Potential allelopathic effects of several invasive wetland plants (Lythrum salicaria, Cirsium palustre, and Rhamnus frangula) on seed germination.

Abstract

Wetlands are dynamic communities that are extremely sensitive to human development. Human development creates disturbances in ecosystems that allow easier access for invasive species. Invasive species can employ allelopathic chemicals to assist in their establishment and dominance in a disturbed community. I examined the potential allelopathic effects of purple loosestrife (Lythrum salicaria), glossy buckthorn (Rhamnus frangula), and European swamp thistle (Cirsium palustre) on the germination of lettuce (Lactuca sativa) and radish seeds (Raphanus sativus). I tested the potential allelopathic effects of these invasive sepcies by exposing the seeds to leachates and volatiles and recording the amount of germination at 12-h time intervals and the final germination numbers. Purple loosestrife showed an initial lag in the germination of lettuce seed treated with the leachate compared with the control, but not on the final germination. Glossy buckthorn showed the most potential for allelopathic chemicals by the reduction of lettuce and radish seed germination of the leachate. The European swamp thistle showed potential allelopathic effects of the leachate on lettuce seeds. There was no statistically significant difference between the volatiles of each invasive species and the control. Since allelopathy has specific inhibitory properties on certain species, data is often inconclusive. Because of this, further studies need to be performed in order to determine what mechanisms invasive species use to gain establishment and dominance in ecosystems. In order to protect the wetlands from these aggressive species, we must first understand the strategies that the invasive species employ.