Draw a labelled diagram of the sectional view of a mature pollen gram in angiosperms. Explain the functions of its different parts.

Explanation

Functions of its parts : A mature pollen grain has two layered wall- the outer exine and the inner intine . The wall encloses a large vegetative cell containing vegetative nucleus and a lenticular generative cell. Their functions are as follows :
Exine : The outer thick exine layer is made up of sporollenin which is resistant to physical and biological decomposition . If provides protection during the hazardous journey of pollen from anther to the stigma. There are one or many germpores on the pollen surface which are directly or indirectly associated with its germination.
Intine : The intine is pecto-cellulosic in nature. It is associated with the formation of pollen tube .
Vegetative cell : The vegetative cell is large and contains abundant food reserve . It has a large vegetative nucleus. The function of vegetative cell is to provide the medium for the movement of male gametes in pollen tube.
Generative cell : The generative cell cytoplasm is highly reduced but it contain the usual cell organelles. It divides mitotically to produce two functional male gametes.