Lignificeret

Lignificeret is a term used especially in Danish to describe tissues that have undergone lignification. Lignification is the deposition of lignin in the cell walls of vascular plants, most prominently in the secondary walls of xylem elements. The result is increased mechanical strength, reduced wall permeability, and enhanced resistance to decay, which supports upright growth and efficient water transport.

Lignin biosynthesis proceeds from the phenylpropanoid pathway. The process starts with phenylalanine and involves enzymes such as phenylalanine ammonia-lyase, cinnamate 4-hydroxylase and 4-coumarate-CoA ligase, culminating in monolignols including coniferyl, sinapyl and p-hydroxyphenyl alcohols. These monolignols are transported to the cell wall and polymerized by oxidative enzymes, notably peroxidases and laccases, forming a complex, cross-linked lignin network that associates with cellulose and hemicellulose.

Lignification patterns vary among plant groups and tissues. Gymnosperms tend to lignify mainly guaiacyl units, while angiosperms contain mixed guaiacyl and syringyl units; the relative composition affects rigidity, porosity, and recalcitrance to chemical processing. Lignification is developmentally programmed, occurring mainly during secondary growth in xylem, but can be influenced by environmental factors such as wounding or pathogen attack.

In research and industry, lignification is studied using histochemical stains and spectroscopic methods and is a key factor in wood quality and biofuel production, because lignin impedes enzymatic access to polysaccharides. Understanding lignificeret helps in crop improvement strategies aimed at modifying lignin content or composition while preserving plant integrity.