Concepedia

Abstract

The existence of apomixis in grain sorghums has been established. Restriction to pollen germination under selfing, the stimulus provided by its own pollen, the possibly autonomous development of the endosperm and a reduction in the competition of sexual embryosacs under selfing seem to have been responsible for the evolution of somatic apospory in this materia1. Embryological studies have shown that as the megaspore mother cell degenerates one of the cells of the nucellus enlarges and acts like the embryosac mother cell. This nocellar cell divides mitotically giving rise to the diploid embryosac. This mechanism of somatic apospory, which appears to be genetically controlled, is expected to provide the means to preserve heterozygote advantage.