$\text{Describe in sequence the events that lead to the development of a 3- celled pollen grain from microspore mother cell in angiosperms. }$

The process of formation of microspores from a pollen mother cell is called microsporogenesis. Microspores, as they are formed are arranged in a cluster of four cells the microspore tetrad. As the anthers mature and dehydrate, the microspores dissociate from each other and develop into pollen grains. When the pollen grain is mature it contains two cells - the vegetative cell and the generative cell. The vegetative cell is bigger, has abundant food reserve, and a large irregular nucleus. The generative cell is small and floats in the cytoplasm of the vegetative cell. It is spindle-shaped with dense cytoplasm and a nucleus. In over 60 percent of angiosperms, pollen is shed at 2 celled stages. In the remaining species, the generative cell divides mitotically to give rise to the two male gametes before pollen grains are shed (3-celled stage).