What is fertilization? Explain double fertilization and mention the changes which occur in the flowers after fertilization.

Fertilization is the fusion of male gamete and female gamete to initiate the development of a new individual organism. After the pollen reaches the stigma, pollen germinates producing a pollen tube that carries the sperm nuclei to the ovary. The tube nucleus degenerates and the generative nucleus divides to form two male gametes. One of them fuses with the female gamete (egg); thereby, forming the zygote. This process is known as syngamy. The other gamete fuses with two polar nuclei and results in the formation of endosperm and called as the triple fusion. Since two fusions are involved, it is known as double fertilisation.

The changes which occur in the flowers after fertilization:

1) Formation of a diploid zygote which develops into an embryo, which forms the future plant.

2) Endosperm cells serve as a source of nutrition for the developing embryo.

3) Ovule becomes the seed and the ovary becomes the fruit.

4) The outer and inner integuments of the ovule become the seed coat of the seed.

5) Petals and sepals fall off.