Transient state characteristics of adaptation to changes in light conditions for the cyanobacterium Oscillatoria agardhii |
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Authors: | Anton F Post |
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Institution: | (1) Laboratorium voor Microbiologie, University of Amsterdam, Nieuwe Achtergracht 127, NL-1018 WS Amsterdam, The Netherlands |
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Abstract: | Transitions in growth irradiance level from 92 to 7 Em-2 s-1 and vice versa caused changes in the pigment contents and photosynthesis of Oscillatoria agardhii. The changes in chlorophyll a and C-phycocyanin contents during the transition from high to low irradiance (HL) were reflected in photosynthetic parameters. In the LH transition light utilization efficiencies of the cells changed faster than pigment contents. This appeared to be related to the lowering of light utilization efficiencies of photosynthesis. As a possible explanation it was hypothesized that excess photosynthate production led to feed back inhibition of photosynthesis. Time-scales of changes in the maximal rate of O2 evolution were discussed as changes in the number of reaction centers of photosystem II in relation to photosynthetic electron transport. Parameters that were subject to change during irradiance transitions obeyed first order kinetics, but hysteresis occurred when comparing HL with LH transients. Interpretation of first order kinetic analysis was discussed in terms of adaptive response vs changes in growth rate.Non-standard abbreviations Chla
chlorophyll a
- CPC
C-phycocyanin
- PS II
photosystem II
- PS I
photosystem I
- RC II
reaction center of photosystem II
- P
photosynthetic O2-evolution
- I
irradiance, Em-2 s-1
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light utilization efficiency of cells, mmol O2·mg dry wt-1·h-1/Em-2 s-1
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light utilization efficiency of photosynthetic apparatus, mol O2·mol Chla
-1·h-1/Em-2 s-1
- Pmax
maximal rate of O2 evolution by cells, mol O2·mg dry wt-1·h-1
- Pmax
maximal rate of O2 evolution by photosynthetic apparatus, mol O2·mol·Chla
-1·h-1
- LL
low light, E m-2 s-1
- HL
high light, E m-2 s-1
- LH
low to high light transition
- HL
high to low light transition
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k
specific rate of adaptation, h-1
-
specific growth rate, h-1
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Q
pool size of cell constituent, mol·mg dry wt-1
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q
net synthesis rate of cell constituent, mol·mg dry wt-1·h-1 |
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Keywords: | Transient state Light limitation Chlorophyll a Phycobiliproteins Cyanobacteria Photosynthesis Light-shade adaptation |
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