DIFFERENTIAL REPAIR OF GAMMA-INDUCED LESIONS IN GERMINATING BARLEY-SEEDS

To aid our analysis of the repair process during the germination period, the potentiating effects of 2,4-dinitrophenol, chloramphenicol and caffeine on γ-ray-induced seedling injury, chromosomal abberation and M2 chlorophyll mutation were studied in resting and germinating barley seeds. Caffeine post-treatment was most pronounced with regard to the enhancement of growth reduction, and significantly increased the frequencies of chromosomal aberrations in the seeds that were irradiated after 2 h of soaking. However, the other two compounds had limited effect on these parameters. After the respective post-treatments, the yield of mutations significantly increased in the sees pre-soaked for 0-4 h, and the ratio of albina mutants to the other types of mutant was reduced to about half in seeds pre-soaked for 0 and 2 h. The post-treatments did not produce any marked change in incorporation of [3H]thymidine into the DNA of germinating embryos, but merely delayed the onset of its incorporation, compared with the effect of γ-irradiation alone. From the differential extents of potentiation of the compounds used, as influenced by the metabolic status of irradiated seeds, it is concluded that physiological reversion, which starts to act soon after the initial water uptake and continues up to the S-phase in the first mitotic division, affects the subsequent repair process of induced lesions. © 1979.