EFFECT OF INDOL-BUTIRIC ACID (IBA) AND TYPE OF CUTTING ON ROOTING OF Gmelina arborea Roxb.

Abstract

In order to develop an operational vegetative propagation system for Gmelina arborea Roxb., a tree species with broad potential for commercial plantings in the tropics, the effect of indol-butiric acid (IBA) level on rooting capacity of several juvenile cutting types of this species was evaluated. Three cutting positions (apical, intermediate, and basal) and four IBA levels (0, 1.0, 1.5 and 2.0 mg g^-1) arranged in a factorial design were included in this trial; initial carbohydrate content of cuttings, as well as rooting and sprouting capacity, and number and length of roots formed, were determined. Apical cuttings showed higher rooting (71.8 %) and sprouting (54.9 %) capacity than the basal ones (43.7 and 38.3 %, respectively), with 30 % more roots formed. IBA application inhibited rooting capacity of apical cuttings, but stimulated it on intermediate and basal cuttings; the highest rooting percentage was obtained on apical cuttings without IBA (80 %) and on intermediate cuttings with 2.0 mg g^-1 IBA (83 %). No significant differences in carbohydrate content were found among cutting types. An effective clonal propagation system for Gmelina arborea can be established (over 80 % rooting capacity) if the adequate level of IBA is applied to basal and intermediate cuttings.