Lignin concentration in oat (Avena byzantina L.) aerial part as measured by four analytical methods

Abstract

The current analytical methods to quantify lignin in forages are not satisfactory. A spectrophotometric method, the acetyl bromide lignin (ABL), has been employed to determine lignin concentration in forages; however, it suffers from the lack of an ideal standard with which the optical density readings of samples are compared to. A lignin, extracted from the plant with a solution of acidic dioxane, was employed to build a calibration curve for this method. This procedure was then compared with other methods (acid detergent lignin - ADL, Klason lignin - KL and potassium permanganate lignin - PerL) to determine lignin content on different fractions (stem, leaf and whole plant) of eight oat cultivars (Avena byzantina L.). There was no agreement among the four methods. In general, ABL and KL methods yielded the highest values while ADL method yielded the lowest, particularly for the young plants. Lignin concentration was higher in the stem fraction as compared to leaf. It was detected influence of maturity stage in the investigated samples. It is concluded that the ABL method employing as standard lignin extracted with acidic dioxane has potential to be employed as a method to determine lignin concentration.