STUDIES OF LIGNIN BIOSYNTHESIS USING ISOTOPIG CARBON: V. COMPARATIVE STUDIES ON DIFFERENT PLANT SPECIES

Abstract

Seven species of higher plants have been tested for their ability to convert radioactive tyrosine to lignin in vivo. A total of 11 species representing 10 families have now been compared and only Triticum vulgare and Calamagrostis inexpansa, both members of the Gramineae, have given positive results. It is suggested that lack of a specific enzyme system may prevent lignin formation from tyrosine in the other species. The metabolic differences appear to be restricted to tyrosine utilization, for both wheat and maple have similar abilities to use a number of labelled cinnamic acid derivatives, as well as phenylalanine. Further evidence is presented that each type of lignin polymer has a corresponding aromatic monomer. Sinapic acid, ferulic acid, and probably p-hydroxycinnamic acid are preferentially transformed to syringyl, guaiacyl, and p-hydroxyphenyl lignins respectively.