The alleviation of cadmium toxicity in oilseed rape (Brassica napus) by the application of salicylic acid

To assess the potential role of salicylic acid (SA) in plants under cadmium (Cd) stress, a study was conducted on three different oilseed rape (Brassica napus) genotypes. Gas exchange parameters, photosynthetic pigments, antioxidant enzymes activities, mineral nutrients concentration, and ultrastructural analysis were carried out for assessment. Interestingly, cadmium treatment reduced gas exchange parameters, photosynthetic pigments, mineral elements [calcium (Ca), magnesium (Mg), and iron] and the activity of catalase (CAT) enzyme. Whereas, a pronounced increase was observed in malondialdehyde content and antioxidant enzymes, cadmium and zinc accumulation. Impressively, SA played its role as an alleviatory agent by reducing the damage to all parameters caused by Cd except internal CO2 concentration which was further decreased by SA. Even more, Cd and SA showed synergistic effects by increasing superoxide dismutase, peroxidases, ascorbate peroxidase, guaiacol peroxidase, glutathione reductase and decreasing CAT. Apart from affecting the enzyme activities of oilseed rape, both Cd and SA had the same inhibitory effects on Ca and Mg concentrations. Damage caused by Cd to chloroplast and other internal organelles were almost rectified by SA. Effective role of SA, in alleviating Cd toxicity, could be attributed to the SA-induced improvement of photosynthetic activities, enhancement of antioxidant enzymes activities, reduction in lipid peroxidation and Cd uptake. These findings reflect the possible role of SA as a potential inhibitor of cadmium toxicity by strengthening the internal immunity in oilseed rape.