Photosynthetic and transpiration characteristics of Corydalis saxicola and its response to light intensity and concentration of CO_2

The gas exchange of Corydalis saxicola was measured in the field with Li-6400 Portable Photosynthesis (Li-Cor Inc., USA). The results were as follows:The light saturation point, light compensation point, maximum photosynthetic rate, and respiration rate for the leaf of Corydalis saxicola were 329.18 μmol·m -2 ·s -1 , 12.76 μmol·m -2 ·s -1 , 2.96 μmol·m -2 ·s -1 and 0.17 μmol·m -2 ·s -1 , respectively. The light saturation and compensation point were low. This indicated that C.saxicola was adapted to weak light, it's a shade plant. The net photosynthetic rate of C.saxicola increased with the raising of the concentration of CO_2 in April. The net photosynthetic rate increased linearly when the concentration of CO_2 was in 50 μmol·mol -1 to 600 μmol·mol -1 , after that, it increased slowly while the concentration of CO_2 increased to 1 000 μmol·mol -1 . It could be estimated from the A-Ci curve that the CO_2 saturation and compensation point and the maximum carboxylation rate were 1 000 μmol·mol -1 , 68.80 μmol·mol -1 and 0.030 8 μmol·m -2 ·s -1 respectively. The water use efficiency (WUE) of C.saxicola varied with the parabola model while the PAR increased. It increased linearly with the increasing of PAR till the PAR was 200 μmol·m -2 ·s -1 and then decreased gradually.