The Cytology of Pollen Abortion in S Cytoplasmic Male‐sterile Corn Anthers

The anther development of the S male‐sterile cytoplasm and the fertile maintainer (N) cytoplasm versions of corn inbred W182BN and the restored S cytoplasm version of inbred NY821LERf was studied by light and electron microscopy and compared to pollen abortion in the C and T types of male‐sterile cytoplasms. The S anthers did not deviate from the non‐male sterile (N) anthers until a very late stage of pollen development. Tapetal cells developed and disappeared normally in the S version which differentiates this cytoplasm from the C and T types. Although some modified membranous structures were seen in a higher frequency in the large vacuole of the sterile S pollen than in the N and restored S counterparts, the mitochondria and other organelles in the S pollen appeared normal up to the time of pollen abortion. Pollen abortion in the S cytoplasm did not occur until the developing pollen was nearly mature. At this time the pollen grains disintegrated abruptly but other anther tissues appeared unaltered. The male sterility of S plants appeared to be determined by the pollen itself without external influence from the tapetum.