| Corn is the largest food crop in China,with the balanced effect of fertilizer and water management on increasing production,close planting has become an important way to further increase production,however,close planting of spring maize brought lodging problems,and lodging seriously affected the mechanized harvest of maize,plant growth regulators can improve the agronomic characters,physiological and biochemical indexes and stem microstructure of maize,therefore,the lodging resistance of maize can be improved under the condition of close planting,the purpose of high yield and close planting,easy mechanized harvest,cost saving and efficiency increasing were achieved.Based on the screening test of lodging resistant maize varieties in the early stage,this study focused on the selection of lodging resistant maize varieties,spring maize varieties jingnongke 728 and Jinnong 738 planted in large area in Zhangjiakou were used as experimental materials,three different planting densities were set:67500 plants.hm-2（M1）,82500 plants.hm-2（M2）,97500 plants.hm-2（M3）,"Yuhuangjin"plant growth regulator was sprayed at the recommended dosage of 300ml/ha and 750 kg/ha at the big bell stage（10 leaf stage）,water spray was used as control,objective to explore the regulatory effect of"Yuhuangjin"plant growth regulator on Lodging Resistance of spring maize stem.The main results are as follows:1.Effects of"Yuhuangjin"on mechanical characteristics and agronomic traits of spring maize under close planting.The crushing strength of each treatment ranged from 170.13～435.57 N.mm-2,Jinnong738 had the highest crushing strength under M1 planting density;The puncture intensity of different treatments ranged from 17.25～59.03 N.mm-2,Jingnongke 728 had the highest puncture intensity under M2 planting density;The height of gravity center was 81.56～95.67 cm,and the height of gravity center of jingnongke 728 was the lowest under M2 planting density.Spraying"Yuhuangjin"could significantly increase crushing strength and puncture strength of stem,and significantly reduce plant height,height of gravity center and internode length of stem base,the smaller the plant height,ear height,center of gravity height,internode length and ear height coefficient,the greater the crushing strength of the plant,the thicker the stem base,the greater the crushing strength and the stronger the lodging resistance of the stem.2.The effect of"Yuhuangjin"on the microstructure of spring maize stem under close planting.The number of vascular bundles in each treatment ranged from 26 to 42,the maximum diameter of vascular bundles ranged from 154 to 200 um,and the xylem area ranged from 6698 to 16734um2,Jingnongke 728 had the least number of vascular bundles,the largest diameter of vascular bundles and the largest xylem area under M2 planting density.The number of vascular bundles was reduced,the diameter of vascular bundles and the thickness of xylem and epidermal cells were increased.The higher the puncture strength and crushing strength of stem,the better the bending resistance of stem.3.Effects of"Yuhuangjin"on physiological and biochemical indexes of spring maize under close planting.The lignin content of spring maize stem was 27.40%～182.83%,phenylalanine ammonia lyase activity was13.53～20.02 mmol·L-1,soluble sugar content was 5.01～5.72 mmol·L-1,soluble protein content was 33.84～50.25 mg·g-1,and spraying"Yuhuangjin"was higher than the control.The results showed that the content of lignin,soluble sugar,soluble protein and chlorophyll increased,the breaking strength of spring maize increased,the activity of phenylalanine ammonia lyase increased,the activity of peroxidase decreased,and the lodging resistance of spring maize increased.4.Effects of"Yuhuangjin"on Yield and lodging rate of spring maize under close planting.The natural lodging rate of spring maize varieties jingnongke 728 and Jinnong 738 sprayed with"Yuhuangjin"at the planting density of 67500 plants·hm-2（M1）was 0,indicating that the natural lodging rate of"Yuhuangjin"treatment was 100%lower than that of the control treatment;The results showed that the natural lodging rate of jingnongke 728 was 54.38%and 17.82%lower than that of the control under the planting densities of 82500 plants·hm-2（M2）and 97500plants·hm-2（M3）,and that of Jinnong 738 was 68.14%and 43.76%lower than that of the control under the planting densities of 92500 plants·hm-2（M2）and 97500 plants·hm-2（M3）,respectively.The yield of spring maize variety jingnongke 728 increased by 10.02%,10.11%and 4.93%under three different planting densities,and that of spring maize variety Jinnong738 increased by 4.21%,15.59%and 0.29%under three different planting densities.In conclusion,the plant growth regulator"Yuhuangjin"can enhance the crushing strength and puncture strength of spring maize stem,improve the agronomic characters,microstructure and physiological and biochemical indexes of spring maize stem,significantly reduce the natural lodging rate of spring maize varieties jingnongke 728 and Jinnong 738,improve the lodging resistance of spring maize stem,facilitate mechanical harvest,increase maize yield and improve economic benefits Benefit. |
