Chapter 1 The Composition and Structure of Wood1Tianjin University of Science C 弦切面：垂直横切面与年轮相切的切面，又称切线 切面Chapter 1 The Composition and Structure of Wood65Tianjin University of Science Chapter 1 The Composition and Structure of Wood81Tianjin University of Science & Technology也可以是不再具有分生能力的细胞，这种细胞发育成长过程中分化为执行不同生理机能的各种永久细胞 ,其中很大一部分细胞分化为构成植物体基干起机械作用和输导作用的永久细胞Chapter 1 The Composition and Structure of Wood82Tianjin University of Science & Technology永久细胞的细胞壁随着细胞的发育而迅速增厚，并在长度方向延伸在细胞停止生长以后,细胞壁仍然继续增厚,细胞内物质逐渐转化为细胞壁物质,其主要化学成分是碳水化合物和木素。
Chapter 1 The Composition and Structure of Wood83Tianjin University of Science & Technology图1-17 木材活细胞成长为植物纤维的过程 Chapter 1 The Composition and Structure of Wood84Tianjin University of Science & Technology植物纤维的概念这种失去生命机能的细长锐端永久细胞称为植物纤维Chapter 1 The Composition and Structure of Wood85Tianjin University of Science & Technology2．植物纤维细胞壁的构造• 胞间层（Middle lamella）• 初生壁(Primary Wall)• 次生壁(Secondary Wall)• 次生壁分外（S1）、中（S2）、内（S3）三层Chapter 1 The Composition and Structure of Wood86Tianjin University of Science & TechnologyFigure 12. Cell wall layers and organization of microfibrils in a softwood tracheid Chapter 1 The Composition and Structure of Wood87Tianjin University of Science & TechnologyFigure 2. Cross section of a Pine (Pinus palustris) latewood tracheid: M is the middle lamella P is the primary wall, S1, S2, and S3 are the outer, middle and inner layers of the secondary wall.Chapter 1 The Composition and Structure of Wood88Tianjin University of Science & Technology3．细胞壁上的纹孔细胞在次生壁增厚时，并非全面均匀的增厚，其中常留有不增厚的部分。
这种不增厚的部分，因为细胞壁比较薄，在显微镜下观察象一些圆形小孔，实际上并不是真正的孔，而是一些薄壁区域这些薄壁区域叫做纹孔（Pit） Chapter 1 The Composition and Structure of Wood89Tianjin University of Science & TechnologyFigure 8. Cross-section of one tracheid showing bordered pits.Chapter 1 The Composition and Structure of Wood90Tianjin University of Science & Technology纹孔的构造:•具缘纹孔(Bordered pit)•单纹孔（Simple Pit )•半具缘纹孔(Half Bordered Pit）Chapter 1 The Composition and Structure of Wood91Tianjin University of Science & TechnologyFigure 13. Profiles of pit pairs (redrawn from Haygreen and Bowyer) 纹孔室 纹孔缘 纹孔口 纹孔膜 纹孔托 Chapter 1 The Composition and Structure of Wood92Tianjin University of Science & Technology具缘纹孔具缘纹孔Chapter 1 The Composition and Structure of Wood93Tianjin University of Science & TechnologyAtomic Force Microscope Image of Bordered Pit (Black Spruce wood) Chapter 1 The Composition and Structure of Wood94Tianjin University of Science & TechnologyHere is another structural view of a softwood bordered pit pair. Two tracheids are connected by the pit pair. The over-arching pit borders are separated by a central “pit membrane“ which bisects the pit chamber.Chapter 1 The Composition and Structure of Wood95Tianjin University of Science & TechnologyHere are two bordered pits which were observed with a scanning electron microscope. More detail of the structure can by seen in this picture. The two pits form a “pit pair“ which is cut open so that we can see the inside or “pit chamber“. Portions of three longitudinal tracheid lumens (dark areas) can be seen here.Chapter 1 The Composition and Structure of Wood96Tianjin University of Science & Technology4．树 木 的 细 胞 类 型（Cell Types of Wood）形态（Shape）：锐端细胞和薄壁细胞；功能（Function）：输导细胞、支撑细胞和贮藏细胞。
Chapter 1 The Composition and Structure of Wood97Tianjin University of Science & Technology输导细胞 支撑细胞 贮藏细胞阔叶材： 导管 木纤维 薄壁细胞针叶材： 管胞 薄壁细胞Chapter 1 The Composition and Structure of Wood98Tianjin University of Science & Technology三．针叶材的生物结构、细胞类型、含 量及形态 （一）针叶材的生物结构1、横切面；2、弦切面；3、径切面Chapter 1 The Composition and Structure of Wood99Tianjin University of Science & TechnologyChapter 1 The Composition and Structure of Wood100Tianjin University of Science & TechnologyChapter 1 The Composition and Structure of Wood101Tianjin University of Science & TechnologyChapter 1 The Composition and Structure of Wood102Tianjin University of Science & TechnologyChapter 1 The Composition and Structure of Wood103Tianjin University of Science & Technology（二）细胞类型、含量及形态1. 管 胞•占木质部细胞容积的90%~95%，•管胞平均长度一般为3~5mm，宽为0.03~0.05mm。
•管胞壁上的纹孔大多为具缘纹孔Chapter 1 The Composition and Structure of Wood104Tianjin University of Science & TechnologyDetail of annual ring.Earlywood and latewood fibres.Chapter 1 The Composition and Structure of Wood105Tianjin University of Science & TechnologyCells from a softwood. Magnification X 50Chapter 1 The Composition and Structure of Wood106Tianjin University of Science & Technology2.木 薄 壁 组 织•木射线管胞和木射线薄壁细胞•木射线细胞占木材体积的5%~10%•Norway云杉和Scots松木射线薄壁细胞的长为：0.01~0.16mm，宽为：2~5μmChapter 1 The Composition and Structure of Wood107Tianjin University of Science & Technology3. 树 脂 道 树脂道是由若干分泌细胞所围绕成形的一种胞间道。
它不是一个细胞，也不是一个组织，而是细胞间隙，中间充满树脂Chapter 1 The Composition and Structure of Wood108Tianjin University of Science & Technology松木树脂道结构图Chapter 1 The Composition and Structure of Wood109Tianjin University of Science & Technology图1-26 纵。