Characteristics of Photosynthesis and Water Utilization Efficiency of Cluster Mulberry Under Different Soil Moisture Conditions

Cluster mulberry is an excellent shrub, which is important in controlling desertified sandy land in arid and semi-arid areas. Photosynthetic characters and water utilization efficiency of cluster mulberry with two-year-old pot-cultured grafting seedlings under 3 kinds of soil moisture conditions were investigated in this paper. The experiment results showed that the diurnal course of net photosynthetic rate (Pn) displayed a two-peak pattern under different soil moisture conditions. Under the normal soil moisture and light drought conditions, the peak value were 17.55 and 15.20 μmol/(m2·s), respectively, which occurred at 11∶00 o'clock. Under the middle drought condition, the peak value was 9.60 μmol/(m2·s), which appeared at 10∶00 o′clock, and the mid-day depression in net photosynthesis started ahead of 1 hour and its duration was longer, both Pn and stomatal conductance (Sc) were decreased. Water utilization efficiency (WUE) culminated in the early morning, WUE in the forenoon was higher than that in the afternoon, and the decrease in daily mean of WUE was less than that of Pn. Whether the stomatal factor acted as limiting factor for photosynthesis depended on the conditions of soil moisture content. While the soil moisture content reduced, the role of non-stomatal limitation increased.