Wirkungsmechanismus und Struktur-Aktivitätsbeziehungen des Aminotriazinon-Herbizids Metribuzin. Hemmung des photosynthetischen Elektronentransports von Chloroplasten durch Metribuzin / Mode of Action and Structure-Acitivity-Relationships of the Aminotriazinone Herbicide Metribuzin. Inhibition of Photosynthetic Electron Transport in 'Chloroplasts by Metribuzin

Abstract

The influence of the aminotriazinone herbicide Metribuzin on photosynthetic reactions of isolated chloroplasts is investigated. Metribuzin inhibits all Hill-reactions when water is the electron donor, but not photoreductions by photosystem I at the expense of an artificial electron donor. The PI₅₀-value is 6.7. Cyclic photophosphorylation is not affected by Metribuzin. Measurements of the prompt and delayed fluorescence of the photosynthetically active chlorophyll support the notion, that Metribuzin inhibits photosynthetic electron flow between the primary and secondary electron acceptor of photosystem II (Q and plastoquinone). The relationship of inhibitory potency to chemical structure is investigated by comparing a number of related aminotriazinones. The effect of various substituents is discussed.