Microsporen

Microsporen, or microspores, are haploid spores produced by the process of microsporogenesis in seed plants. They form the male gametophytes and ultimately become pollen grains in most gymnosperms and angiosperms. Each microspore originates from a diploid microsporocyte (microspore mother cell) located in the microsporangia, typically within the pollen sacs of anthers. Through meiosis, a single microsporocyte yields four haploid microspores, often released as a tetrad before separating.

During development, a haploid microspore generally undergoes mitosis to produce a pollen grain with at least one vegetative cell and a generative cell. In many flowering plants, the generative cell later divides to form two sperm cells, completing the male gametophyte. In gymnosperms, pollen grains carry a male gametophyte that also produces sperm, though the specifics of development can vary by group.

Functionally, microspores are adapted for dispersion and fertilization. The pollen grain protects the male gametophyte during transit to the ovule and germinates to form a pollen tube that delivers sperm to the female gametophyte. This process underpins fertilization and seed formation in seed plants.

Relation to other spores: Microspores are contrasted with megaspores, which arise from female microsporogenesis and develop into the female gametophyte. The term microspore emphasizes their role as the first step in the formation of the male gametophyte.