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Sulfur Accumulation in Red Maple Leaves Exposed to Sulfur Dioxide. C. R. Krause, United States Department of Agriculture, Agricultural Research Service, Nursery Crops Research Laboratory, 359 Main Rd., Delaware, OH 43015; L. S. Dochinger, United States Department of Agriculture, U.S. Forest Service, Forestry Sciences Laboratory, 359 Main Rd., Delaware, OH 43015. Phytopathology 77:1438-1441. Accepted for publication 31 March 1987. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1987. DOI: 10.1094/Phyto-77-1438.

Investigations were conducted to visualize the localization of sulfur in leaf tissue of red maple trees (Acer rubrum) exposed to the common air pollutant, sulfur dioxide (SO2). Cuttings were exposed to charcoal-filtered air or 0.15 ppm of SO2 in environmental chambers for 42 days. Scanning electron microscopy and energy dispersive X-ray analysis revealed accumulations of sulfur (S) in the chloroplasts of mesophyll cells exposed to SO2. Chloroplast perforations were visualized in leaves exposed to SO2 but not in leaves exposed to charcoal-filtered air. Chloroplast perforation and S accumulation could be preliminary stages of cytolysis reported in previous studies and, in part, explain the mode of action of SO2 as a phytotoxicant.

Additional keywords: chloroplast injury, X-ray digital mapping.