Explain the structure of pollen grains in Angiosperms.

Explanation

Structure of pollen grain:
• A mature pollen grain has hard and resistant outer exine made up of sporopollenin and a thin intine made up of cellulose and pectin.
`*` The exine has designs and patterns like knobs, ridges, grooves, etc and also germ pores .
`*` In majority of the angiosperms, at the time of shedding it has two cells, the vegetative cell and generative cell. The generative cell divides and forms two male gametes and the pollen grains are shed at this three celled stage (vegetative cell and two male gametes).
`*` The vegetative cell is larger in size with large amount of reserve food material and a large, irregular nucleus.
`*` The generative cell is smaller in size, spindle shaped and floats inside the cytoplasm of vegetative cell. It has dense cytoplasm and a prominent nucleus.