Question

List the function and characteristic features of tapetum.

Answer 1

Tapetum is the innermost wall of microsporangium. The tapetal cells are large and become filled with dense protoplasmic contents as well as nutrients as the microspore mother cell grows. Tapetal cells either become multi-nucleate or their nucleus becomes polyploid due to endoploidy. Two types of tapetum are found in angiosperms: amoeboid and secretory. In amoeboid, the tapetal cells fuse to form a plasmodium or periplasmodium because it passes in between the sporogenous cells to nourish them. The cells of secretory tapetum pass out substances over the sporogenous cells for their growth and differentiation.
Tapetum has following functions:
1. Nourishment of developing microspore mother cells and pollen grains.
2. It produces lipid rich Ubisch granules containing sporopollenin for exine formation, pollenkitt in case of entomophilous flowers.
3. It secretes enzymes such as callase which is responsible for the degradation of callose wall around pollen tetrad.