双季超级杂交水稻氮素亏缺补偿效应及其生理机制

Nitrogen is one of the most important and active controllable factors affecting rice yield, but the problems that nitrogen application efficiency was low and the yield increasing effects along with the nitrogen fertilizer enhancement was insignificant are popular in China currently. The nitrogen fertilizer applied high efficiency period and inactive period must be ensured for solving the problems, while its precondition is to find out nitrogen requirement critical period and deficiency sensitive period in rice. The former research about the problem generally took the same total nitrogen allotted scheme at the different growth stage, namely nitrogen operation test. Its shortcoming was lack of controlling soil intrinsic fertility, moreover a majority of the nitrogen fertilizer was divided into the basic fertilizer and the residual fraction was allotted at the different growth stage. It could not exclude the interference of the soil indigenous nitrogen supply on the effect of supplemental nitrogen at the different growth stage, and there were few reports about the compensatory effect of nitrogen deficiency and its normal and double amount resuming at the different growth stage too. Yangzi double-season rice drainage area is one of the main paddy rice grain production regions in China, recently years a series of super rice varieties were widely extended and the research about their nitrogen requirement laws are desired to study in_depth . The aim of the research is to find out nitrogen deficiency sensitive period and compensatory effect effective period, the threshold of compensatory effect and highly efficiency compensatory threshold inner the sensitive period through the investigation of the growth and development effect of nitrogen deficiency and its normal and double amount resuming at the different growth stage in double-season super hybrid rice varieties, also explore its physiological mechanism from the nitrogen and dry matter distribution, photosynthesis, enzyme activity and hormones to supply a new sight on rice nitrogen utilization research.

氮素是影响水稻产量最重要、最活跃的可控因子之一，但当前我国普遍存在氮肥利用率低下及增氮增产效果不再明显问题，解决该问题必须确定氮肥施用高效期和迟钝期，前提是查明氮素需求关键期及亏缺敏感期。以往对该问题的研究通常采用相等总氮量不同生育阶段分配方案，即氮素运筹试验，缺点是未控制土壤本身肥力，且将氮肥大部分作基肥，剩余小部分分配于各生育阶段，无法排除土壤背景氮对不同生育阶段追氮效果的干扰，鲜见不同生育阶段氮素亏缺及缺后常量、加倍恢复供应补偿效应的研究报道。长江流域双季稻区是我国稻谷主产区之一，近年来推广了一批超级稻品种，其需氮规律研究亟需深入。本研究旨通过不同生育阶段氮素亏缺及缺后常量、加倍恢复供应对双季超级稻品种生长发育影响的研究，查明氮素亏缺敏感期及补偿有效期，敏感期内产生补偿效应的亏缺阈值与高效补偿阈值，从氮素与干物质分配、光合、酶活性、激素等探讨其生理机制，为水稻氮素研究提供一个新视角。

当前我国水稻生产中普遍存在氮肥利用率低下及由此带来的环境污染问题，解决该问题必须查明氮素需求关键期及亏缺敏感期，以往对该问题通常采用相等总氮量不同生育阶段分配方案，缺点是未控制土壤本身肥力，且将氮肥大部分作基肥，无法排除土壤背景氮对不同生育阶段追氮效果的干扰，鲜见不同生育阶段氮素亏缺及缺后常量、加倍恢复供应补偿效应的研究报道。本项目选用双季超级杂交稻品种及低背景氮土壤，研究不同生育阶段氮素亏缺及缺后下一生育阶段常量、加倍恢复供应对其生长发育及产量形成的影响，并从氮素和干物质积累与分配、光合、酶活性、激素等探讨其生理机制，结果表明：（1）、分蘖期前和抽穗后氮素亏缺对双季超级稻产量影响较小，分蘖期至穗分化期影响大，为其需氮关键期和亏缺敏感期，氮素亏缺补偿有效期为幼穗分化期，补偿临界期为始穗期；超级杂交早稻品种氮素亏缺敏感期分蘖期内产生补偿效应的亏缺阈值和高效补偿阈值分别为分蘖24d和分蘖12d，晚稻分别为分蘖18d和分蘖18d。（2）、同一总施氮量下，双季超级杂交稻分蘖期氮肥亏缺后幼穗分化期倍量补偿供氮处理与各生育阶段氮肥按常量分配对照产量无显著差异，呈现出等量补偿效应；氮素亏缺补偿处理较对照干物质积累、氮素吸收利用率、农学利用率和生理利用率等均得到明显提高；氮素亏缺补偿处理较对照叶片净光合速率、SPAD值、氮代谢酶（硝酸还原酶NR和谷氨酰胺合成酶GS）活性均能维持在较高水平；至补偿后期，氮素亏缺补偿处理稻株叶片脱落酸（ABA） 含量显著低于对照，生长促进类激素之和（GA3＋IAA＋ZR）与生长抑制类激素（ABA） 比值显著高于对照，根系伤流量显著高于对照；表现出较为明显的氮素亏缺补偿效应。该研究可为生产上利用双季超级稻品种自身调节和补偿机制，降低氮流失及水稻奢侈耗氮，提高氮肥利用率提供理论依据，也为当前提倡的降低分蘖期氮肥比例及适当推迟施用时间，提升后期比例提供了一个有力佐证，还为水稻氮素利用研究提供了一个生态学新视角。