SMITH, MARIANNE B*, HARRY T HORNER, AND REID G PALMER. Department of Botany and Bessey Microscopy Facility, and USDA ARS CICGR and Departments of Agronomy and Zoology/Genetics, Iowa State University, Ames, IA 50011. - A developmental microscopic study of a Chinese wild-type soybean line exhibiting male sterility.
It is the purpose of this study to microscopically investigate the
developmental sequence leading to male sterility, and to demarcate the
temporal and spatial parameters that result in degeneration of the
male cells. The first irregularities in development are discernible
after the microspore tetrads have been released from the encasing
callose, between the early and late microspore stages. A succession of
events, whose precise origin has yet to be identified, occurs: instead
of disintegrating timely, the tapetum may persist and press against
the microspores or, contrarily, it may degenerate prematurely and the
tapetal cytoplasm may be found dispersed throughout the locule. At the
same time the middle and/or parietal layer(s) may enlarge grossly.
Progressively, darkly staining, granular material from the tapetum
and/or middle and parietal wall layers amasses in the locule or the
wall layers. The material may be present as a dark layer encircling
the tapetum, or it may be found dispersed in the locule and throughout
the four wall layers. After microspore mitosis, the pollen does not
engorge with reserves but remains highly vacuolated, and becomes
collapsed and aborted at anthesis.
Key words: anther development, male sterility, wild soybean