STUDIES OF LIGNIN BIOSYNTHESIS USING ISOTOPIC CARBON: X. FORMATION OF LIGNIN FROM PHENYLPROPANOIDS IN TISSUE CULTURE OF WHITE PINE

Abstract

The incorporation of phenylalanine-R-C14, p-coumaric acid-2-C14, ferulic acid-2-C14, and sinapic acid-2-C14 into conifer lignin was studied by using tissue culture of white pine. The first three compounds were quite good precursors of conifer lignin. The lignin was degraded by ethanolysis to yield vanilloyl methyl ketone in approximately 0.2% yield of the lignin. When sinapic acid was fed no corresponding syringoyl methyl ketone could be isolated but the vanilloyl methyl ketone was radioactive. This suggests that demethoxylation of sinapyl compounds can occur in lignification. The results show that the enzymes responsible for the biosynthesis of lignin from these precursors are present in the cambium, and that the lignification route via phenylpropanoid acids is operative in this tissue as well as in other species.