Phytotoxic ozone effect on selected plant species in a standardized experimental design

The most phytotoxic atmospheric pollutant is ozone which represents a stress factor for Forest species and for the growth and the production of many plant species used in agriculture, resulting in great economic loss. Experimental protocols for passive and active biomonitoring studies to assess plant injury induced by ozone have been adopted by the United Nations/Economic Commission for Europe (UN/ECE) International Cooperative Programme (ICP-Crops), which aims to quantify crop responses to ozone, contributing to the determination of critical levels for this pollutant. Since 1988, our research group has participated in the ICP-Crops programme, conducting studies in the area of Rome with the aim of characterising the ecophysiological response to tropospheric ozone of species of agrarian interest. In this context, in 1997-1998 we have conducted studies on clones (an ozone-sensitive, NC-S clone, and an ozone resistant, NC-R clone) of Trifolium repens L. cv. Regal at the Botanical Garden of the "La Sapienza" University of Rome, in accordance with the ICP-Crops standard protocol. During the studies, environmental parameters and ozone concentrations were measured. In clover clone experiments, comparison of the two clones in 1997-98 experimental periods revealed both morphologic and biochemical differences associated with the response to tropospheric ozone. The results relative to visible injury, peroxidase activity and chlorophyll content confirmed the greater sensitivity of the NC-S clone to tropospheric ozone.