BIODEGRADATION OF PLANT-CELL WALLS, WALL CARBOHYDRATES, AND WALL AROMATICS IN WHEAT GROWN IN AMBIENT OR ENRICHED CO2 CONCENTRATIONS

Mature internodes from wheat (Triticum aestivum L) grown in control (ambient at c 370 mu mol mol(-1)) or enriched (to 550 mu mol mol(-1)) concentrations of atmospheric CO2 in the free-air CO2 enrichment (FACE) system were analyzed for potential changes in biodegradation of constituents due to predicted increases in atmospheric levels of CO2. The first internodes below the grain were incubated with the lignocellulose-degrading white rot fungus, Phanerochaete chrysosporium K-3, or incubated without microorganisms. Plant samples were then analyzed for dry weight loss, disposition of specific cell types to biodegradation using electron microscopy, carbohydrates and lignin using solid state NMR spectroscopy, and ester- and ether-linked aromatics using gas chromatography. Phanerochaete chrysosporium extensively degraded stems cells (c 75%) and both carbohydrate and aromatic portions of the wheat stems proportionately more carbohydrates were removed by the fungus from the stems. Enriched CO2 did not affect the chemical composition of wheat stems or the biodegradation by P chrysosporium of plant cell walls or wall components for the most part. Data from various methods all indicated that enriched CO2 did not substantially alter the biodegradation of wheat cell wall internodes or wall components. Evidence was not found for an influence on C cycling due to CO2 concentrations in this study.