Fig. 4.

Maximum theoretical soil solution concentrations of 2′-deoxymugineic acid (DMA, μM) after 24 h in the close vicinity of wheat (Triticum aestivum cv Tamaro) roots (0.5 mm distance from the root surface) grown on the calcareous Santomera soil, calculated based on exudation rates obtained in the 24 h stepwise sampling at 33 and 46 d after germination (DAG) and assuming a uniform root diameter (0.5 mm). Closed symbols, theoretical DMA concentrations around root tips assuming hotspot exudation behavior (i.e. active proportion of root biomass is only 20%); open symbols, averaged theoretical DMA concentration across the total root system (TRS i.e. active proportion of root biomass is 100%).