The Northern Pitcher Plant, Sarracenia purpurea shows morphological diversity across latitudinal and environmental gradients and morphological plasticity in response to experimental nutrient availability. S. purpurea morphology differs between two nearby populations in contrasting wetland environments in SE Wisconsin - a minerotrophic neutral pH fen and an ombrotrophic acidic bog. We posed the questions: 1. Despite carnivory, are pitcher plants macronutrient-limited in these wetlands? 2. Are pitcher plant nutrient content and morphology determined by environment or constrained by genetic identity? To address these questions, the study examined how plant nutrient content and morphology of S. purpurea were related to environment using a reciprocal transplant experiment between the two contrasting wetlands. Morphological traits and N and P content of 60 control and transplanted S. purpurea were followed over 2 years, along with irradiance and dissolved nutrient availability and pH in the wetland surface. Functional nutrient limitation and acclimation to the distinct light environments in the two wetlands were examined using chlorophyll a fluorescence.
Results/Conclusions
In the bog, both macronutrient availability and leaf N content were higher than in the fen. Leaf N content was correlated with wetland nitrate availability (r2 = 0.344). Despite the capability for carnivory, nutrient stoichiometry suggested N but not P limitation in all plants, but there was no evidence for reduced quantum yield of photosynthesis related to nutrient limitation. Bog and fen S. purpurea populations were morphologically distinct but leaf N content and morphological parameters of between-wetlands transplants converged with plants in the new environment over 1 – 2 years. The results showed that N content and morphology of the pitcher plants was determined strongly by environmental conditions, rather than genetic identity. Morphological traits of fen-to-bog transplants changed faster than bog-to-fen transplants suggesting that the low pH and irradiance conditions of the bog may impose greater stress on S. pupurea. Plants were acclimated to lower light in the bog, and irradiance may have contributed to morphological responses. Earlier studies showed morphological responses of S. purpurea with experimental inorganic N addition to pitchers. This study demonstrates that leaf nutrients and morphology of S. purpurea also responds to nutrient supply to the roots due to natural wetland nutrient availability.
