(a) Germ pore is present on the pollen grains. It is the place where exine and sporopollenin is absent. The contents of the pollen grain move into the pollen tube through the germ pore.
(b) Sporopollenin is present on the outer surface of pollen grains. Sporopollenin is one of the most resistant organic material known. It can withstand high temperatures and strong acids and alkali. No enzyme that degrades sporopollenin is so far known.
(c) Germinative cell is one of the two cells present inside the pollen grain which gives rise to male gametes through Mitosis.
