The exine is made up of sporopollenin, which is one of the most resistant organic material. The intine layer is made up of cellulose and pectin materials. The exine is hard and hence protects the pollen grains during adverse conditions.
Detailed Answer:
Exine is made up of a substance called "sporopollenin" while intine is made up of pectocellulose.
Sporopollenin is a resistant fatty substance, therefore, exine functions as protective covering of pollen grain. It also possesses the proteins for enzymatic and compatibility reactions.
