The point of disconnection: early-drought fine root shrinkage is driven by plant water use in Pinus radiata.

Fine roots of Pinus radiata shrink during early drought as plant water potential declines from -0.2 MPa to -0.88 MPa, losing 14.8 ± 10.3% area before soil drying begins.

• Why it matters: Root-soil interface timing is unclear because few studies link in-soil root shrinkage to plant water status, leaving drivers and hydraulic implications during drought unresolved.
• What they did: Intact fine roots < 2.5 mm were scanned in soil using synchrotron-based Micro-CT during mild plant drying (before embolism), relating shrinkage to soil (0–72 kPa) and xylem water potential.
• The result: Shrinkage is better predicted by Δplant than Δsoil, with a linear shrinkage–Δplant relationship (normalized to shrinkage at -1 MPa) coordinated with cortical lacunae formation, implying plant water use drives early hydraulic disconnection.