The phloem is a particularly intriguing vascular tissue because of its complex functionality and highly specialized cell types. My lab has characterized a cell biological network that guides phloem sieve element differentiation. Key players in this network constitute a molecular rheostat that finetunes trans-cellular auxin flux and maintains its pronounced polarity through a self-reinforcing mechanism. This module is antagonized by the autocrine action of a pH-sensitive CLE peptide receptor kinase pathway. Gradual apoplastic alkalinization thus permits developing sieve elements to eventually escape the autocrine inhibition of their differentiation, which is also sustained by the largely cell-autonomous action of the brassinosteroid receptor kinase pathway. At the same time, developing sieve elements safeguard the phloem lineage, by maintaining the developmental plasticity of neighboring cell files through paracrine action of sieve element-derived CLE peptides. However, we recently found that CLE peptide signaling is nevertheless also required to initiate the phloem lineage. Moreover, cross-compensation between CLE peptide receptors as observed in the shoot meristem does not operate similarly in the root meristem. We further observed spatiotemporally contrasting CLE signaling requirements for phloem initiation and differentiation. Our findings thus suggest an intricate quantitative interplay between distinct and antagonistic receptor kinase pathways that organizes tissue layer formation in the Arabidopsis root meristem.