Vessel wall structure: an investigation using scanning electron microscopy

Abstract

Scanning electron microscopy has been used to examine the architecture of the internal (lumen) surfaces, and the pits in the walls, of the tracheary elements of 22 species distributed amongst the Gnetaceae and 16 angiosperm families. With the possible exception of Gymnocladus, the vessels of species with vestured pits also have warted internal surfaces; the vessels of Fagus and the tracheids of Bubbia have nonvestured pits, but warted internal surfaces; the vessels of Liquidambar, Ulmus, Daphniphyllum, and Helichrysum have non-vestured pits and non-warted internal surfaces.

The classification of species with vestured pits on the basis of vesture morphology is considered. So, too, is the relationship between warts and vestures. The latter are regarded as fused or conglomerate warts covered by the denatured remains of cell membranes, the whole probably incorporating products of cell senescence and death.

The occurrence of vestured pits in the vessels of Gnetum links the genus with the angiosperms. Their occurrence in fibres of Alstonia and Gonystylus contradicts the belief that vesture formation is linked with a conducting function of cells.