Abstract: By using PV technique, this paper studied the turgor pressure (ψ_P), cell elastic modulus (ε), and relative cell volume (RCV) of super xerophytes Potaninia mongolica, Reaumuria soongorica, Tetraena mongolica and Zygophyllum xanthoxylon in west Alashan, with the relationships among the parameters analyzed. The results showed that R. soongorica had the strongest ability to maintain maximum turgor pressure (a=2.4593). The four plants maintained their turgor pressure by different ways, i. e. , P. mongolica maintained it by elastic adjustment (ε_max=8.4005 MPa),R. soongorica by osmotic adjustment (ψ_π100=-3.1302 MPa; ψ₀=-3.5074 MPa), T. mongolica by both osmotic and elastic adjustment, and Z. xanthoxylon by osmotic adjustment, which had weak adjustment ability. The cell wall of P. mongolica was soft and highly elastic, benefiting to the water absorption by root and stem and to the fast water transmission.T. mongolica also had relatively soft and high elastic cell wall, and its ψ_P and ε changed slowly with decreasing RCV, suggesting that this plant had strong ability of holding water and resisting dehydration.

Key words: Soil particle size fractionation, Loess Plateau, Canadian Prairie