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Effects of Ambient Sulfur Dioxide and Ozone on Eastern White Pine in a Rural Environment. Arthur C. Costonis, Former Plant Pathologist, Southeastern Forest Experiment Station, Forest Service, USDA, Route 3, Box 1250, Asheville, North Carolina 28806, Current address, Department of Energy and Resources Management, Air Management Branch, Phytotoxicology Section, 880 Bay Street, 3rd Floor, Toronto 5, Ontario, Canada; Phytopathology 61:717-720. Accepted for publication 26 January 1971. DOI: 10.1094/Phyto-61-717.

Symptoms observed on current and old foliage of eastern white pine (Pinus strobus) were found in field and laboratory studies to be the syndrome of acute and chronic injury from sulfur dioxide. Occurrences of acute symptoms on susceptible trees in a plantation and on those in adjacent pots were related to increases in the concentration of ambient sulfur dioxide. Sulfur dioxide at a concentration of 6 parts per hundred million of air by volume (pphm) for 4 hr induced acute injury to new needles of field trees and adjacent potted indicator P. strobus plants. Ozone concentrations monitored with sulfur dioxide did not exceed 4 pphm. No injury was correlated with fluctuations in ozone concentrations. Acute symptoms of injury from sulfur dioxide initially appeared as a collapsing of affected needle tissue accompanied by an internal resin secretion. The collapsed, resin-soaked area became yellow to pinkish as mesophyll cells died. Some needle tips ultimately necrosed. Chronic symptoms consisted of chlorosis of current and older foliage and premature casting of older foliage. Trees varied greatly in their susceptibility to sulfur dioxide. Susceptible trees were most sensitive during a 6- to 8-week period when new needles were elongating. Needles protected by sealed polyethylene bags remained symptomless.

Additional keywords: air pollutants, ramets, gas analyzers, lesion severity ratings.