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Background: The fibres dimensions vary along a tree trunk, and these variations are related to the apical
meristem and vascular cambium activities; understanding these variations would guide the best use of
wood. There have been studies on the pattern of fibres dimensions’ variation along the tree trunk in the
radial and longitudinal directions; however, the vast majority do not take into account the structure of
the annual growth rings. Hence, this study aimed to obtain the pattern of fibres dimensions’ variation
and their quality indexes along the tree trunk take into account the structure of the annual growth rings.
Two Eucalyptus urophylla x Eucalyptus grandis hybrid clones were used in the study. Ten-year-old trees
were selected and discs were removed from 13 longitudinal positions. The disks were prepared and the
growth rings were subsequently identified and the samples used for maceration were collected. Twenty
fibres were measured in the annual growth rings present in each longitudinal position.
Results: In the longitudinal direction, within the annual growth rings, the fibre dimensions and their
quality indices did not show a well-defined pattern of variation. In the radial direction, the length, cell
wall thickness, wall fraction, and Runkel ratio of the fibres tended to increase following the pith-bark
direction, while the lumen diameter and flexibility coefficient decreased.
Conclusion: Nevertheless, the fibre width and fibre slenderness index did not present a well-defined
pattern of variation in the radial direction.
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