摘要：

提高种植密度目前仍是玉米增产的主要途径,但增加密度会影响群体光照,易导致叶片早衰,研究胺鲜酯(DA-6)与矮壮素(CCC)复配对密植下玉米叶片光合作用强度及时间的调控效应对玉米密植增产具有重要意义。2018-2019年,选用郑单958为大田试验材料,设置2个种植密度(6.75万,9.00万株/hm²)、2个复配剂喷施浓度(0 mg/L DA-6+0 g/L CCC和15 mg/L DA-6+2 g/L CCC),于玉米7片展叶期全株喷施,研究复配剂调控后不同种植密度下玉米群体的叶面积指数(LAI)、比叶质量(SLW)、叶片光合性能、抗氧化能力及产量差异,以期为化学调控剂在玉米密植增产中应用提供理论依据。结果表明,玉米密度由6.75万株/hm²升高到9.00万株/hm²后,玉米LAI升高,在吐丝后期SLW提高。喷施复配剂的低密度群体LAI降低,而高密度群体无明显变化,与喷施清水相比,复配剂处理提高叶片SLW,但差异不显著;密植后,穗位叶SPAD值和光合作用强度明显下降,叶绿素荧光参数受到负面影响;复配剂处理的密植群体穗位叶SPAD值提高,净光合速率、蒸腾速率、气孔导度、胞间二氧化碳浓度总体上显著升高,最大荧光、可变荧光和最大光量子效率增加,而初始荧光下降。密植后,叶片相对衰老速率增加,抗氧化酶活性降低,而活性氧和丙二醛过量积累,可溶性蛋白含量下降。复配剂处理的密植群体叶片相对衰老速率下降,超氧化物歧化酶、过氧化物酶和过氧化氢酶活性总体上显著升高,活性氧和丙二醛含量总体上显著降低,可溶性蛋白含量升高。密植对玉米雌穗农艺性状产生负面影响,但由于种植群体量升高,所以产量未受到显著影响,喷施复配剂后,玉米穗位叶的光合能力及时间得到提升,因此穗部性状得到改善,产量明显增加,2018,2019年复配剂处理的高密度群体比未处理群体产量分别提高14.61%和6.64%。综上,复配剂通过提高玉米群体光合能力和延长光合作用时间来提高物质积累量,从而增加玉米籽粒产量。

关键词: 玉米, 种植密度, 化学调控, 光合作用, 早衰

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