INHIBITORY EFFECT OF GA(3) ON THE DEVELOPMENT OF THIDIAZURON-INDUCED SOMATIC EMBRYOGENESIS IN GERANIUM (PELARGONIUM X HORTORUM BAILEY) HYPOCOTYL CULTURES

Somatic embryogenesis in geranium (Pelargonium x hortorum Bailey cv 'S carlet Orbit Improved') can be achieved by incubating hypocotyl explan ts on MS medium supplemented with thidiazuron (TDZ; 10 mu M) for 3 day s followed by subculture on medium devoid of any plant growth regulato rs. The presence of gibberellins (GAs) during both the induction and e xpression phases of embryogenesis was significantly detrimental to som atic embryo formation on the hypocotyl explants. The addition of the G A-synthesis inhibitors paclobutrazol, uniconazole or ancymidol during the period of growth and differentiation of somatic embryos increased the number of somatic embryos formed on each explant. However, paclobu trazol added during the period of induction had no significant influen ce on somatic embryo formation. Results suggest that both exogenously supplied as well as endogenous GAs play a role, albeit a negative one, on somatic embryogenesis of geranium.