CHANGES IN PEROXIDASE-ACTIVITY, AUXIN LEVEL AND ETHYLENE PRODUCTION DURING ROOT-FORMATION BY POPLAR SHOOTS RAISED IN-VITRO

Shoots of poplar (Populus tremula x P. tremuloides) were multiplied in vitro and rooted on a rooting medium in the presence of NAA. No rooti ng occurred in the absence of exogenous auxin. A peak of soluble perox idase activity, which corresponded to a decrease in the free IAA level in the shoots, preceded rooting These events were considered as corre sponding to the initiative phase of rooting. They are preceded by a pe ak in free IAA activity which might initiate the inductive phase of th e rooting process. A burst of ethylene production was measured in both rooting and non-rooting shoots, but the ethylene peak from rooting sh oots appeared earlier and was higher. The use of ACC indicated that th e exogenous auxin might have enhanced ACC-synthetase activity.