Relative biological effectiveness of alpha particles and protons varies with biological criteria, and values are mutually correlated in thermal neutron exposure

Abstract

We recently presented a method for simultaneous estimation of relative biological effectiveness (RBE) of alpha particles and protons. Here, we evaluate RBE for chlorophyll mutation rate and four M₁ effects in thermal neutron exposure of barley (Hordeum vulgare L.) seeds. RBEs of both alpha particles and protons were low for germination rate, seedling height, and number of spikes, and high for seed fertility and mutation rate. Thus, M₁ effects are not necessarily accurate as a proxy for mutation rate in comparisons of different types of radiation. RBE of alpha particles for mutation rate was 130.3, much higher than values so far reported in plant materials. RBE of protons for mutation rate was 106.4; as far as we are aware, this is the first value reported for thermal neutron exposure of plant materials. RBEs of alpha particles and protons were significantly correlated (r = 0.939, P < 0.05).