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STUDIES OF SYSTEM II PHOTOCENTERS BY COMPARATIVE MEASUREMENTS OF LUMINESCENCE, FLUORESCENCE, AND OXYGEN EMISSION *

STUDIES OF SYSTEM II PHOTOCENTERS BY COMPARATIVE MEASUREMENTS OF LUMINESCENCE, FLUORESCENCE, AND... Abstract— New results are presented on the emission of oxygen by algae and chloroplasts illuminated by a sequence of short saturating flashes. These results favor the four‐state hypothesis of Kok and co‐workers, in which formation of oxygen requires the accumulation of four oxidants produced by four successive photoreactions. Deactivation of the more oxidized precursor states in the dark is studied under different conditions of preillumination. Our results suggest that both a one step and a two step mechanism of deactivation exist. In order to understand the biological significance of Kok's parameter α—the fraction of photochemical centers unable to react on each flash (“misses”)‐we study reoxidation of acceptor Q after one flash by fluorescence techniques. It appears that a fraction of Q‐ is reoxidized by a back reaction which cancels the effect of the preilluminating flash and is probably responsible for the misses. The results of some luminescence experiments are also reported. These experiments demonstrate that delayed emission of light is associated with the deactivation of states S2 and S3. It is possible that excitons produced by deactivation can be reabsorbed by active photochemical centers, which can modify considerably the deactivation process. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Photochemistry & Photobiology Wiley

STUDIES OF SYSTEM II PHOTOCENTERS BY COMPARATIVE MEASUREMENTS OF LUMINESCENCE, FLUORESCENCE, AND OXYGEN EMISSION *

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References (21)

Publisher
Wiley
Copyright
Copyright © 1971 Wiley Subscription Services, Inc., A Wiley Company
ISSN
0031-8655
eISSN
1751-1097
DOI
10.1111/j.1751-1097.1971.tb06174.x
Publisher site
See Article on Publisher Site

Abstract

Abstract— New results are presented on the emission of oxygen by algae and chloroplasts illuminated by a sequence of short saturating flashes. These results favor the four‐state hypothesis of Kok and co‐workers, in which formation of oxygen requires the accumulation of four oxidants produced by four successive photoreactions. Deactivation of the more oxidized precursor states in the dark is studied under different conditions of preillumination. Our results suggest that both a one step and a two step mechanism of deactivation exist. In order to understand the biological significance of Kok's parameter α—the fraction of photochemical centers unable to react on each flash (“misses”)‐we study reoxidation of acceptor Q after one flash by fluorescence techniques. It appears that a fraction of Q‐ is reoxidized by a back reaction which cancels the effect of the preilluminating flash and is probably responsible for the misses. The results of some luminescence experiments are also reported. These experiments demonstrate that delayed emission of light is associated with the deactivation of states S2 and S3. It is possible that excitons produced by deactivation can be reabsorbed by active photochemical centers, which can modify considerably the deactivation process.

Journal

Photochemistry & Photobiology – Wiley

Published: Sep 1, 1971

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