A histochemical study of meiocytes, microspores, pollen and the tapetum in Kalanchoe

A histochemical study was made of developing sporogenous cells, meiocytes, microspores, pollen and the tapetum in anthers of Kalanchoë morlagei. Storage polysaccharides were seen only in mature pollen. Ascorbic acid was not found in the sporogenous cells, but in meiocytes a high quantity of this compound occurred in the cytoplasm. Spore tetrads, microspores and pollen also had a high ascorbic acid content. The amounts of RNA and proteins were high in the sporogenous cells and in meiocytes during meiosis–I, but a small reduction trend with respect to RNA content was noticed. Microspores in the tetrad showed high amounts of RNA and proteins. In the young microspores RNA and proteins declined. Later, as the microspores matured, an increase in content of RNA and proteins took place. The wall of the young microspores gave a faint green colour with azure B stain, the intensity of which increased and remained high in the exine of the mature pollen. The additional wall thickening around the meiocytes and tetrads gave a strong pink colour with PAS test. This thickening showed presence of silver granules when tested for ascorbic acid, the tapetum synthesized abundant quantities of PAS positive starch, ascorbic acid, RNA and proteins from its appearance in the anther wall until microspore formation. During meiocyte meiosis the tapetum became highly vesicular. Our results indicate that the tapetum constitutes a tissue specialized for storing and supplying basic nutritive substances for the developing pollen in the anther.