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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 in vivo activation of Rubisco was markedly increased in UV-B-treated pea leaves and the underlying mechanisms for these results are discussed.

271 citations

Journal ArticleDOI
TL;DR: The concept of a 'photoinhibition-proof' plant in which photosystem II (PSII) is immune to photodamage is useful as a benchmark for considering the performances of plants with varying mixes of mechanisms which limit the extent of photodammy.
Abstract: Photoinhibition is an inevitable consequence of oxygenic photosynthesis. However, the concept of a ‘photoinhibition-proof’ plant in which photosystem II (PSII) is immune to photodamage is useful as a benchmark for considering the performances of plants with varying mixes of mechanisms which limit the extent of photodamage and which repair photodamage. Some photodamage is bound to occur, and the energy costs of repair are the direct costs of repair plus the photosynthesis foregone during repair. One mechanism permitting partial avoidance of photodamage is restriction of the number of photons incident on the photosynthetic apparatus per unit time, achieved by phototactic movement of motile algae to places with lower incident photosynthetically active radiation (PAR), by phototactic movement of plastids within cells to positions that minimize the incident PAR and by photonastic relative movements of parts of photolithotrophs attached to a substrate. The other means of avoiding photodamage is dissipating excitation of photosynthetic pigments including state transitions, non-photochemical quenching by one of the xanthophyll cycles or some other process and photochemical quenching by increased electron flow through PSII involving CO2 and other acceptors, including the engagement of additional electron transport pathways. These mechanisms inevitably have the potential to decrease the rate of growth. As well as the decreased photosynthetic rates as a result of photodamage and the restrictions on photosynthesis imposed by the repair, avoidance, quenching and scavenging mechanisms, there are also additional energy, nitrogen and phosphorus costs of producing and operating repair, avoidance, quenching and scavenging mechanisms. A comparison is also made between the costs of photoinhibition and those of other plant functions impeded by the occurrence of oxygenic photosynthesis, i.e. the competitive inhibition of the carboxylase activity of ribulose bisphosphate carboxylase-oxygenase by oxygen via the oxygenase activity, and oxygen damage to nitrogenase in diazotrophic organisms.

270 citations

Journal ArticleDOI
31 Mar 2017-Science
TL;DR: It is shown that all three classes of Cyanobacteria independently acquired aerobic respiratory complexes, supporting the hypothesis that aerobic respiration evolved after oxygenic photosynthesis.
Abstract: The origin of oxygenic photosynthesis in Cyanobacteria led to the rise of oxygen on Earth ~2.3 billion years ago, profoundly altering the course of evolution by facilitating the development of aerobic respiration and complex multicellular life. Here we report the genomes of 41 uncultured organisms related to the photosynthetic Cyanobacteria (class Oxyphotobacteria), including members of the class Melainabacteria and a new class of Cyanobacteria (class Sericytochromatia) that is basal to the Melainabacteria and Oxyphotobacteria. All members of the Melainabacteria and Sericytochromatia lack photosynthetic machinery, indicating that phototrophy was not an ancestral feature of the Cyanobacteria and that Oxyphotobacteria acquired the genes for photosynthesis relatively late in cyanobacterial evolution. We show that all three classes independently acquired aerobic respiratory complexes, supporting the hypothesis that aerobic respiration evolved after oxygenic photosynthesis.

270 citations

Journal ArticleDOI
TL;DR: The results establish, for the first time, the suite of biophysical mechanisms that optimize photosynthesis while simultaneously providing photoprotection in symbiotic corals in situ.
Abstract: In zooxanthellate corals, excess excitation energy can be dissipated as heat (nonphotochemical quenching), thereby providing protection against oxidative damage by supraoptimal light in shallow reefs. To identify and quantify the photoprotective mechanisms, we studied the diel variability of chlorophyll fluorescence yields and photosynthetic parameters in situ in corals, using moored and SCUBA-based fast-repetition-rate fluorometers. The results reveal that nonphotochemical quenching is triggered prior to saturation of photosynthetic electron transport by downregulation of the reaction centers of Photosystem II (PSII). This process dissipates up to 80% of the excitation energy. On a sunny day in shallow waters, the daily integrated flux of photons absorbed, and subsequently dissipated as heat, is ;4 times that used for photosynthesis. Fluorescence quenching is further accompanied by a slight reduction in the functional absorption cross section for PSII that results from thermal dissipation of excitation energy in the light-harvesting antennae. These two processes are highly dynamic and adjust to irradiance changes on timescales consistent with the passage of clouds across the sky. Under supraoptimal irradiance, however, up to 30% of PSII reaction centers become photoinhibited, and these are repaired only after several hours of low irradiance. In shallow corals, between 10% and 20% of the reactions centers are chronically photoinhibited and appear to remain permanently nonfunctional throughout the year. Our results establish, for the first time, the suite of biophysical mechanisms that optimize photosynthesis while simultaneously providing photoprotection in symbiotic corals in situ.

269 citations

Journal ArticleDOI
TL;DR: Differences in light demand related to leaf acclimation to high light rather than that to low light in the Acer species, indicating that the response to water limitation plays an important role in leaf photosynthetic acclimations tohigh light in A. rufinerve.
Abstract: Variation in light demand is a major factor in determining the growth and survival of trees in a forest. There is strong relation between the light-demand and the effect of growth irradiance on leaf morphology and photosynthesis in three Acer species: A. rufinerve (light-demanding), A. mono (intermediate) and A. palmatum (shade-tolerant). The increase in mesophyll thickness and surface area of chloroplasts facing the intercellular airspaces (Sc) with growth irradiance was highest in A. rufinerve. Although the increase in light-saturated photosynthesis (Amax) was similar among the species, the increase in water use efficiency (WUE) was much higher in A. rufinerve than that in the other species, indicating that the response to water limitation plays an important role in leaf photosynthetic acclimation to high light in A. rufinerve. The low CO2 partial pressure at the carboxylation site (Cc) in A. rufinerve (130 µmol mol−1) at high irradiance was caused by low stomatal and internal conductance to CO2 diffusion, which minimized the increase in Amax in A. rufinerve despite its high Rubisco content. Under shade conditions, interspecific differences in leaf features were relatively small. Thus, difference in light demand related to leaf acclimation to high light rather than that to low light in the Acer species.

269 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