Radiation-induced Organogenesis and Isoenzyme Patterns in Long-term Callus Cultures of Datura innoxia

Abstract

Effect of gamma irradiation on growth, shoot organogenesis and enzyme activities and isoenzyme patterns of α-amylase and peroxidase during differentiation in long-term calluses of Datura innoxia have been investigated. Radiation in doses of 0.2 and 1.0 kR stimulated the shoot regeneration frequency as well as the number of shoots per regenerating callus. The 0.2 kR dose could induce shoot organogenesis even in calluses incubated in the dark on callusing medium, although with less frequency. Such cultures, however, showed profuse shoot regeneration when sub-cultured onto regeneration medium under light conditions. A higher radiation dose (5.0 kR) was lethal to both growth and shoot differentiation. Prior to shoot regeneration, α-amylase and peroxidase specific activities increased to four- to fivefold and 7–24-fold, respectively. While the amylase isoenzyme pattern remained unchanged, specific changes in the isoperoxidase pattern were observed during shoot differentiation in callus cultures. The most significant change was the appearance of fast-moving anodic bands prior to visible shoot differentiation. Thus, such isoperoxidases provide useful biochemical markers for shoot differentiation.