Why the exine should be hard?

The exine, the outer layer of the pollen grain, should be hard to protect the delicate genetic material inside from environmental stresses, such as UV radiation, desiccation, and microbial attack. A tough exine ensures that the pollen can survive the journey to the stigma of a compatible flower, which is crucial for successful fertilization and reproduction. Additionally, a hardened exine aids in the dispersal of pollen by wind or animals, ensuring that it reaches appropriate locations for germination.