Abstract:

【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 (P＜0.05) 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 (P＜0.05), 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 (P＜0.05). All these result that LY13 had superiority to LD981 (P＜0.05) 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.

Key words: maize, root characteristics, nitrogen use efficiency