Study On Anatomical Characteristics And Formation Mechanism Of Precious Wood Figure

Wood grain was the texture grain presented on the longitudinal section of wood and the number of natural special grain wood was small and the source was unstable,the research on the formation mechanism of precious wood grain is helpful to guide the processing and utilization of precious wood,improve the use effect and added value of precious grain wood,and provide a theoretical basis for the artificial manufacture of special grain wood.The research on the production principle and method of special grain technology wood has been paid more and more attention.The objects of study were wood interlocked grain,wood birdseye grain,wood wavy grain and wood burl grain,and Camphora officinarum,Acer sp.and Lindera metcalfiana wood were selected respectively.The macroscopic structure,anatomical characteristics,cell morphological parameters(fiber,vessel,ray,etc.),grain angle,chemical composition and surface optical properties,and the relationship between the formation of precious wood grains and wood structure was analyzed.The main conclusions of the paper were as follows.(1)Interlocked grain is formed by the regular arrangement of interlacing layers of wood in different directions and angles.The meristem of cambium in interlocked grain wood has seasonal changes,and the grain orientation of the whole cambium is consistent and in the same direction.The microstructure of inclination zone wood was different from that of normal wood,with the radial section having more elliptical vessel grooves and the tangential section showed the grain was inclined.In inclined zone,the number of axial parenchyma was more;the length and wall-cavity ratio of fibers increased,and the fiber diameter and fiber double wall thickness decreased.The fiber inclination angle showed a similar periodic waveform variation grain,and the grain angle varied gradually from-14.9 to 15.6°,and the transition of grain orientation mostly occurs inside the growth rings.The fiber inclination angle in a growth ring fluctuates,but the fiber angle at the beginning and end of the growth ring still has a certain change trend.The glossiness value has a periodic waveform grain,and the glossiness value from inclination zone to transition zone changes rapidly.In inclination zone,glossiness values were in the range of 2.5 ～3.5,and fiber inclination angles were about 4 ～ 15.6° or-14.9 ～-4°;In transition zone,glossiness values were in the range of 4.2 ～ 6,and the fiber inclination angle range was about-4～ 4°.The formation of interlocked grain is affected by multiple factors :(a)the fiber inclination angle and direction of the interlocked layer change periodically.(b)the difference in fiber morphology between transition zone and inclination zone.The above factors work together to cause changes in the reflected light in different zones,thus presenting the grain of light and shade on the radial surface of the wood.(2)The birdseye grain is a special texture formed by the disorder of normal wood texture.The birdseye zone was a conical indentation in the bark running through multiple growth rings toward the pith.Compared with the normal zone,the fiber length in birdseye zone decreased,while the fiber diameter,fiber double wall thickness,wall-cavity ratio and the frequency of rays increased;the diameter and frequency of vessels,the height and width of rays decreased.There are two types of abnormal fibers in the xylem :(a)Some latewood fibers have additional cellulose layers,with obvious birefringence;(b)The innermost layer of the secondary wall of some fiber cells is highly lignified and there is a cellulose layer in the secondary wall.The results of FTIR showed that the characteristic peaks of lignin,cellulose and xylan in birdseye zone were strong.The birdseye of maple is formed by abnormal local stress from bark during its cambium cell division.(3)The wood wavy garin mostly appear in the radial section,showing several alternating light and dark horizontal stripes.Compared with the normal zone,the vessel diameter,ray height and fiber length decreases,and the vessel frequency and ray width increases in wavy zone.The differences in fiber length,vessel diameter,vessel frequency,ray width,ray height and ray frequency between the wavy zone and the normal zone were extremely significant,but there were no significant differences in fiber diameter,fiber double wall thickness and fiber wall-cavity ratio.The wavelength of the grain waveform in wavy zone was about 8518.14 μm,and the average amplitude of the fibers in the S-direction was 333.03 μm with a maximum grain angle of 14.24°;the amplitude in the Z-direction was 245.43 μm with a maximum grain angle of 7.70°.The differences in the amplitude and maximum grain angle of the S and Z-direction fibers were extremely significant.The width of the dark band in the tiger spot zone was 2302.61 μm,the glossiness was 3.8,and the grain angle was greater than 6°;the width of the bright band was1688.58 μm,the glossiness was 5.8,and the fiber inclination angle was about 0 ～ 6°.The wall structure of some fibers in the tiger spot zone of maple changed,and the wall layer with high cellulose concentration appeared in the secondary wall.This cellulose layer exists in the tiger spot zone of different tree species,and typical gelatinous fibers appear in the tiger spot zone of poplar.Tiger spot grain of wood is formed by the response to abnormal local stress during cambium cell division.(4)The wood burl has a pith,the formation process is speculated to be the abnormal division of cambium cells caused by the stimulation of external invasion,and the dedifferentiation of parenchyma cells to form primary tissues.The morphology of cells adjacent to the pith becomes square,and the cell cavity was larger;the number of ray-like parenchyma cells became higher;the pits of vessels were elongated in an elliptical to long strip shape and the order became narrower,and abnormal tissue existed in the xylem.The fibers in burl zone were twisted and distorted,shorter in length and wider in width,and these could be classified into seven types according to their morphology.The morphology of long striped fibers was similar to normal fibers,while other types of fibers were significantly larger in diameter and shorter in length.Compared with the normal zone,the fiber length and ray height decreased;the fiber diameter,fiber double wall thickness and ray width increased in burl zone.