1. A typical angiospermic pollen grain (mature) is a unicellular, uninucleate, spherical or oval haploid structure.
2. The pollen grain is also called microspore.
3. It is covered and protected by a double layered wall called sporoderm.
1. The outer layer of the wall is thick. It is known as exine. The inner layer of the wall is thin. It is known as intine.
2. The exine is made up of a complex substance called sporopollenin. The sporopollenin protects the pollen grain from physical and biological decomposition.
3. The exine is spiny in insect pollinated plants, with sculptured pattern or smooth in wind pollinated plants.
4. The exine is not continuous throughout. It is interrupted, very thin at one or more places by small pores called germ pores.
5. The intine which is composed of cellulose and pectin encloses the protoplasm with a single haploid nucleus.
