Growth limiting effects on various terrestrial plant species by an allelopathic substance, loliolide, from water hyacinth

Water hyacinth (Eichhornia crassipes) is one of the most noxious invasive aquatic plants in many countries due to its rapid growth and reproduction rate. Most practical methods to control water hyacinth are mechanical removal of the plants, and chemical and biological controls with large expense for those treatments. For recovery of control costs, beneficial use options for water hyacinth after mechanical removal would be helpful. Therefore, we investigated possible allelopathic effects of extracts and isolated allelopathic substances in water hyacinth. An aqueous methanol extract of water hyacinth inhibited the growth of roots and shoots of cress (Lepidium sativum), lettuce (Lactuca sativa), alfalfa (Medicago sativa), timothy (Phleum pratense) and ryegrass (Lolium multiflorum). Increasing extract concentration increased the inhibition. These results suggest that water hyacinth may cause allelopathic effects and contain allelopathically active substances. The extract was then purified by several choromatographic runs with monitoring the inhibitory activity during all purification steps, and a main allelopathically active substance was isolated. The chemical structure of the substance was determined by spectral data as loliolide. Loliolide inhibited the growth of cress and ryegrass at concentrations greater than 3 and 10. μM. The concentrations required for 50% inhibition of the root and shoot growth ranged from 12.7-27.5 to 27.5-49.7. μM for cress and ryegrass, respectively. These results suggest that loliolide may be an allelopantic substance and contribute to the growth inhibitory effect of water hyacinth. A water extract of water hyacinth also inhibited all test plant species extract-concentration dependently and contained loliolide. In addition, powder of water hyacinth inhibited germination of barnyard grass in the greenhouse condition with powder-concentration dependently. Therefore, water hyacinth may potentially be useful as soil additive materials to control weeds in the sustainable agriculture.