Culture media and growth conditions The culture medium consisted of MS (Murashige and Skoog’s,1962) salts, vitamins, 3% (w/v) sucrose and the pH of the mediawas adjusted to 5.6 with 0.1 N NaOH or HCl before adding 0.7%(w/v) agar. Media (15 ml) were poured into 25 mm × 150 mm culture tubes (Borosil, Mumbai) and autoclaved at 121◦C for 15 min.The cultures were maintained at 24 ± 2◦C under 16/8 h (light/darkcycle) photoperiod (60 E m−2s−1) and irradiance provided bycool-white fluorescent tubes (Philips, India).