Effects of exogenous nitric oxide on cadmium toxicity and antioxidative system in perennial ryegrass

The effects of sodium nitroprusside (SNP, a donor of NO) on cadmium (Cd) toxicity in ryegrass seedlings (Lolium perenne L.) were studied. 100 and 150 mu M Cd stress had a detrimental effect on ryegrass seedlings. Exposure of 100 and 150 mu M Cd inhibited plant growth, decreased chlorophyll concentration, and reduced the absorption of Fe, Cu and Zn. Excess Cd also altered the activities of antioxidant enzymes, and increased the accumulation of reactive oxygen species (ROS). Exogenous NO alleviated Cd toxicity of ryegrass plants, especially under the stress of 150 mu M Cd, as evidenced by improved plant growth and increased concentrations of chlorophyll and mineral nutrients. Exogenous NO also mitigated oxidative stress by regulating the activities of antioxidant enzymes and the contents of non-antioxidants. Moreover, the absorption of Fe, Cu and Zn was increased, indicating that exogenous NO stimulated H+-ATPase activity to promote sequestration or uptake of ions. The applications of NO also reduced the translocation of Cd from roots to the leaves. These results indicate that the mechanisms of NO for mitigating Cd toxicity may be associated with reduced root-to-shoot translocation of Cd and enhanced capacity of antioxidative systems to protect plants from oxidative stress.