Responses of Growth, Photosynthesis and VOC Emissions of Pinus tabulaeformis Carr. Exposure to Elevated CO2 and/or Elevated O3 in an Urban Area

Responses of growth, photosynthesis and emission of volatile organic compounds of Pinus tabulaeformis exposed to elevated CO2 (700 ppm) and O3 (80 ppb) were studied in open top chambers. Elevated CO2 increased growth, but it did not significantly (p > 0.05) affect net photosynthetic rate, stomatal conductance, chlorophyll content, the maximum quantum yield of photosystem II, or the effective quantum yield of photosystem II electron transport after 90 d of gas exposure. Elevated O3 decreased growth (by 42.2% in needle weight and 25.8% in plant height), net photosynthetic rate and stomatal conductance after 90 d of exposure, but its negative effects were alleviated by elevated CO2. Elevated O3 significantly (p < 0.05) increased the emission rate of volatile organic compounds, which may be a helpful response to protect photosynthetic apparatus against O3 damage.