Microspores

Microspores are haploid spores produced by microsporogenesis in seed plants and represent the male products of the plant’s reproductive cycle. They develop within microsporangia, or pollen sacs, located in the anthers of flowers in angiosperms and in the male cones of gymnosperms. The microsporocytes (microspore mother cells) undergo meiosis to yield four haploid microspores, which may remain in a tetrad or separate as individual spores.

Each microspore typically develops into the male gametophyte, the pollen grain. In flowering plants, a microspore undergoes mitotic divisions to form a vegetative cell and a generative cell; the generative cell later divides to produce two sperm cells. The pollen grain is designed for dispersal and pollen-tube germination during fertilization. The process of pollen development is crucial for successful male gametophyte formation and fertilization in seed plants.

Microspores are encased by a resistant outer wall, the exine, composed largely of sporopollenin, and an inner layer called the intine. The exine often bears apertures or pores that facilitate pollen germination. Pollen morphology and microspore characteristics are widely used in palynology for plant identification and reconstructing past environments, as well as in agriculture to assess pollen viability and compatibility.

In the broader plant life cycle, microspores are part of heterosporous traditions in seed plants, with megaspores forming the female gametophyte. The microspore’s fate is to generate the male gametophyte that delivers sperm to the egg, enabling fertilization and seed development.