水稻根际氮素转化的氧调控机制及其对氮素代谢的影响

Improve nitrogen use efficiency and reduce quantity of nitrogen fertilizer input had important meaning to the sustainable development of rice production. Nitrogen form and concentration in the rhizosphere are the main factors that significant effect on the nitrogen absorption and utilization, while the transformation of nitrogen is mainly controlled by the oxygen content of the rhizosphere. Regulating the nitrogen transformation on the base of oxygen content in the rhizosphere, will be the important way to increase the nitrogen absorption and grain yield. In order to illustrate the relationship between nitrogen transformation, oxygen content in the rhizosphere and the nitrogen metabolism of rice, solution culture experiment and field experiment will be conducted to study the differences for physical and.chemical properties in the rhizosphere, nitrogen transformation, the synthesis andtransfer of nitrogen metabolism related enzyme and the the characteristic of nitrogen metabolism for rice. The rice materials used in this study are cultivars widely used in the production. The regulation mechanism of rhizosphere oxygen on nitrogen trasformation and nitrogen use efficiency will be illustrated, the relationship between nitrogen transformation and nitrogen use efficiency as well as the grain yield will be analyzed, the simulation equation for the relationship between oxygen in rhizosphere and nitrogen metabolism of rice as well as yield will also be constructed. Finally, this study will explore the high-yield culture technique which reduce quality of nitrogen input by regulation of oxygen in the rhizosphere to improve the nitrogen use efficiency.This study can resolve the problemes of low nitrogen use efficiency in rice and high nitrogen losses in paddy field, and can also important scientific significance and practical significance for integrating the cultivation techniques for super high-yielding.

提高水稻氮素利用效率，降低氮肥用量对水稻可持续生产具有重要意义。根际氮素形态和浓度是影响水稻氮素吸收利用的主要因子，而根际氮素的转化和浓度主要受根际氧化还原特性影响。以氧气浓度调控根际氧化还原特性从而实现对氮素转化的调控，将是促进水稻氮素吸收和产量增加的重要途径。本项目拟以生产上大面积应用的籼型、粳型和籼粳亚种间等,三种类型高产杂交稻为材料，采用水培试验和大田试验相结合，系统研究水稻在不同氧环境下的根际环境理化性状、不同氮素形态间的转化动态、氮素代谢相关酶的合成和变化，以及水稻对氮素吸收、同化与运转的特性。阐明根际氧环境对水稻根际氮素转化和水稻氮素代谢的调控机理，明确水稻氮素转化与根际氧环境、氮素利用效率和产量之间的关系，探索基于根际氧气调控的水稻高产、节氮栽培新技术。预期研究结果对于解决水稻氮肥利用效率低、氮肥损失大的难题，创新水稻节氮、高产技术新途径。

节氮增效是关系水稻生产安全和种稻效益的关键问题，而提高水稻氮肥吸收效率是保证水稻产量基础上减少氮肥用量的重要途径。研究稻田土壤氧供应调控根际氧化还原特性从而实现对氮素转化的调控，将是促进水稻氮素吸收和产量增加的重要途径。选用对根际氧需求差异较大且分别属于不同生态类型的水稻（中浙优8号）、旱稻（中旱221）和深水稻（IR45765-3B）为试验材料，研究了不同土壤氧调控（微纳米气泡水增氧灌溉处理、干湿交替灌溉和淹水灌溉）和不同氮肥用量下增氧灌溉处理对稻田土壤氮素含量、不同形态氮素转化特性、相关酶活性、土壤微生物特性、水稻生长和氮素利用影响。初步表明微纳气泡水增氧灌溉显著增加了各处理间水稻产量，中旱221、中浙优8号和IR45765-3B品种2年平均产量分别比淹水灌溉增产12.4%、7.5%和6.7%，产量构成因子贡献最大是有效穗数和每穗粒数。还显著增加水稻叶片叶绿素含量和叶面积指数，并增加干物质积累量、氮收获指数、氮肥偏生产力和氮素籽粒生产效率，降低了水稻了氮转运效率和氮转运贡献率。微纳米气泡水增氧灌溉和干湿交替灌溉可以显著提高稻田土壤微生物生物量碳、氮，中旱221、中浙优8号和IR45765-3B的增氧处理较淹水灌溉处理微生物生物量碳、氮分别增加了30.0 %~46.1%和7.1%~92.1%，并且增氧处理降低了三个水稻品种的微生物量碳氮比；且有助于提高稻田土壤脲酶、蔗糖酶、过氧化氢酶、蛋白酶、羟胺还原酶活性，降低硝酸还原酶活性和亚硝酸还原酶活性。增氧灌溉和氮肥促进水稻氮肥积累，微纳气泡水增氧灌溉和减施氮肥处理下三个品种的氮肥利用率比淹水灌溉和常规施肥处理分别提高了8.8%、11.3%和9.5%。相关分析表明，氮代谢酶活性与同时期叶含氮量及氮素积累量的相关性均呈显著或极显著正相关。研究结果有助于解决水稻生产中氮肥过量施用、氮肥损失较大的问题，实现氮肥减施增效。