MP Board · Class 12 · Biology · Sexual Reproduction in Flowering PlantsExplain the structure of a typical microsporangium with the help of well-labelled descriptions of its wall layers.

In flowering plants, a typical microsporangium is circular in outline and is generally surrounded by four wall layers: the epidermis, endothecium, middle layers, and the tapetum. The outer three layers—epidermis, endothecium, and middle layers—are protective in function and help in the dehiscence of the anther to release the pollen grains. The epidermis is the outermost single-layered protective covering. The endothecium lies just below the epidermis and possesses characteristic fibrous thickenings that assist in anther dehiscence due to their hygroscopic nature. The middle layers consist of one to three layers of cells that undergo degeneration during the maturation of the microsporangium. The innermost layer is the tapetum, which is multinucleate and possesses dense cytoplasm to nourish the developing pollen grains. Tapetum cells also secrete Ubisch bodies, sporopollenin, and pollenkitt, which are essential for the formation of the exine layer of pollen grains and protection against environmental stress.