STUDIES ON PLANT GROWTH‐REGULATING SUBSTANCES

Abstract
A number of polycyclic carboxylic acids have been prepared and their plant growth‐regulating activity has been assessed in the wheat‐cylinder, pea‐curvature and pea‐segment tests. The compounds were selected in relation to a theory on the mode of action of plant‐growth substances which involves the association of three essential groupings in the molecule with specifically sited receptor centres within the plant cell. High activity was found only in those compounds possessing a > CHCOOH grouping adjacent to an aromatic ring. It is concluded that molecular size, stereochemical and electronic considerations may all operate in determining whether compounds of this type show activity. The results obtained together with those of other workers are discussed in relation to current theories on mode of action.