Matrix polymers

Matrix polymers in plant cell walls are polysaccharides (hemicelluloses and pectins) and lignins. In contrast to cellulose, the matrix polysaccharides are synthesized in the Golgi ap­paratus, and deposited into the cell wall network while cellulose is synthesized (26). These polymers form a matrix network directly or indirectly associated with the surface of cel­lulose elementary fibrils. Matrix polysaccharides are non-crystalline structures and vary in glycosidic linkages, branching chemistry, and sugar residues. Lignins are polymers of mono — lignols (phenylpropane derivatives) providing mechanical strength and water resistance for the plant cell wall, as well as resistance of microbial attack (27-29). Lignin deposition is the final differentiation stage of plant cells that have thick secondary cell walls and proceeds via several phases, starting at the cell corners in the region ofthe middle lamella and the primary wall after the S1 layer formation has initiated. When the formation of the polysaccharide matrix of the S2 layer is completed, lignification proceeds through the secondary wall. The bulk of lignins are deposited after cellulose and hemicellulose have been deposited in the S3 layer. This is why lignin concentration is higher in the middle lamella and cell corners than in the S2 secondary wall (29-31).