根区水分对膜下滴灌水稻根系形态生理的调节及与产量形成的关系

Water scarcity and increased food demand are two major challenges for global agriculture in the 21st century. Plastic mulching with drip irrigation of rice was created by Xinjiang Production and Construction Group and reflects the significant effects of water-saving and higher yield potential capability, which is crucial for rice production in the arid area of Northern China. Although the water use efficiency in rice is enhanced under drip irrigation, the yield is still not in expected level, resulted from the theory and technology of water management in plastic mulching with drip irrigation of rice is still unclear. Root system of rice as the research object, the study was conducted to access the moderating effects of water around root zone on root morphology, physiology and spatial distribution, and the effects of root morphological and physiological characteristics on photosynthetic substances accumulate and distribute and yield formation. Water supply pattern will be explored to regulate root growth, optimize root structure, enhance root activity, coordinate the shoot growth, and develop a water management pattern of high yield and water use efficiency increased simultaneously. The results will not only support to develop a water-saving system of high-yield-rice with high water use efficiency, and will also help the selection of drought resistant varieties in breeding.

水资源紧缺和粮食需求增长是21世纪全球农业面临的两大挑战。新疆生产建设兵团创立了水稻膜下滴灌栽培技术，其具有明显的节水效应，生产高效且产量潜力大，对我国北方水资源短缺地区水稻种植具有重大意义。然而，目前有关膜下滴灌水稻根区水分管理的理论与调控技术尚缺乏研究，导致膜下滴灌水稻栽培虽具有较高的水分利用效率，但籽粒产量仍未达到预期目标。本研究以水稻根系为切入点，通过研究膜下滴灌条件下根区水分时空变化对水稻根系形态、生理及其空间分布的调节效应，根系形态生理特性变化对地上部光合物质积累分配及产量形成的影响，探寻通过调控根区水分供应，调节根系生长、优化根系构型、增强根系生理功能，协调植株地上部生长，进而实现产量与水分利用效率同步提高的水分管理模式。研究结果为干旱区水稻节水高产栽培技术体系的制定及抗旱品种的选育提供理论依据和技术支撑。

根系作为水分和营养供应的“源”器官，又是多种激素、氨基酸和有机酸合成的重要场所，其形态生理特性与地上部的生长发育、产量和品质形成有着密切的联系。本项目针对新疆丰富的光热气候资源特点，立足膜下滴灌水稻的技术优势，研究了膜下滴灌水稻根系形态生理特征对根区水分及氮肥的响应，解析了根系形态生理特征变化对地上部光合物质积累分配及产量形成的关系。结果表明：（1）适当减少灌水量至10 200 m3/hm2，可以增加抗旱性品种“T-43”抽穗后20 d的 RLD、SAD、AvgDiam和RVD，促进深层(20-60cm)根系及细根(直径<0.9mm)的生长，并提高根系中ABA的含量，抑制气孔张开、降低地上部蒸腾耗水，同时有效减缓地上部叶片叶绿素的降解，维持较高的有效叶面积、保持较强光合活性。（2）在限量灌溉下(10 200 m3/hm2)配施40%穗粒肥，增加了滴灌水稻抽穗期和抽穗后20天细分枝根长度、粗分支根表面积和根体积，提高了抽穗期0-10cm土层的RLD(47.4%-60.4%)、RSA(50.3%-61.4%)、RVD(18.2%-23.9%)、Z+ZR (1.0%-34.0%)、GA3(1.8%-37.5%)、IAA/ABA(0.9%-114.8%)以及抽穗后20 d叶片GDH(3.1%-2940.0%)和Pn(0.1%-67.1%)。相关分析表明，根系中Z+ZR、GA3、IAA/ABA与滴灌水稻茎、叶、穗干物质积累呈显著正相关叶片，且GDH、Pn与产量和氮利用效率呈显著正相关。合理的水氮管理能够优化根系形态结构，协调根系内源激素平衡，促进同化物向籽粒的分配，同时增强叶片光合特性和氮素运转能力，实现滴灌水稻高效生产。（3）不同栽培模式下(膜下滴灌和传统淹灌)，随着氮肥施用量的增加，抗旱性品种T-43通过调整比叶重和叶绿素的氮分配比例，实现其光合生产能力与光合氮利用效率的最大化。滴灌条件下，光捕获能力的降低与较高的羧化活性和比叶重可能是水稻适应环境变化的重要生长策略。本项目有助于从理论上认识根系形态生理特征与冠层生长的关系，探讨通过根层合理水肥管理，调节根系生长，促进同化物优先向籽粒库转运，进而保证膜下滴灌水稻高产高效生产。