Abstract: A plot experiment with rainproof installation was conducted to study the effects of different soil moisture regimes on the leaf gas exchange and chlorophyll fluorescence parameters of winter wheat during its late growth stage. Five treatments were installed, i.e., natural soil moisture regime (CK), soil water supply coefficient (K_w) of 0.8, 0.6, 0.4 and 0.2, respectively. The leaf chlorophyll content in K_w=0.6  was close to that in K_w=0.8, and significantly higher than that in other treatments (p<0.05). In K_w=0.6, the leaf stomatal conductance and transpiration rate were mildly inhibited, while the photosynthetic rate was higher than that in K_w=0.8. In K_w=0.2, the photosynthetic rate, stomatal conductance, and transpiration rate were the lowest. The stomatal limitation was the highest in K_w=0.4, followed by in K_w=0.2, and smallest in K_w=0.8. Treatment of K_w=0.4 had the highest apparent quantum efficiency. Overall, the light compensation point decreased with decreasing soil moisture content, but the light saturation point and the maximum photosynthetic rate were the highest in K_w=0.6, followed by in K_w=0.8, and lowest in K_w=0.2. The antenna transfer efficiency (F_v′/F_m′), electron transfer rate (ETR), actual quantum efficiency of PSII (Ф_PSII), and photochemical quenching (q_P) were the highest in K_w=0.6, followed by in K_w=0.8, and lowest in K_w=0.2. It was inferred that in K_w=0.2, the photosynthetic rate of winter wheat was mainly limited by non-stomatal limitation factors,whereas in K_w=0.4, the photosynthetic rate was mainly controlled by stomatal limitation factors.

Key words: Korean pine with coarse bark, Korean pine with fine bark, tree ring, climate change, Liangshui Natural Reserve.