| At present,the rational use of chemical regulation technology can regulate the growth and development of maize to change the growth characteristics of the crop to solve the problem of high maize yield and the problem of collapse.In order to explore the mechanism of chemical regulation to influence the high yielding population of spring maize,this experiment selected maize varieties Deka 159 and Xiangyu 998 as the materials,and set four density levels of 60,000 plants/ha,70,000 plants/ha,80,000plants/ha and 90,000 plants/ha,and sprayed the chemical control agent"Yudo Ten(450g/hm~2)"at the 7～8 leaf expansion stage of maize",while setting water spraying as the control,to study the chemical control mechanism of agronomic traits and physiological metabolism of spring maize.1.Plant height,ear height,ear position coefficient and center of gravity height differed among planting densities and chemical control treatments,specifically showing an increasing trend with increasing planting density;HK treatment significantly reduced the basal internode length,plant height,ear position height and center of gravity height significantly,and ear position coefficient slightly.Stem thickness decreased and flattening rate increased with increasing density;stem thickness increased and flattening rate decreased after HK treatment.2.With increasing planting density,LAI increased,the canopy of crop population was depressed,MTA increased in both upper layerv middle layer and lower layer,and SPAD values,Pn,Tr and Gs decreased.Pn,Tr and Gs decreased gradually from the spatting stage to the lactation stage,and SPAD values rose and then decreased,reaching the maximum at the filling stage;after HK treatment,the decline of LAI in the late reproductive stage under high density was delayed,and SPAD values,Pn,Tr and Gs increased in all periods.The MTA was significantly increased in the middle and upper parts of high density.3.Stem transverse fold strength and stem puncture strength differed among treatments.There was a tendency to increase first from the silking stage to the milking stage,and the overall maximum was reached at the mastication stage.The transverse fold strength and puncture strength at basal 2-7 nodes tended to decrease with increasing planting density;HK treatment significantly increased the transverse fold strength and puncture strength of above-ground nodes 3-5.The lignin,cellulose and hemicellulose contents decreased continuously with increasing density,and chemical regulation treatment increased the lignin,cellulose and hemicellulose contents of the stalks at each growth period,after chemical regulation treatment,The dry matter weight and fresh weight of each node decreased,and the dry matter weight per unit length increased.4.With increasing planting density,IAA content decreased,GA content increased,POD,CAT and SOD content decreased and MAD content increased;after chemical regulation treatment,IAA and content increased substantially,GA content decreased,POD,CAT and SOD content increased somewhat and MAD content decreased in all growth periods.5.With increasing planting density,the ear length and ear thickness of both varieties decreased,the bald tip length increased,and the greater the density,the greater the magnitude,the number of rows did not change significantly,the number of grains in rows and 100 grain weight decreased significantly,the lodging rate increased,and the lodging degree increased;after chemical regulation treatment,the cob length,along with the thickness,the number of grains in rows and 100 grain weight of both varieties of maize increased,and DK159 had the largest yield increase at D4 density.With the increase of planting density,the internode length of maize elongated,the plant elevated,the center of gravity shifted upward,the stem thickness decreased,the flattening rate increased,the mechanical properties of transverse fold strength and puncture strength decreased,the lignin,cellulose and hemicellulose content decreased,the strength of stem decreased,and the inversion rate increased;the canopy population was depressed,ventilation and light permeability became poor,individual competition increased,SPAD value,net photosynthetic rate,stomatal conductance The chemical control reduced the adverse effects of increased planting density,reduced plant height,shifted the center of gravity,enhanced stem strength,optimized the crop canopy,and enhanced the physiological activity of individual plants,which ultimately led to increased yield. |
