Sensitivity of ragweed (Ambrosia artemisiifolia) growth to urban ozone concentrations

Abstract

Although the sensitivity of growth and yield to ground-level ozone (O₃) has been determined for a variety of agronomic crops and trees, little information is available for weedy species. Common ragweed (Ambrosia artemisiifolia L.) is recognized both as a common agricultural weed and the principle source of pollen for Fall (late August to November) allergies in North America. To quantify the extent to which ambient O₃ limits growth and reproduction, ragweed was grown from germination to floral initiation at control [carbon filtered (CF), 15.8  nL  O₃  L^–1 air] and treatment levels (63.5 nL O₃ L^–1 air) of tropospheric O₃. This 8-h treatment average is similar to the average 1-h O₃ peak values from May through September in urban areas of Washington D.C. and Baltimore, MD. By 48 d after sowing, during floral initiation, no significant differences in total plant or floral biomass were observed as a function of O₃ concentration, relative to the CF control. Analysis of leaf area ratio, relative growth rate and net assimilation rate at approximately 10-d intervals during early vegetative growth also did not demonstrate any significant effect of O₃. Data from this experiment indicate that ragweed is insensitive to O₃ levels up to four times that of the CF control, and suggests that O₃ levels associated with urban environments may not limit the growth or reproductive development of ragweed.