氮肥供应对穗分化期高温下水稻穗分化与颖花育性的调控及机理研究

The high temperature stress is increasingly becoming one of major constraints for crop production, and has influences on crop growth and development，and also on physiological and biochemical processes. Nitrogen as an essential element for crop growth and development regulates lots of physiological and biochemical processes and grain yield formation. However, the regulation of nitrogen on physiological and biochemical responses to high-temperature stress is still not clear, and less attention has focused on the relationship between N application and acquisition of resistance/tolerance to high temperature stress in rice. In the proposed project, we will investigate effects of various nitrogen application rates (different panicle initiation nitrogen fertilizer application rate, different nitrogen fertilizer application rates as basal and top-dressing during tilling stage) on panicle initiation, spikelet and pollen fertility, grain yield formation under high temperature imposed during panicle initiation duration. On the other hand, we will investigate effects of different nitrogen application rates on nitrogen absorption and distribution to panicle, assimilate acclamation and distribution to panicle, water metabolism, plant hormone metabolism, and changes of reactive oxygen species in panicles and spikelets, and explore the relationships of the effects with panicle initiation and fertility. Thirdly, according to the following outline of “nitrogen application rates — nitrogen absorption and distribution to panicle, assimilate acclamation and distribution to panicle, water metabolism, plant hormone metabolism, and changes of reactive oxygen species — panicle initiation and spikelet fertility — high temperature tolerance/resistance”, the results will be used to explain the regulation of nitrogen fertilizer on panicle initiation and fertility and underlying physiological mechanism, and to reveal the physiological pathway for acquisition and regulation of tolerance/resistance to high temperature stress in rice. The output of the proposed project will provide theoretical basis for optimal nitrogen fertilizer management for enhancing high temperature tolerance/resistance and relieving high temperature injure in rice.

高温正成为制约作物生产的主要逆境之一，影响着作物生长发育与生理生化过程。作为作物所必需的养分之一，氮素调控作物生长发育、产量形成和生理生化过程。然而，氮素调控水稻高温响应特征与高温抗性形成机理的研究相对很少。本项目拟研究幼穗分化期高温下不同氮肥施用量（不同氮穗肥、不同氮基肥和氮分蘖肥）对穗分化、颖花和花粉育性、产量形成的影响，研究不同氮肥施用量对氮吸收分配、同化物积累与分配、穗部水分代谢、穗部激素与活性氧的响应特征及其与穗分化和花粉育性的内在关系。在此基础上，从“施氮量－氮素吸收分配与同化物积累分配、激素与氧自由基代谢、水分代谢-穗分化与颖粉育性－水稻高温抗性”这一思路来探索氮素对水稻穗分化与颖花育性高温响应的调控及其生理机理，阐明氮素调控水稻高温抗性的生理途径，为氮肥优化管理提高水稻高温抗性减缓高温伤害提供理论基础。

高温已成为制约我国水稻生产的主要逆境之一，减少高温伤害越来越受到关注。本项目选用高温抗性和敏感水稻品种，在盆栽条件下研究了幼穗期和抽穗期高温对产量形成的影响，并从氮碳水代谢、内源激素、活性氧代谢、花药发育等角度研究了氮、钾、水供应、外源生长调节物质对穗分化与颖花育性高温响应的调控及生理机理。研究发现：(1)幼穗期和抽穗期高温显著降低了高温敏感品种产量，主要通过影响颖花育性和结实率来降低产量；(2)高温影响了花药和花粉的正常发育(特别是在高温敏感品种)，紊乱的花药和花粉发育是高温下花粉和颖花育性下降的原因之一；(3)抽穗期高温处理下水稻花药和花粉含水量降低是导致花药开裂率和花粉育性降低的原因之一，高温抗性强与颖花蒸腾速率高、降温能力强有关；(4)幼穗分化期高温没有显著影响植株氮积累，但导致氮向籽粒分配的比例下降，向叶片和茎鞘的分配比例增加，不同氮处理下高温抗性不同的品种表现出不同的氮吸收和分配特征；(5)幼穗分化期高温降低水稻(特别是高温敏感品种)穗部(颖花和花药)细胞分裂素总量，分蘖期干湿交替处理、增施氮分蘖肥、增施钾穗肥显著减少穗部活性细胞分裂素含量和细胞分裂素总量的下降幅度，从而促进颖花分化；(6)幼穗分化期高温导致了幼穗糖代谢相关酶活性下降，增施氮素穗肥减少了幼穗磷酸蔗糖合成酶、蔗糖合成酶（合成方向）活性的下降，减少水稻幼穗非结构性碳水化合物浓度的下降幅度，从而提高水稻花粉和颖花育性；(7)幼穗期高温下增施氮素穗肥提高颖花POD酶、花药POD和CAT酶活性，降低花粉ROS水平，从而降低了膜质过氧化程度；（8）总体上，研究表明增施分蘖氮肥、穗氮肥和穗钾肥、适当水分亏缺处理和外源生长调节剂运用可提高水稻品种(特别是高温敏感品种)的高温抗性，显著提高颖花育性和产量。本项目研究结果可为优化肥水栽培管理提高水稻高温抗性、减缓高温伤害提供理论基础。