DIAMINODUREN AS ELECTRON DONOR AND THE EFFECT OF UV-LIGHT ON PHOTOSYNTHETIC REACTIONS IN ISOLATED CHLOROPLASTS.
GOETTINGEN UNIV (WEST GERMANY) INST FOR PLANT PHYSIOLOGY
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Diaminoduren 2,3,5,6-tetramethyl- p-phenylenediamine, DAD reverses the DCMU dichlorphenyl dimethyl ureainhibition of photosynthetic NADP-reduction and therefore acts as electron donor for the electron transport chain. The DAD-system is coupled to ATP-formation and gives the best rates of all electron donor systems known so far. In UV-irradiated chloroplasts the endogenous plastoquinone is destroyed. Such chloroplasts do not evolve oxygen anymore, but are still able to photoreduce NADP at the expense of an artificial electron donor system. Cyclic photo-phosphorylation with PMS as cofactor is less sensitive to UV-irradiation and at a certain stage of damage of the chloroplasts becomes inhibited by antimycin indicating a second phosphorylation site. Author