不同氮素配比对生菜抗坏血酸—谷胱甘肽循环的影响

Effects of different nitrogen ratios on ascorbic acid-glutathione cyclic metabolism in lettuce seedlings

【目的】为了探明适合生菜生长的铵硝态氮配比。【方法】以‘北散生1号’生菜为试验材料,利用水培装置,设置了5个不同的铵硝配比(全铵态氮,75∶25,50∶50,25∶75,全硝态氮),研究了不同铵硝配比对生菜的生长指标以及抗坏血酸-谷胱甘肽循环底物、相关酶和抗氧化酶的影响。【结果】在铵硝比为25∶75时,生菜干鲜重达到最大,生长状况最佳;氧化型抗坏血酸(AOA)、氧化型谷胱甘肽(GSSG)的含量最少,还原型抗坏血酸(AsA)、还原型谷胱甘肽(GSH)的含量最高;在铵硝比为全铵态氮与75∶25时,氧化型抗坏血酸、氧化型谷胱甘肽含量相对较高,还原型抗坏血酸、还原型谷胱甘肽含量相对较少。在铵硝比为75∶25或全铵态氮时抗坏血酸过氧化物酶(APX)、单脱氢抗坏血酸还原酶(MDHAR)、脱氢抗坏血酸还原酶(DHAR)和谷胱甘肽还原酶(GR)活性最高,在铵硝比为25∶75时,活性最低。在铵硝比为75∶25或全铵态氮时,超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)和抗坏血酸过氧化物酶活性最高,在铵硝比为25∶75时,酶活性最低。【结论】在铵硝比为25∶75时,氧化型抗坏血酸和谷胱甘肽转化为还原型程度高于其他处理,受到的氧化胁迫少,较适宜生菜生长。

【Objective】The main forms of nitrogen are nitrate nitrogen(NO3^--N)and ammonium nitrogen(NH4^+-N).The suitable ratio of ammonium nitrate for growth of lettuce was investigated.【Methods】Five different ratios of ammonium and nitrate(total ammonia,75∶25,50∶50,25∶75,total nitrate)were conducted with‘Beishansheng No.1’lettuce by hydroponic equipment.The effects of different ratio of ammonium and nitrate on growth index,ascorbic acid glutathione cycle substrate,related enzymes and antioxidant enzymes of lettuce were studied.【Results】The fresh and dry weights of lettuce reached the maximum and the growth condition was the best at the ratio of ammonium to nitrate 25∶75,the contents of oxidized ascorbic acid(AOA)and oxidized glutathione(GSSG)showed the lowest,while the contents of reduced ascorbic acid(AsA)and reduced glutathione(GSH)were the highest.When the ratio of ammonium to nitrate were total ammonia and 75∶25,the contents of oxidized ascorbic and oxidized glutathione were relatively high,or the contents of reduced ascorbic and reduced glutathione were relatively low.The activities of ascorbic acid peroxidase(APX),monodehydroascorbic acid reductase(MDHAR),dehydroascorbic acid reductase(DHAR)and glutathione reductase(GR)showed the highest at the ammonium-nitrate ratio of 75∶25 or total ammonia,and the lowest at the ammonium-nitrate ratio of 25∶75.The activities of superoxide dismutase(SOD),catalase(CAT),peroxidase(POD)and APX were the highest at the ammonium-nitrate ratios 75∶25 or total ammonia,and the lowest at 25∶75.【Conclusion】When the ratio of ammonium to nitrate was 25∶75,the lettuce plant morphology was better.The degree of conversion of oxidized ascorbic acid and glutathione to reduced type was higher than those of other treatments with less oxidative stress and suitable growth of lettuce.