Chromosome Breakage in Plants Induced by Radioactive Phosphorus (P32)

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Abstract
Seeds of several spp. of plants were divided into 2 equal lots supplied, respectively, with 0.18 and 0.018 microcurie of P32 for each seed (P32 in the form of Na2HPO4). Forty-eight seeds of each sp. were treated; 6 untreated plants of each sp. were controls. The seedlings were transferred to crocks with untreated soil 13 days after germination began. At that time, 90 [plus or minus] 4% of the activity in the original soln. had entered the plants. Pollen mother cells were prepd. by the acetocarmine smear method and were mounted in diaphane. Irregularities were most frequent in the tetraploid durum wheat and the hexaploid aestivum (vulgare) wheat. Both cones. of activity caused rearrangements. There was no clear aberration in barley, and only one of the heads of Einkorn wheat showed possible chromosome breakage and rearrangement. In 22 anthers, configurations characteristic of particular rearrangements were repeated in several or many cells; anthers from several spikelets of one head all had the same rearrangement. Aberrations in division I included chromosome fragments, chains of 3 or 4 chromosomes, rings of 4, and unequal pairs. In division II, anaphase and telophase bridges and fragments were seen. Of 19 anthers from Thatcher wheat plants grown in treated soil, 3 had aberrations involving blocks or clusters of cells. A sunflower head injected with 1.8 microcuries of P32 yielded pollen mother cells 11 days later. Three out of 45 had anaphase-1 bridges.

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