Effects Of Simulated Acid Rain On Growth And Physiological Characteristics In Soybean

The soybean is one of the important cash crops in China. The acid rain (AR) has caused severe soybean yield reduction. Currently, there is no way to fundamentally eliminate acid rain that the study of acid rain to soybean damage mechanism becomes more important. In order to probe into mechanisms of acid rain on growth, yield, antioxidant system and carbon and nitrogen metabolism in soybean, a pot experiment was conducted with two soybean varieties of Nanong1138-2and Kefeng-1. The results were as follows:1Weak acidity of simulated acid rain (pH4.5) stimulated the growth of soybean to some extent, leading to a little (not significant) increase in height, biomass, chlorophyll content, yield and yield components compared with the control (pH5.6).With the increase in the acidity of SAR (pH3.5), it could further promote plant growth, but had no role in promoting inhibitory effect with the increase in processing times for Nannong1138-2, and inhibitory effect had been demonstrated to final production. Continuing increasing the acidity of SAR (pH2.5) would inhibit the growth of plants, biomass and yield reduction. The chlorophyll content would increase with treatment of pH≥3.5, while decrease with pH2.5, in which chlorophyll a was more sensitive than chlorophyll b under acid rain stress. There were differences between the two species, promoting effect of pH3.5to Kefeng-1had been greater than that of pH4.5, but the result was opposite to Nannongl138-2.2Moderate acidity of SAR (pH≥3.5) would further promote the stable structure of the cell, and had no influnce on treatment times, and Nannong1138-2expression was more obvious. High acidity of SAR (pH2.5) made reactive oxygen species’level and antioxidant enzyme activities increased and so as to MDA content, and more processing times more damage. The effects were more serious on Kefeng-1.3Moderate acidity of SAR (pH≥3.5) had no significant effects on carbon and nitrogen metabolism in soybean.When the SAR intensity was too high, it would significantly affect carbon and nitrogen metabolism in soybean leaves. The SAR could promote the synthesis of soluble sugars and free amino acid, accelerate the decomposition of soluble proteins through adjusting the key enzyme activities of carbon and nitrogen metabolism of soybean leaves so that to increase the osmoregulation ability, which could relieve the physiological dehydration of soybean leaves suffered from strong acidity of SAR and maintain the normal metabolism of plant. There’s little difference between two varieties, indicating that the effect mechanism on carbon and nitrogen metabolism mechanism was similar between two varieties subjected to SAR stress.