Cytochemistry and Ultrastructure of the Mucilage Secreting Trichomes of Nymphoides peltata (Menyanthaceae)

The young developing leaves in the buds of Nymphoides peltata are covered by a hyaline mucilage. The mucilage contains free sugars, polysaccharides and proteins. The most abundant monosaccharides of the polysaccharide fraction are arabinose and galactose. Therefore, the major component of the mucilage is probably an arabinogalactan or arabinogalactan protein. The mucilage is secreted by glandular trichomes. It is suggested that both the polysaccharide and the protein fraction of the mucilage are transported to the plasmamembrane by vesicles of the Golgi apparatus (granulocrine secretion). Secretory proteins are probably synthesized in the rough endoplasmic reticulum and transported to the Golgi apparatus via transition vesicles. Polysaccharides were localized in Golgi vesicles by ultracytochemistry. After exocytosis the secretion is accumulated between the cell wall and the cuticle; this leads to the formation of protrusions on the outer walls of the glandular cells. Finally, the cuticle is ruptured and the secretion is released. The biological function of the mucilage is not known. Possibly the mucilage is a lubricant or a protection from desiccation.