title: A major site of bicarbonate effect in system II reaction. Evidence from ESR signal IIvf, fast fluorescence yield changes and delayed light emission.
abstract: In order to determine the major site of bicarbonate action in the electron transport complex of Photosystem II, the following experimental techniques were used: electron spin resonance measurements of Signal IIvf, measurements of chlorophyll a fluorescence yield rise and decay kinetics, and delayed light emission decay. From data obtained using these experimental techniques the following conclusions were made: (1) absence of bicarbonate causes a reversible inactivation of up to 40% of Photosystem II reaction center activity; (2) there is no significant effect of bicarbonate on electron flow from the charge accumulating S state to Z; (3) there is no significant effect of bicarbonate on electron flow from Z to P-680+; (4) electron flow from Q-- to the intersystem electron transport pool is inhibited by from 4- to 6-fold under bicarbonate depletion conditions.
mesh_terms: D001639:Bicarbonates / Q000494:pharmacology*; D002736:Chloroplasts / Q000187:drug effects / Q000378:metabolism*; D004237:Diuron / Q000494:pharmacology; D004578:Electron Spin Resonance Spectroscopy; D004579:Electron Transport; D007834:Lasers; D008027:Light; D010788:Photosynthesis / Q000187:drug effects*; D010944:Plants; D013050:Spectrometry, Fluorescence
chemical_list: D001639:Bicarbonates; D004237:Diuron