Development of the pollen grain
Inner intine wall of the pollen grain
Composed of cellulose
Dehiscence
Once the pollen grains are mature and ready to be released from the anther, the anther dries out and splits along lines of weakness. The pollen grains are exposed to the environment and can be picked up by e.g. insects
Outer exine wall of the pollen grain
A tough layer that prevents desiccation (drying out). This increases the chance of a pollen grain surviving the movement from the anther to the stigma of another flower.
Generative nucleus
Divides to form the male gametes
Tube nucleus
Forms the pollen tube
Generative cell
Has two nuclei: a generative nucleus and tube nucleus
Production
Pollen grains are produced in the anther by meiosis.
Pollen grains contain two cells
Single vegetative (non-reproductive) cell and generative cell