title: Seasonal differences and within-canopy variations of antioxidants in mature spruce (Picea abies) trees under elevated ozone in a free-air exposure system.
abstract: The effect of free-air ozone fumigation and crown position on antioxidants were determined in old-growth spruce (Picea abies) trees in the seasonal course of two consecutive years (2003 and 2004). Levels of total ascorbate and its redox state in the apoplastic washing fluid (AWF) were increased under double ambient ozone concentrations (2xO3), whilst ascorbate concentrations in needle extracts were unchanged. Concentrations of apoplastic and symplastic ascorbate were significantly higher in 2003 compared to 2004 indicating a combined effect of the drought conditions in 2003 with enhanced ozone exposure. Elevated ozone had only weak effects on total glutathione levels in needle extracts, phloem exudates and xylem saps. Total and oxidised glutathione concentrations were higher in 2004 compared to 2003 and seemed to be more affected by enhanced ozone influx in the more humid year 2004 compared to the combined effect of elevated ozone and drought in 2003 as observed for ascorbate.
authors.affiliation: Institute of Forest Botany and Tree Physiology, Chair of Tree Physiology, Albert-Ludwigs-University, Georges-Köhler-Allee 053/054, D-79110 Freiburg, Germany.
authors.forename: Nora
authors.initials: N
authors.lastname: Hofer
authors.forename: Maria
authors.initials: M
authors.lastname: Alexou
authors.forename: Christian
authors.initials: C
authors.lastname: Heerdt
authors.forename: Markus
authors.initials: M
authors.lastname: Löw
authors.forename: Herbert
authors.initials: H
authors.lastname: Werner
authors.forename: Rainer
authors.initials: R
authors.lastname: Matyssek
authors.forename: Heinz
authors.initials: H
authors.lastname: Rennenberg
authors.forename: Kristine
authors.initials: K
authors.lastname: Haberer
mesh_terms: D000393:Air Pollutants / Q000633:toxicity*; D000975:Antioxidants / Q000032:analysis*; D004463:Ecology / Q000379:methods; D005858:Germany; D005978:Glutathione / Q000032:analysis; D010084:Oxidation-Reduction; D010126:Ozone / Q000633:toxicity*; D028222:Picea / Q000737:chemistry*; D018515:Plant Leaves / Q000737:chemistry; D018520:Plant Shoots / Q000737:chemistry; D011891:Rain; D012621:Seasons; D013696:Temperature
chemical_list: D000393:Air Pollutants; D000975:Antioxidants; D010126:Ozone; D005978:Glutathione