Title: Structure and function of wood
Author: Wiedenhoeft, Alex C.; Miller, Regis B.
Source: Handbook of wood chemistry and wood composites. Boca Raton, Fla. : CRC Press, 2005: pages 9-33.
Description: Despite the many human uses to which various woods are suited, at a fundamental level wood is a complex biological structure, itself a composite of many chemistries and cell types acting together to serve the needs of the plant. Although humans have striven to understand wood in the context of wood technology, we have often overlooked the key and basic fact that wood evolved over the course of millions of years to serve three main functions in plants: the conduction of water from the roots to the leaves, the mechanical support of the plant body, and the storage of biochemicals. The need for these three functions has driven the evolution of approximately 20,000 different extant species of woody plants, each with unique properties, uses, and capabilities, in both plant and human contexts. Understanding the basic requirements dictated by these three functions and identifying the structures in wood that perform them allows insights into the realm of human wood use. A scientist with a robust understanding of the interrelationships between form and function can predict the usefulness of a specific wood in a new context. To begin, it is necessary to define and delimit the component parts of wood at a variety of scales. There is a significant difference in the quality and quantity of wood anatomical expertise necessary for a researcher who is using a solid wood beam compared to the knowledge necessary for an engineer designing a glued-laminated beam, and these are in turn different compared to the knowledge required for making a wood-resin composite with wood flour. In the first case, a large-scale anatomical understanding may help to explain and quantify the mechanical properties of the beam. In the second case, an understanding of anatomical effects on mechanical properties must be coupled with chemical knowledge about the efficacy of various adhesives. In the third case, an understanding of particle size distribution and wood cell wall chemistry will be key pieces of knowledge. The differences in the kinds of knowledge in these three cases are related to the scale at which one intends to interact with wood, and in all three cases the technologically different properties are derived from the biological needs of the living tree. For this reason, the structure of wood will be explained in this chapter at decreasing scales, and in ways that demonstrate the biological rationale for a plant to produce wood with such features. Such background will permit the reader to access primary literature related to wood structure with greater ease. Although shrubs and many vines form wood, the remainder of this chapter will focus on the wood from trees. As trees are the predominant source of wood for commercial applications and provide examples of virtually all features that merit discussion, this restriction of scope is warranted.
Keywords: Juvenile wood, plant cell walls, tree-rings, cambium, wood anatomy, sapwood, heartwood, wood identification, wood moisture, reaction wood
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Wiedenhoeft, Alex C.; Miller, Regis B. 2005. Structure and function of wood. Handbook of wood chemistry and wood composites. Boca Raton, Fla. : CRC Press, 2005: pages 9-33.
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