Studies on the Mode of Action of Aminotriazole in the Induction of Chlorosis

The herbicide 3-amino-1, 2, 4-triazole induces complete chlorosis without any morphogenetic effect on Canna edulis leaves. Comparative analyses of the mineral and biochemical composition and also of the physiological properties of normal and bleached leaf cells establish a high specificity of this herbicide for inhibition of formation of chloroplast membranes. The synthesis of membrane lipids and chloroplastic terpenoid derivatives were specifically inhibited. This compound was found to inhibit photosynthetic O(2) evolution and (14)CO(2) fixation at the whole cell level and ferricyanide reduction in isolated chloroplasts immediately after its application. This inhibition was reversible with the addition of a number of unrelated compounds shown to nullify its herbicidal effect.The mechanism of action of this compound in specifically blocking the development of chloroplast membranes in discussed in terms of its primary action on photosynthetic carbon fixation.