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Photosynthesis

About: Photosynthesis is a research topic. Over the lifetime, 19789 publications have been published within this topic receiving 895197 citations.


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Journal ArticleDOI
TL;DR: The physiological, biochemical and molecular aspects of high temperature stress on the process of photosynthesis, as well as the tolerance and adaptive mechanisms involved are summarized.
Abstract: Global warming has led to increased temperature of the earth which is a major abiotic stress posing a serious threat to the plants. Photosynthesis is amongst the plant cell functions that is highly sensitive to high temperature stress and is often inhibited before other cell functions are impaired. The primary sites of targets of high temperature stress are Photosystem II (PSII), ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) while Cytochrome b559 (Cytb559) and plastoquinone (PQ) are also affected. As compared to PSII, PSI is stable at higher temperatures. ROS production, generation of heat shock proteins, production of secondary metabolites are some of the consequences of high temperature stress. In this review we have summarized the physiological, biochemical and molecular aspects of high temperature stress on the process of photosynthesis, as well as the tolerance and adaptive mechanisms involved.

469 citations

Journal ArticleDOI
TL;DR: The model provides a synthetic, mechanistic framework for linking global biogeochemical cycles to cellular-, individual- and community-level processes and supports the hypothesis that the combined effects of body size and temperature on individual metabolic rate impose important constraints on the global C cycle.
Abstract: Summary 1. We present a model that yields ecosystem-level predictions of the flux, storage and turnover of carbon in three important pools (autotrophs, decomposers, labile soil C) based on the constraints of body size and temperature on individual metabolic rate. 2. The model predicts a 10 000-fold increase in C turnover rates moving from tree- to phytoplankton-dominated ecosystems due to the size dependence of photosynthetic rates. 3. The model predicts a 16-fold increase in rates controlled by respiration (e.g. decomposition, turnover of labile soil C and microbial biomass) over the temperature range 0‐30 °C due to the temperature dependence of ATP synthesis in respiratory complexes. 4. The model predicts only a fourfold increase in rates controlled by photosynthesis (e.g. net primary production, litter fall, fine root turnover) over the temperature range 0‐30 °C due to the temperature dependence of Rubisco carboxylation in chloroplasts. 5. The difference between the temperature dependence of respiration and photosynthesis yields quantitative predictions for distinct phenomena that include acclimation of plant respiration, geographic gradients in labile C storage, and differences between the short- and long-term temperature dependence of whole-ecosystem CO2 flux. 6. These four sets of model predictions were tested using global compilations of data on C flux, storage and turnover in ecosystems. 7. Results support the hypothesis that the combined effects of body size and temperature on individual metabolic rate impose important constraints on the global C cycle. The model thus provides a synthetic, mechanistic framework for linking global biogeochemical cycles to cellular-, individual- and community-level processes.

469 citations

Journal ArticleDOI
08 Sep 2000-Science
TL;DR: Phylogenetic analyses of multiple magnesium-tetrapyrrole biosynthesis genes using a combination of distance, maximum parsimony, and maximum likelihood methods indicate that heliobacteria are closest to the last common ancestor of all oxygenic photosynthetic lineages and that green sulfur bacteria and green nonsulfur bacteria are each other's closest relatives.
Abstract: The origin and evolution of photosynthesis have long remained enigmatic due to a lack of sequence information of photosynthesis genes across the entire photosynthetic domain. To probe early evolutionary history of photosynthesis, we obtained new sequence information of a number of photosynthesis genes from the green sulfur bacterium Chlorobium tepidum and the green nonsulfur bacterium Chloroflexus aurantiacus. A total of 31 open reading frames that encode enzymes involved in bacteriochlorophyll/porphyrin biosynthesis, carotenoid biosynthesis, and photosynthetic electron transfer were identified in about 100 kilobase pairs of genomic sequence. Phylogenetic analyses of multiple magnesium-tetrapyrrole biosynthesis genes using a combination of distance, maximum parsimony, and maximum likelihood methods indicate that heliobacteria are closest to the last common ancestor of all oxygenic photosynthetic lineages and that green sulfur bacteria and green nonsulfur bacteria are each other's closest relatives. Parsimony and distance analyses further identify purple bacteria as the earliest emerging photosynthetic lineage. These results challenge previous conclusions based on 16S ribosomal RNA and Hsp60/Hsp70 analyses that green nonsulfur bacteria or heliobacteria are the earliest phototrophs. The overall consensus of our phylogenetic analysis, that bacteriochlorophyll biosynthesis evolved before chlorophyll biosynthesis, also argues against the long-held Granick hypothesis.

467 citations

Journal ArticleDOI
TL;DR: It is concluded that photosynthesis in field-grown Pima cotton leaves is functionally limited by photosynthetic electron transport and RuBP regeneration capacity, not Rubisco activity.
Abstract: Restrictions to photosynthesis can limit plant growth at high temperature in a variety of ways In addition to increasing photorespiration, moderately high temperatures (35‐42 ∞ C) can cause direct injury to the photosynthetic apparatus Both carbon metabolism and thylakoid reactions have been suggested as the primary site of injury at these temperatures In the present study this issue was addressed by first characterizing leaf temperature dynamics in Pima cotton ( Gossypium barbadense ) grown under irrigation in the US desert south-west It was found that cotton leaves repeatedly reached temperatures above 40 ∞ C and could fluctuate as much as 8 or 10 ∞ ∞ ∞ C in a matter of seconds Laboratory studies revealed a maximum photosynthetic rate at 30‐33 ∞ C that declined by 22% at 45 ∞ C The majority of the inhibition persisted upon return to 30 ∞ C The mechanism of this limitation was assessed by measuring the response of photosynthesis to CO 2 in the laboratory The first time a cotton leaf (grown at 30 ∞ ∞ ∞ C) was exposed to 45 ∞ C, photosynthetic electron transport was stimulated (at high CO 2 ) because of an increased flux through the photorespiratory pathway However, upon cooling back to 30 ∞ C, photosynthetic electron transport was inhibited and fell substantially below the level measured before the heat treatment In the field, the response of assimilation ( A ) to various internal levels of CO 2 ( C i ) revealed that photosynthesis was limited by ribulose-1,5-bisphosphate (RuBP) regeneration at normal levels of CO 2 (presumably because of limitations in thylakoid reactions needed to support RuBP regeneration) There was no evidence of a ribulose1,5-bisphosphate carboxylase/oxygenase (Rubisco) limitation at air levels of CO 2 and at no point on any of 30 A ‐ C i curves measured on leaves at temperatures from 28 to 39 ∞ C was RuBP regeneration capacity measured to be in substantial excess of the capacity of Rubisco to use RuBP It is therefore concluded that photosynthesis in field-grown Pima cotton leaves is functionally limited by photosynthetic electron transport and RuBP regeneration capacity, not Rubisco activity

467 citations

Journal ArticleDOI
TL;DR: A better understanding of the mechanisms of tolerance to UV-B radiation and of the interaction betweenUV-B and other environmental factors is needed in order to adequately assess the probable consequences of a change in solar radiation.
Abstract: The photosynthetic apparatus of some plant species appears to be well-protected from direct damage from UV-B radiation. Leaf optical properties of these species apparently minimizes exposure of sensitive targets to UV-B radiation. However, damage by UV-B radiation to Photosystem II and Rubisco has also been reported. Secondary effects of this damage may include reductions in photosynthetic capacity, RuBP regeneration and quantum yield. Furthermore, UV-B radiation may decrease the penetration of PAR, reduce photosynthetic and accessory pigments, impair stomatal function and alter canopy morphology, and thus indirectly retard photosynthetic carbon assimilation. Subsequently, UV-B radiation may limit productivity in many plant species. In addition to variability in sensitivity to UV-B radiation, the effects of UV-B radiation are further confounded by other environmental factors such as CO2, temperature, light and water or nutrient availability. Therefore, we need a better understanding of the mechanisms of tolerance to UV-B radiation and of the interaction between UV-B and other environmental factors in order to adequately assess the probable consequences of a change in solar radiation.

466 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20242
20232,453
20225,090
2021738
2020732
2019616