Physiological response and tolerance of Myriophyllum aquaticum to a wide range of ammonium concentrations.

Myriophyllum aquaticum (M. aquaticum) can be used in constructed wetlands (CWs) to effectively purify swine wastewater with high-ammonia nitrogen (NH 3 –N and NH 4 +-N) concentrations. However, the understanding of its tolerance mechanism to ammonia nitrogen is limited. The physiological response and tolerance mechanism of M. aquaticum to a wide range of NH 4 + concentrations (0–35 mM) were investigated in the present study. The results indicated that M. aquaticum can tolerate NH 4 + concentrations of up to 30 mM for 21 days and grow well with high nutrient (N, P) uptake. A suitable concentration of NH 4 + for a better growth of M. aquaticum was 0.5–20 mM. The free NH 4 + content was no obviously increase at NH 4 + concentration below 15 mM, indicated there was no obviously ammonium accumulation. Exogenous NH 4 + inhibited K+ absorption and improved Ca2+ absorption, indicating mineral cation could mediate NH 4 + homeostasis under NH 4 + stress. Moreover, comparison with those in the control group, the activities of glutamine synthetase (GS), glutamate synthetase (GOGAT) in M. aquaticum increased by 52.7%−115% at 1–20 mM NH 4 +, and superoxide dismutase (SOD) increased by 29.2–143% at 1–35 mM NH 4 +. This indicated that the high NH 4 + tolerance of M. aquaticum was mainly due to the balance of free NH 4 + content in tissues, as well as improved nitrogen metabolism and antioxidant system. This could be attributed to the role of the GS-GOGAT cycle and SOD. In conclusion, M. aquaticum, which tolerates high NH 4 + concentration and has a high N uptake ability, can be used as a good candidate specie to help develop more efficient management strategies for treating high-NH 4 + wastewater in CW systems. • Myriophyllum aquaticum can tolerate high ammonia up to 30 mM. • Improving nitrogen metabolism and antioxidant system can alleviate ammonia stress. • Myriophyllum aquaticum is a good specie for treating high-ammonia wastewater. [ABSTRACT FROM AUTHOR]