Axial sampling height outperforms site as predictor of wood trait variation

Covariation amongst wood traits along the stem axis is important to maintain hydraulic integrity ensuring sufficient sap flow to the canopy. Here, we test how wood traits (co)vary along the trunk and whether two seasonally dry Brazilian habitats (cerrado and caatinga) influence this variation in two co-occurring species, Tocoyena formosa (Rubiaceae) and Tabebuia aurea (Bignoniaceae). The samples were collected at five heights along the main trunk of three individuals per species in both sites. We used light, scanning and transmission electron microscopy to observe the wood traits. Out of 13 wood traits, nine show relationships with sampling height: eight traits predict height in T. formosa and five in T. aurea. Contrastingly, only three traits show differences between sites and only for T. formosa. The intratrunk wood variation is reflected by the hydraulically weighted vessel diameter showing a curvilinear relationship, disagreeing with the prediction of a continuous vessel widening from tip to base. In both species, the largest vessels are linked to the thinnest intervessel pit membranes. Wood density increases basipetally for both species, being site-dependent and correlated with vessel traits in T. formosa, and site-independent and determined by fiber wall thickness in T. aurea. Furthermore, the functional role of rays was found to be different for each species, and may be related to the marked difference in ray composition. In conclusion, both species show a unique adaptation to deal with height-related constraints using species-specific co-variation amongst wood traits, while site does not contribute much to the wood variation.Plant science

Comparative wood anatomy of root and stem of Citharexylum myrianthum (Verbenaceae)

Root and stem wood anatomy of C. myrianthum (Verbenaceae) from a semideciduous seasonal forest in Botucatu municipality (22º52’20”S and 48º26’37”W), São Paulo state, Brazil, were studied. Growth increments demarcated by semi-ring porosity and marginal bands of axial parenchyma were observed in the wood of both root and stem. Many qualitative features were the same in both root and stem: fine helical thickenings, and simple and multiple perforation plates in vessel elements; large quantities of axial parenchyma in the growth rings, grading from marginal bands and confluent forming irregular bands in earlywood to lozenge aliform in latewood; axial parenchyma cells forked, and varied wall projections and undulations; septate fibres; forked and diverse fibre endings. Quantitative features differing between root and stem wood were evaluated using student’s t-test, and vessel frequency, vessel element length, vessel diameter, ray height, and vulnerability and mesomorphy indices differed significantly. Root wood had lower frequency of vessels, narrower and longer vessel elements, and taller rays than wood of the stem. The calculated vulnerability and mesomorphy indices indicated that C. myrianthum plants are mesomorphic. Roots seem to be more susceptible to water stress than the stem.A anatomia da madeira da raiz e do caule de Citharexylum myrianthum (Verbenaceae) que ocorre em uma área de floresta estacional semidecídua próximo à cidade de Botucatu (22º52’20”S e 48º26’37”W), estado de São Paulo, Brasil, foi estudada. Camadas de crescimento distintas, demarcadas por anel semi-poroso e faixas marginais de parênquima axial foram observadas em ambos os órgãos. As características qualitativas observadas tanto em raiz quanto em caule foram: espessamentos helicoidais finos e placas de perfuração simples e múltiplas em elementos de vaso; grandes quantidades de parênquima axial nos anéis de crescimento, em faixas marginais a confluente formando faixas irregulares no lenho inicial a aliforme losangular no lenho tardio; células do parênquima axial bifurcadas, com projeções e ondulações na parede; fibras septadas; fibras bifurcadas e com diversas terminações. Na análise quantitativa comparativa entre raiz e caule foi aplicado teste t-student que mostrou diferenças significativas na frequência e diâmetro de vasos; comprimento dos elementos de vaso; altura dos raios; índices de vulnerabilidade e mesomorfia. A madeira da raiz teve menor frequência de vasos, vasos com menor diâmetro e elementos mais longos, e raios mais altos. Os índices de vulnerabilidade e mesomorfia indicaram que as plantas de C. myrianthum são mesomórficas. As raízes parecem estar mais susceptíveis ao estresse hídrico do que os caules.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Universidade Estadual Paulista (UNESP) Faculdade de Ciências Agronômicas (FCA) Depto. Ciência FlorestalCenter for Wood Anatomy Research Forest Products LaboratoryInstituto de Pesquisas Jardim Botânico do Rio de Janeiro Diretoria de Pesquisas Lab. Botânica EstruturalUniversidade Estadual Paulista (UNESP) Faculdade de Ciências Agronômicas (FCA) Depto. Ciência Floresta

SHEAR STRENGTH IN THE GLUE LINE OF Eucalyptus sp. AND Pinus sp.WOOD

ABSTRACT To evaluate the adhesive efficiency on the union of glued joints in a particular temperature and humidity conditions for a specified time the adhesive must be submitted to specific load tests, such as shear in the glue line. The objective of this study was to evaluate the shear strength in the glue line of Eucalyptus sp and Pinus sp.woods. Five adhesives (castor oil, sodium silicate, modified silicate, , PVA and resorcinol-formaldehyde), three weights (150 g/m2, 200 g/m2, and 250 g/m2) and two species (Eucalyptus sp. and Pinus sp.) of wood were used. Twelve specimens were obtained from each repetition per treatment, corresponding to 108 specimens that were conditioned at a temperature of 23 ± 1°C and relative humidity of 50 ± 2%. The interaction between the weight and type of adhesive was significant for the shear strength in the glue line of eucalyptus wood. However, no interaction between the weight and the adhesive was found for pinus, only the isolated from the adhesive effect. Chemical bonds originated in the polymerization of resorcinol-formaldehyde adhesives and castor bi-component conferred upon these adhesives the greatest resistance in the glue line. Castor and resorcinol-formaldehyde adhesives showed the highest shear strength values in the line of glue and wood failure. Castor adhesive presented satisfactory performance for bonding of eucalyptus and pine woods

Variação intraspecífica do lenho de Pseudopiptadenia contorta (DC.) G.P. Lewis & M.P. Lima (Leguminosae - Mimosoideae) de populações ocorrentes em dois remanescentes de Floresta Atlântica Intraspecific variation in wood anatomy of Pseudopiptadenia contorta (DC) G.P. Lewis & M.P. Lima (Leguminosae -Mimosoidae) in two Atlantic rain forest remnants

O presente trabalho compara populações distintas de Pseudopiptadenia contorta (DC.) G.P. Lewis & M.P. Lima ocorrentes em dois remanescentes de Floresta Atlântica no Estado do Rio de Janeiro. Foram amostradas árvores de diâmetro semelhante retas e sem defeitos aparentes. Os resultados obtidos comprovam estatisticamente a ocorrência de variação intraspecífica na estrutura anatômica da madeira. Os caracteres qualitativos mantiveram-se constantes, enquanto os quantitativos variaram, sendo os significativos, de acordo com o teste t de Student, a freqüencia, comprimento e diâmetro dos elementos vasos, o comprimento e espessura da parede das fibras, a freqüência e largura dos raios. A análise dos componentes principais, utilizando características anatômicas quantitativas ordenou as duas populações separadamente. O eixo I responde por 33% da variância total principalmente pela relação positiva do diâmetro do elemento de vaso, enquanto o eixo II responde por 20% da variância total, principalmente pelo comprimento das fibras.<br>This study compares distinct populations of Pseudopiptadenia contorta (DC) G.P. Lewis & M.P. Lima occurring in two remnants of Atlantic rain forest in Rio de Janeiro state. Trees with similar diameters and with no apparent defects were selected. The results confirm intraspecific variation in wood anatomy. Qualitative features do not change, while according to the Student t test quantitative features showed significant differences in vessel-element frequency, width, and length, fiber length and wall thickness, and ray frequency and width. Principal component analysis showed two separate populations. Factor 1 explains 33% of the total variance, mainly due to the positive relationship of vessel-element tangential diameter; factor 2 explains 20% of the total variance, mainly due to fiber length