Differential Responses to Light and Nutrient Availability by Geographically Isolated Poison Ivy Accessions

The morphology and growth habit of Toxicodendron radicans (Poison Ivy) varies widely across North America. In this study, we evaluated the role of Poison Ivy accession-level diversity on growth habit and performance responses to light and nutrient stress in a common-garden greenhouse environment. We grew Poison Ivy seedlings derived from drupes collected from Iowa (IA), Michigan (MI), Texas (TX), and Virginia (VA) in a glasshouse with factorial arrangements of 2 light treatments (full sun and deep shade) and 3 nutrient treatments (full nutrients, full nutrients minus nitrogen, no nutrients). Seedlings from Iowa grew very poorly across all treatments, whereas plants from MI, TX, and VA showed accessional variation, though treatment effects were stronger than accession-level effects. We observed significant accession-level differences in height, branch number, leaf area, total biomass, chlorophyll, and root: shoot ratio biometrics; the Texas accession generally outperformed the MI and VA accessions across all treatments. Overall, light availability was a much stronger driver of overall performance than nutrient availability; plants grown in shade were smaller, had fewer branches and produced similar to 20% of the biomass compared to those grown in full-sun. Poison Ivy shows accession-level variation in plastic responses to light and nutrient availability, which partially explains the breadth of habitats the species colonizes.