Analysis Of Physiological Characteristics Of High Yield Population Of Resistant Soybean Varieties

In order to explore the changing trends of physiological characteristics of dense-tolerant soybean varieties with different densities,the experiment used the dense-tolerant soybean varieties(Heihe 43,Changmidou 30)and conventional varieties(Jinyuan 73,Jiyu 86)as the test materials,using small-ridge double-row cultivation Ways to study the effects of seedling density(10,20,30,40,500,000 plants/hm~2)on the SPAD value,net photosynthetic rate,leaf area index,chlorophyll fluorescence parameters,root traits,plant agronomic traits and yield components of dense soybean,with a view to providing physiological basis for the selection and breeding of high-yield and dense-tolerant varieties in Northeast China.The results show:1.Effects of planting density on photosynthetic characteristics of soybean canopy.The SPAD value,net photosynthetic rate,maximum photosynthetic quantum yield(Fv/Fm),PS?potential viability(Fv/Fo),chemical quenching coefficient(q P)and PS?electron transfer rate(ETR)of each canopy leaf of dense and conventional varieties showed a downward trend with the increase of planting density,while the non-photochemical quenching coefficient(q N)showed an upward trend and the increase in density-resistant varieties was lower than that of conventional varieties.There was no significant difference in the changes of photosynthetic indexes in the upper leaves,and significant changes in the lower leaves.The decrease in the photosynthetic indexes of the lower leaves was larger than that of the upper leaves.The photosynthetic indexes of dense-tolerant varieties were higher than those of conventional varieties under high-density treatment.The net photosynthetic rate of the canopy leaves of dense-tolerant varieties and conventional varieties showed a downward trend with the growth period,and the decline of each photosynthetic index of late-tolerant varieties during the late growth period Smaller than conventional varieties.Under high-density planting conditions,the PSII light energy conversion efficiency of the conventional varieties is limited,and the lower leaves fall off more than the dense-tolerant varieties,so the conventional varieties are sensitive to density,and the photosynthetic capacity of the dense-tolerant varieties is weaker than the conventional varieties under density stress.2.Effects of planting density on antioxidant enzymes in soybean leaves.The activities of SOD,POD and CAT in the canopy of the two varieties decreased with the increase of planting density.Increasing the planting density mainly affects the activities of SOD,POD and CAT in the soybean lower layer(D10).The SOD activity of the lower layer(D10)of dense varieties(A)did not change significantly with the increase of planting density,while the difference of SOD activity of conventional varieties(B)with the increase of planting density reached a significant level.Under the same density treatment,the POD and CAT activities of each canopy of dense varieties were correspondingly higher than that of conventional varieties;the POD and CAT activities of the same canopy leaves of each treatment of dense varieties were correspondingly higher than that of conventional varieties.It can be seen that the density-resistant varieties have obvious advantages in anti-aging under high density,the conventional varieties have obvious performance under density stress,and the conventional varieties have weak anti-aging ability.3.The effect of planting density on the ability of soybean dry matter to transfer to grain.In the two experimental ecological zones,during the V4-R6 period,the soybean leaf area index showed an increasing trend with the increase of planting density,and it first increased and then decreased with the growth period,and reached the maximum value in the R4 period.The leaf area index of conventional varieties decreased greatly.In the R4 phase,the dry matter weight of each layer of the canopy of different soybean groups was parabolic,each treatment showed a trend of rising first and then decreasing.With the increase of planting density,the level of the maximum dry matter weight of each treatment of the dense-tolerant varieties is basically the same,and the canopy pods are relatively evenly distributed,mainly concentrated at 20-80 cm of the canopy;The maximum dry matter weight of the canopy of the conventional varieties tended to move up,and the pod weight of the canopy showed a trend of increasing first and then decreasing.It shows that the spatial distribution of pods and grains of conventional varieties has an upward trend,and the spatial distribution of pods and grains of dense varieties is relatively uniform.4.The effect of planting density on the characteristics of soybean root system.With the increase of planting density,root length,root surface area,root volume and average diameter of various varieties decreased.In addition,the decline of conventional varieties is significantly greater than that of dense varieties.Compared with R2,each variety of R4 has a longer root system,a larger root surface area and a larger average diameter.5.Effects of planting density on soybean agronomic traits.With the increase of planting density,the plant height,pod height and balance point of all varieties have an increasing trend.And the growth rate of each treatment of dense varieties is correspondingly lower than that of conventional varieties;With the increase of planting density,the stem diameter,effective branch number,stem weight,pod weight per plant,and grain weight per plant have a tendency to decrease;The number of main stem nodes and 100-grain weight did not change significantly with the increase of planting density and the difference was not significant.6.The effect of planting density on soybean yield.With the increase of planting density,the output of dense varieties and conventional varieties showed a trend of increasing first and then decreasing;In Gongzhuling area,the yield of Changmidou 30 reached its maximum when the planting density was 300,000 plants/hm~2,while Jiyu 86 reached its maximum when the planting density was 200,000 plants/hm~2.In the Heihe area,the yield of Heihe 43 reached its maximum when the planting density was 400,000 plants/hm~2,while Jinyuan 73 reached its maximum yield when the planting density was 300,000 plants/hm~2.The output of the four varieties in 2018 has declined compared with 2019,the difference is not significant.The two-year maximum yield of dense varieties is higher than the two-year maximum yield of conventional varieties.