The structure of cellular walls
The structure of the plant cells in trees are similar in every species. There are differences between conifers and deciduous trees. For example the shape of the cell and the order of the cells varies between the species. The cells can be sorted to four different categories.
- The cells responsible for growth
- The cells responsible for nutrients
- The cells responsible for distribution of water
- The cells maintaining the structure.
The structural strength of a tree is dependent on the structure of the cellural walls and the cellular structure
The cellular wall is composed of layers:
- Outer amorphic middle lamel
- The primary cell wall
- Secondary cell wall composed of microfibrils
- Inner plasma membrane.
The cellular walls are composed of
- Cellulose (40-50%), the structural strength of a tree is dependent on this.
- Xylan (20-25%), this also has an impact on the structural strength
- Lignin (20-30%), this acts as an adhesive.
The cellular structure
There are two kinds of cells in a tree:
- Prosenchyma: Narrow, long and tapering cells that are dead by the maturity. Their function is distributing water and strengthening the tree.
- Parenchyma: Round and thinwalled cells. They are located in outer trunk and they store the nutrients.
Conifer trees are mostly composed of tracheids that are responsible of distributing the water. The mechanical qualities of wood are greatly impacted by them. Vascular rays exist in every species. They exist perpendicular to the height axis. For spruce and pine they comprise 6% of the volume of the trunk.
Deciduous trees have a differt kind of structure than conifer trees. The water is distributed in dedicuous trees by lateral tracheas. Deciduous trees are separated by the location of the tracheas into distributed trachea trees and radial trachea trees. In radial trachea trees the tracheas are located only in early wood and in distributed trachea trees they are located all around.
The supporting cells of deciduous trees are called fibers. Fibers consist 40-75% of the wood.