The effect of leaf and shoot tip removal and explant orientation on axillary shoot proliferation of Codiaeum variegatum Blume var. pictum Muell. Arg. cv. Excellent

Abstract

The removal of all developed leaves from 1 to 1.5 cm shoots of Codiaeum variegatum Blume var. pictum Muell. Arg. ‘Excellent’, cultured on the Murashige–Skoog medium containing 4.4 μM (1 mg l −1) 6-benzylamino-purine (BAP) and 5.8 μM (2 mg l −1) gibberellic acid (GA 3), doubled the number of axillary shoots in comparison to non-defoliated controls. An additional increase in shoot numbers was achieved when the shoots were placed on the medium horizontally or vertically in an inverted position with the shoot tip down. Shoot tip removal slightly improved axillary branching, and additional defoliation strengthened this effect. Exogenous indole-3-acetic acid (IAA) decreased shoot numbers, and 2,3,5-triiodobenzoic acid (TIBA) did not replace defoliation nor diminish the size of callus formed at the base of the shoots. Almost all the shoots obtained were able to root on the medium with 4.9 μM (1 mg l −1) indole-3-butyric acid (IBA), and acclimatize in the greenhouse.