Growth Regulation by Organic Compounds

Differential Effects of 2,3,6-Trichlorobenzoic Acid on Growth and Geotropic Curvature of Avena Coleoptiles

“…TClBA apparently functions as an auxin (1,8,9,10,11,12 (fig 8). Second, at 40 C, growth is unaffecte(l by 1 X 10-4 AI TCBA but geotropic curvature is i nihibite(d (fig 6 and 7).…”

Further Evidence for a Chemical Reaction Between Plant Growth-Regulators and a Plant Substrate

“…The larger amount of chloride released from 2,6-dichlorobenzoic acid in experiment 2 was correlated with greater elongation of the sections in the lower concentration of the chemical. At concentrations greater than 2 x 10-4 M the promoting effect of the compound on elongation decreases (16). If one assumes that every chloride ion displaced represents a molecule of 2,6-dichlorobenzoic acid reacting, the data of experiment 2 show that 1.13 x 10-6 mole of the compound reacts per gram of coleoptile tissue and only 28%o of the molecules present actually are involved in the reaction.…”

“…Evidence exists that the ortho effect is operative for indoleacetic acids (9,16). Substitution at the 2 position diminishes the activity of in-doleacetic acid; substitution at the 2 and 4 positions essentially nullifies the activity.…”

“…Materials and methods Avena plants were grown and coleoptile sections were harvested as reported previously (16) except that the sand in which the plants were grown was freed of chloride by heating at 150°F overnight with concentrated sulphuric and nitric acids. The sand was then washed with hot, doubly distilled water until the washings gave a negative sulphate test with barium chloride.…”

The Ortho Effect in Plant Growth-Regulators

“…Test plants were grown and used exactly as described previously (2). The data are expressed as differences in the average percentage elongation of 15 indoleacetic acid.…”