Tapetum - Anther Wall Layers
Tapetum is the innermost and most important layer of the anther wall. It is generally composed of a single layer of cells. These cells completely surround the sporogenous tissue, and they attain maximum development when the sporogenous tissue is at the tetrad stage. The tapetum is of dual origin in most of the angiosperms; the cells of the outer side originate from the derivatives of the PPCs, while those of the inner portion originate from the cells of the connective. Usually tapetal cells of different origin also appear different in size and structure. Tapetum of dual origin is also known as dimorphic tapetum. In Alectra thomsoni, the tapetal cells on the outer side are much smaller than those on the inner side.
Figure: (a) Diagrammatic sketch of transverse section of an anther showing the position of tapetum. (b) A few cells enlarged to show the dense cytoplasm and multinucleate condition of the tapetal cells.