New Plant Growth-Substances with Selective Herbicidal Activity

Abstract

THE pronounced effect on plant growth-regulating activity that results from the introduction of chlorine atoms into certain positions of the benzene ring in benzoic and phenoxyacetic acids is well known¹, and some of these active derivatives, for example, 2 : 4-dichlorophenoxyacetic acid (2 : 4D), 2 : 4 : 5-trichlorophenoxyacetic acid (2 : 4 : 5T) and 2 : 3 : 6-trichlorobenzoic acid have become widely used for selective weed control. Systematic investigations with these groups of compounds have provided much information on the structural requirements necessary for high growth-regulating activity². The influence of nuclear substitution on the activity of phenylacetic acids, however, has not received much attention, although some of these compounds have been examined (see Pybus³).