玉米根系空间重叠区竞争互利增产的形态生理调控机制研究

A reasonable plant density is the key to the realization of maize yield, root completion moves stronger when the density increased. Different plant type and density have different yield-improving effect in root competition. The root system avoid their neighbors by space dislocation, hybrid which is able to loss less and benefit more in root competition would bring higher yield. We don’t know how high yielding and density tolerant hybrid obtain more benefit in spatially overlap area and effect of plant type and density on mutual regulatory mechanism in root competition. Response of root morphology anatomy, root exclusion and inner hormone to plant density and relationship among them was carried out in combination of box soil column cultivation and field experiment by using single and mixture sowing method for different plant type maize hybrid. Mutual benefit mechanism of morphological trait and physiological trait and interaction between morphological and physiological trait of roots in the spatially overlap area was also studied. The objective of this research is to uncover relationship between interaction between morphological and physiological trait of root and nutrient efficient utilization in spatially overlap area in the best high yielding density for different plant type maize hybrid, and to find morphological and physiological regulatory mechanism of mutual benefit of yield-improving in competing roots. The meaning of this research is to provide scientific theoretical basis and practical guidance for improving integrated productivity and resources utilization efficiency further for maize.

合理密植是实现玉米高产的关键，密植引起根系间竞争加剧，不同株型品种和种植密度对根系竞争增产效应各异。根系通过空间错位回避互感邻近根系，根系间竞争损耗小、互利增效大的品种密植可实现高产。关于密植高产玉米根系竞争较激烈的空间重叠区根系通过形态和生理调控如何互利增产，株型和密度对根系竞争的互作调控机制等科学问题尚不明确。本研究拟以不同株型玉米杂交种为研究对象，采用箱式土柱模拟与大田试验验证相结合的方法，通过单播与混播设置不同种植密度（竞争强度），研究空间重叠区根系形态解剖结构、根系分泌物、内源激素等对种植密度的响应及与养分利用的关系，分析竞争重叠区根系间形态互利和生理互利机理及相互作用，揭示不同株型品种高产最佳密度空间重叠区根系形态生理互作与养分高效利用的关系，明确空间重叠区竞争的根系间产生互利增产作用的形态生理调控机理，为进一步提升密植玉米综合生产力和资源利用效率提供科学的理论依据和实践指导。

【背景】植物根系通过空间错位回避互感邻近根系，根系间竞争损耗小、互利增效大的物种密植可实现高产。关于密植高产玉米根系竞争较激烈的空间重叠区根系通过形态和生理调控如何互利增产，株型和密度对根系竞争的互作调控机制等科学问题尚不明确。【研究内容】2017年-2019年，本研究以根系重叠区为切入点，从根系形态生理、养分利用及其它们之间的互作增产调控机理开展了系统研究。【结果】通过研究，首先明确了不同株型玉米杂交种根系重叠区所在区位；其次，在高密逆境条件下，紧凑型玉米在根系竞争深层（10-40cm）区域保持了比平展型玉米相对较高的氮素竞争、吸收与利用的能力，高效的氮素输送效率；第三，明确了紧凑型玉米细根根长（根系直径≤0.5mm）和根表面积（根系直径≤3.0mm）所占比例较高，促进了吐丝期根系重叠区深层根系的氮素吸收，提高了根系相对竞争力和氮素利用效率；第四，明确了调控紧凑型玉米根系重叠区养分资源高效利用的主要化感物质。【结论】紧凑型玉米在生物量积累相对匮乏、根系竞争剧烈的根系重叠区，其根系生物量和形态竞争力均比平展型玉米强，尤其表现在高密和根系重叠区的深层土壤，这种竞争力提高了紧凑型玉米对根系深层重叠区养分的“猎取”能力和资源获取的“优先权”，保证了地上部籽粒灌浆充足的养分供应，成熟期较高的干物质转化效率，最终获得了较高的穗粒重和群体产量。【意义】本研究成果对于协调根冠生长，缓解群体内部矛盾，进一步提高密植玉米的群体综合生产力和资源利用效率具有重要的理论和实践意义。