Redistribution of endogenous indoleacetic acid, abscisic acid and gibberellins in geotropically stimulated Ribes nigrum roots

Abstract

Summary The presence of auxin (IAA), abscisic acid (ABA) and gibberellins (GA's) in extracts of roots of Ribes nigrum was demonstrated by gas-liquid chromatography 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 roots which have been kept horizontal, and which showed a positive geotropic response after 4 h, indicated a redistribution of the hormones during the geotropic stimulation. The ratio of the hormones in lower and upper halves was 1.62:1 and 5:1 for IAA and ABA respectively, whereas the ratio of gibberellins in upper and lower halves was 5.07:1. These data confirmed previous results for the half hour geotropic stimulated Vicia faba roots but provide no evidence for the participation of either ABA or gibberellins in the early development of positive geotropic curvatures.