硅对NO_3^-胁迫下黄瓜幼苗生长及抗氧化酶活性的影响

EFFECTS OF SILICON ON PLANT GROWTH AND ANTIOXIDANT ENZYME ACTIVITIES OF CUCUMBER SEEDLINGS UNDER NO_3^- STRESS

采用营养液培养试验,通过添加不同浓度(0、0.5、1、1.5、2 mmol.L-1)的Na2SiO3作为硅供体,研究外源硅对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1mmol.L-1 Na2SiO3处理7d后,黄瓜幼苗叶片中超氧化物歧化酶(SOD)、愈创木酚过氧化物酶(POD)过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)活性显著升高;丙二醛(MDA)含量显著降低,说明外加1mmol.L-1Na2SiO3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NO 3-胁迫的抗性增强;当Na2SiO3浓度高达2 mmol.L-1时,其叶片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。可见,外加一定浓度的Na2SiO3(0.5～1 mmol.L-1)可通过提高抗氧化酶活性和降低膜脂过氧化来缓解NO3-胁迫对黄瓜幼苗的伤害。

In this study,cucumber seedlings were cultivated in nutrient solution added with different concentration（0,0.5,1,1.5,2 mmol·L-1） Na2SiO3 as Si donor to study the effects of exogenous Si on the growth of cucumber seedlings and the activities of antioxidant enzymes in cucumber leaves under NO-3 stress.Under the stress of 140mmol·L-1,treating with 1mmol·L-1 of Na2SiO3 for 7d increased the leaf superoxidase（SOD）,peroxidase（POD）,catalase（CAT） and ascorbic acid peroxidase（APX） activities,and decreased the leaf malondialdehyde（MDA） content significantly,suggesting that exogenous Si 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 resistance to high concentration NO-3 stress.After the cucumber seedlings grew in 2 mmol·L-1 of Na2SiO3 for 7d,the activities of SOD,POD,CAT and APX in leaves were decreased,and the MDA content was increased,resulting in the injury of cucumber seedlings.It indicates that certain concentration（0.5～1 mmol·L-1） exogenous Si could alleviate the NO-3 stress to cucumber seedlings.