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Publication Type J
Authors Lu, C. M., N. W. Qiu, B. S. Wang and J. H. Zhang
Title Salinity treatment shows no effects on photosystem II photochemistry, but increases the resistance of photosystem II to heat stress in halophyte Suaeda salsa
Source Journal of Experimental Botany
Language English
Author Keywords chlorophyll fluorescence gas exchange heal stress photosystem II photochemistry salinity treatment Suaeda salsa L. a fluorescence transient chlorophyll fluorescence electron-transport higher-plants gas-exchange leaves photosynthesis thermostability temperature glycinebetaine Plant Sciences
Abstract Photosynthetic gas exchange, modulated chlorophyll fluorescence, rapid fluorescence induction kinetics, and the polyphasic fluorescence transients were used to evaluate PSII photochemsitry in the halophyte Suaeda salsa exposed to a combination of high salinity (100-400 mM NaCl) and heat stress (35-47.5 degreesC, air temperature). CO2 assimilation rate increased slightly with increasing salt concentration up to 300 mM NaCl and showed no decrease even at 400 mM NaCl. Salinity treatment showed neither effects on the maximal efficiency of PSII photochemistry (F-v/F-m), the rapid fluorescence induction kinetics, and the polyphasic fluorescence transients in dark-adapted leaves, nor effects on the efficiency of excitation energy capture by open PSII reaction centres (F-v'/F-m') and the actual PSII effciency (Phi(PSII)), photochemical quenching (q(p)), and non-photochemical quenching (q(N)) in light-adapted leaves. The results indicate that high salinity had no effects on PSII photochemistry either in a dark-adapted state or in a light-adapted state. With increasing temperature, CO2 assimilation rate decreased significantly and no net CO2 assimilation was observed at 47.5 degreesC. Salinity treatment had no effect on the response of CO2 assimilation to high temperature when temperature was below 40 degreesC. At 45 degreesC, CO2 assimilation rate in control plants decreased to zero, but the salt-adapted plants still maintained some CO2 assimilation capacity. On the other hand, the responses of PSII photochemistry to heat stress was modified by salinity treatment. When temperature was above 35 degreesC, the declines in F-v/F-m, Phi(PSII), F-v'/F-m', and q(p) were smaller in salt-adapted leaves compared to control leaves. This increased thermostability was independent of the degree of salinity, since no significant changes in the above-described fluorescence parameters were observed among the plants treated with different concentrations of NaCl. During heat stress, a very clear K step as a specific indicator of damage to the O-2-evolving complex in the polyphasic fluorescence transients appeared in control plants, but did not get pronounced in salt-adapted plants. In addition, a greater increase in the ratio (F-i-F-o)/(F-p-F-o) which is an expression of the proportion of the Q(B)-non-reducing PSII centres was observed in control plants rather than in salt-adapted plants. The results suggest that the increased thermostability of PSII seems to be associated with the increased resistance of the O-2-evolving complex and the reaction centres of PSII to high temperature.
Author Address Chinese Acad Sci, Inst Bot, Photosynth Res Ctr, Beijing 100093, Peoples R China. Chinese Acad Sci, Key Lab Photosynth & Environm Mol Physiol, Inst Bot, Beijing 100093, Peoples R China. Shandong Normal Univ, Dept Biol, Jinan 250014, Peoples R China. Hong Kong Baptist Univ, Dept Biol, Hong Kong, Hong Kong, Peoples R China. Zhang, JH (reprint author), Chinese Acad Sci, Inst Bot, Photosynth Res Ctr, Beijing 100093, Peoples R China. jzhang@hkbu.edu.hk
ISSN 0022-0957
ISBN 0022-0957
29-Character Source Abbreviation J. Exp. Bot.
Publication Date Feb
Year Published 2003
Volume 54
Issue 383
Beginning Page 851-860
Digital Object Identifier (DOI) 10.1093/jxb/erg080
Unique Article Identifier WOS:000180964000026
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