Effect of Oxygen on the Frequency of Chromosome Aberrations Produced by Alpha-Rays

Abstract

IN testing the hypothesis that the effect of ionizing radiations on the growth-rate of Vicia faba root tips is primarily due to the production of chromosome aberrations, we have shown¹ that X-irradiation under anaerobic conditions has a much reduced effect on growth, and that this is accompanied by a considerable reduction in the number of cells showing bridges or fragments at anaphase. We have now done an analogous experiment with alpha-radiation, using a modification of the method of Gray and Read² of immersing the roots in radon solution. Four graded doses were given to groups of eight beans in oxygen-free water, and four in water that contained 12 c.c. oxygen per litre. The mean growth of the groups of roots in the ten days following irradiation is plotted against dose in Fig. 1, together with comparable curves obtained after X-irradiation. We note that oxygen has a much greater influence on the effect of X-rays than on the effect of alpha-rays, the dose ratios for equal growth ‘without/with oxygen' being ∼ 2·5 and ∼ 1·3 respectively.