Question

Why do pollen grains remain preserved for long time ?

Answer 1

The pollen grains have a tough outer wall. The wall is made up of cellulose and sporopollenin. Sporopollenin is a substance which is very tough and resistant. This provides protection to the pollen grains from adverse conditions like high temperature, pH, etc. This helps to preserve the pollen grain and prevents from getting denatured for a long period of time.