Can diversity in root architecture explain plant water use efficiency? A modeling study

tDrought stress is a dominant constraint to crop production. Breeding crops with adapted root systemsfor effective uptake of water represents a novel strategy to increase crop drought resistance. Due tocomplex interaction between root traits and high diversity of hydrological conditions, modeling providesimportant information for trait based selection. In this work we use a root architecture model combinedwith a soil-hydrological model to analyze whether there is a root system ideotype of general adaptationto drought or water uptake efficiency of root systems is a function of specific hydrological conditions. Thiswas done by modeling transpiration of 48 root architectures in 16 drought scenarios with distinct soiltextures, rainfall distributions, and initial soil moisture availability. We find that the efficiency in wateruptake of root architecture is strictly dependent on the hydrological scenario. Even dense and deep rootsystems are not superior in water uptake under all hydrological scenarios. Our results demonstrate thatmere architectural description is insufficient to find root systems of optimum functionality. We findthat in environments with sufficient rainfall before the growing season, root depth represents the keytrait for the exploration of stored water, especially in fine soils. Root density, instead, especially nearthe soil surface, becomes the most relevant trait for exploiting soil moisture when plant water supplyis mainly provided by rainfall events during the root system development. We therefore concluded thattrait based root breeding has to consider root systems with specific adaptation to the hydrology of thetarget environmen