Wood

Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic material – a natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin that resists compression. Wood is sometimes defined as only the secondary xylem in the stems of trees, or it is defined more broadly to include the same type of tissue elsewhere such as in the roots of trees or shrubs. In a living tree it performs a support function, enabling woody plants to grow large or to stand up by themselves. It also conveys water and nutrients between the leaves, other growing tissues, and the roots. Wood may also refer to other plant materials with comparable properties, and to material engineered from wood, or wood chips or fiber.

Structure

Wood is a complex, composite material and is the main building block of trees. It is composed of cellulose, hemicellulose, and lignin. Wood is formed in plant cell walls and is made up of many individual cells. The cell walls are composed of three layers: the middle lamella, primary wall, and secondary wall.

Types of Wood

There are two basic types of wood: hardwood and softwood. However, the names do not refer to the properties of the wood: some softwoods can be hard and some hardwoods can be soft. Hardwoods come from flowering trees while softwoods come from conifers.

Uses

Wood has been used for thousands of years for fuel, as a construction material, for making tools and weapons, furniture and paper. More recently it emerged as a feedstock for the production of purified cellulose and its derivatives, such as cellophane and cellulose acetate.

See Also

• Timber
• Lumber
• Woodworking
• Forestry

References

Wood Resources
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