What is double fertilization? Describe the process in brief.

The process of fusion of male gamete with the female gamete to form the diploid zygote (2n) is known as fertilisation. The fusion of one male gamete with egg and that of another male gamete with a secondary nucleus is called double fertilisation. It is the characteristic feature of only angiosperms. All angiosperms are characterised by a unique process called double fertilisation. Double fertilisation is significant because it involves the use of both the male gametes produced by a pollen grain. This avoids the chances of polyembryony and increases the chances of survival of the future plant. It consists of two fusions and results in the formation of two products. First fertilisation restores diploidy in the life cycle. The diploid zygote develops into an embryo which subsequently develops into a new plant. Second fertilisation product, triploid PEN (Primary endosperm nucleus) develops to form a nutritive tissue called endosperm for developing an embryo.