STRUCTURAL FEATURES OF CELL-WALL POLYSACCHARIDES OF POTATO (SOLANUM-TUBEROSUM)

Cell-wall material from the parenchyma of mature potato tubers was fractionated by successive extractions with cyclohexane-trans-1,2-diaminetetra-acetate (CDTA) at 20°, 0.05m Na2CO3 at 1° and 20°, 0.5m and m KOH at 1°, m and 4m KOH at 20°, and 4m KOH + borate at 20° to leave the α-cellulose residue, which contained a significant amount of pectic material. The isolated polymers were fractionated by anion-exchange chromatography. The CDTA-soluble pectic polysaccharides were less branched than those solubilised by Na2CO3. The Na2CO3 (20°) extract contained appreciably more neutral side-chains. The residual cell wall contained cellulose and a highly branched pectic polysaccharide with a significant content of (1→4)-linked galactose residues. There were two main types of xyloglucan that had different degrees of branching. The less branched, solubilised by stronger alkali, were more strongly associated with the cellulose microfibrils. The cell wall contained 1.7% of protein and the content of hydroxyproline was low. Several of the fractions contained protein (0.2-18.0%), but only the fraction solubilised by 4m KOH + borate contained a high level of hydroxyproline. The neutral component of this fraction was also rich in hydroxyproline and contained (1→2)- and (1→3)-linked arabinose. © 1990.