Effect of abscisic acid on growth and indolyl-3-acetic acid levels in maize roots

Abstract

The abscisic acid (ABA) effect on root elongation is first reported comparing intact roots and apical root segments (prepared from primary roots of LG11 maize) treated 1 h by buffered (pH 6.0) ABA then kept 5 h in the dark (humid air or in buffered medium). After 1 h, ABA has no effect except at 10 −4 M for which it caused a small growth inhibition. After 6 h, ABA at 10 −8 M (1 h treatment) enhances the elongation of root segments. But, for 10 −6 M and 10 −4 M it inhibits growth of both intact roots and root segments. In a second set of analyses, endogenous indolyl-3-acetic acid (IAA) of these ABA treated roots is measured. When they were immersed, their auxin content — analysed by gas chromatography-mass spectrometry (GC-MS) — was lower in comparison to roots maintained in humid air. Such decrease in the IAA level was significantly enhanced in ABA treated roots. After 1 h incubation some IAA is detected in the incubation solution containing maize roots. Its concentration increases when intact roots immersed in that solution were incubated in the presence of ABA.