中文摘要：

【目的】研究了低氮胁迫对不同耐低氮性玉米品种苗期生长、伤流性状及根系活力的影响,比较不同耐低氮性玉米品种对低氮胁迫响应的差异,以期为西南丘陵地区耐低氮玉米品种的选育提供理论依据。【方法】以两个耐低氮品种‘正红311’、‘成单30’和两个低氮敏感品种‘先玉508’、‘三北2号’为试验材料进行水培试验,营养液设置4个氮水平：0、0.05、0.5、5 mmol/L。测定了苗期株高等形态指标、干物质积累量、根系活力,计算了根冠比、活跃吸收面积比、伤流液中可溶性蛋白等转运速度及氨基酸/硝态氮浓度的比值。【结果】低氮胁迫下玉米苗期苗高、茎粗、叶面积、SPAD、单株干重、地上部干重、伤流强度,伤流液中可溶性蛋白和可溶性糖转运速度,氨基酸和硝态氮转运速度及浓度,根系活力,根系总吸收面积和根系活跃吸收面积均显著下降,但耐低氮品种各指标的降幅均低于低氮敏感品种。根冠比、伤流液中氨基酸/硝态氮浓度比值均显著升高,可溶性蛋白和可溶性糖浓度随胁迫时间的延长表现出先下降后升高的趋势。耐低氮品种根冠比增幅低于低氮敏感品种,而可溶性蛋白浓度的增幅高于低氮敏感品种,且低氮胁迫下耐低氮品种根系活力、伤流液中可溶性蛋白和可溶性糖浓度显著高于低氮敏感品种。【结论】耐低氮品种在低氮胁迫下能够保持较高的根系活力,进而促进了根系对营养物质的吸收和转运,提高了伤流液中各组分的浓度和转运速度,较好地维持了碳氮循环,从而有效地协调了植株地上、地下部养分和物质的分配,控制了根冠比的增加,维持了地上部的生长。

英文摘要：

【Objectives】 Insufficient nitrogen（N） supply impacts the growth and root activities of crops.Comparison of the bleeding characteristic responses of different low N tolerance maize cultivars will provide a theoretical basis for breeding of low N tolerant maize cultivars. 【Methods】Two low N tolerant cultivars（‘ZH311＇ and ‘CD30＇） and two low N sensitive cultivars（‘XY508＇ and ‘SB2＇） were used as tested materials,and a hydroponic experiment with four N supply levels of 0, 0.05, 0.5 and 5 mmol/L was conducted. The plant height, dry matter accumulation, and root activity were investigated at seedling stage of maize. 【Results】The stem diameters, plant heights, leaf areas, SPAD values, dry biomass of seedlings were decreased with the decreased N supply levels. The bleeding sap intensity, transport speeds of free amino acid, nitrate N, soluble protein and soluble sugar were declined, and the concentrations of free amino acid, nitrate N in bleeding, and the total absorbing areas, actively absorbing areas and root activities were decreased in all the four tested cultivars.However, the decreased ranges of the above indices of the low N tolerant maize cultivars were much lower than those of the low N sensitive ones. With the increase of treating time, the concentrations of soluble protein and soluble sugar showed trends of increasing first and then decreasing. The increased ranges of the root-shoot ratios of the low N tolerant maize cultivars were much lower than those of low N sensitive cultivars, while the increased ranges of concentrations of soluble protein were much higher. The root activities, concentrations of soluble protein and soluble sugar of the low N tolerant maize cultivars were much higher than low N sensitive ones.【Conclusions】Low N tolerant cultivars can keep higher root activities, further promote absorptive capacity and transformation capacity of N. The low N tolerant cultivars can keep stronger carbon and N cycles to coordinate the nutrients and substances distrib