| One-year-old slash pine (Pinus elliottii) seedlings were exposed to charcoal-filtered air (CF) and elevated ozone (E-O3,mean concentration of 150 nL·L-1) for 84 days in six open-top chambers.Growth parameters,pigments content,gas exchange,chlorophyll a fluorescence and antioxidant system were measured after one growing season (AOT40 value of 38.24 μL·L-1·h).At the end of experiment,both current and old needles showed visible symptoms,and the seedlings were harvested for growth parameters measurement.Elevated O3 did not significantly change height growth,diameter increment,total biomass and biomass partition.E-O3 had negative effects on the photosynthetic parameters,e.g.significant decreases in net photosynthetic rate,stomatal conductance,transpiration rate and pigments content.However,chlorophyll a/b ratio,intercellular CO2concentration,water use efficiency,and chlorophyll a fluorescence parameters were not affected significantly by E-O3 in comparison with CF.Furthermore,E-O3 induced slight increase in MDA content,total ascorbate and total phenolic compound contents,and reduction in total antioxidant capacity.The results suggested that O3-induced significant reduction in pigments content contributed to lower photosynthetic rate in slash pine exposed to E-O3. |
