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To determine how root‐to‐shoot abscisic acid (ABA) signalling is regulated by vertical soil moisture gradients, root ABA concentration ([ABA]_root), the fraction of root water uptake from, and root water potential of different parts of the root zone, along with bulk root water potential, were measured to test various predictive models of root xylem ABA concentration [RX‐ABA]_sap. Beans (Phaseolus vulgaris L. cv. Nassau) were grown in soil columns and received different irrigation treatments (top and basal watering, and withholding water for varying lengths of time) to induce different vertical soil moisture gradients. Root water uptake was measured at four positions within the column by continuously recording volumetric soil water content (θ_v). Average θ_v was inversely related to bulk root water potential (Ψ_root). In turn, Ψ_root was correlated with both average [ABA]_root and [RX‐ABA]_sap. Despite large gradients in θ_v …