A METHOD FOR THE DETERMINATION OF THE LIGNIN CONTENT OF FRESH PLANT TISSUE WITHOUT PRELIMINARY DRYING

Abstract

A method of determining the lignin content of fresh plant tissue without preliminary drying has been devised. Prior to the final lignin determination with 72% sulphuric acid, the tissue is cut up, extracted with ether saturated water in a Waring Blendor, refluxed with 1% hydrochloric acid, and finally extracted with ethanol–benzene. For comparison, determinations were carried out by the above method and the standard A.O.A.C. procedure on material that had been air-dried at room temperature. Both greenhouse and field grown oat plants cut at various growth stages were used in this study. The modified method gave lower lignin values than the standard procedure with young succulent tissue. This difference decreased as the age of the tissue increased, and the results by all methods were very similar with oat straw. That the modified procedure on fresh tissue removes more interfering nitrogenous material than the other methods used is indicated by the lower nitrogen content of the lignin isolated. The absolute methoxyl contents of the residues isolated from dried tissue were greater than of those isolated from fresh material (from the same source). This may have been due to the inclusion of more methoxyl-containing carbohydrates in the former residues.