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Diel and seasonal changes in fluorescence rise kinetics of three scleractinian corals

Diel and seasonal changes in fluorescence rise kinetics of three scleractinian corals The effect of diel oscillations in light on the photosynthetic response of three coral species during summer and winter was studied. Fast induction curves revealed detailed information on primary photochemistry as well as redox states of electron acceptors in photosystem II (PSII). The comparison between seasons revealed that similar physiological mechanisms were operating in response to high-light conditions throughout the year and that environmental variables, such as temperature, had no measurable effect between seasons. A diurnal hysteresis was seen in both seasons in F v / F m as well as in the fast induction curves, where photosynthetic capacity was lower in the afternoon than in the morning when light intensities were the same. This suggests the operation of dynamic down regulation, following exposure to midday high light. Fast induction curve analysis revealed a decline in the O, J, I and P steps towards midday and a rapid recovery by the late afternoon. The decrease in J and its rapid recovery indicated a drop in the rate of Q A reduction as a result of an increase in non-photochemical quenching (NPQ). The P step increased in amplitude in the first hours of sunlight, which suggests an increased oxidation of the plastoquinone (PQ) pool and a greater capacity for electron transport. Similarly, a rise in F v / F m was observed within the first hour of sunlight. This response was attributed to the dark reduction of the PQ pool, induced by night time anaerobic conditions and possibly oxygen-dependent chlororespiration, which would lead to a state 2 transition. The early morning removal of chlororespiration and hypoxic conditions would have returned the photosystems to state 1, resulting in the increased photochemical efficiency of the zooxanthellae. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Functional Plant Biology CSIRO Publishing

Diel and seasonal changes in fluorescence rise kinetics of three scleractinian corals

Functional Plant Biology , Volume 32 (6) – Jun 15, 2005

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References (49)

Publisher
CSIRO Publishing
Copyright
CSIRO
ISSN
1445-4408
eISSN
1445-4416
DOI
10.1071/FP05017
Publisher site
See Article on Publisher Site

Abstract

The effect of diel oscillations in light on the photosynthetic response of three coral species during summer and winter was studied. Fast induction curves revealed detailed information on primary photochemistry as well as redox states of electron acceptors in photosystem II (PSII). The comparison between seasons revealed that similar physiological mechanisms were operating in response to high-light conditions throughout the year and that environmental variables, such as temperature, had no measurable effect between seasons. A diurnal hysteresis was seen in both seasons in F v / F m as well as in the fast induction curves, where photosynthetic capacity was lower in the afternoon than in the morning when light intensities were the same. This suggests the operation of dynamic down regulation, following exposure to midday high light. Fast induction curve analysis revealed a decline in the O, J, I and P steps towards midday and a rapid recovery by the late afternoon. The decrease in J and its rapid recovery indicated a drop in the rate of Q A reduction as a result of an increase in non-photochemical quenching (NPQ). The P step increased in amplitude in the first hours of sunlight, which suggests an increased oxidation of the plastoquinone (PQ) pool and a greater capacity for electron transport. Similarly, a rise in F v / F m was observed within the first hour of sunlight. This response was attributed to the dark reduction of the PQ pool, induced by night time anaerobic conditions and possibly oxygen-dependent chlororespiration, which would lead to a state 2 transition. The early morning removal of chlororespiration and hypoxic conditions would have returned the photosystems to state 1, resulting in the increased photochemical efficiency of the zooxanthellae.

Journal

Functional Plant BiologyCSIRO Publishing

Published: Jun 15, 2005

Keywords: chlorophyll a fluorescence, coral bleaching, diurnal hysteresis, down regulation, non-photochemical quenching, OJIP, photosystem II.

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