Ozone sensitivity of currant tomato (Lycopersicon pimpinellifolium), a potential bioindicator species Marcello Iriti a , Lucia Belli a , Cristina Nali b , Giacomo Lorenzini b , Giacomo Gerosa c , Franco Faoro d, * a Istituto di Patologia Vegetale, Universita ` di Milano, Via Celoria 2, 20133 Milan, Italy b Dipartimento di Coltivazione e Difesa delle Specie Legnose ‘‘G. Scaramuzzi’’, Universita ` di Pisa, Via del Borghetto 80, Pisa, Italy c Dipartimento di Matematica e Fisica, Universita ` Cattolica del Sacro Cuore, Via Musei 41, 25121 Brescia, Italy d CNR, Istituto di Virologia Vegetale, Sezione di Milano,Via Celoria, 2 20133 Milan, Italy Received 8 February 2005; accepted 8 August 2005 Currant tomato (Lycopersicon pimpinellifolium) was found to be very sensitive to ozone. Abstract The wild tomato species Lycopersicon pimpinellifolium (currant tomato) was exposed to different O 3 concentration, both in controlled environment fumigation facilities and in open-top chambers, to assess its sensitivity and to verify its potential as a bioindicator plant. Plants appeared particularly sensitive to O 3 at an early stage of growth, responding with typical chlorotic spots within 24 h after exposure to a single pulse of 50 ppb for 3 h, and differentiating peculiar symptoms, such as reddish necrotic stipples, bronzing and extensive necrosis, depending on O 3 concentration. Histo-cytochemical investigations with 3,3#-diaminobenzidine, to localize H 2 O 2 , and Evans blue, to detect dead cells, suggested that currant tomato sensitivity to O 3 could be due to a deficiency in the anti-oxidant pools. The combination of these stainings proved to be useful, either to predict visible symptoms, early before their appearance, and to validate leaf ozone injury. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Ozone; Bioindicator; Lycopersicon pimpinellifolium; Currant tomato 1. Introduction Tropospheric ozone (O 3 ) represents the most widespread air pollutant, with major toxic effects on plants (Benton et al., 2000) and serious problems for human health (Kim et al., 2004). Concentrations have dramatically increased over the last decades (Naja et al., 2003), leading authorities responsible for air quality to extend monitoring networks. The use of plant bioindicators is considered an inexpensive, however reliable complement, to expensive automatic real- time monitors (Manning and Feder, 1980). Furthermore, bioindicators do not require electricity or a climate controlled shelter for effective usage, and have the advantage to indicate a specific symptomatology that reflects the absorbed concen- tration of ozone, which is not necessarily correlated with O 3 external concentration because of the determinant influence of stomatal conductance (Manning, 2003). The most extensively used bioindicator for O 3 has been the extremely sensitive tobacco (Nicotiana tabacum) cv. Bel-W3 (Heggestad, 1991), which displays recognizable and typical necrotic symptoms at a threshold of 40 ppb for 4 h exposure (Larsen and Heck, 1976). However, Bel-W3 plants require at least 8 weeks of culturing before being exposed. Their large and fragile leaves are easily damaged by adverse weather conditions and imply remarkable logistical difficulties in * Corresponding author. Tel.: C39 02 5031 6786; fax: C39 02 5031 6781. E-mail address: f.faoro@ivv.cnr.it (F. Faoro). 0269-7491/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.envpol.2005.08.046 Environmental Pollution 141 (2006) 275e282 www.elsevier.com/locate/envpol