Fig. 3: Comparative illustration of active nutrient uptake via roots only, mycorrhizas only, and roots and mycorrhizas combined.

In each scenario, nutrients are actively transported to the stele through ToS cells, as indicated by dashed arrows. Arbuscules are assumed to be formedevenly across ToS cells. Root cross-sectional area is illustrated with x ToS cell layers. Nutrients released from the arbuscules into the root ToS cells are actively transported to the steleas indicated by the dashed arrows (b, c), similar to the case of non-mycorrhizal roots (a). ToS tissues outside the stele, t cell layer thickness, x number of the ToS celllayer with the innermost layer defined as layer 1, i a given ToS cell layer.