Regulation Mechanism Of Reduced Source On Quality Characters And Lodging Resistance Of Densely Planted Summer Maize Stalks

Relying on increasing the planting density of corn and improving the utilization rate of solar energy can maximize the potential of the group to increase production.Nowadays,high-yield corn in the western region generally depends on increasing the planting density of corn.However,the competition of densely planted corn against resources such as light and fertilizer has intensified,resulting in weak stems,poor quality,and increased risk of lodging.Lodging is one of the main factors limiting the high and stable yield of densely planted corn.For every 1% increase in lodging rate,the yield is reduced by about 108 kg hm-2.Therefore,on the basis of a higher number of harvested ear organs,improving canopy light conditions,optimizing stalk quality traits,and enhancing its lodging resistance is an effective way to obtain high yield of densely planted corn.Earlier studies found that there is leaf redundancy in densely planted corn.Therefore,in this study,the compact corn variety Zhengdan 958 and the semi-compact corn variety Zhengda 12 were used as test materials.Under the high-density planting condition of density of 97500 plants/hectare,the top of the plant was removed leaf by leaf 7 days before spinning,Two,three,and four leaves,using non-defoliated plants as a control,by removing the redundant leaves in the upper canopy leaf by leaf,improve the canopy light distribution of densely planted corn,and tap the photosynthetic potential of the leaf source in the middle and lower canopy;further Exploring the source reduction to enhance the productivity of leaf sources in the middle and lower canopy of densely planted corn,optimize the stem quality traits,enhance its lodging resistance,and simultaneously increase grain yield,with a view to probing the physiological mechanism of densely planted summer corn’s lodging resistance and the simultaneous increase in grain yield,It provides a theoretical basis for stabilizing or improving the productivity of densely planted maize per plant and breeding of dense-tolerant varieties.The main conclusions are as follows:1 Regulation effect of reduced source on canopy structure and photosynthetic performance of densely planted summer maizeThe two-year test results in 2017 and 2018 showed that defoliation can significantly increase the light transmittance of the middle and lower layers of the group,and the effect of regulating the semi-compact variety Zhengda 12 is more obvious.Moderate removal of the top one and two leaves(S1 and S2)of the plant can delay the decay rate of the green leaf area in the middle and late stages of grain filling and maintain a long high LAI duration;while removing the top three leaves(S3)and four leaves(S4)will significantly reduce the leaf area index in the later growth period.The net photosynthetic rate(Pn)and stomatal conductance(Gs)of the leaves of the two plant types increased significantly after removing one and two leaves at the top of the plant(S1 and S2),but after excessive removal of three or four leaves at the top of the plant Pn and Gs were significantly reduced,and the effect of defoliation on the semi-compact variety Zhengda 12 was more obvious.In addition,moderate defoliation(S1 and S2)is conducive to the improvement of the plant’s light energy utilization efficiency,and improves the photosynthesis rate of the population in the later growth period.Compared with the semi-compact variety’s defoliation treatment(S1),the compact Zhengdan 958’s photosynthesis The rate increase effect is more obvious.2 Regulation effect of reduced source on stalk quality traits of densely planted summer maizeThe stem thickness,percentage of internode dry weight and internode dry weight per unit length of corn stalks,puncture strength and crushing strength are closely related to corn lodging,and moderate defoliation(S1 and S2)treatment can significantly reduce plant height and increase stem thickness,Internode dry weight,internode dry weight percentage and internode dry mass per unit length,can also increase the stalk puncture strength and crushing strength of the second and third internodes,soluble sugar content in corn plant internal components,fiber Both hemicellulose content and plant lodging rate were significantly negatively correlated.Under dense planting conditions,population ventilation and light transmission conditions were poor,structural and non-structural compounds in the stalks decreased,slender stalks were prone to lodging,and moderate defoliation(S1 and S2)The treatment can increase the content of soluble sugar in the internodes and the content of cellulose hemicellulose.3 Regulation effect of reduced source on plant lodging of densely planted summer maizeModerate defoliation(S1 and S2)treatment can reduce the lodging rate of densely planted summer corn.Excessive defoliation(S3 S4)treatment has a higher lodging rate.Taking 2018 as an example,Zhengdan 958 varieties S3 and S4 have a higher lodging rate than S0.35.7% and 85.7%,Chia Tai’s 12 varieties S3 and S4 increased by 12.2% and 29% compared with S0 lodging rate.4 The effect of reducing sources on the yield of densely planted summer maizeThere are differences in the regulation of the yield and related traits of compact and semi-compact maize with different degrees of removal of the upper leaves of the corn under dense planting.The results of the two-year experiment showed that moderate defoliation(S1 and S2)treatment can accelerate the grain filling rate,The grain yield was increased by increasing the number of spikes and the weight of the grain.In 2017,Zhengdan 958 moderate defoliation(S1 and S2)treatment increased 9.5% and 8.5% compared to S0 production,and Zhengda 12 moderate defoliation(S1 and S2)treatment increased 8.2% and 14.4% compared to S0 production,but excessive removal Leaf treatment(S3 and S4)will result in a significant reduction in production.Taking 2017 as an example,Zhengdan 958 S3 and S4 treatments have decreased by 4.7% and 5.9% compared to S0 output,and Zhengda 12S3 and S4 treatments have decreased by 11.4% and 27.3% compared to S0 output..In summary,this experiment improved the light distribution of the canopy of densely planted corn by appropriately removing the redundant leaves in the upper part of the canopy(one leaf and two leaves at the top),optimized the stalk quality traits,enhanced the plant’s lodging resistance,and synchronized Increased the grain yield of densely planted corn.The physiological mechanism of the lodging resistance of densely planted summer maize and the simultaneous increase of grain yield were explored,which provided a theoretical basis for stabilizing or improving the productivity of densely planted maize per plant and breeding of tolerant varieties.