Reproduction in flowering plants

After fertilization the zygote becomes the embryo, the endosperm nucleus gives the endosperm, the integuments fuse and harden into the seed coat, the testa, and the ovule becomes the seed. The calyx, corolla, stamens, style and stigma usually wither and fall. The ovary stores food, ripens into the fruit and its wall becomes the pericarp. The ovary makes auxins that help this. The synergids and antipodal cells disappear, but the micropyle stays so that water can enter the seed when it germinates. Seeds are of two kinds. In an endospermic seed the embryo does not use all the endosperm. In monocots such as wheat and maize the ovary wall fuses with the integuments to make a one-seeded fruit called a grain; in dates they do not fuse; and castor, a dicot, also has endosperm left. In a non-endospermic seed the embryo uses all the endosperm and the food is stored in the two cotyledons, as in the bean and pea. Some fruits keep parts of the flower: the calyx and stamens in the pomegranate, the calyx in the eggplant and the date, the corolla in the marrow. In a false fruit a part other than the ovary swells and stores food, as the receptacle does in the apple. Pollination also stimulates the auxins that make the ovary grow into a fruit even if fertilization does not happen. In parthenocarpy a fruit without seeds develops without fertilization, as in banana and pineapple; this can also be done artificially with plant hormones. The ripening of fruit and seeds often ends the plant’s growth and can kill annual plants. If a flower is not pollinated and fertilized, it withers and drops without making a fruit.