| Many reports had showed about agronomic traits and physiological changes in the genetic improvement process of soybean cultivars, but about changes of roots in physiological functions have not been reported, especially about the relationship of root activity and aerial parts of organisms and photosynthesis. This study used soybean varieties bred in Jilin Province since1923to study the photosynthetic characteristics of soybean varieties and root BSW and the biomass of the aboveground, and analyze the relationship of photosynthetic characteristics and yield and the relationship between root BSW and root activity and biomass of aboveground. Aimed to clarify the evolution of the photosynthetic characteristics of leaves in the genetic improvement process of soybean cultivars, and reveal the relationship between the roots and aerial parts, to provide the theoretical basis for the the soybean varieties improvement in Jilin Province.The experiment was conducted in2010and2011, and chose the soybean varieties bred in the1923-2009. Measured the photosynthetic rate, stomatal conductance, transpiration rate, chlorophyll and specific leaf weight of soybean cultivars, and measured the relationship of root BSW and root activity and biomass of aboveground to analyze their relationship further. The study results show that:(1) From1923to2005, the grain yield per hectare in82years increased by80.2%, with an average increase by0.98%per year. The of growth period in82years was shortened by14.7days, with an average increase by1.83days every10year, while the yield were showed an increasing trend with shortening in growth period of soybean varieties; harvest index was raise by58.03%, and the harvest index was extremely significant correlated with yield (r=0.8099**); leaf net photosynthetic rate was increased by3.9196μmolCO2·m-1·s-1, and it was increased by18.09%, an average increase was by0.22%per year; the yield was highly significant positive correlated with net photosynthetic rate (r=0.6102**); leaf stomatal conductance was increased by22.91%, an average increase was by0.27%per year, but the correlation of yield and stomatal conductance did not reach significant level; leaf intercellular CO2concentration was decreased by8.3804μmolCO2·mol-1, an average decrease was by0.1022μmolCO2·mol-1per year; transpiration rate was increased by57.29%, an average increase was by0.69%per year, the yield was increased with the increase of transpiration rate, the correlation coefficient was0.6316, but the moisture use efficiency of leaves was decreased significantly along with the year of release, the decrease was by22.3%with the year of release in82years; the blades apparent mesophyll conductance was increased by49.54%, an average increase was by0.60%, the yield was significant increased with the increase in apparent mesophyll conductance; stomatal limitation in leaf was decreased by8.25%, and the average reduction was by0.10%per year, and the yield was decreased with the increase in stomatal limitation; the specific leaf weight was increased by91.82%, an average increase was by1.12%per year, the yield was increased with the increase in specific leaf weight, a correlation coefficient was0.4464; the chlorophyll content in leaf was increased by17.41%, with an average increase was by0.21%per year, the yield was increased with the increase in chlorophyll content; the area of leaflet was decreased by47.37%, with an average reduction was by0.58%. The yield was highly significant positive correlated with Pn, Pn/Ci, but the correlation between the water use efficiency in leaves and year of release was negative, and the water use efficiency in leaves was highly significant negative correlated with grain yield. In concluding, the three physiological indicators could be as indicators by measure of breeding of grain yield.(2)The analysis on root bleeding sap and root vigor has showed that at V4stage, the root bleeding rate for86years increased by9.10%, the average annual growth rate was0.11%; the root activity grew by10.24%, the average annual growth rate was0.12%; at R2stage, the root bleeding rate increased by18.29%in the86years, the average annual growth rate was0.21%; the root activity grew by27.38%, the average annual growth rate was0.32%; at R4, root injury traffic in1986increased by16.01%, the average annual growth rate was0.19%; root activity grew by24.22%, the average annual growth rate was0.28%; R6of xylem sap weight increase by20.22%in the86years, the average annual growth rate was0.24%; growth of root activity was10.83%, and the average annual growth rate was0.13%. The result showed that at R4, the annual growth rate reached the maximum, and the bleeding sap weight was significant positive correlated with bred era, the R4stage is the key to ensure root activity of soybean cultivation stage, through excellent cultivation measures to guarantee R4and any subsequent higher root activity is to ensure the core soybean yield cultivation technology means.(3) The research results of the biomass and root biomass showed, that in V4period, the aboveground biomass of86years increased by10.81%, the average annual growth rate was0.13%; root biomass increased by28.10%, and the annual average growth rate was0.33%; individual biomass grew by11.68%, the average annual growth rate was0.14%; R2stage, the aboveground biomass increased by6.99%in the86years, the average annual growth rate was0.08%, root biomass increased by17.65%; root biomass average annual growth rate was0.21%; biomass of per plant increased by8.55%, the average annual growth rate was0.10%; R4stage, the aboveground biomass for86years increased by24.76%, the average annual growth rate was0.29%; root biomass increased by21.13%, the average annual growth rate was0.25%; biomass of per plant increased by24.21%, the average annual growth rate was0.28%; the aboveground biomass increased by10.51%in the86years at R6, the average annual growth rate was0.12%; root biomass increased by9.27%, the average annual growth rate was0.11%; biomass of per plant increased by10.05%, the average annual growth rate was0.12%. Therefore, root biomass, aboveground biomass and plant biomass in the R4stage showed a significant positive correlation or very significant positive correlation with bred era, the organ biomass of soybean varieties at V4, R2and R6were also positive correlated with bred era, but did not reach a significant level. This indicates that the ground and underground portion growth of soybean at R4played a crucial role in the production, the genetic improvement of soybean varieties significantly increased the plant organ biomass, these may be associated with the improvement of root biomass and root activity, especially root activity at R4, at the R4stage the xylem fluid weight and root activity were positively correlated with net photosynthetic rate, were also proved the relevance of the underground part and the ground photosynthesis. Therefore, we speculate that the root xylem fluid weight and root activity can be used as indicators of the net photosynthetic rate, and to provide theoretical basis for future breeding high photosynthetic soybean varieties.(4) Root activity and root BSW of soybean varieties is closely related to the accumulation of dry matter. We also found that the aerial parts and the underground coordinated in improvement process, and the genetic improvement of soybean varieties was the result of coordination of the aboveground and underground organ. Correlation between root activity and root BSW and net photosynthetic rate of function leaf was the most significant at R4stage, and correlation between root activity and net photosynthetic rate did not reach significant level. The aerial parts and the underground coordinated better at R2and R4stage. At R6stage root activity significant declined, and root BSW quickly reduced, but net photosynthetic rate of leaves and biomass of underground parts decreased little. It showed that the decline of root activity was earlier than the decline of photosynthesis. So the reason of premature phenomenon in late aging with soybean cultivars may be resulted by the decline in photosynthesis in late aging with plants with the premature aging of roots. So we could delay aging of the root aimed to slow down the decline in photosynthesis in late growth aging, thereby to increase the yield. |
