集约化玉米体系磷与水分互作的根土界面效应及高效利用机理

Low use efficiency of phosphorus and water are key limiting factors in intensive maize production. Under the driving flow by soil water, phosphorus can be taken up mainly through the root-soil interface. However, root-soil interface effects of phosphorus and water interactions and their efficient use mechanism by crop are not fully understood. This is a key question to deeply understand interactive effects of nutrient and water and thus enhance their use efficiency through rhizosphere management. The present study lays emphasis on the root-soil interface effects and regulating mechanism of phosphorus and water interactions in terms of efficient acquisition and use for intensive maize (Zea mays L.) cropping system through field trials and pot experiments in green house. Some key methods and techniques for monitoring dynamic processes and related parameters in the root-soil interface are adopted, including in situ research method for rhizosphere processes, isotopic tracing and labeling, nutrient and water localized supply technique, a novel non-invasive optical method for quantitative visualization of pH dynamics in the rhizosphere and root apoplast, fluorescence dye imaging technique, in situ root exudate collection technique by micro-suction cup, and the rhizosphere nutrition and molecular biological techniques. The main objectives of the present study are to systematically investigate the spatio-temporal distribution and interactions of phosphorus and water in the interface of root and soil interactions, clarify the effects of apoplast pH and root exudates on interactions and efficient use of phosphorus and water, reveal interactive effects of phosphorus and water in the root-soil interface and the molecular-physiological mechanism of regulating phosphorus and water interactions and efficient use by ethylene for maize, examine the effects of different phosphorus and water supply patterns on rhizosphere processes, and thus develop the strategies for rhizosphere/root zone management to enhance phosphorus and water use efficiency for field maize cropping system. This study will provide important scientific bases to better understand the mechanism of phosphorus and water interactions and their effective regulating pathways, and thus improve phosphorus and water use efficiency for farmland towards high-yield and high-efficiency sustainable crop production.

磷与水分利用率低是制约集约化玉米生产的关键因素。磷必须在水分的作用下通过根土界面才能被作物吸收利用，然而集约化农田土壤磷与水分互作的根土界面效应及其高效利用机制并不清楚，这是深入揭示养分水分互作效应进而提高其利用效率的关键问题。本研究通过大田和室内模拟试验，以集约化种植体系玉米为研究对象，以磷与水分在根土界面的互作效应及高效利用的调控机制为研究主线，综合采用根土界面原位监测、同位素标记技术、养分水分局部供应控制、pH微电极和荧光探针检测结合分子生物学手段等方法，系统研究集约化玉米种植体系磷与水分在根土界面的时空分布及互作过程，明确质外体pH和根分泌物对磷和水分的共济效应和高效利用的作用，揭示乙烯调控磷与水分耦合及高效利用的分子生理机制，阐明磷与水分在根土界面的互作效应及调控机制，提出农田磷和水分高效利用的根际/根层调控途径。为提高磷和水分的利用效率，实现玉米高产高效可持续生产提供科学依据。

根土界面磷与水分的有效性是制约其利用效率的关键因素，磷需在水分的作用下通过根土界面才能被作物吸收利用，然而磷与水分互作的根土界面效应及高效利用机制并不清楚。本研究通过创新根际原位研究方法，结合同位素标记、荧光探针检测及分子生物学手段等方法，系统探讨了磷与水分在根土界面的互作效应及高效利用机制，主要进展包括：（1）揭示了集约化玉米种植体系磷与水分在根土界面的时空分布及互作过程，发现根层适宜供磷显著提高玉米的抗旱能力，证明8%深层根系通过提水作用强化了表层磷与水的耦合效应，明确了玉米影响磷有效性的根际范围,缺水使根际磷的补充效率下降50%；（2）首次揭示了豆科作物根分泌物诱导的根际磷异质性分布和有效性是促进玉米根系生长和养分吸收的主要机制，发现玉米等禾本科作物主要依赖根系形态适应缺磷，而豆科作物主要依赖有机酸的分泌；（3）明确了根际酸化和质外体pH对玉米根土界面磷和水分高效利用的调控作用, 发现局部施用磷与铵态氮，显著促进根系增生，诱导根际和质外体强烈酸化，提高了磷的利用；（4）探明了根分泌物对根土界面磷与水分共济效应的作用机制，证明根分泌有机酸和粘液协同修饰根际环境提高了作物对磷与水的利用；（5）揭示了NO参与玉米对不同磷和水分供应的响应及协同利用机制，NO调控叶片气孔导度和根水通道蛋白基因的表达，从而影响水分吸收和光合速率；（6）揭示了乙烯参与调控磷与水分耦合及高效利用的机制，发现缺磷降低玉米根系乙烯释放，明确磷和水分高效利用、NO 与乙烯之间的相互关系；（7）建立了农田磷和水分高效利用的根际/根层调控途径。在主流期刊发表论文33篇，其中SCI论文31篇，有9篇IF>5；已投稿和拟投稿论文5篇；主办国际学术会议1次，在国际学术会议上作大会特邀报告7次，分组报告13次；培养研究生20名（博士8人，硕士12人）。研究成果为提高磷和水分的利用效率，实现玉米节肥增效可持续生产提供了科学依据。