Differences in ozone sensitivity in three varieties of cabbage (Brassica oleracea L.) in the rural Mediterranean area

The effects of air quality with three levels of ozone (O-3) were studied on three cabbage varieties during a one month exposure period in the Valencia area by means of modulated chlorophyll (Chl) a fluorescence, lipid peroxidation and solute leakage. Increasing O-3 exposure reduced the maximum quantum yield of PSII photochemistry (F-v/F-m) in line with a reduction in non-cyclic electron flow (phi(PSII)), lower capacity to reduce the quinone pool (q(P)) and a decrease in the potential phothosynthetic quantum conversion, Rfd ratio. These reductions were more evident in Caramba and Sentinel varieties but lower in Othelo. Ozone and its oxidative derivates weakened the plasmalemma, which caused a leakage of cellular liquids into intercellular spaces. In our results, the ion leakage increased with O-3 concentration. Moreover, data from thiobarbituric acid reactive (TBARS) analysis confirmed the hypothesis that O-3 modified the membrane structure by increasing the lipid peroxidation more in Caramba and Sentinel varieties. These alterations in the membranes reduced the ability to develop non-photochemical quenching (NPQ). The O-3 effects on solute leakage and lipid peroxidation in the Othelo variety were lower than in the other two varieties, which allowed non-photochemical quenching to develop in this variety. These results suggest the possibility adverse effects of ozone on winter crops grown in the Valencia region.