Question

Pollen grains are able to tolerate extremes of temperature and dessication as its exine is made up of

Answer 1

Hey there...
Exine is made up of SPOROPOLLENIN...
It is the most toughest material and is resistant to acids, alkalies and extreme heat..

Hope it is useful...

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 .