Studies of the dependence on energy of the biological effects of fast neutrons. II. Survival of spores of Aspergillus niger and Funaria hygrometrica and a microdosimetrical comparison of these effects in other plant materials

Abstract

A comparison was made between the biological effects of 3·4-MeV and 14·7-MeV neutrons. The investigated effects were the survival of Aspergillus niger and Funaria hygrometrica spores. The neutrons were produced by the reactions 2H(d,n)3He and 3H(d,n)4He using a 600-keV cascade accelerator. The constant reactivity k of the exponential part of the dose effect curves was used as measure of biological effectiveness R(E) (E=neutron energy in MeV). The energy dependence of the neutron effects has been described as the ratio of the effectivenesses for the two neutron energies R(14·7)/R(3·4). The numerical values of this ratio are: 0·63 and 0·35 for the survival of Aspergillus niger and Funaria hygrometrica respectively. These ratios—as well as the ratios R(14·7)/R(gamma) —deviate appreciably from the corresponding values for growth inhibition and induction of chromosome aberrations in Hordeum and Vicia faba, reported in our previous paper. This object dependence can be slightly clarified with very simple suppositions, if the event frequency integrals according to Rossi were applied to microvolumes comparable in size to essential biological structures.