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Elements of Wood Cell Walls: Lignin

The document discusses the main components of wood cell walls, which include cellulose, hemicellulose, and lignin. Cellulose makes up 40-45% of wood, hemicellulose 20-30%, and lignin 20-30%, each playing critical roles in structural integrity and support. Additionally, it highlights the differences in hemicellulose composition between softwood and hardwood, as well as the significance of lignin in the carbon cycle and its slow decomposition rate.

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17 views1 page

Elements of Wood Cell Walls: Lignin

The document discusses the main components of wood cell walls, which include cellulose, hemicellulose, and lignin. Cellulose makes up 40-45% of wood, hemicellulose 20-30%, and lignin 20-30%, each playing critical roles in structural integrity and support. Additionally, it highlights the differences in hemicellulose composition between softwood and hardwood, as well as the significance of lignin in the carbon cycle and its slow decomposition rate.

Uploaded by

jatinpalp92
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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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Elements of wood cell walls

The chief constituent of woody plant cell walls are cellulose, hemicellulose and lignin.
Cellulose comprises about 40-45% of wood, hemicellulose about 25-30% in soft wood and 20-
35% in hard wood and lignin about 20-30%.
Cellulose
• Cellulose is an organic compound with the formula (C 6H10O5)n, a polysaccharide
consisting of a linear chain of several hundred to over ten thousand linked glucose units.
• Cellulose is the structural component of the primary cell wall of green plants.
• About 33% of all plant matter is cellulose (the cellulose content of cotton fiber is 90%,
wood is 40–50% and dried hemp is approximately 45%)
• Cellulose is a straight chain polymer.
Hemicellulose

• They are associated with the cellulose in the cell wall and are carbohydrate polymers.
• Hemicellulose belongs to a group of heterogeneous polysaccharides.
• Like cellulose most hemicellulose function as supporting material in the cell wall.
• The amount of hemicellulose of the dry weight of wood is usually between 20 and
30%.
• The composition and structure of the hemicellulose in the softwood differ in a
characteristic way from those in the heartwood.
• Hemicellulose in Softwood - Mannose is the most important hemicellulosic monomer
followed by xylose, glucose, galactose and arabinose.
• Hemicellulose in Hardwood - Xylose is the most important hemicellulosic monomer
followed by mannose, glucose, galactose, with small amount of arabinose and
rhamnose.
Lignin

• Lignin is a class of complex organic polymers.


• Lignins are one of the main classes of structural materials in the support tissues of
vascular plants and some algae.
• Lignins are particularly important in the formation of cell walls, especially in wood
and bark, because they lend rigidity and do not rot easily.
• Chemically lignins are cross-linked phenol propane polymers.
• Lignin fills the spaces in the cell wall between cellulose, hemicellulose, and pectin
components, especially in xylem tracheids, vessel elements and sclereid cells.
• Lignin plays a significant role in the carbon cycle, sequestering atmospheric carbon into
the living tissues of woody perennial vegetation.
• Lignin is one of the most slowly decomposing components of dead vegetation,
contributing a major fraction of the material that becomes humus as it decomposes.

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