Inclusions of graniferous tracheary elements in the root hemi-parasiteOlax phyllanthi (Olacaceae)

Abstract

Xylem tracheary elements containing structural material in their lumina are reported in the haustorium ofOlax phyllanthi. This is the first detailed description of graniferous tracheary elements in the Olacaceae. The contents of the lumen exist occasionally as granules but more frequently as “amorphous” masses and dispersed material, all with the same tubular structure. A tubular ultrastructural form has not previously been reported in graniferous tracheary elements of parasitic angiosperms. The lumen of the tracheary element may also contain crystalloids, with a regular lattice plane configuration, and various coarse and fine fibrils. At the light microscope level much of the luminal contents stains positively for protein. The ultrastructure of the crystalloids and tubular components is also consistent with a principally proteinaceous material. In contrast, the fine fibrillar material stains positively for polysaccharide using the Thiery reaction on thin sections. With graniferous tracheary elements seemingly no longer conducting sap, the lumen and pit membranes often become secondarily impregnated, apparently by phenolics.