水-肥耦合对新银合欢幼苗抗氧化酶活性及肥力利用能力的影响

Impacts on Antioxidant Activities and Utilization Capacity of Fertility of Leucaena leucocephala under Different Water and Nutrient Conditions

【目的】探讨不同水肥条件协同作用对新银合欢(Leucaena leucocephala)幼苗生长、抗氧化酶活性及肥力利用能力的影响,为新银合欢幼苗栽培和管理提供参考依据。【方法】本文采用室内盆栽控制法培养新银合欢幼苗,设2个水分水平(正常浇水和干旱胁迫50 d)和4个施氮处理[不施氮对照(CK,N_0)、低氮(0.86 g/株,N_1处理)、中氮(1.72 g/株,N_2处理)和高氮(2.58 g/株,N_3处理)],系统测定不同水肥耦合条件下新银合欢幼苗的抗氧化酶活性及肥力利用效率。【结果】水分条件相同时,施氮均能使新银合欢幼苗总生物量及各营养器官(根、茎和叶)的生物量增加,根占比下降;施肥量相同时,正常浇水可促进幼苗根系以上各形态指标上升,干旱胁迫时,N_3处理可提高幼苗单株总生物量及各营养器官生物量。干旱胁迫下适量增施氮肥均可在一定程度上使超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性上升。相关性分析结果表明,SOD、POD和CAT活性间呈极显著正相关(P<0.01),3种酶的协同作用可降低幼苗体内的膜脂过氧化程度,减轻水肥胁迫对幼苗的伤害。从整个植株氮和磷浓度分布看,全氮含量为叶>茎>根;全磷含量为根>茎>叶。在干旱胁迫条件下幼苗的氮和磷运转效率及氮素利用率均以N_2处理最高。【结论】在水分充足条件下,增施氮肥可提高新银合欢幼苗的抗氧化酶活性和对氮和磷的吸收能力;干旱胁迫条件下施用中等浓度氮(1.72 g/株)可有效诱导新银合欢幼苗抗氧化保护酶系统活性增强,从而增强其抗旱性,延缓叶片衰老,同时可显著增加幼苗对氮磷营养物质的吸收,提高氮素的转运及利用效率。

【Objective】The study aimed to explore the combined effects of water and nitrogen level on the growth,antioxidant activities and utilization capacity of fertility of Leucaena leucocephala seedling.【Method】Leucaena leucocephala seedlings were planted in indoor pots,with two water levels(normal watering and drought for 50 days)and four nitrogen levels(0%as control,low:0.86 g/plant,moderate:1.72 g/plant and high:2.58 g).Three antioxidant activities,and utilization capacity of fertility by the seedlings were measured as growth performance.【Result】The nitrogen application led to increase in total biomass and biomass of the roots,stems and leaves,but a decrease in root biomass per seedling under the same water level;normal watering under all nitrogen levels and high nitrogen(N3)under drought improved root growth,total biomass and biomass of the roots,stems and leaves.Moderate nitrogen fertilization increased superoxide dismutase,peroxidase and catalase activities under drought in some extent.There were significantly positive correlations among activities of the three enzymes,indicating that synergistic effects of the three enzymes reduced the peroxidation of membrane lipid and damages from drought and infertility.Total nitrogen and total phosphorus showed a trend of leaf>stem>root and root>stem>leaf,respectively;the conversion efficiency of nitrogen and phosphorus,and utilization rate of nitrogen in the moderate nitrogen(1.72 g/plant)treatment were the highest under drought.【Conclusion】The water and nitrogen level have significant impacts on L.leucocephala seedlings:nitrogen fertilization can improve antioxidative enzyme system activity and fertilizer assimilation when water is abundant,and a moderate level of nitrogen(1.72 g/plant)can improve antioxidative enzyme system activity,fertility utilization under drought stress.