EFFECTS OF ELEVATED CO2 AND O3 ON LEAF AREA, GAS EXCHANGE AND STARCH CONTENTS IN CHINESE PINE (PINUS TABULAEFORMIS CARR.) IN NORTHERN CHINA

Elevated carbon dioxide (CO2) and tropospheric ozone (O-3) are considered to substantially influence forest ecosystem health worldwide. Pines tabuliformis Carr. is dominant species of coniferous forest in northern China. The present study investigated the effects of elevated CO2 and O-3 on leaf area and gas exchange of P. tabuliformis. The contents of starch were also studied to identify how CO2 and O-3 affect photosynthetic function of plant. Gas exchange responses to elevated CO2 and O-3 in terms of net photosynthetic rate (Pn), stomatal conductance (gs) and transpiration rate (Tr) of the plant. After 90 days O-3 exposure, a significant decrease in leaf area, gas exchange and starch contents were observed. However, the photosynthesis of the plant was positively affected in terms of increased leaf area and Pn by elevated CO2. The higher level of starch contents also confirmed that elevated CO2 affect positively photosynthetic functions of the plant. It was also observed that elevated CO2 could reduce damage induced by O-3 to some extent, which was indicated by the positive responses of leaf area, gas exchange and starch contents in the plant under elevated CO2 and O-3 treatment.