Alleviation of silver toxicity by calcium chloride (CaCl2) in Lemna gibba L.

The toxicity effects of silver (Ag) and the protective role of calcium chloride (CaCl2) was studied in Lemna gibba L. (L. gibba) plants. Silver speciation showed that silver toxicity in L. gibba culture medium can be attributed to free ionic Ag(+) concentration. Frond abscission, intracellular reactive oxygen species (ROS) formation and intracellular uptake of Ag(+) were investigated when L. gibba plants were exposed to AgNO3 concentrations (0.5, 1, 5, and 10 μM) supplemented or not by 10 μM CaCl2. An increase in frond abscission, intracellular ROS and intracellular uptake of Ag(+) were detected in L. gibba plants for all tested concentrations of AgNO3 after 24 h treatment. However, addition of 10 μM CaCl2 to the L. gibba culture medium reduced the toxic effects of Ag by decreasing silver uptake into the plant and intracellular ROS formation. The results suggest that Ag-induced toxicity was attributed to Ag(+) accumulation and chloride was able to protect L. gibba plants against Ag toxicity by formation of complexes with Ag and then alleviation of the metal induced oxidative stress.