ALT Hormones control the molecular regulation of vascular development in the primary root meristem of Arabidopsis. A cross-section through a primary root meristem is shown (A) illustrating the known hormones, molecular regulators, and their interactions in the phloem (B) and xylem (C) regions. Hormones are indicated in red; dotted lines illustrate mobility of the hormone or molecular regulator. Note that the presence and locations of some regulators and hormones on the realistic tissue template are not exact to keep the image orderly and due to space limitations. This image also does not represent accurate hormone levels and distributions across the tissue for the same reasons.