Site of Action and Quantitative Structure-Activity Relationship of a Series of Herbicidal N-Aryl-Substituted 3,4-Dimethyl-2-hydroxy-5-oxo-2,5-dihydro-pyrrolones

Pyrrolones, Site of Action, Structure-Activity Relations, Photosynthetic Electron Transport, Herbi­ cidal Action Substituted phenyl-hydroxy pyrrolone derivatives are potential herbicides and are found to be effective inhibitors of photosynthetic electron flow in chloroplasts. Their site of inhibition is localized at the acceptor side of photosystem II similar to DCMU. They have no effect on photophosphoryla­ tion. The correlation of photosynthetic acitivity to chemical structure is studied by comparing 36 derivatives. A clear dependence of inhibitory activity on lipophilicity is found. The dependence of herbicidal activity on chemical structure is more complex.