Chlorophyll fluorescence induction in anaerobic Scenedesmus obliquus |
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Authors: | Ulrich Schreiber William Vidaver |
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Affiliation: | Photobiology Group, Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia Canada |
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Abstract: | Fluorescence time curves (Kautsky effect) were studied in anaerobic Scenedesmus obliquus, with an apparatus capable of simultaneous recording of O2 exchange, and far-red actinic illumination. Results, as interpreted in terms of electron transport reactions, suggest: In the course of becoming anaerobic, fluorescence induction undergoes a series of changes, indicating at least three different effects of the absence of O2 on electron transport. (1) Immediately on removal of O2, once the pool of intermediates between the two photo-systems is reduced by light reaction II, electron flow stops, resulting in high fluorescence yield and a cessation of O2 evolution. O2 appears to regulate linear electron flow and cyclic feedback of electrons to the intermediate pool. (2) An endogenous reductant formed anaerobically reduces the System II acceptors in the dark. The time course of this reduction is at least biphasic, indicative of inhomogeneity of the primary acceptor pool. Prolonged dark anaerobic treatment induces maximal initial fluorescence which decays rapidly in light and with a System I action spectrum. (3) Anaerobic treatment eventually results in deactivation of the oxidizing side of System II, limiting System II even when the acceptors are oxidized by System I pre-illumination. |
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Keywords: | DCMU 3-(3,4-dichlorophenyl)-1, 1-dimethylurea PMS phenazine methosulfate |
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