Lignin Properties

Description

Lignin is a class of complex organic polymers that form important 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.It is one of the most abundant organic polymers on Earth, exceeded only by cellulose.Lignin fills the spaces in the cell wall between cellulose, hemicellulose, and pectin components, especially in xylem tracheids, vessel elements and sclereid cells. It is covalently linked to hemicellulose and therefore crosslinks different plant polysaccharides, conferring mechanical strength to the cell wall and by extension the plant as a whole.It is particularly abundant in compression wood but scarce in tension wood, which are types of reaction wood.Lignin plays a crucial part in conducting water in plant stems.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. Lignin is a cross-linked racemic macromolecule with molecular masses in excess of 10,000 u. It is relatively hydrophobic and aromatic in nature.