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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]
Wood is an organic material and decays under biological and chemical degradation when buried or submerged above water or soil. Wood, an organic material produced by plants, are chemically composed of: carbohydrates (cellulose and hemicellulose), lignin and other components (aliphatic acids, alcohols, proteins and inorganic substances) in a ...
Wood is primarily composed of xylem cells with cell walls made of cellulose and lignin. Xylem is a vascular tissue which moves water and nutrients from the roots to the leaves. Most woody plants form new layers of woody tissue each year, and so increase their stem diameter from year to year, with new wood deposited on the inner side of a ...
The polysaccharide components of plant cell walls are highly hydrophilic and thus permeable to water, whereas lignin is more hydrophobic. The crosslinking of polysaccharides by lignin is an obstacle for water absorption to the cell wall. Thus, lignin makes it possible for the plant's vascular tissue to conduct water efficiently. [15]
The first lignified secondary walls evolved 430 million years ago, creating the structure necessary for vascular plants. The genes used to form the constituents of secondary cells walls have also been found in Physcomitrella patens. This suggests that a duplication of these genes was the driver of secondary cells wall formation. [2]
New evidence reopened the case of actress Natalie Wood’s 1981 drowning death, pointing to her husband, actor Robert Wagner, as a prime suspect. Two witnesses came forward, claiming Wood was ...
Secondary xylem is formed during secondary growth from vascular cambium. Although secondary xylem is also found in members of the gymnosperm groups Gnetophyta and Ginkgophyta and to a lesser extent in members of the Cycadophyta, the two main groups in which secondary xylem can be found are: