Question

Explain the structure of microsporangium and write the functions of its different layers.

Answer 1

Microsporangium is the sporangial structure which contains microspores which are the pollen sacs giving rise to male gametes in an angiosperm. A microsporangium is circular in outline in transverse section and is usually surrounded by four wall layers. The outermost is the single layer of the epidermis. The second layer is endothecium, where cells develop thickenings. The middle layer is made up of 2-4 cells. The innermost layer is tapetum, which provides nutrition to the developing pollen cells. The cells of tapetum may be multinucleate. The outer three layers are protective in function. They also help in dispersal of pollens by dehiscing themselves. There are four pollen sacs present inside. The centre of the microsporangium comprises of compact sporogenous tissue. These tissues undergo meiotic divisions to form microspore tetrads, that further divide to form pollen grains.