In a typical microsporangium, the function of tapetum is -

Nourishment to devleoping pollen grains

The correct answer is Option (3) → Nourishment to devleoping pollen grains 

Atypical stamen has two parts – the long and slender stalk called the filament, and the terminal generally bilobed structure called the anther. The anther is a four-sided (tetragonal) structure consisting of four microsporangia located at the corners, two in each lobe.
The microsporangia develop further and become pollen sacs. They extend longitudinally all through the length of an anther and are packed with pollen grains. In a transverse section, a typical microsporangium appears near circular in outline. It is generally surrounded by four wall layers– the epidermis, endothecium, middle layers and the tapetum. The outer three wall layers perform the function of protection and help in dehiscence of anther to release the pollen. The innermost wall layer is the tapetum. It nourishes the developing pollen grains.

The tapetum is a specialized tissue found within the anther of a flower, specifically surrounding the developing microspores. It plays a crucial role in the development and nourishment of the pollen grains. The tapetum provides essential nutrients, proteins, and enzymes to support the development and maturation of the pollen grains.Cells of the tapetum possess dense cytoplasm and generally have more than one nucleus.