IN-VITRO REGENERATION OF SILKTREE (ALBIZZIA JULIBRISSIN) FROM EXCISEDROOTS

Root segments (1 cm long) were excised from 15-20 day old seedlings of silktree (Albizzia julibrissin) grown on B5 medium. About 50% of the control (no growth regulators added) root explants formed shoot buds w ithin 15 days after placement on the culture medium. After 30 days, th ere were about 4 shoots per control explant. Addition of low levels of various auxins (0.5 mu M) did not influence the formation of shoot bu ds from the explants. Higher concentrations (5 mu M), however, decreas ed shoot regeneration. Kinetin and 2iP did not influence shoot regener ation at the concentrations tested (1 & 10 mu M). Addition of benzylad enine, Zeatin, or thidiazuron to the culture medium increased both the percentage of explants that formed shoots and the number of shoots pe r explant. Thidiazuron was highly effective in stimulating shoot forma tion at low concentrations (<1 mu M). At 0.05 mu M thidiazuron, 95% of the explants produced shoots and about 10 shoots were formed per expl ant. Compared to TDZ, higher concentrations (10 mu M) of benzyladenine and Zeatin were required to enhance shoot formation. Upon excision an d transfer to B5 medium, regenerated shoots developed into normal root ed plantlets.