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Vegetation Injury from the Interaction of Nitrogen Dioxide and Sulfur Dioxide. David T. Tingey, Botanist, Environmental Protection Agency, Raleigh, North Carolina 27607; Richard A. Reinert(2), John A. Dunning(3), and Walter W. Heck(4). (2)(3)(4)Plant Pathologist, Biologist, and Plant Physiologist, respectively, Environmental Protection Agency, Raleigh, North Carolina 27607. Phytopathology 61:1506-1511. Accepted for publication 27 July 1971. DOI: 10.1094/Phyto-61-1506.

Six plant species were exposed for 4 hr to nitrogen dioxide and/or sulfur dioxide in greenhouse exposure chambers. Although concentrations of nitrogen dioxide below 200 pphm and concentrations of sulfur dioxide below 50 pphm caused no leaf injury, injury did develop when plants were exposed to mixtures of 5 to 25 pphm of each of the two gases. Leaf injury from either nitrogen dioxide or sulfur dioxide alone occurred as marginal and/or interveinal necrosis on each leaf surface (bifacial). Injury produced by a mixture of the two gases appeared as chlorotic and necrotic flecking on the upper surface of the interveinal areas of tomato, radish, oats, and tobacco. Reddish-brown lesions (stipple) developed on pinto bean and soybean leaves. Lower leaf-surface injury frequently occurred in the mixed-gas fumigations, with little or no upper surface injury. The concentrations of nitrogen dioxide plus sulfur dioxide which caused plant injury were similar to those found in urban areas, and may result in yield losses for plants grown under field conditions.

Additional keywords: air pollution, synergism.