Physiological and ultrastructural studies on calcium oxalate crystal formation in some plants

Abstract

Results from light, scanning, and transmission electron microscopic examination of CaOx crystal formation in 2 plant species, namely Corchorus olitorius L. and Malva parviflora L., revealed the presence of crystalline deposits. These deposits were of prismatic type in the case of C. olitorius and of druse type in the case of M. parviflora. Ultrastructurally, some differences were observed between crystal idioblast and noncrystal cells. Moreover, the effect of heavy metals and different calcium concentrations on the growth of calcium oxalate crystals in leaves of the 2 plants was investigated. Different analytical techniques were used to determine the influence of exogenous cadmium (Cd), lead (Pb), copper (Cu), and zinc (Zn) on CaOx deposition and to detect the presence of these metals in CaOx crystals. We found a positive correlation between the calcium concentration in the nutrient medium and the production of calcium oxalate crystals in the leaves of hydroponically grown plants. On the other hand, addition of the heavy metals to the nutrient medium decreased the number of crystals. Our investigation suggests that CaOx crystals do not play a major role in heavy metal detoxification in these 2 plant species but do play an important role in bulk calcium regulation. © TÜBITAK.