title: Protection of ash (Fraxinus excelsior) trees from ozone injury by ethylenediurea (EDU): roles of biochemical changes and decreased stomatal conductance in enhancement of growth.
abstract: Treatments with ethylenediurea (EDU) protect plants from ozone foliar injury, but the processes underlying this protection are poorly understood. Adult ash trees (Fraxinus excelsior), with or without foliar ozone symptoms in previous years, were treated with EDU at 450 ppm by gravitational trunk infusion in May-September 2005 (32.5 ppm h AOT40). At 30-day intervals, shoot growth, gas exchange, chlorophyll a fluorescence, and water potential were determined. In September, several biochemical parameters were measured. The protective influence of EDU was supported by enhancement in the number of leaflets. EDU did not contribute its nitrogen to leaf tissue as a fertiliser, as determined from lack of difference in foliar N between treatments. Both biochemical (increase in ascorbate-peroxidase and ascorbic acid, and decrease in apoplastic hydrogen peroxide) and biophysical (decrease in stomatal conductance) processes regulated EDU action. As total ascorbic acid increased only in the asymptomatic trees, its role in alleviating O(3) effects on leaf growth and visible injury is controversial.
authors.affiliation: IPP-CNR, Via Madonna del Piano 10, Sesto Fiorentino, I-50019 Florence, Italy. e.paoletti@ipp.cnr.it
authors.forename: Elena
authors.initials: E
authors.lastname: Paoletti
authors.forename: Nicla
authors.initials: N
authors.lastname: Contran
authors.forename: William J
authors.initials: WJ
authors.lastname: Manning
authors.forename: Antonella
authors.initials: A
authors.lastname: Castagna
authors.forename: Annamaria
authors.initials: A
authors.lastname: Ranieri
authors.forename: Francesco
authors.initials: F
authors.lastname: Tagliaferro
mesh_terms: D000393:Air Pollutants / Q000633:toxicity*; D001205:Ascorbic Acid / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D004463:Ecology / Q000379:methods*; D031661:Fraxinus / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism; D009584:Nitrogen / Q000032:analysis / Q000378:metabolism; D010083:Oxidants, Photochemical / Q000633:toxicity*; D010126:Ozone / Q000633:toxicity*; D009195:Peroxidase / Q000378:metabolism; D010671:Phenylurea Compounds / Q000494:pharmacology*; D010858:Pigmentation; D018520:Plant Shoots / Q000737:chemistry / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D054046:Plant Stomata / Q000187:drug effects / Q000502:physiology; D018526:Plant Transpiration
chemical_list: D000393:Air Pollutants; D010083:Oxidants, Photochemical; D010671:Phenylurea Compounds; D002734:Chlorophyll; C032766:ethylene diurea; D010126:Ozone; D009195:Peroxidase; D009584:Nitrogen; D001205:Ascorbic Acid; D000077194:Chlorophyll A