高密度对超高产春玉米花粒期叶片衰老与根系活力的影响

选用不同穗型、株型品种浚单20、内单314和京单28为材料,在3种种植密度(7.5万、8.25万和9.0万株/hm2)下,比较研究花粒期冠层不同层位叶片光合性能和根层根系活力的垂直变化及其关系,明确高密度条件下超高产春玉米生育后期根冠早衰及其相关机理,探索防衰增产的调控途径。结果表明,花粒期叶片的叶面积指数(LAI)均随密度增加逐渐增大,而不同层位叶片的SPAD值、光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)和根系活力均随密度增加而降低;浚单20各性状对密度变化的反应较内单314和京单28敏感,浚单20在高密度下子粒产量最高;灌浆期浚单20根系活力最大值出现在30～40 cm的土层,内单314和京单28最大值出现在20～30 cm的土层,浚单20根系活力下移速度比内单314和京单28快,这与后期植株叶片的SPAD值、LAI、Pn、Tr和Gs的下降有着必然联系。春玉米衰老过程中地上部与地下部密切相关,叶片衰老进程与根系活力空间下移进程一致。

Effects of High Planting Density on Super High-yielding Spring Maize Leaf Senescence and Root Activity at Anthesis and Kernel Stage

In order to explore the physiological and relational mechanism early senescence of shoot and root under high planting density of super high-yielding spring maize,the regulating pathways of defending senescence and increasing yield were explored.Using different plants and spike types,Xundan20,Neidan314 and Jingdan28 as materials,compared and studied the effects and relation of the different layers of leaves’ photosynthetic characteristics and the vertical changes of root activity in three kinds of plant density (75 000,82 500 and 90 000 plants/ha) at anthesis and kernel stage.The results showed that the LAI of different layers of leaves increased with increasing density,while the SPAD value,Pn,Gs,Tr and root activity continuously were decreasing with increasing density,various traits of Xundan20 were more sensitive than Neidan314 and Jingdan28 on the density reaction.Xundan20 gained maximum yield in high-density and it’s significantly difference than middle-density and low-density.The maximum root activity of Xundan20 lay in 30-40 cm soil layer,while the maximum root activity of Neidan314 and Jingdan28 lay in the 20-30 cmsoil layer at grain filling stage.It was clear that the shoot and root systems were functionally closely related to the aging process,slowing down speed of root activity of Xundan20 was faster than Neidan314 and Jingdan28,which was intrinsically linked to the decline of the leaves’ SPAD value,LAI,Pn,Tr and Gs.The progress of leaf senescence was the same with the root activity space down progress.