Marcelo Zimmer is a Ph.D. student with Dr. Bill Johnson investigating the different glyphosate-resistance mechanisms in giant ragweed (Ambrosia trifida).  The overall objectives of Marcelo's research are to evaluate metabolic and genotypic differences between the rapid response biotype and the non-rapid response biotype and identify and factor that trigger these responses.  Understanding of these resistance mechanisms may be helpful to develop new weed management strategies.