Turnover of cell wall polysaccharides of a Vinca rosea suspension culture

Three‐day‐cultured cells of Vinca rosea L. (in the cell division phase) and 5‐day‐cultured cells (in the cell expansion phase) prelabelled with d ‐[U‐ 14 C] glucose were incubated in a medium containing unlabelled glucose. After various periods of chase, extra‐cellular polysaccharides (ECP) and cell walls were isolated, and cell walls were fractionated into pectic substances, hemicellulose, and cellulose fractions. After acid hydrolysis, the radioactive constituents in the pectic substances and hemicellulose fractions were analyzed. Active turnover was observed in arabinose and galactose in the hemicellulose fraction of cell walls, while the constituents of the pectic substances, and xylose and glucose in the hemicellulose fraction did not undergo active turnover. The proportion of radioactivities of arabinose and galactose in total radioactivity of ECP increased markedly after chasing. These results indicate that arabinogalactan was synthesized, deposited in the cell wall, degraded rapidly, and made soluble in the medium as a part of ECP.