CHROMOSOME BREAKAGE INDUCED BY ABSORBED RADIOACTIVE PHOSPHORUS, P32

Abstract

Radioactive phosphorus (P32) was made available to individual germinating seeds and seedlings of Triticum vulgare, T. durum, T. monococcum, and Hordeum distichon. Each treated plant was provided with either 0.18 or 0.018 micro-curies of P32. Both concentrations were effective in causing chromosome breakage and rearrangements. Many aberrant chromosome configurations occurred in microsporocytes of treated tetraploid and hexaploid plants. Only one chromosome aberration was found in T. monococcum and none in barley. Structural changes occurred also in chromosomes of vulgare wheat grown in soil to which fertilizer containing P32 was added. It is possible that the effectiveness of small amounts of P32 in inducing mutations is increased by its inclusion in chromosome molecules. Emitted beta particles would then be shot off very close to the sensitive target. Further, the recoiling atomic nucleus is almost certain to have enough energy to break any chemical bond. In any case since there is a change in atomic number (from 15 to 16) and in valence (P valence 5, S valence 2), molecular bonds must be released in the process.