Explain the role of tapetum in the formation of pollen-grain wall.

The innermost wall layer of microsporangium is called tapetum. Cells of tapetum have dense cytoplasm and generally have more than one nucleus.

Functions of tapetum –

• It provides nourishment to the developing pollen grains.

• Helps in the formation of exine (the hard outer layer of pollen grain) which is composed of sporopollenin.

• It secretes hormones and enzymes