期刊
PHOTOSYNTHESIS RESEARCH
卷 63, 期 2, 页码 171-182出版社
SPRINGER
DOI: 10.1023/A:1006303510458
关键词
chlorophyll fluorescence; non-photochemical quenching; Photosystem II; thylakoid membranes
The efficiency of oxidized endogenous plastoquinone-9 (PQ-9) as a non-photochemical quencher of chlorophyll fluorescence has been analyzed in spinach thylakoids and PS II membrane fragments isolated by Triton X-100 fractionation of grana stacks. The following results were obtained: (a) After subjection of PS II membrane fragments to ultrasonic treatment in the presence of PQ-9, the area over the induction curve of chlorophyll fluorescence owing to actinic cw light increases linearly with the PQ-9/PS II ratio in the reconstitution assay medium; (b) the difference of the maximum fluorescence levels, F-max, of the induction curves, measured in the absence and presence of DCMU, is much more pronounced in PS II membrane fragments than in thylakoids; (c) the ratio F-max(-DCMU)/F-max(+DCMU) increases linearly with the content of oxidized PQ-9 that is varied in the thylakoids by reoxidation of the pool after preillumination and in PS II membrane fragments by the PQ-9/PS II ratio in the reconstitution assay; (d) the reconstitution procedure leads to tight binding of PQ-9 to PS II membrane fragments, and PQ-9 cannot be replaced by other quinones; (e) the fluorescence quenching by oxidized PQ-9 persists at low temperatures, and (f) oxidized PQ-9 preferentially affects the F695 of the fluorescence emission spectrum at 77 K. Based on the results of this study the oxidized PQ-9 is inferred to act as a non-photochemical quencher via a static mechanism. Possible implications for the nature of the quenching complex are discussed.
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