Anatomical differences of softwood and

hardwoodGroup: 01

Students ID: MS-150501,MS-150509,MS-150510,MS-150512

Definition of wood• Wood is a complex biological structure, a composite

of many chemistries and cell types acting together to serve the needs of a living plant.

• It is a three dimensional, anisotropic and hygroscopic raw material which mainly composed of cellulose hemicelluloses and lignin.

Types of Wood

Hardwood:• Hardwoods are not all have hard, heavy

wood, that come from angiosperms (flowering plants).

• They are typically broadleaf, deciduous trees such as maple (Acer), birch (Betula), and oak (Quercus).

Softwood:• Softwoods are not all soft, lightweight

wood. They are those woods that come from gymnosperms (mostly conifers).

• They are generally needle-leaved evergreen trees such as pine (Pinus) and spruce (Picea)

Vessels (Pores)When viewed from the endgrain, vessels simply appear to be holes in the wood—what are commonly referred to as pores.

In a live tree, vessels serve as the pipelines within the trunk, transporting sap within the tree. Vessel elements are the largest type of cells, and unlike the other hardwood cell types, they can be viewed individually—oftentimes even without any sort of magnification.

Anatomy of Hardwood

ParenchymaParenchyma cells are thin-walled storage units. In hardwoods, parenchyma is long, tapered longitudinal cells, brick shaped epithelium around gum canals, and ray cells.

Anatomy of Hardwood (cont’d)

Apotracheal parenchyma Paratracheal parenchyma

Banded parenchyma

Parenchyma typesAnatomy of Hardwood (cont’d)

• In Hardwoods, Raysmay be:

– Uniserate – one cellwide– Biserate – two cellswide– Multi-serate – manycells wide.

• Ray width variesbetween and withinspecies.

Rays

Multiseriate ray Uniseriate ray

Anatomy of Hardwood (cont’d)

Procumbent ray: In radial view, procumbent ray cells are elongated horizontally.

Upright ray: Upright ray cells are either squarish or vertically oriented

Anatomy of Hardwood (cont’d)Rays

• Saclike or cystlike structures that sometimes develop in a vessel and rarely in a fiber through the proliferation of the protoplast of a parenchyma cell through a pit pair.

• They commonly form in hardwoods as a result of wounding and effectively act to prevent water loss from the area around damaged tissues.

• They may also develop as a result of infection from fungi or bacteria, again to prevent water loss.

Anatomy of Hardwood (cont’d)Tyloses

• In a living tree, hardwood fibers have strong, thick cell walls that mainly serve to support and strengthen the trunk.

• When viewed from the endgrain, fibers are very small and can’t be seen individually.

• Instead, fibers can only be distinguished in a broader sense as colored areas which form the backdrop of the wood’s endgrain.

Anatomy of Hardwood (cont’d)Fibers

Tracheid• Tracheids are long cells

that are often more than 100 times longer (1 to 10 mm) than wide and they are the major component of softwoods, making up over 90% of the volume of the wood.

Anatomy of Softwood

• They serve both the conductive and mechanical needs of softwoods.

Anatomy of Softwood (cont’d)

• Much like tracheids, parenchyma are oriented along the length of the tree-trunk, and are sometimes referred to as longitudinal or axial parenchyma.

• Axial parenchyma cells are similar in size and shape to ray parenchyma cells, but they are vertically oriented and stacked one on top of the other to form a parenchyma strand.

Parenchyma

• With the exception of special fusiform rays, which occur in conjunction with resin canals, regular softwood rays are usually only one to two cells wide.

Anatomy of Softwood (cont’d)Rays

• Because these normal rays are much narrower, and lack unique characteristics that are observable with a 10x hand lens, their usefulness in identification is essentially limited to microscopic examination.

• Resin canals, sometimes referred to as resin ducts, are unique to conifers.

• They are technically not individual cells, but are actually open, tube-like spaces bordered by special cells that have the ability to secrete pitch or resin into the neighboring opening (canal).

• One of the apparent purposes of these ducts is to protect and seal up a wound by exuding resin to cover the damaged area of the tree.

• Accordingly, in rare instances, some softwood species that don’t normally have resin ducts will develop them as a result of trauma.

Anatomy of Softwood (cont’d)Resin Canals

Anatomy of Softwood (cont’d)Resin Canals

1. Bowyer, J.; Shmulsky, R.; Haygreen, J.G. 2003. Forest products and wood science: an introduction. 4th ed. Iowa City, IA: Iowa State Press. 554 p.

2. Desch, H. E., & Dinwoodie, J. M. (1996). Timber structure, properties, conversion and use (No. Ed. 7). MacMillan Press Ltd.

3. Ross, R. J. (2010). Wood handbook: wood as an engineering material.

4. Brunner, I.; Brodbeck, S.; Buchler, U.; Sperisen, C. 2001. Molecular identification of fine roots from trees from the Alps: reliable and fast DNA extraction and PCR-RFLP analyses of plastid DNA. Molecular Ecology. 10: 2079–2087.

5. Brunner, M.; Kucera, L.J.; Zürcher, E. 1994. Major timber trees of Guyana: a lens key. Tropenbos Series 10. Wageningen, Canadian Forest Service, Pacific Forestry Centre. 1999.

References