What is double fertilization?

Explanation

Double fertilization is the fusion of two male gametes brought by a pollen tube to two different.cells of the same female gametophyte in order to produce two different structures. It is found only in angiosperms where it was first discovered by Nawaschin in 1898 in Fritillaria and Lilium. In angiosperms the pollen tube bursts open in one of the two synergids to release the two male gametes. One male gamete fuses with the egg or oosphere to form a diploid zygote or oospore. It is called syngany or generative fertilization. The second male gamete descends down and fuses with the diploid secondary nucleus of the central cell to form a triploid primary endosperm cell. It is known as vegetative fertilization or triple fussion.
Significance of double fertilisation.
1. Double fertilization ensures that the nutritive tissue is formed only when the formation of embryo has taken place by fertilization of the egg. Angiosperms are, therefore, economical and more specialized as compared to gymnosperms where a large nutritive female gametophyte is formed long before fertilization. If fertilization fails, the energy spent on forming it shall go waste.
2. Double fertilization provides the characteristics of the male plant as well to the nutritive tissue.

3. In angiosperms the growth of the female gametophyte or embryo sac stops at the 8-nucleate or 7-celled stage. The second act of fertilization called vegetative fertilization, provides stimulus to one of its cells to resume growth and form a nutritive tissue.
4. Due to its triploid nature, endosperm shows high physiological activity, grows faster and accumulates nutrients.