Exploring the spatial distribution of light interception and photosynthesis of canopies by means of a functional–structural plant model

Science.gov (United States)

Sarlikioti, V.; de Visser, P. H. B.; Marcelis, L. F. M.

2011-01-01

Background and Aims At present most process-based models and the majority of three-dimensional models include simplifications of plant architecture that can compromise the accuracy of light interception simulations and, accordingly, canopy photosynthesis. The aim of this paper is to analyse canopy heterogeneity of an explicitly described tomato canopy in relation to temporal dynamics of horizontal and vertical light distribution and photosynthesis under direct- and diffuse-light conditions. Methods Detailed measurements of canopy architecture, light interception and leaf photosynthesis were carried out on a tomato crop. These data were used for the development and calibration of a functional–structural tomato model. The model consisted of an architectural static virtual plant coupled with a nested radiosity model for light calculations and a leaf photosynthesis module. Different scenarios of horizontal and vertical distribution of light interception, incident light and photosynthesis were investigated under diffuse and direct light conditions. Key Results Simulated light interception showed a good correspondence to the measured values. Explicitly described leaf angles resulted in higher light interception in the middle of the plant canopy compared with fixed and ellipsoidal leaf-angle distribution models, although the total light interception remained the same. The fraction of light intercepted at a north–south orientation of rows differed from east–west orientation by 10 % on winter and 23 % on summer days. The horizontal distribution of photosynthesis differed significantly between the top, middle and lower canopy layer. Taking into account the vertical variation of leaf photosynthetic parameters in the canopy, led to approx. 8 % increase on simulated canopy photosynthesis. Conclusions Leaf angles of heterogeneous canopies should be explicitly described as they have a big impact both on light distribution and photosynthesis. Especially, the vertical

2011 Photosynthesis Gordon Research Conference & Seminar (June 11-17, 2011, Davidson College, Davidson, North Carolina)

Energy Technology Data Exchange (ETDEWEB)

Prof. Krishna Niyogi

2011-06-17

Photosynthesis is the biological process that converts solar energy into chemical energy. Elucidation of the mechanisms of photosynthetic energy conversion at a molecular level is fundamentally important for understanding the biology of photosynthetic organisms, for optimizing biological solar fuels production, and for developing biologically inspired approaches to solar energy conversion. The 2011 Gordon Conference on Photosynthesis will present cutting-edge research focusing on the biochemical aspects of photosynthesis, including: (1) structure, assembly, and function of photosynthetic complexes; (2) the mechanism of water splitting by PSII; (3) light harvesting and quenching; (4) alternative electron transport pathways; (5) biosynthesis of pigments and cofactors; and (6) improvement of photosynthesis for bioenergy and food production. Reflecting the interdisciplinary nature of photosynthesis research, a diverse group of invited speakers will represent a variety of scientific approaches to investigate photosynthesis, such as biochemistry, molecular genetics, structural biology, systems biology, and spectroscopy. Highly interactive poster sessions provide opportunities for graduate students and postdocs to present their work and exchange ideas with leaders in the field. One of the highlights of the Conference is a session featuring short talks by junior investigators selected from the poster presentations. The collegial atmosphere of the Photosynthesis GRC, with programmed discussion sessions as well as informal gatherings in the afternoons and evenings, enables participants to brainstorm, exchange ideas, and forge new collaborations. For the second time, this Conference will be immediately preceded by a Gordon Research Seminar on Photosynthesis (June 11-12, 2011, at the same location), with a focus on 'Photosynthesis, Bioenergy, and the Environment.' The GRS provides an additional opportunity for graduate students and postdocs to present their research

Photosynthesis and Bioconversion

International Nuclear Information System (INIS)

Broda, E.

1983-01-01

This text summarises a talk held by Engelbert Broda at a conference on non-convential energy sources. The talk about photosynthesis and bioconversion is devided in 6 sections: the great physicist and photosynthesis; the influence of photosynthesis on the biosphere (in the past, present and future); the light reactions in photosynthesis; the dark reactions in photosynthesis; bioconversion; respiration and photorespiration. (nowak)

Models for estimating photosynthesis parameters from in situ production profiles

Science.gov (United States)

Kovač, Žarko; Platt, Trevor; Sathyendranath, Shubha; Antunović, Suzana

2017-12-01

The rate of carbon assimilation in phytoplankton primary production models is mathematically prescribed with photosynthesis irradiance functions, which convert a light flux (energy) into a material flux (carbon). Information on this rate is contained in photosynthesis parameters: the initial slope and the assimilation number. The exactness of parameter values is crucial for precise calculation of primary production. Here we use a model of the daily production profile based on a suite of photosynthesis irradiance functions and extract photosynthesis parameters from in situ measured daily production profiles at the Hawaii Ocean Time-series station Aloha. For each function we recover parameter values, establish parameter distributions and quantify model skill. We observe that the choice of the photosynthesis irradiance function to estimate the photosynthesis parameters affects the magnitudes of parameter values as recovered from in situ profiles. We also tackle the problem of parameter exchange amongst the models and the effect it has on model performance. All models displayed little or no bias prior to parameter exchange, but significant bias following parameter exchange. The best model performance resulted from using optimal parameter values. Model formulation was extended further by accounting for spectral effects and deriving a spectral analytical solution for the daily production profile. The daily production profile was also formulated with time dependent growing biomass governed by a growth equation. The work on parameter recovery was further extended by exploring how to extract photosynthesis parameters from information on watercolumn production. It was demonstrated how to estimate parameter values based on a linearization of the full analytical solution for normalized watercolumn production and from the solution itself, without linearization. The paper complements previous works on photosynthesis irradiance models by analysing the skill and consistency of

Mössbauer spectroscopy in studies of photosynthesis

Science.gov (United States)

Burda, Květoslava

2008-02-01

Photosynthesis is a process occurring in certain species of bacteria, algae and higher plants. It transforms solar energy into various forms of energy-rich organic molecules. Photosystem II (PSII) is the “heart” of the photosynthetic apparatus because it delivers electrons and protons for further steps of the light-driven phases of photosynthesis. There are two enigmatic iron binding structures within the core of photosynthetic apparatus, which play an important role in the electron transfer within PSII. Many investigations focus on the determination of their function which is the key to the understanding of the molecular mechanism of the energy and electron transfer within PSII. Among many methods used in this research field, the Mössbauer spectroscopy is a unique one, which gives the possibility to study changes of the valence and spin states of those two iron sites and the dynamical properties of their protein matrix in the presence of various physiological and stress conditions.

Identification and characterization of nuclear genes involved in photosynthesis in Populus

Science.gov (United States)

2014-01-01

Background The gap between the real and potential photosynthetic rate under field conditions suggests that photosynthesis could potentially be improved. Nuclear genes provide possible targets for improving photosynthetic efficiency. Hence, genome-wide identification and characterization of the nuclear genes affecting photosynthetic traits in woody plants would provide key insights on genetic regulation of photosynthesis and identify candidate processes for improvement of photosynthesis. Results Using microarray and bulked segregant analysis strategies, we identified differentially expressed nuclear genes for photosynthesis traits in a segregating population of poplar. We identified 515 differentially expressed genes in this population (FC ≥ 2 or FC ≤ 0.5, P photosynthesis by the nuclear genome mainly involves transport, metabolism and response to stimulus functions. Conclusions This study provides new genome-scale strategies for the discovery of potential candidate genes affecting photosynthesis in Populus, and for identification of the functions of genes involved in regulation of photosynthesis. This work also suggests that improving photosynthetic efficiency under field conditions will require the consideration of multiple factors, such as stress responses. PMID:24673936

Regulation in photosynthesis

International Nuclear Information System (INIS)

Heber, U.

1989-01-01

This short paper focus on an overall perspective of photosynthesis. The author points out that although much progress has been made into the molecular mechanisms of photosynthesis, the picture is still far from complete. The study of interactions in photosynthesis is important because such a complex process must have regulatory mechanisms. The author also discusses the importance of photosynthesis study in the practical world of survival of man and production of food

Modelling C₃ photosynthesis from the chloroplast to the ecosystem.

Science.gov (United States)

Bernacchi, Carl J; Bagley, Justin E; Serbin, Shawn P; Ruiz-Vera, Ursula M; Rosenthal, David M; Vanloocke, Andy

2013-09-01

Globally, photosynthesis accounts for the largest flux of CO₂ from the atmosphere into ecosystems and is the driving process for terrestrial ecosystem function. The importance of accurate predictions of photosynthesis over a range of plant growth conditions led to the development of a C₃ photosynthesis model by Farquhar, von Caemmerer & Berry that has become increasingly important as society places greater pressures on vegetation. The photosynthesis model has played a major role in defining the path towards scientific understanding of photosynthetic carbon uptake and the role of photosynthesis on regulating the earth's climate and biogeochemical systems. In this review, we summarize the photosynthesis model, including its continued development and applications. We also review the implications these developments have on quantifying photosynthesis at a wide range of spatial and temporal scales, and discuss the model's role in determining photosynthetic responses to changes in environmental conditions. Finally, the review includes a discussion of the larger-scale modelling and remote-sensing applications that rely on the leaf photosynthesis model and are likely to open new scientific avenues to address the increasing challenges to plant productivity over the next century. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

Climate changes and photosynthesis

Directory of Open Access Journals (Sweden)

G.Sh Tkemaladze

2016-06-01

Solar energy is environmentally friendly and its conversion to energy of chemical substances is carried out only by photosynthesis – effective mechanism characteristic of plants. However, microorganism photosynthesis occurs more frequently than higher plant photosynthesis. More than half of photosynthesis taking place on the earth surface occurs in single-celled organisms, especially algae, in particular, diatomic organisms.

Estimating phytoplankton photosynthesis by active fluorescence

Energy Technology Data Exchange (ETDEWEB)

Falkowski, P.G.; Kolber, Z.

1992-01-01

Photosynthesis can be described by target theory, At low photon flux densities, photosynthesis is a linear function of irradiance (I), The number of reaction centers (n), their effective absorption capture cross section {sigma}, and a quantum yield {phi}. As photosynthesis becomes increasingly light saturated, an increased fraction of reaction centers close. At light saturation the maximum photosynthetic rate is given as the product of the number of reaction centers (n) and their maximum electron transport rate (I/{tau}). Using active fluorometry it is possible to measure non-destructively and in real time the fraction of open or closed reaction centers under ambient irradiance conditions in situ, as well as {sigma} and {phi} {tau} can be readily, calculated from knowledge of the light saturation parameter, I{sub k} (which can be deduced by in situ by active fluorescence measurements) and {sigma}. We built a pump and probe fluorometer, which is interfaced with a CTD. The instrument measures the fluorescence yield of a weak probe flash preceding (f{sub 0}) and succeeding (f{sub 0}) a saturating pump flash. Profiles of the these fluorescence yields are used to derive the instantaneous rate of gross photosynthesis in natural phytoplankton communities without any incubation. Correlations with short-term simulated in situ radiocarbon measurements are extremely high. The average slope between photosynthesis derived from fluorescence and that measured by radiocarbon is 1.15 and corresponds to the average photosynthetic quotient. The intercept is about 15% of the maximum radiocarbon uptake and corresponds to the average net community respiration. Profiles of photosynthesis and sections showing the variability in its composite parameters reveal a significant effect of nutrient availability on biomass specific rates of photosynthesis in the ocean.

Estimating phytoplankton photosynthesis by active fluorescence

Energy Technology Data Exchange (ETDEWEB)

Falkowski, P.G.; Kolber, Z.

1992-10-01

Photosynthesis can be described by target theory, At low photon flux densities, photosynthesis is a linear function of irradiance (I), The number of reaction centers (n), their effective absorption capture cross section {sigma}, and a quantum yield {phi}. As photosynthesis becomes increasingly light saturated, an increased fraction of reaction centers close. At light saturation the maximum photosynthetic rate is given as the product of the number of reaction centers (n) and their maximum electron transport rate (I/{tau}). Using active fluorometry it is possible to measure non-destructively and in real time the fraction of open or closed reaction centers under ambient irradiance conditions in situ, as well as {sigma} and {phi} {tau} can be readily, calculated from knowledge of the light saturation parameter, I{sub k} (which can be deduced by in situ by active fluorescence measurements) and {sigma}. We built a pump and probe fluorometer, which is interfaced with a CTD. The instrument measures the fluorescence yield of a weak probe flash preceding (f{sub 0}) and succeeding (f{sub 0}) a saturating pump flash. Profiles of the these fluorescence yields are used to derive the instantaneous rate of gross photosynthesis in natural phytoplankton communities without any incubation. Correlations with short-term simulated in situ radiocarbon measurements are extremely high. The average slope between photosynthesis derived from fluorescence and that measured by radiocarbon is 1.15 and corresponds to the average photosynthetic quotient. The intercept is about 15% of the maximum radiocarbon uptake and corresponds to the average net community respiration. Profiles of photosynthesis and sections showing the variability in its composite parameters reveal a significant effect of nutrient availability on biomass specific rates of photosynthesis in the ocean.

Cadmium against higher plant photosynthesis - a variety of effects and where do they possibly come from?

International Nuclear Information System (INIS)

Krupa, Z.

1999-01-01

The complexity of in vivo toxic effects of Cd on higher plants makes almost impossible an accurate distinction between direct and indirect mechanisms of its action on the photosynthetic apparatus. We, therefore, postulate that multiple Cd effects on plant physiological and metabolic processes may finally be focused on photosynthesis. This would also explain the phenomenon that only a small fraction of Cd entering chloroplasts may cause such disastrous changes in their structure and function. In return, the inhibition of photosynthesis affects numerous metabolic pathways dependent on the primary carbon metabolism. (orig.)

Photosynthesis-related quantities for education and modeling.

Science.gov (United States)

Antal, Taras K; Kovalenko, Ilya B; Rubin, Andrew B; Tyystjärvi, Esa

2013-11-01

A quantitative understanding of the photosynthetic machinery depends largely on quantities, such as concentrations, sizes, absorption wavelengths, redox potentials, and rate constants. The present contribution is a collection of numbers and quantities related mainly to photosynthesis in higher plants. All numbers are taken directly from a literature or database source and the corresponding reference is provided. The numerical values, presented in this paper, provide ranges of values, obtained in specific experiments for specific organisms. However, the presented numbers can be useful for understanding the principles of structure and function of photosynthetic machinery and for guidance of future research.

Association genetics and transcriptome analysis reveal a gibberellin-responsive pathway involved in regulating photosynthesis.

Science.gov (United States)

Xie, Jianbo; Tian, Jiaxing; Du, Qingzhang; Chen, Jinhui; Li, Ying; Yang, Xiaohui; Li, Bailian; Zhang, Deqiang

2016-05-01

Gibberellins (GAs) regulate a wide range of important processes in plant growth and development, including photosynthesis. However, the mechanism by which GAs regulate photosynthesis remains to be understood. Here, we used multi-gene association to investigate the effect of genes in the GA-responsive pathway, as constructed by RNA sequencing, on photosynthesis, growth, and wood property traits, in a population of 435 Populus tomentosa By analyzing changes in the transcriptome following GA treatment, we identified many key photosynthetic genes, in agreement with the observed increase in measurements of photosynthesis. Regulatory motif enrichment analysis revealed that 37 differentially expressed genes related to photosynthesis shared two essential GA-related cis-regulatory elements, the GA response element and the pyrimidine box. Thus, we constructed a GA-responsive pathway consisting of 47 genes involved in regulating photosynthesis, including GID1, RGA, GID2, MYBGa, and 37 photosynthetic differentially expressed genes. Single nucleotide polymorphism (SNP)-based association analysis showed that 142 SNPs, representing 40 candidate genes in this pathway, were significantly associated with photosynthesis, growth, and wood property traits. Epistasis analysis uncovered interactions between 310 SNP-SNP pairs from 37 genes in this pathway, revealing possible genetic interactions. Moreover, a structural gene-gene matrix based on a time-course of transcript abundances provided a better understanding of the multi-gene pathway affecting photosynthesis. The results imply a functional role for these genes in mediating photosynthesis, growth, and wood properties, demonstrating the potential of combining transcriptome-based regulatory pathway construction and genetic association approaches to detect the complex genetic networks underlying quantitative traits. © The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights

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

Science.gov (United States)

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

2009-11-04

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

Exploring the spatial distribution of light interception and photosynthesis of canopies by means of a functional-structural plant model

NARCIS (Netherlands)

Sarlikioti, V.; Visser, de P.H.B.; Marcelis, L.F.M.

2011-01-01

Background and Aims - At present most process-based models and the majority of three-dimensional models include simplifications of plant architecture that can compromise the accuracy of light interception simulations and, accordingly, canopy photosynthesis. The aim of this paper is to analyse canopy

2012 Photosynthesis Gordon Research Conference and Seminar, JUL 7-13, 2012

Energy Technology Data Exchange (ETDEWEB)

Debus, Richard [Univ. of California, Riverside, CA (United States)

2012-07-13

The Gordon Research Conference on PHOTOSYNTHESIS was held at Davidson College, Davidson, North Carolina, July 8-13, 2012. The Conference was well-attended with 150 participants (attendees list attached). The attendees represented the spectrum of endeavor in this field coming from academia, industry, and government laboratories, both U.S. and foreign scientists, senior researchers, young investigators, and students. Of the 150 attendees, 65 voluntarily responded to a general inquiry regarding ethnicity which appears on our registration forms. Of the 65 respondents, 20% were Minorities$-$ 5% Hispanic, 15% Asian and 0% African American. Approximately 28% of the participants at the 2012 meeting were women. The Gordon Research Seminar on PHOTOSYNTHESIS held at Davidson College, Davidson, North Carolina, July 7-8, 2012.. The Conference was well-attended with 51 participants (attendees list attached). The attendees represented the spectrum of endeavor in this field coming from academia, industry, and government laboratories, both U.S. and foreign scientists, senior researchers, young investigators, and students. Of the 51 attendees, 22 voluntarily responded to a general inquiry regarding ethnicity which appears on our registration forms. Of the 22 respondents, 14% were Minorities $-$0% Hispanic, 14% Asian and 0% African American. Approximately 35% of the participants at the 2012 meeting were women. Focal points for talks and discussions will include: Artificial photosynthesis and solar energy conversion strategies; Engineering organisms for biofuels and hydrogen production; Electron transport, proton transport, and energy coupling; Photoprotection mechanisms; Photosynthetic reaction center structure and function, including rewiring reaction centers for artificial photosynthesis; Energy capture and light harvesting solutions, including quantum coherence; Structure of the oxygen evolving complex and the mechanism of oxygen production.

Global Analysis of Photosynthesis Transcriptional Regulatory Networks

Science.gov (United States)

Imam, Saheed; Noguera, Daniel R.; Donohue, Timothy J.

2014-01-01

Photosynthesis is a crucial biological process that depends on the interplay of many components. This work analyzed the gene targets for 4 transcription factors: FnrL, PrrA, CrpK and MppG (RSP_2888), which are known or predicted to control photosynthesis in Rhodobacter sphaeroides. Chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-seq) identified 52 operons under direct control of FnrL, illustrating its regulatory role in photosynthesis, iron homeostasis, nitrogen metabolism and regulation of sRNA synthesis. Using global gene expression analysis combined with ChIP-seq, we mapped the regulons of PrrA, CrpK and MppG. PrrA regulates ∼34 operons encoding mainly photosynthesis and electron transport functions, while CrpK, a previously uncharacterized Crp-family protein, regulates genes involved in photosynthesis and maintenance of iron homeostasis. Furthermore, CrpK and FnrL share similar DNA binding determinants, possibly explaining our observation of the ability of CrpK to partially compensate for the growth defects of a ΔFnrL mutant. We show that the Rrf2 family protein, MppG, plays an important role in photopigment biosynthesis, as part of an incoherent feed-forward loop with PrrA. Our results reveal a previously unrealized, high degree of combinatorial regulation of photosynthetic genes and significant cross-talk between their transcriptional regulators, while illustrating previously unidentified links between photosynthesis and the maintenance of iron homeostasis. PMID:25503406

Global analysis of photosynthesis transcriptional regulatory networks.

Directory of Open Access Journals (Sweden)

Saheed Imam

2014-12-01

Full Text Available Photosynthesis is a crucial biological process that depends on the interplay of many components. This work analyzed the gene targets for 4 transcription factors: FnrL, PrrA, CrpK and MppG (RSP_2888, which are known or predicted to control photosynthesis in Rhodobacter sphaeroides. Chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-seq identified 52 operons under direct control of FnrL, illustrating its regulatory role in photosynthesis, iron homeostasis, nitrogen metabolism and regulation of sRNA synthesis. Using global gene expression analysis combined with ChIP-seq, we mapped the regulons of PrrA, CrpK and MppG. PrrA regulates ∼34 operons encoding mainly photosynthesis and electron transport functions, while CrpK, a previously uncharacterized Crp-family protein, regulates genes involved in photosynthesis and maintenance of iron homeostasis. Furthermore, CrpK and FnrL share similar DNA binding determinants, possibly explaining our observation of the ability of CrpK to partially compensate for the growth defects of a ΔFnrL mutant. We show that the Rrf2 family protein, MppG, plays an important role in photopigment biosynthesis, as part of an incoherent feed-forward loop with PrrA. Our results reveal a previously unrealized, high degree of combinatorial regulation of photosynthetic genes and significant cross-talk between their transcriptional regulators, while illustrating previously unidentified links between photosynthesis and the maintenance of iron homeostasis.

Dorsoventral variations in dark chilling effects on photosynthesis and stomatal function in Paspalum dilatatum leaves.

Science.gov (United States)

Soares-Cordeiro, Ana Sofia; Driscoll, Simon P; Arrabaça, Maria Celeste; Foyer, Christine H

2011-01-01

The effects of dark chilling on the leaf-side-specific regulation of photosynthesis were characterized in the C(4) grass Paspalum dilatatum. CO(2)- and light-response curves for photosynthesis and associated parameters were measured on whole leaves and on each leaf side independently under adaxial and abaxial illumination before and after plants were exposed to dark chilling for one or two consecutive nights. The stomata closed on the adaxial sides of the leaves under abaxial illumination and no CO(2) uptake could be detected on this surface. However, high rates of whole leaf photosynthesis were still observed because CO(2) assimilation rates were increased on the abaxial sides of the leaves under abaxial illumination. Under adaxial illumination both leaf surfaces contributed to the inhibition of whole leaf photosynthesis observed after one night of chilling. After two nights of chilling photosynthesis remained inhibited on the abaxial side of the leaf but the adaxial side had recovered, an effect related to increased maximal ribulose-1,5-bisphosphate carboxylation rates (V(cmax)) and enhanced maximal electron transport rates (J(max)). Under abaxial illumination, whole leaf photosynthesis was decreased only after the second night of chilling. The chilling-dependent inhibition of photosynthesis was located largely on the abaxial side of the leaf and was related to decreased V(cmax) and J(max), but not to the maximal phosphoenolpyruvate carboxylase carboxylation rate (V(pmax)). Each side of the leaf therefore exhibits a unique sensitivity to stress and recovery. Side-specific responses to stress are related to differences in the control of enzyme and photosynthetic electron transport activities.

Anoxygenic Photosynthesis Controls Oxygenic Photosynthesis in a Cyanobacterium from a Sulfidic Spring

KAUST Repository

Klatt, Judith M.; Alnajjar, Mohammad Ahmad; Yilmaz, Pelin; Lavik, Gaute; de Beer, Dirk; Polerecky, Lubos

2015-01-01

Before the Earth's complete oxygenation (0.58 to 0.55 billion years [Ga] ago), the photic zone of the Proterozoic oceans was probably redox stratified, with a slightly aerobic, nutrient-limited upper layer above a light-limited layer that tended toward euxinia. In such oceans, cyanobacteria capable of both oxygenic and sulfide-driven anoxygenic photosynthesis played a fundamental role in the global carbon, oxygen, and sulfur cycle. We have isolated a cyanobacterium, Pseudanabaena strain FS39, in which this versatility is still conserved, and we show that the transition between the two photosynthetic modes follows a surprisingly simple kinetic regulation controlled by this organism's affinity for H2S. Specifically, oxygenic photosynthesis is performed in addition to anoxygenic photosynthesis only when H2S becomes limiting and its concentration decreases below a threshold that increases predictably with the available ambient light. The carbon-based growth rates during oxygenic and anoxygenic photosynthesis were similar. However, Pseudanabaena FS39 additionally assimilated NO3 - during anoxygenic photosynthesis. Thus, the transition between anoxygenic and oxygenic photosynthesis was accompanied by a shift of the C/N ratio of the total bulk biomass. These mechanisms offer new insights into the way in which, despite nutrient limitation in the oxic photic zone in the mid-Proterozoic oceans, versatile cyanobacteria might have promoted oxygenic photosynthesis and total primary productivity, a key step that enabled the complete oxygenation of our planet and the subsequent diversification of life.

Anoxygenic Photosynthesis Controls Oxygenic Photosynthesis in a Cyanobacterium from a Sulfidic Spring

KAUST Repository

Klatt, Judith M.

2015-03-15

Before the Earth\\'s complete oxygenation (0.58 to 0.55 billion years [Ga] ago), the photic zone of the Proterozoic oceans was probably redox stratified, with a slightly aerobic, nutrient-limited upper layer above a light-limited layer that tended toward euxinia. In such oceans, cyanobacteria capable of both oxygenic and sulfide-driven anoxygenic photosynthesis played a fundamental role in the global carbon, oxygen, and sulfur cycle. We have isolated a cyanobacterium, Pseudanabaena strain FS39, in which this versatility is still conserved, and we show that the transition between the two photosynthetic modes follows a surprisingly simple kinetic regulation controlled by this organism\\'s affinity for H2S. Specifically, oxygenic photosynthesis is performed in addition to anoxygenic photosynthesis only when H2S becomes limiting and its concentration decreases below a threshold that increases predictably with the available ambient light. The carbon-based growth rates during oxygenic and anoxygenic photosynthesis were similar. However, Pseudanabaena FS39 additionally assimilated NO3 - during anoxygenic photosynthesis. Thus, the transition between anoxygenic and oxygenic photosynthesis was accompanied by a shift of the C/N ratio of the total bulk biomass. These mechanisms offer new insights into the way in which, despite nutrient limitation in the oxic photic zone in the mid-Proterozoic oceans, versatile cyanobacteria might have promoted oxygenic photosynthesis and total primary productivity, a key step that enabled the complete oxygenation of our planet and the subsequent diversification of life.

Expression profiling and functional analysis reveals that TOR is a key player in regulating photosynthesis and phytohormone signaling pathways in Arabidopsis.

Science.gov (United States)

Dong, Pan; Xiong, Fangjie; Que, Yumei; Wang, Kai; Yu, Lihua; Li, Zhengguo; Ren, Maozhi

2015-01-01

Target of rapamycin (TOR) acts as a master regulator to control cell growth by integrating nutrient, energy, and growth factors in all eukaryotic species. TOR plays an evolutionarily conserved role in regulating the transcription of genes associated with anabolic and catabolic processes in Arabidopsis, but little is known about the functions of TOR in photosynthesis and phytohormone signaling, which are unique features of plants. In this study, AZD8055 (AZD) was screened as the strongest active-site TOR inhibitor (asTORi) in Arabidopsis compared with TORIN1 and KU63794 (KU). Gene expression profiles were evaluated using RNA-seq after treating Arabidopsis seedlings with AZD. More than three-fold differentially expressed genes (DEGs) were identified in AZD-treated plants relative to rapamycin-treated plants in previous studies. Most of the DEGs and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways involved in cell wall elongation, ribosome biogenesis, and cell autophagy were common to both AZD- and rapamycin-treated samples, but AZD displayed much broader and more efficient inhibition of TOR compared with rapamycin. Importantly, the suppression of TOR by AZD resulted in remodeling of the expression profile of the genes associated with photosynthesis and various phytohormones, indicating that TOR plays a crucial role in modulating photosynthesis and phytohormone signaling in Arabidopsis. These newly identified DEGs expand the understanding of TOR signaling in plants. This study elucidates the novel functions of TOR in photosynthesis and phytohormone signaling and provides a platform to study the downstream targets of TOR in Arabidopsis.

Photosynthesis in the Archean era.

Science.gov (United States)

Olson, John M

2006-05-01

The earliest reductant for photosynthesis may have been H2. The carbon isotope composition measured in graphite from the 3.8-Ga Isua Supercrustal Belt in Greenland is attributed to H2-driven photosynthesis, rather than to oxygenic photosynthesis as there would have been no evolutionary pressure for oxygenic photosynthesis in the presence of H2. Anoxygenic photosynthesis may also be responsible for the filamentous mats found in the 3.4-Ga Buck Reef Chert in South Africa. Another early reductant was probably H2S. Eventually the supply of H2 in the atmosphere was likely to have been attenuated by the production of CH4 by methanogens, and the supply of H2S was likely to have been restricted to special environments near volcanos. Evaporites, possible stromatolites, and possible microfossils found in the 3.5-Ga Warrawoona Megasequence in Australia are attributed to sulfur-driven photosynthesis. Proteobacteria and protocyanobacteria are assumed to have evolved to use ferrous iron as reductant sometime around 3.0 Ga or earlier. This type of photosynthesis could have produced banded iron formations similar to those produced by oxygenic photosynthesis. Microfossils, stromatolites, and chemical biomarkers in Australia and South Africa show that cyanobacteria containing chlorophyll a and carrying out oxygenic photosynthesis appeared by 2.8 Ga, but the oxygen level in the atmosphere did not begin to increase until about 2.3 Ga.

Improving Photosynthesis

Science.gov (United States)

Evans, John R.

2013-01-01

Photosynthesis is the basis of plant growth, and improving photosynthesis can contribute toward greater food security in the coming decades as world population increases. Multiple targets have been identified that could be manipulated to increase crop photosynthesis. The most important target is Rubisco because it catalyses both carboxylation and oxygenation reactions and the majority of responses of photosynthesis to light, CO2, and temperature are reflected in its kinetic properties. Oxygenase activity can be reduced either by concentrating CO2 around Rubisco or by modifying the kinetic properties of Rubisco. The C4 photosynthetic pathway is a CO2-concentrating mechanism that generally enables C4 plants to achieve greater efficiency in their use of light, nitrogen, and water than C3 plants. To capitalize on these advantages, attempts have been made to engineer the C4 pathway into C3 rice (Oryza sativa). A simpler approach is to transfer bicarbonate transporters from cyanobacteria into chloroplasts and prevent CO2 leakage. Recent technological breakthroughs now allow higher plant Rubisco to be engineered and assembled successfully in planta. Novel amino acid sequences can be introduced that have been impossible to reach via normal evolution, potentially enlarging the range of kinetic properties and breaking free from the constraints associated with covariation that have been observed between certain kinetic parameters. Capturing the promise of improved photosynthesis in greater yield potential will require continued efforts to improve carbon allocation within the plant as well as to maintain grain quality and resistance to disease and lodging. PMID:23812345

Ecological Understanding 1: Ways of Experiencing Photosynthesis.

Science.gov (United States)

Carlsson, Britta

2002-01-01

Investigates 10 student teachers' understanding of the different ways in which the function of the ecosystem could be experienced. Explores the functional aspects of the ecosystem using a system approach. Concludes that the idea of transformation is crucial to more complex ways of understanding photosynthesis. (Contains 62 references.) (Author/YDS)

Anoxygenic photosynthesis controls oxygenic photosynthesis in a cyanobacterium from a sulfidic spring.

Science.gov (United States)

Klatt, Judith M; Al-Najjar, Mohammad A A; Yilmaz, Pelin; Lavik, Gaute; de Beer, Dirk; Polerecky, Lubos

2015-03-01

Before the Earth's complete oxygenation (0.58 to 0.55 billion years [Ga] ago), the photic zone of the Proterozoic oceans was probably redox stratified, with a slightly aerobic, nutrient-limited upper layer above a light-limited layer that tended toward euxinia. In such oceans, cyanobacteria capable of both oxygenic and sulfide-driven anoxygenic photosynthesis played a fundamental role in the global carbon, oxygen, and sulfur cycle. We have isolated a cyanobacterium, Pseudanabaena strain FS39, in which this versatility is still conserved, and we show that the transition between the two photosynthetic modes follows a surprisingly simple kinetic regulation controlled by this organism's affinity for H2S. Specifically, oxygenic photosynthesis is performed in addition to anoxygenic photosynthesis only when H2S becomes limiting and its concentration decreases below a threshold that increases predictably with the available ambient light. The carbon-based growth rates during oxygenic and anoxygenic photosynthesis were similar. However, Pseudanabaena FS39 additionally assimilated NO3 (-) during anoxygenic photosynthesis. Thus, the transition between anoxygenic and oxygenic photosynthesis was accompanied by a shift of the C/N ratio of the total bulk biomass. These mechanisms offer new insights into the way in which, despite nutrient limitation in the oxic photic zone in the mid-Proterozoic oceans, versatile cyanobacteria might have promoted oxygenic photosynthesis and total primary productivity, a key step that enabled the complete oxygenation of our planet and the subsequent diversification of life. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Assessing parameter variability in a photosynthesis model within and between plant functional types using global Fluxnet eddy covariance data

NARCIS (Netherlands)

Groenendijk, M.; Dolman, A.J.; Molen, van der M.K.; Leuning, R.; Arneth, A.; Delpierre, N.; Gash, J.H.C.; Lindroth, A.; Richardson, A.D.; Verbeeck, H.; Wohlfahrt, G.

2011-01-01

The vegetation component in climate models has advanced since the late 1960s from a uniform prescription of surface parameters to plant functional types (PFTs). PFTs are used in global land-surface models to provide parameter values for every model grid cell. With a simple photosynthesis model we

Five Lectures on Photosynthesis

International Nuclear Information System (INIS)

Broda, E.

1979-01-01

These five lectures were held by E. Broda during the International Symposium on Alternative Energies, in September 1979. Lecture 1 – The Great Physicists and Photosynthesis; Lecture 2 – The Influence of Photosynthesis on the Biosphere. Past, Present and Future; Lecture 3 – The Origin of Photosynthesis; Lecture 4 – The Evolution from Photosynthetic Bacteria to Plants; Lecture 5 – Respiration and Photorespiration. (nowak)

Effect of Bradyrhizobium photosynthesis on stem nodulation of Aeschynomene sensitiva

OpenAIRE

Giraud, Eric; Hannibal, Laure; Fardoux, Joël; Verméglio, A.; Dreyfus, Bernard

2000-01-01

Some leguminous species of the genus #Aeschynomene$ are specifically stem-nodulated by photosynthetic bradyrhizobia. To study the effect of bacterial photosynthesis during symbiosis, we generated a photosynthesis-negative mutant of the #Bradyrhizobium$ sp. strain ORS278 symbiont of #Aeschynomene sensitiva$. The presence of a functional photosynthetic unit in bacterioids and the high expression of the photosynthetic genes observed in stem nodules demonstrate that the bacteria are photosyntheti...

Fruit photosynthesis in Satsuma mandarin.

Science.gov (United States)

Hiratsuka, Shin; Suzuki, Mayu; Nishimura, Hiroshi; Nada, Kazuyoshi

2015-12-01

To clarify detailed characteristics of fruit photosynthesis, possible gas exchange pathway and photosynthetic response to different environments were investigated in Satsuma mandarin (Citrus unshiu). About 300 mm(-2) stomata were present on fruit surface during young stages (∼10-30 mm diameter fruit) and each stoma increased in size until approximately 88 days after full bloom (DAFB), while the stomata collapsed steadily thereafter; more than 50% stomata deformed at 153 DAFB. The transpiration rate of the fruit appeared to match with stoma development and its intactness rather than the density. Gross photosynthetic rate of the rind increased gradually with increasing CO2 up to 500 ppm but decreased at higher concentrations, which may resemble C4 photosynthesis. In contrast, leaf photosynthesis increased constantly with CO2 increment. Although both fruit and leaf photosynthesis were accelerated by rising photosynthetic photon flux density (PPFD), fruit photosynthesis was greater under considerably lower PPFD from 13.5 to 68 μmolm(-2)s(-1). Thus, Satsuma mandarin fruit appears to incorporate CO2 through fully developed and non-collapsed stomata, and subject it to fruit photosynthesis, which may be characterized as intermediate status among C3, C4 and shade plant photosynthesis. The device of fruit photosynthesis may develop differently from its leaf to capture CO2 efficiently. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Regulation of bacterial photosynthesis genes by the small noncoding RNA PcrZ.

Science.gov (United States)

Mank, Nils N; Berghoff, Bork A; Hermanns, Yannick N; Klug, Gabriele

2012-10-02

The small RNA PcrZ (photosynthesis control RNA Z) of the facultative phototrophic bacterium Rhodobacter sphaeroides is induced upon a drop of oxygen tension with similar kinetics to those of genes for components of photosynthetic complexes. High expression of PcrZ depends on PrrA, the response regulator of the PrrB/PrrA two-component system with a central role in redox regulation in R. sphaeroides. In addition the FnrL protein, an activator of some photosynthesis genes at low oxygen tension, is involved in redox-dependent expression of this small (s)RNA. Overexpression of full-length PcrZ in R. sphaeroides affects expression of a small subset of genes, most of them with a function in photosynthesis. Some mRNAs from the photosynthetic gene cluster were predicted to be putative PcrZ targets and results from an in vivo reporter system support these predictions. Our data reveal a negative effect of PcrZ on expression of its target mRNAs. Thus, PcrZ counteracts the redox-dependent induction of photosynthesis genes, which is mediated by protein regulators. Because PrrA directly activates photosynthesis genes and at the same time PcrZ, which negatively affects photosynthesis gene expression, this is one of the rare cases of an incoherent feed-forward loop including an sRNA. Our data identified PcrZ as a trans acting sRNA with a direct regulatory function in formation of photosynthetic complexes and provide a model for the control of photosynthesis gene expression by a regulatory network consisting of proteins and a small noncoding RNA.

General lighting requirements for photosynthesis

Energy Technology Data Exchange (ETDEWEB)

Geiger, D.R. [Univ. of Dayton, OH (United States)

1994-12-31

A review of the general lighting requirements for photosynthesis reveals that four aspects of light are important: irradiance, quality, timing and duration. These properties of light affect photosynthesis by providing the energy that drives carbon assimilation as well as by exerting control over physiology, structure and morphology of plants. Irradiance, expressed as energy flux, W m{sup -2}, or photon irradiance, {mu}mol m{sup -2} s{sup -1}, determines the rate at which energy is being delivered to the photosynthetic reaction centers. Spectral quality, the wavelength composition of light, is important because photons differ in their probability of being absorbed by the light harvesting complex and hence their ability to drive carbon assimilation. Also the various light receptors for light-mediated regulation of plant form and physiology have characteristic absorption spectra and hence photons differ in their effectiveness for eliciting responses. Duration is important because both carbon assimilation and regulation are affected by the total energy or integrated irradiance delivered during a given period. Many processes associated with photosynthesis are time-dependent, increasing or decreasing with duration. Timing is important because the effectiveness of light in the regulation of plant processes varies with the phase of the diumal cycle as determined by the plant`s time-measuring mechanisms.

Teaching Photosynthesis with ELL Students

Science.gov (United States)

Piper, Susan; Shaw, Edward Lewis, Jr.

2010-01-01

Although the teaching of photosynthesis occurs yearly in elementary classrooms, one thing that makes it challenging is the inclusion of English language learners (ELLs). This article presents several activities for teaching and assessing of photosynthesis in a third grade classroom. The activities incorporate the photosynthesis content, teaching…

The Evolution of Photosynthesis

International Nuclear Information System (INIS)

Broda, E.

1976-01-01

This Review was written by Engelbert Broda, an Austrian Chemist and Physicist, on February the 10th 1976. The merits of the inductive and the deductive approach in tracing the pathways of evolution are discussed. Using the latter approach, it is concluded that photosynthesis followed fermentation as a method of obtaining energy-rich compounds, especially ATP. Photosynthesis probably arose by utilization of membranes for bioenergetic processes. Originally photosynthesis served photophosphorylation (ATP production), later reducing power was also made, either by open-ended, light-powered, electron flow or driven by ATP; ultimate electron donors were at first hydrogen or sulfur compounds, and later water, the last-named capability Was acquired by prokaryotic algae the earliest plants, similar to the recent blue-greens. When free oxygen entered the atmosphere for the first time, various forms of respiration (oxidative phosphorylation) became possible. Mechanistically, respiration evolved from photosynthesis (‘conversion hypotheses’). Prokaryotic algae are probably the ancestors of the chloroplasts in the eukaryotes, In the evolution of the eukaryotes, not much change in the basic processes of photosynthesis occurred.(author)

Photosynthesis in Hydrogen-Dominated Atmospheres

Science.gov (United States)

Bains, William; Seager, Sara; Zsom, Andras

2014-01-01

The diversity of extrasolar planets discovered in the last decade shows that we should not be constrained to look for life in environments similar to early or present-day Earth. Super-Earth exoplanets are being discovered with increasing frequency, and some will be able to retain a stable, hydrogen-dominated atmosphere. We explore the possibilities for photosynthesis on a rocky planet with a thin H2-dominated atmosphere. If a rocky, H2-dominated planet harbors life, then that life is likely to convert atmospheric carbon into methane. Outgassing may also build an atmosphere in which methane is the principal carbon species. We describe the possible chemical routes for photosynthesis starting from methane and show that less energy and lower energy photons could drive CH4-based photosynthesis as compared with CO2-based photosynthesis. We find that a by-product biosignature gas is likely to be H2, which is not distinct from the hydrogen already present in the environment. Ammonia is a potential biosignature gas of hydrogenic photosynthesis that is unlikely to be generated abiologically. We suggest that the evolution of methane-based photosynthesis is at least as likely as the evolution of anoxygenic photosynthesis on Earth and may support the evolution of complex life. PMID:25411926

Photosynthesis in Hydrogen-Dominated Atmospheres

Directory of Open Access Journals (Sweden)

William Bains

2014-11-01

Full Text Available The diversity of extrasolar planets discovered in the last decade shows that we should not be constrained to look for life in environments similar to early or present-day Earth. Super-Earth exoplanets are being discovered with increasing frequency, and some will be able to retain a stable, hydrogen-dominated atmosphere. We explore the possibilities for photosynthesis on a rocky planet with a thin H2-dominated atmosphere. If a rocky, H2-dominated planet harbors life, then that life is likely to convert atmospheric carbon into methane. Outgassing may also build an atmosphere in which methane is the principal carbon species. We describe the possible chemical routes for photosynthesis starting from methane and show that less energy and lower energy photons could drive CH4-based photosynthesis as compared with CO2-based photosynthesis. We find that a by-product biosignature gas is likely to be H2, which is not distinct from the hydrogen already present in the environment. Ammonia is a potential biosignature gas of hydrogenic photosynthesis that is unlikely to be generated abiologically. We suggest that the evolution of methane-based photosynthesis is at least as likely as the evolution of anoxygenic photosynthesis on Earth and may support the evolution of complex life.

Electromagnetic Radiation Disturbed the Photosynthesis of Microcystis aeruginosa at the Proteomics Level.

Science.gov (United States)

Tang, Chao; Yang, Chuanjun; Yu, Hui; Tian, Shen; Huang, Xiaomei; Wang, Weiyi; Cai, Peng

2018-01-11

Photosynthesis of Microcystis aeruginosa under Electromagnetic Radiation (1.8 GHz, 40 V/m) was studied by using the proteomics. A total of 30 differentially expressed proteins, including 15 up-regulated and 15 down-regulated proteins, were obtained in this study. The differentially expressed proteins were significantly enriched in the photosynthesis pathway, in which the protein expression levels of photosystems II cytochrome b559 α subunit, cytochrome C550, PsbY, and F-type ATP synthase (a, b) decreased. Our results indicated that electromagnetic radiation altered the photosynthesis-related protein expression levels, and aimed at the function of photosynthetic pigments, photosystems II potential activity, photosynthetic electron transport process, and photosynthetic phosphorylation process of M. aeruginosa. Based on the above evidence, that photoreaction system may be deduced as a target of electromagnetic radiation on the photosynthesis in cyanobacteria; the photoreaction system of cyanobacteria is a hypothetical "shared target effector" that responds to light and electromagnetic radiation; moreover, electromagnetic radiation does not act on the functional proteins themselves but their expression processes.

Manganese and the Evolution of Photosynthesis

Science.gov (United States)

Fischer, Woodward W.; Hemp, James; Johnson, Jena E.

2015-09-01

Oxygenic photosynthesis is the most important bioenergetic event in the history of our planet—it evolved once within the Cyanobacteria, and remained largely unchanged as it was transferred to algae and plants via endosymbiosis. Manganese plays a fundamental role in this history because it lends the critical redox behavior of the water-oxidizing complex of photosystem II. Constraints from the photoassembly of the Mn-bearing water-oxidizing complex fuel the hypothesis that Mn(II) once played a key role as an electron donor for anoxygenic photosynthesis prior to the evolution of oxygenic photosynthesis. Here we review the growing body of geological and geochemical evidence from the Archean and Paleoproterozoic sedimentary records that supports this idea and demonstrates that the oxidative branch of the Mn cycle switched on prior to the rise of oxygen. This Mn-oxidizing phototrophy hypothesis also receives support from the biological record of extant phototrophs, and can be made more explicit by leveraging constraints from structural biology and biochemistry of photosystem II in Cyanobacteria. These observations highlight that water-splitting in photosystem II evolved independently from a homodimeric ancestral type II reaction center capable of high potential photosynthesis and Mn(II) oxidation, which is required by the presence of homologous redox-active tyrosines in the modern heterodimer. The ancestral homodimer reaction center also evolved a C-terminal extension that sterically precluded standard phototrophic electron donors like cytochrome c, cupredoxins, or high-potential iron-sulfur proteins, and could only complete direct oxidation of small molecules like Mn2+, and ultimately water.

Photosynthesis down-regulation precedes carbohydrate accumulation under sink limitation in Citrus.

Science.gov (United States)

Nebauer, Sergio G; Renau-Morata, Begoña; Guardiola, José Luis; Molina, Rosa-Victoria

2011-02-01

Photosynthesis down-regulation due to an imbalance between sources and sinks in Citrus leaves could be mediated by excessive accumulation of carbohydrates. However, there is limited understanding of the physiological role of soluble and insoluble carbohydrates in photosynthesis regulation and the elements triggering the down-regulation process. In this work, the role of non-structural carbohydrates in the regulation of photosynthesis under a broad spectrum of source-sink relationships has been investigated in the Salustiana sweet orange. Soluble sugar and starch accumulation in leaves, induced by girdling experiments, did not induce down-regulation of the photosynthetic rate in the presence of sinks (fruits). The leaf-to-fruit ratio did not modulate photosynthesis but allocation of photoassimilates to the fruits. The lack of strong sink activity led to a decrease in the photosynthetic rate and starch accumulation in leaves. However, photosynthesis down-regulation due to an excess of total soluble sugars or starch was discarded because photosynthesis and stomatal conductance reduction occurred prior to any significant accumulation of these carbohydrates. Gas exchange and fluorescence parameters suggested biochemical limitations to photosynthesis. In addition, the expression of carbon metabolism-related genes was altered within 24 h when strong sinks were removed. Sucrose synthesis and export genes were inhibited, whereas the expression of ADP-glucose pyrophosphorylase was increased to cope with the excess of assimilates. In conclusion, changes in starch and soluble sugar turnover, but not sugar content per se, could provide the signal for photosynthesis regulation. In these conditions, non-stomatal limitations strongly inhibited the photosynthetic rate prior to any significant increase in carbohydrate levels.

Leaf structural characteristics are less important than leaf chemical properties in determining the response of leaf mass per area and photosynthesis of Eucalyptus saligna to industrial-age changes in [CO2] and temperature.

Science.gov (United States)

Xu, Cheng-Yuan; Salih, Anya; Ghannoum, Oula; Tissue, David T

2012-10-01

The rise in atmospheric [CO(2)] is associated with increasing air temperature. However, studies on plant responses to interactive effects of [CO(2)] and temperature are limited, particularly for leaf structural attributes. In this study, Eucalyptus saligna plants were grown in sun-lit glasshouses differing in [CO(2)] (290, 400, and 650 µmol mol(-1)) and temperature (26 °C and 30 °C). Leaf anatomy and chloroplast parameters were assessed with three-dimensional confocal microscopy, and the interactive effects of [CO(2)] and temperature were quantified. The relative influence of leaf structural attributes and chemical properties on the variation of leaf mass per area (LMA) and photosynthesis within these climate regimes was also determined. Leaf thickness and mesophyll size increased in higher [CO(2)] but decreased at the warmer temperature; no treatment interaction was observed. In pre-industrial [CO(2)], warming reduced chloroplast diameter without altering chloroplast number per cell, but the opposite pattern (reduced chloroplast number per cell and unchanged chloroplast diameter) was observed in both current and projected [CO(2)]. The variation of LMA was primarily explained by total non-structural carbohydrate (TNC) concentration rather than leaf thickness. Leaf photosynthetic capacity (light- and [CO(2)]-saturated rate at 28 °C) and light-saturated photosynthesis (under growth [CO(2)] and temperature) were primarily determined by leaf nitrogen contents, while secondarily affected by chloroplast gas exchange surface area and chloroplast number per cell, respectively. In conclusion, leaf structural attributes are less important than TNC and nitrogen in affecting LMA and photosynthesis responses to the studied climate regimes, indicating that leaf structural attributes have limited capacity to adjust these functional traits in a changing climate.

Scientific Conceptions of Photosynthesis among Primary School Pupils and Student Teachers of Biology

Directory of Open Access Journals (Sweden)

Darja Skribe Dimec

2017-03-01

Full Text Available Photosynthesis is the most important biochemical process on Earth. Most living beings depend on it directly or indirectly. Knowledge about photosynthesis enables us to understand how the world functions as an ecosystem and how photosynthesis acts as a bridge between the non-living and living worlds. It is, therefore, understandable that photosynthesis is included in national curricula around the world. The practice unfortunately shows that students at all school levels mostly learn about photosynthesis by rote. Consequently, they have difficulties understanding this vital process. Research also shows many misconceptions in relation to photosynthesis among students of different ages. Based on these, the main aim of our study was to explore the scientific conceptions about photosynthesis held by primary school pupils and student teachers of biology. Data were collected using a questionnaire containing seven biology content questions. The sample consisted of 634 participants, 427 primary school pupils (aged 11–14, and 207 student teachers of biology (aged 20–23. We found that the populations of primary school pupils and student teachers of biology differ greatly concerning scientific conceptions of photosynthesis. The student teachers showed good and complex understanding of photosynthesis, while pupils showed some misconceptions (location of chlorophyll and photosynthesis in a plant, transformation of energy in photosynthesis. Analysis of the development of scientific conceptions about photosynthesis with age showed that there is very little progress among primary school pupils and none among biology student teachers. More involvement of student teachers of biology in practical work at primary schools during their study was suggested to make student teachers aware of, and better understand pupils’ misconceptions.

PHOTOSYNTHESIS

Energy Technology Data Exchange (ETDEWEB)

Bryant, Donald A. [Pennsylvania State Univ., University Park, PA (United States)

2002-06-21

The Gordon Research Conference (GRC) on PHOTOSYNTHESIS was held at Roger Williams University, Bristol, RI. Emphasis was placed on current unpublished research and discussion of the future target areas in this field.

Photosynthesis solutions to enhance productivity.

Science.gov (United States)

Foyer, Christine H; Ruban, Alexander V; Nixon, Peter J

2017-09-26

The concept that photosynthesis is a highly inefficient process in terms of conversion of light energy into biomass is embedded in the literature. It is only in the past decade that the processes limiting photosynthetic efficiency have been understood to an extent that allows a step change in our ability to manipulate light energy assimilation into carbon gain. We can therefore envisage that future increases in the grain yield potential of our major crops may depend largely on increasing the efficiency of photosynthesis. The papers in this issue provide new insights into the nature of current limitations on photosynthesis and identify new targets that can be used for crop improvement, together with information on the impacts of a changing environment on the productivity of photosynthesis on land and in our oceans.This article is part of the themed issue 'Enhancing photosynthesis in crop plants: targets for improvement'. © 2017 The Author(s).

Artificial Photosynthesis: Beyond Mimicking Nature

International Nuclear Information System (INIS)

Dau, Holger; Fujita, Etsuko; Sun, Licheng

2017-01-01

In this Editorial, Guest Editors Holger Dau, Etsuko Fujita, and Licheng Sun introduce the Special Issue of ChemSusChem on “Artificial Photosynthesis for Sustainable Fuels”. Here, they discuss the need for non-fossil based fuels, introduce both biological and artificial photosynthesis, and outline various important concepts in artificial photosynthesis, including molecular and solid-state catalysts for water oxidation and hydrogen evolution, catalytic CO 2 reduction, and photoelectrochemical systems.

Annual cycle of Scots pine photosynthesis

Directory of Open Access Journals (Sweden)

P. Hari

2017-12-01

Full Text Available Photosynthesis, i.e. the assimilation of atmospheric carbon to organic molecules with the help of solar energy, is a fundamental and well-understood process. Here, we connect theoretically the fundamental concepts affecting C3 photosynthesis with the main environmental drivers (ambient temperature and solar light intensity, using six axioms based on physiological and physical knowledge, and yield straightforward and simple mathematical equations. The light and carbon reactions in photosynthesis are based on the coherent operation of the photosynthetic machinery, which is formed of a complicated chain of enzymes, membrane pumps and pigments. A powerful biochemical regulation system has emerged through evolution to match photosynthesis with the annual cycle of solar light and temperature. The action of the biochemical regulation system generates the annual cycle of photosynthesis and emergent properties, the state of the photosynthetic machinery and the efficiency of photosynthesis. The state and the efficiency of the photosynthetic machinery is dynamically changing due to biosynthesis and decomposition of the molecules. The mathematical analysis of the system, defined by the very fundamental concepts and axioms, resulted in exact predictions of the behaviour of daily and annual patterns in photosynthesis. We tested the predictions with extensive field measurements of Scots pine (Pinus sylvestris L. photosynthesis on a branch scale in northern Finland. Our theory gained strong support through rigorous testing.

Annual cycle of Scots pine photosynthesis

Science.gov (United States)

Hari, Pertti; Kerminen, Veli-Matti; Kulmala, Liisa; Kulmala, Markku; Noe, Steffen; Petäjä, Tuukka; Vanhatalo, Anni; Bäck, Jaana

2017-12-01

Photosynthesis, i.e. the assimilation of atmospheric carbon to organic molecules with the help of solar energy, is a fundamental and well-understood process. Here, we connect theoretically the fundamental concepts affecting C3 photosynthesis with the main environmental drivers (ambient temperature and solar light intensity), using six axioms based on physiological and physical knowledge, and yield straightforward and simple mathematical equations. The light and carbon reactions in photosynthesis are based on the coherent operation of the photosynthetic machinery, which is formed of a complicated chain of enzymes, membrane pumps and pigments. A powerful biochemical regulation system has emerged through evolution to match photosynthesis with the annual cycle of solar light and temperature. The action of the biochemical regulation system generates the annual cycle of photosynthesis and emergent properties, the state of the photosynthetic machinery and the efficiency of photosynthesis. The state and the efficiency of the photosynthetic machinery is dynamically changing due to biosynthesis and decomposition of the molecules. The mathematical analysis of the system, defined by the very fundamental concepts and axioms, resulted in exact predictions of the behaviour of daily and annual patterns in photosynthesis. We tested the predictions with extensive field measurements of Scots pine (Pinus sylvestris L.) photosynthesis on a branch scale in northern Finland. Our theory gained strong support through rigorous testing.

Photosynthesis in high definition

Science.gov (United States)

Hilton, Timothy W.

2018-01-01

Photosynthesis is the foundation for almost all known life, but quantifying it at scales above a single plant is difficult. A new satellite illuminates plants' molecular machinery at much-improved spatial resolution, taking us one step closer to combined `inside-outside' insights into large-scale photosynthesis.

Global artificial photosynthesis project: a scientific and legal introduction.

Science.gov (United States)

Faunce, Thomas

2011-12-01

With the global human population set to exceed 10 billion by 2050, its collective energy consumption to rise from 400 to over 500 EJ/yr and with the natural environment under increasing pressure from these sources as well as from anthropogenic climate change, political solutions such as the creation of an efficient carbon price and trading scheme may arrive too late. In this context, the scientific community is exploring technological remedies. Central to these options is artificial photosynthesis--the creation, particularly through nanotechnology, of devices capable to doing what plants have done for millions of years - transforming sunlight, water and carbon dioxide into food and fuel. This article argues that a Global Artificial Photosynthesis (GAP) project can raise the public profile and encourage the pace, complexity and funding of scientific collaborations in artificial photosynthesis research. The legal structure of a GAP project will be critical to prevent issues such as state sovereignty over energy and food resources and corporate intellectual monopoly privileges unduly inhibiting the important contribution of artificial photosynthesis to global public health and environmental sustainability. The article presents an introduction to the scientific and legal concepts behind a GAP project.

Connecting Photosynthesis and Cellular Respiration: Preservice Teachers' Conceptions

Science.gov (United States)

Brown, Mary H.; Schwartz, Renee S.

2009-01-01

The biological processes of photosynthesis and plant cellular respiration include multiple biochemical steps, occur simultaneously within plant cells, and share common molecular components. Yet, learners often compartmentalize functions and specialization of cell organelles relevant to these two processes, without considering the interconnections…

Dynamic photosynthesis in different environmental conditions.

Science.gov (United States)

Kaiser, Elias; Morales, Alejandro; Harbinson, Jeremy; Kromdijk, Johannes; Heuvelink, Ep; Marcelis, Leo F M

2015-05-01

Incident irradiance on plant leaves often fluctuates, causing dynamic photosynthesis. Whereas steady-state photosynthetic responses to environmental factors have been extensively studied, knowledge of dynamic modulation of photosynthesis remains scarce and scattered. This review addresses this discrepancy by summarizing available data and identifying the research questions necessary to advance our understanding of interactions between environmental factors and dynamic behaviour of photosynthesis using a mechanistic framework. Firstly, dynamic photosynthesis is separated into sub-processes related to proton and electron transport, non-photochemical quenching, control of metabolite flux through the Calvin cycle (activation states of Rubisco and RuBP regeneration, and post-illumination metabolite turnover), and control of CO₂ supply to Rubisco (stomatal and mesophyll conductance changes). Secondly, the modulation of dynamic photosynthesis and its sub-processes by environmental factors is described. Increases in ambient CO₂ concentration and temperature (up to ~35°C) enhance rates of photosynthetic induction and decrease its loss, facilitating more efficient dynamic photosynthesis. Depending on the sensitivity of stomatal conductance, dynamic photosynthesis may additionally be modulated by air humidity. Major knowledge gaps exist regarding environmental modulation of loss of photosynthetic induction, dynamic changes in mesophyll conductance, and the extent of limitations imposed by stomatal conductance for different species and environmental conditions. The study of mutants or genetic transformants for specific processes under various environmental conditions could provide significant progress in understanding the control of dynamic photosynthesis. © The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Glucose Synthesis in a Protein-Based Artificial Photosynthesis System.

Science.gov (United States)

Lu, Hao; Yuan, Wenqiao; Zhou, Jack; Chong, Parkson Lee-Gau

2015-09-01

The objective of this study was to understand glucose synthesis of a protein-based artificial photosynthesis system affected by operating conditions, including the concentrations of reactants, reaction temperature, and illumination. Results from non-vesicle-based glyceraldehyde-3-phosphate (GAP) and glucose synthesis showed that the initial concentrations of ribulose-1,5-bisphosphate (RuBP) and adenosine triphosphate (ATP), lighting source, and temperature significantly affected glucose synthesis. Higher initial concentrations of RuBP and ATP significantly enhanced GAP synthesis, which was linearly correlated to glucose synthesis, confirming the proper functions of all catalyzing enzymes in the system. White fluorescent light inhibited artificial photosynthesis and reduced glucose synthesis by 79.2 % compared to in the dark. The reaction temperature of 40 °C was optimum, whereas lower or higher temperature reduced glucose synthesis. Glucose synthesis in the vesicle-based artificial photosynthesis system reconstituted with bacteriorhodopsin, F 0 F 1 ATP synthase, and polydimethylsiloxane-methyloxazoline-polydimethylsiloxane triblock copolymer was successfully demonstrated. This system efficiently utilized light-induced ATP to drive glucose synthesis, and 5.2 μg ml(-1) glucose was synthesized in 0.78-ml reaction buffer in 7 h. Light-dependent reactions were found to be the bottleneck of the studied artificial photosynthesis system.

Predicting photosynthesis and transpiration responses to ozone: decoupling modeled photosynthesis and stomatal conductance

Directory of Open Access Journals (Sweden)

D. Lombardozzi

2012-08-01

Full Text Available Plants exchange greenhouse gases carbon dioxide and water with the atmosphere through the processes of photosynthesis and transpiration, making them essential in climate regulation. Carbon dioxide and water exchange are typically coupled through the control of stomatal conductance, and the parameterization in many models often predict conductance based on photosynthesis values. Some environmental conditions, like exposure to high ozone (O₃ concentrations, alter photosynthesis independent of stomatal conductance, so models that couple these processes cannot accurately predict both. The goals of this study were to test direct and indirect photosynthesis and stomatal conductance modifications based on O₃ damage to tulip poplar (Liriodendron tulipifera in a coupled Farquhar/Ball-Berry model. The same modifications were then tested in the Community Land Model (CLM to determine the impacts on gross primary productivity (GPP and transpiration at a constant O₃ concentration of 100 parts per billion (ppb. Modifying the V_cmax parameter and directly modifying stomatal conductance best predicts photosynthesis and stomatal conductance responses to chronic O₃ over a range of environmental conditions. On a global scale, directly modifying conductance reduces the effect of O₃ on both transpiration and GPP compared to indirectly modifying conductance, particularly in the tropics. The results of this study suggest that independently modifying stomatal conductance can improve the ability of models to predict hydrologic cycling, and therefore improve future climate predictions.

Can miscanthus C4 photosynthesis compete with festulolium C3 photosynthesis in a temperate climate?

DEFF Research Database (Denmark)

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

2017-01-01

Miscanthus, a perennial grass with C4 photosynthesis, is regarded as a promising energy crop due to its high biomass productivity. Compared with other C4 species, most miscanthus genotypes have high cold tolerances at 14 °C. However, in temperate climates, temperatures below 14 °C are common...... at each temperature level and still maintained photosynthesis after growing for a longer period at 6/4 °C. Only two of five measured miscanthus genotypes increased photosynthesis immediately after the temperature was raised again. The photosynthetic capacity of festulolium was significantly higher at 10...

Effects of iron limitation on photosynthesis and carbohydrate metabolism in the Antarctic diatom Chaetoceros brevis (Bacillariophyceae)

NARCIS (Netherlands)

van Oijen, T; van Leeuwe, MA; Gieskes, WWC; de Baar, HJW

Iron, one of the structural elements of organic components that play an essential role in photosynthesis and nitrogen assimilation of plants, is available at extremely low concentrations in large parts of the Southern Ocean's surface waters. We tested the hypothesis that photosynthesis is the

First-principles data-driven discovery of transition metal oxides for artificial photosynthesis

Science.gov (United States)

Yan, Qimin

We develop a first-principles data-driven approach for rapid identification of transition metal oxide (TMO) light absorbers and photocatalysts for artificial photosynthesis using the Materials Project. Initially focusing on Cr, V, and Mn-based ternary TMOs in the database, we design a broadly-applicable multiple-layer screening workflow automating density functional theory (DFT) and hybrid functional calculations of bulk and surface electronic and magnetic structures. We further assess the electrochemical stability of TMOs in aqueous environments from computed Pourbaix diagrams. Several promising earth-abundant low band-gap TMO compounds with desirable band edge energies and electrochemical stability are identified by our computational efforts and then synergistically evaluated using high-throughput synthesis and photoelectrochemical screening techniques by our experimental collaborators at Caltech. Our joint theory-experiment effort has successfully identified new earth-abundant copper and manganese vanadate complex oxides that meet highly demanding requirements for photoanodes, substantially expanding the known space of such materials. By integrating theory and experiment, we validate our approach and develop important new insights into structure-property relationships for TMOs for oxygen evolution photocatalysts, paving the way for use of first-principles data-driven techniques in future applications. This work is supported by the Materials Project Predictive Modeling Center and the Joint Center for Artificial Photosynthesis through the U.S. Department of Energy, Office of Basic Energy Sciences, Materials Sciences and Engineering Division, under Contract No. DE-AC02-05CH11231. Computational resources also provided by the Department of Energy through the National Energy Supercomputing Center.

Photosynthesis research in the USSR

Energy Technology Data Exchange (ETDEWEB)

Hall, D.O.

1979-09-27

Current research programs in photosynthesis in the USSR are described. Some of the programs include: (1) research on hydrogenases; (2) computer facilities (3) photochemical reduction of low potential compounds; (4) hydrogen-producing systems using model pigment systems; (5) stabilization of chloroplast membranes; (6) construction of fuel cells using immobilized enzymes; (7) carbon, hydrogen, and nitrogen metabolism of photosynthetic bacteria; (8) methane producing bacteria; (9) growth of photosynthetic bacteria under dark and light conditions; (10) efficiency of photosynthesis and plant productivity; (11) biomass as a future source of energy; (12) mycology; (13) isolation of photosystems; and (14) factors limiting photosynthesis in the leaf. (DC)

A quantum protective mechanism in photosynthesis

Science.gov (United States)

Marais, Adriana; Sinayskiy, Ilya; Petruccione, Francesco; van Grondelle, Rienk

2015-03-01

Since the emergence of oxygenic photosynthesis, living systems have developed protective mechanisms against reactive oxygen species. During charge separation in photosynthetic reaction centres, triplet states can react with molecular oxygen generating destructive singlet oxygen. The triplet product yield in bacteria is observed to be reduced by weak magnetic fields. Reaction centres from plants' photosystem II share many features with bacterial reaction centres, including a high-spin iron whose function has remained obscure. To explain observations that the magnetic field effect is reduced by the iron, we propose that its fast-relaxing spin plays a protective role in photosynthesis by generating an effective magnetic field. We consider a simple model of the system, derive an analytical expression for the effective magnetic field and analyse the resulting triplet yield reduction. The protective mechanism is robust for realistic parameter ranges, constituting a clear example of a quantum effect playing a macroscopic role vital for life.

Physiological and Proteomics Analyses Reveal Low-Phosphorus Stress Affected the Regulation of Photosynthesis in Soybean.

Science.gov (United States)

Chu, Shanshan; Li, Hongyan; Zhang, Xiangqian; Yu, Kaiye; Chao, Maoni; Han, Suoyi; Zhang, Dan

2018-06-06

Previous studies have revealed a significant genetic relationship between phosphorus (P)-efficiency and photosynthesis-related traits in soybean. In this study, we used proteome profiling in combination with expression analysis, biochemical investigations, and leaf ultrastructural analysis to identify the underlying physiological and molecular responses. The expression analysis and ultrastructural analysis showed that the photosynthesis key genes were decreased at transcript levels and the leaf mesophyll and chloroplast were severely damaged after low-P stress. Approximately 55 protein spots showed changes under low-P condition by mass spectrometry, of which 17 were involved in various photosynthetic processes. Further analysis revealed the depression of photosynthesis caused by low-P stress mainly involves the regulation of leaf structure, adenosine triphosphate (ATP) synthesis, absorption and transportation of CO₂, photosynthetic electron transport, production of assimilatory power, and levels of enzymes related to the Calvin cycle. In summary, our findings indicated that the existence of a stringent relationship between P supply and the genomic control of photosynthesis in soybean. As an important strategy to protect soybean photosynthesis, P could maintain the stability of cell structure, up-regulate the enzymes’ activities, recover the process of photosystem II (PSII), and induce the expression of low-P responsive genes and proteins.

Physiological and Environmental Aspects of Photosynthesis

OpenAIRE

Ricardo Alfredo Kluge; Universidade de São Paulo; Jaqueline V. Tezotto-Uliana; Universidade de São Paulo; Paula P. M. da Silva; Universidade de São Paulo

2015-01-01

Undoubtedly, photosynthesis is one of the most important process for the life planet maintenance. The sun releases radiant energy that is able to boost the photosynthetic apparatus of the plants, which produce carbohydrates that will be used in the respiration. Among the most important reactions of photosynthesis is the release of oxygen, essential for respiration, which happens in photosystem II. The products generated in the first phase of photosynthesis or photochemical phase (ATP and NADP...

Potential photosynthesis of crop surfaces.

NARCIS (Netherlands)

Wit, de C.T.

1959-01-01

A formula for calculating the potential photosynthesis of a closed crop surface is proposed, assuming that the leaves of the crop are not arranged in any definite direction. In the Netherlands, values for potential photosynthesis vary from 290 kg. CH2O/ha./day in June to 50 kg./ha./day in December.

Investigation of grapevine photosynthesis using hyperspectral techniques and development of hyperspectral band ratio indices sensitive to photosynthesis.

Science.gov (United States)

Ozelkan, Emre; Karaman, Muhittin; Candar, Serkan; Coskun, Zafer; Ormeci, Cankut

2015-01-01

The photosynthetic rate of 9 different grapevines were analyzed with simultaneous photosynthesis and spectroradiometric measurements on 08.08.2012 (veraison) and 06.09.2012 (harvest). The wavelengths and spectral regions, which most properly express photosynthetic rate, were determined using correlation and regression analysis. In addition, hyperspectral band ratio (BR) indices sensitive to photosynthesis were developed using optimum band ratio (OBRA) method. The relation of BR results with photosynthesis values are presented with the correlation matrix maps created in this study. The examinations were performed for both specific dates (i.e., veraison and harvest) and also in aggregate (i.e., correlation between total spectra and photosynthesis data). For specific dates wavelength based analysis, the photosynthesis were best determined with -0.929 correlation coefficient (r) 609 nm of yellow region at veraison stage, and -0.870 at 641 nm of red region at harvest stage. For wavelength based aggregate analysis, 640 nm of red region was found to be correlated with 0.921 and -0.867 r values respectively and red edge (RE) (695 nm) was found to be correlated with -0.922 and -0.860 r values, respectively. When BR indices results were analyzed with photosynthetic values for specific dates, -0.987 r with R8../R, at veraison stage and -0.911 r with R696/R944 at harvest stage were found most correlated. For aggregate analysis of BR, common BR presenting great correlation with photosynthesis for both measurements was found to be R632/R971 with -0.974, -0.881 r values, respectively and other R610/R760 with -0.976, -0.879 r values. The final results of this study indicate that the proportion of RE region to a region with direct or indirect correlation with photosynthetic provides information about rate of photosynthesis. With the indices created in this study, the photosynthesis rate of vineyards can be determined using in-situ hyperspectral remote sensing. The findings of this

Leaf absorbance and photosynthesis

Science.gov (United States)

Schurer, Kees

1994-01-01

The absorption spectrum of a leaf is often thought to contain some clues to the photosynthetic action spectrum of chlorophyll. Of course, absorption of photons is needed for photosynthesis, but the reverse, photosynthesis when there is absorption, is not necessarily true. As a check on the existence of absorption limits we measured spectra for a few different leaves. Two techniques for measuring absorption have been used, viz. the separate determination of the diffuse reflectance and the diffuse transmittance with the leaf at a port of an integrating sphere and the direct determination of the non-absorbed fraction with the leaf in the sphere. In a cross-check both methods yielded the same results for the absorption spectrum. The spectrum of a Fuchsia leaf, covering the short-wave region from 350 to 2500 nm, shows a high absorption in UV, blue and red, the well known dip in the green and a steep fall-off at 700 nm. Absorption drops to virtually zero in the near infrared, with subsequent absorptions, corresponding to the water absorption bands. In more detailed spectra, taken at 5 nm intervals with a 5 nm bandwidth, differences in chlorophyll content show in the different depths of the dip around 550 nm and in a small shift of the absorption edge at 700 nm. Spectra for Geranium (Pelargonium zonale) and Hibiscus (with a higher chlorophyll content) show that the upper limit for photosynthesis can not be much above 700 nm. No evidence, however, is to be seen of a lower limit for photosynthesis and, in fact, some experiments down to 300 nm still did not show a decrease of the absorption although it is well recognized that no photosynthesis results with 300 nm wavelengths.

Photosynthesis: From De Saussure To Liebig.

Science.gov (United States)

Pennazio, Sergio

2017-01-01

The dawn of photosynthesis, characterized by the research of Priestley, Ingen- Housz and Senebier, culminated in 1804 with a historical essay of Théodore De Saussure. According to the historians, during the first half of the nineteenth century in which the genesis of the cell theory started off, the research on photosynthesis met a phase of stagnation. Indeed, the literature review of the period does not report particular innovation; however, several scientists (botanists, physiologists, and chemists) supported the thesis of De Saussure with a series of analyses that, in our opinion, deserve to be known. Mirbel, De Candolle, Raspail, Berzelius, Payen, Dutrochet, von Mohl, and other scholars attempted to expand knowledge on photosynthesis but were not able to arrive at a theory that was consistent with a functional mechanism, nor with a suitable chemical model to explain the transformation of the water and carbon dioxide into sugars. A classic case of such inadequacy concerns the discovery of chlorophyll. This compound, isolated in 1818 by Pelletier and Caventou, remained an enigma for many years and was never put in relation with the synthesis of starch. The accurate research of von Mohl led this scientist to believe that the granules of chlorophyll were entirely independent of starch granules, although in many cases these latter were observable inside the granules of chlorophyll. Only in the early forties, Justus von Liebig realized that the assimilation of carbon and hydrogen required a series of chemical reactions that, starting from some organic acids, ended in the formation of sugar. In conclusion, our analysis does not lead to define this period as stagnation but rather as transition, in which the concept of photosynthesis was clear, even though difficult to treat under physiological and chemical views. From the sixties, the researches of Julius von Sachs will open a new road, thanks also to the research carried out in the transition period. Copyright: �

A natural variant of NAL1, selected in high-yield rice breeding programs, pleiotropically increases photosynthesis rate

Science.gov (United States)

Takai, Toshiyuki; Adachi, Shunsuke; Taguchi-Shiobara, Fumio; Sanoh-Arai, Yumiko; Iwasawa, Norio; Yoshinaga, Satoshi; Hirose, Sakiko; Taniguchi, Yojiro; Yamanouchi, Utako; Wu, Jianzhong; Matsumoto, Takashi; Sugimoto, Kazuhiko; Kondo, Katsuhiko; Ikka, Takashi; Ando, Tsuyu; Kono, Izumi; Ito, Sachie; Shomura, Ayahiko; Ookawa, Taiichiro; Hirasawa, Tadashi; Yano, Masahiro; Kondo, Motohiko; Yamamoto, Toshio

2013-01-01

Improvement of leaf photosynthesis is an important strategy for greater crop productivity. Here we show that the quantitative trait locus GPS (GREEN FOR PHOTOSYNTHESIS) in rice (Oryza sativa L.) controls photosynthesis rate by regulating carboxylation efficiency. Map-based cloning revealed that GPS is identical to NAL1 (NARROW LEAF1), a gene previously reported to control lateral leaf growth. The high-photosynthesis allele of GPS was found to be a partial loss-of-function allele of NAL1. This allele increased mesophyll cell number between vascular bundles, which led to thickened leaves, and it pleiotropically enhanced photosynthesis rate without the detrimental side effects observed in previously identified nal1 mutants, such as dwarf plant stature. Furthermore, pedigree analysis suggested that rice breeders have repeatedly selected the high-photosynthesis allele in high-yield breeding programs. The identification and utilization of NAL1 (GPS) can enhance future high-yield breeding and provides a new strategy for increasing rice productivity. PMID:23985993

Photosynthesis-dependent isoprene emission from leaf to planet in a global carbon-chemistry-climate model

OpenAIRE

Unger, N.; Harper, K.; Zheng, Y.; Kiang, N. Y.; Aleinov, I.; Arneth, A.; Schurgers, G.; Amelynyck, C.; Goldstein, A.; Guenther, A.; Heinesch, B.; Hewitt, C. N.; Karl, T.; Laffineur, Q.; Langford, B.

2013-01-01

We describe the implementation of a biochemical model of isoprene emission that depends on the electron requirement for isoprene synthesis into the Farquhar–Ball–Berry leaf model of photosynthesis and stomatal conductance that is embedded within a global chemistry-climate simulation framework. The isoprene production is calculated as a function of electron transport-limited photosynthesis, intercellular and atmospheric carbon dioxide concentration, and canopy temperature. Th...

Surviving metabolic arrest: photosynthesis during desiccation and rehydration in resurrection plants.

Science.gov (United States)

Challabathula, Dinakar; Puthur, Jos T; Bartels, Dorothea

2016-02-01

Photosynthesis is the key process that is affected by dehydration in plants. Desiccation-tolerant resurrection plants can survive conditions of very low relative water content. During desiccation, photosynthesis is not operational, but is recovered within a short period after rehydration. While homoiochlorophyllous resurrection plants retain their photosynthetic apparatus during desiccation, poikilochlorophyllous resurrection species dismantle chloroplasts and degrade chlorophyll but resynthesize them again during rehydration. Dismantling the chloroplasts avoids the photooxidative stress in poikilochlorophyllous resurrection plants, whereas it is minimized in homoiochlorophyllous plants through the synthesis of antioxidant enzymes and protective proteins or metabolites. Although the cellular protection mechanisms in both of these species vary, these mechanisms protect cells from desiccation-induced damage and restore photosynthesis upon rehydration. Several of the proteins synthesized during dehydration are localized in chloroplasts and are believed to play major roles in the protection of photosynthetic structures and in recovery in resurrection species. This review focuses on the strategies of resurrection plants in terms of how they protect their photosynthetic apparatus from oxidative stress during desiccation without membrane damage and with full recovery during rehydration. We review the role of the dehydration-induced protection mechanisms in chloroplasts and how photosynthesis is restored during rehydration. © 2015 New York Academy of Sciences.

Long-term structural canopy changes sustain net photosynthesis per ground area in high arctic Vaccinium uliginosum exposed to changes in near-ambient UV-B levels.

Science.gov (United States)

Boesgaard, Kristine S; Albert, Kristian R; Ro-Poulsen, Helge; Michelsen, Anders; Mikkelsen, Teis N; Schmidt, Niels M

2012-08-01

Full recovery of the ozone layer is not expected for several decades and consequently, the incoming level of solar ultraviolet-B (UV-B) will only slowly be reduced. Therefore to investigate the structural and photosynthetic responses to changes in solar UV-B we conducted a 5-year UV-B exclusion study in high arctic Greenland. During the growing season, the gas exchange (H₂O and CO₂) and chlorophyll-a fluorescence were measured in Vaccinium uliginosum. The leaf dry weight, carbon, nitrogen, stable carbon isotope ratio, chlorophyll and carotenoid content were determined from a late season harvest. The net photosynthesis per leaf area was on average 22% higher in 61% reduced UV-B treatment across the season, but per ground area photosynthesis was unchanged. The leaf level increase in photosynthesis was accompanied by increased leaf nitrogen, higher stomatal conductance and F(v)/F(m). There was no change in total leaf biomass, but reduction in total leaf area caused a pronounced reduction of specific leaf area and leaf area index in reduced UV-B. This demonstrates the structural changes to counterbalance the reduced plant carbon uptake seen per leaf area in ambient UV-B as the resulting plant carbon uptake per ground area was not affected. Thus, our understanding of long-term responses to UV-B reduction must take into account both leaf level processes as well as structural changes to understand the apparent robustness of plant carbon uptake per ground area. In this perspective, V. uliginosum seems able to adjust plant carbon uptake to the present amount of solar UV-B radiation in the High Arctic. Copyright © Physiologia Plantarum 2011.

Acetylome analysis reveals the involvement of lysine acetylation in photosynthesis and carbon metabolism in the model cyanobacterium Synechocystis sp. PCC 6803.

Science.gov (United States)

Mo, Ran; Yang, Mingkun; Chen, Zhuo; Cheng, Zhongyi; Yi, Xingling; Li, Chongyang; He, Chenliu; Xiong, Qian; Chen, Hui; Wang, Qiang; Ge, Feng

2015-02-06

Cyanobacteria are the oldest known life form inhabiting Earth and the only prokaryotes capable of performing oxygenic photosynthesis. Synechocystis sp. PCC 6803 (Synechocystis) is a model cyanobacterium used extensively in research on photosynthesis and environmental adaptation. Posttranslational protein modification by lysine acetylation plays a critical regulatory role in both eukaryotes and prokaryotes; however, its extent and function in cyanobacteria remain unexplored. Herein, we performed a global acetylome analysis on Synechocystis through peptide prefractionation, antibody enrichment, and high accuracy LC-MS/MS analysis; identified 776 acetylation sites on 513 acetylated proteins; and functionally categorized them into an interaction map showing their involvement in various biological processes. Consistent with previous reports, a large fraction of the acetylation sites are present on proteins involved in cellular metabolism. Interestingly, for the first time, many proteins involved in photosynthesis, including the subunits of phycocyanin (CpcA, CpcB, CpcC, and CpcG) and allophycocyanin (ApcA, ApcB, ApcD, ApcE, and ApcF), were found to be lysine acetylated, suggesting that lysine acetylation may play regulatory roles in the photosynthesis process. Six identified acetylated proteins associated with photosynthesis and carbon metabolism were further validated by immunoprecipitation and Western blotting. Our data provide the first global survey of lysine acetylation in cyanobacteria and reveal previously unappreciated roles of lysine acetylation in the regulation of photosynthesis. The provided data set may serve as an important resource for the functional analysis of lysine acetylation in cyanobacteria and facilitate the elucidation of the entire metabolic networks and photosynthesis process in this model cyanobacterium.

Synthesis of 2-(6-Acetamidobenzothiazolethioacetic Acid Esters as Photosynthesis Inhibitors

Directory of Open Access Journals (Sweden)

Dusan Loos

1998-04-01

Full Text Available The synthesis and photosynthesis-inhibiting activity of 13 new 2-(6-acetamidobenzothiazolethioacetic acid esters are reported. The new compounds were prepared by acetylation of 2-(alkoxycarbonylmethylthio-6-aminobenzothiazoles with acetic anhydride. The structure of the compounds was verified by 1H NMR spectra. The compounds inhibit photosynthetic electron transfer in spinach chloroplasts. The structure - activity relation was studied. Lipophilicity was found to influence substantially photosynthetic electron transfer.

Recruitment of pre-existing networks during the evolution of C4 photosynthesis.

Science.gov (United States)

Reyna-Llorens, Ivan; Hibberd, Julian M

2017-09-26

During C 4 photosynthesis, CO 2 is concentrated around the enzyme RuBisCO. The net effect is to reduce photorespiration while increasing water and nitrogen use efficiencies. Species that use C 4 photosynthesis have evolved independently from their C 3 ancestors on more than 60 occasions. Along with mimicry and the camera-like eye, the C 4 pathway therefore represents a remarkable example of the repeated evolution of a highly complex trait. In this review, we provide evidence that the polyphyletic evolution of C 4 photosynthesis is built upon pre-existing metabolic and genetic networks. For example, cells around veins of C 3 species show similarities to those of the C 4 bundle sheath in terms of C 4 acid decarboxylase activity and also the photosynthetic electron transport chain. Enzymes of C 4 photosynthesis function together in gluconeogenesis during early seedling growth of C 3 Arabidopsis thaliana Furthermore, multiple C 4 genes appear to be under control of both light and chloroplast signals in the ancestral C 3 state. We, therefore, hypothesize that relatively minor rewiring of pre-existing genetic and metabolic networks has facilitated the recurrent evolution of this trait. Understanding how these changes are likely to have occurred could inform attempts to install C 4 traits into C 3 crops.This article is part of the themed issue 'Enhancing photosynthesis in crop plants: targets for improvement'. © 2017 The Author(s).

When growth and photosynthesis don't match: implications for carbon balance models

Science.gov (United States)

Medlyn, B.; Mahmud, K.; Duursma, R.; Pfautsch, S.; Campany, C.

2017-12-01

Most models of terrestrial plant growth are based on the principle of carbon balance: that growth can be predicted from net uptake of carbon via photosynthesis. A key criticism leveled at these models by plant physiologists is that there are many circumstances in which plant growth appears to be independent of photosynthesis: for example, during the onset of drought, or with rising atmospheric CO2 concentration. A crucial problem for terrestrial carbon cycle models is to develop better representations of plant carbon balance when there is a mismatch between growth and photosynthesis. Here we present two studies providing insight into this mismatch. In the first, effects of root restriction on plant growth were examined by comparing Eucalyptus tereticornis seedlings growing in containers of varying sizes with freely-rooted seedlings. Root restriction caused a reduction in photosynthesis, but this reduction was insufficient to explain the even larger reduction observed in growth. We applied data assimilation to a simple carbon balance model to quantify the response of carbon balance as a whole in this experiment. We inferred that, in addition to photosynthesis, there are significant effects of root restriction on growth respiration, carbon allocation, and carbohydrate utilization. The second study was carried out at the EucFACE Free-Air CO2 Enrichment experiment. At this experiment, photosynthesis of the overstorey trees is increased with enriched CO2, but there is no significant effect on above-ground productivity. These mature trees have reached their maximum height but are at significant risk of canopy loss through disturbance, and we hypothesized that additional carbon taken up through photosynthesis is preferentially allocated to storage rather than growth. We tested this hypothesis by measuring stemwood non-structural carbohydrates (NSC) during a psyllid outbreak that completely defoliated the canopy in 2015. There was a significant drawdown of NSC during

What is the most prominent factor limiting photosynthesis in different layers of a greenhouse cucumber canopy?

Science.gov (United States)

Chen, Tsu-Wei; Henke, Michael; de Visser, Pieter H B; Buck-Sorlin, Gerhard; Wiechers, Dirk; Kahlen, Katrin; Stützel, Hartmut

2014-09-01

Maximizing photosynthesis at the canopy level is important for enhancing crop yield, and this requires insights into the limiting factors of photosynthesis. Using greenhouse cucumber (Cucumis sativus) as an example, this study provides a novel approach to quantify different components of photosynthetic limitations at the leaf level and to upscale these limitations to different canopy layers and the whole plant. A static virtual three-dimensional canopy structure was constructed using digitized plant data in GroIMP. Light interception of the leaves was simulated by a ray-tracer and used to compute leaf photosynthesis. Different components of photosynthetic limitations, namely stomatal (S(L)), mesophyll (M(L)), biochemical (B(L)) and light (L(L)) limitations, were calculated by a quantitative limitation analysis of photosynthesis under different light regimes. In the virtual cucumber canopy, B(L) and L(L) were the most prominent factors limiting whole-plant photosynthesis. Diffusional limitations (S(L) + M(L)) contributed Photosynthesis in the lower canopy was more limited by the biochemical capacity, and the upper canopy was more sensitive to light than other canopy parts. Although leaves in the upper canopy received more light, their photosynthesis was more light restricted than in the leaves of the lower canopy, especially when the light condition above the canopy was poor. An increase in whole-plant photosynthesis under diffuse light did not result from an improvement of light use efficiency but from an increase in light interception. Diffuse light increased the photosynthesis of leaves that were directly shaded by other leaves in the canopy by up to 55%. Based on the results, maintaining biochemical capacity of the middle-lower canopy and increasing the leaf area of the upper canopy would be promising strategies to improve canopy photosynthesis in a high-wire cucumber cropping system. Further analyses using the approach described in this study can be expected to

Relative Sensitivity of Photosynthesis and Respiration to Freeze-Thaw Stress in Herbaceous Species 1

Science.gov (United States)

Steffen, Kenneth L.; Arora, Rajeev; Palta, Jiwan P.

1989-01-01

The relative effect of a freeze-thaw cycle on photosynthesis, respiration, and ion leakage of potato leaf tissue was examined in two potato species, Solanum acaule Bitt. and Solanum commersonii Dun. Photosynthesis was found to be much more sensitive to freezing stress than was respiration, and demonstrated more than a 60% inhibition before any impairment of respiratory function was observed. Photosynthesis showed a slight to moderate inhibition when only 5 to 10% of the total electrolytes had leaked from the tissue (reversible injury). This was in contrast to respiration which showed no impairment until temperatures at which about 50% ion leakage (irreversible injury) had occurred. The influence of freeze-thaw protocol was further examined in S. acaule and S. commersonii, in order to explore discrepancies in the literature as to the relative sensitivities of photosynthesis and respiration. As bath cooling rates increased from 1°C/hour to about 3 or 6°C/hour, there was a dramatic increase in the level of damage to all measured cellular functions. The initiation of ice formation in deeply supercooled tissue caused even greater damage. As the cooling rates used in stress treatments increased, the differential sensitivity between photosynthesis and respiration nearly disappeared. Examination of agriculturally relevant, climatological data from an 11 year period confirmed that air cooling rates in the freezing range do not exceed 2°C/hour. It was demonstrated, in the studies presented here, that simply increasing the actual cooling rate from 1.0 to 2.9°C/hour, in frozen tissue from paired leaflet halves, meant the difference between cell survival and cell death. Images Figure 4 Figure 5 PMID:16666712

Preface: photosynthesis and hydrogen energy research for sustainability.

Science.gov (United States)

Tomo, Tatsuya; Allakhverdiev, Suleyman I

2017-09-01

Energy supply, climate change, and global food security are among the main chalenges facing humanity in the twenty-first century. Despite global energy demand is continuing to increase, the availability of low cost energy is decreasing. Together with the urgent problem of climate change due to CO 2 release from the combustion of fossil fuels, there is a strong requirement of developing the clean and renewable energy system for the hydrogen production. Solar fuel, biofuel, and hydrogen energy production gained unlimited possibility and feasibility due to understanding of the detailed photosynthetic system structures. This special issue contains selected papers on photosynthetic and biomimetic hydrogen production presented at the International Conference "Photosynthesis Research for Sustainability-2016", that was held in Pushchino (Russia), during June 19-25, 2016, with the sponsorship of the International Society of Photosynthesis Research (ISPR) and of the International Association for Hydrogen Energy (IAHE). This issue is intended to provide recent information on the photosynthetic and biohydrogen production to our readers.

Reintroducing Photosynthesis

Science.gov (United States)

Vila, F.; Sanz, A.

2012-01-01

This article reports on conceptual difficulties related to photosynthesis and respiratory metabolism of a Plant Physiology course for undergraduate students that could hinder their better learning of metabolic processes. A survey of results obtained in this area during the last 10 academic years was performed, as well as a specific test, aimed to…

Toward a mechanistic modeling of nitrogen limitation for photosynthesis

Science.gov (United States)

Xu, C.; Fisher, R. A.; Travis, B. J.; Wilson, C. J.; McDowell, N. G.

2011-12-01

The nitrogen limitation is an important regulator for vegetation growth and global carbon cycle. Most current ecosystem process models simulate nitrogen effects on photosynthesis based on a prescribed relationship between leaf nitrogen and photosynthesis; however, there is a large amount of variability in this relationship with different light, temperature, nitrogen availability and CO2 conditions, which can affect the reliability of photosynthesis prediction under future climate conditions. To account for the variability in nitrogen-photosynthesis relationship under different environmental conditions, in this study, we developed a mechanistic model of nitrogen limitation for photosynthesis based on nitrogen trade-offs among light absorption, electron transport, carboxylization and carbon sink. Our model shows that strategies of nitrogen storage allocation as determined by tradeoff among growth and persistence is a key factor contributing to the variability in relationship between leaf nitrogen and photosynthesis. Nitrogen fertilization substantially increases the proportion of nitrogen in storage for coniferous trees but much less for deciduous trees, suggesting that coniferous trees allocate more nitrogen toward persistence compared to deciduous trees. The CO2 fertilization will cause lower nitrogen allocation for carboxylization but higher nitrogen allocation for storage, which leads to a weaker relationship between leaf nitrogen and maximum photosynthesis rate. Lower radiation will cause higher nitrogen allocation for light absorption and electron transport but less nitrogen allocation for carboxylyzation and storage, which also leads to weaker relationship between leaf nitrogen and maximum photosynthesis rate. At the same time, lower growing temperature will cause higher nitrogen allocation for carboxylyzation but lower allocation for light absorption, electron transport and storage, which leads to a stronger relationship between leaf nitrogen and maximum

Genetic control of functional traits related to photosynthesis and water use efficiency in Pinus pinaster Ait. drought response: integration of genome annotation, allele association and QTL detection for candidate gene identification.

Science.gov (United States)

de Miguel, Marina; Cabezas, José-Antonio; de María, Nuria; Sánchez-Gómez, David; Guevara, María-Ángeles; Vélez, María-Dolores; Sáez-Laguna, Enrique; Díaz, Luis-Manuel; Mancha, Jose-Antonio; Barbero, María-Carmen; Collada, Carmen; Díaz-Sala, Carmen; Aranda, Ismael; Cervera, María-Teresa

2014-06-12

Understanding molecular mechanisms that control photosynthesis and water use efficiency in response to drought is crucial for plant species from dry areas. This study aimed to identify QTL for these traits in a Mediterranean conifer and tested their stability under drought. High density linkage maps for Pinus pinaster were used in the detection of QTL for photosynthesis and water use efficiency at three water irrigation regimes. A total of 28 significant and 27 suggestive QTL were found. QTL detected for photochemical traits accounted for the higher percentage of phenotypic variance. Functional annotation of genes within the QTL suggested 58 candidate genes for the analyzed traits. Allele association analysis in selected candidate genes showed three SNPs located in a MYB transcription factor that were significantly associated with efficiency of energy capture by open PSII reaction centers and specific leaf area. The integration of QTL mapping of functional traits, genome annotation and allele association yielded several candidate genes involved with molecular control of photosynthesis and water use efficiency in response to drought in a conifer species. The results obtained highlight the importance of maintaining the integrity of the photochemical machinery in P. pinaster drought response.

Revealing diversity in structural and biochemical forms of C4 photosynthesis and a C3-C4 intermediate in genus Portulaca L. (Portulacaceae).

Science.gov (United States)

Voznesenskaya, Elena V; Koteyeva, Nuria K; Edwards, Gerald E; Ocampo, Gilberto

2010-08-01

Portulacaceae is one of 19 families of terrestrial plants in which species having C(4) photosynthesis have been found. Representative species from major clades of the genus Portulaca were studied to characterize the forms of photosynthesis structurally and biochemically. The species P. amilis, P. grandiflora, P. molokiniensis, P. oleracea, P. pilosa, and P. umbraticola belong to the subgenus Portulaca and are C(4) plants based on leaf carbon isotope values, Kranz anatomy, and expression of key C(4) enzymes. Portulaca umbraticola, clade Umbraticola, is NADP-malic enzyme (NADP-ME)-type C(4) species, while P. oleracea and P. molokiniensis in clade Oleracea are NAD-ME-type C(4) species, all having different forms of Atriplicoid-type leaf anatomy. In clade Pilosa, P. amilis, P. grandiflora, and P. pilosa are NADP-ME-type C(4) species. They have Pilosoid-type anatomy in which Kranz tissues enclose peripheral vascular bundles with water storage in the centre of the leaf. Portulaca cf. bicolor, which belongs to subgenus Portulacella, is an NADP-ME C(4) species with Portulacelloid-type anatomy; it has well-developed Kranz chlorenchyma surrounding lateral veins distributed in one plane under the adaxial epidermis with water storage cells underneath. Portulaca cryptopetala (clade Oleracea), an endemic species from central South America, was identified as a C(3)-C(4) based on its intermediate CO(2) compensation point and selective localization of glycine decarboxylase of the photorespiratory pathway in mitochondria of bundle sheath cells. The C(4) Portulaca species which were examined also have cotyledons with Kranz-type anatomy, while the stems of all species have C(3)-type photosynthetic cells. The results indicate that multiple structural and biochemical forms of C(4) photosynthesis evolved in genus Portulaca.

Community photosynthesis of aquatic macrophytes

DEFF Research Database (Denmark)

Binzer, T.; Sand-Jensen, K.; Middelboe, A. L.

2006-01-01

We compared 190 photosynthesis-irradiance (P-E) experiments with single- and multispecies communities of macroalgae and vascular plants from freshwater and marine habitats. We found a typical hyperbolic P-E relation in all communities and no sign of photosaturation or photoinhibition of photosynt......We compared 190 photosynthesis-irradiance (P-E) experiments with single- and multispecies communities of macroalgae and vascular plants from freshwater and marine habitats. We found a typical hyperbolic P-E relation in all communities and no sign of photosaturation or photoinhibition...

Weak leaf photosynthesis and nutrient content relationships from tropical vegetation

Science.gov (United States)

Domingues, T. F.; Ishida, F. Y.; Feldpaush, T.; Saiz, G.; Grace, J.; Meir, P.; Lloyd, J.

2015-12-01

Evergreen rain forests and savannas are the two major vegetations of tropical land ecosystems, in terms of land area, biomass, biodiversity, biogeochemical cycles and rates of land use change. Mechanistically understanding ecosystem functioning on such ecosystems is still far from complete, but important for generation of future vegetation scenarios in response to global changes. Leaf photosynthetic rates is a key processes usually represented on land surface-atmosphere models, although data from tropical ecosystems is scarce, considering the high biodiversity they contain. As a shortcut, models usually recur to relationships between leaf nutrient concentration and photosynthetic rates. Such strategy is convenient, given the possibility of global datasets on leave nutrients derived from hyperspectral remote sensing data. Given the importance of Nitrogen on enzyme composition, this nutrient is usually used to infer photosynthetic capacity of leaves. Our experience, based on individual measurements on 1809 individual leaves from 428 species of trees and shrubs naturally occurring on tropical forests and savannas from South America, Africa and Australia, indicates that the relationship between leaf nitrogen and its assimilation capacity is weak. Therefore, leaf Nitrogen alone is a poor predictor of photosynthetic rates of tropical vegetation. Phosphorus concentrations from tropical soils are usually low and is often implied that this nutrient limits primary productivity of tropical vegetation. Still, phosphorus (or other nutrients) did not exerted large influence over photosynthetic capacity, although potassium influenced vegetation structure and function. Such results draw attention to the risks of applying universal nitrogen-photosynthesis relationships on biogeochemical models. Moreover, our data suggests that affiliation of plant species within phylogenetic hierarchy is an important aspect in understanding leaf trait variation. The lack of a strong single

The Path of Carbon in Photosynthesis XV. Ribulose and Sedoheptulose

Science.gov (United States)

Benson, A. A.; Bassham, J. A.; Calvin, M.; Hall, A. G.; Hirsch, H.; Kawaguchi, S.; Lynch, V.; Tolbert, N. E.

1952-01-01

The intermediates of carbon dioxide reduction by plants include phosphorylated derivatives of hydroxy acids and sugars. Their identification became possible when the use of labeled carbon dioxide permitted discrimination between the earliest products and the many other components of photosynthetic tissues. A number of compounds were identified by virtue of the chemical and physical properties of the radioactive compounds in tracer amounts and by direct comparison of these properties with those of suspected known metabolic intermediates. It became apparent that several labeled compounds found in short exposures to radioactive carbon dioxide were not substances previously identified as metabolic intermediates. Two phosphate esters in particular were observed in the products of the first few seconds of steady-state photosynthesis by all the photosynthetic microorganisms and higher plants examined in this laboratory. These esters have been isolated by paper chromatography in tracer quantities and enzymatically hydrolyzed to give two sugars, ribulose and sedoheptulose. This paper contains a description of the chemical identification of these sugars and some observations and suggestions regarding the function of their esters. The general importance of these compounds in photosynthesis was summarized before their identification. The products of photosynthesis with C{sup 14}O{sub 2} by each plant included phosphate esters of the same two then unknown compounds in addition to those of the expected glucose, fructose, dihydroxyacetone and glyceric acid. As the time of steady-state photosynthesis in C{sup 14}O{sub 2} decreased, the fractions of total fixed radiocarbon in the esters of the two unidentified compounds increased.

Enhancing (crop) plant photosynthesis by introducing novel genetic diversity.

Science.gov (United States)

Dann, Marcel; Leister, Dario

2017-09-26

Although some elements of the photosynthetic light reactions might appear to be ideal, the overall efficiency of light conversion to biomass has not been optimized during evolution. Because crop plants are depleted of genetic diversity for photosynthesis, efforts to enhance its efficiency with respect to light conversion to yield must generate new variation. In principle, three sources of natural variation are available: (i) rare diversity within extant higher plant species, (ii) photosynthetic variants from algae, and (iii) reconstruction of no longer extant types of plant photosynthesis. Here, we argue for a novel approach that outsources crop photosynthesis to a cyanobacterium that is amenable to adaptive evolution. This system offers numerous advantages, including a short generation time, virtually unlimited population sizes and high mutation rates, together with a versatile toolbox for genetic manipulation. On such a synthetic bacterial platform, 10 000 years of (crop) plant evolution can be recapitulated within weeks. Limitations of this system arise from its unicellular nature, which cannot reproduce all aspects of crop photosynthesis. But successful establishment of such a bacterial host for crop photosynthesis promises not only to enhance the performance of eukaryotic photosynthesis but will also reveal novel facets of the molecular basis of photosynthetic flexibility.This article is part of the themed issue 'Enhancing photosynthesis in crop plants: targets for improvement'. © 2017 The Author(s).

Biochemical approaches to C4 photosynthesis evolution studies: the case of malic enzymes decarboxylases.

Science.gov (United States)

Saigo, Mariana; Tronconi, Marcos A; Gerrard Wheeler, Mariel C; Alvarez, Clarisa E; Drincovich, María F; Andreo, Carlos S

2013-11-01

C4 photosynthesis enables the capture of atmospheric CO2 and its concentration at the site of RuBisCO, thus counteracting the negative effects of low atmospheric levels of CO2 and high atmospheric levels of O2 (21 %) on photosynthesis. The evolution of this complex syndrome was a multistep process. It did not occur by simply recruiting pre-exiting components of the pathway from C3 ancestors which were already optimized for C4 function. Rather it involved modifications in the kinetics and regulatory properties of pre-existing isoforms of non-photosynthetic enzymes in C3 plants. Thus, biochemical studies aimed at elucidating the functional adaptations of these enzymes are central to the development of an integrative view of the C4 mechanism. In the present review, the most important biochemical approaches that we currently use to understand the evolution of the C4 isoforms of malic enzyme are summarized. It is expected that this information will help in the rational design of the best decarboxylation processes to provide CO2 for RuBisCO in engineering C3 species to perform C4 photosynthesis.

Effect and mechanism of TiO2 nanoparticles on the photosynthesis of Chlorella pyrenoidosa.

Science.gov (United States)

Middepogu, Ayyaraju; Hou, Jie; Gao, Xuan; Lin, Daohui

2018-06-14

Titanium dioxide nanoparticles (n-TiO 2 ) have been used in numerous applications, which results in their release into aquatic ecosystems and impact algal populations. A possible toxic mechanism of n-TiO 2 on algae is via the disruption of the photosynthetic biochemical pathways, which yet remains to be demonstrated. In this study, Chlorella pyrenoidosa was exposed to different concentrations (0, 0.1, 1, 5, 10, and 20 mg/L) of a type of anatase n-TiO 2 , and the physiological, biochemical, and molecular responses involved in photosynthesis were investigated. The 96 h half growth inhibition concentration (IC 50 ) of the n-TiO 2 to algae was determined to be 9.1 mg/L. A variety of cellular and sub-cellular damages were observed, especially the blurry lamellar structure of thylakoids, indicating the n-TiO 2 impaired the photosynthetic function of chloroplasts. Malondialdehyde (MDA) and glutathione disulfide (GSSG) significantly increased while the glutathione (GSH) content decreased. This implies the increased consumption of GSH by the increased intracellular oxidative stress upon n-TiO 2 was insufficient to eliminate the lipid peroxidation. The contents of photosynthetic pigments, including chlorophyll a (Chl a) and phycobiliproteins (PBPs) in the exposed algal cells increased along with the up-regulation of genes encoding Chl a and photosystem II (PS II), which could be explained by a compensatory effect to overcome the toxicity induced by the n-TiO 2 . On the other hand, the photosynthetic activity was significantly inhibited, indicating the impairment on the photosynthesis via damaging the reaction center of PS II. In addition, lower productions of adenosine triphosphate (ATP) and glucose, together with the change of gene expressions suggested that the n-TiO 2 disrupted the material and energy metabolisms in the photosynthesis. These findings support a paradigm shift of the toxic mechanism of n-TiO 2 from physical and oxidative damages to metabolic

Aerobic Anoxygenic Photosynthesis Is Commonly Present within the Genus Limnohabitans.

Science.gov (United States)

Kasalický, Vojtěch; Zeng, Yonghui; Piwosz, Kasia; Šimek, Karel; Kratochvilová, Hana; Koblížek, Michal

2018-01-01

The genus Limnohabitans ( Comamonadaceae , Betaproteobacteria ) is a common and a highly active component of freshwater bacterioplanktonic communities. To date, the genus has been considered to contain only heterotrophic species. In this study, we detected the photosynthesis genes pufLM and bchY in 28 of 46 strains from three Limnohabitans lineages. The pufM sequences obtained are very closely related to environmental pufM sequences detected in various freshwater habitats, indicating the ubiquity and potential importance of photoheterotrophic Limnohabitans in nature. Additionally, we sequenced and analyzed the genomes of 5 potentially photoheterotrophic Limnohabitans strains, to gain further insights into their phototrophic capacity. The structure of the photosynthesis gene cluster turned out to be highly conserved within the genus Limnohabitans and also among all potentially photosynthetic Betaproteobacteria strains. The expression of photosynthetic complexes was detected in a culture of Limnohabitans planktonicus II-D5 T using spectroscopic and pigment analyses. This was further verified by a novel combination of infrared microscopy and fluorescent in situ hybridization. IMPORTANCE The data presented document that the capacity to perform anoxygenic photosynthesis is common among the members of the genus Limnohabitans , indicating that they may have a novel role in freshwater habitats. Copyright © 2017 American Society for Microbiology.

Reevaluation of the plant "gemstones": Calcium oxalate crystals sustain photosynthesis under drought conditions.

Science.gov (United States)

Tooulakou, Georgia; Giannopoulos, Andreas; Nikolopoulos, Dimosthenis; Bresta, Panagiota; Dotsika, Elissavet; Orkoula, Malvina G; Kontoyannis, Christos G; Fasseas, Costas; Liakopoulos, Georgios; Klapa, Maria I; Karabourniotis, George

2016-09-01

Land plants face the perpetual dilemma of using atmospheric carbon dioxide for photosynthesis and losing water vapors, or saving water and reducing photosynthesis and thus growth. The reason behind this dilemma is that this simultaneous exchange of gases is accomplished through the same minute pores on leaf surfaces, called stomata. In a recent study we provided evidence that pigweed, an aggressive weed, attenuates this problem exploiting large crystals of calcium oxalate as dynamic carbon pools. This plant is able to photosynthesize even under drought conditions, when stomata are closed and water losses are limited, using carbon dioxide from crystal decomposition instead from the atmosphere. Abscisic acid, an alarm signal that causes stomatal closure seems to be implicated in this function and for this reason we named this path "alarm photosynthesis." The so-far "enigmatic," but highly conserved and widespread among plant species calcium oxalate crystals seem to play a crucial role in the survival of plants.

Soil Temperature Triggers the Onset of Photosynthesis in Korean Pine

Science.gov (United States)

Wu, Jiabing; Guan, Dexin; Yuan, Fenhui; Wang, Anzhi; Jin, Changjie

2013-01-01

In forest ecosystems, the onset of spring photosynthesis may have an important influence on the annual carbon balance. However, triggers for the onset of photosynthesis have yet to be clearly identified, especially for temperate evergreen conifers. The effects of climatic factors on recovery of photosynthetic capacity in a Korean pine forest were investigated in the field. No photosynthesis was detectable when the soil temperature was below 0°C even if the air temperature was far beyond 15°C. The onset of photosynthesis and sap flow was coincident with the time of soil thawing. The rates of recovery of photosynthetic capacity highly fluctuated with air temperature after onset of photosynthesis, and intermittent frost events remarkably inhibited the photosynthetic capacity of the needles. The results suggest that earlier soil thawing is more important than air temperature increases in triggering the onset of photosynthesis in Korean pine in temperate zones under global warming scenarios. PMID:23755227

Estimating Net Photosynthesis of Biological Soil Crusts in the Atacama Using Hyperspectral Remote Sensing

Directory of Open Access Journals (Sweden)

Lukas W. Lehnert

2018-06-01

Full Text Available Biological soil crusts (BSC encompassing green algae, cyanobacteria, lichens, bryophytes, heterotrophic bacteria and microfungi are keystone species in arid environments because of their role in nitrogen- and carbon-fixation, weathering and soil stabilization, all depending on the photosynthesis of the BSC. Despite their importance, little is known about the BSCs of the Atacama Desert, although especially crustose chlorolichens account for a large proportion of biomass in the arid coastal zone, where photosynthesis is mainly limited due to low water availability. Here, we present the first hyperspectral reflectance data for the most wide-spread BSC species of the southern Atacama Desert. Combining laboratory and field measurements, we establish transfer functions that allow us to estimate net photosynthesis rates for the most common BSC species. We found that spectral differences among species are high, and differences between the background soil and the BSC at inactive stages are low. Additionally, we found that the water absorption feature at 1420 nm is a more robust indicator for photosynthetic activity than the chlorophyll absorption bands. Therefore, we conclude that common vegetation indices must be taken with care to analyze the photosynthesis of BSC with multispectral data.

Energy conversion in natural and artificial photosynthesis.

Science.gov (United States)

McConnell, Iain; Li, Gonghu; Brudvig, Gary W

2010-05-28

Modern civilization is dependent upon fossil fuels, a nonrenewable energy source originally provided by the storage of solar energy. Fossil-fuel dependence has severe consequences, including energy security issues and greenhouse gas emissions. The consequences of fossil-fuel dependence could be avoided by fuel-producing artificial systems that mimic natural photosynthesis, directly converting solar energy to fuel. This review describes the three key components of solar energy conversion in photosynthesis: light harvesting, charge separation, and catalysis. These processes are compared in natural and in artificial systems. Such a comparison can assist in understanding the general principles of photosynthesis and in developing working devices, including photoelectrochemical cells, for solar energy conversion. 2010 Elsevier Ltd. All rights reserved.

Revealing diversity in structural and biochemical forms of C4 photosynthesis and a C3–C4 intermediate in genus Portulaca L. (Portulacaceae)

Science.gov (United States)

Voznesenskaya, Elena V.; Koteyeva, Nuria K.; Edwards, Gerald E.; Ocampo, Gilberto

2010-01-01

Portulacaceae is one of 19 families of terrestrial plants in which species having C4 photosynthesis have been found. Representative species from major clades of the genus Portulaca were studied to characterize the forms of photosynthesis structurally and biochemically. The species P. amilis, P. grandiflora, P. molokiniensis, P. oleracea, P. pilosa, and P. umbraticola belong to the subgenus Portulaca and are C4 plants based on leaf carbon isotope values, Kranz anatomy, and expression of key C4 enzymes. Portulaca umbraticola, clade Umbraticola, is NADP-malic enzyme (NADP-ME)-type C4 species, while P. oleracea and P. molokiniensis in clade Oleracea are NAD-ME-type C4 species, all having different forms of Atriplicoid-type leaf anatomy. In clade Pilosa, P. amilis, P. grandiflora, and P. pilosa are NADP-ME-type C4 species. They have Pilosoid-type anatomy in which Kranz tissues enclose peripheral vascular bundles with water storage in the centre of the leaf. Portulaca cf. bicolor, which belongs to subgenus Portulacella, is an NADP-ME C4 species with Portulacelloid-type anatomy; it has well-developed Kranz chlorenchyma surrounding lateral veins distributed in one plane under the adaxial epidermis with water storage cells underneath. Portulaca cryptopetala (clade Oleracea), an endemic species from central South America, was identified as a C3–C4 based on its intermediate CO2 compensation point and selective localization of glycine decarboxylase of the photorespiratory pathway in mitochondria of bundle sheath cells. The C4 Portulaca species which were examined also have cotyledons with Kranz-type anatomy, while the stems of all species have C3-type photosynthetic cells. The results indicate that multiple structural and biochemical forms of C4 photosynthesis evolved in genus Portulaca. PMID:20591900

New Concept of Photosynthesis

Directory of Open Access Journals (Sweden)

Komissarov Gennadiy Germanovich

2014-12-01

Full Text Available The history of the formation of a new concept of photosynthesis proposed by the author is considered for the period since 1966 to 2013. Its essence consists in the following facts: the photosynthetic oxygen (hydrogen source is not water, but exo- and endogenous hydrogen peroxide; thermal energy is a necessary part of the photosynthetic process; along with the carbon dioxide the air (oxygen, inert gases is included in the photosynthetic equation. The mechanism of the photovoltaic (Becquerel effect in films of chlorophyll and its synthetic analogue - phthalocyanine are briefly touched upon in the article. The article presents the works on artificial photosynthesis performed in the laboratory of Photobionics of N.N. Semenov Institute of Chemical Physics, RAS.

Combined effects of simulated acid rain and lanthanum chloride on chloroplast structure and functional elements in rice.

Science.gov (United States)

Hu, Huiqing; Wang, Lihong; Zhou, Qing; Huang, Xiaohua

2016-05-01

Acid rain and rare earth element (REE) pollution exist simultaneously in many agricultural regions. However, how REE pollution and acid rain affect plant growth in combination remains largely unknown. In this study, the combined effects of simulated acid rain and lanthanum chloride (LaCl3) on chloroplast morphology, chloroplast ultrastructure, functional element contents, chlorophyll content, and the net photosynthetic rate (P n) in rice (Oryza sativa) were investigated by simulating acid rain and rare earth pollution. Under the combined treatment of simulated acid rain at pH 4.5 and 0.08 mM LaCl3, the chloroplast membrane was smooth, proteins on this membrane were uniform, chloroplast structure was integrated, and the thylakoids were orderly arranged, and simulated acid rain and LaCl3 exhibited a mild antagonistic effect; the Mg, Ca, Mn contents, the chlorophyll content, and the P n increased under this combined treatment, with a synergistic effect of simulated acid rain and LaCl3. Under other combined treatments of simulated acid rain and LaCl3, the chloroplast membrane surface was uneven, a clear "hole" was observed on the surface of chloroplasts, and the thylakoids were dissolved and loose; and the P n and contents of functional elements (P, Mg, K, Ca, Mn, Fe, Ni, Cu, Zn and Mo) and chlorophyll decreased. Under these combined treatments, simulated acid rain and LaCl3 exhibited a synergistic effect. Based on the above results, a model of the combined effects of simulated acid rain and LaCl3 on plant photosynthesis was established in order to reveal the combined effects on plant photosynthesis, especially on the photosynthetic organelle-chloroplast. Our results would provide some references for further understanding the mechanism of the combined effects of simulated acid rain and LaCl3 on plant photosynthesis.

Techniques in studies of photosynthesis

International Nuclear Information System (INIS)

Kumarasinghe, K.S.

1990-01-01

The use of both stable and radioactive isotopes has led to major advances in the understanding of the basic mechanisms of photosynthesis. An early use of isotopic material in photosynthetic investigations was the demonstration using 18 O, that O 2 evolved in photosynthesis was derived from water rather than from CO 2 . When the long-lived isotope of carbon, 14 C, became available in 1945, its use, coupled with two-dimensional chromatography developed a few years earlier, enabled Calvin and Benson (1948) to devise experiments to elucidate the pathway of photosynthetic 14 CO 2 fixation, 12 refs, 6 figs, 10 tabs

The paleobiological record of photosynthesis.

Science.gov (United States)

William Schopf, J

2011-01-01

Fossil evidence of photosynthesis, documented in Precambrian sediments by microbially laminated stromatolites, cyanobacterial microscopic fossils, and carbon isotopic data consistent with the presence of Rubisco-mediated CO2-fixation, extends from the present to ~3,500 million years ago. Such data, however, do not resolve time of origin of O2-producing photoautotrophy from its anoxygenic, bacterial, evolutionary precursor. Though it is well established that Earth's ecosystem has been based on autotrophy since its very early stages, the time of origin of oxygenic photosynthesis, more than 2,450 million years ago, has yet to be established.

Pectin Methylesterification Impacts the Relationship between Photosynthesis and Plant Growth.

Science.gov (United States)

M Weraduwage, Sarathi; Kim, Sang-Jin; Renna, Luciana; C Anozie, Fransisca; D Sharkey, Thomas; Brandizzi, Federica

2016-06-01

Photosynthesis occurs in mesophyll cells of specialized organs such as leaves. The rigid cell wall encapsulating photosynthetic cells controls the expansion and distribution of cells within photosynthetic tissues. The relationship between photosynthesis and plant growth is affected by leaf area. However, the underlying genetic mechanisms affecting carbon partitioning to different aspects of leaf growth are not known. To fill this gap, we analyzed Arabidopsis plants with altered levels of pectin methylesterification, which is known to modulate cell wall plasticity and plant growth. Pectin methylesterification levels were varied through manipulation of cotton Golgi-related (CGR) 2 or 3 genes encoding two functionally redundant pectin methyltransferases. Increased levels of methylesterification in a line over-expressing CGR2 (CGR2OX) resulted in highly expanded leaves with enhanced intercellular air spaces; reduced methylesterification in a mutant lacking both CGR-genes 2 and 3 (cgr2/3) resulted in thin but dense leaf mesophyll that limited CO2 diffusion to chloroplasts. Leaf, root, and plant dry weight were enhanced in CGR2OX but decreased in cgr2/3. Differences in growth between wild type and the CGR-mutants can be explained by carbon partitioning but not by variations in area-based photosynthesis. Therefore, photosynthesis drives growth through alterations in carbon partitioning to new leaf area growth and leaf mass per unit leaf area; however, CGR-mediated pectin methylesterification acts as a primary factor in this relationship through modulation of the expansion and positioning of the cells in leaves, which in turn drive carbon partitioning by generating dynamic carbon demands in leaf area growth and leaf mass per unit leaf area. © 2016 American Society of Plant Biologists. All Rights Reserved.

NO MECHANISTIC DEPENDENCE OF PHOTOSYNTHESIS ON CALCIFICATION IN THE COCCOLITHOPHORID EMILIANIA HUXLEYI (HAPTOPHYTA)(1).

Science.gov (United States)

Leonardos, Nikos; Read, Betsy; Thake, Brenda; Young, Jeremy R

2009-10-01

There is still considerable uncertainty about the relationship between calcification and photosynthesis. It has been suggested that since calcification in coccolithophorids is an intracellular process that releases CO2 , it enhances photosynthesis in a manner analogous to a carbon-concentrating mechanism (CCM). The ubiquitous, bloom-forming, and numerically abundant coccolithophorid Emiliania huxleyi (Lohmann) W. W. Hay et H. Mohler was studied in nutrient-replete, pH and [CO2 ] controlled, continuous cultures (turbidostats) under a range of [Ca(2+) ] from 0 to 9 mM. We examined the long-term, fully acclimated photosynthesis-light responses and analyzed the crystalline structure of the coccoliths using SEM. The E. huxleyi cells completely lost their coccosphere when grown in 0 [Ca(2+) ], while thin, undercalcified and brittle coccoliths were evident at 1 mM [Ca(2+) ]. Coccoliths showed increasing levels of calcification with increasing [Ca(2+) ]. More robust coccoliths were noted, with no discernable differences in coccolith morphology when the cells were grown in either 5 or 9 mM (ambient seawater) [Ca(2+) ]. In contrast to calcification, photosynthesis was not affected by the [Ca(2+) ] in the media. Cells showed no correlation of their light-dependent O2 evolution with [Ca(2+) ], and in all [Ca(2+) ]-containing turbidostats, there were no significant differences in growth rate. The results show unequivocally that as a process, photosynthesis in E. huxleyi is mechanistically independent from calcification. © 2009 Phycological Society of America.

Challenges in Understanding Photosynthesis in a University Introductory Biosciences Class

Science.gov (United States)

Södervik, Ilona; Virtanen, Viivi; Mikkilä-Erdmann, Mirjamaija

2015-01-01

University students' understanding of photosynthesis was examined in a large introductory biosciences class. The focus of this study was to first examine the conceptions of photosynthesis among students in class and then to investigate how a certain type of text could enhance students' understanding of photosynthesis. The study was based on pre-…

[Experimental study on crop photosynthesis, transpiration and high efficient water use].

Science.gov (United States)

Wang, Huixiao; Liu, Changming

2003-10-01

It is well known that the development of water-saving agriculture is a strategic choice for getting rid of the crisis of water shortage. In this paper, the crop photosynthesis, transpiration, stomatic behavior, and their affecting factors were studied in view of increasing the crop water use efficiency. The experimental results showed that there was a parabola relationship between photosynthesis and transpiration. The transpiration at the maximum photosynthesis was a critical value, above which, transpiration was the luxurious part. The luxurious transpiration could be controlled without affecting photosynthetic production. It is possible that the measures for increasing stomatic resistance and preventing transpiration could save water, and improve photosynthesis and yield as well. The photosynthesis rate increased with photosynthetic active radiation, and the light saturation point for photosynthesis existed. The light saturation point of dry treatment was much lower than that of wet treatment, and the relationship between transpiration and radiation was linear. When the photosynthetic active radiation was bigger than 1,000 mumol.m-2.s-1, some treatments could be carried out for decreasing transpiration and improving photosynthesis.

Interactions of photosynthesis with genome size and function

Science.gov (United States)

Raven, John A.; Beardall, John; Larkum, Anthony W. D.; Sánchez-Baracaldo, Patricia

2013-01-01

Photolithotrophs are divided between those that use water as their electron donor (Cyanobacteria and the photosynthetic eukaryotes) and those that use a different electron donor (the anoxygenic photolithotrophs, all of them Bacteria). Photolithotrophs with the most reduced genomes have more genes than do the corresponding chemoorganotrophs, and the fastest-growing photolithotrophs have significantly lower specific growth rates than the fastest-growing chemoorganotrophs. Slower growth results from diversion of resources into the photosynthetic apparatus, which accounts for about half of the cell protein. There are inherent dangers in (especially oxygenic) photosynthesis, including the formation of reactive oxygen species (ROS) and blue light sensitivity of the water spitting apparatus. The extent to which photolithotrophs incur greater DNA damage and repair, and faster protein turnover with increased rRNA requirement, needs further investigation. A related source of environmental damage is ultraviolet B (UVB) radiation (280–320 nm), whose flux at the Earth's surface decreased as oxygen (and ozone) increased in the atmosphere. This oxygenation led to the requirements of defence against ROS, and decreasing availability to organisms of combined (non-dinitrogen) nitrogen and ferrous iron, and (indirectly) phosphorus, in the oxygenated biosphere. Differential codon usage in the genome and, especially, the proteome can lead to economies in the use of potentially growth-limiting elements PMID:23754816

Reevaluation of the plant “gemstones”: Calcium oxalate crystals sustain photosynthesis under drought conditions

Science.gov (United States)

Tooulakou, Georgia; Giannopoulos, Andreas; Nikolopoulos, Dimosthenis; Bresta, Panagiota; Dotsika, Elissavet; Orkoula, Malvina G.; Kontoyannis, Christos G.; Fasseas, Costas; Liakopoulos, Georgios; Klapa, Maria I.; Karabourniotis, George

2016-01-01

ABSTRACT Land plants face the perpetual dilemma of using atmospheric carbon dioxide for photosynthesis and losing water vapors, or saving water and reducing photosynthesis and thus growth. The reason behind this dilemma is that this simultaneous exchange of gases is accomplished through the same minute pores on leaf surfaces, called stomata. In a recent study we provided evidence that pigweed, an aggressive weed, attenuates this problem exploiting large crystals of calcium oxalate as dynamic carbon pools. This plant is able to photosynthesize even under drought conditions, when stomata are closed and water losses are limited, using carbon dioxide from crystal decomposition instead from the atmosphere. Abscisic acid, an alarm signal that causes stomatal closure seems to be implicated in this function and for this reason we named this path “alarm photosynthesis.” The so-far “enigmatic,” but highly conserved and widespread among plant species calcium oxalate crystals seem to play a crucial role in the survival of plants. PMID:27471886

Secondary Students' Interpretations of Photosynthesis and Plant Nutrition.

Science.gov (United States)

Ozay, Esra; Oztas, Haydar

2003-01-01

Studies misconceptions held by grade 9 students (14-15-years old) in Turkey about photosynthesis and plant nutrition. Uses a questionnaire to test students' conceptions and reports conflicting and often incorrect ideas about photosynthesis, respiration, and energy flow in plants. Suggests that there are difficulties in changing students' prior…

Aerosol-induced thermal effects increase modelled terrestrial photosynthesis and transpiration

International Nuclear Information System (INIS)

Steiner, Allison L.; Chameides, W.L.

2005-01-01

Previous studies suggest that the radiative effects of atmospheric aerosols (reducing total radiation while increasing the diffuse fraction) can enhance terrestrial productivity. Here, simulations using a regional climate/terrestrial biosphere model suggest that atmospheric aerosols could also enhance terrestrial photosynthesis and transpiration through an interaction between solar radiation, leaf temperature and stomatal conductance. During midday, clear-sky conditions, sunlit-leaf temperatures can exceed the optimum for photosynthesis, depressing both photosynthesis and transpiration. Aerosols decrease surface solar radiation, thereby reducing leaf temperatures and enhancing sunlit-leaf photosynthesis and transpiration. This modelling study finds that, under certain conditions, this thermal response of aerosols can have a greater impact on photosynthesis and transpiration than the radiative response. This implies that a full understanding of the impact of aerosols on climate and the global carbon cycle requires consideration of the biophysical responses of terrestrial vegetation as well as atmospheric radiative and thermodynamic effects

Elevated CO2 increases photosynthesis in fluctuating irradiance regardless of photosynthetic induction state

NARCIS (Netherlands)

Kaiser, Elias; Zhou, Dianfan; Heuvelink, Ep; Harbinson, Jeremy; Morales Sierra, A.; Marcelis, Leo F.M.

2017-01-01

Leaves are often exposed to fluctuating irradiance, which limits assimilation. Elevated CO2 enhances dynamic photosynthesis (i.e. photosynthesis in fluctuating irradiance) beyond its effects on steady-state photosynthesis rates. Studying the role of CO2 in dynamic photosynthesis is important for

Impact of the ion transportome of chloroplasts on the optimization of photosynthesis.

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Szabò, Ildikò; Spetea, Cornelia

2017-06-01

Ions play fundamental roles in all living cells, and their gradients are often essential to fuel transport, regulate enzyme activities, and transduce energy within cells. Regulation of their homeostasis is essential for cell metabolism. Recent results indicate that modulation of ion fluxes might also represent a useful strategy to regulate one of the most important physiological processes taking place in chloroplasts, photosynthesis. Photosynthesis is highly regulated, due to its unique role as a cellular engine for growth in the light. Controlling the balance between ATP and NADPH synthesis is a critical task, and availability of these molecules can limit the overall photosynthetic yield. Photosynthetic organisms optimize photosynthesis in low light, where excitation energy limits CO2 fixation, and minimize photo-oxidative damage in high light by dissipating excess photons. Despite extensive studies of these phenomena, the mechanism governing light utilization in plants is still poorly understood. In this review, we provide an update of the recently identified chloroplast-located ion channels and transporters whose function impacts photosynthetic efficiency in plants. © The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Effects of light intensity on the morphology and CAM photosynthesis of Vanilla planifolia Andrews

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María Claudia Díez

2017-01-01

Full Text Available Vanilla planifolia is a neotropical orchid, whose fruits produce the natural vanilla, a fundamental ingredient for the food and cosmetic industry. Because of its importance in the world market, it is cultivated in many tropical countries and recently its cultivation has started in Colombia. This species requires shade for its development; however, the optimal of light conditions are unknown. This work evaluates the effect of different light intensities on CAM photosynthesis, physiology, morphology, and growth of this species. For this, vanilla seedlings were subjected to four treatments of relative illumination (RI (T1=8%, T2=17%, T3=31% and T4=67%. Most CO2 assimilation occurred along night in all treatments, which confirms that vanilla is a strong CAM species. Plants grown under high lighting (67% RI had almost half of the photosynthesis in treatments of intermediate lighting (17 and 31%, which is consistent with the lower nocturnal acid accumulation in that treatment. Likewise, the photochemical efficiency of photosystem II (Fv / Fm showed that in plants of the 67% RI occurred high radiation stress. On the other hand, vanilla plants reached greater length, leaf area, and total biomass when grown under intermediate radiation (17 and 31% RI. These results suggest that high radiation alters the functioning of vanilla plants, inhibiting photosynthesis and growth, and that highly shaded environments not significantly affected the CAM photosynthesis of vanilla; however, in the long-term this species showed higher photosynthesis and growth under intermediate levels of radiation

Photosynthesis and the world food problem

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Jerzy Poskuta

2014-01-01

Full Text Available Studies in the field of photosynthesis are particularly predisposed to play an important role in the solving of the main problem of today food for the world's growing population. The article presents data on the rate of population increase, the size of food production and yields of the most important crop plants. The relationship between the photosynthetic productivity of C3 and C4 plants and their yields is discussed. The problem of the rising atmospheric CO2 concentration and its influence on photosynthesis, photorespiration and accumulation of plant biomass is presented.

Structural biophysics

International Nuclear Information System (INIS)

Anon.

1979-01-01

Summaries of research projects conducted during 1978 and 1979 are presented. The structural biophysics group explores the high-resolution structure of biological macromolecules and cell organelles. Specific subject areas include: the basic characteristics of photosynthesis in plants; the chemical composition of individual fly ash particles at the site of their damaging action in tissues; direct analysis of frozen-hydrated biological samples by scanning electron microscopy; yeast genetics; the optical activity of DNA aggregates; measurement and characterization of lipoproteins; function of lipoproteins; and the effect of radiation and pollutants on mammalian cells

Rising CO2 widens the transpiration-photosynthesis optimality space

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de Boer, Hugo J.; Eppinga, Maarten B.; Dekker, Stefan C.

2016-04-01

). Measurements of gs and V cmax were obtained with a portable photosynthesis system. Our empirical results support the prediction that the V cmax:gs-ratio increases with higher CO2 in both Solanum genotypes. The 'dry' genotype revealed a significantly higher Huber value and lower V cmax than the 'wet' genotype at each CO2 growth level. Moreover, we found that the down-regulation of V cmax under higher CO2 was stronger in the 'dry' genotype than in the 'wet' genotype, whereas no change in the Huber value was observed between CO2 levels. Consistent with the theoretical trade-off between the resulting costs of transpiration and photosynthesis, we found that the CO2-induced increase in the V cmax:gs-ratio was stronger in the 'wet' genotype than in the 'dry' genotype. Given the divergence of V cmax:gs relationships observed, we conclude that rising atmospheric CO2 may widen the V cmax - gs optimality space available for plants to achieve an optimal trade-off between photosynthesis and transpiration. References Prentice, I. C., Dong, N., Gleason, S. M., Maire, V. and Wright, I. J.: Balancing the costs of carbon gain and water transport: testing a new theoretical framework for plant functional ecology, Ecol. Lett., 17(1), 82-91, 2014.

Exploring photosynthesis evolution by comparative analysis of metabolic networks between chloroplasts and photosynthetic bacteria

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Hou Jing

2006-04-01

Full Text Available Abstract Background Chloroplasts descended from cyanobacteria and have a drastically reduced genome following an endosymbiotic event. Many genes of the ancestral cyanobacterial genome have been transferred to the plant nuclear genome by horizontal gene transfer. However, a selective set of metabolism pathways is maintained in chloroplasts using both chloroplast genome encoded and nuclear genome encoded enzymes. As an organelle specialized for carrying out photosynthesis, does the chloroplast metabolic network have properties adapted for higher efficiency of photosynthesis? We compared metabolic network properties of chloroplasts and prokaryotic photosynthetic organisms, mostly cyanobacteria, based on metabolic maps derived from genome data to identify features of chloroplast network properties that are different from cyanobacteria and to analyze possible functional significance of those features. Results The properties of the entire metabolic network and the sub-network that consists of reactions directly connected to the Calvin Cycle have been analyzed using hypergraph representation. Results showed that the whole metabolic networks in chloroplast and cyanobacteria both possess small-world network properties. Although the number of compounds and reactions in chloroplasts is less than that in cyanobacteria, the chloroplast's metabolic network has longer average path length, a larger diameter, and is Calvin Cycle -centered, indicating an overall less-dense network structure with specific and local high density areas in chloroplasts. Moreover, chloroplast metabolic network exhibits a better modular organization than cyanobacterial ones. Enzymes involved in the same metabolic processes tend to cluster into the same module in chloroplasts. Conclusion In summary, the differences in metabolic network properties may reflect the evolutionary changes during endosymbiosis that led to the improvement of the photosynthesis efficiency in higher plants. Our

Long-Term Overgrazing-Induced Memory Decreases Photosynthesis of Clonal Offspring in a Perennial Grassland Plant.

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Ren, Weibo; Hu, Ningning; Hou, Xiangyang; Zhang, Jize; Guo, Huiqin; Liu, Zhiying; Kong, Lingqi; Wu, Zinian; Wang, Hui; Li, Xiliang

2017-01-01

Previous studies of transgenerational plasticity have demonstrated that long-term overgrazing experienced by Leymus chinensis , an ecologically dominant, rhizomatous grass species in eastern Eurasian temperate grassland, significantly affects its clonal growth in subsequent generations. However, there is a dearth of information on the reasons underlying this overgrazing-induced memory effect in plant morphological plasticity. We characterized the relationship between a dwarf phenotype and photosynthesis function decline of L. chinensis from the perspective of leaf photosynthesis by using both field measurement and rhizome buds culture cultivated in a greenhouse. Leaf photosynthetic functions (net photosynthetic rate, stomatal conductance, intercellular carbon dioxide concentration, and transpiration rate) were significantly decreased in smaller L. chinensis individuals that were induced to have a dwarf phenotype by being heavily grazed in the field. This decreased photosynthetic function was maintained a generation after greenhouse tests in which grazing was excluded. Both the response of L. chinensis morphological traits and photosynthetic functions in greenhouse were deceased relative to those in the field experiment. Further, there were significant decreases in leaf chlorophyll content and Rubisco enzyme activities of leaves between bud-cultured dwarf and non-dwarf L. chinensis in the greenhouse. Moreover, gene expression patterns showed that the bud-cultured dwarf L. chinensis significantly down-regulated (by 1.86- to 5.33-fold) a series of key genes that regulate photosynthetic efficiency, stomata opening, and chloroplast development compared with the non-dwarf L. chinensis . This is among the first studies revealing a linkage between long-term overgrazing affecting the transgenerational morphological plasticity of clonal plants and physiologically adaptive photosynthesis function. Overall, clonal transgenerational effects in L. chinensis phenotypic traits

Long-Term Overgrazing-Induced Memory Decreases Photosynthesis of Clonal Offspring in a Perennial Grassland Plant

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Xiangyang Hou

2017-04-01

Full Text Available Previous studies of transgenerational plasticity have demonstrated that long-term overgrazing experienced by Leymus chinensis, an ecologically dominant, rhizomatous grass species in eastern Eurasian temperate grassland, significantly affects its clonal growth in subsequent generations. However, there is a dearth of information on the reasons underlying this overgrazing-induced memory effect in plant morphological plasticity. We characterized the relationship between a dwarf phenotype and photosynthesis function decline of L. chinensis from the perspective of leaf photosynthesis by using both field measurement and rhizome buds culture cultivated in a greenhouse. Leaf photosynthetic functions (net photosynthetic rate, stomatal conductance, intercellular carbon dioxide concentration, and transpiration rate were significantly decreased in smaller L. chinensis individuals that were induced to have a dwarf phenotype by being heavily grazed in the field. This decreased photosynthetic function was maintained a generation after greenhouse tests in which grazing was excluded. Both the response of L. chinensis morphological traits and photosynthetic functions in greenhouse were deceased relative to those in the field experiment. Further, there were significant decreases in leaf chlorophyll content and Rubisco enzyme activities of leaves between bud-cultured dwarf and non-dwarf L. chinensis in the greenhouse. Moreover, gene expression patterns showed that the bud-cultured dwarf L. chinensis significantly down-regulated (by 1.86- to 5.33-fold a series of key genes that regulate photosynthetic efficiency, stomata opening, and chloroplast development compared with the non-dwarf L. chinensis. This is among the first studies revealing a linkage between long-term overgrazing affecting the transgenerational morphological plasticity of clonal plants and physiologically adaptive photosynthesis function. Overall, clonal transgenerational effects in L. chinensis

High salinity helps the halophyte Sesuvium portulacastrum in defense against Cd toxicity by maintaining redox balance and photosynthesis.

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Wali, Mariem; Gunsè, Benet; Llugany, Mercè; Corrales, Isabel; Abdelly, Chedly; Poschenrieder, Charlotte; Ghnaya, Tahar

2016-08-01

NaCl alleviates Cd toxicity in Sesvium portulacastrum by maintaining plant water status and redox balance, protecting chloroplasts structure and inducing some potential Cd (2+) chelators as GSH and proline. It has been demonstrated that NaCl alleviates Cd-induced growth inhibition in the halophyte Sesuvium portulacastrum. However, the processes that mediate this effect are still unclear. In this work we combined physiological, biochemical and ultrastructural studies to highlight the effects of salt on the redox balance and photosynthesis in Cd-stressed plants. Seedlings were exposed to different Cd concentrations (0, 25 and 50 µM Cd) combined with low (0.09 mM) (LS), or high (200 mM) NaCl (HS) in hydroponic culture. Plant-water relations, photosynthesis rate, leaf gas exchange, chlorophyll fluorescence, chloroplast ultrastructure, and proline and glutathione concentrations were analyzed after 1 month of treatment. In addition, the endogenous levels of stress-related hormones were determined in plants subjected to 25 µM Cd combined with both NaCl concentrations. In plants with low salt supply (LS), Cd reduced growth, induced plant dehydration, disrupted chloroplast structure and functioning, decreased net CO2 assimilation rate (A) and transpiration rate (E), inhibited the maximum potential quantum efficiency (Fv/Fm) and the quantum yield efficiency (Φ PSII) of PSII, and enhanced the non-photochemical quenching (NPQ). The addition of 200 mM NaCl (HS) to the Cd-containing medium culture significantly mitigated Cd phytotoxicity. Hence, even at similar internal Cd concentrations, HS-Cd plants were less affected by Cd than LS-Cd ones. Hence, 200 mM NaCl significantly alleviates Cd-induced toxicity symptoms, growth inhibition, and photosynthesis disturbances. The cell ultrastructure was better preserved in HS-Cd plants but affected in LS-Cd plants. The HS-Cd plants showed also higher concentrations of reduced glutathione (GSH), proline and jasmonic acid (JA

Cyanobacterial Oxygenic Photosynthesis is Protected by Flavodiiron Proteins

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Yagut Allahverdiyeva

2015-03-01

Full Text Available Flavodiiron proteins (FDPs, also called flavoproteins, Flvs are modular enzymes widely present in Bacteria and Archaea. The evolution of cyanobacteria and oxygenic photosynthesis occurred in concert with the modulation of typical bacterial FDPs. Present cyanobacterial FDPs are composed of three domains, the β-lactamase-like, flavodoxin-like and flavin-reductase like domains. Cyanobacterial FDPs function as hetero- and homodimers and are involved in the regulation of photosynthetic electron transport. Whilst Flv2 and Flv4 proteins are limited to specific cyanobacterial species (β-cyanobacteria and function in photoprotection of Photosystem II, Flv1 and Flv3 proteins, functioning in the “Mehler-like” reaction and safeguarding Photosystem I under fluctuating light conditions, occur in nearly all cyanobacteria and additionally in green algae, mosses and lycophytes. Filamentous cyanobacteria have additional FDPs in heterocyst cells, ensuring a microaerobic environment for the function of the nitrogenase enzyme under the light. Here, the evolution, occurrence and functional mechanisms of various FDPs in oxygenic photosynthetic organisms are discussed.

Artificial photosynthesis combines biology with technology for sustainable energy transformation

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Moore, Thomas A.; Moore, Ana L.; Gust, Devens

2013-03-01

Photosynthesis supports the biosphere. Currently, human activity appropriates about one fourth of terrestrial photosynthetic net primary production (NPP) to support our GDP and nutrition. The cost to Earth systems of "our cut" of NPP is thought to be rapidly driving several Earth systems outside of bounds that were established on the geological time scale. Even with a fundamental realignment of human priorities, changing the unsustainable trajectory of the anthropocene will require reengineering photosynthesis to more efficiently meet human needs. Artificial photosynthetic systems are envisioned that can both supply renewable fuels and serve as platforms for exploring redesign strategies for photosynthesis. These strategies can be used in the nascent field of synthetic biology to make vast, much needed improvements in the biomass production efficiency of photosynthesis.

Photosynthesis: The Path of Carbon in Photosynthesis and the Primary Quantum Conversion Act of Photosynthesis

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Calvin, Melvin

1952-11-22

This constitutes a review of the path of carbon in photosynthesis as it has been elaborated through the summer of 1952, with particular attention focused on those aspects of carbon metabolism and its variation which have led to some direct information regarding the primary quantum conversion act. An introduction to the arguments which have been adduced in support of the idea that chlorophyll is a physical sensitizer handing its excitation on to thioctic acid, a compound containing a strained 1, 2 -dithiolcyclopentane ring, is given.

Remote sensing of Essential Biodiversity Variables: new measurements linking ecosystem structure, function and composition

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Schimel, D.; Pavlick, R.; Stavros, E. N.; Townsend, P. A.; Ustin, S.; Thompson, D. R.

2017-12-01

Remote sensing can inform a wide variety of essential biodiversity variables, including measurements that define primary productivity, forest structure, biome distribution, plant communities, land use-land cover change and climate drivers of change. Emerging remote sensing technologies can add significantly to remote sensing of EBVs, providing new, large scale insights on plant and habitat diversity itself, as well as causes and consequences of biodiversity change. All current biodiversity assessments identify major data gaps, with insufficient coverage in critical regions, limited observations to monitor change over time, with very limited revisit of sample locations, as well as taxon-specific biased biases. Remote sensing cannot fill many of the gaps in global biodiversity observations, but spectroscopic measurements in terrestrial and marine environments can aid in assessing plant/phytoplankton functional diversity and efficiently reveal patterns in space, as well as changes over time, and, by making use of chlorophyll fluorescence, reveal associated patterns in photosynthesis. LIDAR and RADAR measurements quantify ecosystem structure, and can precisely define changes due to growth, disturbance and land use. Current satellite-based EBVs have taken advantage of the extraordinary time series from LANDSAT and MODIS, but new measurements more directly reveal ecosystem structure, function and composition. We will present results from pre-space airborne studies showing the synergistic ability of a suite of new remote observation techniques to quantify biodiversity and ecosystem function and show how it changes during major disturbance events.

Soil water regulates the control of photosynthesis on diel hysteresis between soil respiration and temperature in a desert shrubland

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Wang, Ben; Zha, Tian Shan; Jia, Xin; Gong, Jin Nan; Bourque, Charles; Feng, Wei; Tian, Yun; Wu, Bin; Qing Zhang, Yu; Peltola, Heli

2017-09-01

Explanations for the occurrence of hysteresis (asynchronicity) between diel soil respiration (Rs) and soil temperature (Ts) have evoked both biological and physical mechanisms. The specifics of these explanations, however, tend to vary with the particular ecosystem or biome being investigated. So far, the relative degree of control of biological and physical processes on hysteresis is not clear for drylands. This study examined the seasonal variation in diel hysteresis and its biological control in a desert-shrub ecosystem in northwest (NW) China. The study was based on continuous measurements of Rs, air temperature (Ta), temperature at the soil surface and below (Tsurf and Ts), volumetric soil water content (SWC), and photosynthesis in a dominant desert shrub (i.e., Artemisia ordosica) over an entire year in 2013. Trends in diel Rs were observed to vary with SWC over the growing season (April to October). Diel variations in Rs were more closely associated with variations in Tsurf than with photosynthesis as SWC increased, leading to Rs being in phase with Tsurf, particularly when SWC > 0.08 m3 m-3 (ratio of SWC to soil porosity = 0.26). However, as SWC decreased below 0.08 m3 m-3, diel variations in Rs were more closely related to variations in photosynthesis, leading to pronounced hysteresis between Rs and Tsurf. Incorporating photosynthesis into a Q10-function eliminated 84.2 % of the observed hysteresis, increasing the overall descriptive capability of the function. Our findings highlight a high degree of control by photosynthesis and SWC in regulating seasonal variation in diel hysteresis between Rs and temperature.

Quantifying seasonal dynamics of canopy structure and function using inexpensive narrowband spectral radiometers

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Vierling, L. A.; Garrity, S. R.; Campbell, G.; Coops, N. C.; Eitel, J.; Gamon, J. A.; Hilker, T.; Krofcheck, D. J.; Litvak, M. E.; Naupari, J. A.; Richardson, A. D.; Sonnentag, O.; van Leeuwen, M.

2011-12-01

Increasing the spatial and temporal density of automated environmental sensing networks is necessary to quantify shifts in plant structure (e.g., leaf area index) and function (e.g., photosynthesis). Improving detection sensitivity can facilitate a mechanistic understanding by better linking plant processes to environmental change. Spectral radiometer measurements can be highly useful for tracking plant structure and function from diurnal to seasonal time scales and calibrating and validating satellite- and aircraft-based spectral measurements. However, dense ground networks of such instruments are challenging to establish due to the cost and complexity of automated instrument deployment. We therefore developed simple to operate, lightweight and inexpensive narrowband (~10nm bandwidth) spectral instruments capable of continuously measuring four to six discrete bands that have proven capacity to describe key physiological processes and structural features of plant canopies. These bands are centered at 530, 570, 675, 800, 880, and 970 nm to enable calculation of the physiological reflectance index (PRI), normalized difference vegetation index (NDVI), green NDVI (gNDVI), and water band index (WBI) collected above and within vegetation canopies. To date, measurements have been collected above grassland, semi-arid shrub steppe, piñon-juniper woodland, dense conifer forest, mixed deciduous-conifer forest, and cropland canopies, with additional measurements collected along vertical transects through a temperate conifer rainforest. Findings from this work indicate not only that key shifts in plant phenology, physiology, and structure can be captured using such instruments, but that the temporally dense nature of the measurements can help to disentangle heretofore unreported complexities of simultaneous phenological and structural change on canopy reflectance.

Underwater Photosynthesis of Submerged Plants – Recent Advances and Methods

Science.gov (United States)

Pedersen, Ole; Colmer, Timothy D.; Sand-Jensen, Kaj

2013-01-01

We describe the general background and the recent advances in research on underwater photosynthesis of leaf segments, whole communities, and plant dominated aquatic ecosystems and present contemporary methods tailor made to quantify photosynthesis and carbon fixation under water. The majority of studies of aquatic photosynthesis have been carried out with detached leaves or thalli and this selectiveness influences the perception of the regulation of aquatic photosynthesis. We thus recommend assessing the influence of inorganic carbon and temperature on natural aquatic communities of variable density in addition to studying detached leaves in the scenarios of rising CO2 and temperature. Moreover, a growing number of researchers are interested in tolerance of terrestrial plants during flooding as torrential rains sometimes result in overland floods that inundate terrestrial plants. We propose to undertake studies to elucidate the importance of leaf acclimation of terrestrial plants to facilitate gas exchange and light utilization under water as these acclimations influence underwater photosynthesis as well as internal aeration of plant tissues during submergence. PMID:23734154

Increased sink strength offsets the inhibitory effect of sucrose on sugarcane photosynthesis.

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Ribeiro, Rafael V; Machado, Eduardo C; Magalhães Filho, José R; Lobo, Ana Karla M; Martins, Márcio O; Silveira, Joaquim A G; Yin, Xinyou; Struik, Paul C

2017-01-01

Spraying sucrose inhibits photosynthesis by impairing Rubisco activity and stomatal conductance (g s ), whereas increasing sink demand by partially darkening the plant stimulates sugarcane photosynthesis. We hypothesized that the stimulatory effect of darkness can offset the inhibitory effect of exogenous sucrose on photosynthesis. Source-sink relationship was perturbed in two sugarcane cultivars by imposing partial darkness, spraying a sucrose solution (50mM) and their combination. Five days after the onset of the treatments, the maximum Rubisco carboxylation rate (V cmax ) and the initial slope of A-C i curve (k) were estimated by measuring leaf gas exchange and chlorophyll fluorescence. Photosynthesis was inhibited by sucrose spraying in both genotypes, through decreases in V cmax , k, g s and ATP production driven by electron transport (J atp ). Photosynthesis of plants subjected to the combination of partial darkness and sucrose spraying was similar to photosynthesis of reference plants for both genotypes. Significant increases in V cmax , g s and J atp and marginal increases in k were noticed when combining partial darkness and sucrose spraying compared with sucrose spraying alone. Our data also revealed that increases in sink strength due to partial darkness offset the inhibition of sugarcane photosynthesis caused by sucrose spraying, enhancing the knowledge on endogenous regulation of sugarcane photosynthesis through the source-sink relationship. Copyright © 2016 Elsevier GmbH. All rights reserved.

Microbial photosynthesis in the harnessing of solar energy

Energy Technology Data Exchange (ETDEWEB)

Pirt, S J

1982-01-01

The shortage of fossil fuels restricts the world supply of reduced carbon compounds and energy sources. Biotechnology offers the most feasible route to renewing the supplies of reduced carbon compounds. This involves recycling of CO/sub 2/ through photosynthesis. Conventional agriculture has little or no potential for supplying biomass and its derivatives on sufficient scale to offer an alternative to the fossil fuels. The agricultural wastes, on the whole, are intractable to conversion into useful carbon and energy sources and in any case are not available in amounts to provide a significant alternative to the fossil fuels. In contrast, microbial photosynthesis, optimised in photobioreactors, has vast potential to provide organic matter on a scale to match the consumption of fossil fuels. The quantative study of microbial photosynthesis as a biotechnological route to biomass has been neglected. As a result there is a chaos of conflicting data on fundamental parameters, for example, the photosynthetic efficiency of biomass production. New photosynthetic biotechnology with fully controlled continuous-culture systems is providing unequivocal values for the parameters. For the scale-up of microbial photosynthesis a tubular-loop reactor is proposed. (Refs. 14).

Observed and predicted measurements of photosynthesis in a phytoplankton culture exposed to natural irradiance

International Nuclear Information System (INIS)

Marra, J.; Heinemann, K.; Landriau, G. Jr.

1985-01-01

Photosynthesis-irradiance (P-I) curves were produced (using artificial illumination) from samples taken at one or more times per day from a continuous culture illuminated with sunlight. The continuous culture housed an oxygen electrode used to measure photosynthesis semi-continuously. Rates of photosynthesis predicted from P-I curves agreed with photosynthesis observed in the culture only for days of low irradiance. For sunny days or for days of variable irradiance, P-I curves predicted neither the morning photosynthesis maximum nor the afternoon depression. Daily integrals of predicted and observed photosynthesis, however, were probably within the possible errors of measurement. (orig.)

The role of carbonic anhydrase in C₄ photosynthesis

Energy Technology Data Exchange (ETDEWEB)

Studer, Anthony [Life Sciences Research Foundation, Baltimore, MD (United States)

2015-10-01

Current pressures on the global food supply have accelerated the urgency for a second green revolution using novel and sustainable approaches to increase crop yield and efficiency. This proposal outlines experiments to address fundamental questions regarding the biology of C₄ photosynthesis, the method of carbon fixation utilized by the most productive food, feed and bioenergy crops. Carbonic anhydrase (CA) has been implicated in multiple cellular functions including nitrogen metabolism, water use efficiency, and photosynthesis. CA catalyzes the first dedicated step in C₄ photosynthesis, the hydration of CO₂ into bicarbonate, and is potentially rate limiting in C₄ grasses. Using insertional mutagenesis, we have generated CA mutants in maize, and propose the characterization of these mutants using phenotypic, physiological, and transcriptomic profiling to assay the plant’s response to altered CA activity. In addition, florescent protein tagging experiments will be employed to study the subcellular localization of CA paralogs, providing critical data for modeling carbon fixation in C₄ plants. Finally, I propose parallel experiments in Setaria viridis to explore its relevance as model C₄ grass. Using a multifaceted approach, this proposal addresses important questions in basic biology, as well as the need for translation research in response to looming global food challenges.

Auxin transport in leafy pea stem cuttings is partially driven by photosynthesis

International Nuclear Information System (INIS)

Kumpula, C.L.; Potter, J.R.

1987-01-01

When 14 C-IAA was applied to the apex of disbudded leafy pea stem cuttings (15 cm long), the movement of 14 C-IAA to the base of the cuttings after 24 h was influenced by the photosynthetic rate. In the absence of photosynthesis, light did not influence 14 C-IAA movement. Photosynthesis was altered by varying light, CO 2 concentration, or stomatal aperature (blocked with an antitranspirant). Radioactivity (identified by co-chromatography) was 25, 60, and 5% IAA, IAA-aspartate, and indolealdehyde respectively regardless of treatment. Adventitious root formation was reduced 50 to 95% and movement of IAA was inhibited 50 to 70% by decreasing gross photosynthesis 90 to 100%. Apparently, photosynthesis partially drives the movement of IAA from the apex to the base where roots arise. This gives a probably role of photosynthesis in rooting, because in this system virtually no rooting will take place without exogenous auxin and at least a low level of gross photosynthesis

Photosynthesis efficiency for different wavelengths; Fotosynthese-efficiency bij verschillende golflengten

Energy Technology Data Exchange (ETDEWEB)

Snel, J.F.H.; Meinen, E.; Bruins, M.A.; Van Ieperen, W.; Hogewoning, S.W.; Marcelis, L.F.M. [Wageningen UR Glastuinbouw, Wageningen (Netherlands)

2012-04-15

LED lighting has recently been introduced into Dutch horticulture. LED development so far indicates that in the near future LED's will be more energy efficient than high pressure sodium lamps. Crop light interception and photosynthesis efficiency are wavelength dependent. Therefore, LED colours for maximum crop photosynthesis, growth and development should be identified. Wageningen UR has investigated light interception and photosynthesis at different wavelengths for tomato, cucumber and rose. Measuring protocols and equipment were developed for leaf photosynthesis measurements in the laboratory and in greenhouses. A crop simulation model was used for up-scaling the leaf level results to crop level photosynthesis. For the vegetable crops the photosynthesis spectra are very similar to the generalised photosynthesis spectrum. Red light is most efficient for leaf photosynthesis. Light from red (ca. 645nm) LED's was maximally 13% more efficient than High Pressure Sodium light. For reddish leaves of the rose cultivar Prestige, red LED light was up to 35% more efficient. These figures apply to the momentary efficiency of leaf photosynthesis at 100 {mu}mol.m{sup -2}.s{sup -1} (PAR) and suggest that use of red light can lead to higher photosynthesis, especially for certain rose cultivars [Dutch] LED verlichting heeft zijn intrede gedaan in de Nederlandse glastuinbouw. De LED ontwikkeling laat zien dat in de nabije toekomst LED's efficiënter zijn dan SON-T verlichting. Lichtonderschepping en fotosynthese efficiëntie zijn afhankelijk van de kleur van het licht. Voor optimale fotosynthese, groei en ontwikkeling zouden de beste LED kleuren uitgezocht moeten worden. Wageningen UR heeft lichtonderschepping en fotosynthese bij verschillende lichtkleuren onderzocht bij tomaat, komkommer en roos. Protocollen en apparatuur werden ontwikkeld voor meting van bladfotosynthese en lichtonderschepping in het laboratorium en in de kas. Met een gewassimulatiemodel werd de

Exploring Undergraduates' Understanding of Photosynthesis Using Diagnostic Question Clusters

Science.gov (United States)

Parker, Joyce M.; Anderson, Charles W.; Heidemann, Merle; Merrill, John; Merritt, Brett; Richmond, Gail; Urban-Lurain, Mark

2012-01-01

We present a diagnostic question cluster (DQC) that assesses undergraduates' thinking about photosynthesis. This assessment tool is not designed to identify individual misconceptions. Rather, it is focused on students' abilities to apply basic concepts about photosynthesis by reasoning with a coordinated set of practices based on a few scientific…

Powered by light: Phototrophy and photosynthesis in prokaryotes and its evolution.

Science.gov (United States)

Nowicka, Beatrycze; Kruk, Jerzy

2016-01-01

Photosynthesis is a complex metabolic process enabling photosynthetic organisms to use solar energy for the reduction of carbon dioxide into biomass. This ancient pathway has revolutionized life on Earth. The most important event was the development of oxygenic photosynthesis. It had a tremendous impact on the Earth's geochemistry and the evolution of living beings, as the rise of atmospheric molecular oxygen enabled the development of a highly efficient aerobic metabolism, which later led to the evolution of complex multicellular organisms. The mechanism of photosynthesis has been the subject of intensive research and a great body of data has been accumulated. However, the evolution of this process is not fully understood, and the development of photosynthesis in prokaryota in particular remains an unresolved question. This review is devoted to the occurrence and main features of phototrophy and photosynthesis in prokaryotes. Hypotheses concerning the origin and spread of photosynthetic traits in bacteria are also discussed. Copyright © 2016 Elsevier GmbH. All rights reserved.

The Path of Carbon in Photosynthesis VIII. The Role of Malic Acid

Science.gov (United States)

Bassham, James A.; Benson, Andrew A.; Calvin, Melvin

1950-01-25

Malonate has been found to inhibit the formation of malic acid during short periods of photosynthesis with radioactive carbon dioxide. This result, together with studies which show the photosynthetic cycle to be operating normally at the same time, indicates that malic acid is not an intermediate in photosynthesis but is probably closely related to some intermediate of the cycle. Absence of labeled succinic and fumaric acids in these experiments, in addition to the failure of malonate to inhibit photosynthesis, precludes the participation of these acids as intermediates in photosynthesis.

Pectin Methylesterification Impacts the Relationship between Photosynthesis and Plant Growth1[OPEN

Science.gov (United States)

Kim, Sang-Jin; Renna, Luciana; Brandizzi, Federica

2016-01-01

Photosynthesis occurs in mesophyll cells of specialized organs such as leaves. The rigid cell wall encapsulating photosynthetic cells controls the expansion and distribution of cells within photosynthetic tissues. The relationship between photosynthesis and plant growth is affected by leaf area. However, the underlying genetic mechanisms affecting carbon partitioning to different aspects of leaf growth are not known. To fill this gap, we analyzed Arabidopsis plants with altered levels of pectin methylesterification, which is known to modulate cell wall plasticity and plant growth. Pectin methylesterification levels were varied through manipulation of cotton Golgi-related (CGR) 2 or 3 genes encoding two functionally redundant pectin methyltransferases. Increased levels of methylesterification in a line over-expressing CGR2 (CGR2OX) resulted in highly expanded leaves with enhanced intercellular air spaces; reduced methylesterification in a mutant lacking both CGR-genes 2 and 3 (cgr2/3) resulted in thin but dense leaf mesophyll that limited CO2 diffusion to chloroplasts. Leaf, root, and plant dry weight were enhanced in CGR2OX but decreased in cgr2/3. Differences in growth between wild type and the CGR-mutants can be explained by carbon partitioning but not by variations in area-based photosynthesis. Therefore, photosynthesis drives growth through alterations in carbon partitioning to new leaf area growth and leaf mass per unit leaf area; however, CGR-mediated pectin methylesterification acts as a primary factor in this relationship through modulation of the expansion and positioning of the cells in leaves, which in turn drive carbon partitioning by generating dynamic carbon demands in leaf area growth and leaf mass per unit leaf area. PMID:27208234

Exploring Photosynthesis and Plant Stress Using Inexpensive Chlorophyll Fluorometers

Science.gov (United States)

Cessna, Stephen; Demmig-Adams, Barbara; Adams, William W., III

2010-01-01

Mastering the concept of photosynthesis is of critical importance to learning plant physiology and its applications, but seems to be one of the more challenging concepts in biology. This teaching challenge is no doubt compounded by the complexity by which plants alter photosynthesis in different environments. Here we suggest the use of chlorophyll…

On the relation between phototaxis and photosynthesis in Rhodospirillum Rubrum

NARCIS (Netherlands)

Thomas, J.B.; Nijenhuis, L.E.

1950-01-01

The relation between phototaxis and photosynthesis in Rhodospirillum rubrum has been studied. The light intensity at which saturation is reached in photosynthesis proved to coincide with that at which the contrast sensitivity starts to decrease. Potassium cyanide, which preferably inhibits the

The primary steps of photosynthesis

International Nuclear Information System (INIS)

Fleming, G.R.; Van Grondelle, R.

1996-01-01

The two important initial steps of photosynthesis-electron transfer and energy transfer occur with great speed and efficiency. New techniques in laser optics and genetic engineering age helping us to understand why. (author). 24 refs. 8 figs

Effects of ammonia from livestock farming on lichen photosynthesis

Energy Technology Data Exchange (ETDEWEB)

Paoli, Luca [Department of Environmental Science ' G. Sarfatti' , University of Siena, via Mattioli 4, I-53100 Siena (Italy); Department of Biology, University of Crete, 71409 Heraklion, Crete (Greece); Pirintsos, Stergios Arg.; Kotzabasis, Kiriakos [Department of Biology, University of Crete, 71409 Heraklion, Crete (Greece); Pisani, Tommaso [Department of Environmental Science ' G. Sarfatti' , University of Siena, via Mattioli 4, I-53100 Siena (Italy); Navakoudis, Eleni [Department of Biology, University of Crete, 71409 Heraklion, Crete (Greece); Loppi, Stefano, E-mail: loppi@unisi.i [Department of Environmental Science ' G. Sarfatti' , University of Siena, via Mattioli 4, I-53100 Siena (Italy)

2010-06-15

This study investigated if atmospheric ammonia (NH{sub 3}) pollution around a sheep farm influences the photosynthetic performance of the lichens Evernia prunastri and Pseudevernia furfuracea. Thalli of both species were transplanted for up to 30 days in a semi-arid region (Crete, Greece), at sites with concentrations of atmospheric ammonia of ca. 60 mug/m{sup 3} (at a sheep farm), ca. 15 mug/m{sup 3} (60 m from the sheep farm) and ca. 2 mug/m{sup 3} (a remote area 5 km away). Lichen photosynthesis was analysed by the chlorophyll a fluorescence emission to identify targets of ammonia pollution. The results indicated that the photosystem II of the two lichens exposed to NH{sub 3} is susceptible to this pollutant in the gas-phase. The parameter PI{sub ABS}, a global index of photosynthetic performance that combines in a single expression the three functional steps of the photosynthetic activity (light absorption, excitation energy trapping, and conversion of excitation energy to electron transport) was much more sensitive to NH{sub 3} than the F{sub V}/F{sub M} ratio, one of the most commonly used stress indicators. - Ammonia from livestock farming affects lichen photosynthesis.

Quantum design of photosynthesis for bio-inspired solar-energy conversion

NARCIS (Netherlands)

Romero, Elisabet; Novoderezhkin, Vladimir I.; van Grondelle, Rienk

2017-01-01

Photosynthesis is the natural process that converts solar photons into energy-rich products that are needed to drive the biochemistry of life. Two ultrafast processes form the basis of photosynthesis: excitation energy transfer and charge separation. Under optimal conditions, every photon that is

Carbohydrate regulation of photosynthesis and respiration from branch girdling in four species of wet tropical rain forest trees.

Science.gov (United States)

Asao, Shinichi; Ryan, Michael G

2015-06-01

How trees sense source-sink carbon balance remains unclear. One potential mechanism is a feedback from non-structural carbohydrates regulating photosynthesis and removing excess as waste respiration when the balance of photosynthesis against growth and metabolic activity changes. We tested this carbohydrate regulation of photosynthesis and respiration using branch girdling in four tree species in a wet tropical rainforest in Costa Rica. Because girdling severs phloem to stop carbohydrate export while leaving xylem intact to allow photosynthesis, we expected carbohydrates to accumulate in leaves to simulate a carbon imbalance. We varied girdling intensity by removing phloem in increments of one-quarter of the circumference (zero, one--quarter, half, three-quarters, full) and surrounded a target branch with fully girdled ones to create a gradient in leaf carbohydrate content. Light saturated photosynthesis rate was measured in situ, and foliar respiration rate and leaf carbohydrate content were measured after destructive harvest at the end of the treatment. Girdling intensity created no consistent or strong responses in leaf carbohydrates. Glucose and fructose slightly increased in all species by 3.4% per one-quarter girdle, total carbon content and leaf mass per area increased only in one species by 5.4 and 5.5% per one-quarter girdle, and starch did not change. Only full girdling lowered photosynthesis in three of four species by 59-69%, but the decrease in photosynthesis was unrelated to the increase in glucose and fructose content. Girdling did not affect respiration. The results suggest that leaf carbohydrate content remains relatively constant under carbon imbalance, and any changes are unlikely to regulate photosynthesis or respiration. Because girdling also stops the export of hormones and reactive oxygen species, girdling may induce physiological changes unrelated to carbohydrate accumulation and may not be an effective method to study carbohydrate feedback

[Photosynthesis and transpiration characteristics of female and male Trichosanthes kirilowii Maxim individuals].

Science.gov (United States)

Liu, Yun; Zhong, Zhang-cheng; Wang, Xiao-xue; Xie, Jun; Yang, Wen-ying

2011-03-01

A field research was conducted on the photosynthesis and transpiration characteristics of dioecious Trichosanthes kirilowii individuals at four key development stages. At vegetative growth stage, the photosynthesis rate, transpiration rate, stomatal conductance, and water use efficiency of male individuals were higher than those of female individuals, and hence, male individuals entered into reproductive growth stage 22 days earlier than female individuals. After entering into reproductive growth stage, male individuals had higher photosynthesis rate, transpiration rate, and stomatal conductance, but slightly lower water use efficiency than female individuals. As the female individuals started to reproductive growth, their photosynthesis rate and water use efficiency were significantly lower, while the transpiration rate and stomatal conductance were higher than those of the male individuals. The effects of climate factors on the growth and development of T. kirilowii mainly occurred at its vegetative growth and early reproductive growth stages, and weakened at later reproductive growth stages. Higher temperature and lower relative humidity benefited the growth and development of T. kirilowii, and illumination could enhance the photosynthesis rate of T. kirilowii, especially its male individuals. After entering into reproductive growth stage, the photosynthesis rate of male individuals increased significantly with increasing illumination, but that of female individuals only had a slight increase, and the transpiration rate of male individuals as well as the photosynthesis rate of female individuals all increased significantly with increasing temperature.

Cyanobacterial photosynthesis under sulfidic conditions: insights from the isolate Leptolyngbya sp. strain hensonii

Science.gov (United States)

Hamilton, Trinity L; Klatt, Judith M; de Beer, Dirk; Macalady, Jennifer L

2018-01-01

We report the isolation of a pinnacle-forming cyanobacterium isolated from a microbial mat covering the sediment surface at Little Salt Spring—a flooded sinkhole in Florida with a perennially microoxic and sulfidic water column. The draft genome of the isolate encodes all of the enzymatic machinery necessary for both oxygenic and anoxygenic photosynthesis, as well as genes for methylating hopanoids at the C-2 position. The physiological response of the isolate to H2S is complex: (i) no induction time is necessary for anoxygenic photosynthesis; (ii) rates of anoxygenic photosynthesis are regulated by both H2S and irradiance; (iii) O2 production is inhibited by H2S concentrations as low as 1 μM and the recovery rate of oxygenic photosynthesis is dependent on irradiance; (iv) under the optimal light conditions for oxygenic photosynthesis, rates of anoxygenic photosynthesis are nearly double those of oxygenic photosynthesis. We hypothesize that the specific adaptation mechanisms of the isolate to H2S emerged from a close spatial interaction with sulfate-reducing bacteria. The new isolate, Leptolyngbya sp. strain hensonii, is not closely related to other well-characterized Cyanobacteria that can perform anoxygenic photosynthesis, which further highlights the need to characterize the diversity and biogeography of metabolically versatile Cyanobacteria. The isolate will be an ideal model organism for exploring the adaptation of Cyanobacteria to sulfidic conditions. PMID:29328062

Cyanobacterial photosynthesis under sulfidic conditions: insights from the isolate Leptolyngbya sp. strain hensonii.

Science.gov (United States)

Hamilton, Trinity L; Klatt, Judith M; de Beer, Dirk; Macalady, Jennifer L

2018-02-01

We report the isolation of a pinnacle-forming cyanobacterium isolated from a microbial mat covering the sediment surface at Little Salt Spring-a flooded sinkhole in Florida with a perennially microoxic and sulfidic water column. The draft genome of the isolate encodes all of the enzymatic machinery necessary for both oxygenic and anoxygenic photosynthesis, as well as genes for methylating hopanoids at the C-2 position. The physiological response of the isolate to H 2 S is complex: (i) no induction time is necessary for anoxygenic photosynthesis; (ii) rates of anoxygenic photosynthesis are regulated by both H 2 S and irradiance; (iii) O 2 production is inhibited by H 2 S concentrations as low as 1 μM and the recovery rate of oxygenic photosynthesis is dependent on irradiance; (iv) under the optimal light conditions for oxygenic photosynthesis, rates of anoxygenic photosynthesis are nearly double those of oxygenic photosynthesis. We hypothesize that the specific adaptation mechanisms of the isolate to H 2 S emerged from a close spatial interaction with sulfate-reducing bacteria. The new isolate, Leptolyngbya sp. strain hensonii, is not closely related to other well-characterized Cyanobacteria that can perform anoxygenic photosynthesis, which further highlights the need to characterize the diversity and biogeography of metabolically versatile Cyanobacteria. The isolate will be an ideal model organism for exploring the adaptation of Cyanobacteria to sulfidic conditions.

A model for chlorophyll fluorescence and photosynthesis at leaf scale

NARCIS (Netherlands)

Tol, van der C.; Verhoef, W.; Rosema, A.

2009-01-01

This paper presents a leaf biochemical model for steady-state chlorophyll fluorescence and photosynthesis of C3 and C4 vegetation. The model is a tool to study the relationship between passively measured steady-state chlorophyll fluorescence and actual photosynthesis, and its evolution during the

Modelling basin-wide variations in Amazon forest productivity – Part 1: Model calibration, evaluation and upscaling functions for canopy photosynthesis

Directory of Open Access Journals (Sweden)

L. M. Mercado

2009-07-01

Full Text Available Given the importance of Amazon rainforest in the global carbon and hydrological cycles, there is a need to parameterize and validate ecosystem gas exchange and vegetation models for this region in order to adequately simulate present and future carbon and water balances. In this study, a sun and shade canopy gas exchange model is calibrated and evaluated at five rainforest sites using eddy correlation measurements of carbon and energy fluxes.

Results from the model-data evaluation suggest that with adequate parameterisation, photosynthesis models taking into account the separation of diffuse and direct irradiance and the dynamics of sunlit and shaded leaves can accurately represent photosynthesis in these forests. Also, stomatal conductance formulations that only take into account atmospheric demand fail to correctly simulate moisture and CO₂ fluxes in forests with a pronounced dry season, particularly during afternoon conditions. Nevertheless, it is also the case that large uncertainties are associated not only with the eddy correlation data, but also with the estimates of ecosystem respiration required for model validation. To accurately simulate Gross Primary Productivity (GPP and energy partitioning the most critical parameters and model processes are the quantum yield of photosynthetic uptake, the maximum carboxylation capacity of Rubisco, and simulation of stomatal conductance.

Using this model-data synergy, we developed scaling functions to provide estimates of canopy photosynthetic parameters for a range of diverse forests across the Amazon region, utilising the best fitted parameter for maximum carboxylation capacity of Rubisco, and foliar nutrients (N and P for all sites.

From molecules to materials pathways to artificial photosynthesis

CERN Document Server

Rozhkova, Elena A

2015-01-01

This interdisciplinary book focuses on the various aspects transformation of the energy from sunlight into the chemical bonds of a fuel, known as the artificial photosynthesis, and addresses the emergent challenges connected with growing societal demands for clean and sustainable energy technologies. The editors assemble the research of world-recognized experts in the field of both molecular and materials artificial systems for energy production. Contributors cover the full scope of research on photosynthesis and related energy processes.

Temporal and spatial transcriptomic and microRNA dynamics of CAM photosynthesis in pineapple.

Science.gov (United States)

Wai, Ching M; VanBuren, Robert; Zhang, Jisen; Huang, Lixian; Miao, Wenjing; Edger, Patrick P; Yim, Won C; Priest, Henry D; Meyers, Blake C; Mockler, Todd; Smith, J Andrew C; Cushman, John C; Ming, Ray

2017-10-01

The altered carbon assimilation pathway of crassulacean acid metabolism (CAM) photosynthesis results in an up to 80% higher water-use efficiency than C 3 photosynthesis in plants making it a potentially useful pathway for engineering crop plants with improved drought tolerance. Here we surveyed detailed temporal (diel time course) and spatial (across a leaf gradient) gene and microRNA (miRNA) expression patterns in the obligate CAM plant pineapple [Ananas comosus (L.) Merr.]. The high-resolution transcriptome atlas allowed us to distinguish between CAM-related and non-CAM gene copies. A differential gene co-expression network across green and white leaf diel datasets identified genes with circadian oscillation, CAM-related functions, and source-sink relations. Gene co-expression clusters containing CAM pathway genes are enriched with clock-associated cis-elements, suggesting circadian regulation of CAM. About 20% of pineapple microRNAs have diel expression patterns, with several that target key CAM-related genes. Expression and physiology data provide a model for CAM-specific carbohydrate flux and long-distance hexose transport. Together these resources provide a list of candidate genes for targeted engineering of CAM into C 3 photosynthesis crop species. © 2017 The Authors The Plant Journal © 2017 John Wiley & Sons Ltd.

Novel Genetic Tools to Accelerate Our Understanding of Photosynthesis and Lipid Accumulation

Science.gov (United States)

2014-08-20

understanding of photosynthesis and lipid accumulation Martin C. Jonikas, Ph.D. Carnegie Institution for Science, Department of Plant Biology 260...knowledge of algal lipid metabolism and photosynthesis . Advances in our basic understanding of these processes will facilitate genetic engineering of...algae to improve lipid yields. Currently, one of the greatest roadblocks in the study of algal photosynthesis and lipid metabolism is the slow pace of

A photosynthesis-based two-leaf canopy stomatal ...

Science.gov (United States)

A coupled photosynthesis-stomatal conductance model with single-layer sunlit and shaded leaf canopy scaling is implemented and evaluated in a diagnostic box model with the Pleim-Xiu land surface model (PX LSM) and ozone deposition model components taken directly from the meteorology and air quality modeling system—WRF/CMAQ (Weather Research and Forecast model and Community Multiscale Air Quality model). The photosynthesis-based model for PX LSM (PX PSN) is evaluated at a FLUXNET site for implementation against different parameterizations and the current PX LSM approach with a simple Jarvis function (PX Jarvis). Latent heat flux (LH) from PX PSN is further evaluated at five FLUXNET sites with different vegetation types and landscape characteristics. Simulated ozone deposition and flux from PX PSN are evaluated at one of the sites with ozone flux measurements. Overall, the PX PSN simulates LH as well as the PX Jarvis approach. The PX PSN, however, shows distinct advantages over the PX Jarvis approach for grassland that likely result from its treatment of C3 and C4 plants for CO2 assimilation. Simulations using Moderate Resolution Imaging Spectroradiometer (MODIS) leaf area index (LAI) rather than LAI measured at each site assess how the model would perform with grid averaged data used in WRF/CMAQ. MODIS LAI estimates degrade model performance at all sites but one site having exceptionally old and tall trees. Ozone deposition velocity and ozone flux along with LH

The Path of Carbon in Photosynthesis XVI. Kinetic Relationships of the Intermediates in Steady State Photosynthesis

Science.gov (United States)

Benson, A. A.; Kawaguchi, S.; Hayes, P.; Calvin, M.

1952-06-05

A kinetic study of the accumulation of C{sup 14} in the intermediates of steady state photosynthesis in C{sup 14}O{sub 2} provides information regarding the sequence of reactions involved. The work described applied the radio-chromatographic technique for analysis of the labeled early products. The simultaneous carboxylation reaction resulting in malic acid as well as phosphoglycerate is demonstrated in experiments at high light intensity. A comparison of radioactivities in a number of phosphorylated sugars as a function of time reveals concurrent synthesis of fructose and sedoheptulose phosphates followed by that of ribulose phosphates and later by that of glucose phosphates. The possibility that the cleavage of C{sub 4} compounds to C{sub 2} carbon dioxide acceptors may involve C{sub 7} and C{sub 5} sugars and evidence for this mechanism is presented.

High spin structure functions

International Nuclear Information System (INIS)

Khan, H.

1990-01-01

This thesis explores deep inelastic scattering of a lepton beam from a polarized nuclear target with spin J=1. After reviewing the formation for spin-1/2, the structure functions for a spin-1 target are defined in terms of the helicity amplitudes for forward compton scattering. A version of the convolution model, which incorporates relativistic and binding energy corrections is used to calculate the structure functions of a neutron target. A simple parameterization of these structure functions is given in terms of a few neutron wave function parameters and the free nucleon structure functions. This allows for an easy comparison of structure functions calculated using different neutron models. (author)

Final report, Feedback limitations of photosynthesis

Energy Technology Data Exchange (ETDEWEB)

Sharkey, Thomas D.

1999-07-22

Final report of research on carbon metabolism of photosynthesis. The feedback from carbon metabolism to primary photosynthetic processes is summarized, and a comprehensive list of published scientific papers is provided.

Efficient direct solar-to-hydrogen conversion by in situ interface transformation of a tandem structure

Science.gov (United States)

May, Matthias M.; Lewerenz, Hans-Joachim; Lackner, David; Dimroth, Frank; Hannappel, Thomas

2015-09-01

Photosynthesis is nature's route to convert intermittent solar irradiation into storable energy, while its use for an industrial energy supply is impaired by low efficiency. Artificial photosynthesis provides a promising alternative for efficient robust carbon-neutral renewable energy generation. The approach of direct hydrogen generation by photoelectrochemical water splitting utilizes customized tandem absorber structures to mimic the Z-scheme of natural photosynthesis. Here a combined chemical surface transformation of a tandem structure and catalyst deposition at ambient temperature yields photocurrents approaching the theoretical limit of the absorber and results in a solar-to-hydrogen efficiency of 14%. The potentiostatically assisted photoelectrode efficiency is 17%. Present benchmarks for integrated systems are clearly exceeded. Details of the in situ interface transformation, the electronic improvement and chemical passivation are presented. The surface functionalization procedure is widely applicable and can be precisely controlled, allowing further developments of high-efficiency robust hydrogen generators.

Photosynthesis Activates Plasma Membrane H+-ATPase via Sugar Accumulation.

Science.gov (United States)

Okumura, Masaki; Inoue, Shin-Ichiro; Kuwata, Keiko; Kinoshita, Toshinori

2016-05-01

Plant plasma membrane H(+)-ATPase acts as a primary transporter via proton pumping and regulates diverse physiological responses by controlling secondary solute transport, pH homeostasis, and membrane potential. Phosphorylation of the penultimate threonine and the subsequent binding of 14-3-3 proteins in the carboxyl terminus of the enzyme are required for H(+)-ATPase activation. We showed previously that photosynthesis induces phosphorylation of the penultimate threonine in the nonvascular bryophyte Marchantia polymorpha However, (1) whether this response is conserved in vascular plants and (2) the process by which photosynthesis regulates H(+)-ATPase phosphorylation at the plasma membrane remain unresolved issues. Here, we report that photosynthesis induced the phosphorylation and activation of H(+)-ATPase in Arabidopsis (Arabidopsis thaliana) leaves via sugar accumulation. Light reversibly phosphorylated leaf H(+)-ATPase, and this process was inhibited by pharmacological and genetic suppression of photosynthesis. Immunohistochemical and biochemical analyses indicated that light-induced phosphorylation of H(+)-ATPase occurred autonomously in mesophyll cells. We also show that the phosphorylation status of H(+)-ATPase and photosynthetic sugar accumulation in leaves were positively correlated and that sugar treatment promoted phosphorylation. Furthermore, light-induced phosphorylation of H(+)-ATPase was strongly suppressed in a double mutant defective in ADP-glucose pyrophosphorylase and triose phosphate/phosphate translocator (adg1-1 tpt-2); these mutations strongly inhibited endogenous sugar accumulation. Overall, we show that photosynthesis activated H(+)-ATPase via sugar production in the mesophyll cells of vascular plants. Our work provides new insight into signaling from chloroplasts to the plasma membrane ion transport mechanism. © 2016 American Society of Plant Biologists. All Rights Reserved.

Application of microbial photosynthesis to energy production and CO2 fixation

International Nuclear Information System (INIS)

Asada, Y.; Miyake, J.

1994-01-01

This paper presents different applications of microbial photosynthesis for energy production and carbon dioxide fixation. The authors discuss about energetic aspects of photosynthesis and features of biological way for solar energy conversion. (TEC). 4 figs., 12 refs

Effect of Zinc Deficiency and Excess on the Growth and Photosynthesis of Winter Wheat

Directory of Open Access Journals (Sweden)

N.M. Kaznina

2017-12-01

Full Text Available Zinc is one of the necessary micronutrients for plants, which performs a number of various functions in their cells. Therefore, the deficiency of this element negatively affects on plants and leads to a significant decrease of their productivity. On the other hand, zinc in high concentrations is toxic to plants, and its accumulation in aerial organs, especially in cereals, represent a real danger to human and animal health. In this investigation the effect of the deficiency (Zn 0 μM and the excess of zinc (Zn 1000 μM on the growth and photosynthesis of the winter wheat (cv. Mironovskaya 39 was studied. As a result, similarities and differences in the response of plants to these two types of stress were revealed. In particular, both with a lack and with an excess of metal in the nutrient solution, shoot growth and photosynthesis rate are inhibited which leads to a decrease in the accumulation of dry biomass. Excess of metal, in contrast to its deficiency, leads to inhibition of root growth, and also a negative impact on pigment content, including light-harvesting complexes, and on maximum quantum yield of PS II. It is assumed that these changes in the photosynthetic apparatus are the main causes of a decrease of photosynthesis rate in plants under these conditions, whereas in the case of zinc deficiency, an inhibition of the process intensity is most likely due to a change in the activity of zinc-containing enzymes involved in the dark reactions of photosynthesis.

Photosynthesis

DEFF Research Database (Denmark)

Pribil, Mathias; Leister, Dario Michael

2017-01-01

on the genetic engineering of developmental or bioenergetic processes, such as photosynthesis. These approaches offer the prospect of a renewal of the Green Revolution, which is urgently required tomeet the continuously increasing demand for superior high-yield crop varieties for human sustenance and industrial...... by exponential population growth and increased demand for crop plants as sources of renewable energy or high-value products. The foreseeable intensification of competition between agronomical and industrial use makes it imperative that the available supply of cropland be used more efficiently. During the Green...... Revolution that began in the 1960s, significant increases in yield could be achieved by more effective farming strategies, innovations in fertilization, and the introduction of dwarfing genes into important crop species like rice (Oryza sativa) and wheat (Triticum aestivum). The last resulted in a shift...

Phytotoxicity of chiral herbicide bromacil: Enantioselectivity of photosynthesis in Arabidopsis thaliana

Energy Technology Data Exchange (ETDEWEB)

Chen, Zunwei; Zou, Yuqin; Wang, Jia [MOE Key Laboratory of Environmental Remediation & Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058 (China); Li, Meichao [Research Center of Analysis and Measurement, Zhejiang University of Technology, Hangzhou 310032 (China); Wen, Yuezhong, E-mail: wenyuezhong@zju.edu.cn [MOE Key Laboratory of Environmental Remediation & Ecosystem Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058 (China)

2016-04-01

With the wide application of chiral herbicides and the frequent detection of photosystem II (PSII) herbicides, it is of great importance to assess the direct effects of PSII herbicides on photosynthesis in an enantiomeric level. In the present study, the enantioselective phytotoxicity of bromacil (BRO), typical photosynthesis inhibition herbicide, on Arabidopsis thaliana was investigated. The results showed that S-BRO exhibited a greater inhibition of electron transmission in photosystem I (PSI) of A. thaliana than R-BRO by inhibiting the transcription of fnr 1. S-BRO also changed the chlorophyll fluorescence parameters Y (II), Y (NO), and Y (NPQ) to a greater extent than R-Bro. Transcription of genes psbO2, Lhcb3 and Lhcb6 was down-regulated in an enantioselective rhythm and S-BRO caused more serious influence, indicating that S-BRO did worse damage to the photosystem II (PSII) of A. thaliana than R-BRO. This study suggested that S-BRO disturbed the photosynthesis of plants to a larger extent than R-BRO and provided a new sight to evaluate the phytotoxicity of chiral herbicides. - Highlights: • It is necessary to assess the direct effects of PSII herbicides on photosynthesis. • Phytotoxicity of bromacil is investigated in an enantiomeric level. • Bromacil disturbed enantioselectively the photosystem II of Arabidopsis thaliana. • S-bromacil caused severer damage to photosynthesis of Arabidopsis than R-bromacil. • Photosynthesis should be considered for phytotoxicity assessment of herbicides.

Phytotoxicity of chiral herbicide bromacil: Enantioselectivity of photosynthesis in Arabidopsis thaliana

International Nuclear Information System (INIS)

Chen, Zunwei; Zou, Yuqin; Wang, Jia; Li, Meichao; Wen, Yuezhong

2016-01-01

With the wide application of chiral herbicides and the frequent detection of photosystem II (PSII) herbicides, it is of great importance to assess the direct effects of PSII herbicides on photosynthesis in an enantiomeric level. In the present study, the enantioselective phytotoxicity of bromacil (BRO), typical photosynthesis inhibition herbicide, on Arabidopsis thaliana was investigated. The results showed that S-BRO exhibited a greater inhibition of electron transmission in photosystem I (PSI) of A. thaliana than R-BRO by inhibiting the transcription of fnr 1. S-BRO also changed the chlorophyll fluorescence parameters Y (II), Y (NO), and Y (NPQ) to a greater extent than R-Bro. Transcription of genes psbO2, Lhcb3 and Lhcb6 was down-regulated in an enantioselective rhythm and S-BRO caused more serious influence, indicating that S-BRO did worse damage to the photosystem II (PSII) of A. thaliana than R-BRO. This study suggested that S-BRO disturbed the photosynthesis of plants to a larger extent than R-BRO and provided a new sight to evaluate the phytotoxicity of chiral herbicides. - Highlights: • It is necessary to assess the direct effects of PSII herbicides on photosynthesis. • Phytotoxicity of bromacil is investigated in an enantiomeric level. • Bromacil disturbed enantioselectively the photosystem II of Arabidopsis thaliana. • S-bromacil caused severer damage to photosynthesis of Arabidopsis than R-bromacil. • Photosynthesis should be considered for phytotoxicity assessment of herbicides.

The effects of instruction on college nonmajors' conceptions of respiration and photosynthesis

Science.gov (United States)

Anderson, Charles W.; Sheldon, Theresa H.; Dubay, Joann

Students in a college nonscience majors' biology course took tests designed to reveal their conceptions of respiration and photosynthesis before and after course instruction. Even though most students had taken at least a full year of biology, serious misconceptions persisted. Most students gave definitions of respiration, photosynthesis, and food which were markedly different from those generally accepted by biologists. These incorrect definitions were associated with more fundamental misunderstandings about how plants and animals function. Most students could not explain how animal cells use either food or oxygen. They understood plants as vaguely analogous to animals, taking in food through their roots instead of mouths. Previous biology instruction seemed neither to improve student performance on the pretest nor to prepare them to master these conceptions during the course. Course instruction did improve student's understanding, but misconceptions persisted for many students. These results raise fundamental questions about the effectiveness of curriculum and instruction in current high school and college biology courses.

Daily xanthophyll cycle photoprotection in developing leaves prior to photosynthesis

Science.gov (United States)

M.N. Angelov; Shi-Jean S. Sung; C.C. Black

1995-01-01

There is widespread agreement that the xanthophyll cycle provides a major photoprotection system for photosynthesis in green leaves.Indeed this type of photoprotection seem to be ubiquitous for photosynthetic organisms. Photoprotection is provided via a rapid, near 10-13 sec, ability of zeaxanthin (Z) to dissipate excess light energy from photosynthesis because the...

Hadron structure functions

International Nuclear Information System (INIS)

Martin, F.

1981-03-01

The x dependence of hadron structure functions is investigated. If quarks can exist in very low mass states (10 MeV for d and u quarks) the pion structure function is predicted to behave like (1-x) and not (1-x) 2 in a x-region around 1. Relativistic and non-relativistic quark bound state pictures of hadrons are considered together with their relation with the Q 2 evolution of structure functions. Good agreement with data is in general obtained

Photon structure function

International Nuclear Information System (INIS)

Bardeen, W.A.

1980-11-01

Theoretical understanding of the photon structure function is reviewed. As an illustration of the pointlike component, the parton model is briefly discussed. However, the systematic study of the photon structure function is presented through the framework of the operator product expansion. Perturbative QCD is used as the theoretical basis for the calculation of leading contributions to the operator product expansion. The influence of higher order QCD effects on these results is discussed. Recent results for the polarized structure functions are discussed

NDH-Mediated Cyclic Electron Flow Around Photosystem I is Crucial for C4 Photosynthesis.

Science.gov (United States)

Ishikawa, Noriko; Takabayashi, Atsushi; Noguchi, Ko; Tazoe, Youshi; Yamamoto, Hiroshi; von Caemmerer, Susanne; Sato, Fumihiko; Endo, Tsuyoshi

2016-10-01

C 4 photosynthesis exhibits efficient CO 2 assimilation in ambient air by concentrating CO 2 around ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) through a metabolic pathway called the C 4 cycle. It has been suggested that cyclic electron flow (CEF) around PSI mediated by chloroplast NADH dehydrogenase-like complex (NDH), an alternative pathway of photosynthetic electron transport (PET), plays a crucial role in C 4 photosynthesis, although the contribution of NDH-mediated CEF is small in C 3 photosynthesis. Here, we generated NDH-suppressed transformants of a C 4 plant, Flaveria bidentis, and showed that the NDH-suppressed plants grow poorly, especially under low-light conditions. CO 2 assimilation rates were consistently decreased in the NDH-suppressed plants under low and medium light intensities. Measurements of non-photochemical quenching (NPQ) of Chl fluorescence, the oxidation state of the reaction center of PSI (P700) and the electrochromic shift (ECS) of pigment absorbance indicated that proton translocation across the thylakoid membrane is impaired in the NDH-suppressed plants. Since proton translocation across the thylakoid membrane induces ATP production, these results suggest that NDH-mediated CEF plays a role in the supply of ATP which is required for C 4 photosynthesis. Such a role is more crucial when the light that is available for photosynthesis is limited and the energy production by PET becomes rate-determining for C 4 photosynthesis. Our results demonstrate that the physiological contribution of NDH-mediated CEF is greater in C 4 photosynthesis than in C 3 photosynthesis, suggesting that the mechanism of PET in C 4 photosynthesis has changed from that in C 3 photosynthesis accompanying the changes in the mechanism of CO 2 assimilation. © 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.

Growth and photosynthesis of lettuce

NARCIS (Netherlands)

Holsteijn, van H.M.C.

1981-01-01

Butterhead lettuce is an important glass-house crop in the poor light period in The Netherlands. Fundamental data about the influence of temperature, light and CO ₂ on growth and photosynthesis are important e.g. to facilitate selection criteria for new cultivars. In

Assessing Photosynthesis by Fluorescence Imaging

Science.gov (United States)

Saura, Pedro; Quiles, Maria Jose

2011-01-01

This practical paper describes a novel fluorescence imaging experiment to study the three processes of photochemistry, fluorescence and thermal energy dissipation, which compete during the dissipation of excitation energy in photosynthesis. The technique represents a non-invasive tool for revealing and understanding the spatial heterogeneity in…

Inhibition of apparent photosynthesis by nitrogen oxides

Energy Technology Data Exchange (ETDEWEB)

Hill, A C; Bennett, J H

1970-01-01

The nitrogen oxides (NO/sub 2/ and NO) inhibited apparent photosynthesis of oats and alfalfa at concentrations below those required to cause visible injury. There appeared to be a threshold concentration of about 0.6 ppm for each pollutant. An additive effect in depressing apparent photosynthesis occurred when the plants were exposed to a mixture of NO and NO/sub 2/. Although NO produced a more rapid effect on the plants, lower concentrations of NO/sub 2/ were required to cause a given inhibition after 2 hour of exposure. Inhibition by nitric oxide was more closely related to its partial pressure than was inhibition by NO/sub 2/.

Advantages and disadvantages on photosynthesis measurement ...

African Journals Online (AJOL)

PROMOTING ACCESS TO AFRICAN RESEARCH ... Through photosynthesis, green plants and cyanobacteria are able to transfer sunlight energy to ... Measurements of this process are useful in order to understand how it might be controlled ...

Enhancement of crop photosynthesis by diffuse light: quantifying the contributing factors.

Science.gov (United States)

Li, T; Heuvelink, E; Dueck, T A; Janse, J; Gort, G; Marcelis, L F M

2014-07-01

Plants use diffuse light more efficiently than direct light. However, experimental comparisons between diffuse and direct light have been obscured by co-occurring differences in environmental conditions (e.g. light intensity). This study aims to analyse the factors that contribute to an increase in crop photosynthesis in diffuse light and to quantify their relative contribution under different levels of diffuseness at similar light intensities. The hypothesis is that the enhancement of crop photosynthesis in diffuse light results not only from the direct effects of more uniform vertical and horizontal light distribution in the crop canopy, but also from crop physiological and morphological acclimation. Tomato (Solanum lycopersicum) crops were grown in three greenhouse compartments that were covered by glass with different degrees of light diffuseness (0, 45 and 71 % of the direct light being converted into diffuse light) while maintaining similar light transmission. Measurements of horizontal and vertical photosynthetic photon flux density (PPFD) distribution in the crop, leaf photosynthesis light response curves and leaf area index (LAI) were used to quantify each factor's contribution to an increase in crop photosynthesis in diffuse light. In addition, leaf temperature, photoinhibition, and leaf biochemical and anatomical properties were studied. The highest degree of light diffuseness (71 %) increased the calculated crop photosynthesis by 7·2 %. This effect was mainly attributed to a more uniform horizontal (33 % of the total effect) and vertical PPFD distribution (21 %) in the crop. In addition, plants acclimated to the high level of diffuseness by gaining a higher photosynthetic capacity of leaves in the middle of the crop and a higher LAI, which contributed 23 and 13 %, respectively, to the total increase in crop photosynthesis in diffuse light. Moreover, diffuse light resulted in lower leaf temperatures and less photoinhibition at the top of the canopy when

Pattern of photosynthesis in saline indica var. of rice Kala Rata

International Nuclear Information System (INIS)

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

1975-01-01

The present investigation on Kala Rata deals with the pattern of photosynthesis and the salt stress effect on the photosynthetic efficiency in rice. It is evident from the investigation that chlorophyll synthesis is enhanced with the increasing concentration of NaCl in the bathing medium. However, the efficiency of photosynthesis does not increase with increased chlorophyll production. All ions in leaves can stimulate CO 2 incorporation but inhibit at higher concentration. Analysis of short term products of photosynthesis revealed that aspartate is the major product to be heavily labelled which is evident from autoradiogram. PGA has also appreciable label, where as, malate has the least. It appears therefore, that in rice, both, Calvin as well as C 4 type of pathways are operating. 'Aspartate former' type of rice does not seem to be efficient in photosynthesis as it has C 3 pathway also in operation. (author)

The influence of temperature on photosynthesis of different tomato genotypes

NARCIS (Netherlands)

Gosiewski, W.; Nilwik, H.J.M.; Bierhuizen, J.F.

1982-01-01

Net photosynthesis and dark respiration from whole plants of various tomato genotypes were measured in a closed system. At low irradiance (27 W m−2) and low external CO2 concentration (550 mg m−3), net photosynthesis of 10 genotypes was found to vary between 0.122 and 0.209 mg CO2 m−2 s−1.

Increased SBPase activity improves photosynthesis and grain yield in wheat grown in greenhouse conditions.

Science.gov (United States)

Driever, Steven M; Simkin, Andrew J; Alotaibi, Saqer; Fisk, Stuart J; Madgwick, Pippa J; Sparks, Caroline A; Jones, Huw D; Lawson, Tracy; Parry, Martin A J; Raines, Christine A

2017-09-26

To meet the growing demand for food, substantial improvements in yields are needed. This is particularly the case for wheat, where global yield has stagnated in recent years. Increasing photosynthesis has been identified as a primary target to achieve yield improvements. To increase leaf photosynthesis in wheat, the level of the Calvin-Benson cycle enzyme sedoheptulose-1,7-biphosphatase (SBPase) has been increased through transformation and expression of a Brachypodium distachyon SBPase gene construct. Transgenic lines with increased SBPase protein levels and activity were grown under greenhouse conditions and showed enhanced leaf photosynthesis and increased total biomass and dry seed yield. This showed the potential of improving yield potential by increasing leaf photosynthesis in a crop species such as wheat. The results are discussed with regard to future strategies for further improvement of photosynthesis in wheat.This article is part of the themed issue 'Enhancing photosynthesis in crop plants: targets for improvement'. © 2017 The Authors.

Direct and Indirect Drivers of Moss Community Structure, Function, and Associated Microfauna Across a Successional Gradient

Science.gov (United States)

Micael Jonsson; Paul Kardol; Michael J. Gundale; Sheel Bansal; Marie-Charlotte Nilsson; Daniel B. Metcalfe; David A. Wardle

2015-01-01

Relative to vascular plants, little is known about what factors control bryophyte communities or how they respond to successional and environmental changes. Bryophytes are abundant in boreal forests, thus changes in moss community composition and functional traits (for example, moisture and nutrient content; rates of photosynthesis and respiration) may have important...

Structural, functional and evolutionary characterization of major drought transcription factors families in maize

Science.gov (United States)

Mittal, Shikha; Banduni, Pooja; Mallikarjuna, Mallana G.; Rao, Atmakuri R.; Jain, Prashant A.; Dash, Prasanta K.; Thirunavukkarasu, Nepolean

2018-05-01

Drought is one of the major threats to maize production. In order to improve the production and to breed tolerant hybrids, understanding the genes and regulatory mechanisms during drought stress is important. Transcription factors (TFs) play a major role in gene regulation and many TFs have been identified in response to drought stress. In our experiment, a set of 15 major TF families comprising 1436 genes was structurally and functionally characterized using in-silico tools and a gene expression assay. All 1436 genes were mapped on 10 chromosome of maize. The functional annotation indicated the involvement of these genes in ABA signaling, ROS scavenging, photosynthesis, stomatal regulation, and sucrose metabolism. Duplication was identified as the primary force in divergence and expansion of TF families. Phylogenetic relationship was developed individually for each TF family as well as combined TF families. Phylogenetic analysis grouped the TF family of genes into TF-specific and mixed groups. Phylogenetic analysis of genes belonging to various TF families suggested that the origin of TFs occurred in the lineage of maize evolution. Gene structure analysis revealed that more number of genes were intron-rich as compared to intronless genes. Drought-responsive CRE’s such as ABREA, ABREB, DRE1 and DRECRTCOREAT have been identified. Expression and interaction analyses identified leaf-specific bZIP TF, GRMZM2G140355, as a potential contributor toward drought tolerance in maize. We also analyzed protein-protein interaction network of 269 drought-responsive genes belonging to different drought-related TFs. The information generated on structural and functional characteristics, expression and interaction of the drought-related TF families will be useful to decipher the drought tolerance mechanisms and to derive drought-tolerant genotypes in maize.

The effect of elevated CO{sub 2} concentration on photosynthesis of Sphagnum fuscum

Energy Technology Data Exchange (ETDEWEB)

Jauhiainen, J; Silvola, J [Joensuu Univ. (Finland). Dept. of Biology

1997-12-31

The objectives of the research were to measure photosynthesis of Sphagnum fuscum in long term exposure to four CO{sub 2} levels at semi-natural conditions, to find out if there is an acclimation of net photosynthesis into prevailing CO{sub 2} concentrations and to measure the moisture dependent net photosynthesis at various CO{sub 2} concentrations of samples grown at different CO{sub 2} concentrations

The effect of elevated CO{sub 2} concentration on photosynthesis of Sphagnum fuscum

Energy Technology Data Exchange (ETDEWEB)

Jauhiainen, J.; Silvola, J. [Joensuu Univ. (Finland). Dept. of Biology

1996-12-31

The objectives of the research were to measure photosynthesis of Sphagnum fuscum in long term exposure to four CO{sub 2} levels at semi-natural conditions, to find out if there is an acclimation of net photosynthesis into prevailing CO{sub 2} concentrations and to measure the moisture dependent net photosynthesis at various CO{sub 2} concentrations of samples grown at different CO{sub 2} concentrations

Some Anilides of 2-Alkylthio- and 2-Chloro-6-Alkylthio-4-Pyridinecarboxylic Acids: Synthesis and Photosynthesis-Inhibiting Activity

Directory of Open Access Journals (Sweden)

Miloš Macháček

2001-06-01

Full Text Available Many compounds containing a -CONH- group display photosynthesis inhibiting activity. Based on this structural feature, a group of anilides of 2-alkylthio-(1b-4f or 2-chloro-6-alkylthio-4-pyridinecarboxylic acids (5a-6c was synthesised. The prepared compounds were tested for their inhibition of the oxygen evolution rate (OER in spinach chloroplasts. A quasi-parabolic dependence between photosynthesis-inhibiting activity and the lipophilicity of the compounds was determined for 1b-4f as well as for 5a-6c. The inhibitory activity of compounds 1b-4f was higher than that of 5a-6c for comparable lipophilicity values.

A quantum protective mechanism in photosynthesis

NARCIS (Netherlands)

Marais, A.; Sinayskiy, I.; Petruccione, F.; van Grondelle, R.

2015-01-01

Since the emergence of oxygenic photosynthesis, living systems have developed protective mechanisms against reactive oxygen species. During charge separation in photosynthetic reaction centres, triplet states can react with molecular oxygen generating destructive singlet oxygen. The triplet product

Multi-functional composite structures

Science.gov (United States)

Mulligan, Anthony C.; Halloran, John; Popovich, Dragan; Rigali, Mark J.; Sutaria, Manish P.; Vaidyanathan, K. Ranji; Fulcher, Michael L.; Knittel, Kenneth L.

2004-10-19

Fibrous monolith processing techniques to fabricate multifunctional structures capable of performing more than one discrete function such as structures capable of bearing structural loads and mechanical stresses in service and also capable of performing at least one additional non-structural function.

Modelling basin-wide variations in Amazon forest photosynthesis

Science.gov (United States)

Mercado, Lina; Lloyd, Jon; Domingues, Tomas; Fyllas, Nikolaos; Patino, Sandra; Dolman, Han; Sitch, Stephen

2010-05-01

Given the importance of Amazon rainforest in the global carbon and hydrological cycles, there is a need to use parameterized and validated ecosystem gas exchange and vegetation models for this region in order to adequately simulate present and future carbon and water balances. Recent research has found major differences in above-ground net primary productivity (ANPP), above ground biomass and tree dynamics across Amazonia. West Amazonia is more dynamic, with younger trees, higher stem growth rates and lower biomass than central and eastern Amazon (Baker et al. 2004; Malhi et al. 2004; Phillips et al. 2004). A factor of three variation in above-ground net primary productivity has been estimated across Amazonia by Malhi et al. (2004). Different hypotheses have been proposed to explain the observed spatial variability in ANPP (Malhi et al. 2004). First, due to the proximity to the Andes, sites from western Amazonia tend to have richer soils than central and eastern Amazon and therefore soil fertility could possibly be highly related to the high wood productivity found in western sites. Second, if GPP does not vary across the Amazon basin then different patterns of carbon allocation to respiration could also explain the observed ANPP gradient. However since plant growth depends on the interaction between photosynthesis, transport of assimilates, plant respiration, water relations and mineral nutrition, variations in plant gross photosynthesis (GPP) could also explain the observed variations in ANPP. In this study we investigate whether Amazon GPP can explain variations of observed ANPP. We use a sun and shade canopy gas exchange model that has been calibrated and evaluated at five rainforest sites (Mercado et al. 2009) to simulate gross primary productivity of 50 sites across the Amazon basin during the period 1980-2001. Such simulation differs from the ones performed with global vegetation models (Cox et al. 1998; Sitch et al. 2003) where i) single plant functional

The Photo-3 model: A Python-based model for C3, C4, and CAM photosynthesis coupled with environmental conditions

Science.gov (United States)

Hartzell, S. R.; Bartlett, M. S., Jr.; Porporato, A. M.

2017-12-01

The ability to depict all three photosynthetic types (C3, C4, and CAM) has important implications for the study of both natural and agroecosystems. Currently no model exists which covers all types of photosynthesis in a consistent way and which can be fully integrated with environmental conditions. This is partially because, despite the fact that Crassulacean acid metabolism (CAM) photosynthesis is prevalent in many plants in arid and semi-arid ecosystems, where it may comprise nearly 50% of all plant biomass, CAM modelling remains understudied. The Photo-3 model takes advantage of recent advances in mechanistic modeling of CAM photosynthesis to provide a direct comparison of CAM functioning with C3 and C4 functioning under a wide range of soil and atmospheric conditions. The model is based on a core Farquhar photosynthetic model with additional functions to represent the spatial and temporal separations of carbon uptake and assimilation in the case of C4 and CAM photosynthesis. We have parameterized the model for one representative species of each photosynthetic type: Opuntia ficus-indica (CAM), Sorghum bicolor (C4), and Triticum aestivum (C3). Results agree well with experimental data on carbon assimilation and water use for the three species. Model runs using climate data from Temple, TX; Sicily, Italy; Zacatecas, Mexico; Pernambuco, Brazil and Adias Ababa, Ethiopia illustrate the high water use efficiency of CAM plants and its cumulative effects on long-term productivity in water-limited environments. The Photo-3 model, which is written in Python, will be made publicly available on GitHub and its outputs may be coupled to existing models of plant growth and phenology. The model may be used to evaluate potential productivity and water use for C3, C4, and CAM plants, and to devise optimal strategies for cropping systems and irrigation in water-limited environments.

Conference Support, 23rd Western Photosynthesis Conference 2014, Final Technical Report

Energy Technology Data Exchange (ETDEWEB)

Wachter, Rebekka [Arizona State Univ., Tempe, AZ (United States)

2015-01-12

The Western Photosynthesis Conference is a regional conference that is held on an annual basis to bring together researchers primarily from the Western United States to share their newest research advances on photosynthetic processes. The 23rd conference was focused on both fundamental and more applied research on the biological conversion of solar energy to various energy storage forms. Several particular areas of solar energy conversion were emphasized in this conference (see below). Some of these topics, such as carbon limitations on photosynthesis, biomimicry and phenotyping, have traditionally not been incorporated extensively in the Western Photosynthesis Conference. We found that these topics have substantially broadened of the scope of this meeting.

Unpolarized Structure Functions

International Nuclear Information System (INIS)

Christy, M.E.; Melnitchouk, W.

2011-01-01

Over the past decade measurements of unpolarized structure functions with unprecedented precision have significantly advanced our knowledge of nucleon structure. These have for the first time allowed quantitative tests of the phenomenon of quark-hadron duality, and provided a deeper understanding of the transition from hadron to quark degrees of freedom in inclusive scattering. Dedicated Rosenbluth-separation experiments have yielded high-precision transverse and longitudinal structure functions in regions previously unexplored, and new techniques have enabled the first glimpses of the structure of the free neutron, without contamination from nuclear effects.

Facultative crassulacean acid metabolism (CAM) plants: powerful tools for unravelling the functional elements of CAM photosynthesis.

Science.gov (United States)

Winter, Klaus; Holtum, Joseph A M

2014-07-01

Facultative crassulacean acid metabolism (CAM) describes the optional use of CAM photosynthesis, typically under conditions of drought stress, in plants that otherwise employ C3 or C4 photosynthesis. In its cleanest form, the upregulation of CAM is fully reversible upon removal of stress. Reversibility distinguishes facultative CAM from ontogenetically programmed unidirectional C3-to-CAM shifts inherent in constitutive CAM plants. Using mainly measurements of 24h CO2 exchange, defining features of facultative CAM are highlighted in five terrestrial species, Clusia pratensis, Calandrinia polyandra, Mesembryanthemum crystallinum, Portulaca oleracea and Talinum triangulare. For these, we provide detailed chronologies of the shifts between photosynthetic modes and comment on their usefulness as experimental systems. Photosynthetic flexibility is also reviewed in an aquatic CAM plant, Isoetes howellii. Through comparisons of C3 and CAM states in facultative CAM species, many fundamental biochemical principles of the CAM pathway have been uncovered. Facultative CAM species will be of even greater relevance now that new sequencing technologies facilitate the mapping of genomes and tracking of the expression patterns of multiple genes. These technologies and facultative CAM systems, when joined, are expected to contribute in a major way towards our goal of understanding the essence of CAM. © The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Estimating Photosynthetic Radiation Use Efficiency Using Incident Light and Photosynthesis of Individual Leaves

OpenAIRE

ROSATI, A.; DEJONG, T. M.

2003-01-01

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 photosynthes...

A 3-D functional-structural grapevine model that couples the dynamics of water transport with leaf gas exchange.

Science.gov (United States)

Zhu, Junqi; Dai, Zhanwu; Vivin, Philippe; Gambetta, Gregory A; Henke, Michael; Peccoux, Anthony; Ollat, Nathalie; Delrot, Serge

2017-12-23

Predicting both plant water status and leaf gas exchange under various environmental conditions is essential for anticipating the effects of climate change on plant growth and productivity. This study developed a functional-structural grapevine model which combines a mechanistic understanding of stomatal function and photosynthesis at the leaf level (i.e. extended Farqhuhar-von Caemmerer-Berry model) and the dynamics of water transport from soil to individual leaves (i.e. Tardieu-Davies model). The model included novel features that account for the effects of xylem embolism (fPLC) on leaf hydraulic conductance and residual stomatal conductance (g0), variable root and leaf hydraulic conductance, and the microclimate of individual organs. The model was calibrated with detailed datasets of leaf photosynthesis, leaf water potential, xylem sap abscisic acid (ABA) concentration and hourly whole-plant transpiration observed within a soil drying period, and validated with independent datasets of whole-plant transpiration under both well-watered and water-stressed conditions. The model well captured the effects of radiation, temperature, CO2 and vapour pressure deficit on leaf photosynthesis, transpiration, stomatal conductance and leaf water potential, and correctly reproduced the diurnal pattern and decline of water flux within the soil drying period. In silico analyses revealed that decreases in g0 with increasing fPLC were essential to avoid unrealistic drops in leaf water potential under severe water stress. Additionally, by varying the hydraulic conductance along the pathway (e.g. root and leaves) and changing the sensitivity of stomatal conductance to ABA and leaf water potential, the model can produce different water use behaviours (i.e. iso- and anisohydric). The robust performance of this model allows for modelling climate effects from individual plants to fields, and for modelling plants with complex, non-homogenous canopies. In addition, the model provides a

Leaf area and net photosynthesis during development of Prunus serotina seedlings

Science.gov (United States)

Stephen B. Horsley; Kurt W. Gottschalk

1993-01-01

We used the plastochron index to study the relationship between plant age, leaf age and development, and net photosynthesis of black cherry (Prtmus serotina Ehrh.) seedlings. Leaf area and net photosynthesis were measured on all leaves >=75 mm of plants ranging in age from 7 to 20 plastochrons. Effects of plant developmental stage...

;Evolution of Photosynthesis' (1970), re-examined thirty years later.

Science.gov (United States)

Olson, J M

2001-01-01

I have re-examined my 1970 article 'Evolution of Photosynthesis' (Olson JM, Science 168: 438-446) to see whether any of my original proposals still survive. My original conviction that the evolution of photosynthesis was intimately connected with the origin of life has been replaced with the realization that photosynthesis may have been invented by the Bacteria after their divergence from the Archea. The common ancestor of all extant photosynthetic bacteria and cyanobacteria probably contained bacteriochlorophyll a, rather than chlorophyll a as originally proposed, and may have carried out CO(2) fixation instead of photoassimilation. The first electron donors were probably reduced sulfur compounds and later ferrous iron. The common ancestor of all extant reaction centers was probably similar to the homodimeric RC1 of present-day green sulfur bacteria (Chlorobiaceae) and heliobacteria. In the common ancestor of proteobacteria and cyanobacteria, the gene for the primordial RC1 was apparently duplicated and one copy split into two genes, one for RC2 and the other for a chlorophyll protein similar to CP43 and CP47 in extant cyanobacteria and chloroplasts. Homodimeric RC1 and homodimeric RC2 functioned in series as in the Z-scheme to deliver electrons from Fe(OH)(+) to NADP(+), while RC1 and/or RC2 separately drove cyclic electron flow for the production of ATP. In the line of evolution leading to proteobacteria, RC1 and the chlorophyll protein were lost, but RC2 was retained and became heterodimeric. In the line leading to cyanobacteria, both RC1 and RC2 replaced bacteriochlorophyll a with chlorophyll a and became heterodimeric. Heterodimeric RC2 further coevolved with a Mn-containing complex to utilize water as the electron donor for CO(2) fixation. The chlorophyll-protein was also retained and evolved into CP43 and CP47. Heliobacteria are the nearest photosynthetic relatives of cyanobacteria. The branching order of photosynthetic genes appears to be (1

Impacts of rising tropospheric ozone on photosynthesis and metabolite levels on field grown soybean.

Science.gov (United States)

Sun, Jindong; Feng, Zhaozhong; Ort, Donald R

2014-09-01

The response of leaf photosynthesis and metabolite profiles to ozone (O3) exposure ranging from 37 to 116 ppb was investigated in two soybean cultivars Dwight and IA3010 in the field under fully open-air conditions. Leaf photosynthesis, total non-structural carbohydrates (TNC) and total free amino acids (TAA) decreased linearly with increasing O3 levels in both cultivars with average decrease of 7% for an increase in O3 levels by 10 ppb. Ozone interacted with developmental stages and leaf ages, and caused higher damage at later reproductive stages and in older leaves. Ozone affected yield mainly via reduction of maximum rate of Rubisco carboxylation (Vcmax) and maximum rates of electron transport (Jmax) as well as a shorter growing season due to earlier onset of canopy senescence. For all parameters investigated the critical O3 levels (∼50 ppb) for detectable damage fell within O3 levels that occur routinely in soybean fields across the US and elsewhere in the world. Strong correlations were observed in O3-induced changes among yield, photosynthesis, TNC, TAA and many metabolites. The broad range of metabolites that showed O3 dose dependent effect is consistent with multiple interaction loci and thus multiple targets for improving the tolerance of soybean to O3. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Proline-rich peptide from the coral pathogen Vibrio shiloi that inhibits photosynthesis of Zooxanthellae.

Science.gov (United States)

Banin, E; Khare, S K; Naider, F; Rosenberg, E

2001-04-01

The coral-bleaching bacterium Vibrio shiloi biosynthesizes and secretes an extracellular peptide, referred to as toxin P, which inhibits photosynthesis of coral symbiotic algae (zooxanthellae). Toxin P was produced during the stationary phase when the bacterium was grown on peptone or Casamino Acids media at 29 degrees C. Glycerol inhibited the production of toxin P. Toxin P was purified to homogeneity, yielding the following 12-residue peptide: PYPVYAPPPVVP (molecular weight, 1,295.54). The structure of toxin P was confirmed by chemical synthesis. In the presence of 12.5 mM NH(4)Cl, pure natural or synthetic toxin P (10 microM) caused a 64% decrease in the photosynthetic quantum yield of zooxanthellae within 5 min. The inhibition was proportional to the toxin P concentration. Toxin P bound avidly to zooxanthellae, such that subsequent addition of NH(4)Cl resulted in rapid inhibition of photosynthesis. When zooxanthellae were incubated in the presence of NH(4)Cl and toxin P, there was a rapid decrease in the pH (pH 7.8 to 7.2) of the bulk liquid, suggesting that toxin P facilitates transport of NH(3) into the cell. It is known that uptake of NH(3) into cells can destroy the pH gradient and block photosynthesis. This mode of action of toxin P can help explain the mechanism of coral bleaching by V. shiloi.

Effects of high CO2 levels on dynamic photosynthesis: carbon gain, mechanisms, and environmental interactions.

Science.gov (United States)

Tomimatsu, Hajime; Tang, Yanhong

2016-05-01

Understanding the photosynthetic responses of terrestrial plants to environments with high levels of CO2 is essential to address the ecological effects of elevated atmospheric CO2. Most photosynthetic models used for global carbon issues are based on steady-state photosynthesis, whereby photosynthesis is measured under constant environmental conditions; however, terrestrial plant photosynthesis under natural conditions is highly dynamic, and photosynthetic rates change in response to rapid changes in environmental factors. To predict future contributions of photosynthesis to the global carbon cycle, it is necessary to understand the dynamic nature of photosynthesis in relation to high CO2 levels. In this review, we summarize the current body of knowledge on the photosynthetic response to changes in light intensity under experimentally elevated CO2 conditions. We found that short-term exposure to high CO2 enhances photosynthetic rate, reduces photosynthetic induction time, and reduces post-illumination CO2 burst, resulting in increased leaf carbon gain during dynamic photosynthesis. However, long-term exposure to high CO2 during plant growth has varying effects on dynamic photosynthesis. High levels of CO2 increase the carbon gain in photosynthetic induction in some species, but have no significant effects in other species. Some studies have shown that high CO2 levels reduce the biochemical limitation on RuBP regeneration and Rubisco activation during photosynthetic induction, whereas the effects of high levels of CO2 on stomatal conductance differ among species. Few studies have examined the influence of environmental factors on effects of high levels of CO2 on dynamic photosynthesis. We identified several knowledge gaps that should be addressed to aid future predictions of photosynthesis in high-CO2 environments.

Broad-Scale Comparison of Photosynthesis in Terrestrial and Aquatic Plant Communities

DEFF Research Database (Denmark)

Sand-Jensen, Kaj; Krause-Jensen, D.

1997-01-01

Comparisons of photosynthesis in terrestrial and aquatic habitats have been impaired by differences in methods and time-scales of measurements. We compiled information on gross photosynthesis at high irradiance and photosynthetic efficiency at low irradiance from 109 published terrestrial studies...... communities probably due to more efficient light utilization and gas exchange in the terrestrial habitats. By contrast only small differences were found within different aquatic plant communities or within different terrestrial plant communities....... of forests, grasslands and crops and 319 aquatic studies of phytoplankton, macrophyte and attached microalgal communities to test if specific differences existed between the communities. Maximum gross photosynthesis and photosynthetic efficiency were systematically higher in terrestrial than in aquatic...

Seasonality of temperate forest photosynthesis and daytime respiration.

Science.gov (United States)

Wehr, R; Munger, J W; McManus, J B; Nelson, D D; Zahniser, M S; Davidson, E A; Wofsy, S C; Saleska, S R

2016-06-30

Terrestrial ecosystems currently offset one-quarter of anthropogenic carbon dioxide (CO2) emissions because of a slight imbalance between global terrestrial photosynthesis and respiration. Understanding what controls these two biological fluxes is therefore crucial to predicting climate change. Yet there is no way of directly measuring the photosynthesis or daytime respiration of a whole ecosystem of interacting organisms; instead, these fluxes are generally inferred from measurements of net ecosystem-atmosphere CO2 exchange (NEE), in a way that is based on assumed ecosystem-scale responses to the environment. The consequent view of temperate deciduous forests (an important CO2 sink) is that, first, ecosystem respiration is greater during the day than at night; and second, ecosystem photosynthetic light-use efficiency peaks after leaf expansion in spring and then declines, presumably because of leaf ageing or water stress. This view has underlain the development of terrestrial biosphere models used in climate prediction and of remote sensing indices of global biosphere productivity. Here, we use new isotopic instrumentation to determine ecosystem photosynthesis and daytime respiration in a temperate deciduous forest over a three-year period. We find that ecosystem respiration is lower during the day than at night-the first robust evidence of the inhibition of leaf respiration by light at the ecosystem scale. Because they do not capture this effect, standard approaches overestimate ecosystem photosynthesis and daytime respiration in the first half of the growing season at our site, and inaccurately portray ecosystem photosynthetic light-use efficiency. These findings revise our understanding of forest-atmosphere carbon exchange, and provide a basis for investigating how leaf-level physiological dynamics manifest at the canopy scale in other ecosystems.

Pronounced gradients of light, photosynthesis and O2 consumption in the tissue of the brown alga Fucus serratus.

Science.gov (United States)

Lichtenberg, Mads; Kühl, Michael

2015-08-01

Macroalgae live in an ever-changing light environment affected by wave motion, self-shading and light-scattering effects, and on the thallus scale, gradients of light and chemical parameters influence algal photosynthesis. However, the thallus microenvironment and internal gradients remain underexplored. In this study, microsensors were used to quantify gradients of light, O2 concentration, variable chlorophyll fluorescence, photosynthesis and O2 consumption as a function of irradiance in the cortex and medulla layers of Fucus serratus. The two cortex layers showed more efficient light utilization compared to the medulla, calculated both from electron transport rates through photosystem II and from photosynthesis-irradiance curves. At moderate irradiance, the upper cortex exhibited onset of photosynthetic saturation, whereas lower thallus layers exhibited net O2 consumption. O2 consumption rates in light varied with depth and irradiance and were more than two-fold higher than dark respiration. We show that the thallus microenvironment of F. serratus exhibits a highly stratified balance of production and consumption of O2 , and when the frond was held in a fixed position, high incident irradiance levels on the upper cortex did not saturate photosynthesis in the lower thallus layers. We discuss possible photoadaptive responses and consequences for optimizing photosynthetic activity on the basis of vertical differences in light attenuation coefficients. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

Invitation to the 17th international congress on photosynthesis research in 2016 : photosynthesis in a changing world

NARCIS (Netherlands)

van Amerongen, Herbert; Croce, Roberta

2016-01-01

The 17th International Congress on Photosynthesis will be held from August 7 to 12, 2016 in Maastricht, The Netherlands. The congress will include an opening reception, 15 plenary lectures, 28 scientific symposia, many poster sessions, displays by scientific companies, excursions, congress dinner,

PHOTOSYNTHESIS AT THE FOREFRONT OF A SUSTAINABLE LIFE

Directory of Open Access Journals (Sweden)

Paul J.D. Janssen

2014-06-01

Full Text Available The development of a sustainable bio-based economy has drawn much attention in recent years, and research to find smart solutions to the many inherent challenges has intensified. In nature, perhaps the best example of an authentic sustainable system is oxygenic photosynthesis. The biochemistry of this intricate process is empowered by solar radiation influx and performed by hierarchically organized complexes composed by photoreceptors, inorganic catalysts, and enzymes which define specific niches for optimizing light-to-energy conversion. The success of this process relies on its capability to exploit the almost inexhaustible reservoirs of sunlight, water, and carbon dioxide to transform photonic energy into chemical energy such as stored in adenosine triphosphate. Oxygenic photosynthesis is responsible for most of the oxygen, fossil fuels, and biomass on our planet. So, even after a few billion years of evolution, this process unceasingly supports life on earth, and probably soon also in outer-space, and inspires the development of enabling technologies for a sustainable global economy and ecosystem. The following review covers some of the major milestones reached in photosynthesis research, each reflecting lasting routes of innovation in agriculture, environmental protection, and clean energy production.

Inhibition of photosynthesis and bleaching of zooxanthellae by the coral pathogen Vibrio shiloi.

Science.gov (United States)

Ben-Haim, Y; Banim, E; Kushmaro, A; Loya, Y; Rosenberg, E

1999-06-01

Vibrio shiloi is the causative agent of bleaching (loss of endosymbiotic zooxanthellae) of the coral Oculina patagonica in the Mediterranean Sea. To obtain information on the mechanism of bleaching, we examined the effect of secreted material (AK1-S) produced by V. shiloi on zooxanthellae isolated from corals. AK1-S caused a rapid inhibition of photosynthesis of the algae, as measured with a Mini-PAM fluorometer. The inhibition of photosynthesis was caused by (i) ammonia produced during the growth of V. shiloi on protein-containing media and (ii) a non-dialysable heat-resistant factor. This latter material did not inhibit photosynthesis of the algae by itself but, when added to different concentrations of NH4Cl, enhanced the inhibition approximately two- to threefold. Ammonia and the enhancer were effective to different degrees on zooxanthellae isolated from four species of coral examined. In addition to the rapid inhibition of photosynthesis, AK1-S caused bleaching (loss of pigmentation) and lysis of zooxanthellae. Bleaching was more rapid than lysis, reaching a peak (25% bleached algae) after 6 h. The factors in AK1-S responsible for bleaching and lysis were different from those responsible for the inhibition of photosynthesis, because they were heat sensitive, non-dialysable and active in the dark. Thus, the coral pathogen V. shiloi produces an array of extracellular materials that can inhibit photosynthesis, bleach and lyse zooxanthellae.

Canopy Photosynthesis: From Basics to Applications

NARCIS (Netherlands)

Hikosaka, Kouki; Niinemets, Ülo; Anten, N.P.R.

2016-01-01

A plant canopy, a collection of leaves, is an ecosystem-level unit of photosynthesis that assimilates carbon dioxide and exchanges other gases and energy with the atmosphere in a manner highly sensitive to ambient conditions including atmospheric carbon dioxide and water vapor concentrations, light

A Forgotten Application of the Starch Test: C[subscript 4] Photosynthesis

Science.gov (United States)

Harley, Suzanne M.

2013-01-01

In many labs on photosynthesis, the presence of starch in leaves is used as an indirect indicator of photosynthetic activity. Students do starch tests on leaves from plants that have been kept under a variety of conditions in order to check parameters for photosynthesis. The starch test can also be used to enable students to discover differences…

Phenotypic engineering of photosynthesis related traits in Arabidopsis thaliana using genome interrogation

NARCIS (Netherlands)

Tol, Niels van

2016-01-01

Photosynthesis is the process that harvests energy from light, and fixes it as chemical energy. It is performed by cyanobacteria, algae, and plants. The overall solar energy to biomass conversion efficiency of plant photosynthesis is widely considered to be very low. Recent models have indicated

Connecting Biochemical Photosynthesis Models with Crop Models to Support Crop Improvement.

Science.gov (United States)

Wu, Alex; Song, Youhong; van Oosterom, Erik J; Hammer, Graeme L

2016-01-01

The next advance in field crop productivity will likely need to come from improving crop use efficiency of resources (e.g., light, water, and nitrogen), aspects of which are closely linked with overall crop photosynthetic efficiency. Progress in genetic manipulation of photosynthesis is confounded by uncertainties of consequences at crop level because of difficulties connecting across scales. Crop growth and development simulation models that integrate across biological levels of organization and use a gene-to-phenotype modeling approach may present a way forward. There has been a long history of development of crop models capable of simulating dynamics of crop physiological attributes. Many crop models incorporate canopy photosynthesis (source) as a key driver for crop growth, while others derive crop growth from the balance between source- and sink-limitations. Modeling leaf photosynthesis has progressed from empirical modeling via light response curves to a more mechanistic basis, having clearer links to the underlying biochemical processes of photosynthesis. Cross-scale modeling that connects models at the biochemical and crop levels and utilizes developments in upscaling leaf-level models to canopy models has the potential to bridge the gap between photosynthetic manipulation at the biochemical level and its consequences on crop productivity. Here we review approaches to this emerging cross-scale modeling framework and reinforce the need for connections across levels of modeling. Further, we propose strategies for connecting biochemical models of photosynthesis into the cross-scale modeling framework to support crop improvement through photosynthetic manipulation.

Connecting Biochemical Photosynthesis Models with Crop Models to Support Crop Improvement

Science.gov (United States)

Wu, Alex; Song, Youhong; van Oosterom, Erik J.; Hammer, Graeme L.

2016-01-01

The next advance in field crop productivity will likely need to come from improving crop use efficiency of resources (e.g., light, water, and nitrogen), aspects of which are closely linked with overall crop photosynthetic efficiency. Progress in genetic manipulation of photosynthesis is confounded by uncertainties of consequences at crop level because of difficulties connecting across scales. Crop growth and development simulation models that integrate across biological levels of organization and use a gene-to-phenotype modeling approach may present a way forward. There has been a long history of development of crop models capable of simulating dynamics of crop physiological attributes. Many crop models incorporate canopy photosynthesis (source) as a key driver for crop growth, while others derive crop growth from the balance between source- and sink-limitations. Modeling leaf photosynthesis has progressed from empirical modeling via light response curves to a more mechanistic basis, having clearer links to the underlying biochemical processes of photosynthesis. Cross-scale modeling that connects models at the biochemical and crop levels and utilizes developments in upscaling leaf-level models to canopy models has the potential to bridge the gap between photosynthetic manipulation at the biochemical level and its consequences on crop productivity. Here we review approaches to this emerging cross-scale modeling framework and reinforce the need for connections across levels of modeling. Further, we propose strategies for connecting biochemical models of photosynthesis into the cross-scale modeling framework to support crop improvement through photosynthetic manipulation. PMID:27790232

Cyanobacteria as an Experimental Platform for Modifying Bacterial and Plant Photosynthesis

Energy Technology Data Exchange (ETDEWEB)

Jensen, Poul Erik [Copenhagen Plant Science Center (CPSC), Department of Plant and Environmental Sciences, University of Copenhagen, Copenhagen (Denmark); Leister, Dario, E-mail: leister@lmu.de [Copenhagen Plant Science Center (CPSC), Department of Plant and Environmental Sciences, University of Copenhagen, Copenhagen (Denmark); Plant Molecular Biology (Botany), Department of Biology I, Ludwig-Maximilians-University Munich, Munich (Germany)

2014-04-21

One of the fascinating characteristics of photosynthesis is its capacity for repair, self-renewal, and energy storage within chemical bonds. Given the evolutionary history of plant photosynthesis and the patchwork nature of many of its components, it is safe to assume that the light reactions of plant photosynthesis can be improved by genetic engineering (Leister, 2012). The evolutionary precursor of chloroplasts was a microorganism whose biochemistry was very similar to that of present-day cyanobacteria. Many cyanobacterial species are easy to manipulate genetically and grow robustly in liquid cultures that can be easily scaled up into photobioreactors. Therefore, cyanobacteria such as Synechocystis sp. PCC 6803 (hereafter “Synechocystis”) have widely been used for decades as model systems to study the principles of photosynthesis (Table 1). Indeed, genetic engineering based on homologous recombination is well-established in Synechocystis. Moreover, new genetic engineering toolkits, including marker-less gene deletion and replacement strategies needing only a single transformation step (Viola et al., 2014) and novel approaches for chromosomal integration and expression of synthetic gene operons (Bentley et al., 2014), allow for large-scale replacement and/or integration of dozens of genes in reasonable time frames. This makes Synechocystis a very attractive basis for the experimental modification of important processes like photosynthesis, and it also suggests innovative ways of improving modules of related eukaryotic pathways, among them the combination of cyanobacterial and eukaryotic elements using the tools of synthetic biology.

Cyanobacteria as an Experimental Platform for Modifying Bacterial and Plant Photosynthesis

International Nuclear Information System (INIS)

Jensen, Poul Erik; Leister, Dario

2014-01-01

One of the fascinating characteristics of photosynthesis is its capacity for repair, self-renewal, and energy storage within chemical bonds. Given the evolutionary history of plant photosynthesis and the patchwork nature of many of its components, it is safe to assume that the light reactions of plant photosynthesis can be improved by genetic engineering (Leister, 2012). The evolutionary precursor of chloroplasts was a microorganism whose biochemistry was very similar to that of present-day cyanobacteria. Many cyanobacterial species are easy to manipulate genetically and grow robustly in liquid cultures that can be easily scaled up into photobioreactors. Therefore, cyanobacteria such as Synechocystis sp. PCC 6803 (hereafter “Synechocystis”) have widely been used for decades as model systems to study the principles of photosynthesis (Table 1). Indeed, genetic engineering based on homologous recombination is well-established in Synechocystis. Moreover, new genetic engineering toolkits, including marker-less gene deletion and replacement strategies needing only a single transformation step (Viola et al., 2014) and novel approaches for chromosomal integration and expression of synthetic gene operons (Bentley et al., 2014), allow for large-scale replacement and/or integration of dozens of genes in reasonable time frames. This makes Synechocystis a very attractive basis for the experimental modification of important processes like photosynthesis, and it also suggests innovative ways of improving modules of related eukaryotic pathways, among them the combination of cyanobacterial and eukaryotic elements using the tools of synthetic biology.

Chlorophyll Can Be Reduced in Crop Canopies with Little Penalty to Photosynthesis1[OPEN

Science.gov (United States)

Drewry, Darren T.; VanLoocke, Andy; Cho, Young B.

2018-01-01

The hypothesis that reducing chlorophyll content (Chl) can increase canopy photosynthesis in soybeans was tested using an advanced model of canopy photosynthesis. The relationship among leaf Chl, leaf optical properties, and photosynthetic biochemical capacity was measured in 67 soybean (Glycine max) accessions showing large variation in leaf Chl. These relationships were integrated into a biophysical model of canopy-scale photosynthesis to simulate the intercanopy light environment and carbon assimilation capacity of canopies with wild type, a Chl-deficient mutant (Y11y11), and 67 other mutants spanning the extremes of Chl to quantify the impact of variation in leaf-level Chl on canopy-scale photosynthetic assimilation and identify possible opportunities for improving canopy photosynthesis through Chl reduction. These simulations demonstrate that canopy photosynthesis should not increase with Chl reduction due to increases in leaf reflectance and nonoptimal distribution of canopy nitrogen. However, similar rates of canopy photosynthesis can be maintained with a 9% savings in leaf nitrogen resulting from decreased Chl. Additionally, analysis of these simulations indicate that the inability of Chl reductions to increase photosynthesis arises primarily from the connection between Chl and leaf reflectance and secondarily from the mismatch between the vertical distribution of leaf nitrogen and the light absorption profile. These simulations suggest that future work should explore the possibility of using reduced Chl to improve canopy performance by adapting the distribution of the “saved” nitrogen within the canopy to take greater advantage of the more deeply penetrating light. PMID:29061904

Selective pressures on C4 photosynthesis evolution in grasses through the lens of optimality

OpenAIRE

Akcay, Erol; Zhou, Haoran; Helliker, Brent

2016-01-01

CO2, temperature, water availability and light intensity were potential selective pressures to propel the initial evolution and global expansion of C4 photosynthesis in grasses. To tease apart the primary selective pressures along the evolutionary trajectory, we coupled photosynthesis and hydraulics models and optimized photosynthesis over stomatal resistance and leaf/fine-root allocation. We also examined the importance of nitrogen reallocation from the dark to the light reactions. Our resul...

Physical stage of photosynthesis charge separation

Science.gov (United States)

Yakovlev, A. G.; Shuvalov, V. A.

2016-06-01

An analytical review is given concerning the biophysical aspects of light-driven primary charge separation in photosynthesis reaction centers (RCs) which are special pigment-protein complexes residing in a cell membrane. The primary (physical) stage of charge separation occurs in the pico- and femtosecond ranges and consists of transferring an electron along the active A-branch of pigments. The review presents vast factual material on both the general issues of primary photosynthesis and some more specific topics, including (1) the role of the inactive B-branch of pigments, (2) the effect of the protein environment on the charge separation, and (3) the participation of monomeric bacteriochlorophyll BA in primary electron acceptance. It is shown that the electron transfer and stabilization are strongly influenced by crystallographic water and tyrosine M210 molecules from the nearest environment of BA. A linkage between collective nuclear motions and electron transfer upon charge separation is demonstrated. The nature of the high quantum efficiency of primary charge separation reactions is discussed.

Ambient UV-B radiation decreases photosynthesis in high arctic Vaccinium uliginosum

DEFF Research Database (Denmark)

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

2008-01-01

). Leaf area, biomass, carbon, nitrogen and UV-B-absorbing compounds were determined from a late season harvest. Compared with the reduced UV-B treatment, the plants in ambient UV-B were found to have a higher content of UV-B-absorbing compounds, and canopy net photosynthesis was as an average 23% lower...... during the season. By means of the JIP-test, it was found that the potential of processing light energy through the photosynthetic machinery was slightly reduced in ambient UV-B. This indicates that not only the UV-B effects on PSII may be responsible for some of the observed reduction of photosynthesis...... on photosynthesis clearly indicates that V. uliginosum is negatively affected by the current level of UV-B....

Metabolic flux ratio analysis and cell staining suggest the existence of C4 photosynthesis in Phaeodactylum tricornutum.

Science.gov (United States)

Huang, A; Liu, L; Zhao, P; Yang, C; Wang, G C

2016-03-01

Mechanisms for carbon fixation via photosynthesis in the diatom Phaeodactylum tricornutum Bohlin were studied recently but there remains a long-standing debate concerning the occurrence of C4 photosynthesis in this species. A thorough investigation of carbon metabolism and the evidence for C4 photosynthesis based on organelle partitioning was needed. In this study, we identified the flux ratios between C3 and C4 compounds in P. tricornutum using (13)C-labelling metabolic flux ratio analysis, and stained cells with various cell-permeant fluorescent probes to investigate the likely organelle partitioning required for single-cell C4 photosynthesis. Metabolic flux ratio analysis indicated the C3/C4 exchange ratios were high. Cell staining indicated organelle partitioning required for single-cell C4 photosynthesis might exist in P. tricornutum. The results of (13)C-labelling metabolic flux ratio analysis and cell staining suggest single-cell C4 photosynthesis exists in P. tricornutum. This study provides insights into photosynthesis patterns of P. tricornutum and the evidence for C4 photosynthesis based on (13)C-labelling metabolic flux ratio analysis and organelle partitioning. © 2015 The Society for Applied Microbiology.

Lipids in the Structure of Photosystem I, Photosystem II and the Cytochrome b6f Complex

NARCIS (Netherlands)

Kern, Jan; Zouni, Athina; Guskov, Albert; Krauss, Norbert; Wada, Hajime; Murata, Norio

2009-01-01

This chapter describes the data accumulated in the last decade regarding the specific function of lipids in oxygenic photosynthesis, based on crystal structures of at least 3.0 Å resolution of the main photosynthetic membrane protein—pigment complexes, photosystem I, photosystem II and cytochrome

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

Photosynthesis: an interactive didactic model’s use to the learning and teaching process

Directory of Open Access Journals (Sweden)

Vanessa Liesenfeld

2015-06-01

Full Text Available Photosynthesis is a complex process that involves the implementation of several reactions which, many times, makes this content difficult for students to understand. The objective of this study was to investigate if an interactive didactic model, crafted with simple materials, could facilitate the understanding and learning of students on photosynthesis. Initially students of first year high school class from a public school Western of Paraná were asked to diagram what they knew about photosynthesis and respond to a questionnaire. It was concluded that many of the students’ prior concepts were general or inaccurate, such as the idea of photosynthesis being the process of respiration in plants, and O2 coming from the CO2, not from the photo-oxidation of water. These prior conceptions were important for planning the approach to the subject. The process of photosynthesis was then covered in lecture and dialogued, using the interactive didactic model to highlight the explanations. A new questionnaire was completed by the students, and concluded that the use of the interactive didactic model was efficient, since it helped to consolidate correct concepts and simultaneously, introduced new ones as well it shook the equivocal relations.

Exploring undergraduates' understanding of photosynthesis using diagnostic question clusters.

Science.gov (United States)

Parker, Joyce M; Anderson, Charles W; Heidemann, Merle; Merrill, John; Merritt, Brett; Richmond, Gail; Urban-Lurain, Mark

2012-01-01

We present a diagnostic question cluster (DQC) that assesses undergraduates' thinking about photosynthesis. This assessment tool is not designed to identify individual misconceptions. Rather, it is focused on students' abilities to apply basic concepts about photosynthesis by reasoning with a coordinated set of practices based on a few scientific principles: conservation of matter, conservation of energy, and the hierarchical nature of biological systems. Data on students' responses to the cluster items and uses of some of the questions in multiple-choice, multiple-true/false, and essay formats are compared. A cross-over study indicates that the multiple-true/false format shows promise as a machine-gradable format that identifies students who have a mixture of accurate and inaccurate ideas. In addition, interviews with students about their choices on three multiple-choice questions reveal the fragility of students' understanding. Collectively, the data show that many undergraduates lack both a basic understanding of the role of photosynthesis in plant metabolism and the ability to reason with scientific principles when learning new content. Implications for instruction are discussed.

A photophysical control mechanism for zeaxanthin-associated radiationless energy dissipation in photosynthesis

Energy Technology Data Exchange (ETDEWEB)

Frank, H.A.; Cua, A. [Connecticut Univ., Storrs, CT (United States). Dept. of Chemistry; Young, A. [Johns Moores Univ., Liverpool (United Kingdom). School of Biological and Earth Sciences; Gosztola, D.; Wasielewski, M.R. [Argonne National Lab., IL (United States)

1994-09-01

Understanding the way in which excess solar energy is dissipated by photosynthetic membranes under high light stress is a major problem in photosynthesis studies. This paper reports femtosecond time-resolved, fast-transient optical spectroscopic analyses of three important xanthophylls: violaxanthin, antheraxanthin, zeoaxanthin. The results support the notion that the enzymatic reactions that interconvert these xanthophylls act as a kind of ``molecular gear shift`` controlling whether the molecules function as light-harvesting pigments performing forward energy transfer or as fluorescence quenchers performing reverse energy transfer.

3-(2-Alkylsulfanyl-6-benzothiazolylaminomethyl-2-benzoxazolethiones - Synthesis and Photosynthesis-Inhibiting Activity in Spinach Chloropasts

Directory of Open Access Journals (Sweden)

Dusan Loos

1999-03-01

Full Text Available The synthesis and photosynthesis-inhibiting activity of 14 new 3-(2-alkylsulfanyl-6-benzothiazolylaminomethyl-2-benzoxazolethiones are reported. The new compounds were prepared by the reaction of 2-alkylsulfanyl-6-aminobenzothiazoles with 3-hydroxymethyl-2-benzoxazolethione. The structures of the compounds were verified by 1H NMR spectra. The compounds inhibit photosynthetic electron transport in spinach chloroplasts. The photosynthetic activity was found to depend on the calculated lipophilicity of the new compounds. Some structure characteristics and quantum chemical parameters were calculated by AM1 method.

Stem Photosynthesis of Twig and Its Contribution to New Organ Development in Cutting Seedlings of Salix Matsudana Koidz.

Directory of Open Access Journals (Sweden)

Junxiang Liu

2018-04-01

Full Text Available The objective of this study was to illustrate the photosynthetic characteristics of current twigs of Salix matsudana Koidz., and clarify the effect of stem photosynthesis on the new organ development in cutting seedlings. Excised twigs were taken as the experimental samples. The response of the stem photosynthesis rate to increasing light intensity and the effective photochemical efficiency of the cross section of the twig were determined. Then, twigs were used as cuttings and exposed to 0, 20, and 100 μmol m−2 s−1 light intensities, respectively, to achieve distinctive stem photosynthetic rates. After 14 days of treatment, stem water and non-structural carbohydrate (NSC content, as well as the biomass and carbon isotopic composition, of new organs in the cutting seedlings under different light treatments were examined. The results showed that the gross photosynthetic rate significantly increased within 400 μmol m−2 s−1 of light intensity, and the maximum rate was approximately 1.27 μmol m−2 s−1. The effective photochemical efficiency of the PSⅡ of the cortex was significantly higher than the inner tissues in the cross section of the twig. When twig cuttings were exposed to different light intensities, stem water and starch content, as well as bud and root biomass, were significantly higher in the cutting seedling subjected to 100 μmol m−2 s−1 than the case treated in darkness; however, the bud δ13C trend was the opposite. Stem photosynthesis played a positive role in the maintenance of stem water and starch supply for the cutting seedlings, and 13C depleted assimilates produced by stem photosynthesis contributed to bud biomass, revealing that stem photosynthesis promotes organ development in cutting seedlings of Salix matsudana.

Photon structure function - theory

International Nuclear Information System (INIS)

Bardeen, W.A.

1984-12-01

The theoretical status of the photon structure function is reviewed. Particular attention is paid to the hadronic mixing problem and the ability of perturbative QCD to make definitive predictions for the photon structure function. 11 references

Carrying photosynthesis genes increases ecological fitness of cyanophage in silico.

Science.gov (United States)

Hellweger, Ferdi L

2009-06-01

Several viruses infecting marine cyanobacteria carry photosynthesis genes (e.g. psbA, hli) that are expressed, yield proteins (D1, HLIP) and help maintain the cell's photosynthesis apparatus during the latent period. This increases energy and speeds up virus production, allowing for a reduced latent period (a fitness benefit), but it also increases the DNA size, which slows down new virus production and reduces burst size (a fitness cost). How do these genes affect the net ecological fitness of the virus? Here, this question is explored using a combined systems biology and systems ecology ('systems bioecology') approach. A novel agent-based model simulates individual cyanobacteria cells and virus particles, each with their own genes, transcripts, proteins and other properties. The effect of D1 and HLIP proteins is explicitly considered using a mechanistic photosynthesis component. The model is calibrated to the available database for Prochlorococcus ecotype MED4 and podovirus P-SSP7. Laboratory- and field-scale in silico survival, competition and evolution (gene packaging error) experiments with wild type and genetically engineered viruses are performed to develop vertical survival and fitness profiles, and to determine the optimal gene content. The results suggest that photosynthesis genes are nonessential, increase fitness in a manner correlated with irradiance, and that the wild type has an optimal gene content.

Nuclear correlations and structure functions

International Nuclear Information System (INIS)

Hu Guoju; Irvine, J.M.

1989-01-01

It is argued that the search for a mass number dependence of the nuclear structure function per nucleon is profitably directed to the region of Bjorken scaling variable x > 1. We show that in the convolution model of the nuclear structure function the nuclear momentum distribution and energy spectrum generated by cluster expansion techniques, here realised in the correlated basis function method, invoking tensor correlations and short-range density-dependent repulsions adequately describes the structure function for 12 C in the region x > 1. The results of structure functions for a number of light-, medium- and heavy-mass nuclei are presented. (author)

Measurement of Solar Spectra Relating to Photosynthesis and Solar Cells: An Inquiry Lab for Secondary Science

Science.gov (United States)

Ruggirello, Rachel M.; Balcerzak, Phyllis; May, Victoria L.; Blankenship, Robert E.

2012-01-01

The process of photosynthesis is central to science curriculum at all levels. This article describes an inquiry-based laboratory investigation developed to explore the impact of light quality on photosynthesis and to connect this process to current research on harvesting solar energy, including bioenergy, artificial photosynthesis, and solar…

Structure-based inference of molecular functions of proteins of unknown function from Berkeley Structural Genomics Center

Energy Technology Data Exchange (ETDEWEB)

Kim, Sung-Hou; Shin, Dong Hae; Hou, Jingtong; Chandonia, John-Marc; Das, Debanu; Choi, In-Geol; Kim, Rosalind; Kim, Sung-Hou

2007-09-02

Advances in sequence genomics have resulted in an accumulation of a huge number of protein sequences derived from genome sequences. However, the functions of a large portion of them cannot be inferred based on the current methods of sequence homology detection to proteins of known functions. Three-dimensional structure can have an important impact in providing inference of molecular function (physical and chemical function) of a protein of unknown function. Structural genomics centers worldwide have been determining many 3-D structures of the proteins of unknown functions, and possible molecular functions of them have been inferred based on their structures. Combined with bioinformatics and enzymatic assay tools, the successful acceleration of the process of protein structure determination through high throughput pipelines enables the rapid functional annotation of a large fraction of hypothetical proteins. We present a brief summary of the process we used at the Berkeley Structural Genomics Center to infer molecular functions of proteins of unknown function.

Photosynthesis-related characteristics of the midrib and the interveinal lamina in leaves of the C3-CAM intermediate plant Mesembryanthemum crystallinum.

Science.gov (United States)

Kuźniak, Elżbieta; Kornas, Andrzej; Kaźmierczak, Andrzej; Rozpądek, Piotr; Nosek, Michał; Kocurek, Maciej; Zellnig, Günther; Müller, Maria; Miszalski, Zbigniew

2016-06-01

Leaf veins are usually encircled by specialized bundle sheath cells. In C4 plants, they play an important role in CO2 assimilation, and the photosynthetic activity is compartmentalized between the mesophyll and the bundle sheath. In C3 and CAM (Crassulacean acid metabolism) plants, the photosynthetic activity is generally attributed to the leaf mesophyll cells, and the vascular parenchymal cells are rarely considered for their role in photosynthesis. Recent studies demonstrate that enzymes required for C4 photosynthesis are also active in the veins of C3 plants, and their vascular system contains photosynthetically competent parenchyma cells. However, our understanding of photosynthesis in veins of C3 and CAM plants still remains insufficient. Here spatial analysis of photosynthesis-related properties were applied to the midrib and the interveinal lamina cells in leaves of Mesembryanthemum crystallinum, a C3-CAM intermediate plant. The midrib anatomy as well as chloroplast structure and chlorophyll fluorescence, diurnal gas exchange profiles, the immunoblot patterns of PEPC (phosphoenolpyruvate carboxylase) and RubisCO (ribulose-1,5-bisphosphate carboxylase/oxygenase), H2O2 localization and antioxidant enzyme activities were compared in the midrib and in the interveinal mesophyll cells in leaves of C3 and CAM plants. Leaf midribs were structurally competent to perform photosynthesis in C3 and CAM plants. The midrib chloroplasts resembled those in the bundle sheath cells of C4 plants and were characterized by limited photosynthetic activity. The metabolic roles of midrib chloroplasts differ in C3 and CAM plants. It is suggested that in leaves of C3 plants the midrib chloroplasts could be involved in the supply of CO2 for carboxylation, and in CAM plants they could provide malate to different metabolic processes and mediate H2O2 signalling. © The Author 2016. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For

Using Evolution as a Guide to Engineer Kranz-Type C4 photosynthesis

Directory of Open Access Journals (Sweden)

Thomas L. Slewinski

2013-07-01

Full Text Available Kranz-type C4 photosynthesis has independently and rapidly evolved over sixty times to dramatically increase radiation use efficiency in both monocots and eudicots. Indeed, it is one of the most exceptional examples of convergent evolution in the history of life. The repeated and rapid evolution of Kranz-type C4 suggests that it may be a derivative of a conserved developmental pathway that is present in all angiosperms. Here, I argue that the Kranz-type C4 photosynthetic system is an extension of the endodermis/starch sheath, that is normally only found in the roots and stems, into photosynthetic structures such as leaves. Support for this hypothesis was recently provided by a study that showed that the same genetic pathway that gives rise to the endodermis in roots, the SCARECROW/SHORT-ROOT radial pattering system, also regulates the development of Kranz anatomy and C4 physiology in leaves. This new hypothesis for the evolution of Kranz-type C4 photosynthesis has opened new opportunities to explore the underlying genetic networks that regulate the development and physiology of C4 and provides new potential avenues for the engineering of the mechanism into C3 crops.

Photosynthesis, plant growth and nitrogen nutrition in Alaskan tussock tundra: Response to experimental warming

Science.gov (United States)

Dynes, E.; Welker, J. M.; Moore, D. J.; Sullivan, P.; Ebbs, L.; Pattison, R.

2009-12-01

Temperature is predicted to rise significantly in northern latitudes over the next century. The Arctic tundra is a fragile ecosystem with low rates of photosynthesis and low nutrient mineralisation. Rising temperatures may increase photosynthetic capacity in the short term through direct stimulation of photosynthetic rates and also in the longer term due to enhanced nutrient availability. Different species and plant functional types may have different responses to warming which may have an impact on plant community structure. As part of the International Tundra Experiment (ITEX) to investigate the effects of warming on arctic vegetation, a series of open top chambers (OTCs) have been established at the Toolik Field Station (68°38’N, 149°36’W, elevation 720 m). This study employs 12 plots; 6 control plots and 6 warming plots covered with OTCs which maintain a temperature on average +1.54 °C degrees higher than ambient temperatures. The response of photosynthesis to temperature was measured using an infra-red gas analyzer (IRGA) with a cooling adaptor to manipulate leaf temperature and determine AMAX in two contrasting species, Eriophorum vaginatum (sedge) and Betula nana (shrub). Temperature within the chamber head of the IRGA was manipulated from 10 through 25 °C. We also measured the leaf area index of plots using a Decagon Accupar Ceptometer to provide insights into potential differences in canopy cover. In both OTC and control plots the photosynthetic rate of B. nana was greater than that of E. vaginatum, with the AMAX of B. nana peaking at 20.08°C and E. vaginatum peaking slightly lower at 19.7°C in the control plots. There was no apparent difference in the temperature optimum of photosynthesis of either species when exposed to the warming treatment. Although there was no difference in temperature optimum there were differences in the peak values of AMAX between treatment and control plots. In the case of B. nana, AMAX was higher in the OTCs than in

In vivo Microscale Measurements of Light and Photosynthesis during Coral Bleaching: Evidence for the Optical Feedback Loop?

Science.gov (United States)

Wangpraseurt, Daniel; Holm, Jacob B; Larkum, Anthony W D; Pernice, Mathieu; Ralph, Peter J; Suggett, David J; Kühl, Michael

2017-01-01

Climate change-related coral bleaching, i.e., the visible loss of zooxanthellae from the coral host, is increasing in frequency and extent and presents a major threat to coral reefs globally. Coral bleaching has been proposed to involve accelerating light stress of their microalgal endosymbionts via a positive feedback loop of photodamage, symbiont expulsion and excess in vivo light exposure. To test this hypothesis, we used light and O 2 microsensors to characterize in vivo light exposure and photosynthesis of Symbiodinium during a thermal stress experiment. We created tissue areas with different densities of Symbiodinium cells in order to understand the optical properties and light microenvironment of corals during bleaching. Our results showed that in bleached Pocillopora damicornis corals, Symbiodinium light exposure was up to fivefold enhanced relative to healthy corals, and the relationship between symbiont loss and light enhancement was well-described by a power-law function. Cell-specific rates of Symbiodinium gross photosynthesis and light respiration were enhanced in bleached P. damicornis compared to healthy corals, while areal rates of net photosynthesis decreased. Symbiodinium light exposure in Favites sp. revealed the presence of low light microniches in bleached coral tissues, suggesting that light scattering in thick coral tissues can enable photoprotection of cryptic symbionts. Our study provides evidence for the acceleration of in vivo light exposure during coral bleaching but this optical feedback mechanism differs between coral hosts. Enhanced photosynthesis in relation to accelerating light exposure shows that coral microscale optics exerts a key role on coral photophysiology and the subsequent degree of radiative stress during coral bleaching.

Ecosystem respiration depends strongly on photosynthesis in a temperate heath

DEFF Research Database (Denmark)

Larsen, Klaus Steenberg; Ibrom, Andreas; Beier, Claus

2007-01-01

We measured net ecosystem CO2 flux (F-n) and ecosystem respiration (R-E), and estimated gross ecosystem photosynthesis (P-g) by difference, for two years in a temperate heath ecosystem using a chamber method. The exchange rates of carbon were high and of similar magnitude as for productive forest...... ecosystems with a net ecosystem carbon gain during the second year of 293 +/- 11 g C m(-2) year(-1) showing that the carbon sink strength of heather-dominated ecosystems may be considerable when C. vulgaris is in the building phase of its life cycle. The estimated gross ecosystem photosynthesis and ecosystem.......65) was improved when the P-g rate was incorporated into the model (second year; R-2 = 0.79), suggesting that daytime R-E increased with increasing photosynthesis. Furthermore, the temperature sensitivity of R-E decreased from apparent Q(10) values of 3.3 to 3.9 by the classic equation to a more realistic Q(10...

O2-insensitive photosynthesis in C3 plants: its occurrence and a possible explanation

International Nuclear Information System (INIS)

Sharkey, T.D.

1985-01-01

Leaves of C 3 plants which exhibit a normal O 2 inhibition of CO 2 fixation at less than saturating light intensity were found to exhibit O 2 -insensitive photosynthesis at high light. This behavior was observed in Phaseolus vulgaris L., Xanthium strumarium L., and Scrophularia desertorum (Shaw.) Munz. O 2 -insensitive photosynthesis has been reported in nine other C 3 species and usually occurred when the intercellular CO 2 pressure was about double the normal pressure. A lack of O 2 inhibition of photosynthesis was always accompanied by a failure of increased CO 2 pressure to stimulate photosynthesis to the expected degree. O 2 -insensitive photosynthesis also occurred after plants had been water stressed. Under such conditions, however, photosynthesis became O 2 and CO 2 insensitive at physiological CO 2 pressures. Postillumination CO 2 exchange kinetics showed that O 2 and CO 2 insensitivity was not the result of elimination of photorespiration. It is proposed that O 2 and CO 2 insensitivity occurs when the concentration of phosphate in the chloroplast stroma cannot be both high enough to allow photophosphorylation and low enough to allow starch and sucrose synthesis at the rates required by the rest of the photosynthetic component processes. Under these conditions, the energy diverted to photorespiration does not adversely affect the potential for CO 2 assimilation

Effects of space environment on chlorophyll fluorescence and photosynthesis characteristics of wheat

International Nuclear Information System (INIS)

Lu Li; Lv Jinyin; Gong Qingzhu; Gao Junfeng

2006-01-01

The effects of the space environment on the chlorophyll fluorescence parameters and photosynthesis characteristics of wheat cultivars, Xinong 1043 M1 and Shaan253 M 1 , were studied. The results showed that the decrement of contents of PS II primary photochemical efficiency (F v /F m ), potential activity (F v /F 0 ), photochemical quenching coefficient (qP) and photosynthesis rate (Pn) were less than that of control, increment of non-photochemical quenching coefficient (qN) were more than that of control. The results suggested that photosynthetic apparatus were damaged, photosynthetic electron transport, photosynthetic primary reaction were inhibited, rate of photosynthesis decreased and growth of M 1 plant were retarded, which leading to thousand kernel weights decreased. (authors)

The importance of micrometeorological variations for photosynthesis and transpiration in a boreal coniferous forest

DEFF Research Database (Denmark)

Schurgers, Guy; Lagergren, F.; Molder, M.

2015-01-01

the importance of vertical variations in light, temperature, CO2 concentration and humidity within the canopy for fluxes of photosynthesis and transpiration of a boreal coniferous forest in central Sweden. A leaf-level photosynthesis-stomatal conductance model was used for aggregating these processes to canopy...... abovecanopy and within-canopy humidity, and despite large gradients in CO2 concentration during early morning hours after nights with stable conditions, neither humidity nor CO2 played an important role for vertical heterogeneity of photosynthesis and transpiration....

Functional materials discovery using energy-structure-function maps.

Science.gov (United States)

Pulido, Angeles; Chen, Linjiang; Kaczorowski, Tomasz; Holden, Daniel; Little, Marc A; Chong, Samantha Y; Slater, Benjamin J; McMahon, David P; Bonillo, Baltasar; Stackhouse, Chloe J; Stephenson, Andrew; Kane, Christopher M; Clowes, Rob; Hasell, Tom; Cooper, Andrew I; Day, Graeme M

2017-03-30

Molecular crystals cannot be designed in the same manner as macroscopic objects, because they do not assemble according to simple, intuitive rules. Their structures result from the balance of many weak interactions, rather than from the strong and predictable bonding patterns found in metal-organic frameworks and covalent organic frameworks. Hence, design strategies that assume a topology or other structural blueprint will often fail. Here we combine computational crystal structure prediction and property prediction to build energy-structure-function maps that describe the possible structures and properties that are available to a candidate molecule. Using these maps, we identify a highly porous solid, which has the lowest density reported for a molecular crystal so far. Both the structure of the crystal and its physical properties, such as methane storage capacity and guest-molecule selectivity, are predicted using the molecular structure as the only input. More generally, energy-structure-function maps could be used to guide the experimental discovery of materials with any target function that can be calculated from predicted crystal structures, such as electronic structure or mechanical properties.

Modeling photosynthesis of Spartina alterniflora (smooth cordgrass) impacted by the Deepwater Horizon oil spill using Bayesian inference

International Nuclear Information System (INIS)

Wu Wei; Biber, Patrick D; Peterson, Mark S; Gong Chongfeng

2012-01-01

To study the impact of the Deepwater Horizon oil spill on photosynthesis of coastal salt marsh plants in Mississippi, we developed a hierarchical Bayesian (HB) model based on field measurements collected from July 2010 to November 2011. We sampled three locations in Davis Bayou, Mississippi (30.375°N, 88.790°W) representative of a range of oil spill impacts. Measured photosynthesis was negative (respiration only) at the heavily oiled location in July 2010 only, and rates started to increase by August 2010. Photosynthesis at the medium oiling location was lower than at the control location in July 2010 and it continued to decrease in September 2010. During winter 2010–2011, the contrast between the control and the two impacted locations was not as obvious as in the growing season of 2010. Photosynthesis increased through spring 2011 at the three locations and decreased starting with October at the control location and a month earlier (September) at the impacted locations. Using the field data, we developed an HB model. The model simulations agreed well with the measured photosynthesis, capturing most of the variability of the measured data. On the basis of the posteriors of the parameters, we found that air temperature and photosynthetic active radiation positively influenced photosynthesis whereas the leaf stress level negatively affected photosynthesis. The photosynthesis rates at the heavily impacted location had recovered to the status of the control location about 140 days after the initial impact, while the impact at the medium impact location was never severe enough to make photosynthesis significantly lower than that at the control location over the study period. The uncertainty in modeling photosynthesis rates mainly came from the individual and micro-site scales, and to a lesser extent from the leaf scale. (letter)

Comparative proteomic analysis reveals the positive effect of exogenous spermidine on photosynthesis and salinity tolerance in cucumber seedlings.

Science.gov (United States)

Sang, Ting; Shan, Xi; Li, Bin; Shu, Sheng; Sun, Jin; Guo, Shirong

2016-08-01

Our results based on proteomics data and physiological alterations proposed the putative mechanism of exogenous Spd enhanced salinity tolerance in cucumber seedlings. Current studies showed that exogenous spermidine (Spd) could alleviate harmful effects of salinity. It is important to increase our understanding of the beneficial physiological responses of exogenous Spd treatment, and to determine the molecular responses underlying these responses. Here, we combined a physiological analysis with iTRAQ-based comparative proteomics of cucumber (Cucumis sativus L.) leaves, treated with 0.1 mM exogenous Spd, 75 mM NaCl and/or exogenous Spd. A total of 221 differentially expressed proteins were found and involved in 30 metabolic pathways, such as photosynthesis, carbohydrate metabolism, amino acid metabolism, stress response, signal transduction and antioxidant. Based on functional classification of the differentially expressed proteins and the physiological responses, we found cucumber seedlings treated with Spd under salt stress had higher photosynthesis efficiency, upregulated tetrapyrrole synthesis, stronger ROS scavenging ability and more protein biosynthesis activity than NaCl treatment, suggesting that these pathways may promote salt tolerance under high salinity. This study provided insights into how exogenous Spd protects photosynthesis and enhances salt tolerance in cucumber seedlings.

The Effect of Silicon on Photosynthesis and Expression of Its Relevant Genes in Rice (Oryza sativa L.) under High-Zinc Stress

Science.gov (United States)

Song, Alin; Li, Ping; Fan, Fenliang; Li, Zhaojun; Liang, Yongchao

2014-01-01

The main objectives of this study were to elucidate the roles of silicon (Si) in alleviating the effects of 2 mM zinc (high Zn) stress on photosynthesis and its related gene expression levels in leaves of rice (Oryza sativa L.) grown hydroponically with high-Zn stress. The results showed that photosynthetic parameters, including net photosynthetic rate, transpiration rate, stomatal conductance, intercellular CO2 concentration, chlorophyll concentration and the chlorophyll fluorescence, were decreased in rice exposed to high-Zn treatment. The leaf chloroplast structure was disordered under high-Zn stress, including uneven swelling, disintegrated and missing thylakoid membranes, and decreased starch granule size and number, which, however, were all counteracted by the addition of 1.5 mM Si. Furthermore, the expression levels of Os08g02630 (PsbY), Os05g48630 (PsaH), Os07g37030 (PetC), Os03g57120 (PetH), Os09g26810 and Os04g38410 decreased in Si-deprived plants under high-Zn stress. Nevertheless, the addition of 1.5 mM Si increased the expression levels of these genes in plants under high-Zn stress at 72 h, and the expression levels were higher in Si-treated plants than in Si-deprived plants. Therefore, we conclude that Si alleviates the Zn-induced damage to photosynthesis in rice. The decline of photosynthesis in Zn-stressed rice was attributed to stomatal limitation, and Si activated and regulated some photosynthesis-related genes in response to high-Zn stress, consequently increasing photosynthesis. PMID:25426937

Carbon dioxide fixation by artificial photosynthesis

Energy Technology Data Exchange (ETDEWEB)

Ibusuki, Takashi; Koike, Kazuhide; Ishitani, Osamu [National Inst. for Resources and Environment, AIST, MITI, Tsukuba, Ibaraki (Japan)

1993-12-31

Green plants can absorb atmospheric CO{sub 2} and transform it to sugars, carbohydrates through their photosynthetic systems, but they become the source of CO{sub 2} when they are dead. This is the reason why artificial leaves which can be alive forever should be developed to meet with global warming due to the increase of CO{sub 2} concentration. The goal of artificial photosynthesis is not to construct the same system as the photosynthetic one, but to mimic the ability of green plants to utilize solar energy to make high energy chemicals. Needless to say, the artificial photosynthetic system is desired to be as simple as possible and to be as efficient as possible. From the knowledge on photosynthesis and the results of previous investigations, the critical components of artificial photosynthetic system are understood as follows: (1) light harvesting chromophore, (2) a center for electron transfer and charge separation, (3) catalytic sites for converting small molecules like water and CO{sub 2} (mutilelectron reactions) which are schematically described.

Box photosynthesis modeling results for WRF/CMAQ LSM

Data.gov (United States)

U.S. Environmental Protection Agency — Box Photosynthesis model simulations for latent heat and ozone at 6 different FLUXNET sites. This dataset is associated with the following publication: Ran, L., J....

Evolution of the Z-scheme of photosynthesis: a perspective.

Science.gov (United States)

Govindjee; Shevela, Dmitriy; Björn, Lars Olof

2017-09-01

The concept of the Z-scheme of oxygenic photosynthesis is in all the textbooks. However, its evolution is not. We focus here mainly on some of the history of its biophysical aspects. We have arbitrarily divided here the 1941-2016 period into three sub-periods: (a) Origin of the concept of two light reactions: first hinted at, in 1941, by James Franck and Karl Herzfeld; described and explained, in 1945, by Eugene Rabinowitch; and a clear hypothesis, given in 1956 by Rabinowitch, of the then available cytochrome experiments: one light oxidizing it and another reducing it; (b) Experimental discovery of the two light reactions and two pigment systems and the Z-scheme of photosynthesis: Robert Emerson's discovery, in 1957, of enhancement in photosynthesis when two light beams (one in the far-red region, and the other of shorter wavelengths) are given together than when given separately; and the 1960 scheme of Robin Hill & Fay Bendall; and (c) Evolution of the many versions of the Z-Scheme: Louis Duysens and Jan Amesz's 1961 experiments on oxidation and reduction of cytochrome f by two different wavelengths of light, followed by the work of many others for more than 50 years.

Operation of trans-thylakoid thiol-metabolizing pathways in photosynthesis

Directory of Open Access Journals (Sweden)

Mohamed eKaramoko

2013-11-01

Full Text Available Thiol oxidation to disulfides and the reverse reaction, i.e. disulfide reduction to free thiols, are under the control of catalysts in vivo. Enzymatically assisted thiol-disulfide chemistry is required for the biogenesis of all energy-transducing membrane systems. However, until recently, this had only been demonstrated for the bacterial plasma membrane. Long considered to be vacant, the thylakoid lumen has now moved to the forefront of photosynthesis research with the realization that its proteome is far more complicated than initially anticipated. Several lumenal proteins are known to be disulfide bonded in Arabidopsis, highlighting the importance of sulfhydryl oxidation in the thylakoid lumen. While disulfide reduction in the plastid stroma is known to activate several enzymatic activities, it appears that it is the reverse reaction, i.e. thiol oxidation that is required for the activity of several lumen-resident proteins. This paradigm for redox regulation in the thylakoid lumen has opened a new frontier for research in the field of photosynthesis. Of particular significance in this context is the discovery of trans-thylakoid redox pathways controlling disulfide bond formation and reduction, which are required for photosynthesis.

Effects of SO/sub 2/ on photosynthesis and nitrogen fixation

Energy Technology Data Exchange (ETDEWEB)

Haellgren, J E; Huss, K

1975-06-15

Responses of photosynthesis and nitrogen fixation to NaHSO/sub 3/ (10/sup -5/ to 5 x 10/sup -3/ M) were investigated in the lichen Stereocaulon paschale (L.) Fr. and the blue-green alga Anabaena cylindrica Lemmermann. The treatments were performed in buffered media with varying pH (5.8 to 8.1) and light conditions (0 to 32 W x m/sup -2/). The activities of the intact organisms were investigated, under the same environmental conditions, with /sup 14/C liquid scintillation and acetylene reduction techniques respectively. The nitrogen fixation proved to be more susceptible than photosynthesis, in both organisms, and in all cases treatments at pH 5.8 were more inhibitory than at higher pH-values. Treatment with 5 x 10/sup -4/ M NaHSO/sub 3/ at pH 5.8 caused no reduction of photosynthesis in S. paschale, while the inhibition of nitrogen fixation was 97%. For A. cylindrica the corresponding values were 40% and 75% respectively. Short-time treatments of A. cylindrica showed that the nitrogen fixation was more rapidly affected than photosynthesis. The inhibition of nitrogenase activity and CO/sub 2/-fixation was smaller in the dark and increased at higher light intensities. Both processes showed a good capacity for recovery after removal of the NaHSO/sub 3/ solution. Also the clumping ability of A. cylindrica was disturbed by NaHSO/sub 3/ treatments.

Photochemistry and enzymology of photosynthesis

Energy Technology Data Exchange (ETDEWEB)

Radmer, R.

1979-07-30

In the first task, a specially designed mass spectrometer system monitors the gas exchange occurring in response to single short flashes of light. This apparatus will be primarily used to study photosystem II donor reactions, such as the photooxidation of hydroxylamine, hydrazine, and hydrogen peroxide. This technique will also be used to study the light-induced exchange of O/sub 2/ and CO/sub 2/ in algae. The second task, biochemical studies, will focus on the role of chloroplast copper in photosynthesis. We propose to isolate, purify, and characterize the chloroplast copper enzyme polyphenol oxidase, and attempt to elucidate its role in photosynthesis. These studies will be integrated with a new program devoted to the biochemical response of the photosynthetic membrane to stress. The third task is a series of studies on the light-harvesting and electron-transport mechanisms of C/sub 4/ plants. This program will address three basic problems: (1) the effect of different preparative procedures on various photosynthetic reactions, with particular emphasis on photosystem II reactions in corn bundle sheath chloroplasts; (2) the development and testing of photosystem II assays; and (3) studies of the stoichiometry of electron carriers in bundle sheath chloroplasts, and whether cyclic phosphorylation could be a major pathway in this tissue.

Structure function monitor

Science.gov (United States)

McGraw, John T [Placitas, NM; Zimmer, Peter C [Albuquerque, NM; Ackermann, Mark R [Albuquerque, NM

2012-01-24

Methods and apparatus for a structure function monitor provide for generation of parameters characterizing a refractive medium. In an embodiment, a structure function monitor acquires images of a pupil plane and an image plane and, from these images, retrieves the phase over an aperture, unwraps the retrieved phase, and analyzes the unwrapped retrieved phase. In an embodiment, analysis yields atmospheric parameters measured at spatial scales from zero to the diameter of a telescope used to collect light from a source.

The Path of Carbon in Photosynthesis VII. Respiration and Photosynthesis

Science.gov (United States)

Benson, A. A.; Calvin, M.

1949-07-21

The relationship of respiration to photosynthesis in barley seedling leaves and the algae, Chlorella and Scenedesmus, has been investigated using radioactive carbon dioxide and the techniques of paper chromatography and radioautography. The plants are allowed to photosynthesize normally for thirty seconds in c{sup 14}O{sub 2} after which they are allowed to respire in air or helium in the light or dark. Respiration of photosynthetic intermediates as evidenced by the appearance of labeled glutomic, isocitric, fumaric and succinic acids is slower in the light than in the dark. Labeled glycolic acid is observed in barley and algae. It disappears rapidly in the dark and is maintained and increased in quantity in the light in C0{sub 2}-free air.

Strategic system development toward biofuel, desertification, and crop production monitoring in continental scales using satellite-based photosynthesis models

Science.gov (United States)

Kaneko, Daijiro

2013-10-01

The author regards fundamental root functions as underpinning photosynthesis activities by vegetation and as affecting environmental issues, grain production, and desertification. This paper describes the present development of monitoring and near real-time forecasting of environmental projects and crop production by approaching established operational monitoring step-by-step. The author has been developing a thematic monitoring structure (named RSEM system) which stands on satellite-based photosynthesis models over several continents for operational supports in environmental fields mentioned above. Validation methods stand not on FLUXNET but on carbon partitioning validation (CPV). The models demand continuing parameterization. The entire frame system has been built using Reanalysis meteorological data, but model accuracy remains insufficient except for that of paddy rice. The author shall accomplish the system that incorporates global environmental forces. Regarding crop production applications, industrialization in developing countries achieved through direct investment by economically developed nations raises their income, resulting in increased food demand. Last year, China began to import rice as it had in the past with grains of maize, wheat, and soybeans. Important agro-potential countries make efforts to cultivate new crop lands in South America, Africa, and Eastern Europe. Trends toward less food sustainability and stability are continuing, with exacerbation by rapid social and climate changes. Operational monitoring of carbon sequestration by herbaceous and bore plants converges with efforts at bio-energy, crop production monitoring, and socio-environmental projects such as CDM A/R, combating desertification, and bio-diversity.

THE GENESIS OF PHOTOSYNTHESIS TYPES AS THE BASIS OF ECOLOGICAL EXPANSION OF HALOPHYTIC PLANTS

Directory of Open Access Journals (Sweden)

Pyurko O.Ye.

2011-12-01

Full Text Available The C3, C4, and CAM photosynthesis types are considerably differed by CO2 absorption intensity, its biochemistry, saturation level, water productivity, biological productivity, and other different features, which secure the plants survival at stress and extreme conditions. The aim of current research was to discover the photosynthesis peculiarities at halophytic plants species (Salicornia europaea L., Halimione pedunculata, Artemisia santonica L., Plantago lanceolata L. by salinity at model and natural conditions, and to generalize data in historical aspect. It was constituted that S. europaea L. was characterized by C3 photosynthesis passage which was switched on CAM CO2 fixation under soil salinity conditions till 4-4,5 %, but glycophyte A.santonica was immanent C4assimilation way of aspartate type.Analysis of literature data and own research allows to find out that in majority the C3photosynthesis dependence from environmental factors described by determinate curve with matched mathematical expression. It was suggested to generalize the data by Lagrange polynomial. The obtained results proved that the pattern of photosynthesis evolution is: C3 → C4 → CAM with commute possibilities: C3 → CAM; C4 → CAM.

Water relations and photosynthesis along an elevation gradient for Artemisia tridentata during an historic drought.

Science.gov (United States)

Reed, Charlotte C; Loik, Michael E

2016-05-01

Quantifying the variation in plant-water relations and photosynthesis over environmental gradients and during unique events can provide a better understanding of vegetation patterns in a future climate. We evaluated the hypotheses that photosynthesis and plant water potential would correspond to gradients in precipitation and soil moisture during a lengthy drought, and that experimental water additions would increase photosynthesis for the widespread evergreen shrub Artemisia tridentata ssp. vaseyana. We quantified abiotic conditions and physiological characteristics for control and watered plants at 2135, 2315, and 2835 m near Mammoth Lakes, CA, USA, at the ecotone of the Sierra Nevada and Great Basin ecoregions. Snowfall, total precipitation, and soil moisture increased with elevation, but air temperature and soil N content did not. Plant water potential (Ψ), stomatal conductance (g s), maximum photosynthetic rate (A max), carboxylation rate (V cmax), and electron transport rate (J max) all significantly increased with elevations. Addition of water increased Ψ, g s, J max, and A max only at the lowest elevation; g s contributed about 30 % of the constraints on photosynthesis at the lowest elevation and 23 % at the other two elevations. The physiology of this foundational shrub species was quite resilient to this 1-in-1200 year drought. However, plant water potential and photosynthesis corresponded to differences in soil moisture across the gradient. Soil re-wetting in early summer increased water potential and photosynthesis at the lowest elevation. Effects on water relations and photosynthesis of this widespread, cold desert shrub species may be disproportionate at lower elevations as drought length increases in a future climate.

The paleobiological record of photosynthesis

OpenAIRE

William Schopf, J.

2010-01-01

Fossil evidence of photosynthesis, documented in Precambrian sediments by microbially laminated stromatolites, cyanobacterial microscopic fossils, and carbon isotopic data consistent with the presence of Rubisco-mediated CO2-fixation, extends from the present to ~3,500 million years ago. Such data, however, do not resolve time of origin of O2-producing photoautotrophy from its anoxygenic, bacterial, evolutionary precursor. Though it is well established that Earth’s ecosystem has been based on...

Misconception of biology education student of teacher training and education of Sriwijaya University to the concept of photosynthesis and respiration

Science.gov (United States)

Susanti, Rahmi

2018-05-01

This study aimed to gain an overview of misconceptions on the concept of photosynthesis and respiration. The study involved 58 students from Biology Education of Sriwijaya University. Collecting data used written test of 16 questions, which are 10 questions of multiple choice and 6 of choice with reason. The results showed that:photosynthesis occurs continuously (37.9%), energy used for photosynthesis are light and heat energy (34.5%), plants take CO2to respiration (47%), plants carry on respiration in the absence of light for photosynthesis (22.4%), respiration in plants occurs only in leaf cells (76.4%), and only animals that take O2 of photosynthesis to respiration (68.9%). The conclusion: 1) on the concept of photosynthesis is still prevailing misconceptions about the concept of the place and time of the occurrence of photosynthesis in plants, the role of the sun in photosynthesis, energy is required in the form of photosynthesis, and the role of photosynthesis for the plant. 2) on the concept of respiration is still prevailing misconceptions about the place of the respiration in plants, gas necessary for respiration of plants, and the plants perform respiration time, as well as the cycle of CO2 and O2 that occurs in nature.

An apparatus for field measurement of photosynthesis activity in plants using radioactive carbon dioxide

International Nuclear Information System (INIS)

Varshney, O.P.

1994-01-01

An apparatus was designed for rapid and accurate determination of photosynthesis rates in the field. It was standardised with respect to exposure time during which maize leaf was exposed to 14 CO 2 labelled air and the photosynthesis rates were measured

Green light drives leaf photosynthesis more efficiently than red light in strong white light: revisiting the enigmatic question of why leaves are green.

Science.gov (United States)

Terashima, Ichiro; Fujita, Takashi; Inoue, Takeshi; Chow, Wah Soon; Oguchi, Riichi

2009-04-01

The literature and our present examinations indicate that the intra-leaf light absorption profile is in most cases steeper than the photosynthetic capacity profile. In strong white light, therefore, the quantum yield of photosynthesis would be lower in the upper chloroplasts, located near the illuminated surface, than that in the lower chloroplasts. Because green light can penetrate further into the leaf than red or blue light, in strong white light, any additional green light absorbed by the lower chloroplasts would increase leaf photosynthesis to a greater extent than would additional red or blue light. Based on the assessment of effects of the additional monochromatic light on leaf photosynthesis, we developed the differential quantum yield method that quantifies efficiency of any monochromatic light in white light. Application of this method to sunflower leaves clearly showed that, in moderate to strong white light, green light drove photosynthesis more effectively than red light. The green leaf should have a considerable volume of chloroplasts to accommodate the inefficient carboxylation enzyme, Rubisco, and deliver appropriate light to all the chloroplasts. By using chlorophylls that absorb green light weakly, modifying mesophyll structure and adjusting the Rubisco/chlorophyll ratio, the leaf appears to satisfy two somewhat conflicting requirements: to increase the absorptance of photosynthetically active radiation, and to drive photosynthesis efficiently in all the chloroplasts. We also discuss some serious problems that are caused by neglecting these intra-leaf profiles when estimating whole leaf electron transport rates and assessing photoinhibition by fluorescence techniques.

Elements Required for an Efficient NADP-Malic Enzyme Type C4 Photosynthesis1[C][W][OPEN

Science.gov (United States)

Wang, Yu; Long, Stephen P.; Zhu, Xin-Guang

2014-01-01

C4 photosynthesis has higher light, nitrogen, and water use efficiencies than C3 photosynthesis. Although the basic anatomical, cellular, and biochemical features of C4 photosynthesis are well understood, the quantitative significance of each element of C4 photosynthesis to the high photosynthetic efficiency are not well defined. Here, we addressed this question by developing and using a systems model of C4 photosynthesis, which includes not only the Calvin-Benson cycle, starch synthesis, sucrose synthesis, C4 shuttle, and CO2 leakage, but also photorespiration and metabolite transport between the bundle sheath cells and mesophyll cells. The model effectively simulated the CO2 uptake rates, and the changes of metabolite concentrations under varied CO2 and light levels. Analyses show that triose phosphate transport and CO2 leakage can help maintain a high photosynthetic rate by balancing ATP and NADPH amounts in bundle sheath cells and mesophyll cells. Finally, we used the model to define the optimal enzyme properties and a blueprint for C4 engineering. As such, this model provides a theoretical framework for guiding C4 engineering and studying C4 photosynthesis in general. PMID:24521879

Measurement of solar spectra relating to photosynthesis and solar cells: an inquiry lab for secondary science.

Science.gov (United States)

Ruggirello, Rachel M; Balcerzak, Phyllis; May, Victoria L; Blankenship, Robert E

2012-07-01

The process of photosynthesis is central to science curriculum at all levels. This article describes an inquiry-based laboratory investigation developed to explore the impact of light quality on photosynthesis and to connect this process to current research on harvesting solar energy, including bioenergy, artificial photosynthesis, and solar cells. This laboratory was used with high-school science teachers who then took this experience back to their classrooms. During this exercise, teachers used an economical spectroradiometer to measure the solar spectrum and relate this to photosynthetic light absorption by determining the quality of light beneath trees. Following this investigation, teachers learned about the plant-inspired dye-sensitized solar cells and constructed one. To connect their light quality investigation to the efficiency of photosynthesis and solar cells, teachers then collected data at locations with varying quality and intensity of light. In sum, this investigation provides a crucial connection between photosynthesis and cutting edge research on solar energy technologies. Our learning experience provides a new instructional model for understanding a little investigated aspect of photosynthesis and connects to authentic scientific research. Copyright © 2012 Wiley Periodicals, Inc.

Promoting the Understanding of Photosynthesis among Elementary School Student Teachers through Text Design

Science.gov (United States)

Södervik, Ilona; Mikkilä-Erdmann, Mirjamaija; Vilppu, Henna

2014-01-01

The purpose of this study was to investigate elementary school pre-service teachers' understanding of photosynthesis and to examine if a refutational text can support understanding of photosynthesis better than a non-refutational text. A total of 91 elementary school pre-service teachers read either a refutational or a non-refutational text…

Inhibition of photosynthesis in the microalga Chaetoceros curvisetus (Bacillariophyta) by macroalga Gracilaria lemaneiformis (Rhodophyta)

Science.gov (United States)

Ye, Changpeng; Zhang, Mengcheng; Yang, Yufeng

2013-11-01

We investigated the effects of dried macroalga Gracilaria lemaneiformis (Rhodophyta) on photosynthesis of the bloom-forming microalga Chaetoceros curvisetus. C. curvisetus was cultured with different amounts of dried G. lemaneiformis under controlled laboratory conditions. We measured the photosynthetic oxygen evolution rate and established the chlorophyll a fluorescence transient (OJIP) curve coupled with its specific parameters. We observed concentration-dependent and time-dependent relationships between dried G. lemaneiformis and inhibition of photosynthesis in C. curvisetus. Co-culture with dried G. lemaneiformis also resulted in a decrease in the light-saturated maximum photosynthetic oxygen evolution rate ( P max) in C. curvisetus, and a decrease in the OJIP curve along with its specific parameters; the maximum photochemical efficiency of PSII ( F v / F m), the amount of active PSII reaction centers per excited cross section at t=0 and t= t FM (RC/CS0 and RC/CSm, respectively), the absorption flux per excited cross section at t =0 (ABS/ CS0), and the efficiency with which a trapped exciton moves an electron into the electron transport chain ( ψ 0). The dark respiration rate ( R d) increased in C. curvisetus co-cultured with dried G. lemaneiformis. The JIP-test and the oxygen evolution results indicated that dried G. lemaneiformis decreased the number of active reaction centers, blocked the electron transport chain, and damaged the oxygen-evolving complex of C. curvisetus. This result indicated that dried fragments of G. lemaneiformis could effectively inhibit photosynthesis of C. curvisetus, and thus, could serve as a functional product to control and mitigate C. curvisetus blooms.

How to Improve the Mastery of Students’ Concept on Photosynthesis Topic?

Science.gov (United States)

Ulfa, K.; Anggraeni, S.; Supriatno, B.

2017-09-01

The PPDP learning strategy in this research is the acronym of Practicum method, Presentation-discussion method, Demonstration method, and Presentation-discussion method. This study aims to describe the effect of applying PPDP learning strategies to mastery of high school students’ concepts on photosynthesis topic. The research method is a weak experiment, with the research design “The One-Group Pretest-Postetst Design”. The implementation of the study involved 35 students in one of the high schools in the city of Palembang. The research instrument used is in the form of test equipment, assessment rubric and questionnaire. Data were analyzed using Microsoft Excel and SPSS 24 Program. The statistical result showed that PPDP learning strategy had an effect on improving conceptual and Effective on the achievement of the value on the minimum criteria set by the school. This is due to the transformation of knowledge from hands-on to minds-on through the discovery of facts about the concept of photosynthesis. This fact leads to the construction of further understanding through cognitive sharing when the activities of the discussions formed similarity and consolidation of the concept of photosynthesis intact. In addition, demonstration activities also cause students’ logic of thinking to develop through observation of factors that may affect the rate of photosynthesis. This PPDP learning strategy can be utilized by teachers in explaining photosynthetic topic.

Continuous background light significantly increases flashing-light enhancement of photosynthesis and growth of microalgae.

Science.gov (United States)

Abu-Ghosh, Said; Fixler, Dror; Dubinsky, Zvy; Iluz, David

2015-01-01

Under specific conditions, flashing light enhances the photosynthesis rate in comparison to continuous illumination. Here we show that a combination of flashing light and continuous background light with the same integrated photon dose as continuous or flashing light alone can be used to significantly enhance photosynthesis and increase microalgae growth. To test this hypothesis, the green microalga Dunaliella salina was exposed to three different light regimes: continuous light, flashing light, and concomitant application of both. Algal growth was compared under three different integrated light quantities; low, intermediate, and moderately high. Under the combined light regime, there was a substantial increase in all algal growth parameters, with an enhanced photosynthesis rate, within 3days. Our strategy demonstrates a hitherto undescribed significant increase in photosynthesis and algal growth rates, which is beyond the increase by flashing light alone. Copyright © 2015 Elsevier Ltd. All rights reserved.

Ecophysiological modeling of photosynthesis and carbon allocation to the tree stem in the boreal forest

Science.gov (United States)

Gennaretti, Fabio; Gea-Izquierdo, Guillermo; Boucher, Etienne; Berninger, Frank; Arseneault, Dominique; Guiot, Joel

2017-11-01

A better understanding of the coupling between photosynthesis and carbon allocation in the boreal forest, together with its associated environmental factors and mechanistic rules, is crucial to accurately predict boreal forest carbon stocks and fluxes, which are significant components of the global carbon budget. Here, we adapted the MAIDEN ecophysiological forest model to consider important processes for boreal tree species, such as nonlinear acclimation of photosynthesis to temperature changes, canopy development as a function of previous-year climate variables influencing bud formation and the temperature dependence of carbon partition in summer. We tested these modifications in the eastern Canadian taiga using black spruce (Picea mariana (Mill.) B.S.P.) gross primary production and ring width data. MAIDEN explains 90 % of the observed daily gross primary production variability, 73 % of the annual ring width variability and 20-30 % of its high-frequency component (i.e., when decadal trends are removed). The positive effect on stem growth due to climate warming over the last several decades is well captured by the model. In addition, we illustrate how we improve the model with each introduced model adaptation and compare the model results with those of linear response functions. Our results demonstrate that MAIDEN simulates robust relationships with the most important climate variables (those detected by classical response-function analysis) and is a powerful tool for understanding how environmental factors interact with black spruce ecophysiology to influence present-day and future boreal forest carbon fluxes.

Sugars from woody tissue photosynthesis reduce xylem vulnerability to cavitation.

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De Baerdemaeker, Niels J F; Salomón, Roberto Luis; De Roo, Linus; Steppe, Kathy

2017-11-01

Reassimilation of internal CO 2 via woody tissue photosynthesis has a substantial effect on tree carbon income and wood production. However, little is known about its role in xylem vulnerability to cavitation and its implications in drought-driven tree mortality. Young trees of Populus nigra were subjected to light exclusion at the branch and stem levels. After 40 d, measurements of xylem water potential, diameter variation and acoustic emission (AE) were performed in detached branches to obtain acoustic vulnerability curves to cavitation following bench-top dehydration. Acoustic vulnerability curves and derived AE 50 values (i.e. water potential at which 50% of cavitation-related acoustic emissions occur) differed significantly between light-excluded and control branches (AE 50,light-excluded  = -1.00 ± 0.13 MPa; AE 50,control  = -1.45 ± 0.09 MPa; P = 0.007) denoting higher vulnerability to cavitation in light-excluded trees. Woody tissue photosynthesis represents an alternative and immediate source of nonstructural carbohydrates (NSC) that confers lower xylem vulnerability to cavitation via sugar-mediated mechanisms. Embolism repair and xylem structural changes could not explain this observation as the amount of cumulative AE and basic wood density did not differ between treatments. We suggest that woody tissue assimilates might play a role in the synthesis of xylem surfactants for nanobubble stabilization under tension. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

Photosynthesis of amphibious and obligately submerged plants in CO2-rich lowland streams.

Science.gov (United States)

Sand-Jensen, Kaj; Frost-Christensen, Henning

1998-11-01

Small unshaded streams in lowland regions receive drainage water with high concentrations of free␣CO 2 , and they support an abundant growth of amphibious and obligately submerged plants. Our first objective was to measure the CO 2 regime during summer in a wide range of small alkaline Danish streams subject to wide variation in temperature, O 2 and CO 2 during the day. The second objective was to determine the effect of these variations on daily changes in light-saturated photosynthesis in water of a homophyllous and a heterophyllous amphibious species that only used CO 2 , and an obligately submerged species capable of using both HCO - 3 and CO 2 . We found that the median CO 2 concentrations of the streams were 11 and 6 times above air saturation in the morning and the afternoon, respectively, but stream sites with dense plant growth had CO 2 concentrations approaching air saturation in the afternoon. In contrast, outlets from lakes had low CO 2 concentrations close to, or below, air saturation. The amphibious species showed a reduction of photosynthesis in water from morning to afternoon along with the decline in CO 2 concentrations, while increasing temperature and O 2 had little effect on photosynthesis. Photosynthesis of the obligately submerged species varied little with the change of CO 2 because of HCO 3 - - use, and variations were mostly due to changes in O 2 concentration. Independent measurements showed that changes in temperature, O 2 and CO 2 could account for the daily variability of photosynthesis of all three species in water. The results imply that CO 2 supersaturation in small lowland streams is important for the rich representation of amphibious species and their contribution to system photosynthesis.

Prokaryotic photosynthesis and phototrophy illuminated

DEFF Research Database (Denmark)

Bryant, Donald A; Frigaard, Niels-Ulrik

2006-01-01

Genome sequencing projects are revealing new information about the distribution and evolution of photosynthesis and phototrophy. Although coverage of the five phyla containing photosynthetic prokaryotes (Chlorobi, Chloroflexi, Cyanobacteria, Proteobacteria and Firmicutes) is limited and uneven...... components that have not yet been described. Metagenomics has already shown how the relatively simple phototrophy based upon rhodopsins has spread laterally throughout Archaea, Bacteria and eukaryotes. In this review, we present examples that reflect recent advances in phototroph biology as a result...

Effects of fully open-air [CO2] elevation on leaf photosynthesis and ultrastructure of Isatis indigotica fort.

Science.gov (United States)

Hao, Xingyu; Li, Ping; Feng, Yongxiang; Han, Xue; Gao, Ji; Lin, Erda; Han, Yuanhuai

2013-01-01

Traditional Chinese medicine relies heavily on herbs, yet there is no information on how these herb plants would respond to climate change. In order to gain insight into such response, we studied the effect of elevated [CO2] on Isatis indigotica Fort, one of the most popular Chinese herb plants. The changes in leaf photosynthesis, chlorophyll fluorescence, leaf ultrastructure and biomass yield in response to elevated [CO2] (550±19 µmol mol(-1)) were determined at the Free-Air Carbon dioxide Enrichment (FACE) experimental facility in North China. Photosynthetic ability of I. indigotica was improved under elevated [CO2]. Elevated [CO2] increased net photosynthetic rate (P N), water use efficiency (WUE) and maximum rate of electron transport (J max) of upper most fully-expended leaves, but not stomatal conductance (gs), transpiration ratio (Tr) and maximum velocity of carboxylation (V c,max). Elevated [CO2] significantly increased leaf intrinsic efficiency of PSII (Fv'/Fm') and quantum yield of PSII(ΦPS II ), but decreased leaf non-photochemical quenching (NPQ), and did not affect leaf proportion of open PSII reaction centers (qP) and maximum quantum efficiency of PSII (Fv/Fm). The structural chloroplast membrane, grana layer and stroma thylakoid membranes were intact under elevated [CO2], though more starch grains were accumulated within the chloroplasts than that of under ambient [CO2]. While the yield of I. indigotica was higher due to the improved photosynthesis under elevated [CO2], the content of adenosine, one of the functional ingredients in indigowoad root was not affected.

Strategies for Efficient Charge Separation and Transfer in Artificial Photosynthesis of Solar Fuels.

Science.gov (United States)

Xu, Yuxing; Li, Ailong; Yao, Tingting; Ma, Changtong; Zhang, Xianwen; Shah, Jafar Hussain; Han, Hongxian

2017-11-23

Converting sunlight to solar fuels by artificial photosynthesis is an innovative science and technology for renewable energy. Light harvesting, photogenerated charge separation and transfer (CST), and catalytic reactions are the three primary steps in the processes involved in the conversion of solar energy to chemical energy (SE-CE). Among the processes, CST is the key "energy pump and delivery" step in determining the overall solar-energy conversion efficiency. Efficient CST is always high priority in designing and assembling artificial photosynthesis systems for solar-fuel production. This Review not only introduces the fundamental strategies for CST but also the combinatory application of these strategies to five types of the most-investigated semiconductor-based artificial photosynthesis systems: particulate, Z-scheme, hybrid, photoelectrochemical, and photovoltaics-assisted systems. We show that artificial photosynthesis systems with high SE-CE efficiency can be rationally designed and constructed through combinatory application of these strategies, setting a promising blueprint for the future of solar fuels. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Functional Insights from Structural Genomics

Energy Technology Data Exchange (ETDEWEB)

Forouhar,F.; Kuzin, A.; Seetharaman, J.; Lee, I.; Zhou, W.; Abashidze, M.; Chen, Y.; Montelione, G.; Tong, L.; et al

2007-01-01

Structural genomics efforts have produced structural information, either directly or by modeling, for thousands of proteins over the past few years. While many of these proteins have known functions, a large percentage of them have not been characterized at the functional level. The structural information has provided valuable functional insights on some of these proteins, through careful structural analyses, serendipity, and structure-guided functional screening. Some of the success stories based on structures solved at the Northeast Structural Genomics Consortium (NESG) are reported here. These include a novel methyl salicylate esterase with important role in plant innate immunity, a novel RNA methyltransferase (H. influenzae yggJ (HI0303)), a novel spermidine/spermine N-acetyltransferase (B. subtilis PaiA), a novel methyltransferase or AdoMet binding protein (A. fulgidus AF{_}0241), an ATP:cob(I)alamin adenosyltransferase (B. subtilis YvqK), a novel carboxysome pore (E. coli EutN), a proline racemase homolog with a disrupted active site (B. melitensis BME11586), an FMN-dependent enzyme (S. pneumoniae SP{_}1951), and a 12-stranded {beta}-barrel with a novel fold (V. parahaemolyticus VPA1032).

Biofuel crops with CAM photosynthesis: Economic potential on moisture-limited lands

Science.gov (United States)

Bartlett, Mark; Hartzell, Samantha; Porporato, Amilcare

2017-04-01

As the demand for food and renewable energy increases, the intelligent utilization of marginal lands is becoming increasingly critical. In marginal lands classified by limited rainfall or soil salinity, the cultivation of traditional C3 and C4 photosynthesis crops often is economically infeasible. However, in such lands, nontraditional crops with crassulacean acid metabolism (CAM) photosynthesis show great economic potential for cultivation. CAM crops including Opuntia (prickly pear) and Ananas (pineapple) achieve a water use efficiency which is three fold higher than C4 crops such as corn and 6-fold higher than C3 crops such as wheat, leading to a comparable annual productivity with only 20% of the water demand. This feature, combined with a shallow rooting depth and a high water storage capacity, allows CAM plants to take advantage of small, infrequent rainfall amounts in shallow, quickly draining soils. Furthermore, CAM plants typically have properties (e.g., high content of non-structural carbohydrates) that are favorable for biofuel production. Here, for marginal lands characterized by low soil moisture availability and/or high salinity, we assess the potential productivity and economic benefits of CAM plants. CAM productivity is estimated using a recently developed model which simulates CAM photosynthesis under a range of soil and climate conditions. From these results, we compare the energy and water resource inputs required by CAM plants to those required by more traditional C3 and C4 crops (corn, wheat, sorghum), and we evaluate the economic potential of CAM crops as sources of food, fodder, or biofuel in marginal soils. As precipitation events become more intense and infrequent, we show that even though marginal land area may increase, CAM crop cultivation shows great promise for maintaining high productivity with minimal water inputs. Our analysis indicates that on marginal lands, widespread cultivation of CAM crops as biofuel feedstock may help

Gaseous NO2 effects on stomatal behavior, photosynthesis and respiration of hybrid poplar leaves

Science.gov (United States)

In this study, we used poplar as a model plant and investigated the effects of gaseous nitrogen dioxide (NO2, 4 microliter per liter) on stomatal conductance, photosynthesis, dark- and photorespiration of Populus alba x Populus berolinensis hybrid leaves using the photosynthesis system and scanning...

Effect of gamma radiation on chlorophylls contents, net photosynthesis and respiration of chlorella pyrenoidosa

International Nuclear Information System (INIS)

Fernandez Gonzalez, J.; Martin Moreno, C.

1983-01-01

The effect of five doses of gamma radiation: 10, 100, 500, 1000 and 5000 Gy on chlorophylls content, net photosynthesis and respiration of chlorella pyrenoidosa has been studied. A decrease in chlorophylls levels is produced after irradiation at 500, 1000 and 5000 Gy, being, at first 'b' chlorophyll affected to a greater extent than 'a' chlorophyll. Net photosynthesis and respiration decline throughout the time of the observations after irradiation, this depressing effect being much more remarkable for the first one. Net photosynthesis inhibition levels of about 30% have got only five hours post irradiation at a dose of 5000 Gy. (author)

Effects of primitive photosynthesis on Earth's early climate system

Science.gov (United States)

Ozaki, Kazumi; Tajika, Eiichi; Hong, Peng K.; Nakagawa, Yusuke; Reinhard, Christopher T.

2018-01-01

The evolution of different forms of photosynthetic life has profoundly altered the activity level of the biosphere, radically reshaping the composition of Earth's oceans and atmosphere over time. However, the mechanistic impacts of a primitive photosynthetic biosphere on Earth's early atmospheric chemistry and climate are poorly understood. Here, we use a global redox balance model to explore the biogeochemical and climatological effects of different forms of primitive photosynthesis. We find that a hybrid ecosystem of H2-based and Fe2+-based anoxygenic photoautotrophs—organisms that perform photosynthesis without producing oxygen—gives rise to a strong nonlinear amplification of Earth's methane (CH4) cycle, and would thus have represented a critical component of Earth's early climate system before the advent of oxygenic photosynthesis. Using a Monte Carlo approach, we find that a hybrid photosynthetic biosphere widens the range of geochemical conditions that allow for warm climate states well beyond either of these metabolic processes acting in isolation. Our results imply that the Earth's early climate was governed by a novel and poorly explored set of regulatory feedbacks linking the anoxic biosphere and the coupled H, C and Fe cycles. We suggest that similar processes should be considered when assessing the potential for sustained habitability on Earth-like planets with reducing atmospheres.

Regulation of Calcium on Peanut Photosynthesis Under Low Night Temperature Stress

Institute of Scientific and Technical Information of China (English)

LIU Yi-fei; HAN Xiao-ri; ZHAN Xiu-mei; YANG Jin-feng; WANG Yu-zhi; SONG Qiao-bo; CHEN Xin

2013-01-01

The effects of different levels of CaCl2 on photosynthesis under low night temperature (8°C) stress in peanuts were studied in order to ifnd out the appropriate concentration of Ca2+ through the artiifcial climate chamber potted culture test. The results indicated that Ca2+, by means of improving the stomatal conductivity of peanut leaves under low night temperature stress, may mitigate the decline of photosynthetic rate in the peanut leaves. The regulation with 15 mmol L-1 CaCl2 (Ca15) was the most effective, compared with other treatments. Subsequently, the improvement of Ca2+ on peanut photosynthesis under low night temperature stress was validated further through spraying withCa15, Ca2+ chelator (ethylene glycol bis(2-aminoethyl) tetraacetic acid; EGTA) and calmodulin antagonists (trilfuonerazine; TFP).And CaM (Ca2+-modulin) played an important role in the nutritional signal transduction for Ca2+ mitigating photosynthesis limitations in peanuts under low night temperature stress.

Spin dependent photon structure functions

International Nuclear Information System (INIS)

Manohar, A.V.; Massachusetts Inst. of Tech., Cambridge

1989-01-01

Spin dependent structure functions of the photon are studied using the operator product expansion. There are new twist-two photon and gluon operators which contribute. The structure functions g 1 and F 3 are calculable in QCD, but differ from their free quark values. The corrections to F 3 are suppressed by 1/log Q 2 . The calculation is an extension of the analysis of Witten for the spin averaged structure functions F 1 and F 2 . (orig.)

Photosynthesis involvement in the mechanism of action of diphenyl ether herbicides.

Science.gov (United States)

Ensminger, M P; Hess, F D

1985-05-01

Photosynthesis is not required for the toxicity of diphenyl ether herbicides, nor are chloroplast thylakoids the primary site of diphenyl ether herbicide activity. Isolated spinach (Spinacia oleracea L.) chloroplast fragments produced malonyl dialdehyde, indicating lipid peroxidation, when paraquat (1,1'-dimethyl-4,4'-bipyridinium ion) or diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] were added to the medium, but no malonyl dialdehyde was produced when chloroplast fragments were treated with the methyl ester of acifluorfen (methyl 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid), oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene], or MC15608 (methyl 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-chlorobenzoate). In most cases the toxicity of acifluorfen-methyl, oxyfluorfen, or MC15608 to the unicellular green alga Chlamydomonas eugametos (Moewus) did not decrease after simultaneous treatment with diuron. However, diuron significantly reduced cell death after paraquat treatment at all but the highest paraquat concentration tested (0.1 millimolar). These data indicate electron transport of photosynthesis is not serving the same function for diphenyl ether herbicides as for paraquat. Additional evidence for differential action of paraquat was obtained from the superoxide scavenger copper penicillamine (copper complex of 2-amino-3-mercapto-3-methylbutanoic acid). Copper penicillamine eliminated paraquat toxicity in cucumber (Cucumis sativus L.) cotyledons but did not reduce diphenyl ether herbicide toxicity.

Calculations of nucleon structure functions

International Nuclear Information System (INIS)

Signal, A.I.

1990-01-01

We present a method of calculating deep inelastic nucleon structure functions using bag model wavefunctions. Our method uses the Peierls - Yoccoz projection to form translation invariant bag states. We obtain the correct support for the structure functions and satisfy the positivity requirements for quark and anti-quark distribution functions. (orig.)

Physiological bases for detecting and predicting photoinhibition of aquatic photosynthesis by PAR and UV radiation

International Nuclear Information System (INIS)

Neale, P.J.; Cullen, J.J.; Lesser, M.P.; Melis, A.

1993-01-01

stress is usually time dependent (12, 36); the light history of the cells must be known to specify the overall effect. The established method for measuring phytoplankton production, photosynthetic incorporation of 14 C into organic carbon during a12-24 h bottle incubation, may seriously misrepresent irradiance regimes actually experienced by phytoplankton in situ. Further discussion of the interaction of photoinhibition and mixing can be found in (36).We propose that an integrated modeling-sampling approach is needed to define the effects of irradiance stress on productivity in situ. The model should incorporate an optical specification of the underwater irradiance environment, abiological weighting function to account for the wavelength-dependence of photoinhibition of photosynthesis, and a response function of biological action during vertical mixing to account for the differences between static incubations and natural movements of phytoplankton. Recently, excellent progress has been made toward defining the individual components of this model (See also Cullen and Neale, this volume). To verify the model, we need to detect reliably the occurrence of irradiance stress in situ. This is the sampling side of the integrated approach. In particular, we would like to differentiate between the effects of PAR and UV. We propose that such detection can be accomplished by indicator assays (or ''diagnostic markers''). Such assays would involve little or no incubation of samples, so that the measurement corresponds as closely as possible to the physiological state of the phytoplankton at time of sampling.Our objective here is to review selected aspects of irradiance stress at biophysical and molecular levels, and then proceed to examine how that information can be used to design indicator assays of irradiance stress for phytoplankton photosynthesis in situ. The effects of PAR and UV at the cellular level and the use of in vivo fluorescence and molecular probes

Crassulacean acid metabolism enhances underwater photosynthesis and diminishes photorespiration in the aquatic plant Isoetes australis

DEFF Research Database (Denmark)

Pedersen, Ole; Rich, S.M.; Pulido Pérez, Cristina

2011-01-01

Underwater photosynthesis by aquatic plants is often limited by low availability of CO2, and photorespiration can be high. Some aquatic plants utilize crassulacean acid metabolism (CAM) photosynthesis. The benefits of CAM for increased underwater photosynthesis and suppression of photorespiration...... photorespiration was evident at a range of O2 concentrations, including values below air equilibrium. At a high O2 concentration of 2.2-fold the atmospheric equilibrium concentration, net photosynthesis was reduced substantially and, although it remained positive in leaves containing high malate concentrations...... were evaluated for Isoetes australis, a submerged plant that inhabits shallow temporary rock pools. • Leaves high or low in malate were evaluated for underwater net photosynthesis and apparent photorespiration at a range of CO2 and O2 concentrations. • CAM activity was indicated by 9.7-fold higher leaf...

Teaching Photosynthesis in a Compulsory School Context. Students’ Reasoning, Understanding and Interactions.

Directory of Open Access Journals (Sweden)

Helena Näs

2011-02-01

Full Text Available According to previous research, students show difficulties in understanding photosynthesis and respiration, and basic ecological concepts like energy flow in ecosystems. There are successful teaching units accomplished in this area and many of them can be described as inquiry-based teaching. One definition of inquiry-based teaching is that it involves everything from finding problems, investigating them, debating with peers and trying to explain and give solutions. Accordingly students need to be confronted with challenging questions and empirical data to reason about and teachers need to implement student-generated inquiry discussion since students often stay silent and do not express their thoughts during science lessons. This thesis will focus on young peoples’ understanding of the functioning of plants, students’ participation during biology lessons, and how biology teaching is accomplished in primary and secondary school.Two school classroom projects focusing on teaching about plants and ecology are described. Four teachers and their 4th, 5th and 6th grade classes plus two science teachers and their three 8th grade classes collaborated. Photosynthesis and respiration were made concrete by using tasks where plants, plant cells, germs, seeds and the gas exchange were used. The aim was to listen to students’ reasoning in both teaching and interview situations. Learning outcome, as described by students’ reasoning in the classrooms and in individual interviews but also by their test results, is especially focused. Student-student and student-teacher interactions have been analysed with an ethnographic approach in the classroom context.The plant tasks encouraged the students’ in primary school to develop scientific reasoning and the interviews confirmed that the students had learned about photosynthesis. The ecology teaching in secondary school showed a substantial understanding confirmed both by students’ oral and written

Ecosystem warming does not affect photosynthesis or aboveground autotrophic respiration for boreal black spruce

Energy Technology Data Exchange (ETDEWEB)

Bronson, D.R. [Wyoming Univ., Laramie, WY (United States). Dept. of Renewable Resources; Gower, S.T. [Wisconsin Univ., Madison, WI (United States). Dept. of Forest Ecology and Management

2010-04-15

Substantial increases in climatic temperatures may cause boreal forests to become a carbon source. An improved understanding of the effect of climatic warming on photosynthesis and autotrophic respiration is needed in order to determine the impact of temperature increases on net carbon balances. This study measured the light-saturated photosynthesis foliage respiration and stem respiration of black spruce in heated and control plots during a 3-year period at a site located in Thompson, Manitoba. Greenhouses and soil-heating cables were used to maintain air and soil temperatures at 5 degrees C above ambient air and soil temperatures. Studies were conducted to determine the influence of soil and air warming; soil-only warming; and greenhouses maintained at ambient temperatures. The study showed that treatment differences for photosynthesis, foliage respiration, and stem respiration were not significant over the 3-year period. Results suggested that black spruce may not have significant changes in photosynthesis or respiration rates in warmer climates. 38 refs., 3 tabs., 4 figs.

Role of seagrass photosynthesis in root aerobic processes.

Science.gov (United States)

Smith, R D; Dennison, W C; Alberte, R S

1984-04-01

The role of shoot photosynthesis as a means of supporting aerobic respiration in the roots of the seagrass Zostera marina was examined. O(2) was transported rapidly (10-15 minutes) from the shoots to the root-rhizome tissues upon shoot illumination. The highest rates of transport were in shoots possessing the greatest biomass and leaf area. The rates of O(2) transport do not support a simple gas phase diffusion mechanism. O(2) transport to the root-rhizome system supported aerobic root respiration and in many cases exceeded respiratory requirements leading to O(2) release from the subterranean tissue. Release of O(2) can support aerobic processes in reducing sediments typical of Z. marina habitats. Since the root-rhizome respiration is supported primarily under shoot photosynthetic conditions, then the daily period of photosynthesis determines the diurnal period of root aerobiosis.

Anthocyanin-dependent anoxygenic photosynthesis in coloured flower petals?

Science.gov (United States)

Lysenko, Vladimir; Varduny, Tatyana

2013-11-01

Chlorophylless flower petals are known to be composed of non-photosynthetic tissues. Here, we show that the light energy storage that can be photoacoustically measured in flower petals of Petunia hybrida is approximately 10-12%. We found that the supposed chlorophylless photosynthesis is an anoxygenic, anthocyanin-dependent process occurring in blue flower petals (ADAPFP), accompanied by non-respiratory light-dependent oxygen uptake and a 1.5-fold photoinduced increase in ATP levels. Using a simple, adhesive tape stripping technique, we have obtained a backside image of an intact flower petal epidermis, revealing sword-shaped ingrowths connecting the cell wall and vacuole, which is of interest for the further study of possible vacuole-related photosynthesis. Approaches to the interpretations of ADAPFP are discussed, and we conclude that these results are not impossible in terms of the known photochemistry of anthocyanins.

Nucleon structure functions

International Nuclear Information System (INIS)

Virchaux, M.

1992-11-01

The present status of experimental measurements of the nucleon structure functions is reviewed. The results from nearly all deep inelastic experiments are in good mutual agreement. Principles of the analysis of these structure function data in the framework of QCD are described. The specific features of the perturbative QCD predictions are observed in the data. This provides quantitative tests of the validity of QCD as well as determinations of the various parton distributions in the nucleon and some of the most precise measurements of the strong coupling constant αs. The future of this field of experimental physics is sketched

Major alterations in transcript profiles between C3-C4 and C4 photosynthesis of an amphibious species Eleocharis baldwinii.

Science.gov (United States)

Chen, Taiyu; Zhu, Xin-Guang; Lin, Yongjun

2014-09-01

Engineering C4 photosynthetic metabolism into C3 crops is regarded as a major strategy to increase crop productivity, and clarification of the evolutionary processes of C4 photosynthesis can help the better use of this strategy. Here, Eleocharis baldwinii, a species in which C4 photosynthesis can be induced from a C3-C4 state under either environmental or ABA treatments, was used to identify the major transcriptional modifications during the process from C3-C4 to C4. The transcriptomic comparison suggested that in addition to the major differences in C4 core pathway, the pathways of glycolysis, citrate acid metabolism and protein synthesis were dramatically modified during the inducement of C4 photosynthetic states. Transcripts of many transporters, including not only metabolite transporters but also ion transporters, were dramatically increased in C4 photosynthetic state. Many candidate regulatory genes with unidentified functions were differentially expressed in C3-C4 and C4 photosynthetic states. Finally, it was indicated that ABA, auxin signaling and DNA methylation play critical roles in the regulation of C4 photosynthesis. In summary, by studying the different photosynthetic states of the same species, this work provides the major transcriptional differences between C3-C4 and C4 photosynthesis, and many of the transcriptional differences are potentially related to C4 development and therefore are the potential targets for reverse genetics studies.

Salinity-dependent limitation of photosynthesis and oxygen exchange in microbial mats

DEFF Research Database (Denmark)

Garcia-Pichel, F.; Kühl, Michael; Nübel, U.

1999-01-01

was specific for each community and in accordance with optimal performance at the respective salinity of origin. This pattern was lost after long-term exposure to varying salinities when responses to salinity were found to approach a general pattern of decreasing photosynthesis and oxygen exchange capacity...... with increasing salinity. Exhaustive measurements of oxygen export in the light, oxygen consumption in the dark and gross photosynthesis indicated that a salinity-dependent limitation of all three parameters occurred. Maximal values for all three parameters decreased exponentially with increasing salinity...

Chromatin Structure and Function

CERN Document Server

Wolffe, Alan P

1999-01-01

The Third Edition of Chromatin: Structure and Function brings the reader up-to-date with the remarkable progress in chromatin research over the past three years. It has been extensively rewritten to cover new material on chromatin remodeling, histone modification, nuclear compartmentalization, DNA methylation, and transcriptional co-activators and co-repressors. The book is written in a clear and concise fashion, with 60 new illustrations. Chromatin: Structure and Function provides the reader with a concise and coherent account of the nature, structure, and assembly of chromatin and its active

Estimating photosynthesis and concurrent export rates in C3 and C4 species at ambient and elevated CO2

International Nuclear Information System (INIS)

Grodzinski, B.; Jiao, J.; Leonardos, E.D.

1998-01-01

The ability of 21 C3 and C4 monocot and dicot species to rapidly export newly fixed C in the light at both ambient and enriched CO2 levels was compared. Photosynthesis and concurrent export rates were estimated during isotopic equilibrium of the transport sugars using a steady-state 14CO2-labeling procedure. At ambient CO2 photosynthesis and export rates for C3 species were 5 to 15 and 1 to 10 micromole C m-2 s-1, respectively, and 20 to 30 and 15 to 22 micromole C m-2 s-1, respectively, for C4 species. A linear regression plot of export on photosynthesis rate of all species had a correlation coefficient of 0.87. When concurrent export was expressed as a percentage of photosynthesis, several C3 dicots that produced transport sugars other than Suc had high efflux rates relative to photosynthesis, comparable to those of C4 species. At high CO2 photosynthetic and export rates were only slightly altered in C4 species, and photosynthesis increased but export rates did not in all C3 species. The C3 species that had high efflux rates relative to photosynthesis at ambient CO2 exported at rates comparable to those of C4 species on both an absolute basis and as a percentage of photosynthesis. At ambient CO2 there were strong linear relationships between photosynthesis, sugar synthesis, and concurrent export. However, at high CO2 the relationships between photosynthesis and export rate and between sugar synthesis and export rate were not as strong because sugars and starch were accumulated

Temperature effects on respiration and photosynthesis in three diatom-dominated benthic communities

DEFF Research Database (Denmark)

Hancke, Kasper; Glud, R.N.

2004-01-01

ABSTRACT: Short-term temperature effects on respiration and photosynthesis were investigated in intact diatom-dominated benthic communities, collected at 2 temperate and 1 high-arctic subtidal sites. Areal rates of total (TOE) and diffusive (DOE) O2 exchange were determined from O2-microsensor....... This can be ascribed to changes in physical and biological controls during resuspension. Gross photosynthesis was measured with the light-dark shift method at the 2 temperate sites. Both areal (Pgross) and volumetric (Pgross,vol) rates increased with temperature to an optimum temperature at 12 and 15°C......, with a Q10 for Pgross of 2.2 and 2.6 for the 2 sites, respectively. The gross photosynthesis response could be categorised as psychrotrophic for both sites and no temperature adaptation was observed between the 2 sites. Our measurements document that temperature stimulates heterotrophic activity more than...

A roadmap for improving the representation of photosynthesis in Earth system models.

Science.gov (United States)

Rogers, Alistair; Medlyn, Belinda E; Dukes, Jeffrey S; Bonan, Gordon; von Caemmerer, Susanne; Dietze, Michael C; Kattge, Jens; Leakey, Andrew D B; Mercado, Lina M; Niinemets, Ülo; Prentice, I Colin; Serbin, Shawn P; Sitch, Stephen; Way, Danielle A; Zaehle, Sönke

2017-01-01

Accurate representation of photosynthesis in terrestrial biosphere models (TBMs) is essential for robust projections of global change. However, current representations vary markedly between TBMs, contributing uncertainty to projections of global carbon fluxes. Here we compared the representation of photosynthesis in seven TBMs by examining leaf and canopy level responses of photosynthetic CO 2 assimilation (A) to key environmental variables: light, temperature, CO 2 concentration, vapor pressure deficit and soil water content. We identified research areas where limited process knowledge prevents inclusion of physiological phenomena in current TBMs and research areas where data are urgently needed for model parameterization or evaluation. We provide a roadmap for new science needed to improve the representation of photosynthesis in the next generation of terrestrial biosphere and Earth system models. No claim to original US Government works New Phytologist © 2016 New Phytologist Trust.

Carotenoids assist in cyanobacterial Photosystem II assembly and function

Directory of Open Access Journals (Sweden)

Tomas eZakar

2016-03-01

Full Text Available Carotenoids (carotenes and xanthophylls are ubiquitous constituents of living organisms. They are protective agents against oxidative stresses and serve as modulators of membrane microviscosity. As antioxidants they can protect photosynthetic organisms from free radicals like reactive oxygen species that originate from water splitting, the first step of photosynthesis. We summarize the structural and functional roles of carotenoids in connection with cyanobacterial Photosystem II. Although carotenoids are hydrophobic molecules, their complexes with proteins also allow cytoplasmic localization. In cyanobacterial cells such complexes are called orange carotenoid proteins, and they protect Photosystem II and Photosystem I by preventing their overexcitation through phycobilisomes. Recently it has been observed that carotenoids are not only required for the proper functioning, but also for the structural stability of phycobilisomes.

The role of photorespiration during the evolution of C4 photosynthesis in the genus Flaveria.

Science.gov (United States)

Mallmann, Julia; Heckmann, David; Bräutigam, Andrea; Lercher, Martin J; Weber, Andreas P M; Westhoff, Peter; Gowik, Udo

2014-06-16

C4 photosynthesis represents a most remarkable case of convergent evolution of a complex trait, which includes the reprogramming of the expression patterns of thousands of genes. Anatomical, physiological, and phylogenetic and analyses as well as computational modeling indicate that the establishment of a photorespiratory carbon pump (termed C2 photosynthesis) is a prerequisite for the evolution of C4. However, a mechanistic model explaining the tight connection between the evolution of C4 and C2 photosynthesis is currently lacking. Here we address this question through comparative transcriptomic and biochemical analyses of closely related C3, C3-C4, and C4 species, combined with Flux Balance Analysis constrained through a mechanistic model of carbon fixation. We show that C2 photosynthesis creates a misbalance in nitrogen metabolism between bundle sheath and mesophyll cells. Rebalancing nitrogen metabolism requires anaplerotic reactions that resemble at least parts of a basic C4 cycle. Our findings thus show how C2 photosynthesis represents a pre-adaptation for the C4 system, where the evolution of the C2 system establishes important C4 components as a side effect.

Chloroplast Chaperonin: An Intricate Protein Folding Machine for Photosynthesis

Directory of Open Access Journals (Sweden)

Qian Zhao

2018-01-01

Full Text Available Group I chaperonins are large cylindrical-shaped nano-machines that function as a central hub in the protein quality control system in the bacterial cytosol, mitochondria and chloroplasts. In chloroplasts, proteins newly synthesized by chloroplast ribosomes, unfolded by diverse stresses, or translocated from the cytosol run the risk of aberrant folding and aggregation. The chloroplast chaperonin system assists these proteins in folding into their native states. A widely known protein folded by chloroplast chaperonin is the large subunit of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco, an enzyme responsible for the fixation of inorganic CO2 into organic carbohydrates during photosynthesis. Chloroplast chaperonin was initially identified as a Rubisco-binding protein. All photosynthetic eucaryotes genomes encode multiple chaperonin genes which can be divided into α and β subtypes. Unlike the homo-oligomeric chaperonins from bacteria and mitochondria, chloroplast chaperonins are more complex and exists as intricate hetero-oligomers containing both subtypes. The Group I chaperonin requires proper interaction with a detachable lid-like co-chaperonin in the presence of ATP and Mg2+ for substrate encapsulation and conformational transition. Besides the typical Cpn10-like co-chaperonin, a unique co-chaperonin consisting of two tandem Cpn10-like domains joined head-to-tail exists in chloroplasts. Since chloroplasts were proposed as sensors to various environmental stresses, this diversified chloroplast chaperonin system has the potential to adapt to complex conditions by accommodating specific substrates or through regulation at both the transcriptional and post-translational levels. In this review, we discuss recent progress on the unique structure and function of the chloroplast chaperonin system based on model organisms Chlamydomonas reinhardtii and Arabidopsis thaliana. Knowledge of the chloroplast chaperonin system may ultimately lead

Oxygenic photosynthesis: translation to solar fuel technologies

Directory of Open Access Journals (Sweden)

Julian David Janna Olmos

2014-12-01

Full Text Available Mitigation of man-made climate change, rapid depletion of readily available fossil fuel reserves and facing the growing energy demand that faces mankind in the near future drive the rapid development of economically viable, renewable energy production technologies. It is very likely that greenhouse gas emissions will lead to the significant climate change over the next fifty years. World energy consumption has doubled over the last twenty-five years, and is expected to double again in the next quarter of the 21st century. Our biosphere is at the verge of a severe energy crisis that can no longer be overlooked. Solar radiation represents the most abundant source of clean, renewable energy that is readily available for conversion to solar fuels. Developing clean technologies that utilize practically inexhaustible solar energy that reaches our planet and convert it into the high energy density solar fuels provides an attractive solution to resolving the global energy crisis that mankind faces in the not too distant future. Nature’s oxygenic photosynthesis is the most fundamental process that has sustained life on Earth for more than 3.5 billion years through conversion of solar energy into energy of chemical bonds captured in biomass, food and fossil fuels. It is this process that has led to evolution of various forms of life as we know them today. Recent advances in imitating the natural process of photosynthesis by developing biohybrid and synthetic “artificial leaves” capable of solar energy conversion into clean fuels and other high value products, as well as advances in the mechanistic and structural aspects of the natural solar energy converters, photosystem I and photosystem II, allow to address the main challenges: how to maximize solar-to-fuel conversion efficiency, and most importantly: how to store the energy efficiently and use it without significant losses. Last but not least, the question of how to make the process of solar

Oryza sativa Chloroplast Signal Recognition Particle 43 (OscpSRP43 Is Required for Chloroplast Development and Photosynthesis.

Directory of Open Access Journals (Sweden)

Xiang-guang Lv

Full Text Available A rice chlorophyll-deficient mutant w67 was isolated from an ethyl methane sulfonate (EMS-induced IR64 (Oryza sativa L. ssp. indica mutant bank. The mutant exhibited a distinct yellow-green leaf phenotype in the whole plant growth duration with significantly reduced levels of chlorophyll and carotenoid, impaired chloroplast development and lowered capacity of photosynthesis compared with the wild-type IR64. Expression of a number of genes associated with chlorophyll metabolism, chloroplast biogenesis and photosynthesis was significantly altered in the mutant. Genetic analysis indicated that the yellow-green phenotype was controlled by a single recessive nuclear gene located on the short arm of chromosome 3. Using map-based strategy, the mutation was isolated and predicted to encode a chloroplast signal recognition particle 43 KD protein (cpSRP43 with 388 amino acid residuals. A single base substitution from A to T at position 160 resulted in a premature stop codon. OscpSRP43 was constitutively expressed in various organs with the highest level in the leaf. Functional complementation could rescue the mutant phenotype and subcellular localization showed that the cpSRP43:GFP fusion protein was targeted to the chloroplast. The data suggested that Oryza sativa cpSRP43 (OscpSRP43 was required for the normal development of chloroplasts and photosynthesis in rice.

Differential expression of photosynthesis-related genes in pentaploid interspecific hybrid and its decaploid of Fragaria spp.

Science.gov (United States)

Wang, Tao; Huang, Dongya; Chen, Baoyu; Mao, Nini; Qiao, Yushan; Ji, Muxiang

2018-03-01

Polyploidization always induces a series of changes in genome, transcriptome and epigenetics, of which changes in gene expression are the immediate causes of genotype alterations of polyploid plants. In our previous study on strawberry polyploidization, genes related to photosynthesis were found to undergo changes in gene expression and DNA methylation. Therefore, we chose 11 genes that were closely related to plant photosynthesis and analysed their expression during strawberry hybridization and chromosome doubling. Most genes of pentaploids showed expression levels between parents and were more similar to F. × ananassa. Gene expression levels of decaploids were higher than those of pentaploids and F. × ananassa. Different types of photosynthesis-related genes responded differently to hybridization and chromosome doubling. Chloroplast genes and regulatory genes showed complex responses. Structural genes of the photosynthetic system were expressed at a constant level and displayed a clear dosage effect. The methylation levels of one CG site on SIGE, which regulates expression of chloroplast genes, were negatively correlated with gene expression. In pentaploids and decaploids, more transcripts were from F. × ananassa than from F. viridis. The ratio of transcripts from from F. × ananassa to those from F. viridis was close to the ratio (4:1) of the genome of F. × ananassa to that of F. viridis in pentaploids and decaploids, but there were also some exceptions with obvious deviation.

The social acceptance of artificial photosynthesis: towards a conceptual framework

Science.gov (United States)

Sovacool, Benjamin K.; Gross, Allan

2015-01-01

Advancements in artificial photosynthesis have the potential to radically transform how societies convert and use energy. Their successful development, however, hinges not only on technical breakthroughs, but also acceptance and adoption by energy users. This article introduces a conceptual framework enabling analysts, planners and even investors to determine environments where artificial photosynthesis may thrive, and those where it may struggle. Drawn from work looking at the barriers and acceptance of solar photovoltaic and wind energy systems, the article proposes that social acceptance has multiple dimensions—socio-political, community and market—that must be met holistically in order for investors and users to embrace new technologies. The article argues that any future market acceptance for artificial photosynthesis will depend upon the prevalence of nine factors, which create conducive environments; the lack of the conditions engenders environments where they will likely be rejected. The conditions are (i) strong institutional capacity; (ii) political commitment; (iii) favourable legal and regulatory frameworks; (iv) competitive installation and/or production costs; (v) mechanisms for information and feedback; (vi) access to financing; (vii) prolific community and/or individual ownership and use; (viii) participatory project siting; and (ix) recognition of externalities or positive public image. PMID:26052424

Hydrogen sulfide can inhibit and enhance oxygenic photosynthesis in a cyanobacterium from sulfidic springs

NARCIS (Netherlands)

Klatt, Judith M.; Haas, Sebastian; Yilmaz, Pelin; de Beer, Dirk; Polerecky, Lubos

We used microsensors to investigate the combinatory effect of hydrogen sulfide (H2S) and light on oxygenic photosynthesis in biofilms formed by a cyanobacterium from sulfidic springs. We found that photosynthesis was both positively and negatively affected by H2S: (i) H2S accelerated the recovery of

Interactive effects of oxygen, carbon dioxide and flow on photosynthesis and respiration in the scleractinian coral Galaxea fascicularis.

Science.gov (United States)

Osinga, Ronald; Derksen-Hooijberg, Marlous; Wijgerde, Tim; Verreth, Johan A J

2017-06-15

Rates of dark respiration and net photosynthesis were measured for six replicate clonal fragments of the stony coral Galaxea fascicularis (Linnaeus 1767), which were incubated under 12 different combinations of dissolved oxygen (20%, 100% and 150% saturation), dissolved carbon dioxide (9.5 and 19.1 µmol l -1 ) and water flow (1-1.6 versus 4-13 cm s -1 ) in a repeated measures design. Dark respiration was enhanced by increased flow and increased oxygen saturation in an interactive way, which relates to improved oxygen influx into the coral tissue. Oxygen saturation did not influence net photosynthesis: neither hypoxia nor hyperoxia affected net photosynthesis, irrespective of flow and pH, which suggests that hyperoxia does not induce high rates of photorespiration in this coral. Flow and pH had a synergistic effect on net photosynthesis: at high flow, a decrease in pH stimulated net photosynthesis by 14%. These results indicate that for this individual of G. fascicularis , increased uptake of carbon dioxide rather than increased efflux of oxygen explains the beneficial effect of water flow on photosynthesis. Rates of net photosynthesis measured in this study are among the highest ever recorded for scleractinian corals and confirm a strong scope for growth. © 2017. Published by The Company of Biologists Ltd.

Bibliography of reviews and methods of photosynthesis-85

Czech Academy of Sciences Publication Activity Database

Šesták, Zdeněk; Čatský, Jiří

2002-01-01

Roč. 39, č. 4 (2002), s. 615-640 ISSN 0300-3604 R&D Projects: GA AV ČR KSK5020115 Institutional research plan: CEZ:AV0Z5038910 Keywords : methods of photosynthesis Subject RIV: EF - Botanics Impact factor: 0.773, year: 2002

In situ temperature relationships of biochemical and stomatal controls of photosynthesis in four lowland tropical tree species.

Science.gov (United States)

Slot, Martijn; Winter, Klaus

2017-12-01

Net photosynthetic carbon uptake of Panamanian lowland tropical forest species is typically optimal at 30-32 °C. The processes responsible for the decrease in photosynthesis at higher temperatures are not fully understood for tropical trees. We determined temperature responses of maximum rates of RuBP-carboxylation (V CMax ) and RuBP-regeneration (J Max ), stomatal conductance (G s ), and respiration in the light (R Light ) in situ for 4 lowland tropical tree species in Panama. G s had the lowest temperature optimum (T Opt ), similar to that of net photosynthesis, and photosynthesis became increasingly limited by stomatal conductance as temperature increased. J Max peaked at 34-37 °C and V CMax ~2 °C above that, except in the late-successional species Calophyllum longifolium, in which both peaked at ~33 °C. R Light significantly increased with increasing temperature, but simulations with a photosynthesis model indicated that this had only a small effect on net photosynthesis. We found no evidence for Rubisco-activase limitation of photosynthesis. T Opt of V CMax and J Max fell within the observed in situ leaf temperature range, but our study nonetheless suggests that net photosynthesis of tropical trees is more strongly influenced by the indirect effects of high temperature-for example, through elevated vapour pressure deficit and resulting decreases in stomatal conductance-than by direct temperature effects on photosynthetic biochemistry and respiration. © 2017 John Wiley & Sons Ltd.

Applying photosynthesis research to increase crop yields

Science.gov (United States)

Clayton C. Black; Shi-Jean S. Sung; Kristina Toderich; Pavel Yu Voronin

2010-01-01

This account is dedicated to Dr. Guivi Sanadze for his career long devotion to science and in recognition of his discovery of isoprene emission by trees during photosynthesis. Investigations on the emission of isoprene and other monoterpenes now have been extended globally to encompass other terrestrial vegetation, algae, waters, and marine life in the world's...

Photosynthate supply and utilization in alfalfa: a developmental shift from a source to a sink limitation of photosynthesis

International Nuclear Information System (INIS)

Baysdorfer, C.; Bassham, J.A.

1985-01-01

Long-term carbon dioxide enrichment, 14 CO 2 feeding, and partial defoliation were employed as probes to investigate source/sink limitations of photosynthesis during the development of symbiotically grown alfalfa. In the mature crop, long-term CO 2 enrichment does not affect the rates of net photosynthesis, relative growth, 14 C export to nonphotosynthetic organs, or the rates of 14 C label incorporation into leaf sucrose, starch, or malate. The rate of glycolate labeling is, however, substantially reduced under these conditions. When the mature crop was partially defoliated, a considerable increase in net photosynthesis occurred in the remaining leaves. In the seedling crop, long-term CO 2 enrichment increased dry matter accumulation, primarily as a result of increases in leaf starch content. Although the higher rates of starch synthesis are not maintained, the growth enhancement of the enriched plants persisted throughout the experimental period. These results imply a source limitation of seedling photosynthesis and a sink limitation of photosynthesis in more mature plants. Consequently, both the supply and the utilization of photosynthate may limit seasonal photosynthesis in alfalfa

Automated photosynthesis of 11C-glucose

International Nuclear Information System (INIS)

Ishiwata, K.; Monma, M.; Iwata, R.; Ido, T.

1982-01-01

Glucose and fructose, labelled with 11 C, were produced by passing 11 CO 2 into an evacuated chamber containing spinach leaves. Photosynthesis was carried out by day light lamp illumination. 75-95% of the 11 CO 2 was absorbed by the leaves and the radioactivity in the leaves was extracted in ethanol as sugars. Radiochemical purity was determined by HPLC. The automated system was controlled by timers. (U.K.)

Significance of cold-season respiration and photosynthesis in a subarctic heath ecosystem in Northern Sweden

DEFF Research Database (Denmark)

Larsen, Klaus Steenberg; Ibrom, Andreas; Jonasson, S.

2007-01-01

While substantial cold-season respiration has been documented in most arctic and alpine ecosystems in recent years, the significance of cold-season photosynthesis in these biomes is still believed to be small. In a mesic, subartic heath during both the cold and warm season, we measured in situ...... ecosystem respiration and photosynthesis with a chamber technique at ambient conditions and at artificially, increased frequency of freeze-thaw (FT) cycles during fall and spring. We fitted the measured ecosystem exchange rates to respiration and photosynthesis models with R-2-values ranging from 0.81 to 0.......85. As expected, estimated cold-season (October, November, April and May) respiration was significant and accounted for at least 22% of the annual respiratory CO2 flux. More surprisingly, estimated photosynthesis during this period accounted for up to 19% of the annual gross CO2 uptake, suggesting that cold...

Suppression of nighttime sap flux with lower stem photosynthesis in Eucalyptus trees.

Science.gov (United States)

Gao, Jianguo; Zhou, Juan; Sun, Zhenwei; Niu, Junfeng; Zhou, Cuiming; Gu, Daxing; Huang, Yuqing; Zhao, Ping

2016-04-01

It is widely accepted that substantial nighttime sap flux (J s,n) or transpiration (E) occurs in most plants, but the physiological implications are poorly known. It has been hypothesized that J s,n or E serves to enhance nitrogen uptake or deliver oxygen; however, no clear evidence is currently available. In this study, sap flux (J s) in Eucalyptus grandis × urophylla with apparent stem photosynthesis was measured, including control trees which were covered by aluminum foil (approximately 1/3 of tree height) to block stem photosynthesis. We hypothesized that the nighttime water flux would be suppressed in trees with lower stem photosynthesis. The results showed that the green tissue degraded after 3 months, demonstrating a decrease in stem photosynthesis. The daytime J s decreased by 21.47%, while J s,n decreased by 12.03% in covered trees as compared to that of control, and the difference was statistically significant (P photosynthesis in covered trees. Predawn (ψ pd) of covered trees was marginally higher than that of control while lower at predawn stomatal conductance (g s), indicating a suppressed water flux in covered trees. There was no difference in leaf carbon content and δ(13)C between the two groups, while leaf nitrogen content and δ(15)N were significantly higher in covered trees than that of the control (P < 0.05), indicating that J s,n was not used for nitrogen uptake. These results suggest that J s,n may act as an oxygen pathway since green tissue has a higher respiration or oxygen demand than non-green tissue. Thus, this study demonstrated the physiological implications of J s,n and the possible benefits of nighttime water use or E by the tree.

Synthesis of Phenolics and Flavonoids in Ginger (Zingiber officinale Roscoe and Their Effects on Photosynthesis Rate

Directory of Open Access Journals (Sweden)

Asmah Rahmat

2010-11-01

Full Text Available The relationship between phenolics and flavonoids synthesis/accumulation and photosynthesis rate was investigated for two Malaysian ginger (Zingiber officinale varieties grown under four levels of glasshouse light intensity, namely 310, 460, 630 and 790 μmol m−2s−1. High performance liquid chromatography (HPLC was employed to identify and quantify the polyphenolic components. The results of HPLC analysis indicated that synthesis and partitioning of quercetin, rutin, catechin, epicatechin and naringenin were high in plants grown under 310 µmol m−2s−1. The average value of flavonoids synthesis in leaves for both varieties increased (Halia Bentong 26.1%; Halia Bara 19.5% when light intensity decreased. Photosynthetic rate and plant biomass increased in both varieties with increasing light intensity. More specifically, a high photosynthesis rate (12.25 µmol CO2 m−2s−1 in Halia Bara and plant biomass (79.47 g in Halia Bentong were observed at 790 µmol m−2s−1. Furthermore, plants with the lowest rate of photosynthesis had highest flavonoids content. Previous studies have shown that quercetin inhibits and salicylic acid induces the electron transport rate in photosynthesis photosystems. In the current study, quercetin was an abundant flavonoid in both ginger varieties. Moreover, higher concentration of quercetin (1.12 mg/g dry weight was found in Halia Bara leaves grown under 310 µmol m−2s−1 with a low photosynthesis rate. Furthermore, a high content of salicylic acid (0.673 mg/g dry weight was detected in Halia Bara leaves exposed under 790 µmol m−2s−1 with a high photosynthesis rate. No salicylic acid was detected in gingers grown under 310 µmol m−2s−1. Ginger is a semi-shade loving plant that does not require high light intensity for photosynthesis. Different photosynthesis rates at different light intensities may be related to the absence or presence of some flavonoid and phenolic compounds.

Synthesis of Phenolics and Flavonoids in Ginger (Zingiber officinale Roscoe) and Their Effects on Photosynthesis Rate

Science.gov (United States)

Ghasemzadeh, Ali; Jaafar, Hawa Z. E.; Rahmat, Asmah

2010-01-01

The relationship between phenolics and flavonoids synthesis/accumulation and photosynthesis rate was investigated for two Malaysian ginger (Zingiber officinale) varieties grown under four levels of glasshouse light intensity, namely 310, 460, 630 and 790 μmol m−2s−1. High performance liquid chromatography (HPLC) was employed to identify and quantify the polyphenolic components. The results of HPLC analysis indicated that synthesis and partitioning of quercetin, rutin, catechin, epicatechin and naringenin were high in plants grown under 310 μmol m−2s−1. The average value of flavonoids synthesis in leaves for both varieties increased (Halia Bentong 26.1%; Halia Bara 19.5%) when light intensity decreased. Photosynthetic rate and plant biomass increased in both varieties with increasing light intensity. More specifically, a high photosynthesis rate (12.25 μmol CO2 m−2s−1 in Halia Bara) and plant biomass (79.47 g in Halia Bentong) were observed at 790 μmol m−2s−1. Furthermore, plants with the lowest rate of photosynthesis had highest flavonoids content. Previous studies have shown that quercetin inhibits and salicylic acid induces the electron transport rate in photosynthesis photosystems. In the current study, quercetin was an abundant flavonoid in both ginger varieties. Moreover, higher concentration of quercetin (1.12 mg/g dry weight) was found in Halia Bara leaves grown under 310 μmol m−2s−1 with a low photosynthesis rate. Furthermore, a high content of salicylic acid (0.673 mg/g dry weight) was detected in Halia Bara leaves exposed under 790 μmol m−2s−1 with a high photosynthesis rate. No salicylic acid was detected in gingers grown under 310 μmol m−2s−1. Ginger is a semi-shade loving plant that does not require high light intensity for photosynthesis. Different photosynthesis rates at different light intensities may be related to the absence or presence of some flavonoid and phenolic compounds. PMID:21151455

Ecophysiological modeling of photosynthesis and carbon allocation to the tree stem in the boreal forest

Directory of Open Access Journals (Sweden)

F. Gennaretti

2017-11-01

Full Text Available A better understanding of the coupling between photosynthesis and carbon allocation in the boreal forest, together with its associated environmental factors and mechanistic rules, is crucial to accurately predict boreal forest carbon stocks and fluxes, which are significant components of the global carbon budget. Here, we adapted the MAIDEN ecophysiological forest model to consider important processes for boreal tree species, such as nonlinear acclimation of photosynthesis to temperature changes, canopy development as a function of previous-year climate variables influencing bud formation and the temperature dependence of carbon partition in summer. We tested these modifications in the eastern Canadian taiga using black spruce (Picea mariana (Mill. B.S.P. gross primary production and ring width data. MAIDEN explains 90 % of the observed daily gross primary production variability, 73 % of the annual ring width variability and 20–30 % of its high-frequency component (i.e., when decadal trends are removed. The positive effect on stem growth due to climate warming over the last several decades is well captured by the model. In addition, we illustrate how we improve the model with each introduced model adaptation and compare the model results with those of linear response functions. Our results demonstrate that MAIDEN simulates robust relationships with the most important climate variables (those detected by classical response-function analysis and is a powerful tool for understanding how environmental factors interact with black spruce ecophysiology to influence present-day and future boreal forest carbon fluxes.

Two rubisco activase genes from ipomoea batatas have different roles in photosynthesis of arabidopsis

International Nuclear Information System (INIS)

Jiang, Y.

2014-01-01

Rubisco activase (RCA) that functions as a molecular chaperone regulates the activity of the Calvin-Benson cycle via regulation of the Rubisco activity. In plants such as Arabidopsis thaliana, Spinacia oleracea, and Oryza sativa, there are two RCA isoforms from two mRNAs that are produced from alternative splicing of the transcribed pre-mRNA of a single RCA gene. However, this research reported that the transcripts of the two IbRCA isoforms in sweet potato (Ipomoea batatas) were transcribed from two different genes. To study the roles of these two IbRCA isoforms in photosynthesis, we inserted these two IbRCA genes into the genome of Arabidopsis with deletion of RCA gene (RCA), resulting in IbRCAs- and IbRCAl-expressing plants, respectively. Analysis of these transgenic Arabidopsis indicated that the IbRCAs-expressing plants were similar to wild-type plants under ambient CO/sub 2/ concentration and 22 degree C conditions, suggesting that expression of IbRCAs gene was sufficient for functional complementation of RCA plants under normal conditions. However, IbRCAs-expressing plants were more susceptible to moderate heat stress (26 degree C) compared to wild-type plants. In contrast, although the IbRCAl-expressing plants had to grow normally in high CO/sub 2/ concentration conditions, there were almost no differences in growth and photosynthesis between normally grown and heat-treated plants, implying that IbRCAl-expressing plants had a better heat-resistance than IbRCAs-expressing plants. (author)

Purely Functional Structured Programming

OpenAIRE

Obua, Steven

2010-01-01

The idea of functional programming has played a big role in shaping today's landscape of mainstream programming languages. Another concept that dominates the current programming style is Dijkstra's structured programming. Both concepts have been successfully married, for example in the programming language Scala. This paper proposes how the same can be achieved for structured programming and PURELY functional programming via the notion of LINEAR SCOPE. One advantage of this proposal is that m...

Proton and neutron structure functions

International Nuclear Information System (INIS)

Rock, S.

1991-01-01

New result on charged lepton scattering from hydrogen and deuterium targets by the BCDMS, NMC and SLAC collaborations have greatly increased our knowledge of the structure functions of protons and neutrons. The disagreement between the high energy muon scattering cross sections obtained by the EMC and BCDMS collaborations have been almost completely resolved by comparison with a global analysis of old and new SLAC data and a reanalysis of EMC data. We now have a consistent set of structure functions which covers an approximate range 1 ≤ Q 2 ≤ 200 (GeV/c) 2 and 0.07 ≤ x ≤ 0.7. The ratio of neutron to proton structure functions decreases with increasing Q 2 for values of x ≥ 0.1. The difference between proton and neutron structure functions approaches zero as x decreases, consistent with the expected √x behavior. (orig.)

Adaxial/abaxial specification in the regulation of photosynthesis and stomatal opening with respect to light orientation and growth with CO2 enrichment in the C4 species Paspalum dilatatum.

Science.gov (United States)

Soares, Ana Sofia; Driscoll, Simon P; Olmos, Enrique; Harbinson, Jeremy; Arrabaça, Maria Celeste; Foyer, Christine H

2008-01-01

Whole-plant morphology, leaf structure and composition were studied together with the effects of light orientation on the dorso-ventral regulation of photosynthesis and stomatal conductance in Paspalum dilatatum cv. Raki plants grown for 6 wk at either 350 or 700 microl l(-1) CO(2). Plant biomass was doubled as a result of growth at high CO(2) and the shoot:root ratio was decreased. Stomatal density was increased in the leaves of the high CO(2)-grown plants, which had greater numbers of smaller stomata and more epidermal cells on the abaxial surface. An asymmetric surface-specific regulation of photosynthesis and stomatal conductance was observed with respect to light orientation. This was not caused by dorso-ventral variations in leaf structure, the distribution of phosphoenolpyruvate carboxylase (PEPC) and ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) proteins or light absorptance, transmittance or reflectance. Adaxial/abaxial specification in the regulation of photosynthesis results from differential sensitivity of stomatal opening to light orientation and fixed gradients of enzyme activation across the leaf.

Chloroplastic and stomatal aspects of ozone-induced reduction of net photosynthesis in plants

Energy Technology Data Exchange (ETDEWEB)

Torsethaugen, Gro

1998-09-01

The present thesis relates to ozone-induced reduction of photosynthesis in plants. As a photochemical oxidant O{sub 3} is formed by the interaction of hydrocarbons, nitrogen oxides and oxygen in sunlight. Ozone (O{sub 3}) is the most phytotoxic of all the air pollutants and is known to reduce plant growth and net photosynthesis, cause stomatal closure, induce visible injury, accelerate senescence and induce or inhibit transcription of a variety of genes with a corresponding increase/decrease in protein products. The underlying cellular mechanisms for many of these changes are unknown. Following fields are investigated: Ozone-induced reduction of net photosynthesis; ozone and the photosynthetic apparatus in the chloroplasts; ozone and stomata; ozone effects on plant membranes; protection against ozone injury in plants. 249 refs., 22 figs., 4 tabs.

Effects of high temperature on photosynthesis and related gene expression in poplar

Science.gov (United States)

2014-01-01

Background High temperature, whether transitory or constant, causes physiological, biochemical and molecular changes that adversely affect tree growth and productivity by reducing photosynthesis. To elucidate the photosynthetic adaption response and examine the recovery capacity of trees under heat stress, we measured gas exchange, chlorophyll fluorescence, electron transport, water use efficiency, and reactive oxygen-producing enzyme activities in heat-stressed plants. Results We found that photosynthesis could completely recover after less than six hours of high temperature treatment, which might be a turning point in the photosynthetic response to heat stress. Genome-wide gene expression analysis at six hours of heat stress identified 29,896 differentially expressed genes (15,670 up-regulated and 14,226 down-regulated), including multiple classes of transcription factors. These interact with each other and regulate the expression of photosynthesis-related genes in response to heat stress, controlling carbon fixation and changes in stomatal conductance. Heat stress of more than twelve hours caused reduced electron transport, damaged photosystems, activated the glycolate pathway and caused H2O2 production; as a result, photosynthetic capacity did not recover completely. Conclusions This study provides a systematic physiological and global gene expression profile of the poplar photosynthetic response to heat stress and identifies the main limitations and threshold of photosynthesis under heat stress. It will expand our understanding of plant thermostability and provides a robust dataset for future studies. PMID:24774695

The role of photorespiration during the evolution of C4 photosynthesis in the genus Flaveria

Science.gov (United States)

Mallmann, Julia; Heckmann, David; Bräutigam, Andrea; Lercher, Martin J; Weber, Andreas PM; Westhoff, Peter; Gowik, Udo

2014-01-01

C4 photosynthesis represents a most remarkable case of convergent evolution of a complex trait, which includes the reprogramming of the expression patterns of thousands of genes. Anatomical, physiological, and phylogenetic and analyses as well as computational modeling indicate that the establishment of a photorespiratory carbon pump (termed C2 photosynthesis) is a prerequisite for the evolution of C4. However, a mechanistic model explaining the tight connection between the evolution of C4 and C2 photosynthesis is currently lacking. Here we address this question through comparative transcriptomic and biochemical analyses of closely related C3, C3–C4, and C4 species, combined with Flux Balance Analysis constrained through a mechanistic model of carbon fixation. We show that C2 photosynthesis creates a misbalance in nitrogen metabolism between bundle sheath and mesophyll cells. Rebalancing nitrogen metabolism requires anaplerotic reactions that resemble at least parts of a basic C4 cycle. Our findings thus show how C2 photosynthesis represents a pre-adaptation for the C4 system, where the evolution of the C2 system establishes important C4 components as a side effect. DOI: http://dx.doi.org/10.7554/eLife.02478.001 PMID:24935935

The Path of Carbon in Photosynthesis

Science.gov (United States)

Bassham, J. A.; Calvin, Melvin

1960-10-01

Biosynthesis begins with photosynthesis. Green plants and other photosynthetic organisms use the energy of absorbed visible light to make organic compounds from inorganic compounds. These organic compounds are the starting point for all other biosynthetic pathways. The products of photosynthesis provide not only the substrate material but also chemical energy for all subsequent biosynthesis. For example, nonphotosynthetic organisms making fats from sugars would first break down the sugars to smaller organic molecules. Some of the smaller molecules might be oxidized with O{sub 2} to CO{sub 2} and water. These reactions are accompanied by a release of chemical energy because O{sub 2} and sugar have a high chemical potential energy towards conversion to CO{sub 2} and H{sub 2}O. In a biochemical system only part of this energy would be released as heat. The heat would be used to bring about the conversion of certain enzymic cofactors to their more energetic forms. These cofactors would then enter into specific enzymic reactions in such a way as to supply energy to drive reactions in the direction of fat synthesis. Fats would be formed from the small organic molecules resulting from the breakdown of sugars. Thus sugar, a photosynthetic product, can supply both the energy and the material for the biosynthesis of fats.

THE PATH OF CARBON IN PHOTOSYNTHESIS

Energy Technology Data Exchange (ETDEWEB)

Bassham, J.A.; Calvin, Melvin

1960-10-01

Biosynthesis begins with photosynthesis. Green plants and other photosynthetic organisms use the energy of absorbed visible light to make organic compounds from inorganic compounds. These organic compounds are the starting point for all other biosynthetic pathways. The products of photosynthesis provide not only the substrate material but also chemical energy for all subsequent biosynthesis. For example, nonphotosynthetic organisms making fats from sugars would first break down the sugars to smaller organic molecules. Some of the smaller molecules might be oxidized with O{sub 2} to CO{sub 2} and water. These reactions are accompanied by a release of chemical energy because O{sub 2} and sugar have a high chemical potential energy towards conversion to CO{sub 2} and H{sub 2}O. In a biochemical system only part of this energy would be released as heat. The heat would be used to bring about the conversion of certain enzymic cofactors to their more energetic forms. These cofactors would then enter into specific enzymic reactions in such a way as to supply energy to drive reactions in the direction of fat synthesis. Fats would be formed from the small organic molecules resulting from the breakdown of sugars. Thus sugar, a photosynthetic product, can supply both the energy and the material for the biosynthesis of fats.

Acclimation of biochemical and diffusive components of photosynthesis in rice, wheat and maize to heat and water deficit: implications for modeling photosynthesis

Directory of Open Access Journals (Sweden)

Juan Alejandro Perdomo

2016-11-01

Full Text Available The impact of the combined effects of heat stress, increased vapor pressure deficit (VPD and water deficit on the physiology of major crops needs to be better understood to help identifying the expected negative consequences of climate change and heat waves on global agricultural productivity. To address this issue, rice, wheat and maize plants were grown under control temperature (CT, 25°C, VPD 1.8 kPa, and a high temperature (HT, 38°C, VPD 3.5 kPa, both under well-watered (WW and water deficit (WD conditions. Gas-exchange measurements showed that, in general, WD conditions affected the leaf conductance to CO2, while growth at HT had a more marked effect on the biochemistry of photosynthesis. When combined, HT and WD had an additive effect in limiting photosynthesis. The negative impacts of the imposed treatments on the processes governing leaf gas-exchange were species-dependent. Wheat presented a higher sensitivity while rice and maize showed a higher acclimation potential to increased temperature. Rubisco and PEPC kinetic constants determined in vitro at 25°C and 38°C were used to estimate Vcmax, Jmax and Vpmax in the modeling of C3 and C4 photosynthesis. The results here obtained reiterate the need to use species-specific and temperature-specific values for Rubisco and PEPC kinetic constants for a precise parameterization of the photosynthetic response to changing environmental conditions in different crop species.

The Center for the Study of Early Events in Photosynthesis. Final report, September 1, 1988--August 31, 1994

Energy Technology Data Exchange (ETDEWEB)

Orr, L.A.

1994-12-31

The ASU Center for the Study of Early Events in Photosynthesis was established in 1988 with funding through a five-year grant from the USDA/DOE/NSF Plant Science Center program and a grant from the NSF Biological Facilities program. Its scientific objective is to elucidate the basic principles that govern photosynthetic energy collection and storage. Understanding these principles is vital to mankind, as photosynthesis provides most of our food, fiber and energy needs. The Center attempts to fulfill this objective through research of the highest standard, coupled inextricably with quality education at the undergraduate, graduate and postdoctoral levels. These goals are met via a network of collaborative, interdisciplinary research groups comprising 100 personnel within the Department of Chemistry and Biochemistry, the Department of Botany, and the Department of Physics and Astronomy. The work of these research groups is facilitated by the Center through a variety of important infrastructural functions.

Mini Heme-Proteins: Designability of Structure and Diversity of Functions.

Science.gov (United States)

Rai, Jagdish

2017-08-30

Natural heme proteins may have heme bound to poly-peptide chain as a cofactor via noncovalent forces or heme as a prosthetic group may be covalently bound to the proteins. Nature has used porphyrins in diverse functions like electron transfer, oxidation, reduction, ligand binding, photosynthesis, signaling, etc. by modulating its properties through diverse protein matrices. Synthetic chemists have tried to utilize these molecules in equally diverse industrial and medical applications due to their versatile electro-chemical and optical properties. The heme iron has catalytic activity which can be modulated and enhanced for specific applications by protein matrix around it. Heme proteins can be designed into novel enzymes for sterio specific catalysis ranging from oxidation to reduction. These designed heme-proteins can have applications in industrial catalysis and biosensing. A peptide folds around heme easily due to hydrophobic effect of the large aromatic ring of heme. The directional property of co-ordinate bonding between peptide and metal ion in heme further specifies the structure. Therefore heme proteins can be easily designed for targeted structure and catalytic activity. The central aromatic chemical entity in heme viz. porphyrin is a very ancient molecule. Its presence in the prebiotic soup and in all forms of life suggests that it has played a vital role in the origin and progressive evolution of living organisms. Porphyrin macrocycles are highly conjugated systems composed of four modified pyrrole subunits interconnected at their α -carbon atoms via methine (=CH-) bridges. Initial minimalist models of hemoproteins focused on effect of heme-ligand co-ordinate bonding on chemical reactivity, spectroscopy, electrochemistry and magnetic properties of heme. The great sensitivity of these spectroscopic features of heme to its surrounding makes them extremely useful in structural elucidation of designed heme-peptide complexes. Therefore heme proteins are

Chloroplast two-component systems: evolution of the link between photosynthesis and gene expression.

Science.gov (United States)

Puthiyaveetil, Sujith; Allen, John F

2009-06-22

Two-component signal transduction, consisting of sensor kinases and response regulators, is the predominant signalling mechanism in bacteria. This signalling system originated in prokaryotes and has spread throughout the eukaryotic domain of life through endosymbiotic, lateral gene transfer from the bacterial ancestors and early evolutionary precursors of eukaryotic, cytoplasmic, bioenergetic organelles-chloroplasts and mitochondria. Until recently, it was thought that two-component systems inherited from an ancestral cyanobacterial symbiont are no longer present in chloroplasts. Recent research now shows that two-component systems have survived in chloroplasts as products of both chloroplast and nuclear genes. Comparative genomic analysis of photosynthetic eukaryotes shows a lineage-specific distribution of chloroplast two-component systems. The components and the systems they comprise have homologues in extant cyanobacterial lineages, indicating their ancient cyanobacterial origin. Sequence and functional characteristics of chloroplast two-component systems point to their fundamental role in linking photosynthesis with gene expression. We propose that two-component systems provide a coupling between photosynthesis and gene expression that serves to retain genes in chloroplasts, thus providing the basis of cytoplasmic, non-Mendelian inheritance of plastid-associated characters. We discuss the role of this coupling in the chronobiology of cells and in the dialogue between nuclear and cytoplasmic genetic systems.

Elevated Temperature and CO2 Stimulate Late-Season Photosynthesis But Impair Cold Hardening in Pine.

Science.gov (United States)

Chang, Christine Y; Fréchette, Emmanuelle; Unda, Faride; Mansfield, Shawn D; Ensminger, Ingo

2016-10-01

Rising global temperature and CO 2 levels may sustain late-season net photosynthesis of evergreen conifers but could also impair the development of cold hardiness. Our study investigated how elevated temperature, and the combination of elevated temperature with elevated CO 2 , affected photosynthetic rates, leaf carbohydrates, freezing tolerance, and proteins involved in photosynthesis and cold hardening in Eastern white pine (Pinus strobus). We designed an experiment where control seedlings were acclimated to long photoperiod (day/night 14/10 h), warm temperature (22°C/15°C), and either ambient (400 μL L -1 ) or elevated (800 μmol mol -1 ) CO 2 , and then shifted seedlings to growth conditions with short photoperiod (8/16 h) and low temperature/ambient CO 2 (LTAC), elevated temperature/ambient CO 2 (ETAC), or elevated temperature/elevated CO 2 (ETEC). Exposure to LTAC induced down-regulation of photosynthesis, development of sustained nonphotochemical quenching, accumulation of soluble carbohydrates, expression of a 16-kD dehydrin absent under long photoperiod, and increased freezing tolerance. In ETAC seedlings, photosynthesis was not down-regulated, while accumulation of soluble carbohydrates, dehydrin expression, and freezing tolerance were impaired. ETEC seedlings revealed increased photosynthesis and improved water use efficiency but impaired dehydrin expression and freezing tolerance similar to ETAC seedlings. Sixteen-kilodalton dehydrin expression strongly correlated with increases in freezing tolerance, suggesting its involvement in the development of cold hardiness in P. strobus Our findings suggest that exposure to elevated temperature and CO 2 during autumn can delay down-regulation of photosynthesis and stimulate late-season net photosynthesis in P. strobus seedlings. However, this comes at the cost of impaired freezing tolerance. Elevated temperature and CO 2 also impaired freezing tolerance. However, unless the frequency and timing of extreme low

Rubisco catalytic properties of wild and domesticated relatives provide scope for improving wheat photosynthesis.

Science.gov (United States)

Prins, Anneke; Orr, Douglas J; Andralojc, P John; Reynolds, Matthew P; Carmo-Silva, Elizabete; Parry, Martin A J

2016-03-01

Rubisco is a major target for improving crop photosynthesis and yield, yet natural diversity in catalytic properties of this enzyme is poorly understood. Rubisco from 25 genotypes of the Triticeae tribe, including wild relatives of bread wheat (Triticum aestivum), were surveyed to identify superior enzymes for improving photosynthesis in this crop. In vitro Rubisco carboxylation velocity (V c), Michaelis-Menten constants for CO2 (K c) and O2 (K o) and specificity factor (S c/o) were measured at 25 and 35 °C. V c and K c correlated positively, while V c and S c/o were inversely related. Rubisco large subunit genes (rbcL) were sequenced, and predicted corresponding amino acid differences analysed in relation to the corresponding catalytic properties. The effect of replacing native wheat Rubisco with counterparts from closely related species was analysed by modelling the response of photosynthesis to varying CO2 concentrations. The model predicted that two Rubisco enzymes would increase photosynthetic performance at 25 °C while only one of these also increased photosynthesis at 35 °C. Thus, under otherwise identical conditions, catalytic variation in the Rubiscos analysed is predicted to improve photosynthetic rates at physiological CO2 concentrations. Naturally occurring Rubiscos with superior properties amongst the Triticeae tribe can be exploited to improve wheat photosynthesis and crop productivity. © The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Regge behaviour of structure functions and evolution of gluon structure function upto next-to-leading order at low-x

International Nuclear Information System (INIS)

Jamil, U.; Sarma, J.K.

2011-01-01

Evolution of gluon structure function from Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) evolution equations upto next-to-leading order at low-x is presented assuming the Regge behaviour of structure functions. We compare our results of gluon structure function with GRV 98 global parameterization and show the compatibility of Regge behaviour of structure functions with PQCD. (author)

Elevated Temperature and CO2 Stimulate Late-Season Photosynthesis But Impair Cold Hardening in Pine[OPEN

Science.gov (United States)

2016-01-01

Rising global temperature and CO2 levels may sustain late-season net photosynthesis of evergreen conifers but could also impair the development of cold hardiness. Our study investigated how elevated temperature, and the combination of elevated temperature with elevated CO2, affected photosynthetic rates, leaf carbohydrates, freezing tolerance, and proteins involved in photosynthesis and cold hardening in Eastern white pine (Pinus strobus). We designed an experiment where control seedlings were acclimated to long photoperiod (day/night 14/10 h), warm temperature (22°C/15°C), and either ambient (400 μL L−1) or elevated (800 μmol mol−1) CO2, and then shifted seedlings to growth conditions with short photoperiod (8/16 h) and low temperature/ambient CO2 (LTAC), elevated temperature/ambient CO2 (ETAC), or elevated temperature/elevated CO2 (ETEC). Exposure to LTAC induced down-regulation of photosynthesis, development of sustained nonphotochemical quenching, accumulation of soluble carbohydrates, expression of a 16-kD dehydrin absent under long photoperiod, and increased freezing tolerance. In ETAC seedlings, photosynthesis was not down-regulated, while accumulation of soluble carbohydrates, dehydrin expression, and freezing tolerance were impaired. ETEC seedlings revealed increased photosynthesis and improved water use efficiency but impaired dehydrin expression and freezing tolerance similar to ETAC seedlings. Sixteen-kilodalton dehydrin expression strongly correlated with increases in freezing tolerance, suggesting its involvement in the development of cold hardiness in P. strobus. Our findings suggest that exposure to elevated temperature and CO2 during autumn can delay down-regulation of photosynthesis and stimulate late-season net photosynthesis in P. strobus seedlings. However, this comes at the cost of impaired freezing tolerance. Elevated temperature and CO2 also impaired freezing tolerance. However, unless the frequency and timing of extreme low

Structure functions from chiral soliton models

International Nuclear Information System (INIS)

Weigel, H.; Reinhardt, H.; Gamberg, L.

1997-01-01

We study nucleon structure functions within the bosonized Nambu-Jona-Lasinio (NJL) model where the nucleon emerges as a chiral soliton. We discuss the model predictions on the Gottfried sum rule for electron-nucleon scattering. A comparison with a low-scale parametrization shows that the model reproduces the gross features of the empirical structure functions. We also compute the leading twist contributions of the polarized structure functions g 1 and g 2 in this model. We compare the model predictions on these structure functions with data from the E143 experiment by GLAP evolving them from the scale characteristic for the NJL-model to the scale of the data

Photosynthesis Involvement in the Mechanism of Action of Diphenyl Ether Herbicides 1

Science.gov (United States)

Ensminger, Michael P.; Hess, F. Dan

1985-01-01

Photosynthesis is not required for the toxicity of diphenyl ether herbicides, nor are chloroplast thylakoids the primary site of diphenyl ether herbicide activity. Isolated spinach (Spinacia oleracea L.) chloroplast fragments produced malonyl dialdehyde, indicating lipid peroxidation, when paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) or diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] were added to the medium, but no malonyl dialdehyde was produced when chloroplast fragments were treated with the methyl ester of acifluorfen (methyl 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid), oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene], or MC15608 (methyl 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-chlorobenzoate). In most cases the toxicity of acifluorfen-methyl, oxyfluorfen, or MC15608 to the unicellular green alga Chlamydomonas eugametos (Moewus) did not decrease after simultaneous treatment with diuron. However, diuron significantly reduced cell death after paraquat treatment at all but the highest paraquat concentration tested (0.1 millimolar). These data indicate electron transport of photosynthesis is not serving the same function for diphenyl ether herbicides as for paraquat. Additional evidence for differential action of paraquat was obtained from the superoxide scavenger copper penicillamine (copper complex of 2-amino-3-mercapto-3-methylbutanoic acid). Copper penicillamine eliminated paraquat toxicity in cucumber (Cucumis sativus L.) cotyledons but did not reduce diphenyl ether herbicide toxicity. PMID:16664206

significance of rice sheath photosynthesis: yield determination by c ...

African Journals Online (AJOL)

ACSS

1State Key Laboratory of Hybrid Rice, Hunan Hybrid Rice Research Center, Changsha 410125, P.R. China. 2School of ... for contribution rates of sheath photosynthesis to economical yield. ..... related processes during ripening in rice plants.

Tracking Seasonal and Diurnal Photosynthesis and Plant Water Status in Maize Using SIF, Eddy Covariance Fluxes, PAM Fluorescence and Gas Exchange

Science.gov (United States)

Chang, C.; Melkonian, J.; Riha, S. J.; Gu, L.; Sun, Y.

2017-12-01

Improving the sensitivity of methods for crop monitoring and yield forecasting is crucial as the frequency of extreme weather events increases. Conventional remote monitoring methods rely on greenness-based indices such as NDVI and EVI, which do not directly measure photosynthesis and are not sufficiently sensitive to rapid plant stress response. Solar-induced chlorophyll fluorescence (SIF) is a promising new technology that serves as a direct functional proxy of photosynthesis. We developed the first system utilizing dual QE Pro spectrometers to continuously measure the diurnal and seasonal cycle of SIF, and deployed the system in a corn field in upstate New York in 2017. To complement SIF, canopy-level measurements of carbon and water fluxes were also measured, along with concurrent leaf-level measurements of gas exchange and PAM fluorescence, midday water potential, leaf pigments, phenology, LAI, and soil moisture. We show that SIF is well correlated to GPP during the growing season and show that both are controlled by similar environmental conditions including PAR and water availability. We also describe diurnal changes in photosynthesis and plant water status and demonstrate the sensitivity of SIF to diurnal plant response.

Leaf and canopy photosynthesis of a chlorophyll deficient soybean mutant.

Science.gov (United States)

Sakowska, Karolina; Alberti, Giorgio; Genesio, Lorenzo; Peressotti, Alessandro; Delle Vedove, Gemini; Gianelle, Damiano; Colombo, Roberto; Rodeghiero, Mirco; Panigada, Cinzia; Juszczak, Radosław; Celesti, Marco; Rossini, Micol; Haworth, Matthew; Campbell, Benjamin W; Mevy, Jean-Philippe; Vescovo, Loris; Cendrero-Mateo, M Pilar; Rascher, Uwe; Miglietta, Franco

2018-03-02

The photosynthetic, optical, and morphological characteristics of a chlorophyll-deficient (Chl-deficient) "yellow" soybean mutant (MinnGold) were examined in comparison with 2 green varieties (MN0095 and Eiko). Despite the large difference in Chl content, similar leaf photosynthesis rates were maintained in the Chl-deficient mutant by offsetting the reduced absorption of red photons by a small increase in photochemical efficiency and lower non-photochemical quenching. When grown in the field, at full canopy cover, the mutants reflected a significantly larger proportion of incoming shortwave radiation, but the total canopy light absorption was only slightly reduced, most likely due to a deeper penetration of light into the canopy space. As a consequence, canopy-scale gross primary production and ecosystem respiration were comparable between the Chl-deficient mutant and the green variety. However, total biomass production was lower in the mutant, which indicates that processes other than steady state photosynthesis caused a reduction in biomass accumulation over time. Analysis of non-photochemical quenching relaxation and gas exchange in Chl-deficient and green leaves after transitions from high to low light conditions suggested that dynamic photosynthesis might be responsible for the reduced biomass production in the Chl-deficient mutant under field conditions. © 2018 John Wiley & Sons Ltd.

Radio photosynthesis of some 14 C-labelled sugars using the unicellular green alga scenedesmus ACUTUS

International Nuclear Information System (INIS)

Barakat, M.F.; Farag, A.N.; Ragab, M.T.; El-Fouly, M.M.; El-Baz, F.K.

1993-01-01

Radiosynthesis has been carried out using the unicellular green alga scenedesmus acutus together with Na H 14 CO 3 solution as a carbon-14 source, in an ordinary photosynthesis chamber. The process is more easier and less laborious than the techniques involving the use of gaseous 14 CO 2 in a tight photosynthesis chamber. Uniformly labelled 14 C-glucose, 14 C-fructose and 14 C-sucrose have been prepared with specific activities of several micro curies per milli mole. The specific activity of the products was found to increase on increasing the photosynthesis time or the initial activity of the Na H 14 CO 3 solution used. 3 tabs

Bibliography of reviews and methods of photosynthesis - 88

Czech Academy of Sciences Publication Activity Database

Šesták, Zdeněk; Čatský, Jiří

2004-01-01

Roč. 42, č. 4 (2004), s. 619-640 ISSN 0300-3604 R&D Projects: GA ČR GA206/97/0120 Institutional research plan: CEZ:AV0Z5038910 Keywords : Bibliographic survey * processes of photosynthesis * accumulation of energy Subject RIV: EF - Botanics Impact factor: 0.734, year: 2004

Dynamics of photosynthesis in Eichhornia crassipes Solms of ...

African Journals Online (AJOL)

2009-11-14

With LI-6400 portable photosynthesis system, the photosynthetic characteristics of artificially cultured Eichhornia crassipes in Jiangsu, China, were monitored from June 1 to November 14, 2009. Both the net photosynthetic rate (Pn) in different positions and light and temperature-response curves of the top fourth leaf were ...

Effect of gamma radiation on chlorophylls content, net photosynthesis and respiration of Chlorella pyrenoidosa

International Nuclear Information System (INIS)

Martin Moreno, C.; Fernandez Gonzalez, J.

1983-01-01

The effect of five doses of gamma radiation: 10, 100, 500, 1000 and 5000 Gy on chlorophylls content, net photosynthesis and respiration of Chlorella pyrenoidosa has been studied. A decrease in chlorophylls levels is produced after irradiation at 500, 1000 and 5000 Gy, being, at first b chlorophyll affected to a greater extent than a chlorophyll. Net photosynthesis and respiration decline throughout the time of the observation after irradiation, this depressing effect being much more remarkable for the first one. Met photosynthesis inhibition levels of about 30% are got only five hours post irradiation at a dose of 5000 Gy. Radio estimation by low doses, although obtained in some cases for tho 10 Gy dose, has not been statistically confirmed. (Author) 23 refs

Understanding of photosynthesis among students of biology and non-biology programmes of study

OpenAIRE

Lekan, Erika

2016-01-01

Photosynthesis is one of the most important processes on Earth, thus knowing at least its basic principles is essential. In Slovenia, the students become acquainted with these principles in the fifth form of elementary school. Due to the complexity of the photosynthesis process, the students hold misconceptions about it since the very beginning of the learning process. Due to several factors and reasons, these misconceptions persist throughout the secondary school and university studies. ...

Sun-induced fluorescence - a new probe of photosynthesis: First maps from the imaging spectrometer HyPlant.

Science.gov (United States)

Rascher, U; Alonso, L; Burkart, A; Cilia, C; Cogliati, S; Colombo, R; Damm, A; Drusch, M; Guanter, L; Hanus, J; Hyvärinen, T; Julitta, T; Jussila, J; Kataja, K; Kokkalis, P; Kraft, S; Kraska, T; Matveeva, M; Moreno, J; Muller, O; Panigada, C; Pikl, M; Pinto, F; Prey, L; Pude, R; Rossini, M; Schickling, A; Schurr, U; Schüttemeyer, D; Verrelst, J; Zemek, F

2015-12-01

Variations in photosynthesis still cause substantial uncertainties in predicting photosynthetic CO2 uptake rates and monitoring plant stress. Changes in actual photosynthesis that are not related to greenness of vegetation are difficult to measure by reflectance based optical remote sensing techniques. Several activities are underway to evaluate the sun-induced fluorescence signal on the ground and on a coarse spatial scale using space-borne imaging spectrometers. Intermediate-scale observations using airborne-based imaging spectroscopy, which are critical to bridge the existing gap between small-scale field studies and global observations, are still insufficient. Here we present the first validated maps of sun-induced fluorescence in that critical, intermediate spatial resolution, employing the novel airborne imaging spectrometer HyPlant. HyPlant has an unprecedented spectral resolution, which allows for the first time quantifying sun-induced fluorescence fluxes in physical units according to the Fraunhofer Line Depth Principle that exploits solar and atmospheric absorption bands. Maps of sun-induced fluorescence show a large spatial variability between different vegetation types, which complement classical remote sensing approaches. Different crop types largely differ in emitting fluorescence that additionally changes within the seasonal cycle and thus may be related to the seasonal activation and deactivation of the photosynthetic machinery. We argue that sun-induced fluorescence emission is related to two processes: (i) the total absorbed radiation by photosynthetically active chlorophyll; and (ii) the functional status of actual photosynthesis and vegetation stress. © 2015 John Wiley & Sons Ltd.

A Mapping Between Structural and Functional Brain Networks.

Science.gov (United States)

Meier, Jil; Tewarie, Prejaas; Hillebrand, Arjan; Douw, Linda; van Dijk, Bob W; Stufflebeam, Steven M; Van Mieghem, Piet

2016-05-01

The relationship between structural and functional brain networks is still highly debated. Most previous studies have used a single functional imaging modality to analyze this relationship. In this work, we use multimodal data, from functional MRI, magnetoencephalography, and diffusion tensor imaging, and assume that there exists a mapping between the connectivity matrices of the resting-state functional and structural networks. We investigate this mapping employing group averaged as well as individual data. We indeed find a significantly high goodness of fit level for this structure-function mapping. Our analysis suggests that a functional connection is shaped by all walks up to the diameter in the structural network in both modality cases. When analyzing the inverse mapping, from function to structure, longer walks in the functional network also seem to possess minor influence on the structural connection strengths. Even though similar overall properties for the structure-function mapping are found for different functional modalities, our results indicate that the structure-function relationship is modality dependent.

Plants growth, water relations and photosynthesis of two bean ...

African Journals Online (AJOL)

... almost all physiological activities were suppressed. The superiority of the genotype Tema against Djadida genotype was attributed to quantitative rather than qualitative physiological response differences. Keywords: Salinity, fluridone, bean, growth, photosynthesis, stomatal conductance. African Journal of Biotechnology ...

Proton structure functions at small x

International Nuclear Information System (INIS)

Hentschinski, Martin

2015-01-01

Proton structure functions are measured in electron-proton collision through inelastic scattering of virtual photons with virtuality Q on protons; x denotes the momentum fraction carried by the struck parton. Proton structure functions are currently described with excellent accuracy in terms of scale dependent parton distribution functions, defined in terms of collinear factorization and DGLAP evolution in Q. With decreasing x however, parton densities increase and are ultimately expected to saturate. In this regime DGLAP evolution will finally break down and non-linear evolution equations w.r.t x are expected to take over. In the first part of the talk we present recent result on an implementation of physical DGLAP evolution. Unlike the conventional description in terms of parton distribution functions, the former describes directly the Q dependence of the measured structure functions. It is therefore physical insensitive to factorization scheme and scale ambiguities. It therefore provides a more stringent test of DGLAP evolution and eases the manifestation of (non-linear) small x effects. It however requires a precise measurement of both structure functions F 2 and F L , which will be only possible at future facilities, such as an Electron Ion Collider. In the second part we present a recent analysis of the small x region of the combined HERA data on the structure function F 2 . We demonstrate that (linear) next-to-leading order BFKL evolution describes the effective Pomeron intercept, determined from the combined HERA data, once a resummation of collinear enhanced terms is included and the renormalization scale is fixed using the BLM optimal scale setting procedure. We also provide a detailed description of the Q and x dependence of the full structure functions F 2 in the small x region, as measured at HERA. Predictions for the structure function F L are found to be in agreement with the existing HERA data. (paper)

Promotion of Cyclic Electron Transport Around Photosystem I with the Development of C4 Photosynthesis.

Science.gov (United States)

Munekage, Yuri Nakajima; Taniguchi, Yukimi Y

2016-05-01

C4 photosynthesis is present in approximately 7,500 species classified into 19 families, including monocots and eudicots. In the majority of documented cases, a two-celled CO2-concentrating system that uses a metabolic cycle of four-carbon compounds is employed. C4 photosynthesis repeatedly evolved from C3 photosynthesis, possibly driven by the survival advantages it bestows in the hot, often dry, and nutrient-poor soils of the tropics and subtropics. The development of the C4 metabolic cycle greatly increased the ATP demand in chloroplasts during the evolution of malic enzyme-type C4 photosynthesis, and the additional ATP required for C4 metabolism may be produced by the cyclic electron transport around PSI. Recent studies have revealed the nature of cyclic electron transport and the elevation of its components during C4 evolution. In this review, we discuss the energy requirements of C3 and C4 photosynthesis, the current model of cyclic electron transport around PSI and how cyclic electron transport is promoted during C4 evolution using studies on the genus Flaveria, which contains a number of closely related C3, C4 and C3-C4 intermediate species. © 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.

Relationship between Hexokinase and the Aquaporin PIP1 in the Regulation of Photosynthesis and Plant Growth

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Kelly, Gilor; Sade, Nir; Attia, Ziv; Secchi, Francesca; Zwieniecki, Maciej; Holbrook, N. Michele; Levi, Asher; Alchanatis, Victor; Moshelion, Menachem; Granot, David

2014-01-01

Increased expression of the aquaporin NtAQP1, which is known to function as a plasmalemma channel for CO2 and water, increases the rate of both photosynthesis and transpiration. In contrast, increased expression of Arabidopsis hexokinase1 (AtHXK1), a dual-function enzyme that mediates sugar sensing, decreases the expression of photosynthetic genes and the rate of transpiration and inhibits growth. Here, we show that AtHXK1 also decreases root and stem hydraulic conductivity and leaf mesophyll CO2 conductance (g m). Due to their opposite effects on plant development and physiology, we examined the relationship between NtAQP1 and AtHXK1 at the whole-plant level using transgenic tomato plants expressing both genes simultaneously. NtAQP1 significantly improved growth and increased the transpiration rates of AtHXK1-expressing plants. Reciprocal grafting experiments indicated that this complementation occurs when both genes are expressed simultaneously in the shoot. Yet, NtAQP1 had only a marginal effect on the hydraulic conductivity of the double-transgenic plants, suggesting that the complementary effect of NtAQP1 is unrelated to shoot water transport. Rather, NtAQP1 significantly increased leaf mesophyll CO2 conductance and enhanced the rate of photosynthesis, suggesting that NtAQP1 facilitated the growth of the double-transgenic plants by enhancing mesophyll conductance of CO2. PMID:24498392

Relationship between hexokinase and the aquaporin PIP1 in the regulation of photosynthesis and plant growth.

Directory of Open Access Journals (Sweden)

Gilor Kelly

Full Text Available Increased expression of the aquaporin NtAQP1, which is known to function as a plasmalemma channel for CO₂ and water, increases the rate of both photosynthesis and transpiration. In contrast, increased expression of Arabidopsis hexokinase1 (AtHXK1, a dual-function enzyme that mediates sugar sensing, decreases the expression of photosynthetic genes and the rate of transpiration and inhibits growth. Here, we show that AtHXK1 also decreases root and stem hydraulic conductivity and leaf mesophyll CO₂ conductance (g(m. Due to their opposite effects on plant development and physiology, we examined the relationship between NtAQP1 and AtHXK1 at the whole-plant level using transgenic tomato plants expressing both genes simultaneously. NtAQP1 significantly improved growth and increased the transpiration rates of AtHXK1-expressing plants. Reciprocal grafting experiments indicated that this complementation occurs when both genes are expressed simultaneously in the shoot. Yet, NtAQP1 had only a marginal effect on the hydraulic conductivity of the double-transgenic plants, suggesting that the complementary effect of NtAQP1 is unrelated to shoot water transport. Rather, NtAQP1 significantly increased leaf mesophyll CO₂ conductance and enhanced the rate of photosynthesis, suggesting that NtAQP1 facilitated the growth of the double-transgenic plants by enhancing mesophyll conductance of CO₂.

What is the most prominent factor limiting photosynthesis in different layers of a greenhouse cucumber canopy?

NARCIS (Netherlands)

Chen, T.W.; Henke, M.; Visser, de P.H.B.; Buck-Sorlin, G.H.; Wiechers, D.; Kahlen, K.; Stützel, H.

2014-01-01

Background and Aims Maximizing photosynthesis at the canopy level is important for enhancing crop yield, and this requires insights into the limiting factors of photosynthesis. Using greenhouse cucumber (Cucumis sativus) as an example, this study provides a novel approach to quantify different

Comparative sensitivity of photosynthesis and translocation to sulfur dioxide damage in Phaseolus vulgaris L

International Nuclear Information System (INIS)

Noyes, R.D.

1978-01-01

The inhibiting effect of sulfur dioxide on photosynthesis in a mature bean leaf and, simultaneously, on the rate of carbohydrate translocation from this same leaf has been examined. The results show a reduction of 0, 13, and 73% in net photosynthesis and 39, 44, and 69% in translocation, at concentrations of 0.1, 1, and 3 ppm sulfur dioxide, respectively. The inhibition of translocation at 0.1 ppm sulfur dioxide without any accompanying inhibition of net photosynthesis indicates that translocation is considerably more sensitive to sulfur dioxide damage. The mechanism of translocation inhibition at 1 ppm sulfur dioxide or less is shown to be independent of photosynthetic inhibition. Whereas, it is suggested that at higher concentrations significant inhibition of photosynthesis causes an additive reduction of translocation due to reduced levels of transport sugars. Autoradiograms of 14 C-labeled source leaves indicate that one possible mechanism of sulfur dioxide damage to translocation is the inhibition of sieve-tube loading. Inhibition of phloem translocation at common ambient levels (0.1 ppm) of sulfur dioxide is important to the overall growth and yield of major agricultural crops sensitive to sulfur dioxide

Relationships between net photosynthesis and foliar nitrogen concentrations in a loblobby pine forest ecosystem grown in elevated atmospheric carbon dioxide

International Nuclear Information System (INIS)

Springer, C. J.; Thomas, R. B.; Delucia, E. H.

2005-01-01

The effects of elevated carbon dioxide concentration on the relationship between light-saturated net photosynthesis and area-based foliar nitrogen concentration in the canopy of a loblobby pine forest at the Duke Forest FACE experiment was examined. Two overstory and four understory tree species were examined at their growth carbon dioxide concentrations during the early summer and late summer of 1999, 2001 and 2002. Light-saturated net photosynthesis and foliar nitrogen relationship were compared to determine if the stimulatory effects of elevated carbon dioxide on net photosynthesis had declined. Results at all three sample times showed no difference in either the slopes, or in the y-intercepts of the net photosynthesis-foliar nitrogen relationship when measured at common carbon dioxide concentrations. Net photosynthesis was also unaffected by growth in elevated carbon dioxide, indicating that these overstory and understory trees continued to show strong stimulation of photosynthesis by elevated carbon dioxide. 46 refs., 6 tabs., 3 figs

Plant functional traits and canopy structure control the relationship between photosynthetic CO2 uptake and far-red sun-induced fluorescence in a Mediterranean grassland under different nutrient availability.

Science.gov (United States)

Migliavacca, Mirco; Perez-Priego, Oscar; Rossini, Micol; El-Madany, Tarek S; Moreno, Gerardo; van der Tol, Christiaan; Rascher, Uwe; Berninger, Anna; Bessenbacher, Verena; Burkart, Andreas; Carrara, Arnaud; Fava, Francesco; Guan, Jin-Hong; Hammer, Tiana W; Henkel, Kathrin; Juarez-Alcalde, Enrique; Julitta, Tommaso; Kolle, Olaf; Martín, M Pilar; Musavi, Talie; Pacheco-Labrador, Javier; Pérez-Burgueño, Andrea; Wutzler, Thomas; Zaehle, Sönke; Reichstein, Markus

2017-05-01

Sun-induced fluorescence (SIF) in the far-red region provides a new noninvasive measurement approach that has the potential to quantify dynamic changes in light-use efficiency and gross primary production (GPP). However, the mechanistic link between GPP and SIF is not completely understood. We analyzed the structural and functional factors controlling the emission of SIF at 760 nm (F 760 ) in a Mediterranean grassland manipulated with nutrient addition of nitrogen (N), phosphorous (P) or nitrogen-phosphorous (NP). Using the soil-canopy observation of photosynthesis and energy (SCOPE) model, we investigated how nutrient-induced changes in canopy structure (i.e. changes in plant forms abundance that influence leaf inclination distribution function, LIDF) and functional traits (e.g. N content in dry mass of leaves, N%, Chlorophyll a+b concentration (Cab) and maximum carboxylation capacity (V cmax )) affected the observed linear relationship between F 760 and GPP. We conclude that the addition of nutrients imposed a change in the abundance of different plant forms and biochemistry of the canopy that controls F 760 . Changes in canopy structure mainly control the GPP-F 760 relationship, with a secondary effect of Cab and V cmax . In order to exploit F 760 data to model GPP at the global/regional scale, canopy structural variability, biodiversity and functional traits are important factors that have to be considered. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

Photosynthesis and carbon isotope discrimination in boreal forest ecosystems: A comparison of functional characteristics in plants from three mature forest types

Science.gov (United States)

Flanagan, Lawrence B.; Brooks, J. Renee; Ehleringer, James R.

1997-12-01

In this paper we compare measurements of photosynthesis and carbon isotope discrimination characteristics among plants from three mature boreal forest types (Black spruce, Jack pine, and aspen) in order to help explain variation in ecosystem-level gas exchange processes. Measurements were made at the southern study area (SSA) and northern study area (NSA) of the boreal forest in central Canada as part of the Boreal Ecosystem-Atmosphere Study (BOREAS). In both the NSA and the SSA there were significant differences in photosynthesis among the major tree species, with aspen having the highest CO2 assimilation rates and spruce the lowest. Within a species, photosynthetic rates in the SSA were approximately twice those measured in the NSA, and this was correlated with similar variations in stomatal conductance. Calculations of the ratio of leaf intercellular to ambient CO2 concentration (ci/ca) from leaf carbon isotope discrimination (Δ) values indicated a relatively low degree of stomatal limitation of photosynthesis, despite the low absolute values of stomatal conductance in these boreal tree species. Within each ecosystem, leaf Δ values were strongly correlated with life-form groups (trees, shrubs, forbs, and mosses), and these differences are maintained between years. Although we observed significant variation in the 13C content of tree rings at the old Jack pine site in the NSA during the past decade (indicating interannual variation in the degree of stomatal limitation), changes in summer precipitation and temperature accounted for only 44% of the isotopic variance. We scaled leaf-level processes to the ecosystem level through analyses of well-mixed canopy air. On average, all three forest types had similar ecosystem-level Δ values (average value ± standard deviation, 19.1‰±0.5‰), calculated from measurements of change in the concentration and carbon isotope ratio of atmospheric CO2 during a diurnal cycle within a forest canopy. However, there were

Diquarks and nucleon structure functions

International Nuclear Information System (INIS)

Linkevich, A.D.; Savrin, V.I.; Skachkov, N.B.

1982-01-01

Formulae for structure functions of the deep-inelastic lepton-nucleon scattering are obtained through relativistic wave functions of systems composed of particles with spins 0, 1/2 and 1, 1/2. These wave functions are solutions of covariant two-particle single-time equations describing the nucleon as a system formed out of a quark and a diquark. Diquark is considered as a boson with the spin 0 and 1. The expressions for the nucleon structure functions are obtained by using the matrix elements of the current operator corresponding to the elastic scattering of the photon on a quark and on a diquark [ru

Future Elementary School Teachers' Conceptual Change Concerning Photosynthesis

Science.gov (United States)

Ahopelto, Ilona; Mikkila-Erdmann, Mirjamaija; Anto, Erkki; Penttinen, Marjaana

2011-01-01

The purpose of this study was to examine conceptual change among future elementary school teachers while studying a scientific text concerning photosynthesis. Students' learning goals in relation to their learning outcomes were also examined. The participants were future elementary school teachers. The design consisted of pre- and post-tests. The…

Photosynthesis versus irradiance relationships in the Atlantic sector ...

African Journals Online (AJOL)

The results show substantial variability in the photosynthesis–irradiance (P vs E) parameters, with phytoplankton communities at stations that were considered iron (Fe)-limited showing low maximum photosynthetic capacity (PBmax) and low quantum efficiency of photosynthesis (αB) for ρNO3, but high PBmax and αB for ...

Significance of rice sheath photosynthesis: Yield determination by ...

African Journals Online (AJOL)

Using high-yielding hybrid rice Liangyopeijiu (LYP9), its male parent 9311 and hybrid rice Shanyou 63 (SY63) as the experimental materials, the photosynthesis of rice sheath was studied by 14C radio-autography. The results showed that rice sheath could trap sunlight and produce photosynthates, and these ...

INTERACTIVE ILUSTRATION FOR PHOTOSYNTHESIS TEACHING

Directory of Open Access Journals (Sweden)

M.R. Pereira

2004-05-01

Full Text Available Computational resources became the major tool in the challenge of making high education moreeasy and motivating. Complex Biochemical pathways can now be presented in interactive and three-dimensional animations. One of the most complex (detailed and interesting metabolic pathway thatstudents must understand in biochemical courses is photosynthesis. The light-dependent reactionsare of special interest since they involve many dierent kinds of mechanisms, as light absorptionby membrane complexes, proteins movement inside membranes, reactions of water hydrolysis, andelectrons ow; making it dicult to understand by static bi-dimensional representations.The resources of animation and ActionScript programming were used to make an interactive ani-mation of photosynthesis, which at some times even simulates three-dimensionality. The animationbegins with a leaf and progressively zooms in, until we have a scheme of a tylakoyd membrane, whereeach of the dierent steps of the pathway can be clicked to reveal a more detailed scheme of it. Whereappropriate, the energy graphs are shown side by side with the reactions. The electron is representedwith a face, so it can be shown to be stressing while going up in the energy graphs. Finally, there isa simplied version of the whole pathway, to illustrate how it all goes together.The objective is to help professors on teaching the subject in regular classes, since currently allthe explanations are omitted. In a future version, texts will be added to each step so it can beself-explicative to the students, helping them even on home or on-line learning.

Interaction of two photoreceptors in the regulation of bacterial photosynthesis genes.

Science.gov (United States)

Metz, Sebastian; Haberzettl, Kerstin; Frühwirth, Sebastian; Teich, Kristin; Hasewinkel, Christian; Klug, Gabriele

2012-07-01

The expression of photosynthesis genes in the facultatively photosynthetic bacterium Rhodobacter sphaeroides is controlled by the oxygen tension and by light quantity. Two photoreceptor proteins, AppA and CryB, have been identified in the past, which are involved in this regulation. AppA senses light by its N-terminal BLUF domain, its C-terminal part binds heme and is redox-responsive. Through its interaction to the transcriptional repressor PpsR the AppA photoreceptor controls expression of photosynthesis genes. The cryptochrome-like protein CryB was shown to affect regulation of photosynthesis genes, but the underlying signal chain remained unknown. Here we show that CryB interacts with the C-terminal domain of AppA and modulates the binding of AppA to the transcriptional repressor PpsR in a light-dependent manner. Consequently, binding of the transcription factor PpsR to its DNA target is affected by CryB. In agreement with this, all genes of the PpsR regulon showed altered expression levels in a CryB deletion strain after blue-light illumination. These results elucidate for the first time how a bacterial cryptochrome affects gene expression.

The regulation of the chloroplast proton motive force plays a key role for photosynthesis in fluctuating light.

Science.gov (United States)

Armbruster, Ute; Correa Galvis, Viviana; Kunz, Hans-Henning; Strand, Deserah D

2017-06-01

Plants use sunlight as their primary energy source. During photosynthesis, absorbed light energy generates reducing power by driving electron transfer reactions. These are coupled to the transfer of protons into the thylakoid lumen, generating a proton motive force (pmf) required for ATP synthesis. Sudden alterations in light availability have to be met by regulatory mechanisms to avoid the over-accumulation of reactive intermediates and maximize energy efficiency. Here, the acidification of the lumen, as an intermediate product of photosynthesis, plays an important role by regulating photosynthesis in response to excitation energy levels. Recent findings reveal pmf regulation and the modulation of its composition as key determinants for efficient photosynthesis, plant growth, and survival in fluctuating light environments. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Study of quark structure functions

International Nuclear Information System (INIS)

Dao, F.T.; Flaminio, E.; Lai, K.; Metcalf, M.; Wang, L.

1977-01-01

The quark structure functions of the proton are determined through a combined analysis of the reactions pN → ll-barX and eN → eX. The valence-quark structure function of the pion is also given by analyzing the πN → μμ-barX data measured by the Branson et al

Photosynthesis-dependent isoprene emission from leaf to planet in a global carbon-chemistry-climate model

Science.gov (United States)

Unger, N.; Harper, K.; Zheng, Y.; Kiang, N. Y.; Aleinov, I.; Arneth, A.; Schurgers, G.; Amelynck, C.; Goldstein, A.; Guenther, A.; Heinesch, B.; Hewitt, C. N.; Karl, T.; Laffineur, Q.; Langford, B.; McKinney, K. A.; Misztal, P.; Potosnak, M.; Rinne, J.; Pressley, S.; Schoon, N.; Serça, D.

2013-10-01

We describe the implementation of a biochemical model of isoprene emission that depends on the electron requirement for isoprene synthesis into the Farquhar-Ball-Berry leaf model of photosynthesis and stomatal conductance that is embedded within a global chemistry-climate simulation framework. The isoprene production is calculated as a function of electron transport-limited photosynthesis, intercellular and atmospheric carbon dioxide concentration, and canopy temperature. The vegetation biophysics module computes the photosynthetic uptake of carbon dioxide coupled with the transpiration of water vapor and the isoprene emission rate at the 30 min physical integration time step of the global chemistry-climate model. In the model, the rate of carbon assimilation provides the dominant control on isoprene emission variability over canopy temperature. A control simulation representative of the present-day climatic state that uses 8 plant functional types (PFTs), prescribed phenology and generic PFT-specific isoprene emission potentials (fraction of electrons available for isoprene synthesis) reproduces 50% of the variability across different ecosystems and seasons in a global database of 28 measured campaign-average fluxes. Compared to time-varying isoprene flux measurements at 9 select sites, the model authentically captures the observed variability in the 30 min average diurnal cycle (R2 = 64-96%) and simulates the flux magnitude to within a factor of 2. The control run yields a global isoprene source strength of 451 TgC yr-1 that increases by 30% in the artificial absence of plant water stress and by 55% for potential natural vegetation.

Photosynthesis-dependent Isoprene Emission from Leaf to Planet in a Global Carbon-chemistry-climate Model

Science.gov (United States)

Unger, N.; Harper, K.; Zeng, Y.; Kiang, N. Y.; Alienov, I.; Arneth, A.; Schurgers, G.; Amelynck, C.; Goldstein, A.; Guenther, A.;

Photosynthesis-dependent isoprene emission from leaf to planet in a global carbon-chemistry-climate model

Energy Technology Data Exchange (ETDEWEB)

Unger, N.; Harper, K.; Zheng, Y.; Kiang, N. Y.; Aleinov, I.; Arneth, Almut; Schurgers, G.; Amelynck, C.; Goldstein, Allen H.; Guenther, Alex B.; Heinesch, B.; Hewitt, C. N.; Karl, T.; Laffineur, Q.; Langford, B.; McKinney, Karena A.; Misztal, P.; Potosnak, M.; Rinne, J.; Pressley, S.; Schoon, N.; Serca, D.

2013-10-22

We describe the implementation of a biochemical model of isoprene emission that depends on the electron requirement for isoprene synthesis into the Farquhar/Ball- Berry leaf model of photosynthesis and stomatal conductance that is embedded within a global chemistry-climate simulation framework. The isoprene production is calculated as a function of electron transport-limited photosynthesis, intercellular carbon dioxide concentration, and canopy temperature. The vegetation biophysics module computes the photosynthetic uptake of carbon dioxide coupled with the transpiration of water vapor and the isoprene emission rate at the 30 min physical integration time step of the global chemistry-climate model. In the model, the rate of carbon assimilation provides the dominant control on isoprene emission variability over canopy temperature. A control simulation representative of the present day climatic state that uses plant functional types (PFTs), prescribed phenology and generic PFT-specific isoprene emission potentials (fraction of electrons available for isoprene synthesis) reproduces 50% of the variability across different ecosystems and seasons in a global database of measured campaign-average fluxes. Compared to time-varying isoprene flux measurements at select sites, the model authentically captures the observed variability in the 30 min average diurnal cycle (R² = 64-96 %) and simulates the flux magnitude to within a factor of 2. The control run yields a global isoprene source strength of 451 TgC yr^-1 that increases by 30% in the artificial absence of plant water stress and by 55% for potential natural vegetation.

Effects of complex effluents on photosynthesis in Lake Erie and Lake Huron

International Nuclear Information System (INIS)

Bridgham, S.D.; McNaught, D.C.; Meadows, C.

1988-01-01

Phytoplankton are the base of the food chain in most large lake ecosystems; if affected by environmental pollutants, significant ecosystem changes can result with potential impact on higher trophic levels. The research determined the effects of a complex effluent discharge from the River Raisin in Monroe County, Michigan, on the Lake Erie ecosystem. The river flows through southern Michigan and has large nutrient and industrial inputs, especially in the Monroe Harbor area. The functional parameters measured were bacterial uptake rate of acetate, zooplankton feeding and reproduction rates, and primary production. The results of the effects of complex effluents on gross photosynthesis, measured as carbon-14 ((14)C) uptake, are presented in the paper

Ecosystem Phenology from Eddy-covariance Measurements: Spring Photosynthesis in a Cool Temperate Bog

Science.gov (United States)

Lafleur, P.; Moore, T. R.; Poon, D.; Seaquist, J.

2005-12-01

The onset and increase of spring photosynthetic flux of carbon dioxide is an important attribute of the carbon budget of northern ecosystems and we used eddy-covariance measurements from March to May over 5 years at the Mer Bleue ombrotrophic bog to establish the important controls. The onset of ecosystem photosynthesis (day-of-year from 86 to 101) was associated with the disappearance on the snow cover and there is evidence that photosynthesis can continue after a thin new snowfall. The growth of photosynthesis during the spring period was partially associated with light (daily photosynthetically active radiation) but primarily with temperature, with the strongest correlation being observed with peat temperature at a depth of 5 and 10 cm, except in one year in which there was a long snow cover. The vegetation comprises mosses, which are able to photosynthesize very early, evergreen shrubs, which appear dependent on soil warming, and deciduous shrubs, which leaf-out only in late spring. We observed changes in shrub leaf colour from brown to green and concomitant increases in foliar nitrogen and chlorophyll concentrations during the spring in this "evergreen" system. We analyzed MODIS images for periods of overlap of tower and satellite data and found a generally strong correlation, though the infrequent satellite measurements were unable to pick out the onset and timing of rapid growth of photosynthesis in this ecosystem.

Photosynthesis by isolated chloroplasts. IV. General concept and comparison of three photochemical reactions

Energy Technology Data Exchange (ETDEWEB)

Arnon, D I; Allen, M B; Whatley, F R

1956-01-01

Procedures are described for the preparation of chloroplasts capable of carrying out three photochemical reactions, each representing an increasingly complex phase of photosynthesis: photolysis of water (Hill reaction), esterification of inorganic phosphate into adenosine triphosphate (photosynthetic phosphorylation) and the reduction of carbon dioxide to the level of carbohydrates with a simultaneous evolution of oxygen. The three photochemical reactions were separable by variations in the technique for preparation of chloroplasts and by differential inhibition by several reagents. Inhibition of a more complex phase of photosynthesis does not affect the simpler one which precedes it and, conversely, the inhibition of a simpler phase of photosynthesis is paralleled by an inhibition of the more complex phase which follows. Reversible inhibition of CO/sub 2/ fixation and photosynthetic phosphorylation, but not of photolysis, by sulfhydryl group inhibitors suggests that sulfhydryl compounds (enzymes, cofactors, or both) are involved in phosphorylation and CO/sub 2/ fixation, but not in the primary conversion of light into chemical energy as measured by the Hill reaction. Evidence is presented in support of the conclusion that the synthesis of ATP by green cells occurs at two distinct sites: anaerobically in chloroplasts by photosynthetic phosphorylation, and acrobically in smaller cytoplasmic particles, presumably mitochondria, by oxidative phosphorylation independent of light. A general scheme of photosynthesis by chloroplasts, consistent with these findings, is presented. 44 references, 8 figures, 4 tables.

Inorganic carbon availability in benthic diatom communities: photosynthesis and migration.

Science.gov (United States)

Marques da Silva, Jorge; Cruz, Sónia; Cartaxana, Paulo

2017-09-05

Diatom-dominated microphytobenthos (MPB) is the main primary producer of many intertidal and shallow subtidal environments, being therefore of critical importance to estuarine and coastal food webs. Owing to tidal cycles, intertidal MPB diatoms are subjected to environmental conditions far more variable than the ones experienced by pelagic diatoms (e.g. light, temperature, salinity, desiccation and nutrient availability). Nevertheless, benthic diatoms evolved adaptation mechanisms to these harsh conditions, including the capacity to move within steep physical and chemical gradients, allowing them to perform photosynthesis efficiently. In this contribution, we will review present knowledge on the effects of dissolved inorganic carbon (DIC) availability on photosynthesis and productivity of diatom-dominated MPB. We present evidence of carbon limitation of photosynthesis in benthic diatom mats and highly productive MPB natural communities. Furthermore, we hypothesize that active vertical migration of epipelic motile diatoms could overcome local depletion of DIC in the photic layer, providing the cells alternately with light and inorganic carbon supply. The few available longer-term experiments on the effects of inorganic carbon enrichment on the productivity of diatom-dominated MPB have yielded inconsistent results. Therefore, further studies are needed to properly assess the response of MPB communities to increased CO 2 and ocean acidification related to climate change.This article is part of the themed issue 'The peculiar carbon metabolism in diatoms'. © 2017 The Author(s).

Hartmut Lichtenthaler: an authority on chloroplast structure and isoprenoid biochemistry.

Science.gov (United States)

Sharkey, Thomas D; Govindjee

2016-05-01

We pay tribute to Hartmut Lichtenthaler for making important contributions to the field of photosynthesis research. He was recently recognized for ground-breaking discoveries in chloroplast structure and isoprenoid biochemistry by the Rebeiz Foundation for Basic Research (RFBR; http://vlpbp.org/ ), receiving a 2014 Lifetime Achievement Award for Photosynthesis. The ceremony, held in Champaign, Illinois, was attended by many prominent researchers in the photosynthesis field. We provide below a brief note on his education, and then describe some of the areas in which Hartmut Lichtenthaler has been a pioneer.

Coordinate changes in photosynthesis, sugar accumulation and antioxidative enzymes improve the performance of Jatropha curcas plants under drought stress

International Nuclear Information System (INIS)

Silva, Evandro N.; Ribeiro, Rafael V.; Ferreira-Silva, Sérgio L.; Vieira, Suyanne A.; Ponte, Luiz F.A.; Silveira, Joaquim A.G.

2012-01-01

The aim of this study was to assess the relationships between photosynthesis, sugars and photo-oxidative protection mechanisms in Jatropha curcas under drought stress. Leaf CO 2 assimilation rate (P N ) and instantaneous carboxylation efficiency decreased progressively as the water deficit increased. The sucrose and reducing sugar concentrations were negatively and highly correlated with photosynthesis indicating a modulation by negative feedback mechanism. The alternative electron sinks (ETR s '/P N ), relative excess of light energy (EXC) and non-photochemical quenching were strongly increased by drought, indicating effective mechanisms of energy excess dissipation. The photochemistry data indicate partial preservation of photosystem II integrity and function even under severe drought. EXC was positively correlated with superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities evidencing an effective role of these enzymes in the oxidative protection against excess of reactive oxygen species in chloroplasts. Leaf H 2 O 2 content and lipid peroxidation were inversely and highly correlated with catalase (CAT) activity indicating that drought-induced inhibition of this enzyme might have allowed oxidative damage. Our data suggest that drought triggers a coordinate down-regulation in photosynthesis through sucrose and reducing sugar accumulation and an energy excess dissipation at PSII level by non-photochemical mechanisms associate with enhancement in photorespiration, restricting photo-damages. In parallel, drought up-regulates SOD and APX activities avoiding accumulation of reactive oxygen species, while CAT activity is not able to avoid H 2 O 2 accumulation in drought-stressed J. curcas leaves. -- Highlights: ► Drought triggers a down-regulation in photosynthesis by sucrose and reducing sugar. ► Drought induces energy dissipation at PSII level and increase in photorespiration. ► Drought up-regulates SOD and APX activities avoiding accumulation of

Chlorophyll fluorescence tracks seasonal variations of photosynthesis from leaf to canopy in a temperate forest.

Science.gov (United States)

Yang, Hualei; Yang, Xi; Zhang, Yongguang; Heskel, Mary A; Lu, Xiaoliang; Munger, J William; Sun, Shucun; Tang, Jianwu

2017-07-01

Accurate estimation of terrestrial gross primary productivity (GPP) remains a challenge despite its importance in the global carbon cycle. Chlorophyll fluorescence (ChlF) has been recently adopted to understand photosynthesis and its response to the environment, particularly with remote sensing data. However, it remains unclear how ChlF and photosynthesis are linked at different spatial scales across the growing season. We examined seasonal relationships between ChlF and photosynthesis at the leaf, canopy, and ecosystem scales and explored how leaf-level ChlF was linked with canopy-scale solar-induced chlorophyll fluorescence (SIF) in a temperate deciduous forest at Harvard Forest, Massachusetts, USA. Our results show that ChlF captured the seasonal variations of photosynthesis with significant linear relationships between ChlF and photosynthesis across the growing season over different spatial scales (R 2  = 0.73, 0.77, and 0.86 at leaf, canopy, and satellite scales, respectively; P chlorophyll content (R 2  = 0.65 for canopy GPP SIF and chlorophyll content; P < 0.0001), leaf area index (LAI) (R 2  = 0.35 for canopy GPP SIF and LAI; P < 0.0001), and normalized difference vegetation index (NDVI) (R 2  = 0.36 for canopy GPP SIF and NDVI; P < 0.0001). Our results suggest that ChlF can be a powerful tool to track photosynthetic rates at leaf, canopy, and ecosystem scales. © 2016 John Wiley & Sons Ltd.

The potential feasibility of chlorinic photosynthesis on exoplanets.

Science.gov (United States)

Haas, Johnson R

2010-11-01

The modern search for life-bearing exoplanets emphasizes the potential detection of O(2) and O(3) absorption spectra in exoplanetary atmospheres as ideal signatures of biology. However, oxygenic photosynthesis may not arise ubiquitously in exoplanetary biospheres. Alternative evolutionary paths may yield planetary atmospheres tinted with the waste products of other dominant metabolisms, including potentially exotic biochemistries. This paper defines chlorinic photosynthesis (CPS) as biologically mediated photolytic oxidation of aqueous Cl(-) to form halocarbon or dihalogen products, coupled with CO(2) assimilation. This hypothetical metabolism appears to be feasible energetically, physically, and geochemically, and could potentially develop under conditions that approximate the terrestrial Archean. It is hypothesized that an exoplanetary biosphere in which chlorinic photosynthesis dominates primary production would tend to evolve a strongly oxidizing, halogen-enriched atmosphere over geologic time. It is recommended that astronomical observations of exoplanetary outgoing thermal emission spectra consider signs of halogenated chemical species as likely indicators of the presence of a chlorinic biosphere. Planets that favor the evolution of CPS would probably receive equivalent or greater surface UV flux than is produced by the Sun, which would promote stronger abiotic UV photolysis of aqueous halides than occurred during Earth's Archean era and impose stronger evolutionary selection pressures on endemic life to accommodate and utilize halogenated compounds. Ocean-bearing planets of stars with metallicities equivalent to, or greater than, the Sun should especially favor the evolution of chlorinic biospheres because of the higher relative seawater abundances of Cl, Br, and I such planets would tend to host. Directed searches for chlorinic biospheres should probably focus on G0-G2, F, and A spectral class stars that have bulk metallicities of +0.0 Dex or greater.

Structure functions and correlations in nuclei

International Nuclear Information System (INIS)

Fantoni, S.

1988-01-01

In this paper the results obtained for the static structure function S(k) and the longitudinal structure function S L (k) of 3 H, 3 He and 4 He nuclei and nuclear matter are presented and discussed. The calculations have been performed using realistic wave functions obtained from Faddeev and variational theories. The Monte Carlo method has been used to calculate the structure functions of finite systems, and the FHNC/SOC method for nuclear matter. The results for the 3 He nucleus are in agreement with the recent Saclay data. The results for nuclear matter are compared with the experimental data relative to heavier nuclei, like e.g. 40 Ca

Effects of light and temperature on duckweed photosynthesis

Energy Technology Data Exchange (ETDEWEB)

Wedge, R M; Burris, J E

1982-06-01

Rates of photosynthesis of Lemna minor L. and Spirodela punctata, two aquatic angiosperms, were measured at different temperatures and light intensities. Photosynthesis was measured both as oxygen evolution and /sup 14/CO/sub 2/ fixation. At temperatures ranging from 15 to 35/sup 0/C, light saturation of photosynthetic O/sub 2/ evolution of Lemna occured from 300-600 ..mu..E m/sup -2/ s/sup -1/, while in Spirodela photosynthetic O/sub 2/ evolution was light saturated at 5600-1200 ..mu..E m/sup -2/ s/sup -1/. Photosynthetic O/sub 2/ evolution of both species was photoinhibited at light intensities greater than 1200 ..mu..E m/sup -2/ s/sup -1/. The optimal temperature for Lemna photosynthetic O/sub 2/ evolution was 30/sup 0/C, while the optimal temperatures for /sup 14/CO/sub 2/ fixation were from 20 to 30/sup 0/C. For Spirodela maximum photosynthetic O/sub 2/, evolution occurred at 35/sup 0/C, while maximum /sup 14/CO/sub 2/ fixation was at 30/sup 0/C.

Biocatalytic photosynthesis with water as an electron donor.

Science.gov (United States)

Ryu, Jungki; Nam, Dong Heon; Lee, Sahng Ha; Park, Chan Beum

2014-09-15

Efficient harvesting of unlimited solar energy and its conversion into valuable chemicals is one of the ultimate goals of scientists. With the ever-increasing concerns about sustainable growth and environmental issues, numerous efforts have been made to develop artificial photosynthetic process for the production of fuels and fine chemicals, thus mimicking natural photosynthesis. Despite the research progress made over the decades, the technology is still in its infancy because of the difficulties in kinetic coupling of whole photocatalytic cycles. Herein, we report a new type of artificial photosynthesis system that can avoid such problems by integrally coupling biocatalytic redox reactions with photocatalytic water splitting. We found that photocatalytic water splitting can be efficiently coupled with biocatalytic redox reactions by using tetracobalt polyoxometalate and Rh-based organometallic compound as hole and electron scavengers, respectively, for photoexcited [Ru(bpy)3](2+). Based on these results, we could successfully photosynthesize a model chiral compound (L-glutamate) using a model redox enzyme (glutamate dehydrogenase) upon in situ photoregeneration of cofactors. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Growth, water relations and photosynthesis of seedlings and resprouts after fire

Science.gov (United States)

Clemente, Adelaide S.; Rego, Francisco C.; Correia, Otília A.

2005-05-01

Seasonal patterns of growth, water relations, photosynthesis and leaf characteristics were compared between obligate seeders ( Cistus monspeliensis and Cistus ladanifer) and resprouters ( Arbutus unedo and Pistacia lentiscus) from the first to the second year after fire. We hypothesized that seedlings would be more water-limited than resprouts due to their shallower root systems. Regarding water use strategies, Cistus species are drought semi-deciduous and A. unedo and P. lentiscus are evergreen sclerophylls, therefore, comparisons were based on the relative deviation from mature conspecific plants. Seedlings and resprouts had higher shoot elongation and leaf production than mature plants, and over an extended period. Differences from mature plants were larger in resprouts, with two-fold transpiration, leaf conductance and photosynthesis in late spring/early summer. Seedlings of C. monspeliensis exhibited higher transpiration and leaf conductance than mature plants, while those of C. ladanifer only exhibited higher water potential. Growth increments and ameliorated water relations and photosynthesis after fire were attributed to an increase in water and nutrient availability. The small differences in water relations and photosynthesis between seedlings and mature conspecifics are in accordance with the prediction of seedlings experiencing higher water limitation than resprouts. We attribute these results to differences in root systems: resprouters benefited from an increase in root/shoot ratios and the presence of deep roots whereas Cistus seedlings relied on very shallow roots, which cannot provide assess to deep water during summer. Nevertheless, seedlings did not show evidence of experiencing a more severe water limitation than mature conspecifics, which we attributed to the presence of efficient mechanisms of avoiding and tolerating water stress. The results are discussed in relation to post-fire demography of seeders and resprouters in Mediterranean

Photosynthesis and Ribulose 1,5-Bisphosphate Concentrations in Intact Leaves of Xanthium strumarium L.

Science.gov (United States)

Mott, K A; Jensen, R G; O'leary, J W; Berry, J A

1984-12-01

The interacting effects of the rate of ribulose 1,5-bisphosphate (RuBP) regeneration and the rate of RuBP utilization as influenced by the amount and activation of RuBP carboxylase on photosynthesis and RuBP concentrations were resolved in experiments which examined the kinetics of the response of photosynthesis and RuBP concentrations after step changes from a rate-saturating to a rate-limiting light intensity in Xanthium strumarium. Because RuBP carboxylase requires several minutes to deactivate in vivo, it was possible to observe the effect of reducing the rate of RuBP regeneration on the RuBP concentration at constant enzyme activation state by sampling very soon after reducing the light intensity. Samples taken over longer time periods showed the effect of changes in enzyme activation at constant RuBP regeneration rate on RuBP concentration and photosynthetic rate. Within 15 s of lowering the light intensity from 1500 to 600 microEinsteins per square meter per second the RuBP concentration in the leaves dropped below the enzyme active site concentration, indicating that RuBP regeneration rate was limiting for photosynthesis. After longer intervals of time, the RuBP concentration in the leaf increased as the RuBP carboxylase assumed a new steady state activation level. No change in the rate of photosynthesis was observed during the interval that RuBP concentration increased. It is concluded that the rate of photosynthesis at the lower light intensity was limited by the rate of RuBP regeneration and that parallel changes in the activation of RuBP carboxylase occurred such that concentrations of RuBP at steady state were not altered by changes in light intensity.

Global Forest Ecosystem Structure and Function Data For Carbon Balance Research

Data.gov (United States)

National Aeronautics and Space Administration — ABSTRACT: A comprehensive global database has been assembled to quantify CO2 fluxes and pathways across different levels of integration (from photosynthesis up to...

Global Forest Ecosystem Structure and Function Data For Carbon Balance Research

Data.gov (United States)

National Aeronautics and Space Administration — A comprehensive global database has been assembled to quantify CO2 fluxes and pathways across different levels of integration (from photosynthesis up to net...

Overexpression of monoubiquitin improves photosynthesis in transgenic tobacco plants following high temperature stress.

Science.gov (United States)

Tian, Fengxia; Gong, Jiangfeng; Zhang, Jin; Feng, Yanan; Wang, Guokun; Guo, Qifang; Wang, Wei

2014-09-01

The ubiquitin/26S proteasome system (Ub/26S) is implicated in abiotic stress responses in plants. In this paper, transgenic tobacco plants overexpressing Ta-Ub2 from wheat were used to study the functions of Ub in the improvement of photosynthesis under high temperature (45°C) stress. We observed higher levels of Ub conjugates in transgenic plants under high temperature stress conditions compared to wild type (WT) as a result of the constitutive overexpression of Ta-Ub2, suggesting increased protein degradation by the 26S proteasome system under high temperature stress. Overexpressing Ub increased the photosynthetic rate (Pn) of transgenic tobacco plants, consistent with the improved ATPase activity in the thylakoid membrane and enhanced efficiency of PSII photochemistry. The higher D1 protein levels following high temperature stress in transgenic plants than WT were also observed. These findings imply that Ub may be involved in tolerance of photosynthesis to high temperature stress in plants. Compared with WT, the transgenic plants showed lower protein carbonylation and malondialdehyde (MDA) levels, less reactive oxygen species (ROS) accumulation, but higher antioxidant enzyme activity under high temperature stress. These findings suggest that the improved antioxidant capacity of transgenic plants may be one of the most important mechanisms underlying Ub-regulated high temperature tolerance. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Resonance contribution to electromagnetic structure functions

International Nuclear Information System (INIS)

Bowling, A.L. Jr.

1974-01-01

The part of the pion and proton electromagnetic structure functions due to direct channel resonances in the virtual Compton amplitude is discussed. After a phenomenological discussion, based on the work of Bloom and Gilman, of resonance production in inelastic electroproduction, the single resonance contribution to the pion and proton structure functions is expressed in terms of transition form factors. Froissart-Gribov representations of the Compton amplitude partial waves are presented and are used to specify the spin dependence of the transition form factors. The dependence of the form factors on momentum transfer and resonance mass is assumed on the basis of the behavior of exclusive resonance electroproduction. The single resonance contributions are summed in the Bjorken limit, and the result exhibits Bjorken scaling. Transverse photons are found to dominate in the Bjorken limit, and the threshold behavior of the resonant part of the structure functions is related to the asymptotic behavior of exclusive form factors at large momentum transfer. The resonant parts of the annihilation structure functions are not in general given by simple analytic continuation in the scaling vari []ble ω' of the electroproduction structure functions. (Diss. Abstr. Int., B)

Phenomenology of the electron structure function

International Nuclear Information System (INIS)

Slominski, W.; Szwed, J.

2001-01-01

The advantages of introducing the electron structure function (ESF) in electron induced processes are demonstrated. Contrary to the photon structure function it is directly measured in such processes. At present energies, a simultaneous analysis of both the electron and the photon structure functions gives an important test of the experimentally applied methods. Estimates of the ESF at LEP momenta are given. At very high momenta contributions from W and Z bosons together with γ-Z interference can be observed. Predictions for the next generation of experiments are given. (orig.)

Artificial photosynthesis: from basic biology to industrial application

National Research Council Canada - National Science Library

Collings, Anthony F; Critchley, Christa

2005-01-01

... some of the same outcomes at rates and scales that far exceed those found in nature. In this field the ubiquitous process is photosynthesis - an ancient process inherent to almost all plants and many prokaryotes on the planet that ultimately enabled the development of earth's animal kingdom. From a practical perspective, the natural process of photosynth...

Modelling soil temperature and moisture and corresponding seasonality of photosynthesis and transpiration in a boreal spruce ecosystem

Science.gov (United States)

Wu, S. H.; Jansson, P.-E.

2013-02-01

Recovery of photosynthesis and transpiration is strongly restricted by low temperatures in air and/or soil during the transition period from winter to spring in boreal zones. The extent to which air temperature (Ta) and soil temperature (Ts) influence the seasonality of photosynthesis and transpiration of a boreal spruce ecosystem was investigated using a process-based ecosystem model (CoupModel) together with eddy covariance (EC) data from one eddy flux tower and nearby soil measurements at Knottåsen, Sweden. A Monte Carlo-based uncertainty method (GLUE) provided prior and posterior distributions of simulations representing a wide range of soil conditions and performance indicators. The simulated results showed sufficient flexibility to predict the measured cold and warm Ts in the moist and dry plots around the eddy flux tower. Moreover, the model presented a general ability to describe both biotic and abiotic processes for the Norway spruce stand. The dynamics of sensible heat fluxes were well described by the corresponding latent heat fluxes and net ecosystem exchange of CO2. The parameter ranges obtained are probably valid to represent regional characteristics of boreal conifer forests, but were not easy to constrain to a smaller range than that produced by the assumed prior distributions. Finally, neglecting the soil temperature response function resulted in fewer behavioural models and probably more compensatory errors in other response functions for regulating the seasonality of ecosystem fluxes.

Differential effects of glyphosate and aminomethylphosphonic acid (AMPA) on photosynthesis and chlorophyll metabolism in willow plants.

Science.gov (United States)

Gomes, Marcelo Pedrosa; Le Manac'h, Sarah Gingras; Maccario, Sophie; Labrecque, Michel; Lucotte, Marc; Juneau, Philippe

2016-06-01

We used a willow species (Salix miyabeana cultivar SX64) to examine the differential secondary-effects of glyphosate and aminomethylphosphonic acid (AMPA), the principal glyphosate by-product, on chlorophyll metabolism and photosynthesis. Willow plants were treated with different concentrations of glyphosate (equivalent to 0, 1.4, 2.1 and 2.8kgha(-1)) and AMPA (equivalent to 0, 0.28, 1.4 and 2.8kgha(-1)) and evaluations of pigment contents, chlorophyll fluorescence, and oxidative stress markers (hydrogen peroxide content and antioxidant enzyme activities) in leaves were performed after 12h of exposure. We observed that AMPA and glyphosate trigger different mechanisms leading to decreases in chlorophyll content and photosynthesis rates in willow plants. Both chemicals induced ROS accumulation in willow leaves although only glyphosate-induced oxidative damage through lipid peroxidation. By disturbing chlorophyll biosynthesis, AMPA induced decreases in chlorophyll contents, with consequent effects on photosynthesis. With glyphosate, ROS increases were higher than the ROS-sensitive threshold, provoking chlorophyll degradation (as seen by pheophytin accumulation) and invariable decreases in photosynthesis. Peroxide accumulation in both AMPA and glyphosate-treated plants was due to the inhibition of antioxidant enzyme activities. The different effects of glyphosate on chlorophyll contents and photosynthesis as described in the literature may be due to various glyphosate:AMPA ratios in those plants. Copyright © 2015 Elsevier Inc. All rights reserved.

A two-dimensional microscale model of gas exchange during photosynthesis in maize (Zea mays L.) leaves.

Science.gov (United States)

Retta, Moges; Ho, Quang Tri; Yin, Xinyou; Verboven, Pieter; Berghuijs, Herman N C; Struik, Paul C; Nicolaï, Bart M

2016-05-01

CO2 exchange in leaves of maize (Zea mays L.) was examined using a microscale model of combined gas diffusion and C4 photosynthesis kinetics at the leaf tissue level. Based on a generalized scheme of photosynthesis in NADP-malic enzyme type C4 plants, the model accounted for CO2 diffusion in a leaf tissue, CO2 hydration and assimilation in mesophyll cells, CO2 release from decarboxylation of C4 acids, CO2 fixation in bundle sheath cells and CO2 retro-diffusion from bundle sheath cells. The transport equations were solved over a realistic 2-D geometry of the Kranz anatomy obtained from light microscopy images. The predicted responses of photosynthesis rate to changes in ambient CO2 and irradiance compared well with those obtained from gas exchange measurements. A sensitivity analysis showed that the CO2 permeability of the mesophyll-bundle sheath and airspace-mesophyll interfaces strongly affected the rate of photosynthesis and bundle sheath conductance. Carbonic anhydrase influenced the rate of photosynthesis, especially at low intercellular CO2 levels. In addition, the suberin layer at the exposed surface of the bundle sheath cells was found beneficial in reducing the retro-diffusion. The model may serve as a tool to investigate CO2 diffusion further in relation to the Kranz anatomy in C4 plants. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Physiological basis of genetic variation in leaf photosynthesis among rice (Oryza sativa L.) introgression lines under drought and well-watered conditions

Science.gov (United States)

Yin, Xinyou

2012-01-01

To understand the physiological basis of genetic variation and resulting quantitative trait loci (QTLs) for photosynthesis in a rice (Oryza sativa L.) introgression line population, 13 lines were studied under drought and well-watered conditions, at flowering and grain filling. Simultaneous gas exchange and chlorophyll fluorescence measurements were conducted at various levels of incident irradiance and ambient CO2 to estimate parameters of a model that dissects photosynthesis into stomatal conductance (g s), mesophyll conductance (g m), electron transport capacity (J max), and Rubisco carboxylation capacity (V cmax). Significant genetic variation in these parameters was found, although drought and leaf age accounted for larger proportions of the total variation. Genetic variation in light-saturated photosynthesis and transpiration efficiency (TE) were mainly associated with variation in g s and g m. One previously mapped major QTL of photosynthesis was associated with variation in g s and g m, but also in J max and V cmax at flowering. Thus, g s and g m, which were demonstrated in the literature to be responsible for environmental variation in photosynthesis, were found also to be associated with genetic variation in photosynthesis. Furthermore, relationships between these parameters and leaf nitrogen or dry matter per unit area, which were previously found across environmental treatments, were shown to be valid for variation across genotypes. Finally, the extent to which photosynthesis rate and TE can be improved was evaluated. Virtual ideotypes were estimated to have 17.0% higher photosynthesis and 25.1% higher TE compared with the best genotype investigated. This analysis using introgression lines highlights possibilities of improving both photosynthesis and TE within the same genetic background. PMID:22888131

Photosynthesis-fermentation hybrid system to produce lipid feedstock for algal biofuel.

Science.gov (United States)

Lu, Yue; Dai, Junbiao; Wu, Qingyu

2013-01-01

To avoid bacterial contamination due to medium replacement in the expanded application of a photosynthesis-fermentation model, an integrated photosynthesis-fermentation hybrid system was set up and evaluated for algal lipid production using Chlorella protothecoides. In this system, the CO2-rich off-gas from the fermentation process was recycled to agitate medium in thephotobioreactor, which could provide initial cells for the heterotrophic fermentation. The cell concentration reached 1.03 +/- 0.07 g/L during photoautotrophic growth and then the concentrated green cells were switched to heterotrophic fermentation after removing over 99.5% ofnitrogen in the medium by a nitrogen removal device. At the end offermentation in the system, the cell concentration could reach as high as 100.51 +/- 2.03 g/L, and 60.05 +/- 1.38% lipid content was achieved simultaneously. The lipid yield (60.36 +/- 2.63 g/L) in the hybrid system was over 700 times higher than that in a photobioreactor and exceeded that by fermentation alone (47.56 +/- 7.31 g/L). The developed photosynthesis-fermentation hybrid system in this study was not only a feasible option to enhance microalgal lipid production, but also an environment-friendly approach to produce biofuel feedstock through concurrent utilization of ammonia nitrogen, CO2, and organic carbons.

Evaluating potential spectral impacts of various artificial lights on melatonin suppression, photosynthesis, and star visibility.

Directory of Open Access Journals (Sweden)

Martin Aubé

Full Text Available Artificial light at night can be harmful to the environment, and interferes with fauna and flora, star visibility, and human health. To estimate the relative impact of a lighting device, its radiant power, angular photometry and detailed spectral power distribution have to be considered. In this paper we focus on the spectral power distribution. While specific spectral characteristics can be considered harmful during the night, they can be considered advantageous during the day. As an example, while blue-rich Metal Halide lamps can be problematic for human health, star visibility and vegetation photosynthesis during the night, they can be highly appropriate during the day for plant growth and light therapy. In this paper we propose three new indices to characterize lamp spectra. These indices have been designed to allow a quick estimation of the potential impact of a lamp spectrum on melatonin suppression, photosynthesis, and star visibility. We used these new indices to compare various lighting technologies objectively. We also considered the transformation of such indices according to the propagation of light into the atmosphere as a function of distance to the observer. Among other results, we found that low pressure sodium, phosphor-converted amber light emitting diodes (LED and LED 2700 K lamps filtered with the new Ledtech's Equilib filter showed a lower or equivalent potential impact on melatonin suppression and star visibility in comparison to high pressure sodium lamps. Low pressure sodium, LED 5000 K-filtered and LED 2700 K-filtered lamps had a lower impact on photosynthesis than did high pressure sodium lamps. Finally, we propose these indices as new standards for the lighting industry to be used in characterizing their lighting technologies. We hope that their use will favor the design of new environmentally and health-friendly lighting technologies.

Effects of enhances ultra violet irradiation on photosynthesis in ...

African Journals Online (AJOL)

Effects of enhances ultra violet irradiation on photosynthesis in anabaena variabilis and phormidium uncinatum. VA Donkor. Abstract. No Abstract. Journal of the Ghana Association Vol. 2 (3) 1999: pp.16-23. Full Text: EMAIL FULL TEXT EMAIL FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT.

Enhanced Thermostability of Arabidopsis Rubisco activase improves photosynthesis and growth rates under moderate heat stress.

Science.gov (United States)

Kurek, Itzhak; Chang, Thom Kai; Bertain, Sean M; Madrigal, Alfredo; Liu, Lu; Lassner, Michael W; Zhu, Genhai

2007-10-01

Plant photosynthesis declines when the temperature exceeds its optimum range. Recent evidence indicates that the reduction in photosynthesis is linked to ribulose-1,5-bis-phosphate carboxylase/oxygenase (Rubisco) deactivation due to the inhibition of Rubisco activase (RCA) under moderately elevated temperatures. To test the hypothesis that thermostable RCA can improve photosynthesis under elevated temperatures, we used gene shuffling technology to generate several Arabidopsis thaliana RCA1 (short isoform) variants exhibiting improved thermostability. Wild-type RCA1 and selected thermostable RCA1 variants were introduced into an Arabidopsis RCA deletion (Deltarca) line. In a long-term growth test at either constant 26 degrees C or daily 4-h 30 degrees C exposure, the transgenic lines with the thermostable RCA1 variants exhibited higher photosynthetic rates, improved development patterns, higher biomass, and increased seed yields compared with the lines expressing wild-type RCA1 and a slight improvement compared with untransformed Arabidopsis plants. These results provide clear evidence that RCA is a major limiting factor in plant photosynthesis under moderately elevated temperatures and a potential target for genetic manipulation to improve crop plants productivity under heat stress conditions.

A two-dimensional microscale model of gas exchange during photosynthesis in maize (Zea mays L.) leaves

NARCIS (Netherlands)

Retta, Moges; Ho, Quang Tri; Yin, Xinyou; Verboven, Pieter; Berghuijs, Herman N.C.; Struik, Paul C.; Nicolaï, Bart M.

2016-01-01

CO₂ exchange in leaves of maize (Zea mays L.) was examined using a microscale model of combined gas diffusion and C₄ photosynthesis kinetics at the leaf tissue level. Based on a generalized scheme of photosynthesis in NADP-malic enzyme type C₄ plants, the model

In situ autumn ozone fumigation of mature Norway spruce - Effects on net photosynthesis

DEFF Research Database (Denmark)

Mikkelsen, Teis Nørgaard; Ro-Poulsen, H.

2002-01-01

concentration. The experiment was conducted during 70 days during the autumn. Our system could not detect any ozone effects on dark respiration, but eventually effects on dark respiration could be masked in signal noise. An inhibition of daily net photosynthesis in ozone treated shoots was apparent......, and it is was found that a mean increase in ozone concentration of 10 nl l(-1) reduced net photosynthesis with 7.4 %. This effect should be related to a pre-exposure during the season of AOT40 12.5 mul l(-1) h....

Tracking diurnal changes of photosynthesis and evapotranspiration using fluorescence, gas exchange and hyperspectral remote sensing measurements

Science.gov (United States)

Wang, S.; Zhang, L.; Guanter, L.; Huang, C.

2017-12-01

Photosynthesis and evapotranspiration (ET) are the two most important activities of vegetation and make a great contribution to carbon, water and energy exchanges. Remote sensing provides opportunities for monitoring these processes across time and space. This study focuses on tracking diurnal changes of photosynthesis and evapotranspiration over soybean using multiple measurement techniques. Diurnal changes of both remote sensing-based indicators, including active and passive chlorophyll fluorescence and biophysical-related parameters, including photosynthesis rate (photo) and leaf stomatal conductance (cond), were observed. Results showed that both leaf-level steady-state fluorescence (Fs) and canopy-level solar-induced chlorophyll fluorescence were linearly correlated to photosynthetically active radiation (PAR) during the daytime. A double-peak diurnal change curve was observed for leaf-level photo and cond but not for Fs or SIF. Photo and cond showed a strong nonlinear (second-order) correlation, indicating that photosynthesis, which might be remotely sensed by SIF, has the opportunity to track short-term changes of ET. Results presented in this report will be helpful for better understanding the relationship between remote-sensing-based indices and vegetation's biophysical processes.

UV-B sensitivity of plant photosynthesis as influenced by visible irradiation

International Nuclear Information System (INIS)

Caldwell, M.M.; Warner, C.W.

1982-01-01

Experiments were made to separate the effects of preconditioning and concomitant visible irradiation and to investigate this with respect to both light-limited and light-saturated photosynthesis. (orig./AJ)

Changes in photosynthesis and activities of enzymes involved in ...

African Journals Online (AJOL)

AJL

2012-04-26

Apr 26, 2012 ... oxygen and carbohydrates. In photosynthesis, a series of redox reactions occur in the electron transport system present in the chloroplast thylakoid membranes. Oxi- dation of water is catalyzed by photosystem II (PSII), a multi-subunit pigment protein complex located in the thylakoid membrane (Hillier and ...

Effects of proline on photosynthesis, root reactive oxygen species ...

African Journals Online (AJOL)

use

2011-12-14

Dec 14, 2011 ... Hoagland's nutrient solution (pH 6.3 to 6.5, EC 2.0 to 2.2 dS m-1). The nutrient .... photosynthesis system (LI-6400, LI-COR, Lincoln, NE, USA). The ..... Duan JJ, Li J, Guo SR, Kang YY (2008). ... Foster JG, Hess JL (1980).

Limited effect of ozone reductions on the 20-year photosynthesis trend at Harvard forest.

Science.gov (United States)

Yue, Xu; Keenan, Trevor F; Munger, William; Unger, Nadine

2016-11-01

Ozone (O 3 ) damage to leaves can reduce plant photosynthesis, which suggests that declines in ambient O 3 concentrations ([O 3 ]) in the United States may have helped increase gross primary production (GPP) in recent decades. Here, we assess the effect of long-term changes in ambient [O 3 ] using 20 years of observations at Harvard forest. Using artificial neural networks, we found that the effect of the inclusion of [O 3 ] as a predictor was slight, and independent of O 3 concentrations, which suggests limited high-frequency O 3 inhibition of GPP at this site. Simulations with a terrestrial biosphere model, however, suggest an average long-term O 3 inhibition of 10.4% for 1992-2011. A decline of [O 3 ] over the measurement period resulted in moderate predicted GPP trends of 0.02-0.04 μmol C m -2  s -1  yr -1 , which is negligible relative to the total observed GPP trend of 0.41 μmol C m -2  s -1  yr -1 . A similar conclusion is achieved with the widely used AOT40 metric. Combined, our results suggest that ozone reductions at Harvard forest are unlikely to have had a large impact on the photosynthesis trend over the past 20 years. Such limited effects are mainly related to the slow responses of photosynthesis to changes in [O 3 ]. Furthermore, we estimate that 40% of photosynthesis happens in the shade, where stomatal conductance and thus [O 3 ] deposition is lower than for sunlit leaves. This portion of GPP remains unaffected by [O 3 ], thus helping to buffer the changes of total photosynthesis due to varied [O 3 ]. Our analyses suggest that current ozone reductions, although significant, cannot substantially alleviate the damages to forest ecosystems. © 2016 John Wiley & Sons Ltd.

Structure and Structure-activity Relationship of Functional Organic Molecules

Institute of Scientific and Technical Information of China (English)

2011-01-01

@@ Research theme The group is made up of junior scientists from the State Key Laboratory of Elemento-organic Chemistry, Nankai University.The scientists focus their studis on the structure and structure-activity relationship of functional organic molecules not only because it has been the basis of their research, but also because the functional study of organic compounds is now a major scientific issue for organic chemists around the world.

Toxic effects of chlorinated organic compounds and potassium dichromate on growth rate and photosynthesis of marine phytoplankton

DEFF Research Database (Denmark)

Kusk, Kresten Ole; Nyholm, Niels

1992-01-01

The toxic effects of potassium dichromate (K2Cr2O7), 3,4-dichloroaniline (DCA) and 2,4-dichlorophenol (DCP) on the photosynthesis of natural marine phytoplankton and five species of marine microalgae were investigated. Effect concentrations corresponding to a 50 % depression of photosynthesis (6h...

Changes in leaf area, nitrogen content and canopy photosynthesis in soybean exposed to an ozone concentration gradient

Science.gov (United States)

Influences of ozone (O3) on light-saturated rates of photosynthesis in crop leaves have been well documented. To increase our understanding of O3 effects on individual- or stand level productivity, a mechanistic understanding of factors determining canopy photosynthesis is necessary. We used a canop...

Photosynthesis-dependent isoprene emission from leaf to planet in a global carbon-chemistry-climate model

Directory of Open Access Journals (Sweden)

N. Unger

2013-10-01

Full Text Available We describe the implementation of a biochemical model of isoprene emission that depends on the electron requirement for isoprene synthesis into the Farquhar–Ball–Berry leaf model of photosynthesis and stomatal conductance that is embedded within a global chemistry-climate simulation framework. The isoprene production is calculated as a function of electron transport-limited photosynthesis, intercellular and atmospheric carbon dioxide concentration, and canopy temperature. The vegetation biophysics module computes the photosynthetic uptake of carbon dioxide coupled with the transpiration of water vapor and the isoprene emission rate at the 30 min physical integration time step of the global chemistry-climate model. In the model, the rate of carbon assimilation provides the dominant control on isoprene emission variability over canopy temperature. A control simulation representative of the present-day climatic state that uses 8 plant functional types (PFTs, prescribed phenology and generic PFT-specific isoprene emission potentials (fraction of electrons available for isoprene synthesis reproduces 50% of the variability across different ecosystems and seasons in a global database of 28 measured campaign-average fluxes. Compared to time-varying isoprene flux measurements at 9 select sites, the model authentically captures the observed variability in the 30 min average diurnal cycle (R2 = 64–96% and simulates the flux magnitude to within a factor of 2. The control run yields a global isoprene source strength of 451 TgC yr−1 that increases by 30% in the artificial absence of plant water stress and by 55% for potential natural vegetation.

Effects of ultraviolet light on photosynthesis and pigments of Antarctic marine phytoplankton

International Nuclear Information System (INIS)

Stephens, F.C.

1989-01-01

This field study was conducted at Palmer Station, Anvers Island, Antarctica, during November-December, 1987. The main objectives were to quantify the effects on photosynthetic rates and pigmentation of short-term and long-term exposures of Antarctic phytoplankton to different levels of UV radiation. Phytoplankton and ice algae were exposed to four levels of UV radiation in outdoor incubation chambers: near ambient UV; UV enhanced by approximately 5% over ambient levels; reduced UV-B; and essentially no UV. Results of 4-hour studies showed that rates of phytoplankton photosynthesis were generally inversely related to UV exposure. Higher photosynthetic rates were maintained over a greater range of irradiance levels when UV was removed in photosynthesis-irradiance studies. Photosynthetic pigments did not change with variations in either visible or UV light. After adaptation for 24 hours, photosynthetic rate measured under conditions of essentially no UV was approximately twice that measured under near ambient UV conditions. Results of photosynthesis-irradiance experiments indicate that photosynthetic efficiencies (α), maximum photosynthetic rates (P max ) and the index of inhibition (I b ) were inversely related to UV levels, probably due at least in part to the loss of chlorophyll a

Inorganic Carbon Source for Photosynthesis in the Seagrass Thalassia hemprichii (Ehrenb.) Aschers.

Science.gov (United States)

Abel, K M

1984-11-01

Photosynthetic carbon uptake of the tropical seagrass Thalassia hemprichii (Ehrenb.) Aschers was studied by several methods. Photosynthesis in buffered seawater in media in the range of pH 6 to pH 9 showed an exponentially increasing rate with decreasing pH, thus indicating that free CO(2) was a photosynthetic substrate. However, these experiments were unable to determine whether photosynthesis at alkaline pH also contained some component due to HCO(3) (-) uptake. This aspect was further investigated by studying photosynthetic rates in a number of media of varying pH (7.8-8.61) and total inorganic carbon (0.75-13.17 millimolar). In these media, photosynthetic rate was correlated with free CO(2) concentration and was independent of the HCO(3) (-) concentration in the medium. Short time-course experiments were conducted during equilibration of free CO(2) and HCO(3) (-) after injection of (14)C labeled solution at acid or alkaline pH. High initial photosynthetic rates were observed when acidic solutions (largely free CO(2)) were used but not with alkaline solutions. The concentration of free CO(2) was found to be a limiting factor for photosynthesis in this plant.

The Structure-Function Linkage Database.

Science.gov (United States)

Akiva, Eyal; Brown, Shoshana; Almonacid, Daniel E; Barber, Alan E; Custer, Ashley F; Hicks, Michael A; Huang, Conrad C; Lauck, Florian; Mashiyama, Susan T; Meng, Elaine C; Mischel, David; Morris, John H; Ojha, Sunil; Schnoes, Alexandra M; Stryke, Doug; Yunes, Jeffrey M; Ferrin, Thomas E; Holliday, Gemma L; Babbitt, Patricia C

2014-01-01

The Structure-Function Linkage Database (SFLD, http://sfld.rbvi.ucsf.edu/) is a manually curated classification resource describing structure-function relationships for functionally diverse enzyme superfamilies. Members of such superfamilies are diverse in their overall reactions yet share a common ancestor and some conserved active site features associated with conserved functional attributes such as a partial reaction. Thus, despite their different functions, members of these superfamilies 'look alike', making them easy to misannotate. To address this complexity and enable rational transfer of functional features to unknowns only for those members for which we have sufficient functional information, we subdivide superfamily members into subgroups using sequence information, and lastly into families, sets of enzymes known to catalyze the same reaction using the same mechanistic strategy. Browsing and searching options in the SFLD provide access to all of these levels. The SFLD offers manually curated as well as automatically classified superfamily sets, both accompanied by search and download options for all hierarchical levels. Additional information includes multiple sequence alignments, tab-separated files of functional and other attributes, and sequence similarity networks. The latter provide a new and intuitively powerful way to visualize functional trends mapped to the context of sequence similarity.

Synthetic system mimicking the energy transfer and charge separation of natural photosynthesis

Energy Technology Data Exchange (ETDEWEB)

Gust, D.; Moore, T.A.

1985-05-01

A synthetic molecular triad consisting of a porphyrin P linked to both a quinone Q and a carotenoid polyene C has been prepared as a mimic of natural photosynthesis for solar energy conversion purposes. Laser flash excitation of the porphyrin moiety yields a charge-separated state Csup(+.)-P-Qsup(-.) within 100 ps with a quantum yield of more than 0.25. This charge-separated state has a lifetime on the microsecond time scale in suitable solvents. The triad also models photosynthetic antenna function and photoprotection from singlet oxygen damge. The successful biomimicry of photosynthetic charge separation is in part the result of multistep electron transfers which rapidly separate the charges and leave the system at high potential, but with a considerable barrier to recombination.

Polarized DIS Structure Functions from Neural Networks

International Nuclear Information System (INIS)

Del Debbio, L.; Guffanti, A.; Piccione, A.

2007-01-01

We present a parametrization of polarized Deep-Inelastic-Scattering (DIS) structure functions based on Neural Networks. The parametrization provides a bias-free determination of the probability measure in the space of structure functions, which retains information on experimental errors and correlations. As an example we discuss the application of this method to the study of the structure function g 1 p (x,Q 2 )

Regressive Evolution of Photosynthesis in the Roseobacter Clade

Czech Academy of Sciences Publication Activity Database

Koblížek, Michal; Zeng, Yonghui; Horák, A.; Oborník, Miroslav

2013-01-01

Roč. 66, č. 2013 (2013), s. 385-405 ISSN 0065-2296 R&D Projects: GA ČR GAP501/10/0221; GA ČR GBP501/12/G055; GA MŠk ED2.1.00/03.0110 Institutional support: RVO:61388971 Keywords : roseobacter clade * photosynthesis * marine microbial communities Subject RIV: EE - Microbiology, Virology Impact factor: 1.740, year: 2013

Structure functions and correlations in nuclei

International Nuclear Information System (INIS)

Schiavilla, R.; Lewart, D.S.; Pandharipande, V.R.

1987-01-01

The static longitudinal structure function S l (k) and the static structure function S(k) of 3 H, 3 He and 4 He nuclei and nuclear matter are calculated using realistic wave functions obtained from Faddeev and variational calculations. In order to study the variation of the structure function with the number of particles in the system we also calculate S(k) of atomic helium liquid drops containing 4, 8, 20, 40, 70, 168 and 240 atoms. Monte Carlo integration is used to calculate the structure functions of finite systems, while those of nuclear matter are calculated with chain summation methods. The behaivior of S(k) and S l (k) at small values of k is discussed. We find that the recent Saclay data on S l (k) of the 3 He nucleus are in agreement with theory. Though the data indicate the the existence of correlations between the two protons in the 3 He nucleus, they are not accurate enough to draw interesting conclusions about the repulsive core in the nucleon-nucleon interaction. The structure functions of atomic helium liquid drops indicate a smooth variation of S(k) with the number of atoms in the drop. The S L (k) of the 4 He nucleus and nuclear matter are very similar for k > 1.5 fm -1 , and it appears plausible that S L (k) of nuclei having A > 3 may not depend significantly on A when k > 1.5 fm -1 . (orig.)

The Chlamydomonas Genome Reveals the Evolution of Key Animal and Plant Functions

Energy Technology Data Exchange (ETDEWEB)

Merchant, Sabeeha S

2007-04-09

Chlamydomonas reinhardtii is a unicellular green alga whose lineage diverged from land plants over 1 billion years ago. It is a model system for studying chloroplast-based photosynthesis, as well as the structure, assembly, and function of eukaryotic flagella (cilia), which were inherited from the common ancestor of plants and animals, but lost in land plants. We sequenced the 120-megabase nuclear genome of Chlamydomonas and performed comparative phylogenomic analyses, identifying genes encoding uncharacterized proteins that are likely associated with the function and biogenesis of chloroplasts or eukaryotic flagella. Analyses of the Chlamydomonas genome advance our understanding of the ancestral eukaryotic cell, reveal previously unknown genes associated with photosynthetic and flagellar functions, and establish links between ciliopathy and the composition and function of flagella.

Enhancement of photosynthesis in Sorghum bicolor by ultraviolet radiation

International Nuclear Information System (INIS)

Johnson, G.A.; Day, T.A.

2002-01-01

We assessed the influence of ultraviolet radiation (UV) on net photosynthetic CO 2 assimilation rate (Pn) in Sorghum bicolor, with particular attention to examining whether UV can enhance Pn via direct absorption of UV and absorption of UV-induced blue fluorescence by photosynthetic pigments. A polychromatic UV response spectrum of leaves was constructed by measuring Pn under different UV supplements using filters that had sharp transmission cut-offs from 280 to 382 nm, against a background of non-saturating visible light. When the abaxial surface was irradiated, P n averaged 4.6% higher with the UV supplement that cut-off UV at 311 nm, compared to lower and higher UV wavelength supplements. This former supplement differed from higher wavelength supplements by primarily providing more UV between 320 and 350 nm. To assess the possibility of direct absorption of UV by photosynthetic pigments, we measured the absorbance of extracted chlorophylls. Chlorophyll a had absorbance peaks at 340 and 389 nm that were 49 and 72% of that at the sorét peak. Chlorophyll b had absorbance peaks at 315 and 346 nm that were both 35% of that at the sorét peak. Since the epidermis transmits some UV, the strong UV absorbance of chlorophyll implies a potential role for irradiance beyond the bounds of the conventionally defined photosynthetically active radiation waveband (400–700 nm). To assess the role of absorption of UV-induced blue fluorescence, we measured the UV-induced fluorescence excitation and emission spectra of leaves. Abaxial excitation peaked at 328 nm, while emission peaked at 446 nm. In this analysis, we used our abaxial fluorescence excitation spectrum and the UV photosynthetic inhibition spectrum of Caldwell et al. (1986) to weight the UV irradiance with each cut-off filter, thereby estimating the potential contribution of UV-induced blue fluorescence to photosynthesis and the inhibitory effects of UV irradiance on photosynthesis, respectively. With a non

Light dependence of carboxylation capacity for C3 photosynthesis models

Science.gov (United States)

Photosynthesis at high light is often modelled by assuming limitation by the maximum capacity of Rubisco carboxylation at low carbon dioxide concentrations, by electron transport capacity at higher concentrations, and sometimes by triose-phosphate utilization rate at the highest concentrations. Pho...

Hpa1 harpin needs nitroxyl terminus to promote vegetative growth and leaf photosynthesis in Arabidopsis.

Science.gov (United States)

Li, Xiaojie; Han, Liping; Zhao, Yanying; You, Zhenzhen; Dong, Hansong; Zhang, Chunling

2014-03-01

Hpa1 is a harpin protein produced by Xanthomonas oryzae, an important bacterial pathogen of rice, and has the growth-promoting activity in plants. To understand the molecular basis for the function of Hpa1, we generated an inactive variant protein, Hpa1 delta NT, by deleting the nitroxyl-terminal region of the Hpa1 sequence and compared Hpa1 delta NT with the full-length protein in terms of the effects on vegetative growth and related physiological responses in Arabidopsis. When Hpa1 was applied to plants, it acted to enhance the vegetative growth but did not affect the floral development. Enhanced plant growth was accompanied by induced expression of growth-promoting genes in plant leaves. The growth-promoting activity of Hpa1 was further correlated with a physiological consequence shown as promoted leaf photosynthesis as a result of facilitated CO2 conduction through leaf stomata and mesophyll cells. On the contrary, plant growth, growth-promoting gene expression, and the physiological consequence changed little in response to the Hpa1 delta NT treatment. These analyses suggest that Hpa1 requires the nitroxyl-terminus to facilitate CO2 transport inside leaf cells and promote leaf photosynthesis and vegetative growth of the plant.

Harpin Hpa1 Interacts with Aquaporin PIP1;4 to Promote the Substrate Transport and Photosynthesis in Arabidopsis.

Science.gov (United States)

Li, Liang; Wang, Hao; Gago, Jorge; Cui, Haiying; Qian, Zhengjiang; Kodama, Naomi; Ji, Hongtao; Tian, Shan; Shen, Dan; Chen, Yanjuan; Sun, Fengli; Xia, Zhonglan; Ye, Qing; Sun, Wei; Flexas, Jaume; Dong, Hansong

2015-11-26

Harpin proteins produced by plant-pathogenic Gram-negative bacteria are the venerable player in regulating bacterial virulence and inducing plant growth and defenses. A major gap in these effects is plant sensing linked to cellular responses, and plant sensor for harpin Hpa1 from rice bacterial blight pathogen points to plasma membrane intrinsic protein (PIP). Here we show that Arabidopsis AtPIP1;4 is a plasma membrane sensor of Hpa1 and plays a dual role in plasma membrane permeability of CO2 and H2O. In particular, AtPIP1;4 mediates CO2 transport with a substantial contribute to photosynthesis and further increases this function upon interacting with Hpa1 at the plasma membrane. As a result, leaf photosynthesis rates are increased and the plant growth is enhanced in contrast to the normal process without Hpa1-AtPIP1;4 interaction. Our findings demonstrate the first case that plant sensing of a bacterial harpin protein is connected with photosynthetic physiology to regulate plant growth.

The three-dimensional structures of bacterial reaction centers.

Science.gov (United States)

Olson, T L; Williams, J C; Allen, J P

2014-05-01

This review presents a broad overview of the research that enabled the structure determination of the bacterial reaction centers from Blastochloris viridis and Rhodobacter sphaeroides, with a focus on the contributions from Duysens, Clayton, and Feher. Early experiments performed in the laboratory of Duysens and others demonstrated the utility of spectroscopic techniques and the presence of photosynthetic complexes in both oxygenic and anoxygenic photosynthesis. The laboratories of Clayton and Feher led efforts to isolate and characterize the bacterial reaction centers. The availability of well-characterized preparations of pure and stable reaction centers allowed the crystallization and subsequent determination of the structures using X-ray diffraction. The three-dimensional structures of reaction centers revealed an overall arrangement of two symmetrical branches of cofactors surrounded by transmembrane helices from the L and M subunits, which also are related by the same twofold symmetry axis. The structure has served as a framework to address several issues concerning bacterial photosynthesis, including the directionality of electron transfer, the properties of the reaction center-cytochrome c 2 complex, and the coupling of proton and electron transfer. Together, these research efforts laid the foundation for ongoing efforts to address an outstanding question in oxygenic photosynthesis, namely the molecular mechanism of water oxidation.

Enhanced limonene production in cyanobacteria reveals photosynthesis limitations.

Science.gov (United States)

Wang, Xin; Liu, Wei; Xin, Changpeng; Zheng, Yi; Cheng, Yanbing; Sun, Su; Li, Runze; Zhu, Xin-Guang; Dai, Susie Y; Rentzepis, Peter M; Yuan, Joshua S

2016-12-13

Terpenes are the major secondary metabolites produced by plants, and have diverse industrial applications as pharmaceuticals, fragrance, solvents, and biofuels. Cyanobacteria are equipped with efficient carbon fixation mechanism, and are ideal cell factories to produce various fuel and chemical products. Past efforts to produce terpenes in photosynthetic organisms have gained only limited success. Here we engineered the cyanobacterium Synechococcus elongatus PCC 7942 to efficiently produce limonene through modeling guided study. Computational modeling of limonene flux in response to photosynthetic output has revealed the downstream terpene synthase as a key metabolic flux-controlling node in the MEP (2-C-methyl-d-erythritol 4-phosphate) pathway-derived terpene biosynthesis. By enhancing the downstream limonene carbon sink, we achieved over 100-fold increase in limonene productivity, in contrast to the marginal increase achieved through stepwise metabolic engineering. The establishment of a strong limonene flux revealed potential synergy between photosynthate output and terpene biosynthesis, leading to enhanced carbon flux into the MEP pathway. Moreover, we show that enhanced limonene flux would lead to NADPH accumulation, and slow down photosynthesis electron flow. Fine-tuning ATP/NADPH toward terpene biosynthesis could be a key parameter to adapt photosynthesis to support biofuel/bioproduct production in cyanobacteria.

Effect of ozone on photosynthesis and respiration of Scenedesmus obtusiusculus Chod. , with a general discussion of effects of air pollutants in plants

Energy Technology Data Exchange (ETDEWEB)

Verkroost, M

1974-01-01

In the present study the mode of action of the air pollutant ozone was investigated by studying its effects on photosynthesis, respiration and some biochemical and structural properties of the unicellular alga, Scenedesmus obtusiusculus CHOD. The extensive literature on the effects of the most important air pollutant gases SO/sub 2/, HF, NO/sub 2/, PAN and O/sub 3/ on the processes of photosynthesis and respiration is reviewed, while possible modes of action of each of these gases are discussed. The procedure for ozone exposure is extensively described. It is shown that photosynthesis and dark respiration are inhibited by previous exposure of the cell suspensions to ozone; the inhibition is increased with the duration of exposure and with temperature during exposure. The effect of an ozone treatment is increased by light during the exposure, and consequently, photosynthesis appears more inhibited in as much as the light-intensity during the preceding exposure to ozone was higher. It is shown that the chlorophyll content decreases by exposure to ozone; the decrease is more pronounced after exposure in the light than after exposure in the dark. It appeared in a preliminary study that there is a substantial loss of lipid in ozone-exposed algae, and there are indications that this in mainly due to oxidation of the unsaturated fatty acid, linoleic acid. A preliminary study showed that there is a very small loss of protein content in ozone-exposed algae, which may be ascribed mainly to oxidation of the acid component serine, and of an unidentified alkaline compound. In ozone exposed algae, ultrastructural changes are observed. 181 references, 21 figures, 11 tables.

A possible form of the pion's structure function

International Nuclear Information System (INIS)

Long Ming; Huang Tao

1986-01-01

The pion's structure function behaviour is discussed by using the Fock state expansion of the hadronic wave function in QCD in this paper. As an example, we employ a model wave function of the Fock state in the light-cone and assume a Regge behaviour of a weight function for higher Fock states, and we get a possible form of the pion's structure function. This form is consistent with experimental data of the pion's structure function

Conceptual change through the use of student-generated analogies of photosynthesis and respiration by college non-science majors

Science.gov (United States)

Hill, Gary D.

Two of the most important and difficult concepts in biology are photosynthesis and respiration. A pilot study was performed using student volunteers from introductory biology classes to assess student alternative frameworks regarding photosynthesis and respiration. The results of the pilot study were used to construct the Instrument for the Assessment of Respiration and Photosynthesis (IFARP). This was an 11-item, three-tier multiple choice instrument designed to conveniently assess the common misconceptions students have about these concepts upon entering a biology course. The first tier of each item of the IFARP contained a multiple choice question about photosynthesis or respiration. The second tier had a multiple choice question regarding the reason for the choice in the first tier. The third tier asked the students to indicate how confident they were in their responses, on a scale from 1 (not very confident) to 5 (very confident). The IFARP was administered as a pretest and posttest to a group of science non-majors in an introductory biology course. No significant changes were observed in student performance as measured by the IFARP between the pretest and posttest administrations. The students did, however, demonstrate a statistical increase in mean confidence levels regarding their knowledge of photosynthesis and respiration. Even though their comprehension and understanding regarding photosynthesis and respiration had not increased, the confidence they had in their responses about these two concepts had increased. The IFARP was also administered to a group of nursing student volunteers in an introductory microbiology course. This group of students also participated in the use of student-generated analogies as a learning strategy to alter conceptual frameworks. One test group of students provided analogies to photosynthesis and respiration, while the other test group provided analogies to two other concepts. No significant changes were observed in the

Functional nanometer-scale structures

Science.gov (United States)

Chan, Tsz On Mario

Nanometer-scale structures have properties that are fundamentally different from their bulk counterparts. Much research effort has been devoted in the past decades to explore new fabrication techniques, model the physical properties of these structures, and construct functional devices. The ability to manipulate and control the structure of matter at the nanoscale has made many new classes of materials available for the study of fundamental physical processes and potential applications. The interplay between fabrication techniques and physical understanding of the nanostructures and processes has revolutionized the physical and material sciences, providing far superior properties in materials for novel applications that benefit society. This thesis consists of two major aspects of my graduate research in nano-scale materials. In the first part (Chapters 3--6), a comprehensive study on the nanostructures based on electrospinning and thermal treatment is presented. Electrospinning is a well-established method for producing high-aspect-ratio fibrous structures, with fiber diameter ranging from 1 nm--1 microm. A polymeric solution is typically used as a precursor in electrospinning. In our study, the functionality of the nanostructure relies on both the nanostructure and material constituents. Metallic ions containing precursors were added to the polymeric precursor following a sol-gel process to prepare the solution suitable for electrospinning. A typical electrospinning process produces as-spun fibers containing both polymer and metallic salt precursors. Subsequent thermal treatments of the as-spun fibers were carried out in various conditions to produce desired structures. In most cases, polymer in the solution and the as-spun fibers acted as a backbone for the structure formation during the subsequent heat treatment, and were thermally removed in the final stage. Polymers were also designed to react with the metallic ion precursors during heat treatment in some

Phytoremediation capacity of poplar (Populus spp. and willow (Salix spp. clonesin relation to photosynthesis

Directory of Open Access Journals (Sweden)

Pajević Slobodanka

2009-01-01

Full Text Available Good photosynthetic features and a favorable water regimes of woody plants improve their survival and remediation potential under unfavorable ecological conditions. Accordingly, we here present results of testing plant tolerance of Pb, Cd, Ni, and diesel fuel based on gas exchange parameters and WUE of four poplar and two willow clones grown in a greenhouse on soil culture. Photosynthesis and transpiration of plants grown on soils with individually applied heavy metals decreased significantly, but this was less obvious in the case of Cd treatment. A heavy metal mixture in the soil induced significant reduction in photosynthesis (by more than 50%. Diesel fuel as the only pollutant in soil caused very strong and significant inhibition of photosynthesis and transpiration of willow clones. The results indicate genotypic specificity of all investigated physiological parameters and mark poplar clones as very useful in phytoextraction technology for the bio-cleaning of chemically polluted soils.

An Experimental Comparison of Two Methods on Photosynthesis Driving Soil Respiration: Girdling and Defoliation.

Science.gov (United States)

Jing, Yanli; Guan, Dexin; Wu, Jiabing; Wang, Anzhi; Jin, Changjie; Yuan, Fenghui

2015-01-01

Previous studies with different experimental methods have demonstrated that photosynthesis significantly influences soil respiration (RS). To compare the experimental results of different methods, RS after girdling and defoliation was measured in five-year-old seedlings of Fraxinus mandshurica from June to September. Girdling and defoliation significantly reduced RS by 33% and 25% within 4 days, and 40% and 32% within the entire treatment period, respectively. The differential response of RS to girdling and defoliation was a result of the over-compensation for RS after girdling and redistribution of stored carbon after defoliation. No significant effect on RS was observed between girdling and defoliation treatment, while the soluble sugar content in fine roots was higher in defoliation than in girdling treatment, indicating that defoliation had less compensation effect for RS after interrupting photosynthates supply. We confirm the close coupling of RS with photosynthesis and recommend defoliation for further studies to estimate the effect of photosynthesis on RS.

Structure-function relationships during segregated and integrated network states of human brain functional connectivity.

Science.gov (United States)

Fukushima, Makoto; Betzel, Richard F; He, Ye; van den Heuvel, Martijn P; Zuo, Xi-Nian; Sporns, Olaf

2018-04-01

Structural white matter connections are thought to facilitate integration of neural information across functionally segregated systems. Recent studies have demonstrated that changes in the balance between segregation and integration in brain networks can be tracked by time-resolved functional connectivity derived from resting-state functional magnetic resonance imaging (rs-fMRI) data and that fluctuations between segregated and integrated network states are related to human behavior. However, how these network states relate to structural connectivity is largely unknown. To obtain a better understanding of structural substrates for these network states, we investigated how the relationship between structural connectivity, derived from diffusion tractography, and functional connectivity, as measured by rs-fMRI, changes with fluctuations between segregated and integrated states in the human brain. We found that the similarity of edge weights between structural and functional connectivity was greater in the integrated state, especially at edges connecting the default mode and the dorsal attention networks. We also demonstrated that the similarity of network partitions, evaluated between structural and functional connectivity, increased and the density of direct structural connections within modules in functional networks was elevated during the integrated state. These results suggest that, when functional connectivity exhibited an integrated network topology, structural connectivity and functional connectivity were more closely linked to each other and direct structural connections mediated a larger proportion of neural communication within functional modules. Our findings point out the possibility of significant contributions of structural connections to integrative neural processes underlying human behavior.

Ambient UV-B radiation decreases photosynthesis in high arctic Vaccinium uliginosum

Energy Technology Data Exchange (ETDEWEB)

Albert, K.R.; Ro-Poulsen, H. (Univ. of Copenhagen, Dept. of Terrestrial Ecology, Copenhagen (DK)); Mikkelsen, T.N. (Technical Univ. of Denmark, Risoe National Laboratory for Sustainable Energy, Biosystems Dept., Roskilde (DK))

2008-06-15

An UV-B-exclusion experiment was established in high arctic Zackenberg, Northeast Greenland, to investigate the possible effects of ambient UV-B on plant performance. During almost a whole growing season, canopy gas exchange and Chl fluorescence were measured on Vaccinium uliginosum (bog blueberry). Leaf area, biomass, carbon, nitrogen and UV-B-absorbing compounds were determined from a late season harvest. Compared with the reduced UV-B treatment, the plants in ambient UV-B were found to have a higher content of UV-B-absorbing compounds, and canopy net photosynthesis was as an average 23% lower during the season. By means of the JIP-test, it was found that the potential of processing light energy through the photosynthetic machinery was slightly reduced in ambient UV-B. This indicates that not only the UV-B effects on PSII may be responsible for some of the observed reduction of photosynthesis but also the effects on other parts of the photosynthetic machinery, e.g. the Calvin cycle, might be important. The 60% reduction of the UV-B irradiance used in this study implies a higher relative change in the UV-B load than many of the supplemental experiments do, but the substantial effect on photosynthesis clearly indicates that V. uliginosum is negatively affected by the current level of UV-B. (au)

Ambient UV-B radiation decreases photosynthesis in high arctic Vaccinium uliginosum.

Science.gov (United States)

Albert, Kristian R; Mikkelsen, Teis N; Ro-Poulsen, Helge

2008-06-01

An UV-B-exclusion experiment was established in high arctic Zackenberg, Northeast Greenland, to investigate the possible effects of ambient UV-B on plant performance. During almost a whole growing season, canopy gas exchange and Chl fluorescence were measured on Vaccinium uliginosum (bog blueberry). Leaf area, biomass, carbon, nitrogen and UV-B-absorbing compounds were determined from a late season harvest. Compared with the reduced UV-B treatment, the plants in ambient UV-B were found to have a higher content of UV-B-absorbing compounds, and canopy net photosynthesis was as an average 23% lower during the season. By means of the JIP-test, it was found that the potential of processing light energy through the photosynthetic machinery was slightly reduced in ambient UV-B. This indicates that not only the UV-B effects on PSII may be responsible for some of the observed reduction of photosynthesis but also the effects on other parts of the photosynthetic machinery, e.g. the Calvin cycle, might be important. The 60% reduction of the UV-B irradiance used in this study implies a higher relative change in the UV-B load than many of the supplemental experiments do, but the substantial effect on photosynthesis clearly indicates that V. uliginosum is negatively affected by the current level of UV-B.

Effects of Kaolin Application on Light Absorption and Distribution, Radiation Use Efficiency and Photosynthesis of Almond and Walnut Canopies

Science.gov (United States)

Rosati, Adolfo; Metcalf, Samuel G.; Buchner, Richard P.; Fulton, Allan E.; Lampinen, Bruce D.

2007-01-01

Background and Aims Kaolin applied as a suspension to plant canopies forms a film on leaves that increases reflection and reduces absorption of light. Photosynthesis of individual leaves is decreased while the photosynthesis of the whole canopy remains unaffected or even increases. This may result from a better distribution of light within the canopy following kaolin application, but this explanation has not been tested. The objective of this work was to study the effects of kaolin application on light distribution and absorption within tree canopies and, ultimately, on canopy photosynthesis and radiation use efficiency. Methods Photosynthetically active radiation (PAR) incident on individual leaves within the canopy of almond (Prunus dulcis) and walnut (Juglans regia) trees was measured before and after kaolin application in order to study PAR distribution within the canopy. The PAR incident on, and reflected and transmitted by, the canopy was measured on the same day for kaolin-sprayed and control trees in order to calculate canopy PAR absorption. These data were then used to model canopy photosynthesis and radiation use efficiency by a simple method proposed in previous work, based on the photosynthetic response to incident PAR of a top-canopy leaf. Key Results Kaolin increased incident PAR on surfaces of inner-canopy leaves, although there was an estimated 20 % loss in PAR reaching the photosynthetic apparatus, due to increased reflection. Assuming a 20 % loss of PAR, modelled photosynthesis and photosynthetic radiation use efficiency (PRUE) of kaolin-coated leaves decreased by only 6·3 %. This was due to (1) more beneficial PAR distribution within the kaolin-sprayed canopy, and (2) with decreasing PAR, leaf photosynthesis decreases less than proportionally, due to the curvature of the photosynthesis response-curve to PAR. The relatively small loss in canopy PRUE (per unit of incident PAR), coupled with the increased incident PAR on the leaf surface on

Clustering aspects in nuclear structure functions

International Nuclear Information System (INIS)

Hirai, M.; Saito, K.; Watanabe, T.; Kumano, S.

2011-01-01

For understanding an anomalous nuclear effect experimentally observed for the beryllium-9 nucleus at the Thomas Jefferson National Accelerator Facility, clustering aspects are studied in structure functions of deep inelastic lepton-nucleus scattering by using momentum distributions calculated in antisymmetrized (or fermionic) molecular dynamics (AMD) and also in a simple shell model for comparison. According to AMD, the 9 Be nucleus consists of two α-like clusters with a surrounding neutron. The clustering produces high-momentum components in nuclear wave functions, which affects nuclear modifications of the structure functions. We investigated whether clustering features could appear in the structure function F 2 of 9 Be along with studies for other light nuclei. We found that nuclear modifications of F 2 are similar in both AMD and shell models within our simple convolution description although there are slight differences in 9 Be. It indicates that the anomalous 9 Be result should be explained by a different mechanism from the nuclear binding and Fermi motion. If nuclear-modification slopes d(F 2 A /F 2 D )/dx are shown by the maximum local densities, the 9 Be anomaly can be explained by the AMD picture, namely by the clustering structure, whereas it certainly cannot be described in the simple shell model. This fact suggests that the large nuclear modification in 9 Be should be explained by large densities in the clusters. For example, internal nucleon structure could be modified in the high-density clusters. The clustering aspect of nuclear structure functions is an unexplored topic which is interesting for future investigations.

Songs about Cancer, Gene Expression, and the Biochemistry of Photosynthesis

Science.gov (United States)

Heineman, Richard H.

2018-01-01

These three biology songs can be used for educational purposes to teach about biochemical concepts. They touch on three different topics: (1) cancer progression and germ cells, (2) gene expression, promoters, and repressors, and (3) electronegativity and the biochemical basis of photosynthesis.

Selective effects of H2O2 on cyanobacterial photosynthesis

Czech Academy of Sciences Publication Activity Database

Drábková, Michaela; Matthijs, H. C. P.; Admiraal, W.; Maršálek, Blahoslav

2007-01-01

Roč. 45, č. 3 (2007), s. 363-369 ISSN 0300-3604 Grant - others:-(XE) EVK2-CT-2002-57004 Institutional research plan: CEZ:AV0Z60050516 Keywords : hydrogen peroxide * cyanobacteria * photosynthesis Subject RIV: EF - Botanics Impact factor: 0.976, year: 2007

A list of personal perspectives with selected quotations, along with lists of tributes, historical notes, Nobel and Kettering awards related to photosynthesis.

Science.gov (United States)

Krogmann, David W

2002-01-01

The history of photosynthesis research can be found in original papers and books. However, a special history is available from the prefatory chapters and the personal perspectives of various researchers who published them in several journals over the last 40 years. We have compiled a list of such perspectives published since 1964. Selection is not easy, especially of authors who were not directly engaged in photosynthesis research; some are included for their special insights related to central issues in the study of photosynthesis. Our journal, Photosynthesis Research, contains other valuable historic data in the occasional tributes, obituaries and historical notes, that have been published. Lists of these items are included. This article ends by listing the Nobel prizes related to photosynthesis and the Kettering Awards for Excellence in Photosynthesis Research. Wherever possible, a web page address is provided. The web page addresses have been taken from the article 'Photosynthesis and the Web: 2001' by Larry Orr and Govindjee, available at http://www.life.uiuc.edu/govindjee/photoweb and at http://photoscience.la.asu.edu/photosyn/ photoweb/default.html.When I find a bit of leisureI trifle with my papers.This is one of the lesserfrailities.'- Horace, Satires I, IV.

Magnetism and Structure in Functional Materials

CERN Document Server

Planes, Antoni; Saxena, Avadh

2005-01-01

Magnetism and Structure in Functional Materials addresses three distinct but related topics: (i) magnetoelastic materials such as magnetic martensites and magnetic shape memory alloys, (ii) the magnetocaloric effect related to magnetostructural transitions, and (iii) colossal magnetoresistance (CMR) and related magnanites. The goal is to identify common underlying principles in these classes of materials that are relevant for optimizing various functionalities. The emergence of apparently different magnetic/structural phenomena in disparate classes of materials clearly points to a need for common concepts in order to achieve a broader understanding of the interplay between magnetism and structure in this general class of new functional materials exhibiting ever more complex microstructure and function. The topic is interdisciplinary in nature and the contributors correspondingly include physicists, materials scientists and engineers. Likewise the book will appeal to scientists from all these areas.

Photosynthesis and sink activity of wasp-induced galls in Acacia pycnantha.

Science.gov (United States)

Dorchin, Netta; Cramer, Michael D; Hoffmann, John H

2006-07-01

Although insect galls are widely known to influence source-sink relationships in plants, the relationship between photosynthesis and gall activity has not been extensively studied. In this study we used 14CO2, photosynthesis, and respiration measurements to examine the capacity of bud galls induced by the wasp Trichilogaster signiventris (Pteromalidae) as carbon sinks in Acacia pycnantha. Galls of this species develop either in vegetative or reproductive buds, depending on the availability of tissues at different times of the year, and effectively eliminate seed production by the plant. Photosynthetic rates in phyllodes subtending clusters of galls were greater than rates in control phyllodes, a result we attributed to photosynthesis compensating for increased carbon demand by the galls. Contrary to previous studies, we found that photosynthesis within galls contributed substantially to the carbon budgets of the galls, particularly in large, mature galls, which exhibited lower specific respiration rates allowing for a net carbon gain in the light. To determine the sink capacity and competitive potential of galls, we measured the proportion of specific radioactivity in galls originating from either vegetative or reproductive buds and found no difference between them. The proportion of the total amount of phyllode-derived 14C accumulated in both clustered and solitary galls was less than that in fruits. Galls and fruits were predominantly reliant on subtending rather than on distant phyllodes for photosynthate. Solitary galls that developed in vegetative buds constituted considerably stronger sinks than galls in clusters on inflorescences where there was competition between galls or fruits for resources from the subtending phyllode. Wasps developing in solitary vegetative galls were correspondingly significantly larger than those from clustered galls. We conclude that, in the absence of inflorescence buds during summer and fall, the ability of the wasps to cause gall

DNA sequence analysis of the photosynthesis region of Rhodobacter sphaeroides 2.4.1T

OpenAIRE

Choudhary, M.; Kaplan, Samuel

2000-01-01

This paper describes the DNA sequence of the photosynthesis region of Rhodobacter sphaeroides 2.4.1T. The photosynthesis gene cluster is located within a ~73 kb AseI genomic DNA fragment containing the puf, puhA, cycA and puc operons. A total of 65 open reading frames (ORFs) have been identified, of which 61 showed significant similarity to genes/proteins of other organisms while only four did not reveal any significant sequence similarity to any gene/protein sequences in the database. The da...

Enhanced Thermostability of Arabidopsis Rubisco Activase Improves Photosynthesis and Growth Rates under Moderate Heat Stress[OA

Science.gov (United States)

Kurek, Itzhak; Chang, Thom Kai; Bertain, Sean M.; Madrigal, Alfredo; Liu, Lu; Lassner, Michael W.; Zhu, Genhai

2007-01-01

Plant photosynthesis declines when the temperature exceeds its optimum range. Recent evidence indicates that the reduction in photosynthesis is linked to ribulose-1,5-bis-phosphate carboxylase/oxygenase (Rubisco) deactivation due to the inhibition of Rubisco activase (RCA) under moderately elevated temperatures. To test the hypothesis that thermostable RCA can improve photosynthesis under elevated temperatures, we used gene shuffling technology to generate several Arabidopsis thaliana RCA1 (short isoform) variants exhibiting improved thermostability. Wild-type RCA1 and selected thermostable RCA1 variants were introduced into an Arabidopsis RCA deletion (Δrca) line. In a long-term growth test at either constant 26°C or daily 4-h 30°C exposure, the transgenic lines with the thermostable RCA1 variants exhibited higher photosynthetic rates, improved development patterns, higher biomass, and increased seed yields compared with the lines expressing wild-type RCA1 and a slight improvement compared with untransformed Arabidopsis plants. These results provide clear evidence that RCA is a major limiting factor in plant photosynthesis under moderately elevated temperatures and a potential target for genetic manipulation to improve crop plants productivity under heat stress conditions. PMID:17933901

Summary of the Photon Structure Functions - Measurements at LEP

International Nuclear Information System (INIS)

Przybycien, M.

2002-01-01

The present status of the photon structure functions measurements at LEP is discussed. The short introduction to the kinematics and theoretical framework of the structure functions measurements at LEP is given first. Then follow presentations of the most important measurements, ranging from the QED photon structure function, through the hadronic structure functions of real and virtual photons, and at the end the first measurement of the electron structure function is shown. (author)

Guard cell photosynthesis is critical for stomatal turgor production, yet does not directly mediate CO2 - and ABA-induced stomatal closing.

Science.gov (United States)

Azoulay-Shemer, Tamar; Palomares, Axxell; Bagheri, Andisheh; Israelsson-Nordstrom, Maria; Engineer, Cawas B; Bargmann, Bastiaan O R; Stephan, Aaron B; Schroeder, Julian I

2015-08-01

Stomata mediate gas exchange between the inter-cellular spaces of leaves and the atmosphere. CO2 levels in leaves (Ci) are determined by respiration, photosynthesis, stomatal conductance and atmospheric [CO2 ]. [CO2 ] in leaves mediates stomatal movements. The role of guard cell photosynthesis in stomatal conductance responses is a matter of debate, and genetic approaches are needed. We have generated transgenic Arabidopsis plants that are chlorophyll-deficient in guard cells only, expressing a constitutively active chlorophyllase in a guard cell specific enhancer trap line. Our data show that more than 90% of guard cells were chlorophyll-deficient. Interestingly, approximately 45% of stomata had an unusual, previously not-described, morphology of thin-shaped chlorophyll-less stomata. Nevertheless, stomatal size, stomatal index, plant morphology, and whole-leaf photosynthetic parameters (PSII, qP, qN, FV '/FM' ) were comparable with wild-type plants. Time-resolved intact leaf gas-exchange analyses showed a reduction in stomatal conductance and CO2 -assimilation rates of the transgenic plants. Normalization of CO2 responses showed that stomata of transgenic plants respond to [CO2 ] shifts. Detailed stomatal aperture measurements of normal kidney-shaped stomata, which lack chlorophyll, showed stomatal closing responses to [CO2 ] elevation and abscisic acid (ABA), while thin-shaped stomata were continuously closed. Our present findings show that stomatal movement responses to [CO2 ] and ABA are functional in guard cells that lack chlorophyll. These data suggest that guard cell CO2 and ABA signal transduction are not directly modulated by guard cell photosynthesis/electron transport. Moreover, the finding that chlorophyll-less stomata cause a 'deflated' thin-shaped phenotype, suggests that photosynthesis in guard cells is critical for energization and guard cell turgor production. © 2015 The Authors The Plant Journal © 2015 John Wiley & Sons Ltd.

The effect of irradiance on long-term skeletal growth and net photosynthesis in Galaxea fascicularis under four light conditions.

NARCIS (Netherlands)

Schutter, M.; Velthoven, van B.; Janse, M.; Osinga, R.; Janssen, M.G.J.; Wijffels, R.H.; Verreth, J.A.J.

2008-01-01

The relation between irradiance, skeletal growth and net photosynthesis was studied for the scleractinian coral Galaxea fascicularis to provide experimental evidence for mediation of light-enhanced calcification through photosynthesis. The hypothesis was tested that skeletal growth and

Effect of traffic pollution on photosynthesis | Durrani | Journal of ...

African Journals Online (AJOL)

Vehicular exhaust is considered as one of the worst form of environmental pollution. To assess the effect of traffic pollution on photosynthesis, leaf samples of four different types of plants at different distances from the busy traffic road were collected from Wah. The samples consisted of sunny, shady and semi shady leaves of ...

The pineapple genome and the evolution of CAM photosynthesis.

Science.gov (United States)

Ming, Ray; VanBuren, Robert; Wai, Ching Man; Tang, Haibao; Schatz, Michael C; Bowers, John E; Lyons, Eric; Wang, Ming-Li; Chen, Jung; Biggers, Eric; Zhang, Jisen; Huang, Lixian; Zhang, Lingmao; Miao, Wenjing; Zhang, Jian; Ye, Zhangyao; Miao, Chenyong; Lin, Zhicong; Wang, Hao; Zhou, Hongye; Yim, Won C; Priest, Henry D; Zheng, Chunfang; Woodhouse, Margaret; Edger, Patrick P; Guyot, Romain; Guo, Hao-Bo; Guo, Hong; Zheng, Guangyong; Singh, Ratnesh; Sharma, Anupma; Min, Xiangjia; Zheng, Yun; Lee, Hayan; Gurtowski, James; Sedlazeck, Fritz J; Harkess, Alex; McKain, Michael R; Liao, Zhenyang; Fang, Jingping; Liu, Juan; Zhang, Xiaodan; Zhang, Qing; Hu, Weichang; Qin, Yuan; Wang, Kai; Chen, Li-Yu; Shirley, Neil; Lin, Yann-Rong; Liu, Li-Yu; Hernandez, Alvaro G; Wright, Chris L; Bulone, Vincent; Tuskan, Gerald A; Heath, Katy; Zee, Francis; Moore, Paul H; Sunkar, Ramanjulu; Leebens-Mack, James H; Mockler, Todd; Bennetzen, Jeffrey L; Freeling, Michael; Sankoff, David; Paterson, Andrew H; Zhu, Xinguang; Yang, Xiaohan; Smith, J Andrew C; Cushman, John C; Paull, Robert E; Yu, Qingyi

2015-12-01

Pineapple (Ananas comosus (L.) Merr.) is the most economically valuable crop possessing crassulacean acid metabolism (CAM), a photosynthetic carbon assimilation pathway with high water-use efficiency, and the second most important tropical fruit. We sequenced the genomes of pineapple varieties F153 and MD2 and a wild pineapple relative, Ananas bracteatus accession CB5. The pineapple genome has one fewer ancient whole-genome duplication event than sequenced grass genomes and a conserved karyotype with seven chromosomes from before the ρ duplication event. The pineapple lineage has transitioned from C3 photosynthesis to CAM, with CAM-related genes exhibiting a diel expression pattern in photosynthetic tissues. CAM pathway genes were enriched with cis-regulatory elements associated with the regulation of circadian clock genes, providing the first cis-regulatory link between CAM and circadian clock regulation. Pineapple CAM photosynthesis evolved by the reconfiguration of pathways in C3 plants, through the regulatory neofunctionalization of preexisting genes and not through the acquisition of neofunctionalized genes via whole-genome or tandem gene duplication.

Growth but not photosynthesis response of a host plant to infection by a holoparasitic plant depends on nitrogen supply.

Directory of Open Access Journals (Sweden)

Hao Shen

Full Text Available Parasitic plants can adversely influence the growth of their hosts by removing resources and by affecting photosynthesis. Such negative effects depend on resource availability. However, at varied resource levels, to what extent the negative effects on growth are attributed to the effects on photosynthesis has not been well elucidated. Here, we examined the influence of nitrogen supply on the growth and photosynthesis responses of the host plant Mikania micrantha to infection by the holoparasite Cuscuta campestris by focusing on the interaction of nitrogen and infection. Mikania micrantha plants fertilized at 0.2, 1 and 5 mM nitrate were grown with and without C. campestris infection. We observed that the infection significantly reduced M. micrantha growth at each nitrate fertilization and more severely at low than at high nitrate. Such alleviation at high nitrate was largely attributed to a stronger influence of infection on root biomass at low than at high nitrate fertilization. However, although C. campestris altered allometry and inhibited host photosynthesis, the magnitude of the effects was independent of nitrate fertilizations. The infection reduced light saturation point, net photosynthesis at saturating irradiances, apparent quantum yield, CO2 saturated rate of photosynthesis, carboxylation efficiency, the maximum carboxylation rate of Rubisco, and maximum light-saturated rate of electron transport, and increased light compensation point in host leaves similarly across nitrate levels, corresponding to a similar magnitude of negative effects of the parasite on host leaf soluble protein and Rubisco concentrations, photosynthetic nitrogen use efficiency and stomatal conductance across nitrate concentrations. Thus, the more severe inhibition in host growth at low than at high nitrate supplies cannot be attributed to a greater parasite-induced reduction in host photosynthesis, but the result of a higher proportion of host resources

Growth but Not Photosynthesis Response of a Host Plant to Infection by a Holoparasitic Plant Depends on Nitrogen Supply

Science.gov (United States)

Shen, Hao; Xu, Shu-Jun; Hong, Lan; Wang, Zhang-Ming; Ye, Wan-Hui

2013-01-01

Parasitic plants can adversely influence the growth of their hosts by removing resources and by affecting photosynthesis. Such negative effects depend on resource availability. However, at varied resource levels, to what extent the negative effects on growth are attributed to the effects on photosynthesis has not been well elucidated. Here, we examined the influence of nitrogen supply on the growth and photosynthesis responses of the host plant Mikania micrantha to infection by the holoparasite Cuscuta campestris by focusing on the interaction of nitrogen and infection. Mikania micrantha plants fertilized at 0.2, 1 and 5 mM nitrate were grown with and without C. campestris infection. We observed that the infection significantly reduced M. micrantha growth at each nitrate fertilization and more severely at low than at high nitrate. Such alleviation at high nitrate was largely attributed to a stronger influence of infection on root biomass at low than at high nitrate fertilization. However, although C. campestris altered allometry and inhibited host photosynthesis, the magnitude of the effects was independent of nitrate fertilizations. The infection reduced light saturation point, net photosynthesis at saturating irradiances, apparent quantum yield, CO2 saturated rate of photosynthesis, carboxylation efficiency, the maximum carboxylation rate of Rubisco, and maximum light-saturated rate of electron transport, and increased light compensation point in host leaves similarly across nitrate levels, corresponding to a similar magnitude of negative effects of the parasite on host leaf soluble protein and Rubisco concentrations, photosynthetic nitrogen use efficiency and stomatal conductance across nitrate concentrations. Thus, the more severe inhibition in host growth at low than at high nitrate supplies cannot be attributed to a greater parasite-induced reduction in host photosynthesis, but the result of a higher proportion of host resources transferred to the parasite at

Effective constraint algebras with structure functions

International Nuclear Information System (INIS)

Bojowald, Martin; Brahma, Suddhasattwa

2016-01-01

This article presents the result that fluctuations and higher moments of a state, by themselves, do not imply quantum corrections in structure functions of constrained systems. Moment corrections are isolated from other types of quantum effects, such as factor-ordering choices and regularization, by introducing a new condition with two parts: (i) having a direct (or faithful) quantization of the classical structure functions, (ii) free of factor-ordering ambiguities. In particular, it is assumed that the classical constraints can be quantized in an anomaly free way, so that properties of the resulting constraint algebras can be derived. If the two-part condition is not satisfied, effective constraints can still be evaluated, but quantum effects may be stronger. Consequences for canonical quantum gravity, whose structure functions encode space–time structure, are discussed. In particular, deformed algebras found in models of loop quantum gravity provide reliable information even in the Planck regime. (paper)

The evolutionary pathway from anoxygenic to oxygenic photosynthesis examined by comparison of the properties of photosystem II and bacterial reaction centers.

Science.gov (United States)

Allen, J P; Williams, J C

2011-01-01

In photosynthetic organisms, such as purple bacteria, cyanobacteria, and plants, light is captured and converted into energy to create energy-rich compounds. The primary process of energy conversion involves the transfer of electrons from an excited donor molecule to a series of electron acceptors in pigment-protein complexes. Two of these complexes, the bacterial reaction center and photosystem II, are evolutionarily related and structurally similar. However, only photosystem II is capable of performing the unique reaction of water oxidation. An understanding of the evolutionary process that lead to the development of oxygenic photosynthesis can be found by comparison of these two complexes. In this review, we summarize how insight is being gained by examination of the differences in critical functional properties of these complexes and by experimental efforts to alter pigment-protein interactions of the bacterial reaction center in order to enable it to perform reactions, such as amino acid and metal oxidation, observable in photosystem II.

Running Head: Control and Adjustment of the Rate of Photosynthesis Above Present CO(sub 2) Levels; FINAL

International Nuclear Information System (INIS)

Ball, J. Timothy

1996-01-01

The adjustment of photosynthesis to different environmental conditions and especially to elevated CO(sub 2) is often characterized in terms of changes in the processes that establish (limit) the net CO(sub 2) assimilation rate. At slightly above present ambient pCO(sub 2) light-saturated photosynthetic responses to CO(sub 2) depart limitation by the catalytic capacity of tissue rubisco content. An hypothesis attributing this departure to limited thylakoid reaction/electron transport capacity is widely accepted, although we find no experimental evidence in the literature supporting this proposition.. The results of several tests point to the conclusion that the capacity of the thyiakoid reactions cannot be generally responsible for the deviation from rubisco limitation. This conclusion leaves a significant gap in the interpretation of gas exchange responses to CO(sub 2). Since the inputs to the photosynthetic carbon reduction cycle (CO(sub 2) and photon-capture/electron-transport products) do not limit photosynthesis on the shoulder of the A=f(c(sub i)) curve, the control of photosynthesis can be characterized as: due to feedback. Several characteristics of gas exchange and fluorescence that occur when steady-states in this region are perturbed by changes in CO(sub 2) or O(sub 2) suggest significant regulation by conditions other than directly by substrate RuBP levels. A strong candidate to explain these responses is the triose-phosphate flux/ inorganic phosphate regulatory sequence, although not all of the gas exchange characteristics expected with ''TPU-limitation'' are present (e.g. oxygen-insensitive photosynthesis). Interest in nitrogen allocation between rubisco and light capture/electron transport as the basis for photosynthetic adjustment to elevated CO(sub 2) may need to be reconsidered as a result of these findings. Contributors to the feedback regulation of photosynthesis (which may include sucrose phosphate synthase and fructose bisphosphatase activities

Photosynthesis and Ribulose 1,5-Bisphosphate Concentrations in Intact Leaves of Xanthium strumarium L. 1

Science.gov (United States)

Mott, Keith A.; Jensen, Richard G.; O'Leary, James W.; Berry, Joseph A.

1984-01-01

The interacting effects of the rate of ribulose 1,5-bisphosphate (RuBP) regeneration and the rate of RuBP utilization as influenced by the amount and activation of RuBP carboxylase on photosynthesis and RuBP concentrations were resolved in experiments which examined the kinetics of the response of photosynthesis and RuBP concentrations after step changes from a rate-saturating to a rate-limiting light intensity in Xanthium strumarium. Because RuBP carboxylase requires several minutes to deactivate in vivo, it was possible to observe the effect of reducing the rate of RuBP regeneration on the RuBP concentration at constant enzyme activation state by sampling very soon after reducing the light intensity. Samples taken over longer time periods showed the effect of changes in enzyme activation at constant RuBP regeneration rate on RuBP concentration and photosynthetic rate. Within 15 s of lowering the light intensity from 1500 to 600 microEinsteins per square meter per second the RuBP concentration in the leaves dropped below the enzyme active site concentration, indicating that RuBP regeneration rate was limiting for photosynthesis. After longer intervals of time, the RuBP concentration in the leaf increased as the RuBP carboxylase assumed a new steady state activation level. No change in the rate of photosynthesis was observed during the interval that RuBP concentration increased. It is concluded that the rate of photosynthesis at the lower light intensity was limited by the rate of RuBP regeneration and that parallel changes in the activation of RuBP carboxylase occurred such that concentrations of RuBP at steady state were not altered by changes in light intensity. PMID:16663982

The notochord: structure and functions.

Science.gov (United States)

Corallo, Diana; Trapani, Valeria; Bonaldo, Paolo

2015-08-01

The notochord is an embryonic midline structure common to all members of the phylum Chordata, providing both mechanical and signaling cues to the developing embryo. In vertebrates, the notochord arises from the dorsal organizer and it is critical for proper vertebrate development. This evolutionary conserved structure located at the developing midline defines the primitive axis of embryos and represents the structural element essential for locomotion. Besides its primary structural function, the notochord is also a source of developmental signals that patterns surrounding tissues. Among the signals secreted by the notochord, Hedgehog proteins play key roles during embryogenesis. The Hedgehog signaling pathway is a central regulator of embryonic development, controlling the patterning and proliferation of a wide variety of organs. In this review, we summarize the current knowledge on notochord structure and functions, with a particular emphasis on the key developmental events that take place in vertebrates. Moreover, we discuss some genetic studies highlighting the phenotypic consequences of impaired notochord development, which enabled to understand the molecular basis of different human congenital defects and diseases.

Model for expressing leaf photosynthesis in terms of weather variables

African Journals Online (AJOL)

A theoretical mathematical model for describing photosynthesis in individual leaves in terms of weather variables is proposed. The model utilizes a series of efficiency parameters, each of which reflect the fraction of potential photosynthetic rate permitted by the different environmental elements. These parameters are useful ...

Phenotyping of field-grown wheat in the UK highlights contribution of light response of photosynthesis and flag leaf longevity to grain yield.

Science.gov (United States)

Carmo-Silva, Elizabete; Andralojc, P John; Scales, Joanna C; Driever, Steven M; Mead, Andrew; Lawson, Tracy; Raines, Christine A; Parry, Martin A J

2017-06-15

Improving photosynthesis is a major target for increasing crop yields and ensuring food security. Phenotyping of photosynthesis in the field is critical to understand the limits to crop performance in agricultural settings. Yet, detailed phenotyping of photosynthetic traits is relatively scarce in field-grown wheat, with previous studies focusing on narrow germplasm selections. Flag leaf photosynthetic traits, crop development, and yield traits were compared in 64 field-grown wheat cultivars in the UK. Pre-anthesis and post-anthesis photosynthetic traits correlated significantly and positively with grain yield and harvest index (HI). These traits included net CO2 assimilation measured at ambient CO2 concentrations and a range of photosynthetic photon flux densities, and traits associated with the light response of photosynthesis. In most cultivars, photosynthesis decreased post-anthesis compared with pre-anthesis, and this was associated with decreased Rubisco activity and abundance. Heritability of photosynthetic traits suggests that phenotypic variation can be used to inform breeding programmes. Specific cultivars were identified with traits relevant to breeding for increased crop yields in the UK: pre-anthesis photosynthesis, post-anthesis photosynthesis, light response of photosynthesis, and Rubisco amounts. The results indicate that flag leaf longevity and operating photosynthetic activity in the canopy can be further exploited to maximize grain filling in UK bread wheat. © The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Introduction to structure functions

International Nuclear Information System (INIS)

Kwiecinski, J.

1996-07-01

The theory of deep inelastic scattering structure functions is reviewed with an emphasis put on the QCD expectations of their behaviour in the region of small values of Bjorken parameter x. (author). 56 refs

A density functional study of backbone structures of polydiacetylene: destabilization of butatriene structure

International Nuclear Information System (INIS)

Katagiri, Hideki; Shimoi, Yukihiro; Abe, Shuji

2004-01-01

Backbone structures of polydiacetylene are studied with first-principles electronic structure method using plane-waves within generalized gradient approximation (GGA) of density functional theory. In spin-restricted calculations a coarse k-point sampling gives a potential energy curve with two local minima corresponding to acetylene and butatriene structures. However, the potential barrier between the two structures rapidly decreases with increasing number of k-points, which results in destabilization of the butatriene structure. Spin polarization effects also destabilize the butatriene structure, inducing atom-centered spin-density-wave state. These potential energies were compared with those obtained by Hartree-Fock, density functional within local density approximation (LDA) and GGA, and hybrid density functional methods using a gaussian basis set. The comparison shows that the density functional methods within LDA and GGA favor the destabilization of the butatriene structure in contrast to the Hartree-Fock method

Effect of Inorganic and Organic Carbon Enrichments (DIC and DOC) on the Photosynthesis and Calcification Rates of Two Calcifying Green Algae from a Caribbean Reef Lagoon.

Science.gov (United States)

Meyer, Friedrich W; Schubert, Nadine; Diele, Karen; Teichberg, Mirta; Wild, Christian; Enríquez, Susana

2016-01-01

Coral reefs worldwide are affected by increasing dissolved inorganic carbon (DIC) and organic carbon (DOC) concentrations due to ocean acidification (OA) and coastal eutrophication. These two stressors can occur simultaneously, particularly in near-shore reef environments with increasing anthropogenic pressure. However, experimental studies on how elevated DIC and DOC interact are scarce and fundamental to understanding potential synergistic effects and foreseeing future changes in coral reef function. Using an open mesocosm experiment, the present study investigated the impact of elevated DIC (pHNBS: 8.2 and 7.8; pCO2: 377 and 1076 μatm) and DOC (added as 833 μmol L-1 of glucose) on calcification and photosynthesis rates of two common calcifying green algae, Halimeda incrassata and Udotea flabellum, in a shallow reef environment. Our results revealed that under elevated DIC, algal photosynthesis decreased similarly for both species, but calcification was more affected in H. incrassata, which also showed carbonate dissolution rates. Elevated DOC reduced photosynthesis and calcification rates in H. incrassata, while in U. flabellum photosynthesis was unaffected and thalus calcification was severely impaired. The combined treatment showed an antagonistic effect of elevated DIC and DOC on the photosynthesis and calcification rates of H. incrassata, and an additive effect in U. flabellum. We conclude that the dominant sand dweller H. incrassata is more negatively affected by both DIC and DOC enrichments, but that their impact could be mitigated when they occur simultaneously. In contrast, U. flabellum can be less affected in coastal eutrophic waters by elevated DIC, but its contribution to reef carbonate sediment production could be further reduced. Accordingly, while the capacity of environmental eutrophication to exacerbate the impact of OA on algal-derived carbonate sand production seems to be species-specific, significant reductions can be expected under future

Effect of Inorganic and Organic Carbon Enrichments (DIC and DOC on the Photosynthesis and Calcification Rates of Two Calcifying Green Algae from a Caribbean Reef Lagoon.

Directory of Open Access Journals (Sweden)

Friedrich W Meyer

Full Text Available Coral reefs worldwide are affected by increasing dissolved inorganic carbon (DIC and organic carbon (DOC concentrations due to ocean acidification (OA and coastal eutrophication. These two stressors can occur simultaneously, particularly in near-shore reef environments with increasing anthropogenic pressure. However, experimental studies on how elevated DIC and DOC interact are scarce and fundamental to understanding potential synergistic effects and foreseeing future changes in coral reef function. Using an open mesocosm experiment, the present study investigated the impact of elevated DIC (pHNBS: 8.2 and 7.8; pCO2: 377 and 1076 μatm and DOC (added as 833 μmol L-1 of glucose on calcification and photosynthesis rates of two common calcifying green algae, Halimeda incrassata and Udotea flabellum, in a shallow reef environment. Our results revealed that under elevated DIC, algal photosynthesis decreased similarly for both species, but calcification was more affected in H. incrassata, which also showed carbonate dissolution rates. Elevated DOC reduced photosynthesis and calcification rates in H. incrassata, while in U. flabellum photosynthesis was unaffected and thalus calcification was severely impaired. The combined treatment showed an antagonistic effect of elevated DIC and DOC on the photosynthesis and calcification rates of H. incrassata, and an additive effect in U. flabellum. We conclude that the dominant sand dweller H. incrassata is more negatively affected by both DIC and DOC enrichments, but that their impact could be mitigated when they occur simultaneously. In contrast, U. flabellum can be less affected in coastal eutrophic waters by elevated DIC, but its contribution to reef carbonate sediment production could be further reduced. Accordingly, while the capacity of environmental eutrophication to exacerbate the impact of OA on algal-derived carbonate sand production seems to be species-specific, significant reductions can be expected

Network structure shapes spontaneous functional connectivity dynamics.

Science.gov (United States)

Shen, Kelly; Hutchison, R Matthew; Bezgin, Gleb; Everling, Stefan; McIntosh, Anthony R

2015-04-08

The structural organization of the brain constrains the range of interactions between different regions and shapes ongoing information processing. Therefore, it is expected that large-scale dynamic functional connectivity (FC) patterns, a surrogate measure of coordination between brain regions, will be closely tied to the fiber pathways that form the underlying structural network. Here, we empirically examined the influence of network structure on FC dynamics by comparing resting-state FC (rsFC) obtained using BOLD-fMRI in macaques (Macaca fascicularis) to structural connectivity derived from macaque axonal tract tracing studies. Consistent with predictions from simulation studies, the correspondence between rsFC and structural connectivity increased as the sample duration increased. Regions with reciprocal structural connections showed the most stable rsFC across time. The data suggest that the transient nature of FC is in part dependent on direct underlying structural connections, but also that dynamic coordination can occur via polysynaptic pathways. Temporal stability was found to be dependent on structural topology, with functional connections within the rich-club core exhibiting the greatest stability over time. We discuss these findings in light of highly variable functional hubs. The results further elucidate how large-scale dynamic functional coordination exists within a fixed structural architecture. Copyright © 2015 the authors 0270-6474/15/355579-10$15.00/0.

Can net photosynthesis and water relations provide a clue on the ...

African Journals Online (AJOL)

user

2011-02-28

Feb 28, 2011 ... cuvette of the Licor-6400 portable photosynthesis system (Licor,. Lincoln, NE, USA). The leaf ... We would like to thank KOICA for the financial supoort. We thank the KOTUCOP (Korea-Tunisian Coperation. Project) research ...

Mind, brain, structure and function

Energy Technology Data Exchange (ETDEWEB)

Aleksander, I

1982-01-01

The author discusses the type of problem one encounters when trying to formalise the nature of a state structure associated with the brain and the origins of this state structure. The paper first defines in broad terms the nature of the structure function problem, and then goes on to separate out those parts of a structure that lead to the variational and adaptive nature of the state structure. It is argued that the relationship between the structure that leads to adaptation and its embedding in an external environment are crucial areas for further study. 4 references.

Artificial photosynthesis: biomimetic approaches to solar energy conversion and storage.

Science.gov (United States)

Kalyanasundaram, K; Graetzel, M

2010-06-01

Using sun as the energy source, natural photosynthesis carries out a number of useful reactions such as oxidation of water to molecular oxygen and fixation of CO(2) in the form of sugars. These are achieved through a series of light-induced multi-electron-transfer reactions involving chlorophylls in a special arrangement and several other species including specific enzymes. Artificial photosynthesis attempts to reconstruct these key processes in simpler model systems such that solar energy and abundant natural resources can be used to generate high energy fuels and restrict the amount of CO(2) in the atmosphere. Details of few model catalytic systems that lead to clean oxidation of water to H(2) and O(2), photoelectrochemical solar cells for the direct conversion of sunlight to electricity, solar cells for total decomposition of water and catalytic systems for fixation of CO(2) to fuels such as methanol and methane are reviewed here. Copyright 2010 Elsevier Ltd. All rights reserved.

Photon-photon collisions and photon structure functions at LEP

CERN Document Server

Patt, J

2000-01-01

The present knowledge of the structure of the photon based on measurements of photon structure functions is discussed. This review covers recent results on QED structure functions and on the hadronic structure function F/sub 2//sup gamma /. (13 refs).

NEMA, a functional-structural model of nitrogen economy within wheat culms after flowering. I. Model description.

Science.gov (United States)

Bertheloot, Jessica; Cournède, Paul-Henry; Andrieu, Bruno

2011-10-01

Models simulating nitrogen use by plants are potentially efficient tools to optimize the use of fertilizers in agriculture. Most crop models assume that a target nitrogen concentration can be defined for plant tissues and formalize a demand for nitrogen, depending on the difference between the target and actual nitrogen concentrations. However, the teleonomic nature of the approach has been criticized. This paper proposes a mechanistic model of nitrogen economy, NEMA (Nitrogen Economy Model within plant Architecture), which links nitrogen fluxes to nitrogen concentration and physiological processes. A functional-structural approach is used: plant aerial parts are described in a botanically realistic way and physiological processes are expressed at the scale of each aerial organ or root compartment as a function of local conditions (light and resources). NEMA was developed for winter wheat (Triticum aestivum) after flowering. The model simulates the nitrogen (N) content of each photosynthetic organ as regulated by Rubisco turnover, which depends on intercepted light and a mobile N pool shared by all organs. This pool is enriched by N acquisition from the soil and N release from vegetative organs, and is depleted by grain uptake and protein synthesis in vegetative organs; NEMA accounts for the negative feedback from circulating N on N acquisition from the soil, which is supposed to follow the activities of nitrate transport systems. Organ N content and intercepted light determine dry matter production via photosynthesis, which is distributed between organs according to a demand-driven approach. NEMA integrates the main feedbacks known to regulate plant N economy. Other novel features are the simulation of N for all photosynthetic tissues and the use of an explicit description of the plant that allows how the local environment of tissues regulates their N content to be taken into account. We believe this represents an appropriate frame for modelling nitrogen in

Continuous Measurements of Canopy-level Solar-Induced Chlorophyll Fluorescence for Inferring Diurnal and Seasonal Dynamics of Photosynthesis in Crop Fields in the Midwestern USA

Science.gov (United States)

Miao, G.; Guan, K.; Yang, X.; Bernacchi, C.; DeLucia, E. H.; Cai, Y.; Masters, M. D.; Peng, B.

2016-12-01

Plants emitted photons of red and far-red light, called chlorophyll fluorescence, after sunlight absorption for photosynthesis. This solar-induced fluorescence (SIF) is generated simultaneously while plants actively photosynthesize. The link between photosynthesis and SIF resulting from the competition for the same excitation energy has long been investigated and applied for inferring the rate of photosynthesis. Recent development of continuous SIF observational technology is furthering the inferring potential as well as our understandings of fluctuations of SIF and photosynthesis with changes in environmental conditions. To better understand this photosynthesis-SIF link at multiple time scales and their relationships with environmental drivers, we deployed two newly developed tower-based SIF systems (FluoSpec) in a corn (Zea mays L., C4 plant) field and a soybean (Glycine max L., C3 plant) field at University of Illinois Energy Farm and conducted continuous near-surface SIF measurements at canopy scale from mid-growing season of 2016. Eddy covariance flux towers were installed in parallel at both sites for canopy-scale gas exchange measurements. Relationship between SIF and flux tower photosynthesis will be analyzed to derive the empirical models for photosynthesis retrieval from SIF signals. Preliminary results indicate that canopy SIF can reflect diurnal and seasonal dynamics of photosynthesis. Mechanistic analysis on SIF fluctuations and responses to environmental variations will be conducted as well for a closer look at mechanism of photosynthetic responses. Corn and soybean SIF and photosynthesis-SIF relationship will be compared to investigate the difference between C4 and C3 plants.

Structure functions are not parton probabilities

International Nuclear Information System (INIS)

Brodsky, Stanley J.; Hoyer, Paul; Sannino, Francesco; Marchal, Nils; Peigne, Stephane

2002-01-01

The common view that structure functions measured in deep inelastic lepton scattering are determined by the probability of finding quarks and gluons in the target is not correct in gauge theory. We show that gluon exchange between the fast, outgoing partons and target spectators, which is usually assumed to be an irrelevant gauge artifact, affects the leading twist structure functions in a profound way. This observation removes the apparent contradiction between the projectile (eikonal) and target (parton model) views of diffractive and small x B phenomena. The diffractive scattering of the fast outgoing quarks on spectators in the target causes shadowing in the DIS cross section. Thus the depletion of the nuclear structure functions is not intrinsic to the wave function of the nucleus, but is a coherent effect arising from the destructive interference of diffractive channels induced by final state interactions. This is consistent with the Glauber-Gribov interpretation of shadowing as a rescattering effect

QCD predictions for weak neutral current structure functions

International Nuclear Information System (INIS)

Wu Jimin

1987-01-01

Employing the analytic expression (to the next leading order) for non-singlet component of structure function which the author got from QCD theory and putting recent experiment result of neutral current structure function at Q 2 = 11 (GeV/C) 2 as input, the QCD prediction for neutral current structure function of their scaling violation behaviours was given

Global and Time-Resolved Monitoring of Crop Photosynthesis with Chlorophyll Fluorescence

Science.gov (United States)

Guanter, Luis; Zhang, Yongguang; Jung, Martin; Joiner, Joanna; Voigt, Maximilian; Berry, Joseph A.; Frankenberg, Christian; Huete, Alfredo R.; Zarco-Tejada, Pablo; Lee, Jung-Eun;

Diffusive boundary layers and photosynthesis of the epilithic algal community of coral reefs

DEFF Research Database (Denmark)

Larkum, Anthony W.D.; Koch, Eva-Maria W.; Kühl, Michael

2003-01-01

The effects of mass transfer resistance due to the presence of a diffusive boundary layer on the photosynthesis of the epilithic algal community (EAC) of a coral reef were studied. Photosynthesis and respiration of the EAC of dead coral surfaces were investigated for samples from two locations......: the Gulf of Aqaba, Eilat (Israel), and One Tree Reef on the Great Barrier Reef (Australia). Microsensors were used to measure O2 and pH at the EAC surface and above. Oxygen profiles in the light and dark indicated a diffusive boundary layer (DBL) thickness of 180–590 µm under moderate flow (~0.08 m s-1...

The impact of the herbicide atrazine on growth and photosynthesis of seagrass, Zostera marina (L.), seedlings

International Nuclear Information System (INIS)

Gao Yaping; Fang Jianguang; Zhang Jihong; Ren Lihua; Mao Yuze; Li Bin; Zhang Mingliang; Liu Dinghai; Du Meirong

2011-01-01

Highlights: → Impact of the widely used herbicide atrazine on eelgrass seedlings was studied. → Atrazine presents a threat to eelgrass seedlings growth and photosynthesis. → The impact of atrazine on eelgrass seedlings is much higher than for adult plants. - Abstract: The impact of the widely used herbicide atrazine on seedling growth and photosynthesis of eelgrass was determined. The long-term impact of the herbicide atrazine (1, 10 and 100 μg/L) on growth of eelgrass Zostera marina (L.) seedlings, maintained in outdoor aquaria, was monitored over 4 weeks. Exposure to 10 μg/L atrazine resulted in significantly lower plant fresh weight and total chlorophyll concentration and up to 86.67% mortality at the 100 μg/L concentration. Short-term photosynthetic stress on eelgrass seedlings was determined and compared with adult eelgrass using chlorophyll fluorescence. The effective quantum yield in eelgrass seedlings was significantly depressed at all atrazine concentrations (2, 4, 8, 16, 32 and 64 μg/L) even within 2 h and remained at a lower level than for adult plants for each concentration. These results indicate that atrazine presents a potential threat to seagrass seedling functioning and that the impact is much higher than for adult plants.

QCD dipole predictions for DIS and diffractive structure functions

International Nuclear Information System (INIS)

Royon, C.

1997-01-01

The proton structure function F 2 , the gluon density F G , and the longitudinal structure function F L are derived in the QCD dipole picture of BFKL dynamics. We use a three parameter fit to describe the 1994 H1 proton structure function F 2 data in the low x, moderate Q 2 range. Without any additional parameter, the gluon density and the longitudinal structure functions are predicted. The diffractive dissociation processes are also discussed within the same framework, and a new prediction for the proton diffractive structure function is obtained

Inhibition of seagrass photosynthesis by ultraviolet-B radiation

International Nuclear Information System (INIS)

Trocine, R.P.; Rice, J.D.; Wells, G.N.

1981-01-01

Effects of ultraviolet-B radiation on the photosynthesis of seagrasses (Halophila engelmanni Aschers, Halodule wrightii Aschers, and Syringodium filiforme (Kuetz) were examined. The intrinsic tolerance of each seagrass to ultraviolet-B, the presence and effectiveness of photorepair mechanisms to ultraviolet-B-induced photosynthetic inhibition, and the role of epiphytic growth as a shield from ultraviolet-B were investigated. Halodule was found to possess the greatest photosynthetic tolerance for ultraviolet-B. Photosynthesis in Syringodium was slightly more sensitive to ultraviolet-B while Halophila showed relatively little photosynthetic tolerance. Evidence for a photorepair mechanism was found only in Halodule. Syringodium appeared to rely primarily on a thick epidermal cell layer to reduce photosynthetic damage. Halophila seemed to have no morphological or photorepair capabilities to deal with ultraviolet-B. This species appeared to rely on epiphytic and detrital shielding and the shade provided by other seagrasses to reduce ultraviolet-B irradiation to tolerable levels. The presence of epiphytes on leaf surfaces was found to reduce the extent of photosynthetic inhibition from ultraviolet-B exposure in all species. Halophila appears to obtain an increased photosynthetic tolerance to ultraviolet-B as an indirect benefit of chloroplast clumping to avoid photo-oxidation by intense levels of photosynthetically active radiation

Do plastic particles affect microalgal photosynthesis and growth?

Science.gov (United States)

Sjollema, Sascha B; Redondo-Hasselerharm, Paula; Leslie, Heather A; Kraak, Michiel H S; Vethaak, A Dick

2016-01-01

The unbridled increase in plastic pollution of the world's oceans raises concerns about potential effects these materials may have on microalgae, which are primary producers at the basis of the food chain and a major global source of oxygen. Our current understanding about the potential modes and mechanisms of toxic action that plastic particles exert on microalgae is extremely limited. How effects might vary with particle size and the physico-chemical properties of the specific plastic material in question are equally unelucidated, but may hold clues to how toxicity, if observed, is exerted. In this study we selected polystyrene particles, both negatively charged and uncharged, and three different sizes (0.05, 0.5 and 6μm) for testing the effects of size and material properties. Microalgae were exposed to different polystyrene particle sizes and surface charges for 72h. Effects on microalgal photosynthesis and growth were determined by pulse amplitude modulation fluorometry and flow cytometry, respectively. None of the treatments tested in these experiments had an effect on microalgal photosynthesis. Microalgal growth was negatively affected (up to 45%) by uncharged polystyrene particles, but only at high concentrations (250mg/L). Additionally, these adverse effects were demonstrated to increase with decreasing particle size. Copyright © 2015 Elsevier B.V. All rights reserved.

Inhibition of photosynthesis by carbon monoxide and suspension of the carbon monoxide inhibition by light

Energy Technology Data Exchange (ETDEWEB)

Gewitz, H S; Voelker, W

1963-08-01

The experimental subject was the autotroph Chlorella pyrenoidosa. It was found that growth conditions determine whether the alga is inhibited by carbon monoxide or not. Respiration and photosynthesis are inhibited by carbon monoxide if the cells have grown rapidly under high light intensities. The inhibition of respiration and photosynthesis found in such cells is completely reversible. The inhibition depends not only on carbon monoxide pressure, but also on the oxygen pressure prevailing at the same time. 5 references, 1 figure, 3 tables.

Long-term effects of elevated UV-B radiation on photosynthesis and ultrastructure of Eriophorum russeolum and Warnstorfia exannulata