Question

Why the exine should be hard?

Answer 1

Pollen grains are the male gametophyte that have two layers.
1.Intine (inner layer): It is a thin layer made up of cellulose and pectin.
2.Exine (outer layer): It is made up of sporopollenin.

Exine is the outermost layer of pollen grains and it helps in the protection of pollen grains development. Sporopollenin is a hard and most resistant organic material that cannot be degraded by enzymes and can withstand severe environmental conditions. Due to the presence of sporopollenin, exine is hard.

Exine protects pollen grains from unfavourable environmental conditions. Thus exine being hard is advantageous.