How does the pollen tube reach and enter an ovule?

After pollination, when pollen grains land on the stigma of a flower, each viable pollen grain absorbs moisture and germinates. The outer wall of the pollen grain (exine) breaks open, and a pollen tube emerges from the pollen grain’s germ pore. This tube grows down through the style, guided by chemical signals from the ovule. The growth is controlled by nutrients secreted by the style tissues, ensuring the tube grows toward the ovary.

The pollen tube carries two male gametes (sperm cells) inside it. When it reaches the ovary, it enters the ovule through a small opening called the micropyle. The tip of the tube then bursts, releasing the two male gametes into the embryo sac — one fuses with the egg cell (fertilization), forming a zygote, and the other fuses with the polar nuclei to form the endosperm (double fertilization). Thus, the pollen tube acts as a passageway for the male gametes, ensuring successful fertilization in flowering plants.