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Influence of Mycorrhizae on the Growth of Loblolly Pine Seedlings Exposed to Ozone and Sulfur Dioxide. M. J. Mahoney, Former graduate research assistant, Department of Plant Pathology, Physiology and Weed Science, Virginia Polytechnic Institute and State University, Blacksburg 24061, Present address of senior author: Chevron Chemical Company, P.O. Box 216, Gilberts, IL 60136; B. I. Chevone(2), J. M. Skelly(3), and L. D. Moore(4). (2)(4)Assistant professor, and full professor, respectively, Department of Plant Pathology, Physiology and Weed Science, Virginia Polytechnic Institute and State University, Blacksburg 24061; (3)Professor and head of the Department of Plant Pathology, Pennsylvania State University, University Park 16802. Phytopathology 75:679-682. Accepted for publication 3 January 1985. 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, 1985. DOI: 10.1094/Phyto-75-679.

Loblolly pine seedlings, with and without ectomycorrhizae, were exposed to ozone (O₃) at 0.07 μl/L and sulfur dioxide (SO₂) at 0.06 μl/L, singly and in combination, 6 hr/day for 5 wk. Exposure to either pollutant alone neither affected mycorrhizal formation nor changed reducing sugar concentrations in the roots. Root growth of nonmycorrhizal seedlings was more severely inhibited by each fumigation treatment than was shoot growth, and the root:shoot ratio in these seedlings was lower than that of unfumigated seedlings. Mycorrhizae altered the pollutant effects on root and shoot growth and promoted root growth so that no pollution treatment effects were evident. Fumigated mycorrhizal seedlings had a higher root:shoot ratio compared to unfumigated mycorrhizal seedlings.