Quantum Yields and Rate Constants of Photochemical and Nonphotochemical Excitation Quenching (Experiment and Model) (original) (raw)
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Biochimica et Biophysica Acta (BBA) - Bioenergetics, 2010
The relationship between the development of photoprotective mechanisms (non-photochemical quenching, NPQ), the generation of the electrochemical proton gradient in the chloroplast and the capacity to assimilate CO 2 was studied in tobacco dark-adapted leaves at the onset of illumination with low light. These conditions induce the generation of a transient NPQ, which relaxes in the light in parallel with the activation of the Calvin cycle. Wild-type plants were compared with a CMSII mitochondrial mutant, which lacks the respiratory complex I and shows a delayed activation of photosynthesis. In the mutant, a slower onset of photosynthesis was mirrored by a decreased capacity to develop NPQ. This correlates with a reduced efficiency to reroute electrons at the PSI reducing side towards cyclic electron flow around PSI and/or other alternative acceptor pools, and with a smaller ability to generate a proton motive force in the light. Altogether, these data illustrate the tight relationship existing between the capacity to evacuate excess electrons accumulated in the intersystem carriers and the capacity to dissipate excess photons during a dark to light transition. These data also underline the essential role of respiration in modulating the photoprotective response in dark-adapted leaves, by poising the cellular redox state.
Photosynthetic activity of far-red light in green plants
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 2005
We have found that long-wavelength quanta up to 780 nm support oxygen evolution from the leaves of sunflower and bean. The far-red light excitations are supporting the photochemical activity of photosystem II, as is indicated by the increased chlorophyll fluorescence in response to the reduction of the photosystem II primary electron acceptor, Q A . The results also demonstrate that the far-red photosystem II excitations are susceptible to non-photochemical quenching, although less than the red excitations. Uphill activation energies of 9.8 T 0.5 kJ mol À1 and 12.5 T 0.7 kJ mol À1 have been revealed in sunflower leaves for the 716 and 740 nm illumination, respectively, from the temperature dependencies of quantum yields, comparable to the corresponding energy gaps of 8.8 and 14.3 kJ mol À1 between the 716 and 680 nm, and the 740 and 680 nm light quanta. Similarly, the non-photochemical quenching of far-red excitations is facilitated by temperature confirming thermal activation of the far-red quanta to the photosystem II core. The observations are discussed in terms of as yet undisclosed far-red forms of chlorophyll in the photosystem II antenna, reversed (uphill) spill-over of excitation from photosystem I antenna to the photosystem II antenna, as well as absorption from thermally populated vibrational sub-levels of photosystem II chlorophylls in the ground electronic state. From these three interpretations, our analysis favours the first one, i.e., the presence in intact plant leaves of a small number of far-red chlorophylls of photosystem II. Based on analogy with the well-known far-red spectral forms in photosystem I, it is likely that some kind of strongly coupled chlorophyll dimers/aggregates are involved. The similarity of the result for sunflower and bean proves that both the extreme long-wavelength oxygen evolution and the local quantum yield maximum are general properties of the plants. D
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 1998
In vivo mechanisms of non-photochemical quenching that contribute to energy dissipation in higher plants are still a source of some controversy. In the present study we used an exogenous oxidized quinone, 5-hydroxy-1,4-naphthoquinone to induce quenching of chlorophyll excited states in photosynthetic light-harvesting antenna and to elucidate the mechanism of non-photochemical quenching of chlorophyll fluorescence by this quinone. Excitation dynamics in isolated spinach thylakoids in the presence of an exogenous fluorescence quencher was studied by a combined analysis of data gathered from Ž. independent techniques fluorescence yields, effective absorption cross-sections and picosecond kinetics. The application of a kinetic model for photosystem II to a combined data set of fluorescence decay kinetics and absorbance cross-section measurements was used to quantify antenna quenching by a model antenna quencher, 5-hydroxy-1,4-naphthoquinone. We observed depressions in F and photosystem II absorption cross-sections, paralleled with an increase of the rate constant for 0 excitation decay in antenna. This approach is a first step towards quantifying the amount of antenna quenching contributing to non-photochemical quenching in vivo, evaluation of the contributions of antenna and reaction centre mechanisms to it and localization of the sites of non-photochemical energy dissipation in intact plant systems. q 1998 Elsevier Science B.V.
Photosynthesis Research, 1992
We tested the two empirical models of the relationship between chlorophyll fluorescence and photosynthesis, previously published by Weis E and Berry JA 1987 (Biochim Biophys Acta 894: 198-208) and Genty Bet al. 1989 (Biochim Biophys Acta 990: 87-92). These were applied to data from different species representing different states of light acclimation, to species with C 3 or C 4 photosynthesis, and to wild-type and a chlorophyll bless chlorina mutant of barley. Photosynthesis measured as CO2-saturated 0 2 evolution and modulated fluorescence were simultaneously monitored over a range of photon flux densities. The quantum yields of 0 2 evolution (002) were based on absorbed photons, and the fluorescence parameters for photochemical (qp) and non-photochemical (qN) quenching, as well as the ratio of variable fluorescence to maximum fluorescence during steady-state illumination (F'v/F~,), were determined. In accordance with the Weis and Berry model, most plants studied exhibited an approximately linear relationship between OO2/qp (i.e., the yield of 02 evolution by open Photosystem II reaction centres) and qN, except for wild-type barley that showed a non-linear relationship. In contrast to the linear relationship reported by Genty et al. for qp x F~/F m (i.e,, the quantum yield of Photosystem II electron transport) and OCO 2, we found a non-linear relationship between qp x F'v/F" ' and OO 2 for all plants, except for the chlorina mutant of barley, which showed a largely linear relationship. The curvilinearity of wild-type barley deviated somewhat from that of other species tested. The non-linear part of the relationship was confined to low, limiting photon flux densities, whereas at higher light levels the relationship was linear. Photoinhibition did not change the overall shape of the relationship between qp x F'/F~ and OO 2 except that the maximum values of the quantum yields of Photosystem II electron transport and photosynthetic 0 2 evolution decreased in proportion to the degree of photoinhibition. This implies that the quantum yield of Photosystem II electron transport under high light conditions may be similar for photoinhibited and non-inhibited plants. Based on our experimental results and theoretical analyses of photochemical and non-photochemical fluoresce quenching processes, we conclude that both models, although not universal for all plants, provide useful means for the prediction of photosynthesis from fluorescence parameters. However, we also discuss that conditions which alter one or more of the rate constants that determine the various fluorescence parameters, as well as differential light penetration in assays for oxygen evolution and fluorescence emission, may have direct effect on the relationships of the two models. Abbreviations: F 0 and F~-fluorescence when all Photosystem II reaction centres are open in dark-and light-acclimated leaves, respectively; F m and F',-fluorescence when all Photosystem II reaction centres are closed in dark and light, respectively; F v-variable fluorescence equal to F m-F0; F S-steady state level of fluorescence in light; F" and F m-variable (F'~-F~) and maximum fluorescence under steady state light conditions; HEPES-N-2-hydroxyethylpiperazine-N-2-ethane-sulphonic acid; QA-the primary, stabile quinone acceptor of Photosystem II; qN-non-photochemical quenching of fluorescence; qp-photochemical quenching of fluorescence; OO 2-quantum yield of CO2-saturated 0 2 evolution based on absorbed photons
Photosynthesis research, 2003
By recording leaf transmittance at 820 nm and quantifying the photon flux density of far red light (FRL) absorbed by long-wavelength chlorophylls of Photosystem I (PS I), the oxidation kinetics of electron carriers on the PS I donor side was mathematically analyzed in sunflower (Helianthus annuus L.), tobacco (Nicotiana tabacum L.) and birch (Betula pendula Roth.) leaves. PS I donor side carriers were first oxidized under FRL, electrons were then allowed to accumulate on the PS I donor side during dark intervals of increasing length. After each dark interval the electrons were removed (titrated) by FRL. The kinetics of the 820 nm signal during the oxidation of the PS I donor side was modeled assuming redox equilibrium among the PS I donor pigment (P700), plastocyanin (PC), and cytochrome f plus Rieske FeS (Cyt f + FeS) pools, considering that the 820 nm signal originates from P700(+) and PC(+). The analysis yielded the pool sizes of P700, PC and (Cyt f + FeS) and associated redox eq...
Relationship between the Quantum Efficiencies of Photosystems I and II in Pea Leaves
Plant Physiology, 1989
The irradiance dependence of the efficiencies of photosystems I and 11 were measured for two pea (Pisum sativum [L.]) varieties grown under cold conditions and one pea variety grown under warm conditions. The efficiencies of both photosystems declined with increasing irradiance for all plants, and the quantum efficiency of photosystem I electron transport was closely correlated with the quantum efficiency of photosystem 11 electron transport. In contrast to the consistent pattern shown by efficiency of the photosystems, the redox state of photosystem 11 (as estimated from the photochemical quenching coefficient of chlorophyll fluorescence) exhibited relationships with both irradiance and the reduction of P-700 that varied with growth environment and genotype. This variability is considered in the context of the modulation of photosystem 11 quantum efficiency by both photochemical and nonphotochemical quenching of excitation energy. 'This work was supported by the Agricultural and Food Research Council via a grant-in-aid to the John Innes Institute. Support was also given to J. H. from
Biochemistry, 1999
The fast and slow reversible components of non-photochemical chlorophyll fluorescence quenching commonly assigned to the qE and the qI mechanism have been studied in isolated pea thylakoids which were prepared from leaves after a moderate photoinhibitory treatment. Chlorophyll fluorescence decays were measured at picosecond resolution and analyzed on the basis of the heterogeneous exciton/ radical pair equilibrium model. Our results show that the fast reversible non-photochemical quenching is completely assigned to the PS II antenna and is related to zeaxanthin. The slow reversible qI type quenching is located at the PS II reaction center and involves enhanced nonradiative decay of the primary charge separated state to its ground state and/or triplet excited state. Apart from its independence from the proton gradient, the qI quenching shows striking similarities to a particular form of qE quenching which is also located at the PS II reaction center and has resently been resolved in isolated thylakoids from darkadapted leaves [Wagner, B., et al. (1996) J. Photochem. Photobiol., B 36, 339-350]. Our data suggest that during exposure to the supersaturating light the reaction center qE component was replaced by qI quenching. This qE to qI transition is supposed to be part of the mechanism of the long-term downregulation of PS II during photoinhibition. It is also evident that under the conditions used in our study zeaxanthindependent antenna quenching is not involved in the slow reversible downregulation of PS II but that it retains its dependence on the proton gradient during exposure to strong light. † This work was supported by the Deutsche Forschungsgemeinschaft (Wi 243/19-2) and Sonderforschungsbereich 189, Heinrich-Heine-Universität, Düsseldorf, and Max-Planck-Institut für Strahlenchemie, Mülheim. 1 Abbreviations: P or P-680, primary donor of PS II; DAS, decayassociated fluorescence spectrum; DCMU, 3-(3,4-dichlorphenyl)-1,1dimethylurea; DTT, dithiothreitol; Fo, Fv, and Fm, initial, variable, and maximal chlorophyll fluorescence yields, respectively; I, pheophytin (primary electron acceptor of PS II); LHC II, light-harvesting complex II; NPQ, non-photochemical chlorophyll fluorescence quenching; PS II, photosystem II; PFD, photon flux density; Q A, primary electronaccepting plastoquinone of PS II; QB, secondary electron-accepting plastoquinone of PS II; qE and qI, fast and slow reversible nonphotochemical quenching, respectively.
Photosynthetica, 2004
The review deals with thermal dissipation of absorbed excitation energy within pigment-protein complexes of thylakoid membranes in higher plants. We focus on the de-excitation regulatory processes within photosystem 2 (PS2) that can be monitored as non-photochemical quenching of chlorophyll (Chl) a fluorescence consisting of three components known as energy-dependent quenching (q E), state-transition quenching (q T), and photoinhibitory quenching (q I). We summarize the role of thylakoid lumen pH, xanthophylls, and PS2 proteins in q E mechanism. Further, both the similarity between q E and q I and specific features of q I are described. The other routes of thermal energy dissipation are also mentioned, that is dissipation within photosystem 1 and dissipation through the triplet Chl pathway. The significance of the individual deexcitation processes in protection against photo-oxidative damage to the photosynthetic apparatus under excess photon supply is stretched.
REGULATION OF LIGHT HARVESTING IN GREEN PLANTS
Annual Review of Plant Physiology and Plant Molecular Biology, 1996
ce has become one of the most powerful methods for assessing photosynthetic performance in plant physiological experiments Krause and Weis, 1991). This has resulted almost entirely from the development of methods to distinguish photochemical and nonphotochemical quenching of fluorescence. Moreover, it is now clear that the process of nonphotochemical quenching itself indicates important regulatory adjustments in the photosynthetic membrane in response to altered external and internal conditions . In particular, the dissipation of excess absorbed excitation that is monitored by the main component of nonphotochemical quenching is a process that is necessary if plants are to avoid photoinhibition and photodestruction under conditions of light stress.