Aims Prunus mongolica is a xeric shrub, a landscape plant, a water and soil conservation plant, and an ancient species in the desert and desert steppe of the Mongolian Plateau, China. It tolerates extreme aridity and poor soil, growing strongly in desert where annual rainfall is <200 mm and annual evaporation is 3 400-4 000 mm. Study of P. mongolica is useful for understanding plant succession on the Mongolian Plateau and for sustaining and restoring the local ecosystem.
Methods The Abbe refractometer method, the natural dehydration method and the PV technique were used to analyze the hydrological characteristic of P. mongolica.
Important findings The relative water content, saturation water content, critical saturation deficit and water potential of P. mongolica seedling leaves were 6 9%, 117%, 48% and -0.85 MPa, respectively. The relative water content, critical water content and leaf water potential of P. mongolica seedlings exposed to drought stress decreased to 48%, 39% and -1.97 MPa, respectively, but the saturation water content and the ratio of bound water/free water increased to 187% and 11.94, respectively. The natural dehydration experiment indicated that P. mongolica seedlings reached equilibrium after 102 h in normal condition, but the dehydration rate decreased and the dehydration equilibrium time was delayed after 3 d of drought stress. This proved that the water-holding ability of P. mongolica increased after drought stress. In comparing the dehydration rates of the xerophytic P. mongolica and the mesophytic P. pedunculata, we discovered that the dehydration tolerance capacity of P. mongolica was higher than that of P. pedunculata. Analysis of PV curve showed that osmotic potential (Ψπ100) of water saturation and osmotic potential (Ψπ0) at turgor loss point of P. mongolica seedling were -2.49 MPa and -3.11 MPa, respectively. The fact that the difference of Ψπ100 andΨπ0 was very large and the values very low showed that P. mongolica had strong ability to regulate turgor pressure. The ratio of bound water/free water was relatively high (7.76), and the modulus elasticity of cell wall was 4.18 MPa. The low leaf water potential and low osmotic potential of P. mongolica were beneficial for absorption of water from soil depths. Our results indicated that P. mongolica was a strong xerophyte in terms of hydrology. Its high ratio of bound water and free water, low osmotic potential at saturation water content, osmotic potential at turgor loss point and low modulus elasticity of cell wall were the physiological fundamentals of its dehydration tolerance.