Growth responses to ozone in plant species from wetlands

Ten wet grassland species were fumigated with four concentrations of ozone (charcoal-filtered air, non-filtered air and non-filtered air pins 25 or 50 nl l(-1) ozone) in open-top chambers during one growing season to investig ate the long-term effect of this air pollutant on various growth variables. Only Eupatorium cannabinum showed ozone-related foliar injury, while five species reacted with significantly ozone-enhanced senescence. Premature sen escence was paralleled by a significant ozone-induced reduction of green le af area in Achillea ptarmica, E. cannabinum and Plantago lanceolata. At the intermediate harvest performed after 28 days shoot weights were significan tly decreased by ozone in A. ptarmica and increased in Molinia caerulea. At the final harvest performed at the end of the growing season two other spe cies, Cirsium dissectum and E. cannabinum had a significantly reduced shoot weight due to ozone. Root biomass was determined only at the intermediate harvest. The root:shoot ratio (RSR) was significantly reduced in C. dissect um, while it increased in ill. caerulea. Seven of the species developed flo wers during the experiment. While no significant ozone effects on flowering date and Rower numbers were detected, flower weights were significantly re duced in E. cannabinum and P. lanceolata. (C) 2000 Elsevier Science B.V. Al l rights reserved.