Question

Why exine should be hard? And what is the function of germ pores

Answer 1

Pollen grain has two coverings which form wall like structure around it. Outer hard covering is called exine which is made up of a substance called sporopollenin. It protects the pollen grain from dessication and other external injuries. Inner wall is called intine. Intine is a continuous structure while exine is discontinuous. Some portion of pollen is exposed through pore like structures called germ pore. Through germ pores, pollen tube comes out from pollen grain upon deposition on stigma of flower. The pollen tube lead the male gamate upto egg/ovule.

Answer 2

Explanation:

$\tt\pink{\underline{Exine}}$

→ It age outer layer of pollen grain and very hard.

→ It age made up of sporopollenin in which is most resistance organic material present in nature .

→Sporopollenin is Resistance to high temperatures stronger acids and alkaline and also to enzyme .