describe 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.

Like other plants, the angiosperms alternate a sporophytic generation with a gametophytic one, a sporic meiosis (see Figure 1 ). Angiosperm sporophytes are the common plants around us—trees, grasses, and garden vegetables. They produce through meiosis (reduction division) two kinds of spores in specialized structures of their flowers, microspores in the anthers and megaspores in the ovules contained within the ovaries. The gametophytes, which develop from the spores, are much reduced in size. The microgametophyte consists of only three cells and is the germinated pollen grain. The megagametophyte is the mature embryo sac, a seven-celled structure in the ovule surrounded by, and dependent upon, sporophyte tissue.

hope this helps.........

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.