The Occurrence of Translocated Antibiotics in Expressed, Plant Sap

The details of a convenient laboratory press are presented anda procedure by which plant sap is readily obtained is described.The pressing procedure has been shown to release 53–74per cent. of the total plant water as expressed sap. Preliminary observations on the uptake and translocation ofantibiotics by higher plants obtained by examining expressedsap are described. It is shown that the assay of expressed sapprovides a measure of the griseofulvin and chloramphenicol concentrationin leaves of plants grown in solutions of these antibioticsthat does not differ significantly from the value obtained bythe assay of water extracts. Extraction of leaves from plants grown in griseofulvin solutionswith organic solvents demonstrates a much greater antibioticcontent than is indicated by the assay of expressed sap. Toexplain this difference a ‘free’ antibiotic fraction,obtainable in expressed sap or water extracts, and a ‘bound’fraction recovered from the leaf only by organic solvent extractionare postulated.