Studies on the Component Responsible for the Oxidation of the Primary Electron Acceptor of Photosystem II in the Presence of 3-(3',4'-Dichlorophenyl)-1,1-Dimethyl Urea : Reactivity to External Reductants

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The dark reoxidation of the photochemically reduced primary electron acceptor of photosystem II, Q, in the presence of 3-(3',4'-dichlorophenyl)-1,1-dimethyl urca (DCMU) by the redox counterpart (here designated Z) of Q was studied by monitoring the dark recovery of the induction of chlorophyll fluorescence. In normal chloroplasts, the dark reoxidation of reduced Q in the presence of DCMU was not affected by the externally added hydrophilic reductants; ascorbate, hydroquinone, hydrogen peroxide, manganous chloride, potassium iodide and potassium ferrocyanide. In chloroplasts whose oxidizing side of photosystem II had been in-activated by heat- or Tris-treatments, reoxidation was inhibited partially. This inhibition increased on the addition of hydrophilic reductants, but was relieved by increasing the redox potential of the suspension medium with the chloroplasts. We concluded that the redox counterpart. Z, of Q in the presence of DCMU is located in a hydrophobic environment which can be denatured by heat- or Tris-treatments to allow the access of normally extruded hydrophilic electron donors.
日本植物生理学会の論文