采用营养液培养试验，通过添加不同浓度(0.05、0.1、0.2、0. mmol·L-1)的硝普钠（SNP）作为NO供体，研究外源NO对NO3-胁迫下黄瓜幼苗生长及叶片抗氧化酶活性的影响.结果表明： 140 mmol·L-1 NO3-胁迫下，外加0.1 mmol·L-1 SNP处理1 d和7 d后，黄瓜幼苗叶片中SOD、CAT和APX活性显著升高;MDA含量显著降低，可溶性蛋白含量增加，说明外加0.1 mmol·L-1 SNP增强了黄瓜幼苗对活性氧的清除能力，降低了膜脂过氧化程度，幼苗生长势增加，对高浓度NO3 -胁迫的抗性增强；当SNP浓度达0.3 mmol·L-1处理7 d后，SOD、POD、CAT和APX活性均开始降低，MDA含量增加，黄瓜幼苗受害加重.外加一定浓度(0.1～0.2 mmol·L-1)的外源NO可缓解NO3-胁迫对黄瓜幼苗的影响.
In this study, cucumber seedlings were cultivated in nutrient solution added with different concentration (0.05, 0.1, 0.2, and 0.3 mmol·L-1) sodium nitroprusside (SNP) as nitric oxide (NO) donor to study the effects of exogenous NO on the growth of cucumber seedlings and the activities of antioxidant enzymes in cucumber leaves under NO3- stress. Under the stress of 140 mmol·L-1 NO3- ,treating with 0.1 mmol·L-1 of SNP for 1 d or 7 d increased the leaf soluble protein content and superoxidase (SOD), catalase (CAT), and ascorbic acid peroxidase (APX) activities, and decreased the leaf malondialdehyde (MDA) content significantly, suggesting that exogenous NO could enhance the capacity of cucumber seedlings in scavenging active oxygen species, protect the seedlings from the peroxidation of membrane lipids, and promote the seedlings growth and increase their resistance to high concentration NO3- stress. After the cucumber seedlings grew in 0.3 mmol·L-1 of SNP for 7 d, the activities of leaf SOD, POD, and CAT decreased, and the MDA content increased, resulting in the injury of cucumber seedlings. It was indicated that certain concentration (0.1-0.2 mmol·L-1) exogenous NO could alleviate the NO3- stress to cucumber seedlings.