Changes in soil matric suction (or matric potential; yₛ) due to plant transpiration affect shallow soil stability. Understanding water transport within the soil-plant-atmosphere continuum (SPAC) is the key to quantify the transpiration-induced changes in yₛ, but this is often challenging due to the difficulties in measuring water potential in all components of the SPAC. Handheld tools are readily available to measure leaf water potential (yₗ), but they only partially explain variations in yₛ. Although root water potential (yᵣ) is known to be much more closely associated with yₛ, data on yᵣ is very scarce. This study presents findings obtained from soil columns cultivated with vetiver grass (Chrysopogon zizanoides L. ). The vegetated columns were subjected to a drought period typical to a tropical climate region, during which various water potential terms, including yₛ and yᵣ, as well as relevant root traits, were measured to understand water transport in this SPAC. Our findings showed a logarithmic increase in the gradient between yₛ and yᵣ. Specific leaf area significantly decreased with yᵣ, indicating hydraulic continuity between roots and leaves. We propose a new power-law correlation between root diameter and yᵣ to facilitate a trait-based understanding of root water uptake.
LEUNG et al. (2025) studied this question.