The plant vasculature is a sophisticated system that has greatly contributed to the evolution of land plants over the past few hundred million years. The formation of the vascular system is a well-organized plant developmental process, but it is also flexible in response to environmental changes. Provascular cells arise after asymmetric cell division in early embryos and differentiate into various vascular cells, including procambial cells, which function as vascular stem cells. Mutual regulation by auxin and cytokinin is essential for vascular pattern formation, in which the xylem, phloem, and procambium are arranged in a species-specific manner. The hierarchical expression of different transcription factors contributes to the sequential development of vascular tissues. These transcription factors sometimes form feedback loops involving plant hormones. Non-cell autonomous signals, including hormones, peptides, and miRNAs, function in the organization of vascular tissue development.
