Boadway, Cassandra , Dock, Jeff , Greer, Gary .
Growth and Nodulation in Trifolium repens and Glycine max in Response to Ailanthus altissima Extracts.
Ailanthus altissima (Tree-of-Heaven) is a successful invasive widely distributed in the U.S. Ailanthus traits promoting invasion include robust growth, even in nutrient poor soils, and toxicity to native herbivores and vegetation. Growth and response to herbivory on nutrient poor soils require novel nitrogen sources. To explore this possibility, we conducted two experiments testing for water soluble compounds in Ailanthus that affect legume growth and nodulation. In experiment 1, white clover (Trifolium repens) seedlings were watered with aqueous extracts of soil supporting an Ailanthus sapling (treatment) and with extracts of an identical soil mix not supporting Ailanthus (control). Ailanthus soil extract reduced growth and allocation to shoots in clover yet substantially increased the number of plants possessing nodules; whether these effects are due to additive or subtractive activity by Ailanthus remains unknown. If Ailanthus exudes a nodule stimulating compound, it should be present in its roots. In experiment 2, we tested for nodule stimulating compound(s) in Ailanthus roots using soybean (Glycine max) as a bioassay. If a stimulant is produced by Ailanthus, we expect production to vary with nitrogen demand. Thus, we also tested for plasticity in stimulant production by Ailanthus. Aqueous root extracts from seedlings grown under high nutrient, low nutrient, and low nutrient + injury (hole punched leaf) treatments were used to water soybean seedlings. Unlike the 1st experiment, soybean total biomass and nodule presence were similar across treatments. In addition, soybean allocation to shoot biomass increased and nodule: root biomass ratio decreased with increasing Ailanthus stress. These results confirm that Ailanthus produces allelopathic compounds that negatively affect legume growth; however, they also cast doubt that Ailanthus exudes nodule stimulating compounds. Numerous variables differ between the two experiments and we are currently performing an experiment using Ailanthus root extracts to test for nodule stimulation in white clover.
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1 - Grand Valley State University, Biology Department, 1 Campus Drive, Allendale, Michigan, 49401, USA
Presentation Type: Poster:Posters for Sections
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM