The photosynthetic parameters in leaves of three-year-old seedlings of Fraxinus rhynchophylla L. were studied under different soil water conditions and CO2 concentrations ([CO2]) with a
LI-COR 6400 portable photosynthesis system. The objective was to investigate the response of photosynthesis and stomatal conductance (gs) to various [CO2] and soil water conditions, and to understand the adaptability of F. rhynchophylla to such conditions. The results showed that the soil water content (RWC) required to maintain high photosynthetic productivity in F. rhynchophylla was 49.5-84.3%; in this range, net photosynthetic rate (PN) rose with [CO2] increasing from 500 to 1,400 μmol mol-1. Outside this RWC range, PN decreased significantly. The apparent maximum photosynthetic rate (Pmax,c) and carboxylation velocity (Vc) increased with increasing RWC and remained relatively high, when RWC was between 49.5 and 96.2%. CO2 compensation points and photorespiration rate exhibited a trend opposite to that of Pmax,c and Vc, indicating that moderate water stress was beneficial for increasing plant assimilation, decreasing photorespiration, and increasing production of photosynthates. gs declined significantly with increasing [CO2] under different water supplies, but the RWC range maintaining high gs increased. gs reached its maximum, when RWC was approximately 73% and then decreased with declining RWC. The maximal gs was found with increasing RWC. Thus, based on photosynthetic characteristics in artificial, vegetation construction in semiarid loess hill and gully area, F. rhynchophylla could be planted in habitats of low soil water content. and S. Y. Zhang ... [et al.].