Mechanisms of action and structure activity relations of herbicides that inhibit photosynthesis

A survey and chemical classification are given for the most important herbicidal inhibitors of photosynthesis. The photochemical reactions involved in photosynthesis are reviewed. The herbicides discussed here all interfere with photosynthetic electron transport in the light reactions. Comments are made on the redox catalysts and the electron transport chain. The mode of action of the herbicides due to inhibition of the light reactions I and II or of photophosphorylation are described. Structure activity correlations according to the regression analysis (Hansch‐approach) are discussed with examples in the classes of acetanilides, benzimidazoles and triazinones. The correlation studies in the series of the Hill‐reaction inhibitors have led to a model for the essential structural elements. Some work on the problem of selectivity and its importance is reviewed.