Question

define double fertilization and also give its significance​

Answer 1

After pollination, the Pollen Grain reaches the ovule by forming a Pollen tube. Inside the ovule one,male nucleus of the Pollen fuses with the female germ cell to form Zygote.

The other mail nucleus called the Secondary Sperm fuses with Secondary Nucleus to form a food storing tissue called the Endosperm

As because two processes of fertilization are taking place so it is known as Double Fertilisation...