Effects of GA3, ancymidol, cycocel and paclobutrazol on direct somatic embryogenesis of Oncidium in vitro

To study the effects of GA(3), ancymidol, cycocel and paclobutrazol on direct somatic embryogenesis, 1-cm-long leaf tip segments of Oncidium 'Gower Ramsey' have been cultured in vitro on a modified 1/2-MS basal medium (BM). The embryogenic responses were scored at four regions, leaf tips, adaxial sides, abaxial sides and cut ends, of leaf explants. GA(3) at 0.1-10 mg l(-1) significantly retarded direct embryo formation on leaf tips, adaxial sides and cut ends. Low concentrations of ancymidol (0.1-2.5 mg l(-1)) significantly promoted direct embryo formation on leaf tips. The higher concentration of ancymidol (10 mg l(-1)) significantly retarded direct embryo formation. Low concentrations of cycocel (0.1 - 2.5 mg l(-1)) significantly retarded direct embryo formation on adaxial sides of leaf tips, but had no significant effects on abaxial sides and cut ends. Higher concentrations of cycocel (5 - 10 mg l(-1)) significantly retarded direct embryo formation in all regions. Paclobutrazol (0.1 - 10 mg l(-1)) significantly promoted direct embryo formation on cut ends, and the embryogenic response of leaf tip regions was enhanced by 5 and 10 mg l(-1) paclobutrazol. The embryo numbers per dish was significantly retarded by 0.1 - 10 mg l(-1) GA(3), 10 mg l(-1) ancymidol and 0.1 - 10 mg l(-1) cycocel, but significantly promoted by 2.5 mg l(-1) ancymidol and 2.5 - 10 mg l(-1) paclobutrazol. Paclobutrazol at 10 mg l(-1) gave doubling of embryo numbers (193.2) per dish compared to the control treatment (89.4) after 8 weeks in culture.