Effects of ozone exposure on growth and photosynthesis of the seedlings of Liriodendron chinense (Hemsl.) Sarg, a native tree species of subtropical China

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 (Phi(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.