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Evaluation of visual symptoms of ozone damage was conducted in the network of bioindicator rural stations of Catalonia (NE Spain) every 14 days from May to October. Damage rates of ozone (and consequently, ozone biomonitoring capacity of bioindicators) were found to vary highly in time and space depending on the local environmental and meteorological conditions. Lower ozone damage to foliage was produced when meteorological conditions favour stomata resistance. Modulatory effects of meteorological conditions need to be considered in biomonitoring and when modeling plant ozone doses and damage. [ABSTRACT FROM AUTHOR]

This paper describes results of experiments carried out by participants of the UN/ECE ICP-Crops to investigate the dose response of plants to long-term ozone exposure. The data were analyzed to determine the influences of climatic and geographical factors upon this dose response. Members of the ICP-Crops carried out experiments at 12 sites inEurope, covering a geographical range from Jokioinen, Finland, to Milan, Italy, to generate the database used in this study. The effects of ozone were determined using N-(2-(2-oxo-1-imidazolidinyl)ethyl)-N'phenylurea (ethylene diurea; EDU) as a protectant against ozone damage. Thus, the ratio of biomass in EDU-treated plants to untreated plants indicated the severity of ozone damage. Simple linear regression produced a low r2 of 0.16 for the dose response. Analysis of the residuals identified three groups in the data depending on their mean residual values. Re-plotting the data into separate dose responses for these three groups produced improvements in the r2 values to 0.33, 0.36 and 0.36, for Groups 1 to 3, respectively. Thedata were subsequently used to train artificial neural network (ANN)models to determine the factors that caused the scatter within the dose response. Vapor pressure deficit and temperature were found to beimportant influences on the dose response whereas longitude, year and altitude were weaker influences. Inclusion of these factors in the ANN model increased the r2 of the model to 0.79. [ABSTRACT FROM AUTHOR]

A field study was conducted from May to October 1995 to assess ozone(O-3) phytotoxicity in Catalonia (NE Spain) by determining a percentage value of leaf area injured by ozone on three tobacco cultivars, Bel-W3, Bel-C and Bel-B as bioindicators. Colorimetric parameters werealso determined in an effort to have an objective assessment of ozone injury. The study was conducted simultaneously on eight sites whereozone levels and several meteorological parameters were continuouslymonitored. Two sets of plants were used at each site. The first one was composed of six plants of each cultivar which were changed every two weeks while the second one involved two plants of each cultivar which were kept in the plots throughout the whole experimental period.Open Top Chambers were also used to test the response of the three cultivars to ozone under controlled conditions. The ozone levels correlated well with ozone injury on the Bel-W3 cultivar but not as well on the other two cultivars. The ozone levels did not fully account forall the observed injury. The response of tobacco plants to ozone concentrations and therefore its biomonitoring capacity depended also ondifferent environmental conditions linked to stomatal behaviour suchas temperature, humidity, wind or altitude. These environmental conditions had some effects on the intensity of Ozone injury. Ozone concentrations accumulated over a threshold of 60 ppb (AOT60) when VPD wasbelow I KPa. Correlated well with the ozone injury and best explained the intensity tobacco injury symptoms. For large plants growing throughout the whole period of study, Bel-C was the best indicator cultivar for AOT60 over the 3 days prior to the last ozone injury assessment. The colorimetric parameters were indicators of seasonal changes but they were not good ozone damage indicators. It is concluded that tobacco cultivars were good bioindicators but meteorological and otherenvironmental factors need to be considered in there use as biomonitors. [ABSTRACT FROM AUTHOR]