The hard outer layer of a pollen grain is made of a highly resistant organic material. However, this layer has prominent apertures where the resistant material is completely absent. Identify these apertures and their primary biological function.

Step-by-step solution

The hard outer layer of the pollen grain is the exine, which is made of the highly resistant organic material sporopollenin. Because sporopollenin is impenetrable, the exine has prominent apertures called germ pores where sporopollenin is absent. During pollen germination on the stigma, the pollen tube emerges through one of these germ pores to carry the male gametes towards the ovule. The micropyle is a small opening in the integuments of an ovule, not an aperture on a pollen grain. While the vegetative cell does