Effects of cadmium and nutrients on the growth of the invasive plant Alternanthera philoxeroides

Plant invasions pose a serious environmental problem around the world. The release of heavy metals and nutrients into natural habitats due to human activities is increasing. However, whether nutrient increase can influence the response of invasive plants to heavy metals has been little studied. We hypothesized that increased nutrient availability promotes the growth of invasive plants under heavy metal stress. To test this hypothesis, we conducted a greenhouse experiment on the invasive, widespread, clonal plant Alternanthera philoxeroides. The experiment used a factorial design: a single clonal fragment of A. philoxeroides at three levels of cadmium (Cd) fully crossed with four levels of nutrient availability for four weeks. Increased nutrient availability significantly increased the growth of plants under Cd stress. Moreover, the responses of node number, main stem length, and root-shoot ratio to Cd stress varied among different levels of nutrient availability, which indicates that nutrients can affect the clonal reproduction, stem morphology and biomass allocation of A. philoxeroides under Cd stress. Our results support the hypothesis that increased nutrient availability alleviates the adverse effects of heavy metals on invasive plants. Invasive species such as A. philoxeroides may successfully grow in heavy metal-polluted areas more easily under high nutrient availability.