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E. Kukkola, P. Saranpää & K. Fagerstedt
Juvenile
and compression wood cell wall layers differ in lignin structure in Norway
spruce and Scots pine
IAWA J. 29 (1): 47-54
Dibenzodioxocin, an 8-ring
substructure of lignin identified in the mid-1990’s, is known to
occur in softwood cell walls especially in the S3-layers of
normal wood. In this study the lignin substructure was immunolocalised in
juvenile and mature wood as well as in different degrees of compression
wood of Norway spruce (Picea abies
(L.) H.Karst.) and Scots pine (Pinus
sylvestris L.). In juvenile wood of Norway spruce, dibenzodioxocin was
hardly present in the tracheid cell wall, while in Scots pine some
dibenzodioxocin was found evenly distributed in the S2-layers.
In mature normal wood, dibenzodioxocin was localised in the S3-layers
in both Scots pine and Norway spruce. In contrast, in compression wood
tracheids of Scots pine, where the S3-layer is not present,
dibenzodioxocin was found in the S1-layers and in the outer part
of the S2-layers, while in Norway spruce the innermost cell wall
layer showed a strong signal. These findings support the idea that in
mature wood the condensed dibenzodioxocin structure is formed in Norway
spruce at the end of lignification, when the supply of monolignols and
probably also hydrogen peroxide is diminishing. The reasons for Scots pine
juvenile and compression wood showing a different pattern of
dibenzodioxocin labelling is discussed.
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