Changes in esterified pectins during development in the flax stems and leaves

Winter oil flax species (Linun usitatissimum L) seedlings were harvested along the development at the dormancy, elongation, maturation and senescence periods, and pectins in stems and leaves were extracted in acid and analysed. The monosaccharides analyses indicated presence of the specific sugar of pectins in the extracts. Co-extraction of arabinogalactan polysaccharides with pectins was possible whereas extraction of hemicellulose material seemed unlikely in regard to the absence of xylose and facose. The yields of pectins extraction from the stems changed over time and decreased along the development, 7% at the dormancy stage and 2% at senescence, whereas the leaves led to constant yields of pectins over ageing (similar to 4%). In the stems, pectins incorporated galacturonic acid as maturation process, from 53% at dormancy to 66% during senescence. In the leaves, the pectins appeared more acidic than in the stems, and changes along development in composition and size were not significant. During development, methylation of acid-soluble pectins was high (80-100%) and varied moderately, whereas the degree of acetylation was important (23-40%) and increased slightly. Globally, modifications of pectins from leaves were more limited compare to stems, and mild acid extraction indicated that high molecular weight esterified pectins are present or still synthesised in flax until senescence. (c) 2006 Elsevier Ltd. All rights reserved.