THE PHENOLIC DOMAIN OF POTATO SUBERIN - STRUCTURAL COMPARISON WITH LIGNINS

Natural and wound-healing potato periderms were analysed using thioaci dolysis, a specific lignin degradative method. The nature and relative frequencies of phenylpropane units and of inter-unit bonds comprising this lignin-like domain were determined. Results confirmed that this domain contains guaiacyl G and syringyl S units, similar to lignins of woody angiosperms. The recovery yield of the G and S thioacidolysis m onomers was, however, about one-tenth of that obtained for wood or str aw lignified cell walls. This result suggests that G and S phenylpropa ne units are relatively few in suberized samples. These units occur in different ratios in the natural and wound potato periderms and are as sembled with the same inter-unit bonds as those found in lignins of wo ody angiosperms, although in different proportions. Both the scarcity of the beta-O-4 and beta-1 bonds, and the high terminal to internal un its ratio, suggest that this lignin-like domain is highly cross-linked .