Influence of Substrate Phosphorus Concentration and Plant Density on Growth and Phosphorus Accumulation of Alternanthera philoxeroides

Abstract

ABSTRACT We investigated the effects of three substrate phosphorus concentration and three plant density on the phenotypic plasticities of the invasive plant, alligator weed (Alternanthera philoxeroide, Amaranthaceae). Phosphorus concentration affected mainly the plant tissue phosphorus accumulation, while plant density affected mainly growth traits, especially those of the stem. The greatest stem mass and stem basal diameter occurred with the combined treatment of medium substrate phosphorus concentration and high plant density (64 ind. m−2), while the greatest stem length and internode number occurred with medium phosphorus concentration and low plant density (16 ind. m−2). Alligator weed had highest leaf, stem, and root phosphorus concentrations with treatment of high phosphorus concentration and low plant density (16 ind. m−2). These results suggest that alligator weed has plasticity in response to substrate phosphorus and plant density and adapts to high phosphorus by accumulating more phosphorus into plant tissues and to high plant density by producing larger but less vegetative individuals, these are strategies that might facilitate invasiveness in eutrophic shallow waters.