Abstract:

In order to clarify the characteristics of the effect of increasing plant density on the source-sink relationship of maize,ZD958 and JQ119 were chosen as the experimental materials,and five different planting densities (45 000,60 000,75 000,90 000 and 120 000 plants/ha) were set to explore the response characteristics and changes of plant morphology,leaf canopy photosynthetic characteristics and establishment of grain sink of different hybrids at anthesis of maize to increase plant density. The results showed that with the increase of plant density,plant height,ear height and ear coefficient increased significantly. The basal intersegmental diameter Ⅲ,the extinction coefficient (k),the leaf area per plant and the ear leaf area of maize were significantly decreased,and the net photosynthetic rate of ear leaf,photosynthetic capacity of ear leaf and kernel number per ear were the same as above. The effects of increasing of plant density on different maize hybrids were generally consistent. When plant density was increased from 45 000 to 120 000 plants/ha,the ear leaf area decreased by 20.63% and 12.30%,the photosynthetic capacity of ear leaf decreased by 33.76% and 33.31%,and the kernel number per ear decreased by 21.55% and 36.07%for ZD958 and JQ119,respectively.The linear relationship between photosynthetic capacity of ear leaf,kernel number per ear and plant density was further established. The linear relationship showed that for every 1×10⁴ plants/ha increase in plant density,the photosynthetic capacity of ear leaf of ZD958 decreases by 0.076 μmol/s and the kernel number per ear by 13.03,while the photosynthetic capacity of ear leaf of JQ119 decreases by 0.088 μmol/s and the kernel number per ear by 27.93.From the linear slope,compared with ZD958,JQ119's leaf source and grain sink were more sensitive to increasing plant density,and the difference between the two hybrids was mainly manifested in the establishment of grain sink. In addition,this linear model can be applied to the simulation and prediction of maize canopy photosynthetic characteristics and grain sink establishment by increasing plant density,which can provide reference for moderately increased plant density for high yield of maize.In summary,enhancing the source and expanding the sink is the key to increasing yield in summer maize under increasing plant density.

Key words: Zea mays L., Planting density, Photosynthetic characteristics, Grain number, Source-sink relationship