The Influence of Auxin, Catechol and Methanolic Tissue Extracts on Root Initiation in Aseptically Cultured Shoot Apices of the Juvenile and Adult Forms of Hedera helix1

There is very little rooting response of juvenile shoot apices to indole-acetic acid (IAA) at concentrations from 1 to 50 mg/liter when the light intensity is 400–500 ft-c. Naphthalene-acetic acid (NAA), however, promotes rooting very markedly with an optimum at 5 to 10 mg/1. There is a strong synergism between IAA at 10 mg/1 and catechol at 5 × 10 −5 M which results in a rooting response equal to that obtained with NAA at its optimum concentration. In low intensity light (50 ft-c) IAA is nearly as effective as IAA + catechol in high light. Rooting of adult apices in high intensity light is essentially zero using IAA, NAA or combinations of these auxins with catechol. In low intensity light rooting occurs using 10 mg/1 IAA and there is a marked synergism between IAA and catechol. The rooting response of adult tips in low intensity light is very similar to that of juvenile shoot tips in high intensity light. Three fractions of methanolic extracts of adult and juvenile shoot tissue promote rooting of juvenile shoot apices in high intensity light. Rooting of adult apices is not affected by these or other fractions.