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

Abstract

The question whether or not the success of invasive plants is due to the combination of an aggressive growth cycle and allelopathic chemicals is important in assessing their potential success. In wetlands, the ability to effectively compete for space and nutrients is a strong factor in the success of plants. Invasive plants can be a problem in United States swamps, where they grow rapidly over existing vegetation. While invasives usually have physical qualities that enhance their success (thick roots, fast growth rate, large seed dispersal capacity), chemical inhibition may play a role too. Our experiment tested both the effect of 1) volatiles and 2) water based leachate on the germination success of lettuce and radish seeds over a 60 hour period. We collected three species of invasives near swamps in the vicinity of Pellston, MI: glossy buckthorn, purple loosestrife and European swamp thistle. They are all non-native, introduced within the last 150 years, and have invaded swamps, bogs, and other wetlands of the United States. We found that glossy buckthorn volatiles and leachate and European swamp thistle leachate inhibited germination in lettuce seeds. Glossy buckthorn leachate inhibited germination in radish seeds. The use of allelochemical agents can involve multiple chemicals in various plant parts. Therefore, our results provide a preliminary assessment of the presence of chemical interactions in wetland invasives.