Seedling developmental defects upon blocking CINNAMATE?4?HYDROXYLASE are caused by perturbations in auxin transport

The phenylpropanoid pathway serves a central role in plant metabolism, providing numerous compounds involved diverse physiological processes. Most carbon entering the is incorporated into lignin. Although several mutants show seedling growth arrest, for lignin and development unexplored. We use complementary pharmacological genetic approaches to block CINNAMATE-4-HYDROXYLASE (C4H) functionality Arabidopsis seedlings set of molecular biochemical techniques investigate underlying phenotypes. Blocking C4H resulted reduced lateral rooting increased adventitious apically hypocotyl. These phenotypes coincided with an inhibition AUX transport. upstream accumulation cis-cinnamic acid was found be likely cause polar transport inhibition. Conversely, downstream depletion perturbed phloem-mediated Restoring deposition effectively reestablished phloem and, accordingly, homeostasis. Our results that bioactive intermediates jointly aberrant upon blocking C4H, demonstrate proper essential establishment distribution seedlings. data position new framework, consolidating their importance development.