RESUMEN
Effects of gamma radiation on physiological responses of the M1 sainfoin plants were investigated. Seeds of sainfoin ecotype 'Koças' were exposed to 0, 400, 500 and 600Gy from a 60Co source at a dose rate of 0.483 kGyh-1. Irradiated and unirradiated seeds were sown into culture vessels containing MS-basal medium to be cultured for 30 days under in vitro conditions. At the end of this period, seedlings, which germinated from the radiated and unirradiated seeds, were transferred into pots in a growth chamber for 30 days more. Chlorophyll contents, activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR), as well as contents of monodehydroascorbate reductase (MDA) and proline were examined in unirradiated and irradiated 60-day-old seedlings. Overall, the activities of the antioxidant enzymes (SOD, CAT and GR) and contents of chlorophyll and proline in the leaves tended to increase after irradiation in a dose-dependent manner. By contrast, the activity of APX decreased. The lipid peroxidation characterized by the MDA content remained unchanged, except after irradiation to 500Gy. The highest CAT activity and the highest proline content were observed after irradiation to the highest dose of 600Gy. The highest SOD and GR activities were observed after irradiation to the lowest tested dose of 400Gy. This is the first study that provided basic information on the impact of gamma radiation on physiological responses of sainfoin and its radiosensitivity. These findings will be useful in development of a mutation breeding program of sainfoin.