Permeability of <Emphasis Type="Italic">Tectona grandis</Emphasis> L. as affected by wood structure

This experiment describes some anatomical features of Tectona grandis L. relating to the variation of liquid permeability in radial and longitudinal directions. Safranine aqueous solution was used to measure the permeability for its brilliant color and staining properties. Even in presence of abundant rays, penetration depth of liquid in radial direction was found very low in comparison with axial flow. Herein ray length and perimeter of cross-sectional area, interparenchymatous pit number and diameter determined the radial permeability. On the other hand, vessel length and diameter, intervessel pit size, and fiber length affected the longitudinal flow of liquids. Following a go-stop-go cycle, penetration speed of liquid decreased over time.     

Liquid penetration in different cells of two hardwood species

Two experimental techniques were used to test the water permeability of two Korean hardwood species: diffuse porous Populus tomentiglandulosa T. Lee (eunsasi poplar) and ring porous white oak, Quercus serrata Thunb (konara oak). The first technique measured the void volume filled at different moisture content (MC) levels. Samples were treated with water via a schedule of full-cell impregnation. A significant relation between MC and permeability (the fractional void volume) was found. A reduction in liquid permeability was observed at MC above the fiber saturation point (FSP), whereas the opposite result was observed at MC below FSP due to the effect of the voids available in the wood. However, the differences of increased permeability from MC level 20% to 0% were found satistically the same in either wood species. The second technique measured the speed of liquid penetration in vessels, fibers, and rays with no application of external pressure. In this method, liquid flow was captured via video and the penetration speed was measured. Vessels, fibers, and rays in poplar were found to be more permeable than those in oak. Different anatomical factors such as cell diameter, cell length, pit number, pit aperture area, and thickness of the pit membrane seemed to be responsible for the variation of liquid flow rate in different cells of the two hardwood species.     

桉树木材超微结构及其对干燥皱缩的影响

以多枝桉等４种桉树木材为材料，采用扫描电镜观察并分析了其导管、纤维和管胞等胞壁上的纹孔和瘤层等超微结构．结果表明，富含侵填体的桉材因其堵塞了导管间的轴向通道，并部分覆盖了管间纹孔及导管—射线间纹孔，严重影响其渗透性，是其干燥皱缩的主要原因．通过热处理后，能使多枝桉和细叶桉木材皱缩发生改善．但对赤桉和红桉无效．     

马尾松木材横向液体渗透性的研究

分析和讨论了影响马尾松木材横向液体渗透性及其各向异性的机理.对马尾松木材的径向液体渗透性和弦向液体渗透性进行了测量.结果表明,马尾松木材的径向液体渗透性大于弦向液体渗透性,并且,马尾松木材的径向液体渗透性和弦向液体渗透性都是从边材向心材逐渐减小,并随着含水率的下降而升高.其原因是径向液体流动的主要通道是木射线和水平树脂道,弦向主要是管胞壁和交叉场上的纹孔.     

胡颓子科2种旱生植物次生木质部的生态解剖学特性

从生态学角度对沙棘和沙枣的木材结构进行对比研究.两树种具有的共同特点为 :生长轮明显,半环孔材,具单穿孔,导管间纹孔交互排列,无分隔木纤维,导管较窄, 环管管胞和纤维状管胞具螺纹加厚,轴向薄壁组织缺失或很少.所选树种明显区别是射线类型、宽度和叠生排列方式:沙棘射线,轴向薄壁组织细胞和导管分子具有明显的叠生排列方式,但沙枣的叠生排列不规则;沙棘射线为异型,1～2列,沙枣射线为同型,2～5列;并且二者之间数量化指标有差异,沙棘导管频率较大,导管分子较短及导管管孔较小,因此V和M值也较小,更能适应干旱环境.两树种导管分子长和纤维长的水平变动不规律,并且树种间和同一树种个体间差异显著.本文最后对该树种的解剖学特征和沙漠环境的适应性进行了讨论 .     

Anatomical Changes During Transition from Juvenile to Adult Wood in Branch and Main Trunk Xylem of Subabul (Leucaena leucocephala [Lam.] de Wit)

The anatomical changes occurring during transition from juvenile to mature wood were studied in the branch and main trunk of Leucaena leucocephala. To confirm the wood maturity in the 5-yr-old tree, the anatomical features were compared with the adult wood collected from the main trunk of a 15-yr-old tree. In both the branch and wood of the trunk, most of the anatomical features—such as increase in dimensions of fibers and vessel elements, and decrease in frequency of vessel elements and rays—were gradual during radial growth from pith to periphery. A noticeable anatomical change is observed in the transition of triseriate rays to multiseriate rays in the region of wood which is about 5.5 cm away from the pith. The ray dimensions and anatomical features of other elements from the periphery of the branch and 5-yr-old trunk xylem match with that of 15-yr-old main trunk wood. This indicates that in both the branches and main trunk of Leucaena, transition from juvenile to adult or mature wood occurs after the trees have attained 14 cm radial growth.     

Investigation on transversal variation of poplar tension wood quality using ultrasound wave parameters

Transversal variations of some ultrasound wave parameters (phase velocity, group velocity, attenuation coefficient and acoustic radiation) were measured from the pith to the bark of poplar tension wood discs in different orthotropic directions. Over 80 cubic specimens of 2 × 2 × 10 cm³ (radial, tangential and longitudinal, respectively) were prepared and tested acoustically. Samples containing tension woods were separated from normal ones using anatomical experiments. Results showed acoustical behaviour of normal and tension wood improved in longitudinal direction while the distance between pith and bark increased; also, wave parameter variations were less important in radial and tangential directions. In addition, phase velocity and acoustic radiation – which significantly varied – were the best parameters for quality assessment of poplar wood compared with group velocity and attenuation coefficients. Since samples near the bark were acoustically better than counterparts near the pith, they could be used in products requiring more strength, like lumber. Finally, acoustic radiation and phase velocity were correlated more strongly with density than group velocity and attenuation.     

长江滩地立木腐朽杨树与正常杨树生长与材性的比较研究

本文对长江滩地意杨的生长和木材材性进行了初步研究，着重讨论长江滩地立木腐朽杨树与正常杨树在树高、胸径生长的差异，通过回归分析，给出了杨树胸径生长与年龄的回归方程。分析研究腐朽木和正常木在年轮宽度、含水率、木材密度、干缩率等方面的差异。通过扫描电镜观测腐朽木和正常木细胞壁层的差异和菌丝在木材细胞的分布状况。研究结果表明：地势低是导致杨树立木腐朽的直接原因；腐朽对杨树的胸径生长和高生长及木材材性有显著影响；腐朽材内部生材含水率远低于正常材内部生材含水率，这是由于腐朽杨树内部导管比量明显比正常材低导致其输导水分功能减弱所致；而腐朽材的密度和干缩率均高于正常材；腐朽木中出现了具有应拉木特征的区域，菌丝入侵立木杨树主要通过夹皮裂隙，然后通过导管和木射线细胞向木纤维中扩散。     

Study of the transverse liquid flow paths in pine and spruce using scanning electron microscopy

Samples of pine (Pinus sylvestris) and spruce (Picea abies) were impregnated with a low-viscous epoxy resin using a vacuum process. The epoxy was cured in situ and the specimens sectioned. Deposits of the cured epoxy was then observed in the wood cavities using a scanning electron microscope. The investigation concentrated on tracing the transverse movements of a viscous liquid in the wood, and special attention was therefore given to the cross-field area between ray cells and longitudinal tracheids. A damage hypothesis is proposed based on the results obtained in the present investigation in combination with those from earlier studies on linseed oil-impregnated pine: In addition to the morphology of the bordered pits, viscous liquid flow in wood is dependent on damage that occurs during the impregnation procedure. For pine sapwood, liquid flow is enabled through disrupted window pit membranes, which divide the longitudinal tracheids and the ray parenchyma cells. A mechanism accounting for the reduced permeability of pine heartwood is believed to be deposits of higher-molecular-weight substances (extractives) in the ray parenchyma cells and on the cell walls. In spruce the thicker ray cells in combination with the smaller pits, which are connected to the longitudinal tracheids, reduce permeability considerably.     

Stiffness of normal, opposite, and tension poplar wood determined using micro-samples in the three material directions

Mechanical tests on micro-samples were performed in the three material directions in normal, opposite, and tension wood collected from a poplar tree. Two custom micro-devices were designed and built in the laboratory to test samples under pure tension in the transverse direction and under 4-point bending conditions in the longitudinal direction. Both devices were designed to handle samples with a small transverse section (a few square mm), which allowed to select zones with homogenous anatomical features. The results indicate a very high longitudinal stiffness in tension wood (up to 35 GPa compared to an average of 18 GPa for normal wood). Considering wood density, the value represents a specific modulus that is nearly 70 % crystalline cellulose. However, tension wood is slightly less stiff in the tangential and radial directions (1,150 vs. 1,500 MPa for normal wood in the radial direction and 430 vs. 530 MPa in the tangential direction).     

Within and between-tree variation in the biometry of wood rays and fibres in cork oak (Quercus suber_L.)

The variability of fibre and ray dimensions was studied at three radial positions (10, 50 and 90% of radius) in 5 cork oaks (Quercus suber L.) approximately 40 years old. Uniseriate ray height and cell number as well as multiseriate ray height and width were measured in tangential sections. Fibre length, width and wall thickness were measured after maceration. The most striking features of cork oak wood were the large multiseriate rays and the frequent homocellular uniseriate rays. On average multiseriate rays were 5.16 mm high and 0.48 mm wide, and uniseriate rays contained 11 cells and were 227 μm high. Neighbour rays presented large dimensional differences but there was no radial variation and there were very small between-tree differences. The radial maintenance of high and wide rays was discussed as a means to improve water shortage in response to water stress. Fibre dimensions increased radially but differed little between trees: on average, 960–1,220 μm length, 18.40–21.49 μm width and 6.66–8.07 μm wall thickness. The ray pattern showed enough variation for visual appreciation while ensuring within and between-tree uniformity. The presence of rays has to be taken into consideration for designing wood drying programs.     

落叶松木材的高强度微波辐照法改性

The larch wood was treated by microwave irradiation under different radiant intensity and treating duration. The microwave-treated wood specimens together with the un-treated for comparison were impregnated by water in pressure vessel and then tested for permeability, mechanical properties and microstructure change by SEM to study the modification performance of microwave treatment on larch wood. The results showed that under suitable conditions of microwave treatment the permeability of larch wood was improved without noticeable decreasing of the modulus of rupture （MOR） and the modulus of elasticity （MOE）. The radial parenchyma and some pit membrane were ruptured, and tiny cracks were formed in the cell walls. The formation of tiny cracks in the cell walls serves as man-made channels of gas and liquid and this contribute to improve the permeability of the wood.     

杨木应拉木微区结构可视化及化学成分分析

木材微区结构与木材宏观性质密切相关,杨木应拉木与对应木宏观性质存在较大差别,探究杨木应拉木和对应木微区结构和化学成分,可为了解杨木应力木的宏观性质提供理论根据。借助光学显微镜、荧光显微镜、显微拉曼成像光谱仪、透射电镜对杨木应拉木微区结构进行可视化研究,并借助X射线衍射技术和美国可再生能源实验室方法,分析杨木应拉木的微晶尺寸、结晶度以及化学成分。结果表明:杨木应拉木中应拉区和对应区纤维细胞微区结构差异显著。光学显微镜下显示应拉区木纤维中胶质层清晰可见,荧光显微镜和拉曼显微镜下显示胶质层的木质素浓度比对应区低。透射电镜下显示应拉区木纤维细胞壁结构由初生壁、次生壁和胶质层组成,未见次生壁外层,各层的平均厚度分别为0.61,1.22和2.53μm。对应区木纤维为典型的初生壁和次生壁结构,次生壁各层平均厚度分别为0.33,2.28和0.14μm。杨木应拉区纤维素含量(58.91%)比对应区(41.53%)高,木质素含量和半纤维素含量均比对应区的低,应拉区木质素和半纤维素含量分别为21.99%和12.01%,对应区分别为28.10%和17.08%。杨木应拉区结晶度(48.06%)比对应区(41.01%)高,应拉区晶区宽度为2.66 nm,长度为8.84 nm;对应区晶区宽度为2.65 nm,长度为9.87 nm。     

流速与压强对马尾松木材气体渗透性的影响(英文)

在1.3×10-6到1.0×10-5m3·s-1的流速条件下,测量马尾松的纵向空气渗透系数.在所使用的流速范围内,空气流速与样品两端的空气压强差呈现线形与非线形的关系,其非线形的分量随空气流速或压强差的增大而增强.空气流速或压强差对样品的纵向空气渗透系数有影响,在6个所测量的试样中,5个试样的纵向空气渗透系数最大值与最小值的相对差在3.1%到5.7%之间,而1个试样的相对差则达到了34.2%.根据本文的研究结果,应该使用不同的气体流速(气体压强差)测量木材样品的气体渗透系数,用所测得的这些结果的几何平均值或以流速与压强差为权重的加权平均值作为样品的气体渗透系数,并指明测量气体渗透系数时不同的气体流速或压强差的范围.     

Comparative study on penetration characteristics of modern wood coatings

Summary The penetration characteristics of five modern wood coatings (three waterborne, one high solid and one solvent borne) into pine sapwood, spruce and dark red meranti have been systematically compared. The degree of coating penetration is mainly determined by the ability of the coating to flow into wood capillaries. Binder type, pigmentation, solid matter content and drying speed appeared to influence this ability. In softwoods the following different coating penetration routes are observed: the flow into open ends of longitudinal early-and latewood tracheids, the flow into ray cells and the transport from rays through the cross-field into longitudinal tracheids adjacent to rays. The possibility for the coating to follow the latter route is strongly influenced by the existing type of cross field pitting and to a lesser degree by the pigmentation of the paint. Clear differences between pine and spruce have been found with respect to the flow into ray parenchym and ray tracheids. The flow into open ends of longitudinal tracheids is strongly influenced by the grain angle of tracheids. Penetration into dark red meranti is mainly limited to vessels and rays. Tylose membranes can prevent the complete filling of vessels. The impact on penetration of the removal of extractives and of sanding of the surface has also been studied but appears to be of only minor importance.The authors want to thank Akzo Nobel Coatings, DSM Resins and Sigma Coatings for their technical support. This research was financed by the the Dutch Innovative Research Program on Coatings under contract number IVE 93-812. Authors also thank the University of Hamburg (BFH) for the use of their electron microscopy facilities.     

林下耕作对滩地杨树木材解剖性质的影响研究

本文对长江滩地这一特定立地条件下经过人为耕作与未耕作模式下的杨树木材解剖性质及其变异的关系进行了比较研究。结果表明：林下耕作纤维长度变化范围在792．67-1114．33μm,属中等长度纤维,林下耕作杨树的纤维长度明显比未耕作的要长,两者纤维长度、宽度差异显著,长宽比差异极显著;林下耕作木材导管比量为29％,木纤维比量为54％,木射线比量为17％,变异系数分别为13．8％、7．4％、23．5％;低于对照木材,提高了材质均匀性;两者导管与木纤维组织比量轴向变化趋势一致,分别呈波动上升与下降的趋势,但木射线组织比量变异趋势存在较大的差别。林下耕作杨木导管比量自髓心向外呈上升趋势,木射线组织比量随着年龄的增加逐渐下降,并呈现一定的波动性：未经耕作的杨树木材组织比量径向变异规律性不明显。     

Ⅰ-69杨湿心材发生、分布及材性的研究*

在湖北省嘉鱼县潘家湾,不同生长条件和不同方式种植的I-69杨活立木及原木都有不同程度的湿心材存在。湿心材的比例与土壤水分含量有关,与种植方式和树木生长速度无关。湿心材的存在和变色由细菌活动引起,已分离和鉴定出5种病原菌(Erwinia carotovora Subsp.carotovora,E.rhapontioi (Millard)Burkhold,E.chrysanthemi Burkholder,Bacilluscereus Frankland,B.sphaericus Neide)。电镜观察和材性分析表明,正常材中细菌很少,纹孔膜保存完好,而湿心材的导管-射线间纹孔和管间纹孔膜几乎都被破坏。与正常材相比,湿心材的pH和酸缓冲容量高,抽提物和灰分含量较高,综纤维素和α-纤维素含量略低。湿心材的密度、干缩系数及力学性质都比正常材低,差异极显著。建议进一步研究如何防止细菌的侵入和活动,阻止湿心材和变色材的发生。     

毛白杨枝条木质部细胞分化的动态变化及其与形成层活动的相互关系

应用定量解剖学和显微图像分析技术 ,得到了毛白杨枝条形成层细胞与其衍生木质部细胞解剖特征在形成层活动期内的变化情况 ,并探讨了两者之间的关系。采用X射线微密度测定技术 ,了解了同一生长轮内木材密度沿径向方向上的变异 ,讨论了其与木质部细胞解剖特征之间的关系。结果表明 ,形成层纺锤形细胞的径向和弦向宽度在活动期不同阶段差异不显著 ,而纤维长度、纤维宽度、壁腔比、微纤丝角、导管分布频率和胞壁率差异极显著 ;导管组织比量差异显著 ;导管分子长度、纤维比量和射线比量差异不显著。同一生长轮内木材密度的径向变异与活动期不同阶段形成的木质部细胞数量及其解剖特征直接相关。形成层带细胞层数与纤维长度、纤维长宽比和壁腔比呈极显著负相关 ,与纤维宽度呈显著正相关 ;形成层纺锤形细胞的径向宽度与纤维长度、纤维长宽比和射线比量呈显著负相关 ;形成层纺锤形细胞的弦向宽度与纤维宽度呈显著正相关。总体看来 ,在整个形成层活动期 ,形成层纺锤形细胞与木纤维的解剖特征之间随时间变化的相关性较好 ,而与导管分子的相关关系则不明显     

木材渗透性可控制原理研究

本文研究了木材渗透性可控制机制,探寻了渗透性可控制原理。结果表明,影响渗透性高低的最主要因素为纹孔膜微孔半径和数量,微孔大而多者,渗透性高;微孔愈小,微孔里气-液界面上毛细管张力愈高,对液体流动的影响愈大,浸注愈难,欲使浸注液深注入木材,必须施一与此微孔半径相应足以克服此张力的压力。若欲改善低渗透树种木材的难浸注性,似应从纹孔入手,用化学的、物理的和生物的等方法增大和增多有效纹孔膜微孔半径和数量,以减小毛细管张力,降低使用压力,增大流量率,提高渗透性。     

Gas flow in hardwoods

Summary A model was developed for describing the axial gas flow through hardwood samples, and gas permeability variations with increasing specimen length. To that effect, the mean vessel length of the wood species () was taken into account, and the intervessel junction was modelled as a perforated plate. Mass and momentum conservation equations were then used to describe the fluid evolution through it. Outside the junction, wood was assumed to be a permeable material of Darcian behaviour. Thus, by combining Darcy's equations with the one derived for the junction zone, a system of equations was obtained modelling the overall fluid flow through the sample.The model was experimentally tested on ceibo (Erythrina crista-galli L.) samples of different lengths. Their gas permeabilities were measured, and the permeability of a zero-length sample (equivalent to that of an ideal specimen of infinitely long vessels) was calculated by means of an existing model. By introducing this last parameter into the above mentioned equation system, a theoretical value for the gas permeability was obtained. A fair agreement was observed between the model and experimental values, the differences between them being attributable to a number of simplifying assumptions that were made in order to render the system mathematically tractable.