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United States Department of Agriculture

Agricultural Research Service

Title: Chemical Composition and Degradability of Xylem and Nonxylem

Authors
item Grabber, John
item Hatfield, Ronald
item Panciera, M - UNIV ALASKA, FAIRBANKS
item Weinberg, P - UNIV ALASKA, FAIRBANKS

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.

Last Modified: 10/21/2014
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