Light Modulates Growth‐Resistance‐Quality Trade‐Offs in Pseudostellaria Heterophylla via a Light‐Induced Microbiota‐Root‐Shoot Axis

ABSTRACT

Plants rely on plant‐microbiota interactions to balance growth, defence, and metabolism under stress. Still, the mechanisms governing growth‐resistance‐quality trade‐offs in the shade‐tolerant medicinal herb Pseudostellaria heterophylla in understory cultivation systems remain unclear. Here, we integrated phenotypic/photosynthetic/quality assays, rhizosphere microbiome sequencing, leaf transcriptomics, and plant‐microbe co‐culture experiments to study responses to graded shading. Shading enhanced yield and disease resistance, reshaped the microbiome (enriching beneficial taxa, suppressing pathogenic Alternaria ), and induced transcriptional reprogramming—upregulating starch‐sucrose/glycerophospholipid metabolism and downregulating flavonoid biosynthesis genes ( CHI/CHS ) to reduce root‐exuded flavonoids that inhibit beneficial bacteria. Functional assays confirmed that these bacteria promote growth and suppress Alternaria ‐mediated disease under low light. Our findings demonstrate trade‐offs in shading coordinates along a bidirectional microbiota‐root‐shoot axis, establishing a framework for sustainable understory medicinal plant cultivation.