Photorespiration and photoinhibition: Some implications for the energetics of photosynthesis
About: This article is published in Biochimica et Biophysica Acta.The article was published on 1981-12-04. It has received 425 citations till now. The article focuses on the topics: Photoinhibition & Photorespiration.
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01 Jun 1999
TL;DR: Whenever the water-water cycle operates properly for scavenging of active oxygens in chloroplasts, it also effectively dissipates excess excitation energy under environmental stress.
Abstract: Photoreduction of dioxygen in photosystem I (PSI) of chloroplasts generates superoxide radicals as the primary product. In intact chloroplasts, the superoxide and the hydrogen peroxide produced via the disproportionation of superoxide are so rapidly scavenged at the site of their generation that the active oxygens do not inactivate the PSI complex, the stromal enzymes, or the scavenging system itself. The overall reaction for scavenging of active oxygens is the photoreduction of dioxygen to water via superoxide and hydrogen peroxide in PSI by the electrons derived from water in PSII, and the water-water cycle is proposed for these sequences. An overview is given of the molecular mechanism of the water-water cycle and microcompartmentalization of the enzymes participating in it. Whenever the water-water cycle operates properly for scavenging of active oxygens in chloroplasts, it also effectively dissipates excess excitation energy under environmental stress. The dual functions of the water-water cycle for protection from photoinihibition are discussed.
3,904 citations
01 Jun 1999
TL;DR: Several photoprotective mechanisms operating within chloroplasts of plants and green algae are summarized, especially with respect to thermal dissipation of excess absorbed light energy, alternative electron transport pathways, chloroplast antioxidant systems, and repair of photosystem II.
Abstract: The involvement of excited and highly reactive intermediates in oxygenic photosynthesis poses unique problems for algae and plants in terms of potential oxidative damage to the photosynthetic apparatus. Photoprotective processes prevent or minimize generation of oxidizing molecules, scavenge reactive oxygen species efficiently, and repair damage that inevitably occurs. This review summarizes several photoprotective mechanisms operating within chloroplasts of plants and green algae. The recent use of genetic and molecular biological approaches is providing new insights into photoprotection, especially with respect to thermal dissipation of excess absorbed light energy, alternative electron transport pathways, chloroplast antioxidant systems, and repair of photosystem II.
1,915 citations
Book•
29 May 2006TL;DR: Reynolds as discussed by the authors provides basic information on composition, morphology and physiology of the main phyletic groups represented in marine and freshwater systems and reviews recent advances in community ecology, developing an appreciation of assembly processes, co-existence and competition, disturbance and diversity.
Abstract: Communities of microscopic plant life, or phytoplankton, dominate the Earth's aquatic ecosystems. This important new book by Colin Reynolds covers the adaptations, physiology and population dynamics of phytoplankton communities in lakes and rivers and oceans. It provides basic information on composition, morphology and physiology of the main phyletic groups represented in marine and freshwater systems and in addition reviews recent advances in community ecology, developing an appreciation of assembly processes, co-existence and competition, disturbance and diversity. Although focussed on one group of organisms, the book develops many concepts relevant to ecology in the broadest sense, and as such will appeal to graduate students and researchers in ecology, limnology and oceanography.
1,856 citations
TL;DR: The results, in conjunction with the analysis of npq mutants of Chlamydomonas, suggest that the role of the xanthophyll cycle in nonphotochemical quenching has been conserved, although different photosynthetic eukaryotes rely on the xathletic cycle to different extents for the dissipation of excess absorbed light energy.
Abstract: A conserved regulatory mechanism protects plants against the potentially damaging effects of excessive light. Nearly all photosynthetic eukaryotes are able to dissipate excess absorbed light energy in a process that involves xanthophyll pigments. To dissect the role of xanthophylls in photoprotective energy dissipation in vivo, we isolated Arabidopsis xanthophyll cycle mutants by screening for altered nonphotochemical quenching of chlorophyll fluorescence. The npq1 mutants are unable to convert violaxanthin to zeaxanthin in excessive light, whereas the npq2 mutants accumulate zeaxanthin constitutively. The npq2 mutants are new alleles of aba1, the zeaxanthin epoxidase gene. The high levels of zeaxanthin in npq2 affected the kinetics of induction and relaxation but not the extent of nonphotochemical quenching. Genetic mapping, DNA sequencing, and complementation of npq1 demonstrated that this mutation affects the structural gene encoding violaxanthin deepoxidase. The npq1 mutant exhibited greatly reduced nonphotochemical quenching, demonstrating that violaxanthin deepoxidation is required for the bulk of rapidly reversible nonphotochemical quenching in Arabidopsis. Altered regulation of photosynthetic energy conversion in npq1 was associated with increased sensitivity to photoinhibition. These results, in conjunction with the analysis of npq mutants of Chlamydomonas, suggest that the role of the xanthophyll cycle in nonphotochemical quenching has been conserved, although different photosynthetic eukaryotes rely on the xanthophyll cycle to different extents for the dissipation of excess absorbed light energy.
932 citations
Cites background from "Photorespiration and photoinhibitio..."
...Photorespiratory oxygen metabolism can maintain linear electron transport and utilization of absorbed light energy, especially under conditions of CO 2 limitation (Osmond, 1981; Heber et al., 1996; Kozaki and Takeba, 1996; Park et al., 1996; Osmond et al., 1997)....
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...Photorespiratory oxygen metabolism can maintain linear electron transport and utilization of absorbed light energy, especially under conditions of CO 2 limitation (Osmond, 1981; Heber et al., 1996; Kozaki and Takeba, 1996; Park et al., 1996; Osmond et al., 1997)....
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TL;DR: In photosynthesis, photoinhibition is characterized by quenching of variable chlorophyll flurescence (Fv) resulting from increased thermal dissipation of excitation energy as mentioned in this paper.
Abstract: Inhibition of photosynthesis by excess excitation energy is initiated in the reaction center of photosystem II The primary site of photoinhibition in the reaction center (components of primary charge separation or secondary electron acceptor QB) is still disputed Photoinhibition is characterized by quenching of variable chlorophyll flurescence (Fv), resulting from increased thermal dissipation of excitation energy Varying responses of initial fluorescence (F0), however, seem to indicate involvement of different mechanisms As far as photoinhibition is reversible within minutes to hours, it can be viewed as a controlled protective mechanism that serves to dissipate excessive energy, Supposedly, another dissipative mechanism, distinguished by its faster kinetics (response within seconds), is related to the energy-dependent fluorescence quenching
894 citations
References
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TL;DR: Various aspects of the biochemistry of photosynthetic carbon assimilation in C3 plants are integrated into a form compatible with studies of gas exchange in leaves.
Abstract: Various aspects of the biochemistry of photosynthetic carbon assimilation in C3 plants are integrated into a form compatible with studies of gas exchange in leaves. These aspects include the kinetic properties of ribulose bisphosphate carboxylase-oxygenase; the requirements of the photosynthetic carbon reduction and photorespiratory carbon oxidation cycles for reduced pyridine nucleotides; the dependence of electron transport on photon flux and the presence of a temperature dependent upper limit to electron transport. The measurements of gas exchange with which the model outputs may be compared include those of the temperature and partial pressure of CO2(p(CO2)) dependencies of quantum yield, the variation of compensation point with temperature and partial pressure of O2(p(O2)), the dependence of net CO2 assimilation rate on p(CO2) and irradiance, and the influence of p(CO2) and irradiance on the temperature dependence of assimilation rate.
7,312 citations
TL;DR: In this paper, it was shown that stomatal aperture capacity is determined by the capacity of the mesophyll tissue to fix carbon, and that the diffusive conductance of the epidermis to CO2 transfer, g, changes in nearly the same proportion as the rate of assimilation of CO2.
Abstract: Previous studies on the Physiology of stomata in higher plants suggest that stomata influence the rate of CO2 fixation in leaf mesophyll tissue. We believe that an equally important stomatal function has not been fully recognised; that stomatal aperture is determined by the capacity of the mesophyll tissue to fix carbon. We altered the capacity of leaves to fix carbon by various means, and found invariably that the diffusive conductance of the epidermis to CO2 transfer, g, (which mainly depends on the number and dimensions of the stomata) changes in nearly the same proportion as the rate of assimilation of CO2. Thus, the intercellular concentration of CO2 (ci), calculated as ci = ca–A/g (where ca is ambient concentration of CO2, A is assimilation rate of CO2), tends to remain constant providing ca is kept constant. We used routine techniques1 to measure A and estimate g in leaves placed singly in chambers. Conductance takes account of CO2 transfer through both stomata and leaf boundary layer, the conductance of the latter being 0.5 mol m−2 s−1.
1,283 citations
854 citations
TL;DR: In this article, the quantum yields of C3 and C4 plants from a number of genera and families as well as from ecologically diverse habitats were measured in normal air of 21% O2 and in 2% CO2.
Abstract: The quantum yields of C3 and C4 plants from a number of genera and families as well as from ecologically diverse habitats were measured in normal air of 21% O2 and in 2% O2. At 30 C, the quantum yields of C3 plants averaged 0.0524 ± 0.0014 mol CO2/absorbed einstein and 0.0733 ± 0.0008 mol CO2/absorbed einstein under 21 and 2% O2. At 30 C, the quantum yields of C4 plants averaged 0.0534 ± 0.0009 mol CO2/absorbed einstein and 0.0538 ± 0.0011 mol CO2/absorbed einstein under 21 and 2% O2. At 21% O2, the quantum yield of a C3 plant is shown to be strongly dependent on both the intercellular CO2 concentration and leaf temperature. The quantum yield of a C4 plant, which is independent of the intercellular CO2 concentration, is shown to be independent of leaf temperature over the ranges measured. The changes in the quantum yields of C3 plants are due to changes in the O2 inhibition. The evolutionary significance of the CO2 dependence of the quantum yield in C3 plants and the ecological significance of the temperature effects on the quantum yields of C3 and C4 plants are discussed.
727 citations
TL;DR: Kinetic properties of soybean net photosynthetic CO(2) fixation and of the carboxylase and oxygenase activities of purified soybean ribulose 1, 5-diphosphate carboxyase were examined and showed equality of kinetic constants, consistent with the notion that the same enzyme catalyzes both reactions.
Abstract: Kinetic properties of soybean net photosynthetic CO(2) fixation and of the carboxylase and oxygenase activities of purified soybean (Glycine max [L.] Merr.) ribulose 1, 5-diphosphate carboxylase (EC 4.1.1.39) were examined as functions of temperature, CO(2) concentration, and O(2) concentration. With leaves, O(2) inhibition of net photosynthetic CO(2) fixation increased when the ambient leaf temperature was increased. The increased inhibition of CO(2) fixation at higher temperatures was caused by a reduced affinity of the leaf for CO(2) and an increased affinity of the leaf for O(2). With purified ribulose 1,5-diphosphate carboxylase, O(2) inhibition of CO(2) incorporation and the ratio of oxygenase activity to carboxylase activity increased with increased temperature. The increased O(2) sensitivity of the enzyme at higher temperature was caused by a reduced affinity of the enzyme for CO(2) and a slightly increased affinity of the enzyme for O(2). The similarity of the effect of temperature on the affinity of intact leaves and of ribulose 1,5-diphosphate carboxylase for CO(2) and O(2) provides further evidence that the carboxylase regulates the O(2) response of photosynthetic CO(2) fixation in soybean leaves. Based on results reported here and in the literature, a scheme outlining the stoichiometry between CO(2) and O(2) fixation in vivo is proposed.Oxygen competitively inhibited carboxylase activity with respect to CO(2), and CO(2) competitively inhibited oxygenase activity with respect to O(2). Within the limits of experimental error, the Michaelis constant (CO(2)) in the carboxylase reaction was identical with the inhibition constant (CO(2)) in the oxygenase reaction, and the Michaelis constant (O(2)) in the oxygenase reaction was identical with the inhibition constant (O(2)) in the carboxylase reaction. The Michaelis constant, (ribulose 1,5-diphosphate) was the same in both the carboxylase and oxygenase reactions. This equality of kinetic constants is consistent with the notion that the same enzyme catalyzes both reactions.
641 citations