The Effect of Oxygen on the Production by Fast Neutrons of Chromosomal Aberrations in Tradescantia Microspores.

HE studies of THODAY and READ (1947) using root-tip cells of Vicia T j a b a demonstrated that oxygen has a marked effect in increasing the frequency of X-ray-induced chromosome aberrations. These investigators later showed (1949) that when alpha rays are used, the oxygen effect is much less, since the yield of aberrations with oxygen present was only slightly greater than in its absence. In experiments on the oxygen effect using Tradescantia microspore chromosomes ( GILES and RILEY 1949, 1950 ; GILES and BEATTY 1950), a pronounced effect of oxygen on X-ray-induced rearrangements has also been demonstrated. Preliminary studies of CONGER (unpublished) further indicate that there is little or no oxygen effect when aberrations are induced in mature pollen grains (exposed in air as compared with nitrogen) by alpha rays, thus agreeing with the observations of THODAY and READ (1949). In view of these results it seemed of interest to investigate the oxygen effect when fast neutrons are used to produce aberrations in Tradescantia, since this radiation is intermediate in effectiveness with respect to chromosome break production between X-rays and alpha particles (cf. KOTVAL and GRAY 1947).