Relative Biological Effectiveness of Fission Neutrons for Producing Micronuclei in the Root-tip Cells of Onion Seedlings after Irradiation as Dry Seeds

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The relative biological effectiveness (RBE) of mixed neutron and gamma-ray radiation emitted at a ^<252>Cf source at the Research Institute for Radiation Biology and Medicine, Hiroshima University, compared with ^<60>Co gamma-ray radiation was determined. The tissueabsorbed dose contribution of the accompanying gamma radiation was about 35.7% to the total tissue-absorbed dose from the ^<252>Cf mixed radiation. The ^<252>Cf mixed radiation and ^<60>Co gamma rays produced approximate linear changes in the frequency of micronuclei induced in root-tip cells of Allium cepa L. onion seedlings after irradiation as dry dormant seeds with varying absorbed doses in onion seeds. Therefore, the RBE for radiation-induced micronuclei was calculated as the ratio of the slopes for the ^<252>Cf mixed radiation and the ^<60>Co gamma rays. The deduced RBE value of ^<252>Cf mixed radiation to ^<60>Co gamma rays to induce micronuclei in dry dormant onion seed cells was about 90.5±3.6 (±1σ); the RBE of neutrons from the ^<252>Cf mixed radiation was about 150±6 (±1σ). Furthermore, the sensitivity ratio of the induction rate of micronuclei in dry dormant seeds to that in seedlings by neutrons from ^<252>Cf mixed radiation was significantly different from that by ^<60>Co gamma rays. From these results, we concluded that the repair efficiency of DNA damage induced by neutrons may be different from that by gamma rays.
日本放射線影響学会の論文