Lignin and lignification with special reference to its down regulation for the improvement of wood and bast fibre quality

Lignin, a phenylpropanoid polymer, is a major constituent of higher plant cell wall especially those of the mechanical and conducting tissues. It has a very complex chemical structure where the monomer lignin-building units join non-specifically to produce specific lignin moiety. Lignin biosynthesis is equally complex and involves long sequence of reactions from intermediate metabolism through the common shikimic acid pathway and specific lignin pathway. Potential economic benefits of modifying lignin quality and quantity of wood and bast fibre have inspired many efforts to understand and control lignifications. The present article reviews our up to date researches on the cellular, biochemical and molecular mechanisms of lignin biosynthesis giving special emphasis to those on woody and phloem fibre yielding plants.