The ultraviolet radiosensitivity of Oedogonium cardiacum cells at various stages of the cell cycle

Abstract

The ultraviolet (UV) radiosensitivity as measured by the loss of reproductive capacity of synchronously growing Oedogonium cardiacum cells cultured under different environmental conditions has been measured during the first generation cycle and compared to the results for ionizing radiation. Both radiosensitivity patterns were approximately the same in shape exhibiting a maximum resistance in the S period and a minimum in the G 2 . Following X-radiation, D 0 and n values varied with age by a factor of 7 and 40 respectively. In contrast, following UV-radiation D 0 varied by a factor of 2·5 and n remained essentially constant. A variation in the magnitude of the UV radiosensitivity was observed between cells cultured in inorganic medium bubbled with 3% CO 2 in air and illuminated with fluorescent lights and cells cultured in diphasic soil-water medium under natural illumination. At all stages of the cell cycle, cells collected from stock cultures grown in the more natural habitat were approximately twice as resistant. A seasonal variation in UV radiosensitivity was also observed in cells collected from this latter group.