Flower parts and their functions 2. How the sperm arrive at the ovum in plants 2. Requirements for pollen tube growth to top The Student Lab to top Introduction Pollen is everywhere. It is in the air we breathe, the water we drink, in the food we eat, and in the soil we walk on. It is the pretty yellow, white, or blue powdery substance that we see in flowers.
Pollen grains contain the male gametes in sexually reproducing plants.
A pollen tube grows from the stigma, through the style, and into the ovary where it enters an ovule. The sperm nuclei then pass through the pollen tube into the ovary where fertilization takes place. We cannot see the growth of the pollen tube because it takes place within the style. However, we can watch the growth of pollen tubes in vitro by germinating them in a liquid medium or on agar plates. Pollen germination depends upon the presence of sucrose, calcium, and boron.