Abstract
The present study was designed to investigate the stimulatory effects of different doses (0.1 to 2.5 mu M) of thidiazuron (TDZ) on in vitro shoot induction and proliferation of mature nodal explants of Tecoma stans. Of the tested concentrations, 2.0 mu M TDZ proved to be optimal for maximum regeneration (91%) with a mean shoot number of 5.6 +/- 0.67, and length of 2.38 +/- 0.08 cm, after 4 wk of incubation. To determine the negative effects of prolonged TDZ exposure, after 4 wk of incubation at optimized level of TDZ, the cultures were transferred to a secondary medium either lacking plant growth regulators or supplemented with benzyladenine (BA) alone, or in combination with different auxins (indole-3-acetic acid, indole-3-butyric acid, or alpha-naphthalene acetic acid; NAA). Among the tested concentrations, 2.5 mu M BA in combination with 0.5 mu M NAA yielded the maximum mean shoot number (16.60 +/- 0.40), and average shoot length (4.76 +/- 0.15 cm) after 4 wk of culture. The best rhizogenesis (93%) was achieved on 1/2 MS medium containing 1.5 mu M NAA, with a mean root number of 7.60 +/- 0.40 and length of 4.11 +/- 0.23 cm, after 4 wk of incubation. The micropropagated plantlets were successfully acclimatized and hardened off in Soilrite (TM) with a 90% survival rate. The plantlets grew well with normal growth, flowering and showed, by gas chromatography-mass spectroscopy, an increase in the number of bioactive compounds compared with the donor plant. This is the first report on T. stans in vitro regeneration using TDZ.