POLLEN ABORTION INDUCED BY GAMMA RADIATION AND ETHANOL IN Gibasis pulchella

Resumen

A comparative study of the effects of gamma radiation and ethanol vapors on the development of the male gametophyte in Gibasis pulchella was carried out. Dose-response curves were constructed for pollen abortion and for other morphological abnormalities of the pollen grains induced both by gamma radiation an
ethanol. The slopes of the curves were similar, but the amplitude of the response was much smaller for the chemical. The sensitive periods in the microsporogenesis cycle were found to be coincident for both agents since the maximum damage was observed between 11 and 15 days after treatment in each case.
In addition to the analysis of pollen abortion, scoring of morphological abnormalities in the pollen grains (double grains and giants) was also carried out. Both agents produced these abnormalities but there were quantitative differences in the response. Furthermore incomplete cytokinesis in pollen mother cells leading
to incomplete separation of grains (strangled grains) appeared only in the lot treated with ethanol. These abnormalities might possibly be due to alterations induced during the premeiotic mitosis.
No inhibition of the flowering state was observed for doses lower than 300 Kr, however, doses larger than that produced a decrease in the numbers of flowers as the dose increased and also induced clefting in the petal margins. Ethanol dose of 166 mg/liter of air/3 hr greatly reduced the floral production.
The nuclear volume for the meristematic cells of the root tip of Gibasis pulchella is 715.26 ± 58.29 m³ and the interphase chromosomal volume is 44.7 m³. The dose necessary to produce 50% pollen abortion was found to be 332 rads and this value falls on the curve obtained by Underbrink et al. (1973) .