In this paper, we present different results obtained by the in vivo approach on the intracellular transport of lipids and fatty acids to the plasma membrane of seven-day-old etiolated leek seedlings. The complexity of the processes involved in plasma membrane biogenesis needs further investigations at both the molecular and cellular levels, but, at the cellular level, this complexity probably exceeds the possibilities of the in vivo analysis.Accordingly, a new approach, based on in vitro cell-free systems, which has proved to be suitable for studies on protein transport, was developped recently to study the membrane transfer of lipids. Some preliminary results concerning this new approach are presented and discussed.

Abstract The effects of monensin on the intracellular distribution of neosynthesized lipids and fatty acids between different membrane fractions prepared from etiolated leek seedlings, were investigated. The penetration of the drug into the seedlings was measured after resolution of monensin by thin-layer chromatography with a solvent system consisting of hexane/diethyl ether/acetic acid (20:80:2, v/v). The concentration of monensin in the microsomal membranes as a function of the external monensin concentration was quantified. The effects of various amounts of the drug on lipid metabolism were studied to determine monensin concentrations having only slight effects on the overall lipid synthesis. Using such conditions, an accumulation of neosynthesized lipids was found in a subcellular membrane fraction enriched in Golgi membranes.