Thin-layer chromatograms of 90% ethanol extracts of dried culture filtrates from P. fluorescens SBW25 and WH6. A. Ninhydrin-stained cellulose TLC chromatograms. B. Ninhydrin-stained GHL-silica TLC chromatograms. Sample preparation and application and the solvent systems used to develop the chromatograms are described in the Methods section. The ninhydrin band corresponding to FVG is indicated on the WH6 chromatogram.