New Growth-Regulating Compounds II. Substituted Benzoic Acids

Abstract

More than 200 substituted benzoic acids were tested for inhibitory by 3 greenhouse or laboratory tests. Only 7 compounds approached 2,4-D in activity. Non-halogen as well as halogen ring substituents confer activity to the molecule, and active compounds contain substituents in practically all position combinations. Responses induced in Red Kidney bean plants by these compounds are similar in many respects to those induced by phenoxy derivatives and comprise curvature, leaf modifications, galls, witches''-broom, and root-tip swellings. The responses appear to be of longer duration than those induced by phenoxy compounds. It has been suggested that the subtituted benzoic acids remain mobile within the plant and continue to migrate to the newly developing leaves at the stem apex. The rate of inactivation within the bean plant appears to be considerably slower than for phenoxy derivatives. The 3-nitro-4-halogen benzoic acids are strong stimulators and can prevent 2,4-D from inhibiting the elongation of intact cucumber roots.