Cadmium (Cd) toxictity and possible role of salicylic acid (SA) in alleviating Cd-induced toxicity were investigated on ornamental hydrophyte Iris hexagona. Compared to the control, treatments with 100 and 500 µM Cd for 7 days significantly decreased dry weight, the contents of chlorophyll, photosynthetic parameters, and increased the content of thiobarbituric acid reactive substance. Pretreatment of the roots of I. hexagona seedlings with 1 µM SA before Cd exposure may increase dry weight, photosynthetic rate, activities of antioxidant enzymes, improve the cell ultrastructure and protect plants from Cd-induced oxidative stress damage. However, SA pretreatment had no significant effect on Cd concentrations in the leaves and roots. It is suggested that SA-induced Cd tolerances in I. hexagona are likely associated with increases in antioxidant enzyme activities and vacuolar compartmentation, rather than Cd uptake.
Keywords: Antioxidant enzyme; Cadmium; Iris hexagona; Salicylic acid; Ultrastructure.