Periplasmic Cuticular Calcium Oxalate Crystal Deposition in Dracaena Sanderiana

The chemical nature and biological basis for crystal deposition in epidermal subcuticular areas are reported here for the angiosperm Dracaena sanderiana. Position, development and identification of crystals in adult leaves of D. sanderiana was carried out using X-ray diffraction, crystal morphology and scanning and transmission electron microscopy techniques. Numerous small (< 1-6 µm) calcium oxalate monohydrate crystals were found between the primary epidermal cell wall and the cuticle. Their formation was highly specific and predictable with respect to location and relative timing of development during leaf ontogeny. The crystals were perisplasmic as, at formation, the nascent epidermal cell wall was external to the crystals. Cuticular crystallization of calcium oxalate monohydrate in D. sanderiana occurred in crystal chambers situated between the plasma membrane and the primary cell wall. Crystal deposition did not occur in developing guard cells. The spatial pattern of calcium oxalate monohydrate within the epidermal cells, orientation of the crystallographic axes and the existence of crystal chambers outside the plasma membrane suggest biologically controlled crystal deposition in D. sanderiana.