Cadmium interacts with nitrogen level and nitrogen form to affect the growth of an invasive plant Alternanthera philoxeroides

Abstract

Both heavy metal pollution and plant invasion are serious global environmental problems. Nutrient availability has been shown to influence the performance of invasive plants in heavy metal polluted environments. However, it is still unclear whether the effects of nutrients differ between different forms. We conducted a greenhouse experiment to test the effects of cadmium (0.5, 1 and 2 mg L⁻¹) and nitrogen concentration (0.5, 2 and 8 mmol L⁻¹) as well as nitrogen form (ammonia nitrogen, nitrate nitrogen and glycine) on the invasive, widespread plant Alternanthera philoxeroides. Cadmium did not affect the overall growth of Alternanthera philoxeroides. In the presence of cadmium, plants grew better when provided with nitrate nitrogen than with ammonia nitrogen or glycine. Cadmium interacted with nitrogen level and nitrogen form to affect the growth. At medium (1 mg L⁻¹) and high (2 mg L⁻¹) cadmium levels, promotion of high level nitrate nitrogen (8 mmol L⁻¹) on plant growth was significantly reduced. Our results suggest that the growth performance of Alternanthera philoxeroides in cadmium polluted water is related to both nitrogen level and form. These findings could provide a basis for predicting the spread of Alternanthera philoxeroides in polluted water.