Calcium Oxalate Dihydrate-Monohydrate Association in Grape (Vitis Vinifera) Endosperm

Calcium oxalate occurs in two forms, monohydrate (whewellite) and dihydrate (weddelite). Both forms occur intracellularly in plants, typically within vacuoles. In particular plant species a given tissue usually has crystals with specific and characteristic morphology. The occurrence of calcium oxalate monohydrate and dihydrate together in the same cell is thought to be extremely rare and has been reported only in Allium and Begonia. In vitro the dihydrate is unstable under certain conditions and may dissolve and reprecipitate as the monohydrate. In this paper we report observations of crystals isolated from grape (Vitis vinifera) endosperm. Using optical methods both calcium oxalate monohydrate and dihydrate, as well as dihydratemonohydrate associations, have been identified.