Question

Describe the structure of a pollen grain and the process of its germination.

Answer 1

A pollen grain has a two-layered wall: a tough, sporopollenin-rich exine, interrupted at germ pores, and an inner cellulose-and-pectin intine. At maturity it commonly contains a large vegetative cell and a smaller generative cell.

On a receptive stigma, compatible pollen absorbs moisture and germinates. The intine emerges through a germ pore as a pollen tube. The vegetative nucleus guides tube growth through the style towards an ovule. The generative cell divides to form two male gametes if it has not already done so. The pollen tube commonly enters through the micropyle and a synergid, then releases the male gametes into the embryo sac.