硝态氮促进柑橘生长和镁素利用的分子生理机制

Citrus production has been seriously suppressed by the magnesium (Mg) deficiency, the researches on occurrence and regulation mechanisms of Mg-deficiency are of great theoretical and practical importance. Project research team has conducted extensive research on citrus Mg-deficiency, and previous results showed that citrus growth and Mg absorption could be promoted by nitrate nutrition. However, the internal regulation mechanisms of nitrate nutrition are still unclear. In this study, sand culture combined with soil and hydroponic split-root culture experiments are used to study (1) the effects of nitrogen and magnesium (N-Mg) interaction on photosynthesis physiology and N-Mg metabolism, to discuss the physiological mechanism of Mg nutrition and plant growth characteristics in response to N forms in citrus; (2) effects of N-Mg interaction on root exudates traits and microbial community characteristics of rhizosphere soil, to reveal the nitrogen nutrition characteristics of root exudates and the influence mechanisms of rhizosphere microbial community structure in citrus; (3) to illustrate the molecular mechanism of nitrate nutrition promoted plant growth and Mg utilization by transcriptome sequencing and identification of differentially expressed genes of N-Mg transporter in citrus. This study, which is based on interaction between nitrogen and magnesium, investigates the mechanisms of the regulated magnesium by nitrogen on citrus from the aspect of nitrogen nutrition characteristics. The results of the study will provide the theoretical basis for improving the quality and efficiency of citrus production by the rational application of nitrogen and magnesium fertilizer.

镁营养缺乏严重制约了我国柑橘产业的发展，研究其发生及调控机制具有重要的理论和现实意义。申请者团队已对柑橘响应镁缺乏进行了广泛研究，并表明硝态氮可促进柑橘生长和镁素吸收，但其确切的分子生理机制尚未阐明。本项目以氮素形态耦合镁营养供应柑橘植株为研究对象，采用砂培、土培和营养液分根培养的方式，主要研究：（1）氮镁互作对柑橘光合生理和氮镁代谢的影响，探讨柑橘植株响应氮素形态的生长特性和镁营养的生理机制；（2）氮镁互作对柑橘根系分泌物类型和根际微生物区系特征的影响，揭示柑橘根系分泌物的氮素营养特性及其根际微生物群落结构的响应机制；（3）通过转录组测序和氮镁转运蛋白差异基因验证，解析硝态氮促进柑橘生长和镁素吸收利用的分子机制。本研究以氮镁互作为基础，从氮素营养特性角度系统研究柑橘以氮调镁的响应机制，项目成果将为生产中氮镁肥合理施用的柑橘产业提质增效提供理论依据。

镁营养缺乏和不合理施氮严重制约了我国柑橘产业的绿色发展，本研究在聚焦柑橘（芦柑和雪柑）实生苗响应缺镁、氮素形态和用量以及氮镁互作的生理分子机制的同时，解析福建省平和县琯溪蜜柚园土壤-植株氮镁营养现状、需求规律和养分管理，以期为柑橘提质增效生产提供理论依据。主要结果如下：.1、阐明了缺镁对柑橘苗侧枝生长的抑制大于主茎，缺镁降低了根和叶中可溶性组分与可移动性镁的分布而增加了细胞壁和细胞器组分与难移动性镁的分布，缺镁促进了镁从主茎向侧枝的转运而调节相关生理生化过程。.2、转录组学揭示了缺镁柑橘叶片增强微管运动和细胞周期调节、提高对生物和非生物刺激的信号转导、上调细胞壁重塑和抗氧化系统、下调光合作用等分子机制；代谢组学揭示了缺镁柑橘叶片上调脂类和类脂分子以及大多数单糖和氨基酸的相对丰度，下调苯丙酸和聚酮类化合物以及大多数叶色素化合物和有机酸含量等代谢特性。.3、阐明了氮素形态和用量对柑橘植株生长、氮代谢、光合电子传递等生理生化特性，首次证实了柑橘是一个铵态氮敏感型植物；同时，揭示了硝态氮促进柑橘生长和镁素吸收的生理分子机制，并发现了充足的镁素供应可适度缓解柑橘的铵毒害。.4、综述了我国柑橘生产中的镁营养现状、原因及国内外研究进展，揭示了平和县蜜柚园土壤化学质量现状和空间分布，定量了蜜柚树表观氮、镁等养分平衡，开展了养分优化管理协同蜜柚高产优质和肥料高效的应用研究，强化了项目成果服务柑橘生产的技术转化。.5、项目资助已发表高质量论文13篇，其中，SCI论文7篇，中文核心论文6篇，另有2篇论文待发表。项目资助培养硕士研究生6名，其中，5名已取得硕士学位（继续攻读博士学位3人），1名在读。项目投入经费29.66万元，其中，直接经费25万元，支出24.3302万元，各项支出基本与预算相符。剩余经费5.3298万元，剩余经费计划用于本项目研究后续支出。