Acute biochemical responses of a submersed macrophyte, Potamogeton crispus L., to high ammonium in an aquarium experiment

Acute biochemical responses of Potamogeton crispus L. to high external ammonium were investigated in an aquarium experiment. Shoots of P. crispus were incubated in aquaria for 24 h or 48 h at five treatments of ammonium-0, 1, 5, 10 and 20 mg/L NH4-N. Soluble sugar content of the shoots declined markedly with increasing ammonium levels, whereas soluble amino acid content increased dramatically. Responses of two antioxidant enzymes as well as soluble protein content fit a lognormal distribution with increasing ammonium levels. High ammonium levels (NH4-N greater than or equal to 5 mg/L) caused significant acute biochemical changes in P. crispus, which potentially could lead to significant biochemical damage.