Hormone effects on in vitro proliferation and rooting of Grevillea explants

Explants of Grevillea rosmarinifolia A. Cunn. and Grevillea x semperflorens RE. Brigs ex. Mullig., obtained from vegetative stem segments, were grown on a modified MS medium, which was supplemented with different contents of cytokinins (BA or K) to evaluate optimal conditions for bud proliferation. Auxins (NAA or IBA) were tested to evaluate rooting. The multiplication rate was often higher in G. rosmarinifolia than in G. x semperflorens. Explant activity varied significantly depending on the cytokinin type and its concentration. The addition of cytokinins to the culture medium often promoted an increase in the number of shoots produced by each propagule, but at the highest BA concentration, shoot differentiation was inhibited in Grevillea x semperflorens. Only the higher concentrations studied (5-10 mg/l) produced better results with K, whereas BA was more effective at 1-2 mg/l. Rooting efficiency of the young shoots was lower in G. rosmarinifolia. than in G. x semperflorens. IBA promoted root development in both species and was more effective at the highest concentration (1 mg/l). NAA gave better results at low concentrations (0.2 mg/l) in G. rosmarinifolia, while it had slight or negative effect on rooting of G. x semperflorens. (C) 2001 Elsevier Science B.V. All rights reserved.