The uptake of phosphate by Carex species from oligotrophic to eutrophic swamp habitats

Phosphate uptake by excised roots of Carex species from a range of oligotrophic to eutrophic swamps was investigated. The range of species from oligotrophic to eutrophic is: C.rostrata Stokes, C.limosa L., C.lasiocarpa Ehrh., C.diandra Schrank, C.hudsonii A.Benn. and C.acutiformis Ehrh. All species showed two phases for P_i uptake in the P_i concentration range of 0.01 – 50 μM. In phase 1, C.rostrata and C.lasiocarpa had relatively high Vmax:s and Km:s, whereas the species from richer areas had intermediate values. The lowest Vmax and Km values were found in C.limosa and C.hudsonii. In phase 2, apart from the high Vmax and Km values found for C.lasiocarpa, the kinetic constants showed little variation, indicating a similar P_i carrier mechanism for all the species. Results on phosphate uptake and leakage are discussed against the phosphate requirement of each species in its specific habitat, and against the literature data of agricultural crops, which generally show a much lower affinity for phosphate uptake.