Biochemical Aspects of Lignification and Heartwood Formation

Abstract

Metabolic differences in the formation of gymnosperm- and angiosperm lignins were explained in terms of the different functions of O-methyltransferase and redacting enzymes which participate in methylation and reduction of hydroxycinnamic acid intermediates in biosynthetic pathway of these two types of lignins. Chemical properties of dehydrogenation polymer (DHP) of sinapyl alcohol were characterized and possible occurrence of syringyl lignins in hardwoods was discussed. DHP and dimers of p-coumaryl alcohol were also characterized and discussed in relation to the formation of grass lignin. Heartwood formation was explained in terms of metabolic changes in ray parenchyma cells in transition wood and the biosynthetic site of heartwood extractives was elucidated.