The Occurrence of Translocated Antibiotics in Expressed Plant Sap

The details of a convenient laboratory press are presented and a procedure by which plant sap is readily obtained is described. The pressing procedure has been shown to release 53-74 per cent, of the total plant water as expressed sap. Preliminary observations on the uptake and translocation of antibiotics by higher plants obtained by examining expressed sap are described. It is shown that the assay of expressed sap provides a measure of the griseofulvin and chloramphenicol concentration in leaves of plants grown in solutions of these antibiotics that does not differ significantly from the value obtained by the assay of water extracts. Extraction of leaves from plants grown in griseofulvin solutions with organic solvents demonstrates a much greater antibiotic content than is indicated by the assay of expressed sap. To explain 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 extraction are postulated.