A function of the Golgi apparatus in polysaccharide synthesis and transport in the root-cap cells of wheat

Abstract

A radioautographic study of the cells of the root tips of wheat incubated with D-[1-or 6-H3] glucose has shown that labelled material is formed in the Golgi apparatus of the root-cap cells. This material passed to the vesicles associated with the Golgi bodies and then moved through the cytoplasm across the plasmalemma and was incorporated into the cell wall and slime layer of the tissue. Analysis of the labelled material extracted from the root tips showed that the bulk of the radioactive material was polysaccharide; there were relatively small amounts of labelled lipids and protein in the tissue. Starch was formed from the exogenous labelled glucose and it was located in the plastids of the cell. The synthesis of starch depended on the metabolic activity of the cells, which varied with the position of the cell in the various tissues of the root tip and with the amount of the exogenous glucose. Isolation of the radioactive polysaccharides from the root tip incubated in the radioactive glucose has shown that the glucose was very rapidly incorporated into the galactosyl residues of the polymers. Analysis of the radioactive polysaccharides has indicated that the material transported in the Golgi vesicles is probably pectic substance. A scheme for the synthesis of the storage and wall polysaccharides by separate routes and their location within the cell has been put forward.