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以‘津春4号’黄瓜为试验材料,采用灌根的方法研究了外源褪黑素(MT)对硝酸盐胁迫下幼苗抗氧化系统的影响,为MT在设施蔬菜生产中的应用提供参考。结果表明:硝酸盐胁迫处理后,黄瓜幼苗叶片中超氧阴离子(O_2~)产生速率、过氧化氢(H_2O_2)和丙二醛(MDA)含量显著增加;抗坏血酸(AsA)和谷胱甘肽(GSH)含量及活性均下降;超氧化物歧化酶(SOD)、过氧化物酶(POD)、抗坏血酸过氧化物酶(APX)、谷胱甘肽还原酶(GR)活性在硝酸盐胁迫3 d时,过氧化氢酶(CAT)活性在胁迫6 d时,脱氢抗坏血酸还原酶(DHAR)活性在胁迫9 d时均达最高,之后又逐渐下降;单脱氢抗坏血酸还原酶(MDHAR)活性则持续降低。MT处理可有效抑制硝酸盐胁迫条件下黄瓜幼苗中O_2~的产生速率及H_2O_2和MDA的积累,提高AsA和GSH含量及活性,增强SOD、POD、CAT、APX、MDHAR、DHAR、GR活性,提高叶片的光合速率及干物质积累。这些结果说明,MT可减缓硝酸盐胁迫的危害,提高黄瓜幼苗对硝酸盐的耐性,且100μmol·L~(-1) MT处理效果最佳。
The effect of exogenous melatonin (MT) on the antioxidant system of seedlings under nitrate stress was studied using ’Jinchun No.4’ cucumber as experimental material, which provided a reference for the application of MT in facility vegetable production . The results showed that the production rate of superoxide anion (O_2 ~ ), the content of H_2O_2 and MDA in leaves of cucumber seedlings increased significantly after nitrate stress treatment. Ascorbate (AsA) and glutathione GSH) content and activity decreased. The activities of superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX) and glutathione reductase (GR) , CAT activity reached the highest at 9 d of stress and then decreased gradually after 6 d of stress. DHAR activity Keep decreasing. MT treatment could effectively inhibit the accumulation of O 2 ~ 中 and the accumulation of H 2 O 2 and MDA in cucumber seedlings under nitrate stress, increase the contents and activities of AsA and GSH, and enhance the activities of SOD, POD, CAT, APX, MDHAR, DHAR and GR, Improve leaf photosynthetic rate and dry matter accumulation. These results indicate that MT can alleviate the damage of nitrate stress and improve the tolerance of cucumber seedlings to nitrate, and the treatment with 100μmol·L -1 MT is the best.