大豆根系特征对氮阻遏的适应性调节

Adaptive Regulation of Nitrogen Inhibitory on Root Characteristics of Soybean

以黑农35为材料,采用盆栽培养方法,在2011年筛选的氮阻遏阈值基础上,设置低量氮、临界氮和阻遏氮3个施氮水平,探讨了大豆根系特征对氮阻遏的响应。结果表明:随着大豆的生长发育,不同氮水平条件下大豆根系形态指标、根瘤数及其干重、根干重及碳氮积累均呈单峰曲线变化,峰值出现在播种后65 d;根冠比、根瘤豆血红蛋白含量随生育进程而降低;在播种后65 d,根碳氮比处于最小值。根干物质重和根磷、氮积累量(播种后45 d除外)与施氮水平正相关,均在阻遏氮水平下(108 mg.kg-1)达最大值,而碳氮比在临界氮水平下达最大值;各个时期,根系形态各指标(播种后45 d根尖数除外)均在临界氮水平下(54 mg.kg-1)出现最大值;根瘤数、根瘤干重(播种后45 d除外)、根瘤豆血红蛋白含量与根系形态各指标变化规律相同。因此,初步认定在本试验条件下适宜大豆根系生长的最佳氮水平为54 mg.kg-1。

Three nitrogen application levels of soybean based on the nitrogen repression threshold of our previous experiments in 2011 were set by using pet experiments targeting Heinong 35 to investigate how root characteristics of soybean response to N inhibitory. The results showed that soybean root morphological indicators, the number and dry weight（DW） of nodule, root DW, C and N accumulation during the soybean growth periods of different nitrogen levels were all unimodal curves, with the peak appeared on the 65th days after sowing; root-shoot ratio and nodule leghemoglobin content decreased with soybean growth ;root C-N ratio reached the minimum on the 65th days after sowing. DW,C and N accumulation of root（ except for 45 days after sowing） was positively correlated with the nitrogen levels,with the maximum appeared at the level of N inhibitory（ 108 mg.kg^-1 ）, but the maximum of C-N ratio appeared in critical nitrogen level. In each period, all the root morphological indicators（ except for tips on 45 days after sowing）reached to the maximum in critical nitrogen level（54 mg. kg^-1） ;the number, DW（ except 45 days after sowing）and leghemoglobin content in nodule had the same change laws. In summary, the critical nitrogen level （54 mg. kg ^- 1 ） in the study is the best nitrogen level for the growth of soybean root.