Integrated Analysis of Rhizosphere Metabolome and Hormones Reveals Regulatory Mechanisms in Intercropped Asparagus cochinchinensis

<title>Abstract</title> <p> Background The increasing demand for high-quality medicinal herbs necessitates efficient land-use strategies. Understory intercropping offers a sustainable solution, yet the biochemical mechanisms governing plant adaptation and quality formation remain unclear. Methods This study investigated the intercropping of Asparagus cochinchinensis ( <italic>A. cochinchinensis</italic> ) under Pinus massoniana ( <italic>P. massoniana</italic> ) plantations. We compared agronomic traits, endogenous phytohormones, and rhizosphere metabolites among three groups, namely <italic>P. massoniana</italic> forest soil (Soil-A), <italic>A. cochinchinensis</italic> monoculture soil (Soil-B), and intercropping soil (Soil-C), using LC-MS-based metabolomics and targeted hormone profiling. Results Intercropping did not alter key agronomic traits but significantly increased total saponin content ( <italic>P</italic>  &lt; 0.05) while decreasing chlorophyll levels ( <italic>P</italic>  &lt; 0.01). Phytohormone analysis revealed a distinct hormonal signature in intercropped plants, characterized by decreased abscisic acid (ABA) and jasmonic acid (JA), alongside elevated salicylic acid (SA), cis-12-oxophytodienoic acid (cis-OPDA), and bioactive cytokinins. Rhizosphere metabolomics identified 25 differential metabolites, with notable enrichment of trans-cinnamic acid and gibberellin A ₄ (GA ₄ ) in Soil-C. KEGG analysis highlighted the significant activation of plant hormone signal transduction and aminobenzoate degradation pathways. Conclusion <italic>A. cochinchinensis</italic> exhibits morphological-metabolic decoupling under intercropping, prioritizing secondary metabolism over structural growth. The accumulation of trans-cinnamic acid and GA ₄ in the rhizosphere appears to interface with endogenous hormone signaling, specifically involving the SA pathway and <italic>cis</italic> -OPDA-mediated regulation, to enhance saponin biosynthesis. This study provides a theoretical basis for optimizing <italic>P. massoniana/A. cochinchinensis</italic> agroforestry systems to achieve stable yields and improved medicinal quality. </p>