Wood Strcuture (Junior Cert Wood Technology): Revision Notes

Wood Structure

Wood structure is essential in wood technology and material science. It determines the mechanical properties and uses of wood. By studying this structure, we can tell the difference between hardwoods and softwoods. Hardwoods come from angiosperm trees, while softwoods come from gymnosperm trees.

Definitions

• Hardwood: A type of wood from angiosperm trees, identified by broad leaves and often losing leaves seasonally.
• Softwood: Wood from gymnosperm trees, like conifers, with needle-like leaves and usually evergreen.
• Tracheids: Long, slender cells aiding in water transport and support in both hardwoods and softwoods.
• Vessels: Tubes mainly in hardwoods, helping in efficient water transportation.
• Fibres: Thick cells providing strength to wood.

Cellular Structure of Wood

• Composition: Wood mainly consists of tracheids, vessels, and fibres.
• Softwoods vs. Hardwoods: Softwoods mostly have tracheids for support and conduction. Hardwoods have complex structures, including vessels (in either ring-porous or diffuse-porous patterns), fibres, and some tracheids.

Characteristics	Softwoods	Hardwoods
Vessels	Absent	Present
Types of Fibres	Mostly tracheids	Mix of fibres and tracheids
Growth Rate	Usually faster	Usually slower

Arrangement and Role of Tracheids, Vessels, and Fibres

• Tracheids: In softwoods, they provide main support and water transport. They contribute to wood's mechanical properties.
• Vessels in Hardwoods: Arranged to impact water transport efficiency; ring-porous patterns enable rapid water flow during growth spurts.
• Fibres: Give mechanical strength and are key structures in both wood types.

Influence of Wood Structure on Physical Properties

• Properties: The cellular structure affects density, strength, and durability. Hardwoods' complex vessel network makes them denser and stronger, whereas softwoods' uniform tracheids make them lighter and more flexible. For example, oak (a hardwood) is denser and stronger than pine (a softwood).
• Application Case Study: In building, hardwoods like oak are chosen for structural beams for strength. Softwoods like pine are preferred in furniture for easy handling.

Growth Rings and Their Significance

• Formation: Growth rings form due to environmental changes; trees grow more in spring, forming distinct layers.
• Significance: Growth rings show a tree's age and past climate. Wider rings suggest favourable conditions like good rainfall, while narrower ones suggest drought.

Summary