The Influence of Temperature on Radiation-Induced Oxygen-Dependent and -Independent Damage in Barley Seeds

Himalaya barley seeds of 10.0% water content were subjected in vacuo to various exposures of60 Co gamma rays at different temperatures ranging from -78 to 50°C. In one set of experiments the seeds were soaked immediately after irradiation in either oxygenated or oxygen-free water at 0°C. In another series of experiments the seeds were stored in vacuo for various periods of time at different temperatures before soaking. Changes in free radical signal during postirradiation storage under comparable conditions were measured by EPR in one experiment. The oxygen enhancement ratio (postirradiation oxygen effect induced by soaking seeds in oxygenated or oxygen-free water after irradiation) was greatest in seeds irradiated at lower temperatures and decreased as the irradiation temperature was increased until there was no observable oxygen-effect (OER = 1) if the seeds were irradiated at 50°C. Although oxygen-dependent damage decreased with increasing irradiation temperature, oxygen-independent damage increased. A...