|Session IV: Wetlands
||Abstract #: 97408
THE CONTRIBUTION OF CARNIVORY TO THE NITROGEN AND PHOSPHORUS GROWTH NEEDS OF THE BLADDERWORT, UTRICULARIA FOLIOSA
Amanda Bern, Jennifer Richards and Brian Fry
Department of Biological Sciences, University Park, Florida International University, Miami FL, 33199
Utricularia foliosa is a free-floating aquatic carnivorous plant found throughout south Florida's freshwater wetlands. Although there is no question that these plants are capable of capturing and digesting small invertebrate prey, the extent to which carnivory supplies nitrogen and phosphorus for growth of U. foliosa is unknown. In order to determine the relative contribution of carnivory to U. foliosa, we estimated carnivory supply of nitrogen and phosphorus versus the plant growth demand. Estimates from the published literature for other Utricularia species suggest that the maximum contribution from carnivory for nitrogen and phosphorus needs of these plants are 26% and 15% respectively. However our observations for U. foliosa show that maximal values for carnivory are closer to 8% nitrogen and 5% phosphorus. Overall, our findings show that these putatively carnivorous plants in fact obtain most of their nitrogen and phosphorus via foliar uptake. This raises the question of why these plants invest such a large percentage of their biomass in making bladders. In fact, U. foliosa investment in carnivorous organs (bladders) is highly variable. Trap allocation usually varies from 18.8% to 52% of the plants total biomass, but at one field site, the entire population of U. foliosa had no bladders. A transplant experiment showed that this plasticity in bladder production was environmentally induced. We are currently investigating the factors that control plant investment in bladders.