Elodea nuttallii: uptake, translocation and release of phosphorus

Based on the wide range of Elodea nuttallii, from oligo-mesotrophic waters to highly eutrophic environments, it is important to determine its potential effect on the phosphorus cycle, particularly in nutrient-poor lake ecosystems. Therefore, the absorption, transport and release of phosphorus by E. nuttallii plants were studied using P-33. The experiments were conducted in a 2-compartment apparatus for translocation studies and in non-partitioned Erlenmeyer flasks for the determination of uptake kinetics. The plants absorbed phosphorus via both roots and shoots. The phosphorus uptake via shoots significantly exceeded the phosphorus uptake via roots. The absorbed phosphorus was equally translocated via acripetal or basipetal movements, and was incorporated in all parts of the plants tested. The determined phosphorus incorporation rate (IRP) was nearly 5 times lower when phosphorus was fed through the root system, than the IRP when phosphorus was fed through the shoots. Additionally, we detected clear evidence for phosphorus recycling via plants. Phosphorus recycling processes have a substantial effect on the balance of phosphorus acquisition by E. nuttallii. However, phosphorus uptake was exclusively detected during illumination. Considering this strong dependency of phosphorus uptake on light, we assume that the absorption and release of phosphorus might be linked with photosynthesis and respiratory processes. Our results suggest that the effect on lake water of a potential leakage of phosphorus via the shoots might be small.