File:Plant Fertilization Cycle.svg

English: 1) Sporophyte;

2)Anther; 3) Ovule; 4) Ovary; 5) Microspore Mother Cell; 6) Megaspore Mother Cell; 7) Microspore; 8) Megaspore; 9) Pollen Grain (Male Gametophyte); 10) Embryo Sac (Mature Female Gametophyte); 11) Seed; 12) Endosperm (3n); 13) Mature Seed; I) diploid (2n); II) haploid (n); III) Meiosis; IV) Mitosis; V) Pollination; VI) Double Fertilization;

The reproductive cycle in flowering plants is a case of alternation of generations and begins with the development of both the male and female gametophytes. The male gametophytes are produced when the microspore mother cell in the pollen sacs of the anther goes through meiosis and produces four microspores (pollen). The female gametophyte is produced when a megaspore mother cell in the ovule goes through meiosis and produces four megaspores. In many flowering plants, three of the four megaspores will disintegrate. The male gametophytes develop into pollen grains and the female megaspore(s) develop into a megagametophyte. When a pollen grain germinates on the stigma, it produces a pollen tube that extends in the style until it reaches an ovule of the ovary. Double fertilization occurs when the pollen tube releases two sperm. One sperm fertilizes the egg to produce a zygote and the other fertilizes the central cell (which has two polar nuclei) producing a triploid endosperm cell. The zygote is a new sporophyte generation; it divides to produce an embryo. The endosperm divides to produce endosperm food for the embryo. The ovule develops into a seed and contains the embryo and the endosperm. When condition are appropriate, the seed germinates, and the embryo develops to produce the plant. The plant becomes a mature sporophyte.