Allelopathy in Dwarf Spikerush (Eleocharis coloradoensis)

Abstract

The production of new shoots of American pondweed (Potamogeton nodosusPoir.) and sago pondweed (P. pectinatusL.) was reduced significantly when winterbuds and tubers of these species were planted in dwarf spikerush [Eleocharis coloradoensis(Britt.) Gilly] sod. In most instances, the number of shoots produced was several times greater when winterbuds and tubers were planted in bare soil than when planted in spikerush sod. Similar results were obtained when the pondweeds were grown in separate aquaria, each aquarium being exposed to 500 ml of leachate per day from spikerush sod. The differences in reproduction of pondweeds could not be attributed to altered water quality nor to reduced levels of nutrients. No appreciable allelopathic response was elicited by the pondweed plants originating from planted tubers or winterbuds. The principal response appeared to be reduction in numbers of new shoots produced from the original propagules, although the reduction in biomass of the pondweeds exposed to the effects of spikerush was obvious. Of the two pondweeds investigated, sago pondweed was most sensitive to the influence of spikerush.