油菜NO_3~–的吸收、分配及氮利用效率对低氮胁迫的响应

Response of NO_3~– uptake and distribution and nitrogen use efficiency in oilseed rape to limited nitrogen stress

【目的】探究油菜NO_3~–的吸收、分配和对低氮胁迫的响应及其氮利用效率,为理解油菜在不同低氮胁迫下相关生理变化及其氮素利用效率提供科学依据。【方法】以常规油菜品种814为研究材料,采用砂培试验,在正常供氮水平(10 mmol/L)和低氮胁迫水平(3 mmol/L、1 mmol/L)下,研究油菜的根系特性、蒸腾作用对低氮胁迫的响应及其氮素吸收效率,并研究油菜NO_3~–的运输分配与同化对低氮胁迫的响应及其氮素利用效率。【结果】与正常供氮处理(10 mmol/L)相比,低氮胁迫处理(3 mmol/L、1 mmol/L)的油菜NO_3~–含量、全氮含量均显著下降,但(NO_3~–)叶/根、(全氮(%))叶/根显著升高,植株根系干物质重、根系吸收面积均显著下降,但根冠比显著升高。油菜植株在低氮胁迫下气孔导度和蒸腾速率显著增加,一方面促进植株对NO_3~–的捕获,另一方面也促使更大比例的NO_3~–分配在植物的地上部分,但植株的水分散失加剧,水分利用效率显著下降。低氮胁迫处理油菜根和叶中NR、GS活性与正常供氮处理之间的差异不显著或有增加,其叶绿素含量、光合速率均显著下降,但光合氮素利用率显著升高。【结论】在低氮胁迫条件下,油菜植株的氮素和干物质累积均显著下降,但NO_3~–在植株的地上部分分配比例的增加以及光合氮素利用率的升高促使植株的氮素利用效率显著提高。

[ Objectives ] This research was conducted in order to investigate response of NOr uptake and distribution to limited nitrogen （N） stress and its influence on nitrogen use efficiency （NUE） in oilseed rape, and supply scientific basis for understanding the physiological and NUE changes under limited-N stress condition. [ Methods ] Oilseed rape genotype 814 was used as plant materials, and sand culture experiment was conducted under normal-N （10 mmol/L） and limited-N （3 mmol/L, 1 mmol/L） levels. The response of root characteristics, transpiration, NO3- distribution and assimilation to limited-N stress and its influence on NO3- uptake efficiency and NUE were studied. [ Results ] Compared with the normal-N level, NO3- content, total N, root biomass and root uptake area were decreased significantly under limited-N level （3 mmol/L, 1 mmol/L）, but ratio of （NOr） shoot/root and （total N） shoot/root, ratio of root biomass/shoot biomass were increased significantly. Stomatal conductance and transpiration rate were increased significantly in oilseed rape under limited-N stress, which not only stimulated NOr uptake, but also higher proportion of NO3- distributed from root to shoot; meanwhile, water use efficiency was decreased significantly. There were no significant differences of NR and GS in root and shoot between normal-N and limited-N treatments, chlorophyll content and photosynthesis were decreased significantly, but photosynthetic NUE was increased significantly. [ Conclusions ] Total N and biomass of oilseed rape plants were decreased significantly under limited-N stress, but the NUE was increased significantly, which is result from the higher proportion of NO3- distributed from root to shoot and higher photosynthetic NUE under limited-N stress.