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Physiology and Biochemistry

The Influence of Soil Moisture on Macroscopic Sulfur Dioxide Injury to Pinto Bean Foliage. J. A. Davids, Former graduate student, Department of Plant Pathology and Center for Air Environment Studies, The Pennsylvania State University, University Park 16802, Current address of senior author: Castle & Cooke Inc., Soquel, CA 95073; D. D. Davis(2), and S. P. Pennypacker(3). (2)(3)Professor, and associate professor, respectively, Department of Plant Pathology and Center for Air Environment Studies, The Pennsylvania State University, University Park 16802. Phytopathology 71:1208-1212. Accepted for publication 12 March 1981. Copyright 1981 The American Phytopathological Society. DOI: 10.1094/Phyto-71-1208.

The influence of soil moisture stress on sulfur dioxide (SO2) injury to pinto bean foliage was investigated in relation to stomatal conductance rate, soil moisture content, and plant water potential. Pinto bean plants were grown at four soil water potentials (1/3, 1, 3, and 5 atm) and exposed to 5,720 μg/m3 (2.2 ppm) SO2 for 3 hr. Macroscopic injury was severe on plants grown at 1/3 and 1 atm soil water potential and negligible on plants grown at 3 and 5 atm water potential. Injury was highly correlated with percentage of soil moisture, and both injury and soil moisture were highly correlated with stomatal conductance rate and water potential of the plants. The duration of soil moisture stress (1, 2, or 3 days) did not affect the amount of macroscopic injury induced by SO2, the stomatal conductance rate, or plant water potential. Stomatal conductance rates of plants grown at 1/3 and 1 atm soil water potential decreased when the plants were exposed to SO2, while those of plants grown at 3 and 5 atm soil water potential were not affected by exposure to SO2.