Symbiodinium expulsion under thermal stress may not fully keep up with accumulation of the damaged cells. There are more photosynthetically damaged Symbiodinium upon prolonged exposure to thermal stress, and corals release them without digestion to prevent their accumulation. This response may be an adaptive strategy to moderate stress to ensure survival, but the accumulation of damaged Symbiodinium, which causes subsequent coral deterioration, may occur when the response cannot cope with the magnitude or duration of environmental stress, and this might be a possible mechanism underlying coral bleaching during prolonged moderate thermal stress.

  4. Moderate Thermal Stress Causes Active and Immediate Expulsion of Photosynthetically Damaged Zooxanthellae (Symbiodinium) from Corals.

    Science.gov (United States)

    Fujise, Lisa; Yamashita, Hiroshi; Suzuki, Go; Sasaki, Kengo; Liao, Lawrence M; Koike, Kazuhiko

    2014-01-01

    The foundation of coral reef biology is the symbiosis between corals and zooxanthellae (dinoflagellate genus Symbiodinium). Recently, coral bleaching, which often results in mass mortality of corals and the collapse of coral reef ecosystems, has become an important issue around the world as coral reefs decrease in number year after year. To understand the mechanisms underlying coral bleaching, we maintained two species of scleractinian corals (Acroporidae) in aquaria under non-thermal stress (27°C) and moderate thermal stress conditions (30°C), and we compared the numbers and conditions of the expelled Symbiodinium from these corals. Under non-thermal stress conditions corals actively expel a degraded form of Symbiodinium, which are thought to be digested by their host coral. This response was also observed at 30°C. However, while the expulsion rates of Symbiodinium cells remained constant, the proportion of degraded cells significantly increased at 30°C. This result indicates that corals more actively digest and expel damaged Symbiodinium under thermal stress conditions, likely as a mechanism for coping with environmental change. However, the increase in digested Symbiodinium expulsion under thermal stress may not fully keep up with accumulation of the damaged cells. There are more photosynthetically damaged Symbiodinium upon prolonged exposure to thermal stress, and corals release them without digestion to prevent their accumulation. This response may be an adaptive strategy to moderate stress to ensure survival, but the accumulation of damaged Symbiodinium, which causes subsequent coral deterioration, may occur when the response cannot cope with the magnitude or duration of environmental stress, and this might be a possible mechanism underlying coral bleaching during prolonged moderate thermal stress.

  5. Effects of irradiance and prey deprivation on growth, cell carbon and photosynthetic activity of the freshwater kleptoplastidic dinoflagellate Nusuttodinium (= Gymnodinium) aeruginosum (Dinophyceae)

    DEFF Research Database (Denmark)

    Drumm, Kirstine; Liebst-Olsen, Mette; Daugbjerg, Niels

    2017-01-01

    not explain the observed growth rates at high irradiances. Cultures of N. aeruginosum subjected to prey starvation were able to survive for at least 27 days in the light. The sequestered chloroplasts maintained their photosynthetic activity during the entire period of starvation, during which the population......The freshwater dinoflagellate Nusuttodinium aeruginosum lacks permanent chloroplasts. Rather it sequesters chloroplasts as well as other cell organelles, like mitochondria and nuclei, from ingested cryptophyte prey. In the present study, growth rates, cell production and photosynthesis were...... measured at seven irradiances, ranging from 10 to 140 µmol photons m-2s-1, when fed the cryptophyte Chroomonas sp. Growth rates were positively influenced by irradiance and increased from 0.025 d-1 at 10 µmol photons m-2s-1 to maximum growth rates of ~0.3 d-1 at irradiances ≥ 40 µmol photons m-2s-1...

  6. Application of heat stress in situ demonstrates a protective role of irradiation on photosynthetic performance in alpine plants

    OpenAIRE

    Buchner, Othmar; STOLL, Magdalena; Karadar, Matthias; Kranner, Ilse; Neuner, Gilbert

    2014-01-01

    The impact of sublethal heat on photosynthetic performance, photosynthetic pigments and free radical scavenging activity was examined in three high mountain species, R hododendron ferrugineum, S enecio incanus and R anunculus glacialis using controlled in situ applications of heat stress, both in darkness and under natural solar irradiation. Heat treatments applied in the dark reversibly reduced photosynthetic performance and the maximum quantum efficiency of photosystem II (Fv/Fm), which rem...

  7. An Evaluation of Semiempirical Models for Partitioning Photosynthetically Active Radiation Into Diffuse and Direct Beam Components

    Science.gov (United States)

    Oliphant, Andrew J.; Stoy, Paul C.

    2018-03-01

    Photosynthesis is more efficient under diffuse than direct beam photosynthetically active radiation (PAR) per unit PAR, but diffuse PAR is infrequently measured at research sites. We examine four commonly used semiempirical models (Erbs et al., 1982, https://doi.org/10.1016/0038-092X(82)90302-4; Gu et al., 1999, https://doi.org/10.1029/1999JD901068; Roderick, 1999, https://doi.org/10.1016/S0168-1923(99)00028-3; Weiss & Norman, 1985, https://doi.org/10.1016/0168-1923(85)90020-6) that partition PAR into diffuse and direct beam components based on the negative relationship between atmospheric transparency and scattering of PAR. Radiation observations at 58 sites (140 site years) from the La Thuille FLUXNET data set were used for model validation and coefficient testing. All four models did a reasonable job of predicting the diffuse fraction of PAR (ϕ) at the 30 min timescale, with site median r2 values ranging between 0.85 and 0.87, model efficiency coefficients (MECs) between 0.62 and 0.69, and regression slopes within 10% of unity. Model residuals were not strongly correlated with astronomical or standard meteorological variables. We conclude that the Roderick (1999, https://doi.org/10.1016/S0168-1923(99)00028-3) and Gu et al. (1999, https://doi.org/10.1029/1999JD901068) models performed better overall than the two older models. Using the basic form of these models, the data set was used to find both individual site and universal model coefficients that optimized predictive accuracy. A new universal form of the model is presented in section 5 that increased site median MEC to 0.73. Site-specific model coefficients increased median MEC further to 0.78, indicating usefulness of local/regional training of coefficients to capture the local distributions of aerosols and cloud types.

  8. Using a simple apparatus to measure direct and diffuse photosynthetically active radiation at remote locations.

    Directory of Open Access Journals (Sweden)

    Michael J Cruse

    Full Text Available Plant canopy interception of photosynthetically active radiation (PAR drives carbon dioxide (CO2, water and energy cycling in the soil-plant-atmosphere system. Quantifying intercepted PAR requires accurate measurements of total incident PAR above canopies and direct beam and diffuse PAR components. While some regional data sets include these data, e.g. from Atmospheric Radiation Measurement (ARM Program sites, they are not often applicable to local research sites because of the variable nature (spatial and temporal of environmental variables that influence incoming PAR. Currently available instrumentation that measures diffuse and direct beam radiation separately can be cost prohibitive and require frequent adjustments. Alternatively, generalized empirical relationships that relate atmospheric variables and radiation components can be used but require assumptions that increase the potential for error. Our goal here was to construct and test a cheaper, highly portable instrument alternative that could be used at remote field sites to measure total, diffuse and direct beam PAR for extended time periods without supervision. The apparatus tested here uses a fabricated, solar powered rotating shadowband and other commercially available parts to collect continuous hourly PAR data. Measurements of total incident PAR had nearly a one-to-one relationship with total incident radiation measurements taken at the same research site by an unobstructed point quantum sensor. Additionally, measurements of diffuse PAR compared favorably with modeled estimates from previously published data, but displayed significant differences that were attributed to the important influence of rapidly changing local environmental conditions. The cost of the system is about 50% less than comparable commercially available systems that require periodic, but not continual adjustments. Overall, the data produced using this apparatus indicates that this instrumentation has the

  9. Effect of Azospirillum brasilense and Burkholderia unamae Bacteria on Maize Photosynthetic Activity Evaluated Using the Photoacoustic Technique

    Science.gov (United States)

    Gordillo-Delgado, F.; Marín, E.; Calderón, A.

    2016-09-01

    In this work, the photosynthetic process of maize plants ( Zea mays), which were grown using seeds inoculated with plant growth promoting bacteria Azospirillum brasilense and Burkholderia unamae, was monitored. Photothermal and photobaric signals obtained by a time-resolved photoacoustic measurement configuration were used for measuring the oxygen evolution rate in situ. A frequency-resolved configuration of the method was utilized to determine the oxygen diffusion coefficient and the thermal diffusivity of the maize leaves. The latter parameters, which can be used as indicators of the photosynthetic activity of maize, are found to vary according to the plant-microbe interaction. Treatment with plant growth promoting bacteria induced a decrease in the oxygen diffusion coefficient of about 20 %.

  10. Photosynthetically-active radiation: sky radiance distributions under clear and overcast conditions

    International Nuclear Information System (INIS)

    Grant, R.H.; Heisler, G.M.; Gao, W.

    1996-01-01

    The photosynthetically active radiation (PAR), defined as the wavelength band of 0.400 μm to 0.700 μm, represents most of the visible solar radiation. Although the proportion of global irradiance that originates from diffuse sky radiation is higher for PAR than for all solar shortwave radiation, it is often assumed that the PAR diffuse sky radiation is distributed identically to that of all shortwave solar radiation. This assumption has not been tested. PAR sky radiance measurements were made in a rural area over a wide range of solar zenith angles. The distribution of PAR sky radiance was modeled using physically-based, non-linear equations.For clear skies, the normalized sky radiance distribution (N) was best modeled using the scattering angle (ψ) and the zenith position in the sky (Θ) as N (Θ, ψ) = 0.0361 [6.3 + (1 + cos 2 Θ / (1 - cos ψ)] [1-e -0.31 sec ( Θ]. The angle Ψ is defined by cos ψ = cos Θ cos Θ * + sin Θ sin Θ * cos Φ, where solar zenith angle is Θ* and the difference in azimuth between the sun and the position in the sky is Φ. Modeling of the overcast sky depended on the visibility of the solar disk. The translucent middle/high cloud overcast conditions (cloud base greater than 300 m above ground level) were best modeled as: N(Θ∗, ψ) = 0.149 + 0.084Θ∗ + 1.305e −2.5ψ while the translucent low cloud overcast conditions (cloud base less than 300 m above ground level) were best modeled as: N(Θ∗, ψ) = 0.080 + 0.058Θ∗ + 0.652e −2.1ψ . The obscured overcast sky condition (solar disk obscured) was best modeled as: N(Θ) = 0.441 [1 + 4.6cos Θ] /[1 + 4.6]. The unit of N for all equations is π Sr −1 , so that integration of each function over the sky hemisphere yields 1.0.These equations can be applied directly to the sky diffuse irradiance on the horizontal, I diff , to provide radiance distributions for the sky. Estimates of actual sky radiance distribution can be estimated from N a (Θ, ψ) = I diff N(Θ,

  11. Scattering of ultraviolet and photosynthetically active radiation by Sorghum bicolor: influence of epicuticular wax

    International Nuclear Information System (INIS)

    Grant, R.H.; Jenks, M.A.; Rich, P.J.; Peters, P.J.; Ashworth, E.N.

    1995-01-01

    Near-isogenic mutants of Sorghum bicolor with genetic alterations affecting epicuticular wax (EW) structure but having similar canopy architecture provided a model system to examine the influence of EW on plant radiation scattering. Differences in canopies with two different sheath EW amounts showed differences in angular reflectance and transmittance. The differences varied with waveband of radiation. Canopy ultraviolet-B (UVB) and photosynthetically active radiation (PAR) backward reflectance in the principal solar plane were higher by wild-type plants (N-15) bearing reflective stalk EW filaments than mutant plants (bm-15) lacking stalk EW filaments. Between panicle emergence to anthesis the backward PAR reflectance increased more in the N-15 than bm-15 canopy. We suspect that the increase was a result of reflections from stalk facets emerging above the surface plane of the canopy foliage and exposing reflective EW. As panicles emerged above the foliage, canopy UVB and PAR forward reflectance by bm-15 increased while forward reflectance by N-15 decreased. The increased forward reflectance from bm-15 may be because of high specular reflectance from the microscopically smooth bm-15 stalk surfaces. Based on comparisons of probability distributions, significant differences in PAR and UVB canopy transmittance were detected between N-15 and bm-15. The median UVB transmittance was greater in the bm-15 canopy than the N-15 canopy, while the median PAR transmittance was the same for the two canopies. The greater transmittance in the N-15 canopy corresponded with lower EW load of the sheaths, but the difference between canopies was within the experimental error. Distinct influences of the stalk EW on canopy reflectance and transmittance were difficult to assess because of the relatively low proportion of surface area containing EW, the experimental errors associated with UVB irradiance field measurements. The optical properties of the S. bicolor canopy varied by waveband

  12. Measuring Photosynthetic Response to Drought Stress using Active and Passive Fluorescence

    Science.gov (United States)

    Helm, L.; Lerdau, M.; Wang, W.; Yang, X.

    2017-12-01

    Photosynthesis, the endothermic reactions involving the absorption of light and fixation and reduction of carbon dioxide by plants, plays important roles in carbon and water cycles, food security, and even weather and climate patterns. Solar radiation provides the energy for photosynthesis, but often plants absorb more solar energy than they can use to reduce carbon dioxide. This excess energy, which is briefly stored as high-energy electrons in the chloroplast, must be removed or damage to the leaf's photosynthetic machinery will occur. One important energy dissipation pathway is for the high energy electrons to return to their lower valance state and, in doing so, release radiation (fluorescence). This fluorescence (known as solar induced fluorescence (SIF) has been found to strongly correlate with gross photosynthesis. Recent advances in the remote sensing of SIF allow for large-scale real-time estimation of photosynthesis. In a warming climate with more frequent stress, remote sensing is necessary for measuring the spatial and temporal variability of photosynthesis. However, the mechanisms that link SIF and photosynthesis are unclear, particularly how the relationship may or may not change under stress. We present data from leaf-level measurements of gas exchange, pulse amplitude modulation (PAM) fluorescence, and SIF in two major tree species in North America. Water-stressed and well-watered plants were compared to determine how SIF and carbon dioxide exchange are modulated by drought diurnally and seasonally. Secondly, photosynthesis and fluorescence under high and low oxygen concentrations were compared to determine how photorespiration alters the relationship between SIF and gross photosynthesis. We find a strong correlation between SIF and steady-state fluorescence measured with conventional PAM fluorometry. Our results also indicate that drought-stress modulates the SIF-photosynthesis relationship, and this may be driven by drought-induced changes in

  13. Modeling the relationship between photosynthetically active radiation and global horizontal irradiance using singular spectrum analysis

    International Nuclear Information System (INIS)

    Zempila, Melina-Maria; Taylor, Michael; Bais, Alkiviadis; Kazadzis, Stelios

    2016-01-01

    We report on the construction of generic models to calculate photosynthetically active radiation (PAR) from global horizontal irradiance (GHI), and vice versa. Our study took place at stations of the Greek UV network (UVNET) and the Hellenic solar energy network (HNSE) with measurements from NILU-UV multi-filter radiometers and CM pyranometers, chosen due to their long (≈1 M record/site) high temporal resolution (≈1 min) record that captures a broad range of atmospheric environments and cloudiness conditions. The uncertainty of the PAR measurements is quantified to be ±6.5% while the uncertainty involved in GHI measurements is up to ≈±7% according to the manufacturer. We show how multi-linear regression and nonlinear neural network (NN) models, trained at a calibration site (Thessaloniki) can be made generic provided that the input–output time series are processed with multi-channel singular spectrum analysis (M-SSA). Without M-SSA, both linear and nonlinear models perform well only locally. M-SSA with 50 time-lags is found to be sufficient for identification of trend, periodic and noise components in aerosol, cloud parameters and irradiance, and to construct regularized noise models of PAR from GHI irradiances. Reconstructed PAR and GHI time series capture ≈95% of the variance of the cross-validated target measurements and have median absolute percentage errors <2%. The intra-site median absolute error of M-SSA processed models were ≈8.2±1.7 W/m"2 for PAR and ≈9.2±4.2 W/m"2 for GHI. When applying the models trained at Thessaloniki to other stations, the average absolute mean bias between the model estimates and measured values was found to be ≈1.2 W/m"2 for PAR and ≈0.8 W/m"2 for GHI. For the models, percentage errors are well within the uncertainty of the measurements at all sites. Generic NN models were found to perform marginally better than their linear counterparts. - Highlights: • Generic linear regression and nonlinear neural network

  14. Measurement and estimation of photosynthetically active radiation from 1961 to 2011 in Central China

    International Nuclear Information System (INIS)

    Wang, Lunche; Gong, Wei; Li, Chen; Lin, Aiwen; Hu, Bo; Ma, Yingying

    2013-01-01

    Highlights: • 6-Year observations were used to show the temporal variability of PAR and PAR/G. • Dependence of PAR on clearness index was studied in model development. • New developed models performed very well at different time scales. • The new all-weather model provided good estimates of PAR at two other sites. • Long-term variations of PAR from 1961 to 2011 in Central China were analyzed. - Abstract: Measurements of photosynthetically active radiation (PAR) and global solar radiation (G) at WHU, Central China during 2006–2011 were used to investigate the seasonal characteristics of PAR and PAR/G (PAR fraction). Both PAR and PAR fraction showed similar seasonal features that peaked in values during summer and reached their lowest in winter with annual mean values being 22.39 mol m −2 d −1 and 1.9 mol M J −1 respectively. By analyzing the dependence of PAR on cosine of solar zenith angle and clearness index at WHU, an efficient all-weather model was developed for estimating PAR values under various sky conditions, which also produced accepted estimations with high accuracy at Lhasa and Fukang. PAR dataset was then reconstructed from G for 1961–2011 through the new developed model. Annual mean daily PAR was about 23.12 mol m −2 d −1 , there was a significant decreasing trend (11.2 mol m −2 per decade) during the last 50 years in Central China, the decreases were sharpest in summer (−24.67 mol m −2 per decade) with relatively small decreases being observed in spring. Meanwhile, results also revealed that PAR began to increase at a rate of 0.1 mol m −2 per year from 1991 to 2011, which was in consistent with variation patterns of global solar radiation in the study area. The proposed all-weather PAR model would be of vital importance for ecological modeling, atmospheric environment, agricultural processes and solar energy application

  15. Effect of different levels of air pollution on photosynthetic activity of some lichens

    Directory of Open Access Journals (Sweden)

    Ewa Niewiadomska

    2014-01-01

    Full Text Available Four lichen species: Hypogymnia physodes, Pseudevernia furfuracea, Parmelia saxatilis, and Platismatia glauca were collected from two sites (S. Poland with a different air pollution level: "Kamienica valley" (less polluted and "Kopa" (more polluted. The thalli were compared with respect to their: net photosynthetic rate (PN, fluorescence parameters (Fv/Fm, Fm, Fm/Fo, chlorophyll a+b content, and phaeophytinization quotient (O.D.435/O.D.415. PN intensity, chlorophyll a+b and O.D.435/O.D.415 were reduced only in Pa furfuracea collected from Kopa, which is in agreement with the Hawksworth-Rose scale of sensitivity of lichens to air pollution. Fluorescence parameters were significantly lowered in all lichens coming from the more polluted site (except of Fv/Fm and Fm/F0 in P. saxatilis. Parameters based on chlorophyll fluorescence measurements enable to reveal the very early signs of decreased photosynthetical capacity of the thalli, caused by air pollution, before changes in the other photosynthetic parameters become mesurable.

  16. Overlapping toxic effect of long term thallium exposure on white mustard (Sinapis alba L.) photosynthetic activity.

    Science.gov (United States)

    Mazur, Radosław; Sadowska, Monika; Kowalewska, Łucja; Abratowska, Agnieszka; Kalaji, Hazem M; Mostowska, Agnieszka; Garstka, Maciej; Krasnodębska-Ostręga, Beata

    2016-09-02

    Heavy metal exposure affect plant productivity by interfering, directly and indirectly, with photosynthetic reactions. The toxic effect of heavy metals on photosynthetic reactions has been reported in wide-ranging studies, however there is paucity of data in the literature concerning thallium (Tl) toxicity. Thallium is ubiquitous natural trace element and is considered the most toxic of heavy metals; however, some plant species, such as white mustard (Sinapis alba L.) are able to accumulate thallium at very high concentrations. In this study we identified the main sites of the photosynthetic process inhibited either directly or indirectly by thallium, and elucidated possible detoxification mechanisms in S. alba. We studied the toxicity of thallium in white mustard (S. alba) growing plants and demonstrated that tolerance of plants to thallium (the root test) decreased with the increasing Tl(I) ions concentration in culture media. The root growth of plants exposed to Tl at 100 μg L(-1) for 4 weeks was similar to that in control plants, while in plants grown with Tl at 1,000 μg L(-1) root growth was strongly inhibited. In leaves, toxic effect became gradually visible in response to increasing concentration of Tl (100 - 1,000 μg L(-1)) with discoloration spreading around main vascular bundles of the leaf blade; whereas leaf margins remained green. Subsequent structural analyses using chlorophyll fluorescence, microscopy, and pigment and protein analysis have revealed different effects of varying Tl concentrations on leaf tissue. At lower concentration partial rearrangement of the photosynthetic complexes was observed without significant changes in the chloroplast structure and the pigment and protein levels. At higher concentrations, the decrease of PSI and PSII quantum yields and massive oxidation of pigments was observed in discolored leaf areas, which contained high amount of Tl. Substantial decline of the photosystem core proteins and disorder of the

  17. Effects of INH, DNP, 2,4-D and CMU on the photosynthetic activity of barley and maize plants

    International Nuclear Information System (INIS)

    Fernandez, J.; Prieto, M. P.

    1979-01-01

    Determinations of the rate of photosynthesis were made in barley and maize leaves treated with INH, DNP, 2,4-D or CMU. 1 ppm of the chemicals in nutritive solutions was absorbed by roots during 24 or 48 hours in both dark and light conditions. After this period, photosynthetic activity, compensation point and 14 C O 2 assimilation were determined. Results show that INH increases the rate of photosynthesis, DNP and 2,4-D do not alter it sensibly and CMU acts as a strong inhibitor of photosynthesis. Some possible applications for ths obtention of labelled compounds by biosynthesis are discussed. (Author) 87 refs

  18. Effects of Heat Shock on Photosynthetic Properties, Antioxidant Enzyme Activity, and Downy Mildew of Cucumber (Cucumis sativus L..

    Directory of Open Access Journals (Sweden)

    Xiaotao Ding

    Full Text Available Heat shock is considered an abiotic stress for plant growth, but the effects of heat shock on physiological responses of cucumber plant leaves with and without downy mildew disease are still not clear. In this study, cucumber seedlings were exposed to heat shock in greenhouses, and the responses of photosynthetic properties, carbohydrate metabolism, antioxidant enzyme activity, osmolytes, and disease severity index of leaves with or without the downy mildew disease were measured. Results showed that heat shock significantly decreased the net photosynthetic rate, actual photochemical efficiency, photochemical quenching coefficient, and starch content. Heat shock caused an increase in the stomatal conductance, transpiration rate, antioxidant enzyme activities, total soluble sugar content, sucrose content, soluble protein content and proline content for both healthy leaves and downy mildew infected leaves. These results demonstrate that heat shock activated the transpiration pathway to protect the photosystem from damage due to excess energy in cucumber leaves. Potential resistance mechanisms of plants exposed to heat stress may involve higher osmotic regulation capacity related to an increase of total accumulations of soluble sugar, proline and soluble protein, as well as higher antioxidant enzymes activity in stressed leaves. Heat shock reduced downy mildew disease severity index by more than 50%, and clearly alleviated downy mildew development in the greenhouses. These findings indicate that cucumber may have a complex physiological change to resist short-term heat shock, and suppress the development of the downy mildew disease.

  19. Influence of exogenous urea on photosynthetic pigments, (14)CO 2 uptake, and urease activity in Elodea densa-environmental implications.

    Science.gov (United States)

    Maleva, Maria; Borisova, Galina; Chukina, Nadezda; Nekrasova, Galina; Prasad, M N V

    2013-09-01

    This paper analyzes the effect of exogenous urea in increased concentration gradient (0, 100, 500 and 1,000 mg L(-1)) on photosynthetic pigments (measured spectrophotometrically), uptake of (14)CO2 (using radioisotope), and urease activity (by measuring ammonia with Nessler's reagent) in leaves of Elodea densa Planch. We have observed that low concentration of urea (100 mg L(-1)) stimulates the accumulation of photosynthetic pigments and intensifies photosynthesis in E. densa, whereas high concentration (1,000 mg L(-1)) suppresses these processes. Urease activity increased by approximately 2.7 and 8 fold when exogenous urea concentrations were 100 and 500 mg L(-1), respectively. However, exogenous urea in high concentration (1,000 mg L(-1)) decreased urease activity by 1.5 fold compared to the control. The necessity of mitigating urea and other nitrogen-containing compounds (NH3 from urea) in water bodies has been discussed with emphasis on the potential for phytoremediation of urea using common water weed viz. E. densa.

  20. Scale dependence of absorption of photosynthetically active radiation in terrestrial ecosystems

    International Nuclear Information System (INIS)

    Asner, G.P.; Wessman, C.A.; Archer, S.

    1998-01-01

    The fraction of photosynthetically active radiation absorbed by plant canopies (fAPAR) is a critical biophysical variable for extrapolating ecophysiological measurements from the leaf to landscape scale. Quantification of fAPAR determinants at the landscape level is needed to improve the interpretation of remote sensing data, to facilitate its use in constraining ecosystem process models, and to improve synoptic-scale links between carbon and nutrient cycles. Most canopy radiation budget studies have focused on light attenuation in plant canopies, with little regard for the importance of the scale-dependent biophysical and structural factors (e.g., leaf and stem optical properties, leaf and stem area, and extent of vegetation structural types) that ultimately determine fAPAR at canopy and landscape scales. Most studies have also assumed that nonphotosynthetic vegetation (litter and stems) contributes little to fAPAR. Using a combined field measurement and radiative transfer modeling approach, we quantified (a) the relative role of the leaf-, canopy-, and landscape-level factors that determine fAPAR in terrestrial ecosystems and (b) the magnitude of PAR absorption by grass litter and woody plant stems. Variability in full spectral-range (400–2500 nm) reflectance/transmittance and PAR (400–700 nm) absorption at the level of individual leaf, stem, and litter samples was quantified for a wide array of broadleaf arborescent and grass species along a 900-km north–south Texas savanna transect. Among woody growth forms, leaf reflectance and transmittance spectra were statistically comparable between populations, species within a genus, and functional types (deciduous vs. evergreen, legume vs. nonlegume). Within the grass life-form, spectral properties were statistically comparable between species and C 3 /C 4 physiologies. We found that tissue-level PAR absorption among species, genera, functional groups, and growth forms and between climatologically diverse regions

  1. Ferredoxin-thioredoxin reductase: a catalytically active dithiol group links photoreduced ferredoxin to thioredoxin functional in photosynthetic enzyme regulation

    International Nuclear Information System (INIS)

    Droux, M.; Miginiac-Maslow, M.; Jacquot, J.P.; Gadal, P.; Crawford, N.A.; Kosower, N.S.; Buchanan, B.B.

    1987-01-01

    The mechanism by which the ferredoxin-thioredoxin system activates the target enzyme, NADP-malate dehydrogenase, was investigated by analyzing the sulfhydryl status of individual protein components with [ 14 C]iodoacetate and monobromobimane. The data indicate that ferredoxin-thioredoxin reductase (FTR)--an iron-sulfur enzyme present in oxygenic photosynthetic organisms--is the first member of a thiol chain that links light to enzyme regulation. FTR possesses a catalytically active dithiol group localized on the 13 kDa (similar) subunit, that occurs in all species investigated and accepts reducing equivalents from photoreduced ferredoxin and transfers them stoichiometrically to the disulfide form of thioredoxin m. The reduced thioredoxin m, in turn, reduces NADP-malate dehydrogenase, thereby converting it from an inactive (S-S) to an active (SH) form. The means by which FTR is able to combine electrons (from photoreduced ferredoxin) with protons (from the medium) to reduce its active disulfide group remains to be determined

  2. Sunlight mediated seasonality in canopy structure and photosynthetic activity of Amazonian rainforests

    International Nuclear Information System (INIS)

    Bi, Jian; Knyazikhin, Yuri; Choi, Sungho; Park, Taejin; Barichivich, Jonathan; Ciais, Philippe; Fu, Rong; Ganguly, Sangram; Hall, Forrest; Hilker, Thomas; Huete, Alfredo; Jones, Matthew; Kimball, John; Lyapustin, Alexei I; Mõttus, Matti; Nemani, Ramakrishna R; Piao, Shilong; Poulter, Benjamin; Saleska, Scott R

    2015-01-01

    Resolving the debate surrounding the nature and controls of seasonal variation in the structure and metabolism of Amazonian rainforests is critical to understanding their response to climate change. In situ studies have observed higher photosynthetic and evapotranspiration rates, increased litterfall and leaf flushing during the Sunlight-rich dry season. Satellite data also indicated higher greenness level, a proven surrogate of photosynthetic carbon fixation, and leaf area during the dry season relative to the wet season. Some recent reports suggest that rainforests display no seasonal variations and the previous results were satellite measurement artefacts. Therefore, here we re-examine several years of data from three sensors on two satellites under a range of sun positions and satellite measurement geometries and document robust evidence for a seasonal cycle in structure and greenness of wet equatorial Amazonian rainforests. This seasonal cycle is concordant with independent observations of solar radiation. We attribute alternative conclusions to an incomplete study of the seasonal cycle, i.e. the dry season only, and to prognostications based on a biased radiative transfer model. Consequently, evidence of dry season greening in geometry corrected satellite data was ignored and the absence of evidence for seasonal variation in lidar data due to noisy and saturated signals was misinterpreted as evidence of the absence of changes during the dry season. Our results, grounded in the physics of radiative transfer, buttress previous reports of dry season increases in leaf flushing, litterfall, photosynthesis and evapotranspiration in well-hydrated Amazonian rainforests. (letter)

  3. NaCl-induced physiological and biochemical changes in two cyanobacteria Nostoc muscorum and Phormidium foveolarum acclimatized to different photosynthetically active radiation.

    Science.gov (United States)

    Kumar, Jitendra; Singh, Vijay Pratap; Prasad, Sheo Mohan

    2015-10-01

    The present study is aimed at investigating physiological and biochemical behavior of two cyanobacteria Nostoc muscorum and Phormidium foveolarum acclimatized to different levels (sub-optimum; 25 ± 0.5, optimum; 75 ± 2.5 and supra-optimum; 225 ± 3.5 μmol photons m(-2) s(-1)) of photosynthetic active radiation (PAR), and subsequently treated with two doses (30 and 90 mM) of NaCl. PAR influences growth in tested cyanobacteria being maximum in supra-optimum PAR acclimatized cells. NaCl-induced maximum percent decline in growth was observed in sub-optimum PAR acclimatized cells, which was in consonance with a decrease in chlorophyll content. Sub-optimum PAR acclimatization stimulated phycocyanin content in control cells, whereas maximum carotenoids content was observed in supra-optimum PAR acclimatized cells. Photosystem II photochemistry viz. Fv/F0, Fv/Fm, Ψ0, ϕE0, PIABS, ABS/RC, TR0/RC, ET0/RC and DI0/RC was also influenced by PAR and NaCl. Maximum percent rise in superoxide radical (SOR), hydrogen peroxide (H2O2) and lipid peroxidation was observed in sub-optimum PAR acclimatized cells exposed to NaCl, which could be correlated with lower values of enzymatic (superoxide dismutase, catalase, peroxidase and glutathione-S-transferase) and non-enzymatic (NP-SH and cysteine) antioxidants. In supra-optimum PAR acclimatized cells level of oxidative stress markers was in parallel with enhanced antioxidants. The results suggest that PAR significantly changes physiological and biochemical responses of studied cyanobacteria under NaCl stress. Besides this, this study also shows that P. foveolarum is more tolerant than N. muscorum under test conditions. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Visualization of water usage and photosynthetic activity of street trees exposed to 2 ppm of SO{sub 2}-A combined evaluation by cold neutron and chlorophyll fluorescence imaging

    Energy Technology Data Exchange (ETDEWEB)

    Matsushima, U. [Faculty of Agriculture, Iwate University (Japan)], E-mail: uzuki@iwate-u.ac.jp; Kardjilov, N.; Hilger, A.; Manke, I. [SF3, Helmholtz Center Berlin for Materials and Energy (Germany); Shono, H. [Faculty of Agriculture, Iwate University (Japan); Herppich, W.B. [Department of Horticultural Engineering, Leibniz Institute for Agricultural Engineering Potsdam-Bornim (Germany)

    2009-06-21

    Photosynthetic efficacy and auto-exhaust-fume resistance of street trees were evaluated by cold neutron radiography (CNR) with D{sub 2}O tracer and chlorophyll fluorescence (CF) imaging. With these techniques, information on the responses of water usage and photosynthetic activity of plants exposed to simulate toxic auto-exhaust fumes (2 ppm SO{sub 2} in air) were obtained. Branches of hibiscus trees were detached, placed into a tub with aerated water and used for the experiments after rooting. A CF image was taken before SO{sub 2} was applied for 1 h. During the experiment, CNR and CF imaging were conduced. H{sub 2}O and D{sub 2}O in the plant container were exchanged every 30 min to observe water uptake. D{sub 2}O tracer clearly showed water uptake into the hibiscus stem during each treatment. When the atmosphere was changed from simulated auto-exhaust fumes to normal air again, the amount of D{sub 2}O and, hence, water uptake increased. CF imaging was well suited to evaluate the effects of SO{sub 2} as simulated toxic auto-exhaust fumes on plants. The maximum photochemical efficiency (F{sub v}/F{sub m}), a sensitive indicator of the efficacy and the integrity of plants' photosynthesis, immediately dropped by 30% after supplying the simulated auto-exhaust fumes. This indicates that toxic auto-exhaust fumes negatively affected the photosynthetic activity of hibiscus leaves. Simultaneous CNR and CF imaging successfully visualized variations of photosynthetic activity and water uptake in the sample. Thus, this combination method was effective to non-destructive analyze the physiological status of plants.

  5. Changes in chlorophyll fluorescence and photosynthetic activity of French bean leaves induced by gamma radiation

    International Nuclear Information System (INIS)

    Saakov, V.; Lang, M.; Schindler, C.; Stober, F.; Lichtenthaler, H.K.

    1992-01-01

    When exposed to gamma-radiation (12, 8 and 3.5 kGy), the growth of bean seedlings (Phaseolus vulgaris L.) was stopped and after some hours or days the plants began to wilt in a dose-dependent manner, starting from the leaf rim. The rate of the dark respiration (R) of leaves increased and that of net photosynthesis (P(N)) was strongly reduced. The regulation of stomata opening and closure was lost and the stomatal conductance (g(s)) of the gamma-ray exposed plants was strongly reduced. The reduced P(N) was only partly due to either the partial or almost full stomata closure. Chlorophyll (Chl) fluorescence measurements witha two-wavelength fluorometer and a PAM fluorometer showed an increasingly reduced variable fluorescence F(v), lower values of R(fd), of ground fluorescence F0, and of the fluorescence ratios F(v)/F(m) and F(v)/F(o). This indicated a damage to the photosynthetic apparatus. The increasing loss of photosynthetic pigments in the 350 krad exposed plants was also detected via an increase in the fluorescence ratio F690/F730. The performance of the light driven xanthophyll cycle (violaxanthin/zeaxanthin transformation) proceeded in the gamma-ray treated plants only at reduced rates. The gamma-ray damage of plants can best be detected by measurements of stomatal conductance, P(N) and various Chl fluorescence ratios such as R(fd), F(v)/F(o) and F(v)/F(m)

  6. Spectral Bio-indicator Simulations for Tracking Photosynthetic Activities in a Corn Field

    Science.gov (United States)

    Cheng, Yen-Ben; Middleton, Elizabeth M.; Huemmrich, K. Fred; Zhang, Qingyuan; Corp, Lawrence; Campbell, Petya; Kustas, William

    2011-01-01

    Accurate assessment of vegetation canopy optical properties plays a critical role in monitoring natural and managed ecosystems under environmental changes. In this context, radiative transfer (RT) models simulating vegetation canopy reflectance have been demonstrated to be a powerful tool for understanding and estimating spectral bio-indicators. In this study, two narrow band spectroradiometers were utilized to acquire observations over corn canopies for two summers. These in situ spectral data were then used to validate a two-layer Markov chain-based canopy reflectance model for simulating the Photochemical Reflectance Index (PRI), which has been widely used in recent vegetation photosynthetic light use efficiency (LUE) studies. The in situ PRI derived from narrow band hyperspectral reflectance exhibited clear responses to: 1) viewing geometry which affects the asset of light environment; and 2) seasonal variation corresponding to the growth stage. The RT model (ACRM) successfully simulated the responses to the variable viewing geometry. The best simulations were obtained when the model was set to run in the two layer mode using the sunlit leaves as the upper layer and shaded leaves as the lower layer. Simulated PRI values yielded much better correlations to in situ observations when the cornfield was dominated by green foliage during the early growth, vegetative and reproductive stages (r = 0.78 to 0.86) than in the later senescent stage (r = 0.65). Further sensitivity analyses were conducted to show the important influences of leaf area index (LAI) and the sunlit/shaded ratio on PRI observations.

  7. Effects of irradiance and prey deprivation on growth, cell carbon and photosynthetic activity of the freshwater kleptoplastidic dinoflagellate Nusuttodinium (= Gymnodinium aeruginosum (Dinophyceae.

    Directory of Open Access Journals (Sweden)

    Kirstine Drumm

    Full Text Available The freshwater dinoflagellate Nusuttodinium aeruginosum lacks permanent chloroplasts. Rather it sequesters chloroplasts as well as other cell organelles, like mitochondria and nuclei, from ingested cryptophyte prey. In the present study, growth rates, cell production and photosynthesis were measured at seven irradiances, ranging from 10 to 140 μmol photons m-2s-1, when fed the cryptophyte Chroomonas sp. Growth rates were positively influenced by irradiance and increased from 0.025 d-1 at 10 μmol photons m-2s-1 to maximum growth rates of ~0.3 d-1 at irradiances ≥ 40 μmol photons m-2s-1. Similarly, photosynthesis ranged from 1.84 to 36.9 pg C cell-1 h-1 at 10 and 140 μmol photons m-2s-1, respectively. The highest rates of photosynthesis in N. aeruginosum only corresponded to ~25% of its own cell carbon content and estimated biomass production. The measured rates of photosynthesis could not explain the observed growth rates at high irradiances. Cultures of N. aeruginosum subjected to prey starvation were able to survive for at least 27 days in the light. The sequestered chloroplasts maintained their photosynthetic activity during the entire period of starvation, during which the population underwent 4 cell divisions. This indicates that N. aeruginosum has some control of the chloroplasts, which may be able to replicate. In conclusion, N. aeruginosum seems to be in an early stage of chloroplast acquisition with some control of its ingested chloroplasts.

  8. Effects of irradiance and prey deprivation on growth, cell carbon and photosynthetic activity of the freshwater kleptoplastidic dinoflagellate Nusuttodinium (= Gymnodinium) aeruginosum (Dinophyceae).

    Science.gov (United States)

    Drumm, Kirstine; Liebst-Olsen, Mette; Daugbjerg, Niels; Moestrup, Øjvind; Hansen, Per Juel

    2017-01-01

    The freshwater dinoflagellate Nusuttodinium aeruginosum lacks permanent chloroplasts. Rather it sequesters chloroplasts as well as other cell organelles, like mitochondria and nuclei, from ingested cryptophyte prey. In the present study, growth rates, cell production and photosynthesis were measured at seven irradiances, ranging from 10 to 140 μmol photons m-2s-1, when fed the cryptophyte Chroomonas sp. Growth rates were positively influenced by irradiance and increased from 0.025 d-1 at 10 μmol photons m-2s-1 to maximum growth rates of ~0.3 d-1 at irradiances ≥ 40 μmol photons m-2s-1. Similarly, photosynthesis ranged from 1.84 to 36.9 pg C cell-1 h-1 at 10 and 140 μmol photons m-2s-1, respectively. The highest rates of photosynthesis in N. aeruginosum only corresponded to ~25% of its own cell carbon content and estimated biomass production. The measured rates of photosynthesis could not explain the observed growth rates at high irradiances. Cultures of N. aeruginosum subjected to prey starvation were able to survive for at least 27 days in the light. The sequestered chloroplasts maintained their photosynthetic activity during the entire period of starvation, during which the population underwent 4 cell divisions. This indicates that N. aeruginosum has some control of the chloroplasts, which may be able to replicate. In conclusion, N. aeruginosum seems to be in an early stage of chloroplast acquisition with some control of its ingested chloroplasts.

  9. [In vivo and in vitro actions of biscarbamates on the photosynthetic activity of chloroplasts].

    Science.gov (United States)

    Chueca, A; Barón, M; López-Gorgé, J

    1982-01-01

    The "photosynthetic inhibition" component in the whole context of plant toxicity, when different concentrations of the bis-carbamate phenmedipham are supplied through the roots or foliar application to spinach plants grown in hydroponic media have been determined. Chloroplasts were isolated after eight days of the herbicide addition, and then determined: electron transport H2O leads to NADP+, H2O leads to ferrycyanide and ascorbate/DPIP leads to NADP+, cyclic and non cyclic photophosphorilation, CO2 assimilation rate and intermediate patterns of CO2 fixation. We have also determined in foliar disks the O2 evolving and the CO2 assimilation capabilities. Type A and type B chloroplasts showed increased inhibition, respectively, of the Phot. II dependent electron transport chains H2O leads to NADP+ and H2O leads to ferricyanide, to the extent that the phenmedipham concentration increased in the hydroponic media and the spraying solution, so that a 50% inhibition of both processes was obtained at 100 microM and 10 microM, respectively, against 0.2 microM in the in vitro experiments. Non cyclic photophosphorylation showed a stronger inhibition than the cyclic one. Concerning the Phot. I dependent electron transport ascorbate/DPIP leads to NADP+, the chloroplast preparations showed a negligible inhibition. We have found a synergistic effect of the above two factors on the CO2 assimilation. The intermediate patterns of CO2 assimilation showed a decrease of the 3C-compounds P-glycerate and trioses-P, with a parallel increase of the sugar mono and diphosphates as well as disaccharides and amino acids.

  10. Relationship of in-coming radiation with photosynthetically active, infra-red and net radiations in Brassica species and rocket salad (Eruca sativa)

    International Nuclear Information System (INIS)

    Nandwal, A.S.; Kuhad, M.S.

    1989-01-01

    Marked variation was observed among genotypes when the data for in-coming solar radiation were monitored horizontally. The regression equation for in-coming solar radiation versus photosynthetically active radiation and incoming solar radiation versus in-coming infra red radiation indicated linear relationship

  11. Elevated temperature altered photosynthetic products in wheat seedlings and organic compounds and biological activity in rhizopshere soil under cadmium stress

    Science.gov (United States)

    Jia, Xia; Zhao, Yonghua; Wang, Wenke; He, Yunhua

    2015-09-01

    The objective of this study was to investigate the effects of slightly elevated atmospheric temperature in the spring on photosynthetic products in wheat seedlings and on organic compounds and biological activity in rhizosphere soil under cadmium (Cd) stress. Elevated temperature was associated with increased soluble sugars, reducing sugars, starch, and total sugars, and with decreased amino acids in wheat seedlings under Cd stress. Elevated temperature improved total soluble sugars, free amino acids, soluble phenolic acids, and organic acids in rhizosphere soil under Cd stress. The activity of amylase, phenol oxidase, invertase, β-glucosidase, and L-asparaginase in rhizosphere soil was significantly improved by elevated temperature under Cd stress; while cellulase, neutral phosphatase, and urease activity significantly decreased. Elevated temperature significantly improved bacteria, fungi, actinomycetes, and total microorganisms abundance and fluorescein diacetate activity under Cd stress. In conclusion, slightly elevated atmospheric temperature in the spring improved the carbohydrate levels in wheat seedlings and organic compounds and biological activity in rhizosphere soil under Cd stress in the short term. In addition, elevated atmospheric temperature in the spring stimulated available Cd by affecting pH, DOC, phenolic acids, and organic acids in rhizosphere soil, which resulted in the improvement of the Cd uptake by wheat seedlings.

  12. Photosynthetic Pigments in Diatoms

    OpenAIRE

    Kuczynska, Paulina; Jemiola-Rzeminska, Malgorzata; Strzalka, Kazimierz

    2015-01-01

    Photosynthetic pigments are bioactive compounds of great importance for the food, cosmetic, and pharmaceutical industries. They are not only responsible for capturing solar energy to carry out photosynthesis, but also play a role in photoprotective processes and display antioxidant activity, all of which contribute to effective biomass and oxygen production. Diatoms are organisms of a distinct pigment composition, substantially different from that present in plants. Apart from light-harvestin...

  13. Ferredoxin-thioredoxin reductase: a catalytically active dithiol group links photoreduced ferredoxin to thioredoxin functional in photosynthetic enzyme regulation

    Energy Technology Data Exchange (ETDEWEB)

    Droux, M.; Miginiac-Maslow, M.; Jacquot, J.P.; Gadal, P.; Crawford, N.A.; Kosower, N.S.; Buchanan, B.B.

    1987-07-01

    The mechanism by which the ferredoxin-thioredoxin system activates the target enzyme, NADP-malate dehydrogenase, was investigated by analyzing the sulfhydryl status of individual protein components with (/sup 14/C)iodoacetate and monobromobimane. The data indicate that ferredoxin-thioredoxin reductase (FTR)--an iron-sulfur enzyme present in oxygenic photosynthetic organisms--is the first member of a thiol chain that links light to enzyme regulation. FTR possesses a catalytically active dithiol group localized on the 13 kDa (similar) subunit, that occurs in all species investigated and accepts reducing equivalents from photoreduced ferredoxin and transfers them stoichiometrically to the disulfide form of thioredoxin m. The reduced thioredoxin m, in turn, reduces NADP-malate dehydrogenase, thereby converting it from an inactive (S-S) to an active (SH) form. The means by which FTR is able to combine electrons (from photoreduced ferredoxin) with protons (from the medium) to reduce its active disulfide group remains to be determined.

  14. Spraying Brassinolide improves Sigma Broad tolerance in foxtail millet (Setaria italica L.) through modulation of antioxidant activity and photosynthetic capacity.

    Science.gov (United States)

    Yuan, Xiang-Yang; Zhang, Li-Guang; Huang, Lei; Yang, Hui-Jie; Zhong, Yan-Ting; Ning, Na; Wen, Yin-Yuan; Dong, Shu-Qi; Song, Xi-E; Wang, Hong-Fu; Guo, Ping-Yi

    2017-09-11

    To explore the role of Brassinolide (BR) in improving the tolerance of Sigma Broad in foxtail millet (Setaria italica L.), effects of 0.1 mg/L of BR foliar application 24 h before 3.37 g/ha of Sigma Broad treatment at five-leaf stage of foxtail millet on growth parameters, antioxidant enzymes, malondialdehyde (MDA), chlorophyll, net photosynthetic rate (P N ), chlorophyll fluorescence and P 700 parameters were studied 7 and 15 d after herbicide treatment, respectively. Results showed that Sigma Broad significantly decreased plant height, activities of superoxide dismutase (SOD), chlorophyll content, P N , PS II effective quantum yield (Y (II)), PS II electron transport rate (ETR (II)), photochemical quantum yield of PSI(Y (I)) and PS I electron transport rate ETR (I), but significantly increased MDA. Compared to herbicide treatment, BR dramatically increased plant height, activities of SOD, Y (II), ETR (II), Y (I) and ETR (I). This study showed BR pretreatment could improve the tolerance of Sigma Broad in foxtail millet through improving the activity of antioxidant enzymes, keeping electron transport smooth, and enhancing actual photochemical efficiency of PS II and PSI.

  15. Photosynthetic fuel for heterologous enzymes

    DEFF Research Database (Denmark)

    Mellor, Silas Busck; Vavitsas, Konstantinos; Nielsen, Agnieszka Janina Zygadlo

    2017-01-01

    of reducing power. Recent work on the metabolic engineering of photosynthetic organisms has shown that the electron carriers such as ferredoxin and flavodoxin can be used to couple heterologous enzymes to photosynthetic reducing power. Because these proteins have a plethora of interaction partners and rely...... on electrostatically steered complex formation, they form productive electron transfer complexes with non-native enzymes. A handful of examples demonstrate channeling of photosynthetic electrons to drive the activity of heterologous enzymes, and these focus mainly on hydrogenases and cytochrome P450s. However......, competition from native pathways and inefficient electron transfer rates present major obstacles, which limit the productivity of heterologous reactions coupled to photosynthesis. We discuss specific approaches to address these bottlenecks and ensure high productivity of such enzymes in a photosynthetic...

  16. SPATIAL HETEROGENEITY OF PHOTOSYNTHETIC ACTIVITY WITHIN DISEASED CORALS FROM THE GREAT BARRIER REEF

    DEFF Research Database (Denmark)

    Roff, George; Ulstrup, Karin Elizabeth; Fine, Maoz

    2008-01-01

    Morphological diagnosis and descriptions of seven disease-like syndromes affecting scleractinian corals were characterized from the southern Great Barrier Reef (GBR). Chl a fluorescence of PSII was measured using an Imaging-PAM (pulse amplitude modulated) fluorometer, enabling visualization...... with white patch syndrome appeared to impact primarily on the symbiotic dinoflagellates, as evidenced by declines in minimum fluorescence (F0) and maximum quantum yield (Fv/Fm), with no indication of degeneration in the host tissues. Our results suggest that for the majority of coral syndromes from the GBR......, pathogenesis occurs in the host tissue, while the impact on the zooxanthellae populations residing in affected corals is minimal....

  17. Effects of fatty acid activation on photosynthetic production of fatty acid-based biofuels in Synechocystis sp. PCC6803

    Directory of Open Access Journals (Sweden)

    Gao Qianqian

    2012-03-01

    Full Text Available Abstract Background Direct conversion of solar energy and carbon dioxide to drop in fuel molecules in a single biological system can be achieved from fatty acid-based biofuels such as fatty alcohols and alkanes. These molecules have similar properties to fossil fuels but can be produced by photosynthetic cyanobacteria. Results Synechocystis sp. PCC6803 mutant strains containing either overexpression or deletion of the slr1609 gene, which encodes an acyl-ACP synthetase (AAS, have been constructed. The complete segregation and deletion in all mutant strains was confirmed by PCR analysis. Blocking fatty acid activation by deleting slr1609 gene in wild-type Synechocystis sp. PCC6803 led to a doubling of the amount of free fatty acids and a decrease of alkane production by up to 90 percent. Overexpression of slr1609 gene in the wild-type Synechocystis sp. PCC6803 had no effect on the production of either free fatty acids or alkanes. Overexpression or deletion of slr1609 gene in the Synechocystis sp. PCC6803 mutant strain with the capability of making fatty alcohols by genetically introducing fatty acyl-CoA reductase respectively enhanced or reduced fatty alcohol production by 60 percent. Conclusions Fatty acid activation functionalized by the slr1609 gene is metabolically crucial for biosynthesis of fatty acid derivatives in Synechocystis sp. PCC6803. It is necessary but not sufficient for efficient production of alkanes. Fatty alcohol production can be significantly improved by the overexpression of slr1609 gene.

  18. Measures and modelling of PAR (photosynthetically-active radiation) for the Northeast of Brazil; Medidas e modelagem da radiacao PAR (photosynthetically-active radiation) para o nordeste do Brasil

    Energy Technology Data Exchange (ETDEWEB)

    Tiba, Chigueru; Leal, Sergio da S.A. [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Dept. de Energia Nuclear], e-mail: tiba@rce.neoline.com.br

    2004-07-01

    Photosynthetically active solar radiation, known by its acronym in the English language as PAR, is the principal driving force of innumerable biological and physical processes related to biomass production, such as, the evolution of vegetal covering, agricultural productivity, and countless environment aspects, among others. Unfortunately in Brazil and particularly in the Northeast of Brazil, the PAR radiation measures are not a routine part of meteorological station measures, and therefore are still rarer than solar irradiation measures. In this context, a station was installed in Recife, Pernambuco in 2003, to carry out simultaneous measures of daily solar irradiation and PAR irradiation, which permits the modelling and valuation of the relationship between these two parameters and thus makes the estimation of PAR radiation possible, where there used to be only information on solar irradiation. Three others stations are being installed, one on Fernando de Noronha-PE, another in Pesqueira-PE, and the other in Xingo-SE, which complete a group of 4 between Latitudes 8 deg and 10 deg South and Longitudes 34 deg to 38 deg West, each having differentiated Equatorial Climates: island maritime, continental maritime, sylvan (Agreste) and semi-arid. (author)

  19. Changes in Leaf Anatomical Traits Enhanced Photosynthetic Activity of Soybean Grown in Hydroponics with Plant Growth-Promoting Microorganisms.

    Science.gov (United States)

    Paradiso, Roberta; Arena, Carmen; De Micco, Veronica; Giordano, Maria; Aronne, Giovanna; De Pascale, Stefania

    2017-01-01

    The use of hydroponic systems for cultivation in controlled climatic conditions and the selection of suitable genotypes for the specific environment help improving crop growth and yield. We hypothesized that plant performance in hydroponics could be further maximized by exploiting the action of plant growth-promoting organisms (PGPMs). However, the effects of PGPMs on plant physiology have been scarcely investigated in hydroponics. Within a series of experiments aimed to identify the best protocol for hydroponic cultivation of soybean [ Glycine max (L.) Merr.], we evaluated the effects of a PGPMs mix, containing bacteria, yeasts, mycorrhiza and trichoderma beneficial species on leaf anatomy, photosynthetic activity and plant growth of soybean cv. 'Pr91m10' in closed nutrient film technique (NFT). Plants were grown in a growth chamber under semi-aseptic conditions and inoculated at seed, seedling and plant stages, and compared to non-inoculated (control) plants. Light and epi-fluorescence microscopy analyses showed that leaves of inoculated plants had higher density of smaller stomata (297 vs. 247 n/mm 2 ), thicker palisade parenchyma (95.0 vs. 85.8 μm), and larger intercellular spaces in the mesophyll (57.5% vs. 52.2%), compared to non-inoculated plants. The modifications in leaf functional anatomical traits affected gas exchanges; in fact starting from the reproductive phase, the rate of leaf net photosynthesis (NP) was higher in inoculated compared to control plants (8.69 vs. 6.13 μmol CO 2 m -2 s -1 at the beginning of flowering). These data are consistent with the better maximal PSII photochemical efficiency observed in inoculated plants (0.807 vs. 0.784 in control); conversely no difference in leaf chlorophyll content was found. The PGPM-induced changes in leaf structure and photosynthesis lead to an improvement of plant growth (+29.9% in plant leaf area) and seed yield (+36.9%) compared to control. Our results confirm that PGPMs may confer benefits in

  20. Changes in Leaf Anatomical Traits Enhanced Photosynthetic Activity of Soybean Grown in Hydroponics with Plant Growth-Promoting Microorganisms

    Directory of Open Access Journals (Sweden)

    Roberta Paradiso

    2017-05-01

    Full Text Available The use of hydroponic systems for cultivation in controlled climatic conditions and the selection of suitable genotypes for the specific environment help improving crop growth and yield. We hypothesized that plant performance in hydroponics could be further maximized by exploiting the action of plant growth-promoting organisms (PGPMs. However, the effects of PGPMs on plant physiology have been scarcely investigated in hydroponics. Within a series of experiments aimed to identify the best protocol for hydroponic cultivation of soybean [Glycine max (L. Merr.], we evaluated the effects of a PGPMs mix, containing bacteria, yeasts, mycorrhiza and trichoderma beneficial species on leaf anatomy, photosynthetic activity and plant growth of soybean cv. ‘Pr91m10’ in closed nutrient film technique (NFT. Plants were grown in a growth chamber under semi-aseptic conditions and inoculated at seed, seedling and plant stages, and compared to non-inoculated (control plants. Light and epi-fluorescence microscopy analyses showed that leaves of inoculated plants had higher density of smaller stomata (297 vs. 247 n/mm2, thicker palisade parenchyma (95.0 vs. 85.8 μm, and larger intercellular spaces in the mesophyll (57.5% vs. 52.2%, compared to non-inoculated plants. The modifications in leaf functional anatomical traits affected gas exchanges; in fact starting from the reproductive phase, the rate of leaf net photosynthesis (NP was higher in inoculated compared to control plants (8.69 vs. 6.13 μmol CO2 m-2 s-1 at the beginning of flowering. These data are consistent with the better maximal PSII photochemical efficiency observed in inoculated plants (0.807 vs. 0.784 in control; conversely no difference in leaf chlorophyll content was found. The PGPM-induced changes in leaf structure and photosynthesis lead to an improvement of plant growth (+29.9% in plant leaf area and seed yield (+36.9% compared to control. Our results confirm that PGPMs may confer benefits in

  1. Elevated atmospheric CO2 affected photosynthetic products in wheat seedlings and biological activity in rhizosphere soil under cadmium stress.

    Science.gov (United States)

    Jia, Xia; Liu, Tuo; Zhao, Yonghua; He, Yunhua; Yang, Mingyan

    2016-01-01

    The objective of this study was to investigate the effects of elevated CO2 (700 ± 23 μmol mol(-1)) on photosynthetic products in wheat seedlings and on organic compounds and biological activity in rhizosphere soil under cadmium (Cd) stress. Elevated CO2 was associated with decreased quantities of reducing sugars, starch, and soluble amino acids, and with increased quantities of soluble sugars, total sugars, and soluble proteins in wheat seedlings under Cd stress. The contents of total soluble sugars, total free amino acids, total soluble phenolic acids, and total organic acids in the rhizosphere soil under Cd stress were improved by elevated CO2. Compared to Cd stress alone, the activity of amylase, phenol oxidase, urease, L-asparaginase, β-glucosidase, neutral phosphatase, and fluorescein diacetate increased under elevated CO2 in combination with Cd stress; only cellulase activity decreased. Bacterial abundance in rhizosphere soil was stimulated by elevated CO2 at low Cd concentrations (1.31-5.31 mg Cd kg(-1) dry soil). Actinomycetes, total microbial abundance, and fungi decreased under the combined conditions at 5.31-10.31 mg Cd kg(-1) dry soil. In conclusion, increased production of soluble sugars, total sugars, and proteins in wheat seedlings under elevated CO2 + Cd stress led to greater quantities of organic compounds in the rhizosphere soil relative to seedlings grown under Cd stress only. Elevated CO2 concentrations could moderate the effects of heavy metal pollution on enzyme activity and microorganism abundance in rhizosphere soils, thus improving soil fertility and the microecological rhizosphere environment of wheat under Cd stress.

  2. A Simple Semi-Empirical Model for the Estimation of Photosynthetically Active Radiation from Satellite Data in the Tropics

    Directory of Open Access Journals (Sweden)

    S. Janjai

    2013-01-01

    Full Text Available This paper presents a simple semi-empirical model for estimating global photosynthetically active radiation (PAR under all sky conditions. The model expresses PAR as a function of cloud index, aerosol optical depth, total ozone column, solar zenith angle, and air mass. The formulation of the model was based on a four-year period (2008–2011 of PAR data obtained from the measurements at four solar monitoring stations in a tropical environment of Thailand. These are Chiang Mai (18.78°N, 98.98°E, Ubon Ratchathani (15.25°N, 104.87°E, Nakhon Pathom (13.82°N, 100.04°E, and Songkhla (7.20°N, 100.60°E. The cloud index was derived from MTSAT-1R satellite, whereas the aerosol optical depth was obtained from MODIS/Terra satellite. For the total ozone column, it was retrieved from OMI/Aura satellite. The model was validated against independent data set from the four stations. It was found that hourly PAR estimated from the proposed model and that obtained from the measurements were in reasonable agreement, with the root mean square difference (RMSD and mean bias difference (MBD of 14.3% and −5.8%, respectively. In addition, for the case of monthly average hourly PAR, RMSD and MBD were reduced to 11.1% and −5.1%, respectively.

  3. Nitrate Activation of Cytosolic Protein Kinases Diverts Photosynthetic Carbon from Sucrose to Amino Acid Biosynthesis

    Science.gov (United States)

    Champigny, Marie-Louise; Foyer, Christine

    1992-01-01

    The regulation of carbon partitioning between carbohydrates (principally sucrose) and amino acids has been only poorly characterized in higher plants. The hypothesis that the pathway of sucrose and amino acid biosynthesis compete for carbon skeletons and energy is widely accepted. In this review, we suggest a mechanism involving the regulation of cytosolic protein kinases whereby the flow of carbon is regulated at the level of partitioning between the pathways of carbohydrate and nitrogen metabolism via the covalent modulation of component enzymes. The addition of nitrate to wheat seedlings (Triticum aestivum) grown in the absence of exogenous nitrogen has a dramatic, if transient, impact on sucrose formation and on the activities of sucrose phosphate synthase (which is inactivated) and phosphoenolpyruvate carboxylase (which is activated). The activities of these two enzymes are modulated by protein phosphorylation in response to the addition of nitrate, but they respond in an inverse fashion. Sucrose phosphate synthase in inactivated and phosphoenolpyruvate carboxylase is activated. Nitrate functions as a signal metabolite activating the cytosolic protein kinase, thereby modulating the activities of at least two of the key enzymes in assimilate partitioning and redirecting the flow of carbon away from sucrose biosynthesis toward amino acid synthesis. PMID:16653003

  4. Differences in hamstring activation characteristics between the acceleration and maximum-speed phases of sprinting.

    Science.gov (United States)

    Higashihara, Ayako; Nagano, Yasuharu; Ono, Takashi; Fukubayashi, Toru

    2018-06-01

    This study aimed to investigate activation characteristics of the biceps femoris long head (BFlh) and semitendinosus (ST) muscles during the acceleration and maximum-speed phases of sprinting. Lower-extremity kinematics and electromyographic (EMG) activities of the BFlh and ST muscles were examined during the acceleration sprint and maximum-speed sprint in 13 male sprinters during an overground sprinting. Differences in hamstring activation during each divided phases and in the hip and knee joint angles and torques at each time point of the sprinting gait cycle were determined between two sprints. During the early stance of the acceleration sprint, the hip extension torque was significantly greater than during the maximum-speed sprint, and the relative EMG activation of the BFlh muscle was significantly higher than that of the ST muscle. During the late stance and terminal mid-swing of maximum-speed sprint, the knee was more extended and a higher knee flexion moment was observed compared to the acceleration sprint, and the ST muscle showed higher activation than that of the BFlh. These results indicate that the functional demands of the medial and lateral hamstring muscles differ between two different sprint performances.

  5. On the ultrasonic irradiation in the photosynthetic activity of aquatic lirium (Eichornia crassipes)

    Energy Technology Data Exchange (ETDEWEB)

    Calderon, A.; Cardona, A.; Juarez G, A. G.; Marin, E.; Munoz H, R. A.; Diaz G, J. A., E-mail: jcalderona@ipn.mx [IPN, Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Calz. Legaria No. 694, Col. Irrigacion, 11500 Mexico D. F. (Mexico)

    2012-10-15

    We report, for the first time, the application of the photoacoustic technique for monitoring the photosynthesis evolution in aquatic lirium (Eichornia crassipes), before and after it was exposed to ultrasonic irradiations. We obtained the disappearance of the phototobaric contribution in the Pa signal measured for the irradiated samples with ultrasound of 17 khz, and therefore of a possible damage in the centers producing the photosynthesis, due to the irradiation. These results show the utility of the ultrasonic irradiation, as well as, of the photosynthesis monitoring by means of the photoacoustic technique, for the elaboration and establishment of methodologies in the control of this aquatic plant, whose propagation causes many consequences extremely unfavorable for the environment, as well as for the diverse human activities that are developed in the bodies of water in the tropical and sub-tropical regions of the world. (Author)

  6. On the ultrasonic irradiation in the photosynthetic activity of aquatic lirium (Eichornia crassipes)

    International Nuclear Information System (INIS)

    Calderon, A.; Cardona, A.; Juarez G, A. G.; Marin, E.; Munoz H, R. A.; Diaz G, J. A.

    2012-10-01

    We report, for the first time, the application of the photoacoustic technique for monitoring the photosynthesis evolution in aquatic lirium (Eichornia crassipes), before and after it was exposed to ultrasonic irradiations. We obtained the disappearance of the phototobaric contribution in the Pa signal measured for the irradiated samples with ultrasound of 17 khz, and therefore of a possible damage in the centers producing the photosynthesis, due to the irradiation. These results show the utility of the ultrasonic irradiation, as well as, of the photosynthesis monitoring by means of the photoacoustic technique, for the elaboration and establishment of methodologies in the control of this aquatic plant, whose propagation causes many consequences extremely unfavorable for the environment, as well as for the diverse human activities that are developed in the bodies of water in the tropical and sub-tropical regions of the world. (Author)

  7. Rubisco activity is associated with photosynthetic thermotolerance in a wild rice (Oryza meridionalis).

    Science.gov (United States)

    Scafaro, Andrew P; Yamori, Wataru; Carmo-Silva, A Elizabete; Salvucci, Michael E; von Caemmerer, Susanne; Atwell, Brian J

    2012-09-01

    Oryza meridionalis is a wild species of rice, endemic to tropical Australia. It shares a significant genome homology with the common domesticated rice Oryza sativa. Exploiting the fact that the two species are highly related but O. meridionalis has superior heat tolerance, experiments were undertaken to identify the impact of temperature on key events in photosynthesis. At an ambient CO(2) partial pressure of 38 Pa and irradiance of 1500 µmol quanta m(-2) s(-1), the temperature optimum of photosynthesis was 33.7 ± 0.8°C for O. meridionalis, significantly higher than the 30.6 ± 0.7°C temperature optimum of O. sativa. To understand the basis for this difference, we measured gas exchange and rubisco activation state between 20 and 42°C and modeled the response to determine the rate-limiting steps of photosynthesis. The temperature response of light respiration (R(light)) and the CO(2) compensation point in the absence of respiration (Γ(*)) were determined and found to be similar for the two species. C3 photosynthesis modeling showed that despite the difference in susceptibility to high temperature, both species had a similar temperature-dependent limitation to photosynthesis. Both rice species were limited by ribulose-1,5-bisphosphate (RuBP) regeneration at temperatures of 25 and 30°C but became RuBP carboxylation limited at 35 and 40°C. The activation state of rubisco in O. meridionalis was more stable at higher temperatures, explaining its greater heat tolerance compared with O. sativa. Copyright © Physiologia Plantarum 2012.

  8. Modelling three-dimensional distribution of photosynthetically active radiation in sloping coniferous stands

    International Nuclear Information System (INIS)

    Knyazikhin, Yu.; Kranigk, J.; Miessen, G.; Panfyorov, O.; Vygodskaya, N.; Gravenhorst, G.

    1996-01-01

    Solar irradiance is a major environmental factor governing biological and physiological processes in a vegetation canopy. Solar radiation distribution in a canopy and its effect are three-dimensional in nature. However, most of the radiation models up to now have been one-dimensional. They can be successfully applied to large-scale studies of forest functioning. The one-dimensional modelling technique, however, does not provide adequate interpretation of small scale processes leading to forest growth. In this article we discuss a modelling strategy for the simulation of three-dimensional radiation distribution in a vegetation canopy of a small area (about 0.25–0.3 ha). We demonstrate its realisation to predict the three-dimensional radiative regime of phytosynthetically active radiation in a real coniferous stand located on hilly surroundings. Our model can be used to investigate the influence of different climatic conditions, forest management methods and field sites on the solar energy available for forest growth in small heterogeneous areas. Further, a three-dimensional process-oriented model helps to derive global variables affecting bio-physiological processes in a vegetation canopy shifting from small scale studies of the functioning of forests to regional, continental, and global scale problems. (author)

  9. Production and photosynthetic activity of Mimosa Verde and Mimosa Roxa lettuce in two farming systems

    Directory of Open Access Journals (Sweden)

    Aline Mabel Rosa

    2014-08-01

    Full Text Available Lettuce (Lactuca sativa L. is the most commonly consumed leaf vegetable in the Brazilian diet, and it is a good source of vitamins and minerals. It is widely grown in the conventional farming system. However, the hydroponic farming system has been gaining importance in the market, wining confidence from consumers, who are becoming increasingly more demanding on food quality. The objective of this study was to evaluate the performance of two lettuce cultivars on hydroponic and conventional farming systems for the production of fresh mass (FM and dry mass (DM, photosynthesis, contents of chlorophyll and anthocyanin. The following two experiments were carried out: hydroponics farming (HF and conventional farming (CF, performed in protect and unprotect environments, respectively, in Florianópolis, SC. Mimosa Verde cultivar (MV showed greater fresh mass than Mimosa Roxa (MR, in both farming systems and the two cultivars presented better performance in the hydroponic system (287.7 g MV and 139.1 g MR than the conventional system (129.7 g MV and 111.8 g MR. Mimosa Verde cultivar presented lower average contents of total chlorophyll (7.7 mg g-¹ FM than Mimosa Roxa (11.8 mg g-¹FM, and both cultivars displayed higher means for this variable in the hydroponic farming system. Mimosa Roxa presented higher contents of anthocyanin in the conventional system (88.24 mg g-¹ FM than the ones in the hydroponic system (36.89 mg g-¹ FM. The best results for CO2 net assimilation rate regarded to photosyntheticaly active photon flux density were found in the hydroponic system, for both lettuce cultivars. Variation in the contents of chlorophyll were also found. Those variations were higher in the protected system than in the hydroponic system and contents of anthocyanin were higher in the conventional system.

  10. Retrieval of Leaf Area Index (LAI and Fraction of Absorbed Photosynthetically Active Radiation (FAPAR from VIIRS Time-Series Data

    Directory of Open Access Journals (Sweden)

    Zhiqiang Xiao

    2016-04-01

    Full Text Available Long-term high-quality global leaf area index (LAI and fraction of absorbed photosynthetically active radiation (FAPAR products are urgently needed for the study of global change, climate modeling, and many other problems. As the successor of the Moderate Resolution Imaging Spectroradiometer (MODIS sensor, the Visible Infrared Imaging Radiometer Suite (VIIRS will continue to provide global environmental measurements. This paper aims to generate longer time series Global LAnd Surface Satellite (GLASS LAI and FAPAR products after the era of the MODIS sensor. To ensure spatial and temporal consistencies between GLASS LAI/FAPAR values retrieved from different satellite observations, the GLASS LAI/FAPAR retrieval algorithms were adapted in this study to retrieve LAI and FAPAR values from VIIRS surface reflectance time-series data. After reprocessing of the VIIRS surface reflectance to remove remaining effects of cloud contamination and other factors, a database generated from the GLASS LAI product and the reprocessed VIIRS surface reflectance for all Benchmark Land Multisite Analysis and Intercomparison of Products (BELMANIP sites was used to train general regression neural networks (GRNNs. The reprocessed VIIRS surface reflectance data from an entire year were entered into the trained GRNNs to estimate the one-year LAI values, which were then used to calculate FAPAR values. A cross-comparison indicates that the LAI and FAPAR values retrieved from VIIRS surface reflectance were generally consistent with the GLASS, MODIS and Geoland2/BioPar version 1 (GEOV1 LAI/FAPAR values in their spatial patterns. The LAI/FAPAR values retrieved from VIIRS surface reflectance achieved good agreement with the GLASS LAI/FAPAR values (R2 = 0.8972 and RMSE = 0.3054; and R2 = 0.9067 and RMSE = 0.0529, respectively. However, validation of the LAI and FAPAR values derived from VIIRS reflectance data is now limited by the scarcity of LAI/FAPAR ground measurements.

  11. MVP: A Simple and Effective Model to Simulate the Mean and Variation of Photosynthetically Active Radiation Under Discrete Forest Canopies

    Science.gov (United States)

    Song, C.; Band, L. E.

    2003-12-01

    The spatial patterns of Photosynthetically Active Radiation (PAR) under forest canopies, including both its mean and spatial variation, are critical factors that determine numerous ecophysiological processes in plant ecosystems. Though numerous models have been developed that can accurately simulate PAR transmission through plant canopies, Beer's law remains the primary model used in ecological models to describe PAR transmission through plant canopies due to the fact that the more accurate models are too complicated to be used operationally. This study developed a simple and computationally efficient model to simulate both the Mean and Variation of PAR (MVP) under the forest canopy. The model provides a careful description of the effects of gaps on the variable light environment under forest canopy, while it simplifies the simulation of multiple scattering of photons. The model assumes that a forest canopy is composed of individual crowns distributed within upper and lower boundaries with two types of gaps: the between- and within-crown gaps. The inputs to the model are canopy structural parameters, including canopy depth, tree count density, tree crown shape, and foliage area volume density (m2/m3, leaf areas per unit crown volume). The between-crown gaps are simulated with geometric optics, and the within-crown gaps are described by Beer's law. The model accounts for the covariance of PAR in space through time, making it possible to simulate both instantaneous variation of PAR and variation of daily accumulated PAR. Validation with observed PAR using ten quantum sensors under the Old Black Spruce stand at the Southern Study Area of the BOREAS project indicates the model captures the mean and variation of PAR under forest canopy reasonably well. The model is simple enough that it can be used by other ecological models, such as ecosystem dynamics and carbon budget models. Further validation and testing of the model with other types forest are needed in the future.

  12. The influence of photosynthetically-active radiation and simulated shadelight on the control of leaf growth of Betula and Acer

    International Nuclear Information System (INIS)

    Taylor, G.; Davies, W.J.

    1988-01-01

    The primary aim of the study was to quantify the effects of photosynthetically-active radiation (PAR) on extension of leaves of silver birch (Betula pendula Roth.) and sycamore (Acer pseudoplatanus L.). Plants grown at 250 μ mol m -2 s -1 were exposed to a range of fluence rates (0-680 μ mol m -2 s -1 ) whilst enclosed in Perspex chambers in which temperature, vapour pressure deficit and photoenvironment were all controlled. Measurements of leaf extension, water relations, and cell wall extensibility (WEX) were made at the end of a 3 h exposure period. For leaves of birch, reducing the fluence rate resulted in reduced leaf extension and a lowering of WEX. Exposure of sycamore seedlings for 3 h to different values of PAR had little effect on the growth of leaves and WEX remained constant. The characteristics of net photosynthesis also differed for the two species and photosynthesis and wall loosening may be linked. Since natural woodland shadelight, in addition to reduced PAR, also has a reduced R/FR ratio, a second group of seedlings were placed in a photoenvironment which simulated shadelight (low PAR, R/FR) for 28 d. This treatment reduced extension rate and final leaf size for both species. Measurements of extension, water relations and WEX made when seedlings were exposed to shadelight whilst held in the Perspex chambers revealed differences in the control of leaf growth for the two species. It is confirmed that leaves of birch are highly responsive to changes in PAR with cell wall loosening the most likely process controlling this response

  13. Modeling Photosynthetically Active Radiation in Water of Tampa Bay, Florida, with Emphasis on the Geometry of Incident Irradiance

    Science.gov (United States)

    Miller, Ronald L.; McPherson, Benjamin F.

    1995-04-01

    Field studies that compare the spatial and temporal variation in light attenuation often neglect effects of solar elevation angle, yet these effects can be significant. To approximately correct for these angular effects, we developed a model that uses a simplified geometric description of incident direct solar beam and diffuse skylight. The model incorporates effects of solar elevation angle and cloudiness on the amount of in-air photosynthetically active radiation (PAR) that passes through the air-water interface and on K0in waters of relatively low turbidity. The model was calibrated with 3266 5-min averages of scalar PAR measured in air and at two depths in water and permits the value of K0to be adjusted approximately for the effects of time of day, season and cloudiness. The model was then used with 255 days of in-air PAR data (15-min averages) to evaluate irradiance that entered the water and attenuation in the water. On an annual basis, 49% of the incident scalar irradiance, or 380 μmol m -2s -1, was estimated to enter the water of Tampa Bay. The value of K0was estimated to vary as much as 41% on a clear summer day due to changes in solar elevation angle. The model was used to make estimates of the depth to which sea-grasses might receive adequate light for survival for a range of values of K0. This approach should be useful for projecting the effect of changes in water clarity on the depth of sea-grass survival and for comparing values of K0collected at different times of day and in different seasons.

  14. The Maximum Free Magnetic Energy Allowed in a Solar Active Region

    Science.gov (United States)

    Moore, Ronald L.; Falconer, David A.

    2009-01-01

    Two whole-active-region magnetic quantities that can be measured from a line-of-sight magnetogram are (sup L) WL(sub SG), a gauge of the total free energy in an active region's magnetic field, and sup L(sub theta), a measure of the active region's total magnetic flux. From these two quantities measured from 1865 SOHO/MDI magnetograms that tracked 44 sunspot active regions across the 0.5 R(sub Sun) central disk, together with each active region's observed production of CMEs, X flares, and M flares, Falconer et al (2009, ApJ, submitted) found that (1) active regions have a maximum attainable free magnetic energy that increases with the magnetic size (sup L) (sub theta) of the active region, (2) in (Log (sup L)WL(sub SG), Log(sup L) theta) space, CME/flare-productive active regions are concentrated in a straight-line main sequence along which the free magnetic energy is near its upper limit, and (3) X and M flares are restricted to large active regions. Here, from (a) these results, (b) the observation that even the greatest X flares produce at most only subtle changes in active region magnetograms, and (c) measurements from MSFC vector magnetograms and from MDI line-of-sight magnetograms showing that practically all sunspot active regions have nearly the same area-averaged magnetic field strength: =- theta/A approximately equal to 300 G, where theta is the active region's total photospheric flux of field stronger than 100 G and A is the area of that flux, we infer that (1) the maximum allowed ratio of an active region's free magnetic energy to its potential-field energy is 1, and (2) any one CME/flare eruption releases no more than a small fraction (less than 10%) of the active region's free magnetic energy. This work was funded by NASA's Heliophysics Division and NSF's Division of Atmospheric Sciences.

  15. The Influence of Red Fruit Oil on Creatin Kinase Level at Maximum Physical Activity

    Science.gov (United States)

    Apollo Sinaga, Fajar; Hotliber Purba, Pangondian

    2018-03-01

    Heavy physical activities can cause the oxidative stress which resulting in muscle damage with an indicator of elevated levels of Creatin Kinase (CK) enzyme. The oxidative stress can be prevented or reduced by antioxidant supplementation. One of natural resources which contain antioxidant is Red Fruit (Pandanus conoideus) Oil (RFO). This study aims to see the effect of Red Fruit Oil on Creatin Kinase (CK) level at maximum physical activity. This study is an experimental research by using the design of randomized control group pretest-posttest. This study was using 24 male mice divided into four groups, the control group was given aquadest, the treatment groups P1, P2, and P3 were given the RFO orally of 0.15 ml/kgBW, 0.3 ml/kgBW, and 0.6 ml/kgBW, respectively, for a month. The level of CK was checked for all groups at the beginning of study and after the maximum physical activity. The obtained data were then tested statistically by using t-test and ANOVA. The result shows the RFO supplementation during exercise decreased the CK level in P1, P2, and P3 groups with p<0.05, and the higher RFO dosage resulted in decreased CK level at p<0.05. The conclusion of this study is the Red Fruit Oil could decrease the level of CK at maximum physical activity.

  16. Influence of Green, Red and Blue Light Emitting Diodes on Multiprotein Complex Proteins and Photosynthetic Activity under Different Light Intensities in Lettuce Leaves (Lactuca sativa L.

    Directory of Open Access Journals (Sweden)

    Sowbiya Muneer

    2014-03-01

    Full Text Available The objective of this study was to investigate the response of light emitting diodes (LEDs at different light intensities (70 and 80 for green LEDs, 88 and 238 for red LEDs and 80 and 238 μmol m−2 s−1 for blue LEDs at three wavelengths in lettuce leaves. Lettuce leaves were exposed to (522 nm, red (639 nm and blue (470 nm LEDs of different light intensities. Thylakoid multiprotein complex proteins and photosynthetic metabolism were then investigated. Biomass and photosynthetic parameters increased with an increasing light intensity under blue LED illumination and decreased when illuminated with red and green LEDs with decreased light intensity. The expression of multiprotein complex proteins including PSII-core dimer and PSII-core monomer using blue LEDs illumination was higher at higher light intensity (238 μmol m−2 s−1 and was lowered with decreased light intensity (70–80 μmol m−2 s−1. The responses of chloroplast sub-compartment proteins, including those active in stomatal opening and closing, and leaf physiological responses at different light intensities, indicated induced growth enhancement upon illumination with blue LEDs. High intensity blue LEDs promote plant growth by controlling the integrity of chloroplast proteins that optimize photosynthetic performance in the natural environment.

  17. Photosynthetic Pigments in Diatoms.

    Science.gov (United States)

    Kuczynska, Paulina; Jemiola-Rzeminska, Malgorzata; Strzalka, Kazimierz

    2015-09-16

    Photosynthetic pigments are bioactive compounds of great importance for the food, cosmetic, and pharmaceutical industries. They are not only responsible for capturing solar energy to carry out photosynthesis, but also play a role in photoprotective processes and display antioxidant activity, all of which contribute to effective biomass and oxygen production. Diatoms are organisms of a distinct pigment composition, substantially different from that present in plants. Apart from light-harvesting pigments such as chlorophyll a, chlorophyll c, and fucoxanthin, there is a group of photoprotective carotenoids which includes β-carotene and the xanthophylls, diatoxanthin, diadinoxanthin, violaxanthin, antheraxanthin, and zeaxanthin, which are engaged in the xanthophyll cycle. Additionally, some intermediate products of biosynthetic pathways have been identified in diatoms as well as unusual pigments, e.g., marennine. Marine algae have become widely recognized as a source of unique bioactive compounds for potential industrial, pharmaceutical, and medical applications. In this review, we summarize current knowledge on diatom photosynthetic pigments complemented by some new insights regarding their physico-chemical properties, biological role, and biosynthetic pathways, as well as the regulation of pigment level in the cell, methods of purification, and significance in industries.

  18. Photosynthetic Pigments in Diatoms

    Directory of Open Access Journals (Sweden)

    Paulina Kuczynska

    2015-09-01

    Full Text Available Photosynthetic pigments are bioactive compounds of great importance for the food, cosmetic, and pharmaceutical industries. They are not only responsible for capturing solar energy to carry out photosynthesis, but also play a role in photoprotective processes and display antioxidant activity, all of which contribute to effective biomass and oxygen production. Diatoms are organisms of a distinct pigment composition, substantially different from that present in plants. Apart from light-harvesting pigments such as chlorophyll a, chlorophyll c, and fucoxanthin, there is a group of photoprotective carotenoids which includes β-carotene and the xanthophylls, diatoxanthin, diadinoxanthin, violaxanthin, antheraxanthin, and zeaxanthin, which are engaged in the xanthophyll cycle. Additionally, some intermediate products of biosynthetic pathways have been identified in diatoms as well as unusual pigments, e.g., marennine. Marine algae have become widely recognized as a source of unique bioactive compounds for potential industrial, pharmaceutical, and medical applications. In this review, we summarize current knowledge on diatom photosynthetic pigments complemented by some new insights regarding their physico-chemical properties, biological role, and biosynthetic pathways, as well as the regulation of pigment level in the cell, methods of purification, and significance in industries.

  19. Influence of photosynthetically active radiation and spectral quality on UV-B-induced polyamine accumulation in soybean

    International Nuclear Information System (INIS)

    Kramer, G.F.; Krizek, D.T.; Mirecki, R.M.

    1992-01-01

    UV-B-sensitive (Essex) and -insensitive (Williams) cultivars of soybean (Glycine max) were grown in growth chambers at photosynthetically active radiation (PAR) levels of 300 or 600 μmol m −2 sec −1 provided by either red- and far-red-deficient (MH) or blue-deficient (HPS/DX) lamps or a combination of both. The combined treatment provided a balanced output, similar to that provided by fluorescent plus incandescent lighting across the visible spectrum. Under the combined lamps, plants were exposed to 12 kJ m −2 day −1 of biologically effective UV-B (UV-B BE ) with 6-hr irradiance periods centred midway through the photoperiod. This irradiance corresponded to a decrease in stratospheric ozone of ca 20% for clear sky conditions at Beltsville, MD on 21 June. Plant growth was significantly inhibited by UV-B at 300 but not at 600 μmol m −2 sec −1 PAR. No cultivar differences were noted in the UV-B-induced inhibition of growth, although visible injury was less in Williams than in Essex. PAR had a large effect on polyamine levels in leaves, with higher levels of putrescine (Put) and spermidine observed at 600 than at 300 μmol m −2 sec −1 in both cultivars. UV-B-induced polyamine accumulation was observed primarily in Williams. Under MH or HPS/DX lamps alone, plants were exposed to two different UV-B levels, 9.9 and 12 kJ m −2 day −1 , corresponding to stratospheric ozone reductions of ca 9 and 20%. UV-B inhibited growth at both 300 and 600 μmol m −2 sec −1 PAR under either radiation source. There was no effect of PAR on the UV-B-induced growth inhibition with the HPS/DX lamps, but a partial amelioration of this inhibition occurred in Williams at 600 μmol m −2 sec −1 PAR under MH lamps. Dose-dependent UV-B-induced polyamine accumulation was also observed in both cultivars. PAR increased Put levels under MH but not HPS/DX lamps. These results indicate that the inhibition of UV-B stress by high PAR may require a balance of red and blue

  20. Uptake of diuron and concomitant loss of photosynthetic activity in leaves as visualized by imaging the red chlorophyll fluorescence.

    Science.gov (United States)

    Lichtenthaler, Hartmut K; Langsdorf, Gabriele; Buschmann, Claus

    2013-10-01

    The principles of the chlorophyll (Chl) fluorescence induction kinetics (known as Kautsky effect) and their change by the photosystem II herbicide diuron are presented together with the Chl fluorescence emission spectra of a normal and diuron-inhibited leaf. By imaging the Chl fluorescence emission of green leaves the successive uptake of diuron and the concomitant loss of photosynthetic quantum conversion from the leaf base to the leaf tip are documented.

  1. Assessing the effects of ultraviolet radiation on the photosynthetic potential in Archean marine environments

    Science.gov (United States)

    Avila-Alonso, Dailé; Baetens, Jan M.; Cardenas, Rolando; de Baets, Bernard

    2017-07-01

    In this work, the photosynthesis model presented by Avila et al. in 2013 is extended and more scenarios inhabited by ancient cyanobacteria are investigated to quantify the effects of ultraviolet (UV) radiation on their photosynthetic potential in marine environments of the Archean eon. We consider ferrous ions as blockers of UV during the Early Archean, while the absorption spectrum of chlorophyll a is used to quantify the fraction of photosynthetically active radiation absorbed by photosynthetic organisms. UV could have induced photoinhibition at the water surface, thereby strongly affecting the species with low light use efficiency. A higher photosynthetic potential in early marine environments was shown than in the Late Archean as a consequence of the attenuation of UVC and UVB by iron ions, which probably played an important role in the protection of ancient free-floating bacteria from high-intensity UV radiation. Photosynthetic organisms in Archean coastal and ocean environments were probably abundant in the first 5 and 25 m of the water column, respectively. However, species with a relatively high efficiency in the use of light could have inhabited ocean waters up to a depth of 200 m and show a Deep Chlorophyll Maximum near 60 m depth. We show that the electromagnetic radiation from the Sun, both UV and visible light, could have determined the vertical distribution of Archean marine photosynthetic organisms.

  2. The maximum specific hydrogen-producing activity of anaerobic mixed cultures: definition and determination.

    Science.gov (United States)

    Mu, Yang; Yang, Hou-Yun; Wang, Ya-Zhou; He, Chuan-Shu; Zhao, Quan-Bao; Wang, Yi; Yu, Han-Qing

    2014-06-10

    Fermentative hydrogen production from wastes has many advantages compared to various chemical methods. Methodology for characterizing the hydrogen-producing activity of anaerobic mixed cultures is essential for monitoring reactor operation in fermentative hydrogen production, however there is lack of such kind of standardized methodologies. In the present study, a new index, i.e., the maximum specific hydrogen-producing activity (SHAm) of anaerobic mixed cultures, was proposed, and consequently a reliable and simple method, named SHAm test, was developed to determine it. Furthermore, the influences of various parameters on the SHAm value determination of anaerobic mixed cultures were evaluated. Additionally, this SHAm assay was tested for different types of substrates and bacterial inocula. Our results demonstrate that this novel SHAm assay was a rapid, accurate and simple methodology for determining the hydrogen-producing activity of anaerobic mixed cultures. Thus, application of this approach is beneficial to establishing a stable anaerobic hydrogen-producing system.

  3. The maximum specific hydrogen-producing activity of anaerobic mixed cultures: definition and determination

    Science.gov (United States)

    Mu, Yang; Yang, Hou-Yun; Wang, Ya-Zhou; He, Chuan-Shu; Zhao, Quan-Bao; Wang, Yi; Yu, Han-Qing

    2014-06-01

    Fermentative hydrogen production from wastes has many advantages compared to various chemical methods. Methodology for characterizing the hydrogen-producing activity of anaerobic mixed cultures is essential for monitoring reactor operation in fermentative hydrogen production, however there is lack of such kind of standardized methodologies. In the present study, a new index, i.e., the maximum specific hydrogen-producing activity (SHAm) of anaerobic mixed cultures, was proposed, and consequently a reliable and simple method, named SHAm test, was developed to determine it. Furthermore, the influences of various parameters on the SHAm value determination of anaerobic mixed cultures were evaluated. Additionally, this SHAm assay was tested for different types of substrates and bacterial inocula. Our results demonstrate that this novel SHAm assay was a rapid, accurate and simple methodology for determining the hydrogen-producing activity of anaerobic mixed cultures. Thus, application of this approach is beneficial to establishing a stable anaerobic hydrogen-producing system.

  4. Flow of light energy in benthic photosynthetic microbial mats

    Energy Technology Data Exchange (ETDEWEB)

    Al-Najjar, Mohammad Ahmad A.

    2010-12-15

    The work in this thesis demonstrates the assessment of the energy budget inside microbial mat ecosystems, and the factors affecting light utilization efficiency. It presents the first balanced light energy budget for benthic microbial mat ecosystems, and shows how the budget and the spatial distribution of the local photosynthetic efficiencies within the euphotic zone depend on the absorbed irradiance (Jabs). The energy budget was dominated by heat dissipation on the expense of photosynthesis. The maximum efficiency of photosynthesis was at light limiting conditions When comparing three different marine benthic photosynthetic ecosystems (originated from Abu-Dhabi, Arctic, and Exmouth Gulf in Western Australia), differences in the efficiencies were calculated. The results demonstrated that the maximum efficiency depended on mat characteristics affecting light absorption and scattering; such as, photopigments ratio and distribution, and the structural organization of the photosynthetic organisms relative to other absorbing components of the ecosystem (i.e., EPS, mineral particles, detritus, etc.). The maximum efficiency decreased with increasing light penetration depth, and increased with increasing the accessory pigments (phycocyanin and fucoxanthin)/chlorophyll ratio. Spatial heterogeneity in photosynthetic efficiency, pigment distribution, as well as light acclimation in microbial mats originating from different geographical locations was investigated. We used a combined pigment imaging approach (variable chlorophyll fluorescence and hyperspectral imaging), and fingerprinting approach. For each mat, the photosynthetic activity was proportional to the local pigment concentration in the photic zone, but not for the deeper layers and between different mats. In each mat, yield of PSII and E1/2 (light acclimation) generally decreased in parallel with depth, but the gradients in both parameters varied greatly between samples. This mismatch between pigments concentration

  5. AM Fungi Influences the Photosynthetic Activity, Growth and Antioxidant Enzymes in Allium sativum L. under Salinity Condition

    Directory of Open Access Journals (Sweden)

    Mahesh BORDE

    2010-12-01

    Full Text Available Potential of Arbuscular mycorrhizal (AM fungi in alleviating adverse salt effects on growth was tested in garlic (Allium sativum L.. Towards this objective we analyzed the AM root colonization and the activities of various antioxidant enzymes like peroxidase, catalase, and superoxide dismutase at 0, 100, 200 and 300 mM salinity levels. The activities of all the antioxidant enzymes studied were found to be increased in AM garlic plants. Antioxidant activity was maximum in 100 and 200 mM NaCl (sodium chloride in AM and non-AM plants. Proline accumulation was induced by salt levels and it was more in leaves as well as roots of AM plants as compared to non-AM plants, this indicating that mycorrhiza reduced salt injury. Growth parameters of garlic plants like leaf area, plant fresh and dry weight and antioxidant enzyme activities were higher at moderate salinity level. This work suggests that the mycorrhiza helps garlic plants to perform better under moderate salinity level by enhancing the antioxidant activity and proline content as compared to non-AM plants.

  6. Fluoranthene induced changes in photosynthetic pigments, biochemical compounds and enzymatic activities in two microalgal species: Chlorella vulgaris Beijerinck and Desmodesmus subspicatus Chodat

    Directory of Open Access Journals (Sweden)

    Miral Patel

    2014-02-01

    Full Text Available The photosynthetic pigments, biochemical and enzymatic activities in two freshwater microalgal species, Chlorella vulgaris and Desmodesmus subspicatus at different fluoranthene concentrations were compared with the control conditions. During 16-days of incubation period when treated with fluoranthene, both microalgal species exhibited variable amount of photosynthetic pigment, biochemical compounds and enzymatic activities. The addition of fluoranthene at concentrations ranged from 1.5 mg l-1; to 10 mg l-1; to microalgal cultures led to changes in all different metabolites but the patterns varied from species to species. Among the two species tested, pigment, biochemical and enzymatic contents were remarkably declined from 7 % to 95% in C. vulgaris. Moreover, all metabolites in D. subspicatus also diminishing significantly by 3% to 88% of fluoranthene doses (10ppm. These results suggest that fluoranthene-induced changes of pigments, biochemical and enzymatic variations in test microalgae, D. subspicatus and C. vulgaris, might reveal its resistance and ability to metabolize PAHs. At the same time, the PAH impact changes on different metabolic activities were higher at 12 and 16 days than at 4 and 8 days in treated microalgae. DOI: http://dx.doi.org/10.3126/ije.v3i1.9941 International Journal of Environment Vol.3(1 2014: 41-55

  7. Photosynthetic water splitting

    Energy Technology Data Exchange (ETDEWEB)

    Greenbaum, E.

    1981-01-01

    The photosynthetic unit of hydrogen evolution, the turnover time of photosynthetic hydrogen production, and hydrogenic photosynthesis are discussed in the section on previous work. Recent results are given on simultaneous photoproduction of hydrogen and oxygen, kinetic studies, microscopic marine algae-seaweeds, and oxygen profiles.

  8. MAXIMUM CORONAL MASS EJECTION SPEED AS AN INDICATOR OF SOLAR AND GEOMAGNETIC ACTIVITIES

    International Nuclear Information System (INIS)

    Kilcik, A.; Yurchyshyn, V. B.; Abramenko, V.; Goode, P. R.; Gopalswamy, N.; Ozguc, A.; Rozelot, J. P.

    2011-01-01

    We investigate the relationship between the monthly averaged maximal speeds of coronal mass ejections (CMEs), international sunspot number (ISSN), and the geomagnetic Dst and Ap indices covering the 1996-2008 time interval (solar cycle 23). Our new findings are as follows. (1) There is a noteworthy relationship between monthly averaged maximum CME speeds and sunspot numbers, Ap and Dst indices. Various peculiarities in the monthly Dst index are correlated better with the fine structures in the CME speed profile than that in the ISSN data. (2) Unlike the sunspot numbers, the CME speed index does not exhibit a double peak maximum. Instead, the CME speed profile peaks during the declining phase of solar cycle 23. Similar to the Ap index, both CME speed and the Dst indices lag behind the sunspot numbers by several months. (3) The CME number shows a double peak similar to that seen in the sunspot numbers. The CME occurrence rate remained very high even near the minimum of the solar cycle 23, when both the sunspot number and the CME average maximum speed were reaching their minimum values. (4) A well-defined peak of the Ap index between 2002 May and 2004 August was co-temporal with the excess of the mid-latitude coronal holes during solar cycle 23. The above findings suggest that the CME speed index may be a useful indicator of both solar and geomagnetic activities. It may have advantages over the sunspot numbers, because it better reflects the intensity of Earth-directed solar eruptions.

  9. Responses of epidermal cell turgor pressure and photosynthetic activity of leaves of the atmospheric epiphyte Tillandsia usneoides (Bromeliaceae) after exposure to high humidity.

    Science.gov (United States)

    Martin, Craig E; Rux, Guido; Herppich, Werner B

    2013-01-01

    It has been well-established that many epiphytic bromeliads of the atmospheric-type morphology, i.e., with leaf surfaces completely covered by large, overlapping, multicellular trichomes, are capable of absorbing water vapor from the atmosphere when air humidity increases. It is much less clear, however, whether this absorption of water vapor can hydrate the living cells of the leaves and, as a consequence, enhance physiological processes in such cells. The goal of this research was to determine if the absorption of atmospheric water vapor by the atmospheric epiphyte Tillandsia usneoides results in an increase in turgor pressure in leaf epidermal cells that subtend the large trichomes, and, by using chlorophyll fluorescence techniques, to determine if the absorption of atmospheric water vapor by leaves of this epiphyte results in increased photosynthetic activity. Results of measurements on living cells of attached leaves of this epiphytic bromeliad, using a pressure probe and of whole-shoot fluorescence imaging analyses clearly illustrated that the turgor pressure of leaf epidermal cells did not increase, and the photosynthetic activity of leaves did not increase, following exposure of the leaves to high humidity air. These results experimentally demonstrate, for the first time, that the absorption of water vapor following increases in atmospheric humidity in atmospheric epiphytic bromeliads is mostly likely a physical phenomenon resulting from hydration of non-living leaf structures, e.g., trichomes, and has no physiological significance for the plant's living tissues. Copyright © 2012 Elsevier GmbH. All rights reserved.

  10. Effect of the temperature, pH and irradiance on the photosynthetic activity by Scenedesmus obtusiusculus under nitrogen replete and deplete conditions.

    Science.gov (United States)

    Cabello, Juan; Toledo-Cervantes, Alma; Sánchez, León; Revah, Sergio; Morales, Marcia

    2015-04-01

    This paper evaluates the effect of the irradiance, pH and temperature on the photosynthetic activity (PA) of Scenedesmus obtusiusculus under N-replete and N-deplete conditions through oxygen measurements. The highest PA values were 160 mgO2 gb(-1) h(-1) at 620 μmol m(-2) s(-1), 35 °C and pH of 8 under N-replete conditions and 3.3 mgO2 gb(-1) h(-1) at 100 μmol m(-2) s(-1), 28.5 °C and pH of 5.5 for N-deplete conditions. Those operation conditions were tested in a flat-panel photobioreactor. The biomass productivity was 0.97 gb L(-1) d(-1) under N-replete conditions with a photosynthetic efficiency (PE) of 4.4% yielding 0.85 gb mol photon(-1). Similar biomass productivity was obtained under N-deplete condition; and the lipid productivity was 0.34 gL L(-1) d(-1) with a PE of 7.8% yielding 0.39 gL mol photon(-1). The apparent activation and deactivation energies were 16.1 and 30 kcal mol(-1), and 11.9 and 15.3 kcal mol(-1), for N-replete and N-deplete conditions, respectively. Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. Conceptual model to determine maximum activity of radioactive waste in near-surface disposal facilities

    International Nuclear Information System (INIS)

    Iarmosh, I.; Olkhovyk, Yu.

    2016-01-01

    For development of the management strategy for radioactive waste to be placed in near - surface disposal facilities (NSDF), it is necessary to justify long - term safety of such facilities. Use of mathematical modelling methods for long - term forecasts of radwaste radiation impact and assessment of radiation risks from radionuclides migration can help to resolve this issue. The purpose of the research was to develop the conceptual model for determining the maximum activity of radwaste to be safely disposed in the NSDF and to test it in the case of Lot 3 Vector NSDF (Chornobyl exclusion zone). This paper describes an approach to the development of such a model. The conceptual model of "9"0 Sr migration from Lot 3 through aeration zone and aquifer soils was developed. The results of modelling are shown. The proposals on further steps for the model improvement were developed

  12. A comparison of muscle activity in concentric and counter movement maximum bench press.

    Science.gov (United States)

    van den Tillaar, Roland; Ettema, Gertjan

    2013-01-01

    The purpose of this study was to compare the kinematics and muscle activation patterns of regular free-weight bench press (counter movement) with pure concentric lifts in the ascending phase of a successful one repetition maximum (1-RM) attempt in the bench press. Our aim was to evaluate if diminishing potentiation could be the cause of the sticking region. Since diminishing potentiation cannot occur in pure concentric lifts, the occurrence of a sticking region in this type of muscle actions would support the hypothesis that the sticking region is due to a poor mechanical position. Eleven male participants (age 21.9 ± 1.7 yrs, body mass 80.7 ± 10.9 kg, body height 1.79 ± 0.07 m) conducted 1-RM lifts in counter movement and in pure concentric bench presses in which kinematics and EMG activity were measured. In both conditions, a sticking region occurred. However, the start of the sticking region was different between the two bench presses. In addition, in four of six muscles, the muscle activity was higher in the counter movement bench press compared to the concentric one. Considering the findings of the muscle activity of six muscles during the maximal lifts it was concluded that the diminishing effect of force potentiation, which occurs in the counter movement bench press, in combination with a delayed muscle activation unlikely explains the existence of the sticking region in a 1-RM bench press. Most likely, the sticking region is the result of a poor mechanical force position.

  13. The ancient Egyptian civilization: maximum and minimum in coincidence with solar activity

    Science.gov (United States)

    Shaltout, M.

    It is proved from the last 22 years observations of the total solar irradiance (TSI) from space by artificial satellites, that TSI shows negative correlation with the solar activity (sunspots, flares, and 10.7cm Radio emissions) from day to day, but shows positive correlations with the same activity from year to year (on the base of the annual average for each of them). Also, the solar constant, which estimated fromth ground stations for beam solar radiations observations during the 20 century indicate coincidence with the phases of the 11- year cycles. It is known from sunspot observations (250 years) , and from C14 analysis, that there are another long-term cycles for the solar activity larger than 11-year cycle. The variability of the total solar irradiance affecting on the climate, and the Nile flooding, where there is a periodicities in the Nile flooding similar to that of solar activity, from the analysis of about 1300 years of the Nile level observations atth Cairo. The secular variations of the Nile levels, regularly measured from the 7 toth 15 century A.D., clearly correlate with the solar variations, which suggests evidence for solar influence on the climatic changes in the East African tropics The civilization of the ancient Egyptian was highly correlated with the Nile flooding , where the river Nile was and still yet, the source of the life in the Valley and Delta inside high dry desert area. The study depends on long -time historical data for Carbon 14 (more than five thousands years), and chronical scanning for all the elements of the ancient Egyptian civilization starting from the firs t dynasty to the twenty six dynasty. The result shows coincidence between the ancient Egyptian civilization and solar activity. For example, the period of pyramids building, which is one of the Brilliant periods, is corresponding to maximum solar activity, where the periods of occupation of Egypt by Foreign Peoples corresponding to minimum solar activity. The decline

  14. Simultaneous Solar Maximum Mission (SMM) and Very Large Array (VLA) observations of solar active regions

    Science.gov (United States)

    Willson, Robert F.

    1991-01-01

    Very Large Array observations at 20 cm wavelength can detect the hot coronal plasma previously observed at soft x ray wavelengths. Thermal cyclotron line emission was detected at the apex of coronal loops where the magnetic field strength is relatively constant. Detailed comparison of simultaneous Solar Maximum Mission (SMM) Satellite and VLA data indicate that physical parameters such as electron temperature, electron density, and magnetic field strength can be obtained, but that some coronal loops remain invisible in either spectral domain. The unprecedent spatial resolution of the VLA at 20 cm wavelength showed that the precursor, impulsive, and post-flare components of solar bursts originate in nearby, but separate loops or systems of loops.. In some cases preburst heating and magnetic changes are observed from loops tens of minutes prior to the impulsive phase. Comparisons with soft x ray images and spectra and with hard x ray data specify the magnetic field strength and emission mechanism of flaring coronal loops. At the longer 91 cm wavelength, the VLA detected extensive emission interpreted as a hot 10(exp 5) K interface between cool, dense H alpha filaments and the surrounding hotter, rarefield corona. Observations at 91 cm also provide evidence for time-correlated bursts in active regions on opposite sides of the solar equator; they are attributed to flare triggering by relativistic particles that move along large-scale, otherwise-invisible, magnetic conduits that link active regions in opposite hemispheres of the Sun.

  15. Electron density variations in the F2 layer maximum during solar activity cycle

    International Nuclear Information System (INIS)

    Besprozvannaya, A.S.; Kozina, P.E.; AN Kazakhskoj SSR, Alma-Ata. Sektor Ionosfery)

    1988-01-01

    R value, characterizing for F2 relation of hourly median values in solar activity minimum and maximum, is calculated by average monthly values of F2 layer critical frequencies for June, October and December 1958 and 1964. R latitudinal-temporal distributions are plotted for different seasons according to the data from the north hemisphere west and east stations, placed within the Φ'=35-70deg latitudes interval. The following peculiarities of F2 lyer ionization relation with solar activity are pointed out. There are day-time hours, they are - winter one characterized by the gain rate increase with the widths increase, and summer one, realizing the opposite regularity. In night-time hours R value is characterized by the abnormally low values (∼ 1.2) at the latitudes to the south of the ionospheric through and to the pole from it. For all three seasons during 24 hours the periods with ionization gain maximal rate, which occur at nights in summer time and in the hours after the sunset - in winter and equinoctial months, are observed. The quantitative explanation of the peculiarities detected concerning the to-day concepts on F2 layer formation mechanisms is given

  16. EQPlanar: a maximum-likelihood method for accurate organ activity estimation from whole body planar projections

    International Nuclear Information System (INIS)

    Song, N; Frey, E C; He, B; Wahl, R L

    2011-01-01

    Optimizing targeted radionuclide therapy requires patient-specific estimation of organ doses. The organ doses are estimated from quantitative nuclear medicine imaging studies, many of which involve planar whole body scans. We have previously developed the quantitative planar (QPlanar) processing method and demonstrated its ability to provide more accurate activity estimates than conventional geometric-mean-based planar (CPlanar) processing methods using physical phantom and simulation studies. The QPlanar method uses the maximum likelihood-expectation maximization algorithm, 3D organ volume of interests (VOIs), and rigorous models of physical image degrading factors to estimate organ activities. However, the QPlanar method requires alignment between the 3D organ VOIs and the 2D planar projections and assumes uniform activity distribution in each VOI. This makes application to patients challenging. As a result, in this paper we propose an extended QPlanar (EQPlanar) method that provides independent-organ rigid registration and includes multiple background regions. We have validated this method using both Monte Carlo simulation and patient data. In the simulation study, we evaluated the precision and accuracy of the method in comparison to the original QPlanar method. For the patient studies, we compared organ activity estimates at 24 h after injection with those from conventional geometric mean-based planar quantification using a 24 h post-injection quantitative SPECT reconstruction as the gold standard. We also compared the goodness of fit of the measured and estimated projections obtained from the EQPlanar method to those from the original method at four other time points where gold standard data were not available. In the simulation study, more accurate activity estimates were provided by the EQPlanar method for all the organs at all the time points compared with the QPlanar method. Based on the patient data, we concluded that the EQPlanar method provided a

  17. Diel tuning of photosynthetic systems in ice algae at Saroma-ko Lagoon, Hokkaido, Japan

    Science.gov (United States)

    Aikawa, Shimpei; Hattori, Hiroshi; Gomi, Yasushi; Watanabe, Kentaro; Kudoh, Sakae; Kashino, Yasuhiro; Satoh, Kazuhiko

    Ice algae are the major primary producers in seasonally ice-covered oceans during the cold season. Diurnal change in solar radiation is inevitable for ice algae, even beneath seasonal sea ice in lower-latitude regions. In this work, we focused on the photosynthetic response of ice algae under diurnally changing irradiance in Saroma-ko Lagoon, Japan. Photosynthetic properties were assessed by pulse-amplitude modulation (PAM) fluorometry. The species composition remained almost the same throughout the investigation. The maximum electron transport rate ( rETRmax), which indicates the capacity of photosynthetic electron transport, increased from sunrise until around noon and decreased toward sunset, with no sign of the afternoon depression commonly observed in other photosynthetic organisms. The level of non-photochemical quenching, which indicates photoprotection activity by dissipating excess light energy via thermal processes, changed with diurnal variations in irradiance. The pigment composition appeared constant, except for xanthophyll cycle pigments, which changed irrespective of irradiance. These results indicate that ice algae tune their photosynthetic system harmonically to achieve efficient photosynthesis under diurnally changing irradiance, while avoiding damage to photosystems. This regulation system may be essential for productive photosynthesis in ice algae.

  18. A framework for consistent estimation of leaf area index, fraction of absorbed photosynthetically active radiation, and surface albedo from MODIS time-series data

    DEFF Research Database (Denmark)

    Xiao, Zhiqiang; Liang, Shunlin; Wang, Jindi

    2015-01-01

    -series MODerate Resolution Imaging Spectroradiometer (MODIS) surface reflectance data. If the reflectance data showed snow-free areas, an ensemble Kalman filter (EnKF) technique was used to estimate leaf area index (LAI) for a two-layer canopy reflectance model (ACRM) by combining predictions from a phenology...... model and the MODIS surface reflectance data. The estimated LAI values were then input into the ACRM to calculate the surface albedo and the fraction of absorbed photosynthetically active radiation (FAPAR). For snow-covered areas, the surface albedo was calculated as the underlying vegetation canopy...... albedo plus the weighted distance between the underlying vegetation canopy albedo and the albedo over deep snow. The LAI/FAPAR and surface albedo values estimated using this framework were compared with MODIS collection 5 eight-day 1-km LAI/FAPAR products (MOD15A2) and 500-m surface albedo product (MCD43...

  19. Effects of lead and chelators on growth, photosynthetic activity and Pb uptake in Sesbania drummondii grown in soil

    International Nuclear Information System (INIS)

    Ruley, Adam T.; Sharma, Nilesh C.; Sahi, Shivendra V.; Singh, Shree R.; Sajwan, Kenneth S.

    2006-01-01

    Effects of lead (Pb) and chelators, such as EDTA, HEDTA, DTPA, NTA and citric acid, were studied to evaluate the growth potential of Sesbania drummondii in soils contaminated with high concentrations of Pb. S. drummondii seedlings were grown in soil containing 7.5 g Pb(NO 3 ) 2 and 0-10 mmol chelators/kg soil for a period of 2 and 4 weeks and assessed for growth profile (length of root and shoot), chlorophyll a fluorescence kinetics (F v /F m and F v /F o ) and Pb accumulations in root and shoot. Growth of plants in the presence of Pb + chelators was significantly higher (P v /F m and F v /F o values of treated seedlings remained unaffected, indicating normal photosynthetic efficiency and strength of plants in the presence of chelators. On application of chelators, while root uptake of Pb increased four-five folds, shoot accumulations increased up to 40-folds as compared to controls (Pb only) depending on the type of chelator used. Shoot accumulations of Pb varied from 0.1 to 0.42% (dry weight) depending on the concentration of chelators used. - Sesbania drummondii tolerates and accumulates high concentrations of Pb

  20. Impacts of diurnal variation of ultraviolet-B and photosynthetically active radiation on phycobiliproteins of the hot-spring cyanobacterium Nostoc sp. strain HKAR-2.

    Science.gov (United States)

    Kannaujiya, Vinod K; Sinha, Rajeshwar P

    2017-01-01

    The effects of diurnal variation of photosynthetically active radiation (PAR; 400-700 nm) and ultraviolet-B (UV-B; 280-315 nm) radiation on phycobiliproteins (PBPs) and photosynthetic pigments (PP) have been studied in the hot-spring cyanobacterium Nostoc sp. strain HKAR-2. The variations in PBPs and PP were monitored by alternating light and dark under PAR, UV-B, and PAR + UV-B radiations over a period of 25 h. There was a decline in the amount of Chl a and PBPs during light periods of UV-B and PAR + UV-B and an increase during dark periods showing a circadian rhythm by destruction and resynthesis of pigment-protein complex. However, a marked induction in carotenoids was recorded during light periods of the same radiations. Moreover, the ratio of Chl a/PE and Chl a/PC was increased in dark periods showing the resynthesis of bleached Chl a. The wavelength shift in emission fluorescence of PBPs toward shorter wavelengths further indicated the bleaching and destruction of PBPs during light periods. Oxidative damage upon exposure to PAR, UV-B, and PAR + UV-B was alleviated by induction of antioxidative enzymes such as superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX). The studied cyanobacterium exhibits a significant increase in the activities of SOD, CAT, and APX upon exposure to UV-B and PAR + UV-B radiations. The results indicate that pigment-protein composition of Nostoc sp. stain HKAR-2 was significantly altered during diurnal variation of light/radiation, which might play an important role in optimization for their productivity in a particular cyanobacterium.

  1. Photosynthetic behavior, growth and essential oil production of Melissa officinalis L. cultivated under colored shade nets

    OpenAIRE

    Graziele C Oliveira; Willyam L Vieira; Suzana C Bertolli; Ana Claudia Pacheco

    2016-01-01

    The modulation of light is of importance during cultivation of medicinal plants to obtain desirable morphological and physiological changes associated with the maximum production of active principles. This study aimed to evaluate the effect of the light spectrum transmitted by colored shade nets on growth, essential oil production and photosynthetic behavior in plants of lemon balm (Melissa officinalis L.) Plants were cultivated in pots for 4-mo under black, red, and blue nets with 50% shadin...

  2. Exploring the Potential Impact of Greenland Meltwater on Stratification, Photosynthetically Active Radiation, and Primary Production in the Labrador Sea

    Science.gov (United States)

    Oliver, Hilde; Luo, Hao; Castelao, Renato M.; van Dijken, Gert L.; Mattingly, Kyle S.; Rosen, Joshua J.; Mote, Thomas L.; Arrigo, Kevin R.; Rennermalm, Åsa K.; Tedesco, Marco; Yager, Patricia L.

    2018-04-01

    In July 2012, the surface of the Greenland Ice Sheet (GrIS) melted to an extent unprecedented over the last 100 years; we questioned the potential for such an extreme melt event to impact marine phytoplankton offshore. We hypothesized that stratification from meltwater could reduce light limitation for phytoplankton, and used a suite of numerical models to quantify the impact for 2003-2012. Because much of the 2012 meltwater discharged from southern Greenland, our study focused on the southwestern and southeastern coasts of Greenland, and the Labrador Sea. A 1-D phytoplankton model used output from a Regional Ocean Modeling System (ROMS) coupled with a Regional Climate Model and a hydrological model of meltwater from runoff sources on the ice sheet, peripheral glaciers, and tundra. ROMS was run with and without meltwater to test the sensitivity of phytoplankton photosynthetic rates to the meltwater input. With meltwater, the pycnocline was shallower during late summer and early fall and thus light limitation on photosynthesis was reduced. Averaged over all years, added meltwater had the potential to increase gross primary production by 3-12% in the summer (July-August), and 13-60% in the fall (September-October). This meltwater effect was amplified when light was more limiting, and thus was greatest in the fall, under cloudier conditions, with higher self-shading, and with more light-sensitive phytoplankton groups. As the GrIS melt is projected to increase, late summer primary production in this region has the potential to increase as well, which could constitute an important biosphere response to high-latitude climate change.

  3. A Kinetic Model to Explain the Maximum in alpha-Amylase Activity Measurements in the Presence of Small Carbohydrates

    NARCIS (Netherlands)

    Baks, T.; Janssen, A.E.M.; Boom, R.M.

    2006-01-01

    The effect of the presence of several small carbohydrates on the measurement of the -amylase activity was determined over a broad concentration range. At low carbohydrate concentrations, a distinct maximum in the -amylase activity versus concentration curves was observed in several cases. At higher

  4. Morning reduction of photosynthetic capacity before midday depression.

    Science.gov (United States)

    Koyama, Kohei; Takemoto, Shuhei

    2014-03-17

    Midday depression of photosynthesis has important consequences for ecosystem carbon exchange. Recent studies of forest trees have demonstrated that latent reduction of photosynthetic capacity can begin in the early morning, preceding the midday depression. We investigated whether such early morning reduction also occurs in an herbaceous species, Oenothera biennis. Diurnal changes of the photosynthetic light response curve (measured using a light-emitting diode) and incident sunlight intensity were measured under field conditions. The following results were obtained: (1) the light-saturated photosynthetic rate decreased beginning at sunrise; (2) the incident sunlight intensity on the leaves increased from sunrise; and (3) combining (1) and (2), the net photosynthetic rate under natural sunlight intensity increased from sunrise, reached a maximum at mid-morning, and then showed midday depression. Our results demonstrate that the latent morning reduction of photosynthetic capacity begins at sunrise, preceding the apparent midday depression, in agreement with previous studies of forest trees.

  5. Proton Fluxes Measured by the PAMELA Experiment from the Minimum to the Maximum Solar Activity for Solar Cycle 24

    Science.gov (United States)

    Martucci, M.; Munini, R.; Boezio, M.; Di Felice, V.; Adriani, O.; Barbarino, G. C.; Bazilevskaya, G. A.; Bellotti, R.; Bongi, M.; Bonvicini, V.; Bottai, S.; Bruno, A.; Cafagna, F.; Campana, D.; Carlson, P.; Casolino, M.; Castellini, G.; De Santis, C.; Galper, A. M.; Karelin, A. V.; Koldashov, S. V.; Koldobskiy, S.; Krutkov, S. Y.; Kvashnin, A. N.; Leonov, A.; Malakhov, V.; Marcelli, L.; Marcelli, N.; Mayorov, A. G.; Menn, W.; Mergè, M.; Mikhailov, V. V.; Mocchiutti, E.; Monaco, A.; Mori, N.; Osteria, G.; Panico, B.; Papini, P.; Pearce, M.; Picozza, P.; Ricci, M.; Ricciarini, S. B.; Simon, M.; Sparvoli, R.; Spillantini, P.; Stozhkov, Y. I.; Vacchi, A.; Vannuccini, E.; Vasilyev, G.; Voronov, S. A.; Yurkin, Y. T.; Zampa, G.; Zampa, N.; Potgieter, M. S.; Raath, J. L.

    2018-02-01

    Precise measurements of the time-dependent intensity of the low-energy (solar activity periods, i.e., from minimum to maximum, are needed to achieve comprehensive understanding of such physical phenomena. The minimum phase between solar cycles 23 and 24 was peculiarly long, extending up to the beginning of 2010 and followed by the maximum phase, reached during early 2014. In this Letter, we present proton differential spectra measured from 2010 January to 2014 February by the PAMELA experiment. For the first time the GCR proton intensity was studied over a wide energy range (0.08–50 GeV) by a single apparatus from a minimum to a maximum period of solar activity. The large statistics allowed the time variation to be investigated on a nearly monthly basis. Data were compared and interpreted in the context of a state-of-the-art three-dimensional model describing the GCRs propagation through the heliosphere.

  6. Effect of planting density on fruit size, light-interception and photosynthetic activity of vertically trained watermelon (Citrullus lanatus (Thunb.) Matsum. et Nakai) plants

    International Nuclear Information System (INIS)

    Watanabe, S.; Nakano, Y.; Okano, K.

    2003-01-01

    Summary The effect of planting density on fruit size of vertically trained watermelon (Citrullus lanatus (Thunb.) Matsum. et Nakai) plants was investigated with regard to light - interception characteristics and photosynthetic production. Watermelon plants, grafted on bottle gourd, were grown in a glasshouse at different planting densities. Two vines per plant were allowed to grow and trained vertically. One hand-pollinated fruit per plant was set around the 15th node on either vine. The solar radiation and photosynthetic rate of individual leaves during fruit development period were determined by an integrated solarimeter film and a portable photosynthesis system, respectively. Fruit size was significantly decreased as the planting density increased, whereas soluble solids content of the fruits was affected little. The solar radiation and the photosynthetic rate of the individual leaves gradually decreased as the leaf position became lower at all planting densities on account of shading; those at lower leaves tended to decrease as the planting density increased. Fruit size was closely related to both the total solar radiation and the photosynthetic production per plant. In conclusion, the difference in fruit size among the planting densities is attributed to the photosynthetic productivity of the whole plant, which is mainly a function of the total solar radiation. This paper appears to be the first trial relating the influence of light interception and photosynthetic rates in high density plantings of vertically trained watermelon plants on fruit size

  7. Impact of Aerosols on Shortwave and Photosynthetically Active Radiation Balance over Sub-tropical Region in South Asia: Observational and Modeling Approach

    Science.gov (United States)

    Subba, T.; Pathak, B.

    2016-12-01

    The North-East Indian Region (NER) (22-30ºN, 89-98ºE) in south Asia sandwiched between two global biodiversity hotspots namely, Himalaya and Indo-Burma, assumes significance owing to its unique topography with mountains in the north, east and south and densely populated Indo Gangetic plains (IGP) towards the west resulting in complex aerosol system. Multi-year (2010-2014) concurrent measurements of aerosol properties and the shortwave radiation budget are examined over four geographically distinct stations of NER operational under Indian Space Research organization's ARFINET (Aerosol Radiative Forcing over India NETwork). An attempt has been made to lessen the ambiguity of forcing estimation by validating the radiative transfer modelled ARF with the CNR4 net radiometer measured values (r2 0.98). The Normalized Difference Vegetation Index and its dependence on the extinction of the photosynthetically active radiation (PAR) due to aerosol are assessed. The spring time enhancement of aerosols in the column has shown significant surface cooling (ARF = -48 ± 5 Wm-2) over the region, while the very high Black Carbon (BC) mass concentrations near the surface (SSA > 0.8) leads to significant atmospheric warming (ARF = +41 ± 7 Wm-2) in the shortwave range. Radiative forcing estimates reveal that the atmospheric forcing by BC could be as high as +30Wm-2 over the western part, which are significantly higher than the eastern part with a consequent heating rate of 1.5 K day-1 revealing an east-west asymmetry over NER. The impact of BC aerosols on the photosynthetic rate varies among different locations ranging from -5±2 Wm-2 to -25±3 Wm-2. Almost 70% of the total atmospheric shortwave radiative absorption is attributed to just 10% contribution of Black Carbon (BC) to total mass concentration and causes a reduction of more than 30% of PAR reaching the surface over Brahmaputra valley due to direct radiative effect. Comparison of previous and the present study shows highest

  8. Radiative transfer in shrub savanna sites in Niger: preliminary results from HAPEX-Sahel. 2. Photosynthetically active radiation interception of the woody layer

    International Nuclear Information System (INIS)

    Bégué, A.; Hanan, N.P.; Prince, S.D.

    1994-01-01

    Interception by the woody layer of photosynthetically active radiation (PAR) was measured and calculated for two Guiera senegalensis J.F. Gmel, shrub savannas in Ouallam, Western Niger, in 1991 as part of the HAPEX-Sahel experiment. Two different scales were considered. At the plant scale, PAR interception was measured throughout the day with amorphous silicon sensors, together with detailed measurements of the structure of the shrubs (size of the ‘envelope’ of the shrub, area index, and angular distribution of the leaves and the branches). These data permitted us to develop and validate a simple radiative transfer model in which the shrubs are represented by porous cylinders; the total transmissivity (or porosity) of the shrubs estimated by the model was approximately 0.4. It indicates that semi-arid shrubs cannot be considered opaque objects and that the fraction of ground covered with plants is a poor indicator of the PAR interception efficiency of the canopy. The model was also applied at a landscape scale to calculate the daily PAR interception of two shrub savanna sites. This value is needed to model primary production in conjunction with remotely sensed and production data acquired simultaneously on the sites. (author)

  9. Differential effects of cadmium and chromium on growth, photosynthetic activity, and metal uptake of Linum usitatissimum in association with Glomus intraradices.

    Science.gov (United States)

    Amna; Ali, Naeem; Masood, Sajid; Mukhtar, Tehmeena; Kamran, Muhammad Aqeel; Rafique, Mazhar; Munis, M Farooq Hussain; Chaudhary, Hassan Javed

    2015-06-01

    The current study was aimed at analyzing the differential effects of heavy metals (cadmium and chromium) and mycorrhizal fungus; Glomus intraradices on growth, chlorophyll content, proline production, and metal accumulation in flax plant (Linum usitatissimum L.). Heavy metal accumulation rate in flax varied from 90 to 95 % for Cd and 61-84 % for Cr at a concentration range of 250 to 500 ppm for both metals in 24 days of experiment. Growth and photosynthetic activity of flax reduced to an average of 21 and 45 %, respectively. However, inoculation of G. intraradices significantly increased the plant biomass even under metal stressed conditions. Additionally, mycorrhizal association also assists the Cd and Cr increased uptake by 23 and 33 %, respectively. Due to metal stress, chlorophyll contents were decreased by 27 and 45 %, while 84 and 71 % increased proline content was observed under Cd and Cr stress, respectively. The present results clearly signify the differential response and potential of flax plant towards heavy metal tolerance and accumulation that can further increase with mycorrhizal fungus.

  10. [Radiometers performance attenuation and data correction in long-term observation of total radiation and photosynthetically active radiation in typical forest ecosystems in China].

    Science.gov (United States)

    Zhu, Zhi-Lin; Sun, Xiao-Min; Yu, Gui-Rui; Wen, Xue-Fa; Zhang, Yi-Ping; Han, Shi-Jie; Yan, Jun-Hua; Wang, Hui-Min

    2011-11-01

    Based on the total radiation and photosynthetically active radiation (PAR) observations with net radiometer (CNR1) and quantum sensor (Li-190SB) in 4 ChinaFLUX forest sites (Changbaishan, Qianyanzhou, Dinghushan, and Xishuangbanna) in 2003-2008, this paper analyzed the uncertainties and the radiometers performance changes in long-term and continuous field observation. The results showed that the 98% accuracy of the total radiation measured with CNR1 (Q(cNR1)) could satisfy the technical criterion for the sites except Xishuangbanna where the Q(CNR1) was averagely about 7% lower than Q(CM11), the radiation measured with high accuracy pyranometer CM11. For most sites, though the temperature had definite effects on the performance of CNR1, the effects were still within the allowable range of the accuracy of the instrument. Besides temperature, the seasonal fog often occurred in tropical rain forests in Xishuangbanna also had effects on the performance of CNR1. Based on the long-term variations of PAR, especially its ratio to total radiation in the 4 sites, it was found that quantum sensor (Li-190SB) had obvious performance attenuation, with the mean annual attenuation rate being about 4%. To correct the observation error caused by Li-190SB, an attempt was made to give a post-correction of the PAR observations, which could basically eliminate the quantum sensor's performance attenuation due to long-term field measurement.

  11. Ultraviolet-B and photosynthetically active radiation interactively affect yield and pattern of monoterpenes in leaves of peppermint (Mentha x piperita L.).

    Science.gov (United States)

    Behn, Helen; Albert, Andreas; Marx, Friedhelm; Noga, Georg; Ulbrich, Andreas

    2010-06-23

    Solar radiation is a key environmental signal in regulation of plant secondary metabolism. Since metabolic responses to light and ultraviolet (UV) radiation exposure are known to depend on the ratio of spectral ranges (e.g., UV-B/PAR), we examined effects of different UV-B radiation (280-315 nm) and photosynthetically active radiation (PAR, 400-700 nm) levels and ratios on yield and pattern of monoterpenoid essential oil of peppermint. Experiments were performed in exposure chambers, technically equipped for realistic simulation of natural climate and radiation. The experimental design comprised four irradiation regimes created by the combination of two PAR levels including or excluding UV-B radiation. During flowering, the highest essential oil yield was achieved at high PAR (1150 micromol m(-2) s(-1)) and approximate ambient UV-B radiation (0.6 W m(-2)). Regarding the monoterpene pattern, low PAR (550 micromol m(-2) s(-1)) and the absence of UV-B radiation led to reduced menthol and increased menthone contents and thereby to a substantial decrease in oil quality. Essential oil yield could not be correlated with density or diameter of peltate glandular trichomes, the epidermal structures specialized on biosynthesis, and the accumulation of monoterpenes. The present results lead to the conclusion that production of high quality oils (fulfilling the requirements of the Pharmacopoeia Europaea) requires high levels of natural sunlight. In protected cultivation, the use of UV-B transmitting covering materials is therefore highly recommended.

  12. Imaging VLBI polarimetry data from Active Galactic Nuclei using the Maximum Entropy Method

    Directory of Open Access Journals (Sweden)

    Coughlan Colm P.

    2013-12-01

    Full Text Available Mapping the relativistic jets emanating from AGN requires the use of a deconvolution algorithm to account for the effects of missing baseline spacings. The CLEAN algorithm is the most commonly used algorithm in VLBI imaging today and is suitable for imaging polarisation data. The Maximum Entropy Method (MEM is presented as an alternative with some advantages over the CLEAN algorithm, including better spatial resolution and a more rigorous and unbiased approach to deconvolution. We have developed a MEM code suitable for deconvolving VLBI polarisation data. Monte Carlo simulations investigating the performance of CLEAN and the MEM code on a variety of source types are being carried out. Real polarisation (VLBA data taken at multiple wavelengths have also been deconvolved using MEM, and several of the resulting polarisation and Faraday rotation maps are presented and discussed.

  13. Simultaneous Solar Maximum Mission (SMM) and very large array observations of solar active regions

    Science.gov (United States)

    Lang, K. R.

    1986-01-01

    The research deals mainly with Very Large Array and Solar Maximum Mission observations of the ubiquitous coronal loops that dominate the structure of the low corona. As illustrated, the observations of thermal cyclotron lines at microwave wavelengths provide a powerful new method of accurately specifying the coronal magnetic field strength. Processes are delineated that trigger solar eruptions from coronal loops, including preburst heating and the magnetic interaction of coronal loops. Evidence for coherent burst mechanisms is provided for both the Sun and nearby stars, while other observations suggest the presence of currents that may amplify the coronal magnetic field to unexpectedly high levels. The existence is reported of a new class of compact, variable moving sources in regions of apparently weak photospheric field.

  14. Evolving a photosynthetic organelle

    Directory of Open Access Journals (Sweden)

    Nakayama Takuro

    2012-04-01

    Full Text Available Abstract The evolution of plastids from cyanobacteria is believed to represent a singularity in the history of life. The enigmatic amoeba Paulinella and its 'recently' acquired photosynthetic inclusions provide a fascinating system through which to gain fresh insight into how endosymbionts become organelles. The plastids, or chloroplasts, of algae and plants evolved from cyanobacteria by endosymbiosis. This landmark event conferred on eukaryotes the benefits of photosynthesis - the conversion of solar energy into chemical energy - and in so doing had a huge impact on the course of evolution and the climate of Earth 1. From the present state of plastids, however, it is difficult to trace the evolutionary steps involved in this momentous development, because all modern-day plastids have fully integrated into their hosts. Paulinella chromatophora is a unicellular eukaryote that bears photosynthetic entities called chromatophores that are derived from cyanobacteria and has thus received much attention as a possible example of an organism in the early stages of organellogenesis. Recent studies have unlocked the genomic secrets of its chromatophore 23 and provided concrete evidence that the Paulinella chromatophore is a bona fide photosynthetic organelle 4. The question is how Paulinella can help us to understand the process by which an endosymbiont is converted into an organelle.

  15. Evolving a photosynthetic organelle.

    Science.gov (United States)

    Nakayama, Takuro; Archibald, John M

    2012-04-24

    The evolution of plastids from cyanobacteria is believed to represent a singularity in the history of life. The enigmatic amoeba Paulinella and its 'recently' acquired photosynthetic inclusions provide a fascinating system through which to gain fresh insight into how endosymbionts become organelles.The plastids, or chloroplasts, of algae and plants evolved from cyanobacteria by endosymbiosis. This landmark event conferred on eukaryotes the benefits of photosynthesis--the conversion of solar energy into chemical energy--and in so doing had a huge impact on the course of evolution and the climate of Earth 1. From the present state of plastids, however, it is difficult to trace the evolutionary steps involved in this momentous development, because all modern-day plastids have fully integrated into their hosts. Paulinella chromatophora is a unicellular eukaryote that bears photosynthetic entities called chromatophores that are derived from cyanobacteria and has thus received much attention as a possible example of an organism in the early stages of organellogenesis. Recent studies have unlocked the genomic secrets of its chromatophore 23 and provided concrete evidence that the Paulinella chromatophore is a bona fide photosynthetic organelle 4. The question is how Paulinella can help us to understand the process by which an endosymbiont is converted into an organelle.

  16. Toward autonomous measurements of photosynthetic electron transport rates: An evaluation of active fluorescence-based measurements of photochemistry

    NARCIS (Netherlands)

    Silsbe, G.M.; Oxborough, K.; Suggett, D.J.; Forster, R.M.; Ihnken, S.; Komárek, O.; Lawrenz, E.; Prášil, O.; Röttgers, R.; Šicner, M.; Simis, S.G.H.; Van Dijk, M.A.; Kromkamp, J.C.

    2015-01-01

    This study presents a methods evaluation and intercalibration of active fluorescence-based measurements of the quantum yield ( inline image) and absorption coefficient ( inline image) of photosystem II (PSII) photochemistry. Measurements of inline image, inline image, and irradiance (E) can be

  17. Magnetic nanoparticle imaging by random and maximum length sequences of inhomogeneous activation fields.

    Science.gov (United States)

    Baumgarten, Daniel; Eichardt, Roland; Crevecoeur, Guillaume; Supriyanto, Eko; Haueisen, Jens

    2013-01-01

    Biomedical applications of magnetic nanoparticles require a precise knowledge of their biodistribution. From multi-channel magnetorelaxometry measurements, this distribution can be determined by means of inverse methods. It was recently shown that the combination of sequential inhomogeneous excitation fields in these measurements is favorable regarding the reconstruction accuracy when compared to homogeneous activation . In this paper, approaches for the determination of activation sequences for these measurements are investigated. Therefor, consecutive activation of single coils, random activation patterns and families of m-sequences are examined in computer simulations involving a sample measurement setup and compared with respect to the relative condition number of the system matrix. We obtain that the values of this condition number decrease with larger number of measurement samples for all approaches. Random sequences and m-sequences reveal similar results with a significant reduction of the required number of samples. We conclude that the application of pseudo-random sequences for sequential activation in the magnetorelaxometry imaging of magnetic nanoparticles considerably reduces the number of required sequences while preserving the relevant measurement information.

  18. Sun Protection Preferences and Behaviors among Young Adult Males during Maximum Ultraviolet Radiation Exposure Activities

    Science.gov (United States)

    Wickenheiser, Marilyn; Baker, Mary Kate; Gaber, Rikki; Blatt, Hanz; Robinson, June K.

    2013-01-01

    This study explores sun protection attitudes, preferences, and behaviors among young adult males participating in an open-field activity with extreme ultraviolet radiation exposure. Male drum corps members (n = 137) responded to survey questions regarding their behavior and willingness to engage in sun protection and barriers to sunscreen usage. A subset of members (n = 31) participated in cognitive interviews exploring various sunscreen products and intervention techniques. Participants were knowledgeable about health risks and protection benefits regarding sun exposure. Generally, males had positive attitudes and normative beliefs about using sunscreen. A barrier to sunscreen re-application was lack of adequate time to reapply sunscreen during the open field activity. Males preferred a towelette application method, but were unfamiliar with its efficacy and proper use. Thus, they were more likely to use the more familiar sunscreen spray. To increase sun protection behaviors and lower skin cancer risk for males participating in open-field activities, breaks must be allotted every 2 h and have sufficient time to allow sunscreen application. Future development and research into delivery systems that rapidly and evenly apply sunscreen may help lower exposure in this population. PMID:23912201

  19. Sun Protection Preferences and Behaviors among Young Adult Males during Maximum Ultraviolet Radiation Exposure Activities

    Directory of Open Access Journals (Sweden)

    June K. Robinson

    2013-07-01

    Full Text Available This study explores sun protection attitudes, preferences, and behaviors among young adult males participating in an open-field activity with extreme ultraviolet radiation exposure. Male drum corps members (n = 137 responded to survey questions regarding their behavior and willingness to engage in sun protection and barriers to sunscreen usage. A subset of members (n = 31 participated in cognitive interviews exploring various sunscreen products and intervention techniques. Participants were knowledgeable about health risks and protection benefits regarding sun exposure. Generally, males had positive attitudes and normative beliefs about using sunscreen. A barrier to sunscreen re-application was lack of adequate time to reapply sunscreen during the open field activity. Males preferred a towelette application method, but were unfamiliar with its efficacy and proper use. Thus, they were more likely to use the more familiar sunscreen spray. To increase sun protection behaviors and lower skin cancer risk for males participating in open-field activities, breaks must be allotted every 2 h and have sufficient time to allow sunscreen application. Future development and research into delivery systems that rapidly and evenly apply sunscreen may help lower exposure in this population.

  20. Effect of cycocel on photosynthetic activity and essential oil of fennel (Foeniculum vulgare Mill. under drought stress

    Directory of Open Access Journals (Sweden)

    Fatemeh Nouri

    2014-12-01

    Full Text Available Drought stress is one of the most important and most common environmental stresses that limit plant growth. Photosynthesis is the main determinant of plant growth and its retention ability under environmental stress condition is important for preservation of growth stability. To study the effect of spraying CCC on photosynthesis activity and essential oil content on 'Foeniculum vulgare', an experiment was done in split plot design based on complete block with four replications in research field of University of Zanjan in 2011. Levels of drought stress included, control, soft stress (when 30% of available water was out of soil, severe stress (when 90% of available water was out of soil, and three concentration of CCC 0, 1500 and 3000 mg/L. The results showed that between rates foliar application on physiologic characteristics as photosynthesis rate, transpiration severity, RWC and TΔ intercellular (Ci, stomata conductivity, mesophyll conductivity and essential oil content was significant. By spraying 3000 mg/L CCC, balanced the plant position against drought stress and could reduce negative effect. Foliar application of CCC caused significant increase in photosynthesis rate, mesophyll conductivity and significant decrease stomata conductivity, transpiration severity under drought stress and could increase essential oil content under soft stress. In this study, foliar application of CCC to content 3000 mg/L had the highest effect on this characters.

  1. THE ACTIVE INTEGRATED CIRCULAR PROCESS – EXPRESSION OF MAXIMUM SYNTHESIS OF SUSTAINABLE DEVELOPMENT

    Directory of Open Access Journals (Sweden)

    Done Ioan

    2015-06-01

    Full Text Available "The accelerated pace of economic growth, prompted by the need to ensure reducing disparities between the various countries, has imposed in the last two decades the adoption of sustainable development principles, particularly as a result of the Rio Declaration on Environment and Development (1992 and the UNESCO Declaration in the fall of 1997. In specific literature, in essence, sustainable development is considered "an economic and social process that is characterized by a simultaneous and concerted action at global, regional and local level. Its objective is to provide living conditions both for the present and forth future. Sustainable development “encompasses the economic, ecological, social and political aspects, linked through cultural and spiritual relationships."(Coşea, 2007In Romania, achieving sustainable development is a major, difficult objective, because it must be done in terms of convergence to the demands of the economic, social, cultural and political context of the EU, and in terms of the completion of the transition to a functioning and competitive market economy. In this context, it is imposed the economic competitiveness through reindustrialization and not least, by harnessing the active integrated circular process. Gross value added and profit chain in the structures of active integrated circular process must reflect the interests of the forces involved(employers, employees and the statethereby forming the basis of respect for the correlation between sustainable development, economic growth and increasing national wealth. The elimination or marginalization of certain links in the value chain and profit causes major disruptions or bankruptcy, with direct implications for recognizing and rewarding performance. Essentially, the building of active integrated circular process will determine the maximization of the profit – the foundation of satisfying all economic interests.

  2. Low and moderate photosynthetically active radiation affects the flavonol glycosides and hydroxycinnamic acid derivatives in kale (Brassica oleracea var. sabellica) dependent on two low temperatures.

    Science.gov (United States)

    Neugart, Susanne; Fiol, Michaela; Schreiner, Monika; Rohn, Sascha; Zrenner, Rita; Kroh, Lothar W; Krumbein, Angelika

    2013-11-01

    Kale (Brassica oleracea var. sabellica) contains a large number of naturally occurring structurally different non-acylated and acylated flavonol glycosides as well as hydroxycinnamic acid derivatives. The objective of this study was to determine the effect of low and moderate photosynthetic active radiation (PAR) and how these levels interact with low temperature in these phenolic compounds. Juvenile kale plants were treated with PAR levels from 200 to 800 μmol m(-2) s(-1) at 5 and 10 °C under defined conditions in climate chambers. Of the investigated 20 compounds, 11 and 17 compounds were influenced by PAR and temperature, respectively. In addition, an interaction between PAR and temperature was found for eight compounds. The response of the phenolic compounds to PAR was structure-dependent. While quercetin triglycosides increased with higher PAR at 5 and 10 °C, the kaempferol triglycosides exhibited the highest concentrations at 400 μmol m(-2) s(-1). In contrast, kaempferol diglycosides exhibited the highest concentrations at increased PAR levels of 600 and 800 μmol m(-2) s(-1) at 10 °C. However, key genes of flavonol biosynthesis were influenced by temperature but remained unaffected by PAR. Furthermore, there was no interaction between the PAR level and the low temperature in the response of hydroxycinnamic acid derivatives in kale with the exception of caffeoylquinic acid, which decreased with higher PAR levels of 600 and 800 μmol m(-2) s(-1) and at a lower temperature. In conclusion, PAR and its interaction with temperature could be a suitable tool for modifying the profile of phenolic compounds. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

  3. Estimation of the fraction of absorbed photosynthetically active radiation (fPAR) in maize canopies using LiDAR data and hyperspectral imagery.

    Science.gov (United States)

    Qin, Haiming; Wang, Cheng; Zhao, Kaiguang; Xi, Xiaohuan

    2018-01-01

    Accurate estimation of the fraction of absorbed photosynthetically active radiation (fPAR) for maize canopies are important for maize growth monitoring and yield estimation. The goal of this study is to explore the potential of using airborne LiDAR and hyperspectral data to better estimate maize fPAR. This study focuses on estimating maize fPAR from (1) height and coverage metrics derived from airborne LiDAR point cloud data; (2) vegetation indices derived from hyperspectral imagery; and (3) a combination of these metrics. Pearson correlation analyses were conducted to evaluate the relationships among LiDAR metrics, hyperspectral metrics, and field-measured fPAR values. Then, multiple linear regression (MLR) models were developed using these metrics. Results showed that (1) LiDAR height and coverage metrics provided good explanatory power (i.e., R2 = 0.81); (2) hyperspectral vegetation indices provided moderate interpretability (i.e., R2 = 0.50); and (3) the combination of LiDAR metrics and hyperspectral metrics improved the LiDAR model (i.e., R2 = 0.88). These results indicate that LiDAR model seems to offer a reliable method for estimating maize fPAR at a high spatial resolution and it can be used for farmland management. Combining LiDAR and hyperspectral metrics led to better performance of maize fPAR estimation than LiDAR or hyperspectral metrics alone, which means that maize fPAR retrieval can benefit from the complementary nature of LiDAR-detected canopy structure characteristics and hyperspectral-captured vegetation spectral information.

  4. An evaluation of the effects of exogenous ethephon, an ethylene releasing compound, on photosynthesis of mustard (Brassica juncea cultivars that differ in photosynthetic capacity

    Directory of Open Access Journals (Sweden)

    Khan NA

    2004-12-01

    Full Text Available Abstract Background The stimulatory effect of CO2 on ethylene evolution in plants is known, but the extent to which ethylene controls photosynthesis is not clear. Studies on the effects of ethylene on CO2 metabolism have shown conflicting results. Increase or inhibition of photosynthesis by ethylene has been reported. To understand the physiological processes responsible for ethylene-mediated changes in photosynthesis, stomatal and mesophyll effects on photosynthesis and ethylene biosynthesis in response to ethephon treatment in mustard (Brassica juncea cultivars differing in photosynthetic capacity were studied. Results The effects of ethephon on photosynthetic rate (PN, stomatal conductance (gS, carbonic anhydrase (CA activity, 1-aminocyclopropane carboxylic acid synthase (ACS activity and ethylene evolution were similar in both the cultivars. Increasing ethephon concentration up to 1.5 mM increased PN, gS and CA maximally, whereas 3.0 mM ethephon proved inhibitory. ACS activity and ethylene evolution increased with increasing concentrations of ethephon. The corresponding changes in gs and CA activity suggest that the changes in photosynthesis in response to ethephon were triggered by altered stomatal and mesophyll processes. Stomatal conductance changed in parallel with changes in mesophyll photosynthetic properties. In both the cultivars ACS activity and ethylene increased up to 3.0 mM ethephon, but 1.5 mM ethephon caused maximum effects on photosynthetic parameters. Conclusion These results suggest that ethephon affects foliar gas exchange responses. The changes in photosynthesis in response to ethephon were due to stomatal and mesophyll effects. The changes in gS were a response maintaining stable intercellular CO2 concentration (Ci under the given treatment in both the cultivars. Also, the high photosynthetic capacity cultivar, Varuna responded less to ethephon than the low photosynthetic capacity cultivar, RH30. The photosynthetic

  5. Active Contour Driven by Local Region Statistics and Maximum A Posteriori Probability for Medical Image Segmentation

    Directory of Open Access Journals (Sweden)

    Xiaoliang Jiang

    2014-01-01

    Full Text Available This paper presents a novel active contour model in a variational level set formulation for simultaneous segmentation and bias field estimation of medical images. An energy function is formulated based on improved Kullback-Leibler distance (KLD with likelihood ratio. According to the additive model of images with intensity inhomogeneity, we characterize the statistics of image intensities belonging to each different object in local regions as Gaussian distributions with different means and variances. Then, we use the Gaussian distribution with bias field as a local region descriptor in level set formulation for segmentation and bias field correction of the images with inhomogeneous intensities. Therefore, image segmentation and bias field estimation are simultaneously achieved by minimizing the level set formulation. Experimental results demonstrate desirable performance of the proposed method for different medical images with weak boundaries and noise.

  6. Spatial variability in photosynthetic and heterotrophic activity drives localized δ13C org fluctuations and carbonate precipitation in hypersaline microbial mats.

    Science.gov (United States)

    Houghton, J; Fike, D; Druschel, G; Orphan, V; Hoehler, T M; Des Marais, D J

    2014-11-01

    Modern laminated photosynthetic microbial mats are ideal environments to study how microbial activity creates and modifies carbon and sulfur isotopic signatures prior to lithification. Laminated microbial mats from a hypersaline lagoon (Guerrero Negro, Baja California, Mexico) maintained in a flume in a greenhouse at NASA Ames Research Center were sampled for δ(13) C of organic material and carbonate to assess the impact of carbon fixation (e.g., photosynthesis) and decomposition (e.g., bacterial respiration) on δ(13) C signatures. In the photic zone, the δ(13) C org signature records a complex relationship between the activities of cyanobacteria under variable conditions of CO2 limitation with a significant contribution from green sulfur bacteria using the reductive TCA cycle for carbon fixation. Carbonate is present in some layers of the mat, associated with high concentrations of bacteriochlorophyll e (characteristic of green sulfur bacteria) and exhibits δ(13) C signatures similar to DIC in the overlying water column (-2.0‰), with small but variable decreases consistent with localized heterotrophic activity from sulfate-reducing bacteria (SRB). Model results indicate respiration rates in the upper 12 mm of the mat alter in situ pH and HCO3- concentrations to create both phototrophic CO2 limitation and carbonate supersaturation, leading to local precipitation of carbonate minerals. The measured activity of SRB with depth suggests they variably contribute to decomposition in the mat dependent on organic substrate concentrations. Millimeter-scale variability in the δ(13) C org signature beneath the photic zone in the mat is a result of shifting dominance between cyanobacteria and green sulfur bacteria with the aggregate signature overprinted by heterotrophic reworking by SRB and methanogens. These observations highlight the impact of sedimentary microbial processes on δ(13) C org signatures; these processes need to be considered when attempting to relate

  7. Photosynthetic activity of cassava plants under weed competition Atividade fotossintética de plantas de mandioca submetidas a competição com plantas daninhas

    Directory of Open Access Journals (Sweden)

    I. Aspiazú

    2010-01-01

    Full Text Available The objective of this work was to evaluate characteristics associated with the photosynthetic activity of cassava plants under weed competition. The trial was carried out under field conditions, and experimental units consisted of 150 dm³ fiberglass boxes containing red yellow Latosol, previously corrected and fertilized. Treatments consisted in the cultivation of cassava plants which were free of weed competition and associated with three weed species: Bidens pilosa, Commelina benghalensis or Brachiaria plantaginea. After manioc sprouting started, 15 days after being planted, weeds that had been sown when manioc was planted were thinned, there were then eight plants left per experimental unit in accordance with specified treatments: cassava free of competition, cassava competing with B. pilosa, cassava competing with C. benghalensis and cassava competing with B. plantaginea. Sixty days after crop emergence leaf internal CO2 concentration (Ci, leaf temperature at the time of evaluation (Tleaf and photosynthetic rate (A were evaluated, also the CO2 consumption rate (ΔC of cassava plants was calculated. A correlation matrix between variables was also obtained. All characteristics associated with photosynthesis in cassava plants were influenced by weed species. Cassava was more affected by B. pilosa and B. plantaginea in which concerns its exposition to solar radiation and water, while C. benghalensis seems to mostly affect the composition of incident light on the culture, allowing cassava to anticipate imposition when competing, even before it reaches harmful levels.Objetivou-se com este trabalho avaliar características associadas à atividade fotossintética de plantas de mandioca sob competição ou não com plantas daninhas. O experimento foi realizado em condições de ambiente aberto, sendo as unidades experimentais compostas por vasos de fibra de vidro de 150 dm³ preenchidos com Latossolo Vermelho Amarelo, previamente adubado. Os

  8. Examination into the maximum rotational frequency for an in-plane switched active waveplate device

    International Nuclear Information System (INIS)

    Davidson, A J; Elston, S J; Raynes, E P

    2005-01-01

    An examination of an active waveplate device using a one-dimensional model, giving numerical and analytical results, is presented. The model calculates the director and twist configuration by minimizing the free energy of the system with simple homeotropic boundary conditions. The effect of varying the in-plane electric field in both magnitude and direction is examined, and it is shown that the twist through the cell is constant in time as the field is rotated. As the electric field is rotated, the director field lags behind by an angle which increases as the frequency of the electric field rotation increases. When this angle reaches approximately π/4 the director field no longer follows the electric field in a uniform way. Using mathematical analysis it is shown that the conditions on which the director profile will fail to follow the rotating electric field depend on the frequency of electric field rotation, the magnitude of the electric field, the dielectric anisotropy and the viscosity of the liquid crystal

  9. Drought-induced photosynthetic inhibition and autumn recovery in two Mediterranean oak species (Quercus ilex and Quercus suber).

    Science.gov (United States)

    Vaz, M; Pereira, J S; Gazarini, L C; David, T S; David, J S; Rodrigues, A; Maroco, J; Chaves, M M

    2010-08-01

    Responses of leaf water relations and photosynthesis to summer drought and autumn rewetting were studied in two evergreen Mediterranean oak species, Quercus ilex spp. rotundifolia and Quercus suber. The predawn leaf water potential (Ψ(lPD)), stomatal conductance (gs) and photosynthetic rate (A) at ambient conditions were measured seasonally over a 3-year period. We also measured the photosynthetic response to light and to intercellular CO₂ (A/PPFD and A/C(i) response curves) under water stress (summer) and after recovery due to autumn rainfall. Photosynthetic parameters, Vc(max), J(max) and triose phosphate utilization (TPU) rate, were estimated using the Farquhar model. RuBisCo activity, leaf chlorophyll, leaf nitrogen concentration and leaf carbohydrate concentration were also measured. All measurements were performed in the spring leaves of the current year. In both species, the predawn leaf water potential, stomatal conductance and photosynthetic rate peaked in spring, progressively declined throughout the summer and recovered upon autumn rainfall. During the drought period, Q. ilex maintained a higher predawn leaf water potential and stomatal conductance than Q. suber. During this period, we found that photosynthesis was not only limited by stomatal closure, but was also downregulated as a consequence of a decrease in the maximum carboxylation rate (Vc(max)) and the light-saturated rate of photosynthetic electron transport (J(max)) in both species. The Vc(max) and J(max) increased after the first autumnal rains and this increase was related to RuBisCo activity, leaf nitrogen concentration and chlorophyll concentration. In addition, an increase in the TPU rate and in soluble leaf sugar concentration was observed in this period. The results obtained indicate a high resilience of the photosynthetic apparatus to summer drought as well as good recovery in the following autumn rains of these evergreen oak species.

  10. Counting viruses and bacteria in photosynthetic microbial mats

    NARCIS (Netherlands)

    Carreira, C; Staal, M.; Middelboe, M.; Brussaard, C.P.D.

    2015-01-01

    Viral abundances in benthic environments are the highest found in aquatic systems. Photosynthetic microbial mats represent benthic environments with high microbial activity and possibly high viral densities, yet viral abundances have not been examined in such systems. Existing extraction procedures

  11. Primary photosynthetic processes: from supercomplex to leaf

    NARCIS (Netherlands)

    Broess, K.

    2009-01-01

    This thesis describes fluorescence spectroscopy experiments on photosynthetic complexes that cover the primary photosynthetic processes, from the absorption of light by photosynthetic pigments to a charge separation (CS) in the reaction center (RC). Fluorescence spectroscopy is a useful tool in

  12. Releasable activity and maximum permissible leakage rate within a transport cask of Tehran Research Reactor fuel samples

    Directory of Open Access Journals (Sweden)

    Rezaeian Mahdi

    2015-01-01

    Full Text Available Containment of a transport cask during both normal and accident conditions is important to the health and safety of the public and of the operators. Based on IAEA regulations, releasable activity and maximum permissible volumetric leakage rate within the cask containing fuel samples of Tehran Research Reactor enclosed in an irradiated capsule are calculated. The contributions to the total activity from the four sources of gas, volatile, fines, and corrosion products are treated separately. These calculations are necessary to identify an appropriate leak test that must be performed on the cask and the results can be utilized as the source term for dose evaluation in the safety assessment of the cask.

  13. Culturing photosynthetic bacteria through surface plasmon resonance

    Energy Technology Data Exchange (ETDEWEB)

    Ooms, Matthew D.; Bajin, Lauren; Sinton, David [Department of Mechanical and Industrial Engineering and Centre for Sustainable Energy, University of Toronto, Toronto M5S 3G8 (Canada)

    2012-12-17

    In this work, cultivation of photosynthetic microbes in surface plasmon enhanced evanescent fields is demonstrated. Proliferation of Synechococcus elongatus was obtained on gold surfaces excited with surface plasmons. Excitation over three days resulted in 10 {mu}m thick biofilms with maximum cell volume density of 20% vol/vol (2% more total accumulation than control experiments with direct light). Collectively, these results indicate the ability to (1) excite surface-bound cells using plasmonic light fields, and (2) subsequently grow thick biofilms by coupling light from the surface. Plasmonic light delivery presents opportunities for high-density optofluidic photobioreactors for microalgal analysis and solar fuel production.

  14. Effect of the Absorbed Photosynthetically Active Radiation Estimation Error on Net Primary Production Estimation - A Study with MODIS FPAR and TOMS Ultraviolet Reflective Products

    International Nuclear Information System (INIS)

    Kobayashi, H.; Matsunaga, T.; Hoyano, A.

    2002-01-01

    Absorbed photosynthetically active radiation (APAR), which is defined as downward solar radiation in 400-700 nm absorbed by vegetation, is one of the significant variables for Net Primary Production (NPP) estimation from satellite data. Toward the reduction of the uncertainties in the global NPP estimation, it is necessary to clarify the APAR accuracy. In this paper, first we proposed the improved PAR estimation method based on Eck and Dye's method in which the ultraviolet (UV) reflectivity data derived from Total Ozone Mapping Spectrometer (TOMS) at the top of atmosphere were used for clouds transmittance estimation. The proposed method considered the variable effects of land surface UV reflectivity on the satellite-observed UV data. Monthly mean PAR comparisons between satellite-derived and ground-based data at various meteorological stations in Japan indicated that the improved PAR estimation method reduced the bias errors in the summer season. Assuming the relative error of the fraction of PAR (FPAR) derived from Moderate Resolution Imaging Spectroradiometer (MODIS) to be 10%, we estimated APAR relative errors to be 10-15%. Annual NPP is calculated using APAR derived from MODIS/ FPAR and the improved PAR estimation method. It is shown that random and bias errors of annual NPP in a 1 km resolution pixel are less than 4% and 6% respectively. The APAR bias errors due to the PAR bias errors also affect the estimated total NPP. We estimated the most probable total annual NPP in Japan by subtracting the bias PAR errors. It amounts about 248 MtC/yr. Using the improved PAR estimation method, and Eck and Dye's method, total annual NPP is 4% and 9% difference from most probable value respectively. The previous intercomparison study among using fifteen NPP models4) showed that global NPP estimations among NPP models are 44.4-66.3 GtC/yr (coefficient of variation = 14%). Hence we conclude that the NPP estimation uncertainty due to APAR estimation error is small

  15. Rice Photosynthetic Productivity and PSII Photochemistry under Nonflooded Irrigation

    Directory of Open Access Journals (Sweden)

    Haibing He

    2014-01-01

    Full Text Available Nonflooded irrigation is an important water-saving rice cultivation technology, but little is known on its photosynthetic mechanism. The aims of this work were to investigate photosynthetic characteristics of rice during grain filling stage under three nonflooded irrigation treatments: furrow irrigation with plastic mulching (FIM, furrow irrigation with nonmulching (FIN, and drip irrigation with plastic mulching (DI. Compared with the conventional flooding (CF treatment, those grown in the nonflooded irrigation treatments showed lower net photosynthetic rate (PN, lower maximum quantum yield (Fv/Fm, and lower effective quantum yield of PSII photochemistry (ΦPSII. And the poor photosynthetic characteristics in the nonflooded irrigation treatments were mainly attributed to the low total nitrogen content (TNC. Under non-flooded irrigation, the PN, Fv/Fm, and ΦPSII significantly decreased with a reduction in the soil water potential, but these parameters were rapidly recovered in the DI and FIM treatments when supplementary irrigation was applied. Moreover, The DI treatment always had higher photosynthetic productivity than the FIM and FIN treatments. Grain yield, matter translocation, and dry matter post-anthesis (DMPA were the highest in the CF treatment, followed by the DI, FIM, and FIN treatments in turn. In conclusion, increasing nitrogen content in leaf of rice plants could be a key factor to improve photosynthetic capacity in nonflooded irrigation.

  16. Photosynthetic performance in Sphagnum transplanted along a latitudinal nitrogen deposition gradient.

    Science.gov (United States)

    Granath, Gustaf; Strengbom, Joachim; Breeuwer, Angela; Heijmans, Monique M P D; Berendse, Frank; Rydin, Håkan

    2009-04-01

    Increased N deposition in Europe has affected mire ecosystems. However, knowledge on the physiological responses is poor. We measured photosynthetic responses to increasing N deposition in two peatmoss species (Sphagnum balticum and Sphagnum fuscum) from a 3-year, north-south transplant experiment in northern Europe, covering a latitudinal N deposition gradient ranging from 0.28 g N m(-2) year(-1) in the north, to 1.49 g N m(-2) year(-1) in the south. The maximum photosynthetic rate (NP(max)) increased southwards, and was mainly explained by tissue N concentration, secondly by allocation of N to the photosynthesis, and to a lesser degree by modified photosystem II activity (variable fluorescence/maximum fluorescence yield). Although climatic factors may have contributed, these results were most likely attributable to an increase in N deposition southwards. For S. fuscum, photosynthetic rate continued to increase up to a deposition level of 1.49 g N m(-2) year(-1), but for S. balticum it seemed to level out at 1.14 g N m(-2) year(-1). The results for S. balticum suggested that transplants from different origin (with low or intermediate N deposition) respond differently to high N deposition. This indicates that Sphagnum species may be able to adapt or physiologically adjust to high N deposition. Our results also suggest that S. balticum might be more sensitive to N deposition than S. fuscum. Surprisingly, NP(max) was not (S. balticum), or only weakly (S. fuscum) correlated with biomass production, indicating that production is to a great extent is governed by factors other than the photosynthetic capacity.

  17. Photosynthetic limitation and mechanisms of photoprotection under drought and recovery of Calotropis procera, an evergreen C3 from arid regions.

    Science.gov (United States)

    Rivas, Rebeca; Frosi, Gabriella; Ramos, Diego G; Pereira, Silvia; Benko-Iseppon, Ana M; Santos, Mauro G

    2017-09-01

    Calotropis procera is a C 3 plant native from arid environmental zones. It is an evergreen, shrubby, non-woody plant with intense photosynthetic metabolism during the dry season. We measured photosynthetic parameters and leaf biochemical traits, such as gas exchange, photochemical parameters, A/C i analysis, organic solutes, and antioxidant enzymes under controlled conditions in potted plants during drought stress, and following recovery conditions to obtain a better insight in the drought stress responses of C. procera. Indeed, different processes contribute to the drought stress resilience of C. procera and to the fast recovery after rehydration. The parameters analyzed showed that C. procera has a high efficiency for energy dissipation. The photosynthetic machinery is protected by a robust antioxidant system and photoprotective mechanisms such as alternative pathways for electrons (photorespiration and day respiration). Under severe drought stress, increased stomatal limitation and decreased biochemical limitation permitted C. procera to maintain maximum rate of Rubisco carboxylation (V c,max ) and photosynthetic rate (A max ). On the other hand, limitation of stomatal or mesophyll CO 2 diffusion did not impair fast recovery, maintaining V c,max , chloroplast CO 2 concentration (C c ) and mesophyll conductance (g m ) unchanged while electron flow used for RuBP carboxylation (J c ) and A max increased. The ability to tolerate drought stress and the fast recovery of this evergreen C 3 species was also due to leaf anti-oxidative stress enzyme activity, and photosynthetic pigments. Thus, these different drought tolerance mechanisms allowed high performance of photosynthetic metabolism by drought stressed plants during the re-watering period. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  18. A compendium of temperature responses of Rubisco kinetic traits: variability among and within photosynthetic groups and impacts on photosynthesis modeling

    Science.gov (United States)

    Galmés, Jeroni; Hermida-Carrera, Carmen; Laanisto, Lauri; Niinemets, Ülo

    2016-01-01

    The present study provides a synthesis of the in vitro and in vivo temperature responses of Rubisco Michaelis–Menten constants for CO2 (Kc) and O2 (Ko), specificity factor (Sc,o) and maximum carboxylase turnover rate (kcatc) for 49 species from all the main photosynthetic kingdoms of life. Novel correction routines were developed for in vitro data to remove the effects of study-to-study differences in Rubisco assays. The compilation revealed differences in the energy of activation (∆Ha) of Rubisco kinetics between higher plants and other photosynthetic groups, although photosynthetic bacteria and algae were under-represented and very few species have been investigated so far. Within plants, the variation in Rubisco temperature responses was related to species’ climate and photosynthetic mechanism, with differences in ∆Ha for kcatc among C3 plants from cool and warm environments, and in ∆Ha for kcatc and Kc among C3 and C4 plants. A negative correlation was observed among ∆Ha for Sc/o and species’ growth temperature for all data pooled, supporting the convergent adjustment of the temperature sensitivity of Rubisco kinetics to species’ thermal history. Simulations of the influence of varying temperature dependences of Rubisco kinetics on Rubisco-limited photosynthesis suggested improved photosynthetic performance of C3 plants from cool habitats at lower temperatures, and C3 plants from warm habitats at higher temperatures, especially at higher CO2 concentration. Thus, variation in Rubisco kinetics for different groups of photosynthetic organisms might need consideration to improve prediction of photosynthesis in future climates. Comparisons between in vitro and in vivo data revealed common trends, but also highlighted a large variability among both types of Rubisco kinetics currently used to simulate photosynthesis, emphasizing the need for more experimental work to fill in the gaps in Rubisco datasets and improve scaling from enzyme kinetics to

  19. Tree Species with Photosynthetic Stems Have Greater Nighttime Sap Flux

    Directory of Open Access Journals (Sweden)

    Xia Chen

    2018-01-01

    Full Text Available An increasing body of evidence has shown that nighttime sap flux occurs in most plants, but the physiological implications and regulatory mechanism are poorly known. The significance of corticular photosynthesis has received much attention during the last decade, however, the knowledge of the relationship between corticular photosynthesis and nocturnal stem sap flow is limited at present. In this study, we divided seven tree species into two groups according to different photosynthetic capabilities: trees of species with (Castanopsis hystrix, Michelia macclurei, Eucalyptus citriodora, and Eucalyptus grandis × urophylla and without (Castanopsis fissa, Schima superba, and Acacia auriculiformis photosynthetic stems, and the sap flux (Js and chlorophyll fluorescence parameters for these species were measured. One-way ANOVA analysis showed that the Fv/Fm (Maximum photochemical quantum yield of PSII and ΦPSII (effective photochemical quantum yield of PSII values were lower in non-photosynthetic stem species compared to photosynthetic stem species. The linear regression analysis showed that Js,d (daytime sap flux and Js,n (nighttime sap flux of non-photosynthetic stem species was 87.7 and 60.9% of the stem photosynthetic species. Furthermore, for a given daytime transpiration water loss, total nighttime sap flux was higher in species with photosynthetic stems (SlopeSMA = 2.680 than in non-photosynthetic stems species (SlopeSMA = 1.943. These results mean that stem corticular photosynthesis has a possible effect on the nighttime water flow, highlighting the important eco-physiological relationship between nighttime sap flux and corticular photosynthesis.

  20. Tree Species with Photosynthetic Stems Have Greater Nighttime Sap Flux.

    Science.gov (United States)

    Chen, Xia; Gao, Jianguo; Zhao, Ping; McCarthy, Heather R; Zhu, Liwei; Ni, Guangyan; Ouyang, Lei

    2018-01-01

    An increasing body of evidence has shown that nighttime sap flux occurs in most plants, but the physiological implications and regulatory mechanism are poorly known. The significance of corticular photosynthesis has received much attention during the last decade, however, the knowledge of the relationship between corticular photosynthesis and nocturnal stem sap flow is limited at present. In this study, we divided seven tree species into two groups according to different photosynthetic capabilities: trees of species with ( Castanopsis hystrix, Michelia macclurei, Eucalyptus citriodora , and Eucalyptus grandis × urophylla ) and without ( Castanopsis fissa, Schima superba , and Acacia auriculiformis ) photosynthetic stems, and the sap flux ( J s ) and chlorophyll fluorescence parameters for these species were measured. One-way ANOVA analysis showed that the F v / F m (Maximum photochemical quantum yield of PSII) and Φ PSII (effective photochemical quantum yield of PSII) values were lower in non-photosynthetic stem species compared to photosynthetic stem species. The linear regression analysis showed that J s,d (daytime sap flux) and J s,n (nighttime sap flux) of non-photosynthetic stem species was 87.7 and 60.9% of the stem photosynthetic species. Furthermore, for a given daytime transpiration water loss, total nighttime sap flux was higher in species with photosynthetic stems (Slope SMA = 2.680) than in non-photosynthetic stems species (Slope SMA = 1.943). These results mean that stem corticular photosynthesis has a possible effect on the nighttime water flow, highlighting the important eco-physiological relationship between nighttime sap flux and corticular photosynthesis.

  1. Tree Species with Photosynthetic Stems Have Greater Nighttime Sap Flux

    Science.gov (United States)

    Chen, Xia; Gao, Jianguo; Zhao, Ping; McCarthy, Heather R.; Zhu, Liwei; Ni, Guangyan; Ouyang, Lei

    2018-01-01

    An increasing body of evidence has shown that nighttime sap flux occurs in most plants, but the physiological implications and regulatory mechanism are poorly known. The significance of corticular photosynthesis has received much attention during the last decade, however, the knowledge of the relationship between corticular photosynthesis and nocturnal stem sap flow is limited at present. In this study, we divided seven tree species into two groups according to different photosynthetic capabilities: trees of species with (Castanopsis hystrix, Michelia macclurei, Eucalyptus citriodora, and Eucalyptus grandis × urophylla) and without (Castanopsis fissa, Schima superba, and Acacia auriculiformis) photosynthetic stems, and the sap flux (Js) and chlorophyll fluorescence parameters for these species were measured. One-way ANOVA analysis showed that the Fv/Fm (Maximum photochemical quantum yield of PSII) and ΦPSII (effective photochemical quantum yield of PSII) values were lower in non-photosynthetic stem species compared to photosynthetic stem species. The linear regression analysis showed that Js,d (daytime sap flux) and Js,n (nighttime sap flux) of non-photosynthetic stem species was 87.7 and 60.9% of the stem photosynthetic species. Furthermore, for a given daytime transpiration water loss, total nighttime sap flux was higher in species with photosynthetic stems (SlopeSMA = 2.680) than in non-photosynthetic stems species (SlopeSMA = 1.943). These results mean that stem corticular photosynthesis has a possible effect on the nighttime water flow, highlighting the important eco-physiological relationship between nighttime sap flux and corticular photosynthesis. PMID:29416547

  2. BOREAS TE-9 NSA Photosynthetic Response Data

    Science.gov (United States)

    Hall, Forrest G.; Curd, Shelaine (Editor); Dang, Qinglai; Margolis, Hank; Coyea, Marie

    2000-01-01

    The Boreal Ecosystem-Atmospheric Study (BOREAS) TE-9 (Terrestrial Ecology) team collected several data sets related to chemical and photosynthetic properties of leaves. This data set describes: (1) the response of leaf and shoot-level photosynthesis to ambient and intercellular CO2 concentration, temperature, and incident photosynthetically active radiation (PAR) for black spruce, jack pine, and aspen during the three intensive field campaigns (IFCs) in 1994 in the Northern Study Area (NSA); (2) the response of stomatal conductance to vapor pressure difference throughout the growing season of 1994; and (3) a range of shoot water potentials (controlled in the laboratory) for black spruce and jack pine. The data are stored in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  3. How well do growing season dynamics of photosynthetic capacity correlate with leaf biochemistry and climate fluctuations?

    Science.gov (United States)

    Way, Danielle A; Stinziano, Joseph R; Berghoff, Henry; Oren, Ram

    2017-07-01

    Accurate values of photosynthetic capacity are needed in Earth System Models to predict gross primary productivity. Seasonal changes in photosynthetic capacity in these models are primarily driven by temperature, but recent work has suggested that photoperiod may be a better predictor of seasonal photosynthetic capacity. Using field-grown kudzu (Pueraria lobata (Willd.) Ohwi), a nitrogen-fixing vine species, we took weekly measurements of photosynthetic capacity, leaf nitrogen, and pigment and photosynthetic protein concentrations and correlated these with temperature, irradiance and photoperiod over the growing season. Photosynthetic capacity was more strongly correlated with photoperiod than with temperature or daily irradiance, while the growing season pattern in photosynthetic capacity was uncoupled from changes in leaf nitrogen, chlorophyll and Rubisco. Daily estimates of the maximum carboxylation rate of Rubisco (Vcmax) based on either photoperiod or temperature were correlated in a non-linear manner, but Vcmax estimates from both approaches that also accounted for diurnal temperature fluctuations were similar, indicating that differences between these models depend on the relevant time step. We advocate for considering photoperiod, and not just temperature, when estimating photosynthetic capacity across the year, particularly as climate change alters temperatures but not photoperiod. We also caution that the use of leaf biochemical traits as proxies for estimating photosynthetic capacity may be unreliable when the underlying relationships between proxy leaf traits and photosynthetic capacity are established outside of a seasonal framework. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  4. Development of a new fast shower maximum detector based on microchannel plates photomultipliers (MCP-PMT) as an active element

    Energy Technology Data Exchange (ETDEWEB)

    Ronzhin, A., E-mail: ronzhin@fnal.gov [Fermilab, Batavia, IL 60510 (United States); Los, S.; Ramberg, E. [Fermilab, Batavia, IL 60510 (United States); Spiropulu, M.; Apresyan, A.; Xie, S. [California Institute of Technology, Pasadena, CA (United States); Kim, H. [University of Chicago, Chicago, IL 60637 (United States); Zatserklyaniy, A. [University of California, Santa Cruz, CA (United States)

    2014-09-21

    One possibility to make a fast and radiation resistant shower maximum (SM) detector is to use a secondary emitter as an active element. We present below test beam results, obtained with different types of photodetectors based on microchannel plates (MCPs) as the secondary emitter. We performed the measurements at the Fermilab Test Beam Facility with 120 GeV proton beam and 12 GeV and 32 GeV secondary beams. The goal of the measurement with 120 GeV protons was to determine time resolution for minimum ionizing particles (MIPs). The SM time resolution we obtained for this new type of detector is at the level of 20–30 ps. We estimate that a significant contribution to the detector response originates from secondary emission of the MCP. This work can be considered as the first step in building a new type of calorimeter based on this principle.

  5. A Global Data Set of Leaf Photosynthetic Rates, Leaf N and P, and Specific Leaf Area

    Data.gov (United States)

    National Aeronautics and Space Administration — This global data set of photosynthetic rates and leaf nutrient traits was compiled from a comprehensive literature review. It includes estimates of Vcmax (maximum...

  6. A long-term time series of global and diffuse photosynthetically active radiation in the Mediterranean: interannual variability and cloud effects

    Directory of Open Access Journals (Sweden)

    P. Trisolino

    2018-06-01

    Full Text Available Measurements of global and diffuse photosynthetically active radiation (PAR have been carried out on the island of Lampedusa, in the central Mediterranean Sea, since 2002. PAR is derived from observations made with multi-filter rotating shadowband radiometers (MFRSRs by comparison with a freshly calibrated PAR sensor and by relying on the on-site Langley plots. In this way, a long-term calibrated record covering the period 2002–2016 is obtained and is presented in this work. The monthly mean global PAR peaks in June, with about 160 W m−2, while the diffuse PAR reaches 60 W m−2 in spring or summer. The global PAR displays a clear annual cycle with a semi amplitude of about 52 W m−2. The diffuse PAR annual cycle has a semi amplitude of about 12 W m−2. A simple method to retrieve the cloud-free PAR global and diffuse irradiances in days characterized by partly cloudy conditions has been implemented and applied to the dataset. This method allows retrieval of the cloud-free evolution of PAR and calculation of the cloud radiative effect, CRE, for downwelling PAR. The cloud-free monthly mean global PAR reaches 175 W m−2 in summer, while the diffuse PAR peaks at about 40 W m−2. The cloud radiative effect, CRE, on global and diffuse PAR is calculated as the difference between all-sky and cloud-free measurements. The annual average CRE is about −14.7 W m−2 for the global PAR and +8.1 W m−2 for the diffuse PAR. The smallest CRE is observed in July, due to the high cloud-free condition frequency. Maxima (negative for the global, and positive for the diffuse component occur in March–April and in October, due to the combination of elevated PAR irradiances and high occurrence of cloudy conditions. Summer clouds appear to be characterized by a low frequency of occurrence, low altitude, and low optical thickness, possibly linked to the peculiar marine boundary layer structure. These properties also contribute

  7. The stereochemistry of chlorophyll-c₃ from the haptophyte Emiliania huxleyi: the (13²R)-enantiomers of chlorophylls-c are exclusively selected as the photosynthetically active pigments in chromophyte algae.

    Science.gov (United States)

    Mizoguchi, Tadashi; Kimura, Yuki; Yoshitomi, Taichi; Tamiaki, Hitoshi

    2011-11-01

    Chlorophyll(Chl)-c pigments in algae, diatoms and some prokaryotes are characterized by the fully conjugated porphyrin π-system as well as the acrylate residue at the 17-position. The precise structural characterization of Chl-c(3) from the haptophyte Emiliania huxleyi was performed. The conformations of the π-conjugated peripheral substituents, the 3-/8-vinyl, 7-methoxycarbonyl and 17-acrylate moieties were evaluated, in a solution, using nuclear Overhauser enhancement correlations and molecular modeling calculations. The rotation of the 17-acrylate residue was considerably restricted, whereas the other three substituents readily rotated at ambient temperature. Moreover, the stereochemistry at the 13²-position was determined by combination of chiral high-performance liquid chromatography (HPLC) with circular dichroism (CD) spectroscopy. Compared with the CD spectra of the structurally related, synthetic (13²R)- and (13²S)-protochlorophyllide(PChlide)-a, naturally occurring Chl-c₃ had exclusively the (13²R)-configuration. To elucidate this natural selection of a single enantiomer, we analyzed the three major Chl-c pigments (Chl-c₁, c₂ and c₃) in four phylogenetically distinct classes of Chl-c containing algae, i.e., heterokontophyta, dinophyta, cryptophyta and haptophyta using chiral HPLC. All the photosynthetic organisms contained only the (13²R)-enantiomerically pure Chls-c, and lacked the corresponding enantiomeric (13²S)-forms. Additionally, Chl-c₂ was found in all the organisms as the common Chl-c. These results throw a light on the biosynthesis as well as photosynthetic function of Chl-c pigments: Chl-c₂ is derived from 8-vinyl-PChlide-a by dehydrogenation of the 17-propionate to acrylate residues as generally proposed, and the (13²R)-enantiomers of Chls-c function as photosynthetically active, light-harvesting pigments together with the principal Chl-a and carotenoids. 2011 Elsevier B.V. All rights reserved.

  8. Superradiance Transition and Nonphotochemical Quenching in Photosynthetic Complexes

    Energy Technology Data Exchange (ETDEWEB)

    Berman, Gennady Petrovich [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Nesterov, Alexander [Universidad de Guadalajara, Departamento de Fısica, Jalisco (Mexico); Lopez, Gustavo [Universidad de Guadalajara, Departamento de Fısica, Jalisco (Mexico); Sayre, Richard Thomas [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-04-23

    Photosynthetic organisms have evolved protective strategies to allow them to survive in cases of intense sunlight fluctuation with the development of nonphotochemical quenching (NPQ). This process allows light harvesting complexes to transfer the excess sunlight energy to non-damaging quenching channels. This report compares the NPQ process with the superradiance transition (ST). We demonstrated that the maximum of the NPQ efficiency is caused by the ST to the sink associated with the CTS. However, experimental verifications are required in order to determine whether or not the NPQ regime is associated with the ST transition for real photosynthetic complexes. Indeed, it can happen that, in the photosynthetic apparatus, the NPQ regime occurs in the “non-optimal” region of parameters, and it could be independent of the ST.

  9. Social networks, leisure activities and maximum tongue pressure: cross-sectional associations in the Nagasaki Islands Study.

    Science.gov (United States)

    Nagayoshi, Mako; Higashi, Miho; Takamura, Noboru; Tamai, Mami; Koyamatsu, Jun; Yamanashi, Hirotomo; Kadota, Koichiro; Sato, Shimpei; Kawashiri, Shin-Ya; Koyama, Zenya; Saito, Toshiyuki; Maeda, Takahiro

    2017-12-06

    Social environment is often associated with health outcomes, but epidemiological evidence for its effect on oral frailty, a potential risk factor for aspiration, is sparse. This study aimed to assess the association between social environment and tongue pressure, as an important measure of oral function. The study focused on family structure, social networks both with and beyond neighbours, and participation in leisure activities. A population-based cross-sectional study. Annual health check-ups in a rural community in Japan. A total of 1982 participants, all over 40 years old. Anyone with missing data for the main outcome (n=14) was excluded. Tongue pressure was measured three times, and the maximum tongue pressure was used for analysis. A multivariable adjusted regression model was used to calculate parameter estimates (B) for tongue pressure. Having a social network involving neighbours (B=2.43, P=0.0001) and taking part in leisure activities (B=1.58, P=0.005) were independently associated with higher tongue pressure, but there was no link with social networks beyond neighbours (B=0.23, P=0.77). Sex-specific analyses showed that for men, having a partner was associated with higher tongue pressure, independent of the number of people in the household (B=2.26, P=0.01), but there was no association among women (B=-0.24, P=0.72; P-interaction=0.059). Having a social network involving neighbours and taking part in leisure activities were independently associated with higher tongue pressure. Marital status may be an important factor in higher tongue pressure in men. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

  10. Climate controls photosynthetic capacity more than leaf nitrogen contents

    Science.gov (United States)

    Ali, A. A.; Xu, C.; McDowell, N. G.

    2013-12-01

    Global vegetation models continue to lack the ability to make reliable predictions because the photosynthetic capacity varies a lot with growth conditions, season and among species. It is likely that vegetation models link photosynthetic capacity to concurrent changes in leaf nitrogen content only. To improve the predictions of the vegetation models, there is an urgent need to review species growth conditions and their seasonal response to changing climate. We sampled the global distribution of the Vcmax (maximum carboxylation rates) data of various species across different environmental gradients from the literature and standardized its value to 25 degree Celcius. We found that species explained the largest variation in (1) the photosynthetic capacity and (2) the proportion of nitrogen allocated for rubisco (PNcb). Surprisingly, climate variables explained more variations in photosynthetic capacity as well as PNcb than leaf nitrogen content and/or specific leaf area. The chief climate variables that explain variation in photosynthesis and PNcb were radiation, temperature and daylength. Our analysis suggests that species have the greatest control over photosynthesis and PNcb. Further, compared to leaf nitrogen content and/or specific leaf area, climate variables have more control over photosynthesis and PNcb. Therefore, climate variables should be incorporated in the global vegetation models when making predictions about the photosynthetic capacity.

  11. Physiological and photosynthetic response of quinoa to drought stress

    Directory of Open Access Journals (Sweden)

    Rachid Fghire

    2015-06-01

    Full Text Available Water shortage is a critical problem touching plant growth and yield in semi-arid areas, for instance the Mediterranean región. For this reason was studied the physiological basis of drought tolerance of a new, drought tolerant crop quinoa (Chenopodium quinoa Willd. tested in Morocco in two successive seasons, subject to four irrigation treatments (100, 50, and 33%ETc, and rainfed. The chlorophyll a fluorescence transients were analyzed by the JIP-test to transíate stress-induced damage in these transients to changes in biophysical parameter's allowing quantification of the energy flow through the photosynthetic apparatus. Drought stress induced a significant decrease in the maximum quantum yield of primary photochemistry (Φpo = Fv/Fm, and the quantum yield of electron transport (Φeo. The amount of active Photosystem II (PSII reaction centers (RC per excited cross section (RC/CS also decreased when exposed to the highest drought stress. The effective antenna size of active RCs (ABS/RC increased and the effective dissipation per active reaction centers (DIo/RC increased by increasing drought stress during the growth season in comparison to the control. However the performance index (PI, was a very sensitive indicator of the physiological status of plants. Leaf area index, leaf water potential and stomatal conductance decreased as the drought increased. These results indicate that, in quinoa leaf, JIP-test can be used as a sensitive method for measuring drought stress effects.

  12. The regulation of starch accumulation in Panicum maximum Jacq ...

    African Journals Online (AJOL)

    ... decrease the starch level. These observations are discussed in relation to the photosynthetic characteristics of P. maximum. Keywords: accumulation; botany; carbon assimilation; co2 fixation; growth conditions; mesophyll; metabolites; nitrogen; nitrogen levels; nitrogen supply; panicum maximum; plant physiology; starch; ...

  13. Special issue of photosynthetic research

    NARCIS (Netherlands)

    Okamura, M.; Wraight, C.A.; van Grondelle, R.

    2014-01-01

    This Special Issue of Photosynthesis Research honors Louis M. N. Duysens, Roderick K. Clayton, and George Feher, three pioneering researchers whose work on bacterial photosynthesis laid much of the groundwork for our understanding of the role of the reaction center in photosynthetic light energy

  14. Photoprotection by carotenoids of Plantago media photosynthetic apparatus in natural conditions.

    Science.gov (United States)

    Golovko, Tamara; Dymova, Olga; Zakhozhiy, Ilya; Dalke, Igor; Tabalenkova, Galina

    2012-01-01

    The study of daily changes in photosynthetic rate, of energy used in photochemical and non-photochemical processes, and of carotenoid composition aimed at evaluating the role of xanthophyll cycle (XC) in protection of hoary plantain plants (Plantago media) in nature. The leaves of sun plants differed from shade plants in terms of CO(2) exchange rate and photosynthetic pigments content. The total pool XC pigments and the conversion state increased from morning to midday in sun plants. An increase in zeaxanthin content occurred concomitantly with the violaxanthin decrease. About 80% violaxanthin was involved in conversion. The maximum of zeaxanthin in XC pigments pool was 60%. The conversion state of XC was twice as lower in shade plants than that in sun plants. The photosynthesis of sun leaves was depressed strongly at midday, but changes of maximum quantum yield of PS2 (F(v)/F(m)) were not apparent at that time. The coefficient qN (non-photochemical quenching) in the sun leaves changed strongly, from 0.3 to 0.9 as irradiance increased. The direct relation between heat dissipation and the conversion state of XC in plantain leaves was revealed. Thus, plantain leaves were found to be resistant to excess solar radiation due to activation of qN mechanisms associated with the XC de-epoxidation.

  15. Terrestrial biosphere models underestimate photosynthetic capacity and CO2 assimilation in the Arctic.

    Science.gov (United States)

    Rogers, Alistair; Serbin, Shawn P; Ely, Kim S; Sloan, Victoria L; Wullschleger, Stan D

    2017-12-01

    Terrestrial biosphere models (TBMs) are highly sensitive to model representation of photosynthesis, in particular the parameters maximum carboxylation rate and maximum electron transport rate at 25°C (V c,max.25 and J max.25 , respectively). Many TBMs do not include representation of Arctic plants, and those that do rely on understanding and parameterization from temperate species. We measured photosynthetic CO 2 response curves and leaf nitrogen (N) content in species representing the dominant vascular plant functional types found on the coastal tundra near Barrow, Alaska. The activation energies associated with the temperature response functions of V c,max and J max were 17% lower than commonly used values. When scaled to 25°C, V c,max.25 and J max.25 were two- to five-fold higher than the values used to parameterize current TBMs. This high photosynthetic capacity was attributable to a high leaf N content and the high fraction of N invested in Rubisco. Leaf-level modeling demonstrated that current parameterization of TBMs resulted in a two-fold underestimation of the capacity for leaf-level CO 2 assimilation in Arctic vegetation. This study highlights the poor representation of Arctic photosynthesis in TBMs, and provides the critical data necessary to improve our ability to project the response of the Arctic to global environmental change. No claim to original US Government works. New Phytologist © 2017 New Phytologist Trust.

  16. Photosynthetic characteristics of Lycoris aurea and monthly ...

    African Journals Online (AJOL)

    The leaf photosynthetic characteristics of Lycoris aurea, the monthly dynamics in lycorine and galantamine contents in its bulb and the correlation among the photosynthetic characteristics and the lycorine and galantamine during the annual growth period were studied by using LI-6400 portable photosynthetic measurement ...

  17. Application of heat stress in situ demonstrates a protective role of irradiation on photosynthetic performance in alpine plants.

    Science.gov (United States)

    Buchner, Othmar; Stoll, Magdalena; Karadar, Matthias; Kranner, Ilse; Neuner, Gilbert

    2015-04-01

    The impact of sublethal heat on photosynthetic performance, photosynthetic pigments and free radical scavenging activity was examined in three high mountain species, Rhododendron ferrugineum, Senecio incanus and Ranunculus glacialis using controlled in situ applications of heat stress, both in darkness and under natural solar irradiation. Heat treatments applied in the dark reversibly reduced photosynthetic performance and the maximum quantum efficiency of photosystem II (Fv /Fm), which remained impeded for several days when plants were exposed to natural light conditions subsequently to the heat treatment. In contrast, plants exposed to heat stress under natural irradiation were able to tolerate and recover from heat stress more readily. The critical temperature threshold for chlorophyll fluorescence was higher under illumination (Tc (')) than in the dark (Tc). Heat stress caused a significant de-epoxidation of the xanthophyll cycle pigments both in the light and in the dark conditions. Total free radical scavenging activity was highest when heat stress was applied in the dark. This study demonstrates that, in the European Alps, heat waves can temporarily have a negative impact on photosynthesis and, importantly, that results obtained from experiments performed in darkness and/or on detached plant material may not reliably predict the impact of heat stress under field conditions. © 2014 The Authors. Plant, Cell & Environment published by John Wiley & Sons Ltd.

  18. Changes in photosynthetic performance and antioxidative strategies during maturation of Norway maple (Acer platanoides L.) leaves.

    Science.gov (United States)

    Lepeduš, Hrvoje; Gaća, Vlatka; Viljevac, Marija; Kovač, Spomenka; Fulgosi, Hrvoje; Simić, Domagoj; Jurković, Vlatka; Cesar, Vera

    2011-04-01

    Different structural and functional changes take place during leaf development. Since some of them are highly connected to oxidative metabolism, regulation of reactive oxygen species (ROS) abundance is required. Most of the reactive oxygen species ROS in plant cells are produced in chloroplasts as a result of highly energetic reactions of photosynthesis. The aim of our study was to examine the changes in concentration of oxidative stress parameters (TBARS - thiobarbituric acid-reacting substances and protein carbonyls) as well as antioxidative strategies during development of maple (Acer platanoides L.) leaves in the light of their enhanced photosynthetic performance. We reveal that biogenesis of the photosynthetic apparatus during maple leaf maturation corresponded with oxidative damage of lipids, but not proteins. In addition, antioxidative responses in young leaves differed from that in older leaves. Young leaves had high values of non-photochemical quenching (NPQ) and catalase (CAT, EC 1.11.1.6) activity which declined during the maturation process. Developing leaves were characterized by an increase in TBARS level, the content of non-enzymatic antioxidants as well as ascorbate peroxidase activity (APX, EC 1.11.1.11), while the content of protein carbonyls decreased with leaf maturation. Fully developed leaves had the highest lipid peroxidation level accompanied by a maximum in ascorbic acid content and superoxide dismutase activity (SOD, EC1.15.1.1). These observations imply completely different antioxidative strategies during leaf maturation enabling them to perform their basic function. Copyright © 2011 Elsevier Masson SAS. All rights reserved.

  19. Bioaccumulation and effect of cadmium in the photosynthetic apparatus of Prosopis juliflora

    Directory of Open Access Journals (Sweden)

    Claudia Yared Michel-López

    2016-10-01

    Full Text Available In the present study Prosopis juliflora plants grown in hydroponics solution were exposed to 50,100 and 1000 μM CdCl2. The cadmium uptake, transport and toxicity on the photosynthetic activities in the plants were measured at 48 h after starting cadmium treatments. The results showed that the concentration of Cd2+ in P. juliflora tended to increase with addition of Cd2+ to hydroponics solution. However, the increase of Cd2+ in roots and leaves varied largely. In this sense, the accumulation of Cd2+ in P. juliflora roots increased significantly in proportion with the addition of this metal. In contrast a relatively low level of Cd2+ transportation index, and bioaccumulation factor were found in P. juliflora at 48 h after of treatments. On the other hand the maximum photochemical efficiency of photosystem II (Fv/Fm and the activity of photosystem II (Fv/Fo ratios in P. juliflora leaf treated with Cd2+ not showed significantly changes during the experiment. These results suggested that the photosynthetic apparatus of P. juliflora was not the primary target of the Cd2+ action. Further studies will be focused in understanding the participation of the root system in Prosopis plants with the rhizosphere activation and root adsorption to soil Cd2+ under natural conditions.

  20. Sustained photosynthetic performance of Coffea spp. under long-term enhanced [CO2].

    Directory of Open Access Journals (Sweden)

    José C Ramalho

    Full Text Available Coffee is one of the world's most traded agricultural products. Modeling studies have predicted that climate change will have a strong impact on the suitability of current cultivation areas, but these studies have not anticipated possible mitigating effects of the elevated atmospheric [CO2] because no information exists for the coffee plant. Potted plants from two genotypes of Coffea arabica and one of C. canephora were grown under controlled conditions of irradiance (800 μmol m(-2 s(-1, RH (75% and 380 or 700 μL CO2 L(-1 for 1 year, without water, nutrient or root development restrictions. In all genotypes, the high [CO2] treatment promoted opposite trends for stomatal density and size, which decreased and increased, respectively. Regardless of the genotype or the growth [CO2], the net rate of CO2 assimilation increased (34-49% when measured at 700 than at 380 μL CO2 L(-1. This result, together with the almost unchanged stomatal conductance, led to an instantaneous water use efficiency increase. The results also showed a reinforcement of photosynthetic (and respiratory components, namely thylakoid electron transport and the activities of RuBisCo, ribulose 5-phosphate kinase, malate dehydrogenase and pyruvate kinase, what may have contributed to the enhancements in the maximum rates of electron transport, carboxylation and photosynthetic capacity under elevated [CO2], although these responses were genotype dependent. The photosystem II efficiency, energy driven to photochemical events, non-structural carbohydrates, photosynthetic pigment and membrane permeability did not respond to [CO2] supply. Some alterations in total fatty acid content and the unsaturation level of the chloroplast membranes were noted but, apparently, did not affect photosynthetic functioning. Despite some differences among the genotypes, no clear species-dependent responses to elevated [CO2] were observed. Overall, as no apparent sign of photosynthetic down

  1. Sustained Photosynthetic Performance of Coffea spp. under Long-Term Enhanced [CO2

    Science.gov (United States)

    Ramalho, José C.; Rodrigues, Ana P.; Semedo, José N.; Pais, Isabel P.; Martins, Lima D.; Simões-Costa, Maria C.; Leitão, António E.; Fortunato, Ana S.; Batista-Santos, Paula; Palos, Isabel M.; Tomaz, Marcelo A.; Scotti-Campos, Paula; Lidon, Fernando C.; DaMatta, Fábio M.

    2013-01-01

    Coffee is one of the world’s most traded agricultural products. Modeling studies have predicted that climate change will have a strong impact on the suitability of current cultivation areas, but these studies have not anticipated possible mitigating effects of the elevated atmospheric [CO2] because no information exists for the coffee plant. Potted plants from two genotypes of Coffea arabica and one of C. canephora were grown under controlled conditions of irradiance (800 μmol m-2 s-1), RH (75%) and 380 or 700 μL CO2 L-1 for 1 year, without water, nutrient or root development restrictions. In all genotypes, the high [CO2] treatment promoted opposite trends for stomatal density and size, which decreased and increased, respectively. Regardless of the genotype or the growth [CO2], the net rate of CO2 assimilation increased (34-49%) when measured at 700 than at 380 μL CO2 L-1. This result, together with the almost unchanged stomatal conductance, led to an instantaneous water use efficiency increase. The results also showed a reinforcement of photosynthetic (and respiratory) components, namely thylakoid electron transport and the activities of RuBisCo, ribulose 5-phosphate kinase, malate dehydrogenase and pyruvate kinase, what may have contributed to the enhancements in the maximum rates of electron transport, carboxylation and photosynthetic capacity under elevated [CO2], although these responses were genotype dependent. The photosystem II efficiency, energy driven to photochemical events, non-structural carbohydrates, photosynthetic pigment and membrane permeability did not respond to [CO2] supply. Some alterations in total fatty acid content and the unsaturation level of the chloroplast membranes were noted but, apparently, did not affect photosynthetic functioning. Despite some differences among the genotypes, no clear species-dependent responses to elevated [CO2] were observed. Overall, as no apparent sign of photosynthetic down-regulation was found, our data

  2. Respiratory processes in non-photosynthetic plastids

    Science.gov (United States)

    Renato, Marta; Boronat, Albert; Azcón-Bieto, Joaquín

    2015-01-01

    Chlororespiration is a respiratory process located in chloroplast thylakoids which consists in an electron transport chain from NAD(P)H to oxygen. This respiratory chain involves the NAD(P)H dehydrogenase complex, the plastoquinone pool and the plastid terminal oxidase (PTOX), and it probably acts as a safety valve to prevent the over-reduction of the photosynthetic machinery in stress conditions. The existence of a similar respiratory activity in non-photosynthetic plastids has been less studied. Recently, it has been reported that tomato fruit chromoplasts present an oxygen consumption activity linked to ATP synthesis. Etioplasts and amyloplasts contain several electron carriers and some subunits of the ATP synthase, so they could harbor a similar respiratory process. This review provides an update on the study about respiratory processes in chromoplasts, identifying the major gaps that need to be addressed in future research. It also reviews the proteomic data of etioplasts and amyloplasts, which suggest the presence of a respiratory electron transport chain in these plastids. PMID:26236317

  3. Respiratory processes in non-photosynthetic plastids

    Directory of Open Access Journals (Sweden)

    Marta eRenato

    2015-07-01

    Full Text Available Chlororespiration is a respiratory process located in chloroplast thylakoids which consists in an electron transport chain from NAD(PH to oxygen. This respiratory chain involves the NAD(PH dehydrogenase complex, the plastoquinone pool and the plastid terminal oxidase (PTOX, and it probably acts as a safety valve to prevent the over-reduction of the photosynthetic machinery in stress conditions. The existence of a similar respiratory activity in non-photosynthetic plastids has been less studied. Recently, it has been reported that tomato fruit chromoplasts present an oxygen consumption activity linked to ATP synthesis. Etioplasts and amyloplasts contain several electron carriers and some subunits of the ATP synthase, so they could harbor a similar respiratory process. This review provides an update on the study about respiratory processes in chromoplasts, identifying the major gaps that need to be addressed in future research. It also reviews the proteomic data of etioplasts and amyloplasts, which suggest the presence of a respiratory electron transport chain in these plastids.

  4. Gaharu Leaf Extract Water Reduce MDA and 8-OHdG Levels and Increase Activities SOD and Catalase in Wistar Rats Provided Maximum Physical Activity

    Directory of Open Access Journals (Sweden)

    I Made Oka Adi Parwata

    2016-09-01

    Full Text Available Background: Oxidative stress occurs due to an imbalance of the number of free radicals by the number of endogenous antioxidant produced by the body i.e. Superoxide Dismutase (SOD, Gluthathione Peroxidase (GPx, and Catalase. The imbalance between the number of free radicals and antioxidants can be overcome with the endogenous antioxidant intake that exogenous oxidative stress can be reduced. One of exogenous antioxidants is natural Gaharu leaf water extract. Objective: This research focus on the effect of Gaharu leaf water extract in reducing MDA and 8-OHdG and increase the activity of SOD and Catalase. Methods: This study was an experimental with post only controls group design. Experiment was divided  into 5 groups of wistar rats, each consisting of 5 animals, i.e. negative control group without extract [K (-], treatment 1 treated 50 mg/kg BW/day of the extract (T1, treatment 2 treated 100 mg/kg BW/day of the extract (T2, treatment 3 treated 200 mg/ kg BW/day of the extract (T3, and positive control group [K (+] treated with vitamin Cat a dose 50 mg/kg BW/day. All groups treated for 10 weeks. Every day, before treatment, each group was given a maximum swimming activity for 1.5 hours for 10 weeks. ELISA was used to measure MDA, 8-OHdG, SOD, and Catalase activities. Result: The research results showed that treatment of extract of  leaves of Gaharu with an higher dose from 50 mg/kg BW up to 200 mg/ kg BW significantly decline (p <0.05 levels of MDA with the average ranging from 6.37±0.23, 5,56±0.27 and 4.32±0.27, 8-OHdG with a mean of 1.64±0.11, 1.26±0.46, and 1.09±0.17. On the other hand the treatment also increase SOD activity with less ranging from 12.15±1.04, 15.70±2.02, and 18.84±1.51, and Catalase ranging from 6,68±0.63, 8.20±1.14 and 9.29±0,79 in the blood of Wistar rats were given a maximum activity compared to the negative control group. This is probably higher phenol compounds (bioflavonoids quantity content of the extract

  5. Phytochromes in photosynthetically competent plants

    Energy Technology Data Exchange (ETDEWEB)

    Pratt, L.H.

    1990-07-01

    Plants utilize light as a source of information in photomorphogenesis and of free energy in photosynthesis, two processes that are interrelated in that the former serves to increase the efficiency with which plants can perform the latter. Only one pigment involved in photomorphogenesis has been identified unequivocally, namely phytochrome. The thrust of this proposal is to investigate this pigment and its mode(s) of action in photosynthetically competent plants. Our long term objective is to characterize phytochrome and its functions in photosynthetically competent plants from molecular, biochemical and cellular perspectives. It is anticipated that others will continue to contribute indirectly to these efforts at the physiological level. The ultimate goal will be to develop this information from a comparative perspective in order to learn whether the different phytochromes have significantly different physicochemical properties, whether they fulfill independent functions and if so what these different functions are, and how each of the different phytochromes acts at primary molecular and cellular levels.

  6. Salt stress-induced protein pattern associated with photosynthetic parameters and andrographolide content in Andrographis paniculata Nees.

    Science.gov (United States)

    Talei, Daryush; Valdiani, Alireza; Maziah, Mahmood; Sagineedu, Sreenivasa Rao; Abiri, Rambod

    2015-01-01

    Andrographis paniculata is a multifunctional medicinal plant and a potent source of bioactive compounds. Impact of environmental stresses such as salinity on protein diversification, as well as the consequent changes in the photosynthetic parameters and andrographolide content (AG) of the herb, has not yet been thoroughly investigated. The present study showed that the salinity affects the protein pattern, and subsequently, it decreased the photosynthetic parameters, protein content, total dry weight, and total crude extract. Exceptionally, the AG content was increased (p ≤ 0.01). Moreover, it was noticed that the salinity at 12 dS m(-1) led to the maximum increase in AG content in all accessions. Interestingly, the leaf protein analysis revealed that the two polymorphic protein bands as low- and medium-sized of 17 and 45 kDa acted as the activator agents for the photosynthetic parameters and AG content. Protein sequencing and proteomic analysis can be conducted based on the present findings in the future.

  7. Role of nitric oxide in cadmium-induced stress on growth, photosynthetic components and yield of Brassica napus L.

    Science.gov (United States)

    Jhanji, Shalini; Setia, R C; Kaur, Navjyot; Kaur, Parminder; Setia, Neelam

    2012-11-01

    Experiments were carried out to study the effect of cadmium (Cd) and exogenous nitric oxide (NO) on growth, photosynthetic attributes, yield components and structural features of Brassica napus L. (cv. GSL 1). Cadmium in the growth medium at different levels (1, 2 and 4 Mm) retarded plant growth viz. shoot (27%) and root (51%) length as compared to control. The accumulation of total dry matter and its partitioning to different plant parts was also reduced by 31% due to Cd toxicity. Photosynthetic parameters viz., leaf area plant(-1) (51%), total Chl (27%), Chl a / Chl b ratio (22%) and Hill reaction activity of chloroplasts (42%) were greatly reduced in Cd-treated plants. Cd treatments adversely affected various yield parameters viz., number of branches (23) and siliquae plant(-1) (246), seed number siliqua(-1) (10.3), 1000-seed weight (2.30g) and seed yield plant(-1) (7.09g). Different Cd treatments also suppressed the differentiation of various tissues like vessels in the root with a maximum inhibition caused by 4mM Cd. Exogenous application of nitric oxide (NO) improved the various morpho-physiological and photosynthetic parameters in control as well as Cd-treated plants.

  8. Effects of gibberellic acid on growth and photosynthetic pigments of ...

    African Journals Online (AJOL)

    The aim of this study was to improve growth performance by enhancing the photosynthetic pigments and enzyme carbonic anhydrase (CA) activity of Hibiscus sabdariffa L. (cv. Sabahia 17) under NaCl stress. Under non-saline condition, application of GA3 enhanced growth parameters (shoot length, shoot fresh weight (FW) ...

  9. Effect of ambient levels of ozone on photosynthetic components and ...

    African Journals Online (AJOL)

    Effect of ambient levels of ozone on photosynthetic components and radical scavenging system in leaves of African cowpea varieties. ... The O3-induced significant reduction in catalase activity was observed in Blackeye at vegetative and reproductive growth stages; and in Asontem at reproductive growth stage. On the other ...

  10. Simplified method of checking the observance of maximum permissible activity of waste forms to be placed in the Konrad shaft for final waste storage

    International Nuclear Information System (INIS)

    Berg, H.P.; Piefke, F.

    1986-10-01

    The requirements to be met by waste forms destined for final storage in the Konrad shaft among others define maximum permissible activity levels which have been determined from the various parts of the safety analyses. For waste forms with very low activity levels, it is suitable to compile all the very specific requirements in one checking list, and to perform the checking as simply as adequate. On the basis of the compilation of requirements defined for normal operation of the storage facility, hypothetical accidents, thermal loads affecting the host rock, and criticality safety, the maximum permissible activities are derived that are to be checked by the simplified control measures explained. The report explains the computer programs for the ANKONA code. (orig.) [de

  11. Detecting in-field variation in photosynthetic capacity of trangenically modifed plants with hyperspectral imaging.

    Science.gov (United States)

    Meacham, K.; Montes, C.; Pederson, T.; Wu, J.; Guan, K.; Bernacchi, C.

    2017-12-01

    Improved photosynthetic rates have been shown to increase crop biomass, making improved photosynthesis a focus for driving future grain yield increases. Improving the photosynthetic pathway offers opportunity to meet food demand, but requires high throughput measurement techniques to detect photosynthetic variation in natural accessions and transgenically modified plants. Gas exchange measurements are the most widely used method of measuring photosynthesis in field trials but this process is laborious and slow, and requires further modeling to estimate meaningful parameters and to upscale to the plot or canopy level. In field trials of tobacco with modifications made to the photosynthetic pathway, we infer the maximum carboxylation rate of Rubisco (Vcmax) and maximum electron transport rate (Jmax) and detect photosynthetic variation from hyperspectral imaging with a partial least squares regression technique. Ground-truth measurements from photosynthetic gas exchange, a full-range (400-2500nm) handheld spectroadiometer with leaf clip, hyperspectral indices, and extractions of leaf pigments support the model. The results from a range of wild-type cultivars and from genetically modified germplasm suggest that the opportunity for rapid selection of top performing genotypes from among thousands of plots. This research creates the opportunity to extend agroecosystem models from simplified "one-cultivar" generic parameterization to better represent a full suite of current and future crop cultivars for a wider range of environmental conditions.

  12. Interactions between heavy metals and photosynthetic materials studied by optical techniques.

    Science.gov (United States)

    Ventrella, Andrea; Catucci, Lucia; Piletska, Elena; Piletsky, Sergey; Agostiano, Angela

    2009-11-01

    In this work studies on rapid inhibitory interactions between heavy metals and photosynthetic materials at different organization levels were carried out by optical assay techniques, investigating the possibility of applications in the heavy metal detection field. Spinach chloroplasts, thylakoids and Photosystem II proteins were employed as biotools in combination with colorimetric assays based on dichlorophenol indophenole (DCIP) photoreduction and on fluorescence emission techniques. It was found that copper and mercury demonstrated a strong and rapid photosynthetic activity inhibition, that varied from proteins to membranes, while other metals like nickel, cobalt and manganese produced only slight inhibition effects on all tested photosynthetic materials. By emission measurements, only copper was found to rapidly influence the photosynthetic material signals. These findings give interesting information about the rapid effects of heavy metals on isolated photosynthetic samples, and are in addition to the literature data concerning the effects of growth in heavy metal enriched media.

  13. Effects of ultraviolet radiation (UVA+UVB) on young gametophytes of Gelidium floridanum: growth rate, photosynthetic pigments, carotenoids, photosynthetic performance, and ultrastructure.

    Science.gov (United States)

    Simioni, Carmen; Schmidt, Eder C; Felix, Marthiellen R de L; Polo, Luz Karime; Rover, Ticiane; Kreusch, Marianne; Pereira, Debora T; Chow, Fungyi; Ramlov, Fernanda; Maraschin, Marcelo; Bouzon, Zenilda L

    2014-01-01

    This study investigated the effects of radiation (PAR+UVA+UVB) on the development and growth rates (GRs) of young gametophytes of Gelidium floridanum. In addition, photosynthetic pigments were quantified, carotenoids identified, and photosynthetic performance assessed. Over a period of 3 days, young gametophytes were cultivated under laboratory conditions and exposed to photosynthetically active radiation (PAR) at 80 μmol photons m(-2) s(-1) and PAR+UVA (0.70 W m(-2))+UVB (0.35 W m(-2)) for 3 h per day. The samples were processed for light and electron microscopy to analyze the ultrastructure features, as well as carry out metabolic studies of GRs, quantify the content of photosynthetic pigments, identify carotenoids and assess photosynthetic performance. PAR+UVA+UVB promoted increase in cell wall thickness, accumulation of floridean starch grains in the cytoplasm and disruption of chloroplast internal organization. Algae exposed to PAR+UVA+UVB also showed a reduction in GR of 97%. Photosynthetic pigments, in particular, phycoerythrin and allophycocyanin contents, decreased significantly from UV radiation exposure. This result agrees with the decrease in photosynthetic performance observed after exposure to ultraviolet radiation, as measured by a decrease in the electron transport rate (ETR), where values of ETRmax declined approximately 44.71%. It can be concluded that radiation is a factor that affects the young gametophytes of G. floridanum at this stage of development. © 2014 The American Society of Photobiology.

  14. Oxyfluorfen toxic effect on S. obliquus evaluated by different photosynthetic and enzymatic biomarkers.

    Science.gov (United States)

    Geoffroy, L; Dewez, D; Vernet, G; Popovic, R

    2003-11-01

    The effect of oxyfluorfen was investigated when alga Scenedesmus obliquus has been exposed to different concentrations (7.5, 15, and 22.5 microg x L(-1)) at 12, 24, and 48 hours of exposure. Toxicity test was done by using 13 biomarkers concerning growth rate, chlorophyll content and indicators of photosynthetic and antioxidant enzyme activities. The change of the 13 parameters showed a great variation of sensitivity indicating differences in parameters' suitability to be used as biomarkers when alga culture was exposed to oxyfluorfen toxicity. The order of sensitivity between those biomarkers was: Antenna size (ABS/RC) > Chlorophyll content > Catalase (CAT) > Operational PSII quantum yield (phiS(PSII)) > Glutathione S-transferase (GST) > Functional plastoquinone pool (Q(PQ)) > Glutathione reductase (GR) > Growth rate > Nonphotochemical quenching (QN) > Proton gradient quenching (Q(Emax)) > Ascorbate peroxidase (APX) > Photochemical quenching (Q(p)) > Maximum PSII quantum yield (Phi(PSII)). The effect of oxyfluorfen on the changes of those parameters was interpreted as a result of herbicide mode of action at molecular level of alga cellular system. This study indicated for some photosynthetic and enzymatic biomarkers to be useful indicators of toxicity effect induced in non-target alga species. Determination of biomarkers' sensitivity order may facilitate their selection to be used in environmental risk assessment of polluted water.

  15. Abscisic Acid Induced Changes in Production of Primary and Secondary Metabolites, Photosynthetic Capacity, Antioxidant Capability, Antioxidant Enzymes and Lipoxygenase Inhibitory Activity of Orthosiphon stamineus Benth.

    Directory of Open Access Journals (Sweden)

    Mohd Hafiz Ibrahim

    2013-07-01

    Full Text Available An experiment was conducted to investigate and distinguish the relationships in the production of total phenolics, total flavonoids, soluble sugars, H2O2, O2−, phenylalanine ammonia lyase (PAL activity, leaf gas exchange, antioxidant activity, antioxidant enzyme activity [ascorbate peroxidase (APX, catalase (CAT, superoxide dismutase (SOD and Lipoxygenase inhibitory activity (LOX] under four levels of foliar abscisic acid (ABA application (0, 2, 4, 6 µM for 15 weeks in Orthosiphon stamineus Benth. It was found that the production of plant secondary metabolites, soluble sugars, antioxidant activity, PAL activity and LOX inhibitory activity was influenced by foliar application of ABA. As the concentration of ABA was increased from 0 to 6 µM the production of total phenolics, flavonoids, sucrose, H2O2, O2−, PAL activity and LOX inhibitory activity was enhanced. It was also observed that the antioxidant capabilities (DPPH and ORAC were increased. This was followed by increases in production of antioxidant enzymes APX, CAT and SOD. Under high application rates of ABA the net photosynthesis and stomatal conductance was found to be reduced. The production of primary and secondary metabolites displayed a significant positive relationship with H2O2 (total phenolics, r2 = 0.877; total flavonoids, r2 = 0.812; p ≤ 0.05 and O2− (total phenolics, r2 = 0.778; total flavonoids, r2 = 0.912; p ≤ 0.05. This indicated that increased oxidative stress at high application rates of ABA, improved the production of phytochemicals.

  16. Effect of CO2 enrichment and high photosynthetic photon flux densities (PPFD) on rubisco and PEP-case activities of in vitro cultured strawberry plants

    International Nuclear Information System (INIS)

    Desjardins, Y.; Beeson, R.; Gosselin, A.

    1989-01-01

    Standard growing conditions in vitro (low light and CO 2 ) are not conducive to autotrophy. An experiment was conducted to improve photosynthesis in vitro in the hope of increasing survival in acclimatization. A factorial experiment was elaborated where CO 2 and PPFD were supplied to in vitro cultured strawberry plants in the rooting stage. Activities of carboxylating enzymes were determined after 4 weeks of culture. The activities of non-activated and activated rubisco and PEP-Case were measured after extraction of the enzymes and a reaction with NaH 14 CO 3 followed by scintillation counting spectroscopy. High CO 2 concentration significantly increased net assimilation rates (NAR) by 165% over the control for both 1650 and 3000 ppm CO 2 . High PPFD only increased NAR by 12 and 35% for 150 and 250 μmol·m -2 ·s -1 respectively over the control. Plants grown at 3000 ppm CO 2 had the highest level of chlorophyll/g FW with 97% more than the control. The activity of PEP-Case was the highest at high light levels and high CO 2 with rates of 1.65 for 1650 ppm versus 1.22 mmol CO 2 mg -1 chl. h -1 at 250 μmol·m -2 ·s -1 . There was no difference in PEP activity at low light levels. The rubisco activity was lower at 1650 and 3000 ppm CO 2 . Increases in NAR correlate more closely to the PEP-Case than to Rubisco activity. Physiological significance of high activity of PEP-Case over rubisco will be discussed

  17. Leaf development and photosynthetic properties of three tropical tree species with delayed greening

    NARCIS (Netherlands)

    Cai, Z.Q.; Slot, M.; Fan, Z.X.

    2005-01-01

    Leaf developmental patterns were characterized for three tropical tree species with delayed greening. Changes in the pigment contents, photosynthetic capacity, stomata development, photosystem 2 efficiency, rate of energy dissipation, and the activity of partial protective enzymes were followed in

  18. Photosynthetic CO{sub 2} fixation and energy production - microalgae as a main subject

    Energy Technology Data Exchange (ETDEWEB)

    Asada, Yasuo [National Inst. of Bioscience and Human-Technology, Tsukuba-shi, Ibaraki-ken (Japan)

    1993-12-31

    Research activities for application of microalgal photosynthesis to CO{sub 2} fixation in Japan are overviewed. Presenter`s studies on energy (hydrogen gas) production by cyanobacteria (blue-green algae) and photosynthetic bacteria are also introduced.

  19. Rubisco mutants of Chlamydomonas reinhardtii enhance photosynthetic hydrogen production.

    Science.gov (United States)

    Pinto, T S; Malcata, F X; Arrabaça, J D; Silva, J M; Spreitzer, R J; Esquível, M G

    2013-06-01

    Molecular hydrogen (H2) is an ideal fuel characterized by high enthalpy change and lack of greenhouse effects. This biofuel can be released by microalgae via reduction of protons to molecular hydrogen catalyzed by hydrogenases. The main competitor for the reducing power required by the hydrogenases is the Calvin cycle, and rubisco plays a key role therein. Engineered Chlamydomonas with reduced rubisco levels, activity and stability was used as the basis of this research effort aimed at increasing hydrogen production. Biochemical monitoring in such metabolically engineered mutant cells proceeded in Tris/acetate/phosphate culture medium with S-depletion or repletion, both under hypoxia. Photosynthetic activity, maximum photochemical efficiency, chlorophyll and protein levels were all measured. In addition, expression of rubisco, hydrogenase, D1 and Lhcb were investigated, and H2 was quantified. At the beginning of the experiments, rubisco increased followed by intense degradation. Lhcb proteins exhibited monomeric isoforms during the first 24 to 48 h, and D1 displayed sensitivity under S-depletion. Rubisco mutants exhibited a significant decrease in O2 evolution compared with the control. Although the S-depleted medium was much more suitable than its complete counterpart for H2 production, hydrogen release was observed also in sealed S-repleted cultures of rubisco mutated cells under low-moderate light conditions. In particular, the rubisco mutant Y67A accounted for 10-15-fold higher hydrogen production than the wild type under the same conditions and also displayed divergent metabolic parameters. These results indicate that rubisco is a promising target for improving hydrogen production rates in engineered microalgae.

  20. Photosynthetic light reactions at the gold interface

    NARCIS (Netherlands)

    Kamran, Muhammad

    2014-01-01

    In the project described in this thesis we studied a simple bio-electronic device for solar energy conversion by surface-assembly of photosynthetic pigment-protein complexes on a bare gold-electrode. Optical excitation of the photosynthetic pigments gives rise to charge separation in the so-called

  1. Spatio-Temporal Convergence of Maximum Daily Light-Use Efficiency Based on Radiation Absorption by Canopy Chlorophyll

    Science.gov (United States)

    Zhang, Yao; Xiao, Xiangming; Wolf, Sebastian; Wu, Jin; Wu, Xiaocui; Gioli, Beniamino; Wohlfahrt, Georg; Cescatti, Alessandro; van der Tol, Christiaan; Zhou, Sha; Gough, Christopher M.; Gentine, Pierre; Zhang, Yongguang; Steinbrecher, Rainer; Ardö, Jonas

    2018-04-01

    Light-use efficiency (LUE), which quantifies the plants' efficiency in utilizing solar radiation for photosynthetic carbon fixation, is an important factor for gross primary production estimation. Here we use satellite-based solar-induced chlorophyll fluorescence as a proxy for photosynthetically active radiation absorbed by chlorophyll (APARchl) and derive an estimation of the fraction of APARchl (fPARchl) from four remotely sensed vegetation indicators. By comparing maximum LUE estimated at different scales from 127 eddy flux sites, we found that the maximum daily LUE based on PAR absorption by canopy chlorophyll (ɛmaxchl), unlike other expressions of LUE, tends to converge across biome types. The photosynthetic seasonality in tropical forests can also be tracked by the change of fPARchl, suggesting the corresponding ɛmaxchl to have less seasonal variation. This spatio-temporal convergence of LUE derived from fPARchl can be used to build simple but robust gross primary production models and to better constrain process-based models.

  2. Distribution of 14C-photosynthetate in the shoot of Vitis vinifera L. cv Cabernet Sauvignon: Pt. I

    International Nuclear Information System (INIS)

    Hunter, J.J.; Visser, J.H.

    1988-01-01

    The distribution of photosynthetates, originating in leaves of different parts of the shoot of Vitis vinifera L. cv Cabernet Sauvignon at berry set, pea size, veraison and ripeness stages, was investigated. Specific photosynthetic activity of the 14 CO 2 -treated leaves gradually decreased during the season. Photosynthetates were hoarded in the leaves at berry set, but were increasingly diverted to the bunches after that. The apical leaves displayed the highest photosynthesis. The leaves opposite and below the bunches accumulated very little photosynthetates, especially from veraison to ripeness. Redistribution of photosynthetates among the basal, middle and apical leaves was generally very restricted at all stages. Multidirectional distribution from the site of application of 14 CO 2 occurred at berry set stage, while from pea size to ripeness photosynthetates were mainly translocated basipetally. Highest accumulation in the bunches occurred at veraison, while the basal leaves were primarily used to nourish the bunch

  3. Effect of Pot Size on Various Characteristics Related to Photosynthetic Matter Production in Soybean Plants

    Directory of Open Access Journals (Sweden)

    Minobu Kasai

    2012-01-01

    Full Text Available Despite the wide uses of potted plants, information on how pot size affects plant photosynthetic matter production is still considerably limited. This study investigated with soybean plants how transplantation into larger pots affects various characteristics related to photosynthetic matter production. The transplantation was analyzed to increase leaf photosynthetic rate, transpiration rate, and stomatal conductance without affecting significantly leaf intercellular CO2 concentration, implicating that the transplantation induced equal increases in the rate of CO2 diffusion via leaf stomata and the rate of CO2 fixation in leaf photosynthetic cells. Analyses of Rubisco activity and contents of a substrate (ribulose-1,5-bisphosphate (RuBP for Rubisco and total protein in leaf suggested that an increase in leaf Rubisco activity, which is likely to result from an increase in leaf Rubisco content, could contribute to the transplantation-induced increase in leaf photosynthetic rate. Analyses of leaf major photosynthetic carbohydrates and dry weights of source and sink organs revealed that transplantation increased plant sink capacity that uses leaf starch, inducing a decrease in leaf starch content and an increase in whole plant growth, particularly, growth of sink organs. Previously, in the same soybean species, it was demonstrated that negative correlation exists between leaf starch content and photosynthetic rate and that accumulation of starch in leaf decreases the rate of CO2 diffusion within leaf. Thus, it was suggested that the transplantation-induced increase in plant sink capacity decreasing leaf starch content could cause the transplantation-induced increase in leaf photosynthetic rate by inducing an increase in the rate of CO2 diffusion within leaf and thereby substantiating an increase in leaf Rubisco activity in vivo. It was therefore concluded that transplantation of soybean plants into larger pots attempted in this study increased the

  4. Distribution of 14C-photosynthetate in the shoot of Vitis vinifera L. cv Cabernet Sauvignon: Pt. II

    International Nuclear Information System (INIS)

    Hunter, J.J.; Visser, J.H.

    1988-01-01

    The effect of partial defoliation of Vitis vinifera L. cv Cabernet Sauvignon on the distribution of photosynthetates, originating in leaves in different positions on the shoot at berry set, pea size, veraison and ripeness stages, was investigated. Partial defoliation (33% and 66%) resulted in a higher apparent photosynthetic effectivity for all the remaining leaves on the shoot. The pattern of distribution of photosynthetates would seem to stay the same between the defoliation treatments. The control vines were found to carry excess foliage. Optimal photosynthetic activity of all the leaves on the vine was therefore not reached

  5. Photosynthetic carbon assimilation in the coccolithophorid Emiliania huxleyi (Haptophyta): Evidence for the predominant operation of the c3 cycle and the contribution of {beta}-carboxylases to the active anaplerotic reaction.

    Science.gov (United States)

    Tsuji, Yoshinori; Suzuki, Iwane; Shiraiwa, Yoshihiro

    2009-02-01

    The coccolithophorid Emiliania huxleyi (Haptophyta) is a representative and unique marine phytoplankton species that fixes inorganic carbon by photosynthesis and calci-fication. We examined the initial process of photosynthetic carbon assimilation by analyses of metabolites, enzymes and genes. When the cells were incubated with a radioactive substrate (2.3 mM NaH(14)CO(3)) for 10 s under illumination, 70% of the (14)C was incorporated into the 80% methanol-soluble fraction. Eighty-five and 15% of (14)C in the soluble fraction was incorporated into phosphate esters (P-esters), including the C(3) cycle intermediates and a C(4) compound, aspartate, respectively. A pulse-chase experiment showed that (14)C in P-esters was mainly transferred into lipids, while [(14)C]aspartate, [(14)C]alanine and [(14)C]glutamate levels remained almost constant. These results indicate that the C(3) cycle functions as the initial pathway of carbon assimilation and that beta-carboxylation contributes to the production of amino acids in subsequent metabolism. Transcriptional analysis of beta-carboxylases such as pyruvate carboxylase (PYC), phosphoenolpyruvate carboxylase (PEPC) and phosphoenolpyruvate carboxykinase (PEPCK) revealed that PYC and PEPC transcripts were greatly increased under illumination, whereas the PEPCK transcript decreased remarkably. PEPC activity was higher in light-grown cells than in dark-adapted cells. PYC activity was detected in isolated chloroplasts of light-grown cells. According to analysis of their deduced N-terminal sequence, PYC and PEPC are predicted to be located in the chloroplasts and mitochondria, respectively. These results suggest that E. huxleyi possesses unique carbon assimila-tion mechanisms in which beta-carboxylation by both PYC and PEPC plays important roles in different organelles.

  6. Effect of gamma radiation on photosynthetic metabolism of Chlorella pyrenoidosa studied by 14CO2 assimilation

    International Nuclear Information System (INIS)

    Martin Moreno, C.; Fernandez Gonzalez, J.

    1983-01-01

    The effect of five dose of gamma radiation (10, 100, 500, 1000 and 5000 Gy) on photosynthetic activity and metabolism of the primary products of photosynthesis has been studied, on Chlorella pyrenoidoBa cultures, by 14 C O 2 assimilation. The photosynthetic assimilation rate is remarkably depressed after irradiation at 500, 1000 and 5000 Gy dose, which also produce a significant change in radioactivity distribution pattern of primary compounds from photosynthesis. No significant effects have been observed on photosynthetic metabolism after irradiation at 10 and 100 Gy. (Author) 19 refs

  7. Liposomal solubilization of new 3-hydroxy-quinolinone derivatives with promising anticancer activity: a screening method to identify maximum incorporation capacity

    DEFF Research Database (Denmark)

    Di Cagno, Massimiliano; Styskala, Jakub; Hlaváč, Jan

    2011-01-01

    Four new 3-hydroxy-quinolinone derivatives with promising anticancer activity could be solubilized using liposomes as vehicle to an extent that allows their in vitro and in vivo testing without use of toxic solvent(s). A screening method to identify the maximum incorporation capacity of hydrophobic......, resulting in a 200-500-fold increase in apparent solubility. Drug-to-lipid ratios in the range of 2-5 µg/mg were obtained. Interestingly, the four quinolinone derivatives have shown different association tendencies with liposomes, probably due to the physicochemical properties of the different group bonded...

  8. The rise of the photosynthetic rate when light intensity increases is delayed in ndh gene-defective tobacco at high but not at low CO2 concentrations

    Directory of Open Access Journals (Sweden)

    Mercedes eMartin

    2015-02-01

    Full Text Available The 11 plastid ndh genes have hovered frequently on the edge of dispensability, being absent in the plastid DNA of many algae and certain higher plants. We have compared the photosynthetic activity of tobacco (Nicotiana tabacum, cv. Petit Havana with five transgenic lines (ndhF, pr-ndhF, T181D, T181A and ndhF FC and found that photosynthetic performance is impaired in transgenic ndhF-defective tobacco plants at rapidly fluctuating light intensities and higher than ambient CO2 concentrations. In contrast to wild type and ndhF FC, which reach the maximum photosynthetic rate in less than one min when light intensity suddenly increases, ndh defective plants (ndhF and T181A show up to a 5 min delay in reaching the maximum photosynthetic rate at CO2 concentrations higher than the ambient 360 ppm. Net photosynthesis was determined at different CO2 concentrations when sequences of 130, 870, 61, 870 and 130 μmol m−2 s−1 PAR sudden light changes were applied to leaves and photosynthetic efficiency and entropy production were determined as indicators of photosynthesis performance. The two ndh-defective plants, ndhF and T181A, had lower photosynthetic efficiency and higher entropy production than wt, ndhF FC and T181D tobacco plants, containing full functional ndh genes, at CO2 concentrations above 400 ppm. We propose that the Ndh complex improves cyclic electron transport by adjusting the redox level of transporters during the low light intensity stage. In ndhF-defective strains, the supply of electrons through the Ndh complex fails, transporters remain over-oxidized (specially at high CO2 concentrations and the rate of cyclic electron transport is low, impairing the ATP level required to rapidly reach high CO2 fixation rates in the following high light phase. Hence, ndh genes could be dispensable at low but not at high atmospheric concentrations of CO2.

  9. Hydrogen production by co-cultures of Lactobacillus and a photosynthetic bacterium, Rhodobacter sphaeroides RV

    Energy Technology Data Exchange (ETDEWEB)

    Asada, Yasuo; Ishimi, Katsuhiro [Department of General Education, College of Science and Technology, Nihon University, Narashinodai, Chiba 274-8501 (Japan); Tokumoto, Masaru; Aihara, Yasuyuki; Oku, Masayo; Kohno, Hideki [Department of Applied Molecular Chemistry, College of Industrial Technology, Nihon University, Izumi-cho, Chiba 275-8575 (Japan); Wakayama, Tatsuki; Miyake, Jun [Research Institute for Cell Engineering, National Institute of Advanced Industrial Science and Technology, Nakoji, Amagasaki, Hyogo 661-0974 (Japan); Tomiyama, Masamitsu [Genetic Diversity Department, National Institute of Agrobiological Science, Tsukuba, Ibaraki 305-8602 (Japan)

    2006-09-15

    Hydrogen production with glucose by using co-immobilized cultures of a lactic acid bacterium, Lactobacillus delbrueckii NBRC13953, and a photosynthetic bacterium, Rhodobacter sphaeroides RV, in agar gels was studied. Glucose was converted to hydrogen gas in a yield of 7.1mol of hydrogen per mole of glucose at a maximum under illuminated conditions. (author)

  10. Seasonal variation of photosynthetic model parameters and leaf area index from global Fluxnet eddy covariance data

    NARCIS (Netherlands)

    Groenendijk, M.; Dolman, A.J.; Ammann, C.; Arneth, A.; Cescatti, A.; Molen, van der M.K.; Moors, E.J.

    2011-01-01

    Global vegetation models require the photosynthetic parameters, maximum carboxylation capacity (Vcm), and quantum yield (a) to parameterize their plant functional types (PFTs). The purpose of this work is to determine how much the scaling of the parameters from leaf to ecosystem level through a

  11. Leaf photosynthetic traits scale with hydraulic conductivity and wood density in Panamanian forest canopy trees.

    Science.gov (United States)

    L.S. Santiago; G. Goldstein; F.C. Meinzer; J.B. Fisher; K. Maehado; D. Woodruff; T. Jones

    2004-01-01

    We investigated how water transport capacity, wood density and wood anatomy were related to leaf photosynthetic traits in two lowland forests in Panama. Leaf-specific hydraulic conductivity (kL) of upper branches was positively correlated with maximum rates of net CO2, assimilation per unit leaf area (Aarea...

  12. Changes of Photosynthetic Behaviors in Kappaphycus alvarezii Infected by Epiphyte.

    Science.gov (United States)

    Pang, Tong; Liu, Jianguo; Liu, Qian; Lin, Wei

    2011-01-01

    Epiphytic filamentous algae (EFA) were noted as a serious problem to reduce the production and quality of K. alvarezii. The morphological studies revealed that the main epiphyte on K. alvarezii was Neosiphonia savatieri in China. Though the harmful effects of EFA on the production of K. alvarezii have been reported, the detailed mechanism of the N. savatieri in limiting the production of K. alvarezii has not been studied yet. The present paper studied the effects of N. savatieri infection on photosynthetic behaviors in K. alvarezii by detecting chlorophyll fluorescence transient in vivo. The results revealed that damage of oxygen-evolving complex (OEC), decrease of active reaction centers (RCs), and the plastoquinone (PQ) pool as well as significant reduction in the performance indexes (PI) of PSII were caused by the infection of N. savatieri. The influence of N. savatieri on photosynthetic activity of K. alvarezii should be one of the important reasons to reduce the production of K. alvarezii infected by N. savatieri.

  13. Photosynthetic rate, dry matter accumulation and yield inter-relationships jn genotypes of rice

    International Nuclear Information System (INIS)

    Devendra, R.; Udaya Kumar, M.; Krishna Sastry, K.S.

    1980-01-01

    The relationship between photosynthetic efficiency, dry matter accumulation and yield in five genotypes of paddy derived from a single cross between Jaya X Halubbalu was studied. Photosynthetic efficiency of younger leaves, on the main tiller was higher than in the older leaves. A significant positive correlation between RuDPcase activity and photosynthetic efficiency was observed in these genotypes. Also a similar positive correlation between dry matter production and photosynthetic efficiency during vegetative period but not during post-anthesis period was observed. Genotypes with high photosynthetic efficiency and also the genotypes with high LAD produced higher dry matter. A reduction in LAD or in photosynthetic efficiency during the post-anthesis period and thus a reduction in source capacity which occurred specially in late types resulted in a lesser ratio between productive and total tillers and also higher percent sterility. Differences in yield amongst the genotypes were not significant, since in the late types MR. 333 and MR. 335, the post-anthesis dry matter production was low due to lesser source capacity. But in the early types, though the total dry matter was less, the post-anthesis source capacity was high. The importance of post-anthesis leaf area of photo-synthetic efficiency in productivity in genotypes of rice is highlighted. (author)

  14. Simultaneous Solar Maximum Mission and Very Large Array (VLA) observations of solar active regions. Semiannual Progress Report, 1 February 1985-30 January 1986

    International Nuclear Information System (INIS)

    Lang, K.R.

    1985-08-01

    Simultaneous observations of solar active regions with the Solar Maximum Mission (SMM) Satellite and the Very Large Array (VLA) have been obtained and analyzed. Combined results enhance the scientific return for beyond that expeted from using either SMM or VLA alone. A total of two weeks of simultaneous SMM/VLA data were obtained. The multiple wavelength VLA observations were used to determine the temperature and magnetic structure at different heights within coronal loops. These data are compared with simultaneous SMM observations. Several papers on the subject are in progress. They include VLA observations of compact, transient sources in the transition region; simultaneous SMM/VLA observations of the coronal loops in one active region and the evolution of another one; and sampling of the coronal plasma using thermal cyclotron lines (magnetic field - VLA) and soft X ray spectral lines (electron density and electron temperaure-SMM)

  15. A remotely sensed pigment index reveals photosynthetic phenology in evergreen conifers

    OpenAIRE

    Gamon, John A.

    2016-01-01

    In evergreen conifers, where the foliage amount changes little with season, accurate detection of the underlying “photosynthetic phenology” from satellite remote sensing has been difficult, presenting challenges for global models of ecosystem carbon uptake. Here, we report a close correspondence between seasonally changing foliar pigment levels, expressed as chlorophyll/carotenoid ratios, and evergreen photosynthetic activity, leading to a “chlorophyll/carotenoid index” (CCI) that tracks ever...

  16. Maximum oxygen uptake and objectively measured physical activity in Danish children 6-7 years of age: the Copenhagen school child intervention study

    DEFF Research Database (Denmark)

    Eiberg, Stig; Hasselstrøm, Henriette; Grønfeldt, Vivian

    2005-01-01

    Objectives: To provide normative data on maximum oxygen uptake (V·O2MAX) and physical activity in children 6-7 years of age and analyse the association between these variables. Methods: VO2MAX was measured in 366 boys (mean (SD) 6.8 (0.4) years of age) and 332 girls (6.7 (0.4) years of age) from.......5 (6.0) v 44.8 (5.6) ml/kg/min (+8%); pgirls. The difference in VO2MAX between boys and girls decreased to +2% when expressed relative to lean body mass (LBM). Absolute VO2MAX was related to LBM, body mass, and stature (all pBoys were more physically active than girls (mean counts...... +9.4%, pboys and girls with the same VO2MAX were compared, boys were more active. The difference in physical activity between the sexes was higher when sustained activity of higher intensity was compared. Conclusions: VO2MAX is higher in boys than girls (+11%), even when...

  17. Hybrid system of semiconductor and photosynthetic protein

    International Nuclear Information System (INIS)

    Kim, Younghye; Shin, Seon Ae; Lee, Jaehun; Yang, Ki Dong; Nam, Ki Tae

    2014-01-01

    Photosynthetic protein has the potential to be a new attractive material for solar energy absorption and conversion. The development of semiconductor/photosynthetic protein hybrids is an example of recent progress toward efficient, clean and nanostructured photoelectric systems. In the review, two biohybrid systems interacting through different communicating methods are addressed: (1) a photosynthetic protein immobilized semiconductor electrode operating via electron transfer and (2) a hybrid of semiconductor quantum dots and photosynthetic protein operating via energy transfer. The proper selection of materials and functional and structural modification of the components and optimal conjugation between them are the main issues discussed in the review. In conclusion, we propose the direction of future biohybrid systems for solar energy conversion systems, optical biosensors and photoelectric devices. (topical reviews)

  18. Separation, identification and quantification of photosynthetic ...

    African Journals Online (AJOL)

    Thirty one photosynthetic pigments (chlorophylls, carotenoids and degradation products) from the seaweeds, Codium dwarkense, (Chlorophyta), , Laurencia obtusa , (Rhodophyta) and , Lobophora variegata, (Phaeophyta), were separated in a single-step procedure by reversed phase high-performance liquid ...

  19. Oxygen Concentration Inside a Functioning Photosynthetic Cell

    OpenAIRE

    Kihara, Shigeharu; Hartzler, Daniel A.; Savikhin, Sergei

    2014-01-01

    The excess oxygen concentration in the photosynthetic membranes of functioning oxygenic photosynthetic cells was estimated using classical diffusion theory combined with experimental data on oxygen production rates of cyanobacterial cells. The excess oxygen concentration within the plesiomorphic cyanobacterium Gloeobactor violaceus is only 0.025 μM, or four orders of magnitude lower than the oxygen concentration in air-saturated water. Such a low concentration suggests that the first oxygenic...

  20. Approximate maximum parsimony and ancestral maximum likelihood.

    Science.gov (United States)

    Alon, Noga; Chor, Benny; Pardi, Fabio; Rapoport, Anat

    2010-01-01

    We explore the maximum parsimony (MP) and ancestral maximum likelihood (AML) criteria in phylogenetic tree reconstruction. Both problems are NP-hard, so we seek approximate solutions. We formulate the two problems as Steiner tree problems under appropriate distances. The gist of our approach is the succinct characterization of Steiner trees for a small number of leaves for the two distances. This enables the use of known Steiner tree approximation algorithms. The approach leads to a 16/9 approximation ratio for AML and asymptotically to a 1.55 approximation ratio for MP.

  1. Atmospheric transmittance model for photosynthetically active radiation

    International Nuclear Information System (INIS)

    Paulescu, Marius; Stefu, Nicoleta; Gravila, Paul; Paulescu, Eugenia; Boata, Remus; Pacurar, Angel; Mares, Oana; Pop, Nicolina; Calinoiu, Delia

    2013-01-01

    A parametric model of the atmospheric transmittance in the PAR band is presented. The model can be straightforwardly applied for calculating the beam, diffuse and global components of the PAR solar irradiance. The required inputs are: air pressure, ozone, water vapor and nitrogen dioxide column content, Ångström's turbidity coefficient and single scattering albedo. Comparison with other models and ground measured data shows a reasonable level of accuracy for this model, making it suitable for practical applications. From the computational point of view the calculus is condensed into simple algebra which is a noticeable advantage. For users interested in speed-intensive computation of the effective PAR solar irradiance, a PC program based on the parametric equations along with a user guide are available online at http://solar.physics.uvt.ro/srms

  2. Renewable sustainable biocatalyzed electricity production in a photosynthetic algal microbial fuel cell (PAMFC)

    Energy Technology Data Exchange (ETDEWEB)

    Strik, David P.B.T.B.; Terlouw, Hilde; Hamelers, Hubertus V.M.; Buisman, Cees J.N. [Wageningen Univ. (Netherlands). Sub-Dept. of Environmental Technology

    2008-12-15

    Electricity production via solar energy capturing by living higher plants and microalgae in combination with microbial fuel cells are attractive because these systems promise to generate useful energy in a renewable, sustainable, and efficient manner. This study describes the proof of principle of a photosynthetic algal microbial fuel cell (PAMFC) based on naturally selected algae and electrochemically active microorganisms in an open system and without addition of instable or toxic mediators. The developed solar-powered PAMFC produced continuously over 100 days renewable biocatalyzed electricity. The sustainable performance of the PAMFC resulted in a maximum current density of 539 mA/m{sup 2} projected anode surface area and a maximum power production of 110 mW/m{sup 2} surface area photobioreactor. The energy recovery of the PAMFC can be increased by optimization of the photobioreactor, by reducing the competition from non-electrochemically active microorganisms, by increasing the electrode surface and establishment of a further-enriched biofilm. Since the objective is to produce net renewable energy with algae, future research should also focus on the development of low energy input PAMFCs. This is because current algae production systems have energy inputs similar to the energy present in the outcoming valuable products. (orig.)

  3. Renewable sustainable biocatalyzed electricity production in a photosynthetic algal microbial fuel cell (PAMFC).

    Science.gov (United States)

    Strik, David P B T B; Terlouw, Hilde; Hamelers, Hubertus V M; Buisman, Cees J N

    2008-12-01

    Electricity production via solar energy capturing by living higher plants and microalgae in combination with microbial fuel cells are attractive because these systems promise to generate useful energy in a renewable, sustainable, and efficient manner. This study describes the proof of principle of a photosynthetic algal microbial fuel cell (PAMFC) based on naturally selected algae and electrochemically active microorganisms in an open system and without addition of instable or toxic mediators. The developed solar-powered PAMFC produced continuously over 100 days renewable biocatalyzed electricity. The sustainable performance of the PAMFC resulted in a maximum current density of 539 mA/m2 projected anode surface area and a maximum power production of 110 mW/m2 surface area photobioreactor. The energy recovery of the PAMFC can be increased by optimization of the photobioreactor, by reducing the competition from non-electrochemically active microorganisms, by increasing the electrode surface and establishment of a further-enriched biofilm. Since the objective is to produce net renewable energy with algae, future research should also focus on the development of low energy input PAMFCs. This is because current algae production systems have energy inputs similar to the energy present in the outcoming valuable products.

  4. Photosynthetic planulae and planktonic hydroids: contrasting strategies of propagule survival

    Directory of Open Access Journals (Sweden)

    Patrizia Pagliara

    2000-12-01

    Full Text Available Settlement delays can be important to prevent propagule waste when proper settling substrates are not immediately available. Under laboratory conditions, the planulae of Clytia viridicans underwent two alternative developmental patterns. Some settled on the bottom, forming a hydranth-gonotheca complex that produced up to four medusae and later either degenerated or gave rise to a hydroid colony. Other planulae settled right below the air-water interface, forming floating colonies that eventually fell to the bottom and settled. Halecium nanum released planulae with a rich population of symbiotic zooxanthellae that survived into a rearing jar for three months. After a long period of apparent quiescence (possibly fuelled by photosynthetic activities of zooxanthellae the planulae produced new colonies. Both photosynthetic planulae and settlement at the interface air-water allow a delay in the passage from a planktonic to a fully functional benthic life.

  5. Photosynthetic carbon reduction by seagrasses exposed to ultraviolet A radiation

    Science.gov (United States)

    1979-01-01

    The seagrasses Halophila engelmannii, Halodule wrightii, and Syringodium filiforme were examined for their intrinsic sensitivity to ultraviolet-A-UV-A and ultraviolet-B-UV-B radiation. The effect of UV-A on photosynthetically active radiation (PAR) was also determined. Ultraviolet-A and ultraviolet-B were studied with emphasis on the greater respective environmental consequence in terms of seagrass distribution and abundance. Results indicate that an intrinsic sensitivity to UV-A alone is apparent only in Halophila, while net photosynthesis in Halodule and Syringodium seems unaffected by the level of UV-A provided. The sensitivity of Halophila to UV-A in the absense of (PAR) indicates that the photosynthetic reaction does not need to be in operation for damage to occur. Other significant results are reported.

  6. BOREAS TE-9 NSA Photosynthetic Capacity and Foliage Nitrogen Data

    Science.gov (United States)

    Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Dang, Qinglai; Margolis, Hank; Coyea, Marie

    2000-01-01

    The Boreal Ecosystem-Atmospheric Study (BOREAS) TE-9 (Terrestrial Ecology) team collected several data sets related to chemical and photosynthetic properties of leaves in boreal forest tree species. This data set describes the spatial and temporal relationship between foliage nitrogen concentration and photosynthetic capacity in the canopies of black spruce, jack pine, and aspen located within the Northern Study Area (NSA). The data were collected from June to September 1994 and are useful for modeling the vertical distribution of carbon fixation for different forest types in the boreal forest. The data are available in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  7. Maximum permissible dose

    International Nuclear Information System (INIS)

    Anon.

    1979-01-01

    This chapter presents a historic overview of the establishment of radiation guidelines by various national and international agencies. The use of maximum permissible dose and maximum permissible body burden limits to derive working standards is discussed

  8. Improving Delivery of Photosynthetic Reducing Power to Cytochrome P450s

    DEFF Research Database (Denmark)

    Mellor, Silas Busck

    at sustainable production of high-value and commodity products. Cytochrome P450 enzymes play key roles in the biosynthesis of important natural products. The electron carrier ferredoxin can couple P450s non-natively to photosynthetic electron supply, providing ample reducing power for catalysis. However......, photosynthetic reducing power feeds into both central and specialized metabolism, which leads to a fiercely competitive system from which to siphon reductant. This thesis explores the optimization of light-driven P450 activity, and proposes strategies to overcome the limitations imposed by competition...... for photosynthetic reducing power. Photosynthetic electron carrier proteins interact with widely different partners because they use relatively non-specific interactions. The mechanistic basis of these interactions and its impact on natural electron transfer complexes is discussed. This particular type...

  9. Simulação estocástica da radiação fotossinteticamente ativa e da temperatura do ar por diferentes métodos Random simulation of photosynthetically active radiation and air temperature through different methods

    Directory of Open Access Journals (Sweden)

    Thomas Newton Martin

    2007-09-01

    Full Text Available O objetivo deste trabalho foi comparar três métodos para simulação de dados de radiação fotossinteticamente ativa e temperatura do ar, com o uso de parâmetros diários de 17 estações do Estado de São Paulo. A simulação foi realizada para o primeiro e o 16º dia de cada mês, conforme: a distribuição normal truncada a mais ou menos 1,96 de desvio-padrão; distribuição triangular assimétrica; e distribuição normal bivariada. As estimativas com os dados simulados foram comparadas com os respectivos parâmetros (obtidos com os dados observados, pelos testes de homogeneidade de variância F e Bartlett, teste t de comparação de médias, coeficiente de correlação de Pearson, índice de concordância de Willmott, índice de desempenho de Camargo, coeficiente angular e o teste de normalidade dos dados. A simulação pela distribuição normal bivariada é a mais adequada para representar as variáveis climáticas.The purpose of this work was to compare three methods for simulating data of photosynthetically active radiation and air temperature, using daily parameters of 17 stations of São Paulo State, Brazil. The simulation of those elements was carried out for de 1st and the 16th day of each month, through three cases: nonsymmetric triangular distribution; normal distribution truncated at 1.96 standard deviation; and bivaried normal distribution. The simulated data were evaluated through the tests of homogeneity of variance F and Bartlett, t test, agreement index of Willmott, angular coefficient of the straight line, the index of performance of Camargo and tack the normal distribution (uni-varied. The simulation using the bi-varied normal distribution is most appropriate for representing the climate variables.

  10. Seasonal changes in photosynthetic capacity of leaves of kiwifruit (Actinidia deliciosa) vines

    International Nuclear Information System (INIS)

    Buwalda, J.G.; Meekings, J.S.; Smith, G.S.

    1991-01-01

    The seasonal trend of photosynthetic capacity of leaves of kiwifruit (Actinidia deliciosa var. deliciosa) vines growing in the field was examined, by measuring the response of net photosynthesis (A) to irradiance (PAR) at monthly intervals for leaves that emerged at different stages of the growing season. A climate controlled minicuvette system was used, to ensure constant environmental conditions, apart from the controlled changes in leaf irradiance. Responses of A to irradiance were described using asymptotic exponential curves, providing estimates of the radiation saturated rate of A (A sat ), and the response of A to increasing incident PAR at low PAR levels (ϕ i ). The change in photosynthetic capacity with leaf age was similar for leaves emerging 1, 2, 3 or 4 months after bud burst. At 1 month after leaf emergence, when leaves were fully expanded, Asat was 9–11 μmol CO 2 m −2 s −1 . Maximum photosynthetic capacity was not attained until 3–5 months after leaf emergence, when Asat was 16–17 μmol CO 2 m −2 s −1 . The increasing photosynthetic capacity during 3–5 months after leaf emergence was closely related to concomitant changes in leaf N and chlorophyll contents. The possibility that N import to the leaf was a significant factor limiting the development of photosynthetic capacity is discussed. (author)

  11. Normalizing the maximum permissible seal failure of the fuel cladding of VVER and the activity of the fission products in the coolant

    International Nuclear Information System (INIS)

    Luzanova, L.M.; Miglo, V.N.; Slavyagin, P.D.

    1993-01-01

    In most countries developing a nuclear power industry based on pressurized water reactors, one of the conditions for issuing a license under normal operating conditions for issuing a license stipulates that the fuel elements may not lose their hermetic seal either under normal operating conditions or during presumable disturbances of the conditions of normal use. At a conference on radiation safety the ALARA principle was taken to be fundamental, it being attempted to keep the activity of the coolant of the primary circuit, including the fission products emerging from unsealed fuel elements, to a level as low as reasonably possible. As many years of experience in the nuclear power industry have shown, nuclear power stations are in many cases operated with nonhermetic fuel elements in the core. Therefore, from the point of view of safety and economy, the best way to operate a power plant is to try to ensure maximum burnup of the fuel of the unsealed elements as they operate within the limits of safe activity of the fission products in the fuel circuits

  12. Oxygen concentration inside a functioning photosynthetic cell.

    Science.gov (United States)

    Kihara, Shigeharu; Hartzler, Daniel A; Savikhin, Sergei

    2014-05-06

    The excess oxygen concentration in the photosynthetic membranes of functioning oxygenic photosynthetic cells was estimated using classical diffusion theory combined with experimental data on oxygen production rates of cyanobacterial cells. The excess oxygen concentration within the plesiomorphic cyanobacterium Gloeobactor violaceus is only 0.025 μM, or four orders of magnitude lower than the oxygen concentration in air-saturated water. Such a low concentration suggests that the first oxygenic photosynthetic bacteria in solitary form could have evolved ∼2.8 billion years ago without special mechanisms to protect them against reactive oxygen species. These mechanisms instead could have been developed during the following ∼500 million years while the oxygen level in the Earth's atmosphere was slowly rising. Excess oxygen concentrations within individual cells of the apomorphic cyanobacteria Synechocystis and Synechococcus are 0.064 and 0.25 μM, respectively. These numbers suggest that intramembrane and intracellular proteins in isolated oxygenic photosynthetic cells are not subjected to excessively high oxygen levels. The situation is different for closely packed colonies of photosynthetic cells. Calculations show that the excess concentration within colonies that are ∼40 μm or larger in diameter can be comparable to the oxygen concentration in air-saturated water, suggesting that species forming colonies require protection against reactive oxygen species even in the absence of oxygen in the surrounding atmosphere. Copyright © 2014 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  13. [Effects of reduced solar radiation on winter wheat flag leaf net photosynthetic rate].

    Science.gov (United States)

    Zheng, You-Fei; Ni, Yan-Li; Mai, Bo-Ru; Wu, Rong-Jun; Feng, Yan; Sun, Jian; Li, Jian; Xu, Jing-Xin

    2011-06-01

    Taking winter wheat Triticum aestivum L. (cv. Yangmai 13) as test material, a field experiment was conducted in Nanjing City to study the effects of simulated reduced solar radiation on the diurnal variation of winter wheat flag leaf photosynthetic rate and the main affecting factors. Five treatments were installed, i. e., 15% (T15), 20% (T20) , 40% (T40), 60% (T60), and 100% (CK) of total incident solar radiation. Reduced solar irradiance increased the chlorophyll and lutein contents significantly, but decreased the net photosynthetic rate (Pn). Under different solar irradiance, the diurnal variation of Pn had greater difference, and the daily maximum Pn was in the order of CK > T60 > T40 > T 20 > T15. In CK, the Pn exhibited a double peak diurnal curve; while in the other four treatments, the Pn showed a single peak curve, and the peak was lagged behind that of CK. Correlation analysis showed that reduced solar irradiance was the main factor affecting the diurnal variation of Pn, but the physiological parameters also played important roles in determining the diurnal variation of Pn. In treatments T60 and T40, the photosynthesis active radiation (PAR), leaf temperature (T1) , stomatal conductance (Gs) , and transpiration rate (Tr) were significantly positively correlated with Pn, suggesting their positive effects on Pn. The intercellular CO2 concentration (Ci) and stomatal limitation (Ls) had significant negative correlations with Pn in treatments T60 and T40 but significant positive correlations with Pn in treatments T20 and T15, implying that the Ci and Ls had negative (or positive) effects on Pn when the solar irradiance was higher (or lower) than 40% of incident solar irradiance.

  14. Study on improvement of continuous hydrogen production by photosynthetic biofilm in interior illuminant reactor.

    Science.gov (United States)

    Liu, Wenhui; Yuan, Linjiang; Wei, Bo

    2016-09-01

    In the present study, a new type of interior optical fiber illuminating reactor was developed for H2 production to solve the problem of luminous intensity attenuation at the center portion of a reactor, and an immobilization technique was used to enhance the stability of a continuous hydrogen production process with attached photosynthetic bacteria, using glucose as a sole carbon substrate for the indigenous photosynthetic bacteria (PSB) Rhodopseudomonas palustris SP-6. Results of the experiments showed that the interior optical fiber illuminating reactor produces H2 more efficiently and productively than the exterior light source reactor, with the cumulative H2 production, the maximum H2 production rate and H2 yield increased by 813ml, 11.3ml l-1 h-1 and 22.3%, respectively. The stability of the product of continuous hydrogen was realized by immobilizing PSB on the surface of powder active carbon(PAC). After adding the dosage of 2.0g l-1 PAC, the continuous steady operation of H2 production gave a high H2 yield of 1.398 mol H2 mol-1 glucose and an average H2 production rate of 35.1ml l-1 h-1 illuminating with a single interior optical fiber light source. Meanwhile, a higher H2 yield of 1.495 mol H2 mol-1 glucose and an average H2 production rate of 38.7ml l-1 h-1 were attained illuminating with a compound lamp in the continuous H2 production for 20 days.

  15. Potassium improves photosynthetic tolerance to and recovery from episodic drought stress in functional leaves of cotton (Gossypium hirsutum L.).

    Science.gov (United States)

    Zahoor, Rizwan; Zhao, Wenqing; Dong, Haoran; Snider, John L; Abid, Muhammad; Iqbal, Babar; Zhou, Zhiguo

    2017-10-01

    To investigate whether potassium (K) application enhances the potential of cotton (Gossypium hirsutum L.) plants to maintain physiological functions during drought and recovery, low K-sensitive (Siza 3) and -tolerant (Simian 3) cotton cultivars were exposed to three K rates (0, 150, and 300 K 2 O kg ha -1 ) and either well-watered conditions or severe drought stress followed by a recovery period. Under drought stress, cotton plants showed a substantial decline in leaf water potential, stomatal conductance, photosynthetic rate, and the maximum and actual quantum yield of PSII, resulting in greater non-photochemical quenching and lipid peroxidation as compared to well-watered plants. However, plants under K application not only showed less of a decline in these traits but also displayed greater potential to recover after rewatering as compared to the plants without K application. Plants receiving K application showed lower lipid peroxidation, higher antioxidant enzyme activities, and increased proline accumulation as compared to plants without K application. Significant relationships between rates of photosynthetic recovery and K application were observed. The cultivar Siza 3 exhibited a more positive response to K application than Simian 3. The results suggest that K application enhances the cotton plant's potential to maintain functionality under drought and facilitates recovery after rewatering. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  16. Long-term water stress leads to acclimation of drought sensitivity of photosynthetic capacity in xeric but not riparian Eucalyptus species.

    Science.gov (United States)

    Zhou, Shuang-Xi; Medlyn, Belinda E; Prentice, Iain Colin

    2016-01-01

    Experimental drought is well documented to induce a decline in photosynthetic capacity. However, if given time to acclimate to low water availability, the photosynthetic responses of plants to low soil moisture content may differ from those found in short-term experiments. This study aims to test whether plants acclimate to long-term water stress by modifying the functional relationships between photosynthetic traits and water stress, and whether species of contrasting habitat differ in their degree of acclimation. Three Eucalyptus taxa from xeric and riparian habitats were compared with regard to their gas exchange responses under short- and long-term drought. Photosynthetic parameters were measured after 2 and 4 months of watering treatments, namely field capacity or partial drought. At 4 months, all plants were watered to field capacity, then watering was stopped. Further measurements were made during the subsequent 'drying-down', continuing until stomata were closed. Two months of partial drought consistently reduced assimilation rate, stomatal sensitivity parameters (g1), apparent maximum Rubisco activity (V'(cmax)) and maximum electron transport rate (J'(max)). Eucalyptus occidentalis from the xeric habitat showed the smallest decline in V'(cmax) and J'(max); however, after 4 months, V'(cmax) and J'(max) had recovered. Species differed in their degree of V'(cmax) acclimation. Eucalyptus occidentalis showed significant acclimation of the pre-dawn leaf water potential at which the V'(cmax) and 'true' V(cmax) (accounting for mesophyll conductance) declined most steeply during drying-down. The findings indicate carbon loss under prolonged drought could be over-estimated without accounting for acclimation. In particular, (1) species from contrasting habitats differed in the magnitude of V'(cmax) reduction in short-term drought; (2) long-term drought allowed the possibility of acclimation, such that V'(cmax) reduction was mitigated; (3) xeric species showed a

  17. Diurnal changes of photosynthetic quantum yield in the intertidal macroalga Sargassum thunbergii under simulated tidal emersion conditions

    Science.gov (United States)

    Yu, Yong Qiang; Zhang, Quan Sheng; Tang, Yong Zheng; Li, Xue Meng; Liu, Hong Liang; Li, Li Xia

    2013-07-01

    In this study, a three-way factorial experimental design was used to investigate the diurnal changes of photosynthetic activity of the intertidal macroalga Sargassum thunbergii in response to temperature, tidal pattern and desiccation during a simulated diurnal light cycle. The maximum (Fv/Fm) and effective (ΦPSII) quantum yields of photosystem II (PSII) were estimated by chlorophyll fluorescence using a pulse amplitude modulated fluorometer. Results showed that this species exhibited sun-adapted characteristics, as evidenced by the daily variation of Fv/Fm and ΦPSII. Both yield values decreased with increasing irradiance towards noon and recovered rapidly in the afternoon suggesting a dynamic photoinhibition. The photosynthetic quantum yield of S. thunbergii thalli varied significantly with temperature, tidal pattern and desiccation. Thalli were more susceptible to light-induced damage at high temperature of 25 °C and showed complete recovery of photosynthetic activity only when exposed to 8 °C. In contrast with the mid-morning low tide period, although there was an initial increase in photosynthetic yield during emersion, thalli showed a greater degree of decline at the end of emersion and remained less able to recover when low tide occurred at mid-afternoon. Short-term air exposure of 2 h did not significantly influence the photosynthesis. However, when exposed to moderate conditions (4 h desiccation at 15 °C or 6 h desiccation at 8 °C), a significant inhibition of photosynthesis was followed by partial or complete recovery upon re-immersion in late afternoon. Only extreme conditions (4 h desiccation at 25 °C or 6 h desiccation at 15 °C or 25 °C) resulted in the complete inhibition, with little indication of recovery until the following morning, implying the occurrence of chronic PSII damage. Based on the magnitude of effect, desiccation was the predominant negative factor affecting the photosynthesis under the simulated daytime irradiance period. These

  18. ENHANCED PRACTICAL PHOTOSYNTHETIC CO2 MITIGATION

    Energy Technology Data Exchange (ETDEWEB)

    Dr. David J. Bayless; Dr. Morgan Vis; Dr. Gregory Kremer; Dr. Michael Prudich; Dr. Keith Cooksey; Dr. Jeff Muhs

    2001-04-16

    This quarterly report documents significant achievements in the Enhanced Practical Photosynthetic CO{sub 2} Mitigation project during the period from 1/03/2001 through 4/02/2001. Many of the activities and accomplishments are continuations of work initiated and reported in last quarter's status report. Major activities and accomplishments for this quarter include: Three sites in Yellowstone National Park have been identified that may contain suitable organisms for use in a bioreactor; Full-scale culturing of one thermophilic organism from Yellowstone has progressed to the point that there is a sufficient quantity to test this organism in the model-scale bioreactor; The effects of the additive monoethanolamine on the growth of one thermophilic organism from Yellowstone has been tested; Testing of growth surface adhesion and properties is continuing; Construction of a larger model-scale bioreactor to improve and expand testing capabilities is completed and the facility is undergoing proof tests; Model-scale bioreactor tests examining the effects of CO{sub 2} concentration levels and lighting levels on organism growth rates are continuing; Alternative fiber optic based deep-penetration light delivery systems for use in the pilot-scale bioreactor have been designed, constructed and tested; An existing slug flow reactor system has been modified for use in this project, and a proof-of-concept test plan has been developed for the slug flow reactor; Research and testing of water-jet harvesting techniques is continuing, and a harvesting system has been designed for use in the model-scale bioreactor; and The investigation of comparative digital image analysis as a means for determining the ''density'' of algae on a growth surface is continuing Plans for next quarter's work and an update on the project's web page are included in the conclusions.

  19. Photosynthetic responses of C3 and C4 species to seasonal water variability and competition.

    Science.gov (United States)

    Niu, Shuli; Yuan, Zhiyou; Zhang, Yanfang; Liu, Weixing; Zhang, Lei; Huang, Jianhui; Wan, Shiqiang

    2005-11-01

    This study examined the impacts of seasonal water variability and interspecific competition on the photosynthetic characteristics of a C3 (Leymus chinensis) and a C4 (Chloris virgata) grass species. Plants received the same amount of water but in three seasonal patterns, i.e. the one-peak model (more water in the summer than in the spring and autumn), the two-peak model (more water in the spring and autumn than in the summer), and the average model (water evenly distributed over the growing season). The effects of water variability on the photosynthetic characteristics of the C3 and C4 species were dependent on season. There were significant differences in the photosynthetic characteristics of the C4 species in the summer and the C3 species in the autumn among the three water treatments. Interspecific competition exerted negative impacts on the C3 species in August and September but had no effects on the C4 species in any of the four measuring dates. The relative competitive capability of the two species was not altered by water availability. The assimilation rate, the maximum quantum yield of net CO2 assimilation, and the maximum rate of carboxylation of the C3 species were 13-56%, 5-11%, and 11-48% greater, respectively, in a monoculture than in a mixture in August and September. The results demonstrated that the photosynthetic characteristics of the C3 and C4 species were affected by water availability, but the effects varied considerably with season.

  20. Solar maximum mission

    International Nuclear Information System (INIS)

    Ryan, J.

    1981-01-01

    By understanding the sun, astrophysicists hope to expand this knowledge to understanding other stars. To study the sun, NASA launched a satellite on February 14, 1980. The project is named the Solar Maximum Mission (SMM). The satellite conducted detailed observations of the sun in collaboration with other satellites and ground-based optical and radio observations until its failure 10 months into the mission. The main objective of the SMM was to investigate one aspect of solar activity: solar flares. A brief description of the flare mechanism is given. The SMM satellite was valuable in providing information on where and how a solar flare occurs. A sequence of photographs of a solar flare taken from SMM satellite shows how a solar flare develops in a particular layer of the solar atmosphere. Two flares especially suitable for detailed observations by a joint effort occurred on April 30 and May 21 of 1980. These flares and observations of the flares are discussed. Also discussed are significant discoveries made by individual experiments

  1. Mycorrhiza symbiosis increases the surface for sunlight capture in Medicago truncatula for better photosynthetic production.

    Directory of Open Access Journals (Sweden)

    Lisa Adolfsson

    Full Text Available Arbuscular mycorrhizal (AM fungi play a prominent role in plant nutrition by supplying mineral nutrients, particularly inorganic phosphate (Pi, and also constitute an important carbon sink. AM stimulates plant growth and development, but the underlying mechanisms are not well understood. In this study, Medicago truncatula plants were grown with Rhizophagus irregularis BEG141 inoculum (AM, mock inoculum (control or with P(i fertilization. We hypothesized that AM stimulates plant growth through either modifications of leaf anatomy or photosynthetic activity per leaf area. We investigated whether these effects are shared with P(i fertilization, and also assessed the relationship between levels of AM colonization and these effects. We found that increased P(i supply by either mycorrhization or fertilization led to improved shoot growth associated with increased nitrogen uptake and carbon assimilation. Both mycorrhized and P(i-fertilized plants had more and longer branches with larger and thicker leaves than the control plants, resulting in an increased photosynthetically active area. AM-specific effects were earlier appearance of the first growth axes and increased number of chloroplasts per cell section, since they were not induced by P(i fertilization. Photosynthetic activity per leaf area remained the same regardless of type of treatment. In conclusion, the increase in growth of mycorrhized and P(i-fertilized Medicago truncatula plants is linked to an increase in the surface for sunlight capture, hence increasing their photosynthetic production, rather than to an increase in the photosynthetic activity per leaf area.

  2. Mycorrhiza Symbiosis Increases the Surface for Sunlight Capture in Medicago truncatula for Better Photosynthetic Production

    Science.gov (United States)

    Adolfsson, Lisa; Keresztes, Áron; Uddling, Johan; Schoefs, Benoît; Spetea, Cornelia

    2015-01-01

    Arbuscular mycorrhizal (AM) fungi play a prominent role in plant nutrition by supplying mineral nutrients, particularly inorganic phosphate (Pi), and also constitute an important carbon sink. AM stimulates plant growth and development, but the underlying mechanisms are not well understood. In this study, Medicago truncatula plants were grown with Rhizophagus irregularis BEG141 inoculum (AM), mock inoculum (control) or with Pi fertilization. We hypothesized that AM stimulates plant growth through either modifications of leaf anatomy or photosynthetic activity per leaf area. We investigated whether these effects are shared with Pi fertilization, and also assessed the relationship between levels of AM colonization and these effects. We found that increased Pi supply by either mycorrhization or fertilization led to improved shoot growth associated with increased nitrogen uptake and carbon assimilation. Both mycorrhized and Pi-fertilized plants had more and longer branches with larger and thicker leaves than the control plants, resulting in an increased photosynthetically active area. AM-specific effects were earlier appearance of the first growth axes and increased number of chloroplasts per cell section, since they were not induced by Pi fertilization. Photosynthetic activity per leaf area remained the same regardless of type of treatment. In conclusion, the increase in growth of mycorrhized and Pi-fertilized Medicago truncatula plants is linked to an increase in the surface for sunlight capture, hence increasing their photosynthetic production, rather than to an increase in the photosynthetic activity per leaf area. PMID:25615871

  3. Effects of INH, DNP, 2,4-D and CMU on the photosynthetic activity of barley and maize plants; Efecto de cuatro inhibidores metabolicos (INH, DNP, 2, 4-D y CMU) sobre la actividad fotosintetica de plantular de cebada (Hordeum vulgare L.) y Maiz (Zea mais L.)

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, J; Prieto, M P

    1979-07-01

    Determinations of the rate of photosynthesis were made in barley and maize leaves treated with INH, DNP, 2,4-D or CMU. 1 ppm of the chemicals in nutritive solutions was absorbed by roots during 24 or 48 hours in both dark and light conditions. After this period, photosynthetic activity, compensation point and 14{sup C}O{sub 2} assimilation were determined. Results show that INH increases the rate of photosynthesis, DNP and 2,4-D do not alter it sensibly and CMU acts as a strong inhibitor of photosynthesis. Some possible applications for ths obtention of labelled compounds by biosynthesis are discussed. (Author) 87 refs.

  4. Photosynthetic recovery and acclimation to excess light intensity in the rehydrated lichen soil crusts.

    Directory of Open Access Journals (Sweden)

    Li Wu

    Full Text Available As an important successional stage and main type of biological soil crusts (BSCs in Shapotou region of China (southeastern edge of Tengger Desert, lichen soil crusts (LSCs often suffer from many stresses, such as desiccation and excess light intensity. In this study, the chlorophyll fluorescence and CO2 exchange in the rehydrated LSCs were detected under a series of photosynthetically active radiation (PAR gradients to study the photosynthetic acclimation of LSCs. The results showed that although desiccation leaded to the loss of photosynthetic activity in LSCs, the fluorescence parameters including Fo, Fv and Fv/Fm of LSCs could be well recovered after rehydration. After the recovery of photosynthetic activity, the effective photosynthetic efficiency ΦPSII detected by Imaging PAM had declined to nearly 0 within both the lichen thallus upper and lower layers when the PAR increased to 200 μE m-2 s-1, however the net photosynthesis detected by the CO2 gas analyzer in the LSCs still appeared when the PAR increased to 1000 μE m-2 s-1. Our results indicate that LSCs acclimating to high PAR, on the one hand is ascribed to the special structure in crust lichens, making the incident light into the lichen thallus be weakened; on the other hand the massive accumulation of photosynthetic pigments in LSCs also provides a protective barrier for the photosynthetic organisms against radiation damage. Furthermore, the excessive light energy absorbed by crust lichens is also possibly dissipated by the increasing non-photochemical quenching, therefore to some extent providing some protection for LSCs.

  5. Maximum Acceleration Recording Circuit

    Science.gov (United States)

    Bozeman, Richard J., Jr.

    1995-01-01

    Coarsely digitized maximum levels recorded in blown fuses. Circuit feeds power to accelerometer and makes nonvolatile record of maximum level to which output of accelerometer rises during measurement interval. In comparison with inertia-type single-preset-trip-point mechanical maximum-acceleration-recording devices, circuit weighs less, occupies less space, and records accelerations within narrower bands of uncertainty. In comparison with prior electronic data-acquisition systems designed for same purpose, circuit simpler, less bulky, consumes less power, costs and analysis of data recorded in magnetic or electronic memory devices. Circuit used, for example, to record accelerations to which commodities subjected during transportation on trucks.

  6. Ultrafast fluorescence of photosynthetic crystals and light-harvesting complexes

    NARCIS (Netherlands)

    Oort, van B.F.

    2008-01-01

    This thesis focuses on the study of photosynthetic pigment protein complexes using time resolved fluorescence techniques. Fluorescence spectroscopy often requires attaching fluorescent labels to the proteins under investigation. With photosynthetic proteins this is not necessary, because these

  7. Use efficiency of photosynthetically active radiation by tomato plants grown in different environments; Eficiência de uso da radiação fotossinteticamente ativa pela cultura do tomateiro em diferentes ambientes

    Energy Technology Data Exchange (ETDEWEB)

    Radin, B.; Bergamaschi, H.; Reisser, Junior, C.; Barni, N. A.; Matzenauer, R.; Didone, I. A.

    2003-09-15

    Crop biomass production is related to the amount of photosynthetically active radiation intercepted and absorbed by the leaves, as well as to their efficiency of conversion of this radiant energy into chemical energy through photosynthesis. The objective of this study was to evaluate the radiation use efficiency by tomato plants (Lycopersicon esculentum Mill.) grown in different environments. Experiments were carried out in plastic-covered greenhouses with and without anti insects screens and at open air plots, in different growth periods (spring-summer and summer-autumn) during the 1999/2000 crop season. Measurements of dry above-ground biomass and leaf area index throughout both crop cycles were performed, and the incident and transmitted radiation fluxes were registered. The greenhouse with anti insects screens had less incident radiation, but resulted in higher use efficiency: 0.44 and 0.60 g dry matter mol{sup -1} during the first and second cycles, respectively. Outside the greenhouses, there was a higher amount of incident radiation, however a lower use efficiency (0.30 and 0.32 g mol{sup -1} for the first and second cycles, respectively), while the greenhouse without anti insects screens had intermediate values (0.45 and 0.53 g mol{sup -1}). (author) [Portuguese] A produção de biomassa pelas culturas está relacionada à quantidade de radiação fotossinteticamente ativa interceptada e absorvida pelas folhas, bem como à eficiência com que estas convertem a energia radiante em energia química, pela fotossíntese. O objetivo deste trabalho foi avaliar a eficiência de uso da radiação fotossinteticamente ativa pelo tomateiro (Lycopersicon esculentum Mill.) cultivado em diferentes ambientes. Os experimentos foram realizados em estufa de plástico com e sem tela lateral antiinsetos e fora da estufa, em duas épocas (primavera-verão e verão-outono), no ano agrícola de 1999/2000. Mediu-se a matéria seca aérea e o índice de área foliar ao longo dos

  8. Emerald zoyzia grass development regarding photosynthetically active radiation in different slopes Desenvolvimento da grama-esmeralda em relação à radiação fotossinteticamente ativa em diferentes declividades

    Directory of Open Access Journals (Sweden)

    Ruchele M. Coan

    2012-06-01

    Full Text Available With this study, the objective was to estimate the photosynthetically active radiation (PAR and to correlate it with the dry matter (MMSPA of the emerald zoysia (Zoysia japonica Steud. on surfaces with different expositions and slopes. The research was conducted at the Experimental Watershed of the Agricultural Engineering Department, School of Agriculture and Veterinary Sciences of São Paulo State University (FCAV/UNESP, Brazil, where the surfaces (H, 10 N, 30 N, 50 N, 10 S, 30 S, 50 S, 10 L, 30 L, 50 L, 10 O, 30 O and 50 O were used. To obtain the global solar radiation, it was installed an automated weather station where the PAR (dependent variable was obtained by the equation y = a + bx, and the global radiation was independent. To compare means of MMSPA, it was used the Tukey test at 5% probability, and to assess the relation PAR/MMSPA, the simple linear correlation coefficient. The result showed that the accumulation of these effects in the PAR increases with North exposure and decreases with the South, and exposure to 50N is most suitable for slopes, not having correlation between the PAR and the MMSPA for the surfaces evaluated for the study period.Com este trabalho, o objetivo foi estimar a radiação fotossinteticamente ativa (PAR e correlacioná-la com a massa de matéria seca (MMSPA da grama-esmeralda (Zoysia japonica Steud., em superfícies com diferentes exposições e declividades. A pesquisa foi desenvolvida na Bacia Hidrográfica Experimental do Departamento de Engenharia Rural, FCAV/UNESP, Brasil, onde foram utilizadas as superfícies (H; 10 N; 30 N; 50 N; 10 S; 30 S; 50 S; 10 L; 30 L; 50 L; 10 O; 30 O e 50 O. Para a obtenção da radiação solar global, foi instalada uma estação meteorológica automatizada, onde a PAR (variável dependente foi obtida por meio da equação y = a + bx, e a radiação global foi a independente. Para comparação de médias da MMSPA, utilizou-se o teste de Tukey, a 5% de probabilidade, e para

  9. Eficiência de uso da radiação fotossinteticamente ativa pela cultura do tomateiro em diferentes ambientes Use efficiency of photosynthetically active radiation by tomato plants grown in different environments

    Directory of Open Access Journals (Sweden)

    Bernadete Radin

    2003-09-01

    Full Text Available A produção de biomassa pelas culturas está relacionada à quantidade de radiação fotossinteticamente ativa interceptada e absorvida pelas folhas, bem como à eficiência com que estas convertem a energia radiante em energia química, pela fotossíntese. O objetivo deste trabalho foi avaliar a eficiência de uso da radiação fotossinteticamente ativa pelo tomateiro (Lycopersicon esculentum Mill. cultivado em diferentes ambientes. Os experimentos foram realizados em estufa de plástico com e sem tela lateral antiinsetos e fora da estufa, em duas épocas (primavera-verão e verão-outono, no ano agrícola de 1999/2000. Mediu-se a matéria seca aérea e o índice de área foliar ao longo dos dois ciclos, assim como os fluxos de radiação incidente e transmitida. O ambiente em estufa com tela lateral antiinsetos teve menos radiação incidente e maior eficiência de seu uso: 0,44 e 0,60 g de matéria seca mol-1, nas primeira e segunda épocas, respectivamente. No ambiente fora da estufa, com mais radiação incidente, houve menor eficiência de seu uso (0,30 e 0,32 g mol-1, enquanto no ambiente em estufa sem tela lateral antiinsetos, foram obtidos valores intermediários de eficiência de uso da radiação (0,45 e 0,53 g mol-1.Crop biomass production is related to the amount of photosynthetically active radiation intercepted and absorbed by the leaves, as well as to their efficiency of conversion of this radiant energy into chemical energy through photosynthesis. The objective of this study was to evaluate the radiation use efficiency by tomato plants (Lycopersicon esculentum Mill. grown in different environments. Experiments were carried out in plastic-covered greenhouses with and without antiinsects screens and at open air plots, in different growth periods (spring-summer and summer-autumn during the 1999/2000 crop season. Measurements of dry above-ground biomass and leaf area index throughout both crop cycles were performed, and the

  10. Maximum Quantum Entropy Method

    OpenAIRE

    Sim, Jae-Hoon; Han, Myung Joon

    2018-01-01

    Maximum entropy method for analytic continuation is extended by introducing quantum relative entropy. This new method is formulated in terms of matrix-valued functions and therefore invariant under arbitrary unitary transformation of input matrix. As a result, the continuation of off-diagonal elements becomes straightforward. Without introducing any further ambiguity, the Bayesian probabilistic interpretation is maintained just as in the conventional maximum entropy method. The applications o...

  11. Maximum power demand cost

    International Nuclear Information System (INIS)

    Biondi, L.

    1998-01-01

    The charging for a service is a supplier's remuneration for the expenses incurred in providing it. There are currently two charges for electricity: consumption and maximum demand. While no problem arises about the former, the issue is more complicated for the latter and the analysis in this article tends to show that the annual charge for maximum demand arbitrarily discriminates among consumer groups, to the disadvantage of some [it

  12. Biomaterials based on photosynthetic membranes as potential sensors for herbicides.

    Science.gov (United States)

    Ventrella, Andrea; Catucci, Lucia; Placido, Tiziana; Longobardi, Francesco; Agostiano, Angela

    2011-08-15

    In this study, ultrathin film multilayers of Photosystem II-enriched photosynthetic membranes (BBY) were prepared and immobilized on quartz substrates by means of a Layer by Layer procedure exploiting electrostatic interactions with poly(ethylenimine) as polyelectrolyte. The biomaterials thus obtained were characterized by means of optical techniques and Atomic Force Microscopy, highlighting the fact that the Layer by Layer approach allowed the BBYs to be immobilized with satisfactory results. The activity of these hybrid materials was evaluated by means of optical assays based on the Hill Reaction, indicating that the biosamples, which preserved about 65% of their original activity even ten weeks after preparation, were both stable and active. Furthermore, an investigation of the biochips' sensitivity to the herbicide terbutryn, as a model analyte, gave interesting results: inhibition of photosynthetic activity was observed at terbutryn concentrations higher than 10(-7)M, thus evidencing the potential of such biomaterials in the environmental biosensor field. Copyright © 2011 Elsevier B.V. All rights reserved.

  13. Difference in photosynthetic performance among three peach ...

    African Journals Online (AJOL)

    The effects of low photosynthetic photon flux density (PPFD) on greenhouse grown peach trees ('Qingfeng': Prunus persica L. Batsch, 'NJN76': Prunus persica L. Batsch and 'Maixiang': P. persica var. nectarine) were investigated. Difference in photosynthesis rate (Pn) and stoma morphology among cultivars were studied.

  14. Photosynthetic carbon metabolism in freshwater phytoplankton

    International Nuclear Information System (INIS)

    Groeger, A.W.

    1986-01-01

    Photosynthetic carbon metabolism of natural assemblages of freshwater phytoplankton was measured by following the flow of inorganic 14 C into the photosynthetic end products polysaccharide protein, lipid, and soluble metabolites. Data were collected from a wide range of physical, chemical, and trophic conditions in six southern United States reservoirs, with the primary environmental variables of interest being light intensity and nutrient supply. Polysaccharide and protein were consistently the primary products of photosynthetic carbon metabolism, comprising an average of 70% of the total carbon fixation over a wide range of light intensities. Polysaccharide was quantitatively more important at higher light intensities, and protein at lower light intensities, as light intensity varied both with depth within the water column and over diurnal cycles. Polysaccharide synthesis was more variable over the diurnal period than was protein synthesis. Phytoplankton in the downlake epilimnion of Normandy Lake, a central Tennessee reservoir, responded to summer nitrogen (N) deficiency by increasing relative rates of lipid synthesis from 10-15% to 20-25% of the total photosynthetic carbon fixation. Phytoplankton in more nitrogen-sufficient areas of the reservoir maintained lower rates of lipid synthesis throughout the summer. These results document the occurrence in nature of a relationship between N-deficiency and increased lipid synthesis previously observed only in laboratory algal culture studies

  15. Natural strategies for photosynthetic light harvesting

    NARCIS (Netherlands)

    Croce, R.; van Amerongen, H.

    2014-01-01

    Photosynthetic organisms are crucial for life on Earth as they provide food and oxygen and are at the basis of most energy resources. They have a large variety of light-harvesting strategies that allow them to live nearly everywhere where sunlight can penetrate. They have adapted their pigmentation

  16. Excitons in intact cells of photosynthetic bacteria.

    Science.gov (United States)

    Freiberg, Arvi; Pajusalu, Mihkel; Rätsep, Margus

    2013-09-26

    Live cells and regular crystals seem fundamentally incompatible. Still, effects characteristic to ideal crystals, such as coherent sharing of excitation, have been recently used in many studies to explain the behavior of several photosynthetic complexes, especially the inner workings of the light-harvesting apparatus of the oldest known photosynthetic organisms, the purple bacteria. To this date, there has been no concrete evidence that the same effects are instrumental in real living cells, leaving a possibility that this is an artifact of unnatural study conditions, not a real effect relevant to the biological operation of bacteria. Hereby, we demonstrate survival of collective coherent excitations (excitons) in intact cells of photosynthetic purple bacteria. This is done by using excitation anisotropy spectroscopy for tracking the temperature-dependent evolution of exciton bands in light-harvesting systems of increasing structural complexity. The temperature was gradually raised from 4.5 K to ambient temperature, and the complexity of the systems ranged from detergent-isolated complexes to complete bacterial cells. The results provide conclusive evidence that excitons are indeed one of the key elements contributing to the energetic and dynamic properties of photosynthetic organisms.

  17. Dissipation of excess photosynthetic energy contributes to salinity tolerance: a comparative study of salt-tolerant Ricinus communis and salt-sensitive Jatropha curcas.

    Science.gov (United States)

    Lima Neto, Milton C; Lobo, Ana K M; Martins, Marcio O; Fontenele, Adilton V; Silveira, Joaquim Albenisio G

    2014-01-01

    The relationships between salt tolerance and photosynthetic mechanisms of excess energy dissipation were assessed using two species that exhibit contrasting responses to salinity, Ricinus communis (tolerant) and Jatropha curcas (sensitive). The salt tolerance of R. communis was indicated by unchanged electrolyte leakage (cellular integrity) and dry weight in leaves, whereas these parameters were greatly affected in J. curcas. The leaf Na+ content was similar in both species. Photosynthesis was intensely decreased in both species, but the reduction was more pronounced in J. curcas. In this species biochemical limitations in photosynthesis were more prominent, as indicated by increased C(i) values and decreased Rubisco activity. Salinity decreased both the V(cmax) (in vivo Rubisco activity) and J(max) (maximum electron transport rate) more significantly in J. curcas. The higher tolerance in R. communis was positively associated with higher photorespiratory activity, nitrate assimilation and higher cyclic electron flow. The high activity of these alternative electron sinks in R. communis was closely associated with a more efficient photoprotection mechanism. In conclusion, salt tolerance in R. communis, compared with J. curcas, is related to higher electron partitioning from the photosynthetic electron transport chain to alternative sinks. Copyright © 2013 Elsevier GmbH. All rights reserved.

  18. UV-B photoreceptor-mediated protection of the photosynthetic machinery in Chlamydomonas reinhardtii.

    Science.gov (United States)

    Allorent, Guillaume; Lefebvre-Legendre, Linnka; Chappuis, Richard; Kuntz, Marcel; Truong, Thuy B; Niyogi, Krishna K; Ulm, Roman; Goldschmidt-Clermont, Michel

    2016-12-20

    Life on earth is dependent on the photosynthetic conversion of light energy into chemical energy. However, absorption of excess sunlight can damage the photosynthetic machinery and limit photosynthetic activity, thereby affecting growth and productivity. Photosynthetic light harvesting can be down-regulated by nonphotochemical quenching (NPQ). A major component of NPQ is qE (energy-dependent nonphotochemical quenching), which allows dissipation of light energy as heat. Photodamage peaks in the UV-B part of the spectrum, but whether and how UV-B induces qE are unknown. Plants are responsive to UV-B via the UVR8 photoreceptor. Here, we report in the green alga Chlamydomonas reinhardtii that UVR8 induces accumulation of specific members of the light-harvesting complex (LHC) superfamily that contribute to qE, in particular LHC Stress-Related 1 (LHCSR1) and Photosystem II Subunit S (PSBS). The capacity for qE is strongly induced by UV-B, although the patterns of qE-related proteins accumulating in response to UV-B or to high light are clearly different. The competence for qE induced by acclimation to UV-B markedly contributes to photoprotection upon subsequent exposure to high light. Our study reveals an anterograde link between photoreceptor-mediated signaling in the nucleocytosolic compartment and the photoprotective regulation of photosynthetic activity in the chloroplast.

  19. UV-B photoreceptor-mediated protection of the photosynthetic machinery in Chlamydomonas reinhardtii

    Science.gov (United States)

    Allorent, Guillaume; Lefebvre-Legendre, Linnka; Chappuis, Richard; Kuntz, Marcel; Truong, Thuy B.; Niyogi, Krishna K.; Goldschmidt-Clermont, Michel

    2016-01-01

    Life on earth is dependent on the photosynthetic conversion of light energy into chemical energy. However, absorption of excess sunlight can damage the photosynthetic machinery and limit photosynthetic activity, thereby affecting growth and productivity. Photosynthetic light harvesting can be down-regulated by nonphotochemical quenching (NPQ). A major component of NPQ is qE (energy-dependent nonphotochemical quenching), which allows dissipation of light energy as heat. Photodamage peaks in the UV-B part of the spectrum, but whether and how UV-B induces qE are unknown. Plants are responsive to UV-B via the UVR8 photoreceptor. Here, we report in the green alga Chlamydomonas reinhardtii that UVR8 induces accumulation of specific members of the light-harvesting complex (LHC) superfamily that contribute to qE, in particular LHC Stress-Related 1 (LHCSR1) and Photosystem II Subunit S (PSBS). The capacity for qE is strongly induced by UV-B, although the patterns of qE-related proteins accumulating in response to UV-B or to high light are clearly different. The competence for qE induced by acclimation to UV-B markedly contributes to photoprotection upon subsequent exposure to high light. Our study reveals an anterograde link between photoreceptor-mediated signaling in the nucleocytosolic compartment and the photoprotective regulation of photosynthetic activity in the chloroplast. PMID:27930292

  20. Photosynthetic capacity of 'Niagara Rosada' grapes grown under transparent plastic covering

    Directory of Open Access Journals (Sweden)

    Bruna Corrêa da Silva de Deus

    2016-06-01

    Full Text Available ABSTRACT: New techniques in tropical regions such as use of transparent plastic covering (TPC, have been employed in grapes to avoid the wetting leaves and fruits, which can reduce the occurrence of fungal diseases, reduce the use of sprays, and reduce damage caused by hail and high winds. TPC may significantly affect the photosynthetic rates of grapevines cultivated in tropical regions, and thus have strong effects on plant productivity and improve fruit quality. However, in the North of Rio de Janeiro region there are lacks of studies related to TPC effects on photosynthetic capacity. The objective of this study was to evaluate the photosynthetic capacity in 'Niagara Rosada' vines grown under TPC and without transparent plastic covering (WTPC. The experiment was conducted between April and June 2013, on Tabuinha farm, located in the 3rd district of São Fidélis, Rio de Janeiro State, Brazil. A completely randomized block design was used with two treatments (TPC and WTPC and twelve replications. Evaluations consisted of climatological variables, gas exchange and maximum quantum efficiency of open photosystem II centers-quantum yield (Fv/Fm It was possible to observe that under TPC maximum temperature increase of 2.3°C, relative humidity reduced 1.5%, vapor pressure deficit increase 0.4kPa, and light intensity reduced 47.7%. These changes did not cause photochemical damage to the leaves. The TPC promoted higher net photosynthetic rate at 800h, which was associated with higher stomatal conductance. Thus, the TPC used in the northern region of Rio de Janeiro State did not impair the photosynthetic capacity of 'Niagara Rosada' vines.

  1. A remotely sensed pigment index reveals photosynthetic phenology in evergreen conifers.

    Science.gov (United States)

    Gamon, John A; Huemmrich, K Fred; Wong, Christopher Y S; Ensminger, Ingo; Garrity, Steven; Hollinger, David Y; Noormets, Asko; Peñuelas, Josep

    2016-11-15

    In evergreen conifers, where the foliage amount changes little with season, accurate detection of the underlying "photosynthetic phenology" from satellite remote sensing has been difficult, presenting challenges for global models of ecosystem carbon uptake. Here, we report a close correspondence between seasonally changing foliar pigment levels, expressed as chlorophyll/carotenoid ratios, and evergreen photosynthetic activity, leading to a "chlorophyll/carotenoid index" (CCI) that tracks evergreen photosynthesis at multiple spatial scales. When calculated from NASA's Moderate Resolution Imaging Spectroradiometer satellite sensor, the CCI closely follows the seasonal patterns of daily gross primary productivity of evergreen conifer stands measured by eddy covariance. This discovery provides a way of monitoring evergreen photosynthetic activity from optical remote sensing, and indicates an important regulatory role for carotenoid pigments in evergreen photosynthesis. Improved methods of monitoring photosynthesis from space can improve our understanding of the global carbon budget in a warming world of changing vegetation phenology.

  2. Photosynthesis of a scots pine shoot: the effect of shoot inclination on the photosynthetic response of a shoot subjected to direct radiation

    International Nuclear Information System (INIS)

    Oker-Blom, P.; Kellomaki, S.; Smolander, H.

    1983-01-01

    A set of photosynthetic responses of a Scots pine (Pinus sylvestris L.) shoot to light was derived from the shoot geometry and the photosynthetic response of a single needle. Computations showed that the shape of the photosynthesis light-curves varies substantially depending on the direction of radiation relative to the shoot position. Differences in the initial and maximum rates of photosynthesis were due to changes in the effective projection area and the irradiated fraction of the shoot, respectively

  3. Melatonin Improves the Photosynthetic Carbon Assimilation and Antioxidant Capacity in Wheat Exposed to Nano-ZnO Stress

    Directory of Open Access Journals (Sweden)

    Zhiyu Zuo

    2017-10-01

    Full Text Available The release of nanoparticles into the environment is inevitable, which has raised global environmental concern. Melatonin is involved in various stress responses in plants. The present study investigated the effects of melatonin on photosynthetic carbon (C assimilation and plant growth in nano-ZnO stressed plants. It was found that melatonin improved the photosynthetic C assimilation in nano-ZnO stressed wheat plants, mainly due to the enhanced photosynthetic energy transport efficiency, higher chlorophyll concentration and higher activities of Rubisco and ATPases. In addition, melatonin enhanced the activities of antioxidant enzymes to protect the photosynthetic electron transport system in wheat leaves against the oxidative burst caused by nano-ZnO stress. These results suggest that melatonin could improve the tolerance of wheat plants to nano-ZnO stress.

  4. Photoinhibition and photosynthetic pigment reorganisation dynamics in light/darkness cycles as photoprotective mechanisms of Porphyra umbilicalis against damaging effects of UV radiation

    Directory of Open Access Journals (Sweden)

    José Aguilera

    2008-03-01

    Full Text Available Porphyra umbilicalis L. Kutzing collected from the upper intertidal zone at Helgoland, North Sea, was exposed to different spectral ranges of UV radiation under both 12/12 h light/dark cycles and continuous irradiation. In light/dark cycles, oscillations of the optimal quantum yield (Fv /Fm were observed during the experiments, reaching maximal values at the end of the light phase followed by lower values during the dark phase. Decreased Fv /Fm was observed in thalli illuminated with photosynthetic active radiation (PAR plus UV-A and PAR+UV-A+UV-B, compared with the PAR control, indicating a certain degree of UV-induced photoinhibition. In addition, a decrease in the percentage of change of the linear initial slope and maximum electron transport rate (ETR estimated from ETR vs. irradiance curves was induced by UV radiation during the light phase. Recovery during the 12 h dark phase was almost completed in UV-A treated plants. PAR+UV-A seemed not to affect the photosynthesis, measured as O2 production. However, a decrease in O2 production was observed in the PAR+UV-A+UV-B treatment, but it recovered to initial values after 48 h of culture. No changes in total content of photosynthetic pigments were observed. However, thallus absorptance and the in vivo absorption cross-section in the PAR range (400-700 nm normalised to Chl a (a* parameter fluctuated during light/dark cycles and were positively correlated with changes in the optimum quantum yield, thus indicating that daily pigment reorganisation in the light-harvesting complex may play a key role in the photosynthetic performance of the algae. Both UV-A and UV-B treatments under continuous irradiation induced a significant reduction in the optimal quantum yield, ETR efficiency and photosynthetic oxygen production during the first 36 h to values around 30% of the initial ones. Thus, different protective mechanisms against UV stress can be observed in P. umbilicalis: dynamic photoinhibition when

  5. Chlorophyll fluorescence analysis revealed essential roles of FtsH 11 protease in regulation of the adaptive responses of photosynthetic systems to high temperature

    Science.gov (United States)

    Background: Photosynthetic systems are known to be sensitive to high temperature stress. To maintain a relatively “normal” level of photosynthetic activities, plants employ a variety of adaptive mechanisms in response to environmental temperature fluctuations. Previously, we reported that the chloro...

  6. Effects of gold nanoparticles on the photophysical and photosynthetic parameters of leaves and chloroplasts.

    Science.gov (United States)

    Torres, Rocio; Diz, Virginia E; Lagorio, M Gabriela

    2018-04-18

    Effects of gold nanoparticles (average diameter: 10-14 nm) on leaves and chloroplasts have been studied. Gold nanoparticles (AuNPs) quenched significantly chlorophyll fluorescence when introduced both in intact leaves and isolated chloroplasts. Additionally, the fluorescence spectra corrected for light re-absorption processes showed a net decrease in the fluorescence ratio calculated as the quotient between the maximum fluorescence at 680 and 735 nm. This fact gave evidence for a reduction in the fluorescence emission of the PSII relative to that of the PSI. Strikingly, the photosynthetic parameters derived from the analysis of the slow phase of Kautsky's kinetics, the rate of oxygen evolution and the rate of photo-reduction of 2,6-dichlorophenolindophenol were increased in the presence of AuNPs indicating an apparent greater photosynthetic capacity. The observed results were consistent with an electron transfer process from the excited PSII, which was thermodynamically possible, and which competed with both the electron transport process that initiated photosynthesis and the deactivation of the excited PSII by fluorescence emission. Additionally, it is here explained, in terms of a completely rational kinetic scheme and their corresponding algebraic expressions, why the photosynthetic parameters and the variable and non-variable fluorescence of chlorophyll are modified in a photosynthetic tissue containing gold nanoparticles.

  7. Tufted hairgrass (Deschampsia caespitosa) exhibits a lower photosynthetic plasticity than Antarctic hairgrass (D. antarctica).

    Science.gov (United States)

    Bystrzejewska-Piotrowska, Grazyna; Urban, Pawel L

    2009-06-01

    The aim of our work was to assess photosynthetic plasticity of two hairgrass species with different ecological origins (a temperate zone species, Deschampsia caespitosa (L.) Beauv. and an Antarctic species, D. antarctica) and to consider how the anticipated climate change may affect vitality of these plants. Measurements of chlorophyll fluorescence showed that the photosystem II (PSII) quantum efficiency of D. caespitosa decreased during 4 d of incubation at 4 degrees C but it remained stable in D. antarctica. The fluorescence half-rise times were almost always lower in D. caespitosa than in D. antarctica, irrespective of the incubation temperature. These results indicate that the photosynthetic apparatus of D. caespitosa has poorer performance in these conditions. D. caespitosa reached the maximum photosynthesis rate at a higher temperature than D. antarctica although the values obtained at 8 degrees C were similar in both species. The photosynthetic water-use efficiency (photosynthesis-to-transpiration ratio, P/E) emerges as an important factor demonstrating presence of mechanisms which facilitate functioning of a plant in non-optimal conditions. Comparison of the P/E values, which were higher in D. antarctica than in D. caespitosa at low and medium temperatures, confirms a high degree of adjustability of the photosynthetic apparatus in D. antarctica and unveils the lack of such a feature in D. caespitosa.

  8. Characterization of photosynthetic gas exchange in leaves under simulated adaxial and abaxial surfaces alternant irradiation.

    Science.gov (United States)

    Zhang, Zi-Shan; Li, Yu-Ting; Gao, Hui-Yuan; Yang, Cheng; Meng, Qing-Wei

    2016-07-05

    Previous investigations on photosynthesis have been performed on leaves irradiated from the adaxial surface. However, leaves usually sway because of wind. This action results in the alternating exposure of both the adaxial and abaxial surfaces to bright sunlight. To simulate adaxial and abaxial surfaces alternant irradiation (ad-ab-alt irradiation), the adaxial or abaxial surface of leaves were exposed to light regimes that fluctuated between 100 and 1,000 μmol m(-2) s(-1). Compared with constant adaxial irradiation, simulated ad-ab-alt irradiation suppressed net photosynthetic rate (Pn) and transpiration (E) but not water use efficiency. These suppressions were aggravated by an increase in alternant frequency of the light intensity. When leaves were transferred from constant light to simulated ad-ab-alt irradiation, the maximum Pn and E during the high light period decreased, but the rate of photosynthetic induction during this period remained constant. The sensitivity of photosynthetic gas exchange to simulated ad-ab-alt irradiation was lower on abaxial surface than adaxial surface. Under simulated ad-ab-alt irradiation, higher Pn and E were measured on abaxial surface compared with adaxial surface. Therefore, bifacial leaves can fix more carbon than leaves with two "sun-leaf-like" surfaces under ad-ab-alt irradiation. Photosynthetic research should be conducted under dynamic conditions that better mimic nature.

  9. Maximum likely scale estimation

    DEFF Research Database (Denmark)

    Loog, Marco; Pedersen, Kim Steenstrup; Markussen, Bo

    2005-01-01

    A maximum likelihood local scale estimation principle is presented. An actual implementation of the estimation principle uses second order moments of multiple measurements at a fixed location in the image. These measurements consist of Gaussian derivatives possibly taken at several scales and/or ...

  10. Robust Maximum Association Estimators

    NARCIS (Netherlands)

    A. Alfons (Andreas); C. Croux (Christophe); P. Filzmoser (Peter)

    2017-01-01

    textabstractThe maximum association between two multivariate variables X and Y is defined as the maximal value that a bivariate association measure between one-dimensional projections αX and αY can attain. Taking the Pearson correlation as projection index results in the first canonical correlation

  11. Changes of Photosynthetic Behaviors in Kappaphycus alvarezii Infected by Epiphyte

    Directory of Open Access Journals (Sweden)

    Tong Pang

    2011-01-01

    Full Text Available Epiphytic filamentous algae (EFA were noted as a serious problem to reduce the production and quality of K. alvarezii. The morphological studies revealed that the main epiphyte on K. alvarezii was Neosiphonia savatieri in China. Though the harmful effects of EFA on the production of K. alvarezii have been reported, the detailed mechanism of the N. savatieri in limiting the production of K. alvarezii has not been studied yet. The present paper studied the effects of N. savatieri infection on photosynthetic behaviors in K. alvarezii by detecting chlorophyll fluorescence transient in vivo. The results revealed that damage of oxygen-evolving complex (OEC, decrease of active reaction centers (RCs, and the plastoquinone (PQ pool as well as significant reduction in the performance indexes (PI of PSII were caused by the infection of N. savatieri. The influence of N. savatieri on photosynthetic activity of K. alvarezii should be one of the important reasons to reduce the production of K. alvarezii infected by N. savatieri.

  12. [Engineering photosynthetic cyanobacterial chassis: a review].

    Science.gov (United States)

    Wu, Qin; Chen, Lei; Wang, Jiangxin; Zhang, Weiwen

    2013-08-01

    Photosynthetic cyanobacteria possess a series of good properties, such as their abilities to capture solar energy for CO2 fixation, low nutritional requirements for growth, high growth rate, and relatively simple genetic background. Due to the high oil price and increased concern of the global warming in recent years, cyanobacteria have attracted widespread attention because they can serve as an 'autotrophic microbial factory' for producing renewable biofuels and fine chemicals directly from CO2. Particularly, significant progress has been made in applying synthetic biology techniques and strategies to construct and optimize cyanobacteria chassis. In this article, we critically summarized recent advances in developing new methods to optimize cyanobacteria chassis, improving cyanobacteria photosynthetic efficiency, and in constructing cyanobacteria chassis tolerant to products or environmental stresses. In addition, various industrial applications of cyanobacteria chassis are also discussed.

  13. Photosynthetic Rates of Citronella and Lemongrass 1

    Science.gov (United States)

    Herath, H. M. Walter; Ormrod, Douglas P.

    1979-01-01

    Ten selections of citronella (Cymbopogon nardus [L.] Rendle) were grown at 32/27, 27/21, or 15/10 C day/night temperatures, and plants from three populations of lemongrass (Cymbopogon citratus [D.C.] Stapf from Japan or Sri Lanka and Cymbopogon flexuosus [D.C.] Stapf from India) were grown at 8- or 15-hour photoperiods. Net photosynthetic rates of mature leaves were measured in a controlled environment at 25 C and 260 microeinsteins per meter2 per second. Rates declined with increasing leaf age, and from the tip to the base of the leaf blade. Rates for citronella leaves grown at 15/10 C were extremely low for all selections. Highest rates of net photosynthesis were recorded for four selections grown at 27/21 C and for two selections grown at 32/27 C. Lemongrass grown at 8-hour photoperiod had higher photosynthetic rates than that grown at 15-hour photoperiod. PMID:16660737

  14. Ionizing radiation and photosynthetic ability of cyanobacteria

    International Nuclear Information System (INIS)

    Agarwal, Rachna; Sainis, Jayashree K.

    2006-01-01

    Unicellular photoautotrophic cyanobacteria, Anacystis nidulans when exposed to lethal dose of 1.5 kGy of 60 Co γ- radiation (D 10 = 257.32 Gy) were as effective photosynthetical as unirradiated controls immediately after irradiation although level of ROS was higher by several magnitudes in these irradiated cells. The results suggested the preservation of the functional integrity of thylakoids even after exposure to lethal dose of ionizing radiation. (author)

  15. Nitrogen control of photosynthetic protein synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, G.W.

    1986-09-01

    Plant growth is severely affected by impaired photosynthesis resulting from nitrogen deficiency. The molecular aspects of this effect are being studied in the green alga Chlamydomonas grown in continuous culture systems. Photosynthetic membranes of nitrogen-limited cells are dramatically depleted in chlorophylls, xanthophylls and proteins of the light-harvesting complexes. In contrast, enzymes of the reductive pentose phosphate cycle and electron transport chain complexes are reduced only 40 to 65% on a per cell basis comparison with nitrogen-sufficient cultures. From analyses of mRNA levels by in vitro translation and hybridization analyses with cloned DNA sequences for photosynthetic proteins, we have found there are rather minor effects of nitrogen deficiency on nuclear or chloroplast gene transcription. Maturation of a transcript of the nuclear-encoded small subunit of ribulose 1,5-bisphosphate carboxylase is inhibited in nitrogen-deficient cells and causes accumulation of large amounts of mRNA precursors. Most of the effects of nitrogen deficiency on photosynthetic proteins appear to result from posttranscriptional regulatory processes: light-harvesting protein synthesis may be sustained but their import into chloroplasts or translocation to photosynthetic membranes is impaired. Nitrogen-deficient cells lack violaxanthin, a pigment that is essential for the structure, function and biogenesis of the major antenna complexes. The absence of this pigment may be a causative factor for the deficiency of light harvesting complexes. Finally, the accumulation of massive amounts of starch and triglycerides in nitrogen-limited cells indicate there are some genes whose maximal expression is dependent upon nitrogen-limiting conditions. 10 refs.

  16. Effect of sodium chloride on photosynthetic 14CO2 assimilation in Portulaca oleracea Linn

    International Nuclear Information System (INIS)

    Joshi, G.V.; Karadge, B.A.

    1979-01-01

    Effect of NaCl on ion uptake, photosynthetic rate and photosynthetic products in a C 4 non-CAM succulent, P. oleracea has been investigated. NaCl causes accumulation of Na as well as Cl ions with decrease in K and Ca contents. Chlorophylls and photosynthetic 14 CO 2 fixation rates are adversely affected due to sodium chloride salinity. Plants grown in the presence of NaCl show increase in C 4 acid percentage with increase in labelling of organic acids in light. Labelling of amino acids (particularly alanine) and sugars (sucrose) is affected by NaCl. Enzyme studies reveal that PEP-carboxylase is stimulated at all concentrations of NaCl but higher concentrations affected the activity of RuBP-Carboxylase. (author)

  17. Interference of Cd2+ in functioning of the photosynthetic apparatus of higher plants

    Directory of Open Access Journals (Sweden)

    Tadeusz Baszyński

    2014-01-01

    Full Text Available The actual opinions concerning the role of Cd2+ in inhibition of photosynthesis have been reviewed. The light phase of photosynthesis, particularly the site of Cd2+ action in the photosynthetic transport chain has been given the greatest attention. Cd2+-induced inhibition of Photosystem II activity as the result of thylakoid membrane degradation has been discussed. The present studies on Cd2+-inhibited dark reactions occurring in stroma has been analysed. Attention has been drawn to the fact that the results of studies in vitro are not always compatible with the changes found in the photosynthetic apparatus of higher plants growing in a Cd2 containing medium.

  18. Biochemical factors affecting the quantum efficiency of hydrogen production by membranes of green photosynthetic bacteria

    Energy Technology Data Exchange (ETDEWEB)

    Bernstein, J.D.; Olson, J.M.

    1981-01-01

    Photohydrogen production, 200-700 ..mu..mol H/sub 2/ h/sup -1/ (mg bacteriochlorophyll a)/sup -1/ has been obtained in a system containing unit membrane vesicles (Complex I) from the green photosynthetic bacterium Chlorobium limicola f. thiosulfatophilum, ascorbate, N,N,N',N'-tetramethyl-p-phenylenediamine, dithioerythritol, an oxygen scavenging mixture, either methyl viologen (MV) or clostridial ferredoxin (CPS Fd) as electron carrier, and either CPS hydrogenase or platinum asbestos as catalyst. All components are necessary for maximum activity, and spinach Fd cannot be substituted for CPS Fd. Higher rates of photohydrogen production are obtained using MV or CPS Fd with hydrogenase than with MV and Pt asbestos. The highest quantum efficiencies (7-10% at 0.2-0.9 mW absorbed light and over 20% at lower light) were obtained with CPS Fd, hydrogenase and non-saturating 812 nm light. With saturating white light, however, rates of photohydrogen production varied relatively little among the various combinations of electron carrier and catalyst tested. The reaction rate is unaffected by 0.03% Triton X-100, and is insensitive to treatment with antimycin a or m-chloro-carbonyl cyanide phenylhydrazone.This indicates that neither electron flow through an endogenous cyclic chain, nor maintenance of a proton gradient are involved in this process.

  19. Protection of the photosynthetic apparatus from extreme dehydration and oxidative stress in seedlings of transgenic tobacco.

    Directory of Open Access Journals (Sweden)

    Concepción Almoguera

    Full Text Available A genetic program that in sunflower seeds is activated by Heat Shock transcription Factor A9 (HaHSFA9 has been analyzed in transgenic tobacco seedlings. The ectopic overexpression of the HSFA9 program protected photosynthetic membranes, which resisted extreme dehydration and oxidative stress conditions. In contrast, heat acclimation of seedlings induced thermotolerance but not resistance to the harsh stress conditions employed. The HSFA9 program was found to include the expression of plastidial small Heat Shock Proteins that accumulate only at lower abundance in heat-stressed vegetative organs. Photosystem II (PSII maximum quantum yield was higher for transgenic seedlings than for non-transgenic seedlings, after either stress treatment. Furthermore, protection of both PSII and Photosystem I (PSI membrane protein complexes was observed in the transgenic seedlings, leading to their survival after the stress treatments. It was also shown that the plastidial D1 protein, a labile component of the PSII reaction center, and the PSI core protein PsaB were shielded from oxidative damage and degradation. We infer that natural expression of the HSFA9 program during embryogenesis may protect seed pro-plastids from developmental desiccation.

  20. Photosynthetic behavior, growth and essential oil production of Melissa officinalis L. cultivated under colored shade nets

    Directory of Open Access Journals (Sweden)

    Graziele C Oliveira

    2016-03-01

    Full Text Available The modulation of light is of importance during cultivation of medicinal plants to obtain desirable morphological and physiological changes associated with the maximum production of active principles. This study aimed to evaluate the effect of the light spectrum transmitted by colored shade nets on growth, essential oil production and photosynthetic behavior in plants of lemon balm (Melissa officinalis L. Plants were cultivated in pots for 4-mo under black, red, and blue nets with 50% shading, and full sunlight exposure. Biometric and anatomical variables, essential oil yield, global solar radiation, photon flux density, chlorophyll content, and gas exchange parameters were measured in M. officinalis leaves. The results showed that despite being considered a partial shade plant, this species is able to adapt to full sunlight conditions without increasing biomass production. The spectral changes provided by colored shade nets did not caused any noticeable change in leaf anatomy of M. officinalis. However, the use of blue net resulted in increments of 116% in plant height, 168% in leaf area, 42% in chlorophyll content and 30% in yield of essential oil in lemon balm plants. These plant's qualities make the use of blue net a cultivation practice suitable for commercial use.

  1. Maximum power point tracking

    International Nuclear Information System (INIS)

    Enslin, J.H.R.

    1990-01-01

    A well engineered renewable remote energy system, utilizing the principal of Maximum Power Point Tracking can be m ore cost effective, has a higher reliability and can improve the quality of life in remote areas. This paper reports that a high-efficient power electronic converter, for converting the output voltage of a solar panel, or wind generator, to the required DC battery bus voltage has been realized. The converter is controlled to track the maximum power point of the input source under varying input and output parameters. Maximum power point tracking for relative small systems is achieved by maximization of the output current in a battery charging regulator, using an optimized hill-climbing, inexpensive microprocessor based algorithm. Through practical field measurements it is shown that a minimum input source saving of 15% on 3-5 kWh/day systems can easily be achieved. A total cost saving of at least 10-15% on the capital cost of these systems are achievable for relative small rating Remote Area Power Supply systems. The advantages at larger temperature variations and larger power rated systems are much higher. Other advantages include optimal sizing and system monitor and control

  2. Comparative Effects of Salt Stress and Extreme pH Stress Combined on Glycinebetaine Accumulation, Photosynthetic Abilities and Growth Characters of Two Rice Genotypes

    Directory of Open Access Journals (Sweden)

    Suriyan CHA-UM

    2009-12-01

    Full Text Available Glycinebetaine (Glybet accumulation, photosynthetic efficiency and growth performance in indica rice cultivated under salt stress and extreme pH stress were investigated. Betaine aldehyde dehydrogenase (BADH activity and Glybet accumulation in the seedlings of salt-tolerant and salt-sensitive rice varieties grown under saline and acidic conditions peaked after treatment for 72 h and 96 h, respectively, and were higher than those grown under neutral pH and alkaline salt stress. A positive correlation was found between BADH activity and Glybet content in both salt-tolerant (r2 = 0.71 and salt-sensitive (r2 = 0.86 genotypes. The chlorophyll a, chlorophyll b, total chlorophyll and total carotenoids contents in the stressed seedlings significantly decreased under both acidic and alkaline stresses, especially in the salt-sensitive genotype. Similarly, the maximum quantum yield of PSII (Fv/Fm, photon yield of PSII (ΦPSII, non-photochemical quenching (NPQ and net photosynthetic rate (Pn in the stressed seedlings were inhibited, leading to overall growth reduction. The positive correlations between chlorophyll a content and Fv/Fm, total chlorophyll content and ΦPSII, ΦPSII and Pn as well as Pn and leaf area in both salt-tolerant and salt-sensitive genotypes were found. Saline acidic and saline alkaline soils may play a key role affecting vegetative growth prior to the reproductive stage in rice plants.

  3. A comparative analysis of simulated and observed photosynthetic CO2 uptake in two coniferous forest canopies

    DEFF Research Database (Denmark)

    Ibrom, A.; Jarvis, P.G.; Clement, R.

    2006-01-01

    -photosynthetically-active-radiation-induced biophysical variability in the simulated Pg. Analysis of residuals identified only small systematic differences between the modeled flux estimates and turbulent flux measurements at high vapor pressure saturation deficits. The merits and limitations of comparative analysis for quality evaluation of both...

  4. Dynamics of photosynthetic photon flux density (PPFD) and estimates in coastal northern California

    Science.gov (United States)

    The seasonal trends and diurnal patterns of Photosynthetically Active Radiation (PAR) were investigated in the San Francisco Bay Area of Northern California from March through August in 2007 and 2008. During these periods, the daily values of PAR flux density (PFD), energy loading with PAR (PARE), a...

  5. Dynamic reorganization of photosynthetic supercomplexes during environmental acclimation

    Directory of Open Access Journals (Sweden)

    Jun eMinagawa

    2013-12-01

    Full Text Available Plants and algae have acquired the ability to acclimate to ever-changing environments in order to survive. During photosynthesis, light energy is converted by several membrane protein supercomplexes into electrochemical energy, which is eventually used to assimilate CO2. The efficiency of photosynthesis is modulated by many environmental factors such as quality and quantity of light, temperature, drought, and CO2 concentration, among others. Accumulating evidence indicates that photosynthetic supercomplexes undergo supramolecular reorganization within a short timeframe during acclimation to an environmental change. This reorganization includes state transitions that balance the excitation of photosystem I and II by shuttling peripheral antenna proteins between the two, thermal energy dissipation that occurs at energy-quenching sites within the light-harvesting antenna generated for negative feedback when excess light is absorbed, and cyclic electron flow that is facilitated between photosystem I and the cytochrome bf complex when cells demand more ATP and/or need to activate energy dissipation. This review will highlight the recent findings regarding these environmental acclimation events in model organisms with particular attention to the unicellular green alga C. reinhardtii and with reference to the vascular plant A. thaliana, which offers a glimpse into the dynamic behavior of photosynthetic machineries in nature.

  6. Height-related changes in leaf photosynthetic traits in diverse Bornean tropical rain forest trees.

    Science.gov (United States)

    Kenzo, Tanaka; Inoue, Yuta; Yoshimura, Mitsunori; Yamashita, Megumi; Tanaka-Oda, Ayumi; Ichie, Tomoaki

    2015-01-01

    Knowledge of variations in morphophysiological leaf traits with forest height is essential for quantifying carbon and water fluxes from forest ecosystems. Here, we examined changes in leaf traits with forest height in diverse tree species and their role in environmental acclimation in a tropical rain forest in Borneo that does not experience dry spells. Height-related changes in leaf physiological and morphological traits [e.g., maximum photosynthetic rate (Amax), stomatal conductance (gs), dark respiration rate (Rd), carbon isotope ratio (δ(13)C), nitrogen (N) content, and leaf mass per area (LMA)] from understory to emergent trees were investigated in 104 species in 29 families. We found that many leaf area-based physiological traits (e.g., A(max-area), Rd, gs), N, δ(13)C, and LMA increased linearly with tree height, while leaf mass-based physiological traits (e.g., A(max-mass)) only increased slightly. These patterns differed from other biomes such as temperate and tropical dry forests, where trees usually show decreased photosynthetic capacity (e.g., A(max-area), A(max-mass)) with height. Increases in photosynthetic capacity, LMA, and δ(13)C are favored under bright and dry upper canopy conditions with higher photosynthetic productivity and drought tolerance, whereas lower R d and LMA may improve shade tolerance in lower canopy trees. Rapid recovery of leaf midday water potential to theoretical gravity potential during the night supports the idea that the majority of trees do not suffer from strong drought stress. Overall, leaf area-based photosynthetic traits were associated with tree height and the degree of leaf drought stress, even in diverse tropical rain forest trees.

  7. Canopy profiles of photosynthetic parameters under elevated CO2 and N fertilization in a poplar plantation

    International Nuclear Information System (INIS)

    Calfapietra, Carlo; Tulva, Ingmar; Eensalu, Eve; Perez, Marta; De Angelis, Paolo; Scarascia-Mugnozza, Giuseppe; Kull, Olevi

    2005-01-01

    A poplar plantation has been exposed to an elevated CO 2 concentration for 5 years using the free air CO 2 enrichment (FACE) technique. Even after such a long period of exposure, leaves of Populus x euramericana have not shown clear signs of photosynthetic acclimation. Only at the end of the growing season for shade leaves was a decrease of maximum velocity of carboxylation (V cmax ) observed. Maximum electron transport rate (J max ) was increased by FACE treatment in July. Assimilation rates at CO 2 partial pressure of 400 (A 400 ) and 600 (A 600 ) μmol mol -1 were not significantly different under FACE treatment. Most notably FACE significantly decreased stomatal conductance (g s ) both on upper and lower canopy leaves. N fertilization increased N content in the leaves on mass basis (N m ) and specific leaf area (SLA) in both CO 2 treatments but did not influence the photosynthetic parameters. These data show that in poplar plantations the long-term effects of elevated CO 2 on photosynthesis do not differ considerably from the short-term ones even with N deposition. - Photosynthetic acclimation occurred only marginally

  8. Maximum entropy methods

    International Nuclear Information System (INIS)

    Ponman, T.J.

    1984-01-01

    For some years now two different expressions have been in use for maximum entropy image restoration and there has been some controversy over which one is appropriate for a given problem. Here two further entropies are presented and it is argued that there is no single correct algorithm. The properties of the four different methods are compared using simple 1D simulations with a view to showing how they can be used together to gain as much information as possible about the original object. (orig.)

  9. A rice plastidial nucleotide sugar epimerase is involved in galactolipid biosynthesis and improves photosynthetic efficiency.

    Directory of Open Access Journals (Sweden)

    Chunlai Li

    2011-07-01

    Full Text Available Photosynthesis is the final determinator for crop yield. To gain insight into genes controlling photosynthetic capacity, we selected from our large T-DNA mutant population a rice stunted growth mutant with decreased carbon assimilate and yield production named photoassimilate defective1 (phd1. Molecular and biochemical analyses revealed that PHD1 encodes a novel chloroplast-localized UDP-glucose epimerase (UGE, which is conserved in the plant kingdom. The chloroplast localization of PHD1 was confirmed by immunoblots, immunocytochemistry, and UGE activity in isolated chloroplasts, which was approximately 50% lower in the phd1-1 mutant than in the wild type. In addition, the amounts of UDP-glucose and UDP-galactose substrates in chloroplasts were significantly higher and lower, respectively, indicating that PHD1 was responsible for a major part of UGE activity in plastids. The relative amount of monogalactosyldiacylglycerol (MGDG, a major chloroplast membrane galactolipid, was decreased in the mutant, while the digalactosyldiacylglycerol (DGDG amount was not significantly altered, suggesting that PHD1 participates mainly in UDP-galactose supply for MGDG biosynthesis in chloroplasts. The phd1 mutant showed decreased chlorophyll content, photosynthetic activity, and altered chloroplast ultrastructure, suggesting that a correct amount of galactoglycerolipids and the ratio of glycolipids versus phospholipids are necessary for proper chloroplast function. Downregulated expression of starch biosynthesis genes and upregulated expression of sucrose cleavage genes might be a result of reduced photosynthetic activity and account for the decreased starch and sucrose levels seen in phd1 leaves. PHD1 overexpression increased photosynthetic efficiency, biomass, and grain production, suggesting that PHD1 plays an important role in supplying sufficient galactolipids to thylakoid membranes for proper chloroplast biogenesis and photosynthetic activity. These

  10. The last glacial maximum

    Science.gov (United States)

    Clark, P.U.; Dyke, A.S.; Shakun, J.D.; Carlson, A.E.; Clark, J.; Wohlfarth, B.; Mitrovica, J.X.; Hostetler, S.W.; McCabe, A.M.

    2009-01-01

    We used 5704 14C, 10Be, and 3He ages that span the interval from 10,000 to 50,000 years ago (10 to 50 ka) to constrain the timing of the Last Glacial Maximum (LGM) in terms of global ice-sheet and mountain-glacier extent. Growth of the ice sheets to their maximum positions occurred between 33.0 and 26.5 ka in response to climate forcing from decreases in northern summer insolation, tropical Pacific sea surface temperatures, and atmospheric CO2. Nearly all ice sheets were at their LGM positions from 26.5 ka to 19 to 20 ka, corresponding to minima in these forcings. The onset of Northern Hemisphere deglaciation 19 to 20 ka was induced by an increase in northern summer insolation, providing the source for an abrupt rise in sea level. The onset of deglaciation of the West Antarctic Ice Sheet occurred between 14 and 15 ka, consistent with evidence that this was the primary source for an abrupt rise in sea level ???14.5 ka.

  11. Pyramiding expression of maize genes encoding phosphoenolpyruvate carboxylase (PEPC) and pyruvate orthophosphate dikinase (PPDK) synergistically improve the photosynthetic characteristics of transgenic wheat.

    Science.gov (United States)

    Zhang, HuiFang; Xu, WeiGang; Wang, HuiWei; Hu, Lin; Li, Yan; Qi, XueLi; Zhang, Lei; Li, ChunXin; Hua, Xia

    2014-09-01

    Using particle bombardment transformation, we introduced maize pepc cDNA encoding phosphoenolpyruvate carboxylase (PEPC) and ppdk cDNA encoding pyruvate orthophosphate dikinase (PPDK) into the C3 crop wheat to generate transgenic wheat lines carrying cDNA of pepc (PC lines), ppdk (PK lines) or both (PKC lines). The integration, transcription, and expression of the foreign genes were confirmed by Southern blot, Real-time quantitative reverse transcription PCR (Q-RT-PCR), and Western blot analysis. Q-RT-PCR results indicated that the average relative expression levels of pepc and ppdk in the PKC lines reached 10 and 4.6, respectively, compared to their expressions in untransformed plants (set to 1). The enzyme activities of PEPC and PPDK in the PKC lines were 4.3- and 2.1-fold higher, respectively, than in the untransformed control. The maximum daily net photosynthetic rates of the PKC, PC, and PK lines were enhanced by 26.4, 13.3, and 4.5%, respectively, whereas the diurnal accumulations of photosynthesis were 21.3, 13.9, and 6.9%, respectively, higher than in the control. The Fv/Fm of the transgenic plants decreased less than in the control under high temperature and high light conditions (2 weeks after anthesis), suggesting that the transgenic wheat transports more absorbed light energy into a photochemical reaction. The exogenous maize C4-specific pepc gene was more effective than ppdk at improving the photosynthetic performance and yield characteristics of transgenic wheat, while the two genes showed a synergistic effect when they were transformed into the same genetic background, because the PKC lines exhibited improved photosynthetic and physiological traits.

  12. Effects of water stress and high temperature on photosynthetic rates of two species of Prosopis.

    Science.gov (United States)

    Delatorre, Jose; Pinto, Manuel; Cardemil, Liliana

    2008-08-21

    The main aim of this research was to compare the photosynthetic responses of two species of Prosopis, Prosopis chilensis (algarrobo) and Prosopis tamarugo (tamarugo) subjected to heat and water stress, to determine how heat shock or water deficit, either individually or combined, affect the photosynthesis of these two species. The photosynthetic rates expressed as a function of photon flow density (PFD) were determined by the O(2) liberated, in seedlings of tamarugo and algarrobo subjected to two water potentials: -0.3 MPa and -2.5 MPa and to three temperatures: 25 degrees C, 35 degrees C and 40 degrees C. Light response curves were constructed to obtain light compensation and light saturation points, maximum photosynthetic rates, quantum yields and dark respiration rates. The photochemical efficiency as the F(v)/F(m) ratio and the amount of RUBISCO were also determined under heat shock, water deficit, and under the combined action of both stress. Photosynthetic rates at a light intensity higher than 500 micromole photons m(-2)s(-1) were not significantly different (P>0.05) between species when measured at 25 degrees C under the same water potential. The maximum photosynthetic rates decreased with temperature in both species and with water deficit in algarrobo. At 40 degrees C and -2.5 MPa, the photosynthetic rate of algarrobo fell to 72% of that of tamarugo. The quantum yield decreased in algarrobo with temperature and water deficit and it was reduced by 50% when the conditions were 40 degrees C and -2.5 MPa. Dark respiration increased by 62% respect to the control at 40 degrees C in tamarugo while remained unchanged in algarrobo. The photochemical efficiency decreased with both, high temperature and water deficit, without differences between species. RUBISCO content increased in algarrobo 35 degrees C. Water deficit reduced the amount of RUBISCO in both species. The results of this work support the conclusion that in both Prosopis species, the interaction between

  13. Effect of Chernobyl radionuclides accumulation on the photosynthetic processes and nitrogen metabolism of Lupines Luteus L

    International Nuclear Information System (INIS)

    Zabolotnyj, A.I.; Goncharova, N.V.; Domash, V.I.; Sheverdov, V.V.; Akadehmiya Navuk Belarusi, Minsk

    1995-01-01

    The 134 Cs, 137 Cs and chlorophyll content activity of photochemical reaction in chloroplasts and symbiotic nitrogen fixation in root modules, activity of neutral protease, BAPAse and trypsin inhibitors were investigated for seeds to yellow lupine (Lupines luteus L). The level of radioactive contamination induced a tendency to change the activity of photosynthetic reaction and nitrogen fixation, significant changes in a set of trypsin inhibitors were found in nature lupine seeds

  14. Maximum Entropy Fundamentals

    Directory of Open Access Journals (Sweden)

    F. Topsøe

    2001-09-01

    Full Text Available Abstract: In its modern formulation, the Maximum Entropy Principle was promoted by E.T. Jaynes, starting in the mid-fifties. The principle dictates that one should look for a distribution, consistent with available information, which maximizes the entropy. However, this principle focuses only on distributions and it appears advantageous to bring information theoretical thinking more prominently into play by also focusing on the "observer" and on coding. This view was brought forward by the second named author in the late seventies and is the view we will follow-up on here. It leads to the consideration of a certain game, the Code Length Game and, via standard game theoretical thinking, to a principle of Game Theoretical Equilibrium. This principle is more basic than the Maximum Entropy Principle in the sense that the search for one type of optimal strategies in the Code Length Game translates directly into the search for distributions with maximum entropy. In the present paper we offer a self-contained and comprehensive treatment of fundamentals of both principles mentioned, based on a study of the Code Length Game. Though new concepts and results are presented, the reading should be instructional and accessible to a rather wide audience, at least if certain mathematical details are left aside at a rst reading. The most frequently studied instance of entropy maximization pertains to the Mean Energy Model which involves a moment constraint related to a given function, here taken to represent "energy". This type of application is very well known from the literature with hundreds of applications pertaining to several different elds and will also here serve as important illustration of the theory. But our approach reaches further, especially regarding the study of continuity properties of the entropy function, and this leads to new results which allow a discussion of models with so-called entropy loss. These results have tempted us to speculate over

  15. Magnetic irone oxide nanoparticles in photosynthetic systems

    International Nuclear Information System (INIS)

    Khalilov, R.I.; Nasibova, A.N.; Khomutov, G.B.

    2014-01-01

    Full text : It was found and studied the effect of biogenic formation of magnetic inclusions in photosynthetic systems - in various higher plants under the influence of some external stress factors (radiation impact, moisture deficit) and in a model system - a suspension of chloroplasts. For registration and characterization of magnetic nanoparticles in the samples used EPR spectrometer because superparamagnetic and ferromagnetic nanoparticles have a chcracteristic signals of electron magnetic resonance. For direct visualization of magnetic nanoparticles it was used the method of transmission electron microscopy

  16. Engineering cyanobacteria as photosynthetic feedstock factories.

    Science.gov (United States)

    Hays, Stephanie G; Ducat, Daniel C

    2015-03-01

    Carbohydrate feedstocks are at the root of bioindustrial production and are needed in greater quantities than ever due to increased prioritization of renewable fuels with reduced carbon footprints. Cyanobacteria possess a number of features that make them well suited as an alternative feedstock crop in comparison to traditional terrestrial plant species. Recent advances in genetic engineering, as well as promising preliminary investigations of cyanobacteria in a number of distinct production regimes have illustrated the potential of these aquatic phototrophs as biosynthetic chassis. Further improvements in strain productivities and design, along with enhanced understanding of photosynthetic metabolism in cyanobacteria may pave the way to translate cyanobacterial theoretical potential into realized application.

  17. Probable maximum flood control

    International Nuclear Information System (INIS)

    DeGabriele, C.E.; Wu, C.L.

    1991-11-01

    This study proposes preliminary design concepts to protect the waste-handling facilities and all shaft and ramp entries to the underground from the probable maximum flood (PMF) in the current design configuration for the proposed Nevada Nuclear Waste Storage Investigation (NNWSI) repository protection provisions were furnished by the United States Bureau of Reclamation (USSR) or developed from USSR data. Proposed flood protection provisions include site grading, drainage channels, and diversion dikes. Figures are provided to show these proposed flood protection provisions at each area investigated. These areas are the central surface facilities (including the waste-handling building and waste treatment building), tuff ramp portal, waste ramp portal, men-and-materials shaft, emplacement exhaust shaft, and exploratory shafts facility

  18. Introduction to maximum entropy

    International Nuclear Information System (INIS)

    Sivia, D.S.

    1988-01-01

    The maximum entropy (MaxEnt) principle has been successfully used in image reconstruction in a wide variety of fields. We review the need for such methods in data analysis and show, by use of a very simple example, why MaxEnt is to be preferred over other regularizing functions. This leads to a more general interpretation of the MaxEnt method, and its use is illustrated with several different examples. Practical difficulties with non-linear problems still remain, this being highlighted by the notorious phase problem in crystallography. We conclude with an example from neutron scattering, using data from a filter difference spectrometer to contrast MaxEnt with a conventional deconvolution. 12 refs., 8 figs., 1 tab

  19. Solar maximum observatory

    International Nuclear Information System (INIS)

    Rust, D.M.

    1984-01-01

    The successful retrieval and repair of the Solar Maximum Mission (SMM) satellite by Shuttle astronauts in April 1984 permitted continuance of solar flare observations that began in 1980. The SMM carries a soft X ray polychromator, gamma ray, UV and hard X ray imaging spectrometers, a coronagraph/polarimeter and particle counters. The data gathered thus far indicated that electrical potentials of 25 MeV develop in flares within 2 sec of onset. X ray data show that flares are composed of compressed magnetic loops that have come too close together. Other data have been taken on mass ejection, impacts of electron beams and conduction fronts with the chromosphere and changes in the solar radiant flux due to sunspots. 13 references

  20. Introduction to maximum entropy

    International Nuclear Information System (INIS)

    Sivia, D.S.

    1989-01-01

    The maximum entropy (MaxEnt) principle has been successfully used in image reconstruction in a wide variety of fields. The author reviews the need for such methods in data analysis and shows, by use of a very simple example, why MaxEnt is to be preferred over other regularizing functions. This leads to a more general interpretation of the MaxEnt method, and its use is illustrated with several different examples. Practical difficulties with non-linear problems still remain, this being highlighted by the notorious phase problem in crystallography. He concludes with an example from neutron scattering, using data from a filter difference spectrometer to contrast MaxEnt with a conventional deconvolution. 12 refs., 8 figs., 1 tab

  1. Functional Maximum Autocorrelation Factors

    DEFF Research Database (Denmark)

    Larsen, Rasmus; Nielsen, Allan Aasbjerg

    2005-01-01

    MAF outperforms the functional PCA in concentrating the interesting' spectra/shape variation in one end of the eigenvalue spectrum and allows for easier interpretation of effects. Conclusions. Functional MAF analysis is a useful methods for extracting low dimensional models of temporally or spatially......Purpose. We aim at data where samples of an underlying function are observed in a spatial or temporal layout. Examples of underlying functions are reflectance spectra and biological shapes. We apply functional models based on smoothing splines and generalize the functional PCA in......\\verb+~+\\$\\backslash\\$cite{ramsay97} to functional maximum autocorrelation factors (MAF)\\verb+~+\\$\\backslash\\$cite{switzer85,larsen2001d}. We apply the method to biological shapes as well as reflectance spectra. {\\$\\backslash\\$bf Methods}. MAF seeks linear combination of the original variables that maximize autocorrelation between...

  2. Regularized maximum correntropy machine

    KAUST Repository

    Wang, Jim Jing-Yan; Wang, Yunji; Jing, Bing-Yi; Gao, Xin

    2015-01-01

    In this paper we investigate the usage of regularized correntropy framework for learning of classifiers from noisy labels. The class label predictors learned by minimizing transitional loss functions are sensitive to the noisy and outlying labels of training samples, because the transitional loss functions are equally applied to all the samples. To solve this problem, we propose to learn the class label predictors by maximizing the correntropy between the predicted labels and the true labels of the training samples, under the regularized Maximum Correntropy Criteria (MCC) framework. Moreover, we regularize the predictor parameter to control the complexity of the predictor. The learning problem is formulated by an objective function considering the parameter regularization and MCC simultaneously. By optimizing the objective function alternately, we develop a novel predictor learning algorithm. The experiments on two challenging pattern classification tasks show that it significantly outperforms the machines with transitional loss functions.

  3. Regularized maximum correntropy machine

    KAUST Repository

    Wang, Jim Jing-Yan

    2015-02-12

    In this paper we investigate the usage of regularized correntropy framework for learning of classifiers from noisy labels. The class label predictors learned by minimizing transitional loss functions are sensitive to the noisy and outlying labels of training samples, because the transitional loss functions are equally applied to all the samples. To solve this problem, we propose to learn the class label predictors by maximizing the correntropy between the predicted labels and the true labels of the training samples, under the regularized Maximum Correntropy Criteria (MCC) framework. Moreover, we regularize the predictor parameter to control the complexity of the predictor. The learning problem is formulated by an objective function considering the parameter regularization and MCC simultaneously. By optimizing the objective function alternately, we develop a novel predictor learning algorithm. The experiments on two challenging pattern classification tasks show that it significantly outperforms the machines with transitional loss functions.

  4. Enhanced photosynthetic capacity and antioxidant potential mediate brassinosteriod-induced phenanthrene stress tolerance in tomato

    International Nuclear Information System (INIS)

    Ahammed, Golam Jalal; Li, Xin; Xia, Xiao-Jian; Shi, Kai; Zhou, Yan-Hong; Yu, Jing-Quan

    2015-01-01

    Photosynthesis, the basal manufacturing process in the earth is habitually restricted by airborne micropollutants such as phenanthrene (PHE). Here, we show that 24-epibrassinolide (EBR), a bioactive plant steroid is able to keep higher photosynthetic capacity consistently for a long period under a shoot-imposed PHE stress in tomato. EBR-promoted photosynthetic capacity and efficiency eventually resulted in a 37.5% increase of biomass under PHE stress. As primary response, transcripts of antioxidant genes were remarkably induced by EBR in PHE-treated plants. Activities of antioxidant and detoxification enzymes were also enhanced by EBR. Notably, EBR-induced higher antioxidant potential was associated with reduced levels of H 2 O 2 and O 2 · — , resulting in a 32.7% decrease of content of malondialdehyde in the end of experiment and relatively healthy chloroplast ultrastructure in EBR + PHE treatment compared with PHE alone. These results indicate that EBR alleviates shoot-imposed PHE phytotoxicity by maintaining a consistently higher photosynthetic capacity and antioxidant potential in tomato. - Highlights: • PHE mist spray gradually inhibits photosynthesis and eventually reduces biomass. • EBR maintains a consistently higher photosynthesis even under PHE stress. • EBR upregulates expression of antioxidant genes as initial response to PHE stress. • EBR reduces oxidative stress by constantly activating strong antioxidant potential. • EBR-induced efficient neutralization of ROS protects chloroplast ultrastructure. - 24-epibrassinolide protects tomato plants from airborne phenanthrene-induced damages by maintaining a consistently higher photosynthetic capacity and antioxidant potential

  5. ENHANCED PRACTICAL PHOTOSYNTHETIC CO2 MITIGATION

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Gregory Kremer; Dr. David J. Bayless; Dr. Morgan Vis; Dr. Michael Prudich; Dr. Keith Cooksey; Dr. Jeff Muhs

    2002-07-15

    This quarterly report documents significant achievements in the Enhanced Practical Photosynthetic CO{sub 2} Mitigation project during the period from 4/2/2001 through 7/01/2002. Most of the achievements are milestones in our efforts to complete the tasks and subtasks that constitute the project objectives, and we are currently on schedule to complete Phase I activities by 10/2002, the milestone date from the original project timeline. As indicated in the list of accomplishments below, our efforts are focused on improving the design of the bioreactor test system, evaluating candidate organisms and growth surfaces, and scaling-up the test facilities from bench scale to pilot scale. Specific results and accomplishments for the second quarter of 2002 include: Organisms and Growth Surfaces: (1) Our collection of cyanobacteria, isolated in YNP was increased to 15 unialgal cultures. (2) Illumination rate about 50 {micro}E/m{sup 2}/sec is not saturated for the growth of 1.2 s.c. (2) isolate. The decrease of illumination rate led to the decrease of doubling time of this isolate. (3) The positive effect of Ca{sup 2+} on the growth of isolate 1.2 s.c. (2) without Omnisil was revealed, though Ca{sup 2+} addition was indifferent for the growth of this isolate at the presence of Omnisil. (4) Calcium addition had a positive effect on the generation of cyanobacterial biofilm on Omnisil surface. (5) The survivability problems with the Tr9.4 organism on Omnisil screens in the CRF2 model-scale bioreactor have been solved. The problems were related to the method used to populate the growth surfaces. When pre-populated screens were placed in the bioreactor the microalgae died within 72 hours, but when the microalgae were cultured while in place in the bioreactor using a continuous-population method they grew well inside of the CRF2 test system and survived for the full 7-day test duration. CRF2 tests will continue as soon as the new combined drip system/harvesting system header pipe

  6. Electrolyte control of photosynthetic electron transport in cyanobacteria

    International Nuclear Information System (INIS)

    Papageorgiou, G.C.

    1986-01-01

    Ion-permeable cells (permeaplasts) of the cyanobacterium Anacystis nidulans were prepared enzymatically and were characterized with respect to several structural and functional indices. The permeaplasts contain intact, ion-impermeable thylakoids and are photosynthetically active. The authors discuss how, employing these cells, they investigated the effects of cations, acting either on the outer, or on the inner thylakoid membrane surface, on photoinduced electron exchanges with anionic donors (Cyt c-550, plastocyanin, innersurface), or anionic acceptors (FeCN 3- ; outer surface). Cations accelerate such exchanges by accumulating near the solution-membrane interfaces and screening the negative surface charge of membranes. Electrostatic screening, however, is not the only contributing factor, and other electrolyte-linked influences must be invoked in order to interpret the experimental observations

  7. Redox regulation of photosynthetic gene expression.

    Science.gov (United States)

    Queval, Guillaume; Foyer, Christine H

    2012-12-19

    Redox chemistry and redox regulation are central to the operation of photosynthesis and respiration. However, the roles of different oxidants and antioxidants in the regulation of photosynthetic or respiratory gene expression remain poorly understood. Leaf transcriptome profiles of a range of Arabidopsis thaliana genotypes that are deficient in either hydrogen peroxide processing enzymes or in low molecular weight antioxidant were therefore compared to determine how different antioxidant systems that process hydrogen peroxide influence transcripts encoding proteins targeted to the chloroplasts or mitochondria. Less than 10 per cent overlap was observed in the transcriptome patterns of leaves that are deficient in either photorespiratory (catalase (cat)2) or chloroplastic (thylakoid ascorbate peroxidase (tapx)) hydrogen peroxide processing. Transcripts encoding photosystem II (PSII) repair cycle components were lower in glutathione-deficient leaves, as were the thylakoid NAD(P)H (nicotinamide adenine dinucleotide (phosphate)) dehydrogenases (NDH) mRNAs. Some thylakoid NDH mRNAs were also less abundant in tAPX-deficient and ascorbate-deficient leaves. Transcripts encoding the external and internal respiratory NDHs were increased by low glutathione and low ascorbate. Regulation of transcripts encoding specific components of the photosynthetic and respiratory electron transport chains by hydrogen peroxide, ascorbate and glutathione may serve to balance non-cyclic and cyclic electron flow pathways in relation to oxidant production and reductant availability.

  8. Photosynthetic pathways of some aquatic plants

    Energy Technology Data Exchange (ETDEWEB)

    Hough, R A [Wayne State Univ., Detroit; Wetzel, R G

    1977-12-01

    Over 40 species of aquatic angiosperms, including submersed, floating and emergent types, have been examined for photosynthetic status as part of a search for possible aquatic C/sub 4/ species. The C/sub 4/ system is viewed as potentially of adaptive value in certain aquatic situations, although evidence for its occurrence there is not conclusive. Emphasis was on plants from North-temperate softwater and hardwater lakes to explore both possibilities of CO/sub 2/ limitation, i.e., low total inorganic carbon in softwater vs. low free CO/sub 2/ in hardwater lakes. On the basis of leaf cross-section anatomy, all plants examined, with one exception, clearly did not show evidence of C/sub 4/ ''Krantz anatomy.'' In the submersed plant Potamogeton praelongus Wulf, large starch-producing chloroplasts were concentrated in cells surrounding vascular bundles and in a narrow band of cells between vascular bundles. The in situ photosynthetic rate of this plant was twice that of a related species, but other evidence including PEP carboxylase content and photorespiratory response to high O/sub 2/ did not confirm the presence of the C/sub 4/ photosynthesis.

  9. Effects of augmented trunk stabilization with external compression support on shoulder and scapular muscle activity and maximum strength during isometric shoulder abduction.

    Science.gov (United States)

    Jang, Hyun-jeong; Kim, Suhn-yeop; Oh, Duck-won

    2015-04-01

    The aim of the present study was to investigate the effects of augmented trunk stabilization with external compression support (ECS) on the electromyography (EMG) activity of shoulder and scapular muscles and shoulder abductor strength during isometric shoulder abduction. Twenty-six women volunteered for the study. Surface EMG was used to monitor the activity of the upper trapezius (UT), lower trapezius (LT), serratus anterior (SA), and middle deltoid (MD), and shoulder abductor strength was measured using a dynamometer during three experimental conditions: (1) no external support (condition-1), (2) pelvic support (condition-2), and (3) pelvic and thoracic supports (condition-3) in an active therapeutic movement device. EMG activities were significantly lower for UT and higher for MD during condition 3 than during condition 1 (p strength was significantly higher during condition 3 than during condition 1 (p isometric shoulder abduction and increasing shoulder abductor strength. Copyright © 2014 Elsevier Ltd. All rights reserved.

  10. Ocean acidification alters the photosynthetic responses of a coccolithophorid to fluctuating ultraviolet and visible radiation.

    Science.gov (United States)

    Jin, Peng; Gao, Kunshan; Villafañe, Virginia E; Campbell, Douglas A; Helbling, E Walter

    2013-08-01

    Mixing of seawater subjects phytoplankton to fluctuations in photosynthetically active radiation (400-700 nm) and ultraviolet radiation (UVR; 280-400 nm). These irradiance fluctuations are now superimposed upon ocean acidification and thinning of the upper mixing layer through stratification, which alters mixing regimes. Therefore, we examined the photosynthetic carbon fixation and photochemical performance of a coccolithophore, Gephyrocapsa oceanica, grown under high, future (1,000 μatm) and low, current (390 μatm) CO₂ levels, under regimes of fluctuating irradiances with or without UVR. Under both CO₂ levels, fluctuating irradiances, as compared with constant irradiance, led to lower nonphotochemical quenching and less UVR-induced inhibition of carbon fixation and photosystem II electron transport. The cells grown under high CO₂ showed a lower photosynthetic carbon fixation rate but lower nonphotochemical quenching and less ultraviolet B (280-315 nm)-induced inhibition. Ultraviolet A (315-400 nm) led to less enhancement of the photosynthetic carbon fixation in the high-CO₂-grown cells under fluctuating irradiance. Our data suggest that ocean acidification and fast mixing or fluctuation of solar radiation will act synergistically to lower carbon fixation by G. oceanica, although ocean acidification may decrease ultraviolet B-related photochemical inhibition.

  11. Feeding sustains photosynthetic quantum yield of a scleractinian coral during thermal stress.

    Science.gov (United States)

    Borell, Esther M; Bischof, Kai

    2008-10-01

    Thermal resistance of the coral-zooxanthellae symbiosis has been associated with chronic photoinhibition, increased antioxidant activity and protein repair involving high demands of nitrogen and energy. While the relative importance of heterotrophy as a source of nutrients and energy for cnidarian hosts, and as a means of nitrogen acquisition for their zooxanthellae, is well documented, the effect of feeding on the thermal sensitivity of the symbiotic association has been so far overlooked. Here we examine the effect of zooplankton feeding versus starvation on the bleaching susceptibility and photosynthetic activity of photosystem II (PSII) of zooxanthellae in the scleractinian coral Stylophora pistillata in response to thermal stress (daily temperature rises of 2-3 degrees C) over 10 days, employing pulse-amplitude-modulated chlorophyll fluorometry. Fed and starved corals displayed a decrease in daily maximum potential quantum yield (F (v)/F (m)) of PSII, effective quantum yield (F/F (m)') and relative electron transport rates over the course of 10 days. However after 10 days of exposure to elevated temperature, F (v)/F (m) of fed corals was still 50-70% higher than F (v)/F (m) of starved corals. Starved corals showed strong signs of chronic photoinhibition, which was reflected in a significant decline in nocturnal recovery rates of PSII relative to fed corals. This was paralleled by the progressive inability to dissipate excess excitation energy via non-photochemical quenching (NPQ). After 10 days, NPQ of starved corals had decreased by about 80% relative to fed corals. Feeding treatment had no significant effect on chlorophyll a and c (2) concentrations and zooxanthellae densities, but the mitotic indices were significantly lower in starved than in fed corals. Collectively the results indicate that exogenous food may reduce the photophysiological damage of zooxanthellae that typically leads to bleaching and could therefore play an important role in mediating the

  12. Novel adaptive photosynthetic characteristics of mesophotic symbiotic microalgae within the reef-building coral, Stylophora pistillata

    Directory of Open Access Journals (Sweden)

    Shai Einbinder

    2016-10-01

    Full Text Available Photosynthetic coral reef structures extend from the shallow sundrenched waters to the dimly lit, twilight mesophotic depths. For their resident endosymbiotic dinoflagellates, primarily from the genus Symbiodinium spp., this represents a photic environment that varies ~15 fold in intensity and also differs in spectral composition. We examined photosynthesis in the scleractinian coral Stylophora pistillata in shallow (3 m and mesophotic settings (65m in the northern Red Sea. Symbiodinium spp. in corals originating from the mesophotic environment consistently performed below their photosynthetic compensation point and also exhibited distinct light harvesting antenna organization. In addition, the non-photochemical quenching activity of Symbiodinium spp. from mesophotic corals was shown to be considerably lower than those found in shallow corals, showing they have fewer defenses to high-light settings. Over a period of almost four years, we extensively utilized closed circuit Trimix rebreather diving to perform the study. Phylogenetic analysis showed that shallow corals (3m transplanted to a deep reef environment (65 m maintained their initial Symbiodinium spp. community (clade A, rather than taking on deep low-light clades (clade C, demonstrating that shallow S. pistillata acclimate to low-light mesophotic environments while maintaining their shallow photosynthetic traits. Mesophotic corals exhibited static depth-related chlorophyll content per cell, a decrease in PSI activity and enhanced sigmoidal fluorescence rise kinetics. The sigmoidal fluorescence rise kinetics we observed in mesophotic corals is an indication of energy transfer between photosynthetic units. We postulate that at mesophotic depths, a community of adapted Symbiodinium spp. utilize a unique adaptation to lower light conditions by shifting their light harvesting to a PSII based system, where PSII is structured near PSI, with additional PCP soluble antenna also trapping light

  13. Research on spatial distribution of photosynthetic characteristics of Winter Wheat

    Science.gov (United States)

    Yan, Q. Q.; Zhou, Q. Y.; Zhang, B. Z.; Han, X.; Han, N. N.; Li, S. M.

    2018-03-01

    In order to explore the spatial distribution of photosynthetic characteristics of winter wheat leaf, the photosynthetic rate on different parts of leaf (leaf base-leaf middle-leaf apex) and that on each canopy (top layer-middle layer-bottom layer) leaf during the whole growth period of winter wheat were measured. The variation of photosynthetic rate with PAR and the spatial distribution of winter wheat leaf during the whole growth periods were analysed. The results showed that the photosynthetic rate of different parts of winter wheat increased with the increase of PAR, which was showed as leaf base>leaf middle>leaf apex. In the same growth period, photosynthetic rate in different parts of the tablet was showed as leaf middle>leaf base>leaf apex. For the different canopy layer of winter wheat, the photosynthetic rate of the top layer leaf was significantly greater than that of the middle layer and lower layer leaf. The photosynthetic rate of the top layer leaf was the largest in the leaf base position. The photosynthetic rate of leaf of the same canopy layer at different growth stages were showed as tasseling stage >grain filling stage > maturation stage.

  14. Large-scale glacitectonic deformation in response to active ice sheet retreat across Dogger Bank (southern central North Sea) during the Last Glacial Maximum

    Science.gov (United States)

    Phillips, Emrys; Cotterill, Carol; Johnson, Kirstin; Crombie, Kirstin; James, Leo; Carr, Simon; Ruiter, Astrid

    2018-01-01

    High resolution seismic data from the Dogger Bank in the central southern North Sea has revealed that the Dogger Bank Formation records a complex history of sedimentation and penecontemporaneous, large-scale, ice-marginal to proglacial glacitectonic deformation. These processes led to the development of a large thrust-block moraine complex which is buried beneath a thin sequence of Holocene sediments. This buried glacitectonic landsystem comprises a series of elongate, arcuate moraine ridges (200 m up to > 15 km across; over 40-50 km long) separated by low-lying ice marginal to proglacial sedimentary basins and/or meltwater channels, preserving the shape of the margin of this former ice sheet. The moraines are composed of highly deformed (folded and thrust) Dogger Bank Formation with the lower boundary of the deformed sequence (up to 40-50 m thick) being marked by a laterally extensive décollement. The ice-distal parts of the thrust moraine complex are interpreted as a "forward" propagating imbricate thrust stack developed in response to S/SE-directed ice-push. The more complex folding and thrusting within the more ice-proximal parts of the thrust-block moraines record the accretion of thrust slices of highly deformed sediment as the ice repeatedly reoccupied this ice marginal position. Consequently, the internal structure of the Dogger Bank thrust-moraine complexes can be directly related to ice sheet dynamics, recording the former positions of a highly dynamic, oscillating Weichselian ice sheet margin as it retreated northwards at the end of the Last Glacial Maximum.

  15. Mathematical Modeling of Acclimation Processes of the Photosynthetic Chain

    Directory of Open Access Journals (Sweden)

    S Heidari

    2016-10-01

    Full Text Available Introduction Photosynthetic energy conversion efficiency is characteristic of a system which is determined by interactions between various components of the system. The complex process of photosynthesis has been studied as a whole system which enables in silico examination of a large number of candidate genes for genetic engineering for a higher photosynthetic energy conversion efficiency. One of the most important environmental factors which influence the photosynthesis efficiency is light regime which can cause producing ROS components. To acclimate to such fluctuations, plants have evolved adaptive mechanisms to minimize damage of the photosynthetic apparatus excess light. A fast compatibility response to high light stresses is non-photochemical quenching process (NPQ, dissipating excessive energy to heat. Light harvested state switches into a quenched state by a conformational change of light harvesting complex (LHCII that regulated by xanthophylls and the PsbS protein within seconds. Low lumen pH activates xanthophyll synthesis via a xanthophyll cycle which consists of the de-epoxidation of violaxanthin to zeaxanthin by violaxanthin de-epoxidase in high light and inversely by zeaxanthin epoxidase in low light which occurs more slowly. Materials and Methods Thale cress (Arabidopsis thaliana (Chlombia-0 were grown on soil at 25/22 °C day/night temperature, with a 16/8 h photoperiod, and 40-70% (depend of plant species relative humidity. The light intensity was 150–200 µE m-2s-1 white light. Intensity of chlorophyll fluorescence was measured with PAM-2000 fluorometer (Heinz Walz, Germany and the manufacturer’s software (PamWin v.2. Results and Discussion In the present study, a dynamic kinetics amplified mathematical model was developed based on differential equations in order to predict short-term changes in NPQ in the process of adaptation to different light conditions. We investigated the stationary and dynamic behavior of the model

  16. Porphyrin and fullerene-based artificial photosynthetic materials for photovoltaics

    International Nuclear Information System (INIS)

    Imahori, Hiroshi; Kashiwagi, Yukiyasu; Hasobe, Taku; Kimura, Makoto; Hanada, Takeshi; Nishimura, Yoshinobu; Yamazaki, Iwao; Araki, Yasuyuki; Ito, Osamu; Fukuzumi, Shunichi

    2004-01-01

    We have developed artificial photosynthetic systems in which porphyrins and fullerenes are self-assembled as building blocks into nanostructured molecular light-harvesting materials and photovoltaic devices. Multistep electron transfer strategy has been combined with our finding that porphyrin and fullerene systems have small reorganization energies, which are suitable for the construction of light energy conversion systems as well as artificial photosynthetic models. Highly efficient photosynthetic electron transfer reactions have been realized at ITO electrodes modified with self-assembled monolayers of porphyrin oligomers as well as porphyrin-fullerene linked systems. Porphyrin-modified gold nanoclusters have been found to have potential as artificial photosynthetic materials. These results provide basic information for the development of nanostructured artificial photosynthetic systems

  17. Variations in morphology and PSII photosynthetic capabilities during the early development of tetraspores of Gracilaria vermiculophylla (Ohmi) Papenfuss (Gracilariales, Rhodophyta).

    Science.gov (United States)

    Xie, Xiujun; Wang, Guangce; Pan, Guanghua; Gao, Shan; Xu, Pu; Zhu, Jianyi

    2010-04-28

    Red algae are primitive photosynthetic eukaryotes, whose spores are ideal subjects for studies of photosynthesis and development. Although the development of red alga spores has received considerable research attention, few studies have focused on the detailed morphological and photosynthetic changes that occur during the early development of tetraspores of Gracilaria vermiculophylla (Ohmi) Papenfuss (Gracilariales, Rhodophyta). Herein, we documented these changes in this species of red algae. In the tetraspores, we observed two types of division, cruciate and zonate, and both could develop into multicellular bodies (disks). During the first 84 hours, tetraspores divided several times, but the diameter of the disks changed very little; thereafter, the diameter increased significantly. Scanning electron microscopy observations and analysis of histological sections revealed that the natural shape of the disk remains tapered over time, and the erect frond grows from the central protrusion of the disk. Cultivation of tissue from excised disks demonstrated that the central protrusion of the disk is essential for initiation of the erect frond. Photosynthetic (i.e., PSII) activities were measured using chlorophyll fluorescence analysis. The results indicated that freshly released tetraspores retained limited PSII photosynthetic capabilities; when the tetraspores attached to a substrate, those capabilities increased significantly. In the disk, the PSII activity of both marginal and central cells was similar, although some degree of morphological polarity was present; the PSII photosynthetic capabilities in young germling exhibited an apico-basal gradient. Attachment of tetraspores to a substrate significantly enhanced their PSII photosynthetic capabilities, and triggered further development. The central protrusion of the disk is the growth point, may have transfer of nutritive material with the marginal cells. Within the young germling, the hetero-distribution of PSII

  18. Variations in morphology and PSII photosynthetic capabilities during the early development of tetraspores of Gracilaria vermiculophylla (Ohmi Papenfuss (Gracilariales, Rhodophyta

    Directory of Open Access Journals (Sweden)

    Gao Shan

    2010-04-01

    Full Text Available Abstract Background Red algae are primitive photosynthetic eukaryotes, whose spores are ideal subjects for studies of photosynthesis and development. Although the development of red alga spores has received considerable research attention, few studies have focused on the detailed morphological and photosynthetic changes that occur during the early development of tetraspores of Gracilaria vermiculophylla (Ohmi Papenfuss (Gracilariales, Rhodophyta. Herein, we documented these changes in this species of red algae. Results In the tetraspores, we observed two types of division, cruciate and zonate, and both could develop into multicellular bodies (disks. During the first 84 hours, tetraspores divided several times, but the diameter of the disks changed very little; thereafter, the diameter increased significantly. Scanning electron microscopy observations and analysis of histological sections revealed that the natural shape of the disk remains tapered over time, and the erect frond grows from the central protrusion of the disk. Cultivation of tissue from excised disks demonstrated that the central protrusion of the disk is essential for initiation of the erect frond. Photosynthetic (i.e., PSII activities were measured using chlorophyll fluorescence analysis. The results indicated that freshly released tetraspores retained limited PSII photosynthetic capabilities; when the tetraspores attached to a substrate, those capabilities increased significantly. In the disk, the PSII activity of both marginal and central cells was similar, although some degree of morphological polarity was present; the PSII photosynthetic capabilities in young germling exhibited an apico-basal gradient. Conclusions Attachment of tetraspores to a substrate significantly enhanced their PSII photosynthetic capabilities, and triggered further development. The central protrusion of the disk is the growth point, may have transfer of nutritive material with the marginal cells. Within

  19. Jatropha curcasand Ricinus communisdisplay contrasting photosynthetic mechanisms in response to environmental conditions

    Directory of Open Access Journals (Sweden)

    Milton Costa Lima Neto

    2015-06-01

    Full Text Available Higher plants display different adaptive strategies in photosynthesis to cope with abiotic stress. In this study, photosynthetic mechanisms and water relationships displayed byJatropha curcasL. (physic nuts andRicinus communisL. (castor bean, in response to variations in environmental conditions, were assessed.R. communis showed higher CO2 assimilation, stomatal and mesophyll conductance thanJ. curcas as light intensity and intercellular CO2 pressure increased. On the other hand,R. communis was less effective in stomatal control in response to adverse environmental factors such as high temperature, water deficit and vapor pressure deficit, indicating lower water use efficiency. Conversely,J. curcas exhibited higher photosynthetic efficiency (gas exchange and photochemistry and water use efficiency under these adverse environmental conditions.R. communisdisplayed higher potential photosynthesis, but exhibited a lowerin vivo Rubisco carboxylation rate (Vcmax and maximum electron transport rate (Jmax. During the course of a typical day, in a semiarid environment, with high irradiation, high temperature and high vapor pressure deficit, but exposed to well-watered conditions, the two studied species presented similar photosynthesis. Losing potential photosynthesis, but maintaining favorable water status and increasing non-photochemical quenching to avoid photoinhibition, are important acclimation mechanisms developed byJ. curcas to cope with dry and hot conditions. We suggest thatJ. curcas is more tolerant to hot and dry environments thanR. communis but the latter species displays higher photosynthetic efficiency under well-watered and non-stressful conditions.

  20. Diversity and abundance of photosynthetic sponges in temperate Western Australia

    Directory of Open Access Journals (Sweden)

    Brümmer Franz

    2009-02-01

    Full Text Available Abstract Background Photosynthetic sponges are important components of reef ecosystems around the world, but are poorly understood. It is often assumed that temperate regions have low diversity and abundance of photosynthetic sponges, but to date no studies have investigated this question. The aim of this study was to compare the percentages of photosynthetic sponges in temperate Western Australia (WA with previously published data on tropical regions, and to determine the abundance and diversity of these associations in a range of temperate environments. Results We sampled sponges on 5 m belt transects to determine the percentage of photosynthetic sponges and identified at least one representative of each group of symbionts using 16S rDNA sequencing together with microscopy techniques. Our results demonstrate that photosynthetic sponges are abundant in temperate WA, with an average of 63% of sponge individuals hosting high levels of photosynthetic symbionts and 11% with low to medium levels. These percentages of photosynthetic sponges are comparable to those found on tropical reefs and may have important implications for ecosystem function on temperate reefs in other areas of the world. A diverse range of symbionts sometimes occurred within a small geographic area, including the three "big" cyanobacterial clades, Oscillatoria spongeliae, "Candidatus Synechococcus spongiarum" and Synechocystis species, and it appears that these clades all occur in a wide range of sponges. Additionally, spongin-permeating red algae occurred in at least 7 sponge species. This study provides the first investigation of the molecular phylogeny of rhodophyte symbionts in sponges. Conclusion Photosynthetic sponges are abundant and diverse in temperate WA, with comparable percentages of photosynthetic to non-photosynthetic sponges to tropical zones. It appears that there are three common generalist clades of cyanobacterial symbionts of sponges which occur in a wide

  1. Impact of heat-wave at high and low VPD on photosynthetic components of wheat and their recovery

    DEFF Research Database (Denmark)

    Rashid, Muhammad Adil; Andersen, Mathias Neumann; Wollenweber, Bernd

    2018-01-01

    relatively insignificant. The processes involved in CO2-use (i.e. in vivo carboxylation efficiency and Vcmax) presented higher sensitivity than the processes involved in light-use (PSII efficiency, quantum yield and chlorophyll content index). Maximum photosynthetic capacity under high temperature......-impact studies. Higher sensitivity of CO2-use suggested that even moderately high temperature-episodes might limit photosynthetic capacity and hence crop productivity, thus reiterating the need to develop crop cultivars with greater tolerance to high temperatures. Abbreviations Asat, maximum net CO2 assimilation......Indirect effects of high temperature through increased vapor pressure deficit (VPD) are vital but often ignored in climate impact studies. We investigated the direct (via heat) and indirect (via VPD) effects of a post-anthesis applied high temperature episode on biochemical and diffusional...

  2. Effect of Mahanarva fimbriolata (Hemiptera: Cercopidae) Attack on Photosynthetic Parameters of Sugarcane Genotypes of Contrasting Susceptibility.

    Science.gov (United States)

    Soares, Bruno Oliveira; Chaves, Vinicius de Vicente; Tomaz, Adriano Cirino; Kuki, Kacilda Naomi; Peternelli, Luiz Alexandre; Barbosa, Márcio Henrique Pereira

    2017-12-05

    The aim of this study was to compare the effect of spittlebug Mahanarva fimbriolata Stål (Hemiptera: Cercopidae) on photosynthetic parameters of both a susceptible (SP81-3250) and a resistant (H.Kawandang) sugarcane genotype. In the first assay, the susceptibility level of genotypes to spittlebug was confirmed by comparing damage score and chlorophyll content of the plants. In the second assay, the effect of spittlebug nymphs on photosynthetic characteristics was assessed using the following parameters: Net photosynthetic rate (A), carboxylation efficiency (A/Ci), stomata conductance (gS), transpiration (E), electron transport rate (ETR), maximum quantum yield of Photosystem 2 (PSII) (FV/FM), effective quantum yield (Y(II)), photochemical quenching (Y(NPQ)), and nonphotochemical quenching (Y(NO)). Spittlebug nymphs affected the photosynthetic process of the susceptible genotype SP81-3250 by decreasing the Chl content, ETR, FV/FM, and Y(II). However, this genotype was able to maintain A probably due to its ability to maintain stomata aperture, increase the carboxylation efficiency of Rubisco, and dissipate excess energy through the xanthophyll cycle, as Y(NPQ) increased under the spittlebug attack. On the other hand, the spittlebug did not affect Chl content and FV/FM of the H.Kawandang genotype. Furthermore, H.Kawandang increased A to compensate for the sink demand by the spittlebug by increasing stomatal aperture and carboxylation efficiency and increasing efficiency of the photochemical apparatus in converting light energy into chemical products. We can conclude that the feeding habits of spittlebug nymphs have different impacts on photosynthesis of susceptible and resistant sugarcane genotypes. © The Author(s) 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  3. The effects of the pre-reversal ExB drift, the EIA asymmetry, and magnetic activity on the equatorial spread F during solar maximum

    Directory of Open Access Journals (Sweden)

    C.-C. Lee

    2005-03-01

    Full Text Available We use a digisonde at Jicamarca and a chain of GPS receivers on the west side of South America to investigate the effects of the pre-reversal enhancement (PRE in ExB drift, the asymmetry (Ia of equatorial ionization anomaly (EIA, and the magnetic activity (Kp on the generation of equatorial spread F (ESF. Results show that the ESF appears frequently in summer (November, December, January, and February and equinoctial (March, April, September, and October months, but rarely in winter (May, June, July, and August months. The seasonal variation in the ESF is associated with those in the PRE ExB drift and Ia. The larger ExB drift (>20m/s and smaller |Ia| (<0.3 in summer and equinoctial months provide a preferable condition to development the ESF. Conversely, the smaller ExB drift and larger |Ia| are responsible for the lower ESF occurrence in winter months. Regarding the effects of magnetic activity, the ESF occurrence decreases with increasing Kp in the equinoctial and winter months, but not in the summer months. Furthermore, the larger and smaller ExB drifts are presented under the quiet (Kp<3 and disturbed (Kp≥3 conditions, respectively. These results indicate that the suppression in ESF and the decrease in ExB drifts are mainly caused by the decrease in the eastward electric field.

  4. The effects of the pre-reversal ExB drift, the EIA asymmetry, and magnetic activity on the equatorial spread F during solar maximum

    Directory of Open Access Journals (Sweden)

    C.-C. Lee

    2005-03-01

    Full Text Available We use a digisonde at Jicamarca and a chain of GPS receivers on the west side of South America to investigate the effects of the pre-reversal enhancement (PRE in ExB drift, the asymmetry (Ia of equatorial ionization anomaly (EIA, and the magnetic activity (Kp on the generation of equatorial spread F (ESF. Results show that the ESF appears frequently in summer (November, December, January, and February and equinoctial (March, April, September, and October months, but rarely in winter (May, June, July, and August months. The seasonal variation in the ESF is associated with those in the PRE ExB drift and Ia. The larger ExB drift (>20m/s and smaller |Ia| (<0.3 in summer and equinoctial months provide a preferable condition to development the ESF. Conversely, the smaller ExB drift and larger |Ia| are responsible for the lower ESF occurrence in winter months. Regarding the effects of magnetic activity, the ESF occurrence decreases with increasing Kp in the equinoctial and winter months, but not in the summer months. Furthermore, the larger and smaller ExB drifts are presented under the quiet (Kp<3 and disturbed (Kp≥3 conditions, respectively. These results indicate that the suppression in ESF and the decrease in ExB drifts are mainly caused by the decrease in the eastward electric field.

  5. VU-B radiation inhibits the photosynthetic electron transport chain in chlamydomonas reinhardtii

    International Nuclear Information System (INIS)

    Cai, W.; Li, X.; Chen, L.

    2016-01-01

    UV radiation of sunlight is one of harmful factors for earth organisms, especially for photoautotrophs because they require light for energy and biomass production. A number of works have already been done regarding the effects of UV-B radiation at biochemical and molecular level, which showed that UV-B radiation could inhibit photosynthesis activity and reduce photosynthetic electron transport. However quite limited information can accurately make out inhibition site of UV-B radiation on photosynthetic electron transport. In this study, this issue was investigated through measuring oxygen evolution activity, chlorophyll a fluorescence and gene expression in a model unicellular green alga Chlamydomonas reinhardtii. Our results indicated that UV-B radiation could evidently decrease photosynthesis activity and inhibit electron transport by blocking electron transfer process from the first plastoquinone electron acceptors QA to second plastoquinone electron acceptors QB, but not impair electron transfer from the water oxidizing complex to QA. The psbA gene expression was also altered by UV-B radiation, where up-regulation occurred at 2, 4 and 6h after exposure and down-regulation happened at 12 and 24 h after exposure. These results suggested that UV-B could affects D1 protein normal turnover, so there was not enough D1 for binding with QB, which may affect photosynthetic electron transport and photosynthesis activity. (author)

  6. Activity of R(+) limonene on the maximum growth rate of fish spoilage organisms and related effects on shelf-life prolongation of fresh gilthead sea bream fillets.

    Science.gov (United States)

    Giarratana, Filippo; Muscolino, Daniele; Beninati, Chiara; Ziino, Graziella; Giuffrida, Alessandro; Panebianco, Antonio

    2016-11-21

    R(+)limonene (LMN) is the major aromatic compound in essential oils obtained from oranges, grapefruits, and lemons. The improvement of preservation techniques to reduce the growth and activity of spoilage microorganisms in foods is crucial to increase their shelf life and to reduce the losses due to spoilage. The aim of this work is to evaluate the effect of LMN on the shelf life of fish fillets. Its effectiveness was preliminarily investigated in vitro against 60 strains of Specific Spoilage Organisms (SSOs) and then on gilt-head sea bream fillets stored at 2±0.5°C for 15days under vacuum. LMN showed a good inhibitory effect against tested SSOs strains. On gilt-head sea bream fillets, LMN inhibited the growth SSOs effectively, and its use resulted in a shelf-life extension of ca. 6-9days of treated fillets, compared to the control samples. The LMN addition in Sparus aurata fillets giving a distinctive smell and like-lemon taste to fish fillets that resulted pleasant to panellists. Its use contributed to a considerable reduction of fish spoilage given that the fillets treated with LMN were still sensory acceptable after 15days of storage. LMN may be used as an effective antimicrobial system to reduce the microbial growth and to improve the shelf life of fresh gilt-head sea bream fillets. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. Influence of sustained submaximal clenching fatigue test on electromyographic activity and maximum voluntary bite forces in healthy subjects and patients with temporomandibular disorders.

    Science.gov (United States)

    Xu, L; Fan, S; Cai, B; Fang, Z; Jiang, X

    2017-05-01

    This study aimed to investigate whether the fatigue induced by sustained motor task in the jaw elevator muscles differed between healthy subjects and patients with temporomandibular disorder (TMD). Fifteen patients with TMD and thirteen age- and sex-matched healthy controls performed a fatigue test consisting of sustained clenching contractions at 30% maximal voluntary clenching intensity until test failure (the criterion for terminating the fatigue test was when the biting force decreased by 10% or more from the target force consecutively for >3 s). The pre- and post-maximal bite forces (MBFs) were measured. Surface electromyographic signals were recorded from the superficial masseter muscles and anterior temporal muscles bilaterally, and the median frequency at the beginning, middle and end of the fatigue test was calculated. The duration of the fatigue test was also quantified. Both pre- and post-MBFs were lower in patients with TMD than in controls (P fatigue test in TMD patients was significantly shorter than that of the controls (P fatigued, but the electromyographic activation process during the fatigue test is similar between healthy subjects and patients with TMD. However, the mechanisms involved in this process remain unclear, and further research is warranted. © 2017 John Wiley & Sons Ltd.

  8. Variability of photosynthetic parameters of Pinus sibirica Du Tour needles under changing climatic factors

    Directory of Open Access Journals (Sweden)

    A.P. Zotikova

    2013-12-01

    Full Text Available The air temperature and relative humidity and the intensity of photosynthetically active radiation are the basic ecological factors determining geographical distribution of a species. Wood plant adaptation depends on the intensity of physiological and biochemicalprocesses of plants as a response to changing environmental factors. Investigations to reveal (detect the variability of modification andgenetic components of the photosynthetic parameters in needles of the Siberian cedar (Pinus sibirica Du Tour mountain ecotypes, distributed in central part of the Altai Mountains, were carried out. Also, the survey was extended to some experiments with these ecotypes introduced to mild climate and flat regions from south-western of Siberia. The length and thickness of needles, the size of chloroplasts, content of the photosynthetic pigments, and the functional activity of chloroplastsat the level of photo system II were the evaluated traits. Growing under mountainous conditions (at about 2000m elevation, the two-year-old needles were shorter and thicker and contained very large in size chloroplasts while the content of chlorophylls and carotinoids was twice lower than that in the local ecotype growing in the lowlands. On the other hand, more green and yellow pigments were found in needles of mountain ecotypes planted in the lowlands compared to the local lowland ectype trees. A decrease in pool of the photosynthetic pigments in the highlands ecotypes is probably due to decreased biosynthesis andincreased photo-destruction caused by severe light and temperature conditions. These parameters are likely to be associated withmodifications due to intense insolation, low temperature, ozone concentration, UV radiation, and other negative factors that are morepronounced at high elevation. Despite the large pool of accumulated photosynthetic pigments, the functional activity of chloroplasts in themountain ecotype at the level

  9. Halogenated 1-Hydroxynaphthalene-2-Carboxanilides Affecting Photosynthetic Electron Transport in Photosystem II

    Czech Academy of Sciences Publication Activity Database

    Goněc, T.; Kos, J.; Pesko, M.; Dohanosová, J.; Oravec, Michal; Liptaj, T.; Králová, K.; Jampílek, J.

    2017-01-01

    Roč. 22, č. 10 (2017), č. článku 1709. ISSN 1420-3049 R&D Projects: GA MŠk(CZ) LO1415 Institutional support: RVO:67179843 Keywords : hydroxynaphthalene-carboxamides * photosynthetic electron transport ( PET ) inhibition * spinach chloroplasts * structure-activity relationships Subject RIV: CE - Biochemistry OBOR OECD: Biochemistry and molecular biology Impact factor: 2.861, year: 2016

  10. Quantification of silver nanoparticle toxicity to algae in soil via photosynthetic and flow-cytometric analyses

    OpenAIRE

    Nam, Sun-Hwa; Il Kwak, Jin; An, Youn-Joo

    2018-01-01

    Soil algae, which have received attention for their use in a novel bioassay to evaluate soil toxicity, expand the range of terrestrial test species. However, there is no information regarding the toxicity of nanomaterials to soil algae. Thus, we evaluated the effects of silver nanoparticles (0–50 mg AgNPs/kg dry weight soil) on the soil alga Chlamydomonas reinhardtii after six days, and assessed changes in biomass, photosynthetic activity, cellular morphology, membrane permeability, esterase ...

  11. The photosynthetic responses to stocking depth and algal mat density in the farmed seaweed Gracilaria lemaneiformis (Gracilariales, Rhodophyta).

    Science.gov (United States)

    Jiang, Heng; Zou, Dinghui; Chen, Weizhou; Yang, Yufeng

    2017-11-01

    The branches and mass of Gracilaria lemaneiformis increase with growth season, and the thalli sink to deeper depths with increasing biomass density during maricultivation. The changing depth and algal mat density may affect the physiology of the algae. In the present study, the photosynthetic behaviors regarding different biomass densities in G. lemaneiformis thalli collected from different stocking depths were determined, to examine how photosynthesis of this farmed alga was affected by the growth depths and algal mat densities. Our results showed that the chlorophyll a (Chl a), carotenoids (Car), phycoerythrin (PE) contents, and irradiance-saturated maximum photosynthetic rates (P max ) of the deeper layer-grown algae were significantly increased relative to the surface layer-grown algae. The P max , apparent photosynthetic efficiency (α) and dark respiration rate (R d ) of G. lemaneiformis thalli, were reduced, whereas the irradiance saturation points (I k ) were increased, with the increasing algal mat density. We proposed that appropriate measures are needed to trade off the stocking depth and biomass density, in an effort to maintain a relative high photosynthetic productivity during G. lemaneiformis maricultivation.

  12. Implications of terminal oxidase function in regulation of salicylic acid on soybean seedling photosynthetic performance under water stress.

    Science.gov (United States)

    Tang, Yanping; Sun, Xin; Wen, Tao; Liu, Mingjie; Yang, Mingyan; Chen, Xuefei

    2017-03-01

    The aim of this study is to investigate whether exogenous application of salicylic acid (SA) could modulate the photosynthetic capacity of soybean seedlings in water stress tolerance, and to clarify the potential functions of terminal oxidase (plastid terminal oxidase (PTOX) and alternative oxidase (AOX)) in SA' s regulation on photosynthesis. The effects of SA and water stress on gas exchange, pigment contents, chlorophyll fluorescence, enzymes (guaiacol peroxidase (POD; EC 1.11.1.7), superoxide dismutase (SOD; EC 1.15.1.1), catalase (CAT; EC 1.11.1.6), ascorbate peroxidase (APX; EC 1.11.1.11) and NADP-malate dehydrogenase (NADP-MDH; EC1.1.1.82)) activity and transcript levels of PTOX, AOX1, AOX2a, AOX2b were examined in a hydroponic cultivation system. Results indicate that water stress significantly decreased the photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (E), pigment contents (Chla + b, Chla/b, Car), maximum quantum yield of PSⅡphotochemistry (Fv/Fm), efficiency of excitation capture of open PSⅡcenter (Fv'/Fm'), quantum efficiency of PSⅡphotochemistry (ΦPSⅡ), photochemical quenching (qP), and increased malondialdehyde (MDA) content and the activity of all the enzymes. SA pretreatment led to significant decreases in Ci and MDA content, and increases in Pn, Gs, E, pigment contents, Fv/Fm, Fv'/Fm', ΦPSⅡ, qP, and the activity of all the enzymes. SA treatment and water stress alone significantly up-regulated the expression of PTOX, AOX1 and AOX2b. SA pretreatment further increased the transcript levels of PTOX and AOX2b of soybean seedling under water stress. These results indicate that SA application alleviates the water stress-induced decrease in photosynthesis may mainly through maintaining a lower reactive oxygen species (ROS) level, a greater PSⅡefficiency, and an enhanced alternative respiration and chlororespiration. PTOX and AOX may play important roles in SA-mediated resistance to water stress. Copyright © 2016

  13. Zooxanthellae Harvested by Ciliates Associated with Brown Band Syndrome of Corals Remain Photosynthetically Competent▿

    Science.gov (United States)

    Ulstrup, Karin E.; Kühl, Michael; Bourne, David G.

    2007-01-01

    Brown band syndrome is a new coral affliction characterized by a local accumulation of yet-unidentified ciliates migrating as a band along the branches of coral colonies. In the current study, morphologically intact zooxanthellae (= Symbiodinium) were observed in great numbers inside the ciliates (>50 dinoflagellates per ciliate). Microscale oxygen measurements and variable chlorophyll a fluorescence analysis along with microscopic observations demonstrated that zooxanthellae within the ciliates are photosynthetically competent and do not become compromised during the progression of the brown band zone. Zooxanthellae showed similar trends in light acclimation in a comparison of rapid light curve and steady-state light curve measures of variable chlorophyll a fluorescence. Extended light exposure of steady-state light curves resulted in higher quantum yields of photosystem II. The brown band tissue exhibited higher photosynthetically active radiation absorptivity, indicating more efficient light absorption due to a higher density of zooxanthellae in the ciliate-dominated zone. This caused relatively higher gross photosynthesis rates in the zone with zooxanthella-containing ciliates compared to healthy coral tissue. The observation of photosynthetically active intracellular zooxanthellae in the ciliates suggests that the latter can benefit from photosynthates produced by ingested zooxanthellae and from photosynthetic oxygen production that alleviates diffusion limitation of oxic respiration in the densely populated brown band tissue. It remains to be shown whether the zooxanthellae form a stable symbiotic association with the ciliate or are engulfed incidentally during grazing on coral tissue and then maintained as active inside the ciliate for a period before being digested and replaced by new zooxanthellae. PMID:17259357

  14. Zooxanthellae harvested by ciliates associated with brown band syndrome of corals remain photosynthetically competent.

    Science.gov (United States)

    Ulstrup, Karin E; Kühl, Michael; Bourne, David G

    2007-03-01

    Brown band syndrome is a new coral affliction characterized by a local accumulation of yet-unidentified ciliates migrating as a band along the branches of coral colonies. In the current study, morphologically intact zooxanthellae (= Symbiodinium) were observed in great numbers inside the ciliates (>50 dinoflagellates per ciliate). Microscale oxygen measurements and variable chlorophyll a fluorescence analysis along with microscopic observations demonstrated that zooxanthellae within the ciliates are photosynthetically competent and do not become compromised during the progression of the brown band zone. Zooxanthellae showed similar trends in light acclimation in a comparison of rapid light curve and steady-state light curve measures of variable chlorophyll a fluorescence. Extended light exposure of steady-state light curves resulted in higher quantum yields of photosystem II. The brown band tissue exhibited higher photosynthetically active radiation absorptivity, indicating more efficient light absorption due to a higher density of zooxanthellae in the ciliate-dominated zone. This caused relatively higher gross photosynthesis rates in the zone with zooxanthella-containing ciliates compared to healthy coral tissue. The observation of photosynthetically active intracellular zooxanthellae in the ciliates suggests that the latter can benefit from photosynthates produced by ingested zooxanthellae and from photosynthetic oxygen production that alleviates diffusion limitation of oxic respiration in the densely populated brown band tissue. It remains to be shown whether the zooxanthellae form a stable symbiotic association with the ciliate or are engulfed incidentally during grazing on coral tissue and then maintained as active inside the ciliate for a period before being digested and replaced by new zooxanthellae.

  15. ENHANCED PRACTICAL PHOTOSYNTHETIC CO2 MITIGATION

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Gregory Kremer; Dr. David J. Bayless; Dr. Morgan Vis; Dr. Michael Prudich; Dr. Keith Cooksey; Dr. Jeff Muhs

    2001-07-25

    This quarterly report documents significant achievements in the Enhanced Practical Photosynthetic CO{sub 2} Mitigation project during the period from 4/03/2001 through 7/02/2001. Most of the achievements are milestones in our efforts to complete the tasks and subtasks that constitute the project objectives. Note that this version of the quarterly technical report is a revision to add the reports from subcontractors Montana State and Oak Ridge National Laboratories The significant accomplishments for this quarter include: Development of an experimental plan and initiation of experiments to create a calibration curve that correlates algal chlorophyll levels with carbon levels (to simplify future experimental procedures); Completion of debugging of the slug flow reactor system, and development of a plan for testing the pressure drop of the slug flow reactor; Design and development of a new bioreactor screen design which integrates the nutrient delivery drip system and the harvesting system; Development of an experimental setup for testing the new integrated drip system/harvesting system; Completion of model-scale bioreactor tests examining the effects of CO{sub 2} concentration levels and lighting levels on Nostoc 86-3 growth rates; Completion of the construction of a larger model-scale bioreactor to improve and expand testing capabilities and initiation of tests; Substantial progress on construction of a pilot-scale bioreactor; and Preliminary economic analysis of photobioreactor deployment. Plans for next quarter's work are included in the conclusions. A preliminary economic analysis is included as an appendix.

  16. A novel potassium channel in photosynthetic cyanobacteria.

    Directory of Open Access Journals (Sweden)

    Manuela Zanetti

    Full Text Available Elucidation of the structure-function relationship of a small number of prokaryotic ion channels characterized so far greatly contributed to our knowledge on basic mechanisms of ion conduction. We identified a new potassium channel (SynK in the genome of the cyanobacterium Synechocystis sp. PCC6803, a photosynthetic model organism. SynK, when expressed in a K(+-uptake-system deficient E. coli strain, was able to recover growth of these organisms. The protein functions as a potassium selective ion channel when expressed in Chinese hamster ovary cells. The location of SynK in cyanobacteria in both thylakoid and plasmamembranes was revealed by immunogold electron microscopy and Western blotting of isolated membrane fractions. SynK seems to be conserved during evolution, giving rise to a TPK (two-pore K(+ channel family member which is shown here to be located in the thylakoid membrane of Arabidopsis. Our work characterizes a novel cyanobacterial potassium channel and indicates the molecular nature of the first higher plant thylakoid cation channel, opening the way to functional studies.

  17. ENHANCED PRACTICAL PHOTOSYNTHETIC CO2 MITIGATION

    Energy Technology Data Exchange (ETDEWEB)

    Dr. David J. Bayless; Dr. Morgan Vis; Dr. Gregory Kremer; Dr. Michael Prudich; Dr. Keith Cooksey; Dr. Jeff Muhs

    2001-01-16

    This is the first quarterly report of the project Enhanced Practical Photosynthetic CO{sub 2} Mitigation. The official project start date, 10/02/2000, was delayed until 10/31/2000 due to an intellectual property dispute that was resolved. However, the delay forced a subsequent delay in subcontracting with Montana State University, which then delayed obtaining a sampling permit from Yellowstone National Park. However, even with these delays, the project moved forward with some success. Accomplishments for this quarter include: Culturing of thermophilic organisms from Yellowstone; Testing of mesophilic organisms in extreme CO{sub 2} conditions; Construction of a second test bed for additional testing; Purchase of a total carbon analyzer dedicated to the project; Construction of a lighting container for Oak Ridge National Laboratory optical fiber testing; Modified lighting of existing test box to provide more uniform distribution; Testing of growth surface adhesion and properties; Experimentation on water-jet harvesting techniques; and Literature review underway regarding uses of biomass after harvesting. Plans for next quarter's work and an update on the project's web page are included in the conclusions.

  18. Photosynthetic efficiency of Chlamydomonas reinhardtii in flashing light

    NARCIS (Netherlands)

    Vejrazka, C.; Janssen, M.G.J.; Streefland, M.; Wijffels, R.H.

    2011-01-01

    Efficient light to biomass conversion in photobioreactors is crucial for economically feasible microalgae production processes. It has been suggested that photosynthesis is enhanced in short light path photobioreactors by mixing-induced flashing light regimes. In this study, photosynthetic

  19. Effects of 1-butanol, neomycin and calcium on the photosynthetic ...

    African Journals Online (AJOL)

    ajl yemi

    2011-10-31

    Oct 31, 2011 ... (Shanghai Jierui Bio-Engineering Co., Ltd.) were used in the total. RNA extraction of ..... PC and reverse through calcium removal agent. EGTA indicating .... Photosynthetic characteristics and tolerance to photo- oxidation of ...

  20. Photosynthetic responses of pea plants (Pisum sativum L. cv. Little ...

    African Journals Online (AJOL)

    STORAGESEVER

    2008-08-04

    Aug 4, 2008 ... (O3) have fundamental effects on CO2 exchange by plants. ... produce responses such as reduced photosynthetic rates and earlier senescence .... quality localities treatments and two soil regimes in Riyadh city, KSA. Pn rates.

  1. Photosynthetic and nitrogen fixation capability in several soybean mutant lines

    International Nuclear Information System (INIS)

    Gandanegara, S.; Hendratno, K.

    1987-01-01

    Photosynthetic and nitrogen fixation capability in several soybean mutant lines. A greenhouse experiment has been carried out to study photosynthetic and nitrogen fixation capability of five mutant lines and two soybean varieties. An amount of 330 uCi of 14 CO 2 was fed to the plants including of the non-fixing reference crop (Chippewa non-nodulating isoline). Nitrogen fixation measurements was carried out using 15 N isotope dilution technique according to A-value concept. Results showed that beside variety/mutant lines, plant growth also has important role in photosynthetic and N fixing capability. Better growth and a higher photosynthetic capability in Orba, mutant lines nos. 63 and 65 resulted in a greater amount of N 2 fixed (mg N/plant) than other mutant lines. (author). 12 refs.; 5 figs

  2. Effect of space mutation on photosynthetic characteristics of soybean varieties

    International Nuclear Information System (INIS)

    Liu Xinlei; Ma Yansong; Luan Xiaoyan; Man Weiqun; Xu Dechun; Meng Lifen; Fu Lixin; Zhao Xiaonan; Liu Qi

    2011-01-01

    In order to elucidate the response of the photosynthetic traits of soybean to space mutation, three soybean varieties (lines) of Heinong 48, Heinong 44 and Ha 2291-Y were carried by artificial satellite in 2006 and the net photosynthetic rate (Pn), stomatal conductance (Cond), intercellular CO 2 concentration (Ci) and stomatal resistance (Rs) from SP 1 to SP 4 generation were determined. The results showed that space mutation affected photosynthesis traits of soybean. The photosynthetic rate of soybean varieties by space mutation occurred different levels of genetic variation and the positive mutation rate were higher. Coefficient of variation among generations were SP 2 > SP 3 > SP 4 > CK. Results suggest that space mutation can effectively create soybean materials with higher photosynthetic rate. (authors)

  3. Carotenoids are essential for the assembly of cyanobacterial photosynthetic complexes

    NARCIS (Netherlands)

    Tóth, T.N.; Chukhutsina, Volha; Domonkos, Ildikó; Knoppová, Jana; Komenda, Josef; Kis, Mihály; Lénárt, Zsófia; Garab, Gyozo; Kovács, László; Gombos, Zoltán; Amerongen, Van Herbert

    2015-01-01

    In photosynthetic organisms, carotenoids (carotenes and xanthophylls) are important for light harvesting, photoprotection and structural stability of a variety of pigment-protein complexes. Here, we investigated the consequences of altered carotenoid composition for the functional organization of

  4. Variability of photosynthetic pigments in the Colombian Pacific ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    Picture series of surface chlorophyll,. SST, wind ... photosynthetic pigments during the time of inten- sification of ... calculation of Ekman pumping (We) using finite- differencing to ..... Legeckis R 1986 A satellite time series sea surface tempera-.

  5. Removal of Anabaena spiroides by potassium permanganate pre-oxidation: effect on photosynthetic capacity and molecular weight distribution.

    Science.gov (United States)

    Qiao, Junlian; Zhang, Xiaodong; Lv, Liping

    2017-11-01

    Bench scale tests were conducted to investigate the effect of potassium permanganate pre-oxidation on the photosynthetic activity and molecular weight distribution of Anabaena spiroides. Different concentrations of potassium permanganate were added into the suspension of Anabaena spiroides, one of the dominant algae in water bloom, and after pre-oxidation of permanganate for 1 h, the results show that the removal rate significantly increases by 33.99~36.35% compared to direct coagulation. Then, the algal characteristics, including photosynthetic ability, the changes in extracellular organic matter three-dimensional fluorescence, and the distribution of molecular weight were conducted and the results show that along with increasing concentration of potassium permanganate, the photosynthetic ability of algae decreases, more extracellular organic matter is secreted, and large molecular weight matter (humic-like and fulvic-like substances) are generated. Therefore, this study demonstrates that potassium permanganate could be used in addressing the algae-rich water.

  6. Photosynthetic energy conversion efficiency: setting a baseline for gauging future improvements in important food and biofuel crops.

    Science.gov (United States)

    Slattery, Rebecca A; Ort, Donald R

    2015-06-01

    The conversion efficiency (ε(c)) of absorbed radiation into biomass (MJ of dry matter per MJ of absorbed photosynthetically active radiation) is a component of yield potential that has been estimated at less than half the theoretical maximum. Various strategies have been proposed to improve ε(c), but a statistical analysis to establish baseline ε(c) levels across different crop functional types is lacking. Data from 164 published ε(c) studies conducted in relatively unstressed growth conditions were used to determine the means, greatest contributors to variation, and genetic trends in ε(c )across important food and biofuel crop species. ε(c) was greatest in biofuel crops (0.049-0.066), followed by C4 food crops (0.046-0.049), C3 nonlegumes (0.036-0.041), and finally C3 legumes (0.028-0.035). Despite confining our analysis to relatively unstressed growth conditions, total incident solar radiation and average growing season temperature most often accounted for the largest portion of ε(c) variability. Genetic improvements in ε(c), when present, were less than 0.7% per year, revealing the unrealized potential of improving ε(c) as a promising contributing strategy to meet projected future agricultural demand. © 2015 American Society of Plant Biologists. All Rights Reserved.

  7. Responses of photosynthetic O2 evolution to PPFD in the CAM epiphyte Tillandsia usneoides L. (Bromeliaceae).

    Science.gov (United States)

    Martin, C E; McKee, J M; Schmitt, A K

    1989-09-01

    Past studies of the effects of varying levels of photosynthetic photon flux density (PPFD) on the morphology and physiology of the epiphytic Crassulacean acid metabolism (CAM) plant Tillandsia usneoides L. (Bromeliaceae) have resulted in two important findings: (1) CAM, measured as integrated nocturnal CO2 uptake or as nocturnal increases in tissue acidity, saturates at relatively low PPFD, and (2) this plant does not acclimate to different PPFD levels, these findings require substantiation using photosynthetic responses immediately attributable to different PPFD levels, e.g., O2 evolution, as opposed to the delayed, nocturnal responses (CO2 uptake and acid accumulation). In the present study, instantaneous responses of O2 evolution to PPFD level were measured using plants grown eight weeks at three PPFD (20-45, 200-350, and 750-800 μmol m(-2)s(-1)) in a growth chamber, and using shoots taken from the exposed upper portions (maximum PPFD of 800 μmol m(-2)s(-1)) and shaded lower portions (maximum PPFD of 140 μmol m(-2)s(-1)) of plants grown ten years in a greenhouse. In addition, nocturnal increases in acidity were measured in the growth chamber plants. Regardless of the PPFD levels during growth, O2 evolution rates saturated around 500 μmol m(-2)s(-1). Furthermore, nocturnal increases in tissue acidity saturated at much lower PPFD. Thus, previous results were confirmed: photosynthesis saturated at low PPFD, and this epiphyte does not acclimate to different levels of PPFD.

  8. Credal Networks under Maximum Entropy

    OpenAIRE

    Lukasiewicz, Thomas

    2013-01-01

    We apply the principle of maximum entropy to select a unique joint probability distribution from the set of all joint probability distributions specified by a credal network. In detail, we start by showing that the unique joint distribution of a Bayesian tree coincides with the maximum entropy model of its conditional distributions. This result, however, does not hold anymore for general Bayesian networks. We thus present a new kind of maximum entropy models, which are computed sequentially. ...

  9. On the photosynthetic potential in the very Early Archean oceans.

    Science.gov (United States)

    Avila, Daile; Cardenas, Rolando; Martin, Osmel

    2013-02-01

    In this work we apply a mathematical model of photosynthesis to quantify the potential for photosynthetic life in the very Early Archean oceans. We assume the presence of oceanic blockers of ultraviolet radiation, specifically ferrous ions. For this scenario, our results suggest a potential for photosynthetic life greater than or similar to that in later eras/eons, such as the Late Archean and the current Phanerozoic eon.

  10. Ultrafast fluorescence of photosynthetic crystals and light-harvesting complexes

    OpenAIRE

    Oort, van, B.F.

    2008-01-01

    This thesis focuses on the study of photosynthetic pigment protein complexes using time resolved fluorescence techniques. Fluorescence spectroscopy often requires attaching fluorescent labels to the proteins under investigation. With photosynthetic proteins this is not necessary, because these proteins contain fluorescent pigments. Each pigment’s fluorescence is influenced by its environment, and thereby may provide information on structure and dynamics of pigment protein complexes in vitro a...

  11. Production of bioplastics and hydrogen gas by photosynthetic microorganisms

    Science.gov (United States)

    Yasuo, Asada; Masato, Miyake; Jun, Miyake

    1998-03-01

    Our efforts have been aimed at the technological basis of photosynthetic-microbial production of materials and an energy carrier. We report here accumulation of poly-(3-hydroxybutyrate) (PHB), a raw material of biodegradable plastics and for production of hydrogen gas, and a renewable energy carrier by photosynthetic microorganisms (tentatively defined as cyanobacteria plus photosynthetic bateria, in this report). A thermophilic cyanobacterium, Synechococcus sp. MA19 that accumulates PHB at more than 20% of cell dry wt under nitrogen-starved conditions was isolated and microbiologically identified. The mechanism of PHB accumulation was studied. A mesophilic Synechococcus PCC7942 was transformed with the genes encoding PHB-synthesizing enzymes from Alcaligenes eutrophus. The transformant accumulated PHB under nitrogen-starved conditions. The optimal conditions for PHB accumulation by a photosynthetic bacterium grown on acetate were studied. Hydrogen production by photosynthetic microorganisms was studied. Cyanobacteria can produce hydrogen gas by nitrogenase or hydrogenase. Hydrogen production mediated by native hydrogenase in cyanobacteria was revealed to be in the dark anaerobic degradation of intracellular glycogen. A new system for light-dependent hydrogen production was targeted. In vitro and in vivo coupling of cyanobacterial ferredoxin with a heterologous hydrogenase was shown to produce hydrogen under light conditions. A trial for genetic trasformation of Synechococcus PCC7942 with the hydrogenase gene from Clostridium pasteurianum is going on. The strong hydrogen producers among photosynthetic bacteria were isolated and characterized. Co-culture of Rhodobacter and Clostriumdium was applied to produce hydrogen from glucose. Conversely in the case of cyanobacteria, genetic regulation of photosynthetic proteins was intended to improve conversion efficiency in hydrogen production by the photosynthetic bacterium, Rhodobacter sphaeroides RV. A mutant acquired by

  12. Photosynthetic metabolism of malate and aspartate in Flaveria trinervia a C4 dicot

    International Nuclear Information System (INIS)

    Moore, B.A.

    1986-01-01

    C 4 species are known to vary in their apparent relative use of malate and aspartate to mediate carbon flux through the C 4 cycle. These studies investigate some of the adjustments in photosynthetic carbon metabolism that occur during a dark to light transition and during expansion of leaves of Flaveria trinervia, a C 4 dicot. Enzyme localization studies with isolated leaf mesophyll and bundle sheath protoplasts, indicated that both C 4 acids are formed in the mesophyll chloroplast, and that aspartate is metabolized to malate in the bundle sheath chloroplast prior to decaroxylation there. During photosynthetic induction, the partitioning of 14 CO 2 between malate and aspartate showed a single oscillation of increased aspartate labelling after 5 min of illumination. Turnover of [4-14C] (malate plus aspartate) was slow initially during illumination, prior to establishment of active pools of C 4 cycle metabolites

  13. Yields, photosynthetic efficiencies, and proximate chemical composition of dense cultures of marine microalgae. A subcontract report

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, W.H.; Seibert, D.L.R.; Alden, M.; Eldridge, P.; Neori, A.

    1983-07-01

    The yields, photosynthetic efficiencies, and proximate composition of several microalgae were compared in dense cultures grown at light intensities up to 70% sunlight. Yields ranged from 3.4 to 21.7 g dry weight/m/sup 2/ day. The highest yield was obtained with Phaeodactylum; the lowest in Botryococcus cultures. The same species had the highest and lowest efficiencies of utilization of photosynthetically active radiation. In nitrogen-sufficient cells of all but one species, most of the dry weight consisted of protein. Lipid content of all species was 20 to 29%, and carbohydrate content 11 to 23%. Lipid content increased somewhat in N-deficient Phaeodactylum and Isochrysis cells, but decreased in deficient Monallanthus cells. Because the overall dry weight yield was reduced by deficiency, lipid yields did not increase. However, since the carbohydrate content increased to about 65% in N-deficient Dunaliella and Tetraselmis cells, the carbohydrate yield increased. In Phaeodactylum the optimum light intensity was about 40% of full sunlight. Most experimets with this alga included a CUSO/sub 4/ filter to decrease infrared irradiance. When this filter was removed, the yield increased because more red light in the photosynthetically active spectral range was included. These results should prove useful to workers attempting to maximize yields and efficiencies, but additional studies are needed. 69 references, 27 figures, 18 tables.

  14. A Study on Photosynthetic Physiological Characteristics of Six Rare and Endangered Species

    Institute of Scientific and Technical Information of China (English)

    Tailin ZHONG; Guangwu ZHAO; Jiamiao CHU; Xiaomin GUO; Genyou LI

    2014-01-01

    The parameters of gas exchange and chlorophyl fluorescence in leaves of six rare and endangered species Neolitsea sericea, Cinnamomum japonicum var. cheni , Sinojackia microcarpa, Discocleidion glabrum var. trichocarpum, Parrotia sub-aequalis, Cercidiphyl um japonicum were measured in fields. The results showed that there were significant differences in photosynthetic capacity, intrinsic water use effi-ciency (WUEi ), the efficiency of primary conversion of light energy of PSⅡ and its potential activity, the quantum yield of PSⅡ electron transport, and the potential ca-pacity of heat dissipation among the six species. However, there was no significant difference in WUE. The highest values of net photosynthetic rate (Pn), transpiration rate (Tr) and stomatal conductance (gs) occurred in D. glabrum var. trichocarpum and the lowest in S. microcarpa. On the contrary, D. glabrum var. trichocarpum had the lowest WUE, intrinsic water use efficiency (WUEi ) and S. microcarpa had the highest. The results indicated that D. glabrum var. trichocarpum had higher photo-synthetic capacity and poorer WUE, while S. microcarpa had lower photosynthetic capacity and greater WUE. Furthermore, the mean values of maximal fluorescence (Fm), potential efficiency of primary conversion of light energy of PSⅡ (Fv/Fm),ΦPSⅡ, actual efficiency of primary conversion of light energy of PSⅡ (F′v/F′m) and non-photochemical quenching coefficient (NPQ) were the highest in S. micro-carpa, indicating that its PSⅡ had higher capacity of heat dissipation and could prevent photosynthetic apparatus from damage by excessive light energy. Correlation analysis showed that there were significant correlations among photosynthetic physi-ological parameters. However, the initial fluorescence (Fo) was not significantly cor-related with any other parameters. This study also revealed the extremely significant positive correlations between Pn and Tr, gs, apparent quantum yield (AQY), be-tween Tr and

  15. Hybrid artificial photosynthetic systems comprising semiconductors as light harvesters and biomimetic complexes as molecular cocatalysts.

    Science.gov (United States)

    Wen, Fuyu; Li, Can

    2013-11-19

    Solar fuel production through artificial photosynthesis may be a key to generating abundant and clean energy, thus addressing the high energy needs of the world's expanding population. As the crucial components of photosynthesis, the artificial photosynthetic system should be composed of a light harvester (e.g., semiconductor or molecular dye), a reduction cocatalyst (e.g., hydrogenase mimic, noble metal), and an oxidation cocatalyst (e.g., photosystem II mimic for oxygen evolution from water oxidation). Solar fuel production catalyzed by an artificial photosynthetic system starts from the absorption of sunlight by the light harvester, where charge separation takes place, followed by a charge transfer to the reduction and oxidation cocatalysts, where redox reaction processes occur. One of the most challenging problems is to develop an artificial photosynthetic solar fuel production system that is both highly efficient and stable. The assembly of cocatalysts on the semiconductor (light harvester) not only can facilitate the charge separation, but also can lower the activation energy or overpotential for the reactions. An efficient light harvester loaded with suitable reduction and oxidation cocatalysts is the key for high efficiency of artificial photosynthetic systems. In this Account, we describe our strategy of hybrid photocatalysts using semiconductors as light harvesters with biomimetic complexes as molecular cocatalysts to construct efficient and stable artificial photosynthetic systems. We chose semiconductor nanoparticles as light harvesters because of their broad spectral absorption and relatively robust properties compared with a natural photosynthesis system. Using biomimetic complexes as cocatalysts can significantly facilitate charge separation via fast charge transfer from the semiconductor to the molecular cocatalysts and also catalyze the chemical reactions of solar fuel production. The hybrid photocatalysts supply us with a platform to study the

  16. Photosynthetic, antioxidative, molecular and ultrastructural responses of young cacao plants to Cd toxicity in the soil.

    Science.gov (United States)

    Pereira de Araújo, Romária; Furtado de Almeida, Alex-Alan; Silva Pereira, Lidiane; Mangabeira, Pedro A O; Olimpio Souza, José; Pirovani, Carlos P; Ahnert, Dário; Baligar, Virupax C

    2017-10-01

    Cadmium (Cd) is a highly toxic metal for plants, even at low concentrations in the soil. The annual production of world cocoa beans is approximately 4 million tons. Most of these fermented and dried beans are used in the manufacture of chocolate. Recent work has shown that the concentration of Cd in these beans has exceeded the critical level (0.6mgkg -1 DM). The objective of this study was to evaluate the toxicity of Cd in young plants of CCN 51 cacao genotype grown in soil with different concentrations of Cd (0, 0.05 and 0.1gkg -1 soil) through photosynthetic, antioxidative, molecular and ultrastructural changes. The increase of Cd concentration in the soil altered mineral nutrient absorption by competition or synergism, changed photosynthetic activity caused by reduction in chloroplastidic pigment content and damage to the photosynthetic machinery evidenced by the Fv/Fm ratio and expression of the psbA gene and increased GPX activity in the root and SOD in leaves. Additionally, ultrastructural alterations in roots and leaves were also evidenced with the increase of the concentration of Cd in the soil, whose toxicity caused rupture of biomembranes in root and leaf cells, reduction of the number of starch grains in foliar cells, increase of plastoglobules in chloroplasts and presence of multivesiculated bodies in root cells. It was concluded, therefore, that soil Cd toxicity caused damage to the photosynthetic machinery, antioxidative metabolism, gene expression and irreversible damage to root cells ultrastructure of CCN 51 cocoa plants, whose damage intensity depended on the exposure time to the metal. Copyright © 2017. Published by Elsevier Inc.

  17. Effects of differnt juvenile mixed plantations on growth and photosynthetic physiology of pinus yunnanensis franch

    International Nuclear Information System (INIS)

    Zheng, Y.; Ou, G. L.; Chen, D. D.; Liu, G. Y.; Li, Q. Q.; Zhang, S. H.; Han, M. Y.; Chen, J. L.

    2017-01-01

    The growth characteristics, photosynthetic gas exchange features, physiological and biochemical resistance, and soil nutrition contents of different juvenile mixed plantations were analyzed. Moreover, the synergic effect mechanism of the different species was elucidated to improve the stand quality of Pinus yunnanensis Franch. plantations and guide the screening of P. yunnanensis mixed plantations. The mixed plantations were P. yunnanensis-Alnus nepalensis-Quercus acutissima, P. yunnanensis-A. nepalensis-Cyclobalanopsis glaucoides, and P. yunnanensis-Q. acutissima-C. glaucoides. Individual juvenile plantations of pure P. yunnanensis, A. nepalensis, Q. acutissima, and C. glaucoides were used as control groups. Results showed that pure P. yunnanensis juvenile plantation consumed more soil organic matter, total nitrogen (TN), total phosphorus (TP), and total potassium (TK) than the other plantations. This plantation also showed poorer growth characteristics, poorer photosynthetic capability, lower water utilization efficiency (WUE), and biochemical resistance in infertile soil, as shown by the nutrition and water competition. Increasing soil organic matters, TN, TP, and TK of the different mixed plantations evidently enhanced height, ground diameter growth rate, net photosynthetic rate (Pn), transpiration rate (Tr), WUE, carboxylation efficiency (CE), soluble sugar (SS) content, and superoxide dismutase (SOD) activity. Moreover, different mixed forests slightly influenced the characteristics of photosynthetic gas exchange and physiological and biochemical resistance of A. nepalensis. All stand types facilitated growth of tree height and basal diameter of Q. acutissima sapling. Although Q. acutissima inhibited physiological and biochemical resistance of leaves to a certain extent, they increased WUE significantly. Different stand types slightly influenced growth features, Pn, Tr, and WUE of C. glaucoides sapling. Moreover, they inhibited the osmotic adjustment system

  18. Multilayer models of photosynthetic membranes. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Brocklehurst, J R; Flanagan, M T

    1982-01-01

    The primary aim of this project has been to build an artificial membrane in which is incorporated, in a functional state, the protein bacteriorhodopsin responsible for generating an electrical potential difference across the membrane of the photosynthetic bacterium, halobacterium halobium, and to investigate the use of this artificial system as the basis of a solar cell. the bacteriorhodopsin has been incorporated into Langmuir-Blodgett multilayers. If ths supporting filter is then illuminated, a potential difference is generated between the two compartments. The lipid in the filter appears to act as a charge carrier for protons, the charge species that forms the electrochemical gradient generated by the bacteriorhodopsin when this molecule absorbs light. The internal resistances of such solar cells were determined and found to be so high that the cells could not be seriously considered as competitors with classical semiconductor cells. Multilayerswere deposited onto filters in which ion carriers that make the filters permeable to sodium ions had been dissolved in the paraffin. The photovoltage obtained indicated that protons transferred from one side of the filter to the other by the action of the bacteriorhodopsin were bing exchanged for sodium ions. A secondary aim of the project has been to examine the possibility of depositing mixed multilayers of a dye and a long chain quinone onto a semiconductor surface. A sensitizing multilayer has been prepared and the mobility of long chain quinones within the layers is high enough to warrant further research. However, it was found that, with the dyes and quinones used, quenched complexes were formed which would not act as sensitizers.

  19. Anaerobic energy metabolism in unicellular photosynthetic eukaryotes.

    Science.gov (United States)

    Atteia, Ariane; van Lis, Robert; Tielens, Aloysius G M; Martin, William F

    2013-02-01

    Anaerobic metabolic pathways allow unicellular organisms to tolerate or colonize anoxic environments. Over the past ten years, genome sequencing projects have brought a new light on the extent of anaerobic metabolism in eukaryotes. A surprising development has been that free-living unicellular algae capable of photoautotrophic lifestyle are, in terms of their enzymatic repertoire, among the best equipped eukaryotes known when it comes to anaerobic energy metabolism. Some of these algae are marine organisms, common in the oceans, others are more typically soil inhabitants. All these species are important from the ecological (O(2)/CO(2) budget), biotechnological, and evolutionary perspectives. In the unicellular algae surveyed here, mixed-acid type fermentations are widespread while anaerobic respiration, which is more typical of eukaryotic heterotrophs, appears to be rare. The presence of a core anaerobic metabolism among the algae provides insights into its evolutionary origin, which traces to the eukaryote common ancestor. The predicted fermentative enzymes often exhibit an amino acid extension at the N-terminus, suggesting that these proteins might be compartmentalized in the cell, likely in the chloroplast or the mitochondrion. The green algae Chlamydomonas reinhardtii and Chlorella NC64 have the most extended set of fermentative enzymes reported so far. Among the eukaryotes with secondary plastids, the diatom Thalassiosira pseudonana has the most pronounced anaerobic capabilities as yet. From the standpoints of genomic, transcriptomic, and biochemical studies, anaerobic energy metabolism in C. reinhardtii remains the best characterized among photosynthetic protists. This article is part of a Special Issue entitled: The evolutionary aspects of bioenergetic systems. Copyright © 2012 Elsevier B.V. All rights reserved.

  20. Photosynthetic capacities of mature tropical forest trees in Rwanda are linked to successional group identity rather than to leaf nutrient content

    Science.gov (United States)

    Dusenge, Mirindi Eric; Wallin, Göran; Gårdesten, Johanna; Adolfsson, Lisa; Niyonzima, Felix; Nsabimana, Donat; Uddling, Johan

    2014-05-01

    Tropical forests are crucial in the global carbon balance, yet information required to estimate how much carbon that enter these ecosystems through photosynthesis is very limited, in particular for Africa and for tropical montane forests. In order to increases the knowledge of natural variability of photosynthetic capacities in tropical tree species in tropical Africa, measurements of leaf traits and gas exchange were conducted on sun and shade leaves of ten tree species growing in two tropical forests in Rwanda in central Africa. Seven species were studied in Ruhande Arboretum, a forest plantation at mid altitude (1700 m), and six species in Nyungwe National Park, a cooler and higher altitude (at 2500 m) montane rainforest. Three species were common to both sites. At Nyungwe, three species each belonged to the successional groups pioneer and climax species. Climax species had considerably lower maximum rates of photosynthetic carboxylation (Vcmax) and electron transport (Jmax) than pioneer species. This difference was not related to leaf nutrient content, but rather seemed to be caused by differences in within-leaf N allocation between the two successional groups. With respect to N, leaves of climax species invested less N into photosynthetic enzymes (as judged by lower Vcmax and Jmax values) and more N into chlorophyll (as judged by higher SPAD values). Photosynthetic capacities, (i.e., Jmax and Vcmax), Jmax to Vcmax ratio and P content were significantly higher in Nyungwe than in Arboretum. Sun leaves had higher photosynthetic capacities and nutrient content than shade leaves. Across the entire dataset, variation in photosynthetic capacities among species was not related to leaf nutrient content, although significant relationships were found within individual species. This study contributes critical tropical data for global carbon models and suggests that, for montane rainforest trees of different functional types, successional group identity is a better

  1. What limits photosynthetic energy conversion efficiency in nature? Lessons from the oceans.

    Science.gov (United States)

    Falkowski, Paul G; Lin, Hanzhi; Gorbunov, Maxim Y

    2017-09-26

    Constraining photosynthetic energy conversion efficiency in nature is challenging. In principle, two yield measurements must be made simultaneously: photochemistry, fluorescence and/or thermal dissipation. We constructed two different, extremely sensitive and precise active fluorometers: one measures the quantum yield of photochemistry from changes in variable fluorescence, the other measures fluorescence lifetimes in the picosecond time domain. By deploying the pair of instruments on eight transoceanic cruises over six years, we obtained over 200 000 measurements of fluorescence yields and lifetimes from surface waters in five ocean basins. Our results revealed that the average quantum yield of photochemistry was approximately 0.35 while the average quantum yield of fluorescence was approximately 0.07. Thus, closure on the energy budget suggests that, on average, approximately 58% of the photons absorbed by phytoplankton in the world oceans are dissipated as heat. This extraordinary inefficiency is associated with the paucity of nutrients in the upper ocean, especially dissolved inorganic nitrogen and iron. Our results strongly suggest that, in nature, most of the time, most of the phytoplankton community operates at approximately half of its maximal photosynthetic energy conversion efficiency because nutrients limit the synthesis or function of essential components in the photosynthetic apparatus.This article is part of the themed issue 'Enhancing photosynthesis in crop plants: targets for improvement'. © 2017 The Author(s).

  2. Introducing extra NADPH consumption ability significantly increases the photosynthetic efficiency and biomass production of cyanobacteria.

    Science.gov (United States)

    Zhou, Jie; Zhang, Fuliang; Meng, Hengkai; Zhang, Yanping; Li, Yin

    2016-11-01

    Increasing photosynthetic efficiency is crucial to increasing biomass production to meet the growing demands for food and energy. Previous theoretical arithmetic analysis suggests that the light reactions and dark reactions are imperfectly coupled due to shortage of ATP supply, or accumulation of NADPH. Here we hypothesized that solely increasing NADPH consumption might improve the coupling of light reactions and dark reactions, thereby increasing the photosynthetic efficiency and biomass production. To test this hypothesis, an NADPH consumption pathway was constructed in cyanobacterium Synechocystis sp. PCC 6803. The resulting extra NADPH-consuming mutant grew much faster and achieved a higher biomass concentration. Analyses of photosynthesis characteristics showed the activities of photosystem II and photosystem I and the light saturation point of the NADPH-consuming mutant all significantly increased. Thus, we demonstrated that introducing extra NADPH consumption ability is a promising strategy to increase photosynthetic efficiency and to enable utilization of high-intensity lights. Copyright © 2016 International Metabolic Engineering Society. Published by Elsevier Inc. All rights reserved.

  3. Sensitivity of the green algae Chlamydomonas reinhardtii to gamma radiation: Photosynthetic performance and ROS formation

    Energy Technology Data Exchange (ETDEWEB)

    Gomes, Tânia, E-mail: tania.gomes@niva.no [Norwegian Institute for Water Research (NIVA), Section of Ecotoxicology and Risk Assessment, Gaustadalléen 21, N-0349, Oslo (Norway); Centre for Environmental Radioactivity, Norwegian University of Life Sciences (NMBU), Post Box 5003, N-1432 Ås (Norway); Xie, Li [Norwegian Institute for Water Research (NIVA), Section of Ecotoxicology and Risk Assessment, Gaustadalléen 21, N-0349, Oslo (Norway); Centre for Environmental Radioactivity, Norwegian University of Life Sciences (NMBU), Post Box 5003, N-1432 Ås (Norway); Brede, Dag; Lind, Ole-Christian [Centre for Environmental Radioactivity, Norwegian University of Life Sciences (NMBU), Post Box 5003, N-1432 Ås (Norway); Department for Environmental Sciences, Faculty of Environmental Science & Technology, Norwegian University of Life Sciences (NMBU), Post Box 5003, N-1432, Ås (Norway); Solhaug, Knut Asbjørn [Centre for Environmental Radioactivity, Norwegian University of Life Sciences (NMBU), Post Box 5003, N-1432 Ås (Norway); Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences (NMBU), Postbox 5003, N-1432, Ås (Norway); Salbu, Brit [Centre for Environmental Radioactivity, Norwegian University of Life Sciences (NMBU), Post Box 5003, N-1432 Ås (Norway); Department for Environmental Sciences, Faculty of Environmental Science & Technology, Norwegian University of Life Sciences (NMBU), Post Box 5003, N-1432, Ås (Norway); and others

    2017-02-15

    Highlights: • Chlorophyll fluorescence parameters affected at higher dose rates. • Changes in PSII associated with electron transport and energy dissipation pathways. • Dose-dependent ROS production in algae exposed to gamma radiation. • Decrease in photosynthetic efficiency connected to ROS formation. - Abstract: The aquatic environment is continuously exposed to ionizing radiation from both natural and anthropogenic sources, making the characterization of ecological and health risks associated with radiation of large importance. Microalgae represent the main source of biomass production in the aquatic ecosystem, thus becoming a highly relevant biological model to assess the impacts of gamma radiation. However, little information is available on the effects of gamma radiation on microalgal species, making environmental radioprotection of this group of species challenging. In this context, the present study aimed to improve the understanding of the effects and toxic mechanisms of gamma radiation in the unicellular green algae Chlamydomonas reinhardtii focusing on the activity of the photosynthetic apparatus and ROS formation. Algal cells were exposed to gamma radiation (0.49–1677 mGy/h) for 6 h and chlorophyll fluorescence parameters obtained by PAM fluorometry, while two fluorescent probes carboxy-H{sub 2}DFFDA and DHR 123 were used for the quantification of ROS. The alterations seen in functional parameters of C. reinhardtii PSII after 6 h of exposure to gamma radiation showed modifications of PSII energy transfer associated with electron transport and energy dissipation pathways, especially at the higher dose rates used. Results also showed that gamma radiation induced ROS in a dose-dependent manner under both light and dark conditions. The observed decrease in photosynthetic efficiency seems to be connected to the formation of ROS and can potentially lead to oxidative stress and cellular damage in chloroplasts. To our knowledge, this is the first

  4. Sensitivity of the green algae Chlamydomonas reinhardtii to gamma radiation: Photosynthetic performance and ROS formation

    International Nuclear Information System (INIS)

    Gomes, Tânia; Xie, Li; Brede, Dag; Lind, Ole-Christian; Solhaug, Knut Asbjørn; Salbu, Brit

    2017-01-01

    Highlights: • Chlorophyll fluorescence parameters affected at higher dose rates. • Changes in PSII associated with electron transport and energy dissipation pathways. • Dose-dependent ROS production in algae exposed to gamma radiation. • Decrease in photosynthetic efficiency connected to ROS formation. - Abstract: The aquatic environment is continuously exposed to ionizing radiation from both natural and anthropogenic sources, making the characterization of ecological and health risks associated with radiation of large importance. Microalgae represent the main source of biomass production in the aquatic ecosystem, thus becoming a highly relevant biological model to assess the impacts of gamma radiation. However, little information is available on the effects of gamma radiation on microalgal species, making environmental radioprotection of this group of species challenging. In this context, the present study aimed to improve the understanding of the effects and toxic mechanisms of gamma radiation in the unicellular green algae Chlamydomonas reinhardtii focusing on the activity of the photosynthetic apparatus and ROS formation. Algal cells were exposed to gamma radiation (0.49–1677 mGy/h) for 6 h and chlorophyll fluorescence parameters obtained by PAM fluorometry, while two fluorescent probes carboxy-H 2 DFFDA and DHR 123 were used for the quantification of ROS. The alterations seen in functional parameters of C. reinhardtii PSII after 6 h of exposure to gamma radiation showed modifications of PSII energy transfer associated with electron transport and energy dissipation pathways, especially at the higher dose rates used. Results also showed that gamma radiation induced ROS in a dose-dependent manner under both light and dark conditions. The observed decrease in photosynthetic efficiency seems to be connected to the formation of ROS and can potentially lead to oxidative stress and cellular damage in chloroplasts. To our knowledge, this is the first report

  5. How oxygen attacks [FeFe] hydrogenases from photosynthetic organisms

    Science.gov (United States)

    Stripp, Sven T.; Goldet, Gabrielle; Brandmayr, Caterina; Sanganas, Oliver; Vincent, Kylie A.; Haumann, Michael; Armstrong, Fraser A.; Happe, Thomas

    2009-01-01

    Green algae such as Chlamydomonas reinhardtii synthesize an [FeFe] hydrogenase that is highly active in hydrogen evolution. However, the extreme sensitivity of [FeFe] hydrogenases to oxygen presents a major challenge for exploiting these organisms to achieve sustainable photosynthetic hydrogen production. In this study, the mechanism of oxygen inactivation of the [FeFe] hydrogenase CrHydA1 from C. reinhardtii has been investigated. X-ray absorption spectroscopy shows that reaction with oxygen results in destruction of the [4Fe-4S] domain of the active site H-cluster while leaving the di-iron domain (2FeH) essentially intact. By protein film electrochemistry we were able to determine the order of events leading up to this destruction. Carbon monoxide, a competitive inhibitor of CrHydA1 which binds to an Fe atom of the 2FeH domain and is otherwise not known to attack FeS clusters in proteins, reacts nearly two orders of magnitude faster than oxygen and protects the enzyme against oxygen damage. These results therefore show that destruction of the [4Fe-4S] cluster is initiated by binding and reduction of oxygen at the di-iron domain—a key step that is blocked by carbon monoxide. The relatively slow attack by oxygen compared to carbon monoxide suggests that a very high level of discrimination can be achieved by subtle factors such as electronic effects (specific orbital overlap requirements) and steric constraints at the active site. PMID:19805068

  6. Carotenoid Photoprotection in Artificial Photosynthetic Antennas

    Energy Technology Data Exchange (ETDEWEB)

    Kloz, Miroslav [VU Univ., Amsterdam (Netherlands); Pillai, Smitha [Arizona State Univ., Tempe, AZ (United States); Kodis, Gerdenis [Arizona State Univ., Tempe, AZ (United States); Gust, Devens [Arizona State Univ., Tempe, AZ (United States); Moore, Thomas A. [Arizona State Univ., Tempe, AZ (United States); Moore, Ana L. [Arizona State Univ., Tempe, AZ (United States); van Grondelle, Rienk [VU Univ., Amsterdam (Netherlands); Kennis, John T. M. [VU Univ., Amsterdam (Netherlands)

    2011-04-14

    . These synthetic systems are providing a deeper understanding of structural and environmental effects on the interactions between carotenoids and tetrapyrroles and thereby better defining their role in controlling natural photosynthetic systems.

  7. EFFECTS OF NITROGEN NUTRIENT ON THE PHOTOSYNTHETIC PIGMENTS ACCUMULATION AND YIELD OF SOLANUM LYCOPERSICUM

    Directory of Open Access Journals (Sweden)

    Adekunle Ajayi ADELUSI

    2015-12-01

    Full Text Available This study investigated photosynthetic pigment accumulation and yield of Solanum lycopersicum so as to ascertain the maximum concentration of nitrogen needed for optimum production. Seeds of S. lycopersicum tagged with VG-TH-017 were firstly raised in nursery bed. At the end of 28th day after sowing, the seedlings with uniform height were transplanted into experimental pots with 4 seedlings per pot under greenhouse. All the experimental pots were 40 in total, 4 levels of nitrogen (KNO3 and NH4NO3 treatment (n, N, 5N, 10N with 10 replicates. All the plants in the four treatments received 200ml of distilled water at 6a.m. in the morning every day. At 6p.m. in the evening, 100 ml of the differential treatments were applied. The photosynthetic pigments were determined spectrophotometrically. The number of flowers and fruits per plant per pot were counted and recorded. The fruit lengths and fruit diameters in each treatment were determined with the use of a Vernier Caliper. The fruits biomass were also determined. The 10N-plants and 5N-plants had leaves with deep-green colouration indicating an increase in chlorophyll content as well as an increase in the photosynthetic capacity. The highest number of flowers and early flowering discovered in 10N-plants and 5N-plants. The best yield was obtained in the treatments for the 5N-plants in which the concentration of nitrogen in the nutrient solution had been increased to a factor of 5. It is therefore suggested that when the seeds of tomato plants VG-TH-017 are to be grown, the 5N treatment is the most suitable level of application.

  8. Worldwide variation in within-canopy photosynthetic acclimation: differences in temporal and environmental controls among plant functional types

    Science.gov (United States)

    Niinemets, Ülo; Keenan, Trevor

    2017-04-01

    formation had lower within canopy plasticity during the growing season and in response to environmental and site modifications than species with high rates of canopy expansion and leaf turnover. The fast canopy-expanding species that grow in highly dynamic light environments, actively modified Aarea by nitrogen reallocation among and partitioning within leaves. In contrast, species with low rate of leaf turnover generally exhibited a passive acclimation response with variation in Aarea primarily determined by light-dependent modifications in leaf structure during leaf growth. Due to limited reacclimation capacity in species with low leaf turnover, within-canopy variation in Aarea decreased with increasing leaf age in these species. Furthermore, the plasticity responded less to modifications in environmental and site characteristics than in species with faster leaf turnover. This analysis concludes that the rate of leaf turnover is the key trait determining the temporal variation and environmental responses of canopy photosynthetic acclimation.

  9. Over-expressing the C3 photosynthesis cycle enzyme Sedoheptulose-1-7 Bisphosphatase improves photosynthetic carbon gain and yield under fully open air CO2 fumigation (FACE)

    Science.gov (United States)

    2011-01-01

    Background Biochemical models predict that photosynthesis in C3 plants is most frequently limited by the slower of two processes, the maximum capacity of the enzyme Rubisco to carboxylate RuBP (Vc,max), or the regeneration of RuBP via electron transport (J). At current atmospheric [CO2] levels Rubisco is not saturated; consequently, elevating [CO2] increases the velocity of carboxylation and inhibits the competing oxygenation reaction which is also catalyzed by Rubisco. In the future, leaf photosynthesis (A) should be increasingly limited by RuBP regeneration, as [CO2] is predicted to exceed 550 ppm by 2050. The C3 cycle enzyme sedoheptulose-1,7 bisphosphatase (SBPase, EC 3.1.3.17) has been shown to exert strong metabolic control over RuBP regeneration at light saturation. Results We tested the hypothesis that tobacco transformed to overexpressing SBPase will exhibit greater stimulation of A than wild type (WT) tobacco when grown under field conditions at elevated [CO2] (585 ppm) under fully open air fumigation. Growth under elevated [CO2] stimulated instantaneous A and the diurnal photosynthetic integral (A') more in transformants than WT. There was evidence of photosynthetic acclimation to elevated [CO2] via downregulation of Vc,max in both WT and transformants. Nevertheless, greater carbon assimilation and electron transport rates (J and Jmax) for transformants led to greater yield increases than WT at elevated [CO2] compared to ambient grown plants. Conclusion These results provide proof of concept that increasing content and activity of a single photosynthesis enzyme can enhance carbon assimilation and yield of C3 crops grown at [CO2] expected by the middle of the 21st century. PMID:21884586

  10. Photochemical efficiency of photosystem II, photon yield of O2 evolution, photosynthetic capacity, and carotenoid composition during the midday depression of net CO2 uptake in Arbutus unedo growing in Portugal.

    Science.gov (United States)

    Demmig-Adams, B; Adams, W W; Winter, K; Meyer, A; Schreiber, U; Pereira, J S; Krüger, A; Czygan, F C; Lange, O L

    1989-03-01

    During the "midday depression" of net CO2 exchange in the mediterranean sclerophyllous shrub Arbutus unedo, examined in the field in Portugal during August of 1987, several parameters indicative of photosynthetic competence were strongly and reversibly affected. These were the photochemical efficiency of photosystem (PS) II, measured as the ratio of variable to maximum chlorophyll fluorescence, as well as the photon yield and the capacity of photosynthetic O2 evolution at 10% CO2, of which the apparent photon yield of O2 evolution was most depressed. Furthermore, there was a strong and reversible increase in the content of the carotenoid zeaxanthin in the leaves that occurred at the expense of both violaxanthin and β-carotene. Diurnal changes in fluorescence characteristics were interpreted to indicate three concurrent effects on the photochemical system. First, an increase in the rate of radiationless energy dissipation in the antenna chlorophyll, reflected by changes in 77K fluorescence of PSII and PSI as well as in chlorophyll a fluorescence at ambient temperature. Second, a state shift characterized by an increase in the proportion of energy distributed to PSI as reflected by changes in PSI fluorescence. Third, an effect lowering the photon yield of O2 evolution and PSII fluorescence at ambient temperature without affecting PSII fluorescence at 77K which would be expected from a decrease in the activity of the water splitting enzyme system, i.e. a donor side limitation.

  11. Stomatal kinetics and photosynthetic gas exchange along a continuum of isohydric to anisohydric regulation of plant water status.

    Science.gov (United States)

    Meinzer, Frederick C; Smith, Duncan D; Woodruff, David R; Marias, Danielle E; McCulloh, Katherine A; Howard, Ava R; Magedman, Alicia L

    2017-08-01

    Species' differences in the stringency of stomatal control of plant water potential represent a continuum of isohydric to anisohydric behaviours. However, little is known about how quasi-steady-state stomatal regulation of water potential may relate to dynamic behaviour of stomata and photosynthetic gas exchange in species operating at different positions along this continuum. Here, we evaluated kinetics of light-induced stomatal opening, activation of photosynthesis and features of quasi-steady-state photosynthetic gas exchange in 10 woody species selected to represent different degrees of anisohydry. Based on a previously developed proxy for the degree of anisohydry, species' leaf water potentials at turgor loss, we found consistent trends in photosynthetic gas exchange traits across a spectrum of isohydry to anisohydry. More anisohydric species had faster kinetics of stomatal opening and activation of photosynthesis, and these kinetics were closely coordinated within species. Quasi-steady-state stomatal conductance and measures of photosynthetic capacity and performance were also greater in more anisohydric species. Intrinsic water-use efficiency estimated from leaf gas exchange and stable carbon isotope ratios was lowest in the most anisohydric species. In comparisons between gas exchange traits, species rankings were highly consistent, leading to species-independent scaling relationships over the range of isohydry to anisohydry observed. © 2017 John Wiley & Sons Ltd.

  12. Assessing boreal forest photosynthetic dynamics through space-borne measurements of greenness, chlorophyll fluorescence and model GPP

    Science.gov (United States)

    Walther, Sophia; Guanter, Luis; Voigt, Maximilian; Köhler, Philipp; Jung, Martin; Joiner, Joanna

    2015-04-01

    sophia.walther@gfz-potsdam.de The seasonality of photosynthesis of boreal forests is an essential driver of the terrestrial carbon, water and energy cycles. However, current carbon cycle model results only poorly represent interannual variability and predict very different magnitudes and timings of carbon fluxes between the atmosphere and the land surface (e.g. Jung et al. 2011, Richardson et al. 2012). Reflectance-based satellite measurements, which give an indication of the amount of green biomass on the Earth's surface, have so far been used as input to global carbon cycle simulations, but they have limitations as they are not directly linked to instantaneous photosynthesis. As an alternative, space-borne retrievals of sun-induced chlorophyll fluorescence (SIF) boast the potential to provide a direct indication of the seasonality of boreal forest photosynthetic activity and thus to improve carbon model performances. SIF is a small electromagnetic signal that is re-emitted from the photosystems in the chloroplasts, which results in a direct relationship to photosynthetic efficiency. In this contribution we examine the seasonality of the boreal forests with three different vegetation parameters, namely greenness, SIF and model simulations of gross primary production (gross carbon flux into the plants by photosynthesis, GPP). We use the enhanced vegetation index (EVI) to represent green biomass. EVI is calculated from NBAR MODIS reflectance measurements (0.05deg, 16 days temporal resolution) for the time from January 2007-May 2013. SIF data originate from GOME-2 measurements on board the MetOp-A satellite in a spatial resolution of 0.5deg for the time from 2007-2011 (Joiner et al. (2013), Köhler et al. (2014)). As a third data source, data-driven GPP model results are used for the time from 2006-2012 with 0.5deg spatial resolution. The method to quantify phenology developed by Gonsamo et al. (2013) is applied to infer the main phenological phases (greenup/onset of

  13. PHOTOINDUCED TRANSFER OF OXYGEN FROM WATER: AN ARTIFICAL PHOTOSYNTHETIC SYSTEM

    Energy Technology Data Exchange (ETDEWEB)

    Willner, Itamar; Otvos, John W.; Ford, William E.; Mettee, Howard; Calvin, Melvin

    1979-11-01

    The photoinduced splitting of water into hydrogen and oxygen has evoked great interest in recent years as a means for energy storag eand fuel production. Photoinduced reduction of water to hydrogen, using visible light, has been described using heterogeneous or homogeneous catalysts. However, the complementary part involving the oxidation of water to oxygen is required in order to create a cyclic artificial 'photosynthetic' fuel system. The major difficulty assocaited with the photooxidation of water involves the requirement for a four electron transfer to produce oxygen. A stepwise one-electron oxidation of water is unfavorable due to the implied formation of active hydroxyl radicals. Very recently, it has been reported that RuO{sub 2} can serve as a heterogeneous charge storage catalyst for oxygen production. On the basis of the limited knowledge about natural photosynthesis, in which manganese ions play an important role in oxygen evolution, synthetic manganese complexes, and in particular dimeric complexes, have been proposed as potential catalysts for oxygen production. So far, efforts directed toward this goal have been unsuccessful. Consequently, using a manganese complex, they attempted to perform a photoinduced oxidation of water whereby the active oxygen is transferred to a trapping substrate. In such a way, the requirement for a dimerization process to evolve molecular oxygen is avoided. They wish to report a photoinduced redox cycle sensitized by a manganese porphyrin, 5-(4{prime}-hexadecylpyridium)-10, 15, 20-tri (4{prime}-pyridyl)-porphinatomanganese(III) (abbreciated to Pn-Mn{sup III}) in which the resultant reaction is the oxidation of water and trapping of the single oxygen atom by a substrate (triphenylphosphine).

  14. Biological optimization systems for enhancing photosynthetic efficiency and methods of use

    Science.gov (United States)

    Hunt, Ryan W.; Chinnasamy, Senthil; Das, Keshav C.; de Mattos, Erico Rolim

    2012-11-06

    Biological optimization systems for enhancing photosynthetic efficiency and methods of use. Specifically, methods for enhancing photosynthetic efficiency including applying pulsed light to a photosynthetic organism, using a chlorophyll fluorescence feedback control system to determine one or more photosynthetic efficiency parameters, and adjusting one or more of the photosynthetic efficiency parameters to drive the photosynthesis by the delivery of an amount of light to optimize light absorption of the photosynthetic organism while providing enough dark time between light pulses to prevent oversaturation of the chlorophyll reaction centers are disclosed.

  15. Effect of space mutation of photosynthetic characteristics of soybean varieties

    International Nuclear Information System (INIS)

    Liu Xinlei; Ma Yansong; Luan Xiaoyan; Man Weiqun; Xu Dechun; Meng Lifen; Fu Lixin; Zhao Xiao'nan; Liu Qi

    2012-01-01

    In order to elucidate the response of the photosynthetic traits of soybean to space mutation, three soybean varieties (lines) of Heinong 48, Heinong 44 and Ha 2291-Y were carried by artificial satellite in 2006 and the net photo synthetic rate (Pn), stomatal conductance (Cond), intercellular CO 2 concentration (Ci) and stomatal resistance (Rs) from SP 1 to SP 4 generation were determined. The results showed that space mutation affected photosynthesis traits of soy bean. The photosynthetic rate of soybean varieties by space mutation occurred different levels of genetic variation and the positive mutation rate were higher. Coefficient of variation among generations were SP 2 >SP 3 >SP 4 >CK. Results suggest that space mutation can effectively create soybean materials with higher photosynthetic rate. (authors)

  16. Cyanobacteria as photosynthetic biocatalysts: a systems biology perspective.

    Science.gov (United States)

    Gudmundsson, Steinn; Nogales, Juan

    2015-01-01

    The increasing need to replace oil-based products and to address global climate change concerns has triggered considerable interest in photosynthetic microorganisms. Cyanobacteria, in particular, have great potential as biocatalysts for fuels and fine-chemicals. During the last few years the biotechnological applications of cyanobacteria have experienced an unprecedented increase and the use of these photosynthetic organisms for chemical production is becoming a tangible reality. However, the field is still immature and many concerns about the economic feasibility of the biotechnological potential of cyanobacteria remain. In this review we describe recent successes in biofuel and fine-chemical production using cyanobacteria. We discuss the role of the photosynthetic metabolism and highlight the need for systems-level metabolic optimization in order to achieve the true potential of cyanobacterial biocatalysts.

  17. Maximum Entropy in Drug Discovery

    Directory of Open Access Journals (Sweden)

    Chih-Yuan Tseng

    2014-07-01

    Full Text Available Drug discovery applies multidisciplinary approaches either experimentally, computationally or both ways to identify lead compounds to treat various diseases. While conventional approaches have yielded many US Food and Drug Administration (FDA-approved drugs, researchers continue investigating and designing better approaches to increase the success rate in the discovery process. In this article, we provide an overview of the current strategies and point out where and how the method of maximum entropy has been introduced in this area. The maximum entropy principle has its root in thermodynamics, yet since Jaynes’ pioneering work in the 1950s, the maximum entropy principle has not only been used as a physics law, but also as a reasoning tool that allows us to process information in hand with the least bias. Its applicability in various disciplines has been abundantly demonstrated. We give several examples of applications of maximum entropy in different stages of drug discovery. Finally, we discuss a promising new direction in drug discovery that is likely to hinge on the ways of utilizing maximum entropy.

  18. Optimal fold symmetry of LH2 rings on a photosynthetic membrane.

    Science.gov (United States)

    Cleary, Liam; Chen, Hang; Chuang, Chern; Silbey, Robert J; Cao, Jianshu

    2013-05-21

    An intriguing observation of photosynthetic light-harvesting systems is the N-fold symmetry of light-harvesting complex 2 (LH2) of purple bacteria. We calculate the optimal rotational configuration of N-fold rings on a hexagonal lattice and establish two related mechanisms for the promotion of maximum excitation energy transfer (EET). (i) For certain fold numbers, there exist optimal basis cells with rotational symmetry, extendable to the entire lattice for the global optimization of the EET network. (ii) The type of basis cell can reduce or remove the frustration of EET rates across the photosynthetic network. We find that the existence of a basis cell and its type are directly related to the number of matching points S between the fold symmetry and the hexagonal lattice. The two complementary mechanisms provide selection criteria for the fold number and identify groups of consecutive numbers. Remarkably, one such group consists of the naturally occurring 8-, 9-, and 10-fold rings. By considering the inter-ring distance and EET rate, we demonstrate that this group can achieve minimal rotational sensitivity in addition to an optimal packing density, achieving robust and efficient EET. This corroborates our findings i and ii and, through their direct relation to S, suggests the design principle of matching the internal symmetry with the lattice order.

  19. Does low stomatal conductance or photosynthetic capacity enhance growth at elevated CO2 in Arabidopsis?

    Science.gov (United States)

    Easlon, Hsien Ming; Carlisle, Eli; McKay, John K; Bloom, Arnold J

    2015-03-01

    The objective of this study was to determine if low stomatal conductance (g) increases growth, nitrate (NO3 (-)) assimilation, and nitrogen (N) utilization at elevated CO2 concentration. Four Arabidopsis (Arabidopsis thaliana) near isogenic lines (NILs) differing in g were grown at ambient and elevated CO2 concentration under low and high NO3 (-) supply as the sole source of N. Although g varied by 32% among NILs at elevated CO2, leaf intercellular CO2 concentration varied by only 4% and genotype had no effect on shoot NO3 (-) concentration in any treatment. Low-g NILs showed the greatest CO2 growth increase under N limitation but had the lowest CO2 growth enhancement under N-sufficient conditions. NILs with the highest and lowest g had similar rates of shoot NO3 (-) assimilation following N deprivation at elevated CO2 concentration. After 5 d of N deprivation, the lowest g NIL had 27% lower maximum carboxylation rate and 23% lower photosynthetic electron transport compared with the highest g NIL. These results suggest that increased growth of low-g NILs under N limitation most likely resulted from more conservative N investment in photosynthetic biochemistry rather than from low g. © 2015 American Society of Plant Biologists. All Rights Reserved.

  20. Alternative oxidase: a respiratory electron transport chain pathway essential for maintaining photosynthetic performance during drought stress.

    Science.gov (United States)

    Vanlerberghe, Greg C; Martyn, Greg D; Dahal, Keshav

    2016-07-01

    Photosynthesis and respiration are the hubs of energy metabolism in plants. Drought strongly perturbs photosynthesis as a result of both diffusive limitations resulting from stomatal closure, and in some cases biochemical limitations that are associated with a reduced abundance of key photosynthetic components. The effects of drought on respiration, particularly respiration in the light (RL ), are less understood. The plant mitochondrial electron transport chain includes a non-energy conserving terminal oxidase called alternative oxidase (AOX). Several studies have shown that drought increases AOX transcript, protein and maximum capacity. Here we review recent studies comparing wild-type (WT) tobacco to transgenic lines with altered AOX protein amount. Specifically during drought, RL was compromised in AOX knockdown plants and enhanced in AOX overexpression plants, compared with WT. Significantly, these differences in RL were accompanied by dramatic differences in photosynthetic performance. Knockdown of AOX increased the susceptibility of photosynthesis to drought-induced biochemical limitations, while overexpression of AOX delayed the development of such biochemical limitations, compared with WT. Overall, the results indicate that AOX is essential to maintaining RL during drought, and that this non-energy conserving respiration maintains photosynthesis during drought by promoting energy balance in the chloroplast. This review also outlines several areas for future research, including the possibility that enhancement of non-energy conserving respiratory electron sinks may be a useful biotechnological approach to increase plant performance during stress. © 2016 Scandinavian Plant Physiology Society.

  1. Salinity-induced modulation of plant growth and photosynthetic parameters in faba bean (vicia faba) cultivars

    International Nuclear Information System (INIS)

    Hussein, M.; Embiale, A.; Husen, A.; Eref, I.E.

    2017-01-01

    Salinity is one of the most severe environmental factors limiting the productivity of agricultural crops. The present study assesses salt-tolerant cultivars of Vicia faba L.on the basis of their growth, biomass and foliar characteristics. Four levels of salt stress (0, 50, 100 and 150mM) were applied to three selected cultivars, viz. Degaga, Dosha and Hachalu. Results revealed significant differences among the cultivars, salt-stress treatments, and their interaction, indicating the cultivars' variability and differential response to salt stress. Salinity stress adversely affected plant growth, plant water status and biomass production. Salt treatments decreased the chlorophyll a and chlorophyll b contents, but cultivar Dosha, which was ahead of others in height, leaf number, relative water content, total biomass and leaf-dry-mass ratio, was least affected. Functional leaf characters, such as photochemical efficiency of PSII (maximum quantum yield = Fv/Fm), stomatal conductance (gs), net photosynthetic rate (Pn) and transpiration rate (E) were also reduced under salt-stress, and againDosha cultivar did better than others except in gs. The relatively less decline in growth, water status, biomass, photosynthetic pigments and functional leaf characters of Dosha exhibits a reasonable tolerance ability of this cultivar, while the other two varieties viz., Degaga and Hachalu proved to be sensitive to salt stress. (author)

  2. Energy transfer in real and artificial photosynthetic systems

    Energy Technology Data Exchange (ETDEWEB)

    Hindman, J.C.; Hunt, J.E.; Katz, J.J.

    1995-02-01

    Fluorescence emission from the photosynthetic organisms Tribonema aequale, Anacystis nidulau, and Chlorelia vulgais and from some chlorophyll model systems have been recorded as a function of excitation wavelength and temperature. Considerable similarity was observed in the effects of excitation wavelength and temperature on the fluorescence from intact photosynthetic organisms and the model systems. The parallelism in behavior suggest that self-assembly processes may occur in both the in vivo and in vitro systems that give rise to chlorophyll species at low temperature that may differ significantly from those present at ambient temperatures.

  3. Thermodynamic efficiency of synthesis, storage and breakdown of the high-energy metabolites by photosynthetic microalgae

    International Nuclear Information System (INIS)

    Sorgüven, Esra; Özilgen, Mustafa

    2013-01-01

    Lipids and carbohydrates are employed in the nature to store internal energy due to the large number of the high energy atomic bonds in their structure. Internal energy stored in the bonds is used to fuel work producing engines or metabolic activity of living organisms. This paper investigates the thermodynamic efficiency of the glucose and lipid synthesis and breakdown by photosynthetic microalgae. Photosynthetic microalgae are able to convert 3.8% of the solar exergy into the chemical exergy of algal lipid. As the microalgae convert the first product of the photosynthesis, i.e. glucose, into lipid, 47–49% of the chemical exergy is lost. If the microalgal cell consumes the photosynthetically produced glucose for its own energy demand, then about 30% of the glucose exergy can be converted into work potential in case of immediate and short-term energy demands. Organism can convert about 22% of the glucose exergy into work potential after a long-term storage. If the algal lipid is harvested for biodiesel production and the produced biodiesel is combusted in a Diesel engine, then about 17% of the exergy of the photosynthetically produced glucose can be converted into useful work. Biodiesel is among the most popular renewable fuels. The lipids are harvested from their storage in the cells to produce biodiesel before following the lipid breakdown path of the cellular metabolism. Our analysis indicates that, extracting the first product of photosynthesis, i.e. glucose or glucose polymers instead of lipids may be more efficient thermodynamically, if new motors capable to extract their bond energy is developed. - Highlights: • Photosynthetic microalgae convert 3.8% of the solar exergy into the chemical exergy of algal lipid. • Converting the first product of the photosynthesis (glucose) into lipid causes 47–49% of exergy loss. • Organism can convert 30% of the glucose exergy into work potential for its own immediate or short-term energy demand. • Organism can

  4. SOUR CHERRY (Prunus cerasus L. GENETIC VARIABILITY AND PHOTOSYNTHETIC EFFICIENCY DURING DROUGHT

    Directory of Open Access Journals (Sweden)

    Marija Viljevac

    2012-12-01

    Full Text Available Sour cherry is an important fruit in Croatian orchards. Cultivar Oblačinska is predominant in existing orchards with noted intracultivar phenotypic heterogeneity. In this study, the genetic variability of 22 genotypes of cvs. Oblačinska, Maraska and Cigančica, as well as standard cvs. Kelleris 14, Kelleris 16, Kereška, Rexelle and Heimann conserved were investigated. Two types of molecular markers were used: microsatellite markers (SSR in order to identify intercultivar, and AFLP in order to identify intracultivar variabilities. A set of 12 SSR markers revealed small genetic distance between cvs. Maraska and Oblačinska while cv. Cigančica is affined to cv. Oblačinska. Furthermore, cvs. Oblačinska, Cigančica and Maraska were characterized compared to standard ones. AFLP markers didn`t confirm significant intracultivar variability of cv. Oblačinska although the variability has been approved at the morphological, chemical and pomological level. Significant corelation between SSR and AFLP markers was found. Identification of sour cherry cultivars tolerant to drought will enable the sustainability of fruit production with respect to the climate change in the future. For this purpose, the tolerance of seven sour cherry genotypes (cvs. Kelleris 16, Maraska, Cigančica and Oblačinska represented by 4 genotypes: OS, 18, D6 and BOR to drought conditions was tested in order to isolate genotypes with the desired properties. In the greenhouse experiment, cherry plants were exposed to drought stress. The leaf relative water content, OJIP test parameters which specify efficiency of the photosynthetic system based on measurements of chlorophyll a fluorescence, and concentrations of photo-synthetic pigments during the experiment were measured as markers of drought tolerance. Photosynthetic performance index (PIABS comprises three key events in the reaction centre of photosystem II affecting the photosynthetic activity: the absorption of energy

  5. Estimating photosynthetic radiation use efficiency using incident light and photosynthesis of individual leaves.

    Science.gov (United States)

    Rosati, A; Dejong, T M

    2003-06-01

    It has been theorized that photosynthetic radiation use efficiency (PhRUE) over the course of a day is constant for leaves throughout a canopy if leaf nitrogen content and photosynthetic properties are adapted to local light so that canopy photosynthesis over a day is optimized. To test this hypothesis, 'daily' photosynthesis of individual leaves of Solanum melongena plants was calculated from instantaneous rates of photosynthesis integrated over the daylight hours. Instantaneous photosynthesis was estimated from the photosynthetic responses to photosynthetically active radiation (PAR) and from the incident PAR measured on individual leaves during clear and overcast days. Plants were grown with either abundant or scarce N fertilization. Both net and gross daily photosynthesis of leaves were linearly related to daily incident PAR exposure of individual leaves, which implies constant PhRUE over a day throughout the canopy. The slope of these relationships (i.e. PhRUE) increased with N fertilization. When the relationship was calculated for hourly instead of daily periods, the regressions were curvilinear, implying that PhRUE changed with time of the day and incident radiation. Thus, linearity (i.e. constant PhRUE) was achieved only when data were integrated over the entire day. Using average PAR in place of instantaneous incident PAR increased the slope of the relationship between daily photosynthesis and incident PAR of individual leaves, and the regression became curvilinear. The slope of the relationship between daily gross photosynthesis and incident PAR of individual leaves increased for an overcast compared with a clear day, but the slope remained constant for net photosynthesis. This suggests that net PhRUE of all leaves (and thus of the whole canopy) may be constant when integrated over a day, not only when the incident PAR changes with depth in the canopy, but also when it varies on the same leaf owing to changes in daily incident PAR above the canopy. The

  6. Habitat reclamation plan to mitigate for the loss of habitat due to oil and gas production activities under maximum efficient rate, Naval Petroleum Reserve No. 1, Kern County, California

    International Nuclear Information System (INIS)

    Anderson, D.C.

    1994-11-01

    Activities associated with oil and gas development under the Maximum Efficiency Rate (MER) from 1975 to 2025 will disturb approximately 3,354 acres. Based on 1976 aerial photographs and using a dot grid methodology, the amount of land disturbed prior to MER is estimated to be 3,603 acres. Disturbances on Naval Petroleum Reserve No. 1 (NPR-1) were mapped using 1988 aerial photography and a geographical information system. A total of 6,079 acres were classified as disturbed as of June, 1988. The overall objective of this document is to provide specific information relating to the on-site habitat restoration program at NPRC. The specific objectives, which relate to the terms and conditions that must be met by DOE as a means of protecting the San Joaquin kit fox from incidental take are to: (1) determine the amount and location of disturbed lands on NPR-1 and the number of acres disturbed as a result of MER activities, (2) develop a long term (10 year) program to restore an equivalent on-site acres to that lost from prior project-related actions, and (3) examine alternative means to offset kit fox habitat loss

  7. Effect of Nitrogen Nutritional Stress on some Mineral Nutrients and Photosynthetic Apparatus of Zea mays L. and Vigna unguiculata L.

    Directory of Open Access Journals (Sweden)

    Akinbode Foluso OLOGUNDUDU

    2013-08-01

    Full Text Available The study investigated the responses of maize (Zea mays L. and cowpea (Vigna unguiculata L. Walp. seedlings metabolic activities and photosynthetic apparatus to nitrogen nutritional stress. Germination of seeds was done using treated sand in sixty plastic pots and the seedlings were divided into four nutrient regimes. A group of the seedlings was nutrient stressed by administering 200 ml of complete nutrient solution minus nitrogen (-N while the other groups were fed with five times (X5N and ten times (X10N the optimal concentration of nitrogen and the last regime was fed with full nutrient solution (FN. The photosynthetic parameters studied included chlorophylls ‘a’ and ‘b’ respectively; carotenes and xanthophyll while the mineral elements investigated include potassium, calcium and magnesium. The result of the growth analysis showed that nitrogen deficiency promotes an increase in the content of abscisic acid (ABA, causing stomatal closure and a reduction in photosynthesis. This explains the higher rate of leaf abscission in -N plants. A comparison of calcium ion and magnesium ion concentrations in both optimal and stressed conditions reveals that the two ions show antagonism in uptake. There is a correlation between nitrogen and magnesium accumulation as magnesium ion plays a vital role in chlorophyll biosynthesis, protein synthesis and photosynthesis. The pattern of accumulation of photosynthetic apparatus in both maize and cowpea follow a similar pattern. Chlorophyll a dictated the growth pattern of other photosynthetic apparatus in both Zea mays and Vigna unguiculata.

  8. Effect of fluoride on the cell viability, cell organelle potential, and photosynthetic capacity of freshwater and soil algae.

    Science.gov (United States)

    Chae, Yooeun; Kim, Dokyung; An, Youn-Joo

    2016-12-01

    Although fluoride occurs naturally in the environment, excessive amounts of fluoride in freshwater and terrestrial ecosystems can be harmful. We evaluated the toxicity of fluoride compounds on the growth, viability, and photosynthetic capacity of freshwater (Chlamydomonas reinhardtii and Pseudokirchneriella subcapitata) and terrestrial (Chlorococcum infusionum) algae. To measure algal growth inhibition, a flow cytometric method was adopted (i.e., cell size, granularity, and auto-fluorescence measurements), and algal yield was calculated to assess cell viability. Rhodamine123 and fluorescein diacetate were used to evaluate mitochondrial membrane potential (MMA, ΔΨ m ) and cell permeability. Nine parameters related to the photosynthetic capacity of algae were also evaluated. The results indicated that high concentrations of fluoride compounds affected cell viability, cell organelle potential, and photosynthetic functions. The cell viability measurements of the three algal species decreased, but apoptosis was only observed in C. infusionum. The MMA (ΔΨ m ) of cells exposed to fluoride varied among species, and the cell permeability of the three species generally decreased. The decrease in the photosynthetic activity of algae may be attributable to the combination of fluoride ions (F - ) with magnesium ions (Mg 2+ ) in chlorophyll. Our results therefore provide strong evidence for the potential risks of fluoride compounds to microflora and microfauna in freshwater and terrestrial ecosystems. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Photoprotection Conferred by Changes in Photosynthetic Protein Levels and Organization during Dehydration of a Homoiochlorophyllous Resurrection Plant1

    Science.gov (United States)

    Charuvi, Dana; Nevo, Reinat; Shimoni, Eyal; Naveh, Leah; Zia, Ahmad; Adam, Zach; Farrant, Jill M.; Kirchhoff, Helmut; Reich, Ziv

    2015-01-01

    During desiccation, homoiochlorophyllous resurrection plants retain most of their photosynthetic apparatus, allowing them to resume photosynthetic activity quickly upon water availability. These plants rely on various mechanisms to prevent the formation of reactive oxygen species and/or protect their tissues from the damage they inflict. In this work, we addressed the issue of how homoiochlorophyllous resurrection plants deal with the problem of excessive excitation/electron pressures during dehydration using Craterostigma pumilum as a model plant. To investigate the alterations in the supramolecular organization of photosynthetic protein complexes, we examined cryoimmobilized, freeze-fractured leaf tissues using (cryo)scanning electron microscopy. These examinations revealed rearrangements of photosystem II (PSII) complexes, including a lowered density during moderate dehydration, consistent with a lower level of PSII proteins, as shown by biochemical analyses. The latter also showed a considerable decrease in the level of cytochrome f early during dehydration, suggesting that initial regulation of the inhibition of electron transport is achieved via the cytochrome b6f complex. Upon further dehydration, PSII complexes are observed to arrange into rows and semicrystalline arrays, which correlates with the significant accumulation of sucrose and the appearance of inverted hexagonal lipid phases within the membranes. As opposed to PSII and cytochrome f, the light-harvesting antenna complexes of PSII remain stable throughout the course of dehydration. Altogether, these results, along with photosynthetic activity measurements, suggest that the protection of retained photosynthetic components is achieved, at least in part, via the structural rearrangements of PSII and (likely) light-harvesting antenna complexes into a photochemically quenched state. PMID:25713340

  10. Maximum stellar iron core mass

    Indian Academy of Sciences (India)

    60, No. 3. — journal of. March 2003 physics pp. 415–422. Maximum stellar iron core mass. F W GIACOBBE. Chicago Research Center/American Air Liquide ... iron core compression due to the weight of non-ferrous matter overlying the iron cores within large .... thermal equilibrium velocities will tend to be non-relativistic.

  11. Maximum entropy beam diagnostic tomography

    International Nuclear Information System (INIS)

    Mottershead, C.T.

    1985-01-01

    This paper reviews the formalism of maximum entropy beam diagnostic tomography as applied to the Fusion Materials Irradiation Test (FMIT) prototype accelerator. The same formalism has also been used with streak camera data to produce an ultrahigh speed movie of the beam profile of the Experimental Test Accelerator (ETA) at Livermore. 11 refs., 4 figs

  12. Maximum entropy beam diagnostic tomography

    International Nuclear Information System (INIS)

    Mottershead, C.T.

    1985-01-01

    This paper reviews the formalism of maximum entropy beam diagnostic tomography as applied to the Fusion Materials Irradiation Test (FMIT) prototype accelerator. The same formalism has also been used with streak camera data to produce an ultrahigh speed movie of the beam profile of the Experimental Test Accelerator (ETA) at Livermore

  13. A portable storage maximum thermometer

    International Nuclear Information System (INIS)

    Fayart, Gerard.

    1976-01-01

    A clinical thermometer storing the voltage corresponding to the maximum temperature in an analog memory is described. End of the measurement is shown by a lamp switch out. The measurement time is shortened by means of a low thermal inertia platinum probe. This portable thermometer is fitted with cell test and calibration system [fr

  14. Neutron spectra unfolding with maximum entropy and maximum likelihood

    International Nuclear Information System (INIS)

    Itoh, Shikoh; Tsunoda, Toshiharu

    1989-01-01

    A new unfolding theory has been established on the basis of the maximum entropy principle and the maximum likelihood method. This theory correctly embodies the Poisson statistics of neutron detection, and always brings a positive solution over the whole energy range. Moreover, the theory unifies both problems of overdetermined and of underdetermined. For the latter, the ambiguity in assigning a prior probability, i.e. the initial guess in the Bayesian sense, has become extinct by virtue of the principle. An approximate expression of the covariance matrix for the resultant spectra is also presented. An efficient algorithm to solve the nonlinear system, which appears in the present study, has been established. Results of computer simulation showed the effectiveness of the present theory. (author)

  15. Reduction of photosynthetically active radiation under extreme stratospheric aerosol loads

    International Nuclear Information System (INIS)

    Gerstl, S.A.W.; Zardecki, A.

    1981-08-01

    The recently published hypothesis that the Cretaceous-Tertiary extinctions might be caused by an obstruction of sunlight is tested by model calculations. First we compute the total mass of stratospheric aerosols under normal atmospheric conditions for four different (measured) aerosol size distributions and vertical profiles. For comparison, the stratospheric dust masses after four volcanic eruptions are also evaluated. Detailed solar radiative transfer calculations are then performed for artificially increased aerosol amounts until the postulated darkness scenario is obtained. Thus we find that a total stratospheric aerosol mass between 1 and 4 times 10 1 g is sufficient to reduce photosynthesis to 10 -3 of normal. We also infer from this result tha the impact of a 0.4- to 3-km-diameter asteroid or a close encounter with a Halley-size comet may deposit that amount of particulates into the stratosphere. The darkness scenario of Alvarez et al. is thus shown to be a possible extinction mechanism, even with smaller size asteroids of comets than previously estimated

  16. Photosynthetic response of an alpine plant, Rhododendron delavayi Franch, to water stress and recovery: the role of mesophyll conductance

    Directory of Open Access Journals (Sweden)

    Yanfei eCai

    2015-12-01

    Full Text Available Rhododendron delavayi Franch is an evergreen shrub or small tree with large scarlet flowers that makes it highly attractive as an ornamental species. The species is native to southwest China and southeast Asia, especially the Himalayan region, showing good adaptability and tolerance to drought. To understand the water stress coping mechanisms of R. delavayi, we analysed the plant’s photosynthetic performance during water stress and recovery. In particular, we looked at the regulation of stomatal (gs and mesophyll conductance (gm, and maximum rate of carboxylation (Vcmax. After four days of water stress treatment, the net CO2 assimilation rate (AN declined slightly while gs and gm were not affected and stomatal limitation (SL was therefore negligible. At this stage mesophyll conductance limitation (MCL and biochemical limitation (BL constituted the main limitation factors. After eight days of water stress treatment, AN, gs and gm had decreased notably. At this stage SL increased markedly and MCL even more so, while BL remained relatively constant. After re-watering, the recovery of AN, gs and gm was rapid, although remaining below the levels of the control plants, while Vcmax fully regained control levels after three days of re-watering. MCL remained the main limitation factor irrespective of the degree of photosynthetic recovery. In conclusion, in our experiment MCL was the main photosynthetic limitation factor of R. delavayi under water stress and during the recovery phase, with the regulation of gm probably being the result of interactions between the environment and leaf anatomical features.

  17. Contrasting Responses of Marine and Freshwater Photosynthetic Organisms to UVB Radiation: A Meta-Analysis

    KAUST Repository

    Jin, Peng; Duarte, Carlos M.; Agusti, Susana

    2017-01-01

    artificial lamps. We found that marine photosynthetic organisms tend to be more sensitive than freshwater photosynthetic organisms to UVB radiation; responses to either decreased or increased UVB radiation vary among taxa; the mortality rate is the most

  18. On the photosynthetic and devlopmental responses of leaves to the spectral composition of light

    NARCIS (Netherlands)

    Hogewoning, S.W.

    2010-01-01

    Key words: action spectrum, artificial solar spectrum, blue light, Cucumis sativus, gas-exchange, light-emitting diodes (LEDs), light interception, light quality, non-photosynthetic pigments, photo-synthetic capacity, photomorphogenesis, photosystem excitation balance, quantum yield, red light.

  19. Enhanced Practical Photosynthetic CO2 Mitigation

    Energy Technology Data Exchange (ETDEWEB)

    Gregory Kremer; David J. Bayless; Morgan Vis; Michael Prudich; Keith Cooksey; Jeff Muhs

    2006-01-15

    This final report highlights significant achievements in the Enhanced Practical Photosynthetic CO{sub 2} Mitigation Project during the period from 10/1/2001 through 01/02/2006. As indicated in the list of accomplishments below, our efforts during this project were focused on the selection of candidate organisms and growth surfaces and initiating long-term tests in the bench-scale and pilot-scale bioreactor test systems. Specific results and accomplishments for the program include: (1) CRF-2 test system: (a) Sampling test results have shown that the initial mass of algae loaded into the Carbon Recycling Facility Version 2 (CRF-2) system can be estimated with about 3% uncertainty using a statistical sampling procedure. (b) The pressure shim header pipe insert design was shown to have better flow for harvesting than the drilled-hole design. (c) The CRF-2 test system has undergone major improvements to produce the high flow rates needed for harvesting (as determined by previous experiments). The main changes to the system are new stainless steel header/frame units, with increased flow capacity and a modified pipe-end-sealing method to improve flow uniformity, and installation and plumbing for a new high flow harvesting pump. Qualitative system tests showed that the harvesting system performed wonderfully, cleaning the growth surfaces within a matter of seconds. (d) Qualitative tests have shown that organisms can be repopulated on a harvested section of a bioreactor screen, demonstrating that continuous bioreactor operation is feasible, with continuous cycles of harvesting and repopulating screens. (e) Final preparations are underway for quantitative, long-term tests in the CRF-2 with weekly harvesting. (2) Pilot-scale test system: (a) The construction of the pilot-scale bioreactor was completed, including the solar collector and light distribution system. Over the course of the project, the solar collector used in the light delivery system showed some degradation, but

  20. Molecular Regulation of Photosynthetic Carbon Dioxide Fixation in Nonsulfur Purple Bacteria

    Energy Technology Data Exchange (ETDEWEB)

    Tabita, Fred Robert [The Ohio State Univ., Columbus, OH (United States)

    2015-12-01

    The overall objective of this project is to determine the mechanism by which a transcriptional activator protein affects CO2 fixation (cbb) gene expression in nonsulfur purple photosynthetic bacteria, with special emphasis to Rhodobacter sphaeroides and with comparison to Rhodopseudomonas palustris. These studies culminated in several publications which indicated that additional regulators interact with the master regulator CbbR in both R. sphaeroides and R. palustris. In addition, the interactive control of the carbon and nitrogen assimilatory pathways was studied and unique regulatory signals were discovered.

  1. Continuous Cultivation of Photosynthetic Bacteria for Fatty Acids Production

    DEFF Research Database (Denmark)

    Kim, Dong-Hoon; Lee, Ji-Hye; Hwang, Yuhoon

    2013-01-01

    In the present work, we introduced a novel approach for microbial fatty acids (FA) production. Photosynthetic bacteria, Rhodobacter sphaeroides KD131, were cultivated in a continuous-flow, stirred-tank reactor (CFSTR) at various substrate (lactate) concentrations.At hydraulic retention time (HRT)....... sphaeroides was around 35% of dry cell weight, mainly composed of vaccenic acid (C18:1, omega-7)....

  2. Effect of Photosynthetic Photon Flux Density on Carboxylation Efficiency 1

    Science.gov (United States)

    Weber, James A.; Tenhunen, John D.; Gates, David M.; Lange, Otto L.

    1987-01-01

    The effect of photosynthetic photon flux density (PPFD) on photosynthetic response (A) to CO2 partial pressures between 35 pascals and CO2 compensation point (Γ) was investigated, especially below PPFD saturation. Spinacia oleracea cv `Atlanta,' Glycine max cv `Clark,' and Arbutus unedo were studied in detail. The initial slope of the photosynthetic response to CO2 (∂A/∂C[Γ]) was constant above a PPFD of about 500 to 600 micromoles per square meter per second for all three species; but declined rapidly with PPFD below this critical level. For Γ there was also a critical PPFD (approximately 200 micromoles per square meter per second for S. oleracea and G. max; 100 for A. unedo) above which Γ was essentially constant, but below which Γ increased with decreasing PPFD. All three species showed a dependence of ∂A/∂C(Γ) on PPFD at low PPFD. Simulated photosynthetic responses obtained with a biochemically based model of whole-leaf photosynthesis were similar to measured responses. PMID:16665640

  3. Coherent memory functions for finite systems: hexagonal photosynthetic unit

    International Nuclear Information System (INIS)

    Barvik, I.; Herman, P.

    1990-10-01

    Coherent memory functions entering the Generalized Master Equation are presented for an hexagonal model of a photosynthetic unit. Influence of an energy heterogeneity on an exciton transfer is an antenna system as well as to a reaction center is investigated. (author). 9 refs, 3 figs

  4. Effects of 1-butanol, neomycin and calcium on the photosynthetic ...

    African Journals Online (AJOL)

    ajl yemi

    Institute of Food Crops, Jiangsu High Quality Rice R&D Center, Jiangsu Academy of Agricultural Sciences, Nanjing,. Jiangsu Province, 210014, China. Accepted 31 October, 2011. The effects .... and blue light source under the open system, with the following conditions: 1200 µmol m-2s-1 photosynthetic photon flux density.

  5. Photosynthetic behaviour of Arabidopsis thaliana (Pa-1 accession ...

    African Journals Online (AJOL)

    The growth reduction observed in many plants caused by salinity is often associated with a decrease in their photosynthetic capacity. This effect could be associated with the partial stomatal closure and/or the non-stomatal limitation which involves the decrease in ribulose-1,5-bisphosphate carboxylase oxygenase ...

  6. Variability of photosynthetic pigments in the Colombian Pacific ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 111; Issue 3. Variability of photosynthetic pigments in the Colombian Pacific Ocean and its relationship with the wind field using ADEOS-I data. Efrain Rodriguez-Rubio Jose Stuardo. Volume 111 Issue 3 September 2002 pp 227-236 ...

  7. Photosynthetic Responses of Seedlings of two Indigenous Plants ...

    African Journals Online (AJOL)

    Bheema

    ABSTRACT. The potential role of exotic tree plantations in facilitating successional processes on degraded areas was evaluated in southern Ethiopia, Munessa-Shashemene forest, by examining photosynthetic responses of Bersamaabyssinica Fres. and Croton macrostachyusDel. seedlings naturally grown inside ...

  8. Abscisic acid effects on water and photosynthetic characteristics of ...

    African Journals Online (AJOL)

    The aim of this study is to compare the water and photosynthetic characteristics of two xerophilic ecotypes of Atriplex halimus (L.). Seeds collected from two different sites Djelfa and Oran are germinated in controlled greenhouse. After 6 months, the plantlets were treated 21 days with increasing concentrations of abscisic ...

  9. An Improved Method for Extraction and Separation of Photosynthetic Pigments

    Science.gov (United States)

    Katayama, Nobuyasu; Kanaizuka, Yasuhiro; Sudarmi, Rini; Yokohama, Yasutsugu

    2003-01-01

    The method for extracting and separating hydrophobic photosynthetic pigments proposed by Katayama "et al." ("Japanese Journal of Phycology," 42, 71-77, 1994) has been improved to introduce it to student laboratories at the senior high school level. Silica gel powder was used for removing water from fresh materials prior to…

  10. Photosynthetic incorporation of 14C by Stevia rebaudiana

    International Nuclear Information System (INIS)

    Ferraresi, M. de L.; Ferraresi Filho, O.; Bracht, A.

    1985-01-01

    The photosynthetic incorporation of 14 by Stevia rebaudiana specimens was investigated. The 14 C incorporation, when the isotope was furnished to the plant in form of 14 CO 2 , was rapid. After 24 hours, the radioactivity has been incorporated into a great number of compounds including pigments, terpenes, glucose, cellulose and also stevioside and its derivatives. (M.A.C.) [pt

  11. The role of energy losses in photosynthetic light harvesting

    NARCIS (Netherlands)

    Kruger, T. P. J.; van Grondelle, R.

    2017-01-01

    Photosynthesis operates at the bottom of the food chain to convert the energy of light into carbohydrates at a remarkable global rate of about 130 TW. Nonetheless, the overall photosynthetic process has a conversion efficiency of a few percent at best, significantly less than bottom-up photovoltaic

  12. effect of ambient levels of ozone on photosynthetic components

    African Journals Online (AJOL)

    ACSS

    To clarify the long-term effects of ambient levels of tropospheric ozone (O3) on ... (Rubisco), thus contributing to the reduction in net photosynthetic rate at the .... USA). During the measurements, atmospheric. CO2 concentrations, air ...... productivity and implications for climate change. Annual Review of Plant Biology 63:.

  13. Non-photosynthetic plastids as hosts for metabolic engineering.

    Science.gov (United States)

    Mellor, Silas Busck; Behrendorff, James B Y H; Nielsen, Agnieszka Zygadlo; Jensen, Poul Erik; Pribil, Mathias

    2018-04-13

    Using plants as hosts for production of complex, high-value compounds and therapeutic proteins has gained increasing momentum over the past decade. Recent advances in metabolic engineering techniques using synthetic biology have set the stage for production yields to become economically attractive, but more refined design strategies are required to increase product yields without compromising development and growth of the host system. The ability of plant cells to differentiate into various tissues in combination with a high level of cellular compartmentalization represents so far the most unexploited plant-specific resource. Plant cells contain organelles called plastids that retain their own genome, harbour unique biosynthetic pathways and differentiate into distinct plastid types upon environmental and developmental cues. Chloroplasts, the plastid type hosting the photosynthetic processes in green tissues, have proven to be suitable for high yield protein and bio-compound production. Unfortunately, chloroplast manipulation often affects photosynthetic efficiency and therefore plant fitness. In this respect, plastids of non-photosynthetic tissues, which have focused metabolisms for synthesis and storage of particular classes of compounds, might prove more suitable for engineering the production and storage of non-native metabolites without affecting plant fitness. This review provides the current state of knowledge on the molecular mechanisms involved in plastid differentiation and focuses on non-photosynthetic plastids as alternative biotechnological platforms for metabolic engineering. © 2018 The Author(s). Published by Portland Press Limited on behalf of the Biochemical Society.

  14. Identification and growth conditions of purple non-sulfur photosynthetic bacteria isolated from palm oil mill effluent

    International Nuclear Information System (INIS)

    Radziah Ariffin

    2004-01-01

    An indigenous strain of the purple non-sulphur photosynthetic bacterium, isolated from palm oil mill effluent was presumably identified as species of Rhodopseudomonas palustris. Cultivation in synthetic medium under different conditions indicated that it gave maximum carotenoid and bacteriophyll synthesis under anaerobic conditions in the light with values of 12.6 and 108.1 mg/g dry cell weight respectively. These values were significantly higher than the pigment content obtained from aerobic cultivation. The specific growth rates in anaerobic was twice those in aerobic conditions in the light. Growth was not occurred in anaerobic or aerobic conditions in the dark. (Author)

  15. Determination of photosynthetic and enzymatic biomarkers sensitivity used to evaluate toxic effects of copper and fludioxonil in alga Scenedesmus obliquus

    International Nuclear Information System (INIS)

    Dewez, David; Geoffroy, Laure; Vernet, Guy; Popovic, Radovan

    2005-01-01

    Modulated PAM fluorometry and Plant Efficiency Analyser methods were used to investigate photosynthetic fluorescence parameters of alga Scenedesmus obliquus exposed to inhibitory effect of fungicides copper sulphate and fludioxonil (N-(4-nitrophenyl)-N'-propyl-uree). The change of those parameters were studied when alga S. obliquus have been exposed during 48 h to different concentrations of fungicides (1, 2 and 3 mg l -1 ). Under the same condition, enzymatic activities of catalase, ascorbate peroxidase, glutathione reductase and glutathione S-transferase were investigated to evaluate antioxidative response to fungicides effects. The change of sensitivity of those parameters was dependent to the mode of fungicide action, their concentration and time of exposure. For copper effects, the most indicative photosynthetic biomarkers were parameters Q N as non-photochemical fluorescence quenching, Q Emax as the proton induced fluorescence quenching and ABS/RC as the antenna size per photosystem II reaction center. Copper induced oxidative stress was indicated by increased activity of catalase serving as the most sensitive and valuable enzymatic biomarker. On the other hand, fludioxonil effect on photosynthetic parameters was very negligible and consequently not very useful as biomarkers. However, fludioxonil induced strong antioxidative activities associated with cytosol enzymes, as we found for catalase, ascorbate peroxidase and glutathione S-transferase activities. By obtained results, we may suggest for the activation of those enzymes to be sensitive and valuable biomarkers of oxidative stress induced by fludioxonil. Determination of biomarkers sensitivity may offer advantages in providing real criteria to use them for ecotoxicological diagnostic studies

  16. On Maximum Entropy and Inference

    Directory of Open Access Journals (Sweden)

    Luigi Gresele

    2017-11-01

    Full Text Available Maximum entropy is a powerful concept that entails a sharp separation between relevant and irrelevant variables. It is typically invoked in inference, once an assumption is made on what the relevant variables are, in order to estimate a model from data, that affords predictions on all other (dependent variables. Conversely, maximum entropy can be invoked to retrieve the relevant variables (sufficient statistics directly from the data, once a model is identified by Bayesian model selection. We explore this approach in the case of spin models with interactions of arbitrary order, and we discuss how relevant interactions can be inferred. In this perspective, the dimensionality of the inference problem is not set by the number of parameters in the model, but by the frequency distribution of the data. We illustrate the method showing its ability to recover the correct model in a few prototype cases and discuss its application on a real dataset.

  17. Temperature responses of photosynthetic capacity parameters were not affected by foliar nitrogen content in mature Pinus sylvestris.

    Science.gov (United States)

    Tarvainen, Lasse; Lutz, Martina; Räntfors, Mats; Näsholm, Torgny; Wallin, Göran

    2018-03-01

    A key weakness in current Earth System Models is the representation of thermal acclimation of photosynthesis in response to changes in growth temperatures. Previous studies in boreal and temperate ecosystems have shown leaf-scale photosynthetic capacity parameters, the maximum rates of carboxylation (V cmax ) and electron transport (J max ), to be positively correlated with foliar nitrogen (N) content at a given reference temperature. It is also known that V cmax and J max exhibit temperature optima that are affected by various environmental factors and, further, that N partitioning among the foliar photosynthetic pools is affected by N availability. However, despite the strong recent anthropogenic influence on atmospheric temperatures and N deposition to forests, little is known about the role of foliar N contents in controlling the photosynthetic temperature responses. In this study, we investigated the temperature dependencies of V cmax and J max in 1-year-old needles of mature boreal Pinus sylvestris (Scots pine) trees growing under low and high N availabilities in northern Sweden. We found that needle N status did not significantly affect the temperature responses of V cmax or J max when the responses were fitted to a peaked function. If such N insensitivity is a common tree trait it will simplify the interpretation of the results from gradient and multi-species studies, which commonly use sites with differing N availabilities, on temperature acclimation of photosynthetic capacity. Moreover, it will simplify modeling efforts aimed at understanding future carbon uptake by precluding the need to adjust the shape of the temperature response curves to variation in N availability. © 2017 Scandinavian Plant Physiology Society.

  18. Maximum Water Hammer Sensitivity Analysis

    OpenAIRE

    Jalil Emadi; Abbas Solemani

    2011-01-01

    Pressure waves and Water Hammer occur in a pumping system when valves are closed or opened suddenly or in the case of sudden failure of pumps. Determination of maximum water hammer is considered one of the most important technical and economical items of which engineers and designers of pumping stations and conveyance pipelines should take care. Hammer Software is a recent application used to simulate water hammer. The present study focuses on determining significance of ...

  19. Maximum Gene-Support Tree

    Directory of Open Access Journals (Sweden)

    Yunfeng Shan

    2008-01-01

    Full Text Available Genomes and genes diversify during evolution; however, it is unclear to what extent genes still retain the relationship among species. Model species for molecular phylogenetic studies include yeasts and viruses whose genomes were sequenced as well as plants that have the fossil-supported true phylogenetic trees available. In this study, we generated single gene trees of seven yeast species as well as single gene trees of nine baculovirus species using all the orthologous genes among the species compared. Homologous genes among seven known plants were used for validation of the finding. Four algorithms—maximum parsimony (MP, minimum evolution (ME, maximum likelihood (ML, and neighbor-joining (NJ—were used. Trees were reconstructed before and after weighting the DNA and protein sequence lengths among genes. Rarely a gene can always generate the “true tree” by all the four algorithms. However, the most frequent gene tree, termed “maximum gene-support tree” (MGS tree, or WMGS tree for the weighted one, in yeasts, baculoviruses, or plants was consistently found to be the “true tree” among the species. The results provide insights into the overall degree of divergence of orthologous genes of the genomes analyzed and suggest the following: 1 The true tree relationship among the species studied is still maintained by the largest group of orthologous genes; 2 There are usually more orthologous genes with higher similarities between genetically closer species than between genetically more distant ones; and 3 The maximum gene-support tree reflects the phylogenetic relationship among species in comparison.

  20. Sun and Shade leaves, SIF, and Photosynthetic Capacity

    Science.gov (United States)

    Berry, J. A.; Badgley, G.

    2016-12-01

    Recent advances in retrieval of solar induced chlorophyll fluorescence (SIF) have opened up new possibilities for remote sensing of canopy physiology and structure. To date most of the emphasis has been placed on SIF as an indicator of stress and photosynthetic capacity. However, it is clear that canopy structure can also have an influence. To this point, simulations of SIF in land surface models tend to under predict observed variation in SIF. Also, large, systematic differences in SIF from different canopy types seem to correlate well with the photosynthetic capacity of these canopies. SIF emissions from pampered crops can be several-fold that from evergreen, needle-leaf forests. Yet, these may have similar vegetation indices and absorb a similar fraction of incident PAR. SIF photons produced in a conifer canopy do have a lower probability of escaping its dense, clumped foliage. However, this does not explain the correlated differences in photosynthetic rate and SIF. It is useful, in this regard, to consider the separate contributions of sun and shade leaves to the SIF emitted by a canopy. Sun leaves tend to be displayed to intercept the direct solar beam, and these highly illuminated leaves are often visible from above the canopy. Sun leaves produce more SIF and a large fraction of it escapes. Therefore, the intensity of SIF may be a sensitive indicator of the partitioning of absorbed PAR to sun and shade leaves. Many models account tor the different photosynthetic capacity of sun and shade leaves in calculating canopy responses. However, the fraction of leaves in each category is usually parameterized by an assumed leaf angle distribution (e.g. spherical). In reality, the sun/shade fraction can vary over a wide range, and it has been difficult to measure. SIF and possibly near-IR reflectance of canopies can be used to specify this key parameter with obvious importance to understanding photosynthetic rate.

  1. Photosynthetic carbon metabolism in the submerged aquatic angiosperm Scirpus subterminalis

    Energy Technology Data Exchange (ETDEWEB)

    Beer, S; Wetzel, R G

    1981-01-01

    Scirpus subterminalis Torr., a submerged angiosperm abundant in many hardwater lakes of the Great Lakes region, was investigated for various photosynthetic carbon fixation properties in relation to available inorganic carbon and levels of carbon fixing enzymes. Photosynthetic experiments were CO/sub 2/ and HCO/sub 3//sup -/ were supplied at various concentrations showed that Scirpus was able to utilize HCO/sub 3//sup -/ at those concentrations close to natural conditions. However, when CO/sub 2/ concentrations were increased above ambient, photosynthetic rates increased markedly. It was concluded that the photosynthetic potential of this plant in many natural situations may be limited by inorganic carbon uptake in the light. Phosphoenolpyruvate carboxylase (PEPcase)/ribulose-1,5-bisphosphate carboxylase (ruBPcase) ratios of the leaves varied between 0.5 and 0.9 depending on substrate concentration during assay. The significance of PEP-mediated carbon fixation of Scirpus (basically a C/sub 3/ plant) in the dark was investigated. Malate accumulated in the leaves during the dark period of a 24-h cycle and malate levels decreased significantly during the following light period. The accumulation was not due to transport of malate from the roots. Carbon uptake rates in the dark by the leaves of Scirpus were lower than malate accumulation rates. Therefore, part of the malate was likely derived from respired CO/sub 2/. Carbon uptake rates in the light were much higher than malate turnover rates. It was estimated that carbon fixation via malate could contribute up to 12% to net photosynthetic rates. The ecological significance of this type of metabolism in submerged aquatics is discussed.

  2. Participation of intracellular and extracellular pH changes in photosynthetic response development induced by variation potential in pumpkin seedlings.

    Science.gov (United States)

    Sherstneva, O N; Vodeneev, V A; Katicheva, L A; Surova, L M; Sukhov, V S

    2015-06-01

    Electrical signals presented in plants by action potential and by variation potential (VP) can induce a reversible inactivation of photosynthesis. Changes in the intracellular and extracellular pH during VP generation are a potential mechanism of photosynthetic response induction; however, this hypothesis requires additional experimental investigation. The purpose of the present work was to analyze the influence of pH changes on induction of the photosynthetic response in pumpkin. It was shown that a burning of the cotyledon induced VP propagation into true leaves of pumpkin seedlings inducing a decrease in the photosynthetic CO2 assimilation and an increase in non-photochemical quenching of fluorescence, whereas respiration was activated insignificantly. The photosynthetic response magnitude depended linearly on the VP amplitude. The intracellular and extracellular concentrations of protons were analyzed using pH-sensitive fluorescent probes, and the VP generation was shown to be accompanied by apoplast alkalization (0.4 pH unit) and cytoplasm acidification (0.3 pH unit). The influence of changes in the incubation medium pH on the non-photochemical quenching of fluorescence of isolated chloroplasts was also investigated. It was found that acidification of the medium stimulated the non-photochemical quenching, and the magnitude of this increase depended on the decrease in pH. Our results confirm the contribution of changes in intracellular and extracellular pH to induction of the photosynthetic response caused by VP. Possible mechanisms of the influence of pH changes on photosynthesis are discussed.

  3. LCLS Maximum Credible Beam Power

    International Nuclear Information System (INIS)

    Clendenin, J.

    2005-01-01

    The maximum credible beam power is defined as the highest credible average beam power that the accelerator can deliver to the point in question, given the laws of physics, the beam line design, and assuming all protection devices have failed. For a new accelerator project, the official maximum credible beam power is determined by project staff in consultation with the Radiation Physics Department, after examining the arguments and evidence presented by the appropriate accelerator physicist(s) and beam line engineers. The definitive parameter becomes part of the project's safety envelope. This technical note will first review the studies that were done for the Gun Test Facility (GTF) at SSRL, where a photoinjector similar to the one proposed for the LCLS is being tested. In Section 3 the maximum charge out of the gun for a single rf pulse is calculated. In Section 4, PARMELA simulations are used to track the beam from the gun to the end of the photoinjector. Finally in Section 5 the beam through the matching section and injected into Linac-1 is discussed

  4. [THE EFFECT OF ACID RAIN ON ULTRASTRUCTURE AND FUNCTIONAL PARAMETERS OF PHOTOSYNTHETIC APPARATUS OF PEA LEAVES].

    Science.gov (United States)

    Polishchuk, A V; Vodka, M V; Belyavskaya, N A; Khomochkin, A P; Zolotareva, E K

    2016-01-01

    The effects of simulated acid rain (SAR) on the ultrastructure and functional parameters of the photosynthetic apparatus were studied using 14-day-old pea leaves as test system. Pea plants were sprayed with an aqueous solution containing NaNO₃(0.2 mM) and Na₂SO₄(0.2 mM) (pH 5.6, a control variant), or with the same solution, which was acidified to pH 2.5 (acid variant). Functional characteristics were determined by chlorophyll fluorescence analysis. Acid rain application caused reduction in the efficiency of the photosynthetic electron transport by 25%, which was accompanied by an increase by 85% in the quantum yield of thermal dissipation of excess light quanta. Ultrastructural changes in chloroplast were registered by transmission electron microscopy (TEM) after two days of the SAR-treatment of pea leaves. In this case, the changes in the structure of grana, heterogeneity of thylakoids packaging in granum, namely, the increase of intra-thylakoid gaps and thickness of granal thylakoids compared to the control were found. The migration of protein complexes in thylakoid membranes of chloroplasts isolated from leaves treated with SAR was suppressed. It was shown also that carbonic anhydrase activity was inhibited in chloroplast preparations isolated from SAR-treated pea leaves. We proposed a hypothesis on the possible inactivation of thylakoid carbonic anhydrase under SAR and its involvement in the inhibition of photochemical activity of chloroplasts. The data obtained allows to suggest that acid rains negatively affect the photosynthetic apparatus disrupting the membrane system of chloroplast.

  5. Thermoluminescence as a complementary technique for the toxicological evaluation of chemicals in photosynthetic organisms

    Energy Technology Data Exchange (ETDEWEB)

    Repetto, Guillermo, E-mail: grepkuh@upo.es [Departamento de Biología Molecular e Ingeniería Bioquímica, Área de Toxicología, Universidad Pablo de Olavide, Carretera de Utrera km. 1, 41013 Seville (Spain); Zurita, Jorge L. [Departamento de Biología Molecular e Ingeniería Bioquímica, Área de Toxicología, Universidad Pablo de Olavide, Carretera de Utrera km. 1, 41013 Seville (Spain); Roncel, Mercedes; Ortega, José M. [Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC, Américo Vespucio 49, 41092 Seville (Spain)

    2015-01-15

    Highlights: • There are very few toxicological applications of thermoluminescence. • It is a luminescence emission induced by heating the sample in the dark. • It is useful for study the photosystem II function and the level of lipid peroxidation. - Abstract: Thermoluminescence is a simple technique very useful for studying electron transfer reactions on photosystem II (standard thermoluminescence) or the level of lipid peroxidation in membranes (high temperature thermoluminescence) in photosynthetic organisms. Both techniques were used to investigate the effects produced on Chlorella vulgaris cells by six compounds: the chemical intermediates bromobenzene and diethanolamine, the antioxidant propyl gallate, the semiconductor indium nitrate, the pesticide sodium monofluoroacetate and the antimalarial drug chloroquine. Electron transfer activity of the photosystem II significantly decreased after the exposure of Chlorella cells to all the six chemicals used. Lipid peroxidation was slightly decreased by the antioxidant propyl gallate, not changed by indium nitrate and very potently stimulated by diethanolamine, chloroquine, sodium monofluoroacetate and bromobenzene. For five of the chemicals studied (not bromobenzene) there is a very good correlation between the cytotoxic effects in Chlorella cells measured by the algal growth inhibition test, and the inhibition of photosystem II activity. The results suggest that one very important effect of these chemicals in Chlorella cells is the inhibition of photosynthetic metabolism by the blocking of photosystem II functionality. In the case of sodium monofluoroacetate, diethanolamine and chloroquine this inhibition seems to be related with the induction of high level of lipid peroxidation in cells that may alter the stability of photosystem II. The results obtained by both techniques supply information that can be used as a supplement to the growth inhibition test and allows a more complete assessment of the effects of

  6. Thermoluminescence as a complementary technique for the toxicological evaluation of chemicals in photosynthetic organisms

    International Nuclear Information System (INIS)

    Repetto, Guillermo; Zurita, Jorge L.; Roncel, Mercedes; Ortega, José M.

    2015-01-01

    Highlights: • There are very few toxicological applications of thermoluminescence. • It is a luminescence emission induced by heating the sample in the dark. • It is useful for study the photosystem II function and the level of lipid peroxidation. - Abstract: Thermoluminescence is a simple technique very useful for studying electron transfer reactions on photosystem II (standard thermoluminescence) or the level of lipid peroxidation in membranes (high temperature thermoluminescence) in photosynthetic organisms. Both techniques were used to investigate the effects produced on Chlorella vulgaris cells by six compounds: the chemical intermediates bromobenzene and diethanolamine, the antioxidant propyl gallate, the semiconductor indium nitrate, the pesticide sodium monofluoroacetate and the antimalarial drug chloroquine. Electron transfer activity of the photosystem II significantly decreased after the exposure of Chlorella cells to all the six chemicals used. Lipid peroxidation was slightly decreased by the antioxidant propyl gallate, not changed by indium nitrate and very potently stimulated by diethanolamine, chloroquine, sodium monofluoroacetate and bromobenzene. For five of the chemicals studied (not bromobenzene) there is a very good correlation between the cytotoxic effects in Chlorella cells measured by the algal growth inhibition test, and the inhibition of photosystem II activity. The results suggest that one very important effect of these chemicals in Chlorella cells is the inhibition of photosynthetic metabolism by the blocking of photosystem II functionality. In the case of sodium monofluoroacetate, diethanolamine and chloroquine this inhibition seems to be related with the induction of high level of lipid peroxidation in cells that may alter the stability of photosystem II. The results obtained by both techniques supply information that can be used as a supplement to the growth inhibition test and allows a more complete assessment of the effects of

  7. Seasonal response of photosynthetic electron transport and energy dissipation in the eighth year of exposure to elevated atmospheric CO2 (FACE) in Pinus taeda (loblolly pine)

    International Nuclear Information System (INIS)

    Logan, B.A.; Combs, A.; Kent, R.; Stanley, L.; Myers, K.; Tissue, D.T.; Western Sydney Univ., Richmond, NSW

    2009-01-01

    This study investigated the biological adaptation of loblolly pine following long-term seasonal exposure to elevated carbon dioxide (CO 2 ) partial pressures (pCO 2 ). Exposure to elevated atmospheric CO 2 (pCO 2 ) usually results in significant stimulation in light-saturated rates of photosynthetic CO 2 assimilation. Plants are protected against photoinhibition by biochemical processes known as photoprotection, including energy dissipation, which converts excess absorbed light energy into heat. This study was conducted in the eighth year of exposure to elevated pCO 2 at the Duke FACE site. The effect of elevated pCO 2 on electron transport and energy dissipation in the pine trees was examined by coupling the analyses of the capacity for photosynthetic oxygen (O 2 ) evolution, chlorophyll fluorescence emission and photosynthetic pigment composition with measurements of net photosynthetic CO 2 assimilation (Asat). During the summer growing season, Asat was 50 per cent higher in current-year needles and 24 per cent higher in year-old needles in elevated pCO 2 in comparison with needles of the same age cohort in ambient pCO 2 . Thus, older needles exhibited greater photosynthetic down-regulation than younger needles in elevated pCO 2 . In the winter, Asat was not significantly affected by growth pCO 2 . Asat was lower in winter than in summer. Growth at elevated pCO 2 had no significant effect on the capacity for photosynthetic oxygen evolution, photosystem 2 efficiencies, chlorophyll content or the size and conversion state of the xanthophyll cycle, regardless of season or needle age. There was no evidence that photosynthetic electron transport or photoprotective energy dissipation responded to compensate for the effects of elevated pCO 2 on Calvin cycle activity. 73 refs., 4 figs

  8. Photosynthetic and Heterotrophic Ferredoxin Isoproteins Are Colocalized in Fruit Plastids of Tomato1

    Science.gov (United States)

    Aoki, Koh; Yamamoto, Miyuki; Wada, Keishiro

    1998-01-01

    Fruit tissues of tomato (Lycopersicon esculentum Mill.) contain both photosynthetic and heterotrophic ferredoxin (FdA and FdE, respectively) isoproteins, irrespective of their photosynthetic competence, but we did not previously determine whether these proteins were colocalized in the same plastids. In isolated fruit chloroplasts and chromoplasts, both FdA and FdE were detected by immunoblotting. Colocalization of FdA and FdE in the same plastids was demonstrated using double-staining immunofluorescence microscopy. We also found that FdA and FdE were colocalized in fruit chloroplasts and chloroamyloplasts irrespective of sink status of the plastid. Immunoelectron microscopy demonstrated that FdA and FdE were randomly distributed within the plastid stroma. To investigate the significance of the heterotrophic Fd in fruit plastids, Glucose 6-phosphate dehydrogenase (G6PDH) activity was measured in isolated fruit and leaf plastids. Fruit chloroplasts and chromoplasts showed much higher G6PDH activity than did leaf chloroplasts, suggesting that high G6PDH activity is linked with FdE to maintain nonphotosynthetic production of reducing power. This result suggested that, despite their morphological resemblance, fruit chloroplasts are functionally different from their leaf counterparts. PMID:9765529

  9. Environmental controls on photosynthetic microbial mat distribution and morphogenesis on a 3.42 Ga clastic-starved platform.

    Science.gov (United States)

    Tice, Michael M

    2009-12-01

    Three morphotypes of microbial mats are preserved in rocks deposited in shallow-water facies of the 3.42 Ga Buck Reef chert (BRC). Morphotype alpha consists of fine anastomosing and bifurcating carbonaceous laminations, which loosely drape underlying detrital grains or form silica-filled lenses. Morphotype beta consists of meshes of fine carbonaceous strands intergrown with detrital grains and dark laminations, which loosely drape coarse detrital grains. Morphotype gamma consists of fine, even carbonaceous laminations that tightly drape underlying detrital grains. Preservation of nearly uncompacted mat morphologies and detrital grains deposited during mat growth within a well-characterized sedimentary unit makes quantitative correlation between morphology and paleoenvironment possible. All mats are preserved in the shallowest-water interval of those rocks deposited below normal wave base and above storm wave base. This interval is bounded below by a transgressive lag formed during regional flooding and above by a small condensed section that marks a local relative sea-level maximum. Restriction of all mat morphotypes to the shallowest interval of the storm-active layer in the BRC ocean reinforces previous interpretations that these mats were constructed primarily by photosynthetic organisms. Morphotypes alpha and beta dominate the lower half of this interval and grew during deposition of relatively coarse detrital carbonaceous grains, while morphotype gamma dominates the upper half and grew during deposition of fine detrital carbonaceous grains. The observed mat distribution suggests that either light intensity or, more likely, small variations in ambient current energy acted as a first-order control on mat morphotype distribution. These results demonstrate significant environmental control on biological morphogenetic processes independent of influences from siliciclastic sedimentation.

  10. Variabilidade sazonal da relação entre a radiação fotossinteticamente ativa e a radiação global na bacia do rio Doce, Estado de Minas Gerais = Seasonal variability of the relationship between the photosynthetically active radiation and the global radiation at the river Doce basin, Minas Gerais State

    Directory of Open Access Journals (Sweden)

    Antonio José Steidle Neto

    2006-07-01

    Full Text Available O conhecimento da Radiação Fotossinteticamente Ativa (RFA é importante para diferentes áreas relacionadas à fisiologia vegetal e ciências agrárias. Modelos de estimativa de RFA a partir da Radiação Global (Rg são extremamente úteis, visto que a Rg é convencionalmente medida nas estações meteorológicas. Assim, analisou-se a variabilidade sazonal da relação RFA/Rg em cinco áreas localizadas na bacia do rio Doce, Estado de Minas Gerais, considerando-se os períodos secos e chuvosos dos anos de 2001 a 2004. As relações RFA/Rg obtidas para os períodos secos e chuvosos, assim como para todos os dados, apresentaram concordância com as relações determinadas por diversos pesquisadores em diferentes áreas do mundo. Analisando-se os resultados, constatou-se que, de maneira geral,as relações RFA/Rg tendem a ser superiores durante os períodos chuvosos comparativamente aos secos. Por este estudo, pôde-se concluir que existe variação interanual desta relação, demonstrando assim a necessidade de se considerar esta variabilidade para estimaradequadamente a RFA a partir da Rg. The knowledge of the Photosynthetically Active Radiation (PAR is important to different areas of vegetal physiology and agricultural sciences. Estimation models of the PAR based on the Global Radiation (GR are extremely useful, since the GR is conventionally measured atthe meteorological stations. Thus, the seasonal variability of the relationship PAR/GR was analyzed in five areas located at the river Doce basin, Minas Gerais State, Brazil, considering the dry and wet periods of the years 2001 to 2004. The relationships PAR/GR obtained for the dry and wet periods, and also to all data, presented agreement with those ones determined by several researchers in different areas of the world. Results showed that the relationshipsPAR/GR generally tend to be greater during the wet periods when compared with the dry ones. By this work, it could be concluded that

  11. Generic maximum likely scale selection

    DEFF Research Database (Denmark)

    Pedersen, Kim Steenstrup; Loog, Marco; Markussen, Bo

    2007-01-01

    in this work is on applying this selection principle under a Brownian image model. This image model provides a simple scale invariant prior for natural images and we provide illustrative examples of the behavior of our scale estimation on such images. In these illustrative examples, estimation is based......The fundamental problem of local scale selection is addressed by means of a novel principle, which is based on maximum likelihood estimation. The principle is generally applicable to a broad variety of image models and descriptors, and provides a generic scale estimation methodology. The focus...

  12. Post optimization paradigm in maximum 3-satisfiability logic programming

    Science.gov (United States)

    Mansor, Mohd. Asyraf; Sathasivam, Saratha; Kasihmuddin, Mohd Shareduwan Mohd

    2017-08-01

    Maximum 3-Satisfiability (MAX-3SAT) is a counterpart of the Boolean satisfiability problem that can be treated as a constraint optimization problem. It deals with a conundrum of searching the maximum number of satisfied clauses in a particular 3-SAT formula. This paper presents the implementation of enhanced Hopfield network in hastening the Maximum 3-Satisfiability (MAX-3SAT) logic programming. Four post optimization techniques are investigated, including the Elliot symmetric activation function, Gaussian activation function, Wavelet activation function and Hyperbolic tangent activation function. The performances of these post optimization techniques in accelerating MAX-3SAT logic programming will be discussed in terms of the ratio of maximum satisfied clauses, Hamming distance and the computation time. Dev-C++ was used as the platform for training, testing and validating our proposed techniques. The results depict the Hyperbolic tangent activation function and Elliot symmetric activation function can be used in doing MAX-3SAT logic programming.

  13. Species-specific and seasonal differences in chlorophyll fluorescence and photosynthetic light response among three evergreen species in a Madrean sky island mixed conifer forest

    Science.gov (United States)

    Potts, D. L.; Minor, R. L.; Braun, Z.; Barron-Gafford, G. A.

    2012-12-01

    Unlike the snowmelt-dominated hydroclimate of more northern mountainous regions, the hydroclimate of the Madrean sky islands is characterized by snowmelt and convective storms associated with the North American Monsoon. These mid-summer storms trigger biological activity and are important drivers of primary productivity. For example, at the highest elevations where mixed conifer forests occur, ecosystem carbon balance is influenced by monsoon rains. Whereas these storms' significance is increasingly recognized at the ecosystem scale, species-specific physiological responses to the monsoon are poorly known. Prior to and following monsoon onset, we measured pre-dawn and light-adapted chlorophyll fluorescence as well as photosynthetic light response in southwestern white pine (Pinus strobiformis), ponderosa pine (Pinus ponderosa), and Douglas fir (Pseudotsuga menziesii) in a Madrean sky island mixed conifer forest near Tucson, Arizona. Photochemical quenching (qp), an indicator of the proportion of open PSII reaction centers, was greatest in P. strobiformis and least in P. menziesii and increased in response to monsoon rains (repeated-measures ANOVA; species, F2,14 = 6.17, P = 0.012; time, F2,14= 8.17, P = 0.013). In contrast, non-photochemical quenching (qN), an indicator of heat dissipation ability, was greatest in P. ponderosa and least in P. menziesii, but was not influenced by monsoon onset (repeated-measures ANOVA; species, F2,12 = 4.18, P = 0.042). Estimated from leaf area-adjusted photosynthetic light response curves, maximum photosynthetic rate (Amax) was greatest in P. ponderosa and least in P. menziesii (repeated-measures ANOVA; species, F2,8= 40.8, P = 0.001). Surprisingly, while the monsoon positively influenced Amax among P. ponderosa and P. strobiformis, Amax of P. menziesii declined with monsoon onset (repeated-measures ANOVA; species x time, F2,8 = 13.8, P = 0.002). Calculated as the initial slope of the photosynthetic light response curve, light

  14. Sensitivity of the green algae Chlamydomonas reinhardtii to gamma radiation: Photosynthetic performance and ROS formation.

    Science.gov (United States)

    Gomes, Tânia; Xie, Li; Brede, Dag; Lind, Ole-Christian; Solhaug, Knut Asbjørn; Salbu, Brit; Tollefsen, Knut Erik

    2017-02-01

    The aquatic environment is continuously exposed to ionizing radiation from both natural and anthropogenic sources, making the characterization of ecological and health risks associated with radiation of large importance. Microalgae represent the main source of biomass production in the aquatic ecosystem, thus becoming a highly relevant biological model to assess the impacts of gamma radiation. However, little information is available on the effects of gamma radiation on microalgal species, making environmental radioprotection of this group of species challenging. In this context, the present study aimed to improve the understanding of the effects and toxic mechanisms of gamma radiation in the unicellular green algae Chlamydomonas reinhardtii focusing on the activity of the photosynthetic apparatus and ROS formation. Algal cells were exposed to gamma radiation (0.49-1677mGy/h) for 6h and chlorophyll fluorescence parameters obtained by PAM fluorometry, while two fluorescent probes carboxy-H 2 DFFDA and DHR 123 were used for the quantification of ROS. The alterations seen in functional parameters of C. reinhardtii PSII after 6h of exposure to gamma radiation showed modifications of PSII energy transfer associated with electron transport and energy dissipation pathways, especially at the higher dose rates used. Results also showed that gamma radiation induced ROS in a dose-dependent manner under both light and dark conditions. The observed decrease in photosynthetic efficiency seems to be connected to the formation of ROS and can potentially lead to oxidative stress and cellular damage in chloroplasts. To our knowledge, this is the first report on changes in several chlorophyll fluorescence parameters associated with photosynthetic performance and ROS formation in microalgae after exposure to gamma radiation. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Effect of carbon limitation on photosynthetic electron transport in Nannochloropsis oculata.

    Science.gov (United States)

    Zavřel, Tomáš; Szabó, Milán; Tamburic, Bojan; Evenhuis, Christian; Kuzhiumparambil, Unnikrishnan; Literáková, Petra; Larkum, Anthony W D; Raven, John A; Červený, Jan; Ralph, Peter J

    2018-04-01

    This study describes the impacts of inorganic carbon limitation on the photosynthetic efficiency and operation of photosynthetic electron transport pathways in the biofuel-candidate microalga Nannochloropsis oculata. Using a combination of highly-controlled cultivation setup (photobioreactor), variable chlorophyll a fluorescence and transient spectroscopy methods (electrochromic shift (ECS) and P 700 redox kinetics), we showed that net photosynthesis and effective quantum yield of Photosystem II (PSII) decreased in N. oculata under carbon limitation. This was accompanied by a transient increase in total proton motive force and energy-dependent non-photochemical quenching as well as slightly elevated respiration. On the other hand, under carbon limitation the rapid increase in proton motive force (PMF, estimated from the total ECS signal) was also accompanied by reduced conductivity of ATP synthase to protons (estimated from the rate of ECS decay in dark after actinic illumination). This indicates that the slow operation of ATP synthase results in the transient build-up of PMF, which leads to the activation of fast energy dissipation mechanisms such as energy-dependent non-photochemical quenching. N. oculata also increased content of lipids under carbon limitation, which compensated for reduced NAPDH consumption during decreased CO 2 fixation. The integrated knowledge of the underlying energetic regulation of photosynthetic processes attained with a combination of biophysical methods may be used to identify photo-physiological signatures of the onset of carbon limitation in microalgal cultivation systems, as well as to potentially identify microalgal strains that can better acclimate to carbon limitation. Copyright © 2018 Elsevier B.V. All rights reserved.

  16. Extreme Maximum Land Surface Temperatures.

    Science.gov (United States)

    Garratt, J. R.

    1992-09-01

    There are numerous reports in the literature of observations of land surface temperatures. Some of these, almost all made in situ, reveal maximum values in the 50°-70°C range, with a few, made in desert regions, near 80°C. Consideration of a simplified form of the surface energy balance equation, utilizing likely upper values of absorbed shortwave flux (1000 W m2) and screen air temperature (55°C), that surface temperatures in the vicinity of 90°-100°C may occur for dry, darkish soils of low thermal conductivity (0.1-0.2 W m1 K1). Numerical simulations confirm this and suggest that temperature gradients in the first few centimeters of soil may reach 0.5°-1°C mm1 under these extreme conditions. The study bears upon the intrinsic interest of identifying extreme maximum temperatures and yields interesting information regarding the comfort zone of animals (including man).

  17. Biofouling of marbles by oxygenic photosynthetic microorganisms.

    Science.gov (United States)

    Karaca, Zeki; Öztürk, Ayten; Çolak, Emel

    2015-08-01

    Phototrophic microorganisms disfigure the surfaces of different types of stone. Stone structure is damaged by the activity of photoautotrophic and other microorganisms. However, to date few, investigations have been undertaken into the relationship between microorganisms and the properties of different types of marble. In this study, biological activity of photoautotrophic microorganisms on three types of marble (Yatagan White, Giallo Anticato and Afyon White) was investigated under laboratory conditions over a short period of time. The three types of marble supported the growth of phototrophic microbial communities on their outer and inner layers, turning their original colour from white to a yellowish green colour. The porosity of the marble types facilitated filamentous microbial growth in the presence of water. Scanning electron microscope analysis revealed the accumulation of aggregates such as small spherical, fibrillar, calcified globular bodies on the inner surfaces of the marbles. This suggests that the microscopic characteristics of particular marble types may stimulate the growth of certain types of microorganisms.

  18. Investigating and comparing uranium and gamma radiation induced effects on photosynthetic parameters for Arabidopsis thaliana

    Energy Technology Data Exchange (ETDEWEB)

    Vanhoudt, Nathalie; Horemans, Nele; Saenen, Eline; Biermans, Geert; Nauts, Robin; Wannijn, Jean; Van Hees, May; Vandenhove, Hildegarde [Belgian Nuclear Research Centre (SCK.CEN), Biosphere Impact Studies, 2400, Mol (Belgium)

    2014-07-01

    As the environment is inevitably exposed to radionuclides and ionizing radiation from natural and anthropogenic sources, it is important to study the effects induced by these stressors on plants. In addition, it is already known that photosynthesis can be affected under various metal exposure situations. The objective of this research is to compare uranium induced effects with gamma radiation induced effects on photosynthetic parameters in Arabidopsis thaliana. First, 18-day-old seedlings were exposed to 50 μM uranium during 4 days. Second, 14-day-old seedlings were exposed to gamma radiation for 7 days to a total dose of 6.7 Gy. By using chlorophyll fluorescence measurements, the photosynthetic performance was assessed. Based on the data obtained during the measurement of induction curves, parameters providing information on the photosynthetic efficiency and heat dissipation can be calculated. For uranium exposed leaves, it was observed that the potential photosynthetic efficiency (measured as Fv/Fm) remained maximal while the effective efficiency of photosystem II (φPSII), which is a measure for the proportion of light absorbed by PSII used in photochemistry, even increased. The increase of φPSII could be related to a decrease in non-photochemical quenching (NPQ), which reflects the protective mechanism against excess light intensity by converting energy into heat, but no alterations in non-regulated energy dissipation (NO). A high NO value would indicate the inefficiency of photochemistry and heat conversion and the plant's inability to regulate the radiation energy. In plants exposed to uranium, NO levels were similar to the control. Under gamma irradiation, the capacity of PSII remained intact and plants started optimizing their photosynthetic process by increasing φPSII and decreasing NPQ. When comparing the NPQ kinetic responses of gamma radiation and uranium exposure, a remarkable difference can be highlighted. While gamma radiation exposure

  19. Species selection for the design of gold nanobioreactor by photosynthetic organisms

    Energy Technology Data Exchange (ETDEWEB)

    Dahoumane, Si Amar [Universite Paris Diderot, Interfaces, Traitements, Organisation et Dynamique des Systemes (ITODYS), UMR 7086, CNRS, Sorbonne Paris Cite (France); Djediat, Chakib; Yepremian, Claude; Coute, Alain [Museum National d' Histoire Naturelle, Departement RDDM, FRE 3206, USM 505 (France); Fievet, Fernand [Universite Paris Diderot, Interfaces, Traitements, Organisation et Dynamique des Systemes (ITODYS), UMR 7086, CNRS, Sorbonne Paris Cite (France); Coradin, Thibaud, E-mail: thibaud.coradin@upmc.fr [UPMC Universites Paris 06, CNRS, Chimie de la Matiere Condensee de Paris (LCMCP), College de France (France); Brayner, Roberta, E-mail: roberta.brayner@univ-paris-diderot.fr [Universite Paris Diderot, Interfaces, Traitements, Organisation et Dynamique des Systemes (ITODYS), UMR 7086, CNRS, Sorbonne Paris Cite (France)

    2012-06-15

    The design of cell-based bioreactors for inorganic particles formation requires both a better understanding of the underlying processes and the identification of most suitable organisms. With this purpose, the process of Au{sup 3+} incorporation, intracellular reduction, and Au{sup 0} nanoparticle release in the culture medium was compared for four photosynthetic microorganisms, Klebsormidium flaccidum and Cosmarium impressulum green algae, Euglena gracilis euglenoid and Anabaena flos-aquae cyanobacteria. At low gold content, the two green algae show maintained photosynthetic activity and recovered particles (ca. 10 nm in size) are similar to internal colloids, indicating a full biological control over the whole process. In similar conditions, the euglenoid exhibits a rapid loss of biological activity, due to the absence of protective extracellular polysaccharide, but could grow again after an adaptation period. This results in a larger particle size dispersity but larger reduction yield. The cyanobacteria undergo rapid cell death, due to their prokaryotic nature, leading to high gold incorporation rate but poor control over released particle size. Similar observations can be made after addition of a larger gold salt concentration when all organisms rapidly die, suggesting that part of the process is not under biological control anymore but also involves extracellular chemical reactions. Overall, fruitful information on the whole biocrystallogenesis process is gained and most suitable species for further bioreactor design can be identified, i.e., green algae with external coating.

  20. Species selection for the design of gold nanobioreactor by photosynthetic organisms

    International Nuclear Information System (INIS)

    Dahoumane, Si Amar; Djediat, Chakib; Yéprémian, Claude; Couté, Alain; Fiévet, Fernand; Coradin, Thibaud; Brayner, Roberta

    2012-01-01

    The design of cell-based bioreactors for inorganic particles formation requires both a better understanding of the underlying processes and the identification of most suitable organisms. With this purpose, the process of Au 3+ incorporation, intracellular reduction, and Au 0 nanoparticle release in the culture medium was compared for four photosynthetic microorganisms, Klebsormidium flaccidum and Cosmarium impressulum green algae, Euglena gracilis euglenoid and Anabaena flos-aquae cyanobacteria. At low gold content, the two green algae show maintained photosynthetic activity and recovered particles (ca. 10 nm in size) are similar to internal colloids, indicating a full biological control over the whole process. In similar conditions, the euglenoid exhibits a rapid loss of biological activity, due to the absence of protective extracellular polysaccharide, but could grow again after an adaptation period. This results in a larger particle size dispersity but larger reduction yield. The cyanobacteria undergo rapid cell death, due to their prokaryotic nature, leading to high gold incorporation rate but poor control over released particle size. Similar observations can be made after addition of a larger gold salt concentration when all organisms rapidly die, suggesting that part of the process is not under biological control anymore but also involves extracellular chemical reactions. Overall, fruitful information on the whole biocrystallogenesis process is gained and most suitable species for further bioreactor design can be identified, i.e., green algae with external coating.

  1. In vivo measurements of the seasonal photosynthetic fluorescence of the Mediterranean coral Cladocora caespitosa (L.

    Directory of Open Access Journals (Sweden)

    Andrea Peirano

    2007-12-01

    Full Text Available In situ photosynthetic fluorescence of the zooxanthellate Mediterranean coral Cladocora caespitosa (L. was measured seasonally on colonies from 5 to 27 m depth using an INF-300 Integrating Natural Fluorometer (Biospherical Instrument Inc.. This oceanographic instrument, used to measure the in vivo phytoplankton chlorophyll a (Chl a fluorescence, was adapted to record the natural fluorescence of C. caespitosa by SCUBA divers. The resulting curves of natural fluorescence of Chl a vs photosynthetically active radiation (PAR 400-700 nm showed that: (1 natural fluorescence was limited by light availability in both deep and shallow colonies in all seasons; (2 photosynthesis occurred in C. caespitosa also in winter, when temperature is low and seawater turbidity contributes significantly to PAR attenuation; and (3 the efficiency of the Chl a fluorescence increased from summer to winter. This last finding outlines the winter coupling between zooxanthellae activity and calcification processes and is consistent with the formation of the high density band in the coral skeleton.

  2. Elevated CO2 causes changes in the photosynthetic apparatus of a toxic cyanobacterium, Cylindrospermopsis raciborskii.

    Science.gov (United States)

    Pierangelini, Mattia; Stojkovic, Slobodanka; Orr, Philip T; Beardall, John

    2014-07-15

    We studied the physiological acclimation of growth, photosynthesis and CO2-concentrating mechanism (CCM) in Cylindrospermopsis raciborskii exposed to low (present day; L-CO2) and high (1300ppm; H-CO2) pCO2. Results showed that under H-CO2 the cell specific division rate (μc) was higher and the CO2- and light-saturated photosynthetic rates (Vmax and Pmax) doubled. The cells' photosynthetic affinity for CO2 (K0.5CO2) was halved compared to L-CO2 cultures. However, no significant differences were found in dark respiration rates (Rd), pigment composition and light harvesting efficiency (α). In H-CO2 cells, non-photochemical quenching (NPQ), associated with state transitions of the electron transport chain (ETC), was negligible. Simultaneously, a reorganisation of PSII features including antenna connectivity (JconPSIIα), heterogeneity (PSIIα/β) and effective absorption cross sectional area (σPSIIα/β) was observed. In relation to different activities of the CCM, our findings suggest that for cells grown under H-CO2: (1) there is down-regulation of CCM activity; (2) the ability of cells to use the harvested light energy is altered; (3) the occurrence of state transitions is likely to be associated with changes of electron flow (cyclic vs linear) through the ETC; (4) changes in PSII characteristics are important in regulating state transitions. Copyright © 2014 Elsevier GmbH. All rights reserved.

  3. Photosynthetic and enzymatic metabolism of Schinus terebinthifolius Raddi seedlings under water deficit

    Directory of Open Access Journals (Sweden)

    Danieli Pieretti Nunes

    Full Text Available ABSTRACT Schinus terebinthifolius Raddi is a tree species that can be used in the recovery of degraded areas, as it exhibits rapid growth and has a very expansive root system, facilitating water uptake from the deeper layers of the soil. The objective of this study was to evaluate photosynthesis and enzymatic activity in S. terebinthifolius seedlings under conditions of water deficit and their potential to recover following re-irrigation. The experiment was conducted in a greenhouse under a plastic covering where plants were distributed into two groups: Group 1 - control plants, where irrigation was maintained at 70% of the water retention capacity, and Group 2 - stressed plants, where irrigation was suspended until the photosynthetic rate neared zero, followed by rehydration for 12 days, then a further suspension of irrigation. At the beginning of the experiment and during the suspension of irrigation and rehydration, plants were evaluated for gas and antioxidant enzyme exchanges. Hydric stress significantly reduced photosynthesis, stomatal transpiration conductance, carboxylation efficiency of Rubisco, and the chlorophyll content of the S. terebinthifolius plants. Following rehydration, plants recovered the carboxylation efficiency of Rubisco, but not the photosynthetic rate. Antioxidant enzyme activity increased in both the aerial part and the root in response to water deficit.

  4. The Impacts of Phosphorus Deficiency on the Photosynthetic Electron Transport Chain1[OPEN

    Science.gov (United States)

    2018-01-01

    Phosphorus (P) is an essential macronutrient, and P deficiency limits plant productivity. Recent work showed that P deficiency affects electron transport to photosystem I (PSI), but the underlying mechanisms are unknown. Here, we present a comprehensive biological model describing how P deficiency disrupts the photosynthetic machinery and the electron transport chain through a series of sequential events in barley (Hordeum vulgare). P deficiency reduces the orthophosphate concentration in the chloroplast stroma to levels that inhibit ATP synthase activity. Consequently, protons accumulate in the thylakoids and cause lumen acidification, which inhibits linear electron flow. Limited plastoquinol oxidation retards electron transport to the cytochrome b6f complex, yet the electron transfer rate of PSI is increased under steady-state growth light and is limited under high-light conditions. Under P deficiency, the enhanced electron flow through PSI increases the levels of NADPH, whereas ATP production remains restricted and, hence, reduces CO2 fixation. In parallel, lumen acidification activates the energy-dependent quenching component of the nonphotochemical quenching mechanism and prevents the overexcitation of photosystem II and damage to the leaf tissue. Consequently, plants can be severely affected by P deficiency for weeks without displaying any visual leaf symptoms. All of the processes in the photosynthetic machinery influenced by P deficiency appear to be fully reversible and can be restored in less than 60 min after resupply of orthophosphate to the leaf tissue. PMID:29540590

  5. The Impacts of Phosphorus Deficiency on the Photosynthetic Electron Transport Chain.

    Science.gov (United States)

    Carstensen, Andreas; Herdean, Andrei; Schmidt, Sidsel Birkelund; Sharma, Anurag; Spetea, Cornelia; Pribil, Mathias; Husted, Søren

    2018-05-01

    Phosphorus (P) is an essential macronutrient, and P deficiency limits plant productivity. Recent work showed that P deficiency affects electron transport to photosystem I (PSI), but the underlying mechanisms are unknown. Here, we present a comprehensive biological model describing how P deficiency disrupts the photosynthetic machinery and the electron transport chain through a series of sequential events in barley ( Hordeum vulgare ). P deficiency reduces the orthophosphate concentration in the chloroplast stroma to levels that inhibit ATP synthase activity. Consequently, protons accumulate in the thylakoids and cause lumen acidification, which inhibits linear electron flow. Limited plastoquinol oxidation retards electron transport to the cytochrome b 6 f complex, yet the electron transfer rate of PSI is increased under steady-state growth light and is limited under high-light conditions. Under P deficiency, the enhanced electron flow through PSI increases the levels of NADPH, whereas ATP production remains restricted and, hence, reduces CO 2 fixation. In parallel, lumen acidification activates the energy-dependent quenching component of the nonphotochemical quenching mechanism and prevents the overexcitation of photosystem II and damage to the leaf tissue. Consequently, plants can be severely affected by P deficiency for weeks without displaying any visual leaf symptoms. All of the processes in the photosynthetic machinery influenced by P deficiency appear to be fully reversible and can be restored in less than 60 min after resupply of orthophosphate to the leaf tissue. © 2018 American Society of Plant Biologists. All Rights Reserved.

  6. Photosystem II excitation pressure and photosynthetic carbon metabolism in Chlorella vulgaris

    International Nuclear Information System (INIS)

    Savitch, L.V.; Maxwell, D.P.; Huner, N.P.A.

    1996-01-01

    Chlorella vulgaris grown at 5 degrees C/150 micromoles m -2 s -1 mimics cells grown under high irradiance (27 degrees C/2200 micromoles m -2 s -1 ). This has been rationalized through the suggestion that both populations of cells were exposed to comparable photosystem II (PSII) excitation pressures measured as the chlorophyll a fluorescence quenching parameter, 1 - qP (D.P. Maxwell, S. Falk, N.P.A. Huner [1995] Plant Physiol 107: 687-694). To assess the possible role(s) of feedback mechanisms on PSII excitation pressure, stromal and cytosolic carbon metabolism were examined. Sucrose phosphate synthase and fructose-1,6-bisphosphatase activities as well as the ratios of fructose-1,6-bisphosphate/fructose-6 phosphate and sucrose/starch indicated that cells grown at 27 degrees C/2200 micromoles m -2 s -1 appeared to exhibit a restriction in starch metabolism. In contrast, cells grown at 5 degrees C/150 micromoles-1 m -2 s -1 appeared to exhibit a restriction in the sucrose metabolism based on decreased cytosolic fructose-1,6-bisphosphatase and sucrose phosphate synthase activities as well as a low sucrose/starch ratio. These metabolic restrictions may feedback on photosynthetic electron transport and, thus, contribute to the observed PSII excitation pressure. We conclude that, although PSII excitation pressure may reflect redox regulation of photosynthetic acclimation to light and temperature in C. vulgaris, it cannot be considered the primary redox signal. Alternative metabolic sensing/signaling mechanisms are discussed

  7. Species selection for the design of gold nanobioreactor by photosynthetic organisms

    Science.gov (United States)

    Dahoumane, Si Amar; Djediat, Chakib; Yéprémian, Claude; Couté, Alain; Fiévet, Fernand; Coradin, Thibaud; Brayner, Roberta

    2012-06-01

    The design of cell-based bioreactors for inorganic particles formation requires both a better understanding of the underlying processes and the identification of most suitable organisms. With this purpose, the process of Au3+ incorporation, intracellular reduction, and Au0 nanoparticle release in the culture medium was compared for four photosynthetic microorganisms, Klebsormidium flaccidum and Cosmarium impressulum green algae, Euglena gracilis euglenoid and Anabaena flos- aquae cyanobacteria. At low gold content, the two green algae show maintained photosynthetic activity and recovered particles (ca. 10 nm in size) are similar to internal colloids, indicating a full biological control over the whole process. In similar conditions, the euglenoid exhibits a rapid loss of biological activity, due to the absence of protective extracellular polysaccharide, but could grow again after an adaptation period. This results in a larger particle size dispersity but larger reduction yield. The cyanobacteria undergo rapid cell death, due to their prokaryotic nature, leading to high gold incorporation rate but poor control over released particle size. Similar observations can be made after addition of a larger gold salt concentration when all organisms rapidly die, suggesting that part of the process is not under biological control anymore but also involves extracellular chemical reactions. Overall, fruitful information on the whole biocrystallogenesis process is gained and most suitable species for further bioreactor design can be identified, i.e., green algae with external coating.

  8. Apparatus and method for measuring single cell and sub-cellular photosynthetic efficiency

    Science.gov (United States)

    Davis, Ryan Wesley; Singh, Seema; Wu, Huawen

    2013-07-09

    Devices for measuring single cell changes in photosynthetic efficiency in algal aquaculture are disclosed that include a combination of modulated LED trans-illumination of different intensities with synchronized through objective laser illumination and confocal detection. Synchronization and intensity modulation of a dual illumination scheme were provided using a custom microcontroller for a laser beam block and constant current LED driver. Therefore, single whole cell photosynthetic efficiency, and subcellular (diffraction limited) photosynthetic efficiency measurement modes are permitted. Wide field rapid light scanning actinic illumination is provided for both by an intensity modulated 470 nm LED. For the whole cell photosynthetic efficiency measurement, the same LED provides saturating pulses for generating photosynthetic induction curves. For the subcellular photosynthetic efficiency measurement, a switched through objective 488 nm laser provides saturating pulses for generating photosynthetic induction curves. A second near IR LED is employed to generate dark adapted states in the system under study.

  9. Photosynthetic parameters and primary production, with focus on large phytoplankton, in a temperate mid-shelf ecosystem

    KAUST Repository

    Moran, Xose Anxelu G.

    2015-01-09

    Annual variability of photosynthetic parameters and primary production (PP), with a special focus on large (i.e. >2μm) phytoplankton was assessed by monthly photosynthesis-irradiance experiments at two depths of the southern Bay of Biscay continental shelf in 2003. Integrated chl a (22-198mgm-2) was moderately dominated by large cells on an annual basis. The March through May dominance of diatoms was replaced by similar shares of dinoflagellates and other flagellates during the rest of the year. Variability of photosynthetic parameters was similar for total and large phytoplankton, but stratification affected the initial slope αB [0.004-0.049mgCmg chl a-1h-1 (μmol photons m-2s-1)-1] and maximum photosynthetic rates PmB (0.1-10.7mgCmg chl a-1h-1) differently. PmB, correlated positively with αB only for the large fraction. PmB tended to respond faster to ambient irradiance than αB, which was negatively correlated with diatom abundance in the >2μm fraction. Integrated PP rates were relatively low, averaging 387 (132-892) for the total and 207 (86-629) mg C m-2d-1 for the large fraction, probably the result of inorganic nutrient limitation. Although similar mean annual contributions of large phytoplankton to total values were found for biomass and PP (~58%), water-column production to biomass ratios (2-26mgCmg chl-1d-1) and light utilization efficiency of the >2μm fraction (0.09-0.84gCg chl-1mol photons-1m2) were minimum during the spring bloom. Our results indicate that PP peaks in the area are not necessarily associated to maximum standing stocks.

  10. Photosynthetic parameters and primary production, with focus on large phytoplankton, in a temperate mid-shelf ecosystem

    KAUST Repository

    Moran, Xose Anxelu G.; Scharek, Renate

    2015-01-01

    Annual variability of photosynthetic parameters and primary production (PP), with a special focus on large (i.e. >2μm) phytoplankton was assessed by monthly photosynthesis-irradiance experiments at two depths of the southern Bay of Biscay continental shelf in 2003. Integrated chl a (22-198mgm-2) was moderately dominated by large cells on an annual basis. The March through May dominance of diatoms was replaced by similar shares of dinoflagellates and other flagellates during the rest of the year. Variability of photosynthetic parameters was similar for total and large phytoplankton, but stratification affected the initial slope αB [0.004-0.049mgCmg chl a-1h-1 (μmol photons m-2s-1)-1] and maximum photosynthetic rates PmB (0.1-10.7mgCmg chl a-1h-1) differently. PmB, correlated positively with αB only for the large fraction. PmB tended to respond faster to ambient irradiance than αB, which was negatively correlated with diatom abundance in the >2μm fraction. Integrated PP rates were relatively low, averaging 387 (132-892) for the total and 207 (86-629) mg C m-2d-1 for the large fraction, probably the result of inorganic nutrient limitation. Although similar mean annual contributions of large phytoplankton to total values were found for biomass and PP (~58%), water-column production to biomass ratios (2-26mgCmg chl-1d-1) and light utilization efficiency of the >2μm fraction (0.09-0.84gCg chl-1mol photons-1m2) were minimum during the spring bloom. Our results indicate that PP peaks in the area are not necessarily associated to maximum standing stocks.

  11. The temporal and species dynamics of photosynthetic acclimation in flag leaves of rice (Oryza sativa) and wheat (Triticum aestivum) under elevated carbon dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, J.; Zeng, Q.; Xie, Z.; Tang, H.; Zhu, C. (Chinese Academy of Sciences. State Key Lab. of Soil and Sustainable Agriculture, Institute of Soil Science, Nanjing (China)); Hasegawa, T. (National Institute for Agro-Environmental Sciences. Agro-Meteorology Div., Tsukuba (Japan)); Ziska, L. (Crop Systems and Global Change Lab., Beltsville, MD (United States)); Jia, X. (Chinese Academic of Sciences/Nanjing Botanical Garden Memorial Sun Yat-Sen. Jiangsu Institute of Botany, Nanjing (China))

    2012-07-15

    In this study, we tested for the temporal occurrence of photosynthetic acclimation to elevated [CO{sub 2}] in the flag leaf of two important cereal crops, rice and wheat. In order to characterize the temporal onset of acclimation and the basis for any observed decline in photosynthetic rate, we characterized net photosynthesis, g{sub s}, g{sub m}, C{sub i}/C{sub a}, C{sub i}/C{sub c}, V{sub cmax}, J{sub max}, cell wall thickness, content of Rubisco, cytochrome (Cyt) f, N, chlorophyll and carbohydrate, mRNA expression for rbcL and petA, activity for Rubisco, sucrose phosphate synthase (SPS) and sucrose synthase (SS) at full flag expansion, mid-anthesis and the late grain-filling stage. No acclimation was observed for either crop at full flag leaf expansion. However, at the mid-anthesis stage, photosynthetic acclimation in rice was associated with RuBP carboxylation and regeneration limitations, while wheat only had the carboxylation limitation. By grain maturation, the decline of Rubisco content and activity had contributed to RuBP carboxylation limitation of photosynthesis in both crops at elevated [CO{sub 2}]; however, the sharp decrease of Rubisco enzyme activity played a more important role in wheat. Although an increase in non-structural carbohydrates did occur during these later stages, it was not consistently associated with changes in SPS and SS or photosynthetic acclimation. Rather, over time elevated [CO{sub 2}] appeared to enhance the rate of N degradation and senescence so that by late-grain fill, photosynthetic acclimation to elevated [CO{sub 2}] in the flag leaf of either species was complete. These data suggest that the basis for photosynthetic acclimation with elevated [CO{sub 2}] may be more closely associated with enhanced rates of senescence, and, as a consequence, may be temporally dynamic, with significant species variation. (Author)

  12. Photosynthetic Energy Transfer at the Quantum/Classical Border.

    Science.gov (United States)

    Keren, Nir; Paltiel, Yossi

    2018-06-01

    Quantum mechanics diverges from the classical description of our world when very small scales or very fast processes are involved. Unlike classical mechanics, quantum effects cannot be easily related to our everyday experience and are often counterintuitive to us. Nevertheless, the dimensions and time scales of the photosynthetic energy transfer processes puts them close to the quantum/classical border, bringing them into the range of measurable quantum effects. Here we review recent advances in the field and suggest that photosynthetic processes can take advantage of the sensitivity of quantum effects to the environmental 'noise' as means of tuning exciton energy transfer efficiency. If true, this design principle could be a base for 'nontrivial' coherent wave property nano-devices. Copyright © 2018 Elsevier Ltd. All rights reserved.

  13. Non-photosynthetic plastids as hosts for metabolic engineering

    DEFF Research Database (Denmark)

    Mellor, Silas Busck; Behrendorff, James Bruce Yarnton H; Nielsen, Agnieszka Janina Zygadlo

    2018-01-01

    Using plants as hosts for production of complex, high-value compounds and therapeutic proteins has gained increasing momentum over the past decade. Recent advances in metabolic engineering techniques using synthetic biology have set the stage for production yields to become economically attractive......, but more refined design strategies are required to increase product yields without compromising development and growth of the host system. The ability of plant cells to differentiate into various tissues in combination with a high level of cellular compartmentalization represents so far the most...... in green tissues, have proven to be suitable for high yield protein and bio-compound production. Unfortunately, chloroplast manipulation often affects photosynthetic efficiency and therefore plant fitness. In this respect, plastids of non-photosynthetic tissues, which have focused metabolisms for synthesis...

  14. Influence of thermal light correlations on photosynthetic structures

    Science.gov (United States)

    de Mendoza, Adriana; Manrique, Pedro; Caycedo-Soler, Felipe; Johnson, Neil F.; Rodríguez, Ferney J.; Quiroga, Luis

    2014-03-01

    The thermal light from the sun is characterized by both classical and quantum mechanical correlations. These correlations have left a fingerprint on the natural harvesting structures developed through five billion years of evolutionary pressure, specially in photosynthetic organisms. In this work, based upon previous extensive studies of spatio-temporal correlations of light fields, we hypothesize that structures involving photosensitive pigments like those present in purple bacteria vesicles emerge as an evolutionary response to the different properties of incident light. By using burstiness and memory as measures that quantify higher moments of the photon arrival statistics, we generate photon-time traces. They are used to simulate absorption on detectors spatially extended over regions comparable to these light fields coherence length. Finally, we provide some insights into the connection between these photo-statistical features with the photosynthetic membrane architecture and the lights' spatial correlation. Facultad de Ciencias Uniandes.

  15. Quantum measurement corrections to CIDNP in photosynthetic reaction centers

    International Nuclear Information System (INIS)

    Kominis, Iannis K

    2013-01-01

    Chemically induced dynamic nuclear polarization is a signature of spin order appearing in many photosynthetic reaction centers. Such polarization, significantly enhanced above thermal equilibrium, is known to result from the nuclear spin sorting inherent in the radical pair mechanism underlying long-lived charge-separated states in photosynthetic reaction centers. We will show here that the recently understood fundamental quantum dynamics of radical-ion-pair reactions open up a new and completely unexpected pathway toward obtaining chemically induced dynamic nuclear polarization signals. The fundamental decoherence mechanism inherent in the recombination process of radical pairs is shown to produce nuclear spin polarizations of the order of 10 4 times (or more) higher than the thermal equilibrium value at the Earth's magnetic field relevant to natural photosynthesis. This opens up the possibility of a fundamentally new exploration of the biological significance of high nuclear polarizations in photosynthesis. (paper)

  16. Light history modulates antioxidant and photosynthetic responses of biofilms to both natural (light) and chemical (herbicides) stressors.

    Science.gov (United States)

    Bonnineau, Chloé; Sague, Irene Gallardo; Urrea, Gemma; Guasch, Helena

    2012-05-01

    In multiple stress situations, the co-occurrence of environmental and chemical factors can influence organisms' ability to cope with toxicity. In this context, the influence of light adaptation on the response of freshwater biofilms to sudden light changes or to herbicides exposure was investigated by determining various parameters: diatom community composition, photosynthetic parameters, chlorophyll a content, antioxidant enzyme activities. Biofilms were grown in microcosms under sub-optimal, saturating, and high light intensities and showed already described characteristics of shade/light adaptation (community structure, photosynthetic adaptation, etc.). Light history modulated antioxidant and photosynthetic responses of biofilms to the stress caused by short-term exposure to sudden light changes or to herbicides. First biofilms adapted to sub-optimal light intensity (shade-adapted) were found to be more sensitive to an increase in light intensity than high-light adapted ones to a reduction in light intensity. Second, while light history influenced biofilms' response to glyphosate, it had little influence on biofilms' response to copper and none on its response to oxyfluorfen. Indeed glyphosate exposure led to a stronger decrease in photosynthetic efficiency of shade-adapted biofilms (EC(50) = 11.7 mg L(-1)) than of high-light adapted communities (EC(50) = 35.6 mg L(-1)). Copper exposure led to an activation of ascorbate peroxidase (APX) in biofilms adapted to sub-optimal and saturating light intensity while the protein content decreased in all biofilms exposed to copper. Oxyfluorfen toxicity was independent of light history provoking an increase in APX activity. In conclusion this study showed that both previous exposure to contaminants and physical habitat characteristics might influence community tolerance to disturbances strongly.

  17. System for memorizing maximum values

    Science.gov (United States)

    Bozeman, Richard J., Jr.

    1992-08-01

    The invention discloses a system capable of memorizing maximum sensed values. The system includes conditioning circuitry which receives the analog output signal from a sensor transducer. The conditioning circuitry rectifies and filters the analog signal and provides an input signal to a digital driver, which may be either linear or logarithmic. The driver converts the analog signal to discrete digital values, which in turn triggers an output signal on one of a plurality of driver output lines n. The particular output lines selected is dependent on the converted digital value. A microfuse memory device connects across the driver output lines, with n segments. Each segment is associated with one driver output line, and includes a microfuse that is blown when a signal appears on the associated driver output line.

  18. Remarks on the maximum luminosity

    Science.gov (United States)

    Cardoso, Vitor; Ikeda, Taishi; Moore, Christopher J.; Yoo, Chul-Moon

    2018-04-01

    The quest for fundamental limitations on physical processes is old and venerable. Here, we investigate the maximum possible power, or luminosity, that any event can produce. We show, via full nonlinear simulations of Einstein's equations, that there exist initial conditions which give rise to arbitrarily large luminosities. However, the requirement that there is no past horizon in the spacetime seems to limit the luminosity to below the Planck value, LP=c5/G . Numerical relativity simulations of critical collapse yield the largest luminosities observed to date, ≈ 0.2 LP . We also present an analytic solution to the Einstein equations which seems to give an unboundedly large luminosity; this will guide future numerical efforts to investigate super-Planckian luminosities.

  19. Maximum mutual information regularized classification

    KAUST Repository

    Wang, Jim Jing-Yan

    2014-09-07

    In this paper, a novel pattern classification approach is proposed by regularizing the classifier learning to maximize mutual information between the classification response and the true class label. We argue that, with the learned classifier, the uncertainty of the true class label of a data sample should be reduced by knowing its classification response as much as possible. The reduced uncertainty is measured by the mutual information between the classification response and the true class label. To this end, when learning a linear classifier, we propose to maximize the mutual information between classification responses and true class labels of training samples, besides minimizing the classification error and reducing the classifier complexity. An objective function is constructed by modeling mutual information with entropy estimation, and it is optimized by a gradient descend method in an iterative algorithm. Experiments on two real world pattern classification problems show the significant improvements achieved by maximum mutual information regularization.

  20. Scintillation counter, maximum gamma aspect

    International Nuclear Information System (INIS)

    Thumim, A.D.

    1975-01-01

    A scintillation counter, particularly for counting gamma ray photons, includes a massive lead radiation shield surrounding a sample-receiving zone. The shield is disassembleable into a plurality of segments to allow facile installation and removal of a photomultiplier tube assembly, the segments being so constructed as to prevent straight-line access of external radiation through the shield into radiation-responsive areas. Provisions are made for accurately aligning the photomultiplier tube with respect to one or more sample-transmitting bores extending through the shield to the sample receiving zone. A sample elevator, used in transporting samples into the zone, is designed to provide a maximum gamma-receiving aspect to maximize the gamma detecting efficiency. (U.S.)

  1. Maximum mutual information regularized classification

    KAUST Repository

    Wang, Jim Jing-Yan; Wang, Yi; Zhao, Shiguang; Gao, Xin

    2014-01-01

    In this paper, a novel pattern classification approach is proposed by regularizing the classifier learning to maximize mutual information between the classification response and the true class label. We argue that, with the learned classifier, the uncertainty of the true class label of a data sample should be reduced by knowing its classification response as much as possible. The reduced uncertainty is measured by the mutual information between the classification response and the true class label. To this end, when learning a linear classifier, we propose to maximize the mutual information between classification responses and true class labels of training samples, besides minimizing the classification error and reducing the classifier complexity. An objective function is constructed by modeling mutual information with entropy estimation, and it is optimized by a gradient descend method in an iterative algorithm. Experiments on two real world pattern classification problems show the significant improvements achieved by maximum mutual information regularization.

  2. Enhanced Practical Photosynthetic CO2 Mitigation. Quarterly Technical Report

    International Nuclear Information System (INIS)

    Gregory Kremer; David J. Bayless; Morgan Vis; Michael Prudich; Keith Cooksey; Jeff Muhs

    2005-01-01

    This report highlights significant achievements in the Enhanced Practical Photosynthetic CO 2 Mitigation Project during the ending 12/31/2004. Specific results and accomplishments for the program include review of pilot scale testing and design of a new bioreactor. Testing confirmed that algae can be grown in a sustainable fashion in the pilot bioreactor, even with intermittent availability of sunlight. The pilot-scale tests indicated that algal growth rate followed photon delivery during productivity testing

  3. Advances in Metabolic Engineering of Cyanobacteria for Photosynthetic Biochemical Production

    OpenAIRE

    Lai, Martin C.; Lan, Ethan I.

    2015-01-01

    Engineering cyanobacteria into photosynthetic microbial cell factories for the production of biochemicals and biofuels is a promising approach toward sustainability. Cyanobacteria naturally grow on light and carbon dioxide, bypassing the need of fermentable plant biomass and arable land. By tapping into the central metabolism and rerouting carbon flux towards desirable compound production, cyanobacteria are engineered to directly convert CO2 into various chemicals. This review discusses the d...

  4. Microbiological Hydrogen Production by Anaerobic Fermentation and Photosynthetic Process

    International Nuclear Information System (INIS)

    Asada, Y.; Ohsawa, M.; Nagai, Y.; Fukatsu, M.; Ishimi, K.; Ichi-ishi, S.

    2009-01-01

    Hydrogen gas is a clean and renewable energy carrier. Microbiological hydrogen production from glucose or starch by combination used of an anaerobic fermenter and a photosynthetic bacterium, Rhodobacter spheroides RV was studied. In 1984, the co-culture of Clostridium butyricum and RV strain to convert glucose to hydrogen was demonstrated by Miyake et al. Recently, we studied anaerobic fermentation of starch by a thermophilic archaea. (Author)

  5. Spring photosynthetic recovery of boreal Norway spruce under conditions of elevated [CO(2)] and air temperature.

    Science.gov (United States)

    Wallin, Göran; Hall, Marianne; Slaney, Michelle; Räntfors, Mats; Medhurst, Jane; Linder, Sune

    2013-11-01

    Accumulated carbon uptake, apparent quantum yield (AQY) and light-saturated net CO2 assimilation (Asat) were used to assess the responses of photosynthesis to environmental conditions during spring for three consecutive years. Whole-tree chambers were used to expose 40-year-old field-grown Norway spruce trees in northern Sweden to an elevated atmospheric CO2 concentration, [CO2], of 700 μmol CO2 mol(-1) (CE) and an air temperature (T) between 2.8 and 5.6 °C above ambient T (TE), during summer and winter. Net shoot CO2 exchange (Anet) was measured continuously on 1-year-old shoots and was used to calculate the accumulated carbon uptake and daily Asat and AQY. The accumulated carbon uptake, from 1 March to 30 June, was stimulated by 33, 44 and 61% when trees were exposed to CE, TE, and CE and TE combined, respectively. Air temperature strongly influenced the timing and extent of photosynthetic recovery expressed as AQY and Asat during the spring. Under elevated T (TE), the recovery of AQY and Asat commenced ∼10 days earlier and the activity of these parameters was significantly higher throughout the recovery period. In the absence of frost events, the photosynthetic recovery period was less than a week. However, frost events during spring slowed recovery so that full recovery could take up to 60 days to complete. Elevated [CO2] stimulated AQY and Asat on average by ∼10 and ∼50%, respectively, throughout the recovery period, but had minimal or no effect on the onset and length of the photosynthetic recovery period during the spring. However, AQY, Asat and Anet all recovered at significantly higher T (average +2.2 °C) in TE than in TA, possibly caused by acclimation or by shorter days and lower light levels during the early part of the recovery in TE compared with TA. The results suggest that predicted future climate changes will cause prominent stimulation of photosynthetic CO2 uptake in boreal Norway spruce forest during spring, mainly caused by elevated T

  6. Asymmetrical effects of mesophyll conductance on fundamental photosynthetic parameters and their relationships estimated from leaf gas exchange measurements.

    Science.gov (United States)

    Sun, Ying; Gu, Lianhong; Dickinson, Robert E; Pallardy, Stephen G; Baker, John; Cao, Yonghui; DaMatta, Fábio Murilo; Dong, Xuejun; Ellsworth, David; Van Goethem, Davina; Jensen, Anna M; Law, Beverly E; Loos, Rodolfo; Martins, Samuel C Vitor; Norby, Richard J; Warren, Jeffrey; Weston, David; Winter, Klaus

    2014-04-01

    Worldwide measurements of nearly 130 C3 species covering all major plant functional types are analysed in conjunction with model simulations to determine the effects of mesophyll conductance (g(m)) on photosynthetic parameters and their relationships estimated from A/Ci curves. We find that an assumption of infinite g(m) results in up to 75% underestimation for maximum carboxylation rate V(cmax), 60% for maximum electron transport rate J(max), and 40% for triose phosphate utilization rate T(u) . V(cmax) is most sensitive, J(max) is less sensitive, and T(u) has the least sensitivity to the variation of g(m). Because of this asymmetrical effect of g(m), the ratios of J(max) to V(cmax), T(u) to V(cmax) and T(u) to J(max) are all overestimated. An infinite g(m) assumption also limits the freedom of variation of estimated parameters and artificially constrains parameter relationships to stronger shapes. These findings suggest the importance of quantifying g(m) for understanding in situ photosynthetic machinery functioning. We show that a nonzero resistance to CO2 movement in chloroplasts has small effects on estimated parameters. A non-linear function with gm as input is developed to convert the parameters estimated under an assumption of infinite gm to proper values. This function will facilitate gm representation in global carbon cycle models. © 2013 John Wiley & Sons Ltd.

  7. Dynamical maximum entropy approach to flocking.

    Science.gov (United States)

    Cavagna, Andrea; Giardina, Irene; Ginelli, Francesco; Mora, Thierry; Piovani, Duccio; Tavarone, Raffaele; Walczak, Aleksandra M

    2014-04-01

    We derive a new method to infer from data the out-of-equilibrium alignment dynamics of collectively moving animal groups, by considering the maximum entropy model distribution consistent with temporal and spatial correlations of flight direction. When bird neighborhoods evolve rapidly, this dynamical inference correctly learns the parameters of the model, while a static one relying only on the spatial correlations fails. When neighbors change slowly and the detailed balance is satisfied, we recover the static procedure. We demonstrate the validity of the method on simulated data. The approach is applicable to other systems of active matter.