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Mode of action of monuron (3- (4-chlorophenyl) -1, 1- dimethylurea. Baldwin, Richard William Ward

Abstract

The herbicidal action of monuron, 3-(4-chlorophenyl)-1, 1-dimethylurea, cannot be completely realized until the mode of action is fully understood. It is believed that the primary site of action is in the photosynthetic complex. The present investigations included: The study of the effects of monuron on some enzyme systems, greenhouse studies on the effects of monuron on the morphology of potato plants, field studies on the yield of barley treated with the substituted urea herbicides, the residual effects of the substituted urea herbicides applied to soil, the effects of monuron and the interaction of monuron and vitamin K on the rate of the photolysis of water by isolated chloroplasts. The photolysis of water was followed by observing changes in potential of a potasium ferricyanide solution containing isolated chloroplasts. Monuron inhibited the protease enzyme system and stimulated the lipase enzyme system. This herbicide reduced the total weight of potato tubers per plant, the root to top ratio and the total weight of barley grain per acre. The top growth of potato plants and the bushel weight of barley were increased with monuron applications. 1 X 10¯⁷ moles of monuron reduced the rate of the Hill reaction by more than 50%. The data presented did not confirm vitamin K as a cofactor in the Hill reaction.

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