Tapetum is the innermost layer of another wall and is derived from the peripheral wall layer and the connective tissue of another lining the anther locule. Thus, the tapetum is dual in origin and gives nourishment to the developing sporogenous tissue, microspore mother cells, and microspores. The cells of the tapetum may be uninucleate or may have more than one nucleus or polyploid nucleus. It also helps in the formation of wall material, sporopollenin, pollenkitt, tryphine and number of proteins that control incompatibility reaction. The fertility and sterility of the microspores or pollen grains are also controlled by tapetum.
Based on the behavior of tapetum, there are two types:
- Secretary tapetum: In this case, original position, and cellular integrity are retained and supplies nourishment to the developing microspore.
- Invasive tapetum: It is otherwise known as periplasmodial type of tapetum. In this type, the cells loose their inner tangential and radial walls and the protoplast of all tapetal cells coalesces to form periplasmodium.
