Lignified

Lignified refers to plant tissue in which the cell walls have become reinforced with lignin, a complex phenolic polymer. Lignification strengthens and waterproofs walls, contributing to mechanical support for stems and to the integrity of vascular tissues involved in water transport.

The process occurs primarily in cells that form part of the plant’s supportive tissues, such as sclerenchyma and the xylem (vessels and tracheids). Lignin is synthesized from monolignols via the phenylpropanoid pathway and is polymerized by enzymes such as peroxidases and laccases. The resulting lignin network binds to cellulose and hemicellulose in a three‑dimensional matrix, giving walls greater rigidity and impermeability.

Lignified tissues are widespread in plants, most notably in wood and bark, where they provide substantial structural support. Grasses and other monocots also exhibit lignification in sclerenchyma fibers. In many cases, cells destined to become lignified tissues lose their protoplasm at maturity, forming a dead but structurally important scaffold.

Properties and implications of lignification include increased mechanical strength, resistance to compression, and reduced permeability to pathogens and water loss. The presence of lignin also influences the color and chemical processing of plant material; wood and other lignified tissues are central to industries such as timber, paper, and bioenergy.