Physiological Mechanism Of Canopy Development In Super High Yield Soybean Population

In order to explore the yield formation mechanism of soybean super high-yielding varieties,this experiment was carried out in the field.Super high-yielding varieties Jiyu86,Zhonghuang 35,Changnong 35,Hemong 71 and common varieties Jiyu 441 were selected as experimental materials to study the effects of different varieties of soybean agronomic and photosynthetic physiological characteristics on yield formation.The relationship between yield formation and SPAD value,net photosynthetic rate,chlorophyll fluorescence parameters,leaf area index,root traits,plant agronomic traits of super high-yielding varieties and common varieties were compared and analyzed.The results show that:1.Yield and composition of soybean: the yield of super high-yielding varieties Jiyu 86,Zhonghuang 35,Changnong 35 and Henong 71 was significantly higher than that of ordinary varieties Jiyu 441,which were 22.4%,18.9%,16.5% and 15.4% higher than that of ordinary varieties,respectively.The pod weight per plant,grain number per plant,grain weight per plant and 100 grain weight of the super high yield variety were higher than those of the common variety Jiyu 441 at maturity stage.2.Photosynthetic characteristics of soybean: SPAD values of different soybean varieties,net photosynthetic rate,the actual photosynthetic efficiency of Y(Ⅱ)and PSⅡ electron transport rate(ETR)in the whole growth period a general trend unimodal growth,in the beginning phase grain super-high-yield soybean varieties above physiological indexes were higher than the ordinary varieties,and reached significant level,in the later super-high-yield varieties physiological index decline rate is lower than the ordinary varieties,Leaf senescence was slow but still maintained high light and capacity.3.The change trend of soybean leaf area index showed a trend of gradual increase at first and then decrease.The leaf area index of super high-yielding varieties Jiyu 86,Zhonghuang 35,Changnong 35 and Henong 71 reached the peak at R5 stage,and the super high-yielding varieties were significantly higher than the common varieties at this stage,which were 20.7%,42.6%,7% and 19.4% higher than the common varieties,respectively.Keeping a high LAI in the first grain stage can improve crop yield.4.Dry matter accumulation of soybean increased significantly with the advance of growth process,dry weight of each organ and total dry matter of soybean were significantly increased,and the total dry matter of soybean R5 and R7 stage was significantly different between super high-yield and common varieties.The proportion of stem,leaf,stalk and pod hull was higher in common varieties,while the proportion of grain weight was higher in super yield varieties.The relationship between source and sink of super high yield varieties was more harmonious,and the relationship between nutrient growth and reproductive growth was better than the total accumulation of dry matter,which was conducive to the increase of pod grain weight and finally higher yield of soybean.5.Soybean root architecture: the total root dry weight,root volume and average root diameter of super high-yielding varieties were higher than those of common varieties,and the difference between super high-yielding varieties and common varieties reached a significant level at the beginning grain stage.The root traits of super high-yielding soybeans were significantly better than those of common varieties,which further indicated that the developed root system was the basis of high yield of soybeans.