Plant and Cell Physiology Advance Access originally published online on February 27, 2009
Plant and Cell Physiology 2009 50(4):730-743; doi:10.1093/pcp/pcp032
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This article appears in the following Plant and Cell Physiology issue: Special Issue Articles: Photosynthesis [View the issue table of contents]
Special Issue - Regular Paper |
Acclimation of Tobacco Leaves to High Light Intensity Drives the Plastoquinone Oxidation System—Relationship Among the Fraction of Open PSII Centers, Non-Photochemical Quenching of Chl Fluorescence and the Maximum Quantum Yield of PSII in the Dark
1Department of Biological and Environmental Science, Faculty of Agriculture, Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501 Japan
2Faculty of Nutrition, Kobegakuin University, Japan
*Corresponding author: E-mail, cmiyake{at}hawk.kobe-u.ac.jp; Fax, +81-78-803-5851.
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Abstract |
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Responses of the reduction–oxidation level of plasto-quinone (PQ) in the photosynthetic electron transport (PET) system of chloroplasts to growth light intensity were evaluated in tobacco plants. Plants grown in low light (150 µmol photons m–2 s–1) (LL plants) were exposed to a high light intensity (1,100 µmol photons m–2 s–1) for 1 d. Subsequently, the plants exposed to high light (LH plants) were returned back again to the low light condition: these plants were designated as LHL plants. Both LH and LHL plants showed higher values of non-photochemical quenching of Chl fluorescence (NPQ) and the fraction of open PSII centers (qL), and lower values of the maximum quantum yield of PSII in the dark (Fv/Fm), compared with LL plants. The dependence of qL on the quantum yield of PSII [
(PSII)] in LH and LHL plants was higher than that in LL plants. To evaluate the effect of an increase in NPQ and decrease in Fv/Fm on qL, we derived an equation expressing qL in relation to both NPQ and Fv/Fm, according to the lake model of photoexcitation of the PSII reaction center. As a result, the heat dissipation process, shown as NPQ, did not contribute greatly to the increase in qL. On the other hand, decreased Fv/Fm did contribute to the increase in qL, i.e. the enhanced oxidation of PQ under photosynthesis-limited conditions. Thylakoid membranes isolated from LH plants, having high qL, showed a higher tolerance against photoinhibition of PSII, compared with those from LL plants. We propose a ‘plastoquinone oxidation system (POS)’, which keeps PQ in an oxidized state by suppressing the accumulation of electrons in the PET system in such a way as to regulate the maximum quantum yield of PSII.
Keywords: Acclimation - Fraction of open PSII reaction centers (qL) - High light stress - Non-photochemical quenching (NPQ) - Photosynthesis - Plastoquinone
Abbreviations: CEF-PSI, cyclic electron flow around PSI; HDP, heat dissipation process; NPQ, non-photochemical quenching of Chl fluorescence; PCO, photorespiratory carbon oxidation; PCR, photosynthetic carbon reduction; PFD, photon flux density; LEF, linear electron flow; LHC, light-harvesting complex; MV, methyl viologen; PET, photosynthetic electron transport; POS, plastoquinone oxidation system; qL, photochemical quenching of Chl fluorescence; PQ, plastoquinone; ROS, reactive oxygen species; WWC, water–water cycle.
(Received December 29, 2008; Accepted February 23, 2009)
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