Ozone Damages to Italian Crops: Environmental Constraints

The main environmental features of Italian cropping systems are described with particular emphasis on their effects on crop responses to ozone pollution. High ozone levels have been recorded all over Italy and daily patterns show, at nighttimes, strong decreases in plain areas, while ozone levels remain high in hilly areas. In the latter sites, therefore, the contribution of nocturnal stomatal conductance (gsto) to ozone uptake should be further studied. It is well known that summer drought and soil salinity reduce the soil water potential, thus causing gsto to decrease. These are likely to be the most important factors reducing crop gas-exchange and yield under environmental conditions occurring in Italy. However, the stressinduced reduction of gsto also restricts ozone uptake and, consequently, its potential damage. In Southern Italy, gasexchange limitations have been also measured in irrigated crops between two successive irrigations. Finally, the effect of water stagnation, which often occurs in clay soils of southern Italy, should be not underestimated. In these soils, in fact, root anoxia will cause stomatal closure and, consequently, will also interfere with ozone uptake and damage.