Carnivorous pitcher plant species (Sarracenia purpurea) increases root growth in response to nitrogen addition

Abstract

Nitrogen (N) deposition from anthropogenic sources can facilitate the encroachment of plant species with high-N demands into nutrient-poor ecosystems such as sphagnum bogs. Prior research has demonstrated that altered leaf morphology of the carnivorous pitcher plant Sarracenia purpurea L. can serve as a biological indicator of increased bog nitrification. Our objective was to assess the effect of N addition on the root morphology of S. purpurea. To make this assessment, nine S. purpurea plants were grown in microcosms with their roots positioned on transparent acrylic tubes so that root growth could be monitored. Three replicate microcosms received either a high-N treatment (1.0 mg NH4-N·L−1), low-N treatment (0.1 mg NH4-N·L−1), or no additional N. After 7 weeks, we scanned the roots with WinRhizo Pro software, recorded leaf dimensions, and measured the dry mass of the roots and leaves. The high-N treatment had significantly greater root length, surface area, and dry biomass than the controls. In contrast, we found no difference in leaf dimensions or aboveground biomass among treatments. The results of this study support our hypothesis that S. purpurea increases root growth to uptake nutrients from the soil under conditions of increased N deposition.