title: Responses of Fraxinus excelsior L. seedlings to ambient ozone exposure in urban and mountain areas based on physiological characteristics and antioxidant activity.
abstract: Effects of ozone on the sensitive tree species Fraxinus excelsior L. exposed to ambient air were investigated. The dynamics of photosynthesis, transpiration, stomatal conductance and the activity of the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) in three-year-old ash seedlings were studied during a four-month period (June-September). Seedlings were exposed to ambient ozone in an urban (the Central City Park of Sofia - Borisova Gradina) and a mountain (Plana Mountain) area in Bulgaria. The sites were located near climate monitoring stations, providing data on ozone concentrations and meteorological parameters. Ozone exposure at the mountain site (AOT40) was more than two times higher compared to the urban site. Significantly higher values of sun radiation, transpiration, stomatal conductance and enzyme activity at the mountain site were also observed. At the urban site higher values of temperature and air humidity were registered. Effects of the measured variables on ash seedlings were complex and interdependent. No direct effect of ozone concentration in ambient air on the leaf physiology and biochemistry could be proved. However, intensified SOD and CAT activity in the presence of elevated ozone suggested antioxidant reaction in response to ozone uptake.
authors.affiliation: Institute of Biodiversity and Ecosystem Research - Bulgarian academy of science, Gagarin Street, Sofia 1113, Bulgaria. petq_parvanova@abv.bg
authors.forename: Petya
authors.initials: P
authors.lastname: Parvanova
authors.forename: Nikolina
authors.initials: N
authors.lastname: Tzvetkova
authors.forename: Svetla
authors.initials: S
authors.lastname: Bratanova-Doncheva
authors.forename: Nesho
authors.initials: N
authors.lastname: Chipev
authors.forename: Radka
authors.initials: R
authors.lastname: Fikova
authors.forename: Evgeni
authors.initials: E
authors.lastname: Donev
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D002031:Bulgaria; D002374:Catalase / Q000378:metabolism; D002947:Cities; D031661:Fraxinus / Q000502:physiology*; D018384:Oxidative Stress; D010126:Ozone / Q000032:analysis*; D010788:Photosynthesis; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D018526:Plant Transpiration; D036226:Seedlings / Q000502:physiology*; D013482:Superoxide Dismutase / Q000378:metabolism
chemical_list: D000393:Air Pollutants; D010940:Plant Proteins; D010126:Ozone; D002374:Catalase; D013482:Superoxide Dismutase