[Physiological responses of Myriophyllum spicatum to ammonium nitrogen]

With the sediment applied with 0, 0.24%, and 0.48% NH4Cl (treatments CK, SN1, and SN2) as the substrate, a greenhouse experiment was conducted to study the physiological responses of Myriophyllum spicatum to ammonium nitrogen. The NH4+ -N concentration in the sediment, pore-water, and overlying-water ranged in 12.35-870.32 mg x kg(-1), 1.09-1036.05 mg x L(-1) and 0.10-24.30 mg x L(-1), respectively. Comparing with those in CK, the plant height, root length, and fresh biomass of M. spicatum in treatments SN1 and SN2 decreased by 15.66% and 55.52%, 45.72% and 67.65%, and 19.69% and 81.16%, respectively. The SOD activity in M. spicatum leaves and roots was SN1 < SN2 < CK, but the peroxidase (POD) and catalase (CAT) activities in the leaves were SN2 < SN1 < CK, while those in the roots were significant higher in SN, and SN2 than in CK. The malondialdehyde (MDA) contents of leaves and roots in SN1 and SN2 were increased by 46.30% and 82.75%, and 19.66% and 55.19%, respectively. It was suggested that NH4+ -N had toxic effects on M. spicatum, and the higher the NH4+ -N concentration in sediment, the more obvious the physiological responses of M. spicatum exhibited.