不同氮效率玉米杂交种的根系生长、氮素吸收与产量形成

以氮效率不同的4个玉米杂交种(组合)为材料,在两个氮水平下分析了根系大小与氮素累积及产量形成方面的相互关系。结果表明,氮高效杂交种(NE1和ND108)吸氮量显著高于氮低效品种,但这种差异主要来自于吐丝后氮累积量,而在前期不同基因型间氮素累积差异不显著。两个氮水平下,氮高效品种NE1和ND108都具有较大的根系;在不施氮条件下,氮低效品种209115的根系干重与ND108相近,而其氮累积量及产量均最低。说明根系大小是决定氮累积量的主导因素,但氮吸收速率的作用也不可忽视。

Root growth, nitrogen uptake and yield formation of hybrid maize with different N efficiency

Breeding selection of high N efficient cultivars is an effective way to increase nitrogen (N) fertilizer efficiency and reduce N loss in arable fields. Nevertheless, the agronomic basis underlining it is still quite vague. Root size and N uptake system are two components determining N accumulation. Solution culture study has already proved the importance of root on N accumulation. However, both root growth and N accumulation are dynamic processes at field conditions. It is not clear how the root growth affects N accumulation and yield formation under different N levels. In this paper, 4 (hybrid) maize cultivars (2 N-efficient and 2 N-inefficient) were adopted to investigate the relationship between root growth and N uptake as well as yield formation under two N levels (with or without N supply). Results showed that N efficient hybrids (NE1 and ND108) took up more N than inefficient hybrids. The difference on the N uptake was mainly attributed to N accumulation after silking, while difference of N accumulation before silking stage was not significant. High N efficient cultivars, NE1 and ND108, had larger root dry weight at both N levels. However, under low N (without N application), 209×115, one inefficient hybrids, had almost the same root weight as ND108 despite the lowest N accumulation and yield. There is a close correlation between post-silking root size and N uptake during the whole growth period. In (N-efficient) hybrids, efficient N uptake before silking helps the build up of a big root system which, in turn, lead to a big N uptake after silking. As the results, N export from leaves was reduced and a longer photosynthetic activity was maintained. The result of this study proved that root size was the dominant factor determining N accumulation; nevertheless, the role of N uptake rate should not be neglected.