Phenotypic plasiticity in response to soil water content in the invasive species Alternanthera philoxeroides

The phenotypic plasticity of the invasive species Alternanthera philoxeroides were studied in four different soil water contents, which correspond to aquatic habitat, moist habitat, mesophytic habitat and xeric habitat respectively. The largest total length of genet, internode length and total biomass of Alternanthera philoxeroides were observed in the moist and mesophytic habitat. Branching intensity decreased significantly, while root/shoot ratios increased significantly with the decrement of soil water content. Allocation of root biomass showed negative correlation with soil water content significantly, while allocation of stems and leaves decreased significantly with the decrement of soil water content. The results indicated that Alternanthera philoxeroides had a high plasticity response to the environments with different soil water contents. Moist habitat might be the optimum, however, Alternanthera philoxeroides could respond to selection from environments on several different phenotypic organs simultaneously, and show adaptive plasticity through the optimum biomass allocation, which help it survive, grow and propagate under diverse environments successfully.