Contrasting responses of salinity-stressed salt-tolerant and intolerant winter wheat (Triticum aestivum L.) cultivars to ozone pollution

Contrasting winter wheat cultivars, salt-tolerant DK961 and intolerant JN17, which sown in no salinity (-S) and salinity (+S) boxes were exposed to charcoal filtered air (CF) and elevated O₃ (+O₃) in open top chambers (OTCs) for 30 days. In-S DK961 and JN17 plants,+O₃ DK961 and JN17 plants had significantly lower light-saturated net photosynthetic rates (A_sat, 26% and 24%), stomatal conductance (g_s, 20% and 32%) and chlorophyll contents (10% and 21%), while O₃ considerably increased foliar electrolyte leakage (13% and 39%), malondialdehyde content (9% and 23%), POD activity and ABA content. However, responses of these parameters to O₃ were significant in DK961 but not in JN17 in+S treatment. Correlation coefficient of DK961 reached significance level of 0.01, but it was not significant in JN17 under interaction of O₃ and salinity. O₃-induced reductions were larger in shoot than in root in both cultivars. Results indicate that the salt-tolerant cultivar sustained less damage from salinity than did the intolerant cultivar but was severely injured by O₃ under+S condition. Therefore, selecting for greater salt tolerance may not lead to the expected gains in yield in areas of moderate (100mM) salinity when O₃ is present in high concentrations. In contrast, salinity-induced stomatal closure effectively reduced sensitivity to O₃ in the salt-intolerant cultivar. Hence we suggest salt-tolerant winter wheat cultivars might be well adapted to areas of high (>100mM) salinity and O₃ stress, while intolerant cultivars might be adaptable to areas of mild/moderate salinity but high O₃ pollution.