Radiation Protection by Calcium Gluconate and Recovery of X-Irradiated Conidia of Neurospora crassa

Abstract

Evidence has been presented that certain doses of x rays stimulate the germination of Neurospora crassa conidia. In some cases this took the form of an increased plating efficiency over that at zero dose; in others it was apparent as a reduced death rate of conidia in comparison with that observed after lower doses. The stimulation is superimposed on the destructive effect of the radiation which becomes apparent at higher doses. In addition to x rays, low temperature and pH treatment were found to stimulate the germination of conidia. It is thought that these effects may be interpreted in terms of changes in cell permeability brought about by a common mechanism. The presence of calcium gluconate (25 mg/ml) during x-irradiation and the subsequent incubation on minimal plating medium of Neurospora crassa conidia caused an increase in the proportion that germinated. Postirradiation leakage of phosphorus-32 was largely prevented, even when x-ray doses as high as 7200 r were used, by the presence of calcium gluconate in the distilled water in which the conidia were irradiated.