Duan Y H, Zhang Y L, Ye L T, Fan X R, Xu G H, Shen Q R
College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, PR China.
Ann Bot. 2007 Jun;99(6):1153-60. doi: 10.1093/aob/mcm051. Epub 2007 Apr 11.
There is increased evidence that partial nitrate (NO3-) nutrition (PNN) improves growth of rice (Oryza sativa), although the crop prefers ammonium (NH4+) to NO3- nutrition. It is not known whether the response to NO3- supply is related to nitrogen (N) use efficiency (NUE) in rice cultivars. Methods Solution culture experiments were carried out to study the response of two rice cultivars, Nanguang (High-NUE) and Elio (Low-NUE), to partial NO3- supply in terms of dry weight, N accumulation, grain yield, NH4+ uptake and ammonium transporter expression [real-time polymerase chain reaction (PCR)].
A ratio of 75/25 NH4+ -N/NO3- -N increased dry weight, N accumulation and grain yield of 'Nanguang' by 30, 36 and 21 %, respectively, but no effect was found in 'Elio' when compared with those of 100/0 NH4+ -N/NO3- -N. Uptake experiments with 15N-NH4+ showed that NO3- increased NH4+ uptake efficiency in 'Nanguang' by increasing Vmax (14 %), but there was no effect on Km. This indicated that partial replacement of NH4+ by NO3- could increase the number of the ammonium transporters but did not affect the affinity of the transporters for NH4+. Real-time PCR showed that expression of OsAMT1s in 'Nanguang' was improved by PNN, while that in 'Elio' did not change, which is in accordance with the differing responses of these two cultivars to PNN. Conclusions Increased NUE by PNN can be attributed to improved N uptake. The rice cultivar with a higher NUE has a more positive response to PNN than that with a low NUE, suggesting that there might be a relationship between PNN and NUE.
越来越多的证据表明，尽管水稻更喜欢铵态氮（NH₄⁺）而非硝态氮（NO₃⁻）营养，但部分硝态氮（NO₃⁻）营养（PNN）能促进水稻（Oryza sativa）生长。目前尚不清楚水稻品种对NO₃⁻供应的响应是否与氮（N）利用效率（NUE）有关。方法 进行溶液培养实验，研究两个水稻品种南光（高NUE）和埃利奥（低NUE）对部分NO₃⁻供应在干重、氮积累、籽粒产量、NH₄⁺吸收和铵转运蛋白表达[实时聚合酶链反应（PCR）]方面的响应。
与100/0 NH₄⁺-N/NO₃⁻-N相比，75/25 NH₄⁺-N/NO₃⁻-N的比例分别使‘南光’的干重、氮积累和籽粒产量提高了30%、36%和21%，但对‘埃利奥’没有影响。用¹⁵N-NH₄⁺进行的吸收实验表明，NO₃⁻通过提高Vmax（14%）增加了‘南光’对NH₄⁺的吸收效率，但对Km没有影响。这表明用NO₃⁻部分替代NH₄⁺可以增加铵转运蛋白的数量，但不影响转运蛋白对NH₄⁺的亲和力。实时PCR表明，PNN提高了‘南光’中OsAMT1s的表达，而‘埃利奥’中的表达没有变化，这与这两个品种对PNN的不同响应一致。结论 PNN提高NUE可归因于氮吸收的改善。NUE较高的水稻品种对PNN的响应比NUE较低的品种更积极这表明PNN与NUE之间可能存在关系。
