Effects of colchicine on survival rate, morphological, physiological and cytological characters of chang daeng orchid (Rhynchostylis gigantean var. rubrum Sagarik) In Vitro

2in comparison with control plantlets. The average number of chloroplasts obtained in tetraploid plantlets was 46 chloroplasts/guard cells, which lower than those of diploid plants. This evident indicated a negative correlation between chloroplast number and ploidy level. Morphological characters of tetraploid plantlets had higher average number of leaves than those of control. In case of root length, tetraploid plantlets was significantly lower than that of control. Cytological observation of root tip revealed that tetraploid plantlets had chromosome number (2n=4x=76) two times higher than those of control (2n=2x=38).