Mechanisms for controlling balance between light input and utilisation in the salt tolerant alga Dunaliella C9AA |
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Authors: | Deborah Rees Chin Bum Lee D James Gilmour Peter Horton |
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Institution: | (1) Robert Hill Institute, Department of Molecular Biology and Biotechnology, University of Sheffield, P.O. Box 594, S10 2UH Western Bank, Sheffield, UK;(2) Present address: Department of Biology, College of Natural Science, Dong-eui University, 614-714 Pusan, Korea |
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Abstract: | The yield of photosynthetic O2 evolution was measured in cultures of Dunaliella C9AA over a range of light intensities, and a range of low temperatures at constant light intensity. Changes in the rate of charge separation at Photosystem I (PS I) and Photosystem II (PS II) were estimated by the parameters PS I and PS II . PS I is calculated on the basis of the proportion of centres in the correct redox state for charge separation to occur, as measured spectrophotometrically. PS II is calculated using chlorophyll fluorescence to estimate the proportion of centres in the correct redox state, and also to estimate limitations in excitation delivery to reaction centres. With both increasing light intensity and decreasing temperature it was found that O2 evolution decreased more than predicted by either PS I or PS II. The results are interpreted as evidence of non-assimilatory electron flow; either linear whole chain, or cyclic around each photosystem.Abbreviations F0
dark level of chlorophyll fluorescence yield (PS II centres open)
- Fm
maximum level of chlorophyll fluorescence yield (PS II centres closed)
- Fv
variable fluorescence (Fm-F0)
- PS I
Photosystem I
- PS II
Photosystem II
- P700
reaction centre chlorophyll(s) of PS I
- qN
coefficient of non-photochemical quenching of chlorophyll fluorescence
- qP
coefficient of photochemical quenching of fluorescence yield
- qE
high-energy-state quenching coefficient
- PS I
yield of PS I
- PS II
yield of PS II
- S
yield of photosynthetic O2 evolution
- P
intrinsic yield of open PS II centres |
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Keywords: | chlorophyll fluorescence Dunaliella photosynthesis quantum efficiency |
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