[Physiological Characteristics and Nitrogen and Phosphorus Uptake of Myriophyllum aquaticum Under High Ammonium Conditions].

Ammonium nitrogen (NH ₄ ⁺ -N) at high concentrations is toxic to plants. In order to explore the NH ₄ ⁺ -N tolerance of Myriophyllum aquaticum ( M. aquaticum ) and its ability of nitrogen (N) and phosphorus (P) uptake, this study used a nutrient solution with three NH ₄ ⁺ -N levels (70, 210, 420 mg·L ^-1 ) to incubate M. aquaticum for 21 d. The characteristics of plant physiology and N and P uptake of M. aquaticum were measured. At NH ₄ ⁺ -N of 70 mg·L ^-1 , M. aquaticum grew healthily, and shoot height and biomass linearly increased with the increase incubation time. Relative shoot height and biomass of M. aquaticum were 40.56 cm and 17.82 g·hole ^-1 on day 21, respectively. Compared to the control with 70 mg·L ^-1 ammonium, malondialdehyde (MDA) content of M. aquaticum was significantly increased; chlorophyll and soluble sugar contents were also high at NH ₄ ⁺ -N of 210 mg·L ^-1 . M. aquaticum suffered from the NH ₄ ⁺ -N stress. However, the stress of 210 mg·L ^-1 NH ₄ ⁺ -N did not affect its normal growth and there was no significant difference in the relative growth rate of the shoot height and biomass compared with the control. At NH ₄ ⁺ -N of 420 mg·L ^-1 , MDA contents of M. aquaticum doubled and the shoot height and biomass growth rate were only 27.4% and 17.9% of those for 70 mg·L ^-1 NH ₄ ⁺ -N, indicating that M. aquaticum was subjected to serious stress that caused unhealthy growth or even death. At three NH ₄ ⁺ -N levels, the ranges of N and P content of M. aquaticum were 30.7-53.4 mg·g ^-1 and 3.8-7.7 mg·g ^-1 , respectively, which indicated that M. aquaticum had a high uptake capacity of N and P. M. aquaticum is an ideal wetland plant that has a good application prospect for constructed wetlands in biological treatment of high-ammonia wastewater.