Luminescence decay kinetics in relation to quenching and stimulation of dark fluorescence from high and low CO2adapted cells ofScenedesmus obliquusandChlamydomonas reinhardtii
✍ Scribed by Lars-Göran Sundblad; Göran Samuelsson; Bosse Wigge; Per Gardeström
- Publisher
- Springer
- Year
- 1990
- Tongue
- English
- Weight
- 857 KB
- Volume
- 23
- Category
- Article
- ISSN
- 0166-8595
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✦ Synopsis
Two green algal species, Chlamydomonas reinhardtii and Scenedesmus obliquus, exhibited a relative maximum during the decay of luminescence, when adapted to low CO2 conditions that was not observed in high CO2 adapted cells.
From the kinetics of transient changes in the level of dark fluorescence, after illumination and parallel to the luminescence maxima, it was concluded that the maximum in Scenedesmus was mainly related to a decrease in nonphotochemical quenching, whereas in Chlamydomonas the maximum was mainly related to a dark reduction of the primary PS II acceptor QA.
ATP/ADP ratios from low CO2 adapted Seenedesmus showed transient high levels after a dark/light transition that was not observed in high CO2 adapted cells. After 30 s of illumination the ATP/ADP ratios however stabilized at the same steady state level as in high CO2 adapted cells.
Dark addition of HCO3 to low CO2 adapted ceils of Chlamydomonas resulted in a rapid transient quenching of luminescence that was not observed in low CO2 adapted cells of neither species.
It is concluded that the luminescence maxima present in both low CO2 adapted Scenedesmus and Chlamydomonas reflect adaptation of the cells to low CO2 conditions. It is further suggested that the difference in mechanistic origin of luminescence maxima in the two species reflects differences in adaptation.
Abbreviations; ADP -adenosine-diphosphate, ATP -adenosine-triphosphate, Ci -inorganic carbon, Fodark fluorescence recorded under dark adapted conditions, F0 -fluorescence with all reaction centers open, FV -variable fluorescence, PSI -photosystem I, PS II -photosystem II, QA -the first quinone acceptor of PS II