Cytological studies on pollen degeneration in male-sterile onions

Abstract

Male-sterile plants were obtained from a variety of the onion, Senshu-Hiragata-Ohtamanegi (a strain Yellow Glove Danvers), in 1944 and 1948. The pollen degeneration of the male-sterile plants was investigated cytologically in 1949 and 1950. The flower buds and anthers of the normal and the male-sterile plants were fixed in CARNOY's fluid. The usual methods of dehydrating and embedding in paraffin were employed. The sections were cut 10μ thick and stained with HEIDENHAIN's iron-alum haematoxylin. The results obtained may be summarized as follows:
1. The maturation divisions of P.M.C's in the male-sterile plants were normal up to the liberation of microspores from tetrads, but the nuclear divisions of microspores were not observed.
2. The cells of the anther tapetum began to behave in an abnormal manner, from late tetrad stage to the liberation of microspores (fig. 3). The boundaries of the tapetal cells broke down, and the contents flowed together to form a periplasmodium (fig. 4).
3. After the periplasmodium has attained maximum development, it began to degenerate (fig. 5). With the complete disintegration of the periplasmodium the microspores were finally destroyed. The anther cavity became empty, except for a dark strand of disintegrating microspores (fig. 6).