Detection of bound ferulic acid in cell walls of the Gramineae by ultraviolet fluorescence microscopy
THE phenolic acids, ferulic and p-coumaric, are bound to cell walls of plants of the Gramineae (which include grasses and cereals) and it was thought that these acids were esterified to lignin and so occurred only in lignified cell walls1-4. But it has been shown recently that in cell walls of Lolium multifiorum Lam., which contain ferulic acid and a small amount of p-coumaric acid mainly as their trans isomers, the acids are esterified at their carboxyl groups to polysaccharides5-7. The digestibility of grasses by ruminants can be predicted by estimating the amounts of the acids released from the plant cell walls after treatment with a commercial cellulase preparation8. The acids could be important in influencing the degradation of plant organic matter in the rumen or in soil and may act as growth inhibitors of plant pathogens9. We now report results obtained by ultraviolet fluorescence microscopy, which indicate that ferulic acid is bound to polysaccharides of the walls of a wide variety of cell types of the Gramineae; these walls give a negative phloroglucinol-HCl test for lignin10.