Exogenously applied calcium alleviates cadmium toxicity in Matricaria chamomilla L. plants

Cadmium (Cd) toxicity in plants leads to serious disturbances of physiological processes, such as inhibition of chlorophyll synthesis, oxidative injury to the plant cells and water and nutrient uptake. Response of Matricaria chamomilla L. to calcium chloride (CaCl2) enrichment in growth medium for reducing Cd toxicity were studied in this study. Hydroponically cultured seedlings were treated with 0, 0.1, 1, and 5 mM CaCl2, under 0, 120, and 180 mu M CdCl2 conditions, respectively. The study included measurements pertaining to physiological attributes such as growth parameters, Cd concentration and translocation, oxidative stress, and accumulation of phenolics. Addition of CaCl2 to growth media decreased the Cd concentration, activity of antioxidant enzymes, and reactive oxygen species accumulation in the plants treated with different CdCl2, but increased the growth parameters. Malondialdehyde and total phenolics in shoots and roots were not much affected when plants were treated only with different CaCl2 levels, but it showed a rapid increase when the plants were exposed to 120 and 180 CdCl2 levels. CaCl2 amendment also ameliorated the CdCl2-induced stress by reducing oxidative injury. The beneficial effects of CaCl2 in ameliorating CdCl2 toxicity can be attributed to the Ca-induced reduction of Cd concentration, by reducing the cell-surface negativity and competing for Cd2+ ion influx, activity enhancement of antioxidant enzymes, and biomass accumulation.