microgametophytes

Microgametophyte is the male gametophyte in seed plants, produced from a microspore by meiosis. It represents the haploid generation in the plant’s life cycle and develops within the microsporangia of the sporophyte, typically inside pollen sacs of anthers. In seed plants, microsporogenesis produces numerous microspores, which then undergo microgametogenesis to become mature microgametophytes known as pollen grains in angiosperms or pollen grains with a reduced cellular makeup in gymnosperms.

In angiosperms, a mature microgametophyte is usually represented by a pollen grain containing two distinct cell types: a vegetative (tube) cell and a generative cell. The generative cell often divides further to form two sperm cells. The pollen grain is encased by a protective exine and an inner intine. Upon pollination, the tube cell forms a pollen tube that transports the sperm cells toward the female gametophyte, enabling fertilization. In flowering plants, this process culminates in double fertilization, where one sperm fertilizes the egg to form a zygote and the other fuses with polar nuclei to develop into endosperm.

In gymnosperms, microgametophytes are exposed within pollen grains that also carry a tube cell and a generative cell, which divides to produce sperm. The pollen tube delivers sperm to the ovule, where fertilization occurs; unlike many angiosperms, gymnosperms generally do not form endosperm through double fertilization.

Overall, the microgametophyte is a highly reduced, dependent male gametophyte that functions primarily to produce and transport sperm to the female gametophyte for fertilization.