Allelopathic effect of invasive wetland plants (Lythrum salicaria, Cirsium palustre, Rhamnus frangula) on seed germination.

Abstract

Wetlands are a very unique and fragile ecosystem supporting a wide variety of rare endemic flora. Human disturbances are having a large negative effect on wetlands. Not only construction but introduction of invasive species is detrimental to wetlands. Many of these invasive species are imported for garden use then escape into wetlands and change components of the ecosystem. In our study we examined potential allelopathic effect of invasive species. Allelopathy may be one way invasives take over a landscape. Volatiles and leacheates from purple loosestrife (Lythrum salicaria), European swamp thistle (Cirsium palustre), and glossy buckthron (Rhamnus frangula) were used to test effects on rate and germination of lettuce and radish seeds. The volatiles had no effect on either rate nor germination. Leachate from the purple loosestrife had no effect on seed germination. The European swamp thistle negatively affect lettuce seed germination. Glossy buckthorn inhibited seed germination of both lettuce and radish seeds. The leachates from all invasive species had an effect on rate of germination of lettuce seeds. Glossy buckthorn has the strongest effect on seed germination and has potential allelopathic effects on native wetland plant species. Allelopathy may be workin in concert with other factors to crowd out native plants. Chemical compounds from the plants may combine with compounds in the soil and then have an allelopathic effect. Studies in the field would provide more practical data on allelopathy and if it plays a role aiding invasives.