Lincoln, Jesse .
Ailanthus altissima increases nodulation in Trifolium pratens: a novel weapon for an invasive species.
Ailanthus altissima (Simaroubaceae) is an invasive tree from China that has spread over much of North America. A number of characteristics contribute to its success, including tolerance of poor soils, rapid growth rates and production of allelopathic compounds. Previous studies indicate increased soil nitrogen at sites invaded by A. altissima. Increased available soil nitrogen through an alleochemical interaction with legumes may subsidize A. altissima’s rapid growth on poor soils. Nitrogen-fixing rhizobia are solicited for nodule development by legumes emitting flavonoids into the rhizosphere under low nitrogen conditions. We investigated if and how A. altissima root exudates impact nodulation and growth in Trifolium pratense (Fabaceae). The following treatments were applied to T. pratense in a full factorial design: soil leachate (from soil with or without A. altissima), leachate source fertilization, and T. pratense fertilization. Treatment effects on T. pratense total biomass and shoot:root ratio were complex; however, A. altissima leachates increased nodule biomass: total biomass ratio and doubled the probability of nodulation regardless of other treatments. We are currently monitoring changes in transcript abundance of genes encoding chalcone synthase and chalcone isomerase in T. pratense in response to A. altissima leachates. These genes are involved in the production of the flavonoid released by T. pratense to solicit rhizobia for nodulation. Flavonoid signaling molecules are analogous to early response defensive genes. We predict increased nodulation results from an upregulation along a defense pathway. This previously unreported plant-plant interaction potentially facilitates rapid growth of A. altissima in poor soils via increased nitrogen fixation in neighboring legumes.
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1 - Grand Valley State University, Biology Department, 1 Campus Drive, Allendale, Michigan, 49401, USA
Presentation Type: Poster:Posters for BSA Sections
Location: Event Tent/Cliff Lodge
Date: Monday, July 27th, 2009
Time: 5:30 PM