Abstract: ‘Katy’ is the main apricot ( Prunus armeniaca L. ) cultivar for plastic greenhouse cultivation presently in Shandong province. Other cultivars, such as‘Golden Sun’ and ‘Daguo’, are also used for plastic greenhouse in some places. Present papers tried to evaluate these three ap ricot cultivars by measuring photosynthetic characters in the open field with 3-year-old trees. The results showed that light compensation points were 42, 39 and 46 μmol·m^{- 2} ·s^{- 1} , while light saturation pointswere 1 050, 1 452 and 965μmol·
m^{- 2} ·s^{- 1} in Katy, Golden Sun and Daguo, respectively. CO₂ compensation point and CO₂ saturation point were 60.3, 87.5 and 66.7 μmol·m^{- 2} ·s^{- 1} , and 682, 856 and 973 μmol·m^{- 2} ·s^{- 1} , respectively, in the three cultivars. Light intensity might reach the light compensation points of Katy and Daguo in plastic green-house. Photosynthetic rate of Katy was as two times as that of Daguo in their light compensation points probably because of a higher requirement of CO₂ for Daguo. The normal plastic greenhouse could hardly meet the light requirement of Golden Sun although it showed a high photosynthetic rate in high light condition. It is suggested that Katy is suitable for normal plastic greenhouse in Shandong province while Golden Sun should be suitable for the greenhouse with good light condition.

Key words: Apricot, Protected cultivation, Photosynthesis, CO₂ , Water useful efficient