Explain life cycle of angiosperm

There is alternation of generations between haploid gametophyte (male gametophyte and female gametophyte) and diploid sporophyte (main plant body) in the life cycle of a plant.

The anthers, which contain microsporangia, produce microspores by meiosis, and the microspores develop into male gametophytes called pollen.

The ovaries, which posses megasporangia simultaneously produce megaspores which grow into female gametophytes, called ovules. It is a seven celled structure with one large central cell containing two polar nuclei and one egg cell.

By the process of pollination, the pollen is transferred to the stigma of the pistil. The pollen grain germinates and a pollen tube grows down into the ovary. Eventually, two sperm nuclei travel down the pollen tube. One sperm nuclei fertilizes the egg forming zygote (which grows into an embryo) and the other two polar nuclei forming triploid cell (endosperm) which often serves as food for the embryo. This is called double fertilization. The Zygote which begins the next sporophyte generation, on complete development forms a seed. When the seed germinates, the sporophyte matures and the life cycle begins again.