Research on the Morphogenesis of Notopterygium incisum Rhizomes and its Mechanism: Multiomics Integration Analysis Reveals the Formation Mechanism of Silkworm-like Rings

Background N. incisum (Umbelliferae) is a rare medicinal plant. Its rhizome product ‘Can Qiang’ is valued for its silkworm-like ring patterns. However, no studies have reported how these rings form. Result The ring structure forms through alternating segments: enlarged stem nodes with root traces and vascular bundles and shortened internodes without accessory structures. The key differentiation period is 126–139 days after germination (around the beginning of autumn). Under certain climatic conditions, cork cambium activity and programmed cell death in the cortex lead to uneven secondary growth. This causes vascular tissue expansion and cortex degeneration, which are facilitated by mechanical pressure from the secondary xylem. Metabolomic and transcriptomic analyses revealed many differentially accumulated metabolites and differentially expressed genes. Flavonoids, coumarins, simple phenylpropanoids, and terpenoids presented the greatest differential accumulation. During development, phenylpropanoid biosynthesis was enriched, structural defense pathways were upregulated, and energy storage pathways were activated. Among these organs, root stem tissues exhibit active proliferation and carbohydrate storage, whereas roots specialize in defense synthesis and nutrient assimilation. Conclusion The silkworm-like ring likely results from a carbon flow allocation strategy triggered by early autumn environmental signals. These signals activate the phospholipid system and transcriptional network, redirecting phenylpropane pathway carbon flux. Lignin precursors accumulate, regulating cork cambium activation and secondary xylem proliferation. This forms multilayered rings and cortical cavities. Lignified rings improve mechanical strength; a hollow cortex buffers heat stress. Together, they maintain organ stability and allow the compartmentalized storage of medicinal components. This study provides a theoretical basis for the cultivation, breeding, and harvesting of N. incisum .