MODIFICATION OF RADIATION-INDUCED INJURY BY POSTTREATMENT WITH OXYGEN

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Abstract
It has been demon-strated in a wide range of biological systems that the presence of oxygen during treatment with X-radiation enhances the degree of detectable injury over that which is observed when organisms are maintained anoxic during treatment. The present report describes conditions under which radiation initiated injury to dry dormant barley seeds may be modified by postradiation hydration in the presence of oxygen. Seeds of Himalaya barley with either 4 or 16% water in the embryo were subjected to various doses of X-radiation and then hydrated in the presence of either oxygen or nitrogen for different periods of time. Subsequently they were grown in Petri dishes for 6 days, at which time seedling height measurements were made. On the basis of these measurements, the seeds with the lowest water content at the time of irradiation evidenced a striking sensitivity to postirradiation hydration in the presence of oxygen. In contrast to this, the seeds with the highest water content evidenced no injury modification that could be attributed to the conditions of hydration. Seeds with the same two water content levels that were subjected to thermal and fast neutron bombardment did not show postirradiation sensitivity to aerobic and anaerobic hydration. The data presented support the view previously expressed, viz., that hydrogen peroxide and free radicals cannot account for significant radiation-induced injury to seeds. Apparently what is of concern is whether or not restoration of radiation-induced lesions to a stable state takes place before oxidation occurs at the site of the lesion.