【作者】 张耀鸿；

【导师】 沈其荣；

【作者基本信息】 南京农业大学 ， 植物营养， 2006， 博士

【摘要】 中国的氮肥施用量占到全世界使用量的1／4强。由于过量施肥导致我国的氮肥利用率一直低于世界水平。南方部分经济相对发达地区稻田的氮肥利用率低于20％。氮肥利用效率低不仅导致氮素的损失，而且还对环境产生严重的影响。氮肥利用率低下在全世界范围内是一个难以解决的问题。有丰富可利用耕地和较少人口的一些发达国家可以通过降低目标产量和减少氮肥投入量来实现。而在中国由于可利用耕地非常有限并且拥有世界上最多的人口，所以需要采取其它方式既要保证作物单产不降低又要对环境不会造成负面影响。因此，应该优化施肥量以达到最佳产量又不会产生环境压力。大量研究结果表明水稻的氮肥利用率存在着基因型差异；通过基因型筛选来提高我国稻田氮肥利用率是可行的。因此，本试验研究了不同水稻基因型的氮素吸收和利用的基因型差异，为筛选氮高效基因型提供试验依据。 考察苗期氮素吸收特征是筛选氮高效水稻基因型的重要途径。水培试验研究了3个基因型水稻（4007、南光、ELIO）苗期氮素吸收利用以及生长特征的差异。测定了3个氮水平下(4，10，40 mg N L^-1)水稻的生物积累量，氮素积累量，总根长，根系表面积，氮素吸收速率和吸收动力学参数。结果表明，低氮处理显著减小了水稻的干物质积累量；ELIO在3个氮水平下的干物质积累量均显著高于4007和南光。氮胁迫(4，10 mg N L^-1)条件下植株的干物质积累量与对照处理(40 mg N L^-1)相比，减小幅度顺序为：南光＞4007＞ELIO。说明南光对低氮条件最为敏感。3个品种间的氮素利用效率没有差异，而ELIO的氮素吸收效率显著高于4007和南光。氮胁迫条件下植株的氮素积累量与对照处理相比，减小幅度顺序为：南光＞4007＞ELIO。说明ELIO的干物质积累量多主要因为它具有较高的氮素吸收效率。ELIO的总根长、根表面积、根尖数均显著大于4007和南光。各个氮水平下ELIO的氮素吸收速率均高于4007和南光。ELIO吸收NH₄⁺和NO₃^-动力学参数V_max大于4007和南光；它们之间的K_m没有差异。因此，ELIO品种苗期高效吸收氮素是根系形态和吸收速率综合作用的结果。 在3个氮水平(4、10、40 mg N L^-1)下，研究了氮素吸收效率不同的3个水稻品种（高吸氮品种ELIO；低吸氮品种4007、南光）的叶片光合特性的差异以及与氮素营养的关系。结果表明，4007和南光的光合速率和气孔导度在各个氮水平下显著低于ELIO。品种间的叶片胞间CO₂浓度没有差异。水稻的光合速率与气孔导度显著正相关，相关系数为0.85^*。低氮处理显著减小了水稻叶面积。4、10 mg N L^-1与40 mg N L^-1水平相比，3个品种叶面积下降幅度顺序为：南光＞4007＞ELIO。4007和南光叶片中更多还原

【Abstract】 China accounts for more than one quarter of the total nitrogen （N） fertilizer used in the world. However, the recovery of N fertilizer by crops has been generally low because of excessive N application. The problems resulting from excessive mineral N fertilizer application in Chinese intensive agricultural regions can be exemplified by the rice production in Eastern China. The century-old double-cropping （irrigated summer rice / upland winter wheat） systems have been transformed from a N -limited to a N -saturated state, with mean N application reaching up to 335 kg N hm^-2 year^-1. The alternating water regime causes high N losses during the N transformations and low crop N uptake efficiencies of 28%-41%. This is leading to large-scale, non-point source pollution of aquifers. Low N use efficiency with high environmental impact is a worldwide problem. It may be resolved by reducing target yield and N input in developed countries with surplus arable land and small population. This is, however, impossible in China since the country is still facing the food unsecurity. Different approachs should be made in order to reduce the environmental impact while the crop yield and productivity can be maintained or even increased at the same time. Therefore, the N input should be optimized to reach the harmonious point between high yield and sound environment. Field experiments have shown that genetic variability for N use efficiency exists in rice plants. There is a possibility of improving N utilization efficiency in rice through genotype selection. Therefore, this study was conducted to select rice cultivars that could exploit N more efficiently in order to minimize loss of N from the soil and make more economic use of the absorbed N.1. Identification of the traits of N uptake and utilization at the seedling stage is considered to be an effective approach for selecting N -efficient rice genotypes. Different levels of N concentration (4, 10, 40 mg N L^-1) were supplied to three rice genotypes （4007, Nanguang and ELIO） that had shown different N use efficiencies. Biomass, N uptake, total root length, root surface, N influx rate and uptake kinetics were determined in all the plants. N deficiency reduced the dry matter accumulation in all the genotypes. ELIO accumulated more dry matter than other two rice genotypes, and the rate of reduction of dry更多还原