甘蓝型油菜苗期氮高效吸收转运特征研究

目的]氮素吸收效率是影响作物氮效率的重要方面,开展油菜氮高效吸收转运特征研究旨在为提升油菜氮吸收效率及产量提供理论依据.方法]为探究油菜氮高效吸收转运机理,以一对氮效率差异显著的油菜种质:氮高效种质'498'和氮低效种质'428'为试验材料,在营养液培养条件下,设置正常供氮(9.5mmol·L-1)和低氮(0.47...

Characteristics of Efficient Nitrogen Uptake and Transport of Rapeseed at Seedling Stage

【Objective】Nitrogen (N) uptake efficiency is one of the important factors affecting crop N efficiency, investigating characteristics of efficient N uptake and transport was the purpose to provide the theoretical basis for improving N efficiency and yield of rapeseed (Brassica napus L.) varieties.【Method】To explore the mechanisms underlying high N uptake and transport in rapeseed, two rapeseed germplasms with contrasting N efficiency (N efficient germplasm ‘498’ and N inefficient germplasm ‘428’) were used in this study under normal N (9.5 mmol·L^-1) and low N (0.475 mmol·L^-1) conditions at three different growth stages (Phenological growth stages 12, 14 and 16) in hydroponic culture. At the same time, the ¹⁵N isotope tracer technique was applied to study the uptake and transport capacity of NO₃^- and NH₄⁺. Additionally, the expression level of genes (BnNPFs, BnNRT2s and BnAMTs）related to N uptake and transport in rapeseed germplasms with contrasting N efficiency were further analyzed by real-time quantitative PCR (RT-qPCR).【Result】Rapeseed germplasm ‘498’ showed superior advantages in plant growth and root development under different N concentrations, and the root morphological indexes (main root length, total root length, root surface area, root volume and lateral root number), biomass, N accumulation and N uptake efficiency were all significantly greater than those of germplasm ‘428’.¹⁵N isotope tracer test also showed that ‘498’ showed greater advantage in the uptake and accumulation of NO₃ ^- and NH₄⁺, especially for NH₄⁺, as indicated by the significant differences in the accumulation of ¹⁵NH₄⁺ between two germplasms. The RT-qPCR analysis further found that under normal N conditions, the relative expressions of BnNPF6.3a, BnNRT2.1e, BnNPF7.2a, BnNPF7.2c, BnNPF6.2c, BnAMT1;2a, BnAMT1;3c, BnAMT1;4a, BnAMT2;1a and BnAMT2;1b (involved in the uptake and transport of NO₃ ^- and NH₄⁺) was significantly higher in ‘498’ than that in ‘428’. While under low N stress, the relative expressions of BnNRT2.4a, BnNRT2.5a and BnNRT2.5b (involved in NO₃ ^-uptake and transport) was significantly lower in the root of ‘498’ than that of ‘428’, but the expression level of BnNPF7.3a and BnNPF6.2c (referred to NO₃ ^- transport and redistribution) was significantly higher in ‘498’ than that in ‘428’, as well as the expression level of BnAMT1;1a, BnAMT1;2a, BnAMT1;3c, BnAMT1;4a, BnAMT2;1a and BnAMT2;1b (involved in NH₄ ⁺ uptake and transport).【Conclusion】Compared with N-inefficient germplasm ‘428’, N-efficient germplasm ‘498’ were superior in root length, root surface area (volume) and lateral root number, additionally with greater ability in N (especially NH₄ ⁺) uptake and accumulation. Under normal N application conditions, the expression of genes involved in NO₃^- and NH₄⁺ absorption and transport were relatively higher in ‘498’, while the relative expression of genes involved in the NO₃ ^- transport and redistribution as well as NH₄⁺ absorption and transport were significantly higher in ‘498’ than that in ‘428’ under low N stress, illustrating the relative higher N uptake efficiency of ‘498’ possibly linked to the higher expressions of several BnNPFs sand BnAMTs.