THE INFLUENCE OF POLYPLOIDY ON THE X-RAY SENSITIVITY OF CELLS

Abstract

A study has been made of the comparative X-ray sensitivity of cells of diploid and tetraploid species of Tradescantia at two different resting stages during the development of the pollen grains. At the resting stage midway between meiosis and the pollen grain division, no significant difference was found in the number of breaks per chromosome in the two species. At the resting stage just following the pollen grain division, the tetraploid chromosomes showed a slightly higher break frequency, a difference which was statistically significant. This increase was due, at least in part, to the presence of a small portion of cells which showed an abnormally high sensitivity. From a detailed study of the cells at each stage and the types of aberrations induced it is concluded that the chromosomes of each species are of equal sensitivity, and that any difference in the reaction of the diploid and tetraploid cells to irradiation is due simply to the numerical difference in the chromosomes of the cells, or to differences in the nuclear stage when X-rayed.