Changes in the concentrations of auxins and polyamines during rooting of in-vitro-propagated walnut shoots

Abstract

Rooting was induced in in-vitro-propagated walnut (Juglans regia L.) shoots by subculturing the shoots on rooting medium containing agar and 3 mg l(-1) indole-3-butyric acid (IBA) for 7 days in darkness. Changes in the concentrations of endogenous free indole-3-acetic acid (IAA), indole-3-acetylaspartic acid (IAAsp) and free polyamines were determined during culture on root-inducing medium. In extracts of whole shoots, the concentration of free IAA showed a transient peak at 60 h (around 48 h in extracts from basal shoot portions) and then remained at a relatively low concentration for the remainder of the 7-day culture period. The concentration of IAAsp in extracts of whole shoots peaked at about the same time as the concentration of free IAA, whereas the IAAsp concentration in extracts from basal shoot portions peaked earlier, at around 12 h. The concentrations of free polyamines in extracts of whole shoots increased soon after the shoots were transferred to root-inducing medium. The concentrations of IAA and IAAsp remained stable when the rooted shoots were transferred to a vermiculite/gelrite mixture (without auxin) and grown in light.