Abstract:

Increasing the planting density is still the main way to improve the yield of maize,but the group light will be affected by increasing planting density,which leads to premature leaf senescence. Therefore,it is of great significance to study the effect of the mixture of diethyl aminoethyl hexanoate(DA-6)and chloroquine(CCC)on the photosynthesis intensity and time of maize leaves in the process of improving maize yield by increasing planting density. In 2018 and 2019,a maize variety of Zhengdan 958 was used as experiment material in field. Two planting densities were set(6.75×10⁴,9.00×10⁴ plants/ha)and the mixtures with two concentrations(0 mg/L DA-6+0 g/L CCC and 15 mg/LDA-6+2 g/L CCC)were sprayed on the whole plant at 7-leaf stage. The leaf area index,specific leaf weight,leaf photosynthetic performance,antioxidant capacity and yield differences of maize population of different planting densities were studied under the control of compounding agents,in order to provide a theoretical basis for the application of chemical regulators in maize dense planting. Results showed that when the planting density increased from 6.75×10⁴ plants/ha to 9.00×10⁴ plants/ha,the leaf area index of maize was increased,and the specific leaf weight was also increased at the late silking stage. The leaf area index of the low-density group sprayed with the compounding agent was decreased,while the high-density group had no significant change. The specific leaf weight in the plants sprayed with the compounding agent enhanced,but the difference was not significant compared to the control. After dense planting,the SPAD value and photosynthesis intensity of ear leaves significantly decreased,and the chlorophyll fluorescence parameters negatively affected. In the dense planting group treated with the compounding agent,the SPAD value,the net photosynthetic rate,transpiration rate,stomatal conductance,intercellular carbon dioxide concentration of ear leaves were significantly increased overall as well as the maximum fluorescence,variable fluorescence and Fv/Fm,and initial fluorescence decreased. After dense planting,the relative senescence rate of leaves increased,the activity of antioxidant enzymes decreased,while reactive oxygen species and malondialdehyde accumulated excessively,and the content of soluble protein decreased. In the dense planting group treated with the compounding agent,the relative senescence rate of leaves decreased,the activity of superoxide dismutase,peroxidase,catalase and soluble protein content significantly increased,and the content of ROS and MDA significantly decreased on the whole. A negative effect on the agronomic traits of ears could be observed in dense planting,but the yield was not significantly affected due to the increase in density. After spraying the compounding agent,the photosynthetic capacity and time of maize ears promoted,resulting in improvement of ear traits and significant increase of yield. Compared to the high-density group non-treated by compounding agent,the yields of the group treated by compounding agent increased by 14.61% and 6.64% in 2018 and 2019,respectively. To sum up,the compounding agent increased the material accumulation by improving the photosynthetic capacity and time of maize group,thereby increasing the maize yield.

Key words: Maize, Planting density, Chemical regulation, Photosynthesis, Premature aging