Single and multiple T-DNA knockouts of genes encoding arogenate dehydratases (ADTs) in Arabidopsis were obtained in homozygous form. These were analyzed for potential differences in lignin contents and compositions, as well as for distinct phenotypes over growth and development. Of these different lines, distinct reductions in lignin contents were obtained, with those having different G:S ratios depending upon the combination of adt genes being knocked out. Results from pyrolysis GC/MS analyses indicated that differential carbon flux occurred into the vascular bundles (vb ) and interfascicular fibers (if ). These results provide additional new insight into factors controlling lignin heterogeneity and configuration.