Attenuation of Sulfur Dioxide Damage to Wheat Seedlings by Co-exposure to Nitric Oxide

The protective function of nitric oxide (NO) has been extensively clarified in plant responses to abiotic stresses. However, little is known about the regulation of NO in plants exposed to sulfur dioxide (SO₂). In the present study, we found that co-exposure to NO significantly attenuated SO₂-induced wheat seedling growth inhibition. Data showed that NO efficiently prevented SO₂-triggered oxidative stress, as indicated by decreasing reactive oxygen species production, lipid peroxidation, and electrolyte leakage. This might be attributed to the regulatory role of NO in antioxidative defense, such as increasing the activities of antioxidative enzymes and the contents of non-enzymatic antioxidants. The SO₂-caused declines in soluble protein and chlorophyll content were efficiently recovered by NO application. Photosynthetic parameters, such as net photosynthetic rate, maximum photochemical efficiency, and actual photochemical efficiency, were protected by NO. In conclusion, this study demonstrated that during SO₂ exposure, co-application of NO can efficiently alleviate plant damage probably by regulating the antioxidative defense, and protecting plant photosynthesis-related process.