Growth Regulation by Organic Compounds.

A large and diverse group of organic compounds is reported to "regulate" plant growth. Many of the determinations of growth regulation, however, do not measure the accelerating effects on growth but the inhibition of growth or toxicity effects. Such evidence does not suffice to identify the substances as growth regulators which may either accelerate or inhibit the growth process depending upon their concentration. Many techniques exist for the quantitative determination of the acceleration of plant growth by organic compounds (4, 9, 10, 11, 16, 17,). Of these the straight growth of Avena coleoptile sections has distinct advantages. This test gives quantitative data on growth response, it enables the study of accessory factors involved in the growth process, it is sensitive to the effects of substances which do not cause an Avena curvature response, and it does not depend on the complicated series of reactions of the pea test. This study was made to determine the similarity of the effects of several organic compounds and the plant auxin, indoleacetic acid (20), on the straight growth of Avena coleoptile sections. Most of the compounds have been studied by other investigators but their results cannot be correlated satisfactorily because of the different techniques employed in the measurement of the growth effects.