Order and Randomness in Lignin and Lignification: Is a New Paradigm for Lignification Required?

to say that other aspects of order in the polymer, such as the alignment of aromatic rings indicated by Raman spectroscopy (Atalla and Agarwal 1985), are impossible. Randomness has been used to imply that the process appeared to have no direct enzymatic control. Obviously, the polymerization of lignin is not completely random, and only a subset of the possible linkages are found. In fact, prior descriptions as ‘random’ presumably never implied a totally random distribution of coupling products; clearly, the coupling of two monomers must be weighted by the propensity for each type of coupling. However, lignin formation has little to do with monomer coupling — lignification, unlike lignan formation, almost entirely involves coupling of a single monomer to a growing oligomer. The idea that the coupling would depend on the types of units involved, their concentrations, the matrix and so on are all issues that can determine what type of coupling arises at any step.