Growth Characteristics And Wood Properties Of Sapwood And Heartwood Of Catalpa Bungei C.A.May

Heartwood is the main material part of precious tree species.The furniture and handicrafts made of precious tree species are well received by people,and the market prospect is broad.The transformation from sapwood to heartwood is an important and complex process in the growth of trees,which results in significant differences between sapwood and heartwood in growth characteristics,structural properties and many other aspects,and ultimately affect the processing and utilization of sapwood.In this paper,the precious hardwood tree Catalpa bungei C.A.Mey was taken as the main object of study.Modern analytical instruments such as tree ring analyzer,scanning electron microscopy,transmission electron microscopy,Micro-Raman method and imaging FT-IR spectroscopy were mainly used to study the variation of growth characteristics,the microstructural characteristics of ray cells,the chemical composition of the cell wall and the physical properties for sapwood and heartwood,revealed the mechanism of the influence of the structural characteristics of sapwood and heartwood on its physical properties.The main results are as follows:(1)The growth characteristics growth characteristics of sapwood and heartwood of Catalpa bungei C.A.Mey such as annual ring width,sapwood to heartwood rate and initial age of heartwood were studied.In the radial direction,the ring width increased first and then decreased with the increased of tree age,and the ring width reached its peak in 10-15 years;in the vertical direction,the ring width decreased with the increased of tree height.The initial age of heartwood was 5.26a,and the rate of heartwood formation was 0.90 rounds/a.The ratio of heart rate,radius of heartwood to width of sapwood decreases with the increased of tree height.The growth characteristics of the heartwood and sapwood of Catalpa bungei C.A.Mey tree were obviously different.(2)The anatomical features of ray cells,vessel cells wall and starch grains on the membrane were studied.There were abundant deposits in wood rays and vessels cell wall and pit membrane in heartwood which near the pith,and more tylose in the vessel near the pith.Ray parenchyma cells in the xylem of Catalpa bungei C.A.Mey,the protoplasts in the cytoplasm and the contents of starch granules and oil droplets gradually degraded from sapwood to heartwood,while the ray parenchyma cells reached the heartwood site were almost completely losed protoplasts.(3)The content and distribution of chemical components in the cell wall of sapwood heartwood were studied.The hemicellulose content increased from sapwood to heartwood and increased with the increase of tree height;lignin content increased from sapwood to heartwood,and increased first and then decreased with the increase of tree height;the cellulose content decreased from sapwood to heartwood.The micro-distribution of chemical components in cell wall of Catalpa bungei C.A.Mey showed that the lignin concentration in cell corner was the highest,the intercellular level was the second,and the secondary wall was the smallest,while the cellulose concentration micro-distribution was the opposite.(4)The variation and mechanism of the surface physical properties of the sapwood heartwood of Catalpa bungei C.A.Mey were revealed.The brightness of wood color from sapwood to heartwood decreased in turn,and the hue value increased first and then decreased from sapwood to heartwood,while the color saturation of heartwood is greater than that of sapwood;the brightness of heartwood decreased with the increased of tree height.The contact angle of sapwood was the smallest and the surface free energy was the largest,which was46.42 m J/m~2;As the increased of tree height,the corresponding surface contact angle of wood showed an increasing trend,and surface free energy of wood decreased from 46.42 to 33.74m J/m2 with the increased of tree height.The impregnatability of sapwood was significantly higher than that of transformation zone,and the impregnatability of heartwood was the worst.The impregnatability of wood decreased with the increased of tree height.The surface physical properties of sapwood and heartwood of Catalpa bungei C.A.Mey were directly affected and controlled by its anatomical structures and chemical components and distribution.