Question

Describe the structure of pollen grain.

Answer 1

1. The process of formation of microspores from diploid microspore mother cell through meiotic cell division inside the microsporangia or pollen sacs is called microsporogenesis.
2. Structure of microspore: 
   Pollen grain/microspore is a non-motile, haploid, unicellular body with a single nucleus. It is surrounded by a two-layered wall called sporoderm. The outer wall is called exine and the inner wall is called intine.
3. Exine: 
   The exine is thick and made up of a complex, non-biodegradable, substance called sporopollenin and it is resistant to chemicals. It may be smooth or with a sculptured pattern (characteristic of the species). At some places, exine is very thin showing thin areas known as germ pores. Germ-pores are meant for the growth of emerging pollen tubes during the germination of the pollen grain.
4. Intine: 
   The inner wall layer, intine consists of cellulose and pectin.