Lignin

Lignin is a complex aromatic polymer deposited in plant cell walls, where it strengthens tissues, stiffens wood, and helps resist decay.

Monolignol: A phenolic alcohol that plants use as a building block for lignin. These precursors are exported to cell walls and polymerized into lignin.
Phenylpropanoid pathway: A plant metabolic pathway that produces phenolic compounds from the amino acid phenylalanine. It supplies the precursors from which lignin monomers are made.
Kraft process: A chemical pulping process that separates cellulose fibers from wood using alkaline sulfide solutions. It removes much of wood’s lignin to produce pulp for paper.
Hemicellulose: A diverse group of branched polysaccharides in plant cell walls. Unlike lignin’s aromatic polymer, hemicellulose is made of sugar units.
Wood: The lignified secondary xylem of trees and other woody plants. Lignin helps give wood the stiffness needed to support upright growth.
Lignification: The process by which lignin is deposited in plant cell walls. It places lignin within walls as cells develop and tissues mature.
Coniferyl alcohol: A monolignol that contributes mainly to guaiacyl units in lignin. It is a major precursor in lignin from conifers and many other plants.
Lignosulfonate: A water-soluble lignin derivative produced during sulfite pulping. This pulping byproduct is used in dispersants, binders, and other products.
Suberin: A hydrophobic biopolymer deposited in protective plant tissues such as cork and root barriers. It also limits water movement but is chemically distinct from lignin.
Xylem: Plant vascular tissue that transports water and dissolved minerals from roots to shoots. Lignified xylem walls resist collapse as water moves under tension.

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