The radio-protective role of gibberellic acid on nucleic acid metabolism in three species of senna

The response of three species of senna, namely Cassia occidentalis, Cassia senna and Cassia italica, to gamma (γ) irradiation treatment (0, 20, 40, 60, 80 krad) and to gibberellic acid (GA 3 ) post-treatment (20 ppm) was investigated with respect to nucleic acid metabolism. Gamma irradiation induced a significant decrease in the level of nucleic acids (DNA and RNA) accompanied by a corresponding induction of hydrolytic activities of DNase and RNase in the developed seedlings in comparison with un-irradiated control. Those changes were more significant at higher γ-ray doses. Post-treatment of irradiated seeds with GA 3 partially alleviated the adverse effects of radiation. It significantly increased nucleic acid levels and repressed the activities of DNase and RNase. The protective role played by GA 3 was more significant at lower γ-ray doses. The three investigated species expressed a differential response to γ-irradiation and to GA 3 post-treatment. The detrimental effects of irradiation on nucleic acid metabolism and the ability of GA 3 in counteracting the adverse effects of irradiation are discussed.