Water stress suppresses the accumulation of oilseed rape biomass and decreases chlorophyll content and leaf water status (Liu et al., 2013). Yin et al. (2005) reported that shoot height, dry mass accumulation, leaf number, total leaf area, and fine root mass significantly decrease under water stress. Biomass is a key parameter that influences plant growth; therefore, the accumulation and distribution of dry mass are major considerations when investigating the effect of water stress on plant growth. Plant photosynthesis is closely affected by environmental factors, such as water stress (Wu et al., 2010). Therefore, research on plant photosynthesis and biomass allocation under water stress is important for revealing the mechanism by which plants adapt to drought.The perennial deciduous shrub Prunus mongolica is an endemic, endangered, and third-class nationally protected species in China. This species is a suitable ecological and landscape plant and an important resource plant in China because its seeds can be used as food, medicine, and fuel. It is mainly distributed in Neimenggu, Ningxia, and Gansu in northwestern China (Siqinbateer and Xiu, 2007). However, natural forests dominated by P. mongolica can only be found in the desert regions and arid slopes