Modulation of cadmium toxicity and enhancing cadmium-tolerance in wheat seedlings by exogenous application of polyamines.

Cadmium (Cd) stress causes several negative physiological, biochemical and structural changes due to the oxidative stress caused through the generation of ROS, leading to a reduction in plant growth. To look for an effective method to increase Cd tolerance of wheat seedlings, the effect of presoaking Triticum aestivum L. seeds in spermidine (Spd; 2mM) or spermine (Spm; 2mM) on seedling growth, physiological attributes and antioxidant defence system under 1mM Cd stress were investigated. Spm or Spd alleviated the adverse effects of Cd stress to convergent degrees. Presoaking wheat seeds in either polyamine increased the seedling growth and the activities of antioxidant enzymes compared to the control, but other attributes were slightly affected. Under Cd stress, presoaking seeds in either polyamine significantly increased seedling growth, membrane stability index, relative water content, concentrations of protein, starch, ascorbic acid, total glutathione, Spm and Spd, and the activities of superoxide dismutase and catalase. In contrast, electrolyte leakage, concentrations of proline, total soluble sugars, malondialdehyde, hydrogen peroxide and Cd(2+), and the activities of peroxidase and ascorbate peroxidase were reduced compared to the control. These results are important as the potential of Spd or Spm to alleviate the harmful effects of Cd stress offer an opportunity to increase the resistance of wheat seedlings to growth under Cd stress conditions.