OZONE EFFECTS ON WATERMELON PLANTS AT THE EBRO DELTA (SPAIN) - SYMPTOMATOLOGY

Symptoms thought to be of ozone (O3) injury were first observed at the Migjorn farm on the Ebro Delta in 1976. Since then, O3 symptoms have been observed every growing season, including 1990. In 1987 the first account of the suspected symptoms was published by Salleras. In order to confirm the cause of the symptoms and to determine the effects on crops, an experimental field with open-top chambers was established on the farm in 1988. There were three treatments: ambient air (AA), charcoal-filtered air (CF) and non-filtered plots (NF), with five replicates each. Visible injury was followed during the growing season and the symptoms were much less developed in the CF treatment than in AA or NF treatments. It was concluded from these observations, and data on ozone concentrations, that the Spanish Mediterranean coast has a significant air pollution problem.