Variation in wood properties among five full-sib families of Norway spruce (Picea abies)

Genetic- and environmental variation and correlation patterns were characterized for modulus of elasticity (MOE), modulus of rupture (MOR) and related wood traits: latewood proportion, wood density, spiral grain, microfibril angle and lignin content in five full-sib families of Norway spruce. The families were evaluated on the basis of clearwood specimens from the juvenile -mature wood transition zone of 93 sampled trees at age 30 year from seed. Family-means varied significantly ($p$ < 0.05) for all wood traits studied except lignin content. MOE varied between 7.9–14.1 GPa among trees and 9.4–11.0 GPa among families. MOR varied between 47–87 MPa among trees and 61–71 MPa among families. Families remained significantly different in an analysis of specific MOE (MOE/density) and MOR (MOR/density). Hence, solely relying on wood density as a wood quality trait in tree breeding would not fully yield the potential genetic gain for MOE and MOR. Correlations between wood structural traits and specific MOE and MOR are presented and discussed.Variabilité des propriétés du bois pour cinq familles de pleins-frères d'épicéa commun (Picea abies). La variabilité génétique et environnementale pour le module d'élasticité (MOE), le module de rupture (MOR) et certaines autres propriétés de base du bois (proportion de bois final, densité du bois, angle du fil, angle des microfibrilles et teneur en lignine) ont été étudiées au sein de cinq familles de pleins-frères d'épicéa commun ainsi que la liaison entre caractères. L'analyse a été réalisée à partir d'échantillons sans défaut issus de la zone de transition entre bois juvenile et bois mature de 93 arbres âgés de 30 ans (depuis la graine). Des différences significatives ($p$ < 0.05) entre familles ont été observées pour tous les caractères sauf pour la teneur en lignine. Les valeurs de MOE variaient entre 7.9–14.1 GPa entre arbres et entre 9.4–11.0 GPa entre familles. Pour MOR, ces valeurs s'échelonnaient entre 47–87 MPa entre arbres et entre 61–71 MPa entre familles. Les différences entre familles pour MOE et MOR sont restées significatives après normalisation pour la densité du bois. Il est noté que l'utilisation seule de la densité du bois comme critère de sélection ne permettrait pas d'obtenir les gains génétiques potentiels escomptés d'une sélection directe pour MOE et MOR. Les corrélations entre propriétés de base du bois et les valeurs normalisées de MOE et MOR sont présentées et discutées

Phenolic compounds and expression of 4CL genes in silver birch clones and Pt4CL1a lines

A small multigene family encodes 4-coumarate:CoA ligases (4CLs) catalyzing the CoA ligation of hydroxycinnamic acids, a branch point step directing metabolites to a flavonoid or monolignol pathway. In the present study, we examined the effect of antisense Populus tremuloides 4CL (Pt4CL1) to the lignin and soluble phenolic compound composition of silver birch (Betula pendula) Pt4CL1a lines in comparison with non-transgenic silver birch clones. The endogenous expression of silver birch 4CL genes was recorded in the stems and leaves and also in leaves that were mechanically injured. In one of the transgenic Pt4CL1a lines, the ratio of syringyl (S) and guaiacyl (G) lignin units was increased. Moreover, the transcript levels of putative silver birch 4CL gene (Bp4CL1) were reduced and contents of cinnamic acid derivatives altered. In the other two Pt4CL1a lines changes were detected in the level of individual phenolic compounds. However, considerable variation was found in the transcript levels of silver birch 4CLs as well as in the concentration of phenolic compounds among the transgenic lines and non-transgenic clones. Wounding induced the expression of Bp4CL1 and Bp4CL2 in leaves in all clones and transgenic lines, whereas the transcript levels of Bp4CL3 and Bp4CL4 remained unchanged. Moreover, minor changes were detected in the concentrations of phenolic compounds caused by wounding. As an overall trend the wounding decreased the flavonoid content in silver birches and increased the content of soluble condensed tannins. The results indicate that by reducing the Bp4CL1 transcript levels lignin composition could be modified. However, the alterations found among the Pt4CL1a lines and the non-transgenic clones were within the natural variation of silver birches, as shown in the present study by the clonal differences in the transcripts levels of 4CL genes, soluble phenolic compounds and condensed tannins

A Comparison of Wood Density between Classical Cremonese and Modern Violins

Classical violins created by Cremonese masters, such as Antonio Stradivari and Giuseppe Guarneri Del Gesu, have become the benchmark to which the sound of all violins are compared in terms of their abilities of expressiveness and projection. By general consensus, no luthier since that time has been able to replicate the sound quality of these classical instruments. The vibration and sound radiation characteristics of a violin are determined by an instrument's geometry and the material properties of the wood. New test methods allow the non-destructive examination of one of the key material properties, the wood density, at the growth ring level of detail. The densities of five classical and eight modern violins were compared, using computed tomography and specially developed image-processing software. No significant differences were found between the median densities of the modern and the antique violins, however the density difference between wood grains of early and late growth was significantly smaller in the classical Cremonese violins compared with modern violins, in both the top (Spruce) and back (Maple) plates (p = 0.028 and 0.008, respectively). The mean density differential (SE) of the top plates of the modern and classical violins was 274 (26.6) and 183 (11.7) gram/liter. For the back plates, the values were 128 (2.6) and 115 (2.0) gram/liter. These differences in density differentials may reflect similar changes in stiffness distributions, which could directly impact vibrational efficacy or indirectly modify sound radiation via altered damping characteristics. Either of these mechanisms may help explain the acoustical differences between the classical and modern violins