Winter wheat (Triticum aestivum L. cv. Jingdong 8) was exposed to short-term high ozone treatment after anthesis and then was either well irrigated with soil water content (SWC) of 80-85 % (O 3 +W) or drought treated (SWC 35-40 %, O 3 +D). Short-term ozone exposure significantly decreased irradiance-saturated net photosynthetic rate (P N ) of winter wheat. Under good SWC, P N of the O 3 -treated plant was similar to that of control on 2 d after O 3 -exposure (6 DAA), but decreased significantly after 13 DAA, indicating that O 3 exposure accelerated leaf senescence. Meanwhile, green flag leaf area was reduced faster than that of control. As a result, grain yield of O 3 +W was significantly decreased. P N of O 3 +D was further notably decreased and green flag leaf area was reduced more than that in O 3 +W. Consequently, substantial yield loss of O 3 +D was observed compared to that of O 3 +W. Although P N was significantly positively correlated with stomatal conductance, it also had notable positive correlation with the maximum photochemical efficiency in the dark adapted leaves (F v /F m ), electron transport rate (ETR), photochemical quenching (q P ), as well as content of chlorophyll, suggesting that the depression of P N was mainly caused by non-stomatal limitation. Hence optimal soil water condition should be considered in order to reduce the yield loss caused by O 3 pollution.

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