CALCIUM-CONTAINING CRYSTALS IN TELFAIRIA HOOKER (CUCURBITACEAE).

ABSTRACT

Polarized light and scanning electron microscopy were used to examine the distribution, location and form of crystals in the leaves, probracts, stems, flowers and seed-coats of Telfairia pedata (Sims) Hooker and T. occidentalis Hooker fil. Energy-dispersive X-ray analysis showed that calcium is the primary crystal cation. Histochemical tests confirmed that the crystals are mainly calcium oxalate and these are particularly abundant around and within the vascular tissues. Cystolith - like crystals of calcium carbonate are also numerous at the bases of macrohairs and as heavy incrustations within the midrib and major veins of mature leaves. The crystal types include solitary, acicular, druse (cluster) and combinations of two or more of these. Substantial amounts of soluble oxalate were also found to be present, especially in the leaf laminae of T. occidentalis. The total oxalate contents of the edible portions of T. occidentalis were determined and compared with values published for other vegetables.