Endothecium - Anther Wall Layers
The layer of cells lying immediately next to the epidermis is the endothecium, which is responsible for the dehiscence of the anther. It is usually single-layered, but sometimes multilayered as in Nicotiana tabacum. You may recall that the endothecium originates from the PPCs. The endothecium mostly differentiates in the four protuberant or bulging parts of the anther. Sometimes, it also develops near the connective region of the anther. In some plants like Triticale an entire ring of endothecium is present.
Figure: (a) Diagrammatic sketch of the transverse section of an anther showing the position of the endothecium (small arrows). Large arrows point to the two dehiscing regions of the anthers showing longitudinal dehiscence. (b) A few endothecial cells enlarged to show the characteristic endothecial thickenings.
The endothecial cells are radially elongated. Their full development is attained by the time the anther is ready to dehisce to discharge the pollen grains. At maturity the endothecial cells can be easily recognized by the presence of fibrous bands. They usually arise from the inner tangential walls. The fibrous bands radiate outwards and upwards ending near the outer wall of each cell. Hence, the inner tangential wall appears thick, whereas the outer tangential wall appears thin. These thickenings contain a high proportion of cellulose and a small amount of pectin.