Use of ethylenediurea (EDU) to ameliorate ozone effects on purple coneflower (Echinacea purpurea)

Purple coneflower plants (Echinacea purpurea) were placed into open-top chambers (OTCs) for 6 and 12 weeks in 2003 and 2004, respectively, and exposed to charcoal-filtered air (CF) or twice-ambient (2×) ozone (O3) in 2003, and to CF, 2× or non-filtered (NF), ambient air in 2004. Plants were treated with ethylenediurea (EDU) weekly as a foliar spray. Foliar symptoms were observed in >95% of the plants in 2×-treated OTCs in both years. Above-ground biomass was not affected by 2× treatments in 2003, but root and total-plant biomass decreased in 2004. As a result of higher concentrations of select cell wall constituents (% ADF, NDF and lignin) nutritive quality was lower for plants exposed to 2×-O3 in 2003 and 2004 (26% and 17%, respectively). Significant EDU × O3 interactions for concentrations of cell wall constituents in 2003 indicated that EDU ameliorated O3 effects on nutritive quality. Interactions observed in 2004 were inconsistent.