Lignin is an aromatic polymer deposited in the cell walls of higher land plants, and accounts for up to 30% of the earth’s non-fossil organic carbon. Lignin provides mechanical support to the plant and contributes to shootward water transport. However, its recalcitrant nature is an important limiting factor in the processing of cellulose present in plant biomass to fermentable sugars. Lowering lignin content in the plant therefore has strong economical relevance, but unfortunately also results in smaller plants. The underlying cause for this dwarfism and its associated growth phenotypes has been studied for decades, and the most widely accepted model states that the reduced growth is caused by a perturbed water transport. In this regard, we recently made a breakthrough discovery by showing that lowering lignin content causes an impairment of auxin transport through the phloem (El Houari et al., 2021). We also determined that this is likely a secondary result following an impairment in water transport. This relationship between lignin, water transport and phloem transport is remarkable, and could provide an answer to a multitude of as of yet unexplained observations in lignin deficient plants. Via this project I will now capitalize on these previous findings, and hereby provide explanation to the underlying cause for lignin mutant phenotypes.