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Sample records for net photosynthetic rate

  1. Relationship Between Diurnal Changes of Net Photosynthetic Rate and Influencing Factors in Rice under Saline Sodic Stress

    Directory of Open Access Journals (Sweden)

    Fu Yang

    2008-06-01

    Full Text Available The net photosynthetic rate of flag leaves and influencing factors under saline sodic soil conditions were investigated at the full heading stage of rice. The net photosynthetic rate of rice leaves showed a double-peak curve in a day in both non-saline sodic and saline sodic soil treatments. The first peak of the net photosynthetic rate appeared at 9:00–10:00 and 9:00 in the saline sodic and non-saline sodic soil treatments, respectively, whereas the second peak both at 14:00. The midday depression of the net photosynthetic rate always appeared regardless of non-saline sodic or saline sodic soil conditions. In addition, the net photosynthetic rate significantly decreased in all day under saline sodic conditions compared with that under non-saline sodic conditions. Some differences were observed in correlation characters between the net photosynthetic rate and all influencing factors during 9:00–13:00. Under non-saline sodic conditions, the diurnal changes of the net photosynthetic rate in a day were mainly caused by stomatal conductance, and the limitation value and the stomatal factors served as determinants; whereas under saline sodic stress, the diurnal changes of the net photosynthetic rate in a day were mainly caused by non stomatal factors including light intensity and air temperature.

  2. Relationship Between Diurnal Changes of Net Photosynthetic Rate and Influencing Factors in Rice under Saline Sodic Stress

    OpenAIRE

    Fu Yang; Zheng-wei Liang; Zhi-chun Wang; Yuan Chen

    2008-01-01

    The net photosynthetic rate of flag leaves and influencing factors under saline sodic soil conditions were investigated at the full heading stage of rice. The net photosynthetic rate of rice leaves showed a double-peak curve in a day in both non-saline sodic and saline sodic soil treatments. The first peak of the net photosynthetic rate appeared at 9:00–10:00 and 9:00 in the saline sodic and non-saline sodic soil treatments, respectively, whereas the second peak both at 14:00. The midday depr...

  3. A kinetic model for estimating net photosynthetic rates of cos lettuce leaves under pulsed light.

    Science.gov (United States)

    Jishi, Tomohiro; Matsuda, Ryo; Fujiwara, Kazuhiro

    2015-04-01

    Time-averaged net photosynthetic rate (P n) under pulsed light (PL) is known to be affected by the PL frequency and duty ratio, even though the time-averaged photosynthetic photon flux density (PPFD) is unchanged. This phenomenon can be explained by considering that photosynthetic intermediates (PIs) are pooled during light periods and then consumed by partial photosynthetic reactions during dark periods. In this study, we developed a kinetic model to estimate P n of cos lettuce (Lactuca sativa L. var. longifolia) leaves under PL based on the dynamics of the amount of pooled PIs. The model inputs are average PPFD, duty ratio, and frequency; the output is P n. The rates of both PI accumulation and consumption at a given moment are assumed to be dependent on the amount of pooled PIs at that point. Required model parameters and three explanatory variables (average PPFD, frequency, and duty ratio) were determined for the simulation using P n values under PL based on several combinations of the three variables. The model simulation for various PL levels with a wide range of time-averaged PPFDs, frequencies, and duty ratios further demonstrated that P n under PL with high frequencies and duty ratios was comparable to, but did not exceed, P n under continuous light, and also showed that P n under PL decreased as either frequency or duty ratio was decreased. The developed model can be used to estimate P n under various light environments where PPFD changes cyclically.

  4. [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.

  5. [Effects of lead stress on net photosynthetic rate, SPAD value and ginsenoside production in Ginseng (Panax ginseng)].

    Science.gov (United States)

    Liang, Yao; Jiang, Xiao-Li; Yang, Fen-Tuan; Cao, Qing-Jun; Li, Gang

    2014-08-01

    The paper aimed to evaluate the effects of lead stress on photosynthetic performance and ginsenoside content in ginseng (Panax ginseng). To accomplish this, three years old ginseng were cultivated in pot and in phytotron with different concentrations of lead, ranging from 0 to 1000 mg x kg(-1) soil for a whole growth period (about 150 days). The photosynthetic parameters in leaves and ginsenoside content in roots of ginseng were determined in green fruit stage and before withering stage, respectively. In comparison with the control, net photosynthetic rate and SPAD value in ginseng leaves cultivated with 100 and 250 mg x kg(-1) of lead changed insignificantly, however, ginseng supplied with 500 and 1 000 mg x kg(-1) of lead showed a noticeably decline in the net rate of photosynthesis and SPAD value (P lead, with decline of 57.8%,11.0%, respectively. Total content of ginsenoside in ginseng roots cultivated with 100 mg x kg(-1) of lead showed insignificantly change compared to the control, but the content increased remarkably in treatments supplied with 250, 500, 1 000 mg x kg(-1) of lead (P lead. The net photosynthetic rate and SPAD value in leaves of ginseng both showed significantly negative linear correlations with lead stress level (P lead concentration was also observed (P lead negatively affects photosynthetic performance in ginseng leaves, but benefits for accumulation of secondary metabolism (total content of ginsenoside) in ginseng root.

  6. Light environment alters ozone uptake per net photosynthetic rate in black cherry trees.

    Science.gov (United States)

    Fredericksen, T S; Kolb, T E; Skelly, J M; Steiner, K C; Joyce, B J; Savage, J E

    1996-05-01

    Foliar ozone uptake rates of different-sized black cherry (Prunus serotina Ehrh.) trees were compared within a deciduous forest and adjacent openings in north-central Pennsylvania during one growing season. Study trees included open-grown seedlings and saplings, forest understory seedlings and saplings, and sunlit and shaded portions of mature canopy tree crowns. Instantaneous ozone uptake rates were highest in high-light environments primarily because of higher stomatal conductances. Low ozone uptake rates of seedlings and saplings in the forest understory could be attributed partially to lower average ambient ozone concentrations compared to the canopy and open environments. Among the tree size and light combinations tested, ozone uptake rates were highest in open-grown seedlings and lowest in forest-grown seedlings. Despite lower ozone uptake rates of foliage in shaded environments, ozone uptake per net photosynthesis of foliage in shaded environments was significantly higher than that of foliage in sunlit environments because of weaker coupling between net photosynthesis and stomatal conductance in shaded environments. The potential for greater ozone injury in shaded environments as a result of greater ozone uptake per net photosynthesis is consistent with previous reports of greater ozone injury in shaded foliage than in sunlit foliage.

  7. Modeled dosage-response relationship on the net photosynthetic rate for the sensitivity to acid rain of 21 plant species.

    Science.gov (United States)

    Deng, Shihuai; Gou, Shuzhen; Sun, Baiye; Lv, Wenlin; Li, Yuanwei; Peng, Hong; Xiao, Hong; Yang, Gang; Wang, Yingjun

    2012-08-01

    This study investigated the sensitivity of plant species to acid rain based on the modeled dosage-response relationship on the net photosynthetic rate (P (N)) of 21 types of plant species, subjected to the exposure of simulated acid rain (SAR) for 5 times during a period of 50 days. Variable responses of P (N) to SAR occurred depending on the type of plant. A majority (13 species) of the dosage-response relationship could be described by an S-shaped curve and be fitted with the Boltzmann model. Model fitting allowed quantitative evaluation of the dosage-response relationship and an accurate estimation of the EC(10), termed as the pH of the acid rain resulting in a P (N) 10 % lower than the reference value. The top 9 species (Camellia sasanqua, Cinnamomum camphora, etc. EC(10) ≤ 3.0) are highly endurable to very acid rain. The rare, relict plant Metasequoia glyptostroboides was the most sensitive species (EC(10) = 5.1) recommended for protection.

  8. A new method to estimate photosynthetic parameters through net assimilation rate-intercellular space CO2 concentration (A-Ci ) curve and chlorophyll fluorescence measurements.

    Science.gov (United States)

    Moualeu-Ngangue, Dany P; Chen, Tsu-Wei; Stützel, Hartmut

    2017-02-01

    Gas exchange (GE) and chlorophyll fluorescence (CF) measurements are widely used to noninvasively study photosynthetic parameters, for example the rates of maximum Rubisco carboxylation (Vcmax ), electron transport rate (J), daytime respiration (Rd ) and mesophyll conductance (gm ). Existing methods for fitting GE data (net assimilation rate-intercellular space CO2 concentration (A-Ci ) curve) are based on two assumptions: gm is unvaried with CO2 concentration in the intercellular space (Ci ); and light absorption (α) and the proportion of quanta absorbed by photosystem II (β) are constant in the data set. These may result in significant bias in estimating photosynthetic parameters. To avoid the above-mentioned hypotheses, we present a new method for fitting A-Ci curves and CF data simultaneously. This method was applied to a data set obtained from cucumber (Cucumis sativus) leaves of various leaf ages and grown under eight different light conditions. The new method had significantly lower root mean square error and a lower rate of failures compared with previously published methods (6.72% versus 24.1%, respectively) and the effect of light conditions on Vcmax and J was better observed. Furthermore, the new method allows the estimation of a new parameter, the fraction of incoming irradiance harvested by photosystem II, and the dependence of gm on Ci . © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

  9. Coordinated modifications in mesophyll conductance, photosynthetic potentials and leaf nitrogen contribute to explain the large variation in foliage net assimilation rates across Quercus ilex provenances.

    Science.gov (United States)

    Peguero-Pina, José Javier; Sisó, Sergio; Flexas, Jaume; Galmés, Jeroni; Niinemets, Ülo; Sancho-Knapik, Domingo; Gil-Pelegrín, Eustaquio

    2017-08-01

    Leaf dry mass per unit area (LMA) has been suggested to negatively affect the mesophyll conductance to CO2 (gm), the most limiting factor for photosynthesis per unit leaf area (AN) in many evergreens. Several anatomical traits (i.e., greater leaf thickness and thicker cell walls) constraining gm could explain the negative scaling of gm and AN with LMA across species. However, the Mediterranean sclerophyll Quercus ilex L. shows a major within-species variation in functional traits (greater LMA associated with higher nitrogen content and AN) that might contrast the worldwide trends. The objective of this study was to elucidate the existence of variations in other leaf anatomical parameters determining gm and/or biochemical traits improving the capacity of carboxylation (Vc,max) that could modulate the relationship of AN with LMA across this species. The results revealed that gm was the most limiting factor for AN in all the studied Q. ilex provenances from Spain and Italy. The within-species differences in gm can be partly attributed to the variation in several leaf anatomical traits, mainly cell-wall thickness (Tcw), chloroplast thickness (Tchl) and chloroplast exposed surface area facing intercellular air spaces (Sc/S). A positive scaling of gm and AN with Vc,max was also found, associated with an increased nitrogen content per area. A strong correlation of maximum photosynthetic electron transport (Jmax) with AN further indicated a coordination between the carboxylase activity and the electron transport chain. In conclusion, we have confirmed the strong ecotypic variation in the photosynthetic performance of individual provenances of Q. ilex. Thus, the within-species increases found in AN for Q. ilex with increasing foliage robustness can be explained by a synergistic effect among anatomical (at the subcellular and cellular level) and biochemical traits, which markedly improved gm and Vc,max. © The Author 2017. Published by Oxford University Press. All rights

  10. Variations in Photosynthetic Rates of Fourteen Coleus Cultivars

    Science.gov (United States)

    Rouhani, Iraj; Khosh-Khui, Morteza

    1977-01-01

    Fourteen cultivars of coleus (Coleus blumei Benth) were found to vary in chlorophyll content, photosynthetic rate, anthocyanin content and number of stomates. Cultivars `Gaslight' and `Velvet Rainbow' had 0.17 and 0.92 mg chlorophyll per g of leaves, fresh weight, respectively. Maximum photosynthetic rate (18.7 mg CO2/mg Chl·hr) was found in the leaves of `Pastle Rainbow' and minimum (2.7) in the `Velvet Rainbow.' PMID:16659778

  11. 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.

  12. Empirical model of Skeletonema costatum photosynthetic rate, with applications in the San Francisco Bay estuary

    Science.gov (United States)

    Cloern, J.E.

    1978-01-01

    An empirical model of Skeletonema costatum photosynthetic rate is developed and fit to measurements of photosynthesis selected from the literature. Because the model acknowledges existence of: 1) a light-temperature interaction (by allowing optimum irradiance to vary with temperature), 2) light inhibition, 3) temperature inhibition, and 4) a salinity effect, it accurately estimates photosynthetic rates measured over a wide range of temperature, light intensity, and salinity. Integration of predicted instantaneous rate of photosynthesis with time and depth yields daily net carbon assimilation (pg C cell-1 day-1) in a mixed layer of specified depth, when salinity, temperature, daily irradiance and extinction coefficient are known. The assumption of constant carbon quota (pg C cell-1) allows for prediction of mean specific growth rate (day-1), which can be used in numerical models of Skeletonema costatum population dynamics. Application of the model to northern San Francisco Bay clearly demonstrates the limitation of growth by low light availability, and suggests that large population densities of S. costatum observed during summer months are not the result of active growth in the central deep channels (where growth rates are consistently predicted to be negative). But predicted growth rates in the lateral shallows are positive during summer and fall, thus offering a testable hypothesis that shoals are the only sites of active population growth by S. costatum (and perhaps other neritic diatoms) in the northern reach of San Francisco Bay. ?? 1978.

  13. Mutualistic damselfish induce higher photosynthetic rates in their host coral.

    Science.gov (United States)

    Garcia-Herrera, Nur; Ferse, Sebastian C A; Kunzmann, Andreas; Genin, Amatzia

    2017-05-15

    Coral reefs are amongst the most diverse ecosystems on Earth where complex inter-specific interactions are ubiquitous. An example of such interactions is the mutualistic relationship between damselfishes and branching corals in the Northern Red Sea, where the fish use corals as shelter and provide them with nutrients, enhance the flow between their branches, and protect them from predators. By enhancing the flow between the coral branches, the fish ventilate the coral's inner zone, mitigating hypoxic conditions that otherwise develop within that zone during the night. Here, we tested, for the first time, the effects of the damselfish Dascyllus marginatus on photosynthesis and respiration in its host coral Stylophora pistillata Laboratory experiments using an intermittent-flow respirometer showed that the presence of fish between the coral branches under light conditions augmented the coral's photosynthetic rate. No effect on the coral's respiration was found under dark conditions. When a fish was allowed to enter the inner zone of a dead coral skeleton, its respiration was higher than when it was in a live coral. Field observations indicated that damselfish were present between coral branches 18-34% of the time during daylight hours and at all times during the night. Considering the changes induced by the fish together with the proportion of time they were found between coral branches in the field, the effect of the fish amounted to an augmentation of 3-6% of the coral's daily photosynthesis. Our findings reveal a previously unknown positive contribution of coral-dwelling fish to their host's photosynthesis. © 2017. Published by The Company of Biologists Ltd.

  14. Optimizing Photosynthetic and Respiratory Parameters Based on the Seasonal Variation Pattern in Regional Net Ecosystem Productivity Obtained from Atmospheric Inversion

    Science.gov (United States)

    Chen, Z.; Chen, J.; Zheng, X.; Jiang, F.; Zhang, S.; Ju, W.; Yuan, W.; Mo, G.

    2014-12-01

    In this study, we explore the feasibility of optimizing ecosystem photosynthetic and respiratory parameters from the seasonal variation pattern of the net carbon flux. An optimization scheme is proposed to estimate two key parameters (Vcmax and Q10) by exploiting the seasonal variation in the net ecosystem carbon flux retrieved by an atmospheric inversion system. This scheme is implemented to estimate Vcmax and Q10 of the Boreal Ecosystem Productivity Simulator (BEPS) to improve its NEP simulation in the Boreal North America (BNA) region. Simultaneously, in-situ NEE observations at six eddy covariance sites are used to evaluate the NEE simulations. The results show that the performance of the optimized BEPS is superior to that of the BEPS with the default parameter values. These results have the implication on using atmospheric CO2 data for optimizing ecosystem parameters through atmospheric inversion or data assimilation techniques.

  15. 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...

  16. 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 — ABSTRACT: This global data set of photosynthetic rates and leaf nutrient traits was compiled from a comprehensive literature review. It includes estimates of Vcmax...

  17. The effect of leaf age on the photosynthetic rate of Themeda triandra ...

    African Journals Online (AJOL)

    The apparent photosynthesis of progressively older leaves of Themeda triandra was recorded in a controlled environment by means of gas exchange measurements. Photosynthetic rate increased with increasing leaf age and was maximal in the third fully expanded leaf. Thereafter, photosynthesis dropped sharply, but the ...

  18. Enigmatic relationship between chlorophyll a concentrations and photosynthetic rates at Station ALOHA.

    Science.gov (United States)

    Laws, E A; Bidigare, R R; Karl, D M

    2016-09-01

    An ordinary least squares (OLS) analysis of the relationship between chlorophyll a (chl a) concentrations and photosynthetic rates at depths of 5 and 25 m at Station ALOHA produced a slope that was only 28% of the mean productivity index at those depths and an intercept at zero chl a that equaled 70% of the mean photosynthetic rate. OLS regression lines are known to produce a slope and intercept that are biased estimates of the true slope and intercept when the explanatory variable, X, is uncontrolled, but in this case the measurement errors and natural variability of the chl a concentrations were much too small to explain the apparent bias. The bias was traceable to the fact that the photosynthetic rates were determined by more than one explanatory variable, a source of variability that is typically overlooked in discussions of OLS bias. Modeling the photosynthetic rates as a function of the product of chl a and surface irradiance produced a much more accurate and realistic description of the data, but the OLS continued to be biased, presumably because the photosynthetic rates were functions of factors in addition to chl a and surface irradiance (e.g., temperature, macronutrients, trace metals, and vitamins). The results underscore the need to recognize that the absence of bias in an OLS when X is not controlled implies that all scatter in the data about the OLS is due to errors in the dependent variable, an unlikely scenario. In most cases, resolution of the bias problem will require identification of the explanatory variables in addition to X that determine the dependent variable.

  19. Enigmatic relationship between chlorophyll a concentrations and photosynthetic rates at Station ALOHA

    Directory of Open Access Journals (Sweden)

    E.A. Laws

    2016-09-01

    Full Text Available An ordinary least squares (OLS analysis of the relationship between chlorophyll a (chl a concentrations and photosynthetic rates at depths of 5 and 25 m at Station ALOHA produced a slope that was only 28% of the mean productivity index at those depths and an intercept at zero chl a that equaled 70% of the mean photosynthetic rate. OLS regression lines are known to produce a slope and intercept that are biased estimates of the true slope and intercept when the explanatory variable, X, is uncontrolled, but in this case the measurement errors and natural variability of the chl a concentrations were much too small to explain the apparent bias. The bias was traceable to the fact that the photosynthetic rates were determined by more than one explanatory variable, a source of variability that is typically overlooked in discussions of OLS bias. Modeling the photosynthetic rates as a function of the product of chl a and surface irradiance produced a much more accurate and realistic description of the data, but the OLS continued to be biased, presumably because the photosynthetic rates were functions of factors in addition to chl a and surface irradiance (e.g., temperature, macronutrients, trace metals, and vitamins. The results underscore the need to recognize that the absence of bias in an OLS when X is not controlled implies that all scatter in the data about the OLS is due to errors in the dependent variable, an unlikely scenario. In most cases, resolution of the bias problem will require identification of the explanatory variables in addition to X that determine the dependent variable.

  20. Effect of Different Organic Material Turnover on Soil Structure and Maize Photosynthetic Rate

    Directory of Open Access Journals (Sweden)

    ZHANG Jiu-ming

    2014-02-01

    Full Text Available The effect of different organic material turnover on soil structure and maize photosynthetic rate was researched in this paper. The results showed that comparing the control treatment, the soil bulk density of two treatments of shallow reversing and chiseling plow with straw returning and organic fertilizer were decreased by 0.13 g·cm-3and 0.09 g·cm-3, respectively. The application of shallow reversing and chiseling plow with straw turnover,organic fertilizer, green organic fertilizer and bio-fertilizer could reduce soil hardness, change the soil three phase state, improve the soil physics structure. Organic fertilizer and green organic fertilizer and bio-fertilizer increased the maize photosynthetic rate at trumpet period by 2.1~7.6 μmol·m-2·s-1. The transpiration rate of straw turnover and bio-fertilizer treatments was decreased by57% and 56% separately. Conductances of all treatments were lower than that of the control treatment at trumpet period. Meanwhile stomatal conductance was increased at filling stage which may lead to the decreasing CO2concentration with the reason that reducing of stomatal booster caused the lower CO2concentration. Returning of organic materials could reduce soil bulk density and com paction, make the soil three phase state having a reasonable range, improve crop photosynthetic rate, decrease the transpiration rate, especially the treatments of straw returning and organic fertilize. In short, protection tillage and organic materials returning to field play a positive role for improving soil fertility, soil physical characteristics, crop photosynthetic rate and crop yields.

  1. Non-linear direct effects of acid rain on leaf photosynthetic rate of terrestrial plants.

    Science.gov (United States)

    Dong, Dan; Du, Enzai; Sun, Zhengzhong; Zeng, Xuetong; de Vries, Wim

    2017-12-01

    Anthropogenic emissions of acid precursors have enhanced global occurrence of acid rain, especially in East Asia. Acid rain directly suppresses leaf function by eroding surface waxes and cuticle and leaching base cations from mesophyll cells, while the simultaneous foliar uptake of nitrates in rainwater may directly benefit leaf photosynthesis and plant growth, suggesting a non-linear direct effect of acid rain. By synthesizing data from literature on acid rain exposure experiments, we assessed the direct effects of acid rain on leaf photosynthesis across 49 terrestrial plants in China. Our results show a non-linear direct effect of acid rain on leaf photosynthetic rate, including a neutral to positive effect above pH 5.0 and a negative effect below that pH level. The acid rain sensitivity of leaf photosynthesis showed no significant difference between herbs and woody species below pH 5.0, but the impacts above that pH level were strongly different, resulting in a significant increase in leaf photosynthetic rate of woody species and an insignificant effect on herbs. Our analysis also indicates a positive effect of the molar ratio of nitric versus sulfuric acid in the acid solution on leaf photosynthetic rate. These findings imply that rainwater acidity and the composition of acids both affect the response of leaf photosynthesis and therefore result in a non-linear direct effect. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Photosynthetic rates influence the population dynamics of understory herbs in stochastic light environments.

    Science.gov (United States)

    Westerband, Andrea C; Horvitz, Carol C

    2017-02-01

    Temporal variability in light from gaps in the tree canopy strongly influences the vital rates of understory plants. From 2012 to 2015, we estimated the size-specific vital rates of two herbs, Calathea crotalifera and Heliconia tortuosa, over a range of light environments. We estimated maximum photosynthetic capacity (A max ) for a subset of individuals each year during three annual censuses, and modelled future size as a linear function of current size (a plant trait that changes ontogenetically), canopy openness (an environmental variable), and A max (a potentially plastic physiological trait). We estimated what the demographic success would be of a population comprised of individuals with a particular fixed A max for each of several levels of canopy openness if the environment remained constant, by evaluating corresponding Integral Projection Models and their deterministic growth rates (λ). We then estimated their demographic success in the stochastic light environment (λ S ) and its elasticities. As light increased, deterministic λ increased for Calathea by 33% but decreased for Heliconia by 52%, and increasing A max had no effect on λ for Calathea but increased λ for Heliconia in low light. As A max increased, λ S increased for Heliconia, but not Calathea. We also investigated whether photosynthetic rates would influence the elasticities of λ S, including its response to perturbation of vital rates in each environment (E S β ), vital rates over all environments (E S ), and variability of vital rates among environments (E S σ ). E S , E S σ , and E S β were influenced by A max for Heliconia but not Calathea. Events that affect some vital rates in high light have a greater impact on overall fitness than events that affect the same vital rates in shady environments, and there is greater potential for selection on traits of large individuals in high light than in low light for Heliconia, while the reverse was true for Calathea. Photosynthetic rates

  3. Annual variation in the net longshore sediment transport rate

    CSIR Research Space (South Africa)

    Schoonees, JS

    2000-05-01

    Full Text Available from wave data spanning a number of years, or by measuring continuously the longshore transport over a number of years. In both cases, it must be known over how many consecutive years either the computations or the measurements should be done. Ž... the annual variation in the net longshore transport rates over a period of 7 years. In a study Ž . Žby Shi-Leng and Teh-Fu 1987 , a longshore sediment transport formula the Bijker, .1967 method was calibrated against short-term measurements at Nouakchott...

  4. Measurement of Carbon Fixation Rates in Leaf Samples — Use of carbon-14 labeled sodium bicarbonate to estimate photosynthetic rates

    OpenAIRE

    sprotocols

    2014-01-01

    Author: David R. Caprette ### Generation of a Light Curve To address the hypothesis concerning photosynthetic efficiency it is necessary to expose sun and shade leaves to a range of light intensities long enough for them to fix significant amounts of carbon. It is necessary to expose identical surface areas under favorable conditions which are identical for all leaves except for light intensity (the experimental variable). A means of measuring the rate of carbon fixation is also neces...

  5. The effect of net foreign assets on saving rate

    Directory of Open Access Journals (Sweden)

    Ben David Nissim

    2014-01-01

    Full Text Available Observing empirical data we find that many countries try to delay the decision of increasing saving rate in order to avoid a decrease of the living standards. However the delay leads a deterioration of countries financial stability. We present a simple theoretical model that connects between countries' saving rate and their net foreign assets. Using cross section data set of 135 countries in 2010 we estimated the econometric relation between saving rate in 2010 as dependent variable and two explanatory variables: the current account in 2010 and the aggregated current account during 1980-2010. Our findings show that industrial countries in a bad financial state tend to decrease their saving rate as external debt is larger causing to deterioration in external debt while countries with good financial state tend to increase their saving rate and the tendency increase as financial state becomes better. Only in countries with a very large external debt saving rate tends to grow. The results point that gross foreign debt will keep increasing and will worsen world financial state causing increased risk of getting into a world crisis.

  6. 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 ...

  7. 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.

  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. 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.

    Science.gov (United States)

    Martín, Mercedes; Noarbe, Dolores M; Serrot, Patricia H; Sabater, Bartolomé

    2015-01-01

    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 (ΔndhF, pr-ΔndhF, 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 1 min when light intensity suddenly increases, ndh defective plants (ΔndhF 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 (Sg) were determined as indicators of photosynthesis performance. The two ndh-defective plants, ΔndhF and T181A, had lower photosynthetic efficiency and higher Sg 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.

  10. Changes in photosynthetic rate and pigment content of blue-green algae in Lake Mendota.

    Science.gov (United States)

    Konopka, A; Brock, T D

    1978-03-01

    Blue-green algal blooms were present in Lake Mendota (Dane County, Wis.) from June to November 1976. Concentrations of total algal biomass and of particular algal species were monitored and compared with the pigment contents (chlorophyll a and phycocyanin) and photosynthetic rate of the algal populations. The specific photosynthetic rate (micrograms of C fixed per microgram of chlorophyll a per hour) was a good measure of the physiological state of the algae because this quantity increased just before each population increase and decreased before algal densities diminished. Since the quantity of light in the epilimnion which was available for photosynthesis by algal cells decreased in summer when the high algal densities attenuated incoming radiation, we investigated the possibility that the organisms would utilize lower light intensities more efficiently by increasing their pigment contents. Although some evidence of enhanced utilization of low light levels was found in the period from July to October, this result was not due to increasing chlorophyll and phycocyanin contents. There was a decrease in the phycocyanin content of the algae during this period, perhaps related to the availability of inorganic nitrogen.

  11. iTRAQ-based analysis of developmental dynamics in the soybean leaf proteome reveals pathways associated with leaf photosynthetic rate.

    Science.gov (United States)

    Qin, Jun; Zhang, Jianan; Liu, Duan; Yin, Changcheng; Wang, Fengmin; Chen, Pengyin; Chen, Hao; Ma, Jinbing; Zhang, Bo; Xu, Jin; Zhang, Mengchen

    2016-08-01

    Photosynthetic rate which acts as a vital limiting factor largely affects the potential of soybean production, especially during the senescence phase. However, the physiological and molecular mechanisms that underlying the change of photosynthetic rate during the developmental process of soybean leaves remain unclear. In this study, we compared the protein dynamics during the developmental process of leaves between the soybean cultivar Hobbit and the high-photosynthetic rate cultivar JD 17 using the iTRAQ (isobaric tags for relative and absolute quantification) method. A total number of 1269 proteins were detected in the leaves of these two cultivars at three different developmental stages. These proteins were classified into nine expression patterns depending on the expression levels at different developmental stages, and the proteins in each pattern were also further classified into three large groups and 20 small groups depending on the protein functions. Only 3.05-6.53 % of the detected proteins presented a differential expression pattern between these two cultivars. Enrichment factor analysis indicated that proteins involved in photosynthesis composed an important category. The expressions of photosynthesis-related proteins were also further confirmed by western blotting. Together, our results suggested that the reduction in photosynthetic rate as well as chloroplast activity and composition during the developmental process was a highly regulated and complex process which involved a serial of proteins that function as potential candidates to be targeted by biotechnological approaches for the improvement of photosynthetic rate and production.

  12. [Effects of NO3- stress on photosynthetic rate, photochemical efficiency of PS II and light energy allocation in cucumber seedling leaves].

    Science.gov (United States)

    Su, Xiu-Rong; Wang, Xiu-Feng; Yang, Feng-Juan; Wei, Min

    2007-07-01

    This paper studied the effects of different NO3- concentration on the photosynthetic rate, photochemical efficiency, and absorbed light energy allocation in cucumber seedling leaves. The results indicated that when the available NO3- concentration in the medium was low (14-98 mmol NO3- x L(-1)), an appropriate supplement of NO3- could enhance the capability of cucumber leaves in capturing light energy, and promote the photosynthesis. However, with further increase of NO3-, the photochemical efficiency of PS II decreased, electron transfer restrained, and net photosynthetic rate as well as the absorbed light energy used in photochemical reaction of PS II decreased. At the same time, the light energy used in antenna heat dissipation increased, while the photochemical efficiency decreased. After treated with 140 and 182 mmol NO3- x L(-1) for 6 days, the photosynthetic rate (P(n)) was decreased by 35% and 78%, respectively, maximal PS II efficiency at open centers in the absence of NPQ (F(v)/F(m)), antenna efficiency at open centers in the presence of NPQ (F(v)'/F(m)'), actual PS II efficiency (phi (PSII ) and photochemical quenching (q(P)) were lower, non-photochemical quenching (NPQ) was higher, and the deviation from full balance between PS I and PS II (beta/alpha - 1) was improved significantly, compared with the control. The fluctuant ranges of these chlorophyll fluorescence parameters were increased at higher NO3- concentration, compared with those at lower NO3- concentration. The absorbed light energy allocated to the photochemical reaction of PS II (P) was reduced by high light intensity and high NO3- concentration. Meanwhile, the proportion allocated in antenna heat dissipation (D) increased significantly. Antenna heat dissipation was the main way for excessive energy dissipation.

  13. Intercropping with wheat lowers nutrient uptake and biomass accumulation of maize, but increases photosynthetic rate of the ear leaf.

    Science.gov (United States)

    Gou, Fang; van Ittersum, Martin K; Couëdel, Antoine; Zhang, Yue; Wang, Yajun; van der Putten, Peter E L; Zhang, Lizhen; van der Werf, Wopke

    2018-02-01

    Intercropping is an ancient agricultural practice that provides a possible pathway for sustainable increases in crop yields. Here, we determine how competition with wheat affects nutrient uptake (nitrogen and phosphorus) and leaf traits, such as photosynthetic rate, in maize. In a field experiment, maize was planted as a sole crop, in three different intercrop configurations with wheat (a replacement intercrop and two add-row intercrops), and as a skip-row system with one out of each three maize rows omitted. Nitrogen and phosphorus uptake were determined at flowering and maturity. Specific leaf area, leaf nitrogen concentration, chlorophyll content and photosynthetic rate of the ear leaf were determined at flowering. Nitrogen and phosphorus concentrations were significantly lower in intercropped maize than in sole maize and skip-row maize at flowering, but these differences were smaller at maturity. At flowering, specific leaf area was significantly greater in intercrops than in skip-row maize. Leaf nitrogen concentration was significantly lower in add-row intercrops than in sole maize, skip-row maize or maize in the replacement intercrop. Leaf chlorophyll content was highest in sole and skip-row maize, intermediate in maize in the replacement intercrop and lowest in maize grown in add-row intercrops. On the contrary, photosynthetic rate was significantly higher in the replacement intercrop than in sole maize, skip-row maize and the intercrop with an additional maize row. The findings indicate that competition with intercropped wheat severely constrained nutrient uptake in maize, while photosynthetic rate of the ear leaf was not negatively affected. Possible mechanisms for higher photosynthesis rate at lower leaf nitrogen content in intercropped maize are discussed.

  14. Increased Ratio of Electron Transport to Net Assimilation Rate Supports Elevated Isoprenoid Emission Rate in Eucalypts under Drought1[W][OPEN

    Science.gov (United States)

    Dani, Kaidala Ganesha Srikanta; Jamie, Ian McLeod; Prentice, Iain Colin; Atwell, Brian James

    2014-01-01

    Plants undergoing heat and low-CO2 stresses emit large amounts of volatile isoprenoids compared with those in stress-free conditions. One hypothesis posits that the balance between reducing power availability and its use in carbon assimilation determines constitutive isoprenoid emission rates in plants and potentially even their maximum emission capacity under brief periods of stress. To test this, we used abiotic stresses to manipulate the availability of reducing power. Specifically, we examined the effects of mild to severe drought on photosynthetic electron transport rate (ETR) and net carbon assimilation rate (NAR) and the relationship between estimated energy pools and constitutive volatile isoprenoid emission rates in two species of eucalypts: Eucalyptus occidentalis (drought tolerant) and Eucalyptus camaldulensis (drought sensitive). Isoprenoid emission rates were insensitive to mild drought, and the rates increased when the decline in NAR reached a certain species-specific threshold. ETR was sustained under drought and the ETR-NAR ratio increased, driving constitutive isoprenoid emission until severe drought caused carbon limitation of the methylerythritol phosphate pathway. The estimated residual reducing power unused for carbon assimilation, based on the energetic status model, significantly correlated with constitutive isoprenoid emission rates across gradients of drought (r2 > 0.8) and photorespiratory stress (r2 > 0.9). Carbon availability could critically limit emission rates under severe drought and photorespiratory stresses. Under most instances of moderate abiotic stress levels, increased isoprenoid emission rates compete with photorespiration for the residual reducing power not invested in carbon assimilation. A similar mechanism also explains the individual positive effects of low-CO2, heat, and drought stresses on isoprenoid emission. PMID:25139160

  15. A Conceptual Model for Projecting Coccolithophorid Growth, Calcification and Photosynthetic Carbon Fixation Rates in Response to Global Ocean Change

    Directory of Open Access Journals (Sweden)

    Natasha A. Gafar

    2018-01-01

    Full Text Available Temperature, light and carbonate chemistry all influence the growth, calcification and photosynthetic rates of coccolithophores to a similar degree. There have been multiple attempts to project the responses of coccolithophores to changes in carbonate chemistry, but the interaction with light and temperature remains elusive. Here we devise a simple conceptual model to derive a fit equation for coccolithophorid growth, photosynthetic and calcification rates in response to simultaneous changes in carbonate chemistry, temperature and light conditions. The fit equation is able to account for up to 88% of the variability in measured metabolic rates. Equation projections indicate that temperature, light and carbonate chemistry all have different modulating effects on both optimal growth conditions and the sensitivity of responses to extreme environmental conditions. Calculations suggest that a single extreme environmental condition (CO2, temperature, light will reduce maximum rates regardless of how optimal the other environmental conditions may be. Thus, while the response of coccolithophores to ocean change depends on multiple variables, the one which is least optimal will have the most impact on overall rates. Finally, responses to ocean change are usually reported in terms of cellular rates. However, changes in cellular rates can be a poor predictor for assessing changes in production at the community level. We therefore introduce a new metric, the calcium carbonate production potential (CCPP, which combines the independent effects of changes in growth rate and cellular calcium carbonate content to assess how environmental changes will impact coccolith production. Direct comparison of CO2 impacts on cellular CaCO3 production rates and CCPP shows that while the former is still at 45% of its pre-industrial capacity at 1,000 μatm, the latter is reduced to 10%.

  16. Research of the relationship between delayed fluorescence and net photosynthesis rate in spinach under NaCl stress

    Science.gov (United States)

    Zhang, Lingrui; Xing, Da

    2006-09-01

    Under NaCl stress conditions, the relationship between delayed fluorescence (DF) and net photosynthesis rate (Pn) in detached leaves of spinach (Spinacia oleracea L.) was surveyed. Results showed that the changes in DF intensity of the spinach leaves directly exposed to different NaCl concentrations demonstrated considerably high consistency with that in Pn. Incubation of the leaves in 200mmol/L NaCl induced a gradual increase and subsequent decline of the DF intensity and Pu, whereas incubation of the leaves in 300mmol/L NaCl induced a continuous decline of the DF intensity and Pn, suggesting that DF bad the same response to duration of treatment of different NaC1 concentrations with Pn. Both DF and Pn showed maximal Ca 2+ antagonism effects on stress of high concentration NaC1 when the concentration of CaC1 II reached l5mmolfL. All the results demonstrated that DF has an excellent correlation with Pn and can be used as a sensitive test for the state of photosynthetic apparatus under salt stress physiology.

  17. Optimizing kick rate and amplitude for Paralympic swimmers via net force measures.

    Science.gov (United States)

    Fulton, Sacha K; Pyne, David; Burkett, Brendan

    2011-02-01

    Kicking is a key component of freestyle swimming yet the optimum combination of kick rate and kick amplitude remains unknown. For Paralympic swimmers, with upper and lower limb disabilities, the influence of the kick plays an important role in net force production. To determine optimum kick characteristics, 12 Paralympic swimmers aged 19.8 ± 2.9 years (mean ± s) were towed at their individual peak freestyle speed. The experimental conditions were (i) a prone streamline glide for passive trials and (ii) maximal freestyle kicking in a prone streamline for active trials at different speeds and kick amplitudes. Kick rate was quantified using inertial sensor technology. Towing speed was assessed using a novel and validated dynamometer, and net force was assessed using a Kistler force-platform system. When peak speed was increased by 5%, the active force increased 24.2 ± 5.3% (90% confidence limits), while kick rate remained at approximately 150 kicks per minute. Larger amplitude kicking increased the net active force by 25.1 ± 10.6%, although kick rate decreased substantially by 13.6 ± 5.1%. Based on the current kick rate and amplitude profile adopted by Paralympic swimmers, these characteristics are appropriate for optimizing net force.

  18. The Impact of Alternative Trait-Scaling Hypotheses for the Maximum Photosynthetic Carboxylation Rate (V (sub cmax)) on Global Gross Primary Production

    Science.gov (United States)

    Walker, Anthony P.; Quaife, Tristan; Van Bodegom, Peter M.; De Kauwe, Martin G.; Keenan, Trevor F.; Joiner, Joanna; Lomas, Mark R.; MacBean, Natasha; Xu, Chongang; Yang, Xiaojuan; hide

    2017-01-01

    The maximum photosynthetic carboxylation rate (V (sub cmax)) is an influential plant trait that has multiple scaling hypotheses, which is a source of uncertainty in predictive understanding of global gross primary production (GPP). Four trait-scaling hypotheses (plant functional type, nutrient limitation, environmental filtering, and plant plasticity) with nine specific implementations were used to predict global V(sub cmax) distributions and their impact on global GPP in the Sheffield Dynamic Global Vegetation Model (SDGVM). Global GPP varied from 108.1 to 128.2 petagrams of Carbon (PgC) per year, 65 percent of the range of a recent model intercomparison of global GPP. The variation in GPP propagated through to a 27percent coefficient of variation in net biome productivity (NBP). All hypotheses produced global GPP that was highly correlated (r equals 0.85-0.91) with three proxies of global GPP. Plant functional type-based nutrient limitation, underpinned by a core SDGVM hypothesis that plant nitrogen (N) status is inversely related to increasing costs of N acquisition with increasing soil carbon, adequately reproduced global GPP distributions. Further improvement could be achieved with accurate representation of water sensitivity and agriculture in SDGVM. Mismatch between environmental filtering (the most data-driven hypothesis) and GPP suggested that greater effort is needed understand V(sub cmax) variation in the field, particularly in northern latitudes.

  19. Single interval longwave radiation scheme based on the net exchanged rate decomposition with bracketing

    Czech Academy of Sciences Publication Activity Database

    Geleyn, J.- F.; Mašek, Jan; Brožková, Radmila; Kuma, P.; Degrauwe, D.; Hello, G.; Pristov, N.

    2017-01-01

    Roč. 143, č. 704 (2017), s. 1313-1335 ISSN 0035-9009 R&D Projects: GA MŠk(CZ) LO1415 Keywords : numerical weather prediction * climate models * clouds * parameterization * atmospheres * formulation * absorption * scattering * accurate * database * longwave radiative transfer * broadband approach * idealized optical paths * net exchanged rate decomposition * bracketing * selective intermittency Impact factor: 3.444, year: 2016

  20. Spatial variation in tuber depletion by swans explained by differences in net intake rates

    NARCIS (Netherlands)

    Nolet, BA; Langevoord, O; Bevan, RM; Engelaar, KR; Klaassen, M; Mulder, RJW

    We tested whether the spatial variation in resource depletion by Tundra Swans (Cygnus columbianus) foraging on belowground tubers of sage pondweed (Potnmogeton pectinatus) was caused by differences in net energy intake rates. The variation in giving up densities within the confines of one lake was

  1. Spatial variation in tuber depletion by swans explained by differences in net intake rates

    NARCIS (Netherlands)

    Nolet, B.A.; Langevoord, O.; Bevan, R.M.; Engelaar, K.R.; Klaassen, M.R.J.; Mulder, R.J.W.; Van Dijk, S.

    2001-01-01

    We tested whether the spatial variation in resource depletion by Tundra Swans (Cygnus columbianus) foraging on belowground tubers of sage pondweed (Potnmogeton pectinatus) was caused by differences in net energy intake rates. The variation in giving up densities within the confines of one lake was

  2. Effect of mono- and dichromatic light quality on growth rates and photosynthetic performance of Synechococcus sp. PCC 7002.

    Science.gov (United States)

    Bernstein, Hans C; Konopka, Allan; Melnicki, Matthew R; Hill, Eric A; Kucek, Leo A; Zhang, Shuyi; Shen, Gaozhong; Bryant, Donald A; Beliaev, Alexander S

    2014-01-01

    Synechococcus sp. PCC 7002 was grown to steady state in optically thin turbidostat cultures under conditions for which light quantity and quality was systematically varied by modulating the output of narrow-band LEDs. Cells were provided photons absorbed primarily by chlorophyll (680 nm) or phycocyanin (630 nm) as the organism was subjected to four distinct mono- and dichromatic regimes. During cultivation with dichromatic light, growth rates were generally proportional to the total incident irradiance at values light conditions, cultures exhibited similar growth rates only when they were irradiated with 630 nm light; cultures irradiated with only 680 nm light grew at rates that were 60-70% of those under other light quality regimes at equivalent irradiances. The functionality of photosystem II and associated processes such as maximum rate of photosynthetic electron transport, rate of cyclic electron flow, and rate of dark respiration generally increased as a function of growth rate. Nonetheless, some of the photophysiological parameters measured here displayed distinct patterns with respect to growth rate of cultures adapted to a single wavelength including phycobiliprotein content, which increased under severely light-limited growth conditions. Additionally, the ratio of photosystem II to photosystem I increased ~40% over the range of growth rates, although cells grown with 680 nm light only had the highest ratios. These results suggest the presence of effective mechanisms which allow acclimation of Synechococcus sp. PCC 7002 acclimation to different irradiance conditions.

  3. The OsPS1-F gene regulates growth and development in rice by modulating photosynthetic electron transport rate.

    Science.gov (United States)

    Ramamoorthy, Rengasamy; Vishal, Bhushan; Ramachandran, Srinivasan; Kumar, Prakash P

    2017-11-17

    Ds insertion in rice OsPS1-F gene results in semi-dwarf plants with reduced tiller number and grain yield, while genetic complementation with OsPS1-F rescued the mutant phenotype. Photosynthetic electron transport is regulated in the chloroplast thylakoid membrane by multi-protein complexes. Studies about photosynthetic machinery and its subunits in crop plants are necessary, because they could be crucial for yield enhancement in the long term. Here, we report the characterization of OsPS1-F (encoding Oryza sativa PHOTOSYSTEM 1-F subunit) using a single copy Ds insertion rice mutant line. The homozygous mutant (osps1-f) showed striking difference in growth and development compared to the wild type (WT), including, reduction in plant height, tiller number, grain yield as well as pale yellow leaf coloration. Chlorophyll concentration and electron transport rate were significantly reduced in the mutant compared to the WT. OsPS1-F gene was highly expressed in rice leaves compared to other tissues at different developmental stages tested. Upon complementation of the mutant with proUBI::OsPS1-F, the observed mutant phenotypes were rescued. Our results illustrate that OsPS1-F plays an important role in regulating proper growth and development of rice plants.

  4. Net capital flows to and the real exchange rate of Western Balkan countries

    Directory of Open Access Journals (Sweden)

    Gabrisch Hubert

    2015-01-01

    Full Text Available This paper uses Granger causality tests to assess the linkages between changes in the real exchange rate and net capital inflows using the example of Western Balkan countries, which have suffered from low competitiveness and external imbalances for many years. The real exchange rate is a measure of a country’s price competitiveness, and the paper uses two concepts: relative unit labour cost and relative inflation differential. The sample consists of six Western Balkan countries for the period 1996-2012, relative to the European Union (EU. The main finding is that changes in the net capital flows precede changes in relative unit labour costs and not vice versa. Also, there is evidence that net capital flows affect the inflation differential of countries, although to a less discernible extent. This suggests that the increasing divergence in the unit labour cost between the EU and Western Balkan countries up to the global financial crisis was at least partly the result of net capital inflows. The paper adds to the ongoing debate on improving cost competitiveness through wage restrictions as the main vehicle to avert the accumulation of current account imbalances. It shows the importance of changes in the exchange rate regime, reform of the interaction between the financial and the real sector, and financial supervision and structural change.

  5. Photosynthetic rates of sun versus shade leaves of Hyptis emoryi Torr

    Energy Technology Data Exchange (ETDEWEB)

    Nobel, P.S.

    1976-08-01

    Leaves on a bush of Hyptis emoryi Torr, varied in length from less than 1 cm when development occurred in full sunlight (e.g. 40 Mjoules m/sup -2/) to over 7 cm when the total daily solar irradiance was less than 3 Mjoules m/sup -2/. The 1-cm sun leaves were 3-fold higher than the 7-cm shade leaves in chlorophyll per unit area, mesophyll thickness, and the internal to external leaf area ratio (A/sup mes//A). The higher A/sup mes//A caused a 1.2-cm leaf to have a 3-fold lower CO/sub 2/ liquid phase resistance than did a 7.1-cm leaf. Large thin shade leaves captured photosynthetically active radiation effectively (less than 7 percent passed through), but were not adapted to full sunlight. Specifically, when a 6.9-cm leaf was placed at 910 w m/sup -2/ for 30 min, its temperature exceeded that of the air by nearly 8/sup 0/C. For the common daytime air temperatures above 30/sup 0/C for this desert shrub, large shade leaves would have temperatures far in excess of that optimum for photosynthesis for H. emoryi, 29 to 32/sup 0/C.

  6. Photosynthetic Rates of Sun versus Shade Leaves of Hyptis emoryi Torr. 1

    Science.gov (United States)

    Nobel, Park S.

    1976-01-01

    Leaves on a bush of Hyptis emoryi Torr. varied in length from less than 1 cm when development occurred in full sunlight (e.g. 40 Mjoules m−2) to over 7 cm when the total daily solar irradiance was less than 3 Mjoules m−2. The 1-cm sun leaves were 3-fold higher than the 7-cm shade leaves in chlorophyll per unit area, mesophyll thickness, and the internal to external leaf area ratio (Ames/A). The higher Ames/A caused a 1.2-cm leaf to have a 3-fold lower CO2 liquid phase resistance than did a 7.1-cm leaf. Large thin shade leaves captured photosynthetically active radiation effectively (less than 7% passed through), but were not adapted to full sunlight. Specifically, when a 6.9-cm leaf was placed at 910 w m−2 for 30 min, its temperature exceeded that of the air by nearly 8 C. For the common daytime air temperatures above 30 C for this desert shrub, large shade leaves would have temperatures far in excess of that optimum for photosynthesis for H. emoryi, 29 to 32 C. PMID:16659651

  7. Effect of mono- and dichromatic light quality on growth rates and photosynthetic performance of Synechococcus sp. PCC 7002

    Directory of Open Access Journals (Sweden)

    Hans C Bernstein

    2014-09-01

    Full Text Available Synechococcus sp. PCC 7002 was grown to steady state in optically thin turbidostat cultures under conditions for which light quantity and quality was systematically varied by modulating the output of narrow-band LEDs. Cells were provided photons absorbed primarily by chlorophyll (680 nm or phycocyanin (630 nm as the organism was subjected to four distinct mono- and dichromatic regimes. During cultivation with dichromatic light, growth rates displayed by Synechococcus sp. PCC 7002 were generally proportional to the total incident irradiance at values < 275 µmol photons m-2 s-1 and were not affected by the ratio of 630:680 nm wavelengths. Notably, under monochromatic light conditions, cultures exhibited similar growth rates only when they were irradiated with 630 nm light; cultures irradiated with only 680 nm light grew at rates that were 60 – 70% of those under other light quality regimes at equivalent irradiances. The functionality of photosystem II and associated processes such as maximum rate of photosynthetic electron transport, rate of cyclic electron flow, and rate of dark respiration generally increased as a function of growth rate. Nonetheless, some of the photophysiological parameters measured here displayed distinct patterns with respect to growth rate of cultures adapted to a single wavelength including phycobiliprotein content, which increased under severely light-limited growth conditions. Additionally, the ratio of photosystem II to photosystem I increased approximately 40% over the range of growth rates, although cells grown with 680 nm light only had the highest ratios. These results suggest the presence of effective mechanisms which allow acclimation of Synechococcus sp. PCC 7002 acclimation to different irradiance conditions.

  8. Effect of mono- and dichromatic light quality on growth rates and photosynthetic performance of Synechococcus sp. PCC 7002

    Energy Technology Data Exchange (ETDEWEB)

    Bernstein, Hans C.; Konopka, Allan; Melnicki, Matthew R.; Hill, Eric A.; Kucek, Leo A.; Zhang, Shuyi; Shen, Gaozhong; Bryant, Donald A.; Beliaev, Alex S.

    2014-09-19

    Synechococcus sp. PCC 7002 was grown to steady state in optically thin turbidostat cultures under conditions for which light quantity and quality was systematically varied by modulating the output of narrow-band LEDs. Cells were provided photons absorbed primarily by chlorophyll (680 nm) or phycocyanin (630 nm) as the organism was subjected to four distinct mono- and dichromatic regimes. During cultivation with dichromatic light, growth rates displayed by Synechococcus sp. PCC 7002 were generally proportional to the total incident irradiance at values < 275 µmol photons m-2 s-1 and were not affected by the ratio of 630:680 nm wavelengths. Notably, under monochromatic light conditions, cultures exhibited similar growth rates only when they were irradiated with 630 nm light; cultures irradiated with only 680 nm light grew at rates that were 60 – 70% of those under other light quality regimes at equivalent irradiances. The functionality of photosystem II and associated processes such as maximum rate of photosynthetic electron transport, rate of cyclic electron flow, and rate of dark respiration generally increased as a function of growth rate. Nonetheless, some of the photophysiological parameters measured here displayed distinct patterns with respect to growth rate of cultures adapted to a single wavelength including phycobiliprotein content, which increased under severely light-limited growth conditions. Additionally, the ratio of photosystem II to photosystem I increased approximately 40% over the range of growth rates, although cells grown with 680 nm light only had the highest ratios. These results suggest the presence of effective mechanisms which allow acclimation of Synechococcus sp. PCC 7002 acclimation to different irradiance conditions.

  9. Hyperspectral reflectance sensing to assess the growth and photosynthetic properties of wheat cultivars exposed to different irrigation rates in an irrigated arid region.

    Science.gov (United States)

    El-Hendawy, Salah; Al-Suhaibani, Nasser; Hassan, Wael; Tahir, Mohammad; Schmidhalter, Urs

    2017-01-01

    Simultaneous indirect assessment of multiple and diverse plant parameters in an exact and expeditious manner is becoming imperative in irrigated arid regions, with a view toward creating drought-tolerant genotypes or for the management of precision irrigation. This study aimed to evaluate whether spectral reflectance indices (SRIs) in three parts of the electromagnetic spectrum ((visible-infrared (VIS), near-infrared (NIR)), and shortwave-infrared (SWIR)) could be used to track changes in morphophysiological parameters of wheat cultivars exposed to 1.00, 0.75, and 0.50 of the estimated evapotranspiration (ETc). Significant differences were found in the parameters of growth and photosynthetic efficiency, and canopy spectral reflectance among the three cultivars subjected to different irrigation rates. All parameters were highly and significantly correlated with each other particularly under the 0.50 ETc treatment. The VIS/VIS- and NIR/VIS-based indices were sufficient and suitable for assessing the growth and photosynthetic properties of wheat cultivars similar to those indices based on NIR/NIR, SWIR/NIR, or SWIR/SWIR. Almost all tested SRIs proved to assess growth and photosynthetic parameters, including transpiration rate, more efficiently when regressions were analyzed for each water irrigation rate individually. This study, the type of which has rarely been conducted in irrigated arid regions, indicates that spectral reflectance data can be used as a rapid and non-destructive alternative method for assessment of the growth and photosynthetic efficiency of wheat under a range of water irrigation rates.

  10. Hyperspectral reflectance sensing to assess the growth and photosynthetic properties of wheat cultivars exposed to different irrigation rates in an irrigated arid region

    Science.gov (United States)

    Al-Suhaibani, Nasser; Hassan, Wael; Tahir, Mohammad; Schmidhalter, Urs

    2017-01-01

    Simultaneous indirect assessment of multiple and diverse plant parameters in an exact and expeditious manner is becoming imperative in irrigated arid regions, with a view toward creating drought-tolerant genotypes or for the management of precision irrigation. This study aimed to evaluate whether spectral reflectance indices (SRIs) in three parts of the electromagnetic spectrum ((visible-infrared (VIS), near-infrared (NIR)), and shortwave-infrared (SWIR)) could be used to track changes in morphophysiological parameters of wheat cultivars exposed to 1.00, 0.75, and 0.50 of the estimated evapotranspiration (ETc). Significant differences were found in the parameters of growth and photosynthetic efficiency, and canopy spectral reflectance among the three cultivars subjected to different irrigation rates. All parameters were highly and significantly correlated with each other particularly under the 0.50 ETc treatment. The VIS/VIS- and NIR/VIS-based indices were sufficient and suitable for assessing the growth and photosynthetic properties of wheat cultivars similar to those indices based on NIR/NIR, SWIR/NIR, or SWIR/SWIR. Almost all tested SRIs proved to assess growth and photosynthetic parameters, including transpiration rate, more efficiently when regressions were analyzed for each water irrigation rate individually. This study, the type of which has rarely been conducted in irrigated arid regions, indicates that spectral reflectance data can be used as a rapid and non-destructive alternative method for assessment of the growth and photosynthetic efficiency of wheat under a range of water irrigation rates. PMID:28829809

  11. Effects of p-Cresol on photosynthetic and respiration rates of a filamentous green alga (spirogyra)

    Energy Technology Data Exchange (ETDEWEB)

    Stout, J. (Michigan State Univ., East Lansing); Kilham, S.S.

    1983-01-01

    The effects of spilled phenols and cresols from coal gasification plants on the green alga SPIROYRA was investigated in experimental streams built by the US EPA near Monticello, Minnesota. P-Cresol at low concentrations inhibited photosynthesis and increased algal respiration rates. (JMT)

  12. Baseline Assessment of Net Calcium Carbonate Accretion Rates on U.S. Pacific Reefs.

    Directory of Open Access Journals (Sweden)

    Bernardo Vargas-Ángel

    Full Text Available This paper presents a comprehensive quantitative baseline assessment of in situ net calcium carbonate accretion rates (g CaCO3 cm(-2 yr(-1 of early successional recruitment communities on Calcification Accretion Unit (CAU plates deployed on coral reefs at 78 discrete sites, across 11 islands in the central and south Pacific Oceans. Accretion rates varied substantially within and between islands, reef zones, levels of wave exposure, and island geomorphology. For forereef sites, mean accretion rates were the highest at Rose Atoll, Jarvis, and Swains Islands, and the lowest at Johnston Atoll and Tutuila. A comparison between reef zones showed higher accretion rates on forereefs compared to lagoon sites; mean accretion rates were also higher on windward than leeward sites but only for a subset of islands. High levels of spatial variability in net carbonate accretion rates reported herein draw attention to the heterogeneity of the community assemblages. Percent cover of key early successional taxa on CAU plates did not reflect that of the mature communities present on surrounding benthos, possibly due to the short deployment period (2 years of the experimental units. Yet, net CaCO3 accretion rates were positively correlated with crustose coralline algae (CCA percent cover on the surrounding benthos and on the CAU plates, which on average represented >70% of the accreted material. For foreeefs and lagoon sites combined CaCO3 accretion rates were statistically correlated with total alkalinity and Chlorophyll-a; a GAM analysis indicated that SiOH and Halimeda were the best predictor variables of accretion rates on lagoon sites, and total alkalinity and Chlorophyll-a for forereef sites, demonstrating the utility of CAUs as a tool to monitor changes in reef accretion rates as they relate to ocean acidification. This study underscores the pivotal role CCA play as a key benthic component and supporting actively calcifying reefs; high Mg-calcite exoskeletons

  13. Baseline Assessment of Net Calcium Carbonate Accretion Rates on U.S. Pacific Reefs.

    Science.gov (United States)

    Vargas-Ángel, Bernardo; Richards, Cristi L; Vroom, Peter S; Price, Nichole N; Schils, Tom; Young, Charles W; Smith, Jennifer; Johnson, Maggie D; Brainard, Russell E

    2015-01-01

    This paper presents a comprehensive quantitative baseline assessment of in situ net calcium carbonate accretion rates (g CaCO3 cm(-2) yr(-1)) of early successional recruitment communities on Calcification Accretion Unit (CAU) plates deployed on coral reefs at 78 discrete sites, across 11 islands in the central and south Pacific Oceans. Accretion rates varied substantially within and between islands, reef zones, levels of wave exposure, and island geomorphology. For forereef sites, mean accretion rates were the highest at Rose Atoll, Jarvis, and Swains Islands, and the lowest at Johnston Atoll and Tutuila. A comparison between reef zones showed higher accretion rates on forereefs compared to lagoon sites; mean accretion rates were also higher on windward than leeward sites but only for a subset of islands. High levels of spatial variability in net carbonate accretion rates reported herein draw attention to the heterogeneity of the community assemblages. Percent cover of key early successional taxa on CAU plates did not reflect that of the mature communities present on surrounding benthos, possibly due to the short deployment period (2 years) of the experimental units. Yet, net CaCO3 accretion rates were positively correlated with crustose coralline algae (CCA) percent cover on the surrounding benthos and on the CAU plates, which on average represented >70% of the accreted material. For foreeefs and lagoon sites combined CaCO3 accretion rates were statistically correlated with total alkalinity and Chlorophyll-a; a GAM analysis indicated that SiOH and Halimeda were the best predictor variables of accretion rates on lagoon sites, and total alkalinity and Chlorophyll-a for forereef sites, demonstrating the utility of CAUs as a tool to monitor changes in reef accretion rates as they relate to ocean acidification. This study underscores the pivotal role CCA play as a key benthic component and supporting actively calcifying reefs; high Mg-calcite exoskeletons makes CCA

  14. Generation time, net reproductive rate, and growth in stage-age-structured populations

    DEFF Research Database (Denmark)

    Steiner, Uli; Tuljapurkar, Shripad; Coulson, Tim

    2014-01-01

    Abstract Major insights into the relationship between life-history features and fitness have come from Lotka's proof that population growth rate is determined by the level (expected amount) of reproduction and the average timing of reproduction of an individual. But this classical result is limited...... to age-structured populations. Here we generalize this result to populations structured by stage and age by providing a new, unique measure of reproductive timing (Tc) that, along with net reproductive rate (R0), has a direct mathematical relationship to and approximates growth rate (r). We use simple...... features of the life history determine population growth rate r and reveal a complex interplay of trait dynamics, timing, and level of reproduction. Our results contribute to a new framework of population and evolutionary dynamics in stage-and-age-structured populations....

  15. The RUBISCO to Photosystem II Ratio Limits the Maximum Photosynthetic Rate in Picocyanobacteria.

    Science.gov (United States)

    Zorz, Jackie K; Allanach, Jessica R; Murphy, Cole D; Roodvoets, Mitchell S; Campbell, Douglas A; Cockshutt, Amanda M

    2015-02-04

    Marine Synechococcus and Prochlorococcus are picocyanobacteria predominating in subtropical, oligotrophic marine environments, a niche predicted to expand with climate change. When grown under common low light conditions Synechococcus WH 8102 and Prochlorococcus MED 4 show similar Cytochrome b6f and Photosystem I contents normalized to Photosystem II content, while Prochlorococcus MIT 9313 has twice the Cytochrome b6f content and four times the Photosystem I content of the other strains. Interestingly, the Prochlorococcus strains contain only one third to one half of the RUBISCO catalytic subunits compared to the marine Synechococcus strain. The maximum Photosystem II electron transport rates were similar for the two Prochlorococcus strains but higher for the marine Synechococcus strain. Photosystem II electron transport capacity is highly correlated to the molar ratio of RUBISCO active sites to Photosystem II but not to the ratio of cytochrome b6f to Photosystem II, nor to the ratio of Photosystem I: Photosystem II. Thus, the catalytic capacity for the rate-limiting step of carbon fixation, the ultimate electron sink, appears to limit electron transport rates. The high abundance of Cytochrome b6f and Photosystem I in MIT 9313, combined with the slower flow of electrons away from Photosystem II and the relatively low level of RUBISCO, are consistent with cyclic electron flow around Photosystem I in this strain.

  16. Understanding the low photosynthetic rates of sun and shade coffee leaves: bridging the gap on the relative roles of hydraulic, diffusive and biochemical constraints to photosynthesis.

    Directory of Open Access Journals (Sweden)

    Samuel C V Martins

    Full Text Available It has long been held that the low photosynthetic rates (A of coffee leaves are largely associated with diffusive constraints to photosynthesis. However, the relative limitations of the stomata and mesophyll to the overall diffusional constraints to photosynthesis, as well as the coordination of leaf hydraulics with photosynthetic limitations, remain to be fully elucidated in coffee. Whether the low actual A under ambient CO2 concentrations is associated with the kinetic properties of Rubisco and high (photorespiration rates also remains elusive. Here, we provide a holistic analysis to understand the causes associated with low A by measuring a variety of key anatomical/hydraulic and photosynthetic traits in sun- and shade-grown coffee plants. We demonstrate that leaf hydraulic architecture imposes a major constraint on the maximisation of the photosynthetic gas exchange of coffee leaves. Regardless of the light treatments, A was mainly limited by stomatal factors followed by similar limitations associated with the mesophyll and biochemical constraints. No evidence of an inefficient Rubisco was found; rather, we propose that coffee Rubisco is well tuned for operating at low chloroplastic CO2 concentrations. Finally, we contend that large diffusive resistance should lead to large CO2 drawdown from the intercellular airspaces to the sites of carboxylation, thus favouring the occurrence of relatively high photorespiration rates, which ultimately leads to further limitations to A.

  17. Electrochemical Field-Effect Transistor Utilization to Study the Coupling Success Rate of Photosynthetic Protein Complexes to Cytochrome c.

    Science.gov (United States)

    Takshi, Arash; Yaghoubi, Houman; Wang, Jing; Jun, Daniel; Beatty, J Thomas

    2017-03-30

    Due to the high internal quantum efficiency, reaction center (RC) proteins from photosynthetic organisms have been studied in various bio-photoelectrochemical devices for solar energy harvesting. In vivo, RC and cytochrome c (cyt c ; a component of the biological electron transport chain) can form a cocomplex via interprotein docking. This mechanism can be used in vitro for efficient electron transfer from an electrode to the RC in a bio-photoelectrochemical device. Hence, the success rate in coupling RCs to cyt c is of great importance for practical applications in the future. In this work, we use an electrochemical transistor to study the binding of the RC to cytochrome. The shift in the transistor threshold voltage was measured in the dark and under illumination to estimate the density of cytochrome and coupled RCs on the gate of the transistor. The results show that ~33% of the cyt c s on the transistor gate were able to effectively couple with RCs. Due to the high sensitivity of the transistor, the approach can be used to make photosensors for detecting low light intensities.

  18. Oxygen dynamics in photosynthetic membranes.

    Science.gov (United States)

    Savikhin, Sergei; Kihara, Shigeharu

    2008-03-01

    Production of oxygen by oxygenic photosynthetic organisms is expected to raise oxygen concentration within their photosynthetic membranes above normal aerobic values. These raised levels of oxygen may affect function of many proteins within photosynthetic cells. However, experiments on proteins in vitro are usually performed in aerobic (or anaerobic) conditions since the oxygen content of a membrane is not known. Using theory of diffusion and measured oxygen production rates we estimated the excess levels of oxygen in functioning photosynthetic cells. We show that for an individual photosynthetic cell suspended in water oxygen level is essentially the same as that for a non-photosynthetic sell. These data suggest that oxygen protection mechanisms may have evolved after the development of oxygenic photosynthesis in primitive bacteria and was driven by the overall rise of oxygen concentration in the atmosphere. Substantially higher levels of oxygen are estimated to occur in closely packed colonies of photosynthetic bacteria and in green leafs.

  19. The Chance Model: A Tool For Separating The Photosynthetic and Respiration Components of Forest Net Ecosystem Exchange and For Data Gap Filling In The Eddy Covariance Measurement Database

    Science.gov (United States)

    Longdoz, B.; Aubinet, M.; Francois, L.

    The CHANCE model simulates CO2, H2O and energy fluxes in temperate forest ecosystems. It has been calibrated and validated for a beech forest located in Viel- salm (Belgium), an experimental site included in the CARBOEUROFLUX network and equipped with an eddy covariance system measuring CO2, latent and sensible heat net fluxes exchanged between the ecosystem and the atmosphere. CHANCE has been used to fill the gaps in the eddy covariance measurement database. The results of this method are compared with those obtained by the interpolation and parameterization usually adopted in the CARBOEUROFLUX community. Each term of the net CO2 flux (CO2 exchanges by leaf, aerial wood and soil) are computed by CHANCE. The time integration of these terms provides estimates of the gross primary productivity (GPP) and ecosystem respiration (Re). The temporal evolution of GPP and Re during the year is analysed.

  20. Low rate loading-induced convection enhances net transport into the intervertebral disc in vivo.

    Science.gov (United States)

    Gullbrand, Sarah E; Peterson, Joshua; Mastropolo, Rosemarie; Roberts, Timothy T; Lawrence, James P; Glennon, Joseph C; DiRisio, Darryl J; Ledet, Eric H

    2015-05-01

    The intervertebral disc primarily relies on trans-endplate diffusion for the uptake of nutrients and the clearance of byproducts. In degenerative discs, diffusion is often diminished by endplate sclerosis and reduced proteoglycan content. Mechanical loading-induced convection has the potential to augment diffusion and enhance net transport into the disc. The ability of convection to augment disc transport is controversial and has not been demonstrated in vivo. To determine if loading-induced convection can enhance small molecule transport into the intervertebral disc in vivo. Net transport was quantified via postcontrast enhanced magnetic resonance imaging (MRI) into the discs of the New Zealand white rabbit lumbar spine subjected to in vivo cyclic low rate loading. Animals were administered the MRI contrast agent gadodiamide intravenously and subjected to in vivo low rate loading (0.5 Hz, 200 N) via a custom external loading apparatus for either 2.5, 5, 10, 15, or 20 minutes. Animals were then euthanized and the lumbar spines imaged using postcontrast enhanced MRI. The T1 constants in the nucleus, annulus, and cartilage endplates were quantified as a measure of gadodiamide transport into the loaded discs compared with the adjacent unloaded discs. Microcomputed tomography was used to quantify subchondral bone density. Low rate loading caused the rapid uptake and clearance of gadodiamide in the nucleus compared with unloaded discs, which exhibited a slower rate of uptake. Relative to unloaded discs, low rate loading caused a maximum increase in transport into the nucleus of 16.8% after 5 minutes of loading. Low rate loading increased the concentration of gadodiamide in the cartilage endplates at each time point compared with unloaded levels. Results from this study indicate that forced convection accelerated small molecule uptake and clearance in the disc induced by low rate mechanical loading. Low rate loading may, therefore, be therapeutic to the disc as it

  1. 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.

  2. Effect of Salinity Stress and Foliar Application of Methyl Jasmonate on Photosynthetic Rate, Stomatal Conductance, Water Use Efficiency and Yield of German Chamomile

    Directory of Open Access Journals (Sweden)

    fatemeh Salimi

    2014-09-01

    Full Text Available Jasmonate is new plant growth regulator that plays an essential role at increasing plants resistance to the environmental stresses like salinity stress. Hence, in this research the effect of foliar application of methyl jasmonate on some physiological indices and yield of German chamomile under salinity conditions was studied. A factorial experiment was laid out based on randomized complete block design (RCBD with three replications in the greenhouse condition. Foliar application of methyl jasmonate was five levels (MJ1; 0, MJ2; 75, MJ3; 150, MJ4; 225 and MJ5; 300 μM and salinity stress was four levels (S1; 2, S2; 6, S3; 10, S4; 14 dS m-1. The effect of methyl jasmonate, salinity condition treatments and their interaction was significant for traits of photosynthesis rate, stomata conductance, transpiration rate, carboxylation efficiency, intercellular CO2 concentration and yield of flower. The highest values of photosynthetic rate, stomata conductance, transpiration rate, carboxylation efficiency and yield of flower (3.76 g pot-1 and the lowest intercellular CO2 concentration were achieved at MJ×S treatment. Maximum value of photosynthetic water use efficiency was revealed at MJ5×S2 treatment. With decreasing stomata conductance, photosynthetic water use efficiency and intercellular CO2 concentration were increased. In general, it seems that application of methyl jasmonate by lower dose (MJ2 under salinity conditions especially mild salinity stress (S2 can improve physiological indices and yield of chamomile.

  3. A New Approach for Mobile Advertising Click-Through Rate Estimation Based on Deep Belief Nets

    Directory of Open Access Journals (Sweden)

    Jie-Hao Chen

    2017-01-01

    Full Text Available In recent years, with the rapid development of mobile Internet and its business applications, mobile advertising Click-Through Rate (CTR estimation has become a hot research direction in the field of computational advertising, which is used to achieve accurate advertisement delivery for the best benefits in the three-side game between media, advertisers, and audiences. Current research on the estimation of CTR mainly uses the methods and models of machine learning, such as linear model or recommendation algorithms. However, most of these methods are insufficient to extract the data features and cannot reflect the nonlinear relationship between different features. In order to solve these problems, we propose a new model based on Deep Belief Nets to predict the CTR of mobile advertising, which combines together the powerful data representation and feature extraction capability of Deep Belief Nets, with the advantage of simplicity of traditional Logistic Regression models. Based on the training dataset with the information of over 40 million mobile advertisements during a period of 10 days, our experiments show that our new model has better estimation accuracy than the classic Logistic Regression (LR model by 5.57% and Support Vector Regression (SVR model by 5.80%.

  4. Sink Status and Photosynthetic Rate of the Leaflet Galls Induced by Bystracoccus mataybae (Eriococcidae on Matayba guianensis (Sapindaceae

    Directory of Open Access Journals (Sweden)

    Denis C. Oliveira

    2017-07-01

    Full Text Available The galling insect Bystracoccus mataybae (Eriococcidae induces green and intralaminar galls on leaflets of Matayba guianensis (Sapindaceae, and promotes a high oxidative stress in host plant tissues. This biotic stress is assumed by the histochemical detection of hydrogen peroxide, a reactive oxygen species (ROS, whose production alters gall physiology. Thus, we hypothesize that high levels of nutrients are accumulated during gall development in response to a local maintenance of photosynthesis and to the galling insect activity. Moreover, the maintenance of low levels of photosynthesis may guarantee O2 production and CO2 consumption, as well as may avoid hypoxia and hypercarbia in gall tissues. To access the photosynthesis performance, the distribution of chlorophyllous tissues and the photochemical and carboxylation rates in gall tissues were analyzed. In addition, histochemical tests for hydrogen peroxide and phenolic derivatives were performed to confirm the biotic stress, and set the possible sites where stress dissipation occurs. The contents of sugars and nitrogen were evaluated to quantify the gall sink. Currently, we assume that the homeostasis in gall tissues is ruptured by the oxidative stress promoted by the galling insect activity. Thus, to supply the demands of gall metabolism, the levels of water-soluble polysaccharides and starch increase in gall tissues. The low values of maximum quantum efficiency of PSII (Fv/Fm indicate a low photosynthetic performance in gall tissues. In addition, the decrease of PSII operating efficiency, (F’m–F’/F’m, and Rfd (instantaneous fluorescence decline ratio in light, to measure tissue vitality demonstrate that the tissues of B. mataybae galls are more susceptible to damage caused by stressors than the non-galled tissues. Thus, the high oxidative stress in gall developmental sites is dissipated not only by the accumulation of phenolic derivatives in the protoplast, but also of lignins in the

  5. Biomass rather than growth rate determines variation in net primary production by giant kelp.

    Science.gov (United States)

    Reed, Daniel C; Rassweiler, Andrew; Arkema, Katie K

    2008-09-01

    Net primary production (NPP) is influenced by disturbance-driven fluctuations in foliar standing crop (FSC) and resource-driven fluctuations in rates of recruitment and growth, yet most studies of NPP have focused primarily on factors influencing growth. We quantified NPP, FSC, recruitment, and growth rate for the giant kelp, Macrocystis pyrifera, at three kelp forests in southern California, U.S.A., over a 54-month period and determined the relative roles of FSC, recruitment, and growth rate in contributing to variation in annual NPP. Net primary production averaged between 0.42 and 2.38 kg dry mass x m(-2) x yr(-1) at the three sites. The initial FSC present at the beginning of the growth year and the recruitment of new plants during the year explained 63% and 21% of the interannual variation observed in NPP, respectively. The previous year's NPP and disturbance from waves collectively accounted for 80% of the interannual variation in initial FSC. No correlation was found between annual growth rate (i.e., the amount of new kelp mass produced per unit of existing kelp mass) and annual NPP (i.e., the amount of new kelp mass produced per unit area of ocean bottom), largely because annual growth rate was consistent compared to initial FSC and recruitment, which fluctuated greatly among years and sites. Although growth rate was a poor predictor of variation in annual NPP, it was principally responsible for the high mean values observed for NPP by Macrocystis. These high mean values reflected rapid growth (average of approximately 2% per day) of a relatively small standing crop (maximum annual mean = 444 g dry mass/m2) that replaced itself approximately seven times per year. Disturbance-driven variability in FSC may be generally important in explaining variation in NPP, yet it is rarely examined because cycles of disturbance and recovery occur over timescales of decades or more in many systems. Considerable insight into how variation in FSC drives variation in NPP may

  6. Hyperspectral reflectance sensing to assess the growth and photosynthetic properties of wheat cultivars exposed to different irrigation rates in an irrigated arid region.

    Directory of Open Access Journals (Sweden)

    Salah El-Hendawy

    Full Text Available Simultaneous indirect assessment of multiple and diverse plant parameters in an exact and expeditious manner is becoming imperative in irrigated arid regions, with a view toward creating drought-tolerant genotypes or for the management of precision irrigation. This study aimed to evaluate whether spectral reflectance indices (SRIs in three parts of the electromagnetic spectrum ((visible-infrared (VIS, near-infrared (NIR, and shortwave-infrared (SWIR could be used to track changes in morphophysiological parameters of wheat cultivars exposed to 1.00, 0.75, and 0.50 of the estimated evapotranspiration (ETc. Significant differences were found in the parameters of growth and photosynthetic efficiency, and canopy spectral reflectance among the three cultivars subjected to different irrigation rates. All parameters were highly and significantly correlated with each other particularly under the 0.50 ETc treatment. The VIS/VIS- and NIR/VIS-based indices were sufficient and suitable for assessing the growth and photosynthetic properties of wheat cultivars similar to those indices based on NIR/NIR, SWIR/NIR, or SWIR/SWIR. Almost all tested SRIs proved to assess growth and photosynthetic parameters, including transpiration rate, more efficiently when regressions were analyzed for each water irrigation rate individually. This study, the type of which has rarely been conducted in irrigated arid regions, indicates that spectral reflectance data can be used as a rapid and non-destructive alternative method for assessment of the growth and photosynthetic efficiency of wheat under a range of water irrigation rates.

  7. 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...

  8. Association between minor loading vein architecture and light- and CO2-saturated rates of photosynthetic oxygen evolution among Arabidopsis thaliana ecotypes from different latitudes

    Directory of Open Access Journals (Sweden)

    Christopher M Cohu

    2013-07-01

    Full Text Available Through microscopic analysis of veins and assessment of light- and CO2-saturated rates of photosynthetic oxygen evolution, we investigated the relationship between minor loading vein anatomy and photosynthesis of mature leaves in three ecotypes of Arabidopsis thaliana grown under four different combinations of temperature and photon flux density (PFD. All three ecotypes exhibited greater numbers and cross-sectional area of phloem cells as well as higher photosynthesis rates in response to higher PFD and especially lower temperature. The Swedish ecotype exhibited the strongest response to these conditions, the Italian ecotype the weakest response, and the Col-0 ecotype exhibited an intermediate response. Among all three ecotypes, strong linear relationships were found between light- and CO2-saturated rates of photosynthetic oxygen evolution and the number and area of either sieve elements or of companion and phloem parenchyma cells in foliar minor loading veins, with the Swedish ecotype showing the highest number of cells in minor loading veins (and largest minor veins coupled with unprecedented high rates of photosynthesis. Linear, albeit less significant, relationships were also observed between number and cross-sectional area of tracheids per minor loading vein versus light- and CO2-saturated rates of photosynthetic oxygen evolution. We suggest that sugar distribution infrastructure in the phloem is co-regulated with other features that set the upper limit for photosynthesis. The apparent genetic differences among Arabidopsis ecotypes should allow for future identification of the gene(s involved in augmenting sugar-loading and -transporting phloem cells and maximal rates of photosynthesis.

  9. The Impact of Rate Design and Net Metering on the Bill Savings from Distributed PV for Residential Customers in California

    Energy Technology Data Exchange (ETDEWEB)

    Darghouth, Naim; Barbose, Galen; Wiser, Ryan

    2010-03-30

    Net metering has become a widespread policy in the U.S. for supporting distributed photovoltaics (PV) adoption. Though specific design details vary, net metering allows customers with PV to reduce their electric bills by offsetting their consumption with PV generation, independent of the timing of the generation relative to consumption - in effect, compensating the PV generation at retail electricity rates (Rose et al. 2009). While net metering has played an important role in jump-starting the residential PV market in the U.S., challenges to net metering policies have emerged in a number of states and contexts, and alternative compensation methods are under consideration. Moreover, one inherent feature of net metering is that the value of the utility bill savings it provides to customers with PV depends heavily on the structure of the underlying retail electricity rate, as well as on the characteristics of the customer and PV system. Consequently, the value of net metering - and the impact of moving to alternative compensation mechanisms - can vary substantially from one customer to the next. For these reasons, it is important for policymakers and others that seek to support the development of distributed PV to understand both how the bill savings varies under net metering, and how the bill savings under net metering compares to other possible compensation mechanisms. To advance this understanding, we analyze the bill savings from PV for residential customers of California's two largest electric utilities, Pacific Gas and Electric (PG&E) and Southern California Edison (SCE). The analysis is based on hourly load data from a sample of 215 residential customers located in the service territories of the two utilities, matched with simulated hourly PV production for the same time period based on data from the nearest of 73 weather stations in the state.

  10. Net herbage accumulation rate and crude protein content of Urochloa brizantha cultivars under shade intensities

    Directory of Open Access Journals (Sweden)

    Paulo Roberto de Lima Meirelles

    2013-12-01

    Full Text Available The use of silvopastoral systems is a sustainable alternative for animal production in various regions of the Brazil. However to obtain satisfactory results in these systems, the selection of forage species that grows well in the shade should be done. The tolerance of plants to light restriction and the correctly choice of species, considering good nutritional values for these conditions has great importance. The study of artificial shading for forage production helps the clarification of issues related to the behavior of plants under reduced light prior to use in integrations with forests. The aim of the study was to evaluate the net herbage accumulation rate of forage (HAR and crude protein (CP of Urochloa brizantha cultivars (Marandu and Piatã under natural light and shading of 30 and 60%. The experiment was conducted at FMVZ - UNESP, Botucatu. The experimental design was a randomized block in factorial arrangement 3 x 2 (three shading levels: 0, 30 and 60%, two cultivars: Marandu and Piatã with three replications and repeated measures (3 cuts. Sample collection occurred when the cultivars reached 35 cm in height. The treatments with shading showed lower cutting intervals as compared to those subjected to full sunlight, because they have reached in a shorter time to time as determined cut-off criterion (mean of 37, 45 and 61 days for reduction of 60%, reduction of 30% and full sun. Significant effects (P<0.05 interaction cultivar x shade x cut on the net herbage accumulation rate (HAR. Most HAR (P<0.05 was observed for cv. Marandu 60% reduction in lightness (127 kg/ha/day due to increased production of stem during the first growing cycle. The lower HAR also occurred to Marandu, but under natural light in the third cut (34 kg/ha/day due to adverse weather conditions during the growth interval. The shadow effect and the cutting (P<0.05 affected CP. The percentage of CP on cultivars showed the highest values (average value of 9.27% in 60

  11. Difference in leaf water use efficiency/photosynthetic nitrogen use efficiency of Bt-cotton and its conventional peer.

    Science.gov (United States)

    Guo, Ruqing; Sun, Shucun; Liu, Biao

    2016-09-15

    This study is to test the effects of Bt gene introduction on the foliar water/nitrogen use efficiency in cotton. We measured leaf stomatal conductance, photosynthetic rate, and transpiration rate under light saturation condition at different stages of a conventional cultivar (zhongmian no. 16) and its counterpart Bt cultivar (zhongmian no. 30) that were cultured on three levels of fertilization, based on which leaf instantaneous water use efficiency was derived. Leaf nitrogen concentration was measured to calculate leaf photosynthetic nitrogen use efficiency, and leaf δ(13)C was used to characterize long term water use efficiency. Bt cultivar was found to have lower stomatal conductance, net photosynthetic rates and transpiration rates, but higher instantaneous and long time water use efficiency. In addition, foliar nitrogen concentration was found to be higher but net photosynthetic rate was lower in the mature leaves of Bt cultivar, which led to lower photosynthetic nitrogen use efficiency. This might result from the significant decrease of photosynthetic rate due to the decrease of stomatal conductance. In conclusion, our findings show that the introduction of Bt gene should significantly increase foliar water use efficiency but decrease leaf nitrogen use efficiency in cotton under no selective pressure.

  12. The Impact of Rate Design and Net Metering on the Bill Savings from Distributed PV for Residential Customers in California

    Energy Technology Data Exchange (ETDEWEB)

    Energy and Resources Group, University of California, Berkeley; Darghouth, Naim R.; Barbose, Galen; Wiser, Ryan

    2011-06-01

    Net metering has become a widespread mechanism in the U.S. for supporting customer adoption of distributed photovoltaics (PV), but has faced challenges as PV installations grow to a larger share of generation in a number of states. This paper examines the value of the bill savings that customers receive under net metering, and the associated role of retail rate design, based on a sample of approximately two hundred residential customers of California's two largest electric utilities. We find that the bill savings per kWh of PV electricity generated varies by more than a factor of four across the customers in the sample, which is largely attributable to the inclining block structure of the utilities' residential retail rates. We also compare the bill savings under net metering to that received under three potential alternative compensation mechanisms, based on California's Market Price Referent (MPR). We find that net metering provides significantly greater bill savings than a full MPR-based feed-in tariff, but only modestly greater savings than alternative mechanisms under which hourly or monthly net excess generation is compensated at the MPR rate.

  13. Data filtering and expected muon and neutrino event rates in the KM3NeT neutrino telescope

    Energy Technology Data Exchange (ETDEWEB)

    Shanidze, Rezo [ECAP, University of Erlangen-Nuremberg, Erwin-Rommel-Str.1, 91058 Erlangen (Germany); Collaboration: ANTARES-KM3NeT-Erlangen-Collaboration

    2011-07-01

    KM3NeT is a future Mediterranean deep sea neutrino telescope with an instrumented volume of several cubic kilometres. The neutrino and muon events in KM3NeT will be reconstructed from the signals collected from the telescope's photo detectors. However, in the deep sea the dominant source of photon signals are the decays of K40 nuclei and bioluminescence. The selection of neutrino and muon events requires the implementation of fast and efficient data filtering algorithms for the reduction of accidental background event rates. Possible data filtering and triggering schemes for the KM3NeT neutrino telescope and expected muon and neutrino event rates are discussed.

  14. Low inflation, a high net savings surplus and institutional restrictions keep the Japanese long-term interest rate low

    NARCIS (Netherlands)

    Jansen, Pieter W.

    2006-01-01

    This paper explains that the interest rate on long-term Japanese government bonds is low in comparison with other industrialised countries for four main reasons: lower inflation, net savings surplus, institutional restrictions and home bias. Monetary policy and institutionalised purchases of

  15. Leaf lifetime photosynthetic rate and leaf demography in whole plants of Ipomoea pes-caprae growing with a low supply of calcium, a 'non-mobile' nutrient.

    Science.gov (United States)

    Suárez, N

    2010-03-01

    The adaptive significance of leaf longevity has been established in relation to restrictive nutrients that can be retranslocated within the plant. However, the effect of deficiencies in 'non-mobile' nutrients on leaf lifespan and photosynthetic carbon gain is uncertain. Calcium is frequently given as an example of an essential nutrient with low phloem mobility that may alter the leaf senescence process. This study has been designed to estimate leaf lifespan, leaf production (L(p)) and leaf death (L(d)) rates, the age structure of leaves, and the decline in maximum photosynthetic rate (A(max)) with age in plants of Ipomoea pes-caprae growing with a full supply of nutrients and with a low Ca supply. The Ca deficiency produced reductions in L(p) and leaf lifespan compared with control plants. In spite of the differences in the demographic parameters between treatments in control and low-Ca plants, the percentage of leaves of a given leaf age class is maintained in such a way that the number of leaves per plant continues to increase. No relationship was found between Ca supply and A(max). However, the decline in A(max) with leaf senescence was rather sudden in control plants compared with plants growing with a low Ca supply. The importance of simultaneously using the total leaf demographic census and the assimilation rate along with leaf lifespan data in order to understand the performance of whole plants under constrained conditions is discussed.

  16. Leaf lifetime photosynthetic rate and leaf demography in whole plants of Ipomoea pes-caprae growing with a low supply of calcium, a ‘non-mobile’ nutrient

    Science.gov (United States)

    Suárez, N.

    2010-01-01

    The adaptive significance of leaf longevity has been established in relation to restrictive nutrients that can be retranslocated within the plant. However, the effect of deficiencies in ‘non-mobile’ nutrients on leaf lifespan and photosynthetic carbon gain is uncertain. Calcium is frequently given as an example of an essential nutrient with low phloem mobility that may alter the leaf senescence process. This study has been designed to estimate leaf lifespan, leaf production (Lp) and leaf death (Ld) rates, the age structure of leaves, and the decline in maximum photosynthetic rate (Amax) with age in plants of Ipomoea pes-caprae growing with a full supply of nutrients and with a low Ca supply. The Ca deficiency produced reductions in Lp and leaf lifespan compared with control plants. In spite of the differences in the demographic parameters between treatments in control and low-Ca plants, the percentage of leaves of a given leaf age class is maintained in such a way that the number of leaves per plant continues to increase. No relationship was found between Ca supply and Amax. However, the decline in Amax with leaf senescence was rather sudden in control plants compared with plants growing with a low Ca supply. The importance of simultaneously using the total leaf demographic census and the assimilation rate along with leaf lifespan data in order to understand the performance of whole plants under constrained conditions is discussed. PMID:20080828

  17. Net Metering and Market Feedback Loops: Exploring the Impact of Retail Rate Design on Distributed PV Deployment

    Energy Technology Data Exchange (ETDEWEB)

    Darghouth, Naïm R. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Wiser, Ryan [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Barbose, Galen [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Mills, Andrew [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2015-01-13

    The substantial increase in deployment of customer-sited solar photovoltaics (PV) in the United States has been driven by a combination of steeply declining costs, financing innovations, and supportive policies. Among those supportive policies is net metering, which in most states effectively allows customers to receive compensation for distributed PV generation at the full retail electricity price. The current design of retail electricity rates and the presence of net metering have elicited concerns that the possible under-recovery of fixed utility costs from PV system owners may lead to a feedback loop of increasing retail prices that accelerate PV adoption and further rate increases. However, a separate and opposing feedback loop could offset this effect: increased PV deployment may lead to a shift in the timing of peak-period electricity prices that could reduce the bill savings received under net metering where time-varying retail electricity rates are used, thereby dampening further PV adoption. In this paper, we examine the impacts of these two competing feedback dynamics on U.S. distributed PV deployment through 2050 for both residential and commercial customers, across states. Our results indicate that, at the aggregate national level, the two feedback effects nearly offset one another and therefore produce a modest net effect, although their magnitude and direction vary by customer segment and by state. We also model aggregate PV deployment trends under various rate designs and net-metering rules, accounting for feedback dynamics. Our results demonstrate that future adoption of distributed PV is highly sensitive to retail rate structures. Whereas flat, time-invariant rates with net metering lead to higher aggregate national deployment levels than the current mix of rate structures (+5% in 2050), rate structures with higher monthly fixed customer charges or PV compensation at levels lower than the full retail rate can dramatically erode aggregate customer

  18. Characterization of photosynthetic performance during senescence in stay-green and quick-leaf-senescence Zea mays L. inbred lines.

    Directory of Open Access Journals (Sweden)

    Zishan Zhang

    Full Text Available The net photosynthetic rate, chlorophyll content, chlorophyll fluorescence and 820 nm transmission were investigated to explore the behavior of the photosynthetic apparatus, including light absorption, energy transformation and the photoactivities of photosystem II (PSII and photosystem I (PSI during senescence in the stay-green inbred line of maize (Zea mays Q319 and the quick-leaf-senescence inbred line of maize HZ4. The relationship between the photosynthetic performance and the decrease in chlorophyll content in the two inbred lines was also studied. Both the field and laboratory data indicated that the chlorophyll content, net photosynthetic rate, and the photoactivities of PSII and PSI decreased later and slower in Q319 than in HZ4, indicating that Q319 is a functional stay-green inbred line. In order to avoid the influence of different development stages and environmental factors on senescence, age-matched detached leaf segments from the two inbred lines were treated with ethephon under controlled conditions to induce senescence. The net photosynthetic rate, light absorption, energy transformation, the activities of PSII acceptor side and donor side and the PSI activities decreased much slower in Q319 than in HZ4 during the ethephon-induced senescence. These results suggest that the retention of light absorption, energy transformation and activity of electron transfer contribute to the extended duration of active photosynthesis in Q319. Although the chlorophyll content decreased faster in HZ4, with decrease of chlorophyll content induced by ethephon, photosynthetic performance of Q319 deteriorated much more severely than that of HZ4, indicating that, compared with Q319, HZ4 has an advantage at maintaining higher photosynthetic activity with decrease of chlorophyll although HZ4 is a quick-leaf-senescence inbred line. We conclude that attention should be paid to two favorable characteristics in breeding long duration of active

  19. Characterization of photosynthetic performance during senescence in stay-green and quick-leaf-senescence Zea mays L. inbred lines.

    Science.gov (United States)

    Zhang, Zishan; Li, Geng; Gao, Huiyuan; Zhang, Litao; Yang, Cheng; Liu, Peng; Meng, Qingwei

    2012-01-01

    The net photosynthetic rate, chlorophyll content, chlorophyll fluorescence and 820 nm transmission were investigated to explore the behavior of the photosynthetic apparatus, including light absorption, energy transformation and the photoactivities of photosystem II (PSII) and photosystem I (PSI) during senescence in the stay-green inbred line of maize (Zea mays) Q319 and the quick-leaf-senescence inbred line of maize HZ4. The relationship between the photosynthetic performance and the decrease in chlorophyll content in the two inbred lines was also studied. Both the field and laboratory data indicated that the chlorophyll content, net photosynthetic rate, and the photoactivities of PSII and PSI decreased later and slower in Q319 than in HZ4, indicating that Q319 is a functional stay-green inbred line. In order to avoid the influence of different development stages and environmental factors on senescence, age-matched detached leaf segments from the two inbred lines were treated with ethephon under controlled conditions to induce senescence. The net photosynthetic rate, light absorption, energy transformation, the activities of PSII acceptor side and donor side and the PSI activities decreased much slower in Q319 than in HZ4 during the ethephon-induced senescence. These results suggest that the retention of light absorption, energy transformation and activity of electron transfer contribute to the extended duration of active photosynthesis in Q319. Although the chlorophyll content decreased faster in HZ4, with decrease of chlorophyll content induced by ethephon, photosynthetic performance of Q319 deteriorated much more severely than that of HZ4, indicating that, compared with Q319, HZ4 has an advantage at maintaining higher photosynthetic activity with decrease of chlorophyll although HZ4 is a quick-leaf-senescence inbred line. We conclude that attention should be paid to two favorable characteristics in breeding long duration of active photosynthesis hybrids: 1

  20. Response of the leaf photosynthetic rate to available nitrogen in erect panicle-type rice (Oryza sativa L. cultivar, Shennong265

    Directory of Open Access Journals (Sweden)

    Chihiro Urairi

    2016-07-01

    Full Text Available Increasing the yield of rice per unit area is important because of the demand from the growing human population in Asia. A group of varieties called erect panicle-type rice (EP achieves very high yields under conditions of high nitrogen availability. Little is known, however, regarding the leaf photosynthetic capacity of EP, which may be one of the physiological causes of high yield. We analyzed the factors contributing to leaf photosynthetic rate (Pn and leaf mesophyll anatomy of Nipponbare, Takanari, and Shennong265 (a EP type rice cultivar varieties subjected to different nitrogen treatments. In the field experiment, Pn of Shennong265 was 33.8 μmol m−2 s−1 in the high-N treatment, and was higher than that of the other two cultivars because of its high leaf nitrogen content (LNC and a large number of mesophyll cells between the small vascular bundles per unit length. In Takanari, the relatively high value of Pn (31.5 μmol m−2 s−1 was caused by the high stomatal conductance (gs; .72 mol m−2 s−1 in the high-N treatment. In the pot experiment, the ratio of Pn/Ci to LNC, which may reflect mesophyll conductance (gm, was 20–30% higher in Nipponbare than in Takanari or Shennong265 in the high N availability treatment. The photosynthetic performance of Shennong265 might be improved by introducing the greater ratio of Pn/Ci to LNC found in Nipponbare and greater stomatal conductance found in Takanari.

  1. Gill net selectivity and catch rates of pelagic fish in tropical coastal ...

    African Journals Online (AJOL)

    The fish species and size selectivity of gillnets design with monofilament nylon polyethylene netting materials were investigated in Lagos Lagoon, Nigeria between September and December 2005. The gillnets floats and sinkers were improvised from rubber slippers and lead metallic objects which were attached at intervals ...

  2. The effect of interspecific variation in photosynthetic plasticity on 4-year growth rate and 8-year survival of understorey tree seedlings in response to gap formations in a cool-temperate deciduous forest.

    Science.gov (United States)

    Oguchi, Riichi; Hiura, Tsutom; Hikosaka, Kouki

    2017-08-01

    Gap formation increases the light intensity in the forest understorey. The growth responses of seedlings to the increase in light availability show interspecific variation, which is considered to promote biodiversity in forests. At the leaf level, some species increase their photosynthetic capacity in response to gap formation, whereas others do not. Here we address the question of whether the interspecific difference in the photosynthetic response results in the interspecific variation in the growth response. If so, the interspecific difference in photosynthetic response would also contribute to species coexistence in forests. We also address the further relevant question of why some species do not increase their photosynthetic capacity. We assumed that some cost of photosynthetic plasticity may constrain acquisition of the plasticity in some species, and hypothesized that species with larger photosynthetic plasticity exhibit better growth after gap formation and lower survivorship in the shade understorey of a cool-temperate deciduous forest. We created gaps by felling canopy trees and studied the relationship between the photosynthetic response and the subsequent growth rate of seedlings. Naturally growing seedlings of six deciduous woody species were used and their mortality was examined for 8 years. The light-saturated rate of photosynthesis (Pmax) and the relative growth rate (RGR) of the seedlings of all study species increased at gap plots. The extent of these increases varied among the species. The stimulation of RGR over 4 years after gap formation was strongly correlated with change in photosynthetic capacity of newly expanded leaves. The increase in RGR and Pmax correlated with the 8-year mortality at control plots. These results suggest a trade-off between photosynthetic plasticity and the understorey shade tolerance. Gap-demanding species may acquire photosynthetic plasticity, sacrificing shade tolerances, whereas gap-independent species may acquire

  3. Antisense reductions in the PsbO protein of photosystem II leads to decreased quantum yield but similar maximal photosynthetic rates.

    Science.gov (United States)

    Dwyer, Simon A; Chow, Wah Soon; Yamori, Wataru; Evans, John R; Kaines, Sarah; Badger, Murray R; von Caemmerer, Susanne

    2012-08-01

    Photosystem (PS) II is the multisubunit complex which uses light energy to split water, providing the reducing equivalents needed for photosynthesis. The complex is susceptible to damage from environmental stresses such as excess excitation energy and high temperature. This research investigated the in vivo photosynthetic consequences of impairments to PSII in Arabidopsis thaliana (ecotype Columbia) expressing an antisense construct to the PsbO proteins of PSII. Transgenic lines were obtained with between 25 and 60% of wild-type (WT) total PsbO protein content, with the PsbO1 isoform being more strongly reduced than PsbO2. These changes coincided with a decrease in functional PSII content. Low PsbO (less than 50% WT) plants grew more slowly and had lower chlorophyll content per leaf area. There was no change in content per unit area of cytochrome b6f, ATP synthase, or Rubisco, whereas PSI decreased in proportion to the reduction in chlorophyll content. The irradiance response of photosynthetic oxygen evolution showed that low PsbO plants had a reduced quantum yield, but matched the oxygen evolution rates of WT plants at saturating irradiance. It is suggested that these plants had a smaller pool of PSII centres, which are inefficiently connected to antenna pigments resulting in reduced photochemical efficiency.

  4. The role of electron transport in determining the temperature dependence of the photosynthetic rate in spinach leaves grown at contrasting temperatures.

    Science.gov (United States)

    Yamori, Wataru; Noguchi, Ko; Kashino, Yasuhiro; Terashima, Ichiro

    2008-04-01

    The temperature response of the uncoupled whole-chain electron transport rate (ETR) in thylakoid membranes differs depending on the growth temperature. However, the steps that limit whole-chain ETR are still unclear and the question of whether the temperature dependence of whole-chain ETR reflects that of the photosynthetic rate remains unresolved. Here, we determined the whole-chain, PSI and PSII ETR in thylakoid membranes isolated from spinach leaves grown at 30 degrees C [high temperature (HT)] and 15 degrees C [low temperature (LT)]. We measured temperature dependencies of the light-saturated photosynthetic rate at 360 microl l(-1) CO2 (A360) in HT and LT leaves. Both of the temperature dependences of whole-chain ETR and of A360 were different depending on the growth temperature. Whole-chain ETR was less than the rates of PSI ETR and PSII ETR in the broad temperature range, indicating that the process was limited by diffusion processes between the PSI and PSII. However, at high temperatures, whole-chain ETR appeared to be limited by not only the diffusion processes but also PSII ETR. The C3 photosynthesis model was used to evaluate the limitations of A360 by whole-chain ETR (Pr) and ribulose bisphosphate carboxylation (Pc). In HT leaves, A360 was co-limited by Pc and Pr at low temperatures, whereas at high temperatures, A360 was limited by Pc. On the other hand, in LT leaves, A360 was solely limited by Pc over the entire temperature range. The optimum temperature for A360 was determined by Pc in both HT and LT leaves. Thus, this study showed that, at low temperatures, the limiting step of A360 was different depending on the growth temperature, but was limited by Pc at high temperatures regardless of the growth temperatures.

  5. The mechanisms by which phenanthrene affects the photosynthetic apparatus of cucumber leaves.

    Science.gov (United States)

    Jin, Liqiao; Che, Xingkai; Zhang, Zishan; Li, Yuting; Gao, Huiyuan; Zhao, Shijie

    2017-02-01

    Phenanthrene is a polycyclic aromatic hydrocarbon (PAH) that is widely distributed in the environment and seriously affects the growth and development of plants. To clarify the mechanisms of the direct effects of phenanthrene on the plant photosynthetic apparatus, we measured short-term phenanthrene-treated cucumber leaves. Phenanthrene inhibited Rubisco carboxylation activity, decreasing photosynthesis rates (Pn). And phenanthrene inhibited photosystem II (PSII) activity, thereby blocking photosynthetic electron transport. The inhibition of the light and dark reactions decreased the photosynthetic electron transport rate (ETR) and increased the excitation pressure (1-qP). Under high light, the maximum photochemical efficiency of photosystem II (Fv/Fm) in phenanthrene-treated cucumber leaves decreased significantly, but photosystem I (PSI) activity (Δ I/Io) did not. Phenanthrene also caused a J-point rise in the OJIP curve under high light, which indicated that the acceptor side of PSII QA to QB electron transfer was restricted. This was primarily due to the net degradation of D1 protein, which is caused by the accumulation of reactive oxygen species (ROS) in phenanthrene-treated cucumber leaves under high light. This study demonstrated that phenanthrene could directly inhibit photosynthetic electron transport and Rubisco carboxylation activity to decrease net Pn. Under high light, phenanthrene caused the accumulation of ROS, resulting in net increases in D1 protein degradation and consequently causing PSII photoinhibition. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Photosynthetic temperature responses of Eucalyptus globulus and Eucalyptus nitens

    Energy Technology Data Exchange (ETDEWEB)

    Battaglia, M.; Beadle, C. [Commonwealth Scientific and Industrial Research Organization (CSIRO), Canberra, ACT (Australia). Div. of Forestry and Forest Products; Loughead, S. [Tasmania Univ., Hobart, TAS (Australia)

    1996-01-01

    Photosynthetic responses to temperature variations of four year old Eucalyptus globulus and Eucalyptus nitens were investigated. Temperatures varied between 10 degrees C and 35 degrees C, and were measured at approximately monthly intervals from early spring until midwinter. The photosynthetic temperature optimum was found to be linearly related to the average temperature of the preceding week during the entire nine month period. For E. globulus the optimum temperature for net photosynthesis increased from 17 degrees C to 23 degrees C as the mean daily temperature increased from 7 degrees C to 16 degrees. The corresponding values for E. nitens were 14 to 20 degrees C as the mean daily temperature increased from 7 to 19 degrees C. The photosynthetic performance of E. nitens was less sensitive to temperatures above and below the optimum than E. globulus. In a second experiment E. globulus clones were acclimated in temperature-controlled greenhouses, and in a shadehouse in four climatically different regions of Tasmania. A comparison of light response curves of the plants showed that the maximum rate of net photosynthesis was affected by the growth temperature, whereas apparent quantum efficiency remained unchanged. 25 refs., 3 tabs., 8 figs.

  7. 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...

  8. Níveis de nitrogênio e a taxa fotossintética do mamoeiro "golden" Nitrogen levels and photosynthetic rate of papaya 'golden'

    Directory of Open Access Journals (Sweden)

    Jailson Lopes Cruz

    2007-02-01

    Full Text Available Objetivou-se neste trabalho, avaliar o efeito da nutrição nitrogenada sobre alguns aspectos relacionados à taxa fotossintética em plantas de mamão da variedade "Golden". As plantas foram cultivadas em vasos sob condições de casa de vegetação, em soluções nutritivas contendo três concentrações de N-N3- (1,0; 5,0 e 8,0molm-3. O delineamento experimental foi em blocos casualizados, com sete repetições. As avaliações foram realizadas 61 dias após o início do experimento. Observou-se que a deficiência de nitrogênio reduziu a matéria seca total; no entanto, a relação raiz:parte aérea foi maior nessas plantas. A taxa fotossintética líquida foi reduzida pela menor disponibilidade de nitrogênio. Os resultados observados para a condutância estomática e a correlação negativa encontrada entre a taxa fotossintética e a concentração interna de CO2 claramente indicam que a menor taxa fotossintética não foi devida à limitação estomática. Adicionalmente, a redução verificada nas concentrações de pigmentos foliares, como as clorofilas a e b e os carotenóides, também pode ter contribuído para a menor taxa fotossintética e o menor crescimento das plantas. A taxa transpiratória foi maior para as plantas cultivadas sob estresse; como conseqüência, observou-se, para essas plantas, menor ganho de CO2 por unidade de água transpirada.This research was aimed at evaluating the effect of nitrogen (N levels on some aspects related to the photosynthetic rate in plants of papaya Cv. Golden. The plants were cultivated under greenhouse conditions on different nutritional solutions with three concentrations of N-N3- (1.0; 5.0; 8.0molm-3. The experiment was carried out under a randomized blocks experimental design, with seven repetitions. The evaluations occurred on the 61st day after the beginning of the experiment. The nitrogen deficiency reduced the total dry mass; however, the relation root:shoot was highest for these

  9. Net Reaction Rate and Neutrino Cooling Rate for the Urca Process in Departure from Chemical Equilibrium in the Crust of Fast-accreting Neutron Stars

    Science.gov (United States)

    Wang, Wei-Hua; Huang, Xi; Zheng, Xiao-Ping

    We discuss the effect of compression on Urca shells in the ocean and crust of accreting neutron stars, especially in superbursting sources. We find that Urca shells may be deviated from chemical equilibrium in neutron stars which accrete at several tenths of the local Eddington accretion rate. The deviation depends on the energy threshold of the parent and daughter nuclei, the transition strength, the temperature, and the local accretion rate. In a typical crust model of accreting neutron stars, the chemical departures range from a few tenths of kBT to tens of kBT for various Urca pairs. If the Urca shell can exist in crusts of accreting neutron stars, compression may enhance the net neutrino cooling rate by a factor of about 1-2 relative to the neutrino emissivity in chemical equilibrium. For some cases, such as Urca pairs with small energy thresholds and/or weak transition strength, the large chemical departure may result in net heating rather than cooling, although the released heat can be small. Strong Urca pairs in the deep crust are hard to be deviated even in neutron stars accreting at the local Eddington accretion rate.

  10. Photosynthetic capacity of senescent leaves for a subtropical broadleaf deciduous tree species Liquidambar formosana Hance.

    Science.gov (United States)

    Luo, Zidong; Guan, Huade; Zhang, Xinping; Liu, Na

    2017-07-24

    Photosynthetic capacity and leaf life span generally determine how much carbon a plant assimilates during the growing season. Leaves of deciduous tree species start senescence in late season, but whether the senescent leaves still retain capacity of carbon assimilation remains a question. In this study, we investigated leaf phenology and photosynthesis of a subtropical broadleaf deciduous tree species Liquidambar formosana Hance in the central southern continental China. The results show that L. formosana has extended leaf senescence (more than 2 months) with a substantial number of red leaves persisting on the tree. Leaf photosynthetic capacity decreases over season, but the senescent red leaves still maintain relatively high photosynthetic capacity at 42%, 66% and 66% of the mature leaves for net photosynthesis rate, apparent quantum yield, and quantum yield at the light compensation point, respectively. These results indicate that L. formosana may still contribute to carbon sink during leaf senescence.

  11. Toxicological effects of copper oxide nanoparticles on the growth rate, photosynthetic pigment content, and cell morphology of the duckweed Landoltia punctata.

    Science.gov (United States)

    Lalau, Cristina Moreira; Mohedano, Rodrigo de Almeida; Schmidt, Éder C; Bouzon, Zenilda L; Ouriques, Luciane C; dos Santos, Rodrigo W; da Costa, Cristina H; Vicentini, Denice S; Matias, William Gerson

    2015-01-01

    Recently, the application of copper oxide nanoparticles (CuO-NPs) has increased considerably, primarily in scientific and industrial fields. However, studies to assess their health risks and environmental impacts are scarce. Therefore, the present study aims to evaluate the toxicological effects of CuO-NPs on the duckweed species Landoltia punctata, which was used as a test organism. To accomplish this, duckweed was grown under standard procedures according to ISO DIS 20079 and exposed to three different concentrations of CuO-NPs (0.1, 1.0, and 10.0 g L(-1)), with one control group (without CuO-NPs). The toxicological effects were measured based on growth rate inhibition, changes in the plant's morphology, effects on ultrastructure, and alterations in photosynthetic pigments. The morphological and ultrastructural effects were evaluated by electronic, scanning and light microscopic analysis, and CuO-NPs were characterized using transmission electron microscopy (TEM), zeta potential, and superficial area methods of analysis. This analysis was performed to evaluate nanoparticle size and form in solution and sample stability. The results showed that CuO-NPs affected morphology more significantly than growth rate. L. punctata also showed the ability to remove copper ions. However, for this plant to be representative within the trophic chain, the biomagnification of effects must be assessed.

  12. Net accumulation rates derived from ice core stable isotope records of Pío XI glacier, Southern Patagonia Icefield

    Directory of Open Access Journals (Sweden)

    M. Schwikowski

    2013-10-01

    Full Text Available Pío XI, the largest glacier of the Southern Patagonia Icefield, reached its neoglacial maximum extent in 1994 and is one of the few glaciers in that area which is not retreating. In view of the recent warming it is important to understand glacier responses to climate changes. Due to its remoteness and the harsh conditions in Patagonia, no systematic mass balance studies have been performed. In this study we derived net accumulation rates for the period 2000–2006 from a 50 m (33.2 4 m weq ice core collected in the accumulation area of Pío XI (2600 m a.s.l., 49°16'40"S, 73°21'14"W. Borehole temperatures indicate near temperate ice, but the average melt percent is only 16 ± 14%. Records of stable isotopes are well preserved and were used for identification of annual layers. Net accumulation rates range from 3.4–7.1 water equivalent (m weq with an average of 5.8 m weq, comparable to precipitation amounts at the Chilean coast, but not as high as expected for the Icefield. Ice core stable isotope data correlate well with upper air temperatures and may be used as temperature proxy.

  13. Interspecific prediction of photosynthetic light response curves using specific leaf mass and leaf nitrogen content: effects of differences in soil fertility and growth irradiance.

    Science.gov (United States)

    Lachapelle, Pierre-Philippe; Shipley, Bill

    2012-05-01

    Previous work has shown that the entire photosynthetic light response curve, based on both Mitscherlich and Michaelis-Menten functions, could be predicted in an interspecific context through allometric relations linking the parameters of these functions to two static leaf traits: leaf nitrogen (N) content and leaf mass per area (LMA). This paper describes to what extent these allometric relations are robust to changes in soil fertility and the growth irradiance of the plants. Plants of 25 herbaceous species were grown under controlled conditions in factorial combinations of low/high soil fertility and low/high growth irradiance. Net photosynthetic rates per unit dry mass were measured at light intensities ranging from 0 to 700 µmol m(-2) s(-1) photosynthetically active radiation (PAR). The differing growth environments induced large changes in N, LMA and in each of the parameter estimates of the Mitscherlich and Michaelis-Menten functions. However, the differing growth environments induced only small (although significant) changes in the allometric relationships linking N and LMA to the parameters of the two functions. As a result, 88 % (Mitcherlich) and 89 % (Michaelis-Menten) of the observed net photosynthetic rates over the full range of light intensities (0-700 µmol m(-2) s(-1) PAR) and across all four growth environments could be predicted using only N and LMA using the same allometric relations. These results suggest the possibility of predicting net photosynthetic rates in nature across species over the full range of light intensities using readily available data.

  14. Effects of ploidy level and haplotype on variation of photosynthetic traits: Novel evidence from two Fragaria species.

    Directory of Open Access Journals (Sweden)

    Song Gao

    Full Text Available To reveal the effects of ploidy level and haplotype on photosynthetic traits, we chose 175 genotypes of wild strawberries belonging to two haplotypes at two types of ploidy levels (diploidy and tetraploidy and measured photosynthetic traits. Our results revealed that ploidy significantly affected the characteristics of light-response curves, CO2-response curves, and leaf gas exchange parameters, except intercellular CO2 concentration (Ci. Tetraploid species had a lower light saturation point (LSP and CO2 saturation point (CSP, higher light compensation point (LCP, dark respiration (Rd, and CO2 compensation point (CCP than diploid species. Furthermore, tetraploid species have lower photosynthetic capacity than diploid species, including net photosynthetic rate (Pn, stomatal conductivity (Gs, and transpiration rate (Tr. In addition, haplotype had a significant effect on LSP, CSP, Tr, and Ci as well as a significant interactive effect between ploidy and haplotype on the maximal photosynethic rate of the light-response curve and Rd. Most of the variance existed within haplotypes among individuals. These results suggest that polyploidization was the main driver for the evolution of photosynthesis with increasing ploidy level (i.e. from diploidy to tetraploidy in Fragaria species, while the origin of a chromosome could also affect the photosynthetic traits and the polyploidization effect on photosynthetic traits.

  15. Changes in transpiration and photosynthetic rates of various leaves during treatment with ozonated hexene or ozone gas

    Energy Technology Data Exchange (ETDEWEB)

    Todd, G.W.; Propst, B.

    1963-01-01

    Measurements were made on the rates of photosynthesis and transpiration of bean, tomato and coleus leaves during and immediately following fumigation with either ozone or ozonated hexene gas. Both fumigants caused marked decreases in the rate of photosynthesis in all 3 species although in tomato and coleus leaves, the reduction in photosynthesis took place only during the fumigation with ozonated hexene gas and afterwards the rate returned to normal. Ozone fumigation caused decreases in transpiration but the decrease was not as large as that obtained for photosynthesis. Transpiration in tomato and coleus leaves showed little response to ozonated hexene gas although bean leaves responsed in much the same way as they did when they were treated with ozone alone. The white portions of coleus leaves (where the green outer portion had been removed) were used for similar fumigations and an increase in respiration and a decrease in transpiration with ozonated hexene was noted. There were no changes in transpiration from these leaves following ozone fumigations. Increases in respiration after ozone and ozonated hexene fumigations were obtained for bean, tomato and intact coleus leaves as had been reported previously for bean leaves. It was postulated that part of the decrease in growth (not accompanied by visible injury) obtained when plants were treated with ozonated hexene gas might be due directly to the reduction in photosynthesis. It would not appear in the species tested that the more resistant species close their stomates and thereby prevent the fumigant from entering.

  16. Effect of stroke rate on the distribution of net mechanical power in rowing

    NARCIS (Netherlands)

    Hofmijster, M.J.; Landman, E.H.; Smith, R.M.; van Soest, A.J.

    2007-01-01

    The aim of this study was to assess the effect of manipulating stroke rate on the distribution of mechanical power in rowing. Two causes of inefficient mechanical energy expenditure were identified in rowing. The ratio between power not lost at the blades and generated mechanical power (P̄

  17. Photosynthetic and respiratory characterization of field grown tomato.

    Science.gov (United States)

    Bolaños, J A; Hsiao, T C

    1991-04-01

    The photosynthetic responses of tomato (Lycopersicum esculentum Mill.) leaves to environmental and ontogenetic factors were determined on plants grown in the field under high radiation and high nitrogen fertilization. Response curves showed net photosynthesis to only approach light saturation at a photosynthetic photon flux density (PPFD) of 2200 μmol m(-2) s(-1), with rates of approx. 40 μmol CO2 m(-2) s(-1). A broad temperature optimum was observed between 25° and 35°C, with 50% of the photosynthetic rates remaining even at 47°C. The high rate, the lack of saturation at the equivalent of full sunlight, and the tolerance to high temperature of tomato were unusual in light of the literature on this C3 species. Apparently, acclimation to the field environment of high radiation and hot daytime temperature, coupled with the high nitrogen nutrition, made possible the high photosynthetic performance normally associated with C4 species.Photosynthetic ability of the leaf reached a maximum near the time of its full expansion and declined steadily thereafter, regardless of the time of leaf initiation. Leaf nitrogen content showed a similar decline with leaf ontogeny. Photosynthesis was linearly correlated with nitrogen content, whether the nitrogen variation was due to leaf age or rates of nitrogen fertilization. Internal CO2 concentrations (Ci) of the leaf indicated that stomatal function was well coordinated with photosynthetic capacity as leaf age and fluence rate varied down to a PPFD of 500 μmol m(-2) s(-1). As PPFD decreased further, there was less stomatal control and Ci increased to as high as 320 μ bar bar(-1).Dark respiration was highest for expanding leaves and increased nearly exponentially with temperature. Respiration was also highest for young and expanding fruits, and next highest for fruits just turning pink. Fruit respiration increased approximately linearly with temperature, and was estimated to be an important component of the CO2 flux of the

  18. Contrasting Strategies of Photosynthetic Energy Utilization Drive Lifestyle Strategies in Ecologically Important Picoeukaryotes

    Directory of Open Access Journals (Sweden)

    Kimberly H. Halsey

    2014-04-01

    Full Text Available The efficiency with which absorbed light is converted to net growth is a key property for estimating global carbon production. We previously showed that, despite considerable evolutionary distance, Dunaliella tertiolecta (Chlorophyceae and Thalassiosira weissflogii (Bacillariophyceae share a common strategy of photosynthetic energy utilization and nearly identical light energy conversion efficiencies. These findings suggested that a single model might be appropriate for describing relationships between measures of phytoplankton production. This conclusion was further evaluated for Ostreococcus tauri RCC1558 and Micromonas pusilla RCC299 (Chlorophyta, Prasinophyceae, two picoeukaryotes with contrasting geographic distributions and swimming abilities. Nutrient-dependent photosynthetic efficiencies in O. tauri were similar to the previously studied larger algae. Specifically, absorption-normalized gross oxygen and carbon production and net carbon production were independent of nutrient limited growth rate. In contrast, all measures of photosynthetic efficiency were strongly dependent on nutrient availability in M. pusilla. This marked difference was accompanied by a diminished relationship between Chla:C and nutrient limited growth rate and a remarkably greater efficiency of gross-to-net energy conversion than the other organisms studied. These results suggest that the cost-benefit of decoupling pigment concentration from nutrient availability enables motile organisms to rapidly exploit more frequent encounters with micro-scale nutrient patches in open ocean environments.

  19. Net Ecosystem Carbon Flux

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Net Ecosystem Carbon Flux is defined as the year-over-year change in Total Ecosystem Carbon Stock, or the net rate of carbon exchange between an ecosystem and the...

  20. Features of the photosynthetic tissue in the sheaths of rice (Oryza sativa L.)

    Science.gov (United States)

    Guo, Zhao Wu; He, Qiang; Feng, Deng Hua

    The photosynthesis of rice sheath plays a significant role to furnish rice yield, and it is accounted for 10 to 20% of the final yield. But, limited studies have been done to address this phenomenon and to characterize the features of the photosynthetic tissue in rice sheath. In this paper, a super hybrid rice and a hybrid rice were studied as the experimental materials, and the characteristics of the photosynthetic tissue in rice sheaths were examined by microscopic and super-microscopic observation. The results showed that the photosynthetic tissue of rice sheath was rich in the intact mesophyllous cells full of chloroplasts, grana and thylakoids, which were much the same as those of rice blade. The stomatal density in the outer epidermises of the sheaths was comparable to those in the up- and down-epidermises of the blades. The mesophyllous cells in the sheaths were also rich in chlorophylls, and had the net photosynthetic rate (Pn). Therefore, rice sheath was also full of the intact photosynthetic apparatus similar to those in rice blade, and had capabilities of photosynthesis.

  1. Diurnal variations in gas exchange and chlorophyll fluorescence in rice leaves: the cause for midday depression in CO2 photosynthetic rate

    Directory of Open Access Journals (Sweden)

    Debabrata Panda

    2011-12-01

    Full Text Available Gas exchange and chlorophyll fluorescence analysis were carried out to investigate the diurnal variations in photosynthesis in leaves of rice (Oryza sativa L.. Leaf CO2 photosynthetic rate (Pn showed a bimodal diurnal pattern and midday depression in Pn was observed at 13:00 h. Depression in Pn at midday was mostly attributed to stomatal limitation since the reduction in Pn was followed by the significant reduction in stomatal conductance (Gs. Midday depression in Pn was found to be associated with reversible inactivation of Photo-system II (PS II reaction centers and increase of photo-inhibition in response to high intensity as evidenced by the maximum efficiency of PS II (Fv/Fm decreased with increase of light intensity from 6:00 h to 16:00 h of a day. The minimal fluorescence (Fo gradually increased with increasing light intensity and reached its highest value at 13:00 h and on contrary the maximal fluorescence (Fm decreased and reached its lowest value at 13:00 h. Quantification of several chlorophyll fluorescence parameters (JIP-test like area above the fluorescence curve between Fo and Fm, phenomenological energy fluxes like electron transport per cross section (ETo/CS, active PS II reaction center per exited cross-section (RC/CSo and performance index (Pi were low in early morning, increasing with time and reaching a maximum at 9:00 h subsequently decreasing and reaching a minimum value at 13.00 h. On contrary the dissipation per cross-section (Dio/CS gradually increased with increasing light intensity and reached its highest value at 13:00 h. It is likely that PS II down-regulation and heat dissipation co-operated together to prevent the chloroplast from photo damage.

  2. Sink Status and Photosynthetic Rate of the Leaflet Galls Induced byBystracoccus mataybae(Eriococcidae) onMatayba guianensis(Sapindaceae).

    Science.gov (United States)

    Oliveira, Denis C; Moreira, Ana Silvia F P; Isaias, Rosy M S; Martini, Vitor; Rezende, Uiara C

    2017-01-01

    The galling insect Bystracoccus mataybae (Eriococcidae) induces green and intralaminar galls on leaflets of Matayba guianensis (Sapindaceae), and promotes a high oxidative stress in host plant tissues. This biotic stress is assumed by the histochemical detection of hydrogen peroxide, a reactive oxygen species (ROS), whose production alters gall physiology. Thus, we hypothesize that high levels of nutrients are accumulated during gall development in response to a local maintenance of photosynthesis and to the galling insect activity. Moreover, the maintenance of low levels of photosynthesis may guarantee O 2 production and CO 2 consumption, as well as may avoid hypoxia and hypercarbia in gall tissues. To access the photosynthesis performance, the distribution of chlorophyllous tissues and the photochemical and carboxylation rates in gall tissues were analyzed. In addition, histochemical tests for hydrogen peroxide and phenolic derivatives were performed to confirm the biotic stress, and set the possible sites where stress dissipation occurs. The contents of sugars and nitrogen were evaluated to quantify the gall sink. Currently, we assume that the homeostasis in gall tissues is ruptured by the oxidative stress promoted by the galling insect activity. Thus, to supply the demands of gall metabolism, the levels of water-soluble polysaccharides and starch increase in gall tissues. The low values of maximum quantum efficiency of PSII ( F v / F m ) indicate a low photosynthetic performance in gall tissues. In addition, the decrease of PSII operating efficiency, ( F 'm- F ')/ F 'm, and Rfd (instantaneous fluorescence decline ratio in light, to measure tissue vitality) demonstrate that the tissues of B. mataybae galls are more susceptible to damage caused by stressors than the non-galled tissues. Thus, the high oxidative stress in gall developmental sites is dissipated not only by the accumulation of phenolic derivatives in the protoplast, but also of lignins in the walls

  3. Photosynthetic traits of Siebold's beech seedlings in changing light conditions by removal of shading trees under elevated CO₂.

    Science.gov (United States)

    Watanabe, M; Kitaoka, S; Eguchi, N; Watanabe, Y; Satomura, T; Takagi, K; Satoh, F; Koike, T

    2016-01-01

    The purpose of this study was to obtain basic information on acclimation capacity of photosynthesis in Siebold's beech seedlings to increasing light intensity under future elevated CO2 conditions. We monitored leaf photosynthetic traits of these seedlings in changing light conditions (before removal of shade trees, the year after removal of shade trees and after acclimation to open conditions) in a 10-year free air CO2 enrichment experiment in northern Japan. Elevated CO2 did not affect photosynthetic traits such as leaf mass per area, nitrogen content and biochemical photosynthetic capacity of chloroplasts (i.e. maximum rate of carboxylation and maximum rate of electron transport) before removal of the shade trees and after acclimation to open conditions; in fact, a higher net photosynthetic rate was maintained under elevated CO2 . However, in the year after removal of the shade trees, there was no increase in photosynthesis rate under elevated CO2 conditions. This was not due to photoinhibition. In ambient CO2 conditions, leaf mass per area and nitrogen content were higher in the year after removal of shade trees than before, whereas there was no increase under elevated CO2 conditions. These results indicate that elevated CO2 delays the acclimation of photosynthetic traits of Siebold's beech seedlings to increasing light intensity. © 2015 German Botanical Society and The Royal Botanical Society of the Netherlands.

  4. Uncertainties in the Value of Bill Savings from Behind-the-Meter, Residential Photovoltaic Systems: The Roles of Electricity Market Conditions, Retail Rate Design, and Net Metering

    Science.gov (United States)

    Darghouth, Naim Richard

    Net metering has become a widespread policy mechanism in the U.S. for supporting customer adoption of distributed photovoltaics (PV), allowing customers with PV systems to reduce their electric bills by offsetting their consumption with PV generation, independent of the timing of the generation relative to consumption. Although net metering is one of the principal drivers for the residential PV market in the U.S., the academic literature on this policy has been sparse and this dissertation contributes to this emerging body of literature. This dissertation explores the linkages between the availability of net metering, wholesale electricity market conditions, retail rates, and the residential bill savings from behind-the-meter PV systems. First, I examine the value of the bill savings that customers receive under net metering and alternatives to net metering, and the associated role of retail rate design, based on current rates and a sample of approximately two hundred residential customers of California's two largest electric utilities. I find that the bill savings per kWh of PV electricity generated varies greatly, largely attributable to the increasing block structure of the California utilities' residential retail rates. I also find that net metering provides significantly greater bill savings than alternative compensation mechanisms based on avoided costs. However, retail electricity rates may shift as wholesale electricity market conditions change. I then investigate a potential change in market conditions -- increased solar PV penetrations -- on wholesale prices in the short-term based on the merit-order effect. This demonstrates the potential price effects of changes in market conditions, but also points to a number of methodological shortcomings of this method, motivating my usage of a long-term capacity investment and economic dispatch model to examine wholesale price effects of various wholesale market scenarios in the subsequent analysis. By developing

  5. A study of photosynthetic biogas upgrading based on a high rate algal pond under alkaline conditions: Influence of the illumination regime.

    Science.gov (United States)

    Franco-Morgado, Mariana; Alcántara, Cynthia; Noyola, Adalberto; Muñoz, Raúl; González-Sánchez, Armando

    2017-08-15

    Microalgal-bacterial processes have emerged as environmental friendly systems for the cost-effective treatment of anaerobic effluents such as biogas and nutrients-laden digestates. Environmental parameters such as temperature, irradiation, nutrient concentration and pH effect the performance of the systems. In this paper, the potential of a microalgal-bacterial photobioreactor operated under high pH (≈9.5) and high alkalinity to convert biogas into biomethane was evaluated. The influence of the illumination regime (continuous light supply vs 12h/12h light/dark cycles) on the synthetic biogas upgrading efficiency, biomass productivity and nutrient removal efficiency was assessed in a High-Rate Algal Pond interconnected to a biogas absorption bubble column. No significant differences in the removal efficiency of CO2 and H2S (91.5±2% and 99.5%±0.5, respectively) were recorded regardless of the illumination regime. The high fluctuations of the dissolved oxygen concentration during operation under light/dark cycles allowed to evaluate the specific growth rate and the specific partial degradation rate of the microalgae biomass by photosynthesis and respiration, respectively. The respiration reduced the net microalgae biomass productivity under light/dark cycles compared with process operation under the continuous light supply. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. UV sensitivity of planktonic net community production in ocean surface waters

    OpenAIRE

    Regaudie de Gioux, Aurore; Agustí, Susana; Duarte, Carlos M.

    2014-01-01

    The net plankton community metabolism of oceanic surface waters is particularly important as it more directly affects the partial pressure of CO2 in surface waters and thus the air-sea fluxes of CO2. Plankton communities in surface waters are exposed to high irradiance that includes significant ultraviolet blue (UVB, 280-315 nm) radiation. UVB radiation affects both photosynthetic and respiration rates, increase plankton mortality rates, and other metabolic and chemical processes. Here we tes...

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

    African Journals Online (AJOL)

    RuBPCase), Ca2+- adenosinetriphosphatase (Ca2+-ATPase) and Mg2+- adenosine triphosphatase (Mg2+-ATPase) activities, together with nicotinamide adenine dinucleotide phosphate (NADPH) content and photosynthetic O2 evolution rate ...

  8. [Analysis of photosynthetic characteristics and its influencing factors of medicinal plant Mirabilis himalaica].

    Science.gov (United States)

    Guo, Qi-Qiang; Quan, Hong; Lan, Xiao-Zhong; Li, Lian-Qiang; Li, Hui-E

    2014-07-01

    To study photosynthetic characteristics and its influencing factors in leaves of medicinal plant Mirabilis himalaica, and provide an evidence for guiding artificial planting and improving the quantity. The light-response and diurnal photosynthesis course of leaves at the booting stages of 1-3 year old M. himalaica were measured with LI-6400 system. The Results showed that the light response curves were fitted well by non rectangle hyperbola equation (R2 > or = 0.98). The values of the maximum photosynthetic rate (Pmax) and light use efficiency of three-year old M. himalaica leaves were higher than those of 1-2 year old individuals. The diurnal variation of net photosynthetic rate (Pn) and stomatal conductance (Gs) of 2-3 year old M. himalaica were typical double-peak curves determinately regulated by stomatal conductance. However, transpiration rate (Tr) of 1-3 year old plants leaves were single-peak curve, which was self-protection of harm reduction caused by the higher temperature at noontime. Correlation analysis showed that the changes between photosynthetic active radiation (PFD), air temperature (T ) and Pn, were significant positive related. Therefore, M. himalaica is a typical sun plant, which should be planted under the sufficient sunshine field and prolong the growing ages suitably in order to improve the yield.

  9. Mosquito abundance, bed net coverage and other factors associated with variations in sporozoite infectivity rates in four villages of rural Tanzania

    DEFF Research Database (Denmark)

    Kweka, Eliningaya J; Nkya, Watoky M M; Mahande, Aneth M

    2008-01-01

    . Sporozoite infectivity rates, mosquito host blood meal source, bed net coverage and mosquito abundance were assessed in this study. METHODOLOGY: A longitudinal survey was conducted in four villages in two regions of Tanzania. Malaria vectors were sampled using the CDC light trap and pyrethrum spray catch......,628 (81.8%) Anopheles arabiensis, 1,100 (15.9%) Culex quinquefasciatus, 89 (1.4%) Anopheles funestus, and 66 (0.9%) Anopheles gambiae s.s. Of the total mosquitoes collected 3,861 were captured by CDC light trap and 3,022 by the pyrethrum spray catch method. The overall light trap: spray catch ratio was 1.......3:1. Mosquito densities per room were 96.5 and 75.5 for light trap and pyrethrum spray catch respectively. Mosquito infectivity rates between villages that have high proportion of bed net owners and those without bed nets was significant (P

  10. Effects of a clearcut on the net rates of nitrification and N mineralization in a northern hardwood forest, Catskill Mountains, New York, USA

    Science.gov (United States)

    Burns, Douglas A.; Murdoch, Peter S.

    2005-01-01

    The Catskill Mountains of southeastern New York receive among the highest rates of atmospheric nitrogen (N) deposition in eastern North America, and ecosystems in the region may be sensitive to human disturbances that affect the N cycle. We studied the effects of a clearcut in a northern hardwood forest within a 24-ha Catskill watershed on the net rates of N mineralization and nitrification in soil plots during 6 years (1994-1999) that encompassed 3-year pre- and post-harvesting periods. Despite stream NO3- concentrations that increased by more than 1400 ??mol l-1 within 5 months after the clearcut, and three measures of NO3- availability in soil that increased 6- to 8-fold during the 1st year after harvest, the net rates of N mineralization and nitrification as measured by in situ incubation in the soil remained unchanged. The net N-mineralization rate in O-horizon soil was 1- 2 mg N kg-1 day-1 and the net nitrification rate was about 1 mg N kg-1 day-1, and rates in B-horizon soil were only one-fifth to one-tenth those of the O-horizon. These rates were obtained in single 625 m2 plots in the clearcut watershed and reference area, and were confirmed by rate measurements at 6 plots in 1999 that showed little difference in N-mineralization and nitrification rates between the treatment and reference areas. Soil temperature increased 1 ?? 0.8??C in a clearcut study plot relative to a reference plot during the post-harvest period, and soil moisture in the clearcut plot was indistinguishable from that in the reference plot. These results are contrary to the initial hypothesis that the clearcut would cause net rates of these N-cycling processes to increase sharply. The in situ incubation method used in this study isolated the samples from ambient roots and thereby prevented plant N uptake; therefore, the increases in stream NO3- concentrations and export following harvest largely reflect diminished uptake. Changes in temperature and moisture after the clearcut were

  11. Disentangling the contributions of ontogeny and water stress to photosynthetic limitations in almond trees.

    Science.gov (United States)

    Egea, Gregorio; González-Real, María M; Baille, Alain; Nortes, Pedro A; Diaz-Espejo, Antonio

    2011-06-01

    Very few studies have attempted to disentangle the respective role of ontogeny and water stress on leaf photosynthetic attributes. The relative significance of both effects on photosynthetic attributes has been investigated in leaves of field-grown almond trees [Prunus dulcis (Mill.) D. A. Webb] during four growth cycles. Leaf ontogeny resulted in enhanced leaf dry weight per unit area (W(a)), greater leaf dry-to-fresh weight ratio and lower N content per unit of leaf dry weight (N(w)). Concomitantly, area-based maximum carboxylation rate (V(cmax)), maximum electron transport rate (J(max)), mesophyll conductance to CO₂ diffusion (gm)' and light-saturated net photosynthesis (A(max)) declined in both well-watered and water-stressed almond leaves. Although g(m) and stomatal conductance (g(s)) seemed to be co-ordinated, a much stronger coordination in response to ontogeny and prolonged water stress was observed between g(m) and the leaf photosynthetic capacity. Under unrestricted water supply, the leaf age-related decline of A(max) was equally driven by diffusional and biochemical limitations. Under restricted soil water availability, A(max) was mainly limited by g(s) and, to a lesser extent, by photosynthetic capacity and g(m). When both ontogeny and water stress effects were combined, diffusional limitations was the main determinant of photosynthesis limitation, while stomatal and biochemical limitations contributed similarly. © 2011 Blackwell Publishing Ltd.

  12. Measuring the impact of motivation on achievement and course completion rates in MarineNet distance education

    OpenAIRE

    Lindshield, Timothy D.

    2016-01-01

    Approved for public release; distribution is unlimited The Marine Corps Distance Learning Network (MarineNet) is the primary source for distance education (DE) and online training for the Marine Corps. This research applies the learning theory of human motivation to archival MarineNet data to determine if motivation factors impact academic performance and course completion. The literature on motivation divides this variable into multiple types of intrinsic and extrinsic motivations. Each t...

  13. 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

  14. Kinetics of H+ ion binding by the P+QA-state of bacterial photosynthetic reaction centers: rate limitation within the protein.

    Science.gov (United States)

    Maróti, P; Wraight, C A

    1997-07-01

    The kinetics of flash-induced H+ ion binding by isolated reaction centers (RCs) of Rhodobacter sphaeroides, strain R-26, were measured, using pH indicators and conductimetry, in the presence of terbutryn to block electron transfer between the primary and secondary quinones (QA and QB), and in the absence of exogenous electron donors to the oxidized primary donor, P+, i.e., the P+QA-state. Under these conditions, proton binding by RCs is to the protein rather than to any of the cofactors. After light activation to form P+QA-, the kinetics of proton binding were monoexponential at all pH values studied. At neutral pH, the apparent bimolecular rate constant was close to the diffusional limit for proton transfer in aqueous solution (approximately 10(11) M-1 s-1), but increased significantly in the alkaline pH range (e.g., 2 x 10(13) M-1 s-1 at pH 10). The average slope of the pH dependence was -0.4 instead of -1.0, as might be expected for a H+ diffusion-controlled process. High activation energy (0.54 eV at pH 8.0) and weak viscosity dependence showed that H+ ion uptake by RCs is not limited by diffusion. The salt dependence of the H+ ion binding rate and the pK values of the protonatable amino acid residues of the reaction center implicated surface charge influences, and Gouy-Chapman theory provided a workable description of the ionic effects as arising from modulation of the pH at the surface of the RC. Incubation in D2O caused small increases in the pKs of the protonatable groups and a small, pH (pD)-dependent slowing of the binding rate. The salt, pH, temperature, viscosity, and D2O dependences of the proton uptake by RCs in the P+QA- state were accounted for by three considerations: 1) parallel pathways of H+ delivery to the RC, contributing to the observed (net) H+ disappearance; 2) rate limitation of the protonation of target groups within the protein by conformational dynamics; and 3) electrostatic influences of charged groups in the protein, via the surface pH.

  15. Discussion of Yellow Starthistle Response to Photosynthetic Irradiance, Photoperiod, and CO2

    Science.gov (United States)

    Bubenheim, David

    2017-01-01

    Yellow Starthistle (Centaurea solstitialis) is a native annual weed of Eurasia and since introduction into the United STates has become an invasive and noxious weed. It grows in a rosette habit during the vegetative state and usually bolts in summer to produce a large and branched flowering stem. Time to flowering in Yellow Starthistle has been attributed to photoperiod, nitrogen nutrition, temperature, and water stress. We executed a series of studies to investigate the role of light, both photoperiod and photosynthetic photon flux, on flowering and development in Yellow Starthistle. Treatments were presented in 4 ways: 1) varying day length with constant photosynthetic photon flus (PPF) providing increasing daily integrated Photosynthetic Photon (PP) exposure with longer day lengths 2) varying day length while adjusting PPF to maintain daily PP exposure for all treatments 3) extending photoperiod treatments beyond common 12-h photosynthetic period with low light levels to maintain both PPF and daily PP across all treatments4)reciprocal exchange of plant among photoperiod treatments Yellow Starthistle appears to be a long-day plant with a critical day length requirement between 14-h and 16-h to induce transition from vegetative to floral stages in development. PPF and daily absorbed photons did not affect time to vegetative floral stage transition, but did affect factors such as biomass accumulation and canopy parameters such as specific leaf mass. Reciprocal exchange of plants between floral inducing and inhibiting photoperiod treatments, starting at 2-weeks post germination, had no effect on to flower. Flowering was determined by photoperiod experienced during the first 2-weeks (or less) post germination.Yellow Starthistle net photosynthetic response to elevated atmospheric CO2 concentrations over a range of photosynthetically active radiation flux rates and temperatures will also be presented and discussed.

  16. In situ filtering rate variability in egg and larval surveys off the Pacific coast of Japan: Do plankton nets clog or over-filter in the sea?

    Science.gov (United States)

    Takasuka, Akinori; Tadokoro, Kazuaki; Okazaki, Yuji; Ichikawa, Tadafumi; Sugisaki, Hiroya; Kuroda, Hiroshi; Oozeki, Yoshioki

    2017-02-01

    In situ filtering rate variability was examined for vertical tows of plankton nets in egg and larval surveys off the Pacific coast of Japan, based on a data set pooled over large spatial and temporal scales (76,444 sampling tows from 1978 to 2013). The filtering rate showed unimodal distributions and was highly variable for the four net types: Long NORPAC (LNP), NORPAC (NOR), Maru-toku B (MTB), and Maru-naka (MNK). Despite the high variability at the individual tow level, the median values of the filtering rate for the overall data approximated the theoretical value of 1.0, in particular, for LNP, although the median values differed among the net types. For LNP, the differences in the median values among the 26 years, the 12 months, and the 4 regions were small relative to the overall variability at the individual level. The present study quantified the extent of underestimation/overestimation when the theoretical value of 1.0 is used due to the lack of the actual filtering rate data. The filtering rate was almost on a balance of resistance effect of net and cod-end, clogging effect of collected organisms, and over-inflow effect of currents over large scales. The present analysis implies that the filtering rate is mainly influenced by small-scale transient variability of ocean conditions such as wind speed, current intensity, rolling, turbulence, and mixing rather than large-scale variability related to climate regime, seasonality, or water masses. The results will allow the utilization of historical data lacking flow-meter data for large-scale comparative analyses.

  17. 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

  18. Biophysical consequences of photosynthetic temperature acclimation for climate

    Science.gov (United States)

    Smith, Nicholas G.; Lombardozzi, Danica; Tawfik, Ahmed; Bonan, Gordon; Dukes, Jeffrey S.

    2017-03-01

    Photosynthetic temperature acclimation is a commonly observed process that is increasingly being incorporated into Earth System Models (ESMs). While short-term acclimation has been shown to increase carbon storage in the future, it is uncertain whether acclimation will directly influence simulated future climate through biophysical mechanisms. Here, we used coupled atmosphere-biosphere simulations using the Community Earth System Model (CESM) to assess how acclimation-induced changes in photosynthesis influence global climate under present-day and future (RCP 8.5) conditions. We ran four 30 year simulations that differed only in sea surface temperatures and atmospheric CO2 (present or future) and whether a mechanism for photosynthetic temperature acclimation was included (yes or no). Acclimation increased future photosynthesis and, consequently, the proportion of energy returned to the atmosphere as latent heat, resulting in reduced surface air temperatures in areas and seasons where acclimation caused the biggest increase in photosynthesis. However, this was partially offset by temperature increases elsewhere, resulting in a small, but significant, global cooling of 0.05°C in the future, similar to that expected from acclimation-induced increases in future land carbon storage found in previous studies. In the present-day simulations, the photosynthetic response was not as strong and cooling in highly vegetated regions was less than warming elsewhere, leading to a net global increase in temperatures of 0.04°C. Precipitation responses were variable and rates did not change globally in either time period. These results, combined with carbon-cycle effects, suggest that models without acclimation may be overestimating positive feedbacks between climate and the land surface in the future.

  19. Red and Blue Lights Significantly Affect Photosynthetic Properties and Ultrastructure of Mesophyll Cells in Senescing Grape Leaves

    Directory of Open Access Journals (Sweden)

    Shuai Wang

    2016-03-01

    Full Text Available Light quality significantly affects photosynthetic efficiency in plants. The mechanisms for how light quality affects photosynthesis in grape is poorly understood. Therefore, to investigate the effects of different light qualities on chloroplast ultrastructure and photosynthesis efficiency, two grape cultivars ‘Italia’ (slower speed of leaf senescence and ‘Centennial Seedless’ (faster speed of leaf senescence grown under protected and delayed conditions were used. The three treatments, replicated three times, were control (no supplemental lighting, red light and blue light. Chlorophyll content, net photosynthetic rate, and the ratio of Fv/Fm significantly increased in red light relative to the control. The opposite trend was observed in blue light in the early phase of leaf senescence. At later stages, physiological indexes were gradually higher than that of control, resulting in a delay in leaf senescence. Compared to the control, red and blue light both significantly increased the chlorophyll a/b ratio. Electron microscopy showed that blue light caused severe damage to the fine structure of chloroplasts at early stages of leaf senescence, but effects at later stages of leaf senescence became less severe compared to the control. The degradation of chloroplast ultrastructure was apparently delayed in red light throughout the experimental timeframe compared to other treatments. In this experiment, ‘Italia’ showed higher chlorophyll content, net photosynthetic rate, ratios of Fv/Fm, chlorophyll a/b and better preserved chloroplast ultrastructure relative to ‘Centennial Seedless’, resulting in a slower rate of leaf senescence.

  20. The Influence of Different Interstock Lengths of Minneola Tanjelo on Photosynthetic Parameters and Fruit Yield of Star Ruby Grapefruit

    Directory of Open Access Journals (Sweden)

    Bilge Yılmaz

    2014-04-01

    Full Text Available In this study, Minneola Tangelo hybrid, a cross of grapefruit and mandarin (Duncan grapefruit x Dancy mandarin, used as interstock to Star Ruby grapefruit with different lengths. Effects of different interstock lengths on fruit yield and quality, plant development and photosynthetic parameters were investigated. According to the results, different interstock lengths significantly affected fruit yield and size. The highest fruit yield was determined in T-M20-S whereas the lowest was on T-M5-S. The highest fruit size were determined in Star Ruby fruits on T-M5-S and T-M40-S whereas the lowest on T-M20-S and T-S (control. T-M40-S and T-M20-S treatments markedly reduced stem diameter and tree canopy in comparison to other treatments and control. Usage of different interstock lengths did not significantly affected some of fruit quality traits, net photosynthetic rate, stomatal conductance, leaf transpiration rate, leaf water usage efficiency and leaf chlorophyll concentration. In regards to seasonal changes, net photosynthetic rate were higher in spring and summer seasons then winter and fall seasons.

  1. Do photosynthetic limitations of evergreen Quercus ilex leaves change with long-term increased drought severity?

    Science.gov (United States)

    Limousin, Jean-Marc; Misson, Laurent; Lavoir, Anne-Violette; Martin, Nicolas K; Rambal, Serge

    2010-05-01

    Seasonal drought can severely impact leaf photosynthetic capacity. This is particularly important for Mediterranean forests, where precipitation is expected to decrease as a consequence of climate change. Impacts of increased drought on the photosynthetic capacity of the evergreen Quercus ilex were studied for two years in a mature forest submitted to long-term throughfall exclusion. Gas exchange and chlorophyll fluorescence were measured on two successive leaf cohorts in a control and a dry plot. Exclusion significantly reduced leaf water potential in the dry treatment. In both treatments, light-saturated net assimilation rate (A(max)), stomatal conductance (g(s)), maximum carboxylation rate (V(cmax)), maximum rate of electron transport (J(max)), mesophyll conductance to CO2 (g(m)) and nitrogen investment in photosynthesis decreased markedly with soil water limitation during summer. The relationships between leaf photosynthetic parameters and leaf water potential remained identical in the two treatments. Leaf and canopy acclimation to progressive, long-term drought occurred through changes in leaf area index, leaf mass per area and leaf chemical composition, but not through modifications of physiological parameters.

  2. Response of Eustoma Leaf Phenotype and Photosynthetic Performance to LED Light Quality

    Directory of Open Access Journals (Sweden)

    Md Zohurul Kadir Roni

    2017-10-01

    Full Text Available In a controlled environment, light from light-emitting diodes (LEDs has been associated with affecting the leaf characteristics of Eustoma. LEDs help plant growth and development, yet little is known about photosynthetic performance and related anatomical features in the early growth stage of Eustoma leaves. In this study, we examined the effects of blue (B, red (R, and white (W LEDs on the photosynthetic performance of Eustoma leaves, as well as leaf morphology and anatomy including epidermal layer thickness, palisade cells, and stomatal characteristics. Leaves grown under B LEDs were thicker and had a higher chlorophyll content than those grown under the R and W LEDs. Leaves under B LEDs had greater net photosynthetic rates (A, stomatal conductance (gs, and transpiration rates (E, especially at a higher photon flux density (PPFD, that resulted in a decrease in the intercellular CO2 concentration (Ci, than leaves under the W and R LEDs. B LEDs resulted in greater abaxial epidermal layer thickness and palisade cell length and width than the R and W LED treatments. The palisade cells also developed a more cylindrical shape in response to the B LEDs. B LED leaves also showed greater guard cell length, breadth, and area, and stomatal density, than W or R LEDs, which may contribute to increased A, gs and E at higher PPFDs.

  3. Variation of photosynthetic tolerance of rice cultivars (Oryza sativa L ...

    African Journals Online (AJOL)

    STORAGESEVER

    2010-03-01

    Mar 1, 2010 ... Photosynthetic characteristics of two cultivars tolerant (c.v. Taipei309 and Wuyujing3), two cultivars sensitive (c.v.CA212 and ... Key words: Rice, chilling tolerance, photosynthetic rate, photo-system, chilling stress, photooxidation, gluthione ...... response to low temperature: an overview.-Lyons JM. Low.

  4. Low temperature leaf photosynthesis of a Miscanthus germplasm collection correlates positively to shoot growth rate and specific leaf area

    DEFF Research Database (Denmark)

    Jiao, Xiurong; Sørensen, Kirsten Kørup; Andersen, Mathias Neumann

    2016-01-01

    were selected and grown under warm (24 °C) and cold (14 °C) conditions in a controlled environment. Dark-adapted chlorophyll fluorescence, specific leaf area (SLA) and net photosynthetic rate at a photosynthetically active radiation (PAR) of 1000 μmol m–2 s–1 (A1000) were measured. Photosynthetic light......Background and Aims The C4 perennial grass miscanthus has been found to be less sensitive to cold than most other C4 species, but still emerges later in spring than C3 species. Genotypic differences in miscanthus were investigated to identify genotypes with a high cold tolerance at low temperatures...

  5. Net Locality

    DEFF Research Database (Denmark)

    de Souza e Silva, Adriana Araujo; Gordon, Eric

    Provides an introduction to the new theory of Net Locality and the profound effect on individuals and societies when everything is located or locatable. Describes net locality as an emerging form of location awareness central to all aspects of digital media, from mobile phones, to Google Maps...... of emerging technologies, from GeoCities to GPS, Wi-Fi, Wiki Me, and Google Android....

  6. Net Neutrality

    DEFF Research Database (Denmark)

    Savin, Andrej

    2017-01-01

    Repealing “net neutrality” in the US will have no bearing on Internet freedom or security there or anywhere else.......Repealing “net neutrality” in the US will have no bearing on Internet freedom or security there or anywhere else....

  7. Reduction of Net Sulfide Production Rate by Nitrate in Wastewater Bioreactors. Kinetics and Changes in the Microbial Community

    DEFF Research Database (Denmark)

    Villahermosa, Desiree; Corzo, Alfonso; Gonzalez, J M

    2013-01-01

    Nitrate addition stimulated sulfide oxidation by increasing the activity of nitrate-reducing sulfide-oxidizing bacteria (NR-SOB), decreasing the concentration of dissolved H2S in the water phase and, consequently, its release to the atmosphere of a pilot-scale anaerobic bioreactor. The effect...... of four different concentrations of nitrate (0.12, 0.24, 0.50, and 1.00 mM) was investigated for a period of 3 days in relation to sulfide concentration in two bioreactors set up at Guadalete wastewater treatment plant (Jerez de la Frontera, Spain). Physicochemical variables were measured in water and air......, and the activity of bacteria implicated in the sulfur and nitrogen cycles was analyzed in the biofilms and in the water phase of the bioreactors. Biofilms were a net source of sulfide for the water and gas phases (7.22 ± 5.3 μmol s−1) in the absence of nitrate dosing. Addition of nitrate resulted in a quick...

  8. Photosynthetic stimulation under long-term CO2 enrichment and fertilization is sustained across a closed Populus canopy profile (EUROFACE).

    Science.gov (United States)

    Liberloo, Marion; Tulva, Ingmar; Raïm, Olaf; Kull, Olevi; Ceulemans, Reinhart

    2007-01-01

    The long-term response of leaf photosynthesis to rising CO2 concentrations [CO2] depends on biochemical and morphological feedbacks. Additionally, responses to elevated [CO2] might depend on the nutrient availability and the light environment, affecting the net carbon uptake of a forest stand. After 6 yr of exposure to free-air CO2 enrichment (EUROFACE) during two rotation cycles (with fertilization during the second cycle), profiles of light, leaf characteristics and photosynthetic parameters were measured in the closed canopy of a poplar (Populus) short-rotation coppice. Net photosynthetic rate (A(growth)) was 49% higher in poplars grown in elevated [CO2], independently of the canopy position. Jmax significantly increased (15%), whereas leaf carboxylation capacity (Vcmax), leaf nitrogen (N(a)) and chlorophyll (Chl(a)) were unaffected in elevated [CO2]. Leaf mass per unit area (LMA) increased in the upper canopy. Fertilization created more leaves in the top of the crown. These results suggest that the photosynthetic stimulation by elevated [CO2] in a closed-canopy poplar coppice might be sustained in the long term. The absence of any down-regulation, given a sufficient sink capacity and nutrient availability, provides more carbon for growth and storage in this bioenergy plantation.

  9. Synergic effect of salinity and CO2 enrichment on growth and photosynthetic responses of the invasive cordgrass Spartina densiflora.

    Science.gov (United States)

    Mateos-Naranjo, Enrique; Redondo-Gómez, Susana; Alvarez, Rosario; Cambrollé, Jesús; Gandullo, Jacinto; Figueroa, M Enrique

    2010-06-01

    Spartina densiflora is a C(4) halophytic species that has proved to have a high invasive potential which derives from its clonal growth and its physiological plasticity to environmental factors, such as salinity. A greenhouse experiment was designed to investigate the synergic effect of 380 and 700 ppm CO(2) at 0, 171, and 510 mM NaCl on the growth and the photosynthetic apparatus of S. densiflora by measuring chlorophyll fluorescence parameters, gas exchange and photosynthetic pigment concentrations. PEPC activity and total ash, sodium, potassium, calcium, magnesium, and zinc concentrations were determined, as well as the C/N ratio. Elevated CO(2) stimulated growth of S. densiflora at 0 and 171 mM NaCl external salinity after 90 d of treatment. This growth enhancement was associated with a greater leaf area and improved leaf water relations rather than with variations in net photosynthetic rate (A). Despite the fact that stomatal conductance decreased in response to 700 ppm CO(2) after 30 d of treatment, A was not affected. This response of A to elevated CO(2) concentration might be explained by an enhanced PEPC carboxylation capacity. On the whole, plant nutrient concentrations declined under elevated CO(2), which can be ascribed to the dilution effect caused by an increase in biomass and the higher water content found at 700 ppm CO(2). Finally, CO(2) and salinity had a marked overall effect on the photochemical (PSII) apparatus and the synthesis of photosynthetic pigments.

  10. Pressures on safety net access: the level of managed care penetration and uninsurance rate in a community

    National Research Council Canada - National Science Library

    Cunningham, P J

    1999-01-01

    To examine the effects of managed care penetration and the uninsurance rate in an area on access to care of low-income uninsured persons and to compare differences in access between low-income insured...

  11. 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.

  12. 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.

  13. The HLA-net GENE[RATE] pipeline for effective HLA data analysis and its application to 145 population samples from Europe and neighbouring areas.

    Science.gov (United States)

    Nunes, J M; Buhler, S; Roessli, D; Sanchez-Mazas, A

    2014-05-01

    In this review, we present for the first time an integrated version of the Gene[rate] computer tools which have been developed during the last 5 years to analyse human leukocyte antigen (HLA) data in human populations, as well as the results of their application to a large dataset of 145 HLA-typed population samples from Europe and its two neighbouring areas, North Africa and West Asia, now forming part of the Gene[va] database. All these computer tools and genetic data are, from now, publicly available through a newly designed bioinformatics platform, HLA-net, here presented as a main achievement of the HLA-NET scientific programme. The Gene[rate] pipeline offers user-friendly computer tools to estimate allele and haplotype frequencies, to test Hardy-Weinberg equilibrium (HWE), selective neutrality and linkage disequilibrium, to recode HLA data, to convert file formats, to display population frequencies of chosen alleles and haplotypes in selected geographic regions, and to perform genetic comparisons among chosen sets of population samples, including new data provided by the user. Both numerical and graphical outputs are generated, the latter being highly explicit and of publication quality. All these analyses can be performed on the pipeline after scrupulous validation of the population sample's characterisation and HLA typing reporting according to HLA-NET recommendations. The Gene[va] database offers direct access to the HLA-A, -B, -C, -DQA1, -DQB1, -DRB1 and -DPB1 frequencies and summary statistics of 145 population samples having successfully passed these HLA-NET 'filters', and representing three European subregions (South-East, North-East and Central-West Europe) and two neighbouring areas (North Africa, as far as Sudan, and West Asia, as far as South India). The analysis of these data, summarized in this review, shows a substantial genetic variation at the regional level in this continental area. These results have main implications for population genetics

  14. 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.

  15. Growth and photosynthetic responses of the cordgrass Spartina maritima to CO2 enrichment and salinity.

    Science.gov (United States)

    Mateos-Naranjo, E; Redondo-Gómez, S; Andrades-Moreno, L; Davy, A J

    2010-10-01

    Future climatic scenarios combine increasing concentrations of atmospheric CO(2) and rising sea levels. Spartina maritima is a C(4) halophyte that is an important pioneer and ecosystem engineer in salt marshes of the Atlantic coast of southern Europe. A glasshouse experiment investigated the combined effects on its growth and photosynthetic apparatus of approximately doubling CO(2) concentration (from 380 to 700 μmol mol(-1)) at a range of salinity (0, 171 and 510 mM NaCl). We measured relative growth rates, gas exchange, chlorophyll fluorescence parameters, photosynthetic pigment concentrations, and total ash, Na(+), K(2+), Ca(2+) and N concentrations. Elevated CO(2) stimulated growth of S. maritima by c. 65% at all external salinities; this growth enhancement was associated with greater net photosynthetic rate (A) and improved leaf water relations. A increased despite a drop in stomatal conductance in response to 700 μmol mol(-1) CO(2). CO(2) and salinity had a marked overall effect on the photochemical (PSII) apparatus and the synthesis of photosynthetic pigments. Φ(PSII) values at midday decreased significantly with external salinity in plants grown at 380 μmol mol(-1) CO(2); and F(v)/F(m) and Φ(PSII) values were higher at 700 μmol mol(-1) CO(2) in presence of NaCl. Plant nutrient concentrations declined under elevated CO(2), which can be ascribed to the dilution effect caused by an increase in biomass. The results suggest that the productivity S. maritima and the ecosystem services it provides will increase in likely future climatic scenarios. Copyright © 2010 Elsevier Ltd. All rights reserved.

  16. Tingkat Insidensi Malaria di Wilayah Pemanasan Kelambu Berinsektisida Tahan Lama dan Wilayah Kontrol (MALARIA INCIDENCE RATE OF HEAT ASSISTED REGENERATION LONG LASTING INSECTICIDAL NETS AREA AND CONTROL

    Directory of Open Access Journals (Sweden)

    Etih Sudarnika

    2012-03-01

    Full Text Available Long lasting insecticidal nets (LLIN is one effective way to prevent malaria. Permethrin treatedLLIN is one type of LLIN which is recommended by WHO. Several studies have shown that these types ofLLIN requiring heat assisted regeneration after washing to enhance the biological activity of insecticidethat contained in the LLIN fibers. This study aimed to compare the incidence rates of malaria in childrenunder five years old who live in the intervention area (where the heat assisted regeneration on LLIN afterwashing was applied and control area (where the heat assisted regeneration on LLIN after washing wasnot applied. Data of malaria cases was collected from laboratory log book at all health centers in BangkaDistrict, in the period of June June 2007 until July 2008. Data were analyzed with Poisson regressionmodels. The results showed that the incidence rate of malaria in children under five years old was notsignificantly different between the treatment and control areas.

  17. Beneficial roles of melatonin on redox regulation of photosynthetic electron transport and synthesis of D1 protein in tomato seedlings under salt stress

    Directory of Open Access Journals (Sweden)

    Xiaoting Zhou

    2016-11-01

    Full Text Available Melatonin is important in the protection of plants suffering various forms of abiotic stress. The molecular mechanisms underlying the melatonin-mediated protection of their photosynthetic machinery are not completely resolved. This study investigates the effects of exogenous melatonin applications on salt-induced damage to the light reaction components of the photosynthetic machinery of tomato seedlings. The results show that melatonin pretreatments can help maintain growth and net photosynthetic rate (PN under salt stress conditions. Pretreatment with melatonin increased the effective quantum yield of photosystem II (ΦPSII, the photochemical quenching coefficient (qP and the proportion of PSII centers that are ‘open’ (qL under saline conditions. In this way, damage to the photosynthetic electron transport chain (PET in photosystem II (PSII is mitigated. In addition, melatonin pretreatment facilitated the repair of PSII by maintaining the availability of D1 protein that was otherwise reduced by salinity. The ROS levels and the gene expressions of the chloroplast TRXs and PRXs were also investigated. Salt stress resulted in increased levels of reactive oxygen species (ROS, which were mitigated by melatonin. In tomato leaves under salt stress, the expressions of PRXs and TRXf declined but the expressions of TRXm1/4 and TRXm2 increased. Melatonin pretreatment promoted the expression of TRXf and the abundances of TRXf and TRXm gene products but had no effects on the expressions of PRXs. In summary, melatonin improves the photosynthetic activities of tomato seedlings under salt stress. The mechanism could be that: (1 Melatonin controls ROS levels and prevents damaging elevations of ROS caused by salt stress. (2 Melatonin facilitates the recovery of PET and D1 protein synthesis, thus enhancing the tolerance of photosynthetic activities to salinity. (3 Melatonin induces the expression of TRXf and regulates the abundance of TRXf and TRXm gene

  18. 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)

  19. RESTful NET

    CERN Document Server

    Flanders, Jon

    2008-01-01

    RESTful .NET is the first book that teaches Windows developers to build RESTful web services using the latest Microsoft tools. Written by Windows Communication Foundation (WFC) expert Jon Flanders, this hands-on tutorial demonstrates how you can use WCF and other components of the .NET 3.5 Framework to build, deploy and use REST-based web services in a variety of application scenarios. RESTful architecture offers a simpler approach to building web services than SOAP, SOA, and the cumbersome WS- stack. And WCF has proven to be a flexible technology for building distributed systems not necessa

  20. Photosynthetic oxygen production in a warmer ocean: the Sargasso Sea as a case study

    Science.gov (United States)

    Richardson, Katherine; Bendtsen, Jørgen

    2017-08-01

    Photosynthetic O2 production can be an important source of oxygen in sub-surface ocean waters especially in permanently stratified oligotrophic regions of the ocean where O2 produced in deep chlorophyll maxima (DCM) is not likely to be outgassed. Today, permanently stratified regions extend across approximately 40% of the global ocean and their extent is expected to increase in a warmer ocean. Thus, predicting future ocean oxygen conditions requires a better understanding of the potential response of photosynthetic oxygen production to a warmer ocean. Based on our own and published observations of water column processes in oligotrophic regions, we develop a one-dimensional water column model describing photosynthetic oxygen production in the Sargasso Sea to quantify the importance of photosynthesis for the downward flux of O2 and examine how it may be influenced in a warmer ocean. Photosynthesis is driven in the model by vertical mixing of nutrients (including eddy-induced mixing) and diazotrophy and is found to substantially increase the downward O2 flux relative to physical-chemical processes alone. Warming (2°C) surface waters does not significantly change oxygen production at the DCM. Nor does a 15% increase in re-mineralization rate (assuming Q10 = 2; 2°C warming) have significant effect on net sub-surface oxygen accumulation. However, changes in the relative production of particulate (POM) and dissolved organic material (DOM) generate relatively large changes in net sub-surface oxygen production. As POM/DOM production is a function of plankton community composition, this implies plankton biodiversity and food web structure may be important factors influencing O2 production in a warmer ocean. This article is part of the themed issue 'Ocean ventilation and deoxygenation in a warming world'.

  1. Photosynthetic responses to understory shade and elevated carbon dioxide concentration in four northern hardwood tree species.

    Science.gov (United States)

    Sefcik, Lesley T; Zak, Donald R; Ellsworth, David S

    2006-12-01

    Seedling responses to elevated atmospheric CO(2) concentration ([CO(2)]) and solar irradiance were measured over two growing seasons in shade-tolerant Acer saccharum Marsh. and Fagus grandifolia J.F. Ehrh. and shade-intolerant Prunus serotina, a J.F. Ehrh. and Betula papyrifera Marsh. Seedlings were exposed to a factorial combination of [CO2] (ambient and elevated (658 micromol mol-1)) and understory shade (deep and moderate) in open-top chambers placed in a forest understory. The elevated [CO(2)] treatment increased mean light-saturated net photosynthetic rate by 63% in the shade-tolerant species and 67% in the shade-intolerant species. However, when measured at the elevated [CO(2)], long-term enhancement of photosynthesis was 10% lower than the instantaneous enhancement seen in ambient-[CO(2)]-grown plants (P < 0.021). Overall, growth light environment affected long-term photosynthetic enhancement by elevated [CO(2)]: as the growth irradiance increased, proportional enhancement due to elevated [CO(2)] decreased from 97% for plants grown in deep shade to 47% for plants grown in moderate shade. Results suggest that in N-limited northern temperate forests, trees grown in deep shade may display greater photosynthetic gains from a CO(2)-enriched atmosphere than trees growing in more moderate shade, because of greater downregulation in the latter environment. If photosynthetic gains by deep-shade-grown plants in response to elevated [CO(2)] translate into improved growth and survival of shade-intolerant species, it could alter the future composition and dynamics of successional forest communities.

  2. NetSig

    DEFF Research Database (Denmark)

    Horn, Heiko; Lawrence, Michael S; Chouinard, Candace R

    2018-01-01

    Methods that integrate molecular network information and tumor genome data could complement gene-based statistical tests to identify likely new cancer genes; but such approaches are challenging to validate at scale, and their predictive value remains unclear. We developed a robust statistic (Net......Sig) that integrates protein interaction networks with data from 4,742 tumor exomes. NetSig can accurately classify known driver genes in 60% of tested tumor types and predicts 62 new driver candidates. Using a quantitative experimental framework to determine in vivo tumorigenic potential in mice, we found that Net......Sig candidates induce tumors at rates that are comparable to those of known oncogenes and are ten-fold higher than those of random genes. By reanalyzing nine tumor-inducing NetSig candidates in 242 patients with oncogene-negative lung adenocarcinomas, we find that two (AKT2 and TFDP2) are significantly amplified...

  3. Genotypic variations in photosynthetic and physiological adjustment to potassium deficiency in cotton (Gossypium hirsutum).

    Science.gov (United States)

    Wang, Ning; Hua, Hanbai; Eneji, A Egrinya; Li, Zhaohu; Duan, Liusheng; Tian, Xiaoli

    2012-05-02

    A hydroponic culture experiment was conducted to determine genotypic variation in photosynthetic rate and the associated physiological changes in response to potassium (K) deficiency in cotton (Gossypium hirsutum L.) seedlings with contrasting two cotton cultivars in K efficiency. The K-efficient Liaomian18 produced 66.7% more biomass than the K-inefficient NuCOTN99(B) under K deficiency, despite their similar biomass under K sufficiency. Compared with NuCOTN99(B), Liaomian18 showed 19.4% higher net photosynthetic rate (P(n), per unit leaf area) under K deficient solutions and this was associated with higher photochemical efficiency and faster export of soluble sugars from the phloem. The lower net P(n) of NuCOTN99(B) was attributed to higher capacity for nitrate assimilation and lower export of soluble sugars. Furthermore, NuCOTN99(B) showed 38.4% greater ETR/P(n) than Liaomian18 under K deficiency, indicating that more electrons were driven to other sinks. Higher superoxide dismutase (SOD) and lower catalase (CAT) and ascorbate peroxidase (APX) activities resulted in higher levels of reactive oxygen species (ROS; e.g. O(2)(-)and H(2)O(2)) in NuCOTN99(B) relative to Liaomian18. Thus, the K inefficiency of NuCOTN99(B), indicated by lower biomass and net P(n) under K deficiency, was associated with excessively high nitrogen assimilation, lower export of carbon assimilates, and greater ROS accumulation in the leaf. Crown Copyright © 2012. Published by Elsevier B.V. All rights reserved.

  4. Petri Nets

    Indian Academy of Sciences (India)

    Associate Professor of. Computer Science and. Automation at the Indian. Institute of Science,. Bangalore. His research interests are broadly in the areas of stochastic modeling and scheduling methodologies for future factories; and object oriented modeling. GENERAL I ARTICLE. Petri Nets. 1. Overview and Foundations.

  5. Petri Nets

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 4; Issue 8. Petri Nets - Overview and Foundations. Y Narahari. General Article Volume 4 Issue 8 August 1999 pp ... Author Affiliations. Y Narahari1. Department ot Computer Science and Automation, Indian Institute of Science, Bangalore 560 012, India.

  6. Variation in growth rate, carbon assimilation, and photosynthetic efficiency in response to nitrogen source and concentration in phytoplankton isolated from upper San Francisco Bay.

    Science.gov (United States)

    Berg, Gry Mine; Driscoll, Sara; Hayashi, Kendra; Ross, Melissa; Kudela, Raphael

    2017-06-01

    Six species of phytoplankton recently isolated from upper San Francisco Bay were tested for their sensitivity to growth inhibition by ammonium (NH 4 + ), and for differences in growth rates according to inorganic nitrogen (N) growth source. The quantum yield of photosystem II (F v /F m ) was a sensitive indicator of NH 4 + toxicity, manifested by a suppression of F v /F m in a dose-dependent manner. Two chlorophytes were the least sensitive to NH 4 + inhibition, at concentrations of >3,000 μmoles NH 4 +  · L -1 , followed by two estuarine diatoms that were sensitive at concentrations >1,000 μmoles NH 4 +  · L -1 , followed lastly by two freshwater diatoms that were sensitive at concentrations between 200 and 500 μmoles NH 4 +  · L -1 . At non-inhibiting concentrations of NH 4 + , the freshwater diatom species grew fastest, followed by the estuarine diatoms, while the chlorophytes grew slowest. Variations in growth rates with N source did not follow taxonomic divisions. Of the two chlorophytes, one grew significantly faster on nitrate (NO 3 - ), whereas the other grew significantly faster on NH 4 + . All four diatoms tested grew faster on NH 4 + compared with NO 3 - . We showed that in cases where growth rates were faster on NH 4 + than they were on NO 3 - , the difference was not larger for chlorophytes compared with diatoms. This holds true for comparisons across a number of culture investigations suggesting that diatoms as a group will not be at a competitive disadvantage under natural conditions when NH 4 + dominates the total N pool and they will also not have a growth advantage when NO 3 - is dominant, as long as N concentrations are sufficient. © 2017 The Authors Journal of Phycology published by Wiley Periodicals, Inc. on behalf of Phycological Society of America.

  7. Photosynthetic efficiency and oxygen evolution of Chlamydomonas reinhardtii under continuous and flashing light.

    Science.gov (United States)

    Vejrazka, Carsten; Janssen, Marcel; Benvenuti, Giulia; Streefland, Mathieu; Wijffels, René H

    2013-02-01

    As a result of mixing and light attenuation in a photobioreactor (PBR), microalgae experience light/dark (L/D) cycles that can enhance PBR efficiency. One parameter which characterizes L/D cycles is the duty cycle; it determines the time fraction algae spend in the light. The objective of this study was to determine the influence of different duty cycles on oxygen yield on absorbed light energy and photosynthetic oxygen evolution. Net oxygen evolution of Chlamydomonas reinhardtii was measured for four duty cycles (0.05, 0.1, 0.2, and 0.5) in a biological oxygen monitor (BOM). Oversaturating light flashes were applied in a square-wave fashion with four flash frequencies (5, 10, 50, and 100 Hz). Algae were precultivated in a turbidostat and acclimated to a low photon flux density (PFD). A photosynthesis-irradiance (PI) curve was measured under continuous illumination and used to calculate the net oxygen yield, which was maximal between a PFD of 100 and 200 μmol m⁻² s⁻¹. Net oxygen yield under flashing light was duty cycle-dependent: the highest yield was observed at a duty cycle of 0.1 (i.e., time-averaged PFD of 115 μmol m⁻² s⁻¹). At lower duty cycles, maintenance respiration reduced net oxygen yield. At higher duty cycles, photon absorption rate exceeded the maximal photon utilization rate, and, as a result, surplus light energy was dissipated which led to a reduction in net oxygen yield. This behavior was identical with the observation under continuous light. Based on these data, the optimal balance between oxygen yield and production rate can be determined to maximize PBR productivity.

  8. Effects of nitrogen application rates on net annual global warming potential and greenhouse gas intensity in double-rice cropping systems of the Southern China.

    Science.gov (United States)

    Chen, Zhongdu; Chen, Fu; Zhang, Hailin; Liu, Shengli

    2016-12-01

    The net global warming potential (NGWP) and net greenhouse gas intensity (NGHGI) of double-rice cropping systems are not well documented. We measured the NGWP and NGHGI including soil organic carbon (SOC) change and indirect emissions (IE) from double-crop rice fields with fertilizing systems in Southern China. These experiments with three different nitrogen (N) application rates since 2012 are as follows: 165 kgN ha -1 for early rice and 225 kgN ha -1 for late rice (N1), which was the local N application rates as the control; 135 kgN ha -1 for early rice and 180 kgN ha -1 for late rice (N2, 20 % reduction); and 105 kgN ha -1 for early rice and 135 kgN ha -1 for late rice (N3, 40 % reduction). Results showed that yields increased with the increase of N application rate, but without significant difference between N1 and N2 plots. Annual SOC sequestration rate under N1 was estimated to be 1.15 MgC ha -1  year -1 , which was higher than those under other fertilizing systems. Higher N application tended to increase CH 4 emissions during the flooded rice season and significantly increased N 2 O emissions from drained soils during the nonrice season, ranking as N1 > N2 > N3 with significant difference (P < 0.05). Two-year average IE has a huge contribution to GHG emissions mainly coming from the higher N inputs in the double-rice cropping system. Reducing N fertilizer usage can effectively decrease the NGWP and NGHGI in the double-rice cropping system, with the lowest NGHGI obtained in the N2 plot (0.99 kg CO 2 -eq kg -1 yield year -1 ). The results suggested that agricultural economic viability and GHG mitigation can be simultaneously achieved by properly reducing N fertilizer application in double-rice cropping systems.

  9. Effects of an experimental increase of temperature and drought on the photosynthetic performance of two ericaceous shrub species along a north-south European gradient

    DEFF Research Database (Denmark)

    Llorens, L.; Penuelas, J.; Beier, C.

    2004-01-01

    Plant ecophysiological changes in response to climatic change may be different in northern and southern European countries because different abiotic factors constrain plant physiological activity. We studied the effects of experimental warming and drought on the photosynthetic performance of two...... ericaceous shrubs (Erica multiflora and Calluna vulgaris) along a European gradient of temperature and precipitation (UK, Denmark, The Netherlands, and Spain). At each site, a passive warming treatment was applied during the night throughout the whole year, whereas the drought treatment excluded rain events...... with the geographical gradient in water availability. Accordingly, there was a strong correlation between net photosynthetic rates and the accumulated rainfall over the growing season. Droughted plants showed lower leaf gas exchange rates than control plants in the four sites. Interestingly, although leaf...

  10. Correlated interaction fluctuations in photosynthetic complexes

    CERN Document Server

    Vlaming, Sebastiaan M

    2011-01-01

    The functioning and efficiency of natural photosynthetic complexes is strongly influenced by their embedding in a noisy protein environment, which can even serve to enhance the transport efficiency. Interactions with the environment induce fluctuations of the transition energies of and interactions between the chlorophyll molecules, and due to the fact that different fluctuations will partially be caused by the same environmental factors, correlations between the various fluctuations will occur. We argue that fluctuations of the interactions should in general not be neglected, as these have a considerable impact on population transfer rates, decoherence rates and the efficiency of photosynthetic complexes. Furthermore, while correlations between transition energy fluctuations have been studied, we provide the first quantitative study of the effect of correlations between interaction fluctuations and transition energy fluctuations, and of correlations between the various interaction fluctuations. It is shown t...

  11. Photosynthetic Characteristics of Flag Leaves in Rice White Stripe Mutant 6001 During Senescence Process

    Directory of Open Access Journals (Sweden)

    Xiao-hui ZHEN

    2014-11-01

    Full Text Available Physiological, biochemical and electron microscopy analyses were used to investigate the photosynthetic performance of flag leaves in rice white stripe mutant 6001 during the senescence process. Results showed that the chlorophyll content at the heading and milk-ripe stages in rice mutant 6001 were about 34.78% and 3.00% less than those in wild type 6028, respectively. However, the chlorophyll content at the fully-ripe stage in rice mutant 6001 was higher than that in wild type 6028. At the heading stage, the net photosynthetic rate (Pn in rice mutant 6001 was lower than that in wild type 6028. Rice mutant 6001 also exhibited a significantly slower decrease rate of Pn than wild type 6028 during the senescence progress, especially at the later stage. Furthermore, Ca2+-ATPase, Mg2+-ATPase and photophosphorylation activities exhibited the similar trends as the Pn. During the senescence process, the 68 kDa polypeptide concentrations in the thylakoid membrane proteins exhibited a significant change, which was one of the critical factors that contributed to the observed change in photosynthesis. We also observed that the chloroplasts of rice mutant 6001 exhibited higher integrity than those of wild type 6028, and the chloroplast membrane of rice mutant 6001 disintegrated more slow during the senescence process. In general, rice mutant 6001 had a relatively slower senescence rate than wild type 6028, and exhibited anti-senescence properties.

  12. 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.

  13. Potassium deficiency affects water status and photosynthetic rate of the vegetative sink in green house tomato prior to its effects on source activity.

    Science.gov (United States)

    Kanai, Synsuke; Moghaieb, Reda E; El-Shemy, Hany A; Panigrahi, R; Mohapatra, Pravat K; Ito, J; Nguyen, Nguyen T; Saneoka, Hirofumi; Fujita, Kounosuke

    2011-02-01

    The potassium requirement of green house tomatoes is very high for vegetative growth and fruit production. Potassium deficiency in plants takes long time for expression of visible symptoms. The objective of this study is to detect the deficiency early during the vegetative growth and define the roles of aquaporin and K-channel transporters in the process of regulation of water status and source-sink relationship. The tomato plants were grown hydroponically inside green house of Hiroshima University, Japan and subjected to different levels of K in the rooting medium. Potassium deficiency stress decreased photosynthesis, expansion and transport of ¹⁴C assimilates of the source leaf, but the effects became evident only after diameter expansion of the growing stem (sink) was down-regulated. The depression of stem diameter expansion is assumed to be associated with the suppression of water supply more than photosynthate supply to the organ. The stem diameter expansion is parameterized by root water uptake and leaf transpiration rates. The application of aquaporin inhibitor (AgNO₃) decreased leaf water potential, stem expansion and root hydraulic conductance within minutes of application. Similar results were obtained for application of the K-channel inhibitors. These observations suggested a close relationship between stem diameter expansion and activities of aquaporins and K-channel transporters in roots. The deficiency of potassium might have reduced aquaporin activity, consequently suppressing root hydraulic conductance and water supply to the growing stem for diameter expansion and leaf for transpiration. We conclude that close coupling between aquaporins and K-channel transporters in water uptake of roots is responsible for regulation of stem diameter dynamics of green house tomato plants. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

  14. NETS FOR PEACH PROTECTED CULTIVATION

    Directory of Open Access Journals (Sweden)

    Evelia Schettini

    2012-06-01

    Full Text Available The aim of this paper was to investigate the radiometric properties of coloured nets used to protect a peach cultivation. The modifications of the solar spectral distribution, mainly in the R and FR wavelength band, influence plant photomorphogenesis by means of the phytochrome and cryptochrome. The phytochrome response is characterized in terms of radiation rate in the red wavelengths (R, 600-700 nm to that in the farred radiation (FR, 700-800 nm, i.e. the R/FR ratio. The effects of the blue radiation (B, 400-500 nm is investigated by the ratio between the blue radiation and the far-red radiation, i.e. the B/FR ratio. A BLUE net, a RED net, a YELLOW net, a PEARL net, a GREY net and a NEUTRAL net were tested in Bari (Italy, latitude 41° 05’ N. Peach trees were located in pots inside the greenhouses and in open field. The growth of the trees cultivated in open field was lower in comparison to the growth of the trees grown under the nets. The RED, PEARL, YELLOW and GREY nets increased the growth of the trees more than the other nets. The nets positively influenced the fruit characteristics, such as fruit weight and flesh firmness.

  15. Evaluating a new method to estimate the rate of leaf respiration in the light by analysis of combined gas exchange and chlorophyll fluorescence measurements

    NARCIS (Netherlands)

    Yin, X.; Sun, Z.; Struik, P.C.; Gu, J.

    2011-01-01

    Day respiration (R(d)) is an important parameter in leaf ecophysiology. It is difficult to measure directly and is indirectly estimated from gas exchange (GE) measurements of the net photosynthetic rate (A), commonly using the Laisk method or the Kok method. Recently a new method was proposed to

  16. 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

  17. 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

  18. Effects of light, temperature and canopy position on net photosynthesis and isoprene emission from sweetgum (Liquidambar styraciflua) leaves.

    Science.gov (United States)

    Harley, P.; Guenther, A.; Zimmerman, P.

    1996-01-01

    In June 1993, net photosynthetic rates, stomatal conductance and isoprene emission rates of sweetgum leaves (Liquidambar styraciflua L.) were measured at the top of the forest canopy (sun leaves) and within the canopy at a height of 8-10 m above ground level (shade leaves). Large differences in net photosynthetic rates and stomatal conductance were found between sun and shade leaves. Mean rates of isoprene emission, expressed on a leaf area basis, were significantly lower in shade leaves than in sun leaves (4.1 versus 17.1 nmol m(-2) s(-1)); however, because specific leaf area of sun leaves was lower than that of shade leaves (0.0121 versus 0.0334 m(2) g(-1)), the difference between sun and shade leaves was less, though still significant, when isoprene emissions were expressed on a dry mass basis (45.5 versus 29.0 micro g C g(-1) h(-1)). Saturation of both net photosynthesis and isoprene emission occurred at lower PPFDs in shade leaves than in sun leaves. The effect of leaf temperature on isoprene emissions also differed between sun and shade leaves. Sun leaves lost a significantly greater percentage of fixed carbon as isoprene than shade leaves. The leaf-level physiological measurements were used to derive parameters for a canopy-level isoprene flux model. The importance of incorporating differences between sun- and shade-leaf properties into existing models is discussed.

  19. Evolutionary bursts in Euphorbia (Euphorbiaceae) are linked with photosynthetic pathway.

    Science.gov (United States)

    Horn, James W; Xi, Zhenxiang; Riina, Ricarda; Peirson, Jess A; Yang, Ya; Dorsey, Brian L; Berry, Paul E; Davis, Charles C; Wurdack, Kenneth J

    2014-12-01

    The mid-Cenozoic decline of atmospheric CO2 levels that promoted global climate change was critical to shaping contemporary arid ecosystems. Within angiosperms, two CO2 -concentrating mechanisms (CCMs)-crassulacean acid metabolism (CAM) and C4 -evolved from the C3 photosynthetic pathway, enabling more efficient whole-plant function in such environments. Many angiosperm clades with CCMs are thought to have diversified rapidly due to Miocene aridification, but links between this climate change, CCM evolution, and increased net diversification rates (r) remain to be further understood. Euphorbia (∼2000 species) includes a diversity of CAM-using stem succulents, plus a single species-rich C4 subclade. We used ancestral state reconstructions with a dated molecular phylogeny to reveal that CCMs independently evolved 17-22 times in Euphorbia, principally from the Miocene onwards. Analyses assessing among-lineage variation in r identified eight Euphorbia subclades with significantly increased r, six of which have a close temporal relationship with a lineage-corresponding CCM origin. Our trait-dependent diversification analysis indicated that r of Euphorbia CCM lineages is approximately threefold greater than C3 lineages. Overall, these results suggest that CCM evolution in Euphorbia was likely an adaptive strategy that enabled the occupation of increased arid niche space accompanying Miocene expansion of arid ecosystems. These opportunities evidently facilitated recent, replicated bursts of diversification in Euphorbia. © 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.

  20. Direct chemical measurement of DNA synthesis and net rates of differentiation of rat lens epithelial cells in vivo: applied to the selenium cataract.

    Science.gov (United States)

    Cenedella, R J

    1987-05-01

    This report describes a direct chemical method for rapidly estimating DNA synthesis and net rates of epithelial cell differentiation in the ocular lens in vivo. DNA synthesis in the lens of control and selenium-treated rats (12- or 13 days of age) was estimated by chemically isolating and measuring trichloroacetic acid (TCA)-insoluble 3H from the lens following injection of [3H]thymidine. Labeled substrate for DNA synthesis peaked in the lens at 1 hr after injection, decreased markedly by the third hour and was essentially gone by hour 12. Synthesis of labeled DNA in the lens was largely complete by about 3 hr. The [3H]DNA content of the whole lens, measured as TCA-insoluble 3H, remained constant for at least 4 months. The distribution of labeled epithelial cells between the epithelial-cell layer and fiber-cell mass was followed for up to 1 month after injection by measuring the ratio of [3H]DNA in the capsule (epithelial-cell layer) to lens body. Between days 2-3 and day 14 after injection, the ratio of [3H]DNA in the epithelial-cell layer to lens fiber cells decreased linearly in a semilogarithmic plot of the ratio vs. time; i.e. the rate of change of the ratio followed first-order kinetics. Thus, the rate constant (k) for the rate of change in the ratio of [3H]DNA in the capsule layer to lens body can provide an estimate of the percentage of the labeled epithelial cells which leave the capsule per day through differentiation into fiber cells. An apparent rate constant of 0.27 day-1 was estimated from the mean of five experiments; i.e. 27% of labeled epithelial cells were differentiating into cortical fiber cells per day. Therefore, about 70% of the germinative epithelial cells would be replaced every 4 days in these rats. This value is in good agreement with results of studies using autoradiographic technics. The selenium cataract is reported to involve rapid damage to lens epithelial cells. Incorporation of [3H]thymidine into DNA was decreased by at least 60

  1. Growth and photosynthetic responses to salinity of the salt-marsh shrub Atriplex portulacoides.

    Science.gov (United States)

    Redondo-Gómez, Susana; Mateos-Naranjo, Enrique; Davy, Anthony J; Fernández-Muñoz, Francisco; Castellanos, Eloy M; Luque, Teresa; Figueroa, M Enrique

    2007-09-01

    Atriplex (Halimione) portulacoides is a halophytic, C(3) shrub. It is virtually confined to coastal salt marshes, where it often dominates the vegetation. The aim of this study was to investigate its growth responses to salinity and the extent to which these could be explained by photosynthetic physiology. The responses of young plants to salinity in the range 0-700 mol m(-3) NaCl were investigated in a glasshouse experiment. The performance of plants was examined using classical growth analysis, measurements of gas exchange (infrared gas analysis), determination of chlorophyll fluorescence characteristics (modulated fluorimeter) and photosynthetic pigment concentrations; total ash, sodium, potassium and nitrogen concentrations, and relative water content were also determined. Plants accumulated Na(+) approximately in proportion to external salinity. Salt stimulated growth up to an external concentration of 200 mol m(-3) NaCl and some growth was maintained at higher salinities. The main determinant of growth response to salinity was unit leaf rate. This was itself reflected in rates of CO(2) assimilation, which were not affected by 200 mol m(-3) but were reduced at higher salinities. Reductions in net photosynthetic rate could be accounted for largely by lower stomatal conductance and intercellular CO(2) concentration. Apart from possible effects of osmotic shock at the beginning of the experiment, salinity did not have any adverse effect on photosystem II (PSII). Neither the quantum efficiency of PSII (Phi(PSII)) nor the chlorophyll fluorescence ratio (F(v)/F(m)) were reduced by salinity, and lower mid-day values recovered by dawn. Mid-day F(v)/F(m) was in fact depressed more at low external sodium concentration, by the end of the experiment. The growth responses of the hygro-halophyte A. portulacoides to salinity appear largely to depend on changes in its rate of photosynthetic gas exchange. Photosynthesis appears to be limited mainly through stomatal conductance

  2. Effects of selenium on the growth and photosynthetic characteristics of flue-cured tobacco (Nicotiana tabacum L.

    Directory of Open Access Journals (Sweden)

    Chaoqiang Jiang

    2015-03-01

    Full Text Available The objective of this study was to investigate the effect of Selenium (Se supply (0, 3, 6, 12, 24 mg kg−1 on the growth, photosynthetic characteristics, Se accumulation and distribution of flue-cured tobacco (Nicotiana tabacum L.. Results showed that low-dose Se treatments (≤6 mg kg−1 stimulated plant growth but high-dose Se treatments (≥12 mg kg−1 hindered plant growth. Optimal Se dose (6 mg kg−1 stimulated plant growth by reducing MDA content and improving photosynthetic capability. However, excess Se (24 mg kg−1 increased MDA content by 28%, decreased net photosynthetic rate and carboxylation efficiency by 34% and 39%, respectively. The Se concentration in the roots, stems, and leaves of the tobacco plants significantly increased with increasing Se application. A linear correlation (R = 0.95, P leaf > stem. The Se concentration in the roots was 3.17 and 7.57 times higher than that in the leaves and stems, respectively, after treatment with 24 mg kg−1 Se. In conclusion, the present study suggested that optimal Se dose (6 mg kg−1 improved the plant growth mainly by enhancing photosynthesis, stomatal conductance, carboxylation efficiency and Rubisco content in the flue-cured tobacco leaves. However, the inhibition of excess Se on tobacco growth might be due to high accumulation of Se in roots and the damage of photosynthesis in leaves.

  3. Parametric Net Influx Rate Images of68Ga-DOTATOC and68Ga-DOTATATE: Quantitative Accuracy and Improved Image Contrast.

    Science.gov (United States)

    Ilan, Ezgi; Sandström, Mattias; Velikyan, Irina; Sundin, Anders; Eriksson, Barbro; Lubberink, Mark

    2017-05-01

    68 Ga-DOTATOC and 68 Ga-DOTATATE are radiolabeled somatostatin analogs used for the diagnosis of somatostatin receptor-expressing neuroendocrine tumors (NETs), and SUV measurements are suggested for treatment monitoring. However, changes in net influx rate ( K i ) may better reflect treatment effects than those of the SUV, and accordingly there is a need to compute parametric images showing K i at the voxel level. The aim of this study was to evaluate parametric methods for computation of parametric K i images by comparison to volume of interest (VOI)-based methods and to assess image contrast in terms of tumor-to-liver ratio. Methods: Ten patients with metastatic NETs underwent a 45-min dynamic PET examination followed by whole-body PET/CT at 1 h after injection of 68 Ga-DOTATOC and 68 Ga-DOTATATE on consecutive days. Parametric K i images were computed using a basis function method (BFM) implementation of the 2-tissue-irreversible-compartment model and the Patlak method using a descending aorta image-derived input function, and mean tumor K i values were determined for 50% isocontour VOIs and compared with K i values based on nonlinear regression (NLR) of the whole-VOI time-activity curve. A subsample of healthy liver was delineated in the whole-body and K i images, and tumor-to-liver ratios were calculated to evaluate image contrast. Correlation ( R 2 ) and agreement between VOI-based and parametric K i values were assessed using regression and Bland-Altman analysis. Results: The R 2 between NLR-based and parametric image-based (BFM) tumor K i values was 0.98 (slope, 0.81) and 0.97 (slope, 0.88) for 68 Ga-DOTATOC and 68 Ga-DOTATATE, respectively. For Patlak analysis, the R 2 between NLR-based and parametric-based (Patlak) tumor K i was 0.95 (slope, 0.71) and 0.92 (slope, 0.74) for 68 Ga-DOTATOC and 68 Ga-DOTATATE, respectively. There was no bias between NLR and parametric-based K i values. Tumor-to-liver contrast was 1.6 and 2.0 times higher in the parametric

  4. Photosynthetic control of electron transport and the regulation of gene expression

    NARCIS (Netherlands)

    Foyer, C.H.; Neukermans, J.; Queval, G.; Noctor, G.; Harbinson, J.

    2012-01-01

    The term ‘photosynthetic control’ describes the short- and long-term mechanisms that regulate reactions in the photosynthetic electron transport (PET) chain so that the rate of production of ATP and NADPH is coordinated with the rate of their utilization in metabolism. At low irradiances these

  5. Growth and photosynthetic responses of wheat plants grown in space

    Science.gov (United States)

    Tripathy, B. C.; Brown, C. S.; Levine, H. G.; Krikorian, A. D.

    1996-01-01

    Growth and photosynthesis of wheat (Triticum aestivum L. cv Super Dwarf) plants grown onboard the space shuttle Discovery for 10 d were examined. Compared to ground control plants, the shoot fresh weight of space-grown seedlings decreased by 25%. Postflight measurements of the O2 evolution/photosynthetic photon flux density response curves of leaf samples revealed that the CO2-saturated photosynthetic rate at saturating light intensities in space-grown plants declined 25% relative to the rate in ground control plants. The relative quantum yield of CO2-saturated photosynthetic O2 evolution measured at limiting light intensities was not significantly affected. In space-grown plants, the light compensation point of the leaves increased by 33%, which likely was due to an increase (27%) in leaf dark-respiration rates. Related experiments with thylakoids isolated from space-grown plants showed that the light-saturated photosynthetic electron transport rate from H2O through photosystems II and I was reduced by 28%. These results demonstrate that photosynthetic functions are affected by the microgravity environment.

  6. Increased light-use efficiency sustains net primary productivity of shaded coffee plants in agroforestry system.

    Science.gov (United States)

    Charbonnier, Fabien; Roupsard, Olivier; le Maire, Guerric; Guillemot, Joannès; Casanoves, Fernando; Lacointe, André; Vaast, Philippe; Allinne, Clémentine; Audebert, Louise; Cambou, Aurélie; Clément-Vidal, Anne; Defrenet, Elsa; Duursma, Remko A; Jarri, Laura; Jourdan, Christophe; Khac, Emmanuelle; Leandro, Patricia; Medlyn, Belinda E; Saint-André, Laurent; Thaler, Philippe; Van Den Meersche, Karel; Barquero Aguilar, Alejandra; Lehner, Peter; Dreyer, Erwin

    2017-08-01

    In agroforestry systems, shade trees strongly affect the physiology of the undergrown crop. However, a major paradigm is that the reduction in absorbed photosynthetically active radiation is, to a certain extent, compensated by an increase in light-use efficiency, thereby reducing the difference in net primary productivity between shaded and non-shaded plants. Due to the large spatial heterogeneity in agroforestry systems and the lack of appropriate tools, the combined effects of such variables have seldom been analysed, even though they may help understand physiological processes underlying yield dynamics. In this study, we monitored net primary productivity, during two years, on scales ranging from individual coffee plants to the entire plot. Absorbed radiation was mapped with a 3D model (MAESPA). Light-use efficiency and net assimilation rate were derived for each coffee plant individually. We found that although irradiance was reduced by 60% below crowns of shade trees, coffee light-use efficiency increased by 50%, leaving net primary productivity fairly stable across all shade levels. Variability of aboveground net primary productivity of coffee plants was caused primarily by the age of the plants and by intraspecific competition among them (drivers usually overlooked in the agroforestry literature) rather than by the presence of shade trees. © 2017 John Wiley & Sons Ltd.

  7. Hydrogen photoproduction by use of photosynthetic organisms and biomimetic systems.

    Science.gov (United States)

    Allakhverdiev, Suleyman I; Kreslavski, Vladimir D; Thavasi, Velmurugan; Zharmukhamedov, Sergei K; Klimov, Vyacheslav V; Nagata, Toshi; Nishihara, Hiroshi; Ramakrishna, Seeram

    2009-02-01

    Hydrogen can be important clean fuel for future. Among different technologies for hydrogen production, oxygenic natural and artificial photosyntheses using direct photochemistry in synthetic complexes have a great potential to produce hydrogen, since both use clean and cheap sources: water and solar energy. Artificial photosynthesis is one way to produce hydrogen from water using sunlight by employing biomimetic complexes. However, splitting of water into protons and oxygen is energetically demanding and chemically difficult. In oxygenic photosynthetic microorganisms such as algae and cyanobacteria, water is split into electrons and protons, which during primary photosynthetic process are redirected by photosynthetic electron transport chain, and ferredoxin, to the hydrogen-producing enzymes hydrogenase or nitrogenase. By these enzymes, e- and H+ recombine and form gaseous hydrogen. Biohydrogen activity of hydrogenase can be very high but it is extremely sensitive to photosynthetic O2. In contrast, nitrogenase is insensitive to O2, but has lower activity. At the moment, the efficiency of biohydrogen production is low. However, theoretical expectations suggest that the rates of photon conversion efficiency for H2 bioproduction can be high enough (>10%). Our review examines the main pathways of H2 photoproduction by using of photosynthetic organisms and biomimetic photosynthetic systems.

  8. [Effect of ridge & terraced ecological rice farming on rice photosynthetic characteristics and yield].

    Science.gov (United States)

    Zheng, Hua-Bin; Liu, Jian-Xia; Yao, Lin; He, Hui; Huang, Huang

    2014-09-01

    Taking super hybrid rice Y-liangyou 1, and hybrid rice Xianyou 63 and conventional rice Huanghuazhan as test materials, a field experiment was conducted in Changsha City of Hunan Province in 2011 and 2012 to investigate the effects of ridge & terraced ecological rice farming (RT) and bed ecological rice farming (B) on rice grain yield and photosynthetic characteristics. Compared with conventional rice farming (CK) , yield of Y-liangyou 1 in the RT was increased significantly by 28.7%, the effective panicles per unit area and spikelets per panicle were increased by 16.1% and 6.8%, respectively. Yields of Xianyou 63 and Huanghuazhan in the RT and B were 24.3% and 19.7%, 12.0% and 16.2% higher than those of CK, respectively. Leaf area index, dry matter accumulation before and after full-heading, total dry matter accumulation of Y-liangyou 1 in the RT was higher than that of CK. Number of spikelets/leaf area, number of filled grains/leaf area, grain mass/leaf area of Y-liangyou 1 in the RT were 8.1%, 14.8% and 15.8% higher than those of CK, respectively, the photosynthetic potential was increased by 32.2% while the net assimilation rate was declined by 9.3%.

  9. Controls on declining carbon balance with leaf age among 10 woody species in Australian woodland: do leaves have zero daily net carbon balances when they die?

    Science.gov (United States)

    Reich, Peter B; Falster, Daniel S; Ellsworth, David S; Wright, Ian J; Westoby, Mark; Oleksyn, Jacek; Lee, Tali D

    2009-01-01

    * Here, we evaluated how increased shading and declining net photosynthetic capacity regulate the decline in net carbon balance with increasing leaf age for 10 Australian woodland species. We also asked whether leaves at the age of their mean life-span have carbon balances that are positive, zero or negative. * The net carbon balances of 2307 leaves on 53 branches of the 10 species were estimated. We assessed three-dimensional architecture, canopy openness, photosynthetic light response functions and dark respiration rate across leaf age sequences on all branches. We used YPLANT to estimate light interception and to model carbon balance along the leaf age sequences. * As leaf age increased to the mean life-span, increasing shading and declining photosynthetic capacity each separately reduced daytime carbon gain by approximately 39% on average across species. Together, they reduced daytime carbon gain by 64% on average across species. * At the age of their mean life-span, almost all leaves had positive daytime carbon balances. These per leaf carbon surpluses were of a similar magnitude to the estimated whole-plant respiratory costs per leaf. Thus, the results suggest that a whole-plant economic framework, including respiratory costs, may be useful in assessing controls on leaf longevity.

  10. Net Gain

    International Development Research Centre (IDRC) Digital Library (Canada)

    %) in malaria disease rates following introduction of ITNs. The results of standard clinical trials (randomized, controlled, and using sufficiently large samples) that measured impact on malaria disease in Africa are shown in Table 1. Other studies ...

  11. Arsenic biomethylation by photosynthetic organisms

    Science.gov (United States)

    Ye, Jun; Rensing, Christopher; Rosen, Barry P.; Zhu, Yong-Guan

    2013-01-01

    Arsenic (As) is a ubiquitous element that is widespread in the environment and causes numerous health problems. Biomethylation of As has implications for its mobility and toxicity. Photosynthetic organisms may play a significant role in As geochemical cycling by methylating it to different As species, but little is known about the mechanisms of methylation. Methylated As species have been found in many photosynthetic organisms, and several arsenite S-adenosylmethionine (SAM) methyltransferases have been characterized in cyanobacteria and algae. However, higher plants may not have the ability to methylate As. Instead, methylated arsenicals in plants probably originate from microorganisms in soils and the rhizosphere. Here, we propose possible approaches for developing ‘smart’ photosynthetic organisms with an enhanced and sensitive biomethylation capacity for bioremediation and safer food. PMID:22257759

  12. UV sensitivity of planktonic net community production in ocean surface waters

    Science.gov (United States)

    Regaudie-de-Gioux, Aurore; Agustí, Susana; Duarte, Carlos M.

    2014-05-01

    The net plankton community metabolism of oceanic surface waters is particularly important as it more directly affects the partial pressure of CO2 in surface waters and thus the air-sea fluxes of CO2. Plankton communities in surface waters are exposed to high irradiance that includes significant ultraviolet blue (UVB, 280-315 nm) radiation. UVB radiation affects both photosynthetic and respiration rates, increase plankton mortality rates, and other metabolic and chemical processes. Here we test the sensitivity of net community production (NCP) to UVB of planktonic communities in surface waters across contrasting regions of the ocean. We observed here that UVB radiation affects net plankton community production at the ocean surface, imposing a shift in NCP by, on average, 50% relative to the values measured when excluding partly UVB. Our results show that under full solar radiation, the metabolic balance shows the prevalence of net heterotrophic community production. The demonstration of an important effect of UVB radiation on NCP in surface waters presented here is of particular relevance in relation to the increased UVB radiation derived from the erosion of the stratospheric ozone layer. Our results encourage design future research to further our understanding of UVB effects on the metabolic balance of plankton communities.

  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. Special issue of photosynthetic research.

    Science.gov (United States)

    Okamura, Melvin; Wraight, Colin A; van Grondelle, Rienk

    2014-05-01

    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 conversion. Their key discoveries are briefly summarized and an overview of the special issue is presented.

  15. Interacting effects of elevated temperature and additional water on plant physiology and net ecosystem carbon fluxes in a high Arctic ecosystem

    Science.gov (United States)

    Maseyk, Kadmiel; Seibt, Ulrike; Lett, Céline; Lupascu, Massimo; Czimczik, Claudia; Sullivan, Patrick; Welker, Jeff

    2013-04-01

    Arctic ecosystems are experiencing temperature increases more strongly than the global average, and increases in precipitation are also expected amongst the climate impacts on this region in the future. These changes are expected to strongly influence plant physiology and soil biogeochemistry with subsequent implications for system carbon balance. We have investigated the effects of a long-term (10 years) increase in temperature, soil water and the combination of both on a tundra ecosystem at a field manipulation experiment in NW Greenland. Leaf gas exchange, chlorophyll fluorescence, carbon (C) and nitrogen (N) content and leaf isotopic composition, and leaf morphology were measured on Salix arctica plants in treatment and control plots in June-July 2011, and continuous measurements of net plant and soil fluxes of CO2 and water were made using automatic chambers coupled to a trace gas laser analyzer. Plants in the elevated temperature (T2) treatment had the highest photosynthetic capacity in terms of net CO2 assimilation rates and photosystem II efficiencies, and lowest rates of non-photochemical energy dissipation during photosynthesis. T2 plants also had the highest leaf N content, specific leaf area (SLA) and saturation light level of photosynthesis. It appears that warming increases soil N availability, which the plants direct towards increasing photosynthetic capacity and producing larger thinner leaves. On the other hand, the plants in the plots with both elevated temperatures and additional water (T2W) had the lowest photosystem II efficiencies and the highest rates of non-photochemical energy dissipation, due more to higher levels of constitutive energy dissipation than regulated thermal quenching. Watering, both in combination with higher temperatures and alone (W treatment), also reduced leaf SLA and leaf N relative to control plots. However, net photosynthetic rates remained similar to control plants, due in part to higher stomatal conductance (W) and

  16. Photosynthetic Response of Soybean to Microclimate in 26-Year-Old Tree-Based Intercropping Systems in Southern Ontario, Canada.

    Directory of Open Access Journals (Sweden)

    Xiaobang Peng

    Full Text Available In order to study the effect of light competition and microclimatic modifications on the net assimilation (NA, growth and yield of soybean (Glycine max L. as an understory crop, three 26-year-old soybean-tree (Acer saccharinum Marsh., Populus deltoides X nigra, Juglans nigra L. intercropping systems were examined. Tree competition reduced photosynthetically active radiation (PAR incident on soybeans and reduced net assimilation, growth and yield of soybean. Soil moisture of 20 cm depth close (< 3 m to the tree rows was also reduced. Correlation analysis showed that NA and soil water content were highly correlated with growth and yield of soybean. When compared with the monoculture soybean system, the relative humidity (RH of the poplar-soybean, silver maple-soybean, and black walnut-soybean intercropped systems was increased by 7.1%, 8.0% and 5.9%, soil water content was reduced by 37.8%, 26.3% and 30.9%, ambient temperature was reduced by 1.3°C, 1.4°C and 1.0°C, PAR was reduced by 53.6%, 57.9% and 39.9%, and air CO2 concentration was reduced by 3.7μmol·mol(-1, 4.2μmol·mol(-1 and 2.8μmol·mol(-1, respectively. Compared to the monoculture, the average NA of soybean in poplar, maple and walnut treatments was also reduced by 53.1%, 67.5% and 46.5%, respectively. Multivariate stepwise regression analysis showed that PAR, ambient temperature and CO2 concentration were the dominant factors influencing net photosynthetic rate.

  17. MISR Level 3 Component Global Land product in netCDF format covering a day V004

    Data.gov (United States)

    National Aeronautics and Space Administration — The MISR Level 3 Component Global Land Product in netCDF contains a daily statistical summary of directional hemispherical reflectance (DHR), photosynthetically...

  18. Metabolic Engineering and Modeling of Metabolic Pathways to Improve Hydrogen Production by Photosynthetic Bacteria

    Energy Technology Data Exchange (ETDEWEB)

    Jiao, Y. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Navid, A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2014-12-19

    traits act as the biocatalysts of the process designed to both enhance the system efficiency of CO2 fixation and the net hydrogen production rate. Additionally we applied metabolic engineering approaches guided by computational modeling for the chosen model microorganisms to enable efficient hydrogen production.

  19. 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

  20. Growing season net ecosystem CO2 exchange of two desert ecosystems with alkaline soils in Kazakhstan

    Science.gov (United States)

    Li, Longhui; Chen, Xi; van der Tol, Christiaan; Luo, Geping; Su, Zhongbo

    2014-01-01

    Central Asia is covered by vast desert ecosystems, and the majority of these ecosystems have alkaline soils. Their contribution to global net ecosystem CO2 exchange (NEE) is of significance simply because of their immense spatial extent. Some of the latest research reported considerable abiotic CO2 absorption by alkaline soil, but the rate of CO2 absorption has been questioned by peer communities. To investigate the issue of carbon cycle in Central Asian desert ecosystems with alkaline soils, we have measured the NEE using eddy covariance (EC) method at two alkaline sites during growing season in Kazakhstan. The diurnal course of mean monthly NEE followed a clear sinusoidal pattern during growing season at both sites. Both sites showed significant net carbon uptake during daytime on sunny days with high photosynthetically active radiation (PAR) but net carbon loss at nighttime and on cloudy and rainy days. NEE has strong dependency on PAR and the response of NEE to precipitation resulted in an initial and significant carbon release to the atmosphere, similar to other ecosystems. These findings indicate that biotic processes dominated the carbon processes, and the contribution of abiotic carbon process to net ecosystem CO2 exchange may be trivial in alkaline soil desert ecosystems over Central Asia. PMID:24455157

  1. Effect of plant density on the characteristics of photosynthetic ...

    African Journals Online (AJOL)

    ajl yemi

    2011-11-14

    Nov 14, 2011 ... of stand density on the photosynthetic apparatus of the garlic plant. These effects were found to ... correlation between crop growth rate (CGR) and the leaf area index ..... and Quantity of garlic as Affected by Different Farming Systems and. Garlic Clones. Pak. ... light and carbon dioxide? Bioscience, 47(11): ...

  2. Photosynthetic activity of isolated chloroplast fragments of Spirogyra

    NARCIS (Netherlands)

    Thomas, J.B.; Haans, A.J.M.; Leun, A.A.J. van der; Koning, J.

    1957-01-01

    Suspensions of fragmented Spirogyra chloroplasts were prepared and their capacity for photosynthetic oxygen evolution and carbon dioxide reduction was studied by means of manometry and mass spectrometry. No special substances, enzymes or cofactors were added to the suspensions. The rates of

  3. 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

  4. 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.

  5. Responses of the photosynthetic apparatus to winter conditions in broadleaved evergreen trees growing in warm temperate regions of Japan.

    Science.gov (United States)

    Tanaka, Chizuru; Nakano, Takashi; Yamazaki, Jun-Ya; Maruta, Emiko

    2015-01-01

    Photosynthetic characteristics of two broadleaved evergreen trees, Quercus myrsinaefolia and Machilus thunbergii, were compared in autumn and winter. The irradiance was similar in both seasons, but the air temperature was lower in winter. Under the winter conditions, net photosynthesis under natural sunlight (Anet) in both species dropped to 4 μmol CO2 m(-2) s(-1), and the quantum yield of photosystem II (PSII) photochemistry in dark-adapted leaves (Fv/Fm) also dropped to 0.60. In both species the maximum carboxylation rates of Rubisco (V(cmax)) decreased, and the amount of Rubisco increased in winter. A decline in chlorophyll (Chl) concentration and an increase in the Chl a/b ratio in winter resulted in a reduction in the size of the light-harvesting antennae. From measurements of Chl a fluorescence parameters, both the relative fraction and the energy flux rates of thermal dissipation through other non-photochemical processes were markedly elevated in winter. The results indicate that the photosynthetic apparatus in broadleaved evergreen species in warm temperate regions responds to winter through regulatory mechanisms involving the downregulation of light-harvesting and photosynthesis coupled with increased photoprotective thermal energy dissipation to minimize photodamage in winter. These mechanisms aid a quick restart of photosynthesis without the development of new leaves in the following spring. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

  6. Effects of Arbuscular Mycorrhiza on Osmotic Adjustment and Photosynthetic Physiology of Maize Seedlings in Black Soils Region of Northeast China

    Directory of Open Access Journals (Sweden)

    Hongwen Xu

    Full Text Available ABSTRACT To investigate the effect of arbuscular mycorrhiza fungi on maize growth, osmoregulation substances and photosynthetic physiology, a popular maize variety ZD 958 was measured under potted condition. Arbuscular mycorrhiza (AM symbiosis promoted plant growth, and enhanced plant height, leaf length, mean leaf width and dry weight. Higher soluble sugar and protein, but lower proline concentrations were detected in AM seedlings than corresponding non-AM seedlings. Quantum yield of PSII photochemistry and potential photochemical efficiency increased by arbuscular mycorrhiza fungi, meanwhile, AM plants had lower primary fluorescence but higher maximal fluorescence and variable fluorescence than non-AM plants. AM enhanced apparent quantum efficiency, maximum net photosynthetic rate, dark respiration rate and light saturation point, but reduced light compensation point. The conclusion was that, after the seedling inoculated with Glomus. tortuosum, AM symbioses could protect cell from being hurt through regulating substances related to osmotic adjustment, besides, the efficiency of light utilization, the capacity of using low light and the capacity of fitting and using high light were all increased by AM symbiosis.

  7. 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.

  8. Acclimation to UV-B radiation and visible light in Lactuca sativa involves up-regulation of photosynthetic performance and orchestration of metabolome-wide responses.

    Science.gov (United States)

    Wargent, J J; Nelson, B C W; McGhie, T K; Barnes, P W

    2015-05-01

    UV-B radiation is often viewed as a source of stress for higher plants. In particular, photosynthetic function has been described as a common target for UV-B impairment; yet as our understanding of UV-B photomorphogenesis increases, there are opportunities to expand the emerging paradigm of regulatory UV response. Lactuca sativa is an important dietary crop species and is often subjected to rapid sunlight exposure at field transfer. Acclimation to UV-B and visible light conditions in L. sativa was dissected using gas exchange and chlorophyll fluorescence measurements, in addition to non-destructive assessments of UV epidermal shielding (SUV ). After UV-B treatment, seedlings were subjected to wide-range metabolomic analysis using liquid chromatography hybrid quadrupole time-of-flight high-resolution mass spectrometry (LC-QTOF-HRMS). During the acclimation period, net photosynthetic rate increased in UV-treated plants, epidermal UV shielding increased in both subsets of plants transferred to the acclimatory conditions (UV+/UV- plants) and Fv /Fm declined slightly in UV+/UV- plants. Metabolomic analysis revealed that a key group of secondary compounds was up-regulated by higher light conditions, yet several of these compounds were elevated further by UV-B radiation. In conclusion, acclimation to UV-B radiation involves co-protection from the effects of visible light, and responses to UV-B radiation at a photosynthetic level may not be consistently viewed as damaging to plant development. © 2014 John Wiley & Sons Ltd.

  9. Photoconversion of organic substrates into hydrogen using photosynthetic bacteria

    Energy Technology Data Exchange (ETDEWEB)

    Weaver, P. F.

    1981-03-01

    Under nitrogen-limited conditions, photosynthetic bacteria photoconvert a wide variety of organic substrates nearly totally into H/sub 2/ and CO/sub 2/. More than 98% of the chemical energy of defined organic compounds even from dilute solutions can be recovered as combustible energy of the H/sub 2/ produced. Not calculating the chemical energy input, radiant (solar) energy recoveries are approximately 5% over a wide range of incident light intensities. Batch cultures can photoproduce H/sub 2/ at rates of 175 ml per gram dry weight of cells per hour (equal to a volume of H/sub 2/ per equivalent volume of liquid medium every 4 to 6 hours) when incubated in saturating light. With periodic refeeding, rates remain constant for several weeks. In closed containers H/sub 2/ pressures of 735 psig can be generated. In principle, this pressure can be used to decrease storage volume of the gas, to move it through pipelines or to provide required process pressures. Alcohol stillage and food processing wastes are excellent photoconvertible substances. When non-photosynthetic bacteria synthesizing appropriate polysaccharases are included in co-culture with photosynthetic bacteria, cellulose and other polysaccharides can be converted to H/sub 2/ and CO/sub 2/, albeit at low rates. Prospects for enhancing the photoconversion reactions of photosynthetic bacteria by environmental and genetic manipulations are discussed.

  10. Effects of Light Intensity on the Growth, Photosynthetic Characteristics, and Flavonoid Content of Epimedium pseudowushanense B.L.Guo

    Directory of Open Access Journals (Sweden)

    Junqian Pan

    2016-11-01

    Full Text Available Epimedium pseudowushanense B.L.Guo is used in traditional medicine as an aphrodisiac and to strengthen muscles and bones. Several recent reports have shown that flavonoids from Epimedium also significantly affect the treatment of breast cancer, liver cancer, and leukemia. However, few studies have examined the medicinal-ingredient yield of Epimedium, a light-demanding shade herb, under different light intensities. To investigate the effects of light intensity on medicinal-ingredient yields, Epimedium was exposed to five levels of light intensity until harvest time. Leaf dry biomass under L4 was the highest among different light treatments. L4 was also associated with the highest net photosynthetic rate. Quantification of epimedin A, epimedin B, epimedin C, and icariin showed that L3 produced the highest amount of epimedin C, and that flavonoid content responded to light levels differently. Results indicated that L3 and L4 were the optimal light levels for medicinal-ingredient yield.

  11. Effects of Light Intensity on the Growth, Photosynthetic Characteristics, and Flavonoid Content of Epimedium pseudowushanense B.L.Guo.

    Science.gov (United States)

    Pan, Junqian; Guo, Baolin

    2016-11-04

    Epimedium pseudowushanense B.L.Guo is used in traditional medicine as an aphrodisiac and to strengthen muscles and bones. Several recent reports have shown that flavonoids from Epimedium also significantly affect the treatment of breast cancer, liver cancer, and leukemia. However, few studies have examined the medicinal-ingredient yield of Epimedium, a light-demanding shade herb, under different light intensities. To investigate the effects of light intensity on medicinal-ingredient yields, Epimedium was exposed to five levels of light intensity until harvest time. Leaf dry biomass under L4 was the highest among different light treatments. L4 was also associated with the highest net photosynthetic rate. Quantification of epimedin A, epimedin B, epimedin C, and icariin showed that L3 produced the highest amount of epimedin C, and that flavonoid content responded to light levels differently. Results indicated that L3 and L4 were the optimal light levels for medicinal-ingredient yield.

  12. Partitioning of photosynthetic electron flow between CO2 and O 2 reduction in a C 3 leaf (Phaseolus vulgaris L.) at different CO 2 concentrations and during drought stress.

    Science.gov (United States)

    Cornic, G; Briantais, J M

    1991-01-01

    Photosystem II chlorophyll fluorescence and leaf net gas exchanges (CO2 and H2O) were measured simultaneously on bean leaves (Phaseolus vulgaris L.) submitted either to different ambient CO2 concentrations or to a drought stress. When leaves are under photorespiratory conditions, a simple fluorescence parameter ΔF/ Fm (B. Genty et al. 1989, Biochem. Biophys. Acta 990, 87-92; ΔF = difference between maximum, Fm, and steady-state fluorescence emissions) allows the calculation of the total rate of photosynthetic electron-transport and the rate of electron transport to O2. These rates are in agreement with the measurements of leaf O2 absorption using (18)O2 and the kinetic properties of ribulose-1,5bisphosphate carboxylase/oxygenase. The fluorescence parameter, ΔF/Fm, showed that the allocation of photosynthetic electrons to O2 was increased during the desiccation of a leaf. Decreasing leaf net CO2 uptake, either by decreasing the ambient CO2 concentration or by dehydrating a leaf, had the same effect on the partitioning of photosynthetic electrons between CO2 and O2 reduction. It is concluded that the decline of net CO2 uptake of a leaf under drought stress is only due, at least for a mild reversible stress (causing at most a leaf water deficit of 35%), to stomatal closure which leads to a decrease in leaf internal CO2 concentration. Since, during the dehydration of a leaf, the calculated internal CO2 concentration remained constant or even increased we conclude that this calculation is misleading under such conditions.

  13. [Effects of different LED light qualities on growth, photosynthetic characteristics and nutritional quality of savoy].

    Science.gov (United States)

    Chen, Xiang-Wei; Liu, Shi-Qi; Wang, Yue; Liu, Jing-Kai; Feng, Lei

    2014-07-01

    LED lighting has several unique advantages over traditional lighting, including the ability to control spectral composition, the ability to produce very high light levels with low radiant heat output when cooled properly, and the ability to maintain useful light output for years without replacement. LED light sources have the capability of controlling true spectral composition, allowing wavelengths to match plant photoreceptors to provide more optimal production to regulate plant morphology and nutritional quality. In this paper, the effects of different light qualities on the growth, photosynthetic response and nutritional quality of savoy were studied. With 'Juhua-Xiaobaye' savoy as the test plant, full red light, full blue light, red/blue (3/1) light, red/blue (7/1) light and white/red/blue (3/2/1) light generated by light-emitting diodes were applied with white light generated by fluorescent lamps as control. The results showed that red light could increase biomass and stem diameter, but blue light showed the opposite effect. The chlorophyll (a+b) content was the highest in the red/blue (7/1) light treatment, and chlorophyll (a+b) content was correlated with the red/blue ratio positively. Blue light decreased chlorophyll (a + b) content of savoy, and increased chlorophyll a/b. The photosynthetic rate (Pn) and transpiration rate under red light were the highest, and increased by 43.8% and 55.1% compared with the control. Intercellular CO2 concentration and conductance were the highest under blue light. The fluorescence parameters of the plant were significantly affected by light quality. Values of the maximal photochemical efficiency of PS II (Fv/Fm), Fv/Fo and Phi(PS II) were the highest under white light. Soluble sugar, soluble protein and vitamin C contents were the highest under red, blue and white light, respectively. Comprehensive analysis indicated that red/blue (7/1) light was the best light combination to increase leaf chlorophyll (a+b) content and net

  14. NA-NET numerical analysis net

    Energy Technology Data Exchange (ETDEWEB)

    Dongarra, J. [Tennessee Univ., Knoxville, TN (United States). Dept. of Computer Science]|[Oak Ridge National Lab., TN (United States); Rosener, B. [Tennessee Univ., Knoxville, TN (United States). Dept. of Computer Science

    1991-12-01

    This report describes a facility called NA-NET created to allow numerical analysts (na) an easy method of communicating with one another. The main advantage of the NA-NET is uniformity of addressing. All mail is addressed to the Internet host ``na-net.ornl.gov`` at Oak Ridge National Laboratory. Hence, members of the NA-NET do not need to remember complicated addresses or even where a member is currently located. As long as moving members change their e-mail address in the NA-NET everything works smoothly. The NA-NET system is currently located at Oak Ridge National Laboratory. It is running on the same machine that serves netlib. Netlib is a separate facility that distributes mathematical software via electronic mail. For more information on netlib consult, or send the one-line message ``send index`` to netlib{at}ornl.gov. The following report describes the current NA-NET system from both a user`s perspective and from an implementation perspective. Currently, there are over 2100 members in the NA-NET. An average of 110 mail messages pass through this facility daily.

  15. NA-NET numerical analysis net

    Energy Technology Data Exchange (ETDEWEB)

    Dongarra, J. (Tennessee Univ., Knoxville, TN (United States). Dept. of Computer Science Oak Ridge National Lab., TN (United States)); Rosener, B. (Tennessee Univ., Knoxville, TN (United States). Dept. of Computer Science)

    1991-12-01

    This report describes a facility called NA-NET created to allow numerical analysts (na) an easy method of communicating with one another. The main advantage of the NA-NET is uniformity of addressing. All mail is addressed to the Internet host na-net.ornl.gov'' at Oak Ridge National Laboratory. Hence, members of the NA-NET do not need to remember complicated addresses or even where a member is currently located. As long as moving members change their e-mail address in the NA-NET everything works smoothly. The NA-NET system is currently located at Oak Ridge National Laboratory. It is running on the same machine that serves netlib. Netlib is a separate facility that distributes mathematical software via electronic mail. For more information on netlib consult, or send the one-line message send index'' to netlib{at}ornl.gov. The following report describes the current NA-NET system from both a user's perspective and from an implementation perspective. Currently, there are over 2100 members in the NA-NET. An average of 110 mail messages pass through this facility daily.

  16. Net photosynthesis and respiration of sago pondweed (Potamogeton pectinatus) exposed to herbicides

    Science.gov (United States)

    Fleming, W.J.; Ailstock, M.S.; Momot, J.J.; Hughes, Jane S.; Biddinger, Gregory R.; Mones, Eugene

    1995-01-01

    We determined net photosynthesis and respiration rates for sago pondweed (potamogeton pectinatus) exposed to various concentrations of 11 herbicides widely used in Maryland during the past decade. Net photosynthesis and respiration were determined by measuring changes in the. oxygen content of solutions containing dilutions of technical grade herbicides. At 20-22? C and 58 umol/m2/sec of photosynthetically active radiation (PAR), oxygen production of undosed plants averaged 0.72-2.03 mg/g fresh wt/h. Respiration rates of undosed plants averaged 0.46-0.60 mg O2/g fresh wt/h. Nominal herbicide concentrations (ng/L) that reduced net photosynthesis by 5O percent (IC5O) were: metribuzin, 8; atrazine, 29; cyanazine, 32; linuron, 70; simazine, 164; and paraquat, 240. IC5O values for 2,4-D, acifluorfen, glyphosate and metolachlor exceeded the maximum test concentration of 10,000 ng/L. The IC5O value for alachlor was estimated to be between 1,000 and 10,000 ng/L. None of the herbicides tested had a significant effect on dark respiration.

  17. Net Gain: A New Method for Preventing Malaria Deaths | CRDI ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    A finely spun net could prevent as many as one-third of all child deaths in Africa, reports IDRC's new publication, Net Gain. Studies conducted in Gambia, Ghana, and Kenya show that the insecticide-treated mosquito net reduced the mortality rate of children under 5 years of age by up to 63 percent. Net Gain reviews and ...

  18. 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

  19. Variability in leaf morphology and photosynthetic responses of arctic woody shrubs to warming and shifts in snow induced thermal insulation

    Science.gov (United States)

    Flower, C. E.; Pereyra, G.; Welker, J. M.; Trumbore, S.; Gonzalez-Meler, M. A.

    2013-12-01

    Permafrost warming in the climate sensitive Arctic tundra has been linked to shifts in vegetation, from tussock dominated to tussock/shrub systems. This vegetation shift has the potential to not only impact the abiotic conditions, but also the energy balance and biogeochemical cycling of these systems; as plant assimilation, respiration, C allocation, and rooting depth may differ between plant functional groups. We assessed leaf morphology and constructed light response curves at ambient (400 ppm) and elevated (800 ppm) CO2 concentrations to assess photosynthetic responses of dwarf birch and diamond-leaf willow to a natural and induced simulated warming experiment at the Toolik Field Station in Alaska. Results indicate a positive correlation between summer soil thaw depth and leaf surface area indicating hydrological responses of both species. Additionally, leaf area was higher in warmed plots relative to non warmed plots in both the snow addition and the control treatments. Furthermore, we found that diamond-leaf willow exhibits elevated assimilation rates relative to dwarf birch. Both species exhibited similar photosynthetic responses to elevated CO2 increasing assimilation by ~34%. These responses highlight the forcing imposed by woody vegetation in arctic regions with the potential to increase net primary production in addition to positive feedbacks on winter snow depth, soil temperature, and moisture.

  20. Synergic effect of salinity and zinc stress on growth and photosynthetic responses of the cordgrass, Spartina densiflora

    Science.gov (United States)

    Redondo-Gómez, Susana; Andrades-Moreno, Luis; Mateos-Naranjo, Enrique; Parra, Raquel; Valera-Burgos, Javier; Aroca, Ricardo

    2011-01-01

    Spartina densiflora is a C4 halophytic species that has proved to have a high invasive potential which derives from its physiological plasticity to environmental factors, such as salinity. It is found in coastal marshes of south-west Spain, growing over sediments with between 1 mmol l−1 and 70 mmol l−1 zinc. A glasshouse experiment was designed to investigate the synergic effect of zinc from 0 mmol l−1 to 60 mmol l−1 at 0, 1, and 3% NaCl on the growth and the photosynthetic apparatus of S. densiflora by measuring chlorophyll fluorescence parameters and gas exchange, and its recovery after removing zinc. Antioxidant enzyme activities and total zinc, sodium, calcium, iron, magnesium, manganese, phosphorus, potassium, and nitrogen concentrations were also determined. Spartina densiflora showed the highest growth at 1 mmol l−1 zinc and 1% NaCl after 90 d of treatment; this enhanced growth was supported by the measurements of net photosynthetic rate (A). Furthermore, there was a stimulatory effect of salinity on accumulation of zinc in tillers of this species. Zinc concentrations >1 mmol l−1 reduced growth of S. densiflora, regardless of salinity treatments. This declining growth may be attributed to a decrease in A caused by diffusional limitation of photosynthesis, owing to the modification of the potassium/calcium ratio. Also, zinc and salinity had a marked overall effect on the photochemical (photosystem II) apparatus, partially mediated by the accumulation of H2O2 and subsequent oxidative damage. However, salinity favoured the recovery of the photosynthetic apparatus to the toxic action of zinc, and enhanced the nutrient uptake. PMID:21841175

  1. Effects of plant density on the photosynthetic and chloroplast characteristics of maize under high-yielding conditions

    Science.gov (United States)

    Ren, Baizhao; Liu, Wei; Zhang, Jiwang; Dong, Shuting; Liu, Peng; Zhao, Bin

    2017-04-01

    Plant density has been recognized as a major factor determining the grain yield. The photosynthetic performance changes as the density increases. The main objective of this research was to evaluate responses of photosynthetic performance and chloroplast ultrastructure to planting densities in two summer maize ( Zea mays L.) hybrids Denghai661 (DH661) and Nongda108 (ND108). DH661 was planted at densities of 30,000, 45,000, 60,000, 75,000, 90,000, 105,000, 120,000, or 135,000 plants ha-1. ND108 was planted at densities of 30,000, 45,000, 60,000, 75,000, or 90,000 plants ha-1. Research variables included leaf area, grain yield, chlorophyll content, leaf gas exchange parameters, number of chloroplasts, and chloroplast ultrastructure. As plant density increased, chlorophyll a and b content significantly decreased; carotenoids initially decreased and then increased; the net photosynthetic rate during each growth period significantly decreased; the membrane structure of mesophyll cells was gradually damaged; the number of chloroplasts significantly decreased; the external form of chloroplasts shifted from long and oval to elliptical or circular; the number of grana significantly decreased, while the number of grana lamellae increased; grana gradually became hypogenetic and eventually dissolved; plot yield increased; and yield per plant significantly decreased. The yield per plant of DH661 at 135,000 plants ha-1 and that of ND108 at 90,000 plants ha-1 decreased by 65.8 and 42.5%, respectively, compared with those at 30,000 plants ha-1.

  2. Texture Based Image Analysis With Neural Nets

    Science.gov (United States)

    Ilovici, Irina S.; Ong, Hoo-Tee; Ostrander, Kim E.

    1990-03-01

    In this paper, we combine direct image statistics and spatial frequency domain techniques with a neural net model to analyze texture based images. The resultant optimal texture features obtained from the direct and transformed image form the exemplar pattern of the neural net. The proposed approach introduces an automated texture analysis applied to metallography for determining the cooling rate and mechanical working of the materials. The results suggest that the proposed method enhances the practical applications of neural nets and texture extraction features.

  3. Photosynthetic acclimation and the estimation of temperate ice algal primary production in Saroma-ko Lagoon, Japan

    Science.gov (United States)

    Kudoh, Sakae; Robineau, Brigitte; Suzuki, Yoshihiro; Fujiyoshi, Yoshihiro; Takahashi, Masayuki

    1997-02-01

    Temporal changes in the sea ice environment, ice algal biomass and photosynthetic characteristics were studied at Saroma-ko Lagoon in Japan, the area where the southernmost seasonal sea ice in the northern hemisphere occurs. In 1992, the sea ice started to develop in early January and covered the entire lagoon surface in late January, when water temperatures at the center of the lagoon decreased below -1.7°C. High concentrations of ice algae in the bottom layer of the sea ice, where light levels were 0.5-2.8% of the surface irradiance, were visually confirmed in mid-February. The biomass increased in late February to a maximum of 38.25 mg Chl am -2 then suddenly decreased during stormy weather in early March. Afterwards it remained rather constant, with high values of 20-30 mg Chl am -2 until mid-March. Photosynthesis vs. light analysis revealed that ice algae in this lagoon had a low dark respiration rate of 0.024 mg C mg Chl a-1h -1 on average while the increase of photosynthesis at light levels lower than 25 μmol m -2s -1 showed gentle linear increases with increments of light intensity. However, the maximum photosynthetic rate and the efficiency of the photosynthesis at low light levels were rather low compared with values from previous studies in the polar sea ice areas. Nevertheless, in situ estimates of net diel photosynthesis and production, which were calculated with a numerical model using the photosynthetic parameters and hourly averaged light at the ice algal habitat, suggested that large positive values were expected throughout this study. In temperate sea ice areas like Saroma-ko, where there are day/night light cycles, ice algae that have a small net loss of carbon at night due to dark respiration could achieve positive photosynthesis and growth even though they do not show the efficient photosynthesis under low light as shown by polar ice algae.

  4. Professional Enterprise NET

    CERN Document Server

    Arking, Jon

    2010-01-01

    Comprehensive coverage to help experienced .NET developers create flexible, extensible enterprise application code If you're an experienced Microsoft .NET developer, you'll find in this book a road map to the latest enterprise development methodologies. It covers the tools you will use in addition to Visual Studio, including Spring.NET and nUnit, and applies to development with ASP.NET, C#, VB, Office (VBA), and database. You will find comprehensive coverage of the tools and practices that professional .NET developers need to master in order to build enterprise more flexible, testable, and ext

  5. Lettuce irrigated with contaminated water: Photosynthetic effects, antioxidative response and bioaccumulation of microcystin congeners.

    Science.gov (United States)

    Bittencourt-Oliveira, Maria do Carmo; Cordeiro-Araújo, Micheline Kézia; Chia, Mathias Ahii; Arruda-Neto, João Dias de Toledo; de Oliveira, Ênio Tiago; dos Santos, Flávio

    2016-06-01

    The use of microcystins (MCs) contaminated water to irrigate crop plants represents a human health risk due to their bioaccumulation potential. In addition, MCs cause oxidative stress and negatively influence photosynthetic activities in plants. The present study was aimed at investigating the effect of MCs on photosynthetic parameters and antioxidative response of lettuce. Furthermore, the bioaccumulation factor (BAF) of total MCs, MC-LR and MC-RR in the vegetable after irrigation with contaminated water was determined. Lettuce crops were irrigated for 15 days with water containing cyanobacterial crude extracts (Microcystis aeruginosa) with MC-LR (0.0, 0.5, 2.0, 5.0 and 10.0 µg L(-1)), MC-RR (0.0, 0.15, 0.5, 1.5 and 3.0 µg L(-1)) and total MCs (0.0, 0.65, 2.5, 6.5 and 13.0 µg L(-1)). Increased net photosynthetic rate, stomatal conductance, leaf tissue transpiration and intercellular CO2 concentration were recorded in lettuce exposed to different MCs concentrations. Antioxidant response showed that glutathione S-transferase activity was down-regulated in the presence of MCs. On the other hand, superoxide dismutase, catalase and peroxidase activities were upregulated with increasing MCs concentrations. The bioaccumulation factor (BAF) of total MCs and MC-LR was highest at 6.50 and 5.00 µg L(-1), respectively, while for MC-RR, the highest BAF was recorded at 1.50 µg L(-1) concentration. The amount of total MCs, MC-LR and MC-RR bioacumulated in lettuce was highest at the highest exposure concentrations. However, at the lowest exposure concentration, there were no detectable levels of MC-LR, MC-RR and total MCs in lettuce. Thus, the bioaccumulation of MCs in lettuce varies according to the exposure concentration. In addition, the extent of physiological response of lettuce to the toxins relies on exposure concentrations. Copyright © 2016 Elsevier Inc. All rights reserved.

  6. 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

  7. Ambient UV-B radiation reduces PSII performance and net photosynthesis in high Arctic Salix arctica

    DEFF Research Database (Denmark)

    Albert, Kristian Rost; Mikkelsen, Teis Nørgaard; Ro-Poulsen, Helge

    2011-01-01

    Ambient ultraviolet-B (UV-B) radiation potentially impacts the photosynthetic performance of high Arctic plants. We conducted an UV-B exclusion experiment in a dwarf shrub heath in NE Greenland (74°N), with open control, filter control, UV-B filtering and UV-AB filtering, all in combination......, nitrogen and UV-B absorbing compounds. Compared to a 60% reduced UV-B irradiance, the ambient solar UV-B reduced net photosynthesis in Salix arctica leaves fixed in the 45° position which exposed leaves to maximum natural irradiance. Also a reduced Calvin Cycle capacity was found, i.e. the maximum rate...... across position in the vegetation. These findings add to the evidence that the ambient solar UV-B currently is a significant stress factor for plants in high Arctic Greenland....

  8. Ambient UV-B radiation reduces PSII performance and net photosynthesis in high Arctic Salix arctica

    DEFF Research Database (Denmark)

    Albert, Kristian Rost; Mikkelsen, Teis Nørgaard; Ro-Poulsen, H.

    2011-01-01

    Ambient ultraviolet-B (UV-B) radiation potentially impacts the photosynthetic performance of high Arctic plants. We conducted an UV-B exclusion experiment in a dwarf shrub heath in NE Greenland (74°N), with open control, filter control, UV-B filtering and UV-AB filtering, all in combination...... was characterized by simultaneous gas exchange and chlorophyll fluorescence measurements and the PSII performance through the growing season was investigated with fluorescence measurements. Leaf harvest towards the end of the growing season was done to determine the specific leaf area and the content of carbon......, nitrogen and UV-B absorbing compounds. Compared to a 60% reduced UV-B irradiance, the ambient solar UV-B reduced net photosynthesis in Salix arctica leaves fixed in the 45° position which exposed leaves to maximum natural irradiance. Also a reduced Calvin Cycle capacity was found, i.e. the maximum rate...

  9. Effect of Low pH and Aluminum Toxicity on the Photosynthetic Characteristics of Different Fast-Growing Eucalyptus Vegetatively Propagated Clones

    Science.gov (United States)

    Yang, Mei; Tan, Ling; Xu, Yuanyuan; Zhao, Yihui; Cheng, Fei; Ye, Shaoming; Jiang, Weixin

    2015-01-01

    Knowing how acid soils and aluminum in soils may limit the growth of Eucalyptus trees in plantations is important because these plantations grow in many tropical and subtropical regions. Seedlings of four vegetatively propagated Eucalyptus clones, E. grandis × E. urophylla ‘GLGU9’(G9), E. grandis × E. urophylla ‘GLGU12’ (G12), E. urophylla × E. camaldulensis ‘GLUC3’ (G3) and E. urophylla ‘GLU4’(G4), were subjected to liquid culture with Hoagland nutrient solution for 40 days, then treated with four different treatments of acid and aluminum for 1 day. The four treatments used either pH 3.0 or 4.0 with or without added aluminum (4.4 mM) in all possible combinations; a control used no added aluminum at pH 4.8. Subsequently, the photosynthetic parameters and morphology of leaves from eucalypt seedlings were determined and observed. The results showed that the tested chlorophyll content, net photosynthetic rate, transpiration rate and water use efficiency were apparently inhibited by aluminum. Under uniform Al concentration (4.4 mM), the Al-induced limitation to photosynthetic parameters increased with pH, indicating acid stimulation to Al toxicity. Among all treatments, the most significant reduction was found in the combination of pH 3.0 and 4.4 mM Al. The photosynthetic and transpiration rates showed similar trends with G9 > G12 > G3 > G4, suggesting that G9 and G12 had higher Al-tolerance than other two clones. Microscopic observation revealed changes in leaf morphology when exposed to Al stress; for example, a reduced thickness of leaf epidermis and palisade tissue, the descendant palisade tissue/spongy tissue ratio and leaf tissue looseness. Overall, the acid and aluminum stress exerted negative effects on the photosynthetic activity of eucalypt seedlings, but the differences in tolerance to Al toxicity between the clones were favorable, offering potential to improve Eucalyptus plantation productivity by selecting Al tolerant clones. PMID

  10. Hydrogen Production by the Photosynthetic Bacterium Rhodospirillum rubrum

    Science.gov (United States)

    Zürrer, Hans; Bachofen, Reinhard

    1979-01-01

    Continuous photosynthetic production of hydrogen by Rhodospirillum rubrum in batch cultures was observed up to 80 days with the hydrogen donor, pure lactate or lactic acid-containing wastes, supplied periodically. Hydrogen was produced at an average rate of 6 ml/h per g (dry weight) of cells with whey as a hydrogen donor. In continuous cultures with glutamate as a growth-limiting nitrogen source and lactate as a hydrogen donor, hydrogen was evolved at a rate of 20 ml/h per g (dry weight). The composition of the gas evolved remained practically constant (70 to 75% H2, 25 to 30% CO2). Photosynthetic bacteria processing specific organic wastes could be an advantage in large-scale production of hydrogen together with food protein of high value, compared to other biological systems. Images PMID:16345375

  11. Hydrogen production by the photosynthetic bacterium Rhodospirillum rubrum

    Energy Technology Data Exchange (ETDEWEB)

    Zuerrer, H.; Bachofen, R.

    1979-05-01

    Continuous photosynthetic production of hydrogen by Rhodospirillum rubrum in batch cultures was observed up to 80 days with the hydrogen donor, pure lactate or lactic acid-containing wastes, supplied periodically. Hydrogen was produced at an average rate of 6 ml/h per g (dry weight) of cells with whey as a hydrogen donor. In continuous cultures with glutamate as a growth-limiting nitrogen source and lactate as a hydrogen donor, hydrogen was evolved at a rate of 20 ml/h per g (dry weight). The composition of the gas evolved remained practically constant (70 to 75% H/sub 2/, 25 to 30% CO/sub 2/). Photosynthetic bacteria processing specific organic wastes could be an advantage in large-scale production of hydrogen together with food protein of high value, compared to other biological systems.

  12. [Effects of exogenous 24-epibrassinolde on leaf morphology and photosynthetic characteristics of tomato seedlings under low light stress].

    Science.gov (United States)

    Li, Ning; Guo, Shi-rong; Shu, Sheng; Sun, Jin

    2015-03-01

    This study investigated the effects of exogenous 24-epibrassinolide (EBR) on the leaf morphology and photosynthetic characteristics of tomato seedlings (cv. Jiersi) cultured hydroponically under low light stress. The results showed that low light stress induced adaptive changes in the leaf morphology of tomato seedling. Low light stress significantly increased the leaf area, specific leaf area, angle between stem and leaf, vertical angle and cable bent, but significantly decreased the dry mass of leaf. Low light stress also significantly decreased the maximum net photosynthetic rate,. apparent quantum yield, dark respiration rate, carboxylation efficiency and Rubisco large subunit content. The light compensation point and carbon dioxide compensation point were dramatically enhanced under low light stress. However, foliar spraying EBR significantly increased the leaf area, leaf dry mass, angle between stem and leaf, vertical angle by 14.1%, 57.1%, 12.3% and 7.7% under low light stress, respectively. EBR significantly decreased the specific leaf area and cable bent by 30.5% and 10.6% in low light stressed plants. In addition, EBR significantly enhanced the apparent quantum yield, dark respiration rate and carboxylation efficiency by 20.4%, 17.9% and 9.3%, respectively, but significantly reduced the light compensation point and carbon dioxide compensation point by 21.9% and 4.3% under low light stress. Moreover, EBR also significantly increased the Rubisco large subunit content in low light stressed leaves. These results suggested that application of exogenous EBR could effectively alleviate the inhibition of photosynthesis induced by low light stress via improving the apparent quantum yield, dark respiration rate, carboxylation efficiency and Rubisco content, and maintaining the stability of leaf morphology, thus low light tolerance of tomato seedlings.

  13. Gill net and trammel net selectivity in the northern Aegean Sea, Turkey

    Directory of Open Access Journals (Sweden)

    F. Saadet Karakulak

    2008-09-01

    Full Text Available Fishing trials were carried out with gill nets and trammel nets in the northern Aegean Sea from March 2004 to February 2005. Four different mesh sizes for the gill nets and the inner panel of trammel nets (16, 18, 20 and 22 mm bar length were used. Selectivity parameters for the five most economically important species, bogue (Boops boops, annular sea bream (Diplodus annularis, striped red mullet (Mullus surmuletus, axillary sea bream (Pagellus acarne and blotched picarel (Spicara maena, caught by the two gears were estimated. The SELECT method was used to estimate the selectivity parameters of a variety of models. Catch composition and catch proportion of several species were different in gill and trammel nets. The length frequency distributions of the species caught by the two gears were significantly different. The bi-modal model selectivity curve gave the best fit for gill net and trammel net data, and there was little difference between the modal lengths of these nets. However, a clear difference was found in catching efficiency. The highest catch rates were obtained with the trammel net. Given that many discard species and small fish are caught by gill nets and trammel nets with a mesh size of 16 mm, it is clear that these nets are not appropriate for fisheries. Consequently, the best mesh size for multispecies fisheries is 18 mm. This mesh size will considerably reduce the numbers of small sized individuals and discard species in the catch.

  14. Differential allocation to photosynthetic and non-photosynthetic nitrogen fractions among native and invasive species.

    Science.gov (United States)

    Funk, Jennifer L; Glenwinkel, Lori A; Sack, Lawren

    2013-01-01

    Invasive species are expected to cluster on the "high-return" end of the leaf economic spectrum, displaying leaf traits consistent with higher carbon assimilation relative to native species. Intra-leaf nitrogen (N) allocation should support these physiological differences; however, N biochemistry has not been examined in more than a few invasive species. We measured 34 leaf traits including seven leaf N pools for five native and five invasive species from Hawaii under low irradiance to mimic the forest understory environment. We found several trait differences between native and invasive species. In particular, invasive species showed preferential N allocation to metabolism (amino acids) rather than photosynthetic light reactions (membrane-bound protein) by comparison with native species. The soluble protein concentration did not vary between groups. Under these low irradiance conditions, native species had higher light-saturated photosynthetic rates, possibly as a consequence of a greater investment in membrane-bound protein. Invasive species may succeed by employing a wide range of N allocation mechanisms, including higher amino acid production for fast growth under high irradiance or storage of N in leaves as soluble protein or amino acids.

  15. Estimating the net effect of progesterone elevation on the day of hCG on live birth rates after IVF: a cohort analysis of 3296 IVF cycles.

    Science.gov (United States)

    Venetis, Christos A; Kolibianakis, Efstratios M; Bosdou, Julia K; Lainas, George T; Sfontouris, Ioannis A; Tarlatzis, Basil C; Lainas, Tryfon G

    2015-03-01

    What is the proper way of assessing the effect of progesterone elevation (PE) on the day of hCG on live birth in women undergoing fresh embryo transfer after in vitro fertilization (IVF) using GnRH analogues and gonadotrophins? This study indicates that a multivariable approach, where the effect of the most important confounders is controlled for, can lead to markedly different results regarding the association between PE on the day of hCG and live birth rates after IVF when compared with the bivariate analysis that has been typically used in the relevant literature up to date. PE on the day of hCG is associated with decreased pregnancy rates in fresh IVF cycles. Evidence for this comes from observational studies that mostly failed to control for potential confounders. This is a retrospective analysis of a cohort of fresh IVF/intracytoplasmic sperm injection cycles (n = 3296) performed in a single IVF centre during the period 2001-2013. Patients in whom ovarian stimulation was performed with gonadotrophins and GnRH analogues. Natural cycles and cycles where stimulation involved the administration of clomiphene were excluded. In order to reflect routine clinical practice, no other exclusion criteria were imposed on this dataset. The primary outcome measure for this study was live birth defined as the delivery of a live infant after 24 weeks of gestation. We compared the association between PE on the day of hCG (defined as P > 1.5 ng/ml) and live birth rates calculated by simple bivariate analyses with that derived from multivariable logistic regression. The multivariable analysis controlled for female age, number of oocytes retrieved, number of embryos transferred, developmental stage of embryos at transfer (cleavage versus blastocyst), whether at least one good-quality embryo was transferred, the woman's body mass index, the total dose of FSH administered during ovarian stimulation and the type of GnRH analogues used (agonists versus antagonists) during ovarian

  16. Effects of salinity and short-term elevated atmospheric CO2on the chemical equilibrium between CO2fixation and photosynthetic electron transport of Stevia rebaudiana Bertoni.

    Science.gov (United States)

    Hussin, Sayed; Geissler, Nicole; El-Far, Mervat M M; Koyro, Hans-Werner

    2017-09-01

    The effect of water salinity on plant growth and photosynthetic traits of Stevia rebaudiana was investigated to determine its level and mechanisms of salinity tolerance. It was also attempted to assess how short-term elevated CO 2 concentration would influence the boundaries and mechanisms of its photosynthetic capacity. The plants were grown in gravel/hydroponic system under controlled greenhouse conditions and irrigated with four different salinity levels (0, 25, 50 and 100 mol m -3 NaCl). Low salinity did not significantly alter the plant fresh weight, which was substantially decreased by 67% at high salinity treatment. Salinity tolerance threshold was reached at 50 mol m -3  NaCl while C50 was between 50 and 100 mol m -3  NaCl, indicating that S. rebaudiana is a moderate salt tolerant species. Salt-induced growth reduction was apparently linked to a significant decline of about 47% in the photosynthetic rates (A net ) at high salinity treatment, leading consequently to a disequilibrium between CO 2 -assimilation and electron transport rates (indicated by enhanced ETR max /A gross ratio). Elevated atmospheric CO 2 enhanced CO 2 assimilation rates by 65% and 80% for control and high-salt-stressed plants respectively, likely due to significant increases in intercellular CO 2 concentration (indicated by enhanced C i /C a ). The priority for Stevia under elevated atmospheric CO 2 was not to save water but to maximize photosynthesis so that the PWUE was progressively improved and the threat of oxidative stress was diminished (decline in ETR max /A gross ). The results imply that elevated CO 2 level could ameliorate some of the detrimental effects of salinity, conferring higher tolerance and survival of S. rebaudiana, a highlydesired feature with the forthcoming era of global changes. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  17. Photosynthetic efficiency of Chlamydomonas reinhardtii in flashing light.

    Science.gov (United States)

    Vejrazka, Carsten; Janssen, Marcel; Streefland, Mathieu; Wijffels, René H

    2011-12-01

    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 efficiency and growth of the green microalga Chlamydomonas reinhardtii were measured using LED light to simulate light/dark cycles ranging from 5 to 100 Hz at a light-dark ratio of 0.1 and a flash intensity of 1000 µmol m(-2) s(-1). Light flashing at 100 Hz yielded the same photosynthetic efficiency and specific growth rate as cultivation under continuous illumination with the same time-averaged light intensity (i.e., 100 µmol m(-2) s(-1)). The efficiency and growth rate decreased with decreasing flash frequency. Even at 5 Hz flashing, the rate of linear electron transport during the flash was still 2.5 times higher than during maximal growth under continuous light, suggesting storage of reducing equivalents during the flash which are available during the dark period. In this way the dark reaction of photosynthesis can continue during the dark time of a light/dark cycle. Understanding photosynthetic growth in dynamic light regimes is crucial for model development to predict microalgal photobioreactor productivities. Copyright © 2011 Wiley Periodicals, Inc.

  18. WaveNet

    Science.gov (United States)

    2015-10-30

    Coastal Inlets Research Program WaveNet WaveNet is a web-based, Graphical-User-Interface ( GUI ) data management tool developed for Corps coastal...generates tabular and graphical information for project planning and design documents. The WaveNet is a web-based GUI designed to provide users with a...data from different sources, and employs a combination of Fortran, Python and Matlab codes to process and analyze data for USACE applications

  19. Coloured Petri Nets

    DEFF Research Database (Denmark)

    Jensen, Kurt

    1991-01-01

    This paper describes how Coloured Petri Nets (CP-nets) have been developed — from being a promising theoretical model to being a full-fledged language for the design, specification, simulation, validation and implementation of large software systems (and other systems in which human beings and...... use of CP-nets — because it means that the function representation and the translations (which are a bit mathematically complex) no longer are parts of the basic definition of CP-nets. Instead they are parts of the invariant method (which anyway demands considerable mathematical skills...

  20. Game Coloured Petri Nets

    DEFF Research Database (Denmark)

    Westergaard, Michael

    2006-01-01

    This paper introduces the notion of game coloured Petri nets. This allows the modeler to explicitly model what parts of the model comprise the modeled system and what parts are the environment of the modeled system. We give the formal definition of game coloured Petri nets, a means of reachability...... analysis of this net class, and an application of game coloured Petri nets to automatically generate easy-to-understand visualizations of the model by exploiting the knowledge that some parts of the model are not interesting from a visualization perspective (i.e. they are part of the environment...

  1. Programming NET Web Services

    CERN Document Server

    Ferrara, Alex

    2007-01-01

    Web services are poised to become a key technology for a wide range of Internet-enabled applications, spanning everything from straight B2B systems to mobile devices and proprietary in-house software. While there are several tools and platforms that can be used for building web services, developers are finding a powerful tool in Microsoft's .NET Framework and Visual Studio .NET. Designed from scratch to support the development of web services, the .NET Framework simplifies the process--programmers find that tasks that took an hour using the SOAP Toolkit take just minutes. Programming .NET

  2. Annotating Coloured Petri Nets

    DEFF Research Database (Denmark)

    Lindstrøm, Bo; Wells, Lisa Marie

    2002-01-01

    -net. An example of such auxiliary information is a counter which is associated with a token to be able to do performance analysis. Modifying colour sets and arc inscriptions in a CP-net to support a specific use may lead to creation of several slightly different CP-nets – only to support the different uses...... a method which makes it possible to associate auxiliary information, called annotations, with tokens without modifying the colour sets of the CP-net. Annotations are pieces of information that are not essential for determining the behaviour of the system being modelled, but are rather added to support...

  3. Using the quantum yields of photosystem II and the rate of net photosynthesis to monitor high irradiance and temperature stress in chrysanthemum (Dendranthema grandiflora)

    DEFF Research Database (Denmark)

    Wakjera, Eshetu Janka; Körner, Oliver; Rosenqvist, Eva

    2015-01-01

    Under a dynamic greenhouse climate control regime, temperature is adjusted to optimise plant physiological responses to prevailing irradiance levels; thus, both temperature and irradiance are used by the plant to maximise the rate of photosynthesis, assuming other factors are not limiting...... irradiance, the maximum Pn and ETR were reached at 24 °C. Increased irradiance decreased the PSII operating efficiency and increased NPQ, while both high irradiance and temperature had a significant effect on the PSII operating efficiency at temperatures >28 °C. Under high irradiance and temperature, changes...... in the NPQ determined the PSII operating efficiency, with no major change in the fraction of open PSII centres (qL) (indicating a QA redox state). We conclude that 1) chrysanthemum plants cope with excess irradiance by non-radiative dissipation or a reversible stress response, with the effect on the Pn...

  4. Hydrogen sulfide alleviates lead-induced photosynthetic and ultrastructural changes in oilseed rape.

    Science.gov (United States)

    Ali, B; Song, W J; Hu, W Z; Luo, X N; Gill, R A; Wang, J; Zhou, W J

    2014-04-01

    The role of hydrogen sulfide (H2S) in alleviating lead (Pb) induced stress in oilseed rape (Brassica napus L.) was studied under laboratory conditions. Plants were grown hydroponically in greenhouse conditions under three levels (0, 100, and 400 µM) of Pb and three levels (0, 100 and 200 µM) of H2S donor, sodium hydrosulfide (NaHS). Application of H2S significantly improved the plant growth, root morphology, chlorophyll contents and photosynthetic activity in leaves of B. napus under Pb stress. Moreover, exogenously applied H2S significantly lowered the Pb concentration in shoots and roots of plants under Pb stress. The microscopic examination indicated that application of exogenous H2S enabled a clean mesophyll cell having a well developed chloroplast with thylakoid membranes and starch grains. A number of modifications could be observed in root tip cell i.e. mature mitochondria, long endoplasmic reticulum and golgibodies under combined application of H2S and Pb. On the basis of these findings, it can be concluded that application of exogenous H2S has a protective role on plant growth, net photosynthesis rate and ultrastructural changes in B. napus plants under high Pb exposures. Copyright © 2014 Elsevier Inc. All rights reserved.

  5. [Effects of elevated rhizosphere CO2 concentration on the photosynthetic characteristics, yield, and quality of muskmelon].

    Science.gov (United States)

    Liu, Yi-Ling; Sun, Zhou-Ping; Li, Tian-Lai; Gu, Feng-Ying; He, Yu

    2013-10-01

    By using aeroponics culture system, this paper studied the effects of elevated rhizosphere CO2 concentration on the leaf photosynthesis and the fruit yield and quality of muskmelon during its anthesis-fruiting period. In the fruit development period of muskmelon, as compared with those in the control (350 microL CO2 x L (-1)), the leaf chlorophyll content, net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular CO2 concentration (Ci), and the maximal photochemical efficiency of PS II (Fv/Fm) in treatments 2500 and 5000 microL CO2 x L(-1) decreased to some extents, but the stomatal limitation value (Ls) increased significantly, and the variation amplitudes were larger in treatment 5000 microL CO2 x L(-1) than in treatment 2500 microL CO2 x L(-1). Under the effects of elevated rhizosphere CO2 concentration, the fruit yield per plant and the Vc and soluble sugar contents in fruits decreased markedly, while the fruit organic acid content was in adverse. It was suggested that when the rhizosphere CO2 concentration of muskmelon during its anthesis-fruiting period reached to 2500 microL x L(-1), the leaf photosynthesis and fruit development of muskmelon would be depressed obviously, which would result in the decrease of fruit yield and quality of muskmelon.

  6. Exogenous calcium alleviates low night temperature stress on the photosynthetic apparatus of tomato leaves.

    Directory of Open Access Journals (Sweden)

    Guoxian Zhang

    Full Text Available The effect of exogenous CaCl2 on photosystem I and II (PSI and PSII activities, cyclic electron flow (CEF, and proton motive force of tomato leaves under low night temperature (LNT was investigated. LNT stress decreased the net photosynthetic rate (Pn, effective quantum yield of PSII [Y(II], and photochemical quenching (qP, whereas CaCl2 pretreatment improved Pn, Y(II, and qP under LNT stress. LNT stress significantly increased the non-regulatory quantum yield of energy dissipation [Y(NO], whereas CaCl2 alleviated this increase. Exogenous Ca2+ enhanced stimulation of CEF by LNT stress. Inhibition of oxidized PQ pools caused by LNT stress was alleviated by CaCl2 pretreatment. LNT stress reduced zeaxanthin formation and ATPase activity, but CaCl2 pretreatment reversed both of these effects. LNT stress caused excess formation of a proton gradient across the thylakoid membrane, whereas CaCl2 pretreatment decreased the said factor under LNT. Thus, our results showed that photoinhibition of LNT-stressed plants could be alleviated by CaCl2 pretreatment. Our findings further revealed that this alleviation was mediated in part by improvements in carbon fixation capacity, PQ pools, linear and cyclic electron transports, xanthophyll cycles, and ATPase activity.

  7. Improvement of Photosynthetic Efficiency Through Reduction of Chlorophyll Antenna Size

    Energy Technology Data Exchange (ETDEWEB)

    Blankinship, S.L.; Greenbaum, E.; Lee, J.W.; Mets, L.

    1999-05-03

    We have previously presented a graphical illustration of a strategy to improve photosynthetic conversion efficiencies by a reduction of the antenna size in photosynthetic reaction centers. During the current reporting period, we have made progress in demonstrating the conceptual correctness of this idea. Light-saturation studies for CO, in air were performed with an antenna-deficient mutant of Chlamydomonas (DS521) and the wild type (DES15). The light-saturated rate for CO(2), assimilation in mutant DS521 was about two times higher (187 Mu-mol.h(-1).mg chl(-1)) than that of the wild type, DES15 (95 Mu-mol.h(-1).mg chl(-1). Significantly, a partial linearization of the light-saturation curve was also observed. The light intensities that give half-saturation of the photosynthetic rate were 276 and 152 Mu-E.m(-2).s(-1) in DS521 and DES15, respectively. These results confirmed that DS521 has a smaller chlorophyll antenna size and demonstrated that the reduction of antenna size can indeed improve the overall efficiency of photon utilization. Corresponding experiments were also performed with CO(2), in helium. Under this anaerobic condition, no photoinhibition was observed, even at elevated light intensities. Photoinhibition occurs under aerobic conditions. The antenna-deficient mutant DS521 can also provide significant resistance to photoinhibition, in addition to the improvement in the overall efficiency in CO(2), fixation.

  8. Anatomical structure of moss leaves and their photosynthetic activity

    Directory of Open Access Journals (Sweden)

    Jan Krupa

    2014-01-01

    Full Text Available The photosynthetic activity of the leaf area unit increases depending on the degree of differentiation of the anatomical structure of the leaves of six chosen moss species. There is a correlation between the leaf area and the degree of differentiation of the anatomical structure resulting in enlargement of the area of contact of the assimilating cells with air. The leaves of Catharinea undulata having a one-layer blade and provided with several lamellae show a higher photosynthesis per 1 cm2 of their surface than the one-layer leaves of Mniurnm or Funaria. Aloina leaves are the smallest in area among those of the moss species discussed, however, their photosynthetic rate is almost 4.5 times higher than in Funaria leaves. By analogy to the structure of leaves and their function in vascular, plants, these changes and correlations may be considered as attempts of primeval adaptation of mosses to terrestrial conditions of living.

  9. Net zero water

    CSIR Research Space (South Africa)

    Lindeque, M

    2013-01-01

    Full Text Available Is it possible to develop a building that uses a net zero amount of water? In recent years it has become evident that it is possible to have buildings that use a net zero amount of electricity. This is possible when the building is taken off...

  10. SolNet

    DEFF Research Database (Denmark)

    Jordan, Ulrike; Vajen, Klaus; Bales, Chris

    2014-01-01

    SolNet, founded in 2006, is the first coordinated International PhD education program on Solar Thermal Engineering. The SolNet network is coordinated by the Institute of Thermal Engineering at Kassel University, Germany. The network offers PhD courses on solar heating and cooling, conference...

  11. Kunstige neurale net

    DEFF Research Database (Denmark)

    Hørning, Annette

    1994-01-01

    Artiklen beskæftiger sig med muligheden for at anvende kunstige neurale net i forbindelse med datamatisk procession af naturligt sprog, specielt automatisk talegenkendelse.......Artiklen beskæftiger sig med muligheden for at anvende kunstige neurale net i forbindelse med datamatisk procession af naturligt sprog, specielt automatisk talegenkendelse....

  12. Importance of Fluctuations in Light on Plant Photosynthetic Acclimation.

    Science.gov (United States)

    Vialet-Chabrand, Silvere; Matthews, Jack S A; Simkin, Andrew J; Raines, Christine A; Lawson, Tracy

    2017-04-01

    The acclimation of plants to light has been studied extensively, yet little is known about the effect of dynamic fluctuations in light on plant phenotype and acclimatory responses. We mimicked natural fluctuations in light over a diurnal period to examine the effect on the photosynthetic processes and growth of Arabidopsis (Arabidopsis thaliana). High and low light intensities, delivered via a realistic dynamic fluctuating or square wave pattern, were used to grow and assess plants. Plants subjected to square wave light had thicker leaves and greater photosynthetic capacity compared with fluctuating light-grown plants. This, together with elevated levels of proteins associated with electron transport, indicates greater investment in leaf structural components and photosynthetic processes. In contrast, plants grown under fluctuating light had thinner leaves, lower leaf light absorption, but maintained similar photosynthetic rates per unit leaf area to square wave-grown plants. Despite high light use efficiency, plants grown under fluctuating light had a slow growth rate early in development, likely due to the fact that plants grown under fluctuating conditions were not able to fully utilize the light energy absorbed for carbon fixation. Diurnal leaf-level measurements revealed a negative feedback control of photosynthesis, resulting in a decrease in total diurnal carbon assimilated of at least 20%. These findings highlight that growing plants under square wave growth conditions ultimately fails to predict plant performance under realistic light regimes and stress the importance of considering fluctuations in incident light in future experiments that aim to infer plant productivity under natural conditions in the field. © 2017 American Society of Plant Biologists. All Rights Reserved.

  13. Leaf hydraulic evolution led a surge in leaf photosynthetic capacity during early angiosperm diversification.

    Science.gov (United States)

    Brodribb, Tim J; Feild, Taylor S

    2010-02-01

    Angiosperm evolution transformed global ecology, and much of this impact derives from the unrivalled vegetative productivity of dominant angiosperm clades. However, the origins of high photosynthetic capacity in angiosperms remain unknown. In this study, we describe the steep trajectory of leaf vein density (D(v)) evolution in angiosperms, and predict that this leaf plumbing innovation enabled a major shift in the capacity of leaves to assimilate CO(2). Reconstructing leaf vein evolution from an examination of 504 angiosperm species we found a rapid three- to fourfold increase in D(v) occurred during the early evolution of angiosperms. We demonstrate how this major shift in leaf vein architecture potentially allowed the maximum photosynthetic capacity in angiosperms to rise above competing groups 140-100 Ma. Our data suggest that early terrestrial angiosperms produced leaves with low photosynthetic rates, but that subsequent angiosperm success is linked to a surge in photosynthetic capacity during their early diversification.

  14. Effect of ambient-level gas-phase peroxides on foliar injury, growth, and net photosynthesis in Japanese radish (Raphanus sativus)

    Energy Technology Data Exchange (ETDEWEB)

    Chen Xuan, E-mail: xuan66chen@yahoo.co.j [Chinese Research Academy of Environmental Science, No.8, Dayangfang, Anwai, Chaoyang District, Beijing 100012 (China); Aoki, Masatoshi [Faculty of Agriculture, Tokyo University of Agriculture and Technology, Saiwaicho 3-5-8, Fuchu-shi, Tokyo 183-8509 (Japan); Takami, Akinori [National Institute for Environmental Studies, Onogawa 16-2, Tsukuba-shi, Ibaraki 305-8506 (Japan); Chai Fahe [Chinese Research Academy of Environmental Science, No.8, Dayangfang, Anwai, Chaoyang District, Beijing 100012 (China); Hatakeyama, Shiro [Faculty of Agriculture, Tokyo University of Agriculture and Technology, Saiwaicho 3-5-8, Fuchu-shi, Tokyo 183-8509 (Japan)

    2010-05-15

    To investigate the effects of ambient-level gas-phase peroxides concurrent with O{sub 3} on foliar injury, photosynthesis, and biomass in herbaceous plants, we exposed Japanese radish (Raphanus sativus) to clean air, 50 ppb O{sub 3}, 100 ppb O{sub 3}, and 2-3 ppb peroxides + 50 ppb O{sub 3} in outdoor chambers. Compared with exposure to 100 ppb O{sub 3}, exposure to 2-3 ppb peroxides + 50 ppb O{sub 3} induced greater damage in foliar injury, net photosynthetic rates and biomass; the pattern of foliar injury and the cause of net photosynthetic rate reduction also differed from those occurring with O{sub 3} exposure alone. These results indicate for the first time that sub-ppb peroxides + 50 ppb O{sub 3} can cause more severe damage to plants than 100 ppb O{sub 3}, and that not only O{sub 3}, but also peroxides, could be contributing to the herbaceous plant damage and forest decline observed in Japan's air-polluted urban and remote mountains areas. - Ambient-level gas-phase peroxides coexisted with 50 ppb O{sub 3} may contribute to the herbaceous plants damage and forest decline observed in Japan.

  15. Photosynthetic characteristics and biomass distribution of the dominant vascular plant species in a high Arctic tundra ecosystem, Ny-Alesund, Svalbard: implications for their role in ecosystem carbon gain.

    Science.gov (United States)

    Muraoka, Hiroyuki; Noda, Hibiki; Uchida, Masaki; Ohtsuka, Toshiyuki; Koizumi, Hiroshi; Nakatsubo, Takayuki

    2008-03-01

    Studies on terrestrial ecosystems in the high Arctic region have focused on the response of these ecosystems to global environmental change and their carbon sequestration capacity in relation to ecosystem function. We report here our study of the photosynthetic characteristics and biomass distribution of the dominant vascular plant species, Salix polaris, Dryas octopetala and Saxifraga oppositifolia, in the high Arctic tundra ecosystem at Ny-Alesund, Svalbard (78.5 degrees N, 11.5 degrees E). We also estimated net primary production (NPP) along both the successional gradient created by the proglacial chronosequence and the topographical gradient. The light-saturated photosynthesis rate (A (max)) differed among the species, with approximately 124.1 nmol CO(2) g(-1)leaf s(-1) for Sal. polaris, 57.8 for D. octopetala and 24.4 for Sax. oppositifolia, and was highly correlated with the leaf nitrogen (N) content for all three species. The photosynthetic N use efficiency was the highest in Sal. polaris and lowest in Sax. oppositifolia. Distributions of Sal. polaris and D. octopetala were restricted to the area where soil nutrient availability was high, while Sax. oppositifolia was able to establish at the front of a glacier, where nutrient availability is low, but tended to be dominated by other vascular plants in high nutrient areas. The NPP reflected the photosynthetic capacity and biomass distribution in that it increased with the successional status; the contribution of Sal. polaris reached as high as 12-fold that of Sax. oppositifolia.

  16. Environmental influence on photosynthetic efficiency

    Science.gov (United States)

    Zilinskas, Barbara A.

    Photosynthesis is arguably the single most important metabolic process on earth. Through a series of reactions, ranging from 10-15 sec for absorption of light to 106 sec for primary productivity of a field crop, atmospheric CO2 is assimilated into carbohydrate necessary for the sustenance of all life forms. The process involves movement of electrons from water to CO2 through a series of charge transfer reactions. The ultimate source of energy to drive these reactions is solar energy absorbed by a collection of light-harvesting pigment-proteins and specialized reaction centers. Approximately half of the solar irradiance is useful in photosynthesis, but of this only 2-3% is converted into organic matter. Usually, light does not limit photosynthesis, but other environmental factors do, most often CO2 and water availability. Three different biochemical pathways for CO2 assimilation have independently evolved. These provide C3, C4 and CAM plants (names designating the different means of assimilating CO2) with adaptive advantages under the various environmental conditions encountered by plants in nature. Our current understanding of the photosynthetic light and carbon-fixing reactions now permits a closer look at responses of photosynthesis to changes in the environment, particularly with regard to making predictive models for absolute efficiencies of light, CO2 and water utilization.

  17. Design principles of photosynthetic light-harvesting.

    Science.gov (United States)

    Fleming, Graham R; Schlau-Cohen, Gabriela S; Amarnath, Kapil; Zaks, Julia

    2012-01-01

    Photosynthetic organisms are capable of harvesting solar energy with near unity quantum efficiency. Even more impressively, this efficiency can be regulated in response to the demands of photosynthetic reactions and the fluctuating light-levels of natural environments. We discuss the distinctive design principles through which photosynthetic light-harvesting functions. These emergent properties of photosynthesis appear both within individual pigment-protein complexes and in how these complexes integrate to produce a functional, regulated apparatus that drives downstream photochemistry. One important property is how the strong interactions and resultant quantum coherence, produced by the dense packing of photosynthetic pigments, provide a tool to optimize for ultrafast, directed energy transfer. We also describe how excess energy is quenched to prevent photodamage under high-light conditions, which we investigate through theory and experiment. We conclude with comments on the potential of using these features to improve solar energy devices.

  18. Hybrid system of semiconductor and photosynthetic protein

    Science.gov (United States)

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

    2014-08-01

    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.

  19. 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 ...

  20. CULTURE CONDITIONS AND THE DEVELOPMENT OF THE PHOTOSYNTHETIC MECHANISM : IV. INFLUENCE OF LIGHT INTENSITY ON PHOTOSYNTHETIC CHARACTERISTICS OF CHLORELLA.

    Science.gov (United States)

    Myers, J

    1946-07-20

    1. Chlorella pyrenoidosa has been grown in a continuous-culture apparatus under various light intensities provided by incandescent lamps, other conditions of culture being maintained constant. Light intensity curves for cells immersed in the No. 11 Warburg buffer and in Knop's solution + 4.4 per cent CO(2) at a saturating light intensity were determined as characteristics of the photosynthetic mechanism. These characteristics were referred to the centrifuged cell volume as an index of quantity of cellular material. 2. Cells grown at intensities in the range of about 35 f.-c. develop a capacity for a high rate of photosynthesis (c.mm. O(2)/hour/c.mm. cells). At culture intensities above or below this range the cells produced have a lower capacity for photosynthesis. A similar effect is observed for rate of photosynthesis per unit dry weight or rate per unit cell nitrogen. 3. The rate of photosynthesis per cell or rate per unit chlorophyll shows no maximum at any light intensity of culture but increases continuously throughout the range of light intensities studied. 4. Maximum rate of growth is attained at a light intensity of about 100 f.-c. The hypothesis is advanced that at culture intensities above that needed to give maximum rate of growth (100 f.-c.) a mechanism is developed which opposes the photosynthetic process and removes the photosynthetic products. 5. The low capacity for photosynthesis shown by cells grown at culture intensities below 35 f.-c. finds no immediate explanation. 6. The shape of the light intensity curve is markedly affected by the light intensity at which the cells have been cultured. Cells grown at lower intensities give light intensity curves approaching the Blackman type with a short transitional region between light limitation and light saturation.

  1. Photosynthetic Light Responses May Explain Vertical Distribution of Hymenophyllaceae Species in a Temperate Rainforest of Southern Chile.

    Directory of Open Access Journals (Sweden)

    María José Parra

    Full Text Available Some epiphytic Hymenophyllaceae are restricted to lower parts of the host ( 1000 μmol photons m(-2 s(-1. Our aim was to study the photosynthetic light responses of two Hymenophyllaceae species in relation to their contrasting distribution. We determined light tolerance of Hymenoglossum cruentum and Hymenophyllum dentatum by measuring gas exchange, PSI and PSII light energy partitioning, NPQ components, and pigment contents. H. dentatum showed lower maximum photosynthesis rates (A max than H. cruentum, but the former species kept its net rates (An near Amax across a wide light range. In contrast, in the latter one, An declined at PPFDs > 60 μmol photons m(-2 s(-1. H. cruentum, the shadiest plant, showed higher chlorophyll contents than H. dentatum. Differences in energy partitioning at PSI and PSII were consistent with gas exchange results. H. dentatum exhibited a higher light compensation point of the partitioning of absorbed energy between photochemical Y(PSII and non-photochemical Y(NPQ processes. Hence, both species allocated energy mainly toward photochemistry instead of heat dissipation at their light saturation points. Above saturation, H. cruentum had higher heat dissipation than H. dentatum. PSI yield (YPSI remained higher in H. dentatum than H. cruentum in a wider light range. In both species, the main cause of heat dissipation at PSI was a donor side limitation. An early dynamic photo-inhibition of PSII may have caused an over reduction of the Qa+ pool decreasing the efficiency of electron donation to PSI. In H. dentatum, a slight increase in heat dissipation due to acceptor side limitation of PSI was observed above 300 μmol photons m(-2s(-1. Differences in photosynthetic responses to light suggest that light tolerance and species plasticity could explain their contrasting vertical distribution.

  2. [Effects of different tillage methods on photosynthetic characteristics, dry matter production and economic benefit of double cropping soybean].

    Science.gov (United States)

    Tang, Jiang-hua; Su, Li-li; Li, Ya-jie; Xu, Wen-xiu; Peng, Jiang-long

    2016-01-01

    In order to explore suitable mode of high yield cultivation of double cropping soybean after wheat under drip irrigation in northern Xinjiang, field trials were set in 2013-2014 to investigate physiological indices and agronomic traits of double cropping soybean under different tillage methods under drip irrigation. The results showed that leaf area index (LAI), chlorophyll content (SPAD), leaf net photosynthetic rate (Pn), transpiration rate (Tr) and stomatal conductance (g(s)) during the determination period under different tillage methods were in the order of tillage plus film covering (TP)> tillage (T)> rotary tillage (RT) > no-tillage (NT) , and the concentration of intercellular CO₂(Ci) was the opposite. LAI, SPAD, Pn, Tr, and g(s) of TP were higher than that with NT by 55.0%, 9.1%, 41.8%, 37.5% and 56.4%, respectively, and Ci was decreased by 22.1%. TP enhanced the photosynthetic efficiency of soybean and improved the ability of CO₂assimilation, consequently leading to the increase of soybean yield under TP compared to NT. The plant dry matter accumulation of TP treatment was improved greatly, with the pod number and seeds number per plant, 100-seed mass and yield of quadric sowing soybean being increased by 50.3%, 48.1%, 11.8% and 20.8% compared with that under NT, and the differences were significant. Therefore, the plastic film mulching combined with tillage under drip irrigation technology was suitable for double cropping soybean after wheat in northern Xinjiang under this experimental condition.

  3. 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.

  4. The role of energy losses in photosynthetic light harvesting

    Science.gov (United States)

    Krüger, T. P. J.; van Grondelle, R.

    2017-07-01

    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 cells. The primary photosynthetic steps, consisting of light harvesting and charge separation, are often presented as having near-unity quantum efficiency but this holds only true under ideal conditions. In this review, we discuss the importance of energy loss mechanisms to establish robustness in photosynthetic light harvesting. Thermal energy dissipation of light-harvesting complexes (LHCs) in different environments is investigated and the relationships and contrasts between concentration quenching of high pigment concentrations, photoprotection (non-photochemical quenching), quenching due to protein aggregation, and fluorescence blinking are discussed. The role of charge-transfer states in light harvesting and energy dissipation is highlighted and the importance of controlled protein structural disorder to switch the light-harvesting antennae between effective light harvesters and efficient energy quenchers is underscored. The main LHC of plants, LHCII, is used as a prime example.

  5. Pro NET Best Practices

    CERN Document Server

    Ritchie, Stephen D

    2011-01-01

    Pro .NET Best Practices is a practical reference to the best practices that you can apply to your .NET projects today. You will learn standards, techniques, and conventions that are sharply focused, realistic and helpful for achieving results, steering clear of unproven, idealistic, and impractical recommendations. Pro .NET Best Practices covers a broad range of practices and principles that development experts agree are the right ways to develop software, which includes continuous integration, automated testing, automated deployment, and code analysis. Whether the solution is from a free and

  6. Getting to Net Zero

    Energy Technology Data Exchange (ETDEWEB)

    2016-09-01

    The technology necessary to build net zero energy buildings (NZEBs) is ready and available today, however, building to net zero energy performance levels can be challenging. Energy efficiency measures, onsite energy generation resources, load matching and grid interaction, climatic factors, and local policies vary from location to location and require unique methods of constructing NZEBs. It is recommended that Components start looking into how to construct and operate NZEBs now as there is a learning curve to net zero construction and FY 2020 is just around the corner.

  7. Instant Lucene.NET

    CERN Document Server

    Heydt, Michael

    2013-01-01

    Filled with practical, step-by-step instructions and clear explanations for the most important and useful tasks. A step-by-step guide that helps you to index, search, and retrieve unstructured data with the help of Lucene.NET.Instant Lucene.NET How-to is essential for developers new to Lucene and Lucene.NET who are looking to get an immediate foundational understanding of how to use the library in their application. It's assumed you have programming experience in C# already, but not that you have experience with search techniques such as information retrieval theory (although there will be a l

  8. Interactive effects of elevated CO2 concentration and irrigation on photosynthetic parameters and yield of maize in Northeast China.

    Directory of Open Access Journals (Sweden)

    Fanchao Meng

    Full Text Available Maize is one of the major cultivated crops of China, having a central role in ensuring the food security of the country. There has been a significant increase in studies of maize under interactive effects of elevated CO2 concentration ([CO2] and other factors, yet the interactive effects of elevated [CO2] and increasing precipitation on maize has remained unclear. In this study, a manipulative experiment in Jinzhou, Liaoning province, Northeast China was performed so as to obtain reliable results concerning the later effects. The Open Top Chambers (OTCs experiment was designed to control contrasting [CO2] i.e., 390, 450 and 550 µmol·mol(-1, and the experiment with 15% increasing precipitation levels was also set based on the average monthly precipitation of 5-9 month from 1981 to 2010 and controlled by irrigation. Thus, six treatments, i.e. C550W+15%, C550W0, C450W+15%, C450W0, C390W+15% and C390W0 were included in this study. The results showed that the irrigation under elevated [CO2] levels increased the leaf net photosynthetic rate (Pn and intercellular CO2 concentration (Ci of maize. Similarly, the stomatal conductance (Gs and transpiration rate (Tr decreased with elevated [CO2], but irrigation have a positive effect on increased of them at each [CO2] level, resulting in the water use efficiency (WUE higher in natural precipitation treatment than irrigation treatment at elevated [CO2] levels. Irradiance-response parameters, e.g., maximum net photosynthetic rate (Pnmax and light saturation points (LSP were increased under elevated [CO2] and irrigation, and dark respiration (Rd was increased as well. The growth characteristics, e.g., plant height, leaf area and aboveground biomass were enhanced, resulting in an improved of yield and ear characteristics except axle diameter. The study concluded by reporting that, future elevated [CO2] may favor to maize when coupled with increasing amount of precipitation in Northeast China.

  9. Interactive effects of elevated CO2 concentration and irrigation on photosynthetic parameters and yield of maize in Northeast China.

    Science.gov (United States)

    Meng, Fanchao; Zhang, Jiahua; Yao, Fengmei; Hao, Cui

    2014-01-01

    Maize is one of the major cultivated crops of China, having a central role in ensuring the food security of the country. There has been a significant increase in studies of maize under interactive effects of elevated CO2 concentration ([CO2]) and other factors, yet the interactive effects of elevated [CO2] and increasing precipitation on maize has remained unclear. In this study, a manipulative experiment in Jinzhou, Liaoning province, Northeast China was performed so as to obtain reliable results concerning the later effects. The Open Top Chambers (OTCs) experiment was designed to control contrasting [CO2] i.e., 390, 450 and 550 µmol·mol(-1), and the experiment with 15% increasing precipitation levels was also set based on the average monthly precipitation of 5-9 month from 1981 to 2010 and controlled by irrigation. Thus, six treatments, i.e. C550W+15%, C550W0, C450W+15%, C450W0, C390W+15% and C390W0 were included in this study. The results showed that the irrigation under elevated [CO2] levels increased the leaf net photosynthetic rate (Pn) and intercellular CO2 concentration (Ci) of maize. Similarly, the stomatal conductance (Gs) and transpiration rate (Tr) decreased with elevated [CO2], but irrigation have a positive effect on increased of them at each [CO2] level, resulting in the water use efficiency (WUE) higher in natural precipitation treatment than irrigation treatment at elevated [CO2] levels. Irradiance-response parameters, e.g., maximum net photosynthetic rate (Pnmax) and light saturation points (LSP) were increased under elevated [CO2] and irrigation, and dark respiration (Rd) was increased as well. The growth characteristics, e.g., plant height, leaf area and aboveground biomass were enhanced, resulting in an improved of yield and ear characteristics except axle diameter. The study concluded by reporting that, future elevated [CO2] may favor to maize when coupled with increasing amount of precipitation in Northeast China.

  10. Net Zero Energy Buildings

    DEFF Research Database (Denmark)

    Marszal, Anna Joanna; Bourrelle, Julien S.; Musall, Eike

    2010-01-01

    and identify possible renewable energy supply options which may be considered in calculations. Finally, the gap between the methodology proposed by each organisation and their respective national building code is assessed; providing an overview of the possible changes building codes will need to undergo......The international cooperation project IEA SHC Task 40 / ECBCS Annex 52 “Towards Net Zero Energy Solar Buildings”, attempts to develop a common understanding and to set up the basis for an international definition framework of Net Zero Energy Buildings (Net ZEBs). The understanding of such buildings...... parameters used in the calculations are discussed and the various renewable supply options considered in the methodologies are summarised graphically. Thus, the paper helps to understand different existing approaches to calculate energy balance in Net ZEBs, highlights the importance of variables selection...

  11. PhysioNet

    Data.gov (United States)

    U.S. Department of Health & Human Services — The PhysioNet Resource is intended to stimulate current research and new investigations in the study of complex biomedical and physiologic signals. It offers free...

  12. [Influence of drought on leaf photosynthetic capacity and root growth of soybeans at grain filling stage].

    Science.gov (United States)

    Guo, Shu-jin; Yang, Kai-min; Huo, Jin; Zhou, Yong-hang; Wang, Yan-ping; Li, Gui-quan

    2015-05-01

    A drought-resistant soybean cultivar Jinda 70 and a drought-sensitive soybean cultivar Jindou 26 were taken as test materials. At the grain filling stage, the cultivars were subject to three water treatments including sufficient water supply, light drought stress, and severe drought stress by using pot experiments for research on influence of drought on leaf photosynthetic capacity and root growth of soybeans. The results showed that as the degree of drought stress was aggravated, all of the indices including leaf area, chlorophyll content, net photosynthetic rates (Pn), stomatal conductance (g(s)), transpiration rate (Tr), intercellular CO2 concentration (Ci), plant mass, plant height, seed yield, and harvest index in the two cultivars declined. The root length and root mass increased under light drought stress, and decreased under severe drought stress. Root-shoot ratio ascended as the degree of drought stress was aggravated. Under severe drought stress, the increase of root-shoot ratio of the drought-resistant soybean cultivar Jinda 70 was up to 135.7%, which was higher than the that (116.7%) of the drought-sensitive soybean cultivar Jindou 26. Simultaneously, leaf area and chlorophyll content in Jinda 70 were respectively 69.3% and 85.5% of those in the control, which were better than those of Jindou 26. g(s) and Pn of Jinda 70 respectively declined 67.9% and 77.9%, but still lower than those of Jindou 26. Therefore, the decline range of harvest index of Jinda 70 was 43.8%, which was lower than the range of 78.8% of Jindou 26. The Biplot revealed that under different dry treatments, there were significant positive correlations among the six indexes including leaf area, chlorophyll content, Pn, g(s), Tr, and Ci of the two cultivars. There were also significant positive correlations among the six indices including plant mass, plant height, root length, root mass, seed yield, and harvest index. Root-shoot ratio only had significant positive correlation with root

  13. Temperature response of leaf photosynthetic capacity in seedlings from seven temperate tree species.

    Science.gov (United States)

    Dreyer, E; Le Roux, X; Montpied, P; Daudet, F A; Masson, F

    2001-03-01

    Seedlings of seven temperate tree species (Acer pseudoplatanus L., Betula pendula Roth, Fagus sylvatica L., Fraxinus excelsior L., Juglans regia L., Quercus petraea Matt. Liebl. and Quercus robur L.) were grown in a nursery under neutral filters transmitting 45% of incident global irradiance. During the second or third year of growth, leaf photosynthetic capacity (i.e., maximal carboxylation rate, Vcmax, maximal photosynthetic electron transport rate, Jmax, and dark respiration, Rd) was estimated for five leaves from each species at five or six leaf temperatures (10, 18, 25, 32, 36 and 40 degrees C). Values of Vcmax and Jmax were obtained by fitting the equations of the Farquhar model on response curves of net CO2 assimilation (A) to sub-stomatal CO2 mole fraction (ci), at high irradiance. Primary parameters describing the kinetic properties of Rubisco (specificity factor, affinity for CO2 and for O2, and their temperature responses) were taken from published data obtained with spinach and tobacco, and were used for all species. The temperature responses of Vcmax and Jmax, which were fitted to a thermodynamic model, differed. Mean values of Vcmax and Jmax at a reference temperature of 25 degrees C were 77.3 and 139 micromol m(-2) s(-1), respectively. The activation energy was higher for Vcmax than for Jmax (mean values of 73.1 versus 57.9 kJ mol(-1)) resulting in a decrease in Jmax/Vcmax ratio with increasing temperature. The mean optimal temperature was higher for Vcmax than for Jmax (38.9 versus 35.9 degrees C). In addition, differences in these temperature responses were observed among species. Temperature optima ranged between 35.9 and above 45 degrees C for Vcmax and between 31.7 and 43.3 degrees C for Jmax, but because of data scatter and the limited range of temperatures tested (10 to 40 degrees C), there were few statistically significant differences among species. The optimal temperature for Jmax was highest in Q. robur, Q. petraea and J. regia, and lowest

  14. The role of 24-epibrassinolide in the regulation of photosynthetic characteristics and nitrogen metabolism of tomato seedlings under a combined low temperature and weak light stress.

    Science.gov (United States)

    Shu, Sheng; Tang, Yuanyuan; Yuan, Yinghui; Sun, Jin; Zhong, Min; Guo, Shirong

    2016-10-01

    In the present study, we aimed to investigate the effects of exogenous 24-epibrassinolide (EBR) on growth, photosynthetic characteristics, chlorophyll fluorescence imaging, and nitrogen metabolism of tomato leaves under low temperature and weak light conditions. The results showed that foliar application of EBR significantly alleviated the inhibition of plant growth, and increased the fresh and dry weights of tomato plants under a combined low temperature and weak light stress. Moreover, EBR also increased the net photosynthetic rate (Pn), light saturation point (LSP), maximal quantum yield of PSII photochemistry (Fv/Fm), actual photochemical efficiency of PSII (ФPSII), and photochemical quenching coefficient (qP), but decreased the intercellular CO2 concentration (Ci), light compensation point (LCP) and apparent quantum efficiency (AQE) under low temperature and weak light conditions. In addition, application of EBR to tomato leaves significantly enhanced the activities of nitrate reductase (NR), glutamate dehydrogenase (GDH), glutamine synthetase (GS), and glutamate synthase (GOGAT), but decreased the ammonium content and nitrite reductase (NiR) activity. We observed that EBR remarkably increased the contents of aspartic acid, threonine, serine, glycine, and phenylalanine, while decreasing the accumulation of cysteine, methionine, arginine, and proline under a combined low temperature and light stress. These results suggest that EBR could alleviate the combined stress-induced harmful effects on photosynthesis and nitrogen metabolism, thus leading to improved plant growth. Copyright © 2016. Published by Elsevier Masson SAS.

  15. Photosynthetic Performance of the Red Alga Pyropia haitanensis During Emersion, With Special Reference to Effects of Solar UV Radiation, Dehydration and Elevated CO2 Concentration.

    Science.gov (United States)

    Xu, Juntian; Gao, Kunshan

    2015-11-01

    Macroalgae distributed in intertidal zones experience a series of environmental changes, such as periodical desiccation associated with tidal cycles, increasing CO2 concentration and solar UVB (280-315 nm) irradiance in the context of climate change. We investigated how the economic red macroalga, Pyropia haitanensis, perform its photosynthesis under elevated atmospheric CO2 concentration and in the presence of solar UV radiation (280-400 nm) during emersion. Our results showed that the elevated CO2 (800 ppmv) significantly increased the photosynthetic carbon fixation rate of P. haitanensis by about 100% when the alga was dehydrated. Solar UV radiation had insignificant effects on the net photosynthesis without desiccation stress and under low levels of sunlight, but significantly inhibited it with increased levels of desiccation and sunlight intensity, to the highest extent at the highest levels of water loss and solar radiation. Presence of UV radiation and the elevated CO2 acted synergistically to cause higher inhibition of the photosynthetic carbon fixation, which exacerbated at higher levels of desiccation and sunlight. While P. haitanensis can benefit from increasing atmospheric CO2 concentration during emersion under low and moderate levels of solar radiation, combined effects of elevated CO2 and UV radiation acted synergistically to reduce its photosynthesis under high solar radiation levels during noon periods. © 2015 The American Society of Photobiology.

  16. 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.

  17. TideNet

    Science.gov (United States)

    2015-10-30

    query tide data sources in a desired geographic region of USA and its territories (Figure 1). Users can select a tide data source through the Google Map ...select data sources according to the desired geographic region. It uses the Google Map interface to display data from different sources. Recent...Coastal Inlets Research Program TideNet The TideNet is a web-based Graphical User Interface (GUI) that provides users with GIS mapping tools to

  18. Building Neural Net Software

    OpenAIRE

    Neto, João Pedro; Costa, José Félix

    1999-01-01

    In a recent paper [Neto et al. 97] we showed that programming languages can be translated on recurrent (analog, rational weighted) neural nets. The goal was not efficiency but simplicity. Indeed we used a number-theoretic approach to machine programming, where (integer) numbers were coded in a unary fashion, introducing a exponential slow down in the computations, with respect to a two-symbol tape Turing machine. Implementation of programming languages in neural nets turns to be not only theo...

  19. Interaction Nets in Russian

    OpenAIRE

    Salikhmetov, Anton

    2013-01-01

    Draft translation to Russian of Chapter 7, Interaction-Based Models of Computation, from Models of Computation: An Introduction to Computability Theory by Maribel Fernandez. "In this chapter, we study interaction nets, a model of computation that can be seen as a representative of a class of models based on the notion of 'computation as interaction'. Interaction nets are a graphical model of computation devised by Yves Lafont in 1990 as a generalisation of the proof structures of linear logic...

  20. Programming NET 35

    CERN Document Server

    Liberty, Jesse

    2009-01-01

    Bestselling author Jesse Liberty and industry expert Alex Horovitz uncover the common threads that unite the .NET 3.5 technologies, so you can benefit from the best practices and architectural patterns baked into the new Microsoft frameworks. The book offers a Grand Tour" of .NET 3.5 that describes how the principal technologies can be used together, with Ajax, to build modern n-tier and service-oriented applications. "

  1. Overexpression of SbSI-1, A Nuclear Protein from Salicornia brachiata Confers Drought and Salt Stress Tolerance and Maintains Photosynthetic Efficiency in Transgenic Tobacco.

    Science.gov (United States)

    Kumari, Jyoti; Udawat, Pushpika; Dubey, Ashish K; Haque, Md Intesaful; Rathore, Mangal S; Jha, Bhavanath

    2017-01-01

    A novel Salicornia brachiata Salt Inducible (SbSI-1) gene was isolated and overexpressed in tobacco for in planta functional validation subjected to drought and salt stress. SbSI-1 is a nuclear protein. The transgenic tobacco overexpressing SbSI-1 gene exhibited better seed germination, growth performances, pigment contents, cell viability, starch accumulation, and tolerance index under drought and salt stress. Overexpression of SbSI-1 gene alleviated the build-up of reactive oxygen species (ROS) and curtailed the ROS-induced oxidative damages thus improved the physiological health of transgenic tobacco under stressed conditions. The higher activities of antioxidant enzymes, lower accumulation of ROS, higher membrane stability, relative water content, and polyphenol contents indicated the better survival of the transgenic tobacco than wild-type (WT) tobacco under stressed conditions. Transgenic tobacco had a higher net photosynthetic rate, PSII operating efficiency, and performance index under drought and salt stress. Higher accumulation of compatible solutes and K+/Na+ ratio in transgenic tobacco than WT showed the better osmotic and redox homeostasis under stressed conditions. The up-regulation of genes encoding antioxidant enzymes (NtSOD, NtAPX, and NtCAT) and transcription factors (NtDREB2 and NtAP2) in transgenic tobacco under stressed conditions showed the role of SbSI-1 in ROS alleviation and involvement of this gene in abiotic stress tolerance. Multivariate data analysis exhibited statistical distinction among growth responses, physiological health, osmotic adjustment, and photosynthetic responses of WT and transgenic tobacco under stressed conditions. The overexpression of SbSI-1 gene curtailed the ROS-induced oxidative damages and maintained the osmotic homeostasis under stress conditions thus improved physiological health and photosynthetic efficiencies of the transgenic tobacco overexpressing SbSI-1 gene.

  2. Overexpression of SbSI-1, A Nuclear Protein from Salicornia brachiata Confers Drought and Salt Stress Tolerance and Maintains Photosynthetic Efficiency in Transgenic Tobacco

    Directory of Open Access Journals (Sweden)

    Jyoti Kumari

    2017-07-01

    Full Text Available A novel SalicorniabrachiataSalt Inducible (SbSI-1 gene was isolated and overexpressed in tobacco for in planta functional validation subjected to drought and salt stress. SbSI-1 is a nuclear protein. The transgenic tobacco overexpressing SbSI-1 gene exhibited better seed germination, growth performances, pigment contents, cell viability, starch accumulation, and tolerance index under drought and salt stress. Overexpression of SbSI-1 gene alleviated the build-up of reactive oxygen species (ROS and curtailed the ROS-induced oxidative damages thus improved the physiological health of transgenic tobacco under stressed conditions. The higher activities of antioxidant enzymes, lower accumulation of ROS, higher membrane stability, relative water content, and polyphenol contents indicated the better survival of the transgenic tobacco than wild-type (WT tobacco under stressed conditions. Transgenic tobacco had a higher net photosynthetic rate, PSII operating efficiency, and performance index under drought and salt stress. Higher accumulation of compatible solutes and K+/Na+ ratio in transgenic tobacco than WT showed the better osmotic and redox homeostasis under stressed conditions. The up-regulation of genes encoding antioxidant enzymes (NtSOD, NtAPX, and NtCAT and transcription factors (NtDREB2 and NtAP2 in transgenic tobacco under stressed conditions showed the role of SbSI-1 in ROS alleviation and involvement of this gene in abiotic stress tolerance. Multivariate data analysis exhibited statistical distinction among growth responses, physiological health, osmotic adjustment, and photosynthetic responses of WT and transgenic tobacco under stressed conditions. The overexpression of SbSI-1 gene curtailed the ROS-induced oxidative damages and maintained the osmotic homeostasis under stress conditions thus improved physiological health and photosynthetic efficiencies of the transgenic tobacco overexpressing SbSI-1 gene.

  3. Net accumulation of the Greenland ice sheet

    DEFF Research Database (Denmark)

    Kiilsholm, Sissi; Christensen, Jens Hesselbjerg; Dethloff, Klaus

    2003-01-01

    improvement compared to the driving OAGCM. Estimates of the regional net balance are also better represented by the RCM. In the future climate the net balance for the Greenland Ice Sheet is reduced in all the simulation, but discrepancies between the amounts when based on ECHAM4/OPYC3 and HIRHAM are found....... In both scenarios, the estimated melt rates are larger in HIRHAM than in the driving model....

  4. Effects of ozone on growth, net photosynthesis and yield of two African varieties of Vigna unguiculata.

    Science.gov (United States)

    Tetteh, Rashied; Yamaguchi, Masahiro; Wada, Yoshiharu; Funada, Ryo; Izuta, Takeshi

    2015-01-01

    To assess the effects of O(3)on growth, net photosynthesis and yield of two African varieties of cowpea(Vigna unguiculata L.), Blackeye and Asontem were exposed as potted plants to air that was either filtered to remove O(3) (FA), non-filtered air (NF), non-filtered with added O3 of approximately 50 nL L(-1) (ppb) from 11:00 to 16:00 (NF + O(3)) for 88 days in open-top chambers. The mean O(3) concentration (11:00-16:00) during the exposure period had a range from 16 ppb in the FA treatment to 118 ppb in the NF + O(3) treatment. Net photosynthetic rate and leaf area per plant were significantly reduced by exposure to O(3), reducing the growth of both varieties. Exposure to O(3) significantly reduced the 100-seed weight and number of seeds per pod. As a result, cowpea yield was significantly reduced by long-term exposure to O(3), with no difference in sensitivity between the varieties.

  5. Taxa alimentar no desempenho de juvenis de robalo-peva em tanque-rede=Feeding rate in the performance of juveniles of fat-snook Centropomus parallelus in net cage.

    Directory of Open Access Journals (Sweden)

    Vinicius Ronzani Cerqueira

    2011-10-01

    Full Text Available O conhecimento da taxa ótima de alimentação para uma determinada espécie não só é importante para promover o maior crescimento e a melhor eficiência na alimentação, mas também para prevenir a deterioração de qualidade de água como resultado do excesso de alimento. O presente estudo teve como objetivo avaliar o desempenho do robalo-peva, Centropomus parallelus cultivado em tanques-rede flutuantes sob o efeito de diferentes taxas alimentares (1; 1,5; 2 e 2,5% da biomassa ao dia e a taxa controle que foi até a saciedade, em condições de cultivo no ambiente natural. Durante 40 dias, cada tratamento foi avaliado em triplicatas e foram verificados os parâmetros biológicos (sobrevivência, taxa de crescimento específico, peso e comprimentos médios finais e nutricionais (taxa de conversão alimentar aparente. A análise de regressão polinomial da taxa de crescimento específico sugere que em temperaturas médias de 25°C a taxa alimentar que resulta em melhor crescimento para juvenis de robalo-peva é de 1,7% da biomassa viva por dia.Knowing the optimal feeding rate for a given species is important not only to promote higher growth and greater feeding efficiency, but also to prevent the deterioration of water quality resulting from excess food. This study aimed to evaluate the performance of the fat-snook Centropomus parallelus cultivated in net cages under the effect of different feeding rates (1, 1.5, 2 and 2.5% live biomass daily and control rate up to apparent satiation in natural environment conditions. For 40 days, each treatment was evaluated in triplicate, in which the biological parameters (survival, specific growth rate, final average weight and length and nutritional parameters (feed conversion ratio were assessed. A polynomial regression analysis of specific growth rate suggests that in average temperatures of 25°C, the feeding rate which results in best growth for juvenile fat-snook is 1.7% of live biomass per day.

  6. CO2 elevation improves photosynthetic performance in progressive warming environment in white birch seedlings [v1; ref status: indexed, http://f1000r.es/up

    Directory of Open Access Journals (Sweden)

    Shouren Zhang

    2013-01-01

    Full Text Available White birch (Betula paperifera Mash seedlings were exposed to progressively warming in greenhouses under ambient and elevated CO2 concentrations for 5 months to explore boreal tree species’ potential capacity to acclimate to global climate warming and CO2 elevation. In situ foliar gas exchange, in vivo carboxylation characteristics and chlorophyll fluorescence were measured at temperatures of 26oC and 37oC. Elevated CO2 significantly increased net photosynthetic rate (Pn at both measurement temperatures, and Pn at 37oC was higher than that at 26oC under elevated CO2. Stomatal conductance (gs was lower at 37oC than at 26oC, while transpiration rate (E was higher at 37oC than that at 26oC. Elevated CO2 significantly increased instantaneous water-use efficiency (WUE at both 26oC and 37oC, but WUE was markedly enhanced at 37oC under elevated CO2. The effect of temperature on maximal carboxylation rate (Vcmax, PAR-saturated electron transport rate (Jmax and triose phosphate utilization (TPU varied with CO2, and the Vcmax and Jmax were significantly higher at 37oC than at 26oC under elevated CO2. However, there were no significant interactive effects of CO2 and temperature on TPU. The actual photochemical efficiency of PSII (DF/ Fm’, total photosynthetic linear electron transport rate through PSII (JT and the partitioning of JT to carboxylation (Jc were higher at 37oC than at 26oC under elevated CO2. Elevated CO2 significantly suppressed the partitioning of JT to oxygenation (Jo/JT. The data suggest that the CO2 elevation and progressive warming greatly enhanced photosynthesis in white birch seedlings in an interactive fashion.

  7. 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.

  8. Photosynthetic gas exchange responses of Swietenia macrophylla King and Melia azedarach L. plantations under drought conditions.

    Science.gov (United States)

    Jhou, Hong-Chyi; Wang, Ya-Nan; Wu, Chung-Shien; Yu, Jui-Chu; Chen, Chung-I

    2017-12-02

    The environmental stresses caused by climate change have become more severe in recent decades, affecting tree growth and physiology. Tropical forests have great potential for global carbon sequestration. However, they suffer from heavy rainfall and prolonged dry periods due to climate change. Swietenia macrophylla King and Melia azedarach L. are economically valuable trees that are widely planted in southern Taiwan. Plantations are exposed to either prolonged dry periods or heavy rainfall within the seasons of tropical monsoon areas. Photo-physiological comparisons may provide information that can improve management of S. macrophylla and M. azedarach plantations in tropical regions. Both species exhibited a midday depression in leaf photosynthesis regardless of the season. The net photosynthetic rate (P N), stomatal conductance (g s), and transpiration rate (E) in the dry season all significantly decreased in both tree species. In addition, M. azedarach used water more efficiently than did S. macrophylla during the dry season, but S. macrophylla had higher P N compared with that in M. azedarach during the wet season. Temperature and vapor pressure deficit influenced P N variation in S. macrophylla and M. azedarach, respectively. Our data suggested that the P N and g s of M. azedarach, but not of S. macrophylla, were linearly correlated during the dry season. The reduction of the leaf area was more sever in M. azedarach than in S. macrophylla, thus preventing water loss more efficiently. M. azedarach adapted to drought by reducing total leaf area and maintaining higher P N, g s, E, and WUE compared with those measured in S. macrophylla during the dry season. M. azedarach is more drought adaptation and more suitable for both humid and semi-humid areas than S. macrophylla, whereas the latter should be limited to more humid areas.

  9. Photosynthetic pigments and gas exchange in castor bean under conditions of above the optimal temperature and high CO2

    Directory of Open Access Journals (Sweden)

    Fabiola França Silva

    2015-08-01

    Full Text Available The castor bean plant, a Euphorbiaceae oil seed C3-metabolism rustic and drought-resistant plant, is cultivated in a wide range of environments due to its good adaptive capacity. However, given the current environmental changes, many biochemical and physiological impacts may affect the productivity of important crops, such as castor bean. This work aimed to evaluate the impacts of the castor bean gas exchange in response to high temperature and increased CO2concentration.Our experiment was conducted in a phytotron located at Embrapa Algodão in 2010. We adopted a completely randomized design, with four treatments in a factorial combination of two temperatures (30/20 and 37/30°C and two CO2 levels (400 and 800 mmol L-1; four replications were performed, obtained in five surveys over the growth cycle, for a total of 80 sample units. An infrared gas analyzer (IRGA - Infra Red Gas Analyzer was used for the quantification of the photosynthetic rate, stomatal conductance and transpiration. An increase in the atmospheric CO2 concentration and temperature negatively affected the physiology of the castor bean plants, decreasing the net rate of photosynthesis, transpiration and stomatal conductance.

  10. Effects of exogenous epibrassinolide on photosynthetic characteristics in tomato (Lycopersicon esculentum Mill) seedlings under weak light stress.

    Science.gov (United States)

    Wang, Ming; Jiang, Weijie; Yu, Hongjun

    2010-03-24

    The effects of three concentrations (0.1, 0.01, 0.001 mg/kg) of exogenous 24-epibrassinolide on leaf photosynthesis, chlorophyll content, chlorophyll fluorescence, and parameters of light response curve in tomato seedlings under 150 micromol x m(-2) x s(-1) weak light stress were studied, with two tomato cultivars, 'Zhongza9', tolerant, and 'Zhongshu6', sensitive to weak light stress. The results showed that the net photosynthetic rate (Pn), maximal photochemical quantum efficiency of PSII (Fv/Fm), light saturation point (LSP), and dark respiration rate (Rd) decreased remarkably under weak light, but the chlorophyll content, especially chlorophyll b (chlb) content, increased obviously compared with normal light intensity control. However, exogenous 24-epibrassinolide alleviated the decrease of leaf Pn and Fv/Fm and induced the further increase of chlb content as well as the further decrease of Rd and chla/chlb under weak light stress, which indicated that exogenous 24-epibrassinolide could enhance plant tolerance to weak light and diminish damage from weak light. However, the optimum concentrations were different between the two cultivars; 0.1 mg/kg 24-epibrassinolide showed the best induction effects in 'Zhongshu6', and the best level for 'Zhongza9' was 0.01 mg/kg 24-epibrassinolide.

  11. La plataforma .NET

    OpenAIRE

    Fornas Estrada, Miquel

    2008-01-01

    L'aparició de la plataforma .NET Framework ha suposat un canvi molt important en la forma de crear i distribuir aplicacions, degut a que incorpora una sèrie d'innovacions tècniques i productives que simplifiquen molt les tasques necessàries per desenvolupar un projecte. La aparición de la plataforma. NET Framework ha supuesto un cambio muy importante en la forma de crear y distribuir aplicaciones, debido a que incorpora una serie de innovaciones técnicas y productivas que simplifican mucho...

  12. Biological Petri Nets

    CERN Document Server

    Wingender, E

    2011-01-01

    It was suggested some years ago that Petri nets might be well suited to modeling metabolic networks, overcoming some of the limitations encountered by the use of systems employing ODEs (ordinary differential equations). Much work has been done since then which confirms this and demonstrates the usefulness of this concept for systems biology. Petri net technology is not only intuitively understood by scientists trained in the life sciences, it also has a robust mathematical foundation and provides the required degree of flexibility. As a result it appears to be a very promising approach to mode

  13. Morphological, photosynthetic and physiological responses of rapeseed leaf to different combinations of red and blue lights at the rosette stage

    Directory of Open Access Journals (Sweden)

    Chang Shengxin

    2016-08-01

    Full Text Available Rapeseed (Brassica napus L. is sensitive to light quality. The factory production of rapeseed seedlings for vegetable use and for transplanting in the field requires an investigation of the responses of rapeseed to light quality. This study evaluated the responses of the leaf of rapeseed (cv. ‘Zhongshuang 11’ to different ratios of red-photonflux (RPF and blue-photonflux (BPF from light emitting diodes (LEDs. The treatments were set as monochromatic lights, including 100R:0B% and 0R:100B%, and compound lights (CLs, including 75R:25B%, 50R:50B% and 25R:75B%. The total photonflux in all of the treatments was set as 550 μmolm-2s-1. With an increase of BPF, the rapeseed leaves changed from wrinkled blades and down-rolled margins to flat blades and slightly up-rolled margins, and the compact degree of palisade tissue increased. One layer of the cells of palisade tissue was present under 100R:0B%, whereas two layers were present under the other treatments. Compared to 100R:0B%, 0R:100B% enhanced the indexes of leaf thickness, leaf mass per area (LMA, stomatal density, chlorophyll (Chl content per weight and photosynthetic capacity (Pmax, and the CLs with high BPF ratios enhanced these indexes. However, the 100R:0B% and CLs with high RPF ratios enhanced the net photosynthetic rate (Pn. The leaves under the CLs showed growth vigor, whereas the leaves under 100R:0B% or 0R:100B% were stressed with a low Fv/Fm (photosynthetic maximum quantum yield and a high content of O2.- and H2O2. The top second leaves under 100R:0B% or 0R:100B% showed stress resistance responses with a high activity of antioxidase, but the top third leaves showed irreversible damage and inactivity of antioxidase. Our results showed that the rapeseed leaves grown under 0R:100B% or CLs with a high BPF ratio showed higher ability to utilize high photonflux, while the leaves grown under 100R:0B% or CLs with a low BPF ratio showed higher efficiency in utilizing low photonflux. Under

  14. Morphological, Photosynthetic, and Physiological Responses of Rapeseed Leaf to Different Combinations of Red and Blue Lights at the Rosette Stage.

    Science.gov (United States)

    Shengxin, Chang; Chunxia, Li; Xuyang, Yao; Song, Chen; Xuelei, Jiao; Xiaoying, Liu; Zhigang, Xu; Rongzhan, Guan

    2016-01-01

    Rapeseed (Brassica napus L.) is sensitive to light quality. The factory production of rapeseed seedlings for vegetable use and for transplanting in the field requires an investigation of the responses of rapeseed to light quality. This study evaluated the responses of the leaf of rapeseed (cv. "Zhongshuang 11") to different ratios of red-photonflux (RPF) and blue-photonflux (BPF) from light emitting diodes (LEDs). The treatments were set as monochromatic lights, including 100R:0B% and 0R:100B%, and compound lights (CLs), including 75R:25B%, 50R:50B%, and 25R:75B%. The total photonflux in all of the treatments was set as 550 μmolm(-2)s(-1). With an increase of BPF, the rapeseed leaves changed from wrinkled blades and down-rolled margins to flat blades and slightly up-rolled margins, and the compact degree of palisade tissue increased. One layer of the cells of palisade tissue was present under 100R:0B%, whereas two layers were present under the other treatments. Compared to 100R:0B%, 0R:100B% enhanced the indexes of leaf thickness, leaf mass per area (LMA), stomatal density, chlorophyll (Chl) content per weight and photosynthetic capacity (P max), and the CLs with high BPF ratios enhanced these indexes. However, the 100R:0B% and CLs with high RPF ratios enhanced the net photosynthetic rate (P n). The leaves under the CLs showed growth vigor, whereas the leaves under 100R:0B% or 0R:100B% were stressed with a low F v/F m (photosynthetic maximum quantum yield) and a high content of [Formula: see text] and H2O2. The top second leaves under 100R:0B% or 0R:100B% showed stress resistance responses with a high activity of antioxidase, but the top third leaves showed irreversible damage and inactivity of antioxidase. Our results showed that the rapeseed leaves grown under 0R:100B% or CLs with a high BPF ratio showed higher ability to utilize high photonflux, while the leaves grown under 100R:0B% or CLs with a low BPF ratio showed higher efficiency in utilizing low

  15. Spring Hydrology Determines Summer Net Carbon Uptake in Northern Ecosystems

    Science.gov (United States)

    Yi, Yonghong; Kimball, John; Reichle, Rolf H.

    2014-01-01

    Increased photosynthetic activity and enhanced seasonal CO2 exchange of northern ecosystems have been observed from a variety of sources including satellite vegetation indices (such as the Normalized Difference Vegetation Index; NDVI) and atmospheric CO2 measurements. Most of these changes have been attributed to strong warming trends in the northern high latitudes (greater than or equal to 50N). Here we analyze the interannual variation of summer net carbon uptake derived from atmospheric CO2 measurements and satellite NDVI in relation to surface meteorology from regional observational records. We find that increases in spring precipitation and snow pack promote summer net carbon uptake of northern ecosystems independent of air temperature effects. However, satellite NDVI measurements still show an overall benefit of summer photosynthetic activity from regional warming and limited impact of spring precipitation. This discrepancy is attributed to a similar response of photosynthesis and respiration to warming and thus reduced sensitivity of net ecosystem carbon uptake to temperature. Further analysis of boreal tower eddy covariance CO2 flux measurements indicates that summer net carbon uptake is positively correlated with early growing-season surface soil moisture, which is also strongly affected by spring precipitation and snow pack based on analysis of satellite soil moisture retrievals. This is attributed to strong regulation of spring hydrology on soil respiration in relatively wet boreal and arctic ecosystems. These results document the important role of spring hydrology in determining summer net carbon uptake and contrast with prevailing assumptions of dominant cold temperature limitations to high-latitude ecosystems. Our results indicate potentially stronger coupling of boreal/arctic water and carbon cycles with continued regional warming trends.

  16. Modest net autotrophy in the oligotrophic ocean

    Science.gov (United States)

    Letscher, Robert T.; Moore, J. Keith

    2017-04-01

    The metabolic state of the oligotrophic subtropical ocean has long been debated. Net community production (NCP) represents the balance of autotrophic carbon fixation with heterotrophic respiration. Many in vitro NCP estimates based on oxygen incubation methods and the corresponding scaling relationships used to predict the ecosystem metabolic balance have suggested the ocean gyres to be net heterotrophic; however, all in situ NCP methods find net autotrophy. Reconciling net heterotrophy requires significant allochthonous inputs of organic carbon to the oligotrophic gyres to sustain a preponderance of respiration over in situ production. Here we use the first global ecosystem-ocean circulation model that contains representation of the three allochthonous carbon sources to the open ocean, to show that the five oligotrophic gyres exhibit modest net autotrophy throughout the seasonal cycle. Annually integrated rates of NCP vary in the range 1.5-2.2 mol O2 m-2 yr-1 across the five gyre systems; however, seasonal NCP rates are as low as 1 ± 0.5 mmol O2 m-2 d-1 for the North Atlantic. Volumetric NCP rates are heterotrophic below the 10% light level; however, they become net autotrophic when integrated over the euphotic zone. Observational uncertainties when measuring these modest autotrophic NCP rates as well as the metabolic diversity encountered across space and time complicate the scaling up of in vitro measurements to the ecosystem scale and may partially explain the previous reports of net heterotrophy. The oligotrophic ocean is autotrophic at present; however, it could shift toward seasonal heterotrophy in the future as rising temperatures stimulate respiration.

  17. 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

  18. Leaf-level photosynthetic capacity in lowland Amazonian and high-elevation Andean tropical moist forests of Peru.

    Science.gov (United States)

    Bahar, Nur H A; Ishida, F Yoko; Weerasinghe, Lasantha K; Guerrieri, Rossella; O'Sullivan, Odhran S; Bloomfield, Keith J; Asner, Gregory P; Martin, Roberta E; Lloyd, Jon; Malhi, Yadvinder; Phillips, Oliver L; Meir, Patrick; Salinas, Norma; Cosio, Eric G; Domingues, Tomas F; Quesada, Carlos A; Sinca, Felipe; Escudero Vega, Alberto; Zuloaga Ccorimanya, Paola P; Del Aguila-Pasquel, Jhon; Quispe Huaypar, Katherine; Cuba Torres, Israel; Butrón Loayza, Rosalbina; Pelaez Tapia, Yulina; Huaman Ovalle, Judit; Long, Benedict M; Evans, John R; Atkin, Owen K

    2017-05-01

    We examined whether variations in photosynthetic capacity are linked to variations in the environment and/or associated leaf traits for tropical moist forests (TMFs) in the Andes/western Amazon regions of Peru. We compared photosynthetic capacity (maximal rate of carboxylation of Rubisco (Vcmax ), and the maximum rate of electron transport (Jmax )), leaf mass, nitrogen (N) and phosphorus (P) per unit leaf area (Ma , Na and Pa , respectively), and chlorophyll from 210 species at 18 field sites along a 3300-m elevation gradient. Western blots were used to quantify the abundance of the CO2 -fixing enzyme Rubisco. Area- and N-based rates of photosynthetic capacity at 25°C were higher in upland than lowland TMFs, underpinned by greater investment of N in photosynthesis in high-elevation trees. Soil [P] and leaf Pa were key explanatory factors for models of area-based Vcmax and Jmax but did not account for variations in photosynthetic N-use efficiency. At any given Na and Pa , the fraction of N allocated to photosynthesis was higher in upland than lowland species. For a small subset of lowland TMF trees examined, a substantial fraction of Rubisco was inactive. These results highlight the importance of soil- and leaf-P in defining the photosynthetic capacity of TMFs, with variations in N allocation and Rubisco activation state further influencing photosynthetic rates and N-use efficiency of these critically important forests. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

  19. 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.

  20. Photosynthetic capacity of red spruce during winter

    Science.gov (United States)

    P.G. Schaberg; J.B. Shane; P.F. Cali; J.R. Donnelly; G.R. Strimbeck

    1998-01-01

    We measured the photosynthetic capacity (Pmax) of plantation-grown red spruce (Picea rubens Sarg.) during two winter seasons (1993-94 and 1994-95) and monitored field photosynthesis of these trees during one winter (1993-94). We also measured Pmax for mature montane trees from January through May 1995....

  1. Chemiosmotic coupling in oxidative and photosynthetic phosphorylation

    National Research Council Canada - National Science Library

    Mitchell, Peter

    2011-01-01

    ... in oxidative phosphorylation in mitochondria is that, for the equivalent of each pair of electrons traversing the respiratory chain, up to 3 anhydrobond equivalents may normally traverse the h/d pathway from adenosine diphosphate plus inorganic phosphate (ADP + P i ) to water. In photosynthetic phosphorylation the stoichiometry is less certain, and it is thought...

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

    African Journals Online (AJOL)

    AJL

    2012-02-21

    Feb 21, 2012 ... Medicinal Plant Resources, Key Laboratory of Hunan Higher Education for Hunan-western Medicinal Plant and. Ethnobotany ... lycorine and galantamine during the annual growth period were studied by using LI-6400 portable photosynthetic ... ingredients of several medicinal plants. Their production.

  3. Photosynthetic antenna engineering to improve crop yields.

    Science.gov (United States)

    Kirst, Henning; Gabilly, Stéphane T; Niyogi, Krishna K; Lemaux, Peggy G; Melis, Anastasios

    2017-05-01

    Evidence shows that decreasing the light-harvesting antenna size of the photosystems in tobacco helps to increase the photosynthetic productivity and plant canopy biomass accumulation under high-density cultivation conditions. Decreasing, or truncating, the chlorophyll antenna size of the photosystems can theoretically improve photosynthetic solar energy conversion efficiency and productivity in mass cultures of algae or plants by up to threefold. A Truncated Light-harvesting chlorophyll Antenna size (TLA), in all classes of photosynthetic organisms, would help to alleviate excess absorption of sunlight and the ensuing wasteful non-photochemical dissipation of excitation energy. Thus, solar-to-biomass energy conversion efficiency and photosynthetic productivity in high-density cultures can be increased. Applicability of the TLA concept was previously shown in green microalgae and cyanobacteria, but it has not yet been demonstrated in crop plants. In this work, the TLA concept was applied in high-density tobacco canopies. The work showed a 25% improvement in stem and leaf biomass accumulation for the TLA tobacco canopies over that measured with their wild-type counterparts grown under the same ambient conditions. Distinct canopy appearance differences are described between the TLA and wild type tobacco plants. Findings are discussed in terms of concept application to crop plants, leading to significant improvements in agronomy, agricultural productivity, and application of photosynthesis for the generation of commodity products in crop leaves.

  4. Photosynthetic performance, epiphyte biomass and nutrient content ...

    African Journals Online (AJOL)

    Heavy nutrient loads in coastal waters often lead to excessive growth of microalgal and macroalgal epiphytes on seagrass leaves, with varying effects on the underlying seagrasses. This study evaluates the photosynthetic performance, epiphytic biomass and tissue nutrient content of two tropical seagrasses, Cymodocea ...

  5. Petri Nets-Applications

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 4; Issue 9. Petri Nets - Applications. Y Narahari. General Article Volume 4 Issue 9 September 1999 pp 44-52. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/004/09/0044-0052. Author Affiliations. Y Narahari ...

  6. Safety nets or straitjackets?

    DEFF Research Database (Denmark)

    Ilsøe, Anna

    2012-01-01

    Does regulation of working hours at national and sector level impose straitjackets, or offer safety nets to employees seeking working time flexibility? This article compares legislation and collective agreements in the metal industries of Denmark, Germany and the USA. The industry has historically...

  7. Coloured Petri Nets

    CERN Document Server

    Jensen, Kurt

    2009-01-01

    Coloured Petri Nets (CPN) is a graphical language for modelling and validating concurrent and distributed systems, and other systems in which concurrency plays a major role. This book introduces the constructs of the CPN modelling language and presents the related analysis methods. It provides a comprehensive road map for the practical use of CPN.

  8. Boom Booom Net Radio

    DEFF Research Database (Denmark)

    Grimshaw, Mark Nicholas; Yong, Louisa; Dobie, Ian

    1999-01-01

    of an existing Internet radio station; Boom Booom Net Radio. Whilst necessity dictates some use of technology-related terminology, wherever possible we have endeavoured to keep such jargon to a minimum and to either explain it in the text or to provide further explanation in the appended glossary....

  9. Game Theory .net.

    Science.gov (United States)

    Shor, Mikhael

    2003-01-01

    States making game theory relevant and accessible to students is challenging. Describes the primary goal of GameTheory.net is to provide interactive teaching tools. Indicates the site strives to unite educators from economics, political and computer science, and ecology by providing a repository of lecture notes and tests for courses using…

  10. Coloured Petri Nets

    DEFF Research Database (Denmark)

    Jensen, Kurt; Kristensen, Lars Michael

    Coloured Petri Nets (CPN) is a graphical language for modelling and validating concurrent and distributed systems, and other systems in which concurrency plays a major role. The development of such systems is particularly challenging because of inherent intricacies like possible nondeterminism...

  11. Chemical composition and photosynthetically active radiation of forage grasses under irrigation

    Directory of Open Access Journals (Sweden)

    Edilane Aparecida da Silva

    2012-03-01

    Full Text Available The present study aimed to estimate the photosynthetically active radiation of tropical forage grasses in ten cutting dates, under irrigation. The following treatments were used: Brachiaria decumbens grass (Brachiaria decumbens cultivar Basilisk, Marandu grass (Brachiaria brizantha cultivar Marandu, Xaraes grass (Brachiaria brizantha, cultivar Xaraes, Mombaça grass (Panicum maximum cultivar Mombaça, Tanzania grass (Panicum maximum, cultivar Tanzania and Tifton 85 grass (Cynodon spp cultivar Tifton 85. The weather parameters were collected by an automatic meteorological station installed in the location and used for irrigation management. The experiment was arranged in a split-plot completely randomized block design, considering the grasses as plots and cutting seasons as subplots, with four replications in a 6 × 10 factorial arrangement, six grasses and ten cutting seasons. The results indicated increased use of photosynthetically active radiation in the wet season, in relation to the dry-wet season transition. Basilisk presented the highest values of photosynthetically active radiation (1,648.9 mE. The variables studied were affected by photosynthetically active radiation. The grass cultivars presented different light interceptions. The values of 87; 90; 90; 88; 92 and 77% were found for grass cultivars Basilisk, Marandu, Mombaça, Tanzania, Xaraes and Tifton 85, respectively. Differences were observed in forage accumulation rates for the grass plants studied. The grasses with the best productive performance were Brachiaria decumbens cultivar Basilisk and B. brizantha cultivar Xaraes. The highest values of crude protein and neutral detergent fiber were observed for Tifton 85. The use of photosynthetically active radiation was different among the grasses evaluated. There is a positive association between photosynthetically active radiation and dry matter production. Besides, photosynthetically active radiation indirectly affects crude protein

  12. Photosynthetic performance in Antarctic lichens with different growth forms reflect the diversity of lichenized algal adaptation to microhabitats

    Directory of Open Access Journals (Sweden)

    Cao Shunan

    2015-06-01

    Full Text Available Lichens, as typical obligate associations between lichenized fungi and their photosynthetic partners, are dominant in Antarctica. Three Antarctic lichens, Ochrolechia frigida, Umbilicaria antarctica, and Usnea aurantiacoatra with different growth forms, were sampled nearby the Great Wall Station, King George Island. Molecular data revealed that the photosynthetic algae in these three lichens were Trebouxia jamesii. The net photo− synthesis (Pn of three individuals from these species, together with environmental factors such as light and temperature, were recorded by CO2 gas exchange measurements using a CI−340 portable photosynthetic system in situ. Differences between T(leaf (the temperature of the thalli and T(air (the air temperature for these lichens were not consistent, which reflected that environment and the growth form of thalli could affect T(leaf significantly. Strong irradiation was expected to have adverse effects on Pn of Ochrolechia frigida and Umbilicaria antarctica whose thalli spread flat; but this photoinhibition had little effect on Usnea aurantiacoatra with exuberant tufted thallus. These results indicated that photosynthetic activity in lichens was affected by the growth forms of thalli besides microhabitat factors. One species of lichenized alga could exhibit diversified types of photosynthetic behavior when it was associated with various lichenized fungi in different microhabitats. It will be helpful for understanding how lichens are able to adapt to and colonize in extreme environments.

  13. 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

    A series of phthalocyanine-carotenoid dyads in which a phenylamino group links a phthalocyanine to carotenoids having 8-11 backbone double bonds were examined by visible and near-infrared femtosecond pump-probe spectroscopy combined with global fitting analysis. The series of molecules has permitted investigation of the role of carotenoids in the quenching of excited states of cyclic tetrapyrroles. The transient behavior varied dramatically with the length of the carotenoid and the solvent environment. Clear spectroscopic signatures of radical species revealed photoinduced electron transfer as the main quenching mechanism for all dyads dissolved in a polar solvent (THF), and the quenching rate was almost independent of carotenoid length. However, in a nonpolar solvent (toluene), quenching rates displayed a strong dependence on the conjugation length of the carotenoid and the mechanism did not include charge separation. The lack of any rise time components of a carotenoid S1 signature in all experiments in toluene suggests that an excitonic coupling between the carotenoid S1 state and phthalocyanine Q state, rather than a conventional energy transfer process, is the major mechanism of quenching. A pronounced inhomogeneity of the system was observed and attributed to the presence of a phenyl-amino linker between phthalocyanine and carotenoids. On the basis of accumulated work on various caroteno-phthalocyanine dyads and triads, we have now identified three mechanisms of tetrapyrrole singlet excited state quenching by carotenoids in artificial systems: (i) Car-Pc electron transfer and recombination; (ii)1Pc to Car S1 energy transfer and fast internal conversion to the Car ground state; (iii) excitonic coupling between 1Pc and Car S1 and ensuing internal conversion to the ground state of the carotenoid. The dominant mechanism depends upon the exact molecular architecture and solvent environment

  14. Sea-ice melt CO2-carbonate chemistry in the western Arctic Ocean: meltwater contributions to air-sea CO2 gas exchange, mixed layer properties and rates of net community production under sea ice

    Science.gov (United States)

    Bates, N. R.; Garley, R.; Frey, K. E.; Shake, K. L.; Mathis, J. T.

    2014-01-01

    The carbon dioxide (CO2)-carbonate chemistry of sea-ice melt and co-located, contemporaneous seawater has rarely been studied in sea ice covered oceans. Here, we describe the CO2-carbonate chemistry of sea-ice melt (both above sea ice as "melt ponds" and below sea ice as "interface waters") and mixed layer properties in the western Arctic Ocean in the early summer of 2010 and 2011. At nineteen stations, the salinity (~ 0.5 to 1500 μatm) with the majority of melt ponds acting as potentially strong sources of CO2 to the atmosphere. The pH of melt pond waters was also highly variable ranging from mildly acidic (6.1 to 7) to slightly more alkaline than underlying seawater (8 to 10.7). All of observed melt ponds had very low (pH/Ωaragonite than the co-located mixed layer beneath. Sea-ice melt thus contributed to the suppression of mixed layer pCO2 enhancing the surface ocean's capacity to uptake CO2 from the atmosphere. Meltwater contributions to changes in mixed-layer DIC were also used to estimate net community production rates (mean of 46.9 ±29.8 g C m-2 for the early-season period) under sea-ice cover. Although sea-ice melt is a transient seasonal feature, above-ice melt pond coverage can be substantial (10 to > 50%) and under-ice interface melt water is ubiquitous during this spring/summer sea-ice retreat. Our observations contribute to growing evidence that sea-ice CO2-carbonate chemistry is highly variable and its contribution to the complex factors that influence the balance of CO2 sinks and sources (and thereby ocean acidification) is difficult to predict in an era of rapid warming and sea ice loss in the Arctic Ocean.

  15. Older Thinopyrum intermedium (Poaceae) plants exhibit superior photosynthetic tolerance to cold stress and greater increases in two photosynthetic enzymes under freezing stress compared with young plants.

    Science.gov (United States)

    Jaikumar, Nikhil S; Snapp, Sieglinde S; Sharkey, Thomas D

    2016-08-01

    Effects of plant age on resource acquisition and stress tolerance processes is a largely unstudied subject in herbaceous perennials. In a field experiment, we compared rates of photosynthesis (A), ribulose-1,5-bisphosphate (RuBP) carboxylation capacity (V Cmax), maximum electron transport rate (J max), and triose phosphate utilization (TPU), as well as concentrations of Rubisco and sucrose-phosphate synthase (SPS) in 5-year-old and 2-year-old intermediate wheatgrass (Thinopyrum intermedium) under both optimal growing conditions and cold stress in early spring and autumn. This species is a relative of wheat undergoing domestication. An additional experiment compared photosynthetic rates in different cohorts at mid-season and under colder conditions. We hypothesized that photosynthetic capacity in older plants would be lower under favorable conditions but higher under cold stress. Our hypothesis was generally supported. Under cold stress, 5-year-old plants exhibited higher A, TPU, and temperature-adjusted V Cmax than younger plants, as well as 50% more SPS and 37% more Rubisco. In contrast, at mid-season, photosynthetic capacities in older plants were lower than in younger plants in one experiment, and similar in the other, independent of differences in water status. Both cohorts increased A, temperature-adjusted TPU and J max, [Rubisco], and [SPS] under cold stress, but changes were greater in older plants. Photosynthetic differences were largest at 1.2 ºC in very early spring, where older plants had 200% higher A and maintained up to 17% of their peak photosynthetic capacity. We find evidence of increased cold tolerance in older cohorts of wheatgrass, consistent with a growing body of research in woody perennials. © The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology.

  16. Impact of cloudiness on net ecosystem exchange of carbon dioxide in different types of forest ecosystems in China

    Science.gov (United States)

    Zhang, M.; Yu, G.-R.; Zhang, L.-M.; Sun, X.-M.; Wen, X.-F.; Han, S.-J.; Yan, J.-H.

    2010-02-01

    Clouds can significantly affect carbon exchange process between forest ecosystems and the atmosphere by influencing the quantity and quality of solar radiation received by ecosystem's surface and other environmental factors. In this study, we analyzed the effects of cloudiness on net ecosystem exchange of carbon dioxide (NEE) in a temperate broad-leaved Korean pine mixed forest at Changbaishan (CBS) and a subtropical evergreen broad-leaved forest at Dinghushan (DHS), based on the flux data obtained during June-August from 2003 to 2006. The results showed that the response of NEE of forest ecosystems to photosynthetically active radiation (PAR) differed under clear skies and cloudy skies. Compared with clear skies, the light-saturated maximum photosynthetic rate (Pec,max) at CBS under cloudy skies during mid-growing season (from June to August) increased by 34%, 25%, 4% and 11% in 2003, 2004, 2005 and 2006, respectively. In contrast, Pec,max of the forest ecosystem at DHS was higher under clear skies than under cloudy skies from 2004 to 2006. When the clearness index (kt) ranged between 0.4 and 0.6, the NEE reached its maximum at both CBS and DHS. However, the NEE decreased more dramatically at CBS than at DHS when kt exceeded 0.6. The results indicate that cloudy sky conditions are beneficial to net carbon uptake in the temperate forest ecosystem and the subtropical forest ecosystem. Under clear skies, vapor pressure deficit (VPD) and air temperature increased due to strong light. These environmental conditions led to greater decrease in gross ecosystem photosynthesis (GEP) and greater increase in ecosystem respiration (Re) at CBS than at DHS. As a result, clear sky conditions caused more reduction of NEE in the temperate forest ecosystem than in the subtropical forest ecosystem. The response of NEE of different forest ecosystems to the changes in cloudiness is an important factor that should be included in evaluating regional carbon budgets under climate change

  17. Alternating electron and proton transfer steps in photosynthetic water oxidation.

    Science.gov (United States)

    Klauss, André; Haumann, Michael; Dau, Holger

    2012-10-02

    Water oxidation by cyanobacteria, algae, and plants is pivotal in oxygenic photosynthesis, the process that powers life on Earth, and is the paradigm for engineering solar fuel-production systems. Each complete reaction cycle of photosynthetic water oxidation requires the removal of four electrons and four protons from the catalytic site, a manganese-calcium complex and its protein environment in photosystem II. In time-resolved photothermal beam deflection experiments, we monitored apparent volume changes of the photosystem II protein associated with charge creation by light-induced electron transfer (contraction) and charge-compensating proton relocation (expansion). Two previously invisible proton removal steps were detected, thereby filling two gaps in the basic reaction-cycle model of photosynthetic water oxidation. In the S(2) → S(3) transition of the classical S-state cycle, an intermediate is formed by deprotonation clearly before electron transfer to the oxidant (Y Z OX). The rate-determining elementary step (τ, approximately 30 µs at 20 °C) in the long-distance proton relocation toward the protein-water interface is characterized by a high activation energy (E(a) = 0.46 ± 0.05 eV) and strong H/D kinetic isotope effect (approximately 6). The characteristics of a proton transfer step during the S(0) → S(1) transition are similar (τ, approximately 100 µs; E(a) = 0.34 ± 0.08 eV; kinetic isotope effect, approximately 3); however, the proton removal from the Mn complex proceeds after electron transfer to . By discovery of the transient formation of two further intermediate states in the reaction cycle of photosynthetic water oxidation, a temporal sequence of strictly alternating removal of electrons and protons from the catalytic site is established.

  18. Photosynthetic response to fluctuating environments and photoprotective strategies under abiotic stress.

    Science.gov (United States)

    Yamori, Wataru

    2016-05-01

    Plants in natural environments must cope with diverse, highly dynamic, and unpredictable conditions. They have mechanisms to enhance the capture of light energy when light intensity is low, but they can also slow down photosynthetic electron transport to prevent the production of reactive oxygen species and consequent damage to the photosynthetic machinery under excess light. Plants need a highly responsive regulatory system to balance the photosynthetic light reactions with downstream metabolism. Various mechanisms of regulation of photosynthetic electron transport under stress have been proposed, however the data have been obtained mainly under environmentally stable and controlled conditions. Thus, our understanding of dynamic modulation of photosynthesis under dramatically fluctuating natural environments remains limited. In this review, first I describe the magnitude of environmental fluctuations under natural conditions. Next, I examine the effects of fluctuations in light intensity, CO2 concentration, leaf temperature, and relative humidity on dynamic photosynthesis. Finally, I summarize photoprotective strategies that allow plants to maintain the photosynthesis under stressful fluctuating environments. The present work clearly showed that fluctuation in various environmental factors resulted in reductions in photosynthetic rate in a stepwise manner at every environmental fluctuation, leading to the conclusion that fluctuating environments would have a large impact on photosynthesis.

  19. Photosynthetically supplemental lighting for vegetable crop production with super-bright laser diode

    Science.gov (United States)

    Hu, Yongguang; Li, Pingping; Shi, Jintong

    2007-02-01

    Although many artificial light sources like high-pressure sodium lamp, metal halide lamp, fluorescent lamp and so on are commonly used in horticulture, they are not widely applied because of the disadvantages of unreasonable spectra, high cost and complex control. Recently new light sources of light-emitting diode (LED) and laser diode (LD) are becoming more and more popular in the field of display and illumination with the improvement of material and manufacturing, long life-span and increasingly low cost. A new type of super-bright red LD (BL650, central wavelength is 650 nm) was selected to make up of the supplemental lighting panel, on which LDs were distributed with regular hexagon array. Drive circuit was designed to power it and adjust light intensity. System performance including temperature rise and light intensity distribution under different vertical/horizontal distances were tested. Photosynthesis of sweet pepper and eggplant leaf under LD was measured with LI-6400 to show the supplemental lighting effects. The results show that LD system can supply the maximum light intensity of 180 μmol/m2 •s at the distance of 50 mm below the panel and the temperature rise is little within 1 °C. Net photosynthetic rate became faster when LD system increased light intensity. Compared with sunlight and LED supplemental lighting system, LD's promotion on photosynthesis is in the middle. Thus it is feasible for LD light source to supplement light for vegetable crops. Further study would focus on the integration of LD and other artificial light sources.

  20. Seasonal photosynthetic responses of European oaks to drought and elevated daytime temperature.

    Science.gov (United States)

    Arend, M; Brem, A; Kuster, T M; Günthardt-Goerg, M S

    2013-01-01

    Oaks are commonly considered as drought- and heat-tolerant trees that might benefit from a warmer and drier climate. Their tolerance to drought has been frequently studied in the past, whereas studies dealing with elevated temperature or its combination with drought are very limited in number. In this study we investigated seasonal photosynthetic patterns in three European oak species (Quercus robur, Q. petraea, Q. pubescens) exposed in lysimeter-based open-top chambers (OTC) to elevated daytime temperature, drought and their combination. Stomatal and non-stomatal traits of photosynthesis were followed over an entire growing season and related to changes in daytime temperature, soil moisture and pre-dawn leaf water potential (Ψ(PD) ). Elevated daytime temperature enhanced net photosynthesis (P(N) ) in a season-dependent manner, with higher mid-summer rates than in controls exposed to ambient temperature. Drought imposed in early and mid-summer reduced the soil moisture content and caused a gradual decline in Ψ(PD) , stomatal conductance (g(S) ) and P(N) . Drought effects on Ψ(PD) and P(N) were exacerbated when drought was combined with elevated daytime temperature. In general, P(N) tended to be more affected by low soil moisture content or low Ψ(PD) in Q. robur than in Q. petraea and Q. pubescens. Non-stomatal limitations may have contributed to the drought-induced decline of P(N) in Q. robur, as indicated by a down-regulation of PSII photochemistry (F(V) /F(M) ) and decreased chlorophyll content. Taken together, our findings show that European oaks may benefit from elevated temperature, but detrimental effects can be expected when elevated temperature occurs simultaneously with drought. © 2012 German Botanical Society and The Royal Botanical Society of the Netherlands.

  1. Combined effects of lanthanum (III) chloride and acid rain on photosynthetic parameters in rice.

    Science.gov (United States)

    Wang, Lihong; Wang, Wen; Zhou, Qing; Huang, Xiaohua

    2014-10-01

    Rare earth elements (REEs) pollution and acid rain are environmental issues, and their deleterious effects on plants attract worldwide attention. These two issues exist simultaneously in many regions, especially in some rice-growing areas. However, little is known about the combined effects of REEs and acid rain on plants. Here, the combined effects of lanthanum chloride (LaCl3), one type of REE salt, and acid rain on photosynthesis in rice were investigated. We showed that the combined treatment of 81.6 μM LaCl3 and acid rain at pH 4.5 increased net photosynthetic rate (Pn), stomatic conductance (Gs), intercellular CO2 concentration (Ci), Hill reaction activity (HRA), apparent quantum yield (AQY) and carboxylation efficiency (CE) in rice. The combined treatment of 81.6 μM LaCl3 and acid rain at pH 3.5 began to behave toxic effects on photosynthesis (decreasing Pn, Gs, HRA, AQY and CE, and increasing Ci), and the maximally toxic effects were observed in the combined treatment of 2449.0 μM LaCl3 and acid rain at pH 2.5. Moreover, the combined effects of LaCl3 and acid rain on photosynthesis in rice depended on the growth stage of rice, with the maximal effects occurring at the booting stage. Furthermore, the combined treatment of high-concentration LaCl3 and low-pH acid rain had more serious effects on photosynthesis in rice than LaCl3 or acid rain treatment alone. Finally, the combined effect of LaCl3 and acid rain on Pn in rice resulted from the changes in stomatic (Gs, Ci) and non-stomatic (HRA, AQY and CE) factors. Copyright © 2014 Elsevier Ltd. All rights reserved.

  2. Lack of photosynthetic or stomatal regulation after 9 years of elevated [CO2] and 4 years of soil warming in two conifer species at the alpine treeline.

    Science.gov (United States)

    Streit, Kathrin; Siegwolf, Rolf T W; Hagedorn, Frank; Schaub, Marcus; Buchmann, Nina

    2014-02-01

    Alpine treelines are temperature-limited vegetation boundaries. Understanding the effects of elevated [CO2 ] and warming on CO2 and H2 O gas exchange may help predict responses of treelines to global change. We measured needle gas exchange of Larix decidua Mill. and Pinus mugo ssp. uncinata DC trees after 9 years of free air CO2 enrichment (575 µmol mol(-1) ) and 4 years of soil warming (+4 °C) and analysed δ(13) C and δ(18) O values of needles and tree rings. Tree needles under elevated [CO2 ] showed neither nitrogen limitation nor end-product inhibition, and no down-regulation of maximal photosynthetic rate (Amax ) was found. Both tree species showed increased net photosynthetic rates (An ) under elevated [CO2 ] (L. decidua: +39%; P. mugo: +35%). Stomatal conductance (gH2O ) was insensitive to changes in [CO2 ], thus transpiration rates remained unchanged and intrinsic water-use efficiency (iWUE) increased due to higher An . Soil warming affected neither An nor gH2O . Unresponsiveness of gH2O to [CO2 ] and warming was confirmed by δ(18) O needle and tree ring values. Consequently, under sufficient water supply, elevated [CO2 ] induced sustained enhancement in An and lead to increased C inputs into this ecosystem, while soil warming hardly affected gas exchange of L. decidua and P. mugo at the alpine treeline. © 2013 John Wiley & Sons Ltd.

  3. Dynamic control of photosynthetic photon flux for lettuce production in CELSS

    Science.gov (United States)

    Chun, C.; Mitchell, C. A.

    1996-01-01

    A new dynamic control of photosynthetic photon flux (PPF) was tested using lettuce canopies growing in the Minitron II plant-growth/canopy gas-exchange system. Canopy photosynthetic rates (Pn) were measured in real time and fedback for further environment control. Pn can be manipulated by changing PPF, which is a good environmental parameter for dynamic control of crop production in a Controlled Ecological Life-Support Systems CELSS. Decision making that combines empirical mathematical models with rule sets developed from recent experimental data was tested. With comparable yield indices and potential for energy savings, dynamic control strategies will contribute greatly to the sustainability of space-deployed CELSS.

  4. Effects of grafting on key photosynthetic enzymes and gene expression in the citrus cultivar Huangguogan.

    Science.gov (United States)

    Liao, L; Cao, S Y; Rong, Y; Wang, Z H

    2016-03-04

    Grafting influences scion photosynthetic capacity and fruit quality. Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), which strongly affects photosynthetic rate, and Rubisco activase (RCA), which regulates Rubisco activity, are two key photosynthetic enzymes. However, little information is available regarding the effect of grafting on the concentration and expression of Rubisco and RCA in the citrus cultivar Huangguogan. The objective of this study was to investigate the effect of grafting Huangguogan plants onto trifoliate orange, tangerine, and orange on: 1) the concentration of Rubisco and RCA; 2) the mRNA levels of rbcL, rbcS, and rca; and 3) fruit quality. Overall, the results showed that when Huangguogan plants budded on tangerine and orange, they had better fruit quality, while on trifoliate orange they had higher Rubisco concentration. Tangerine and orange are probably the most suitable rootstocks for Huangguogan plants given the environmental conditions of Sichuan Province, China.

  5. Interactive effects of cadmium and acid rain on photosynthetic light reaction in soybean seedlings.

    Science.gov (United States)

    Sun, Zhaoguo; Wang, Lihong; Chen, Minmin; Wang, Lei; Liang, Chanjuan; Zhou, Qing; Huang, Xiaohua

    2012-05-01

    Interactive effects of cadmium (Cd(2+)) and acid rain on photosynthetic light reaction in soybean seedlings were investigated under hydroponic conditions. Single treatment with Cd(2+) or acid rain and the combined treatment decreased the content of chlorophyll, Hill reaction rate, the activity of Mg(2+)-ATPase, maximal photochemical efficiency and maximal quantum yield, increased initial fluorescence and damaged the chloroplast structure in soybean seedlings. In the combined treatment, the change in the photosynthetic parameters and the damage of chloroplast structure were stronger than those of any single pollution. Meanwhile, Cd(2+) and acid rain had the interactive effects on the test indices in soybean seedlings. The results indicated that the combined pollution of Cd(2+) and acid rain aggravated the toxic effect of the single pollution of Cd(2+) or acid rain on the photosynthetic parameters due to the serious damage to the chloroplast structure. Copyright © 2011 Elsevier Inc. All rights reserved.

  6. Food Safety Nets:

    OpenAIRE

    Haggblade, Steven; Diallo, Boubacar; Staatz, John; Theriault, Veronique; Traoré, Abdramane

    2013-01-01

    Food and social safety nets have a history as long as human civilization. In hunter gatherer societies, food sharing is pervasive. Group members who prove unlucky in the short run, hunting or foraging, receive food from other households in anticipation of reciprocal consideration at a later time (Smith 1988). With the emergence of the first large sedentary civilizations in the Middle East, administrative systems developed specifically around food storage and distribution. The ancient Egyptian...

  7. Net technical assessment

    OpenAIRE

    Wegmann, David G.

    1989-01-01

    Approved for public release; distribution is unlimited. The present and near term military balance of power between the U.S. and the Soviet Union can be expressed in a variety of net assessments. One can examine the strategic nuclear balance, the conventional balance in Europe, the maritime balance, and many others. Such assessments are essential not only for policy making but for arms control purposes and future force structure planning. However, to project the future military balance, on...

  8. Dynamic Balancing of Isoprene Carbon Sources Reflects Photosynthetic and Photorespiratory Responses to Temperature Stress1[W][OPEN

    Science.gov (United States)

    Chambers, Jeffrey; Alves, Eliane G.; Teixeira, Andrea; Garcia, Sabrina; Holm, Jennifer; Higuchi, Niro; Manzi, Antonio; Abrell, Leif; Fuentes, Jose D.; Nielsen, Lars K.; Torn, Margaret S.; Vickers, Claudia E.

    2014-01-01

    The volatile gas isoprene is emitted in teragrams per annum quantities from the terrestrial biosphere and exerts a large effect on atmospheric chemistry. Isoprene is made primarily from recently fixed photosynthate; however, alternate carbon sources play an important role, particularly when photosynthate is limiting. We examined the relative contribution of these alternate carbon sources under changes in light and temperature, the two environmental conditions that have the strongest influence over isoprene emission. Using a novel real-time analytical approach that allowed us to examine dynamic changes in carbon sources, we observed that relative contributions do not change as a function of light intensity. We found that the classical uncoupling of isoprene emission from net photosynthesis at elevated leaf temperatures is associated with an increased contribution of alternate carbon. We also observed a rapid compensatory response where alternate carbon sources compensated for transient decreases in recently fixed carbon during thermal ramping, thereby maintaining overall increases in isoprene production rates at high temperatures. Photorespiration is known to contribute to the decline in net photosynthesis at high leaf temperatures. A reduction in the temperature at which the contribution of alternate carbon sources increased was observed under photorespiratory conditions, while photosynthetic conditions increased this temperature. Feeding [2-13C]glycine (a photorespiratory intermediate) stimulated emissions of [13C1–5]isoprene and 13CO2, supporting the possibility that photorespiration can provide an alternate source of carbon for isoprene synthesis. Our observations have important implications for establishing improved mechanistic predictions of isoprene emissions and primary carbon metabolism, particularly under the predicted increases in future global temperatures. PMID:25318937

  9. Using WordNet for Building WordNets

    CERN Document Server

    Farreres, X; Farreres, Xavier; Rodriguez, Horacio; Rigau, German

    1998-01-01

    This paper summarises a set of methodologies and techniques for the fast construction of multilingual WordNets. The English WordNet is used in this approach as a backbone for Catalan and Spanish WordNets and as a lexical knowledge resource for several subtasks.

  10. Artificial photosynthetic systems for production of hydrogen.

    Science.gov (United States)

    Fukuzumi, Shunichi

    2015-04-01

    The rapid consumption of fossil fuels has caused unacceptable environmental problems such as the greenhouse effect, which may lead to disastrous climatic consequences. Because fossil fuels are the products of long-term photosynthesis, it is highly desirable to develop artificial photosynthetic systems for the production of renewable and clean energy such as hydrogen. This article summarizes recent advances on studies of artificial photosynthetic systems for photocatalytic production of hydrogen with hydrogenases and their functional mimics including hybrids of natural and artificial components. Because it is highly desired to convert gaseous H2 to an easily storable form, recent progress on storage of hydrogen as liquid or solid form has also been described in this article. Copyright © 2014 Elsevier Ltd. All rights reserved.

  11. Reconciling catch differences from multiple fishery independent gill net surveys

    Science.gov (United States)

    Kraus, Richard T.; Vandergoot, Christopher; Kocovsky, Patrick M.; Rogers, Mark W.; Cook, H. Andrew; Brenden, Travis O.

    2017-01-01

    Fishery independent gill net surveys provide valuable demographic information for population assessment and resource management, but relative to net construction, the effects of ancillary species, and environmental variables on focal species catch rates are poorly understood. In response, we conducted comparative deployments with three unique, inter-agency, survey gill nets used to assess walleye Sander vitreus in Lake Erie. We used an information-theoretic approach with Akaike’s second-order information criterion (AICc) to evaluate linear mixed models of walleye catch as a function of net type (multifilament and two types of monofilament netting), mesh size (categorical), Secchi depth, temperature, water depth, catch of ancillary species, and interactions among selected variables. The model with the greatest weight of evidence showed that walleye catches were positively associated with potential prey and intra-guild predators and negatively associated with water depth and temperature. In addition, the multifilament net had higher average walleye catches than either of the two monofilament nets. Results from this study both help inform decisions about proposed gear changes to stock assessment surveys in Lake Erie, and advance our understanding of how multispecies associations explain variation in gill net catches. Of broader interest to fishery-independent gill net studies, effects of abiotic variables and ancillary species on focal specie’s catch rates were small in comparison with net characteristics of mesh size or twine type.

  12. Intracellular spectral recompositioning of light enhances algal photosynthetic efficiency.

    Science.gov (United States)

    Fu, Weiqi; Chaiboonchoe, Amphun; Khraiwesh, Basel; Sultana, Mehar; Jaiswal, Ashish; Jijakli, Kenan; Nelson, David R; Al-Hrout, Ala'a; Baig, Badriya; Amin, Amr; Salehi-Ashtiani, Kourosh

    2017-09-01

    Diatoms, considered as one of the most diverse and largest groups of algae, can provide the means to reach a sustainable production of petrochemical substitutes and bioactive compounds. However, a prerequisite to achieving this goal is to increase the solar-to-biomass conversion efficiency of photosynthesis, which generally remains less than 5% for most photosynthetic organisms. We have developed and implemented a rapid and effective approach, herein referred to as intracellular spectral recompositioning (ISR) of light, which, through absorption of excess blue light and its intracellular emission in the green spectral band, can improve light utilization. We demonstrate that ISR can be used chemogenically, by using lipophilic fluorophores, or biogenically, through the expression of an enhanced green fluorescent protein (eGFP) in the model diatom Phaeodactylum tricornutum. Engineered P. tricornutum cells expressing eGFP achieved 28% higher efficiency in photosynthesis than the parental strain, along with an increased effective quantum yield and reduced nonphotochemical quenching (NPQ) induction levels under high-light conditions. Further, pond simulator experiments demonstrated that eGFP transformants could outperform their wild-type parental strain by 50% in biomass production rate under simulated outdoor sunlight conditions. Transcriptome analysis identified up-regulation of major photosynthesis genes in the engineered strain in comparison with the wild type, along with down-regulation of NPQ genes involved in light stress response. Our findings provide a proof of concept for a strategy of developing more efficient photosynthetic cell factories to produce algae-based biofuels and bioactive products.

  13. 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.

  14. Nonclassical energy transfer in photosynthetic FMO complex

    Directory of Open Access Journals (Sweden)

    Abramavicius Vytautas

    2013-03-01

    Full Text Available Excitation energy transfer in a photosynthetic FMO complex has been simulated using the stochastic Schrödinger equation. Fluctuating chromophore transition energies are simulated from the quantum correlation function which allows to properly include the finite temperature. The resulting excitation dynamics shows fast thermalization of chromophore occupations into proper thermal equilibrium. The relaxation process is characterized by entropy dynamics, which shows nonclassical behavior.

  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

    2003-04-15

    This quarterly report documents significant achievements in the Enhanced Practical Photosynthetic CO{sub 2} Mitigation project during the period from 1/2/2003 through 4/01/2003. As indicated in the list of accomplishments below we are progressing with long-term model scale bioreactor tests and are completing final preparations for pilot scale bioreactor testing. Specific results and accomplishments for the first quarter of 2003 are included.

  16. CO2-induced photosynthetic and stoichiometric responses to phosphorus limitation

    Science.gov (United States)

    de Boer, Hugo; di Lallo, Giacomo; van Dijk, Jerry

    2017-04-01

    Carbon fertilisation from rising atmospheric CO2 concentrations increases the productivity of plants globally. Meanwhile, the global cycles of Nitrogen (N) and Phosphorus (P) are also altered due to anthropogenic emissions. In general, the additional supply of N is expected to exceed that of P, leading to an increase in P limitation in natural ecosystems. Although the direct carbon fertilisation effect and the interaction with available N is relatively well understood, it remains uncertain how carbon fertilisation is confounded by the availability of P. It is hypothesised that (i) the photosynthetic P-use efficiency increases at elevated CO2 owing to a direct increase in photosynthesis and (ii) the photosynthetic maximum carboxylation rate (Vcmax) and electron transport rate (Jmax) are down-regulated in response to a combination of elevated CO2 and P-limitation via a coordinated reduction of leaf N and P content per unit leaf area. In this study we examined the hypothesised effects of P limitation and CO2 fertilisation on the photosynthetic and stoichiometric responses of three plant species: Holcus lanatus (C3 grass), Panicum miliaceum (C4 grass) and Solanum dulcamara (C3 herb). Individuals of these species were grown at sub-ambient (150 ppm), modern (450 ppm) and elevated CO2 concentrations (800 ppm) and exposed to an N:P treatment consisting of either severe nitrogen limitation at an N:P ratio of 1:1, or severe P limitation at an N:P ratio of 45:1, with a similar supply rate of N. Our results show significant effects of growth CO2 and P supply on Vcmax and Jmax, as well as the whole-plant biomass at the point of harvest. Interaction effects between growth CO2 and P supply were observed for the light-saturated photosynthesis rate, stomatal conductance, leaf P content, and the N:P ratio of the leaf. No significant change in the leaf N content was observed across treatments. These results suggest that limited availability of P constrains the biochemical potential

  17. Photosynthetic responses of thalli and isolated protoplasts of Bryopsis hypnoides (Bryopsidales, Chlorophyta) during dehydration

    Science.gov (United States)

    Lü, Fang; Wang, Guangce; Jin, Haochen

    2011-03-01

    Bryopsis hypnoides Lamouroux is a unique intertidal siphonous green alga whose extruded protoplasm can aggregate spontaneously in seawater to form numerous new cells that can develop into mature algal thalli. In this study, the photosynthetic responses during dehydration of both the thalli and protoplasts isolated from B. hypnoides were measured using a Dual-PAM (pulse amplitude modulation)-100 fluorometer. The results show that the photosynthetic rates of B. hypnoides thalli were maintained for an initial period, beyond which continued desiccation resulted in reduced rates of PSI and PSII. However, the photosynthetic performances of the isolated protoplasts dehydrated in air (CO2 concentration 600-700 mg/L) showed a slight increase of Y(II) at 20% water loss, but the rates decreased thereafter with declining water content. When protoplasts were dehydrated in CO2 deficient conditions (CO2 concentration 40-80 mg/L), the values of Y(II) declined steadily with increased dehydration without an initial rise. These results indicated that the thalli and isolated protoplasts of this alga can utilize CO2 in ambient air effectively, and the photosynthetic performances of the isolated protoplasts were significantly different from that of the thalli during dehydration. Thus the protoplasts may be an excellent system for the study of stress tolerance.

  18. Proof nets for lingusitic analysis

    NARCIS (Netherlands)

    Moot, R.C.A.

    2002-01-01

    This book investigates the possible linguistic applications of proof nets, redundancy free representations of proofs, which were introduced by Girard for linear logic. We will adapt the notion of proof net to allow the formulation of a proof net calculus which is soundand complete for the

  19. Teaching Tennis for Net Success.

    Science.gov (United States)

    Young, Bryce

    1989-01-01

    A program for teaching tennis to beginners, NET (Net Easy Teaching) is described. The program addresses three common needs shared by tennis students: active involvement in hitting the ball, clearing the net, and positive reinforcement. A sample lesson plan is included. (IAH)

  20. Net4Care Ecosystem Website

    DEFF Research Database (Denmark)

    Christensen, Henrik Bærbak; Hansen, Klaus Marius; Rasmussen, Morten

    2012-01-01

    is a tele-monitoring scenario in which Net4Care clients are deployed in a gateway in private homes. Medical devices then connect to these gateways and transmit their observations to a Net4Care server. In turn the Net4Care server creates valid clinical HL7 documents, stores them in a national XDS repository...

  1. Enhanced Practical Photosynthetic CO2 Mitigation

    Energy Technology Data Exchange (ETDEWEB)

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

    2003-07-22

    This quarterly report documents significant achievements in the Enhanced Practical Photosynthetic CO{sub 2} Mitigation project during the period from 4/2/2003 through 7/01/2003. As indicated in the list of accomplishments below we have completed some long-term model scale bioreactor tests and are prepared to begin pilot scale bioreactor testing. Specific results and accomplishments for the second quarter of 2003 include: (1) Bioreactor support systems and test facilities: (a) Qualitative long-term survivability tests for S.C.1.2(2) on Omnisil have been successfully completed and results demonstrate a growth rate that appears to be acceptable. (b) Quantitative tests of long-term growth productivity for S.C.1.2(2) on Omnisil have been completed and initial results are promising. Initial results show that the mass of organisms doubled (from 54.9 grams to 109.8 grams) in about 5 weeks. Full results will be available as soon as all membranes and filters are completely dried. The growth rate should increase significantly with the initiation of weekly harvesting during the long term tests. (c) The phase 1 construction of the pilot scale bioreactor has been completed, including the solar collector and light distribution system. We are now in the phase of system improvement as we wait for CRF-2 results in order to be able to finalize the design and construction of the pilot scale system. (d) A mass transfer experimental setup was constructed in order to measure the mass transfer rate from the gas to the liquid film flowing over a membrane and to study the hydrodynamics of the liquid film flowing over a membrane in the bioreactor. Results were reported for mass transfer coefficient, film thickness, and fluid velocity over an Omnisil membrane with a ''drilled hole'' header pipe design. (2) Organisms and Growth Surfaces: (a) A selectivity approach was used to obtain a cyanobacterial culture with elevated resistance to acid pH. Microlonies of ''3

  2. Differential responses of net ecosystem exchange of carbon dioxide to light and temperature between spring and neap tides in subtropical mangrove forests.

    Science.gov (United States)

    Li, Qing; Lu, Weizhi; Chen, Hui; Luo, Yiqi; Lin, Guanghui

    2014-01-01

    The eddy flux data with field records of tidal water inundation depths of the year 2010 from two mangroves forests in southern China were analyzed to investigate the tidal effect on mangrove carbon cycle. We compared the net ecosystem exchange (NEE) and its responses to light and temperature, respectively, between spring tide and neap tide inundation periods. For the most time of the year 2010, higher daytime NEE values were found during spring tides than during neap tides at both study sites. Regression analysis of daytime NEE to photosynthetically active radiation (PAR) using the Landsberg model showed increased sensitivity of NEE to PAR with higher maximum photosynthetic rate during spring tides than neap tides. In contrast, the light compensation points acquired from the regression function of the Landsberg model were smaller during spring tides than neap tides in most months. The dependence of nighttime NEE on soil temperature was lower under spring tide than under neap tides. All these results above indicated that ecosystem carbon uptake rates of mangrove forests were strengthened, while ecosystem respirations were inhibited during spring tides in comparison with those during neap tides, which needs to be considered in modeling mangrove ecosystem carbon cycle under future sea level rise scenarios.

  3. Differential Responses of Net Ecosystem Exchange of Carbon Dioxide to Light and Temperature between Spring and Neap Tides in Subtropical Mangrove Forests

    Directory of Open Access Journals (Sweden)

    Qing Li

    2014-01-01

    Full Text Available The eddy flux data with field records of tidal water inundation depths of the year 2010 from two mangroves forests in southern China were analyzed to investigate the tidal effect on mangrove carbon cycle. We compared the net ecosystem exchange (NEE and its responses to light and temperature, respectively, between spring tide and neap tide inundation periods. For the most time of the year 2010, higher daytime NEE values were found during spring tides than during neap tides at both study sites. Regression analysis of daytime NEE to photosynthetically active radiation (PAR using the Landsberg model showed increased sensitivity of NEE to PAR with higher maximum photosynthetic rate during spring tides than neap tides. In contrast, the light compensation points acquired from the regression function of the Landsberg model were smaller during spring tides than neap tides in most months. The dependence of nighttime NEE on soil temperature was lower under spring tide than under neap tides. All these results above indicated that ecosystem carbon uptake rates of mangrove forests were strengthened, while ecosystem respirations were inhibited during spring tides in comparison with those during neap tides, which needs to be considered in modeling mangrove ecosystem carbon cycle under future sea level rise scenarios.

  4. Master Robotic Net

    Directory of Open Access Journals (Sweden)

    Vladimir Lipunov

    2010-01-01

    Full Text Available The main goal of the MASTER-Net project is to produce a unique fast sky survey with all sky observed over a single night down to a limiting magnitude of 19-20. Such a survey will make it possible to address a number of fundamental problems: search for dark energy via the discovery and photometry of supernovae (including SNIa, search for exoplanets, microlensing effects, discovery of minor bodies in the Solar System, and space-junk monitoring. All MASTER telescopes can be guided by alerts, and we plan to observe prompt optical emission from gamma-ray bursts synchronously in several filters and in several polarization planes.

  5. Art/Net/Work

    DEFF Research Database (Denmark)

    Andersen, Christian Ulrik; Lindstrøm, Hanne

    2006-01-01

    The seminar Art|Net|Work deals with two important changes in our culture. On one side, the network has become essential in the latest technological development. The Internet has entered a new phase, Web 2.0, including the occurrence of as ‘Wiki’s’, ‘Peer-2-Peer’ distribution, user controlled...... the praxis of the artist. We see different kinds of interventions and activism (including ‘hacktivism’) using the network as a way of questioning the invisible rules that govern public and semi-public spaces. Who ‘owns’ them? What kind of social relationships do they generate? On what principle...

  6. Helminth.net: expansions to Nematode.net and an introduction to Trematode.net

    Science.gov (United States)

    Martin, John; Rosa, Bruce A.; Ozersky, Philip; Hallsworth-Pepin, Kymberlie; Zhang, Xu; Bhonagiri-Palsikar, Veena; Tyagi, Rahul; Wang, Qi; Choi, Young-Jun; Gao, Xin; McNulty, Samantha N.; Brindley, Paul J.; Mitreva, Makedonka

    2015-01-01

    Helminth.net (http://www.helminth.net) is the new moniker for a collection of databases: Nematode.net and Trematode.net. Within this collection we provide services and resources for parasitic roundworms (nematodes) and flatworms (trematodes), collectively known as helminths. For over a decade we have provided resources for studying nematodes via our veteran site Nematode.net (http://nematode.net). In this article, (i) we provide an update on the expansions of Nematode.net that hosts omics data from 84 species and provides advanced search tools to the broad scientific community so that data can be mined in a useful and user-friendly manner and (ii) we introduce Trematode.net, a site dedicated to the dissemination of data from flukes, flatworm parasites of the class Trematoda, phylum Platyhelminthes. Trematode.net is an independent component of Helminth.net and currently hosts data from 16 species, with information ranging from genomic, functional genomic data, enzymatic pathway utilization to microbiome changes associated with helminth infections. The databases’ interface, with a sophisticated query engine as a backbone, is intended to allow users to search for multi-factorial combinations of species’ omics properties. This report describes updates to Nematode.net since its last description in NAR, 2012, and also introduces and presents its new sibling site, Trematode.net. PMID:25392426

  7. 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

  8. 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

    2002-01-15

    This quarterly report documents significant achievements in the Enhanced Practical Photosynthetic CO{sub 2} Mitigation project during the period from 10/3/2001 through 1/02/2002. Most of the achievements are milestones in our efforts to complete the tasks and subtasks that constitute the project objectives. Our research team has made significant progress towards completion of our Phase I objectives, and our current efforts remain focused on fulfilling these research objectives in accordance with the project timeline. Overall, we believe that we are on schedule to complete Phase I activities by 10/2002, which is the milestone date from the original project timeline. Specific results and accomplishments for the fourth quarter of 2001 include: (1) New procedures and protocols have been developed to increase the chances of successful implementation in the bioreactor of organisms that perform well in the lab. The new procedures include pre-screening of organisms for adhesion characteristics and a focus on identifying the organisms with maximum growth rate potential. (2) Preliminary results show an increase in adhesion to glass and a decrease in overall growth rates when using growth media prepared with tap water rather than distilled water. (3) Several of the organisms collected from Yellowstone National Park using the new procedures are currently being cultured in preparation for bioreactor tests. (4) One important result from a test of growth surface temperature distribution as a function of gas stream and drip-fluid temperatures showed a high dependence of membrane temperature on fluid temperature, with gas stream temperature having minimal effect. This result indicates that bioreactor growth surface temperatures can be controlled using fluid delivery temperature. The possible implications for implementation of the bioreactor concept are encouraging, since it may be possible to use the bioreactor with very high gas stream temperatures by controlling the temperature

  9. Some characteristics of photosynthetic apparatus under conditions of spaceflight.

    Science.gov (United States)

    Volovik, O I; Kordyum, E L; Guikema, J A

    1999-07-01

    During colonization of space by humans, the bioregenerative life-support systems on board the space ships will require the plants with a highly efficient photosynthesis, a process producing food and O2 and removing CO2-Therefore, in recent years the scientists increasingly focus the their attention to study on photosynthetic apparatus of plants grown in space. Although the available data are quite scanty and, at times, controversial, it is Considered that the space grown plants differ from around control plants by growth and development, many structural and functional indices and metabolism. Data exist showing changes in the chlorophyll (Chl) content, structure and number of chloroplasts in the cell, swelling of thylakoids and decrease in the number and size of starch grains in the chloroplasts (for reviews, see Halstead and Dutcher, 1987; Kordyum, 1997). The decrease of shoot fresh weight and reduction of CO2-saturated photosynthetic rate at saturating light intensities in space grown wheat plants in comparison with ground control have been reported by Tripathy et al. (1996). The thylakoids isolated from space grown plants displayed lower rates of electron transport through photosystems I and II (PSI and PSII) and in a whole chain. This study aimed to examine the electron transport rates through PSI and PSII in the isolated thylakoids, to elucidate if there are any differences in accumulation of thylakoid membranes between space grown Brassica rapa plants and ground control plants (based on Chl quantity) and to measure the Chl a/b ratio in isolated thylakoids. These studies were part of the Collaborative US/Ukrainian program during the STS-87 mission (1997).

  10. Photosynthetic responses of subtidal seagrasses to a daily light cycle in Torres Strait: A comparative study

    Science.gov (United States)

    Campbell, Stuart J.; Kerville, Simon P.; Coles, Robert G.; Short, Fred

    2008-09-01

    In this study, we examined the photosynthetic responses of five common seagrass species from a typical mixed meadow in Torres Strait at a depth of 5-7 m using pulse amplitude modulated (PAM) fluorometry. The photosynthetic response of each species was measured every 2 h throughout a single daily light cycle from dawn (6 am) to dusk (6 pm). PAM fluorometry was used to generate rapid light curves from which measures of electron transport rate (ETR max), photosynthetic efficiency ( α), saturating irradiance ( E k) and light-adapted quantum yield (Δ F/ F' m) were derived for each species. The amount of light absorbed by leaves (absorption factor) was also determined for each species. Similar diurnal patterns were recorded among species with 3-4 fold increases in maximal electron rate from dawn to midday and a maintenance of ETR max in the afternoon that would allow an optimal use of low light by all species. Differences in photosynthetic responses to changes in the daily light regime were also evident with Syringodium isoetifolium showing the highest photosynthetic rates and saturating irradiances suggesting a competitive advantage over other species under conditions of high light. In contrast Halophila ovalis, Halophila decipiens and Halophila spinulosa were characterised by comparatively low photosynthetic rates and minimum light requirements (i.e. low E k) typical of shade adaptation. The structural makeup of each species may explain the observed differences with large, structurally complex species such as Syringodium isoetifolium and Cymodocea serrulata showing high photosynthetic effciciencies ( α) and therefore high-light-adapted traits (e.g. high ETR max and E k) compared with the smaller Halophila species positioned lower in the canopy. For the smaller Halophila species these shade-adapted traits are features that optimise their survival during low-light conditions. Knowledge of these characteristics and responses improves our understanding of the underlying

  11. Efficiency of light harvesting in a photosynthetic bacterium adapted to different levels of light.

    Science.gov (United States)

    Timpmann, Kõu; Chenchiliyan, Manoop; Jalviste, Erko; Timney, John A; Hunter, C Neil; Freiberg, Arvi

    2014-10-01

    In this study, we use the photosynthetic purple bacterium Rhodobacter sphaeroides to find out how the acclimation of photosynthetic apparatus to growth conditions influences the rates of energy migration toward the reaction center traps and the efficiency of charge separation at the reaction centers. To answer these questions we measured the spectral and picosecond kinetic fluorescence responses as a function of excitation intensity in membranes prepared from cells grown under different illumination conditions. A kinetic model analysis yielded the microscopic rate constants that characterize the energy transfer and trapping inside the photosynthetic unit as well as the dependence of exciton trapping efficiency on the ratio of the peripheral LH2 and core LH1 antenna complexes, and on the wavelength of the excitation light. A high quantum efficiency of trapping over 80% was observed in most cases, which decreased toward shorter excitation wavelengths within the near infrared absorption band. At a fixed excitation wavelength the efficiency declines with the LH2/LH1 ratio. From the perspective of the ecological habitat of the bacteria the higher population of peripheral antenna facilitates growth under dim light even though the energy trapping is slower in low light adapted membranes. The similar values for the trapping efficiencies in all samples imply a robust photosynthetic apparatus that functions effectively at a variety of light intensities. Copyright © 2014 Elsevier B.V. All rights reserved.

  12. A comparative study of the photosynthetic capacity in two green tide macroalgae using chlorophyll fluorescence.

    Science.gov (United States)

    Wang, Ying; Qu, Tongfei; Zhao, Xinyu; Tang, Xianghai; Xiao, Hui; Tang, Xuexi

    2016-01-01

    Green tides have occurred in the Yellow Sea, China, every year from 2007 to 2015. The free-floating Ulva prolifera (Müller) J. Agardh was the causative macroalgal species. The co-occurring, attached U. intestinalis was also observed. Photosynthetic capacities were determined using chlorophyll fluorescence in situ and after 7 days lab acclimation, and a significant differences were noted. Pigment composition showed no obvious differences, but concentrations varied significantly, especially chlorophyll b in U. prolifera two times increase was observed after acclimation. The optimal photochemical efficiency of PS II (Fv/Fm) was significantly higher in U. prolifera. Photosynthetic rate (α), maximum relative electron transport rate (rETRmax), and minimum saturating irradiance (Ek), obtained from rapid light response curves (RLCs), showed almost the same photosynthetic physiological status as Fv/Fm. Quenching coefficients and low temperature (77 K) chlorophyll fluorescence emission spectra of thylakoid membranes analysis showed U. prolifera has a better recovery activity and plasticity of PSII than U. intestinalis. Furthermore, energy dissipation via non-photochemical quenching (NPQ) and state transitions showed efficacious photoprotection solution especially in U. prolifera suffered from the severe stresses. Results in the present study suggested that U. prolifera's higher photosynthetic capacity would contribute to its free-floating proliferation, and efficacious photoprotection in addition to favorable oceanographic conditions and high nutrient levels support its growth and aggregation.

  13. Enhanced photosynthetic activity in Spinacia oleracea by spectral modification with a photoluminescent light converting material.

    Science.gov (United States)

    Xia, Qi; Batentschuk, Miroslaw; Osvet, Andres; Richter, Peter; Häder, Donat P; Schneider, Juergen; Brabec, Christoph J; Wondraczek, Lothar; Winnacker, Albrecht

    2013-11-04

    The spectral conversion of incident sunlight by appropriate photoluminescent materials has been a widely studied issue for improving the efficiency of photovoltaic solar energy harvesting. By using phosphors with suitable excitation/emission properties, also the light conditions for plants can be adjusted to match the absorption spectra of chlorophyll dyes, in this way increasing the photosynthetic activity of the plant. Here, we report on the application of this principle to a high plant, Spinacia oleracea. We employ a calcium strontium sulfide phosphor doped with divalent europium (Ca0.4Sr0.6S:Eu(2+), CSSE) on a backlight conversion foil in photosynthesis experiments. We show that this phosphor can be used to effectively convert green to red light, centering at a wavelength of ~650 nm which overlaps the absorption peaks of chlorophyll a/b pigments. A measurement system was developed to monitor the photosynthetic activity, expressed as the CO2 assimilation rate of spinach leaves under various controlled light conditions. Results show that under identical external light supply which is rich in green photons, the CO2 assimilation rate can be enhanced by more than 25% when the actinic light is modified by the CSSE conversion foil as compared to a purely reflecting reference foil. These results show that the phosphor could be potentially applied to modify the solar spectrum by converting the green photons into photosynthetically active red photons for improved photosynthetic activity.

  14. [Photosynthetic characteristics of Bothriochloa ischaemum under drought stress and elevated CO2 concentration].

    Science.gov (United States)

    Zhang, Chang-Sheng; Liu, Guo-Bin; Xue, Sha; Ji, Zhi-Qing; Zhang, Chao

    2012-11-01

    A pot experiment was conducted to study the variations of the photo-physiological characteristics of native bluestem (Bothriochloa ischaemum) in loess hilly-gully region under different soil moisture condition (80% and 40% field capacity) and different atmospheric CO2 concentration (375 micromol x m(-2) x s(-1) and 750 micromol x m(-2) x s(-1). The results showed that drought stress decreased the maximum photosynthetic rate (Pn max), apparent quantum efficiency (AQE), stomatal conductance (ga), transpiration rate (Tx), maximum photochemical efficiency (F/Fm), potential photochemical efficiency (Fv/Fo), and photosynthetic pigments contents, and increased the malondialdehyde (MDA) and proline (Pro) contents. Under sufficient moisture condition, elevated CO2 concentration didn't change the P n max and the, MDA and Pro contents significantly; under drought stress, elevated CO2 improved the maximal fluorescence (Fm), Fv/Fm, Fv/Fo, photosynthetic pigments contents, and AQE, and the Pn max under elevated CO2 was increased significantly by 23.3%, and the MDA and Pro contents were decreased significantly, as compared with those under ambient CO2 concentration. All the results suggested that elevated CO2 concentration had definite compensation effect on the photosynthetic reduction of B. ischaemum induced by drought stress, and alleviated the damage of drought stress on B. ischaemum.

  15. Utilization of insecticide treated nets in Arbaminch Town and the ...

    African Journals Online (AJOL)

    Bernt Lindtjorn

    using structured, pretested, interviewer-administered questionnaire. Data entry and analysis was performed using SPSS. 11.0 for windows. Univariate, bivariate and multivariate analyses were carried out. Results: The coverage for any net and ITN was 75.1% and 58.8% respectively; the utilization rate for any net and ITN.

  16. Managing the Microbial Ecology of a Cyanobacteria-Based Photosynthetic Factory Direct!, Final Report for EE0006100

    Energy Technology Data Exchange (ETDEWEB)

    Rittmann, Bruce [Arizona State Univ., Tempe, AZ (United States); Krajmalnik‐Brown, Rosa [Arizona State Univ., Tempe, AZ (United States); Zevin, Alexander [Arizona State Univ., Tempe, AZ (United States); Nguyen, Binh [Arizona State Univ., Tempe, AZ (United States); Patel, Megha [Arizona State Univ., Tempe, AZ (United States)

    2015-02-28

    The grandest challenge facing human society today is providing large amounts of energy and industrial chemicals that are renewable and carbon-neutral. An outstanding opportunity lies in employing photosynthetic microorganisms, which have the potential to generate energy and chemical feedstock from sunlight and CO2 at rates 10 to 100 times greater than plants. Major challenges for solar-powered production using photosynthetic microorganisms are associated with the harvesting and downstream processing of biomass to yield the usable energy or material feedstock e.g. The technical challenges and costs of downstream processing could be avoided if, powered by solar energy, the photosynthetic microorganisms were to convert CO2 directly to the desired product, which they release for direct harvesting. This approach creates a true photosynthetic factory, our goal for Photosynthetic Factory Direct! Our team is able to genetically modify the cyanobacterium Synechocystis sp. PCC 6803 so that it produces and excretes a range of renewable energy and chemical products directly from CO2 and sunlight. Essential to realizing the potential of the photosynthetic factory is an engineered Advanced Photobioreactor (APBR) for reliable synthesis and harvest of the products.

  17. Autumn photosynthetic decline and growth cessation in seedlings of white spruce are decoupled under warming and photoperiod manipulations.

    Science.gov (United States)

    Stinziano, Joseph R; Way, Danielle A

    2017-08-01

    Climate warming is expected to increase the seasonal duration of photosynthetic carbon fixation and tree growth in high-latitude forests. However, photoperiod, a crucial cue for seasonality, will remain constant, which may constrain tree responses to warming. We investigated the effects of temperature and photoperiod on weekly changes in photosynthetic capacity, leaf biochemistry and growth in seedlings of a boreal evergreen conifer, white spruce [Picea glauca (Moench) Voss]. Warming delayed autumn declines in photosynthetic capacity, extending the period when seedlings had high carbon uptake. While photoperiod was correlated with photosynthetic capacity, short photoperiods did not constrain the maintenance of high photosynthetic capacity under warming. Rubisco concentration dynamics were affected by temperature but not photoperiod, while leaf pigment concentrations were unaffected by treatments. Respiration rates at 25 °C were stimulated by photoperiod, although respiration at the growth temperatures was increased in warming treatments. Seedling growth was stimulated by increased photoperiod and suppressed by warming. We demonstrate that temperature is a stronger control on the seasonal timing of photosynthetic down-regulation than is photoperiod. Thus, while warming can stimulate carbon uptake in boreal conifers, the extra carbon may be directed towards respiration rather than biomass, potentially limiting carbon sequestration under climate change. © 2017 John Wiley & Sons Ltd.

  18. [Comparative studies on photosynthetic characteristics of Notopterygium incisum and N. forbesii].

    Science.gov (United States)

    Chen, Tiezhu; Jiang, Shunyuan; Sun, Hui; Zhou, Yi; Ma, Xiaojun; Li, Xiwen; Tang, Xuefang

    2009-03-01

    To compare the photosynthetic characteristics of Notopterygium incisum and N. forbesii in order to provide basic data for introduction and cultivation of the two wild medicinal species. The light-response, CO2-response and Chlorophy II fluorescence parameters of leaves at the booting stages between N. incisum and N. forbesii, were analyzed in situ by Li-6400 Portable Photosynthesis system under natural conditions. 1) The light saturation point (LSP) was 1539 micromol x m(-2) x s(-1) for N. incisum and 1464 micromol x m(-2) x s(-1) for N. forbesii, the maximum net photosynthetic rate (Pmax) was 22.95 micromol x m(-2) x s(-1) for N. incisum and 19.65 micromol x m(-2) x s(-1) for N. forbesii, the apparent quantum yield (AQY) was 0.0509 for N. incisum and 0.0470 for N. forbesii, LSP, AQY and Pmax of N. incisum were significantly higher than those of N. forbesii; the light compensation point (LCP) was 17.92 micromol x m(-2) x s(-1) for N. incisum and 26.69 micromol x m(-2) x s(-1) for N. forbesii, LCP of N. incisum was significantly lower than that of N. forbesii. 2) The carbondioxide compensation point (CCP) were 33.41 micromol x mol(-1) for N. incisum and 37.82 micromol x mol(-1) for N. forbesii, the carbon dioxide saturation point (CSP) were 988 micromol x mol(-1) for N. incisum and 1150 micromol x mol(-1) for N. forbesii, CCP and CSP of N. incisum were significantly lower than N. forbesii; the carboxylation efficiency (CE) were 0.0591 for N. incisum and 0.0459 for N. forbesii; the maximum rate of RuBP regeneration (Jmax) were 28.18 micromol x m(-2) x s(-1) for N. incisum and 25.32 micromol x m(-2) x s(-1) for N. forbesii; the light respiration rate (Rd) were 1.971 micromol x m(-2) x s(-1) for N. incisum and 1.736 micromol x m(-2) x s(-1) for N. forbesii, CE, Jmax and Rd of N. incisum were higher than those of N. forbesii. 3) The primary light energy conversion of PS II (Fv/Fm) was 0.8213 for N. incisum and 0.8257 for N. forbesii, wihich didn't showed significant

  19. Net ecosystem carbon exchange in three contrasting Mediterranean ecosystems – the effect of drought

    Directory of Open Access Journals (Sweden)

    T. S. David

    2007-09-01

    Full Text Available Droughts reduce gross primary production (GPP and ecosystem respiration (Reco, contributing to most of the inter-annual variability in terrestrial carbon sequestration. In seasonally dry climates (Mediterranean, droughts result from reductions in annual rainfall and changes in rain seasonality. We compared carbon fluxes measured by the eddy covariance technique in three contrasting ecosystems in southern Portugal: an evergreen oak woodland (savannah-like with ca.~21% tree crown cover, a grassland dominated by herbaceous annuals and a coppiced short-rotation eucalyptus plantation. During the experimental period (2003–2006 the eucalyptus plantation was always the strongest sink for carbon: net ecosystem exchange rate (NEE between −861 and −399 g C m−2 year−1. The oak woodland and the grassland were much weaker sinks for carbon: NEE varied in the oak woodland between −140 and −28 g C m−2 year−1 and in the grassland between −190 and +49 g C m−2 year−1. The eucalyptus stand had higher GPP and a lower proportion of GPP spent in respiration than the other systems. The higher GPP resulted from high leaf area duration (LAD, as a surrogate for the photosynthetic photon flux density absorbed by the canopy. The eucalyptus had also higher rain use efficiency (GPP per unit of rain volume and light use efficiency (the daily GPP per unit incident photosynthetic photon flux density than the other two ecosystems. The effects of a severe drought could be evaluated during the hydrological-year (i.e., from October to September of 2004–2005. Between October 2004 and June 2005 the precipitation was only 40% of the long-term average. In 2004–2005 all ecosystems had GPP lower than in wetter years and carbon sequestration was strongly restricted (less negative NEE. The grassland was a net source of carbon dioxide (+49 g C m−2 year−1. In the oak woodland a large proportion of GPP resulted from carbon assimilated by its annual vegetation

  20. The equivalency between logic Petri workflow nets and workflow nets.

    Science.gov (United States)

    Wang, Jing; Yu, ShuXia; Du, YuYue

    2015-01-01

    Logic Petri nets (LPNs) can describe and analyze batch processing functions and passing value indeterminacy in cooperative systems. Logic Petri workflow nets (LPWNs) are proposed based on LPNs in this paper. Process mining is regarded as an important bridge between modeling and analysis of data mining and business process. Workflow nets (WF-nets) are the extension to Petri nets (PNs), and have successfully been used to process mining. Some shortcomings cannot be avoided in process mining, such as duplicate tasks, invisible tasks, and the noise of logs. The online shop in electronic commerce in this paper is modeled to prove the equivalence between LPWNs and WF-nets, and advantages of LPWNs are presented.

  1. C4 photosynthetic machinery: insights from maize chloroplast proteomics

    Directory of Open Access Journals (Sweden)

    Qi eZhao

    2013-04-01

    Full Text Available C4 plants exhibit much higher CO2 assimilation rates than C3 plants. The specialized differentiation of mesophyll cell (M and bundle sheath cell (BS type chloroplasts is unique to C4 plants and improves photosynthesis efficiency. Maize (Zea mays is an important crop and model with C4 photosynthetic machinery. Current high-throughput quantitative proteomics approaches (e.g., 2DE, iTRAQ, and shotgun proteomics have been employed to investigate maize chloroplast structure and function. These proteomic studies have provided valuable information on C4 chloroplast protein components, photosynthesis, and other metabolic mechanisms underlying chloroplast biogenesis, stromal and membrane differentiation, as well as response to salinity, high/low temperature, and light stress. This review presents an overview of proteomics advances in maize chloroplast biology.

  2. Quantum Coherent Dynamics at Ambient Temperature in Photosynthetic Molecules

    CERN Document Server

    Walters, Zachary B

    2011-01-01

    Photosynthetic antenna complexes are responsible for absorbing energy from sunlight and transmitting it to remote locations where it can be stored. Recent experiments have found that this process involves long-lived quantum coherence between pigment molecules, called chromophores, which make up these complexes. Expected to decay within 100 fs at room temperature, these coherences were instead found to persist for picosecond time scales, despite having no apparent isolation from the thermal environment of the cell. This paper derives a quantum master equation which describes the coherent evolution of a system in strong contact with a thermal environment. Conditions necessary for long coherence lifetimes are identified, and the role of coherence in efficient energy transport is illuminated. Static spectra and exciton transfer rates for the PE545 complex of the cryptophyte algae CS24 are calculated and shown to have good agreement with experiment.

  3. Combined Effects of Experimental Acidification and Eutrophication on Reef Sponge Bioerosion Rates

    Directory of Open Access Journals (Sweden)

    Alice E. Webb

    2017-09-01

    Full Text Available Health of tropical coral reefs depends largely on the balance between constructive (calcification and cementation and destructive forces (mechanical-chemical degradation. Gradual increase in dissolved CO2 and the resulting decrease in carbonate ion concentration (“ocean acidification” in ocean surface water may tip the balance toward net mass loss for many reefs. Enhanced nutrients and organic loading in surface waters (“eutrophication”, may increase the susceptibility of coral reef and near shore environments to ocean acidification. The impacts of these processes on coral calcification have been repeatedly reported, however the synergetic effects on bioerosion rates by sponges are poorly studied. Erosion by excavating sponges is achieved by a combination of chemical dissolution and mechanical chip removal. In this study, Cliona caribbaea, a photosymbiont-bearing excavating sponge widely distributed in Caribbean reef habitats, was exposed to a range of CO2 concentrations, as well as different eutrophication levels. Total bioerosion rates, estimated from changes in buoyant weights over 1 week, increased significantly with pCO2 but not with eutrophication. Observed chemical bioerosion rates were positively affected by both pCO2 and eutrophication but no interaction was revealed. Net photosynthetic activity was enhanced with rising pCO2 but not with increasing eutrophication levels. These results indicate that an increase in organic matter and nutrient renders sponge bioerosion less dependent on autotrophic products. At low and ambient pCO2, day-time chemical rates were ~50% higher than those observed at night-time. A switch was observed in bioerosion under higher pCO2 levels, with night-time chemical bioerosion rates becoming comparable or even higher than day-time rates. We suggest that the difference in rates between day and night at low and ambient pCO2 indicates that the benefit of acquired energy from photosynthetic activity surpasses

  4. Coloured Petri Nets

    DEFF Research Database (Denmark)

    Jensen, Kurt; Kristensen, Lars Michael

    studies that illustrate the practical use of CPN modelling and validation for design, specification, simulation, verification and implementation in various application domains. Their presentation primarily aims at readers interested in the practical use of CPN. Thus all concepts and constructs are first......Coloured Petri Nets (CPN) is a graphical language for modelling and validating concurrent and distributed systems, and other systems in which concurrency plays a major role. The development of such systems is particularly challenging because of inherent intricacies like possible nondeterminism...... and the immense number of possible execution sequences. In this textbook, Jensen and Kristensen introduce the constructs of the CPN modelling language and present the related analysis methods in detail. They also provide a comprehensive road map for the practical use of CPN by showcasing selected industrial case...

  5. Nitric oxide in marine photosynthetic organisms.

    Science.gov (United States)

    Kumar, Amit; Castellano, Immacolata; Patti, Francesco Paolo; Palumbo, Anna; Buia, Maria Cristina

    2015-05-01

    Nitric oxide is a versatile and powerful signaling molecule in plants. However, most of our understanding stems from studies on terrestrial plants and very little is known about marine autotrophs. This review summarizes current knowledge about the source of nitric oxide synthesis in marine photosynthetic organisms and its role in various physiological processes under normal and stress conditions. The interactions of nitric oxide with other stress signals and cross talk among secondary messengers are also highlighted. Copyright © 2015 Elsevier Inc. All rights reserved.

  6. 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

  7. Photoprotective, excited-state quenching mechanisms in diverse photosynthetic organisms.

    Science.gov (United States)

    Magdaong, Nikki Cecil M; Blankenship, Robert E

    2018-01-03

    Light-harvesting complexes (LHCs) serve a dual role in photosynthesis, depending on the prevailing light conditions. In low light, they ensure photosynthetic efficiency by maximizing the light absorption cross-section and subsequent energy storage. Under excess light conditions, LHCs perform photoprotective quenching functions to prevent harmful chemical species such as triplet chlorophyll and singlet oxygen from forming and damaging the photosynthetic apparatus. In this minireview, various photoprotective quenching mechanisms that have been identified in different photosynthetic organisms are surveyed and summarized, and implications for improving photosynthetic productivity are briefly discussed. Published under license by The American Society for Biochemistry and Molecular Biology, Inc.

  8. Photosynthetic sulfide oxidation by Chloroflexus aurantiacus, a filamentous, photosynthetic, gliding bacterium.

    Science.gov (United States)

    Madigan, M T; Brock, T D

    1975-01-01

    Chloroflexus, a newly described genus of filamentous, photosynthetic, gliding bacteria, oxidizes sulfide anaerobically under photoautotrophic or photoheterotrophic growh conditions and deposits elemental sulfur outside the cell. The formation of sulfur granules outside the cell supports the idea that this organism is related to the green sulfur bacteria (Chlorobiaceae). Images PMID:1092670

  9. [Effects of water and nitrogen management modes on the leaf photosynthetic characters and yield formation of cotton with under-mulch drip irrigation].

    Science.gov (United States)

    Luo, Hong-Hai; Zhang, Hong-Zhi; Tao, Xian-Ping; Zhang, Ya-Li; Zhang, Wang-feng

    2013-02-01

    Taking different genotype cotton varieties as test materials, a soil column culture experiment was conducted to study the effects of water and nitrogen management modes on the photosynthetic characters and yield formation of cotton with under-mulch drip irrigation in Xinjiang, Northwest China. Under the management mode W4N2, i.e., pre-sowing irrigation + limited drip irrigation before full-flowering + abundant drip irrigation after full-flowering in combining with basal 20% N + topdressing 80% N, the chlorophyll content, net photosynthetic rate (Pn), stomatal conductance (gs) , actual photochemical efficiency of photosystem II (Psi PSII), and photochemical quenching coefficient (qp) at full-flowering stage all decreased significantly, the non-photochemical quenching (NPQ) increased, and the aboveground dry matter accumulation was inhibited, as compared with those under common drip irrigation. From full-flowering stage to boll-opening stage, the chlorophyll content, gs, Pn, Psi PSII, and qp increased with increasing water and nitrogen supply, and the aboveground dry matter accumulation was enhanced by compensation, which benefited the translocation and distribution of photosynthates to seed cotton. Under the fertilization mode of basal 20% N + topdressing 80% N, the seed cotton yield of Xinluzaol3 was the highest in treatment pre-sowing irrigation + common drip irrigation (W3), but that of Xinluzao43 was the highest in treatment pre-sowing irrigation + limited drip irrigation before full-flowering + abundant drip irrigation after full-flowering (W4). It was concluded that under the condition of pre-sowing irrigation, to appropriately decrease the water and nitrogen supply before full-flowering stage and increase the water and nitrogen supply at middle and late growth stages could extend the active photosynthesis duration and promote the photosynthates allocation to reproductive organ, which would fully exploit the yield-increasing potential of cotton with under

  10. Growth and Accumulation of Secondary Metabolites in Perilla as Affected by Photosynthetic Photon Flux Density and Electrical Conductivity of the Nutrient Solution

    Directory of Open Access Journals (Sweden)

    Na Lu

    2017-05-01

    Full Text Available The global demand for medicinal plants is increasing. The quality of plants grown outdoors, however, is difficult to control. Myriad environmental factors influence plant growth and directly impact biosynthetic pathways, thus affecting the secondary metabolism of bioactive compounds. Plant factories use artificial lighting to increase the quality of medicinal plants and stabilize production. Photosynthetic photon flux density (PPFD and electrical conductivity (EC of nutrient solutions are two important factors that substantially influence perilla (Perilla frutescens, Labiatae plant growth and quality. To identify suitable levels of PPFD and EC for perilla plants grown in a plant factory, the growth, photosynthesis, and accumulation of secondary metabolites in red and green perilla plants were measured at PPFD values of 100, 200, and 300 μmol m-2 s-1 in nutrient solutions with EC values of 1.0, 2.0, and 3.0 dS m-1. The results showed significant interactive effects between PPFD and EC for both the fresh and dry weights of green perilla, but not for red perilla. The fresh and dry weights of shoots and leafy areas were affected more by EC than by PPFD in green perilla, whereas they were affected more by PPFD than by EC in red perilla. Leaf net photosynthetic rates were increased as PPFD increased in both perilla varieties, regardless of EC. The perillaldehyde concentration (mg g-1 in red perilla was unaffected by the treatments, but accumulation in plants (mg per plant was significantly enhanced as the weight of dry leaves increased. Perillaldehyde concentrations in green perilla showed significant differences between combinations of the highest PPFD with the highest EC and the lowest PPFD with the lowest EC. Rosmarinic acid concentration (mg g-1 was increased in a combination of low EC and high PPFD conditions. Optimal cultivation conditions of red and green perilla in plant factory will be discussed in terms of plant growth and contents of

  11. 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.

  12. Exploring the Potential use of Photo-Selective Nets for Fruit Growth Regulation in Apple Explorando el uso Potencial de Mallas Foto-Selectivas para la Regulación del Crecimiento de Fruto en Manzano

    Directory of Open Access Journals (Sweden)

    Richard M Bastías

    2012-06-01

    Full Text Available The effect of shading (i.e. reduction of sunlight availability on fruit growth physiology has been widely studied in apple (Malus domestica Borkh., but little knowledge exist about fruit growth responses to changes in the light spectrum. The aim of the present research was to study the effect of use of colored nets with differential sunlight transmission in the blue (B, 400-500 nm, red (R, 600-700 nm and far-red (FR, 700-800 nm spectra on apple fruit growth and physiological associated responses. Three year old 'Fuji' apple trees were covered with 40% photo-selective blue and red shade nets, 40% neutral grey shade net, and 20% neutral white net as control. Red and blue net reduced in the same proportion (27% the photosynthetically active radiation with respect to control. However, blue net increased by 30% and reduced by 10% the B:R and R:FR the light relations, respectively. Maximal fruit growth rate under blue and grey nets was 15-20% greater than control. Fruit weight under blue net was 17% greater than control, but no significant differences in fruit weight were found among red net and control. Leaf photosynthesis and total leaf area under blue net were 28% and 30% higher than control, respectively; with ensuing positive effect on tree net C assimilation rate and total dry matter production. Results suggest that shifting the B, R, and FR light composition with photo-selective nets could be a useful tool to manipulate the photosynthetic and morphogenetic process regulating the carbohydrate availability for apple fruit growth.El efecto del sombreado (i.e. reducción de la cantidad de luz solar sobre la fisiología de crecimiento de fruto ha sido ampliamente estudiado en manzano (Malus domestica Borkh., pero existe poco conocimiento sobre respuestas de crecimiento del fruto a cambios en el espectro de la luz. El objetivo de la presente investigación fue estudiar el efecto del uso de mallas de color con transmisión diferencial de la luz en el

  13. 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.

  14. Variability in photosynthetic production of dissolved and particulate organic carbon in the North Pacific Subtropical Gyre

    Directory of Open Access Journals (Sweden)

    Donn A. Viviani

    2015-10-01

    Full Text Available The partitioning of photosynthetically-derived organic carbon between particulate and dissolved phases has important implications for marine carbon cycling. In this study we utilized 14C-bicarbonate assimilation to quantify rates of photosynthetic production of both particulate and dissolved organic carbon (DOC at Station ALOHA (22˚45’N, 158˚W in the North Pacific Subtropical Gyre (NPSG. At near-monthly time scales over ~5 years, we examined retention of 14C-labeled organic matter by both glass fiber filters and 0.2 µm pore size polycarbonate membrane filters that are commonly used for measurements of 14C-based plankton productivity. Use of polycarbonate filters resulted in significantly lower (averaging 60% estimates of 14C-production compared to glass fiber filters. Coincident measurements of chlorophyll a concentrations from both 0.2 µm polycarbonate and glass fiber filters were not significantly different, suggesting the differences in 14C-productivity between these filter-types did not derive from differences in retention of photosynthetic biomass by these filters. Moreover, consistent with previous studies, results from experiments aimed at quantifying retention of organic matter by these filters suggested the difference between these two types of filters resulted from retention of DOC by glass fiber filters. We also quantified rates of 14C-DOC production to evaluate the partitioning of photosynthetic production between dissolved and particulate phases over daily to monthly time scales in this ecosystem. Unlike the strong depth-dependence observed in measurements of particulate organic carbon production, measured rates of 14C-DOC demonstrated no clear depth-dependence. On average, depth-integrated (0-75 m rates of 14C-DOC production rates were equivalent to 18 ± 10% of the total (particulate and dissolved productivity. Our findings indicate that in this oligotrophic ecosystem, rates of dissolved and particulate production can be

  15. Photosynthetic performance of rock-colonising lichens in the Mountain Zebra National Park, South Africa

    Directory of Open Access Journals (Sweden)

    Dirk Wessels

    1993-09-01

    Full Text Available The photosynthetic behaviour of endolithic andepilithic lichens characteristic of sedimentary and volcanic rock was investigated in situ in the Mountain Zebra National Park, South Africa. The park forms part of an inland semi-desert known as the Karoo, in the Cape Province. Temperatures within Balfour sandstone were monitored, the results showing that during the early morning, temperatures within the sandstone were nearly 5@C lower than ambient air temperatures. This may enhance the frequency of water condensing on the sandstone, which may be particularly important for the endoliths Leciclea aff. sarcogynoides and Sarcogyne cf. austroafricana. Maximum photosynthetic rates of the investigated species were found at temperatures between 20@C and 30@C, far higher than the recorded optimum temperatures for lichens from temperate and desert regions. Parmelia chlorea was the most productive species. Compared to the other epiliths, Peltula capensis was found to be a moderately productive species. The photosynthetic gain of Leciclea aff. sarcogynoides and Sarcogyne cf. austro-africana was low, but the photosynthetic gain of these two species still exceeded that of Acarospora sp.

  16. 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.

  17. Thermal responses of Symbiodinium photosynthetic carbon assimilation

    Science.gov (United States)

    Oakley, Clinton A.; Schmidt, Gregory W.; Hopkinson, Brian M.

    2014-06-01

    The symbiosis between hermatypic corals and their dinoflagellate endosymbionts, genus Symbiodinium, is based on carbon exchange. This symbiosis is disrupted by thermally induced coral bleaching, a stress response in which the coral host expels its algal symbionts as they become physiologically impaired. The disruption of the dissolved inorganic carbon (DIC) supply or the thermal inactivation of Rubisco have been proposed as sites of initial thermal damage that leads to the bleaching response. Symbiodinium possesses a highly unusual Form II ribulose bisphosphate carboxylase/oxygenase (Rubisco), which exhibits a lower CO2:O2 specificity and may be more thermally unstable than the Form I Rubiscos of other algae and land plants. Components of the CO2 concentrating mechanism (CCM), which supplies inorganic carbon for photosynthesis, may also be temperature sensitive. Here, we examine the ability of four cultured Symbiodinium strains to acquire and fix DIC across a temperature gradient. Surprisingly, the half-saturation constant of photosynthesis with respect to DIC concentration ( K P), an index of CCM function, declined with increasing temperature in three of the four strains, indicating a greater potential for photosynthetic carbon acquisition at elevated temperatures. In the fourth strain, there was no effect of temperature on K P. Finding no evidence for thermal inhibition of the CCM, we conclude that CCM components are not likely to be the primary sites of thermal damage. Reduced photosynthetic quantum yields, a hallmark of thermal bleaching, were observed at low DIC concentrations, leaving open the possibility that reduced inorganic carbon availability is involved in bleaching.

  18. Non-photosynthetic pigments as potential biosignatures

    Science.gov (United States)

    Schwieterman, E. W.; Cockell, C. S.; Meadows, V. S.

    2014-03-01

    Photosynthetic organisms on Earth produce potentially detectable surface reflectance biosignatures due in part to the spectral location and strength of pigment absorption. However, life on Earth uses pigments for a multitude of purposes other than photosynthesis, including coping with extreme environments. Macroscopic environments exist on Earth where the surface reflectance is significantly altered by a nonphotosynthetic pigment, such as the case of hypersaline lakes and ponds (Oren et al. 1992). Here we explore the nature and potential detectability of non-photosynthetic pigments in disk-averaged planetary observations using a combination of laboratory measurements and archival reflectance spectra, along with simulated broadband photometry and spectra. The in vivo visible reflectance spectra of a cross section of pigmented microorganisms are presented to illustrate the spectral diversity of biologically produced pigments. Synthetic broadband colors are generated to show a significant spread in color space. A 1D radiative transfer model (Meadows & Crisp 1996; Crisp 1997) is used to approximate the spectra of scenarios where pigmented organisms are widespread on planets with Earth-like atmospheres. Broadband colors are revisited to show that colors due to surface reflectivity are not robust to the addition of scattering and absorption effects from the atmosphere. We consider a èbest case' plausible scenario for the detection of nonphotosynthetic pigments by using the Virtual Planetary Laboratory's 3D spectral Earth model (Robinson et al. 2011) to explore the detectability of the surface biosignature produced by pigmented halophiles that are widespread on an Earth-analog planet.

  19. Identification of large variation in the photosynthetic induction response among 37 soybean [Glycine max (L.) Merr.] genotypes that is not correlated with steady-state photosynthetic capacity.

    Science.gov (United States)

    Soleh, M A; Tanaka, Y; Kim, S Y; Huber, S C; Sakoda, K; Shiraiwa, T

    2017-03-01

    Irradiance continuously fluctuates during the day in the field. The speed of the induction response of photosynthesis in high light affects the cumulative carbon gain of the plant and could impact growth and yield. The photosynthetic induction response and its relationship with the photosynthetic capacity under steady-state conditions (P max) were evaluated in 37 diverse soybean [Glycine max (L.) Merr.] genotypes. The induction response of leaf photosynthesis showed large variation among the soybean genotypes. After 5 min illumination with strong light, genotype NAM23 had the highest leaf photosynthetic rate of 33.8 µmol CO2 m-2 s-1, while genotype NAM12 showed the lowest rate at 4.7 µmol CO2 m-2 s-1. Cumulative CO2 fixation (CCF) during the first 5 min of high light exposure ranged from 5.5 mmol CO2 m-2 for NAM23 to 0.81 mmol CO2 m-2 for NAM12. The difference in the induction response among genotypes was consistent throughout the growth season. However, there was no significant correlation between CCF and P max among genotypes suggesting that different mechanisms regulate P max and the induction response. The observed variation in the induction response was mainly attributed to ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activation, but soybean lines differing in the induction response did not differ in the leaf content of Rubisco activase α- and β-proteins. Future studies will be focused on identifying molecular determinants of the photosynthetic induction response and determining whether this trait could be an important breeding target to achieve improved growth of soybeans in the field.

  20. Mathematical Modeling of Acclimation Processes of the Photosynthetic Chain

    Directory of Open Access Journals (Sweden)

    S Heidari

    2016-10-01

    and systematically analyze the dependence of system key characteristic such as rate constant and pool size. For medium and high light intensity, experimental evidence has been predicted with high accuracy by simulation. In low light intensity (100μE m-2s-1 in a few seconds the light phase, a temporary increase in the rate of NPQ was observed after about 60 seconds it reaches to a steady state level. Model simulation of the induction of NPQ relaxation is more accurate than previous predictions, due to the introduction of more stringent quenching agents (xanthophylls cycle and also the light-harvesting complex protonations. The results showed that the pH drop in the transition from darkness to light and high light intensity increases. For low light intensity quenching process occurs with a more gentle slope to the prediction model based on previous experiments is more realistic. In low light conditions, the proton concentration can easily be balanced by ATP synthase activity. This leads to a reduction in current proton-proton feedback gathered during few seconds is balanced. Thus, at high light intensities ATP levels remained stable in the new model is more consistent with reality. Conclusions A simple mathematical model which has been developed in this paper provides a more detailed description of this process and be able to predict the various components and parameters associated with it. Comparison of simulation results with experimental data revealed that protonated light harvesting complex and Zeaxanthin simultaneously induce NPQ quenching processes. The results can be seen as theoretical basis for developing more accurate models to study molecular mechanisms of acclimation processes of the photosynthetic chain.

  1. Widespread positive selection in the photosynthetic Rubisco enzyme

    Directory of Open Access Journals (Sweden)

    Filatov Dmitry A

    2007-05-01

    Full Text Available Abstract Background Rubisco enzyme catalyzes the first step in net photosynthetic CO2 assimilation and photorespiratory carbon oxidation and is responsible for almost all carbon fixation on Earth. The large subunit of Rubisco is encoded by the chloroplast rbcL gene, which is widely used for reconstruction of plant phylogenies due to its conservative nature. Plant systematicists have mainly used rbcL paying little attention to its function, and the question whether it evolves under Darwinian selection has received little attention. The purpose of our study was to evaluate how common is positive selection in Rubisco among the phototrophs and where in the Rubisco structure does positive selection occur. Results We searched for positive selection in rbcL sequences from over 3000 species representing all lineages of green plants and some lineages of other phototrophs, such as brown and red algae, diatoms, euglenids and cyanobacteria. Our molecular phylogenetic analysis found the presence of positive selection in rbcL of most analyzed land plants, but not in algae and cyanobacteria. The mapping of the positively selected residues on the Rubisco tertiary structure revealed that they are located in regions important for dimer-dimer, intradimer, large subunit-small subunit and Rubisco-Rubisco activase interactions, and that some of the positively selected residues are close to the active site. Conclusion Our results demonstrate that despite its conservative nature, Rubisco evolves under positive selection in most lineages of land plants, and after billions of years of evolution Darwinian selection still fine-tunes its performance. Widespread positive selection in rbcL has to be taken into account when this gene is used for phylogenetic reconstructions.

  2. Genetic and epigenetic drivers of neuroendocrine tumours (NET).

    Science.gov (United States)

    Di Domenico, Annunziata; Wiedmer, Tabea; Marinoni, Ilaria; Perren, Aurel

    2017-09-01

    Neuroendocrine tumours (NET) of the gastrointestinal tract and the lung are a rare and heterogeneous group of tumours. The molecular characterization and the clinical classification of these tumours have been evolving slowly and show differences according to organs of origin. Novel technologies such as next-generation sequencing revealed new molecular aspects of NET over the last years. Notably, whole-exome/genome sequencing (WES/WGS) approaches underlined the very low mutation rate of well-differentiated NET of all organs compared to other malignancies, while the engagement of epigenetic changes in driving NET evolution is emerging. Indeed, mutations in genes encoding for proteins directly involved in chromatin remodelling, such as DAXX and ATRX are a frequent event in NET. Epigenetic changes are reversible and targetable; therefore, an attractive target for treatment. The discovery of the mechanisms underlying the epigenetic changes and the implication on gene and miRNA expression in the different subgroups of NET may represent a crucial change in the diagnosis of this disease, reveal new therapy targets and identify predictive markers. Molecular profiles derived from omics data including DNA mutation, methylation, gene and miRNA expression have already shown promising results in distinguishing clinically and molecularly different subtypes of NET. In this review, we recapitulate the major genetic and epigenetic characteristics of pancreatic, lung and small intestinal NET and the affected pathways. We also discuss potential epigenetic mechanisms leading to NET development. © 2017 Society for Endocrinology.

  3. 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

  4. 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/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

  5. 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

  6. Fishing with bed nets on Lake Tanganyika: a randomized survey.

    Science.gov (United States)

    McLean, Kate A; Byanaku, Aisha; Kubikonse, Augustine; Tshowe, Vincent; Katensi, Said; Lehman, Amy G

    2014-10-07

    Malaria is among the most common causes of death along Lake Tanganyika, a problem which many aid organizations have attempted to combat through the distribution of free mosquito bed nets to high-risk communities. The Lake Tanganyika Floating Health Clinic (LTFHC), a health-based non-governmental organization (NGO), has observed residents of the Lake Tanganyika basin using bed nets to fish small fry near the shoreline, despite a series of laws that prohibit bed net use and other fine-gauge nets for fishing, implemented to protect the near-shore fish ecology. The LTFHC sought to quantify the sources of bed nets and whether they were being used for fishing. The LTFHC conducted a survey of seven lakeside villages in Lagosa Ward, Tanzania. The government has divided each village into two to six pre-existing geographic sub-villages depending on population size. Seven households per sub-village were chosen at random for survey administration. The survey consisted of 23 questions regarding mosquito bed net practices, including the use of bed nets for fishing, as well as questions pertaining to any perceived changes to the fish supply. A total of 196 surveys were administered over a four-week period with a 100% response rate. Over 87% of households surveyed have used a mosquito bed net for fishing at some point. The majority of respondents reported receiving their bed net for free (96.4%), observing "many" residents of their village using bed nets for fishing (97.4%), and noticing a subjective decrease in the fish supply over time (64.9%). The findings of this study raise concerns that the use of free malaria bed nets for fishing is widespread along Lake Tanganyika, and that this dynamic will have an adverse effect on fish ecology. Further studies are indicated to fully define the scope of bed net misuse and the effects of alternative vector control strategies in water-based communities.

  7. 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

  8. Effect of plant density on the characteristics of photosynthetic ...

    African Journals Online (AJOL)

    ajl yemi

    2011-11-14

    Nov 14, 2011 ... At such densities, garlic developed a powerful photosynthetic apparatus and the bulbs were large and uniform. Key words: Garlic, plant density, leaf number per plant, leaf area, LAI. INTRODUCTION. The photosynthetic apparatus performs photosynthesis, which involves the production of organic matter.

  9. Linear Logic on Petri Nets

    DEFF Research Database (Denmark)

    Engberg, Uffe Henrik; Winskel, Glynn

    This article shows how individual Petri nets form models of Girard's intuitionistic linear logic. It explores questions of expressiveness and completeness of linear logic with respect to this interpretation. An aim is to use Petri nets to give an understanding of linear logic and give some apprai...

  10. Reference Guide Microsoft.NET

    NARCIS (Netherlands)

    Zee M van der; Verspaij GJ; Rosbergen S; IMP; NMD

    2003-01-01

    Developers, administrators and managers can get more understanding of the .NET technology with this report. They can also make better choices how to use this technology. The report describes the results and conclusions of a study of the usability for the RIVM of this new generation .NET development

  11. Net neutrality and audiovisual services

    NARCIS (Netherlands)

    van Eijk, N.; Nikoltchev, S.

    2011-01-01

    Net neutrality is high on the European agenda. New regulations for the communication sector provide a legal framework for net neutrality and need to be implemented on both a European and a national level. The key element is not just about blocking or slowing down traffic across communication

  12. Slowly developing drought stress increases photosynthetic acclimation of Catharanthus roseus.

    Science.gov (United States)

    Kim, Jongyun; van Iersel, Marc W

    2011-10-01

    Our understanding of plant responses to drought has improved over the decades. However, the importance of the rate of drought imposition on the response is still poorly understood. To test the importance of the rate at which drought stress develops, whole-plant photosynthesis (P(net) ), respiration (R(dark) ), daily carbon gain (DCG), daily evapotranspiration (DET) and water use efficiency (WUE) of vinca (Catharanthus roseus), subjected to different drought imposition rates, were investigated. We controlled the rate at which the substrate dried out with an automated irrigation system that allowed pot weight to decrease gradually throughout the drying period. Fast, intermediate and slow drying treatments reached their final pot weight [500 g, substrate water content (θ) ≈ 0.10 m³ m(-3) ] after 3.1, 6.6 and 10 days, respectively. Although all drying treatments decreased P(net) and R(dark) , slow drying reduced P(net) and R(dark) less than fast drying. At a θ < 0.10 m³ m(-3) , DCG and DET in the slow drying treatment were reduced by ≈50%, whereas DCG and DET in the fast drying treatment were reduced by 85 and 70% at a θ of 0.16 m(3) m(-3) . Plants exposed to slow drought imposition maintained a high WUE, even at θ < 0.10 m³ m(-3) . Overall, physiological responses to low θ were less severe in plants subjected to slow drying as compared with fast drying, even though the final θ was lower for plants exposed to slow drying. This suggests that the rate at which drought stress develops has important implications for the level of acclimation that occurs. Copyright © Physiologia Plantarum 2011.

  13. Annual net primary productivity of a cyanobacteria-dominated biological soil crust in the Gulf Savannah, Queensland, Australia

    Science.gov (United States)

    Büdel, Burkhard; Williams, Wendy J.; Reichenberger, Hans

    2018-01-01

    Biological soil crusts (biocrusts) are a common element of the Queensland (Australia) dry savannah ecosystem and are composed of cyanobacteria, algae, lichens, bryophytes, fungi and heterotrophic bacteria. Here we report how the CO2 gas exchange of the cyanobacteria-dominated biocrust type from Boodjamulla National Park in the north Queensland Gulf Savannah responds to the pronounced climatic seasonality and on their quality as a carbon sink using a semi-automatic cuvette system. The dominant cyanobacteria are the filamentous species Symplocastrum purpurascens together with Scytonema sp. Metabolic activity was recorded between 1 July 2010 and 30 June 2011, during which CO2 exchange was only evident from November 2010 until mid-April 2011, representative of 23.6 % of the 1-year recording period. In November at the onset of the wet season, the first month (November) and the last month (April) of activity had pronounced respiratory loss of CO2. The metabolic active period accounted for 25 % of the wet season and of that period 48.6 % was net photosynthesis (NP) and 51.4 % dark respiration (DR). During the time of NP, net photosynthetic uptake of CO2 during daylight hours was reduced by 32.6 % due to water supersaturation. In total, the biocrust fixed 229.09 mmol CO2 m-2 yr-1, corresponding to an annual carbon gain of 2.75 g m-2 yr-1. Due to malfunction of the automatic cuvette system, data from September and October 2010 together with some days in November and December 2010 could not be analysed for NP and DR. Based on climatic and gas exchange data from November 2010, an estimated loss of 88 mmol CO2 m-2 was found for the 2 months, resulting in corrected annual rates of 143.1 mmol CO2 m-2 yr-1, equivalent to a carbon gain of 1.7 g m-2 yr-1. The bulk of the net photosynthetic activity occurred above a relative humidity of 42 %, indicating a suitable climatic combination of temperature, water availability and light intensity well above 200 µmol photons m-2 s-1

  14. A Small Universal Petri Net

    Directory of Open Access Journals (Sweden)

    Dmitry A. Zaitsev

    2013-09-01

    Full Text Available A universal deterministic inhibitor Petri net with 14 places, 29 transitions and 138 arcs was constructed via simulation of Neary and Woods' weakly universal Turing machine with 2 states and 4 symbols; the total time complexity is exponential in the running time of their weak machine. To simulate the blank words of the weakly universal Turing machine, a couple of dedicated transitions insert their codes when reaching edges of the working zone. To complete a chain of a given Petri net encoding to be executed by the universal Petri net, a translation of a bi-tag system into a Turing machine was constructed. The constructed Petri net is universal in the standard sense; a weaker form of universality for Petri nets was not introduced in this work.

  15. Contrasting Responses of Marine and Freshwater Photosynthetic Organisms to UVB Radiation: A Meta-Analysis

    KAUST Repository

    Jin, Peng

    2017-03-14

    Ultraviolet-B (UVB) radiation is a global stressor that has profound impacts on freshwater and marine ecosystems. However, an analysis of the patterns of sensitivity to UVB radiation across aquatic photosynthetic organisms has not yet been published. Here, we performed a meta-analysis on results reported in 214 studies compiled from the published literature to quantify and compare the magnitude of responses of aquatic photosynthetic organisms to changes in UVB radiation. The meta-analysis was conducted on observations of marine (n = 893) and freshwater macroalgae (n = 126) and of marine (n = 1,087) and freshwater (n = 2,889) microalgae (total n = 4,995). Most of these studies (85%) analyzed the performance of organisms exposed to natural solar radiation when UVB was partially or totally reduced compared with the organismal performance under the full solar radiation spectrum, whereas the remaining 15% of the studies examined the responses of organisms to elevated UVB radiation mostly using 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 sensitive of the trait responses to elevated UVB radiation, followed by changes in cellular and molecular traits; the sensitivity of microalgae to UVB radiation is dependent on size, with small-celled microalgae more sensitive than large-celled microalgae to UVB radiation. Thick macroalgae morphotypes were the less sensitive to UVB, but this effect could not be separated from phylogenetic differences. The high sensitivity of marine species, particularly the smallest photosynthetic organisms, to increased UVB radiation suggests that the oligotrophic ocean, a habitat comprising 70% of the world\\'s oceans with high UVB penetration and dominated by picoautotrophs, is extremely vulnerable to changes in UVB radiation.

  16. 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

  17. Antenna organization in green photosynthetic bacteria

    Energy Technology Data Exchange (ETDEWEB)

    Blankenship, R.E.

    1987-01-01

    This project is concerned with the structure and function of the unique antenna system found in the green photosynthetic bacteria. The antenna system in these organisms is contained within a vesicle known as a chlorosome, which is attached to the cytoplasmic side of the cell membrane. Additional antenna pigments and reaction centers are contained in integral membrane proteins. Energy absorbed by the bacteriochlorophyll c (BChl c) pigments in the chlorosome is transferred via a baseplate'' array of BChl a antenna pigments into the membrane and to the reaction center. A schematic model of chlorosome structure is shown. This project is aimed at increasing our understanding of the organization of the pigments in the chlorosome and how the antenna system functions.

  18. Modifiable chromatophore proteins in photosynthetic bacteria.

    Science.gov (United States)

    Hui, K M; Hurlbert, R E

    1979-01-01

    The chromatophores of Chromatium vinosum, as well as six other photosynthetic bacteria, contained two or more proteins which were insoluble when heated in the presence of sodium dodecyl sulfate (SDS) and 2-mercaptoethanol (beta-ME). When the chromatophores were dissolved at room temperature in SDS-beta-ME, these proteins were present in the SDS-polyacrylamide gel electrophoresis profiles, but when the samples were dissolved at 100 degrees C, they were absent or considerably diminished. When one-dimensional gels of chromatophores solubilized at room temperature were soaked in the SDS-beta-ME solution and heated to 100 degrees C and the gels were run in a second dimension, the proteins became immobilized in the original first-dimension gel, where they could be detected by staining. The two major proteins so affected in C. vinosum had apparent molecular weights of 28,000 and 21,000. The chromatophores of several other photosynthetic bacteria also contained predominant proteins between 30,000 and 19,000 molecular weight, which became insoluble when heated in the presence of SDS and beta-ME. In at least two of the species examined, these appeared to be reaction center proteins. The conditions causing the proteins to become insoluble were complex and involved temperature, SDS concentration, and the presence of sulfhydryl reagents. The chromatophores of four of the Chromatiaceae species and two strains of one of the Rhodospirillaceae species examined had a protein-pigment complex that was visible in SDS-polyacrylamide gel profiles of samples dissolved at room temperature but was absent in samples dissolved at 100 degrees C. Images PMID:438130

  19. Effects of Insect-Proof Net Cultivation, Rice-Duck Farming, and Organic Matter Return on Rice Dry Matter Accumulation and Nitrogen Utilization.

    Science.gov (United States)

    Liu, Xin; Xu, Guochun; Wang, Qiangsheng; Hang, Yuhao

    2017-01-01

    Insect-proof net cultivation (IPN), rice-duck farming (RD), and organic matter return (OM) are important methods to realize sustainable development of rice production. A split-plot field experiment was performed to study the effects of IPN, RD, and OM on the rice yield, dry matter accumulation and N utilization. Results showed that compared to inorganic N fertilizer (IN), wheat straw return, and biogas residue return increased the rice yield by 2.11-4.28 and 4.78-7.67%, respectively, and also improved dry matter and N accumulation after the elongation stage (EG), dry matter and N translocation, and N recovery efficiency (NRE). These results attributed to an increase in leaf SPAD values and net photosynthetic rate (Pn) after the EG. Compared to conventional rice farming (CR), RD promoted the rice yield by 1.52-3.74%, and contributed to higher the leaf photosynthesis, dry matter and N accumulation, dry matter and N translocation, and NRE. IPN decreased the intensity of sun radiation in the nets due to the coverage of the insect-proof nets, which declined the leaf Pn, dry matter accumulation and translocation, N absorption and translocation, and NRE compared to open field cultivation (OFC). The rice yield of IPN were 2.48-4.98% lower than that of OFC. Compared to the interaction between CR and IN, the interaction between RD and OM improved the rice yield by 5.26-9.33%, and increased dry matter and N accumulation after the EG, dry matter and N translocation, and NRE. These results indicated that OM, RD and the interaction between RD and OM could promote dry matter accumulation and N utilization, which was beneficial to improve the rice yield.

  20. Effects of Insect-Proof Net Cultivation, Rice-Duck Farming, and Organic Matter Return on Rice Dry Matter Accumulation and Nitrogen Utilization

    Science.gov (United States)

    Liu, Xin; Xu, Guochun; Wang, Qiangsheng; Hang, Yuhao

    2017-01-01

    Insect-proof net cultivation (IPN), rice-duck farming (RD), and organic matter return (OM) are important methods to realize sustainable development of rice production. A split-plot field experiment was performed to study the effects of IPN, RD, and OM on the rice yield, dry matter accumulation and N utilization. Results showed that compared to inorganic N fertilizer (IN), wheat straw return, and biogas residue return increased the rice yield by 2.11–4.28 and 4.78–7.67%, respectively, and also improved dry matter and N accumulation after the elongation stage (EG), dry matter and N translocation, and N recovery efficiency (NRE). These results attributed to an increase in leaf SPAD values and net photosynthetic rate (Pn) after the EG. Compared to conventional rice farming (CR), RD promoted the rice yield by 1.52–3.74%, and contributed to higher the leaf photosynthesis, dry matter and N accumulation, dry matter and N translocation, and NRE. IPN decreased the intensity of sun radiation in the nets due to the coverage of the insect-proof nets, which declined the leaf Pn, dry matter accumulation and translocation, N absorption and translocation, and NRE compared to open field cultivation (OFC). The rice yield of IPN were 2.48–4.98% lower than that of OFC. Compared to the interaction between CR and IN, the interaction between RD and OM improved the rice yield by 5.26–9.33%, and increased dry matter and N accumulation after the EG, dry matter and N translocation, and NRE. These results indicated that OM, RD and the interaction between RD and OM could promote dry matter accumulation and N utilization, which was beneficial to improve the rice yield. PMID:28174589

  1. High-level Petri Nets

    DEFF Research Database (Denmark)

    High-level Petri nets are now widely used in both theoretical analysis and practical modelling of concurrent systems. The main reason for the success of this class of net models is that they make it possible to obtain much more succinct and manageable descriptions than can be obtained by means...... of low-level Petri nets - while, on the other hand, they still offer a wide range of analysis methods and tools. The step from low-level nets to high-level nets can be compared to the step from assembly languages to modern programming languages with an elaborated type concept. In low-level nets...... there is only one kind of token and this means that the state of a place is described by an integer (and in many cases even by a boolean). In high-level nets each token can carry a complex information/data - which, e.g., may describe the entire state of a process or a data base. Today most practical...

  2. Biome-specific effects of nitrogen and phosphorus on the photosynthetic characteristics of trees at a forest-savanna boundary in Cameroon

    OpenAIRE

    Ferreira Domingues, Tomas; Ishida, F. Yoko; Feldpausch, Ted R.; Grace, John; Meir, Patrick; Saiz, Gustavo; Sene, Olivier; Schrodt, Franziska; Sonk?, Bonaventure; Taedoumg, Herman; Veenendaal, Elmar M.; Lewis, Simon; Lloyd, Jon

    2015-01-01

    Photosynthesis/nutrient relationships of proximally growing forest and savanna trees were determined in an ecotonal region of Cameroon (Africa). Although area-based foliar N concentrations were typically lower for savanna trees, there was no difference in photosynthetic rates between the two vegetation formation types. Opposite to N, area-based P concentrations were?on average?slightly lower for forest trees; a dependency of photosynthetic characteristics on foliar P was only evident for sava...

  3. Effects of Foliar Application of Nano Zinc Chelate and Zinc Sulfate on Zinc Content, Pigments and Photosynthetic Indices of Holy Basil (Ocimum sanctum(

    Directory of Open Access Journals (Sweden)

    Zohreh Moghimi pour

    2017-02-01

    Full Text Available Introduction: Holy basil is a perennial plant belongs to Lamiaceae family. The plant is a perennial and thrives well in the hot and humid climate. Its aerial parts have been in use for food, pharmaceuticals, cosmetics and perfumery industries. Leaves contain 0.5-1.5% essential oil and main oil components are eugenol, methyl eugenol, carvacrol, methyl chavicol and1,8-cineole. A balanced fertilization program with macro and micronutrients is very important in producing high quality yield. Zinc is involved in IAA production, chlorophyll biosynthesis, carbon assimilation, saccharids accumulation, reactive oxygen radicals scavenging and finally carbon utilization in volatile oil biosynthesis. Material and methods: In order to evaluate the effect on zinc foliar application on zinc content of leaves, photosynthetic indices and pigments of holy basil, an experiment was carried out in 2013 at a research farm of Horticultural Science, Shahid Chamran University (31°20'N latitude and 48°40'E longitude and 22.5 m mean sea level, Ahvaz (Iran, a region characterized by semi-dry climate. The experiment was arranged based on Randomized Complete Block Design (RCBD with six treatments and three replications. The treatments were nano zinc chelate (0, 0.5, 1 and 1.5 g.l-1 and zinc sulfate (1 and 1.5 g.l-1 fertilizers. Land preparation includes disking and the formation of raising beds (15cm high and 45cm wide across the top using a press-pan-type bed shaper. Holy basil seeds were sown on two rows on each bed, with 15 cm in-row and 40 cm between-row spacing. The plants were irrigated weekly as needed. Foliar application of zinc fertilizers was done at six-eight leaf stage and were repeated with interval 15 days until full bloom stage. Zinc content, stomata conductance (gs, CO2 under stomata (Ci, transpiration rate (E, net photosynthesis (Pn, light use efficiency (LUE, water use efficiency (WUE and also chlorophyll a, chlorophyll b, chlorophyll a+b and carotenoid

  4. Loss of protection with insecticide-treated nets against pyrethroid-resistant Culex quinquefasciatus mosquitoes once nets become holed: an experimental hut study

    Directory of Open Access Journals (Sweden)

    Irish SR

    2008-06-01

    Full Text Available Abstract Background An important advantage of pyrethroid-treated nets over untreated nets is that once nets become worn or holed a pyrethroid treatment will normally restore protection. The capacity of pyrethroids to kill or irritate any mosquito that comes into contact with the net and prevent penetration of holes or feeding through the sides are the main reasons why treated nets continue to provide protection despite their condition deteriorating over time. Pyrethroid resistance is a growing problem among Anopheline and Culicine mosquitoes in many parts of Africa. When mosquitoes become resistant the capacity of treated nets to provide protection might be diminished, particularly when holed. An experimental hut trial against pyrethroid-resistant Culex quinquefasciatus was therefore undertaken in southern Benin using a series of intact and holed nets, both untreated and treated, to assess any loss of protection as nets deteriorate with use and time. Results There was loss of protection when untreated nets became holed; the proportion of mosquitoes blood feeding increased from 36.2% when nets were intact to between 59.7% and 68.5% when nets were holed to differing extents. The proportion of mosquitoes blood feeding when treated nets were intact was 29.4% which increased to 43.6–57.4% when nets were holed. The greater the number of holes the greater the loss of protection regardless of whether nets were untreated or treated. Mosquito mortality in huts with untreated nets was 12.9–13.6%; treatment induced mortality was less than 12%. The exiting rate of mosquitoes into the verandas was higher in huts with intact nets. Conclusion As nets deteriorate with use and become increasingly holed the capacity of pyrethroid treatments to restore protection is greatly diminished against resistant Culex quinquefasciatus mosquitoes.

  5. Pro asynchronous programming with .NET

    CERN Document Server

    Blewett, Richard; Ltd, Rock Solid Knowledge

    2014-01-01

    Pro Asynchronous Programming with .NET teaches the essential skill of asynchronous programming in .NET. It answers critical questions in .NET application development, such as: how do I keep my program responding at all times to keep my users happy how do I make the most of the available hardware how can I improve performanceIn the modern world, users expect more and more from their applications and devices, and multi-core hardware has the potential to provide it. But it takes carefully crafted code to turn that potential into responsive, scalable applications.With Pro Asynchronous Programming

  6. Conformal Nets II: Conformal Blocks

    Science.gov (United States)

    Bartels, Arthur; Douglas, Christopher L.; Henriques, André

    2017-08-01

    Conformal nets provide a mathematical formalism for conformal field theory. Associated to a conformal net with finite index, we give a construction of the `bundle of conformal blocks', a representation of the mapping class groupoid of closed topological surfaces into the category of finite-dimensional projective Hilbert spaces. We also construct infinite-dimensional spaces of conformal blocks for topological surfaces with smooth boundary. We prove that the conformal blocks satisfy a factorization formula for gluing surfaces along circles, and an analogous formula for gluing surfaces along intervals. We use this interval factorization property to give a new proof of the modularity of the category of representations of a conformal net.

  7. Variação sazonal da fotossíntese, condutância estomática e potencial da água na folha de laranjeira 'Valência' Seasonal variation of photosynthetic rates, stomatal conductance and leaf water potential in 'Valencia' orange trees

    Directory of Open Access Journals (Sweden)

    Eduardo Caruso Machado

    2002-03-01

    Full Text Available Em espécies perenes podem ocorrer variações nas taxas de trocas gasosas e nas relações hídricas em função da variação das condições ambientais, durante os diferentes meses do ano. Avaliaram-se, em laranjeira ´Valência´ enxertada sobre quatro espécies de porta-enxerto, mantida sem deficiência hídrica, as taxas de fotossíntese (A e de transpiração (E, a condutância estomática (g e o potencial da água na folha (psi f , medidos nos períodos da manhã (9h00 às 11h00 e da tarde (13h00 às 15h00 nos meses de janeiro, março e julho em Campinas - SP. As espécies de porta-enxertos não tiveram efeitos sobre as variáveis medidas. Independente do porta-enxerto A, g e Y f foram menores no período da tarde. A queda de A deve estar relacionada com a queda de g que diminuiu em resposta ao aumento do déficit de pressão de vapor entre o ar e a folha (DPVar-folha nos horários mais quentes do dia. Apesar de ocorrer fechamento parcial dos estômatos no período da tarde E foi similar ao período da manhã, devido ao aumento do DPVar-folha. Também observou-se queda em A e em g no sentido de janeiro para julho. Sugere-se que a queda em A e em g ocorrida em março em comparação a janeiro esteja relacionada à queda da atividade de crescimento da planta, afetando as relações fonte-dreno, visto que as condições ambientais nestes dois meses foram semelhantes. As quedas de A e de g observadas em julho, em relação à janeiro e março, parecem estar relacionadas tanto à queda na temperatura noturna quanto à queda na atividade de crescimento.Seasonal variation in environmental conditions may influence gas exchange rates as well as water relations in perennial species. This work was carried out to evaluate photosynthetic rates (A, transpiration (E, stomatal conductance (g and leaf water potential (psi f in 'Valencia' orange trees grafted on four different rootstocks. Measurements were made twice a day: from 9h00 to 11h00 a.m. and

  8. Anatomical and diffusional determinants inside leaves explain the difference in photosynthetic capacity between Cypripedium and Paphiopedilum, Orchidaceae.

    Science.gov (United States)

    Yang, Zhong-Hui; Huang, Wei; Yang, Qiu-Yun; Chang, Wei; Zhang, Shi-Bao

    2017-11-20

    Comparing with other angiosperms, most members within the family Orchidaceae have lower photosynthetic capacities. However, the underlying mechanisms remain unclear. Cypripedium and Paphiopedilum are closely related phylogenetically in Orchidaceae, but their photosynthetic performances are different. We explored the roles of internal anatomy and diffusional conductance in determining photosynthesis in three Cypripedium and three Paphiopedilum species, and quantitatively analyzed their diffusional and biochemical limitations to photosynthesis. Paphiopedilum species showed lower light-saturated photosynthetic rate (A N), stomatal conductance (g s), and mesophyll conductance (g m) than Cypripedium species. A N was positively correlated with g s and g m. And yet, in both species A N was more strongly limited by g m than by biochemical factors or g s. The greater g s of Cypripedium was mainly affected by larger stomatal apparatus area and smaller pore depth, while the less g m of Paphiopedilum was determined by the reduced surface area of mesophyll cells and chloroplasts exposed to intercellular airspace per unit of leaf area, and much thicker cell wall thickness. These results suggest that leaf anatomical structure is the key factor affecting g m, which is largely responsible for the difference in photosynthetic capacity between those two genera. Our findings provide new insight into the photosynthetic physiology and functional diversification of orchids.

  9. Life history and resource acquisition: Photosynthetic traits in selected accessions of three perennial cereal species compared with annual wheat and rye.

    Science.gov (United States)

    Jaikumar, Nikhil S; Snapp, Sieglinde S; Sharkey, Thomas D

    2013-12-01

    Few previous studies have considered how plant age affects photosynthetic physiology in herbaceous perennials or how photosynthetic capacity in annual cereals compares to perennial relatives. Newly developed perennial cereals offer novel systems for addressing these questions. Our study makes a novel contribution by considering how life history differences affect photosynthetic physiology. In two linked field studies, we evaluated effects of life history and plant age on photosynthetic rates (A), and related biochemical, morphological, and water-relations traits, comparing 1- and 2-yr-old cohorts of perennial wheat, intermediate wheatgrass, and perennial rye to close annual relatives (wheat and rye). Photosynthetic rates (A) were 10-50% higher in perennial cereals compared to annuals. In wheatgrass, elevated A was associated with higher carboxylation (VC), triose phosphate utilization (TPU) and electron transport rates (J), and higher leaf soluble protein and chlorophyll. Younger wheatgrass plants maintained higher A, TPU, J, and VC than older plants did. Perennial wheat and rye differed from annual relatives in some but not all of these parameters. Differences in stomatal limitation were not involved, while differences in stomatal conductance (gs) became evident under drier conditions. This study demonstrates that some perennial cereal species can maintain higher midseason A than their annual crop relatives. These changes are not fully explainable by increased access to soil water and may reflect trade-offs between allocation to reproduction and to resource acquisition. We also found evidence for age-related changes in photosynthetic physiology in a herbaceous perennial plant.

  10. 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

    Major light gradients, characteristically 10- to 50-fold, constitute the most prominent feature of plant canopies. These gradients drive within-canopy variation in foliage structural, chemical and physiological traits. As a key acclimation response to variation in light availability, foliage photosynthetic capacity per area (Aarea) increases with increasing light availability within the canopy, maximizing whole canopy photosynthesis. Recently, a worldwide database including 831 within-canopy gradients with standardized light estimates for 304 species belonging to major vascular plant functional types was constructed and within-canopy variation in photosynthetic acclimation was characterized (Niinemets Ü, Keenan TF, Hallik L (2015) Tansley review. A worldwide analysis of within-canopy variations in leaf structural, chemical and physiological traits across plant functional types. The New Phytologist 205: 973-993). However, the understanding of how within-canopy photosynthetic gradients vary during the growing season and in response to site and stand characteristics is still limited. Here we analyzed temporal, environmental and site (nutrient availability, stand density, ambient CO2 concentration, water availability) sources of variation in within-canopy photosynthetic acclimation in different plant functional types. Variation in key structural (leaf dry mass per unit area, MA), chemical (nitrogen content per dry mass, NM, and area, NA) and physiological (photosynthetic nitrogen use efficiency, EN) photosynthetic capacity per dry mass, Amass and area, Aarea) was examined. The analysis demonstrates major, typically 1.5-2-fold, time-, environment and site-dependent modifications in within-canopy variation in foliage photosynthetic capacity. However, the magnitude and direction of temporal and environmental variations in plasticity significantly varied among functional types. Species with longer leaf life span and low rates of canopy expansion or flush-type canopy

  11. Importance of structure and density of macroalgae communities (Fucus serratus) for photosynthetic production and light utilisation

    DEFF Research Database (Denmark)

    Binzer, Thomas; Sand-Jensen, Kaj

    2002-01-01

    Determination of photosynthetic production in plant communities is essential for evaluating plant growth rates and carbon fluxes in ecosystems, but it cannot easily be derived from the photosynthetic response of individual leaves or thalli, which has been the focus of virtually all previous aquatic...... day-night cycle is attained at an LAI of 5 to 6. Maximum gross production was about 3-fold lower in F. serratus communities than in terrestrial communities in forests, grasslands and crops. Manipulating F. serratus communities to a more vertical structure increased light penetration and gross...

  12. Growth, photosynthetic pigments and production of essential oil of long-pepper under different light conditions

    Directory of Open Access Journals (Sweden)

    VANDIMILLI A. LIMA

    Full Text Available ABSTRACT Piper hispidinervum C. DC. is popularly known as long-pepper and it owns a commercial value due to the essential oil it produces. Long-pepper oil is rich in safrole and eugenoln components that have insecticidal, fungicidal and bactericidal activity. It has been establish that to medicinal plants light influences not only growth but also essential oil production. The growth, the content of photosynthetic pigments and the essential oil production of Piper hispidinervum at greenhouses with different light conditions was evaluated. The treatments were characterized by cultivation of plants for 180 days under different light conditions, produced by shading greenhouses with 50% and 30% of natural incident irradiance, two colored shading nets red (RN and blue (BN both blocking 50% of the incident radiation and one treatment at full-sun (0% of shade. The results showed that the treatments of 50% shade and RN and BN were the ones which stimulated the greater growth. Blue and red light also had the best production of photosynthetic pigments. Essential oil yielded more under full sun therefore this is the most indicated condition to produce seedlings for the chemical and pharmaceutical industry.

  13. Growth, photosynthetic pigments and production of essential oil of long-pepper under different light conditions.

    Science.gov (United States)

    Lima, Vandimilli A; Pacheco, Fernanda V; Avelar, Rafaella P; Alvarenga, Ivan C A; Pinto, José Eduardo B P; Alvarenga, Amauri A DE

    2017-01-01

    Piper hispidinervum C. DC. is popularly known as long-pepper and it owns a commercial value due to the essential oil it produces. Long-pepper oil is rich in safrole and eugenoln components that have insecticidal, fungicidal and bactericidal activity. It has been establish that to medicinal plants light influences not only growth but also essential oil production. The growth, the content of photosynthetic pigments and the essential oil production of Piper hispidinervum at greenhouses with different light conditions was evaluated. The treatments were characterized by cultivation of plants for 180 days under different light conditions, produced by shading greenhouses with 50% and 30% of natural incident irradiance, two colored shading nets red (RN) and blue (BN) both blocking 50% of the incident radiation and one treatment at full-sun (0% of shade). The results showed that the treatments of 50% shade and RN and BN were the ones which stimulated the greater growth. Blue and red light also had the best production of photosynthetic pigments. Essential oil yielded more under full sun therefore this is the most indicated condition to produce seedlings for the chemical and pharmaceutical industry.

  14. Long-term photosynthetic acclimation to increased atmospheric CO{sub 2} concentration in young birch (Betula pendula) trees

    Energy Technology Data Exchange (ETDEWEB)

    Rey, A.; Jarvis, P. G. [Edinburgh Univ. (United Kingdom)

    1998-07-01

    Long-term response of photosynthesis to elevated carbon dioxide concentration in silver birch trees was studied. Eighteen trees grown in the field were subjected to varying concentrations of carbon dioxide for four consecutive growing seasons. Maximum photosynthetic rates, stomatal and carbon dioxide response curves were measured over the fourth growing season with a portable photosynthesis system. Elevated carbon dioxide concentrations caused photosynthesis to increase by 33 per cent over the growing season, however, the photosynthetic capacity of the trees grown in elevated carbon dioxide concentration was reduced. Analysis of the response curves showed that acclimation to elevated carbon dioxide decreased carboxylation efficiency and regeneration capacity. Analysis of leaf components revealed that the reduced photosynthetic capacity was accompanied by an accumulation of starch in the leaves as well as reduced chlorophyll, soluble protein and nitrogen concentration. Stomatal conductance although reduced, was considerably less limited in the elevated than in the ambient carbon dioxide treatment. 65 refs., 4 tabs., 6 figs.

  15. Petri Net Tool Overview 1986

    DEFF Research Database (Denmark)

    Jensen, Kurt; Feldbrugge, Frits

    1987-01-01

    This paper provides an overview of the characteristics of all currently available net based tools. It is a compilation of information provided by tool authors or contact persons. A concise one page overview is provided as well....

  16. Understanding Net Zero Energy Buildings

    DEFF Research Database (Denmark)

    Salom, Jaume; Widén, Joakim; Candanedo, José

    2011-01-01

    Although several alternative definitions exist, a Net-Zero Energy Building (Net ZEB) can be succinctly described as a grid-connected building that generates as much energy as it uses over a year. The “net-zero” balance is attained by applying energy conservation and efficiency measures...... and by incorporating renewable energy systems. While based on annual balances, a complete description of a Net ZEB requires examining the system at smaller time-scales. This assessment should address: (a) the relationship between power generation and building loads and (b) the resulting interaction with the power grid....... This paper presents and categorizes quantitative indicators suitable to describe both aspects of the building’s performance. These indicators, named LMGI - Load Matching and Grid Interaction indicators, are easily quantifiable and could complement the output variables of existing building simulation tools...

  17. PolicyNet Publication System

    Data.gov (United States)

    Social Security Administration — The PolicyNet Publication System project will merge the Oracle-based Policy Repository (POMS) and the SQL-Server CAMP system (MSOM) into a new system with an Oracle...

  18. KM3NeT

    CERN Multimedia

    KM3NeT is a large scale next-generation neutrino telescope located in the deep waters of the Mediterranean Sea, optimized for the discovery of galactic neutrino sources emitting in the TeV energy region.

  19. Net Neutrality: Background and Issues

    National Research Council Canada - National Science Library

    Gilroy, Angele A

    2006-01-01

    .... The move to place restrictions on the owners of the networks that compose and provide access to the Internet, to ensure equal access and nondiscriminatory treatment, is referred to as "net neutrality...

  20. Spectral effects of light-emitting diodes on photosynthetic characteristics and secondary metabolism in greenhouse plants

    DEFF Research Database (Denmark)

    Ouzounis, Theoharis

    2014-01-01

    , photo-synthetic performance, and secondary metabolism of different plants. As model plants we used rose (Rosa hybrida), chrysanthemum (Chrysanthemum morifolium), campanula (Campanula portenschlagiana), orchid (Phalaenopsis), and lettuce (Lactuca sativa). In our first experiment, by growing roses......, chrysanthemums, and campanulas under four different LED combinations, we report that a fraction of 20 – 40% blue LED light was adequate to amend morphological abnormalities. Stomatal conductance increased with increasing blue light, but net photosynthesis remained unaffected. In our second experiment, we show...... fluorescence measurements. In all three experiments, we also addressed the effects of supplementary blue and red LED lighting on phytochemicals. With increasing amount of blue light, roses, chrysanthemums, and campanulas increased their phenolic amount; Phalaenopsis cultivars increased their pigment content...

  1. Modeling Net Growth of Phaeocystis antarctica Based on Physiological and Optical Responses to Light and Temperature Co-limitation

    Directory of Open Access Journals (Sweden)

    Tiffany A. Moisan

    2018-02-01

    Full Text Available Temperature and light are fundamental environmental variables which regulate phytoplankton growth rates when nutrients are in excess. For polar coastal oceans that are undergoing changes in sea ice cover and warming, light, and temperature are particularly important for bloom dynamics. Using colonial Phaeocystis antarctica cultures grown at steady-state, we assessed the combined effect of these two environmental controls on net growth rate (μn, chlorophyll-specific absorption of light (aph* (λ, and quantum yields for growth (ϕμ. Specific net growth rates (μn varied from 0.04 to 0.34 day−1 within a matrix of light and temperature ranging from 14 to 542 μmol quanta m−2 s−1 and −1.5 to 4°C. Values of aph* (λ varied significantly with light but only slightly with temperature. Values of ϕμ ranged from 0.003 to 0.09 mol C (mol quanta absorbed−1 with highest values at low light and 4°C. For excess irradiances or low temperatures where growth rate is inhibited, quantum yields were low. The low ϕμ values are attributed both to increased absorption by photoprotective pigments compared to photosynthetic pigments and thermodynamic control of dark reaction enzymes. The systematic changes in photophysiological properties of P. antarctica in relation to temperature and light were used to develop a series of nested light- and temperature-dependent models for μn, aph* (λ, and ϕμ. A model for aph* (300–700 nm was developed that takes into account the systematic changes in aph* (λ due to pigment packaging effects and cellular concentrations of chlorophylls and photoprotective pigments. Also, a model for ϕμ was developed based on a cumulative one-hit Poisson probability function. These model parameterizations for absorption and quantum yield are combined into an overall model of net growth that can be applied easily to P. antarctica bloom dynamics using remote sensing data for temperature, light, and chlorophyll a. Furthermore

  2. Petri Nets in Cryptographic Protocols

    DEFF Research Database (Denmark)

    Crazzolara, Federico; Winskel, Glynn

    2001-01-01

    A process language for security protocols is presented together with a semantics in terms of sets of events. The denotation of process is a set of events, and as each event specifies a set of pre and postconditions, this denotation can be viewed as a Petri net. By means of an example we illustrate...... how the Petri-net semantics can be used to prove security properties....

  3. The Economics of Net Neutrality

    OpenAIRE

    Hahn, Robert W.; Wallsten, Scott

    2006-01-01

    This essay examines the economics of "net neutrality" and broadband Internet access. We argue that mandating net neutrality would be likely to reduce economic welfare. Instead, the government should focus on creating competition in the broadband market by liberalizing more spectrum and reducing entry barriers created by certain local regulations. In cases where a broadband provider can exercise market power the government should use its antitrust enforcement authority to police anticompetitiv...

  4. Response of photosynthetic characters to CO2 change on C3 and C4 cereal crops grown in Lunar Palace 1

    Science.gov (United States)

    Wang, Minjuan; Liu, Hong; Fu, Yuming; Shao, Lingzhi; Dong, Chen; Liu, Guanghui

    Lunar Palace 1, as an integrative experiment facility for Permanent Astrobase Life-support Artificial Closed Ecosystem (P.A.L.A.C.E.), provides a largely closed environment for crop growth tests for Bioregenerative Life Support System (BLSS). In this study, we evaluated the response of photosynthetic characters of two soybean cultivars (Glycine max (L.) Merr., ‘Zhonghuang13’and ‘Heihe35’) of C _{3} plants and one maize ( Zea mays L.) of C _{4} plants, which were selected as candidates for cultivation in BLSS. Plants were cultivated in stainless steel pots equipped with the porous-tube nutrient delivery system (PTNDS) and grew under controlled environmental conditions of Lunar Palace 1 (12 h photoperiod, light intensity 500 umol m (-2) s (-1) , temperature regime 26/22 (o) C light/dark). Fertigation was performed with a standard Hoagland solution, in which pH was kept at 5.8. A gas exchange/chlorophyII fluorescence analysis was performed to determine their net photosynthesis (Pn), stomatal (g _{s}) and mesophyll (g _{m}) conductances, intercellular CO _{2} concentration (Ci), and transpiration rate (E) under different elevated CO _{2} concentration. In order to partially describe how leaf physiology responds to the elevated CO _{2}, Chl content and the activity and amount of rubisco were analyzed. This study provides a theoretical basis for the crop selection in BLSS.

  5. [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.

  6. [Effects of light intensity on growth and photosynthetic characteristics of Chrysanthemum morifolium].

    Science.gov (United States)

    Wang, Yanru; Guo, Qiaosheng; Jin, Miao

    2009-07-01

    To investigate the effect of light intensity on growth and photosynthetic of Chrysanthemum morifolium. The growth characteristics of C. morifolium were measured under different treatments (100%, 80%, 60%, 40% and 20% of full sunlight). The photosynthetic characteristics and chlorophyll fluorescence parameters of leaves under different light intensity were determined by a LI-6400 photosynthesis system and a PAM-2100 chlorophyll fluorescence system. With the reduction of irradiance, the diameter of the stem reduced, plant height, leaf length, leaf width and length/width raised, assimilation product increased; Content of photosynthetic pigment increased between light intensity 100%-40% reduced under 20% treatment, chlorophyll a/b decreased. Light compensation point (LCP), apparent quantum yield (AQY) increased first and reduced later, photosynthesis rate (P(n)), stomatal conductance (G(s)), intercellular CO2 concentration (C(i)) and transpiration rate (T(r)) decreased, stomatal limitation value (L(s)) rose. Chlorophyll fluorescence parameters F(v)/F(m) increased, phiPS II, F(v)'/F(m)', ETR and qP increased between irradiance 100%-60%, NPQ decreased, such as phiPS II decreased and NPQ increased when irradiance was lower than 40%. Weak light condition was unfavorable to the growth of C. morifolium and the light conditions of culture should be control between 80%-60% of full sunlight.

  7. 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.

  8. Effect of elevated CO2 concentration on photosynthetic characteristics of hyperaccumulator Sedum alfredii under cadmium stress.

    Science.gov (United States)

    Li, Tingqiang; Tao, Qi; Di, Zhenzhen; Lu, Fan; Yang, Xiaoe

    2015-07-01

    The combined effects of elevated CO2 and cadmium (Cd) on photosynthetic rate, chlorophyll fluorescence and Cd accumulation in hyperaccumulator Sedum alfredii Hance were investigated to predict plant growth under Cd stress with rising atmospheric CO2 concentration. Both pot and hydroponic experiments were conducted and the plants were grown under ambient (350 µL L(-1)) or elevated (800 µL L(-1)) CO2 . Elevated CO2 significantly (P < 0.05) increased Pn (105%-149%), Pnmax (38.8%-63.0%) and AQY (20.0%-34.8%) of S. alfredii in all the Cd treatments, but reduced chlorophyll concentration, dark respiration and photorespiration. After 10 days growth in medium with 50 µM Cd under elevated CO2 , PSII activities were significantly enhanced (P < 0.05) with Pm, Fv/Fm, Φ(II) and qP increased by 66.1%, 7.5%, 19.5% and 16.4%, respectively, as compared with ambient-grown plants. Total Cd uptake in shoot of S. alfredii grown under elevated CO2 was increased by 44.1%-48.5%, which was positively correlated with the increase in Pn. These results indicate that elevated CO2 promoted the growth of S. alfredii due to increased photosynthetic carbon uptake rate and photosynthetic light-use efficiency, and showed great potential to improve the phytoextraction of Cd by S. alfredii. © 2014 Institute of Botany, Chinese Academy of Sciences.

  9. State transitions--the molecular remodeling of photosynthetic supercomplexes that controls energy flow in the chloroplast.

    Science.gov (United States)

    Minagawa, Jun

    2011-08-01

    In oxygen-evolving photosynthesis, the two photosystems-photosystem I and photosystem II-function in parallel, and their excitation levels must be balanced to maintain an optimal photosynthetic rate under natural light conditions. State transitions in photosynthetic organisms balance the absorbed light energy between the two photosystems in a short time by relocating light-harvesting complex II proteins. For over a decade, the understanding of the physiological consequences, the molecular mechanism, and its regulation has increased considerably. After providing an overview of the general understanding of state transitions, this review focuses on the recent advances of the molecular aspects of state transitions with a particular emphasis on the studies using the green alga Chlamydomonas reinhardtii. This article is part of a Special Issue entitled: Regulation of Electron Transport in Chloroplasts. Copyright © 2010 Elsevier B.V. All rights reserved.

  10. 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 C3 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/Ci 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 (Vc,max) and photosynthetic rate (Amax). On the other hand, limitation of stomatal or mesophyll CO2 diffusion did not impair fast recovery, maintaining Vc,max, chloroplast CO2 concentration (Cc) and mesophyll conductance (gm) unchanged while electron flow used for RuBP carboxylation (Jc) and Amax increased. The ability to tolerate drought stress and the fast recovery of this evergreen C3 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.

  11. Importance of Fluctuations in Light on Plant Photosynthetic Acclimation1[OPEN

    Science.gov (United States)

    2017-01-01

    The acclimation of plants to light has been studied extensively, yet little is known about the effect of dynamic fluctuations in light on plant phenotype and acclimatory responses. We mimicked natural fluctuations in light over a diurnal period to examine the effect on the photosynthetic processes and growth of Arabidopsis (Arabidopsis thaliana). High and low light intensities, delivered via a realistic dynamic fluctuating or square wave pattern, were used to grow and assess plants. Plants subjected to square wave light had thicker leaves and greater photosynthetic capacity compared with fluctuating light-grown plants. This, together with elevated levels of proteins associated with electron transport, indicates greater investment in leaf structural components and photosynthetic processes. In contrast, plants grown under fluctuating light had thinner leaves, lower leaf light absorption, but maintained similar photosynthetic rates per unit leaf area to square wave-grown plants. Despite high light use efficiency, plants grown under fluctuating light had a slow growth rate early in development, likely due to the fact that plants grown under fluctuating conditions were not able to fully utilize the light energy absorbed for carbon fixation. Diurnal leaf-level measurements revealed a negative feedback control of photosynthesis, resulting in a decrease in total diurnal carbon assimilated of at least 20%. These findings highlight that growing plants under square wave growth conditions ultimately fails to predict plant performance under realistic light regimes and stress the importance of considering fluctuations in incident light in future experiments that aim to infer plant productivity under natural conditions in the field. PMID:28184008

  12. 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.

  13. Energy transfer dynamics in an RC-LH1-PufX tubular photosynthetic membrane

    Science.gov (United States)

    Hsin, J.; Strümpfer, J.; Şener, M.; Qian, P.; Hunter, C. N.; Schulten, K.

    2010-08-01

    Light absorption and the subsequent transfer of excitation energy are the first two steps in the photosynthetic process, carried out by protein-bound pigments, mainly bacteriochlorophylls (BChls), in photosynthetic bacteria. BChls are anchored in light-harvesting (LH) complexes, such as light-harvesting complex I (LH1), which directly associates with the reaction center (RC), forming the RC-LH1 core complex. In Rhodobacter sphaeroides, RC-LH1 core complexes contain an additional protein, PufX, and assemble into dimeric RC-LH1-PufX core complexes. In the absence of LH complex II (LH2), the former complexes can aggregate into a helically ordered tubular photosynthetic membrane. We have examined the excitation transfer dynamics in a single RC-LH1-PufX core complex dimer using the hierarchical equations of motion for dissipative quantum dynamics that accurately, yet in a computationally costly manner, treat the coupling between BChls and their protein environment. A widely employed description, the generalized Förster (GF) theory, was also used to calculate the transfer rates of the same excitonic system in order to verify the accuracy of this computationally cheap method. Additionally, in light of the structural uncertainties in the Rba. sphaeroides RC-LH1-PufX core complex, geometrical alterations were introduced into the BChl organization. It is shown that the energy transfer dynamics are not affected by the considered changes in the BChl organization and that the GF theory provides accurate transfer rates. An all-atom model for a tubular photosynthetic membrane is then constructed on the basis of electron microscopy data, and the overall energy transfer properties of this membrane are computed.

  14. Multidisciplinary Research on Canopy Photosynthetic Productivity in a Cool-Temperate Deciduous Broadleaf Forest in Japan

    Science.gov (United States)

    Muraoka, H.; Noda, H. M.; Saitoh, T. M.; Nagai, S.

    2014-12-01

    Forest canopy has crucial roles in regulating energy and material exchange between the atmosphere and terrestrial ecosystems and in ecological processes with respect to carbon cycle and growth in the ecosystems. Challenges to the canopy of tall forests for such research involve the access to the leaves for ecophysiological observations, responses of leaves to the changing environments from seconds to years, and up-scaling the leaf-level phenomena to canopy and landscape-levels. A long-term, multidisciplinary approach has been conducted in a cool-temperate deciduous broadleaf forest in Takayama site (ca. 1400m a.s.l.) in central Japan. This forest canopy is dominated by Quercus crispula and Betula ermanii. We have been focusing on the phenology of photosynthetic productivity from a single leaf to canopy, and to landscape level, by combining leaf ecophysiological research, optical observations by spectroradiometers and time-laps cameras with the aid of "Phenological Eyes Network (PEN)", and process-based modellings. The canopy-level photosynthesis is then compared with the micrometeorolgical observation of CO2 flux at the site. So far we have been clarifying that (1) inter-annual variations in seasonal growth rate and senescence rate of leaf photosynthetic capacity and canopy leaf area are largely responsible for the inter-annual change in forest photosynthesis, and (2) spectral vegetation indices such as enhanced vegetation index (EVI) and chlorophyll index (CCI) can be the indicator to observe the phenology of forest canopy photosynthesis. In addition to these efforts since 2003, we established an open-field warming experiment on the branches of the canopy trees, to investigate the possible influence of temperature increase on leaf photosynthetic and optical properties and then to examine whether the optical satellite remote sensing can detect the changes in photosynthetic capacity and phenology by ongoing global warming.

  15. 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

  16. 26 CFR 1.904(f)-3 - Allocation of net operating losses and net capital losses.

    Science.gov (United States)

    2010-04-01

    ... 26 Internal Revenue 9 2010-04-01 2010-04-01 false Allocation of net operating losses and net....904(f)-3 Allocation of net operating losses and net capital losses. For rules relating to the allocation of net operating losses and net capital losses, see § 1.904(g)-3T. ...

  17. 29 CFR 4204.13 - Net income and net tangible assets tests.

    Science.gov (United States)

    2010-07-01

    ... 29 Labor 9 2010-07-01 2010-07-01 false Net income and net tangible assets tests. 4204.13 Section....13 Net income and net tangible assets tests. (a) General. The criteria under this section are that either— (1) Net income test. The purchaser's average net income after taxes for its three most recent...

  18. Biome-specific effects of nitrogen and phosphorus on the photosynthetic characteristics of trees at a forest-savanna boundary in Cameroon.

    Science.gov (United States)

    Domingues, Tomas Ferreira; Ishida, F Yoko; Feldpausch, Ted R; Grace, John; Meir, Patrick; Saiz, Gustavo; Sene, Olivier; Schrodt, Franziska; Sonké, Bonaventure; Taedoumg, Herman; Veenendaal, Elmar M; Lewis, Simon; Lloyd, Jon

    2015-07-01

    Photosynthesis/nutrient relationships of proximally growing forest and savanna trees were determined in an ecotonal region of Cameroon (Africa). Although area-based foliar N concentrations were typically lower for savanna trees, there was no difference in photosynthetic rates between the two vegetation formation types. Opposite to N, area-based P concentrations were-on average-slightly lower for forest trees; a dependency of photosynthetic characteristics on foliar P was only evident for savanna trees. Thus savanna trees use N more efficiently than their forest counterparts, but only in the presence of relatively high foliar P. Along with some other recent studies, these results suggest that both N and P are important modulators of woody tropical plant photosynthetic capacities, influencing photosynthetic metabolism in different ways that are also biome specific. Attempts to find simple unifying equations to describe woody tropical vegetation photosynthesis-nutrient relationships are likely to meet with failure, with ecophysiological distinctions between forest and savanna requiring acknowledgement.

  19. Elementary Energy Transfer Pathways in Allochromatium vinosum Photosynthetic Membranes

    Energy Technology Data Exchange (ETDEWEB)

    Lüer, Larry; Carey, Anne-Marie; Henry, Sarah; Maiuri, Margherita; Hacking, Kirsty; Polli, Dario; Cerullo, Giulio; Cogdell, Richard J.

    2015-11-01

    Allochromatium vinosum (formerly Chromatium vinosum) purple bacteria are known to adapt their light-harvesting strategy during growth according to environmental factors such as temperature and average light intensity. Under low light illumination or low ambient temperature conditions, most of the LH2 complexes in the photosynthetic membranes form a B820 exciton with reduced spectral overlap with LH1. To elucidate the reason for this light and temperature adaptation of the LH2 electronic structure, we performed broadband femtosecond transient absorption spectroscopy as a function of excitation wavelength in A. vinosum membranes. A target analysis of the acquired data yielded individual rate constants for all relevant elementary energy transfer (ET) processes. We found that the ET dynamics in high-light-grown membranes was well described by a homogeneous model, with forward and backward rate constants independent of the pump wavelength. Thus, the overall B800→B850→B890→ Reaction Center ET cascade is well described by simple triexponential kinetics. In the low-light-grown membranes, we found that the elementary backward transfer rate constant from B890 to B820 was strongly reduced compared with the corresponding constant from B890 to B850 in high-light-grown samples. The ET dynamics of low-light-grown membranes was strongly dependent on the pump wavelength, clearly showing that the excitation memory is not lost throughout the exciton lifetime. The observed pump energy dependence of the forward and backward ET rate constants suggests exciton diffusion via B850→ B850 transfer steps, making the overall ET dynamics nonexponential. Our results show that disorder plays a crucial role in our understanding of low-light adaptation in A. vinosum.

  20. Elementary Energy Transfer Pathways in Allochromatium vinosum Photosynthetic Membranes

    Science.gov (United States)

    Lüer, Larry; Carey, Anne-Marie; Henry, Sarah; Maiuri, Margherita; Hacking, Kirsty; Polli, Dario; Cerullo, Giulio; Cogdell, Richard J.

    2015-01-01

    Allochromatium vinosum (formerly Chromatium vinosum) purple bacteria are known to adapt their light-harvesting strategy during growth according to environmental factors such as temperature and average light intensity. Under low light illumination or low ambient temperature conditions, most of the LH2 complexes in the photosynthetic membranes form a B820 exciton with reduced spectral overlap with LH1. To elucidate the reason for this light and temperature adaptation of the LH2 electronic structure, we performed broadband femtosecond transient absorption spectroscopy as a function of excitation wavelength in A. vinosum membranes. A target analysis of the acquired data yielded individual rate constants for all relevant elementary energy transfer (ET) processes. We found that the ET dynamics in high-light-grown membranes was well described by a homogeneous model, with forward and backward rate constants independent of the pump wavelength. Thus, the overall B800→B850→B890→ Reaction Center ET cascade is well described by simple triexponential kinetics. In the low-light-grown membranes, we found that the elementary backward transfer rate constant from B890 to B820 was strongly reduced compared with the corresponding constant from B890 to B850 in high-light-grown samples. The ET dynamics of low-light-grown membranes was strongly dependent on the pump wavelength, clearly showing that the excitation memory is not lost throughout the exciton lifetime. The observed pump energy dependence of the forward and backward ET rate constants suggests exciton diffusion via B850→ B850 transfer steps, making the overall ET dynamics nonexponential. Our results show that disorder plays a crucial role in our understanding of low-light adaptation in A. vinosum. PMID:26536265

  1. 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.

  2. 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.

  3. Photocurrent of a single photosynthetic protein

    Science.gov (United States)

    Gerster, Daniel; Reichert, Joachim; Bi, Hai; Barth, Johannes V.; Kaniber, Simone M.; Holleitner, Alexander W.; Visoly-Fisher, Iris; Sergani, Shlomi; Carmeli, Itai

    2012-10-01

    Photosynthesis is used by plants, algae and bacteria to convert solar energy into stable chemical energy. The initial stages of this process--where light is absorbed and energy and electrons are transferred--are mediated by reaction centres composed of chlorophyll and carotenoid complexes. It has been previously shown that single small molecules can be used as functional components in electric and optoelectronic circuits, but it has proved difficult to control and probe individual molecules for photovoltaic and photoelectrochemical applications. Here, we show that the photocurrent generated by a single photosynthetic protein--photosystem I--can be measured using a scanning near-field optical microscope set-up. One side of the protein is anchored to a gold surface that acts as an electrode, and the other is contacted by a gold-covered glass tip. The tip functions as both counter electrode and light source. A photocurrent of ~10 pA is recorded from the covalently bound single-protein junctions, which is in agreement with the internal electron transfer times of photosystem I.

  4. Antenna organization in green photosynthetic bacteria

    Energy Technology Data Exchange (ETDEWEB)

    Blankenship, R.E.

    1987-01-01

    This project is concerned with the structure and function of the unique antenna system found in the green photosynthetic bacteria. The antenna system in these organisms is contained within a vesicle known as a chlorosome, which is attached to the cytoplasmic side of the cell membrane. Additional antenna pigments and reaction centers are contained in integral membrane proteins. Energy absorbed by the bacteriochlorophyll c (BChl c) pigments in the chlorosome is transferred via a baseplate'' array of BChl a antenna pigments into the membrane and to the reaction center. This system is similar in some respects to the phycobilisome antenna system found in cyanobacteria and some types of algae, in that a membrane-associated structure absorbs light and transfers it to the membrane where conversion to chemical energy takes place. However, the overall structure, the type of pigments utilized and the nature of the proteins in these two types of membrane-associated antenna bodies are entirely different, and they clearly represent two independent evolutionary solutions to the problem of light collection and excitation transfer.

  5. Mass distribution of free insecticide-treated nets do not interfere with continuous net distribution in Tanzania.

    Science.gov (United States)

    Eze, Ikenna C; Kramer, Karen; Msengwa, Amina; Mandike, Renata; Lengeler, Christian

    2014-05-27

    To protect the most vulnerable groups from malaria (pregnant women and infants) the Tanzanian Government introduced a subsidy (voucher) scheme in 2004, on the basis of a public-private partnership. These vouchers are provided to pregnant women at their first antenatal care visit and mothers of infants at first vaccination. The vouchers are redeemed at registered retailers for a long-lasting insecticidal net against the payment of a modest top-up price. The present work analysed a large body of data from the Tanzanian National Voucher Scheme, focusing on interactions with concurrent mass distribution campaigns of free nets. In an ecologic study involving all regions of Tanzania, voucher redemption data for the period 2007-2011, as well as data on potential determinants of voucher redemption were analysed. The four outcome variables were: pregnant woman and infant voucher redemption rates, use of treated bed nets by all household members and by under- five children. Each of the outcomes was regressed with selected determinants, using a generalized estimating equation model and accounting for regional data clustering. There was a consistent improvement in voucher redemption rates over the selected time period, with rates >80% in 2011. The major determinants of redemption rates were the top-up price paid by the voucher beneficiary, the retailer- clinic ratio, and socio-economic status. Improved redemption rates after 2009 were most likely due to reduced top-up prices (following a change in policy). Redemption rates were not affected by two major free net distribution campaigns. During this period, there was a consistent improvement in net use across all the regions, with rates of up to 75% in 2011. The key components of the National Treated Nets Programme (NATNETS) seem to work harmoniously, leading to a high level of net use in the entire population. This calls for the continuation of this effort in Tanzania and for emulation by other countries with endemic malaria.

  6. Daily variation in net primary production and net calcification in coral reef communities exposed to elevated pCO2

    Science.gov (United States)

    Comeau, Steeve; Edmunds, Peter J.; Lantz, Coulson A.; Carpenter, Robert C.

    2017-07-01

    The threat represented by ocean acidification (OA) for coral reefs has received considerable attention because of the sensitivity of calcifiers to changing seawater carbonate chemistry. However, most studies have focused on the organismic response of calcification to OA, and only a few have addressed community-level effects, or investigated parameters other than calcification, such as photosynthesis. Light (photosynthetically active radiation, PAR) is a driver of biological processes on coral reefs, and the possibility that these processes might be perturbed by OA has important implications for community function. Here we investigate how CO2 enrichment affects the relationships between PAR and community net O2 production (Pnet), and between PAR and community net calcification (Gnet), using experiments on three coral communities constructed to match (i) the back reef of Mo'orea, French Polynesia, (ii) the fore reef of Mo'orea, and (iii) the back reef of O'ahu, Hawaii. The results were used to test the hypothesis that OA affects the relationship between Pnet and Gnet. For the three communities tested, pCO2 did not affect the Pnet-PAR relationship, but it affected the intercept of the hyperbolic tangent curve fitting the Gnet-PAR relationship for both reef communities in Mo'orea (but not in O'ahu). For the three communities, the slopes of the linear relationships between Pnet and Gnet were not affected by OA, although the intercepts were depressed by the inhibitory effect of high pCO2 on Gnet. Our result indicates that OA can modify the balance between net calcification and net photosynthesis of reef communities by depressing community calcification, but without affecting community photosynthesis.

  7. Daily variation in net primary production and net calcification in coral reef communities exposed to elevated pCO2

    Directory of Open Access Journals (Sweden)

    S. Comeau

    2017-07-01

    Full Text Available The threat represented by ocean acidification (OA for coral reefs has received considerable attention because of the sensitivity of calcifiers to changing seawater carbonate chemistry. However, most studies have focused on the organismic response of calcification to OA, and only a few have addressed community-level effects, or investigated parameters other than calcification, such as photosynthesis. Light (photosynthetically active radiation, PAR is a driver of biological processes on coral reefs, and the possibility that these processes might be perturbed by OA has important implications for community function. Here we investigate how CO2 enrichment affects the relationships between PAR and community net O2 production (Pnet, and between PAR and community net calcification (Gnet, using experiments on three coral communities constructed to match (i the back reef of Mo'orea, French Polynesia, (ii the fore reef of Mo'orea, and (iii the back reef of O'ahu, Hawaii. The results were used to test the hypothesis that OA affects the relationship between Pnet and Gnet. For the three communities tested, pCO2 did not affect the Pnet–PAR relationship, but it affected the intercept of the hyperbolic tangent curve fitting the Gnet–PAR relationship for both reef communities in Mo'orea (but not in O'ahu. For the three communities, the slopes of the linear relationships between Pnet and Gnet were not affected by OA, although the intercepts were depressed by the inhibitory effect of high pCO2 on Gnet. Our result indicates that OA can modify the balance between net calcification and net photosynthesis of reef communities by depressing community calcification, but without affecting community photosynthesis.

  8. 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

  9. Cultivar variation in cotton photosynthetic performance under different temperature regimes

    Science.gov (United States)

    Cotton (Gossypium hirsutum L.) yields are impacted by overall photosynthetic production. Factors that influence crop photosynthesis are the plants genetic makeup and the environmental conditions. This study investigated cultivar variation in photosynthesis when plants were grown in the field under...

  10. 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

  11. Quantifying the effects of light intensity on bioproduction and maintenance energy during photosynthetic growth of Rhodobacter sphaeroides.

    Science.gov (United States)

    Imam, Saheed; Fitzgerald, Colin M; Cook, Emily M; Donohue, Timothy J; Noguera, Daniel R

    2015-02-01

    Obtaining a better understanding of the physiology and bioenergetics of photosynthetic microbes is an important step toward optimizing these systems for light energy capture or production of valuable commodities. In this work, we analyzed the effect of light intensity on bioproduction, biomass formation, and maintenance energy during photoheterotrophic growth of Rhodobacter sphaeroides. Using data obtained from steady-state bioreactors operated at varying dilution rates and light intensities, we found that irradiance had a significant impact on biomass yield and composition, with significant changes in photopigment, phospholipid, and biopolymer storage contents. We also observed a linear relationship between incident light intensity and H2 production rate between 3 and 10 W m(-2), with saturation observed at 100 W m(-2). The light conversion efficiency to H2 was also higher at lower light intensities. Photosynthetic maintenance energy requirements were also significantly affected by light intensity, with links to differences in biomass composition and the need to maintain redox homeostasis. Inclusion of the measured condition-dependent biomass and maintenance energy parameters and the measured photon uptake rate into a genome-scale metabolic model for R. sphaeroides (iRsp1140) significantly improved its predictive performance. We discuss how our analyses provide new insights into the light-dependent changes in bioenergetic requirements and physiology during photosynthetic growth of R. sphaeroides and potentially other photosynthetic organisms.

  12. Influence on photosynthesis of starlight, moonlight, planetlight, and light pollution (reflections on photosynthetically active radiation in the universe).

    Science.gov (United States)

    Raven, J A; Cockell, C S

    2006-08-01

    Photosynthesis on Earth can occur in a diversity of organisms in the photosynthetically active radiation (PAR) range of 10 nmol of photons m(-2) s(-1) to 8 mmol of photons m(-2) s(-1). Similar considerations would probably apply to photosynthetic organisms on Earth-like planets (ELPs) in the continuously habitable zone of other stars. On Earth, starlight PAR is inadequate for photosynthetically supported growth. An increase in starlight even to reach the minimum theoretical levels to allow for photosynthesis would require a universe that was approximately ten million times older, or with a ten million times greater density of stars, than is the case for the present universe. Photosynthesis on an ELP using PAR reflected from a natural satellite with the same size as our Moon, but at the Roche limit, could support a low rate of photosynthesis at full Moon. Photosynthesis on an ELP-like satellite of a Jupiter-sized planet using light reflected from the planet could be almost 1% of the rate in full sunlight on Earth when the planet was full. These potential contributions to photosynthesis require that the contribution is compared with the rate of photosynthesis driven by direct radiation from the star. Light pollution on Earth only energizes photosynthesis by organisms that are very close to the light source. However, effects of light pollution on photosynthesis can be more widespread if the photosynthetic canopy is retained for more of the year, caused by effects on photoperiodism, with implications for the influence of civilizations on photosynthesis.

  13. Engineering photosynthetic organisms for the production of biohydrogen

    OpenAIRE

    Dubini, Alexandra; Ghirardi, Maria L.

    2014-01-01

    Oxygenic photosynthetic organisms such as green algae are capable of absorbing sunlight and converting the chemical energy into hydrogen gas. This process takes advantage of the photosynthetic apparatus of these organisms which links water oxidation to H2 production. Biological H2 has therefore the potential to be an alternative fuel of the future and shows great promise for generating large scale sustainable energy. Microalgae are able to produce H2 under light anoxic or dark anoxic conditio...

  14. 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

  15. 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.

  16. Multiple independent constraints help resolve net ecosystem carbon exchange under nutrient limitation

    Science.gov (United States)

    Thornton, P. E.; Metcalfe, D.; Oren, R.; Ricciuto, D. M.

    2014-12-01

    The magnitude, spatial distribution, and variability of land net ecosystem exchange of carbon (NEE) are important determinants of the trajectory of atmospheric carbon dioxide concentration. Independent observational constraints provide important clues regarding NEE and its component fluxes, with information available at multiple spatial scales: from cells, to leaves, to entire organisms and collections of organisms, to complex landscapes and up to continental and global scales. Experimental manipulations, ecosystem observations, and process modeling all suggest that the components of NEE (photosynthetic gains, and respiration and other losses) are controlled in part by the availability of mineral nutrients, and that nutrient limitation is a common condition in many biomes. Experimental and observational constraints at different spatial scales provide a complex and sometimes puzzling picture of the nature and degree of influence of nutrient availability on carbon cycle processes. Photosynthetic rates assessed at the cellular and leaf scales are often higher than the observed accumulation of carbon in plant and soil pools would suggest. We infer that a down-regulation process intervenes between carbon uptake and plant growth under conditions of nutrient limitation, and several down-regulation mechanisms have been hypothesized and tested. A recent evaluation of two alternative hypotheses for down-regulation in the light of whole-plant level flux estimates indicates that some plants take up and store extra carbon, releasing it to the environment again on short time scales. The mechanism of release, either as additional autotrophic respiration or as exudation belowground is unclear, but has important consequences for long-term ecosystem state and response to climate change signals. Global-scale constraints from atmospheric concentration and isotopic composition data help to resolve this question, ultimately focusing attention on land use fluxes as the most uncertain

  17. Impact of cloudiness on net ecosystem exchange of carbon dioxide in different types of forest ecosystems in China

    Directory of Open Access Journals (Sweden)

    M. Zhang

    2010-02-01

    Full Text Available Clouds can significantly affect carbon exchange process between forest ecosystems and the atmosphere by influencing the quantity and quality of solar radiation received by ecosystem's surface and other environmental factors. In this study, we analyzed the effects of cloudiness on net ecosystem exchange of carbon dioxide (NEE in a temperate broad-leaved Korean pine mixed forest at Changbaishan (CBS and a subtropical evergreen broad-leaved forest at Dinghushan (DHS, based on the flux data obtained during June–August from 2003 to 2006. The results showed that the response of NEE of forest ecosystems to photosynthetically active radiation (PAR differed under clear skies and cloudy skies. Compared with clear skies, the light-saturated maximum photosynthetic rate (Pec,max at CBS under cloudy skies during mid-growing season (from June to August increased by 34%, 25%, 4% and 11% in 2003, 2004, 2005 and 2006, respectively. In contrast, Pec,max of the forest ecosystem at DHS was higher under clear skies than under cloudy skies from 2004 to 2006. When the clearness index (kt ranged between 0.4 and 0.6, the NEE reached its maximum at both CBS and DHS. However, the NEE decreased more dramatically at CBS than at DHS when kt exceeded 0.6. The results indicate that cloudy sky conditions are beneficial to net carbon uptake in the temperate forest ecosystem and the subtropical forest ecosystem. Under clear skies, vapor pressure deficit (VPD and air temperature increased due to strong light. These environmental conditions led to greater decrease in gross ecosystem photosynthesis (GEP and greater increase in ecosystem respiration (Re at CBS than at DHS. As a result, clear sky conditions caused more reduction of NEE in the temperate forest ecosystem than in the subtropical forest ecosystem. The response of NEE of different forest ecosystems to the changes in

  18. Contributions of photosynthetic and non-photosynthetic cell types to leaf respiration in Vicia faba L. and their responses to growth temperature.

    Science.gov (United States)

    Long, Benedict M; Bahar, Nur H A; Atkin, Owen K

    2015-11-01

    In intact leaves, mitochondrial populations are highly heterogeneous among contrasting cell types; how such contrasting populations respond to sustained changes in the environment remains, however, unclear. Here, we examined respiratory rates, mitochondrial protein composition and response to growth temperature in photosynthetic (mesophyll) and non-photosynthetic (epidermal) cells from fully expanded leaves of warm-developed (WD) and cold-developed (CD) broad bean (Vicia faba L.). Rates of respiration were significantly higher in mesophyll cell protoplasts (MCPs) than epidermal cell protoplasts (ECPs), with both protoplast types exhibiting capacity for cytochrome and alternative oxidase activity. Compared with ECPs, MCPs contained greater relative quantities of porin, suggesting higher mitochondrial surface area in mesophyll cells. Nevertheless, the relative quantities of respiratory proteins (normalized to porin) were similar in MCPs and ECPs, suggesting that ECPs have lower numbers of mitochondria yet similar protein complement to MCP mitochondria (albeit with lower abundance serine hydroxymethyltransferase). Several mitochondrial proteins (both non-photorespiratory and photorespiratory) exhibited an increased abundance in response to cold in both protoplast types. Based on estimates of individual protoplast respiration rates, combined with leaf cell abundance data, epidermal cells make a small but significant (2%) contribution to overall leaf respiration which increases twofold in the cold. Taken together, our data highlight the heterogeneous nature of mitochondrial populations in leaves, both among contrasting cell types and in how those populations respond to growth temperature. © 2015 John Wiley & Sons Ltd.

  19. Engineering analysis of potential photosynthetic bacterial hydrogen-production systems

    Science.gov (United States)

    Herlevich, A.; Karpuk, M. E.

    1982-06-01

    Photosynthetic bacteria (PSB) are capable of generating hydrogen from organics in effluents from food processing, pulp and paper, and chemical and pharmaceutical industries. Hydrogen evolution takes place under light in the absence of air. The rate of hydrogen production is expected to range between 300 to 600 scf of hydrogen per 1000 galloons of waste stream treated per hour. This hydrogen production system has been demonstrated at a bench-scale level and is ready for engineering development. A conceptual design for a PSB hydrogen production system is described. The system is expected to be sited adjacent to a waste stream source which will be pretreated by fermentation and pH adjustment, innoculated with bacteria, and then passed into the reactor. The reactor effluent can either be discharged into a rapid infiltration system, an irrigation ditch, and/or recycled back into the reactor. Several potential reactor designs have been developed, analyzed, and costed. A large covered pond appears to be the most economical design approach.

  20. Spatial distribution of leaf nitrogen and photosynthetic capacity within the foliage of individual trees: disentangling the effects of local light quality, leaf irradiance, and transpiration.

    Science.gov (United States)

    Frak, Ela; Le Roux, Xavier; Millard, Peter; Adam, Boris; Dreyer, Erwin; Escuit, Cynthia; Sinoquet, Hervé; Vandame, Marc; Varlet-Grancher, Claude

    2002-11-01

    There is presently no consensus about the factor(s) driving photosynthetic acclimation and the intra-canopy distribution of leaf characteristics under natural conditions. The impact was tested of local (i) light quality (red/far red ratio), (ii) leaf irradiance (PPFD(i)), and (iii) transpiration rate (E) on total non-structural carbohydrates per leaf area (TNC(a)), TNC-free leaf mass-to-area ratio (LMA), total leaf nitrogen per leaf area (N(a)), photosynthetic capacity (maximum carboxylation rate and light-saturated electron transport rate), and leaf N partitioning between carboxylation and bioenergetics within the foliage of young walnut trees grown outdoors. Light environment (quantity and quality) was controlled by placing individual branches under neutral or green screens during spring growth, and air vapour pressure deficit (VPD) was prescribed and leaf transpiration and photosynthesis measured at branch level by a branch bag technique. Under similar levels of leaf irradiance, low air vapour pressure deficit decreased transpiration rate but did not influence leaf characteristics. Close linear relationships were detected between leaf irradiance and leaf N(a), LMA or photosynthetic capacity, and low R/FR ratio decreased leaf N(a), LMA and photosynthetic capacity. Irradiance and R/FR also influenced the partitioning of leaf nitrogen into carboxylation and electron light transport. Thus, local light level and quality are the major factors driving photosynthetic acclimation and intra-canopy distribution of leaf characteristics, whereas local transpiration rate is of less importance.

  1. Starch Content in Leaf Sheath Controlled by CO2-Responsive CCT Protein is a Potential Determinant of Photosynthetic Capacity in Rice.

    Science.gov (United States)

    Morita, Ryutaro; Inoue, Kanako; Ikeda, Ken-Ichi; Hatanaka, Tomoko; Misoo, Shuji; Fukayama, Hiroshi

    2016-11-01

    CO2-responsive CCT protein (CRCT) is the suggested positive regulator of starch synthesis in vegetative organs, particularly the leaf sheath of rice. In this study, we analyzed the effects of the starch level in the leaf sheath on the photosynthetic rate in the leaf blade using CRCT overexpression and RNA interference (RNAi) knockdown transgenic rice grown under ambient (38 Pa) or elevated (100 Pa) CO2 conditions. In leaf sheath, the starch content was markedly changed in relation to CRCT expression levels under both CO2 conditions. In contrast, the soluble sugar and starch contents of the leaf blade were markedly increased in the knockdown line grown under elevated CO2 conditions. The overexpression or RNAi knockdown of CRCT did not cause large effects on the photosynthetic rate of the transgenic lines grown under ambient CO2 condition. However, the photosynthetic rate of the overexpression line was enhanced, while that of the knockdown line was substantially decreased under elevated CO2 conditions. These photosynthetic rates were weakly correlated with the nitrogen contents and negatively correlated with the total non-structural carbohydrate contents. Thus, the capacity for starch synthesis in leaf sheath, which is controlled by CRCT, can indirectly affect the carbohydrate content, and then the photosynthetic rate in the leaf blade of rice grown under elevated CO2 conditions. © The Author 2016. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

  2. Low-temperature leaf photosynthesis of a Miscanthus germplasm collection correlates positively to shoot growth rate and specific leaf area.

    Science.gov (United States)

    Jiao, Xiurong; Kørup, Kirsten; Andersen, Mathias Neumann; Petersen, Karen Koefoed; Prade, Thomas; Jeżowski, Stanisław; Ornatowski, Szymon; Górynowicz, Barbara; Spitz, Idan; Lærke, Poul Erik; Jørgensen, Uffe

    2016-06-01

    The C4 perennial grass miscanthus has been found to be less sensitive to cold than most other C4 species, but still emerges later in spring than C3 species. Genotypic differences in miscanthus were investigated to identify genotypes with a high cold tolerance at low temperatures and quick recovery upon rising temperatures to enable them to exploit the early growing season in maritime cold climates. Suitable methods for field screening of cold tolerance in miscanthus were also identified. Fourteen genotypes of M. sacchariflorus, M. sinensis, M. tinctorius and M. × giganteus were selected and grown under warm (24 °C) and cold (14 °C) conditions in a controlled environment. Dark-adapted chlorophyll fluorescence, specific leaf area (SLA) and net photosynthetic rate at a photosynthetically active radiation (PAR) of 1000 μmol m(-2) s(-1) (A1000) were measured. Photosynthetic light and CO2 response curves were obtained from 11 of the genotypes, and shoot growth rate was measured under field conditions. A positive linear relationship was found between SLA and light-saturated photosynthesis (Asat) across genotypes, and also between shoot growth rate under cool field conditions and A1000 at 14 °C in a climate chamber. When lowering the temperature from 24 to 14 °C, one M. sacchariflorus exhibited significantly higher Asat and maximum photosynthetic rate in the CO2 response curve (Vmax) than other genotypes at 14 °C, except M × giganteus 'Hornum'. Several genotypes returned to their pre-chilling A1000 values when the temperature was increased to 24 °C after 24 d growth at 14 °C. One M. sacchariflorus genotype had similar or higher photosynthetic capacity than M × giganteus, and may be used for cultivation together with M × giganteus or for breeding new interspecies hybrids with improved traits for temperate climates. Two easily measured variables, SLA and shoot growth rate, may be useful for genotype screening of productivity and cold tolerance. © The

  3. On thermodynamic inconsistencies in several photosynthetic and solar cell models and how to fix them.

    Science.gov (United States)

    Gelbwaser-Klimovsky, David; Aspuru-Guzik, Alán

    2017-02-01

    We analyze standard theoretical models of solar energy conversion developed to study solar cells and photosynthetic systems. We show that assuming the energy transfer to the reaction center/electric circuit is through a decay rate or "sink", contradicts the second law of thermodynamics. We put forward a thermodynamically consistent alternative by explicitly considering parts of the reaction center/electric circuit and by employing a Hamiltonian transfer. The predicted energy transfer by the new scheme differs from the one found using a decay rate, casting doubts on the validity of the conclusions obtained by models which include the latter.

  4. Photosynthetically oxygenated salicylate biodegradation in a continuous stirred tank photobioreactor.

    Science.gov (United States)

    Muñoz, Raul; Köllner, Claudia; Guieysse, Benoit; Mattiasson, Bo

    2004-09-20

    A consortium consisting of a Chlorella sorokiniana strain and a Ralstonia basilensis strain was able to carry out sodium salicylate biodegradation in a continuous stirred tank reactor (CSTR) using exclusively photosynthetic oxygenation. Salicylate biodegradation depended on algal activity, which itself was a function of microalgal concentration, light intensity, and temperature. Biomass recirculation improved the photobioreactor performance by up to 44% but the results showed the existence of an optimal biomass concentration above which dark respiration started to occur and the process efficiency started to decline. The salicylate removal efficiency increased by a factor of 3 when illumination was increased from 50-300 microE/m2.s. In addition, the removal rate of sodium salicylate was shown to be temperature-dependent, increasing from 14 to 27 mg/l.h when the temperature was raised from 26.5 to 31.5 degrees C. Under optimized conditions (300 microE/m2.s, 30 degrees C, 1 g sodium salicylate/l in the feed and biomass recirculation) sodium salicylate was removed at a maximum constant rate of 87 mg/l.h, corresponding to an estimated oxygenation capacity of 77 mg O2/l.h (based on a BOD value of 0.88 g O2/g sodium salicylate for the tested bacterium), which is in the range of the oxygen transfer capacity of large-scale mechanical surface aerators. Thus, although higher degradation rates were attained in the control reactor, the photobioreactor is a cost-efficient process which reduces the cost of aeration and prevents volatilization problems associated with the degradation of toxic volatile organic compounds under aerobic conditions. Copyright 2004 Wiley Periodicals, Inc.

  5. Responses to sheep browsing at different stocking rates: water ...

    African Journals Online (AJOL)

    Keywods: botany; browsing; carbohydrates; carbon; carbon allocation; Eastern Sweet Grassveld; Eriocephalus ericoides; palatability; photosynthesis; polyphenols; Pteronia tricephala; response; semi-arid; sheep; shrubs; South Africa; stocking rates; water relations; acceptability; elevation; karoo; photosynthetic rate; plant ...

  6. TimeNET Optimization Environment

    Directory of Open Access Journals (Sweden)

    Christoph Bodenstein

    2015-12-01

    Full Text Available In this paper a novel tool for simulation-based optimization and design-space exploration of Stochastic Colored Petri nets (SCPN is introduced. The working title of this tool is TimeNET Optimization Environment (TOE. Targeted users of this tool are people modeling complex systems with SCPNs in TimeNET who want to find parameter sets that are optimal for a certain performance measure (fitness function. It allows users to create and simulate sets of SCPNs and to run different optimization algorithms based on parameter variation. The development of this tool was motivated by the need to automate and speed up tests of heuristic optimization algorithms to be applied for SCPN optimization. A result caching mechanism is used to avoid recalculations.

  7. A new setup for in vivo fluorescence imaging of photosynthetic activity.

    Science.gov (United States)

    Johnson, Xenie; Vandystadt, Guillaume; Bujaldon, Sandrine; Wollman, Francis-André; Dubois, Rémi; Roussel, Pierre; Alric, Jean; Béal, Daniel

    2009-10-01

    Here, we describe a new imaging setup able to assess in vivo photosynthetic activity. The system specifically measures time-resolved chlorophyll fluorescence in response to light. It is composed of a fast digital camera equipped with a wide-angle lens for the analysis of samples up to 10 x 10 cm, i.e. entire plants or petri dishes. In the choice of CCD, we have opted for a 12-bits high frame rate [150 fps (frames per second)] at the expense of definition (640 x 480 pixels). Although the choice of digital camera is always a compromise between these two related features, we have designed a flexible system allowing the fast sampling of images (down to 100 micros) with a maximum spatial resolution. This image readout system, synchronized with actinic light and saturating pulses, allows a precise determination of F(0) and F(M), which is required to monitor PSII activity. This new imaging system, together with image processing techniques, is useful to investigate the heterogeneity of photosynthetic activity within leaves or to screen large numbers of unicellular algal mutant colonies to identify those with subtle changes in photosynthetic electron flow.

  8. [Chloroplast ultrastructure and photosynthetic characteristics of five kinds of dandelion (Taraxacum) leaves in northeast China].

    Science.gov (United States)

    Ning, Wei; Wu, Jie; Zhao, Ting; Zhao, Xin; Li, Tianlai

    2012-05-01

    The paper adopted the JEM-100CX II transmission electron microscope to observe chloroplast ultrastructure of five kinds of dandelion (Taraxacum) leaves in northeast, and the LI-6400 portable photosynthesis system was used to compare the chlorophyll fluorescence and the photosynthesis characteristics of five kinds of dandelions in Northeast China. Chloroplast ultrastructure showed: in the five kinds of dandelion, larger chloroplast, grana with more layers, regular thylakoid, without starch grains and so on, these chloroplasts characteristics decided to bigger photosynthetic rate. The five kinds of dandelion P(n) exhibited a "double peak" diurnal curve: stomatal limitation is the main adjustment factors for the midday depression phenomenon. The P(n),G(s),C(i) content of T. mongolicum are the highest, and T. asiaticum are the lowest among them. The relation between P(n) and G(s),C(i) is direct ratio, P(n) and T(r) is in an inverse proportion among the five kinds of dandelion. In addition, P(n) is positively correlated with Chla, Chlb, and the relationship with Chlb is bigger. The paper demonstrates the Mongolian dandelion photosynthetic efficiency is the highest, it is an higher photosynthetic efficiency dandelion,it provide theoretical basis for assessment and use of the resource of dandelion.

  9. ASSESSMENT OF PHOTOSYNTHETIC PERFORMANCE OF PORPHYRA YEZOENSIS (BANGIALES, RHODOPHYTA) IN CONCHOCELIS PHASE(1).

    Science.gov (United States)

    Xu, Dong; Qiao, Hongjin; Zhu, Jianyi; Xu, Pu; Liang, Chengwei; Zhang, Xiaowen; Ye, Naihao; Yang, Wanxin

    2012-04-01

    Photosynthetic characteristics of four Porphyra yezoensis Ueda [a taxonomic synonym of Pyropia yezoensis (Ueda) M. S. Hwang et H. G. Choi] strains in conchocelis phase were investigated and compared with one wildtype of P. yezoensis and two strains of Porphyra haitanensis T. J. Chang et B. F. Zheng [a taxonomic synonym of Pyropia haitanensis (T. J. Chang et B. F. Zheng) N. Kikuchi et M. Miyata]. Results showed that experimental strains had higher contents of chl a and carotenoids, but a lower content of total phycobiliproteins than the wildtype. Meanwhile, photochemical efficiency of PSII was measured using pulse amplitude modulation (PAM) fluorometry technology. The value of PSII photosynthetic parameters of P. yezoensis strains were all higher than the wild strain, and the maximal quantum yields (Fv /Fm ), effective quantum yields Y(II), and relative photosynthetic electron transport rates (rETR) of P. haitanensis were higher than those of P. yezoensis. The present study verified the possibility of selective breeding of P. yezoensis using the filamentous sporophyte instead of the gametophytic thallus, the advantages being (i) nonrequirement of control of life cycle and (ii) direct and rapid cultivar improvement by artificial selection. We consider the method to be a promising technique for selective breeding of P. yezoensis cultivars. © 2012 Phycological Society of America.

  10. Plant water stress effects on the net dispersal rate of the insect vector Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae) and movement of its egg parasitoid, Gonatocerus ashmeadi Girault (Hymenoptera: Mymaridae)

    Science.gov (United States)

    Homalodisca vitripennis, one of the main vectors of Xylella fastidiosa, is associated with citrus plantings in California, USA. Infested citrus orchards act as a source of vectors to adjacent vineyards where X. fastidiosa causes Pierce’s disease (PD). An analysis of the pattern and rate of movement ...

  11. 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.

  12. Photosynthetic resource-use efficiency and demographic variability in desert winter annual plants.

    Science.gov (United States)

    Huxman, Travis E; Barron-Gafford, Greg; Gerst, Katharine L; Angert, Amy L; Tyler, Anna P; Venable, D Lawrence

    2008-06-01

    We studied a guild of desert winter annual plants that differ in long-term variation in per capita reproductive success (lb, the product of per capita survival from germination to reproduction, l, times per capita reproduction of survivors, b) to relate individual function to population and community dynamics. We hypothesized that variation in lb should be related to species' positions along a trade-off between relative growth rate (RGR) and photosynthetic water-use efficiency (WUE) because lb is a species-specific function of growing-season precipitation. We found that demographically variable species have greater RGR and greater leaf carbon isotope discrimination (Delta, a proxy inversely related to WUE). We examined leaf nitrogen and photosynthetic characteristics and found that, in this system, variation in Delta is a function of photosynthetic demand rather than stomatal regulation of water loss. The physiological characteristics that result in low Delta in some species may confer greater photosynthetic performance during the reliably moist but low temperature periods that immediately follow winter rainfall in the Sonoran Desert or alternatively during cool periods of the day or early growing season. Conversely, while species with high Delta and high RGR exhibit low leaf N, they have high biomass allocation to canopy leaf area display. Such trait associations may allow for greater performance during the infrequent conditions where high soil moisture persists into warmer conditions, resulting in high demographic variance. Alternatively, high variance could arise from specialization to warm periods of the day or season. Population dynamic buffering via stress tolerance (low RGR and Delta) correlates negatively with buffering via seed banks, as predicted by bet-hedging theory. By merging analyses of population dynamics with functional trait relationships, we develop a deeper understanding of the physiological, ecological, and evolutionary mechanisms involved in

  13. Implementing NetScaler VPX

    CERN Document Server

    Sandbu, Marius

    2014-01-01

    An easy-to-follow guide with detailed step-by step-instructions on how to implement the different key components in NetScaler, with real-world examples and sample scenarios.If you are a Citrix or network administrator who needs to implement NetScaler in your virtual environment to gain an insight on its functionality, this book is ideal for you. A basic understanding of networking and familiarity with some of the different Citrix products such as XenApp or XenDesktop is a prerequisite.

  14. Net4Care PHMR Library

    DEFF Research Database (Denmark)

    2014-01-01

    The Net4Care PHMR library contains a) A GreenCDA approach for constructing a data object representing a PHMR document: SimpleClinicalDocument, and b) A Builder which can produce a XML document representing a valid Danish PHMR (following the MedCom profile) document from the SimpleClinicalDocument......The Net4Care PHMR library contains a) A GreenCDA approach for constructing a data object representing a PHMR document: SimpleClinicalDocument, and b) A Builder which can produce a XML document representing a valid Danish PHMR (following the MedCom profile) document from the Simple...

  15. Pro DLR in NET 4

    CERN Document Server

    Wu, Chaur

    2011-01-01

    Microsoft's Dynamic Language Runtime (DLR) is a platform for running dynamic languages such as Ruby and Python on an equal footing with compiled languages such as C#. Furthermore, the runtime is the foundation for many useful software design and architecture techniques you can apply as you develop your .NET applications. Pro DLR in .NET 4 introduces you to the DLR, showing how you can use it to write software that combines dynamic and static languages, letting you choose the right tool for the job. You will learn the core DLR components such as LINQ expressions, call sites, binders, and dynami

  16. Hierarchies in Coloured Petri Nets

    DEFF Research Database (Denmark)

    Huber, Peter; Jensen, Kurt; Shapiro, Robert M.

    1991-01-01

    The paper shows how to extend Coloured Petri Nets with a hierarchy concept. The paper proposes five different hierarchy constructs, which allow the analyst to structure large CP-nets as a set of interrelated subnets (called pages). The paper discusses the properties of the proposed hierarchy...... constructs, and it illustrates them by means of two examples. The hierarchy constructs can be used for theoretical considerations, but their main use is to describe and analyse large real-world systems. All of the hierarchy constructs are supported by the editing and analysis facilities in the CPN Palette...

  17. Resistance of Arabidopsis thaliana L. photosynthetic apparatus to UV-B is reduced by deficit of phytochromes B and A.

    Science.gov (United States)

    Khudyakova, Aleksandra Yu; Kreslavski, Vladimir D; Shirshikova, Galina N; Zharmukhamedov, Sergey K; Kosobryukhov, Anatoly A; Allakhverdiev, Suleyman I

    2017-04-01

    The photosynthetic responses of 25-day-old Arabidopsis phyA phyB double mutant (DM) compared with the wild type (WT) to UV-B radiation (1Wm(-2), 30min) were investigated. UV-B irradiation led to reduction of photosystem 2 (PS-2) activity and the photosynthetic rate. In plants grown under both white and red light (λm - 660nm) the reduction was greater in DM plants compared to the WT. Without UV-B irradiation a decrease in PS-2 activity was observed in DM grown under RL only. It is assumed that the lower content of UV-absorbing pigments and carotenoids observed in DM may be one of the reasons of reduced PS-2 resistance to UV-B. Higher decrease in activities under UV in DM plants grown under RL compared to DM plants grown under white light is likely due to the lack of activity of cryptochromes in plants grown under red light. Rates of post-stress recovery of photosynthetic activity of DM compared with WT plants under white and red light of low intensity were studied. Almost complete recovery of the activity was found which was not observed under dark conditions and in the presence of a protein synthesis inhibitor, chloramphenicol. It is assumed that phytochrome system participates in stress-protective mechanisms of the photosynthetic apparatus to UV-radiation. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Transitions in photosynthetic parameters of midvein and interveinal regions of leaves and their importance during leaf growth and development.

    Science.gov (United States)

    Walter, A; Rascher, U; Osmond, B

    2004-01-01

    The areal development of photosynthetic efficiency and growth patterns in expanding leaves of two different dicotyledonous species - Coccoloba uvifera and Sanchezia nobilis - was investigated by imaging both processes repeatedly over 32 days. Measurements were performed using combined imaging systems for chlorophyll fluorescence and growth, with the same spatial resolution. Significant differences in potential quantum yield of photosynthesis (F (v)/F (m)), a parameter indicating the functional status of photosystem II, were found between midvein and interveinal tissue. Although base-tip gradients and spatial patchiness were observed in the distribution of relative growth rate, neither midvein nor interveinal tissue showed such patterns in F (v)/F (m). In young leaves, F (v)/F (m) of the midvein was higher than F (v)/F (m) of interveinal tissue. This difference declined gradually with time, and upon cessation of growth, F (v)/F (m) of interveinal regions exceeded those of midvein tissue. Images of chlorophyll fluorescence quenching showed that DeltaF/F (m)' in the different tissues correlated with F (v)/F (m), indicating that, in these uniformly illuminated leaves, transitions in photosynthetic electron transport activity follow those of predawn quantum efficiency. We explore the implications of these observations during leaf development, discuss effects of sucrose delivery from veins to interveinal areas on relative rates of photosynthetic development in these tissues, and propose that the initially higher photosynthetic activity in the midvein compared to the intervein tissues may supply carbohydrates and energy for leaf growth processes.

  19. New Optimality Approach for Photosynthetic Parameterization in Terrestrial Biosphere Models: Development and Testing of VIC-VEO

    Science.gov (United States)

    Quebbeman, J.; Ramirez, J.

    2016-12-01

    Photosynthesis is intricately linked to the carbon, energy, and water cycles of our planet, and yet is commonly estimated in terrestrial biosphere models using grossly simplified descriptions and parameterizations. As our climate changes, vegetation both adapts and acclimates in ways not captured in these traditional modeling schemes. One of the most ubiquitous models of photosynthesis is the Farquhar, von Caemmerer, and Berry model, which considers at a minimum, two systems of so-called light and dark reactions. Critical parameters for each of these systems include the maximum rate of electron transport (Jmax), and the maximum rate of carboxylation (Vcmax), respectively. Although critical, these parameters are commonly either fixed at a reference temperature using estimates from literature, or follow simplified rules independent of climate. Here, we consider a new optimality approach allocating available nitrogen within the leaf such that the expectation of carbon assimilation is maximized. Further, the new approach responds dynamically to the environment, including non-stomatal down-regulation during water shortages. This new approach is discussed along with a case study replicating seasonal variability of photosynthetic capacity. Further, we introduce the VIC-VEO (VEgetal Optimality) model that implements the photosynthetic optimality approach, which is then applied across the Colorado River Basin in a water supply vulnerability case study. Results of this study show significant differences in both assimilation and transpiration between static and dynamic parameterizations of the photosynthetic system, emphasizing the need for more robust photosynthetic parameterization schemes in contemporary terrestrial biosphere models, such as utilizing optimality approaches.

  20. Generalized Net Model of Brevibacterium flavul 22LD Fermentation Process

    Directory of Open Access Journals (Sweden)

    Olympia Roeva

    2005-04-01

    Full Text Available In order to render the specific peculiarities of the fermentation processes, as well as to avoid the complexity of mathematical description with systems of differential equations, the elaboration of some new methods and approaches for their modelling and control is predetermined. As a new, alternative approach for modelling of fermentation processes, an application of generalized nets is presented in this paper. The theory of generalized nets is applied to the fermentation process of Brevibacterium flavul 22LD for L-lysine production. A generalized net model of considered process is developed. For comparison and completeness, model with differential equations is also provided. The generalized nets model developed for the fed-batch cultivation of Brevibacterium flavul 22LD allows changing the concentration of the feeding solution and the aeration rate. In this way some inhibition effects are prevented and a possibility for optimal carrying out of the considered fermentation process is provided.

  1. Leaf senescence and late-season net photosynthesis of sun and shade leaves of overstory sweetgum (Liquidambar styraciflua) grown in elevated and ambient carbon dioxide concentrations.

    Science.gov (United States)

    Herrick, Jeffrey D; Thomas, Richard B

    2003-02-01

    We examined the effects of elevated CO2 concentration ([CO2]) on leaf demography, late-season photosynthesis and leaf N resorption of overstory sweetgum (Liquidambar styraciflua L.) trees in the Duke Forest Free Air CO2 Enrichment (FACE) experiment. Sun and shade leaves were subdivided into early leaves (formed in the overwintering bud) and late leaves (formed during the growing season). Overall, we found that leaf-level net photosynthetic rates were enhanced by atmospheric CO2 enrichment throughout the season until early November; however, sun leaves showed a greater response to atmospheric CO2 enrichment than shade leaves. Elevated [CO2] did not affect leaf longevity, emergence date or abscission date of sun leaves or shade leaves. Leaf number and leaf area per shoot were unaffected by CO2 treatment. A simple shoot photosynthesis model indicated that elevated [CO2] stimulated photosynthesis by 60% in sun shoots, but by only 3% in shade shoots. Whole-shoot photosynthetic rate was more than 12 times greater in sun shoots than in shade shoots. In senescent leaves, elevated [CO2] did not affect residual leaf nitrogen, and nitrogen resorption was largely unaffected by atmospheric CO2 enrichment, except for a small decrease in shade leaves. Overall, elevated [CO2] had little effect on the number of leaves per shoot at any time during the season and, therefore, did not change seasonal carbon gain by extending or shortening the growing season. Stimulation of carbon gain by atmospheric CO2 enrichment in sweetgum trees growing in the Duke Forest FACE experiment was the result of a strong stimulation of photosynthesis throughout the growing season.

  2. Photosynthetic temperature adaptation of Pinus cembra within the timberline ecotone of the Central Austrian Alps

    Science.gov (United States)

    Wieser, Gerhard; Oberhuber, Walter; Walder, Lisa; Spieler, Daniela; Gruber, Andreas

    2011-01-01

    Temperature is suggested to determine the upper limit of tree life. Therefore, future climate warming may be of importance for tree distribution within the European Alps, where low temperatures limit carbon metabolism. We focused on the effects of air and soil temperature on net photosynthesis (Pn) of Pinus cembra an evergreen climax species of the timberline ecotone of the Central Austrian Alps. Light response and temperature response curves were estimated along an altitudinal gradient ranging from the forest limit up to the krummholz limit in both summer and fall. In general, Pn was significantly lower in fall as compared to summer. Nevertheless, independent from season mean Pn values tended to increase with elevation and were positively correlated with root zone temperatures. The specific leaf area by contrast declined with increasing elevation. Furthermore, the temperature optimum of net photosynthesis declined with increasing elevation and was positively correlated with the mean maximum air temperature of the 10 days prior the date of measurement. Thus, our findings appear to reflect a long-term adaptation of the photosynthetic apparatus of Pinus cembra to the general temperature conditions with respect to elevation combined with a short term acclimation to the prevailing temperature regime. PMID:21379394

  3. Photosynthetic Response of Soybean Leaf to Wide Light-Fluctuation in Maize-Soybean Intercropping System.

    Science.gov (United States)

    Yao, Xingdong; Zhou, Hongli; Zhu, Qian; Li, Chunhong; Zhang, Huijun; Wu, Jun-Jiang; Xie, Futi

    2017-01-01

    In maize-soybean intercropping system, soybean plants will be affected by the wide light-fluctuation, which resulted from the shading by maize plants, as the shading of maize the light is not enough for soybean in the early morning and late afternoon, but at noon, the light is strong as the maize shading disappeared. The objective of this study is to evaluate the photosynthetic response of soybean leaf to the wide light-fluctuation. The data of diurnal variation of photosynthetic characters showed that the photosynthetic rate of intercropped soybean was weaker than that of monocropped soybean. The chlorophyll content, ratio of chlorophyll a/b, and AQE (apparent quantum efficiency) were increased and Rd (dark respiration rate) was decreased for the more efficient interception and absorption of light and carbon gain in intercropping. δRo (The efficiency/probability with which an electron from the intersystem electron carriers was transferred to reduce end electron acceptors at the PSI acceptor side) and φRo (the quantum yield for the reduction of the end electron acceptors at the PSI acceptor side) in intercropped soybean leaf were lower compared to those in monocropped one, which showed that the acceptor side of PSI might be inhibited, and also it was the main reason that soybean plants showed a low photosynthetic capacity in intercropping. ψEo (the efficiency/probability with an electron moves further than QA-) in monocropping and intercropping decreased 5.8, and 35.7%, respectively, while φEo (quantum yield for electron transport) decreased 27.7 and 45.3% under the high radiation at noon, which suggested that the acceptor side of PSII was inhibited, while the NPQ became higher. These were beneficial to dissipate excess excitation energy in time, and protect the photosynthetic apparatus against photo-damage. The higher performance index on the absorption basis (PIABS) and lower δRo, φRo, ψEo, and φEo of intercropped soybeans compared to monocropping under

  4. Photosynthetic Response of Soybean Leaf to Wide Light-Fluctuation in Maize-Soybean Intercropping System

    Directory of Open Access Journals (Sweden)

    Xingdong Yao

    2017-09-01

    Full Text Available In maize-soybean intercropping system, soybean plants will be affected by the wide light-fluctuation, which resulted from the shading by maize plants, as the shading of maize the light is not enough for soybean in the early morning and late afternoon, but at noon, the light is strong as the maize shading disappeared. The objective of this study is to evaluate the photosynthetic response of soybean leaf to the wide light-fluctuation. The data of diurnal variation of photosynthetic characters showed that the photosynthetic rate of intercropped soybean was weaker than that of monocropped soybean. The chlorophyll content, ratio of chlorophyll a/b, and AQE (apparent quantum efficiency were increased and Rd (dark respiration rate was decreased for the more efficient interception and absorption of light and carbon gain in intercropping. δRo (The efficiency/probability with which an electron from the intersystem electron carriers was transferred to reduce end electron acceptors at the PSI acceptor side and φRo (the quantum yield for the reduction of the end electron acceptors at the PSI acceptor side in intercropped soybean leaf were lower compared to those in monocropped one, which showed that the acceptor side of PSI might be inhibited, and also it was the main reason that soybean plants showed a low photosynthetic capacity in intercropping. ψEo (the efficiency/probability with an electron moves further than QA- in monocropping and intercropping decreased 5.8, and 35.7%, respectively, while φEo (quantum yield for electron transport decreased 27.7 and 45.3% under the high radiation at noon, which suggested that the acceptor side of PSII was inhibited, while the NPQ became higher. These were beneficial to dissipate excess excitation energy in time, and protect the photosynthetic apparatus against photo-damage. The higher performance index on the absorption basis (PIABS and lower δRo, φRo, ψEo, and φEo of intercropped soybeans compared to

  5. Photosynthetic performance of the aquatic macrophyte Althenia orientalis to solar radiation along its vertical stems.

    Science.gov (United States)

    Conde-Álvarez, Rafael M; Bañares-España, Elena; Nieto-Caldera, José Ma; Flores-Moya, Antonio; Figueroa, Félix L

    2011-08-01

    We have studied the plasticity of the photosynthetic apparatus in the endangered aquatic macrophyte Althenia orientalis to the gradient of light availability within its meadow canopy. We determined diurnal change in situ irradiance, light quality, in vivo chlorophyll a fluorescence, ex situ oxygen evolution rates, respiration rate and pigment concentration. The levels of photosynthetic photon flux density (PFD) and ultraviolet radiation (UVR) and the red/far-red ratio decreased with depth within the canopies of A. orientalis. Apical leaves had a greater decrease of the maximal quantum yield (F(v)/F(m)) in the morning and a faster recovery rate in the afternoon than those in the basal ones. The relative electron transport rate (ETRr) was not saturated at any time of the day, even in the apical leaves that received the highest light. The maximum light-saturated rate of gross photosynthesis (GP(max)) took place in apical leaves around noon. The chlorophyll a/b ratio values were higher, and the chlorophyll/carotenoid ratio values lower, in apical leaves than basal ones. The highest concentrations in total carotenoids were reached in the apical leaves around noon. A. orientalis has a high capacity to acclimatize to the changes in the light environment, both in quality and quantity, presenting sun and shade leaves in the same stem through the vertical gradient in the canopy.

  6. D.NET case study

    International Development Research Centre (IDRC) Digital Library (Canada)

    lremy

    developing products, marketing tools and building capacity of the grass root telecentre workers. D.Net recognized that it had several ideas worth developing into small interventions that would make big differences, but resource constraints were a barrier for scaling-up these initiatives. More demands, limited resources.

  7. Surgery for GEP-NETs

    DEFF Research Database (Denmark)

    Knigge, Ulrich; Hansen, Carsten Palnæs

    2012-01-01

    Surgery is the only treatment that may cure the patient with gastroentero-pancreatic (GEP) neuroendocrine tumours (NET) and neuroendocrine carcinomas (NEC) and should always be considered as first line treatment if R0/R1 resection can be achieved. The surgical and interventional procedures for GEP...

  8. Net Neutrality in the Netherlands

    NARCIS (Netherlands)

    van Eijk, N.

    2014-01-01

    The Netherlands is among the first countries that have put specific net neutrality standards in place. The decision to implement specific regulation was influenced by at least three factors. The first was the prevailing social and academic debate, partly due to developments in the United States. The

  9. Complexity Metrics for Workflow Nets

    DEFF Research Database (Denmark)

    Lassen, Kristian Bisgaard; van der Aalst, Wil M.P.

    2009-01-01

    Process modeling languages such as EPCs, BPMN, flow charts, UML activity diagrams, Petri nets, etc.\\ are used to model business processes and to configure process-aware information systems. It is known that users have problems understanding these diagrams. In fact, even process engineers and system...

  10. High success rates of sedation-free brain MRI scanning in young children using simple subject preparation protocols with and without a commercial mock scanner-the Diabetes Research in Children Network (DirecNet) experience

    Energy Technology Data Exchange (ETDEWEB)

    Barnea-Goraly, Naama; Marzelli, Matt J.; Mazaika, Paul K. [Center for Interdisciplinary Brain Sciences Research, Department of Psychiatry and Behavioral Sciences, Stanford, CA (United States); Weinzimer, Stuart A. [Yale University, Pediatric Endocrinology, New Haven, CT (United States); Ruedy, Katrina J.; Beck, Roy W.; Kollman, Craig; Cheng, Peiyao [Jaeb Center for Health Research, Tampa, FL (United States); Mauras, Nelly; Fox, Larry [Nemours Children' s Clinic, Pediatric Endocrinology, Jacksonville, FL (United States); Aye, Tandy [Stanford University, Department of Pediatrics, Stanford, CA (United States); White, Neil H. [Washington University in St. Louis, Department of Pediatrics, St. Louis, MO (United States); Tsalikian, Eva [University of Iowa, Pediatric Endocrinology, Iowa City, IA (United States); Reiss, Allan L. [Center for Interdisciplinary Brain Sciences Research, Department of Psychiatry and Behavioral Sciences, Stanford, CA (United States); Stanford University, Department of Pediatrics, Stanford, CA (United States); Stanford University, Department of Radiology, Diabetes Research in Children Network (DirecNet), Stanford, CA (United States); Collaboration: on behalf of the Diabetes Research in Children Network (DirecNet)

    2014-02-15

    The ability to lie still in an MRI scanner is essential for obtaining usable image data. To reduce motion, young children are often sedated, adding significant cost and risk. We assessed the feasibility of using a simple and affordable behavioral desensitization program to yield high-quality brain MRI scans in sedation-free children. 222 children (4-9.9 years), 147 with type 1 diabetes and 75 age-matched non-diabetic controls, participated in a multi-site study focused on effects of type 1 diabetes on the developing brain. T1-weighted and diffusion-weighted imaging (DWI) MRI scans were performed. All children underwent behavioral training and practice MRI sessions using either a commercial MRI simulator or an inexpensive mock scanner consisting of a toy tunnel, vibrating mat, and video player to simulate the sounds and feel of the MRI scanner. 205 children (92.3%), mean age 7 ± 1.7 years had high-quality T1-W scans and 174 (78.4%) had high-quality diffusion-weighted scans after the first scan session. With a second scan session, success rates were 100% and 92.5% for T1-and diffusion-weighted scans, respectively. Success rates did not differ between children with type 1 diabetes and children without diabetes, or between centers using a commercial MRI scan simulator and those using the inexpensive mock scanner. Behavioral training can lead to a high success rate for obtaining high-quality T1-and diffusion-weighted brain images from a young population without sedation. (orig.)

  11. Photosynthetic terpene hydrocarbon production for fuels and chemicals

    Energy Technology Data Exchange (ETDEWEB)

    Wang, X; Ort, DR; Yuan, JS

    2015-01-28

    Photosynthetic hydrocarbon production bypasses the traditional biomass hydrolysis process and represents the most direct conversion of sunlight energy into the next-generation biofuels. As a major class of biologically derived hydrocarbons with diverse structures, terpenes are also valuable in producing a variety of fungible bioproducts in addition to the advanced drop-in' biofuels. However, it is highly challenging to achieve the efficient redirection of photosynthetic carbon and reductant into terpene biosynthesis. In this review, we discuss four major scientific and technical barriers for photosynthetic terpene production and recent advances to address these constraints. Collectively, photosynthetic terpene production needs to be optimized in a systematic fashion, in which the photosynthesis improvement, the optimization of terpene biosynthesis pathway, the improvement of key enzymes and the enhancement of sink effect through terpene storage or secretion are all important. New advances in synthetic biology also offer a suite of potential tools to design and engineer photosynthetic terpene platforms. The systemic integration of these solutions may lead to disruptive' technologies to enable biofuels and bioproducts with high efficiency, yield and infrastructure compatibility.

  12. Photosynthetic terpene hydrocarbon production for fuels and chemicals.

    Science.gov (United States)

    Wang, Xin; Ort, Donald R; Yuan, Joshua S

    2015-02-01

    Photosynthetic hydrocarbon production bypasses the traditional biomass hydrolysis process and represents the most direct conversion of sunlight energy into the next-generation biofuels. As a major class of biologically derived hydrocarbons with diverse structures, terpenes are also valuable in producing a variety of fungible bioproducts in addition to the advanced 'drop-in' biofuels. However, it is highly challenging to achieve the efficient redirection of photosynthetic carbon and reductant into terpene biosynthesis. In this review, we discuss four major scientific and technical barriers for photosynthetic terpene production and recent advances to address these constraints. Collectively, photosynthetic terpene production needs to be optimized in a systematic fashion, in which the photosynthesis improvement, the optimization of terpene biosynthesis pathway, the improvement of key enzymes and the enhancement of sink effect through terpene storage or secretion are all important. New advances in synthetic biology also offer a suite of potential tools to design and engineer photosynthetic terpene platforms. The systemic integration of these solutions may lead to 'disruptive' technologies to enable biofuels and bioproducts with high efficiency, yield and infrastructure compatibility. © 2015 Society for Experimental Biology, Association of Applied Biologists and John Wiley & Sons Ltd.

  13. Photosynthetic biomaterials: a pathway towards autotrophic tissue engineering.

    Science.gov (United States)

    Schenck, Thilo Ludwig; Hopfner, Ursula; Chávez, Myra Noemi; Machens, Hans-Günther; Somlai-Schweiger, Ian; Giunta, Riccardo Enzo; Bohne, Alexandra Viola; Nickelsen, Jörg; Allende, Miguel L; Egaña, José Tomás

    2015-03-01

    Engineered tissues are highly limited by poor vascularization in vivo, leading to hypoxia. In order to overcome this challenge, we propose the use of photosynthetic biomaterials to provide oxygen. Since photosynthesis is the original source of oxygen for living organisms, we suggest that this could be a novel approach to provide a constant source of oxygen supply independently of blood perfusion. In this study we demonstrate that bioartificial scaffolds can be loaded with a solution containing the photosynthetic microalgae Chlamydomonas reinhardtii, showing high biocompatibility and photosynthetic activity in vitro. Furthermore, when photosynthetic biomaterials were engrafted in a mouse full skin defect, we observed that the presence of the microalgae did not trigger a native immune response in the host. Moreover, the analyses showed that the algae survived for at least 5 days in vivo, generating chimeric tissues comprised of algae and murine cells. The results of this study represent a crucial step towards the establishment of autotrophic tissue engineering approaches and suggest the use of photosynthetic cells to treat a broad spectrum of hypoxic conditions. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  14. Caught in the Net: Perineuronal Nets and Addiction

    Directory of Open Access Journals (Sweden)

    Megan Slaker

    2016-01-01

    Full Text Available Exposure to drugs of abuse induces plasticity in the brain and creates persistent drug-related memories. These changes in plasticity and persistent drug memories are believed to produce aberrant motivation and reinforcement contributing to addiction. Most studies have explored the effect drugs of abuse have on pre- and postsynaptic cells and astrocytes; however, more recently, attention has shifted to explore the effect these drugs have on the extracellular matrix (ECM. Within the ECM are unique structures arranged in a net-like manner, surrounding a subset of neurons called perineuronal nets (PNNs. This review focuses on drug-induced changes in PNNs, the molecules that regulate PNNs, and the expression of PNNs within brain circuitry mediating motivation, reward, and reinforcement as it pertains to addiction.

  15. Waterscape determinants of net mercury methylation in a tropical wetland.

    Science.gov (United States)

    Lázaro, Wilkinson L; Díez, Sergi; da Silva, Carolina J; Ignácio, Áurea R A; Guimarães, Jean R D

    2016-10-01

    The periphyton associated with freshwater macrophyte roots is the main site of Hg methylation in different wetland environments in the world. The aim of this study was to test the use of connectivity metrics of water bodies, in the context of patches, in a tropical waterscape wetland (Guapore River, Amazonia, Brazil) as a predictor of potential net methylmercury (MeHg) production by periphyton communities. We sampled 15 lakes with different patterns of lateral connectivity with the main river channel, performing net mercury methylation potential tests in incubations with local water and Eichhornia crassipes root-periphyton samples, using (203)HgCl2 as a tracer. Physico-chemical variables, landscape data (morphological characteristics, land use, and lateral connection type of water bodies) using GIS resources and field data were analyzed with Generalized Additive Models (GAM). The net Me(203)Hg production (as % of total added (203)Hg) was expressive (6.2-25.6%) showing that periphyton is an important matrix in MeHg production. The model that best explained the variation in the net Me(203)Hg production (76%) was built by the variables: connection type, total phosphorus and dissolved organic carbon (DOC) in water (AICc=48.324, p=0.001). Connection type factor was the best factor to model fit (r(2)=0.32; p=0.008) and temporarily connected lakes had higher rates of net mercury methylation. Both DOC and total phosphorus showed positive significant covariation with the net methylation rates (r(2)=0.26; p=0.008 and r(2)=0.21; p=0.012 respectively). Our study suggests a strong relationship between rates of net MeHg production in this tropical area and the type of water body and its hydrological connectivity within the waterscape. Copyright © 2016 Elsevier Inc. All rights reserved.

  16. Army Net Zero Prove Out. Army Net Zero Training Report

    Science.gov (United States)

    2014-11-20

    sensors were strategically placed throughout the installation by magnetically attaching them to water main valve stems. The sensors check sound...Recycle Wrap  Substitutes for Packaging Materials  Re-Use of Textiles and Linens  Setting Printers to Double-Sided Printing Net Zero Waste...can effectively achieve source reduction. Clean and Re-Use Shop Rags - Shop rags represent a large textile waste stream at many installations. As a

  17. Army Net Zero Prove Out. Net Zero Waste Best Practices

    Science.gov (United States)

    2014-11-20

    Anaerobic Digesters – Although anaerobic digestion is not a new technology and has been used on a large-scale basis in wastewater treatment , the...technology and has been used on a large-scale basis in wastewater treatment , the use of the technology should be demonstrated with other...approaches can be used for cardboard and cellulose -based packaging materials. This approach is in line with the Net Zero Waste hierarchy in terms of

  18. Long-term adaptive response to high-frequency light signals in the unicellular photosynthetic eukaryote Dunaliella salina.

    Science.gov (United States)

    Combe, Charlotte; Hartmann, Philipp; Rabouille, Sophie; Talec, Amelie; Bernard, Olivier; Sciandra, Antoine

    2015-06-01

    Productivity of microalgal cultivation processes is tightly related to photosynthetic efficiency, and therefore to light availability at the cell scale. In an agitated, highly turbid suspension,the light signal received by a single phytoplankton cell moving in a dense culture is a succession of flashes. The growth characteristics of microalgae under such dynamic light conditions are thus fundamental information to understand nonlinear properties of the photosynthetic process and to improve cultivation process design and operation. Studies of the long term consequences of dynamic illumination regime on photosynthesis require a very specific experimental set-up where fast varying signals are applied on the long term. In order to investigate the growth response of the unicellular photosynthetic eukaryote Dunaliella salina (Chlorophyceae) to intermittent light exposure, different light regimes using LEDs with the same average total light dose were applied in continuous cultures. Flashing light with different durations of light flashes (△t of 30 s, 15 s, 2 s and 0.1 s) followed by dark periods of variable length (0.67 ≤ L:D ≤ 2) yielding flash frequencies in the range 0.017-5 Hz, were compared to continuous illumination. Specific growth rate, photosynthetic pigments, lipid productivity and elemental composition were measured on two duplicates for each irradiance condition. The different treatments of intermittent light led to specific growth rates ranging from 0.25 to 0.93 day(-1) . While photosynthetic efficiency was enhanced with increased flash frequency, no significant differences were observed in the particular carbon and chlorophyll content. Pigment analysis showed that within this range of flash frequency, cells progressively photoacclimated to the average light intensity. © 2015 Wiley Periodicals, Inc.

  19. Night Light-Adaptation Strategies for Photosynthetic Apparatus in Yellow-Poplar (Liriodendron tulipifera L. Exposed to Artificial Night Lighting

    Directory of Open Access Journals (Sweden)

    Myeong Ja Kwak

    2018-02-01

    Full Text Available Plants can undergo external fluctuations in the natural light and dark cycle. The photosynthetic apparatus needs to operate in an appropriate manner to fluctuating environmental factors, especially in light. Yellow-poplar seedlings were exposed to nighttime artificial high-pressure sodium (HPS lighting to evaluate night light-adaptation strategies for photosynthetic apparatus fitness relative to pigment contents, photosystem II photochemistry, photosynthetic parameters, histochemical analysis of reactive oxygen species, and plant biomass. As a result, seedlings exhibited dynamic changes including the enhancement of accessory pigments, the reduction of photosystem II photochemistry, increased stomatal limitation, downregulation of photosynthesis, and the decreased aboveground and belowground biomass under artificial night lighting. Histochemical analysis with 3,3′-diaminobenzidine (DAB and nitroblue tetrazolium (NBT staining indicates the accumulation of in situ superoxide radicals (O2− and hydrogen peroxide (H2O2 in leaves exposed to the lowest level of artificial night lighting compared to control. Moreover, these leaves exposed to artificial night lighting had a lower nighttime respiration rate. These results indicated that HPS lighting during the night may act as a major factor as repressors of the fitness of photosynthesis and growth patterns, via a modification of the photosynthetic light harvesting apparatus.

  20. Preillumination of lettuce seedlings with red light enhances the resistance of photosynthetic apparatus to UV-A.

    Science.gov (United States)

    Kreslavski, Vladimir D; Lyubimov, Valery Yu; Shirshikova, Galina N; Shmarev, Alexander N; Kosobryukhov, Anatoly A; Schmitt, Franz-Josef; Friedrich, Thomas; Allakhverdiev, Suleyman I

    2013-05-05

    Seedlings of 10-day-old lettuce (Lactuca sativa L., cultivar Berlin) were preilluminated by low intensity red light (λmax=660 nm, 10 min, 5 μmol quanta m(-2) s(-1)) and far-red light (λmax=730 nm, 10 min, 5 μmol quanta m(-2) s(-1)) to study the effect of pre-treatment on photosynthesis, photochemical activity of photosystem II (PSII), the contents of photosynthetic and UV-A-absorbing pigments (UAPs) and H2O2, as well as total and ascorbate peroxidase activities in cotyledonary leaves of seedlings exposed to UV-A. UV radiation reduced the photosynthetic rate (Pn), the activity of PSII, and the contents of Chl a and b, carotenoids and UAPs in the leaves, but increased the content of H2O2 and the total peroxidase activity. Preillumination with red light removed these effects of UV. In turn, the illumination with red light, then far-red light removed the effect of the red light. Illumination with red light alone increased the content of UAPs, as well as peroxidase activity. It is suggested that higher resistance of the lettuce photosynthetic apparatus to UV-A radiation is associated with involvement of the active form of phytochrome B, thereby increasing peroxidase activities as well as UAPs and saving preservation of photosynthetic pigment contents due to pre-illumination with red light. Copyright © 2013 Elsevier B.V. All rights reserved.