Growth inhibition in cereal seedlings induced by gamma irradiation at different oxygen tensions

Abstract

The reaction of barley and rye seeds to anaerobic and aerobic γ-irradiation was studied, with special emphasis on such properties where the action of neutrons has been found qualitatively different from that of (aerobic) γ-or X-irradiation. The reaction of anaerobic γ-irradiation was found similar to that of neutrons, and unlike that of aerobic γ-irradiation, in the following respects: (a) a more linear dose dependence of the radiation induced growth inhibition of seedlings; (b) a relatively greater inhibition of root growth; (c) a smaller variation of seedling heights; the coefficient of variation of seedling height following anaerobic γ-irradiation or neutron irradiation is equal to that of the unirradiated control samples; after aerobic γ-irradiation (in air or in high pressure oxygen) the coefficient of variation at 50 per cent growth reduction is 2–3 times the control value; (d) no influence of the water content of the seeds on their radiation sensitivity, within the range of water contents investigated (6–20%) (indicated in comparison of different experiments). The findings are discussed in the light of investigations of especially H oward-F landers (19) and C aldecott (6), demonstrating that in the absence of oxygen, the γ-irradiation is active exclusively through high LET segments of the total track length, i.e. chiefly through δ-rays. RBE of fission neutrons relative to anaerobic γ-radiation is found to be around 50.