Which layer of microsporangium nourishes the developing pollen grains?

Tapetum

The correct answer is Option (4) - Tapetum

The tapetum is the innermost layer of cells in the wall of the microsporangium specifically surrounding the developing microspores.Its primary function is to provide nourishment and support to the developing pollen grains. The tapetum cells are rich in cytoplasm and contain various nutrients, including carbohydrates, proteins, and lipids.

During microsporogenesis, the tapetum supplies essential nutrients and metabolites to the developing pollen grains, promoting their growth, maturation, and viability. It also synthesizes and secretes enzymes and proteins that are involved in the development of the pollen wall and exine, the outer layer of the pollen grain.