Journal Article

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

Chikahiro Miyake, Katsumi Amako, Naomasa Shiraishi and Toshio Sugimoto

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 50, issue 4, pages 730-743
Published in print April 2009 | ISSN: 0032-0781
Published online February 2009 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcp032
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

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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 [Φ(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

Journal Article.  8255 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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