| Wood in routine life and technology is the internal part of a tree located under the bark. Fabrics or a set of fabrics formed from procambium or cambium are understood as wood or xylem.
Wood formation:
Wood is one of the components of the fibro-vascular bundle and is referred to the usual component of the bundle occurring from this procambium or cambium – the inner bark or phloem. Two cases are observed during the formation of the fibrovascular bundle from procambium: all the procambium cells transform into elements of wood and inner bark – obtained so-called closed bundles (higher cryptogamous, monocotyledonous and some dicotyledonous plants) or a layer of active fabric is left on the border between the wood and inner bark – cambium and open bundles are obtained (dicotyledonous and gymnospermous).
In the first case the quantity of wood remains constant and the plant is incapable of becoming thicker; in the second case, thanks to the activity of cambium, every year the quantity of wood increases and the plant trunk grows thicker and thicker gradually. In the Russian wood species, wood is concentrated at the center of the tree (axis) and the inner bark close to the circle (periphery). The other relative positioning of the wood and inner bark is observed in some other plants. Already, dead cell elements with stiffened thick coats form the composition of wood; the inner bark is made, on the contrary, of live elements, with live protoplasm, cell sap and a thin un-stiffened coat. Even if dead, the thick-walls are found in the inner bark and on the contrary, live elements are found in wood, but from this, however, the general rule does not change substantially. Both parts of the fibrovascular bundle differ from each other according to physiological function: the so-called raw sap, i.e. water is present with substances dissolved in it, they move upwards from the soil to the leaves along the wood and the formed plastic sap, moves downwards along the inner bark. The stiffening phenomena of the cell coats are caused by the impregnation of the cellulose coat by special substances, compounds usually under the general name “lignin”. The availability of lignin and at the same time, the stiffening of the coat is easily identified by means of some reactions. Thanks to stiffening, the plant coats become stronger, firm and elastic; at the same time, at easy water permeability, they lose the ability to absorb water and to inflate.
Valuable wood species:
The value of various wood species depends on their strength, durability and originality of pattern. Such wood is used for manufacturing fine furniture, parquet, doors, various interior objects, which are considered elite by taking into consideration the initial high cost and the amount of effort spent for its treatment. In Russia, the following species are extensively found: oak, cherry, beech, pear, rosewood mahogany walnut and maple (white, sugar, acutifoliate).
Basic operating features:
* Hardness - the indicator of the service life of the top layer of the wood. Deterioration is slow if the wood is hard;
* Stability and shrink level - indicates the compatibility of various wood species during use in the combination (in parquet, incrustations etc.). Also shows the suitability of their use in various climatic conditions;
* Degree of oxidation - shows the change in the color of the wood under the influence of light. If the degree of oxidation is more, then the wood becomes much darker;
* Expressiveness of texture - this influences the visual perception of the person. At a high contrast a high exciting effect is created;
* Durability to loads - the ability of wood to withstand any type of load.
All the properties can be different for each species (sometimes even for various parts of the tree) and this depends on various conditions in which the tree grows.
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