Charge separation as a component of the structural requirements for hormone activity

THE establishment of a theory which would satisfactorily predict the relationship between molecular structure and plant hormone activity would be of major importance in improving our fundamental knowledge of plant growth regulation and would be of great practical significance to the agrochemical industry. The subject of auxin structure–activity relationships has been widely reviewed1–7 but each theory has been found, in some respect, defective. Techniques of theoretical chemistry, biochemistry and plant physiology are used here to draw attention to the probability that charge separation as a component of the structural requirements for auxin activity has been prematurely6 rejected.