Changes in the chemical composition of a cambial cell during its differentiation into xylem and phloem tissue in trees. 2. Carbohydrate constituents of each main component

Publisher Website
Google Scholar
Abstract
The carbohydrate composition of the a-cellu-lose, hemicellulose and pectic substances of the cell walls in the phleom, cambial, sapwood and heartwood regions of 4 trees (Fraxinus elatior, Betula platyphylla, Acer pseudoplatanus, Pinus ponderosa) has been determined. Secondary thickening in the angiosperms was accompanied by the formation of glucans, 56-67%; xylans, 20-33%; uronic anhydride, 8-11%; and mannans, 2-6%. Little change occurred in the amount per cell of arabans. The amount of galactans decreased. Secondary thickening in the gymnosperm was accompanied by the formation of larger amounts of mannans (22%), arabans (1%) and galactans (0.3%) and correspondingly lower percentages of other constituents. The xylans formed during secondary thickening appeared to contain greater amounts of uronic anhydride than that deposited in the primary cell wall. The transition of a sapwood cell into the heartwood involved further formation of glucans and mannans in the angiosperms and of xylans in the gymnosperm. Pectic substances (galactan, araban and polygalacturonic acid) are lost during the development of a cambial cell of the angiosperms into a heartwood cell. Rhamnose appears to be a minor constituent of the pectic substances isolated from all 4 trees. It also occurs in the polysaccharides of the hemicellulose fraction and in both cases it is found only in the primary cell wall. The carbohydrate composition of the cambial cell wall was very similar in each species. The composition and development of the ash, a ring-porous angiosperm, were found to be intermediary between the diffuse porous angiosperm and the gymnosperm.