Multimedia Gallery
Components of Cell Wall in Xylem
Both lignin and cellulose are found in the rigid cell walls of the xylem cells (those that conduct water) in the primitive plant Selaginella.
Biologists have discovered that a fundamental building block in the cells of flowering plants evolved independently, yet almost identically, on a separate branch of the evolutionary tree--in an ancient plant group called lycophytes that originated at least 420 million years ago.
This image accompanied NSF press release, "When Plants 'Think' Alike."
Credit: Zina Deretsky, National Science Foundation; Selaginella cross section SEM by Jing-Ke Weng, Clint Chapple, Purdue University; Lignin structure from Wout Bergjan, John Ralph, Marie Baucher (Annual Review of Plant Biology, Vol. 54:519-546, June 2003); Cellulose structure from http://www.chusa.jussieu.fr/disc/bio_cell/
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