Effects of-fast Neutron Versus X-irradiation on Development, Differentiation and Peroxidase Isozymes in a Genetically Tumorous<i>Nicotiana</i>Amphiploid and Its Parents

Abstract

SummaryThe relative biological effectiveness of fast (fission) neutrons versus 250 kVp x-rays was determined for three genotypes–Nicotiana suaveolens N. langsdorffii, and their tumour-prone amphiploid–on the basis of four criteria: cotyledon emergence, leaf development, tumorization, and peroxidase isozymes. These very different responses monitored a range of absorbed doses; and the magnitude of the RBE values, which varied from 3·9 to 14·3, was inversely related to dose. This relationship could be expressed by the linear regression log N − 1·4 + 1·3 = log X, the significance of which is discussed. None of the dose-response curves was exponential; the slope of the linear part was related to interphase chromosome volume.