What is pollination ? How does it occur in plants? How does pollination lead to fertilization? Explain.

Explanation

The transfer of pollens from anther to the stigma of a flower is called pollination.
The transfer is accomplished by an external agency such as wind (anemophily), water (hydrophily), insects (entomophily), birds (ornithophily), bats (chiropterophily), etc. Both wind and water are abiotic agencies while insects, birds, bats etc. are biotic agencies of pollination.
After falling on stigma, the pollen grain absorbs water and nutrients. It produces a tube called pollen tube. Pollen tube grows through style and reaches the ovary. Its tip contains a tube nucleus and two male gametes or sperm cells. The advancing pollen tube enters an ovule, generally through micropyle and reaches the interior of the embryo sac. Here the tube bursts to release its two male gametes. One male gamete fuses with egg to form zygote and the second male gamete fuses with binucleate central cells which forms endosperm.