JXB Advance Access first published online on May 6, 2009
This version published online on May 19, 2009
Journal of Experimental Botany, doi:10.1093/jxb/erp131
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© 2009 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
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RESEARCH PAPER |
Transient winter leaf reddening in Cistus creticus characterizes weak (stress-sensitive) individuals, yet anthocyanins cannot alleviate the adverse effects on photosynthesis
Laboratory of Plant Physiology, Section of Plant Biology, Department of Biology, University of Patras, GR-265 00, Greece
* To whom correspondence should be addressed: E-mail: petropo{at}upatras.gr
Under apparently similar field conditions individual plants of Cistus creticus turn transiently red during winter, while neighbouring plants remain green. These two phenotypes provide a suitable system for comparing basic photosynthetic parameters and assessing critically two hypotheses, i.e. anthocyanins afford photoprotection and anthocyanins induce shade characteristics on otherwise exposed leaves. With that aim, pigment levels and in vivo chlorophyll fluorescence parameters were monitored in dark-acclimated (JIP-test) and light-acclimated (saturation pulse method) leaves during both the green and the red period of the year. No evidence for actual photoprotection by anthocyanins was obtained. On the contrary, all fluorescence parameters related to yields and probabilities of photochemical energy conversion and electron flow, from initial light trapping to final reduction of ultimate electron acceptors in PSI, declined in the red phenotype after leaf reddening. Moreover, the pool sizes of final electron acceptors of PSII diminished, indicating that both photosystems were negatively affected. Vulnerability to winter stress was also indicated by sustained chlorophyll loss, inability to increase the levels of photoprotective xanthophylls and increased quantum yield of non-regulated energy loss during reddening. However, during the same period, the relative PSII antenna size increased, indicating an apparent shade acclimation after anthocyanin accumulation, while changes in the photosynthetic pigment ratios were also compatible to the shade acclimation hypothesis. All parameters recovered to pre-reddening values upon re-greening. It is concluded that the photosynthetic machinery of the red leaf phenotype has an inherently low capacity for winter stress tolerance, which is not alleviated by anthocyanin accumulation.
Key words: Cistus creticus, electron transport, epoxidation state, OJIP curves, photoinhibition, photoprotection, pigments, PSI, PSII, shade acclimation
This paper has been versioned to become open access.
Received 15 December 2008; Revised 27 March 2009 Accepted 5 April 2009