Inhibition of Photosystem II by uncouplers at alkaline pH and its reversal by artificial electron donors |
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Authors: | Dunell E Cohn William S Cohen Walter Bertsch |
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Institution: | 1. Department of Biological Sciences, Hunter College, New York, N.Y. 10021 U.S.A.;2. Plant Physiology Unit, CSIRO Division of Food Research, School of Biological Sciences, Macquarie University, North Ryde, Sydney, N.S.W. 2113 Australia |
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Abstract: | When chloroplasts are aged for 5 min at pH 9.6, or are exposed to uncouplers at pH 8.5–9.0, electron flow from water to Hill acceptors is inhibited. Both treatments induce rapid millisecond dark decay of delayed light emission. 3-(3,4-Dichlorophenyl)-1,1-dimethylurea-sensitive electron transport through Photosystem II can be regenerated in both types of inhibited chloroplasts by the artificial electron donor, 1,5-diphenylcarbohydrazide. Neither treatment inhibits electron flow through Photosystem I. Uncouplers at alkaline pH, when added in the light, are less effective in producing the inhibition than when added in the dark. These results are interpreted as indicating inhibition of the oxygen-evolving apparatus by alkaline intrathylakoid pH. |
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Keywords: | DCMU 3-(3 4-dichlorophenyl)-1 1-dimethylurea DCPIP 2 6-dichlorophenolindophenol DPC 1 5-diphenylcarbohydrazide FMN flavin mononucleotide |
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