Bacterial　intraspecies　and　interspecies　communication　in　the　rhizosphere　is　mediated　by　diffusible　signal　molecules.　Many　Gram-negative　bacteria　use　N-acyl-homoserine　lactones　(AHLs)　as　autoinducers　in　the　quorum　sensing　response.　While　bacterial　signalling　is　well　described,　the　fate　of　AHLs　in　contact　with　plants　is　much　less　known.　Thus,　adsorption,　uptake　and　translocation　of　N-hexanoyl-　(C6-HSL),　N-octanoyl-　(C8-HSL)　and　N-decanoyl-homoserine　lactone　(C10-HSL)　were　studied　in　axenic　systems　with　barley　(Hordeum　vulgare　L.)　and　the　legume　yam　bean　(Pachyrhizus　erosus　(L.)　Urban)　as　model　plants　using　ultra-performance　liquid　chromatography　(UPLC),　Fourier　transform　ion　cyclotron　resonance　mass　spectrometry　(FTICR-MS)　and　tritium-labelled　AHLs.　Decreases　in　AHL　concentration　due　to　abiotic　adsorption　or　degradation　were　tolerable　under　the　experimental　conditions.　The　presence　of　plants　enhanced　AHL　decline　in　media　depending　on　the　compounds＇　lipophilicity,　whereby　the　legume　caused　stronger　AHL　decrease　than　barley.　All　tested　AHLs　were　traceable　in　root　extracts　of　both　plants.　While　all　AHLs　except　C10-HSL　were　detectable　in　barley　shoots,　only　C6-HSL　was　found　in　shoots　of　yam　bean.　Furthermore,　tritium-labelled　AHLs　were　used　to　determine　short-term　uptake　kinetics.　Chiral　separation　by　GC-MS　revealed　that　both　plants　discriminated　D-AHL　stereoisomers　to　different　extents.　These　results　indicate　substantial　differences　in　uptake　and　degradation　of　different　AHLs　in　the　plants　tested.　©　2007　Springer-Verlag.