Journal Article

Separation of Light-induced Linear, Cyclic and Stroma-sourced Electron Fluxes to P700<sup>+</sup> in Cucumber Leaf Discs after Pre-Illumination at a Chilling Temperature

Da-Yong Fan, Alexander B. Hope, Husen Jia and Wah Soon Chow

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 49, issue 6, pages 901-911
Published in print June 2008 | ISSN: 0032-0781
Published online June 2008 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcn064
Separation of Light-induced Linear, Cyclic and Stroma-sourced Electron Fluxes to P700+ in Cucumber Leaf Discs after Pre-Illumination at a Chilling Temperature

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Pre-illumination of cucumber leaf discs at 4°C with low-irradiance white light (i) led to a marked decrease in the extent of photo-oxidation of P700 (the special chlorophyll pair in the PSI reaction center) in actinic light at room temperature and (ii) hastened the post-illumination re-reduction of P700+. Quantifying the linear, cyclic and stroma-sourced electron fluxes to P700+ in two actinic light regimes, we found that there was no increase in cyclic or linear electron fluxes to account for these changes. Rather, we observed a decrease in the maximum extent of P700 photo-oxidation assayed by a strong flash superimposed on continuous, background light of wavelength 723 nm, which we interpret to represent a loss of stable charge separation in PSI due to enhanced charge recombination as a result of the pre-illumination treatment. The funneling of electrons towards fewer non-damaged PSI complexes could explain the hastened post-illumination re-reduction of P700+, aided by a slight increase in a stroma-sourced electron flux after prolonged pre-illumination at 4°C. Quantifying the separate fluxes to P700+ helps to elucidate the effects of chilling of cucumber leaf discs in the light and the reasons for the hastened post-illumination re-reduction of P700+.

Keywords: Cucumis sativus; Cyclic electron flow; P700; Photoinactivation; Photoinhibition; PSI

Journal Article.  6851 words.  Illustrated.

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

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