Interazione tra stress tipici dell’area mediterranea (salino e da ozono) su colture erbacee

Stomatal closure and the biosynthesis of antioxidant molecules are two fundamental components of the physiological machinery that leads to stress adaptation during plants exposure to soil and water salinity. Since high stomatal resistance and high antioxidative power may also contribute to counteract ozone damages, we hypothesized that soil salinization may actually increase the ozone tolerance threshold in crop species. A 2-year experiment was performed with alfalfa grown in Filtered and Not-Filtered Open Top Chambers. Alfalfa yield was reduced by ozone (-33%) only in the plants irrigated with regular water, while the increasing levels of salinity (Soil EC from 0.29 to 1.06 dS m-1) reduced the stomatal conductance and the plant ozone uptake, thus linearly increasing the ozone associated relative yield at a rate of 41% per dS m-1 of soil salinity. Such increase was significantly correlated with the decrease of cumulative stomatal ozone uptake due to the salinity effects on stomatal conductance (RY = 165-33.4CUO; R2=0.98). Therefore a reliable flux-based model for assessing the effects of ozone on crops yield should take into account the soil salinity.