The exine is the outer layer of the pollen grain and is primarily composed of a tough substance called sporopollenin. This layer protects the pollen from environmental factors, such as moisture and UV radiation, ensuring the viability of the male gametes during their journey to fertilize the ovule in plants. Exine has a unique structure that can vary among different plant species, often featuring intricate patterns and textures. These characteristics can aid in the identification of plant species and play a role in the interaction between pollen and pollinators, as the surface properties can influence how pollen adheres to insects or other vectors.