Abstract: Loquat trees(Eriobotrya japonica Lindl．)grown in two open-top growth chambers at CO₂ concentrations of 400 μmol·mol^-1 and 700 μmol·mol^-1 were used to study the effects of elevated atmospheric CO₂ ，concentration and water stress on photosynthesis．chlorophyll fluorescence and acting of an tioxidative enzymes in leaves．The results showed that elevated atmospheric CO₂ concentration(700 μmol·mol^-1) significantly enhanced the photosynthesis under various levels of water stress． Furthermore，under high CO₂ condition, the values of Fv/Fm ， Fv／Fo and PSⅡ were also higher than at normal atmospheric CO₂ ，concentration，but the diference between the aterstressed
plants and well—watered plants was not significant． In addition， elevated atm ospheric CO₂ concentration considerably jncreased the ach vities of SOD， POD an d CAT． Such jnerease， however， was farless significan t liBder water stress condition．The MDA content also showed less increase under the latter condition． The results indicate that high CO₂ concentration seems to have ameliorating effect on drought—induced oxidative damage．

Key words: Loquat Trees, Elevated CO₂, Water-stress, Photosynthesis, Chlorophyll fluorescence, Antioxidative enzyme