Polysaccharide compositions of primary cell walls of the palms Phoenix canariensis and Rhopalostylis sapida

The polysaccharide compositions of unlignified primary cell walls from two species of palms were examined. Cell-wall preparations were isolated from t he stem apex, including the pre-emergent leaflets and rachides, of Phoenix canariensis (Canary Island date palm), and from leaflets and rachides disse cted from pre-emergent leaves in the stem apex of Rhopalostylis sapida (Nik au palm). The non-cellulosic polysaccharides in the cell-wall preparations from both species had similar monosaccharide compositions, with arabinose a nd galactose being the predominant neutral monosaccharides, together with l arge amounts of galacturonic acid. These monosaccharide compositions indica ted the presence of large proportions of pectic polysaccharides, including homogalacturonans. This was confirmed by linkage analyses of the cell-wall preparations which showed the presence of large proportions of pectic arabi nans, together with pectic galactans and/or Type I arabinogalactans. Eviden ce for rhamnogalacturonan I and small amounts of rhamnogalacturonan II was also obtained. In addition to pectic polysaccharides, the cell-wall prepara tions contained smaller amounts of xyloglucans and even smaller amounts of heteroxylans, probably glucuronoarabinoxylans, and glucomannans and/or gala ctoglucomannans; (1-->3,1-->4)-beta-D-glucans were not present. Although pa lms (Arecaceae) are commelinoid monocotyledons, the polysaccharide composit ions of their primary cell walls resemble those of non-commelinoid monocoty ledons and dicotyledons. These compositions contrast with those of primary cell walls of other commelinoid families which have glucuronoarabinoxylans rather than pectic polysaccharides as the major non-cellulosic polysacchari des. The results are discussed in relation to the possible evolution of the composition of primary cell walls of monocotyledons. (C) 2000 Editions sci entifiques et medicales Elsevier SAS.