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Contributions to the understanding of the fine structure of the wood cell wall were also made by Albert Frey-Wyssling and Reginald Dawson Preston, who employed light microscopy-based techniques. In parallel, Johannes Liese integrated his expertise in wood anatomy and decay mechanisms with extensive studies on wood protection. [21]
Wood is a structural tissue/material found as xylem in the stems and roots of trees and other woody plants.It is an organic material – a natural composite of cellulosic fibers that are strong in tension and embedded in a matrix of lignin that resists compression.
There are often pits on the cell walls of tracheids, which allows for water flow between cells. Tracheids are dead at functional maturity and do not have a protoplast. The wood of gymnosperms such as pines and other conifers is mainly composed of tracheids. [2] Tracheids are also the main conductive cells in the primary xylem of ferns. [3]
Idealized structure of lignin from a softwood. Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. [1] Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity and do not rot easily.
The first xylem to develop is called 'protoxylem'. In appearance, protoxylem is usually distinguished by narrower vessels formed of smaller cells. Some of these cells have walls that contain thickenings in the form of rings or helices. Functionally, protoxylem can extend: the cells can grow in size and develop while a stem or root is elongating.
Medullary rays, also known as vascular rays or pith rays, are cellular structures found in some species of wood. They appear as radial planar structures, perpendicular to the growth rings, which are visible to the naked eye. In a transverse section they appear as radiating lines from the centre of the log.
In plants, a secondary cell wall is a thicker additional layer of cellulose which increases wall rigidity. Additional layers may be formed by lignin in xylem cell walls, or suberin in cork cell walls. These compounds are rigid and waterproof, making the secondary wall stiff. Both wood and bark cells of trees have secondary walls.
The secondary cell wall is a structure found in many plant cells, located between the primary cell wall and the plasma membrane. The cell starts producing the secondary cell wall after the primary cell wall is complete and the cell has stopped expanding. [ 1 ]