Question

Describe the events that take place between pollination and fertilization in plants.

Answer 1

1. After pollination, a pollen grain germinates on the stigma, producing a pollen tube.
2. The pollen tube grows through the style towards the ovary and then enters the ovule, typically through the micropyle (porogamy).
3. The pollen tube enters the embryo sac at the micropylar end.
4. The tip of the pollen tube bursts inside the embryo sac, releasing two male gametes.
5. One male gamete fuses with the egg cell, forming a diploid zygote (fertilization or syngamy).
6. The second male gamete fuses with the two polar nuclei, forming a triploid primary endosperm nucleus (triple fusion).
7. This process of one sperm fertilizing the egg and the other sperm fertilizing the polar nuclei is called double fertilization, unique to angiosperms.
8. The primary endosperm nucleus divides to form nutritive tissue (endosperm) for the developing embryo.