Abstract: Seedlings of five provenances of Chinese pine (Pinus tabulaeformis Carr.) , including Zhongtiao (ZT) Mountains, Lvliang (LL) Mountains, Taihang (TH) Mountains, Luonan (LN) county and Huangling (HL) county in Shanxi, were transplanted in pots in a greenhouse and treated with progressive soil drought. The net photosynthetic rate (P_n), transpiration rate (T_r), stomatal conductance (G_s), intercellular CO₂ concentration (C_i) and water use efficiency (WUE) of them were measured with LI-6400 Portable Photosynthesis System. The quantitative relationships between their P_n and soil water content (SWC) were analyzed. The results showed that P_n, T_r and G_s of them firstly increased, then decreased with increased soil drought. The provenance of TH had the maximum P_n, T_r and G_s, while HL and HN had lower values than others. On the 4th day of treatment (SWC was 15~25%), P_n, T_r and G_s of five provenances reached the maximum values during the period of 13 days. On the 7th day of treatment (SWC was 7~9%), significant differences were observed in P_n, T_r, G_s and WUE among these provenances (P<0.01), and an order of ZT>TH>LL>HL>LN was found in P_n, T_r, G_s and WUE. After the 10th day of treatment (SWC was under 5%), only respiration was observed for LL, TH, LN and HL. According to SWC values at P_n=0 in the quadratic equations (R²=0.980~0.997) of P_n with SWC, drought resistance was reduced with an order of TH>ZT>LL>HL>LN. There were distinctive differences among five provenances in their responses to progressive soil drought.

Key words: Net photosynthetic rate, Transpiration rate, Water use efficiency, Soil water content