CBSE Class 10 Answered

This occurs in angiosperms.

Each pollen grain after germination forms 2 male gametes. Both these male gametes participate in the process of fusion and the fusion takes place twice at two places. This phenomenon is called double fertilization.

Process of double fertilization:

During fertilization, the tip of the pollen tube enters the ovule through the micropyle. Then it enters the embryo sac. Here it absorbs moisture from the synergids and gets ruptured to liberate both the male gametes. One of the male gametes fuses with the egg to form diploid zygote while the other male gamete fuses with diploid secondary nucleus to form triploid primary endosperm nucleus. So 2 fusions are occuring here simultaneously. Double fertilization triggers the embryonic development which leads to formation of seeds and fruits.