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EFFECTS OF POTASSIUM ON THE PHOTOSYNTHETIC RECOVERY OF THE TERRESTRIAL CYANOBACTERIUM, NOSTOC FLAGELLIFORME (CYANOPHYCEAE) DURING REHYDRATION 1
Author(s) -
Qiu Baosheng,
Zhang Aihong,
Zhou Wenbin,
Wei Jiamian,
Dong Hui,
Liu Zhili
Publication year - 2004
Publication title -
journal of phycology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.85
H-Index - 127
eISSN - 1529-8817
pISSN - 0022-3646
DOI - 10.1111/j.1529-8817.2004.03152.x
Subject(s) - plastoquinone , potassium , dcmu , photosystem , electron transport chain , electron acceptor , biology , photosynthesis , cytochrome f , nostoc , photosystem ii , cytochrome b6f complex , electron transfer , thylakoid , plastocyanin , photochemistry , photosystem i , biophysics , botany , chemistry , cyanobacteria , biochemistry , chloroplast , organic chemistry , genetics , gene , bacteria
Effects of potassium on the photosynthetic recovery of Nostoc flagelliforme (Berk. & Curtis) Bornet & Flahault were investigated to determine its exact role during rehydration. Potassium enhanced recovery of the ability to reduce the primary quinone‐type acceptor (Q A ) and plastoquinone (PQ) pool and the area over the fluorescence rise curve was increased by 127%. The proportions of closed PSII reaction centers at phases J and I and the net rate of closure of PSII reaction centers were decreased by, respectively, 19%, 8%, and 23% with the addition of potassium, due to changes in the ability of PSII for multiple turnovers needed to reduce the PQ pool. Potassium significantly enhanced the probability of electron transfer beyond Q A and the recovery of electron transport flux per PSII reaction center. Electron transport from water to methyl viologen for samples rehydrated in K + ‐free BG 11 medium was 54% of those with the addition of potassium. However, electron flow from water to p ‐benzoquinone and from reduced 2,6‐dichlorophenol‐indophenol to methyl viologen showed little change with the addition of potassium. The fast phase and slow phase of millisecond delayed light emission and the ATP content for samples rehydrated in K + ‐free BG 11 medium were, respectively, 71.6%, 50.7%, and 77.1% of those with the addition of potassium. These suggested that potassium affected electron transfer from PQ to plastocyanin through the cytochrome b 6 f complex and the proton motive force across the thylakoid membranes, probably reflecting its role in charge balance during H + transport by the cytochrome b 6 f complex.