中文摘要：

【目的】研究玉米根系时空分布对不同供氮水平的响应及其与植株氮素吸收的关系,对于充分挖掘氮高效基因型,探讨氮高效栽培途径具有重要意义。【方法】以氮高效玉米品种（郑单958、金山27）和氮低效玉米品种（蒙农2133、内单314）为材料,以不施氮为对照（N0）,施氮300 kg/hm~2为适量处理（N300）、450 kg/hm~2为过量处理（N450）,进行了两年田间试验,调查了玉米根重、根长的时空分布及其与植株氮素吸收量的关系。【结果】对照（N0）和适量施氮（N300）条件下,氮高效品种的根系生物量显著高于氮低效品种,过量施氮（N450）条件下二者在吐丝前无显著差异,吐丝后氮高效品种根重降低缓慢,根系生物量高于氮低效品种。N0和N300条件下,氮高效品种0—100 cm土层根长均显著高于氮低效品种,吐丝期到乳熟期,N0处理0—20 cm耕层和40cm以下土层内,氮高效品种的根系降低比率显著低于氮低效品种;施氮条件下,两类型品种0—40 cm土层内根系降低比率无显著差异,但40 cm以下土层氮高效品种根系降低比率显著低于氮低效品种。吐丝前氮素吸收量在N0和N300条件下,单位根长氮吸收速率对氮素吸收的直接作用较大,直接通径系数是0.590和0.649,在N450条件下,根长对于氮素吸收的直接作用较大,直接通径系数是0.536;吐丝后氮素吸收量在N0和N300条件下,根长对氮素的吸收直接作用较大,直接通径系数是1.148和0.623,在N450条件下,单位根长氮吸收速率对氮素吸收的直接作用较大,直接通径系数是0.858。【结论】不同氮效率玉米品种根系分布和氮素吸收对氮肥的响应存在明显差异。在低氮和适量施氮条件下,氮高效品种较氮低效品种表现出较高的根系生物量、根长和较低的根系衰老速率,其吐丝前氮素吸收主要与单位根长氮吸收速率有关,吐丝后则主要与根长有关;过量施氮条件下,其吐丝前

英文摘要：

【Objectives】The temporal and spatial distribution of roots in soils affects the nitrogen uptake efficiency and yield of crops. Clarifying the response of maize with genotypes of high or low nitrogen efficiency to the nitrogen fertilizer rate is of great importance for exploiting the potential of genotype in nitrogen use efficiency. 【Methods】High N efficient hybrids（Zhengdan958 and Jinshan27） and low N efficient hybrids（ Mengnong2133 and Neidan314） were used as tested materials in a two-years＇ field experiment. With no nitrogen fertilizer as control（N0）, N 300 and 450 kg/hm~2 were used as treatments of suitable and excessive nitrogen rates（ N300 and N450）. The root mass and temporal and spatial distribution of root length in soils, andthe relationship with nitrogen uptake were investigated. 【Results】In N450 treatment, there was no difference in root mass before anthesis period between the two genotypes, but the root mass of high N genotype maize was significantly greater than that of low N genotype after anthesis. Root mass of high N genotype was greater than that of low N genotype at N0 and N300. In N0 and N300 treatments, root length at 0–100 cm soil layer of high N efficient genotypes was remarkably greater than that of low N efficient genotypes. From silking to milking stage, root decreasing rate of high N efficient genotypes was clearly lower than that of low N efficient genotypes at 0–20 cm and below 40 cm layer at N0. The situation was quite different when N was applied.There was no difference in root decreasing rate at 0–40 cm layer, but high N efficient genotypes showed significant lower root decreasing rate below 0–40 cm layer compared to low N efficient genotypes. Pre-anthesis nitrogen uptake at zero and moderate nitrogen treatments was primary controlled by unit root N uptake rate,direct path coefficients were 0.590 and 0.649, but when excessive nitrogen was applied, it was mainly controlled by root length, direct path coefficient was 0.536. Post-anthesis nitrogen