Effects Of NO₂^-derived Nitric Oxide On Relieving Salt And Cold Stress For Maize Seedlings

Plants are often experienced various stress conditions because of growing in an open system in nature. And they formed a serious of adaptive mechanisms to mitigate the damage of adversity in the long-term evolution, in which the chemical signal molecules play an important role. The evidence of pharmacology and molecular genetics techniques showed that gas signaling molecule nitric oxide play a key role in plant tolerance to abiotic stresses. Compared with animals, the source of NO in plant is more diverse, and they were divided into oxidative routes and reductive routes. NO2- was used as a substrate to synthesize NO by enzymatic pathway and non-enzymatic pathway in reductive routes. Under acidic conditions, the reducing agent like Vc and GSH can reduce NO2- to NO. In previous studies, we have shown that NO2--derived non-enzymatic NO can significantly improve the resistance of maize to drought and heavy metals. In order to approve the broad spectrum resistance of NO sourced from NO2-, in the present studied we researched and discussed the function of this type NO in maize(Zea mays L.) seedlings resisting to salt stress and cold stress. The main results are as follows:(1) The residues of GSH or Vc in the solution of NO2- and GSH/Vc were tested, the results showed that the contents of Vc suddenly decreased in the first 10 min and can hardly detected after 20 min. Rapid decrease of the GSH contents were detected in the first 20 min in the solution, and the concentration of GSH dropped from 0.15 mg/m L to 0.04 mg/m L. The decrease speed of GSH decelerated later and turned to zero after 140 min.(2) NO2--derived non-enzymatic NO can remarkably promote the germination of maize seeds under salt stress. Compared with the salt treatment group, the maize seeds treated with NO had significant advantages in germinate rate, vigor index, root length and shoot length. NO2--derived non-enzymatic NO can also significantly increase the plant height, stem diameter and leaf area of the maize seedings under salt stress. The content of Chlorophyll and GSH were much higher than other groups. Besides, the treatment of NO can also enhance the activity of antioxidant enzyme, and decrease the content of ROS and MDA.(3) NO2--derived non-enzymatic NO can obviously relieve the growth inhibition of maize seedlings by cold stress, underlying the mechanism of enhancing the activity of antioxidant enzyme, such as CAT, APX and POD, increasing the GSH content and decreasing the content of ROS and MDA.So, NO2--derived non-enzymatic NO could significantly enhance the resistance of maize seedlings to salt stress and cold stress. Given the convenient source and the simple action, NO sourced from this pathway have potential application value.