Allelopathic effects of several invasive wetland plants Lythrum salicaria, Rhamnus frangula, Cirsium palustre on seed germination.

Abstract

Wetlands are unique and valuable environments supporting a wide array of specialized flora and fauna. These fragile ecosystems play an important role in flood prevention, shoreline protection, and nutrient cycling. Wetland integrity is threatened by human development and the invasion of exotic species. This study focused on potential allelopathic mechanisms by which several invasive wetland plants threaten native plant viability. We tested volative and water-soluble chemicals from purple loosestrife (Lythrum salicaria), glossy buckthorn (Rhamnus frangula), and European swamp thistle (Cirsium palustre) for allelopathic effects on germination of lettuce and radish seeds. Of the three plants, glossy buckthorn exhibited the most threatening allelopathic potential; leachates from this plant both slowed and reduced germination of lettuce and radish seeds. Leachates of European swamp thistle also slowed and reduced germination of lettuce seeds, but had no effect on radish seeds. Purple loosestrife leachates slowed germination of lettuce, but had no effect of final percent germination. Volatiles from each of the plants showed no allelopathic effects on seed germination. Allelopathy can be a very specific process, affecting only certain species, at certain times, with particular concentrations of allelopathic compounds; therefore, laboratory studies often find allelopathic agents in plants that are of no consequence in field. In this in vitro study, we found that glossy buckthorn inhibited germination of the seeds of two unrelated plants, so it is likely that allelopathic compounds of glossy buckthorn are general in their inhibitory effects. The chance of allelopathic interactions playing a role in the superior competitve nature of glossy buckthorn in the field should be investigated further.