Under aseptic conditions, the surface-sterilized rhizome (2-3 cm long) had been cut into 3 parts (Figure 2). Only the top portion (number 1) was selected and excised into 4 equal pieces (a to d). Each section was then placed on Murashige and Skoog (MS) basal medium[13] supplemented with or without 2.5 mg/l BAP (6-benzylamino purine) in combination with 0 and 0.1% activated charcoal. These media had previously been adjusted to pH 5.7, solidified with 0.8% (w/v) agar, and autoclaved at 121 °C and 15 psi for 20 minutes. Cultures were incubated in a growth room under dark condition or 16 hours of illumination from daylight fluorescent lamps (26.50 μmol/m2/s light intensity) and 8 hours of darkness at 25±2°C. Data from 15 replications were collected for 4 weeks. For statistical analysis, a completely
randomized design (CRD) was employed in the experiments. Analysis of variance (ANOVA) was first performed at the significance level of P