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Age of Pine Seedlings with Primary Needles Affects Sensitivity to Ozone and Sulfur Dioxide. C. R. Berry, Principal Plant Pathologist, USDA Forest Service, Southeastern Forest Experiment Station, Forestry Sciences Laboratory, Athens, Georgia 30602; Phytopathology 64:207-209. Accepted for publication 17 August 1973. DOI: 10.1094/Phyto-64-207.

Seedlings of Virginia (Pinus virginiana), shortleaf (P. echinata), slash (P. elliottii var. elliottii), and loblolly (P. taeda) pines at ages 2, 4, 6, 8, and 10 wk were exposed to individual dosages of ozone and sulfur dioxide. Exposures were 2 hr at 655.0 ± 65 µg/m3 for SO2 and 477.5 ± 48 µg/m3 for O3 (25 ± 2.5 parts per hundred million). The two gases were equally injurious to all species, and all species were equally sensitive to each gas. Maximum sensitivity of the seedlings to the two gases, however, occurred at different ages. For ozone the greatest sensitivity was 2 wk or younger, and for sulfur dioxide at 8 to 10 wk or older.

Additional keywords: air pollution, relative sensitivity, primary needle stage.