Electron Microscopic Investigation of the Coating Found on Torus-Bearing Pit Membranes of Botrychium Dissectum, the Common Grape Fern

Abstract

TEM investigation of the torus-bearing pit membranes in tracheids of Botrychium dissectum wood has revealed in some specimens a coating that covers the pit membrane and torus, and sometimes lines the lumen-side of the tracheary wall. Such coatings have been associated with wound response in dicot woods, but have not previously been reported in the wood of Botrychium. In response to wounding, rhizome sampIes incubated on water-saturated filter paper produced the coating material within 4 days. Rhizome sampIes that were incubated with an ethylene inhibitor for a maximum incubation time of 20 days did not develop the wound-response coating. Therefore, based on experimental evidence the wound response appeared to be ethylene mediated. Field sampIes which were artificially grazed by removing the leaf/spike complex exhibited a displaced wound-response coating in the rhizome. Histochemical studies indicate that the coating material has both pectin and phenolic components.