No abstract

production en poids sec due à l'exposition à l'ozone; cette perte se situait à -10 % pour les plantes traitées avec de l'eau par rapport aux plantes traitées avec l'EDU et à -19,8 % pour la récolte finale des plantes exposées à l'air non-filtré, par rapport à celles exposées à l'air filtré.

This report presents the results of an ozone monitoring experience performed with tobacco indicator plants (Nicotiana tabacum L. cv. 'Bel-W3'). These bioindicators were exposed to ambient air in 23 sites in Northern Italy from 27 April 1987 to 21 October 1987. Typical ozone-induced leaf necrosis was observed in every site. The percentage increase in injured leaf area was estimated weekly and a Leaf Injury Index (LII) was calculated. The weekly series of LIIs were statistically inspected for spatial and temporal relationships. Sample correlation coefficients were statistically significant for almost every possible pair of sites. The time series properties of ten series of LIIs with no missing data were analyzed using Box-Jenkins models. An autoregressive first order model, or AR(1), was selected to remove the autocorrelation from these series. Linear correlation coefficients between 'prewhitened' (i.e. from which autocorrelation had been removed) pairs of LII series were statistically significant. Hence synchronous variations in leaf necrosis could only be related to the regional diffusion of tropospheric ozone.

Tobacco plants (Nicotiana tabacum L. cv. 'Bel-W3') were exposed to ambient air for 25 weeks during the 1987 growing season next to an air pollution monitoring station in Brera (Milan, Italy). The research objective was to study the influence of selected environmental parameters on leaf damage in this plant, which is widely used as an ozone indicator. A multiple linear correlation model was estimated between leaf damage and available meteorological and air pollution data. Leaf injury was positively correlated with ozone integrated exposure and temperature, but negatively with vapour pressure deficit. A linear correlation model was used to estimate ozone integrated exposure from the leaf injury index.

-Experiments with plants grown in filtered and unfiltered open-top chambers have been conducted for a decade at two sites in the Po Valley (Northern Italy). Substantial yield losses were often recorded, showing a varying sensitivity between plants (forage, horticultural and semi-natural plants). The response to ambient air ozone doses seems moreover connected to air temperature and humidity. The need for incorporating selected modifying factors in level-II ozone critical levels is advocated for regions, like the Po Valley, where peculiar climatic conditions and high concentrations of ozone are usually present. ozone / crops / yield / Italy / open-top chambersRésumé -Réponse en relation à la productivité de plantes exposées à l'ozone dans la Vallée du Pô (Italie). Pendant une dizaine d'années on a effectué des essais sur les plantes cultivées en chambres à ciel ouvert avec air filtré et non filtré, installées dans deux postes situés dans la Vallée du Pô (Italie du Nord). On a souvent observé des pertes importantes sur la récolte des plantes exposées à des taux élevés d'ozone (air ambiant non filtré) malgré une diversité entre les espèces utilisées (plantes fourragères, horticoles et demi-naturelles). La réponse aux doses d'ozone troposphérique peut être aussi modifiée par la température et l'humidité de l'air. Il est nécessaire d'incorporer plusieurs facteurs différents de modification dans la formulation des niveaux critiques pour l'ozone (niveau II). Cela est surtout important pour des régions géographiques, telles la Vallée du Pô, où les conditions climatiques particulières et de hautes concentrations d'ozone sont une caractéristique durant l'été. ozone / plantes cultivées / production agricole / Italie / chambres à ciel ouvert