How Soil Texture Modulates Root Adaptation to Water Stress Through Structural Reinforcement, Energy Supply, and Nutrient Acquisition

ABSTRACT

The interaction between soil texture and water shapes root adaptation, though the underlying mechanisms remain unclear. This study investigated the physiological and transcriptional mechanisms by which soil texture regulates tomato root responses to water stress. We conducted using three soil textures—silty clay (SC), loam (L), and sandy loam (SL) under two irrigation regimes: well‐watered (WW, 70%–90% field capacity, FC) and water deficit (WD, 40%–60% FC). Among SC, L, and SL, available water content (AWC) and penetration resistance (PR) gradually increased, while air‐filled porosity (AFP) decreased and water stress further reduced AWC and increase both PR and AFP. Weighted gene co‐expression network analysis (WGCNA) of root physiological, transcriptomics, and soil physical properties revealed that soil texture modulates the adaptive strategies of tomato roots to water stress. Under water stress, roots in SC upregulate respiratory enzymes to enhance root respiratory activity, and also upregulate lignin biosynthesis‐related genes, leading to earlier lignin accumulation. In SL, roots upregulated genes involved in lignin synthesis and cell wall expansion, accelerating lignin deposition and cell wall thickening, while respiratory activity decreased. In L, roots upregulated nitrate transporter and aquaporin genes to coordinate nitrogen and water uptake, while maintaining relatively high respiratory activity. Partial least squares structural equation modelling (PLS‐SEM) was employed to construct pathways elucidating the relationships among key genes, soil physical properties, and root physiological indicators. The study unravelled the cooperative mechanism by which soil texture and water stress modulate root growth through soil physical properties, providing a scientific basis for managing different soil textures under water‐limiting conditions.