| Edge row advantage of maize refers to the performance of yield per plant,photosynthetic performance,male and female ear development characteristics of maize in edge row compared with that of inner row.The size and play of edge row advantage of maize can be reflected by marginal effect index.The marginal effect index is an important index to evaluate the density resistance of maize in China.The yield per plant directly reflects the response of maize hybrids to density.The yield of maize can be significantly increased by proper close planting,which puts forward new requirements for breeding of hybrids with high density tolerance.The aim of this paper is to study the dominant characteristics of different maize hybrids and the regulation effect of planting density on them,so as to provide the basis for the breeding of high-yield hybrids and high-yield and high-efficiency cultivation techniques.During 2021-2022,Denghai 111(DH111)and Zheng Yuanyu 432(ZYY432),Denghai 605(DH605)and Zheng Dan 958(ZD958)were selected as the experimental materials,and two planting densities were set as 67500 p/ha and 82500 p/ha.There are 8 districts in total.Each districts was sampled from rows 1-5,7 and 9.There were a total of 56 treatments,and each treatment was repeated by 3 times.The rows with advantages in yield and trait indexes were defined as side rows,and the rows with advantages disappearing or within were defined as internal population.The differences between rows and density regulation effects of different maize hybrids were discussed from yield and its components,plant traits,photosynthetic characteristics,and the development characteristics of male and female ears.1.The average yield per plant of different maize hybrids and the difference of its constituent factors between rows and density regulationThe average yield per plant of different maize hybrids and its constituent factors were significantly different.The yield of different maize hybrids in the side row was significantly higher than that in the inside row,showing a trend of D1 decreasing first and then stabilizing from D1 to the inside row.There was no significant difference in mid-early maturity hybrids DH111 and ZYY432 from D1 to D3,while there was no significant difference in mid-late maturity hybrids DH605 and ZD958 from D1 to D4.Compared with the non-population,the within-population decreases of different maize hybrids were different.Under the planting condition of 67500 p/ha,DH111,ZYY432,DH605 and ZD958 decreased by 14.5%-18.6%,22.4%-25.2%,26.1%-38.7%and 32.3%-32.6%,respectively.Under the condition of 82500 p/ha,DH111,ZYY432,DH605 and ZD958 decreased by 27.2%-36.7%,26.1%-34.8%,32.7%51.6%and 37.1%-38.8%,respectively.Under different planting densities,the average yield per plant in the inner and outer rows of the medium and early maturing cultivars DH111 and ZYY432 showed little difference.With the increases of planting density,the average yield per plant in the population of DH111 and ZYY432 decreased by 7.8%and 7.1%,respectively,while that of DH605 and ZD958 decreased by 8.9%and 8.2%,respectively.The decline rate of midlate maturity hybrids was greater than that of mid-early maturity hybrids.Grain number per spike and 1000-grain weight of different maize hybrids in edge row were significantly higher than those in inner row,which was consistent with the change trend of yield.There were significant differences in the marginal effect index of yield among different maize hybrids.Under different planting density,the mid-early maturity cultivars DH111 and ZYY432 were smaller than the mid-late maturity cultivars DH605 and ZD958.2.Interrow variation of dry matter accumulation of different maize hybrids and its density regulationThere were significant differences in dry matter accumulation among different maize cultivars.Dry matter accumulation of different maize hybrids in the edge row was significantly higher than that in the inside row,which was basically consistent with the yield change.Under 67500 p/ha,the internal dry matter accumulation of DH111,ZYY432,DH605 and ZD958 decreased by 24.2%,23.8%,26.1%and 28.9%compared with D1,respectively.Under 82500 p/ha,the internal dry matter accumulation of DH111,ZYY432,DH605 and ZD958 decreased by 28.2%,27.7%,37.0%and 35.5%compared with D1,respectively.Under the same planting density,mid-early maturity cultivars DH111 and ZYY432 showed smaller decreases in dry matter accumulation than mid-late maturity cultivars DH605 and ZD958.With the increases of density,dry matter accumulation of different maize hybrids decreased,especially DH111,ZYY432,DH605 and ZD958 decreased by 12.8%,10.6%,22.3%and 17.3%,respectively.The decrease of mid-early maturity was less than that of mid-late maturity.3.Interrow differences of plant traits and density regulation in different maize hybridsThe plant height and ear height of maize cultivars were significantly different between the side row and the inner row,and the plant height and ear height of the side row were significantly lower than that of the inner row.The plant height of different maize varieties decreased from D1 to D3 and had no significant difference.Under the planting condition of 67500 p/ha,there was no significant difference in ear height between medium-early maturity hybrids DH111 and ZYY432 from D1 to D3,while there was no significant difference in ear height between medium-late maturity hybrids DH605 and ZD958 from D1 to D2.Under the planting condition of 82500 p/ha,the spike height of the four hybrids(DH111,ZYY432,DH605 and ZD958)gradually increased from D1 to D2,and then there was no significant difference.The ear height of mid-late maturity cultivars DH605 and ZD958 was significantly higher than that of midearly maturity cultivars DH111 and ZYY432.The leaf stem-leaf angles in the upper and panicle layers of the mid-early maturity hybrids were smaller than those of the mid-late maturity varieties,and the leaf orientation value was larger than that of the mid-late maturity hybrids4.Interrow difference and density regulation of photosynthetic characteristics of different maize hybridsUnder different planting densities,the leaf area index(LAI)of the middle and early maturing hybrids DH111 and ZYY432 was significantly lower than that of the middle and late maturing hybrids DH605 and ZD958 was significantly higher than that of the middle and late maturing varieties at R6,and the trend of SPAD of functional leaves was basically consistent with that of leaf area index.Under the condition of different planting density,the light transmittance of the ear layer between different rows of the same maize variety showed an order of D1-D2>D3-D4>D5-D6.The light translucency of the bottom and panicle layers of the midearly maturity hybrids was significantly higher than that of the mid-late maturity hybrids.The stomatal size,stomatal density,and stomatal SPI in the edge row of different maize hybrids were significantly higher than those in the inner row,and the spatial arrangement of the edge row stomata was more regular.Compared with the inner row,the structure and function of chloroplast in the edge row of different maize hybrids were more perfect.Under different planting conditions,the decrease of chloroplast number,gramer number and gramer lamellae number in the inner population of DH111 was smaller than that of DH605.The decrease of chloroplast number and grana number in DH111 population was less than that in DH605 population,while the increase of grana lamella number was more than that in DH605 population.The net photosynthetic rate of side-row functional leaves in VT and R3 was significantly higher than that of inrow functional leaves in different maize hybrids.Under different planting conditions,the decrease of net photosynthetic rate of mid-early maturity cultivar DH111 was smaller than that of mid-late maturity cultivar DH605 in VT and R3 compared with D1.With the increases of density,the net photo synthetic rate of both DH111 and DH605 decreased,and the decrease of DH111 was always smaller than that of DH605 in VT and R3.5.Inter-row differences and density regulation of ear development characteristics between male and female of different maize hybridsThere were significant differences in the number of florets in the male ear among different maize varieties,which were ZD958>ZYY432>DH605>DH111 under different planting densities The number of panicle florets in DH111,ZYY432,DH605 and ZD958 populations decreased by 0.6%,6.1%,9.1%and 10.3%,respectively.Under the condition of different planting density,the ear sterility rate of different maize hybrids in edge row was significantly lower than that in inside row.Under high-density planting conditions,the rate of male panicle sterility of mid-early maturity hybrids was significantly lower than that of mid-late maturity hybrids.The number of fertilization filaments in the side row of different maize hybrids was significantly higher than that in the inside row.With the increase of planting density,the number of fertilized filament in DH111,ZYY432,DH605 and ZD958 decreased by 2.9%,2.5%,5.1%and 5.2%,respectively.Under the planting condition of 82500 p/ha,the seed setting rate of flosmall flowers in the side row of different maize hybrids was significantly higher than that in the inside row.The seed setting rate of florets was negatively correlated with planting density within the population of different maize hybrids.The total seed setting rate of different maize hybrids in the side row was significantly higher than that in the inside row.Under high-density planting conditions,the total seed setting rate of the mid-early maturity variety DH111 was significantly higher than that of the other three hybrids.With the increases of planting density,the total seed setting rate in DH111,ZYY432,DH605 and ZD958 populations decreased by 4.6%,6.5%,12.6%and 7.0%,respectively.The edge row advantage of maize could be directly reflected in yield,dry matter accumulation,photosynthetic characteristics and ear development characteristics of male and female,and the edge row advantage was maintained from the first row to the third or fourth row.Medium and early maturing hybrids have smaller yield and marginal effect index,and less edge row advantage.First of all,the difference of dry matter accumulation,photosynthetic rate,panicle development characteristics of the middle and early maturing hybrids between the edge row and the inner row was small,the yield marginal effect index was small,and the yield difference between the inside and outside row was small.With the increase of density,the yield and trait marginal effect index of medium and early maturing hybrids changed less.Secondly,in the middle and early mature hybrids,the upper leaf Angle is smaller,and the leaf direction value is larger.Under the condition of high density,the upper and middle leaves have better light transmission conditions,which is in line with the ideal plant type of dense tolerant hybrids.It can be concluded that DH111 and ZYY432 have the potential of tolerance to dense planting. |
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