Question

Important function of tapetum

Answer 1

The main function of tapetum tissue is briefly outlined below:

i. Secretion of the enzyme callase (β-1,3- glucanase) to dissolve the callosic wall of the tetrad and set them free. Stieglitz and Stern (1973) measured the callase activity separately in anther wall and the microsporocytes from early meiosis to tetrad dissociation.

ii. Secretion of polysaccharides into the locules during the free microspore stage, which are absorbed by microspores.

iii. The role of the tapetal cells in the secretion of sporopollenin precursor is non-ambiguous however, its role in the synthesis of sporopolle­nin is not clear. In taxa with secretory tapetum, sporopollenin is deposited in the form of orbicules on the inner phase of the tapetal cells. In taxa with plasmodial tapetum sporopollenin material is present in the thecal fluid.

iv. Tapetal cells have other activities that result in formation of different structures, which characterize some families. For instance in Onagraceae tapetal cells play a role in formation of fine flexible threads, known as viscin threads, in continuation with the outer layer of the exine. In Asteraceae the tapetum forms an acetolysis resistant membrane outside the sporogenous tissue. This membrane is known as the culture sac or peritapetal membrane.

v. Formation of Ubisch Bodies

vi. Formation of pollenkitt, and tryphine, which are deposited on the pollen surface and helps to bind pollen grains together, and for efficient insect pollination. Ultrastructural studies have shown that both of these substances are synthesized in a special population of plastids in the tapetal cells.

vii. Formation of pollen wall during post-meiotic period.

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Answer 2

Tapetum is important for nutrition nad development of pollen grains as well as a source of precursors for the pollen ciat