Exploring root developmental plasticity to nitrogen with a three-dimensional architectural model

Background and aims Root plasticity is a key process affecting the root system foraging capacity while itself being affected by the nutrient availability around the root environment. Root system architecture is determined by three types of plastic responses: chemotropism, spacing of lateral roots, hierarchy between laterals and their mother root. Methods We attempt a systematic comparison of the effect of each mechanism on the whole root plasticity when the root is grown under four distinct nutrient distribution scenarios using a functional-structural root model. Nutrient distributions included i) a completely random distribution, ii) a layered distribution, iii) a patch distribution, and iv) a gradient distribution. Root length, volume, total uptake, uptake efficiency as well as the soil profiles are given as model outputs. Results Root uptake was more efficient in a soil with a gradient nutrient distribution and less so in a patch distribution for all mechanisms. In terms of mechanisms uptake was more efficient for the spacing (elongation) mechanism than the hierarchy (branching) mechanism. Conclusions Root mechanisms play a different role in the foraging of the root with chemotropism being a global tracking mechanism, whereas spacing and hierarchy are ways to proliferate in a zone with locally available nutrients.