In Vitro Micropropagation and Conservation of Rhynchostylis retusa BL.

Micropropagation of the endangered orchid, Rhynchostylis retusa, was conducted through culture of thin root section, thin leaf section and seedling. When the three different explants were cultured on half strength Murashige and Skoog (1/2 MS) medium containing thidiazuron (TDZ) alone or in combination with naphthalene acetic acid (NAA) and activated charcoal (AC), only seedlings promoted shoot and root formation while other explants did not respond at all. Combinations of higher concentrations of NAA and lower concentrations of TDZ gave superior shoot and root formation. The best response was recorded on the medium containing 1.0 ㎎?L -1 NAA and 1.1 ㎎?L -1 TDZ. Seedlings cultured on the medium containing 0.1 ㎎?L -1 6-benzylaminopurine (BA) and AC (1 g?L -1 ) showed distinctly superior growth response to those without AC. AC could show stimulatory effect on growth of this species. About 3-cm-height plantlets with well-developed roots were successfully acclimatized in the green house. Chromosome number of the in vitro plantlets was revealed as 2n=2X=38.