Which of the following has proved helpful in preserving pollen as fossils?

Sporopollenin is resistant to enzymes, strong acids, alkalis, and high temperatures. Hence, pollen grains are well-preserved in fossils due to the presence of this organic material in its exine.
(1) Pollen kitt is an oily, thick, viscous, hydrophobic layer over the surface of pollen grains of many insect-pollinated species. It imparts stickiness, odor and colour to the pollen grains and the substance is transferred by tapetum. It has carotenoid or fl avonoid pigments that impart yellow or orange colour to the pollen grains. Stickiness is due to the presence of glycoproteins, lipids, glycolipids and monosaccharides. It is present over exine in entomophilous plants and in the germ pores in anemophilous plants.

(2) Cellulose is present in the intine of pollen grains, which forms the wall of pollen tube. It is degradable.

(3) Oil content is present over the exine and it is responsible for hydrophobic nature of pollen grains of entomophilous species.