We have studied rooting of 1-mm thick apple stem slices in relation to indoleacetic acid (IAA) depletion of the medium. When slices were cultured in the dark close to one another on a 3-mm thick medium (20 ml in a 9-cm Petri dish), the IAA concentration in the medium beneath the slices dropped to 20 % of the initial concentration during the first day of culture. This was due to uptake, enzymatic oxidation and slow replenishment from medium in other areas of the Petri dish. Because of depletion, the rate of IAA uptake decreased with time. When medium was renewed daily, the rate of IAA uptake remained the same. When the slices were cultured scattered over the Petri dish or on a thick layer of medium (6-mm instead of 3-mm thick), they took up more IAA. As could be expected, differences in uptake amongst the various conditions (slices cultured scattered or close to one another; 20 or 40 ml of medium) were small during the first day of culture but large after that. Because the rhizogenic action of IAA occurs not immediately at the start of culture but later (viz., from 24 to 72 h after the start of culture; DE KLERK et al., 1995; J. Exp. Bot. 46, 965-972), rooting at the various conditions corresponded closely to the amount of IAA taken up from 24 to 72h. Since the various incubation conditions resulted in the same maximal root number (but at different IAA concentrations), there was only depletion of the medium with respect to IAA.
|Number of pages||5|
|Journal||Journal of Applied Botany|
|Publication status||Published - Nov 1997|