Seasonal Development Of Ozone-Induced Foliar Injury On Tall Milkweed (ASCLEPIAS EXALTATA) In Great Smoky Mountains National Park

The southeastern United States, including Great Smoky Mountains National Park (GRSM), experience high ozone concentrations. These concentrations are high enough to cause visible injury on a wide variety of plants in GRSM. One plant that is particularly sensitive to the impacts of ozone is the perennial herb tall milkweed (Asclepias exaltata). This species may be a bioindicator for ozone at mid- to high elevations in the Park. However, little is known concerning the seasonal progression of injury on this species, nor the threshold levels of ozone necessary to elicit a response, both of which are necessary to better characterize this species for use as a bioindicator.