水稻根系代谢的氧调控机理及对氮素利用效率的影响

Root is the important metabolic organ for rice growth, and its metabolic condition directly affects the growth of rice shoots and the yield formation. The oxygen content in the rhizosphere is crucial limiting factor for the metabolism of rice root, and it can directly affect the hormone synthesis and nitrogen metabolism relating to the leaf senescence. Maintaining the metabolic activity of rice root will be the important way to increase the grain filling and yield of rice. In order to illustrate the relationship between metabolic activity in rice root, 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 synthesis and transfer of auxin, cytokinin, abscisic acid and the characteristic of nitrogen metabolism for rice. The rice materials used in this study are cultivar showing different response characteristic to rhizosphere oxygen. The regulation mechanism of rhizosphere oxygen on root metabolic activity and nitrogen use efficiency will be illustrated, the relationship between metabolic activity of rice root and nitrogen use efficiency as well as the leaf senescence 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 preventing early senescence by regulation of oxygen in the rhizosphere to improve the metabolic activity of rice root. The results will show important scientific significance and practical significance for screening the cultivars resistant to premature, taking measures for preventing premature, and integrating the cultivation techniques for super high-yielding.

根系是水稻重要的代谢器官，其代谢状况直接制约着水稻地上部的生长和产量形成；而根际氧气状况是影响水稻根系代谢的关键因子，直接影响与叶片衰老密切相关的激素合成和氮素代谢。维持根系代谢活性，将是提高水稻籽粒灌浆和产量的重要途径。本项目拟以对氧气响应典型差异的水稻为材料，采用水培试验和大田试验相结合，系统研究不同类型水稻在不同根际氧气环境下的根系生长素、细胞分裂素、脱落酸等合成、传递差异及碳氮代谢特性，重点探讨根系代谢活性与根际氧气含量和水稻氮素代谢的关系。阐明根际氧气对水稻根系代谢活性和氮素利用效率的调控机理，明确根系代谢活性与水稻氮素利用效率和叶片衰老的关系，建立根际氧气和根系代谢活性与水稻氮素代谢和产量之间的模拟方程，探索基于根际氧气调控根系代谢活性的水稻防早衰高产栽培技术。预期研究结果对于抗早衰组合（品种）选育和生产上防早衰措施制定，集成水稻超高产生产技术，均具有重要的科学意义和实践意义。

根际氧气状况是影响水稻生长和氮素吸收代谢的关键因子。以中浙优1号（水稻）、IR45765-3B（深水稻）和中旱221（旱稻）3种不同生态型水稻品种为材料，分别在可遮雨水泥池中设置增施过氧化钙、微纳气泡水灌溉和表土湿润灌溉及淹水对照进行田间试验；同时在水培条件下设置1.0 mg/L、3.0 mg/L、5.5 mg/L、7.5 mg/L等不同溶解氧浓度进行试验，研究不同处理下水稻叶片光合特性、干物质积累量、产量形成、稻田氮素转化和水稻氮素吸收积累特性。结果表明，田间条件下增施过氧化钙和微纳气泡水灌溉有助于提高水稻叶片叶绿素含量、叶面积指数和光合作用能力，并显著增加水稻干物质积累和产量；增施过氧化钙处理下，中浙优1号、IR45765-3B和中旱221产量分别较对照增加了22.38 %、18.27 %和18.17 %；微纳气泡水灌溉处理下3品种产量分别较对照增加了13.89 %、10.67 %和8.85 %；表土湿润灌溉处理下，产量分别比对照减少 5.86 %、8.19 %和 6.16 %。增氧处理显著增加水稻的氮素吸收与利用，与对照相比较，增氧处理下IR45765-3B和中浙优1号氮肥偏生产力均显著升高；施用过氧化钙和微纳气泡水增氧灌溉处理下水稻氮素转运效率和氮素转运贡献降低，但齐穗期后两品种的氮素吸收量显著增加，齐穗期后IR45765-3B和中浙优1号在施用过氧化钙处理下的氮素吸收量较对照分别增加了73.4 %和119.2 %，微纳气泡水灌溉处理下的氮素吸收量较对照分别增加了128.7 %和106.5 %。增氧处理下水稻氮素利用率增加主要是因为增氧处理有效改善稻田土壤氧化还原状况，而显著增强稻田氮的硝化而减少氮素损失，从而提高水稻氮素积累量和氮素收获指数。水培条件下不同根际氧浓度试验表明，水稻生长前期根际溶解氧1.0 mg/L和3.0 mg/L处理有利于水稻对氮素的吸收；灌浆后期增氧处理在一定程度上可增加植株氮素积累，但氧浓度过高不利于氮素向籽粒中转运。3水稻品种 3.0 mg/L处理氮素利用效率最高，比低氧处理 1.0 mg/L分别提高 6.9 %、12.8 %和 13.8 %；根际氧浓度升高有利于增加水稻营养生长阶段的氮素干物质生产效率。研究结果有助于水稻氮素高效管理和高产栽培技术的发展。