Birds and Bees – Fertilization

This year we're exploring the fascinating world of plant reproduction in a series called "Birds and Bees." So far, we have mastered a few terms, and learned about the role pollinators play in bringing pollen and plants together. Now we're ready to enter the amazing events surrounding the fertilization of a flower's eggs.

Before fertilization can occur, each ovule within the ovary must be ready with a mature egg. When compatible pollen lands on the stigma, two cells within the pollen grain jump into action. One of the cells grows into a long pollen tube, through the cells of the pistil, in search of a microscopic opening in one of the ovules. If there are multiple ovules in the ovary, each ovule typically requires its own pollen tube.

Flower lifecycle – (C)2006 Merriam-Webster, Inc.

The second cell divides to become two sperm  cells that travel through the pollen tube to enter the ovule. One of the sperm unites with the egg in the ovule to form a zygote, the fertilized egg. The other sperm combines with another cell in the ovule to produce the endosperm, which is food storage tissue. The endosperm nourishes the zygote as it grows into an embryo, the immature plant within a seed. Amazing!