What is a pollen bank?

Assertion $\left(\mathrm{A}\right):$ Pollengrains are well preserved as fossils

Reason $\left(\mathrm{R}\right):$ The exine of pollen grains is made up of sporopollenin, which can withstand high temperatures, strong acids and alkali.

Assertion $\left(\mathrm{A}\right):$ Xenogamy involves transfer of pollen grains from the flower of one plant to the stigma of another plant.

Reason $\left(\mathrm{R}\right):$ This is the only type of pollination which brings genetically different types of pollen grains to the stigma.

The correct answer is:

Among the following statements related to pollens, choose the correct one.

Statement $\mathrm{I}$: In $40\%$ of angiosperms pollen grains are shed at the $3$—celled stage.

Statement $\mathrm{II}$: Intine is made of cellulose and pectin, and it is discontinuous with germ pores.