The rind shows a higher density of vascular elements made from thick-walled cells. The pith section (shown longitudinally) shows a greater number of thin-walled parenchyma cells. Overall, most cellulose needed for biomass conversion is located in the rind, although the pith represents most of the stem volume. Closeups of a cell-wall pit also are shown (~150,000×). These structures are thought to aid transfer of chemicals and enzymes used in processing within the biomass bulk.
Credit or Source: Biological and Environmental Research Information System, Oak Ridge National Laboratory. Sponsored by the U.S. Department of Energy Biological and Environmental Research Program.
U.S. DOE. 2006. Breaking the Biological Barriers to Cellulosic Ethanol: A Joint Research Agenda, DOE/SC/EE-0095, U.S. Department of Energy Office of Science and Office of Energy Efficiency and Renewable Energy. (p. 40) (website)