Effect of Ammonia Stress on Physiological and Biochemical Character of Phragmites australis in Constructed Wetland

The function of a constructed wetland system may be affected by high ammonia concentrations, which are toxic to wetland plants. This research was conducted to assess the tolerance of Phragmites australis to ammonia. P. australis is a reed species commonly used in constructed wetlands. The photosynthetic rate (Pn), peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD) activities and the proline and malondialdehyde (MDA) contents were investigated under different concentrations of ammonia (0, 80, 160, 320, and 640 mg L^-1). P. australis grew well at ammonia concentrations of up to 160 mg L^-1, but growth was inhibited at higher levels. Ammonia also induced the activity of antioxidative enzymes such as SOD, POD, and CAT, suggesting that ammonia can cause oxidative stress. Oxidative stress may be part of the mechanism of ammonia toxicity. Thus, ammonia concentrations should be managed to maintain the effectiveness of constructed wetland systems.