极端干旱玉米的冠状根复水后粗型一级侧根产生及其功能调控的机制研究

Studies have indicated that root system architecture can strongly affect crop yield through regulating water and nutrient use efficiencies. We previously found that under exceptional altered-water condition the growth of a newtype lateral roots structure was induced with the emergence of crown roots of maize during reproductive period. The emergence of the newtype lateral roots has changed maize’s root architecture observably. However, the physiology mechanism and function of such structure have never be identified before. Hence, it is valuable to initiate the theoretical research on the differences of physiology mechanism and ecological functions between newtype lateral roots and common lateral roots. Based on preliminary study, our research will focus on four aspects: 1) to analyze the contents of endogenous auxin and the expression of PIN genes during the development of the two types of lateral root to figure out the physiological mechanism of the newtype lateral roots formation regulated by the major hormone; 2) to analyze the root hydraulic conductivity and the absorption efficiencies of N15 and to find the differences of the contents of endogenous abscisic acid, the aquaporin activities and the expression of ZmNrt2.1 and ZmNrt2.1 between two kind of lateral roots to figure out the mechanism of the newtype lateral roots on the absorption of nutrients and water; 3) to analyze the contents of endogenous gibberellin and the anatomical structures of xylem of crown roots to figure out the mechanism of new-structure root system on the transportation of water; 4) to analyze the differences of yields between the maize with different root structures to figure out the important function of newtype lateral roots on the recovery of maize. Based on the studies, we hope to identify the physiological mechanism of the newtype lateral roots formation and examine the role of the special root structure in the restoration and enhancement of water and nutrients uptakes and transport in maize roots under exceptional altered-water condition. Our study could contribute to the basis for the adaptive management and variety breeding of cereal crops under special precipitation pattern.

作物根系生长影响水分和养分吸收，决定作物产量。极端干旱复水后，玉米冠状根侧根由普通鲱骨型变成粗型侧根，改变了根系构型。粗型侧根形成机制及其在恢复水分供应后在物质吸收、运输方面的功能及其生理调控机制尚不明晰。通过变水逆境模拟实验，结合抑制剂控制试验，对玉米粗型侧根与普通侧根进行比较研究。本研究的目标：1）分析复水前后生长素含量及其输出载体PIN基因表达动态，揭示主导调控激素在粗型侧根发生中的调控作用；2）分析侧根产生后根系水导和N15吸收，比较内源脱落酸含量、水通蛋白活性及养分转运蛋白编码基因表达变化，阐明侧根在物质吸收方面的功能差异；3）通过冠状根赤霉素含量及其解剖结构特征，明确根系构型在物质运输方面的功能差异；4）通过复水后的产量差异，明确新的根系构型在作物弹性恢复过程中的重要作用。研究结果对揭示冠状根粗型侧根形成机制及功能恢复的调控机制，为制定作物适应性栽培管理和作物选育提供理论依据。

农业系统的变水逆境严重威胁到云南省粮食安全及农业的可持续发展，根系形态和构型是植物水分及养分利用效率的重要指标，根系结构的深入研究与调控正成为粮食增产途径的重要方向。本研究拟在前期发现玉米冠状根新型侧根结构的基础上，通过分析比较与普通侧根在形态、生理特性及功能上的差异。研究结果表明，通过分析不同根系构型侧根产生后内源脱落酸含量（特殊根系构型较普通根系构型在复水7天后高78%）、水通蛋白活性（抑制剂处理后特殊根系构型下降显著22%，普通根系构型平均下降7%）及养分转运蛋白编码基因表达变化（特殊根系构型较普通根系构型ZmNrt2.1高25%，ZmNrt2.2高60%），阐明两种不同侧根在物质吸收方面的功能差异；在物质运输方面，复水21天后特殊根系构型赤霉素含量较普通根系高6%, 特殊根系构型在根部截面的木质部导管和皮层厚度上也表现出优势较普通根系构型高19% 和13%，揭示作物特殊根系构型在抵抗逆境和个体性能恢复过程中的生态学意义；通过稳定性同位素示踪技术发现6种不同基因型在养分利用效率及分配上差异显著，该研究为云南省玉米作物田间养分管理技术的完善与应对极端气候的减灾抗灾体制的形成提供新的理论依据。本研究证明了干旱期特殊根系构型的形成在作物后期弹性恢复过程中发挥着重要的作用，在适应水分胁迫和补偿机制上均有积极的效应，尤其在提高作物水分和养分利用效率方面的特征及功能，可为制定特殊降水格局下玉米等禾谷类作物选育及生产的适应性管理措施提供科学的理论依据；同时项目研究中发现前期作物在根部形成的抗旱结构及特征在复水后对作物的恢复性生长有着重要的影响。因此作物在进行育种及栽培管理时应将前期的抗旱功能与后期恢复过程结合起来，从抗性功能与弹性恢复功能两个方面同时进行研究，更有利于作物在生长及产量上提高稳定性，减少气候事件对产量的影响。项目预期研究成果为3篇学术论文，通过已有研究发表论文 1 篇，在审稿论文 2 篇，获得发明专利1项，获软件著作权1项。