Redistribution of Endogenous Indoleacetic Acid, Abscisic Acid and Gibberellins in Geotropically Stimulated Ribes nigrum Shoots

Abstract

AbstractThe presence of IAA, ABA and gibberellins in extracts of shoots of Ribes nigrum was demonstrated by gas‐liquid chroma‐tography (GLC) for both IAA and ABA and by the lettuce hypocotyl assay for gibberellins. Quantitative estimation of the three substances in extracts from upper and lower halves of shoots which had been kept horizontal, and which showed negative geotropic response after 4 h, indicated a redistribution of hormones during the geotropic stimulation. The ratio of the hormones in lower and upper halves was 3.8:1 and 2.8:1 for IAA and giberellins respectively, whereas the ratio of ABA in upper and lower halves was 2.1:1. There is, however, no evidence for the participation of gibberellins and ABA in the early development of negative geotropic curvatures, since shoots of intact Vicia faba seedlings treated with 100 mg/1 solution of GA3, ABA and 10 mg/1 IAA for 30 min prior to geotropic stimulation, developed negative geotropic curvatures, although shoots pretreated with 50 and 100 mg/1 IAA did not develop curvature.