As a formal definition, the Merriam-Webster dictionary defines wood as “The hard fibrous substance consisting basically of xylem that makes up the greater part of the stems, branches, and roots of trees or shrubs beneath the bark and is found to a limited extent in herbaceous plants”. Definition of Wikipedia , on the other hand, is a bit more scientific: “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.” As a whole; wood is an organic material that has many distinct characteristics.
If we were to look at a tree, we could see that it has three layers. The bark, the heartwood, and the thin layer between the bark and the inner wood. The vascular cambium mentioned as thin layer is the main meristem in the stem, producing undifferentiated wood cells inwards and bark cells outwards. This process causes the tree’s diameter to expand, and creates the characteristic growth rings which represents the age of the tree.
The living part of the tree is the cambium which is responsible for the formation of new cells. Sapwood, also called alburnum, outer, living layers of the secondary wood of trees, which engage in transport of water and minerals to the crown of the tree. As the time passes, the tree no longer needs the entire trunk to conduct sap and the cells in middle die. This dead wood in the center is called heartwood. Structure of the heartwood marks the wood’s resistance to rot and decay and its relative hardness.
Generally woods are classified as hardwood or softwood. However, this classification is not directly related with the hardness of the wood. Those labels really refer more to the type of tree; hardwoods generally come from deciduous trees that drop their leaves in the fall. Softwoods come from conifers or evergreens.
Hardness of the trees are measured according to Janka Scale. The test measures the force required to push a steel ball with a diameter of 0.444 inches (11.28 millimeters) into the surface of the wood to a depth of 0.222 inches (one half of the ball’s diameter). Although hardwoods’ hardness scale is usually higher than softwoods, some hardwoods like Poplar, Basswood and
Balsa rank lower than softwoods like Douglas Fir and Pine.
Wood has proved itself useful, throughout the centuries for sheltering, tool making, construction, fuel, paper and etc. It is not only extremely useful but it is also renewable.Besides, its obvious benefits to the nature and human kind, the best feature of wood is the sensation it gives, which comes as natural as breathing.
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