ESTRUTURA DO LENHO DE Plathymenia reticulata E ALGUMAS IMPLICAÇÕES NA EFICIÊNCIA HIDRÁULICA E RESISTÊNCIA MECÂNICA

Investigou-se a variação anatômica, velocidade de propagação do som (v), densidade aparente (ρap) e módulo de elasticidade dinâmico (MOEd) na madeira de Plathymenia reticulata. Verificou-se como as variações nessas características podem influenciar na eficiência hidráulica e resistência mecânica. Para a anatomia, empregaram-se as metodologias usuais, a (v) foi medida com equipamento de ultrassom, a (ρap) foi determinada pelo método da balança hidrostática, e a partir dos valores de (v) e (ρap) foi calculado o (MOEd). O diâmetro de vasos aumentou na direção da casca, o que deve acarretar melhor eficiência hidráulica. A frequência de vasos e o MOEd correlacionaram-se negativamente na região da medula, indicando madeira mais flexível e mais resistente à ação dos ventos. Raios mais frequentes diminuem a (v), e como esta também indica a rigidez, regiões com maior frequência de raios apresentam maior flexibilidade. Fibras com paredes mais espessas na base do fuste podem aumentar a resistência das árvores ao receberem uma carga extra. A relação negativa entre ρap e lume das fibras deve-se ao fato de o lume representar espaços vazios que não contribuem na massa. Raios mais largos na direção da casca podem auxiliar no armazenamento de amido, que, quando hidrolisado, também atua na recuperação de vasos embolizados.Palavras-chave: Amarelinho; anatomia da madeira; propriedades da madeira; variação axial; variação radial. AbstractWood structure of Plathymenia reticulata and some implications on hydraulic efficiency and mechanical strength. We investigated the anatomical variation, speed of sound propagation (v), specific gravity (ρap) and dynamic modulus of elasticity (MOEd) in the wood of Plathymenia reticulate Benth. The aim was to determine how variations in these characteristics may influence the hydraulic efficiency and mechanical strength. The anatomical features were analyzed according to usual techniques; (v) was measured with ultrasound equipment, (ρap) was determined with “balança hidrostática” method and from (v) and (ρap) values was calculated (MOEd). The results showed that increase in vessel diameter from pith to bark can result in better hydraulic efficiency. The negative correlation between vessels frequency and MOEd in the pith indicates more flexible wood, contributing to the resistance of young tree to wind action. Rays more frequent decreased (v), as this is also an indication of stiffness; regions with the highest ray frequency provide higher flexibility. Fibers with thicker walls at the base of the stem can increase the tree resistance when they receive an extra load. The negative relationship between ρap and fibers lumen is due increase in empty spaces that no contributed in wood mass. Wider rays in the bark direction can contributed in the storage of starch, which when hydrolyzed can retrieve embolized vessels.Keywords: Amarelinho; wood anatomy; wood properties; axial variation; radial variation. We investigated the anatomical variation, speed of sound propagation (v), specific gravity (ρap) and dynamic modulus of elasticity (MOEd) in the wood of Plathymenia reticulate Benth. The aim was to determine how variations in these characteristics may influence the hydraulic efficiency and mechanical strength. The anatomical features were analyzed according to usual techniques; (v) was measured with ultrasound equipment, (ρap) was determined with “balança hidrostática” method and from (v) and (ρap) values was calculated (MOEd). The results showed that increase in vessel diameter from pith to bark can result in better hydraulic efficiency. The negative correlation between vessels frequency and MOEd in the pith indicates more flexible wood, contributing to the resistance of young tree to wind action. Rays more frequent decreased (v), as this is also an indication of stiffness; regions with the highest ray frequency provide higher flexibility. Fibers with thicker walls at the base of the stem can increase the tree resistance when they receive an extra load. The negative relationship between ρap and fibers lumen is due increase in empty spaces that no contributed in wood mass. Wider rays in the bark direction can contributed in the storage of starch, which when hydrolyzed can retrieve embolized vessels