Visible Foliar Injury and Physiological Responses to Ozone in Italian Provenances ofFraxinus excelsiorandF. ornus
We compared leaf visible injury and physiological responses (gas exchange and chlorophyll a fluorescence) to high O3exposure (150 nmol mol–1h, 8 h day–1, 35–40 days) of two woody species of the same genus with different ecological features: the mesophilic green ash (Fraxinus excelsior) and the xerotolerant manna ash (F. ornus). We also studied how provenances from northern (Piedmont) and central (Tuscany) Italy, within the two species, responded to O3exposure. Onset and extent of visible foliar injury suggested thatF. excelsiorwas more O3sensitive thanF. ornus. The higher stomatal conductance inF. ornusthan inF. excelsiorsuggested a larger potential O3uptake, in disagreement to lower visible foliar injury. The higher carbon assimilation inF. ornussuggested a higher potential of O3detoxification and/or repair. Contrasting geographical variations of ash sensitivity to O3were recorded, as Piedmont provenances reduced gas exchange less than Tuscan provenances inF. excelsiorand more inF. ornus. Visible injury was earlier and more severe inF. excelsiorfrom Piedmont than from Tuscany, while the provenance did not affect visible injury onset and extent inF. ornus.