Anatomical responses of Cedrus libani (Lebanon Cedar) wood to mechanical stress

Barbaros Yaman , Esra Pulat, Mirela Tulik

Wood (secondary xylem) is a source of information about events that occurred during their lifespan. The aim of our research was to provide the pattern of modification of Lebanon cedar wood under the influence of mechanical stress, as a result of binding its trunk with string or wire. The wood samples were taken from a young Cedrus libani (14 years old - evaluated based on the number of growth rings) growing in the Agdaci campus of Faculty of Forestry, Bartin University. They were taken from three different levels of the trunk including the strangulation point, and above and below this point. Using standard protocols, cross-sections of the taken wood were prepared. Then, the morpho-anatomical features of wood were examined: (i) tracheid radial diameter (TRD), (ii) cell wall thickness of tracheid (CWT), (iii) tracheid radial diameter divided by cell wall thickness (TRD/CWT), (iv) tracheid number per mm2 (TN), (v) tracheid length (TL), (vi) ray number per mm (RN), (vii) ray density per mm2 (RD), (viii) ray height (RH), (ix) parenchyma cell number in rays per mm2 (PCN), (x) percent of uniseriate rays (PUR), and (xi) percent of biseriate rays (PBR). Among the analyzed biometric features, those concerning the rays and parenchyma cells differed significantly between the wood samples taken from different trunk levels at p < 0.01. Both axial and radial traumatic resin ducts were observed. There was no significant difference in TRD, CWT and TRD/CWT between levels. We postulate that increased the amount of parenchyma in wound secondary xylem by producing both uni- and biseriate rays as well as traumatic resin ducts facilitates compartmentalization and wound closure and reflect the phenotypic plasticity and structural adaptations of the cedar wood to respond to injury and physiological needs.