Required for correct root growth and vascular development, probably by modulating both cell division rate in meristems and cell elongation in roots. Negative regulator of the ethylene signaling pathway that modulates microtubule cytoskeleton dynamics and auxin transport and homeostasis, and possibly cytokinin signaling, thus influencing root growth and lateral root development. Mostly expressed in the embryonic root from the heart stage and in the seedling primary and lateral root tips, especially in the columella initials and lateral root cap. Also detectable in aerial parts of the seedling, sepals and leaves, principally in vascular tissues of the lamina and petiole. First observed in embryos from the heart stage and throughout embryo development, restricted to the basal part, constituting the developing radicle. During the curled cotyledonary stage, strongly expressed in the radicle and detectable in the cotyledons. On germination, mostly present in root tips, but also at low levels in the cotyledons and hypocotyl. In flowering plants, restricted to the root tip and to the silique wall. Repressed by ethylene (ACC) and cytokinin, but induced by auxin (1-NAA and 2,4-D). Defective in root growth and leaf vascularization, characterized by more anchor roots at the root-hypocotyl junction. Cells of the root meristem and the cortex of the primary root are short and more radially expanded. Reduced meristem cell divisions in meristems and reduced axial cell elongation in roots. Enhanced ethylene-response, hyperresponsiveness to cytokinin, defective auxin transport and homeostasis, and altered microtubule sensitivity to inhibitors. Belongs to the POLARIS peptide family.