Nitrate (NO3- -N) and ammonium ( NH4+ -N) are two major inorganic nitrogen forms in eutrophic water. Study on NO3- -N and NH4+ -N uptake kinetics of aquatic plants can help to find the hydrophytes that efficient removal of nitrogen in eutrophic water. The nutrient uptake kinetics of Iris louisiana, Myriophyllum verticillatum, Zizania latifolia and Oenanthe clecumbens were investigated using the concentration gradient method after plants were grown for 15 days in Hogland nutrition liquid. Results showed that NO3- -N and NH4+ -N uptake kinetics of the 4 species could be expressed by the Michaelis-Menten equation. The NO3- -N and NH4+ -N uptake rates of hydrophytes enhanced with increasing NO3- -N and NH4+ -N content; however, when the solution increased to 2.0 mmol/L, the increasing amplitude of the uptake rates would reduce. The maximum rate ( Vmn) of uptake NO3- -N and NH4+ -N by the 4 species of hydrophytes followed the order: Oenanthe clecumbens > Zizania latifolia > Iris louisiana > Myriophyllum verticillatum. The chemical affinity( Km ) of NO3- -N followed the order: Oenanthe clecumbens > Iris louisiana = Zizania latifolia = Myriophyllum verticillatum. The Km of NH4+ -N followed the order; Oenanthe clecumbens > Myriophyllum verticillatum > Iris Louisiana = Zizania latifolia. According to parameters( Vmta , Km ) of uptake kinetics, as a conclusion, Oenanthe clecumbens is suitable for purifying high NO3~ -N and NH4+ -N content waters, but Zizania latifolia, Iris louisiana and Myriophyllum verticillatum are just opposite. The four hydrophytes have showed different preferences of uptake NO3- -N and NH4+ -N form solution. The potential of uptake NO3- -N form solution by Iris louisiana was higher than that of uptake NH4+ -N, but the chemical affinity of uptake NH4+ -N was higher than that of uptake NO3 -N, this show that Iris Louisiana preferentially uptake NH4+ -N from high NO3- -N content water. Myriophyllum verticillatum and Oenanthe clecumbens are equivalent in absorbing NO3- -N and NH4+ -N. Zaania latifolia showed higher potential and chemical affinity of uptake NH4+ -N than N03- -N.%采用浓度梯度法,研究了鸢尾(Iris louisiana)、狐尾藻(Myriophyllum verticillatum)、茭白(Zizania latifolia)和水芹(Oenanthe clecumbens)对硝态氮(NO3--N)和铵态氮(NH4+-N)吸收动力学特征.结果表明:4种水生植物对水体NO3--N和NH;-N吸收可用Michaelis-Menten酶动力学方程描述,随溶液NO3--N和NH4+-N浓度增加,植物吸收NO3--N和NH4+-N速率增加,当溶液NO3--N和NH4+-N浓度接近于2.0 mmol/L时,吸收速率增加趋缓；4种水生植物对NO3--N和NH4+-N的Vmax值大小为水芹＞茭白＞鸢尾＞狐尾藻,对NO3--N的Km值大小为水芹＞鸢尾=茭白=狐尾藻,对NH4+-N的Km值大小为水芹＞狐尾藻＞茭白=鸢尾.根据吸收动力学参数(Vmax,Km)判断水芹适宜于净化NO3--N和NH4+-N浓度较高的水体,茭白、鸢尾和狐尾藻适合净化NO3--N和NH4+-N浓度较低水体；4种水生植物对NO3--N、NH4+-N表现出不同的吸收偏好性,鸢尾吸收NO32--N的潜力大于吸收NH4+-N的,但对NH4+-N的亲和力大于NO3--N,表明能在NO3--N浓度较高环境中优先吸收NH4+-N.狐尾藻和水芹对NO3--N和NH4+-N能均衡吸收.茭白对NH4+-N具有较高的吸收潜力与亲和力.
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