Fig. 2: Schematic illustration of nutrient (solid purple circles) uptake by plant roots without mycorrhizal association.
From: Root anatomy governs bi-directional resource transfer in mycorrhizal symbiosis

Cells in the ToS use energy derived from respiration to drive nutrient uptake across ToS cells (represented by dashed arrows across the ToS). ToS tissues outside the stele, ATP adenosine triphosphate, kec the amount of ATP per unit of photosynthetic carbon respired, kner the amount of nutrient uptake per unit of ATP invested by roots.