Changes in peroxidase activity,auxin level and ethylene production during root formation by poplar shoots raised in vitro

Shoots of poplar (Populus tremula × P. tremuloïdes) were multiplied in vitro and rooted on a rooting medium in the presence of NAA. No rooting occurred in the absence of exogenous auxin. A peak of soluble peroxidase activity, which corresponded to a decrease in the free IAA level in the shoots, preceded rooting These events were considered as corresponding to the initiative phase of rooting. They are preceded by a peak in free IAA activity which might initiate the inductive phase of the rooting process. A burst of ethylene production was measured in both rooting and non-rooting shoots, but the ethylene peak from rooting shoots appeared earlier and was higher. The use of ACC indicated that the exogenous auxin might have enhanced ACC-synthetase activity.Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - NAA naphthaleneacetic acid - IAA indole-3-acetic acid - 2-iP 2-isopentenyladenine - IAAsp indole-3-acetylaspartic acid - IBA indole-3-butyric acid - GC gas-chromatography