Growth and resource allocation of water hyacinth as affected by gradually increasing nutrient concentrations

The effect of gradually increasing level of nutrient on plant growth, nutrient acquisition and resource allocation of water hyacinth (Eichhornia crassipes (Mart.) Solms) was examined in greenhouse aquaria with a gradually increasing level and two constant levels (high and low) of nutrient supply. After 8 weeks, plant biomass, total plant N and P, and ramet number were about the same after growing on the media with gradually increasing and high level nutrient treatments. The ratio of below/above-ground biomass decreased continually during the experimental period when nutrient concentration was regularly increased, but not at two constant nutrient treatments. The relative allocations of biomass and nitrogen (N) to roots, leaf stalks and leaves were unaffected by treatment, but the phosphorus (P) allocation ratio differed significantly between treatments. These results indicate that plant growth is stimulated and water hyacinth can duly regulate biomass allocation to optimize resource acquisition when the plants are exposed to an environment where the nutrient concentration is increasing. (C) 2004 Elsevier B.V. All rights reserved.