Structural features of CDTA-soluble pectins from flax hypocotyls

摘要

Polymers extracted with CDTA-Na_2 (trans-diaminocyclohexane-N, N, N, N′-tetra-acetic acid partially neutralized with NaOH) after a boiling water treatment from cell walls of 3-day-old seedlings of flax, germinated on water and in darkness, contained three main components: (1) rhamnogalacturonan Ⅰ (RG-I)-like polymers with ratios of rhamnose to galacturonic acid which increased with their molecular mass; (2) neutral polysaccharides including galactans as well as arabinans; and (3) galacturonic-acid enriched polymers. High degrees of acetylation were estimated for most of the rhamnogalactur-onans but a minor RG-I-like fraction with a ratio of rhamnose to galacturonic acid of unity was acetylated (29%) as well as methylesterified (40%). However, the calcium activity coefficients of the fractionated polymers measured in solution were quite high which implies that these polyelectrolytes did not behave like linear ones. These polymers which reacted in solution as well as in situ not only with ruthenium red but also with ferric hydroxylamine, and which contained large amounts of acetylated RG-I-like blocks might be considered as early markers of the differentiation of the cellulosic fibre cells in flax.