Abstract
The effects of gamma radiation and monochromatic lights on growth of in vitro shoot cultures of orchid, Dendrobium sonia, were investigated. The gamma irradiated shoot cultures grown under white, blue, yellow and red monochromatic lights exhibited differential growth pattern. Shoot cultures gamma irradiated at 15-45 Gy showed reduced shoot length, fresh weight and leaf area. The monochromatic light significantly influenced survival rate and growth of irradiated shoots. The yellow and red light treatments positively influenced survival of gamma irradiated shoots with significant increase in fresh weight, shoot length and chlorophyll content. Yellow light was found to be most effective as leaf area was increased across the radiation dose range (15-100 Gy) compared to red light. The results demonstrated that the method of post-irradiation exposure could be useful to improve growth of gamma irradiated in vitro shoots, and help to recover orchid mutants with novel modifications.