减源对密植夏玉米叶源光合性能和根源吸收特性调控机制研究

Increasing plant density is one of the main approaches of achieving higher yields for modern maize crops. However, the poor solar radiation intercepted by leaves at middle or lower stratas leads to poor quality of leaf and root, which reduced the productivity of individual plant and suppressed the further increase in grain yield of high-density summer maize. Our previous research has found that there exists leaf redundance when maize crops were planted at high density, and the leaves of the upper canopy shade more competent leaves at the middle strata. Hence, on the basis of previous research, Zhengdan958, a corn cultivar planted widely across China, is selected for our project, which will be grown at the density of 97500 plants ha-1 until seven days after silking. At this time, plants will be subjected to the removal of one, two, three, four or five leaves from top of individual plants, respectively, with all leaves left intact as control. We will investigate (1) the regulation effects of leaf removal on photosynthetic performances of group and individual leaves at middle or lower stratas, (2) the coordinated effects on the distribution of 13C-photosynthates in root and grain, (3) the optimized effects on absorption characteristics of root, and (4) the regulation effects on grain yield of high-density summer maize. The overall aim is to verify the physiological mechanisms of both enhanced leaf photosynthetic capacity and root absorption characteristics of high-density summer maize, which will provide a theoretical basis for maintaining or improving the productivity of individual plants and density-resistant varieties breeding.

增加种植密度是当前玉米增产的关键措施之一。然而，密植玉米冠层中下部叶片光照条件弱，叶源、根源质量性能差，单株生产力低，严重制约了密植玉米产量的进一步提升。我们前期研究发现密植玉米存在叶片冗余，上部叶片遮挡了更有生产能力的中部叶片。为此，本项目在前期研究基础上，以生产中大面积推广的紧凑型玉米品种郑单958为试验材料，在97500株/公顷高密度种植条件下，于吐丝后一周逐叶去除植株顶部一片、两片、三片、四片和五片叶，以不去叶植株为对照，系统分析减源（1）对密植夏玉米中下部叶源及群体叶源光合性能的调控效应，（2）对13C同化产物在根系及籽粒分配的协调效应，（3）对根源吸收特性的优化效应，（4）对籽粒产量的调节效应，以期探明密植夏玉米叶源生产力及根源吸收特性同步增强的生理机制，为稳定或提高密植玉米单株生产力及耐密品种选育提供理论依据。

增加种植密度是当前玉米增产的关键措施之一。然而，密植玉米冠层中下部叶片光照条件弱，叶源、根源质量性能差，单株生产力低，严重制约了密植玉米产量的进一步提升。我们前期研究发现密植玉米存在叶片冗余，上部叶片遮挡了更有生产能力的中部叶片。为此，本项目在前期研究基础上，以生产中大面积推广的紧凑型玉米品种郑单958为试验材料，在97500株/公顷高密度种植条件下，于吐丝后一周逐叶去除植株顶部叶片，以不去叶植株为对照，系统分析减源（1）对密植夏玉米中下部叶源及群体叶源光合性能的调控效应，（2）对13C同化产物在根系及籽粒分配的协调效应，（3）对根源吸收特性的优化效应，（4）对籽粒产量的调控效应，以期探明密植夏玉米叶源生产力及根源吸收特性同步增强的生理机制，为稳定或提高密植玉米单株生产力及耐密品种选育提供理论依据。主要研究结果为：高密度种植条件下，去除植株顶部两片叶（1）可有效调控两株型玉米生育后期群体光合速率、穗位叶光合特性及活性氧清除能力，能较好地协调高密度群体与个体的关系。（2）促进了13C同化物向籽粒的分配比例， 而过度去叶使大量13C同化物滞留在茎秆和苞叶中，不利于籽粒产量的形成。（3）使密植玉米植株在花后49天有高于对照5.75%的根干重。（4）显著增加了密植玉米粒重及收获穗数，最终提升了密植玉米籽粒产量。