Response of Common Milkweed to Oxidant Air Pollution in the Shenandoah National Park in Virginia

Abstract

The effects of ambient doses of ozone on A. syriaca, common milkweed, were determined in twelve 10 ft diameter plots in the Big Meadows area of the Shenandoah National Park in Virginia. Chlorosis and purple stippling on the adaxial leaf surface were observed on milkweeds grown in ambient air chambers and open plots; those grown in charcoal-filtered air were asymptomatic and taller than those in other treatments. In the laboratory, ozone at 0.05, 0.10 and 0.15 ppm for 6 h/day for 7 days induced symptoms identical to those observed in the field.