Abstract: In this study，pot experiments were conducted to investigate whether arbuscular mycorrhizal fungi （Glomus mosseae） influenced physiology of Populus euphratica seedlings under a short-term soil water deficit in an extreme arid area. Two-year-old native P. euphratica seedlings inoculated with 20 ml of Glomus mosseae inoculum，a mixture of spores，mycorrhizal root fragments，and rhizospheric soil（Spore density was 50 spores /ml）. Non-inoculated seedlings were put under water deficit treatments at outdoor for a period of 21 days in the lower reaches of Tarim River. The water deficit treatments were imposed by withholding irrigation. The results showed that soil water deficit affected the physiology of Populus euphratica seedlings. However，compared with the non-inoculated seedlings under severe soil water deficit，the inoculated seedlings had greater stomatal conductance，actual photochemical quantum yield of PSII，and photochemistry quenching. After 6 and 15 days of water withholding，the daily changing trend in actual quantum yield of photosystem II （PSII） was similar between the inoculated and non-inoculated groups but not the daily changing ranges. The daily changing ranges of actual quantum yield in the inoculated group were 0.42 and 0.45 while those in the non-inoculated group were 0.48 and 0.51 after 6 and 15 days respectively. The photochemical quenching coefficients in the inoculated group were 0.08-0.11 which was higher than those in the non-inoculated group. During the progressive water deficit，inoculated seedlings had new lateral branches grow out but not the non-inoculated seedlings. The increases of the height and base diameter of the inoculated seedlings were more than those of the non-inoculated seedlings. This study shed a light on the mechanisms of stress-resistance of the plant in arid regions and could provide scientific basis for fully utilizing the Glomus mosseae resources to improve the protection of Populus euphratica from drought stresses in arid regions.

Key words: arbuscular mycorrhizal, water deficit, stress, response