title: 3D imaging and mechanical modeling of helical buckling in Medicago truncatula plant roots.
abstract: We study the primary root growth of wild-type Medicago truncatula plants in heterogeneous environments using 3D time-lapse imaging. The growth medium is a transparent hydrogel consisting of a stiff lower layer and a compliant upper layer. We find that the roots deform into a helical shape just above the gel layer interface before penetrating into the lower layer. This geometry is interpreted as a combination of growth-induced mechanical buckling modulated by the growth medium and a simultaneous twisting near the root tip. We study the helical morphology as the modulus of the upper gel layer is varied and demonstrate that the size of the deformation varies with gel stiffness as expected by a mathematical model based on the theory of buckled rods. Moreover, we show that plant-to-plant variations can be accounted for by biomechanically plausible values of the model parameters.
authors.affiliation: Department of Physics, Cornell University, Ithaca, NY 14853, USA. JLS533@cornell.edu
authors.forename: Jesse L
authors.initials: JL
authors.lastname: Silverberg
authors.forename: Roslyn D
authors.initials: RD
authors.lastname: Noar
authors.forename: Michael S
authors.initials: MS
authors.lastname: Packer
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Harrison
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Henley
authors.forename: Itai
authors.initials: I
authors.lastname: Cohen
authors.forename: Sharon J
authors.initials: SJ
authors.lastname: Gerbode
mesh_terms: D001696:Biomechanical Phenomena; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D046913:Medicago truncatula; D008954:Models, Biological; D009024:Morphogenesis / Q000502:physiology*; D018517:Plant Roots / Q000033:anatomy & histology* / Q000254:growth & development*
chemical_list: D020136:Hydrogel, Polyethylene Glycol Dimethacrylate