Distribution of insoluble polysaccharides, neutral lipids, and proteins in the developing anthers of Campsis radicans (L.) Seem. (Bignoniaceae)

In this study, distribution of polysaccharides, lipids, and proteins in the developing anthers of Campsis radicans (L.) Seem. was examined from sporogenous cell stage to mature pollen, using cytochemical methods. To detect the distribution and dynamic changes of insoluble polysaccharides, lipid bodies, and proteins in the anthers through progressive developmental stages, semi-thin sections of anthers at different developmental stages were stained with periodic-acid-Schiff (PAS) reagent, Sudan black B, and Coomassie brilliant blue, respectively, and examined under light microscope. Ultrastructural observations with TEM were also carried out to determine the storage form of starch in the connective tissue, and storage form of lipids in the tapetal cells. In sporogenous cell stage, anther wall contains numerous insoluble polysaccharides. However, from the sporogenous cell stage to the vacuolated microspore stage, the amount of insoluble polysaccharides in the anther wall decreases gradually. At bicellular pollen stage, tapetum degenerates completely and polysaccharides are not seen in the anther wall. Lipid bodies are observed in the cytoplasm of both middle layer and tapetal cells at tetrad stage, whereas they disappear in the vacuolated microspore stage. Compared with polysaccharides, proteins are limited in the anther wall at early stages of development. During pollen development, polysaccharides, proteins, and lipid bodies are scarce in the cytoplasm of sporogenous cells, but their amount increases at premeiotic stage. From tetrad stage to bicellular pollen stage, microspore cytoplasm contains variable amount of insoluble polysaccharide grains, lipid and protein bodies. At bicellular pollen stage, plentiful amount of starch granules are stored in the cytoplasm of the pollen grains. Proteins and lipid bodies are also present in the cytoplasm.