Biomonitoring ozone phytotoxicity in eastern Spain

High ozone (O-3) levels have been recorded in eastern Spain. A project was developed to identify the areas of elevated O-3 and determine if these levels were above critical concentrations for plant damage. Thus, a network of bioindicators was established in two Autonomous Communities of Spain: Catalunya (31.930 km(2)) and Valencia (23.305 km(2)) to assess O-3 phytotoxicity. Three tobacco cultivars, (Bel-W3, Bel-C and Bel-B) were used during the 1994 growing season in both Regions. In Catalunya the highest O-3 phytotoxicity was recorded in coastal areas, while the phytotoxicity decreased as plants were grown further in-land. A lower O-3 phytotoxicity was observed in coastal sites of the Valencia Autonomous Community, compared to Catalunya, although the O-3 injury was observed downwind from Valencia city in the most resistant cultivar Bel-B. The results in the Valencian Community were difficult to interpret, since plant viruses were widely distributed, not only in indicator plants, but also in commercial crops grown in the area. The analysis of O-3 concentrations, meteorological parameters and visible injury at the Catalan sites showed that high relative humidity levels could favour O-3 phytotoxicity. Therefore, the interactions between O-3 exposure and environmental conditions on plant response should be further studied for the establishment of sound critical levels.