Abstract: Photosynthesis characteristics in seedlings of three cucumber cultivars，i.e. Jinyou No. 35，Deltasta and Yuanfengyuan No.6，under and 30 μmol / (m²·s) light density were studied. The results showed that under the weak light condition photosynthetic rate (Pn) ，conductance to H2O(Gs)，transpiration rate (Tr) ，water utility efficiency (WUE) ，light compensation point (LCP) ，saturation light intensity (SL) ，maximum photosynthetic rate (Pmax) and dark respiration rate (Rd) of cucumber seedlings decreased，but apparent quantum yield (AQY) increased. Intercellular CO2 concentration(Ci) of Jinyou No. 35 and Deltasta decreased and stomatal limitation value(Ls) increased. But Ci of Yuanfengyuan No. 6 increased and Ls decreased. The decrease in Pn of protected field cultivar was the result of stomatal limitation，that in open field cultivar was the result of photosynthetic activity decreasing. The important reason of Pmax decreasing was the decline in RuBPCase activity. Among three cucumber cultivars，Jinyou No. 35 with lower LCP and Rd，AQY increase by a bigger margin under weak light was a cultivar with weak-light adaptability.

Key words: Cucumber, Weak light, Photosynthetic characteristics, RuBPCase

CLC Number: 

• S62.22.+1