Allelopathic potential of Echinacea angustifolia D.C.

Abstract

Echinacea angustifolia D.C., the common purple coneflower of the western Great Plains, has been shown to produce many biologically active compounds. The allelopathic potential of water soluble and volatile compounds from E. angustifolia plants from three separate populations was examined. Lettuce seeds ( Lactuca sativa), the common allelopathy bioassay system, as well as seeds from two native species, Switchgrass ( Panicum virgatum) and Prairie Dropseed ( Sporobolus heterolepis), potential competitors of Echinacea, were germinated in the presence of aqueous extracts or crushed Echinacea tissues. Percent seed germination, root and shoot elongation and shoot chlorophyll content of the treated seedlings were measured. After 4 days (or 2 weeks for the native species), root extracts and volatiles caused inhibition of seed germination and/or root elongation in all three species. Extracts and volatiles from Echinacea shoots were generally less inhibitory to seed germination and growth. Chlorophyll content was lower in the seedlings treated with the Echinacea extracts and volatiles, with Echinacea roots again eliciting greater effects than shoots. The genetic source of the Echinacea volatiles and extracts also influenced the severity of allelopathic effects. Molecular genetic studies have shown that E. angustifolia plants are highly polymorphic and the wide range of growth inhibition effects produced by extracts and volatiles from different Echinacea plants is consistent with these genetic studies.