RESUMO
The effect of sugars, gibberellic acid (GA3) and abscisic acid (ABA) on somatic embryogenesis from internodal explant-derived callus of Tylophora indica (Burm. f.) Merrill has been investigated. Embryogenic calli were produced from internodal explants and the best result was achieved by using MS medium supplemented with 4micromol/L 2, 4-Dichlorophenoxyacetic acid (2, 4-D). Up to 69% of such embryogenic calli differentiated into somatic embryos with an average of 25 embryos per explant (per gram of the calli) on Murashige and Skoog (MS) medium containing 6micromol/L kinetin (Kn). The individual effect of sucrose and glucose together with 6micromol/L Kn was evaluated. There was a significant difference among concentrations of sugar and among kinds of sugar tested in somatic embryogenesis. Sucrose at 200mmol/L with 6micromol/L Kn gave rise to a maximum embryogenesis (71%) with an average of 49 embryos per explant. However, glucose together with 6micromol/L Kn or a combination of glucose, sucrose and 6micromol/L Kn reduced the percentage of embryogenesis culture and the number of embryos per explant. The presence of GA3 and ABA at particular concentrations promoted somatic embryogenesis in T. indica. The addition of 10mol/L GA3 into the 200mmol/L sucrose-containing medium gave a 98% embryogenesis response with an average of 51 embryos per explant. Somatic embryogenesis was significantly enhanced by the addition of 2micromol/L ABA to 200mmol/L sucrose-containing medium. On this medium 95% embryogenesis with an average of 44 embryos per explant was observed. The study reported here indicates that 200mmol/L sucrose with 6micromol/L Kn, 200mmol/L sucrose with 10micromol/L GA3 and 200mmol/L sucrose with 2micromol/L ABA significantly improved somatic embryogenesis in T. indica whereas glucose alone or in combination with sucrose had an inhibitory role. The embryos obtained developed normally and were easily converted into plants.