Assessing ozone damage to cutleaf coneflower in an ozone bioindicator garden

To collect data on ozone pollution and foliar damage, we established the first Philadelphia Ozone Bioindicator Garden at The Franklin Institute Science Museum. In this paper, we examine the relationship between ozone concentrations in an urban environment and changes in foliar damage in cutleaf coneflower (Rudbeckia laciniata) plants. Higher ozone concentrations were observed during Summer 2015 than during Summer 2014 at our site. Diurnal analysis reveals a nightly diminishment of ozone's rate of dissipation around 4am, which we attributed to intrusions of air from the residual layer (the layer of air above the boundary layer). We saw that visible foliar injury starts relatively slowly and accelerates beginning in late July for stippling and early August for chlorosis and necrosis. We found that injury ratings on ozone-damaged leaves progress faster later in the season despite lower ambient ozone concentrations; we hypothesized that this is evidence of a “latency period” in the cutleaf coneflower's foliar injury response to ozone. Cutleaf coneflowers may serve as engaging tools to alert and inform Philadelphians about air quality issues. Our results suggest that these plants are good candidates for future work in developing bioindicators of ozone where direct monitoring is not feasible.