Journal Article

Inhibition of Photosystems I and II and Enhanced Back Flow of Photosystem I Electrons in Cucumber Leaf Discs Chilled in the Light

Sun-Ju Kim, Choon-Hwan Lee, AlexanderB. Hope and Wah Soon Chow

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 42, issue 8, pages 842-848
Published in print August 2001 | ISSN: 0032-0781
Published online August 2001 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pce109
Inhibition of Photosystems I and II and Enhanced Back Flow of
Photosystem I Electrons in Cucumber Leaf Discs Chilled in the
Light

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  • Biochemistry
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Pre-illumination of cucumber leaf discs at a chilling temperature in low-irradiance white light resulted in accelerated re-reduction of P700+[ the special Chl pair in the photosystem I (PSI) reaction centre] when the far-red measuring light was turned off. Measurements (in ± methyl viologen or ± DCMU conditions) of the re-reduction half time suggest that accelerated re-reduction of P700+ appeared to be predominantly due to charge recombination and only partly due to reductants sustained by previous cyclic electron flow around PSI. Apparently, charge recombination in PSI was greatly enhanced by inhibition of forward, linear electron flow. Inhibition of PSII electron transport was observed to occur to a lesser extent than that of PSI, but only if the measurement of PSII functionality was free from complications due to downstream accumulation of electrons in pools. We suggest that promotion of controlled charge recombination and cyclic electron flow round PSI during chilling of leaves in the light may partly prevent further damage to both photosystems.

Keywords: Key words: Chilling — Cucumis sativus L. — Charge recombination — Cyclic electron transport — Photosystem I — Photosystem II.; Abbreviations: DBMIB, 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone; Fo, Fm, minimum and maximum Chl fluorescence yield corresponding to open and closed PSII, respectively, after dark pre-treatment; Fo′, Fm′, minimum and maximum Chl fluorescence yield corresponding to open and closed PSII during illumination, respectively; Fv = Fm – Fo; NDH, NAD(P)H dehydrogenase; P700, special Chl pair in the PSI reaction centre; PQ, plastoquinone; QA, primary quinone acceptor in PSII; qp, photochemical quenching coefficient.

Journal Article.  4926 words.  Illustrated.

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

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