The mallet I made in Seely Copse - Vicky

The mallet I made at Seely Copse – Vicky Mitchell.

According to Tabor (2000, p.7) “Wood is the tough, lignified, fibrous substance between the pith and cambium of trees and shrubs.” (Lignified means to “make rigid and woody by the deposition of lignin in cell walls,” The Oxford English Dictionary, 2010).

Tabor (2000, p. 7) describes living wood as being made up of over 50% water, some of which are found in the cell walls. The cell walls are mostly made up celluloses, long chains of glucose. Cellulose is the most important single compound in wood, providing the wood's strength. Cellulose is a product of photosynthesis. In photosynthesis, glucose and other sugars are manufactured from water and carbon dioxide.  Other compounds such as lignin are also present in the older cells. Lignin is a polymer that acts as a binding agent to hold cells together. Lignin also occurs within cell walls to impart rigidity.   

The structure and growth of wood.

Bark – The outermost layer of the tree is mostly dead cells “penetrated by corky layers that render it waterproof.” (Tabor, 2000, p. 8). 

Cambium – A layer of living cells between the wood and the innermost bark of a tree found between the phloem and the xylem. Each growing season the cambium cells divide rapidly adding a new layer of cells on the wood already formed, as well as a layer of inner bark on the cambium's outer face. Their function is to produce the water and sugar transporting cells used to increase the trees diameter and height. The cambium is damaged easily by heat, impact or gnawing which can cause all or part of the stem to die. (Tabor, 2000, p. 8)

Xylem and phloem make up the transportation system of vascular plants. The phloem is situated between the cambium and the bark and its function is to transport glucose within the tree. The xylem is responsible for transporting water and minerals and is situated on the inner side of the cambium. These vessels run vertically through the tree, providing an optimal structure to move the substances to where they are required. (Tabor, 2000, p.8). The phloem is living, however, the xylem tissue dies after one year and then develops anew (rings in the tree trunk). (Biology4kids.com, 2012).

Tree growth is more rapid in the spring and according to Tabor (2000, p. 8) vessels are larger, whilst in the summer they are smaller. “In deciduous trees the visible difference in the size of spring and summer wood vessels creates the annual rings” we can see in the cross section and use to age a tree (Tabor, 2000, p.8). The rings are caused by the tree photosynthesising (converting carbon dioxide and water from the xylem into glucose) and sending the glucose down the phloem to be converted into wood (Tabor, 2000, p.8).      

References:

http://www.biology4kids.com/files/plants_xylemphloem.html (Accessed: 8 April 2012).

Tabor, R. (2000) The Encyclopedia of Green Woodworking. Bristol: Eco-Logic Books.