中文摘要：

【目的】比较不同氮素利用效率夏玉米的根系时空分布特性及其氮素吸收利用的差异,探讨玉米氮高效的生理机制。【方法】以氮高效玉米杂交种蠡玉13（LY13）和氮低效玉米杂交种鲁单981（LD981）为试验材料,以大田箱式土柱栽培方式,研究两个氮素水平下（0和4.29 g N/plant）玉米根系时空分布及氮素吸收利用的差异。【结果】LY13开花后具有较高的根系干重,根冠比显著高于LD981（P〈0.05）,土壤深层根系分布多,根系空间分布合理,后期根系活力高,根系功能期长,导致其库容量大,库调节能力强,氮素积累总量高,氮素转移率、贡献率和氮素利用效率均显著高于LD981（P〈0.05）,施氮条件下优势更加明显。LY13在两种氮素水平下的籽粒产量、生物产量、千粒重、收获指数均显著高于LD981。【结论】氮高效型玉米品种根系总量多、深层根系多、空间分布合理、根系活力高且持续期长是其氮积累量增加的主要原因;库容量大,库调解能力强促使氮素转运效率高,向籽粒分配比例大是其籽粒产量高、氮效率高的根本原因。

英文摘要：

【Objective】The aim of this study is to investigate the physiological mechanism of high nitrogen use efficiency of corn by comparing the differences in uptake and utilization of nitrogen,spatial and temporal characteristics of roots of summer corns with different nitrogen use efficiency（NUE）.【Method】Using different NUE corn varieties as materials,one is high NUE variety,LY13,and another is low NUE variety,LD981.The plant sample was separated to two parts,the aboveground（stem,leaf,grain） and underground（0-20,20-40,40-60,60-100 cm root） part.At two nitrogen levels（0 and 4.29 g·plant-1）,samples were collected at male tetrad,flowering,filling,milky and maturity stages to study their root spatial and temporal distribution,the difference in nitrogen uptake and utilization.【Result】Compared with LD981,the root weight and root/shoot ratio of LY13 were maintained at significantly higher levels（P0.05） post-anthesis.The domination in root spacing distribution,number of roots in deeper layer,root activity at later stage,and root functional period promote more absorption of nitrogen in LY13.The total nitrogen accumulation amount of LY13 overweighed LD981 significantly（P0.05）,which were more distinct at the high nitrogen level.This tendency could be found in nitrogen transportation efficiency,nitrogen contribution rate and nitrogen utilization efficiency（P0.05）.All these result that LY13 had superiority to LD981（P0.05） in grain yield,biological yield,1000-kernel weight,seed set and harvest index at either nitrogen level.【Conclusion】As for LY13,the higher nitrogen accumulation was mainly attributed to its more total root weight,more root in deeper layer,more rational root distribution,and longer duration of strong root activity;and the primary cause of its higher grain yield and nitrogen use efficiency were bigger seed set and stronger seed set adjustment ability promoting nitrogen translocation efficiency,leading to more nitrogen distributed to grain.