ARS | Publication request: CHEMICAL COMPOSITION AND DEGRADABILITY OF XYLEM AND NONXYLEM

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: November 4, 1999
Publication Date: N/A

Technical Abstract: Alfalfa degradability declines significantly with plant maturation due to accumulation of a highly lignified xylem ring in stems. Xylem and nonxylem tissues dissected from Vernal alfalfa internodes were analyzed for cell- wall constituents and degradability as an initial step in identifying how lignin restricts fiber degradability. Cell walls comprised 730 g kg-1 of xylem and 500 g kg-1 of nonxylem tissues. Fungal enzymes released only 200 g kg-1 of total sugars from xylem walls containing 286 g kg-1 of acetyl bromide lignin. Nonxylem walls, with 42% less lignin, had a 350% greater release of total sugars indicating that lignin-matrix interactions differed between tissue types. In both tissues, the release of sugars from glucuronoxylans was extremely low. Unlike grasses, poor xylan degradation was not related to ferulate-lignin cross-linking. Elucidation of lignin- xylan interactions may reveal strategies for improving alfalfa degradability.