This study aims to identify the growth, nutrient uptake, and purification efficiency of Ipomoea aquatica, Lolium multiflorum, and Sorghum sudanense under different nitrogen levels. In comparison with NH4+, or NO3- as the sole N source, the relative growth rate (RGR) and biomass of three species culture in the NH4NO3 solution increased significantly (p<0.05); the maximum uptake capacity (V-max) of NH4+ was higher than that of NO3- whereas the K-m were slightly lower than that of NO3- of three species; the addition of NO3- to the NH4+ solutions stimulated the NH4+ uptake, whereas, the addition of NH4+ to the NO3-solutions suppressed NO3- uptake of three species; L multiflorum at the studied supply rates of nitrogen exhibited a higher uptake capacity and a lower affinity for ammonium, conforming with adaptation to a high NH4+ nutrient levels. However, the S. sudanense has a competitive advantage over the other two species at high NO3- nutrient levels; the NH4+; and NO3- purification efficiency had obvious changes when High-nitrogen and Low-nitrogen wastewater were treated by three species. These findings would help select a suitable species to remove contamination and improve water quality in constructed wetland treatment systems. (C) 2011 Elsevier B.V. All rights reserved.