The process of formation of microspore from a pollen mother cell by meiosis...
Structure of Microsporangium
A typical microsporangium appears circular in outline and is surrounded by four walls:
Epidermis: It is the outermost single layer of cell which is protective in nature.
Endothecium: It is the second layer with thick cells, help in dehiscence and is protective in nature.
Middle layer: It is the third layer composed of 1-3 layers of cells, help in dehiscence and is protective in nature.
Tapetum: It is the fourth and innermost layer of cell with dense cytoplasm and many nuclei. It provides nourishment to the developing pollen grains.
The centre of each microsporangium is filled with closely arranged similar cells called sporogenous cells.
At maturity, pollen sac is formed by fusion of two microsporangium in each lobe.
Microsporogenesis
The process of formation of microspore from a pollen mother cell by meiosis is called microsporogenesis.
Each cell of the sporogenous tissue in a microsporangium acts as a potential pollen mother cell (PMC) or microspore mother cell.
PMC undergoes meiotic divisions to form cluster of four cells called microspore tetrad.
On maturity, the anther dehydrates and the microspores separate from each other to form pollen grains.