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 (Asat, 26% and 24%), stomatal conductance (gs, 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 (100 mM) 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 (>100 mM) salinity and O3 stress, while intolerant cultivars might be adaptable to areas of mild/moderate salinity but high O3 pollution.