| Chromosome aberrations in Einkorn wheat induced by
X-rays By Seiji MATSUMURA National Institute of Genetics, Misima With regard to the relation between the frequency of chromosome aberrations in the PMC's of Triticum monococcum and the dose or wave length of X-rays, the same materials reported by MATSUMURA and FUJII in the foregoing paper were used, and the results of previous experiments at 30-90 KVP (MATSUMURA 1951) have been confirmed. The data are shown in Table 1, The frequency of ears with chromosome aberrations (mostly reciprocal translocations) increases with X-ray dose. It is also fairly certain that the shorter the wave length of X-rays, the higher the frequency of chromosome aberrations. These facts can be again explained on the basis of the difference in the distribution of ionization within the nuclei and the chromosomes. The chromosome breaks induced by hard rays are widely scattered on the same chromosome or on different chromosomes, so that a union of broken ends of different origin, or interchange, takes place more easily than in the case with soft-ray irradiation, which produces more closely adjacent breaks, and is liable to give a high proportion of restitution. In all cases of different dosages the frequency of chromosome aberrations was higher in var. vulgare than in var. flavescens. Thus, var. flavescens showed always higher tolerance to X-rays than vat. vulgare. These results are generally in good accord with those of experiments concerned with the rate of gene mutations described in the foregoing report. |