铅胁迫下三叶鬼针草内源一氧化氮的生成及其对氧化损伤的缓解效应

Generation of endogenous NO and its ameliorating effects on oxidative damage in Bidens pilosa L. seedlings under Pb stress

对不同浓度铅(Pb)胁迫下三叶鬼针草(Bidens pilosa L.)叶、茎和根中内源一氧化氮(NO)和活性氧(ROS)的生成机制及根系活力的变化,内源NO对Pb胁迫下三叶鬼针草幼苗氧化损伤的缓解效应进行了研究。结果显示,在0~1000 mg/L范围内,随着Pb浓度的增加,叶片中NO含量呈升高趋势,根中NO含量呈先升高后降低的趋势,但仍高于对照,Pb浓度在0~400 mg/L范围内,茎中NO含量与对照持平,Pb浓度大于600 mg/L时,茎中NO含量低于对照;600 mg/L Pb处理能显著增强叶、茎和根中一氧化氮合成酶(NOS)和硝酸还原酶(NR)活性,显著增加叶和茎中亚硝酸根离子(NO_2^-)和类胡萝卜素(Car)含量,NOS、NR、NO_2^-和Car均能促进叶片中内源NO的生成,NOS是根中内源NO生成的主要途径。Pb胁迫使超氧阴离子(O_2^(·-))产生速率、过氧化氢(H_2O_2)含量、丙二醛(MDA)含量和相对电导率(REC)显著升高,从而造成幼苗严重的膜脂过氧化损伤,而胁迫诱发产生的NO能降低根中ROS的产生,促进幼苗根系活力,进而缓解胁迫造成的膜脂过氧化损伤。

In this study,the generation patterns of endogenous nitric oxide（ NO） and reactive oxygen species（ ROS） and the changes in root activity of Bidens pilosa L. seedlings under Pb stress were investigated, with the ameliorating effects of NO on oxidative damage also analyzed. Results showed that the content of NO in the leaves increased with the increase in Pb concentration within the range of 0-1000 mg/L,and the content of NO in the roots first increased and then decreased but was still higher than that in the control. In the Pb concentration range of 0-400 mg/L,the content of NO in the stem was the same as that of the control,but was lower than that of the control when the concentration was greater than600 mg/L. At a concentration of 600 mg/L,Pb significantly increased NO synthase（ NOS）and nitrate reductase（ NR） activities in the roots,stems,and leaves and increased nitrite ion（NO2^-） and carotenoid（ Car） content in the stems and leaves. NOS,NR,NO2^-,and Carsignificantly influenced NO content in the leaves and NOS was the major pathway for the formation of endogenous NO in the roots. Pb stress significantly increased the superoxide anion（ O2^·-） production rate,hydrogen peroxide（ H2O2） concentration,malondialdehyde（ MDA） content,and relative electrical conductivity（ REC）,resulting in severe membrane lipid peroxidation injury in the B. pilosa L. seedlings. However,NO induced by Pb stress may have reduced the production of ROS in the roots,promoted root activity in seedlings,and relieved membrane lipid peroxidation damage caused by stress.