Question

Why do you think the exine should be hard

Answer 1

Exine protects the pollen grains from adverse conditions...though the pollen tube or germ tube comes out....The exine protects the pollen grains....hence the exine should be hard

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 .