State the formation of seed in a flower.
Asked by priyanshi Shah | 24th Feb, 2013, 09:29: PM
After pollination, the pollen tube carrying the two male gametes grows towards the ovule. When the two sperm cells enter the embryo sac, both participate in fertilization. One sperm cell fuses with the egg, forming a zygote that grows by mitosis and develops into a multicellular embryo in the seed. The second sperm cell fuses with the two haploid polar nuclei of the central cell to form a triploid cell that grows by mitosis and develops into endosperm, a nutrient tissue that nourishes the embryo. This fertilization process occuring in angiosperms is called double fertilization.
After fertilization, the ovules mature into seeds, the ovary develops into a fruit. The wall of the ovary develops into the wall of fruit called pericarp.
The seed is the final product of sexual reproduction. Seeds are formed inside fruits. A seed typically consists of seed coat, cotyledon and an embryo axis. The cotyledons of the embryo are simple structures, generally thick and swollen due to storage of food reserves. Integuments of ovules harden as tough protective seed coats. The micropyle remains as a small pore in the seed coat. This facilitates entry of oxygen and water into the seed during germination. As the seed matures, its water content is reduced and seeds become relatively dry. The general metabolic activity of the embryo slows down. The embryo may enter into dormancy (a state of inactivity), or if favourable conditions are available they germinate.
Answered by | 25th Feb, 2013, 05:54: AM
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