Allelopathic potential of aquatic plants associated with wild rice (Zizania palustris): I. Bioassay with plant and lake sediment samples

The allelopathic potential of eight aquatic plants associated with wild ric e was investigated using lettuce and wild rice seedling bioassays. Rhizome aqueous extracts of Scirpus acutus, Potamogeton natans, Nymphaea odorata, N uphar variegatum; shoot extract of Eleocharis smallii; whole plant extract of Myriophyllum verticillatum; and leaf extract of P. natans significantly reduced the root length of lettuce and wild rice seedlings. The lettuce see dling bioassay was more sensitive than the wild rice bioassay. Shoot growth was less affected than the root growth. Water extract of sediments associa ted with the aquatic plants had little growth inhibitory effect on wild ric e. Our study did not yield any conclusive evidence that the wild rice-assoc iated aquatic plants have allelopathic effects on wild rice. We emphasize t he use of target species as a bioassay material in allelopathic studies. Fu rther investigation on allelopathic effects of lake sediments associated wi th the neighboring plants of wild rice is necessary to evaluate their ecolo gical significance.