Abstract
ABSTRACT Tension wood is an important anatomical structure for its participation in the orientation of the trunk and the architecture of the branches as a function of structural reinforcement. However, its presence in large amounts significantly affects the technological properties of wood, just as in the rubber tree. Nevertheless, there is still demand for information about the origin, distribution and structural features in this species. Thus, this study aims to characterize the cellular structures in tension and opposite wood in Hevea brasiliensis (rubber tree), as well as its radial and longitudinal distribution. Discs at the base and the middle of the commercial logs were collected from three trees in a commercial plantation located in Tabapoã - SP. Tangential diameter of vessels, fiber length (gelatinous and non-gelatinous fibers), microfibril angle and proportionality of cellular elements (vessels, axial parenchyma, ray, gelatinous fibers and non-gelatinous fibers) were measured, and influence of gelatinous fiber presence in vessel diameter was observed. Gelatinous fibers were observed in the two types of wood and in the two trunk heights. Both types of wood were distinguished by gelatinous fiber length and the proportion of axial parenchyma. The tension wood in mid-trunk was the most different, with long gelatinous fibers and less abundant, larger vessel diameter and vessel proportion. Moreover, smaller vessel diameter was observed in the regions with a high proportion of gelatinous fibers, suggesting that the plant invests more support than in liquid transport.
Highlights
Wood presents variations in its technological properties according to its structural direction, which may have genotypic or phenotypic origin
This study aims to characterize the cellular structures in tension and opposite wood in Hevea brasiliensis, as well as its radial and longitudinal distribution
This study analyzed the cellular characteristics of tension and opposite wood in rubber trees
Summary
Wood presents variations in its technological properties according to its structural direction, which may have genotypic or phenotypic origin. Tension wood is often defined as a specialized tissue that can force the trunk and branches of the tree to maintain a certain orientation, being assigned to the reorientation function of the trunk and branch architecture (FISHER; STEVENSON, 1981). It can be observed in upright/straight trunks (CÔTÉ; DAY; TIMELL, 1969), and this fact brings into question the function of reestablishing the trunk’s position (FOURNIER et al, 2014). The main characteristic of this type of wood is the presence of long fibers which have a thick cellulose layer in its interior known as gelatinous layer, almost entirely filling the lumen (DÉJARDIN et al, 2010). This layer provides particular biochemical, mechanical and ultrastructural characteristics (PRAMOD et al, 2013)
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