DIFFERENTIAL CYTOKININ EFFECTS ON THE STIMULATION OF IN-VITRO SHOOT PROLIFERATION FROM MERISTEMATIC EXPLANTS OF CASTOR (RICINUS-COMMUNIS L)

A highly efficient and reproducible method of in vitro propagation usi ng meristematic explants has been developed for castor. Embryo axes an d shoot tips were cultured on Murashige and Skoog (MS) medium suppleme nted with 0.5-10.0 mg/l of adenine, N-6-benzyladenine (BA), kinetin (K n), thiadiazuron (TDZ) and zeatin. TDZ (1.0-10.0 mg/l) gave the maximu m number of shoots (37.8-40.0) from embryo axes, while BA (2.0 mg/l) w as found superior to other cytokinins for obtaining the highest number of shoots (46.7) from the shoot apex. Adenine and Kn at all of the te sted concentrations resulted in low proliferation rates from embryo ax es. The carryover effect of the cytokinins was tested by subculturing proliferating shoot cultures from various media onto the medium fortif ied with 0.5 mg/l BA. There was no significant influence of the cytoki nins on subsequent proliferation from the two explant types except for TDZ with embryo axes. The number of shoots from TDZ-habituated embryo axes ranged between 36.0 and 81.7, while it varied from 5.7 to 22.0 a nd 3.7 to 28.3 in axillary buds and embryo axes, respectively, on the other media. For elongation of shoots, gibberellic acid (GA(3)) (0.1-1 .0 mg/l) was added to the medium supplemented with 0.2-0.5 mg/l BA. In corporation of GA(3) (0.1 mg/l) significantly enhanced the frequency o f elongated shoots but drastically reduced the multiplication ability. Hence, proliferating shoot clusters were periodically transferred to the medium supplemented with 0.5 and 0.2 mg/l BA for further multiplic ation and elongation. Well-developed shoots were rooted on half-streng th MS medium supplemented with 1.0 mg/l indole-3-butyric acid. The roo ted plantlets were acclimatized with more than 60% success.