EFFECTS OF PHOTOSYSTEM II INHIBITORS ON ELECTRON PARAMAGNETIC RESONANCE SIGNAL II OF SPINACH CHLOROPLASTS |
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| Authors: | RICHARD H. LOZIER WARREN L. BUTLER |
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| Affiliation: | Department of Biology, Revelle College, University of California, San Diego, La Jolla, California 92037, U.S.A. |
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| Abstract: | Abstract— In isolated spinach chloroplasts the light-induced electron paramagnetic resonance signal (signal II) associated with the oxygen evolving photosystem (photosystem II) decays slowly and incompletely in the dark. Tris-washing, hydroxylamine, or carbonylcyanide m -chlorophenylhydrazone (CCCP) enhance the decay of signal II, which can still be induced by red (645 nm) but not by far-red (735 nm) radiation. Although 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) alone has no effect on signal II, it blocks the induction of signal II in the presence of hydroxylamine or CCCP. These data suggest that signal II is an indicator of an oxidized intermediate on the water-splitting side of photosystem II. |
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