Root responses to mechanical heterogeneity are shaped by pore geometry and root-soil biomechanics

Abstract

Mechanical limitations to root growth occur when pressure exerted by turgor within root cells is counteracted by excessive resistance of the surrounding soil as well as by that of the cell walls. In a natural soil, however, heterogeneity allows roots to find paths of least resistance, though the governing principles behind this process have yet to be identified. Here, we combined artificial substrates, high-throughput live imaging, advanced image analysis, and mechanical modelling to uncover the principles governing the ability of a root to penetrate or deflect from zones of high mechanical impedance within a heterogeneous substrate. Our findings show that root responses to substrate heterogeneity can be accurately predicted from the pore-matrix geometry when both the mechanical properties of the substrate and those of the roots are known. Consequently, a crucial step toward understanding the physical limitations to root growth may lie in a detailed characterisation of soil mechanical properties.