Influence Of Simulated Acid Rain On Photosynthetic Characteristics And Yield Of Soybean

The acid rain had become one of the major environmental problems in our country with a tendency to expand to the north.The environmental pollution,ecological damage and other problems had been very severe.The damage of acid rain may further exacerbate with the acceleration of industrial growth.China is an agricultural country,the impact of acid rain on growth and yield of crops had caused widespread concern in the community.In this paper,a pot experiment to study the photosynthetic characteristics,plant height and yield of soybean（precocious No.1）with the simulated acid rain at the levels of pH 5.6（CK）,pH4.0（T₁）,pH2.4（T₂）,studying the photosynthetic characteristics,plant height and yield trends of soybean processed with different intensity of acid rain,and providing scientific basis for preventing the impact of acid rain on agricultural production.The results showed that:（1）Acid rain stress had different degrees of inhibition on the Net Photosynthetic Rate at different growth period of soybean（branching period,flowering period,pod period,seed filling period）.One hand,the impact of acid rain stress on net photosynthetic rate of soybean leaves is not obvious,compared with CK,the net photosynthetic rate soybean leaves respectively processed by method net T₁,T₂ in the pod period decreased by 10.5% and 20.3%.Another hand,the impact of acid rain stress on the net photosynthetic rate of soybean leaves in branching period,flowering period,grain drum is more obvious,compared with CK,the net photosynthetic rate of soybean leaves respectively processed by method T₁,T₂ in branching period were reduced by 41.1 % and 64.3%;Compared with CK,the net photosynthetic rate of soybean leaves respectively processed by method T₁,T₂ in flowering period decreased by 27.4% and 43.7%;The net photosynthetic rates of soybean leaves respectively processed by method T₁,T₂ in seed filling period is 49.5% and 26.8% lower than CK.Correlation analysis of acid rain pH and net photosynthetic rate of soybean leaves in different developmental periods showed that,in addition to pod period,acid rain’s pH and the net photosynthetic rate of soybean leaves in branching period,flowering period,seed filling period were significantly or very significantly correlated with the correlation coefficient was r = 0.618 **,r = 0.405 *,r = 0.369 *.（2）The stress of acid rain on soybean branching and flowering period is not obvious for the transpiration rate of soybean leaf.With the stress of acid rain continued,the stress on soybean leaf transpiration rate becomes more obvious from the beginning to the soybean pod of soybean seed filling period,and the inhibition of soybean leaf transpiration rate more obvious with decreasing pH value of acid rain.Compared with CK,transpiration rate of soybean pod leaf which respectively processed by method T₁ and T₂ were reduced by 13.5% and 32.9%;In the filling period of soybean seed,the transpiration rate rates of soybean leaf which respectively processed by method T₁ and T₂ were 16.9% and 28.0% lower than CK.Correlation analysis of acid rain pH and various growth period of soybean leaf transpiration rate showed that the pH of acid rain were significantly or very significantly correlated with the leaf transpiration rate of flowering period,the pod period,drum grain beside the branches period of soybeans,and correlation coefficients is r = 0.384 *,r = 0.368 *,r = 0.505 **.（3）Overall,with the decreasing pH value of acid rain,the soybean stomatal conductance showed a decreasing trend,but acid rain stress on stomatal conductance of all growth stages（branching period,flowering period,pod period,seed filling period）of soybean is not obvious.（4）With the decreasing pH of acid rain,The utilization efficiency of soybean leaf water tended to decrease in general,especially it is more obvious differences in the soybean branching period,compared with CK,the leaf water use efficiency of soybean pod leaf which respectively processed by method T₁ and T₂ were reduced by 30.5% and 46.8%;The multiple comparisons for the soybean leaves water use efficiency with different pH values of acid rain acid showed the differences of impact of leaves water use efficiency that acid rain stress on soybean flowering period,pod period,filling period is not obvious,the difference the soybean leaf water use efficiency in the branching period is obvious.Correlation analysis of acid rain pH and various growth period of soybean leaf water use efficiency also showed that acid rain pH and water use efficiency of soybean branching stage was significantly correlated with a correlation coefficient of r = 0.583 **.（5）With the decreasing pH of acid rain,soybean plant height decreased.Compared with CK,the height of soybean plant which respectively processed by method T₁ and T₂ respectively decreased by 8.74%,18.8%.Correlation analysis of acid rain pH and soybean plant height also showed that acid rain pH and soybean plant height was significantly correlated with a correlation coefficient of r = 0.389 *.The multiple comparisons for soybean plant height with different pH levels of acid rain showed that compared with CK,the difference is that the height of soybean plant which processed by method T₂ reached significant levels（p <0.05）,and T₂ method had obvious different impact on soybean plant height with CK method.（6）With the stress of acid rain,significantly reduce happened in soybean yields,the most obvious performance of it is that soybean pods per plant,seeds per pod,seed weight per hundred,yield per plant showed a declining trend.Compared with CK,the pods per plant of soybean which respectively processed by method T₁ and T₂ were reduced by 22.6%,27.8%,soybean seeds per pod were reduced by 8.7%,17.4%,seed weight per hundred were reduced by 15.9%,23.6% and yield per plant decreased by 27.8% and 45.3%.Correlation analysis of acid rain pH and soybean yield components also showed that the pH of acid rain and soybean pods per plant,seed weight per hundred,yield per plant were significant or highly significant correlation,the correlation coefficient is r = 0.474 **,r = 0.928 **,r = 0.893 **.