Ozone pollution effects on gas exchange, growth and biomass yield of salinity-treated winter wheat cultivars.

A sand-culture experiment was conducted in four Open-Top-Chambers to assess the effects of O3 on salinity-treated winter wheat. Two winter wheat cultivars, salt-tolerant Dekang961 and salt-sensitive Lumai15, were grown under saline (100 mM NaCl) and/or O3 (80±5 nmol mol(-1)) conditions for 35 days. Significant (P<0.05) O3-induced decreases were noted for both cultivars in terms of gas exchange, relative water content, growth and biomass yield in the no-salinity treatment. Significant (P<0.01) corresponding decreases were measured in Dekang961 but not in Lumai15 in the salinity treatment. Soluble sugar and proline contents significantly increased in both cultivars in combined salinity and O3 exposure. O3-induced down-regulation in the gradients of A-C(i) and A-PPFD response curves were much larger in Dekang961 than in Lumai15 under saline conditions. Significant (P<0.05) interactions were noted in both salinity×cultivars and salinity×O3 stresses. The results clearly demonstrated that O3 injuries were closely correlated with plant stomatal conductance (g(s)); the salt-tolerant wheat cultivar might be damaged more severely than the salt-sensitive cultivar by O3 due to its higher g(s) in saline conditions.