聚天门冬氨酸（PASP）促进水稻氮素吸收利用的机理研究

To meet the demands of modern agriculture, not only the increase in rice production is need, but also the use of natural resources and damage to the environment must be minimized. However, low nitrogen (N) use efficiency is a universal phenomenon in paddy fields in China. Polyaspartic acid (PASP), a new type of eco-friendly and high-efficiency nitrogen synergist, is selected from a five-year experiment, by which the reduction in paddy N loss, improvement in N accumulation and utilization efficiency were observed by using PAS-urea. Nevertheless, the mechanism of PASP on improving N use efficiency is limited. In this project, field and phytotron experiments will conducted to investigate the spatial and temporal distribution characteristics of PASP-urea in soil, including its transportation, decomposition, and transformation, using 15N isotopic-tracer technology. Riphzosphere environment, root growth, and expression of N transport related genes well investigated to evaluate the effect of PASP on N assimilation using biochemical-enzymic method, Illumina MiSeq high throughput sequencing, and real-time quantitative PCR, etc. Moreover, biochemical substances, key enzymes activity, and genes expression, which are associated with N utilization well measured to assume the physiological and biochemical mechanism of PASP on enhancing N use efficiency of rice. We believe that the results can explain the synergistic mechanism of PASP on increasing nitrogen use efficiency, and provide the theoretical basis for the popularization and application of PASP in agricultural production and research.

我国稻田普遍存在氮肥利用率偏低的现象，聚天门冬氨酸（PASP）是一种能提高肥料利用率的新型环境友好型氮肥增效剂。但目前PASP促进水稻提高氮素利用率的机理尚不清晰。申请者经连续5年田间试验表明，PASP氮肥减少了稻田氮素流失，促进了水稻对氮素的吸收，提高了氮素利用率。为明确PASP促进水稻根系高效吸收氮素和植株对氮素高效利用的机制，拟采用田间试验、人工气候室控制试验与15N同位素示踪相结合的方法分析PASP氮肥在稻田土壤中的运移、分解、转化和时空分布特点，并采用生化酶学法、Real time PCR等技术对根际环境、根系生长和根系吸收土壤铵态氮和硝态氮的转运蛋白基因表达，以及对植株氮素利用相关的生化物质、关键酶活性和基因表达的调控进行深入分析，从而阐明PASP提高氮素吸收利用效率的机理。本研究将为进一步利用PASP提高水稻氮素利用率和产量提供理论支撑。

我国水稻生产存在氮肥施用量大而利用率低的问题，新型氮肥的研发和应用是提高稻田肥料利用率的有效途径。聚天门冬氨酸（PASP）多肽氮肥（以下简称多肽尿素）是一种新型环境友好型增效肥。本项目结合大田、盆栽和根箱试验，从氮素的转化、运移和时空分布，微生物群落结构差异和功能基因表达等土壤氮素行为，结合根构型和根系氮素吸收利用关键基因表达差异，从土壤-根系-植株系统揭示了多肽尿素提高氮素吸收利用效率的机理。.研究结果表明，多肽尿素的淋溶和氨挥发损失比普通氮肥分别降低了28.3%和21.7%，参与土壤硝化作用的关键功能菌属硝化螺菌属（nitrospira）和亚硝化单胞菌（nitrosomonadaceae，MND1）以及与氨单氧化酶（AMO）和八羟基氢氨还原酶（HAO）相关的4个功能基因在多肽尿素处理下的浅土层中均上调表达，最终导致0-10cm表土层中硝态氮的含量在施肥后15-30d显著高于普通尿素。.土壤硝态氮含量和分布的差异导致根构型和氮素吸收的改变。分蘖肥施用后第10d不同氮肥处理下的根构型开始出现差异，多肽尿素的根系更趋向于横向分散型生长，并在拔节期达差异最大值。在分蘖后期根尖数、根表面积和细根（直径为0-0.5mm）长度高于施用普通尿素的处理，多肽尿素处理下0-10cm土层根干重比普通尿素处理提高了20.8%-25.2%，促进了浅层横向分散型根系的形成。.根构型与土壤硝态氮的时空分布相匹配，进一步促进了根系对硝态氮的吸收利用。硝态氮吸收转运关键基因NRT1.1A，NRT1.1B，NRT2.3b和NPL3在多肽尿素处理下均显著或极显著上调表达，使水稻植株氮素积累量和产量显著提高。多年试验与实践结果表明，与普通尿素相比，多肽尿素施用后平均增产6.8%，氮素积累量增加14.3%。本研究结果为新型高效肥料的开发和应用提供了理论支撑和实践验证，将进一步提高水稻氮肥利用率和产量，实现减肥不减产，促进农业的绿色高效生产。