Tapetum is the innermost layer of the anther wall. Its functions are as follows:

1. It is a nutritive layer that provides nourishment to the growing microspores.

2. It also secretes sporopollenin which forms the outer layer of exine around the pollen grains.

3. It also secretes an enzyme 'callase' which helps in the separation of microspores from the microspore tetrad formed after microsporogenesis.

4. It also secretes pollen kit which helps in adhering the pollen grains together for their effective dispersal during pollination.