The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Stephen P Long - One of the best experts on this subject based on the ideXlab platform.
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photosynthetic efficiency and mesophyll conductance are unaffected in arabidopsis thaliana aquaporin knock out lines
Journal of Experimental Botany, 2019Co-Authors: Stephen P Long, Johannes Kromdijk, Katarzyna GlowackaAbstract:Improving photosynthetic efficiency is widely regarded as a major route to achieving much-needed yield gains in crop plants. In plants with C3 Photosynthesis, increasing the diffusion conductance for CO2 transfer from substomatal cavity to chloroplast stroma (gm) could help to improve the efficiencies of CO2 assimilation and photosynthetic water use in parallel. The diffusion pathway from substomatal cavity to chloroplast traverses cell wall, plasma membrane, cytosol, chloroplast envelope membranes, and chloroplast stroma. Specific membrane intrinsic proteins of the aquaporin family can facilitate CO2 diffusion across membranes. Some of these aquaporins, such as PIP1;2 in Arabidopsis thaliana, have been suggested to exert control over gm and the magnitude of the CO2 assimilation flux, but the evidence for a direct physiological role of aquaporins in determining gm is limited. Here, we estimated gm with four different methods under a range of light intensities and CO2 concentrations in two previously characterized pip1;2 knock-out lines as well as pip1;3 and pip2;6 knock-out lines, which have not been previously evaluated for a role in gm. This study presents the most in-depth analysis of gm in Arabidopsis aquaporin knock-out mutants to date. Surprisingly, all methods failed to show any significant differences between the pip1;2, pip1;3, or pip2;6 mutants and the Col-0 control.
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enhancing soybean photosynthetic co2 assimilation using a cyanobacterial membrane protein ictb
Journal of Plant Physiology, 2017Co-Authors: William T Hay, Stephen P Long, Saadia Bihmidine, Nedim Mutlu, Khang Le Hoang, Tala Awada, Donald P Weeks, Thomas ClementeAbstract:Soybean C3 Photosynthesis can suffer a severe loss in efficiency due to photorespiration and the lack of a carbon concentrating mechanism (CCM) such as those present in other plant species or cyanobacteria. Transgenic soybean (Glycine max cv. Thorne) plants constitutively expressing cyanobacterial ictB (inorganic carbon transporter B) gene were generated using Agrobacterium-mediated transformation. Although more recent data suggest that ictB does not actively transport HCO3-/CO2, there is nevertheless mounting evidence that transformation with this gene can increase higher plant Photosynthesis. The hypothesis that expression of the ictB gene would improve Photosynthesis, biomass production and seed yield in soybean was tested, in two independent replicated greenhouse and field trials. Results showed significant increases in photosynthetic CO2 uptake (Anet) and dry mass in transgenic relative to wild type (WT) control plants in both the greenhouse and field trials. Transgenic plants also showed increased photosynthetic rates and biomass production during a drought mimic study. The findings presented herein demonstrate that ictB, as a single-gene, contributes to enhancement in various yield parameters in a major commodity crop and point to the significant role that biotechnological approaches to increasing photosynthetic efficiency can play in helping to meet increased global demands for food.
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a physiological and biophysical model of coppice willow salix spp production yields for the contiguous usa in current and future climate scenarios
Plant Cell and Environment, 2015Co-Authors: Dan Wang, Andrew D B Leakey, Deepak Jaiswal, David Lebauer, Timothy M Wertin, German A Bollero, Stephen P LongAbstract:High-performance computing has facilitated development of biomass production models that capture the key mechanisms underlying production at high spatial and temporal resolution. Direct responses to increasing [CO2 ] and temperature are important to long-lived emerging woody bioenergy crops. Fast-growing willow (Salix spp.) within short rotation coppice (SRC) has considerable potential as a renewable biomass source, but performance over wider environmental conditions and under climate change is uncertain. We extended the bioenergy crop modeling platform, BioCro, to SRC willow by adding coppicing and C3 Photosynthesis subroutines, and modifying subroutines for perennation, allocation, morphology, phenology and development. Parameterization with measurements of leaf Photosynthesis, allocation and phenology gave agreement of modeled with measured yield across 23 sites in Europe and North America. Predictions for the continental USA suggest yields of ≥17 Mg ha(-1) year(-1) in a 4 year rotation. Rising temperature decreased predicted yields, an effect partially ameliorated by rising [CO2 ]. This model, based on over 100 equations describing the physiological and biophysical mechanisms underlying production, provides a new framework for utilizing mechanism of plant responses to the environment, including future climates. As an open-source tool, it is made available here as a community resource for further application, improvement and adaptation.
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e Photosynthesis a comprehensive dynamic mechanistic model of C3 Photosynthesis from light capture to sucrose synthesis
Plant Cell and Environment, 2013Co-Authors: Xinguang Zhu, Donald R Ort, Yu Wang, Stephen P LongAbstract:Photosynthesis is arguably the most researched of all plant processes. A dynamic model of leaf Photosynthesis that includes each discrete process from light capture to carbohydrate synthesis, e-Photosynthesis, is described. It was developed by linking and extending our previous models of photosystem II (PSII) energy transfer and photosynthetic C3 carbon metabolism to include electron transfer processes around photosystem I (PSI), ion transfer between the lumen and stroma, ATP synthesis and NADP reduction to provide a complete representation. Different regulatory processes linking the light and dark reactions are also included: Rubisco activation via Rubisco activase, pH and xanthophyll cycle-dependent non-photochemical quenching mechanisms, as well as the regulation of enzyme activities via the ferredoxin-theoredoxin system. Although many further feedback and feedforward controls undoubtedly exist, it is shown that e-Photosynthesis effectively mimics the typical kinetics of leaf CO₂ uptake, O₂ evolution, chlorophyll fluorescence emission, lumen and stromal pH, and membrane potential following perturbations in light, [CO₂] and [O₂] observed in intact C3 leaves. The model provides a framework for guiding engineering of improved photosynthetic efficiency, for evaluating multiple non-invasive measures used in emerging phenomics facilities, and for quantitative assessment of strengths and weaknesses within the understanding of Photosynthesis as an integrated process.
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what is the maximum efficiency with which Photosynthesis can convert solar energy into biomass
Current Opinion in Biotechnology, 2008Co-Authors: Xinguang Zhu, Stephen P Long, Donald R OrtAbstract:Photosynthesis is the source of our food and fiber. Increasing world population, economic development, and diminishing land resources forecast that a doubling of productivity is critical in meeting agricultural demand before the end of this century. A starting point for evaluating the global potential to meet this goal is establishing the maximum efficiency of photosynthetic solar energy conversion. The potential efficiency of each step of the photosynthetic process from light capture to carbohydrate synthesis is examined. This reveals the maximum conversion efficiency of solar energy to biomass is 4.6% for C3 Photosynthesis at 30 °C and today's 380 ppm atmospheric [CO2], but 6% for C4 Photosynthesis. This advantage over C3 will disappear as atmospheric [CO2] nears 700 ppm.
Wenwen Kong - One of the best experts on this subject based on the ideXlab platform.
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molecular changes in mesembryanthemum crystallinum guard cells underlying the C3 to cam transition
Plant Molecular Biology, 2020Co-Authors: Theresa M Kelley, Wenwen Kong, Mijeong Yoo, Dan Zhu, Jerald D Noble, Matias Kirst, Sarah M AssmannAbstract:The timing and transcriptomic changes during the C3 to CAM transition of common ice plant support the notion that guard cells themselves can shift from C3 to CAM. Crassulacean acid metabolism (CAM) is a specialized type of Photosynthesis: stomata close during the day, enhancing water conservation, and open at night, allowing CO2 uptake. Mesembryanthemum crystallinum (common ice plant) is a facultative CAM species that can shift from C3 Photosynthesis to CAM under salt or drought stresses. However, the molecular mechanisms underlying the stress induced transition from C3 to CAM remain unknown. Here we determined the transition time from C3 to CAM in M. crystallinum under salt stress. In parallel, single-cell-type transcriptomic profiling by 3′-mRNA sequencing was conducted in isolated stomatal guard cells to determine the molecular changes in this key cell type during the transition. In total, 495 transcripts showed differential expression between control and salt-treated samples during the transition, including 285 known guard cell genes, seven CAM-related genes, 18 transcription factors, and 185 other genes previously not found to be expressed in guard cells. PEPC1 and PPCK1, which encode key enzymes of CAM Photosynthesis, were up-regulated in guard cells after seven days of salt treatment, indicating that guard cells themselves can shift from C3 to CAM. This study provides important information towards introducing CAM stomatal behavior into C3 crops to enhance water use efficiency.
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molecular changes in mesembryanthemum crystallinum guard cells underlying the C3 to cam transition
Plant Molecular Biology, 2020Co-Authors: Theresa M Kelley, Wenwen Kong, Mijeong Yoo, Dan Zhu, Jerald D Noble, Matias Kirst, Sarah M AssmannAbstract:ABSTARCT KEY MESSAGE: The timing and transcriptomic changes during the C3 to CAM transition of common ice plant support the notion that guard cells themselves can shift from C3 to CAM. Crassulacean acid metabolism (CAM) is a specialized type of Photosynthesis: stomata close during the day, enhancing water conservation, and open at night, allowing CO2 uptake. Mesembryanthemum crystallinum (common ice plant) is a facultative CAM species that can shift from C3 Photosynthesis to CAM under salt or drought stresses. However, the molecular mechanisms underlying the stress induced transition from C3 to CAM remain unknown. Here we determined the transition time from C3 to CAM in M. crystallinum under salt stress. In parallel, single-cell-type transcriptomic profiling by 3'-mRNA sequencing was conducted in isolated stomatal guard cells to determine the molecular changes in this key cell type during the transition. In total, 495 transcripts showed differential expression between control and salt-treated samples during the transition, including 285 known guard cell genes, seven CAM-related genes, 18 transcription factors, and 185 other genes previously not found to be expressed in guard cells. PEPC1 and PPCK1, which encode key enzymes of CAM Photosynthesis, were up-regulated in guard cells after seven days of salt treatment, indicating that guard cells themselves can shift from C3 to CAM. This study provides important information towards introducing CAM stomatal behavior into C3 crops to enhance water use efficiency.
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molecular changes in mesembryanthemum crystallinum guard cells underlying the C3 to cam transition
bioRxiv, 2019Co-Authors: Theresa M Kelley, Wenwen Kong, Mijeong Yoo, Jerald D Noble, Matias Kirst, Sarah M Assmann, Sixue ChenAbstract:ABSTRACT Crassulacean acid metabolism (CAM) is a specialized type of Photosynthesis: stomata close during the day, enhancing water conservation, and open at night, allowing CO2 uptake. Mesembryanthemum crystallinum (common ice plant) is a facultative CAM species that can shift from C3 Photosynthesis to CAM under salt or drought stresses. However, the molecular mechanisms underlying the stress induced transition from C3 to CAM remain unknown. Here we determined the transition time from C3 to CAM in M. crystallinum under salt stress. In parallel, single-cell-type transcriptomic profiling by 3’-mRNA sequencing was conducted in guard cells to determine the molecular changes in this key cell type during the transition. In total, 495 transcripts showed differential expression between control and salt-treated samples during the transition, including 285 known guard cell genes, seven CAM-related genes, 18 transcription factors, and 185 other genes previously not found to be expressed in guard cells. PEPC1 and PPCK1, which encode key enzymes of CAM Photosynthesis, were up-regulated in guard cells after seven days of salt treatment, indicating that guard cells themselves can transition from C3 to CAM. This study provides important information towards introducing CAM stomatal behavior into C3 crops to enhance water use efficiency. Summary statement We determined the timing of salt induced transition of common ice plant from C3 to CAM and identified transcriptomic changes during the transition. The data support the notion that guard cells themselves can transition from C3 to CAM.
Klaus Winter - One of the best experts on this subject based on the ideXlab platform.
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low level cam Photosynthesis in a succulent leaved member of the urticaceae pilea peperomioides
Functional Plant Biology, 2021Co-Authors: Klaus Winter, Milton N Garcia, Aurelio Virgo, Andrew J C SmithAbstract:Pilea peperomioides Diels (Urticaceae) is a semi-succulent herbaceous species native to south-western China that has become popular in cultivation as an ornamental plant. To investigate whether this species possesses the capacity for CAM Photosynthesis, measurements were made of CO2 gas exchange and titratable acidity in plants under both well-watered and water-deficit conditions. Plants were found to assimilate CO2 almost exclusively in the light via C3 Photosynthesis. However, distinct transient reductions in the rate of net nocturnal CO2 release were consistently observed during the course of the dark period, and under water-deficit conditions one plant exhibited a brief period of net nocturnal CO2 uptake, providing unequivocal evidence of CAM activity. Furthermore, nocturnal increases in titratable acidity in both leaf laminas and petioles were observed in all plants exposed to wet-dry-wet cycles. This is the first report of CAM in the family Urticaceae. The results are discussed in relation to the phylogenetic position of Pilea and the partially shaded montane habitats in which this species is typically found. An updated list of all plant families currently known to contain species with CAM is presented.
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ecophysiology of constitutive and facultative cam Photosynthesis
Journal of Experimental Botany, 2019Co-Authors: Klaus WinterAbstract:In plants exhibiting crassulacean acid metabolism (CAM), CAM Photosynthesis almost always occurs together with C3 Photosynthesis, and occasionally with C4 Photosynthesis. Depending on species, ontogeny, and environment, CAM input to total carbon gain can vary from values of <1% to 100%. The wide range of CAM phenotypes between and within species is a fascinating example of functional diversity and plasticity, but poses a significant challenge when attempting to define CAM. CO2 gas exchange experiments designed for this review illustrate key patterns of CAM expression and highlight distinguishing features of constitutive and facultative CAM. Furthermore, they help to address frequently recurring questions on CAM terminology. The functional and evolutionary significance of contrasting CAM phenotypes and of intermediate states between extremes is discussed. Results from a study on nocturnal malate accumulation in 50 species of Aizoaceae exposed to drought and salinity stress suggest that facultative CAM is more widespread amongst vascular plants than previously thought.
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multiple isoforms of phosphoenolpyruvate carboxylase in the orchidaceae subtribe oncidiinae implications for the evolution of crassulacean acid metabolism
Journal of Experimental Botany, 2014Co-Authors: Klaus Winter, Katia Silvera, Leticia B Rodriguez, Rebecca L Albion, John C. CushmanAbstract:Phosphoenolpyruvate carboxylase (PEPC) catalyses the initial fixation of atmospheric CO2 into oxaloacetate and subsequently malate. Nocturnal accumulation of malic acid within the vacuole of photosynthetic cells is a typical feature of plants that perform crassulacean acid metabolism (CAM). PEPC is a ubiquitous plant enzyme encoded by a small gene family, and each member encodes an isoform with specialized function. CAM-specific PEPC isoforms probably evolved from ancestral non-photosynthetic isoforms by gene duplication events and subsequent acquisition of transcriptional control elements that mediate increased leaf-specific or photosynthetic-tissue-specific mRNA expression. To understand the patterns of functional diversification related to the expression of CAM, ppc gene families and photosynthetic patterns were characterized in 11 closely related orchid species from the subtribe Oncidiinae with a range of photosynthetic pathways from C3 Photosynthesis (Oncidium cheirophorum, Oncidium maduroi, Rossioglossum krameri, and Oncidium sotoanum) to weak CAM (Oncidium panamense, Oncidium sphacelatum, Gomesa flexuosa and Rossioglossum insleayi) and strong CAM (Rossioglossum ampliatum, Trichocentrum nanum, and Trichocentrum carthagenense). Phylogenetic analysis revealed the existence of two main ppc lineages in flowering plants, two main ppc lineages within the eudicots, and three ppc lineages within the Orchidaceae. Our results indicate that ppc gene family expansion within the Orchidaceae is likely to be the result of gene duplication events followed by adaptive sequence divergence. CAM-associated PEPC isoforms in the Orchidaceae probably evolved from several independent origins.
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Environment or development? Lifetime net CO2 exchange and control of the expression of Crassulacean acid metabolism in Mesembryanthemum crystallinum.
Plant physiology, 2006Co-Authors: Klaus Winter, Joseph A. M. HoltumAbstract:The relative influence of plant age and environmental stress signals in triggering a shift from C3 Photosynthesis to Crassulacean acid metabolism (CAM) in the annual halophytic C3-CAM species Mesembryanthemum crystallinum was explored by continuously monitoring net CO2 exchange of whole shoots from the seedling stage until seed set. Plants exposed to high salinity (400 mm NaCl) in hydroponic culture solution or grown in saline-droughted soil acquired between 11% and 24% of their carbon via net dark CO2 uptake involving CAM. In contrast, plants grown under nonsaline, well-watered conditions were capable of completing their life cycle by operating in the C3 mode without ever exhibiting net CO2 uptake at night. These observations are not consistent with the widely expressed view that the induction of CAM by high salinity in M. crystallinum represents an acceleration of preprogrammed developmental processes. Rather, our study demonstrates that the induction of the CAM pathway for carbon acquisition in M. crystallinum is under environmental control.
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multiple origins of crassulacean acid metabolism and the epiphytic habit in the neotropical family bromeliaceae
Proceedings of the National Academy of Sciences of the United States of America, 2004Co-Authors: Darren M Crayn, Klaus Winter, Andrew J C SmithAbstract:The large Neotropical family Bromeliaceae presents an outstanding example of adaptive radiation in plants, containing a wide range of terrestrial and epiphytic life-forms occupying many distinct habitats. Diversification in bromeliads has been linked to several key innovations, including water- and nutrient-impounding phytotelmata, absorptive epidermal trichomes, and the water-conserving mode of Photosynthesis known as crassulacean acid metabolism (CAM). To clarify the origins of CAM and the epiphytic habit, we conducted a phylogenetic analysis of nucleotide sequences for 51 bromeliad taxa by using the plastid loci matK and the rps16 intron, combined with a survey of photosynthetic pathway determined by carbon-isotope ratios for 1,873 species representing 65% of the family. Optimization of character-states onto the strict consensus tree indicated that the last common ancestor of Bromeliaceae was a terrestrial C3 mesophyte, probably adapted to moist, exposed, nutrient-poor habitats. Both CAM Photosynthesis and the epiphytic habit evolved a minimum of three times in the family, most likely in response to geological and climatic changes in the late Tertiary. The great majority of epiphytic forms are now found in two lineages: in subfamily Tillandsioideae, in which C3 Photosynthesis was the ancestral state and CAM developed later in the most extreme epiphytes, and in subfamily Bromelioideae, in which CAM Photosynthesis predated the appearance of epiphytism. Subsequent radiation of the bromelioid line into less xeric habitats has led to reversion to C3 Photosynthesis in some taxa, showing that both gain and loss of CAM have occurred in the complex evolutionary history of this family.
Xiaohan Yang - One of the best experts on this subject based on the ideXlab platform.
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conservation and diversification of circadian rhythmicity between a model crassulacean acid metabolism plant kalanchoe fedtschenkoi and a model C3 Photosynthesis plant arabidopsis thaliana
Frontiers in Plant Science, 2018Co-Authors: Robert C Moseley, Ritesh Mewalal, Francis C Motta, Gerald A Tuskan, Steve Haase, Xiaohan YangAbstract:Crassulacean acid metabolism (CAM) improves photosynthetic efficiency under limited water availability relative to C3 Photosynthesis. It is widely accepted that CAM plants have evolved from C3 plants and it is hypothesized that CAM is under the control of the internal circadian clock. However, the role that the circadian clock plays in the evolution of CAM is not well understood. To identify the molecular basis of circadian control over CAM evolution, rhythmic gene sets were identified in a CAM model plant species (Kalanchoe fedtschenkoi) and a C3 model plant species (Arabidopsis thaliana) through analysis of diel time-course gene expression data using multiple periodicity detection algorithms. Based on protein sequences, ortholog groups were constructed containing genes from each of these two species. The ortholog groups were categorized into five gene sets based on conservation and diversification of rhythmic gene expression. Interestingly, minimal functional overlap was observed when comparing the rhythmic gene sets of each species. Specifcally, metabolic processes were enriched in the gene set under circadian control in K. fedtschenkoi and numerous genes were found to have retained or gained rhythmic expression in K. fedtsechenkoi. Additonally, several rhythmic orthologs, including CAM-related orthologs, displayed phase shifts between species. Results of this analysis point to several mechanisms by which the circadian clock plays a role in the evolution of CAM. These genes provide a set of testable hypotheses for future experiments.
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the kalanchoe genome provides insights into convergent evolution and building blocks of crassulacean acid metabolism
Nature Communications, 2017Co-Authors: Karolina Heyduk, Xiaohan Yang, Rongbin Hu, Jerry Jenkins, Haibao Tang, Deborah Weighill, Jungmin Ha, David GoodsteinAbstract:Crassulacean acid metabolism (CAM) is a water-use efficient adaptation of Photosynthesis that has evolved independently many times in diverse lineages of flowering plants. We hypothesize that convergent evolution of protein sequence and temporal gene expression underpins the independent emergences of CAM from C3 Photosynthesis. To test this hypothesis, we generate a de novo genome assembly and genome-wide transcript expression data for Kalanchoe fedtschenkoi, an obligate CAM species within the core eudicots with a relatively small genome (~260 Mb). Our comparative analyses identify signatures of convergence in protein sequence and re-scheduling of diel transcript expression of genes involved in nocturnal CO2 fixation, stomatal movement, heat tolerance, circadian clock, and carbohydrate metabolism in K. fedtschenkoi and other CAM species in comparison with non-CAM species. These findings provide new insights into molecular convergence and building blocks of CAM and will facilitate CAM-into-C3 Photosynthesis engineering to enhance water-use efficiency in crops.
Wataru Yamori - One of the best experts on this subject based on the ideXlab platform.
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rubisco activity is associated with photosynthetic thermotolerance in a wild rice oryza meridionalis
Physiologia Plantarum, 2012Co-Authors: Andrew P Scafaro, Wataru Yamori, Susanne Von Caemmerer, Elizabete A Carmosilva, Michael E Salvucci, Brian J AtwellAbstract:Oryza meridionalis is a wild species of rice, endemic to tropical Australia. It shares a significant genome homology with the common domesticated rice Oryza sativa. Exploiting the fact that the two species are highly related but O. meridionalis has superior heat tolerance, experiments were undertaken to identify the impact of temperature on key events in Photosynthesis. At an ambient CO2 partial pressure of 38 Pa and irradiance of 1500 μmol quanta m-2 s-1, the temperature optimum of Photosynthesis was 33.7 ± 0.8°C for O. meridionalis, significantly higher than the 30.6 ± 0.7°C temperature optimum of O. sativa. To understand the basis for this difference, we measured gas exchange and rubisco activation state between 20 and 42°C and modeled the response to determine the rate-limiting steps of Photosynthesis. The temperature response of light respiration (Rlight) and the CO2 compensation point in the absence of respiration (Γ*) were determined and found to be similar for the two species. C3 Photosynthesis modeling showed that despite the difference in susceptibility to high temperature, both species had a similar temperature-dependent limitation to Photosynthesis. Both rice species were limited by ribulose-1,5-bisphosphate (RuBP) regeneration at temperatures of 25 and 30°C but became RuBP carboxylation limited at 35 and 40°C. The activation state of rubisco in O. meridionalis was more stable at higher temperatures, explaining its greater heat tolerance compared with O. sativa.
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the rate limiting step for co 2 assimilation at different temperatures is influenced by the leaf nitrogen content in several c 3 crop species
Plant Cell and Environment, 2011Co-Authors: Wataru Yamori, Takeshi Nagai, Amane MakinoAbstract:Effects of nitrogen (N) supply on the limiting step of CO2 assimilation rate (A) at 380 µmol mol−1 CO2 concentration (A380) at several leaf temperatures were studied in several crops, since N nutrition alters N allocation between photosynthetic components. Contents of leaf N, ribulose 1·5-bisphosphate carboxylase/oxygenase (Rubisco) and cytochrome f (cyt f) increased with increasing N supply, but the cyt f/Rubisco ratio decreased. Large leaf N content was linked to a high stomatal (gs) and mesophyll conductance (gm), but resulted in a lower intercellular (Ci) and chloroplast CO2 concentration (Cc) because the increase in gs and gm was insufficient to compensate for change in A380. The A-Cc response was used to estimate the maximum rate of RuBP carboxylation (Vcmax) and chloroplast electron transport (Jmax). The Jmax/Vcmax ratio decreased with reductions in leaf N content, which was consistent with the results of the cyt f/Rubisco ratio. Analysis using the C3 Photosynthesis model indicated that A380 tended to be limited by RuBP carboxylation in plants grown at low N concentration, whereas it was limited by RuBP regeneration in plants grown at high N concentration. We conclude that the limiting step of A380 depends on leaf N content and is mainly determined by N partitioning between Rubisco and electron transport components.
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phenotypic plasticity in photosynthetic temperature acclimation among crop species with different cold tolerances
Plant Physiology, 2010Co-Authors: Wataru Yamori, Ko Noguchi, Kouki Hikosaka, Ichiro TerashimaAbstract:While interspecific variation in the temperature response of Photosynthesis is well documented, the underlying physiological mechanisms remain unknown. Moreover, mechanisms related to species-dependent differences in photosynthetic temperature acclimation are unclear. We compared photosynthetic temperature acclimation in 11 crop species differing in their cold tolerance, which were grown at 15°C or 30°C. Cold-tolerant species exhibited a large decrease in optimum temperature for the photosynthetic rate at 360 μL L−1 CO2 concentration [Opt (A360)] when growth temperature decreased from 30°C to 15°C, whereas cold-sensitive species were less plastic in Opt (A360). Analysis using the C3 Photosynthesis model shows that the limiting step of A360 at the optimum temperature differed between cold-tolerant and cold-sensitive species; ribulose 1,5-bisphosphate carboxylation rate was limiting in cold-tolerant species, while ribulose 1,5-bisphosphate regeneration rate was limiting in cold-sensitive species. Alterations in parameters related to photosynthetic temperature acclimation, including the limiting step of A360, leaf nitrogen, and Rubisco contents, were more plastic to growth temperature in cold-tolerant species than in cold-sensitive species. These plastic alterations contributed to the noted growth temperature-dependent changes in Opt (A360) in cold-tolerant species. Consequently, cold-tolerant species were able to maintain high A360 at 15°C or 30°C, whereas cold-sensitive species were not. We conclude that differences in the plasticity of photosynthetic parameters with respect to growth temperature were responsible for the noted interspecific differences in photosynthetic temperature acclimation between cold-tolerant and cold-sensitive species.
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effects of internal conductance on the temperature dependence of the photosynthetic rate in spinach leaves from contrasting growth temperatures
Plant and Cell Physiology, 2006Co-Authors: Wataru Yamori, Ko Noguchi, Yuko T Hanba, Ichiro TerashimaAbstract:The photosynthetic rate may be strongly limited by internal conductance from the intercellular airspace to the chloroplast stroma (gi). However, the effects of growth and leaf temperature on gi are still unclarified. In this work, we determined the temperature dependence of gi in spinach leaves grown at 30/258C (high temperature; HT) and 15/108C (low temperature; LT), using the concurrent measurements of the gas exchange rate and stable carbon isotope ratio. Moreover, we quantified the effects of gi on the temperature dependence of the photosynthetic rate. We measured gi and the photosynthetic rate at a CO2 concentration of 360m ll � 1 under saturating light (A360) at different leaf temperatures. The optimum temperature for A360 was 28.58C in HT leaves and 22.98C in LT leaves. The optimum temperatures for gi were almost similar to those of A360 in both HT and LT leaves. There was a strong linear relationship between A360 and gi. The photosynthetic rates predicted from the C3 Photosynthesis model taking account of gi agreed well with A360 in both HT and LT leaves. The temperature coefficients (Q10 )o fgi between 10 and 208C were 2.0 and 1.8 in HT and LT leaves, respectively. This suggests that gi was determined not only by physical diffusion but by processes facilitated by protein(s). The limitation of the photosynthetic rate imposed by gi increased with leaf temperature and was greater than the limitation of the stomatal conductance at any temperature, in both HT and LT leaves. This study suggests that gi substantially limits the photosynthetic rate, especially at higher temperatures.
