Experimental quantification of hydrodynamic effects on plant cutting roots development

This paper focuses on the development of azimuthal root asymmetry in plant cuttings and related effects on the resistance to flow erosion in poorly cohesive sediment. We aim to differentiate the effects that hydrodynamic forces acting on the plant (cutting) stem (dynamotropism) exert on root architecture from that of hyporheic flow (hydropatterning). Laboratory experiments were performed using Salix cuttings growing in quartz sand-filled rhizoboxes within a flume stream and undergoing different treatment conditions aimed at isolating hydropatterning from dynamotropism. In parallel, field-scale experiments were conducted in selected field sites along the Allondon River near Geneva where planted cuttings of the same species are undergoing natural flow conditions. We discuss initial results of these combined experiments and provide first insights into various tropisms, especially dynamotropism, as well as about the biomechanics and resistance to erosion of cuttings with asymmetric root structure.