Journal Article

Action Spectrum of Photoinhibition in Leaves of Wild Type and <i>npq1-2</i> and <i>npq4-1</i> Mutants of <i>Arabidopsis thaliana</i>

Päivi Sarvikas, Marja Hakala, Eija Pätsikkä, Taina Tyystjärvi and Esa Tyystjärvi

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 47, issue 3, pages 391-400
Published in print March 2006 | ISSN: 0032-0781
Published online March 2006 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcj006
Action Spectrum of Photoinhibition in Leaves of Wild Type and npq1-2 and npq4-1 Mutants of Arabidopsis thaliana

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Photoinhibition is light-induced inactivation of PSII. Hypotheses about the photoreceptor(s) of photoinhibition include the Chl antenna of PSII, manganese of the oxygen-evolving complex (OEC), uncoupled Chl and iron–sulfur centres. We measured the action spectrum of photoinhibition in vivo from wild-type Arabidopsis thaliana L. and from the npq1-2 and npq4-1 mutants defective in non-photochemical quenching (NPQ) of excitations of the PSII antenna. The in vivo action spectrum was found to resemble closely the in vitro action spectra published for photoinhibition. We compared the action spectrum with absorbance spectra of model compounds of the OEC complex and other potential photoreceptors of photoinhibition. The comparison suggests that both manganese and Chl function as photoreceptors in photoinhibition. In accordance with the function of two types of photoreceptors in photoinhibition, NPQ was found to offer only partial protection against photoinhibition at visible wavelengths. The low protective efficiency of NPQ supports the conclusion that the Chl antenna of PSII is not the only photoreceptor of photoinhibition. Comparison of the action spectrum of photoinhibition with the emission spectrum of sunlight shows that the UV part of sunlight is responsible for the major part of photoinhibition under natural conditions.

Keywords: Manganese; Non-photochemical quenching; Photoinhibition; Photoreceptor; PSII; Ultraviolet; FM, maximum fluorescence; FM′, maximum fluorescence measured during illumination; F0, minimum fluorescence of dark-adapted leaf; F0′, minimum fluorescence immediately after illumination; ΦPSII, quantum yield of PSII electron transport; FS, fluorescence measured during illumination; NPQ, non-photochemical quenching of excitation energy; OEC, oxygen-evolving complex; P680, primary donor of PSII; PFD, photon flux density; PPFD, photosynthetic photon flux density; QA, primary quinone electron acceptor of PSII; qL and qP, measures of photochemical quenching

Journal Article.  7856 words.  Illustrated.

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

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