ARS | Publication request: Ambient ozone effects on gas exchange and total non-structural carbohydrate levels in cutleaf coneflower (Rudbeckia laciniata L.) growing in Great Smoky Mountains National Park

Submitted to: Environmental Pollution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 3, 2011
Publication Date: October 17, 2011
Citation: Neufeld, H.S., Peoples, S.J., Davison, A.W., Chappelka, A., Somers, G.L., Thomley, J.E., Booker, F.L. 2011. Ambient ozone effects on gas exchange and total non-structural carbohydrate levels in cutleaf coneflower (Rudbeckia laciniata L.) growing in Great Smoky Mountains National Park. Environmental Pollution. 160:74-81.

Interpretive Summary: Ozone in the lower atmosphere causes visible injury and reduced growth of many plants. Plant sensitivity to ozone varies among species and genotypes, but the biological basis for this is not well understood, especially in native wild plant species. To investigate physiological traits that may influence sensitivity to ozone, ozone-sensitive and -tolerant individuals of the perennial herbaceous cutleaf coneflower (Rudbeckia laciniata L.) were compared for their gas exchange characteristics and total non-structural carbohydrates in the Great Smoky Mountains National Park USA. Net photosynthesis decreased with increased foliar injury (stipple). Sensitive plants had lower photosynthetic rates for all leaves except the very youngest and oldest when compared to tolerant plants. Stomatal conductance decreased with increasing leaf age/position, but no sensitivity differences were found. Lower leaves had less starch than upper ones while leaves on sensitive plants had less than those on tolerant plants. These results show that ambient levels of ozone in Great Smoky Mountains National Park can adversely affect gas exchange, water use efficiency and leaf starch content in sensitive individuals of coneflower. Differences in ozone sensitivity between genotypes were not due to differences in ozone uptake. Persistence of sensitive genotypes in the Park may be due to physiological recovery in low ozone years.

Technical Abstract: Ozone-sensitive and -tolerant individuals of the perennial herbaceous cutleaf coneflower (Rudbeckia laciniata L.) were compared for their gas exchange characteristics and total non-structural carbohydrates in the Great Smoky Mountains National Park USA. Net photosynthesis decreased with increased foliar injury (stipple). Sensitive plants had lower photosynthetic rates for all leaves except the very youngest and oldest when compared to tolerant plants. Stomatal conductance decreased with increasing leaf age/position, but no sensitivity differences between genotypes were found. Lower leaves had less starch than upper ones while leaves on sensitive plants had less than those on tolerant plants. These results show that ambient levels of ozone in Great Smoky Mountains National Park can adversely affect gas exchange, water use efficiency and leaf starch content in sensitive individuals of coneflower. Persistence of sensitive genotypes in the Park may be due to physiological recovery in low ozone years.