Micro-mechanical approaches to characterize tip growth: Insights into Root Hair Elasto-Viscoplastic Properties

Abstract

Root hairs are outgrowths of the epidermal cells of plant roots. They increase the root’s exchange surface with the soil and provide it with good anchorage in the soil. Root hairs are an emblematic model of apical growth, a process also used by yeasts and hyphae to invade their environment. From a mechanical perspective, the root hair is considered as an elastic cylinder under pressure, closed by a dome that behaves like a yield fluid. We introduce here two innovative mechanical setups and protocols to characterize the mechanical properties of single growing root hairs in Arabidopsis thaliana. In the first setup, root hairs grow against an elastic obstacle until buckling. By measuring the critical buckling force, we determine the surface modulus and estimate the Young’s modulus of the cell wall, which aligns with previous measurements. Using a 1D elasto-viscoplastic model of root hair growth, we assess the excess pressure beyond the yield threshold (the driver of tip growth) and estimate the axial stiffness of the root hair, reflecting its elastic resistance to compression. For the second protocol, we designed a setup where a single root hair grows against a cantilever with variable stiffness, a technique adapted from our earlier work on rigidity sensing by animal cells. This method provides an independent estimate of the root hair’s axial stiffness, confirming our initial findings and suggesting that this stiffness primarily involves tip compression and depends mainly on turgor pressure, at least within the low deformation regime explored.

Plant phenotyping relevance

単一根毛の力学特性を定量する革新的な実験セットアップとプロトコルを開発・検証しており、植物表現型の取得手法が研究の中心です。

Code and data availability

The paper reports root hair micromechanical measurements (buckling force, stiffness-jump growth rates) analyzed in Matlab/FIJI, but no public dataset, image, or code deposit is provided. The only availability statement is on-request access.

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