Induced Pollen Lethals from Seeds of Datura Stramonium Treated with Thermal Neutrons

Abstract

Chromosomal and genic aberrations in D. stramonium can be distinguished by type of pollen abortion, chromosomal type giving small, shriveled, and empty grains in proportions of 25%, 50%, 75% or, rarely, 100%, genic type giving subnormal to very small grains with degenerated contents in proportions of 25% or 50%. Seeds from 3 capsules of an inbred standard 1 line were divided into 4 lots, one of which was untreated and the other 3 treated with thermal neutrons for 2, 4 and 6 hrs. resp. at a flux of approx. 4.6 x 108 Nth/cm2/sec. Pollen was examined from a single flower from each fork of the plants tested. The seedling stands for control, 2, 4, and 6 hrs. were 93%, 85%, 76% and 22%, resp., the mature plant stands, 76%, 74%, 36%, and 3.5%, resp., and frequencies of plants with abnormal pollen, 0%, 76%, 86%, and 89%, resp. Pollen abortion was detd. for 2034 flowers in 2 hr. treatment, 897 in 4 hr. treatment, and 84 in 6 hr. treatment. The 2 hr. treatment gave chromosomal types of abnormal pollen in 52% of flowers, gene types in 8%, and both types in 6%, making a total of 66% of flowers with abnormal pollen. The 4 hr. treatment had 67% of flowers with chromosomal types, 7% with gene types, and 11% with both types (84% with abnormal pollen). The 6 hr. treatment had 68% of flowers with chromosomal types, 4% with gene types, and 20% with both types (92% with abnormal pollen). Diploid (2n) sized pollen grains were found in 7% of plants for 2 hr. treatment, 10% for 4 hrs. and 21% for 6 hrs. Since the no. of plants having a single type of pollen abortion in all their flowers increased from 27% in the 2-hr. group to 47% in the 6-hr. group, severity of exposure may have caused death of most of the cells giving rise to pollen grains, with one lightly hit cell surviving. Most of plants having a single pollen abortion type had chromosomal type of mutation. A significant positive correlation seemed to exist between pollen abortion and morphological aberrations, although at higher treatments it was difficult to delimit sectors clearly. No differences were detected between plants from neutron- and from X-irradiated seed with respect to developmental or morphological disturbances or lethality patterns.