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t r a c tPlants of one evergreen oak (Quercus ilex) and three deciduous oaks (Q. faginea, with small leaves; Q. pyrenaica and Q. robur, with large leaves) were exposed both to filtered air and to enhanced ozone levels in Open-Top Chambers. Q. faginea and Q. pyrenaica were studied for the first time. Based on visible injury, gas exchange, chlorophyll content and biomass responses, Q. pyrenaica was the most sensitive species, and Q. ilex was the most tolerant, followed by Q. faginea. Functional leaf traits of the species were related to differences in sensitivity, while accumulated ozone flux via stomata (POD 1.6 ) partly contributed to the observed differences. For risk assessment of Mediterranean vegetation, the diversity of responses detected in this study should be taken into account, applying appropriate critical levels.

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Measurements of modulated chlorophyll a fluorescence emission and chlorophyll content were made in thalli of Parmelia quercina collected from northern Castellon(Spain). Althoug high air pollution concentrations have been measured in this area, the ratio of variable to maximal fluorescence is unaffected. Following dark-adaptation, the response to irradiance of chlorophyll fluorescence was examined. With respect to control samples, thalli collected in northern Castellon consistently showed differences in fluorescence quenching, the efficiency of excitation energy capture and quenching of basal fluorescence. However, the quantum ield of photochemistry and non-cyclic electron flow were not affected. The changes in chlorophyll fluorescence parameters were observed in the absence of both visual injuries and decrease in chlorophyll content. The results are discussed with regard to the possible role of environmental stress in chlorophyll fluorescence yield.

Five tomato cultivars (Nikita, Ailsa Craig, Moneymaker, UC 82 L and Piedmont) were exposed in open-top chambers to three ozone treatments: charcoal-filtered air (F); non-filtered air (NF); and non-filtered air plus 70 ppb ozone (NF+, 8 h, 133 days). Ozone-specific visible symptoms were recorded for all cultivars in the NF and NF+ treatments. All cultivars showed a reduction of root biomass in the NF+ treatment, root-biomass reductions were also observed in the NF treatment in Nikita (29%) and UC 82 L (33%). Four cultivars from the NF+ treatment showed reductions in aboveground dry biomass (25-50%). The sensitive cultivar Nikita also decreased its aboveground dry biomass (28%) at the end of crop cultivation in the NF treatment. Crop production showed generalized reductions in the total number of ripe and unripe fruits in the NF+ treatment (53-73%), with Nikita presenting a 24% decrease in the total number of ripe fruits in the NF treatment as well. A decreased ripeness rate was detected in all cultivars in NF+ and in three cultivars in the NF treatment (Nikita, Moneymaker and Piedmont). The effect of ozone on total crop production (kg m −2 ) was more important in the early harvest (50-63%) than in the late harvest. The ozone doses in the NF+ treatment affected fruit quality in all cultivars with the exception of Piedmont. Nikita and Ailsa Craig also showed fruit quality changes in the NF treatment. Nikita seems to be an ozonesensitive cultivar, UC 82 L and Piedmont are more ozone-tolerant and the other two cultivars are in an intermediate position.