RESPONSE OF POTASSIUM RETENTIVITY AND SURVIVAL OF YEAST TO FAR-ULTRAVIOLET, NEAR-ULTRAVIOLET AND VISIBLE, AND X-RADIATION

Potassium retentivity and survival of yeast were studied after exposure to various kinds and conditions of irradiation. The radiations used were: 2537 A ultraviolet, 3500 to 4900 A long-ultraviolet and short visible, and 250 kvp(1) x-rays. Both potassium retentivity and survival are decreased by these radiations. The dose-response of survival is about 16 times as sensitive as is potassium retentivity after 2537 A irradiation. Potassium retentivity is about twice as sensitive as survival after irradiation of 3500 to 4900 A. Survival after x-irradiation under aerobic conditions is five times as sensitive as potassium retentivity. Survival of cells irradiated with x-rays under anaerobic conditions was about half as sensitive as under aerobic conditions. The response of potassium retentivity to x-radiation at 25°C. under anaerobic conditions is only slightly affected below 160 kr, at which dose the slope abruptly increases to that obtained under aerobic conditions; lowering the temperature to 0°C. moves this point to about 300 kr. These differential effects are indicative of interaction of radiations with the yeast cell at sites that independently control survival and the retention of potassium.