Genetics and development of morphological and physiological characters of male sterility in Oenothera

Summary Male sterility in Oenothera is influenced by two nuclear genes,fr andster. Their function is independent of the plastomes. Development of anthers, fertile and sterile male, was studied by electron microscopy and histochemical methods. Both genes act on lipid metabolism but at different developmental stages. Infr/fr homozygotes the disturbance is expressed as a lack of sporopollenin in the exine, while amorphous lipid material is deposited in the loculus. Inster/ster homozygotes sporopollenin is formed normally in the endexine but the paracristalline structure of the ektexine is missing. In both mutants the disturbance leads to complete destruction of the pollen grain. The deviation from fertile pollen development is correlated with abnormalities of the tapetum and outer cell layers of the anther wall.