Question

What is double fertilisation?

Answer 1

Double fertilization is a phenomenon that occurs in flowering plants i.e. Angiosperms. After pollination, when pollen grain falls on stigma, it forms a pollen tube that travels all the way through style to reach ovary. Most successful pollen tube reaches embryo sac of ovule & fuses with it. Inside pollen tube, there are 2 sperm cells which are released in embryo sac. One of them fertilizes the egg to form zygote & the second one fertilizes with two polar nuclei to form secondary nucleus (triple fusion). After double fertilization the fertilized ovary is able to form fruit & seed. It is because of double fertilization that seed forms endosperm which nurtures the growing embryo. The process of double fertilization has played significant role in evolution of flowering plants.