title: Ozone foliar symptoms in woody plant species assessed with ultrastructural and fluorescence analysis.
abstract: This paper compares the responses to ozone in five woody species: Fagus sylvatica (FS), Acer pseudoplatanus (AP), Fraxinus excelsior (FE), Viburnum lantana (VL) and Ailanthus altissima (AA). The hypothesis being tested was that the strategies that plants adopt to resist oxidative pressure are species-specific. The study was carried out on field grown plants in an area in Northern Italy characterized by elevated levels of ozone pollution. The observations were made both at ultrastructural (using light and electronic microscopy) and physiological (using chlorophyll a transient fluorescence and microspectral fluorometry) level. Common responses were: the hypersensitive response (i.e. the death of palisade mesophyll cells) and the formation of callose layers separating injured from healthy cells. FS and AP were capable of thickening the palisade mesophyll cell walls. This thickening process involved changes in cell wall chemical structure, evidenced by the accumulation of yellow autofluorescence compounds. Species-specific behaviours were observed with the fluorescence analysis, with special reference to the photochemical de-excitation constant (Kp). This value increased in FE and AP, and decreased in AA. The observed responses are interpreted as adaptative strategies against the ozone stress. The increase of Kp indicates that the reaction centres were working as more effective quenchers.
authors.affiliation: Department of Plant Biology, University of Florence. Piazzale delle Cascine 28, 50144 Firenze, Italy. filippo.bussotti@unifi.it
authors.forename: Filippo
authors.initials: F
authors.lastname: Bussotti
authors.forename: Giovanni
authors.initials: G
authors.lastname: Agati
authors.forename: Rosanna
authors.initials: R
authors.lastname: Desotgiu
authors.forename: Paolo
authors.initials: P
authors.lastname: Matteini
authors.forename: Corrado
authors.initials: C
authors.lastname: Tani
mesh_terms: D002734:Chlorophyll / Q000502:physiology; D000077194:Chlorophyll A; D005453:Fluorescence; D005470:Fluorometry; D019684:Magnoliopsida / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D010126:Ozone / Q000633:toxicity*; D018515:Plant Leaves / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure*; D013045:Species Specificity
chemical_list: D002734:Chlorophyll; D010126:Ozone; D000077194:Chlorophyll A