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Little is known about the response of trees to elevated ozone (O 3 ) in the subtropical region of China, where ambient O 3 concentrations are high enough to damage plants. In this study, pigment content, gas exchange and chlorophyll (Chl) a fluorescence in leaves of Liriodendron chinense (Hemsl.) Sarg seedlings, a deciduous broadleaf tree species native in subtropical regions, were investigated at 15, 40, and 58 days after O 3 fumigation (DAF) at a concentration of 150 mm 3 m -3 (E-O 3 ). At the end of experiment, seedlings were harvested for biomass measurement. E-O 3 caused visible injuries on the mature leaves e.g. necrotic patches and accelerated early defoliation. Relative to the charcoal-filtered air (CF) treatment, E-O 3 significantly decreased shoot and root biomass, pigment content, light-saturated net photosynthesis (P Nsat ), stomatal conductance (g s ), maximum rate of carboxylation (V cmax ) , photochemical quenching coefficient (q p ) and effective quantum yield of PSII photochemistry (Ф PSII ), and also caused a slight reduction in relative increase of basal diameter. Therefore, L. chinense can be assumed to be an O 3 -sensitive tree species, which will be threatened by increasing ambient O 3 concentrations in China.