Effect of NaCl on Cd stress modulation, antioxidant system and Cd uptake and accumulation in Malva parviflora L.

This study aimed to investigate the effect of mild salinity on cadmium (Cd)-induced toxicity in Malva parviflora. Forty days after sowing the seeds in trays containing Peat Moss soil, the plants were transferred to nutrient solutions under controlled light and temperature conditions. After one week, the plants were transferred to complete nutrient solutions with four treatments including 50 µM Cd, two levels of NaCl (25 and 50 mM) along with 50 µM Cd and control. Six days after the treatments, the plants were harvested and some biochemical and growth indices were evaluated. Both levels of salinity, especially 25 mM, resulted in increased length, weight and chlorophyll content in the plants exposed to Cd. In leaves and roots, the salinity reduced levels of lipid peroxidation, proline and soluble proteins contents, as well as activity of catalase, guaiacol peroxidase (GPX) and superoxide dismutase (SOD) in the plants treated with Cd. In addition, both salinity treatments reduced Cd content in roots and shoots. Investigation of electrophoretic pattern of enzyme extract in all studied plants revealed two isoenzymes of GPX. For SOD, three isoenzymes were observed in the leaves for all treatments. In the roots, five isoenzymes were detected for all plants exposed to Cd. Based on the results of this study, it seems that both levels of salinity can modulate the toxic effects of Cd and induction of oxidative stress and improve plant tolerance to Cd stress by reducing metal accumulation in M. parviflora.