Regulation Of Density And Ethephon On Lodging Resistance Of Summer Maize

Summer maize yield could be increased by increasing planting density,but too high planting density often leads to lodging,as a result of lower yield.The huang-huai-hai region is located in the temperate monsoon climate,where summer maize is often affected by lodging due to heavy rainfall and strong winds in summer.In field production,suitable hybrids were selected,planting density was adjusted and chemical control reagents were applied to increase lodging resistance of summer maize.Therefore,it is of great significance to study the physiological mechanism of lodging resistance of summer maize and its regulation.Xundan 20(No lodging resistance summer maize hybrid)and Denghai 605(lodging resistance summer maize hybrid)was used as the experimental materials,Three planting densities of 60000 plants/ha,75000 plants/ha and 90000 plants/ha were designed,and spraying ethephon.Based on yiled,stem morphological characteristics and lignin metabolism,this study is to explore the physiological mechanism of lodging resistance regulated by hybrids,plant density and exogenous ethephon.1.The plant density and exogenous ethephon of different maize hybrids regulated yield.The yield of both hybrid increased with the increase of planting density,but the yield decreased when Xundan 20 was planted in too high density.There was no significant difference in leaf area index(LAI),SPAD value,dry matter accumulation and other indicators between Denghai 605 and Xundan 20.After spraying ethephon,The leaf area index(LAI),SPAD value and dry matter accumulation of the two hybrids had the same change amplitude.Leaf area index(LAI)and dry matter accumulation of population decreased significantly in both hybrid.The change trend of SPAD value was just the opposite to LAI.SPAD value of the two hybrid increased significantly after ethephon was sprayed.2.The plant density and exogenous ethephon of different maize hybrids regulated lodging rate.Denghai 605 lodging rate was significantly lower than Xundan 20,and lodging rate of both hybrid increased with the planting density increase.After spraying ethephon,the lodging rate of both hybrid decreased,and the decrease rate of Xundan 20 was much higher than that of Denghai 605.Lodging resistance of Denghai 605 was significantly higher than that of Xundan 20,and the lodging resistance decreased with the planting density increase.After spraying ethephon,the lodging resistance of both hybrid increased,and the elevation of Xundan 20 was significantly higher than Denghai 605.3.The plant density and exogenous ethephon of different maize hybrids regulated stem morphology.Both stem diameter and stem puncture strength of the two hybrid decreased with the increase of planting density.After spraying ethephon,the stem diameter and stem puncture strength of the two cultivars were significantly increased,and the improvement of stem diameter and stem puncture strength of the Xundan 20 was higher than that of denghai 605.The internode length and center of gravity of the two hybrid increased with the increase of planting density,and the internode length and center of gravity of the two hybrid were significantly reduced after ethephon spraying,and the reduction rate of Xundan 20 was higher than Denghai 605.the number of vascular bundles,thickness of thick wall tissue,thickness of cortex and vascular bundle area decreased with the increase of planting density.Under the same planting density condition,Denghai 605 thick-wall tissue thickness,cortex thickness and vascular bundle area were significantly higher than Xundan 20.After spraying ethephon,The number of vascular bundles,thickness of thick wall tissue,thickness of cortex and area of vascular bundles were significantly increased.4.The plant density and exogenous ethephon of different maize hybrids regulated lignin metabolism.The lignin accumulation amount,S-type lignin monomer and G-type lignin monomer of the two hybrid decreased with the increase of planting density.and the lignin accumulation amount of Denghai 605,S type lignin monomer and G type lignin monomer were significantly higher than that of Xundan 20 under the same planting density.The accumulation of lignin,S-type lignin monomer and G-type lignin monomer increased significantly after ethrel injection.Two hybrid of four kinds of lignin metabolism in key enzymes(phenylalanine ammonia enzyme solution(PAL),4-coumaric acid ligase(4CL),peroxidase(POD),cinnamyl alcohol dehydrogenase(CAD)with decreased with increasing planting density,under the condition of the same planting density Denghai 605 lignin metabolism in key enzyme activity was significantly higher than that of Xundan 20.The activity of key enzymes in lignin metabolism pathway was significantly increased after spraying ethephon.In summary,summer maize varieties with high content of lignin and good morphological characteristics of stem have strong lodging resistance.Density and ethephon affect the lodging resistance of summer maize by regulating lignin metabolism and stem morphology.Therefore,it requires us to choose summer maize varieties with strong lodging resistance in field production,and to ensure that summer maize will not have large area lodging under the condition of high planting density through appropriate planting density and spraying ethephon,so as to ensure the high and stable yield of summer maize.