The effect of abscisic acid (ABA) and 3,5-diiodo-4-hydroxy-benzoic acid (DIHB) on elongation and geotropic development of lettuce and cress roots

Abstract

Summary The elongation and the course of the geotropic curvatures in roots of lettuce ( Lactuca sativa L. cv. Grand Rapids) and cress ( Lepidium sativum L.) has been followed in white light and darkness at 21°C after exogenous application of 0.1 mM DIHB and/or different concentrations of cis-trans-DL-ABA. In both species of untreated (control) plants significantly larger curvatures were observed in the roots stimulated in light than in darkness. There was a large difference in the elongation of cress roots kept in light and darkness whereas elongation of lettuce roots was only slightly dependent on light conditions. Application of 0.1 mM DIHB increased the curvature and the rate of elongation of lettuce roots independent of the light conditions. Exogenously applied 0.1 mM DIHB showed an inhibitory effect on the development of geotropic curvature of cress roots. The elongation rate was not significantly influenced. ABA was found to reduce both the rate of root elongation and the development of geotropic curvature in lettuce roots. Both inhibitions were counteracted by DIHB.