中文摘要：

二氧化氮是一种主要的空气污染物,通过气孔进入植物叶片后快速转化为硝酸盐和亚硝酸盐,引发作物减产或品质下降。研究了外施水杨酸对小麦幼苗应答二氧化氮胁迫的调节作用,目的是减轻NO2对植物的伤害。供试水杨酸浓度为0.5mM·L^-1,NO2浓度为20μl·L^-1。NO2的暴露方法为：将10天龄的小麦幼苗置入密闭的玻璃熏气箱中,NO2气体由钢瓶输出,于玻璃瓶中与炭滤空气混合,通入熏气箱中。采用动式熏气,NO2浓度由烟气分析仪在线监测。每天熏气3h,连续4d。对照植株只通入炭滤空气。结果表明,该浓度NO2造成植物急性伤害,如生长速率显著降低、叶片变黄、叶尖死亡;电解质渗透率与丙二醛含量则显著升高。外施水杨酸有效减缓了NO2暴露引发的上述伤害症状。其作用机理至少与水杨酸处理提高叶片的可溶性糖、游离脯氨酸以及超氧化物歧化酶、过氧化物酶和过氧化氢酶活性有关。

英文摘要：

Nitrogen dioxide（NO2）is a main air pollutant,and enters into plant leaves by stomata to rapidly accumulate nitrate（NO3^-）and nitrite（NO2^-）resulting in reduction and deterioration in crop yield and quality.In the present study,we investigated the regulatory role of exogenous salicylic acid（SA）in wheat seedling response to NO2,and aimed to alleviate the NO2-induced damage to plants.The SA concentration tested was 0.5mM·L^-1,and NO2 was 202μl·L^-1.The SA was applied by seedling foliar spraying.For NO2 exposure,10-day-old wheat plants were transferred to a glass chamber and NO2 gas was supplied directly from cylinders,into a dilution reservoir into which charcoal filtered air was drawn.Using dynamic fumigation,the concentrations of NO2 in the chamber are measured by on-line flue gas analyzer.Plants were fumigated during the light period for 3hper day for 4days.For the control,charcoal filtered air alone was supplied.Results show that NO2 at the tested concentration causes acute damage to plant seedlings,with a reduction in plant growth,yellowish leaves,and leaf apex death. Under NO2 stress,plant leaf electrolyte leakage and malondialdehyde content dramatically increase.The application of SA efficiently alleviated the above-mentioned damage symptom.This may be associated at least partially with SA-enhanced contents of soluble sugar and proline,and activities of superoxide dismutase,peroxidase and catalase.