Exogenous abscisic acid alleviates the toxicity of nickel in wheat seedlings

In order to evaluate the effects of exogenous abscisic acid (ABA) in alleviating nickel (Ni) stress in wheat plants. We studied the changes of biochemical and physiological in wheat seedlings exposed to 250 μM Ni with or without different treatments of ABA. Exposed to Ni (250 μM) caused adverse effect on growth of wheat seedlings, which was accompanied by increased the concentrations of superoxide anion（O2 − ） and malondialdehyde (MDA). However, exogenous application of ABA (2.5 and 5 μM) alleviated the Ni-induced inhibition of plant growth, decreased the concentrations of O2 − and MDA in wheat shoots. Further, application of ABA significantly modulated the activities of antioxidant enzymes and enhanced content of proline and soluble sugar in Ni-stressed wheats, but the application of 20 μM of ABA had no different significantly response for these parameters. The results indicated that application of ABA enhanced the antioxidant defense activities in Ni-stressed wheats, thus alleviating Ni-induced oxidative injury and enhancing Ni tolerance.