microsporogenese

Microsporogenesis is the process by which microspores, the male haploid spores, are formed from microsporocytes through meiosis in the sporogenous tissue of the microsporangia, typically located in the anthers of flowering plants and in the microsporangia of gymnosperms. It is a key stage in the formation of the male gametophyte.

In the anther, diploid pollen mother cells arise from sporogenous tissue. Each pollen mother cell undergoes meiosis I and II, producing four haploid microspores that are initially arranged as a tetrad. Before or during meiosis, a callose wall encapsulates the developing cells, isolating each tetrad.

After meiosis, the callose is degraded and the individual microspores are released into the locule. Each microspore then develops a two-layered cell wall: an outer exine and an inner intine. The exine is rich in sporopollenin and is largely produced or patterned with help from the tapetum, a nutritive layer of the anther wall, which also supplies materials for microspore maturation.

In many angiosperms, a mitotic division of the microspore’s germ line forms a bicellular pollen grain containing a vegetative cell and a generative cell. The generative cell may later divide to form two sperm cells, resulting in a tricellular pollen grain at maturity; in other species, pollen remains bicellular at maturity.

Microsporogenesis provides the male gametophytes necessary for fertilization. Abnormal microsporogenesis can lead to male sterility, affecting fertility and breeding programs. The process is closely tied to tapetal function and to the development of the anther wall.