Oxidative Processes in Photosystem I of Thermophilic Cyanobacteria at High Temperatures

Oxidative Processes in Photosystem I of Thermophilic Cyanobacteria at High Temperatures We studied the mechanisms of the relationships between the generation of millisecond delayed fluorescence in photosystem I (DF) and the oxidative destruction of chlorophyll in the membranes of a thermophilic cyanobacteria Synechococcus elongatusin the temperature range 60–80°C at various irradiation levels and in the presence of substances affecting the intensity of DF. Light and temperature dependencies of the chlorophyll oxidation rates were similar to those of the DF of PSI. Anions Cl–, Br–, and NO– 3, which quench the triplet states of chlorophyll, almost completely inhibited the chlorophyll oxidation and reduced the intensity of the DF maximum by 70%. Under anaerobic conditions and in the presence of sodium ascorbate, the rate of chlorophyll oxidation also markedly decreased. We found that the long-wavelength chlorophyll forms were the most susceptible to oxidation and related the temperature-dependent changes in the DF of PSI and in the oxidative processes in the membranes of thermophilic cyanobacteria to an increase in the concentration of the triplet states of P700and other chlorophyll forms. The latter result from the temperature-dependent inactivation of carotenoids and the inhibition of electron transfer to ferredoxin in PSI. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Russian Journal of Plant Physiology Springer Journals

Oxidative Processes in Photosystem I of Thermophilic Cyanobacteria at High Temperatures

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Publisher
Kluwer Academic Publishers-Plenum Publishers
Copyright
Copyright © 2001 by MAIK “Nauka/Interperiodica”
Subject
Life Sciences; Plant Sciences
ISSN
1021-4437
eISSN
1608-3407
D.O.I.
10.1023/A:1016764220646
Publisher site
See Article on Publisher Site

Abstract

We studied the mechanisms of the relationships between the generation of millisecond delayed fluorescence in photosystem I (DF) and the oxidative destruction of chlorophyll in the membranes of a thermophilic cyanobacteria Synechococcus elongatusin the temperature range 60–80°C at various irradiation levels and in the presence of substances affecting the intensity of DF. Light and temperature dependencies of the chlorophyll oxidation rates were similar to those of the DF of PSI. Anions Cl–, Br–, and NO– 3, which quench the triplet states of chlorophyll, almost completely inhibited the chlorophyll oxidation and reduced the intensity of the DF maximum by 70%. Under anaerobic conditions and in the presence of sodium ascorbate, the rate of chlorophyll oxidation also markedly decreased. We found that the long-wavelength chlorophyll forms were the most susceptible to oxidation and related the temperature-dependent changes in the DF of PSI and in the oxidative processes in the membranes of thermophilic cyanobacteria to an increase in the concentration of the triplet states of P700and other chlorophyll forms. The latter result from the temperature-dependent inactivation of carotenoids and the inhibition of electron transfer to ferredoxin in PSI.

Journal

Russian Journal of Plant PhysiologySpringer Journals

Published: Oct 10, 2004

References

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