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We investigated whether there is a relationship between nitrate accumulation and geographic origin of Haloxylon ammodendron C. A. Mey, a xero-halophyte growing in both saline and sandy deserts in Central Asia. A pot culture experiment was conducted with two NaCl levels (1 and 300 mmol/L) factorially combined with three nitrate levels (0.05, 1 and 10 mmol/L) as Ca(NO3)(2) and KNO3 under greenhouse conditions. The results indicated that root biomass and root relative growth rate in the plants from a saline desert population were significantly reduced at 300 mmol/L NaCl, while no significant effect was observed in the plants from a sandy desert population. Meanwhile, salinity led to a significant increase in the concentrations of NO3- in the roots of both populations, and the increase of nitrate concentration in plants from the sandy desert population was significantly greater than that of the saline desert population. The estimated contribution of NO3- to osmotic potential in roots of the sandy desert population at 300 mmol/L NaCl was about 2.9 times those of the saline desert population. It is concluded that H. ammodendron from the sandy desert population may exert superior NO3- uptake ability in the roots compared with the saline desert population. This trait was related to the variations of inherently different root growth, which was the result of selection and adaptation to different desert environments.