ENDOGENOUS AUXINS, IAA-OXIDASE AND ROOTING IN Vigna radiata L. Wilczek INDUCED BY EXOGENOUS FREE AND CONJUGATED AUXIN

Abstract

Plant regeneration of special phenotypes has a critical phase in adventitious rooting, which is promoted by auxin treatment. Avalilability of free auxin plays an important role in plant development; auxin conjugation-deconjugation and oxidative degradation have an influence on it. No report was found in which synthetic auxin conjugates had been evaluated for promoting changes in endogenous auxin during rooting. This study analized the auxin content in plant cuttings after administration of indole-3-acetil-p-nitrophenyl ester (IAP) (a synthetic auxin-conjugate). The effect of exogenous auxins indole-3-acetic acid (IAA), indole-3-butyric acid (IBA) and IAP on endogenous levels of IAA and IBA, in three different seedling sections and on IAA-oxidase activity, were compared during the first 6 d of adventitious root formation in Vigna radiata L. Wilczeck. Endogenous IAA level increased significantly on the 3rd day of rooting induction in all treatments, specially in the apical section, with the exception of IAP which only induced a slight increase. IAA-ox activity reached the highest rate at day 3 and then became reduced gradually to day 6. The highest adventitious rooting was obtained with IAP, and the lowest with IAA.