Wednesday, November 15, 2006

Edaphic Controls on the Phytochemistry of the Invasive Plant Alliaria petiolata.

Anna Abts1, Kimberly Lang1, Sherri Morris1, Steven F. Vaughn2, and Kelly D. McConnaughay1. (1) Bradley University, 1501 W. Bradley Avenue, Peoria, IL 61625, (2) USDA-ARS, NCAUR, 1815 N. University St., Peoria, IL 61606

Alliaria petiolata (garlic mustard), an invasive species in temperate forests throughout North America, is associated with decreases in above and belowground species diversity and alterations to nutrient turnover.  Garlic mustard produces a set of secondary chemicals in the glucosinolate family, specifically sinigrin and glucotropaeolin, which are carbon-rich plant products derived from amino acids, containing both nitrogen and sulfur.  When plant cells rupture, the glucosinolates in the vacuoles become hydrolyzed, resulting in the production of biocidal cyanide-releasing compounds.  It is believed that these glucosinolates contribute to the plants’ success as an invasive species.  We hypothesizde that carbon and nitrogen availability in the environment will modulate internal (tissue level) C and N availability, which in turn modulate glucosinolate production.  We predicted that glucosinolate levels will increase with carbon and nitrogen availability.  We examined glucosinolate production, tissue carbon, and nitrogen in natural populations of garlic mustard.  We examined light availability and soil chemical and physical characteristics to determine impacts on plant growth and chemical production.  Root sinigrin content, carbon content, and root mass differed across light environments as did soil pH, bulk density, and moisture.  Sinigrin concentration in roots of second year plants was significantly positively correlated with soil pH across sites and negatively correlated with sinigrin levels of first year plants.  This leads to the possibility that garlic mustard affects soil properties. We detected an increase in soil respiration as we increased glucosinolate concentrations using short-term laboratory incubations.  This suggests that glucosinolates cause a change in the microbial community either by altering microbial density or diversity.  Garlic mustard’s phytochemistry contributes strongly to its role as an ecological change agent, therefore, understanding the factors that regulate glucosinolate production will improve our ability to manage systems that are, or could become, dominated by this aggressive invader.