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Volume 10, Pages 512-527
Research Article

Early Events in Populus Hybrid and Fagus sylvatica Leaves Exposed to Ozone

1Dipartimento di Biotecnologie Agrarie, Sezione di Botanica Applicata e Ambientale, Università di Firenze, Italy
2Dipartimento di Produzione Vegetale, Università di Milano, Italy
3Istituto di Fisica Applicata “Nello Carrara” - IFAC Consiglio Nazionale delle Ricerche, Firenze, Italy
4Dipartimento di Matematica e Fisica Università di Cattolica del Sacro Cuore, Brescia and Fondazione Lombardia per l'Ambiente, Milano, Italy

Received 10 January 2010; Revised 16 March 2010; Accepted 17 March 2010

Academic Editor: Arthur Chappelka

Copyright © 2010 R. Desotgiu et al.


This paper aims to investigate early responses to ozone in leaves of Fagus sylvatica (beech) and Populus maximowiczii x Populus berolinensis (poplar). The experimental setup consisted of four open-air (OA) plots, four charcoal-filtered (CF) open-top chambers (OTCs), and four nonfiltered (NF) OTCs. Qualitative and quantitative analyses were carried out on nonsymptomatic (CF) and symptomatic (NF and OA) leaves of both species. Qualitative analyses were performed applying microscopic techniques: Evans blue staining for detection of cell viability, CeCl3 staining of transmission electron microscope (TEM) samples to detect the accumulation of H2O2, and multispectral fluorescence microimaging and microspectrofluorometry to investigate the accumulation of fluorescent phenolic compounds in the walls of the damaged cells. Quantitative analyses consisted of the analysis of the chlorophyll a fluorescence transients (fast kinetics). The early responses to ozone were demonstrated by the Evans blue and CeCl3 staining techniques that provided evidence of plant responses in both species 1 month before foliar symptoms became visible. The fluorescence transients analysis, too, demonstrated the breakdown of the oxygen evolving system and the inactivation of the end receptors of electrons at a very early stage, both in poplar and in beech. The accumulation of phenolic compounds in the cell walls, on the other hand, was a species-specific response detected in poplar, but not in beech. Evans blue and CeCl3 staining, as well as the multispectral fluorescence microimaging and microspectrofluorometry, can be used to support the field diagnosis of ozone injury, whereas the fast kinetics of chlorophyll fluorescence provides evidence of early physiological responses.