Journal Article

Enhancement of Cyclic Electron Flow Around PSI at High Light and its Contribution to the Induction of Non-Photochemical Quenching of Chl Fluorescence in Intact Leaves of Tobacco Plants

Chikahiro Miyake, Yuki Shinzaki, Momoko Miyata and Ken-ichi Tomizawa

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 45, issue 10, pages 1426-1433
Published in print October 2004 | ISSN: 0032-0781
Published online October 2004 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pch163
Enhancement of Cyclic Electron Flow Around PSI at High Light and its Contribution to the Induction of Non-Photochemical Quenching of Chl Fluorescence in Intact Leaves of Tobacco Plants

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  • Biochemistry
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Non-photochemical quenching (NPQ) of Chl fluorescence is a mechanism for dissipating excess photon energy and is dependent on the formation of a ΔpH across the thylakoid membranes. The role of cyclic electron flow around photosystem I (PSI) (CEF-PSI) in the formation of this ΔpH was elucidated by studying the relationships between O2-evolution rate [V(O2)], quantum yield of both PSII and PSI [Φ(PSII) and Φ(PSI)], and Chl fluorescence parameters measured simultaneously in intact leaves of tobacco plants in CO2-saturated air. Although increases in light intensity raised V(O2) and the relative electron fluxes through both PSII and PSI [Φ(PSII)×PFD and Φ(PSI)×PFD] only Φ(PSI)×PFD continued to increase after V(O2) and Φ(PSII)×PFD became light saturated. These results revealed the activity of an electron transport reaction in PSI not related to photosynthetic linear electron flow (LEF), namely CEF-PSI. NPQ of Chl fluorescence drastically increased after Φ(PSII)×PFD became light saturated and the values of NPQ correlated positively with the relative activity of CEF-PSI. At low temperatures, the light-saturation point of Φ(PSII)×PFD was lower than that of Φ(PSI)×PFD and NPQ was high. On the other hand, at high temperatures, the light-dependence curves of Φ(PSII)×PFD and Φ(PSI)×PFD corresponded completely and NPQ was not induced. These results indicate that limitation of LEF induced CEF-PSI, which, in turn, helped to dissipate excess photon energy by driving NPQ of Chl fluorescence.

Keywords: Keywords: Chl Fluorescence — Cyclic electron flow — Non-photochemical quenching (NPQ) — Photosynthesis — P700 — PSI.

Journal Article.  5486 words.  Illustrated.

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

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