Phenolic acids in wheat coleoptile cell walls.

The phenolic constituent of nonvascular cell walls of wheat (Triticum aestivum L.) coleoptiles, which yields vanillin upon nitrobenzene oxidation, is not lignin as I previously claimed. It seems to be mainly ferulic acid bonded to carbohydrate, probably by an ester linkage. The acid is associated with a fraction of the wall rich in arabinose and xylose, although it is not known whether it is esterified directly with these pentose residues. The phenolic-carbohydrate complex is released by cellulase, but not by pronase or a mixture of hemicellulases.