Postirradiation Hypoxia and the Recovery of G 1 and G 2 Cells and DNA Synthesis in Cultured Root Meristems

Abstract

Recovery after 300 Rγ rays by G1 and G2 stationary phase meristematic cells of cultured pea roots was measured under aerobic and hypoxic culture conditions. The recovery indices used were the initiation of DNA synthesis by former G1 cells, the rate of DNA synthesis when the G1 cells were subsequently in S, and the appearance of G2 cells in mitosis. The results showed that G1 and G2 cell recovery was confined to the period occupied by the cell at the time of irradiation and that the subsequent transit of S and G2 was performed at rates equivalent to that of the un-irradiated control. They also revealed that the duration of delay was equal for G1 and G2 cells when the postirradiation conditions were aerobic. When the postirradiation conditions were hypoxic, the recovery of G1 cells was not impaired while that of the G2 cells was greatly reduced. DNA synthesis by former G1 cells generally reflected the extent of recovery determined cytologically. The one exception was an unusually accelerated3 H- T incorpora...