Where is the gametophyte generation in an angiosperm

A typical angiosperm life cycle is shown in Figure below. The flower in Figure above is obviously an innovation in the angiosperm life cycle. Flowers form on the dominant sporophyte plant. They consist of highly specialized male and female reproductive organs. Flowers produce spores that develop into gametophytes. Male gametophytes consist of just a few cells within a pollen grain and produce sperm. Female gametophytes produce eggs inside the ovaries of flowers.

Flowers also attract animal pollinators. If pollination and fertilization occur, a diploid zygote forms within an ovule in the ovary. The zygote develops into an embryo inside a seed, which forms from the ovule and also contains food to nourish the embryo. The haploid gametophytes—the gamete-producing generation—are the male pollen grains the microgametophytes and the female, 7-celled structure the megagametophyte that lies within the ovule.

In a process called double fertilization that is unique to angiosperms, the male gametophyte produces two sperm cells that fertilize two cells within the female gametophyte. One fertilized cell becomes the zygote, which develops into the embryo new sporophyte , while the other becomes a unique triploid nutritive tissue endosperm that feeds the developing embryo.

View all the text for this animation. Once the spores germinate, they produce new gametophyte plants and the cycle continues. Tracheophytes are plants that contain vascular tissue; two of the major classes of tracheophytes are gymnosperms conifers and angiosperms flowering plants. Tracheophytes, unlike bryophytes, have developed seeds that encase and protect their embryos.

The dominant phase in the tracheophyte life cycle is the diploid sporophyte stage. The gametophytes are very small and cannot exist independent of the parent plant. The reproductive structures of the sporophyte cones in gymnosperms and flowers in angiosperms , produce two different kinds of haploid spores: microspores male and megaspores female. This phenomenon of sexually differentiated spores is called heterospory. These spores give rise to similarly sexually differentiated gametophytes, which in turn produce gametes.

Fertilization occurs when a male and female gamete join to form a zygote.