Abstract
Response of eastern white pine (Pinusstrobus L.) to ozone (O3) and sulfur dioxide (SO2) was studied utilizing controlled fumigation chambers in the greenhouse. Tolerant and sensitive clones were fumigated for 6 h at concentrations of 5, 10, 30, and 60 parts per hundred million (p.p.h.m.) O3, 2.5, 5, 15, and 45 p.p.h.m. SO2, and 2.5 p.p.h.m. SO2 plus 5 p.p.h.m. O3 in combination. Response was judged by needle elongation and two indices of direct needle damage.Ozone exposures did not produce a consistent response among tolerant and sensitive classes, while injury caused by SO2 and SO2 plus O3 correlated well with field observations of damage under ambient conditions. The most sensitive clone was injured by concentrations of SO2 as low as 2.5 ± 1 p.p.h.m. Sixty percent of the tolerant clones were injured by 5 and 15 p.p.h.m. SO2, and all tolerant material was injured at 45 p.p.h.m. SO2. The interaction of SO2 and O3 at low concentrations was established as more serious than that caused by either pollutant alone at similar levels.
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