Inhibition of photosystems I and II and enhanced back flow of photosystem I electrons in cucumber [Cucumis sativus] leaf discs chilled in the light

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 1 (PS1) reaction centre] when the far-red measuring light was turned off. Measurements (in =+- methyl viologen or =...

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Bibliographic Details
Published in:Plant and cell physiology 2001-08, Vol.42 (8), p.842-848
Main Authors: Kim, S.J. (Australian National Univ., Canberra (Australia)), Lee, C.H, Hope, A.B, Chow, W.S
Format: Article
Language:English
Subjects:
Chlorophyll - metabolism
Chlorophyll - radiation effects
Chloroplasts - metabolism
Chloroplasts - radiation effects
Cold Temperature
COOLING
CUCUMIS SATIVUS
Cucumis sativus - metabolism
Cucumis sativus - radiation effects
Electrochemistry
Electron Transport - radiation effects
Electrons
In Vitro Techniques
Kinetics
LEAVES
Light
Light-Harvesting Protein Complexes
LIGHTING
Oxidation-Reduction
OXIDOREDUCTIONS
Oxygen - metabolism
Photosynthetic Reaction Center Complex Proteins - antagonists & inhibitors
Photosynthetic Reaction Center Complex Proteins - metabolism
Photosynthetic Reaction Center Complex Proteins - radiation effects
Photosystem I Protein Complex
PHOTOSYSTEMS
Plant Leaves - metabolism
Plant Leaves - radiation effects
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Summary: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 1 (PS1) 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 PS1. Apparently, charge recombination in PS1 was greatly enhanced by inhibition of forward, linear electron flow. Inhibition of PS2 electron transport was observed to occur to a lesser extent than that of PS1, but only if the measurement of PS2 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 PS1 during chilling of leaves in the light may partly prevent further damage to both photosystems.
ISSN:0032-0781
1471-9053
DOI:10.1093/pcp/pce109