• Acid rain;
  • air pollution;
  • nutrients;
  • nitrogen fixation;
  • photosynthesis


The responses of several physiological processes and indices were studied in soybean plants [Glycine max (L.) Merr. cv. ‘Davis’] exposed to combinations of polluted air (0.1 μl l−1 SO2+ 0.05 μl l−1 O3) and simulated acid rain (pH 3.4, 4.2 and 5.0). Plants exposed to the gaseous air pollutants had lower foliar concentrations of mineral nutrients and chlorophyll. Leaf abscission was increased and photosynthesis, nitrogen fixation, and vegetative growth were inhibited by SO2+ O3. There was no evidence of adverse effects from acid rain on the physiology of this cultivar, regardless of the gaseous pollutant treatment. In the absence of fundamental physiological dysfunctions, acid rain is unlikely to reduce yield; hence, this study with ‘Davis’ soybeans supports the conclusion of those field studies that have indicated no adverse effects of acid rain on soybeans.