Fernandes Anwesha N, Chen Xinyong, Scotchford Colin A, Walker James, Wells Darren M, Roberts Clive J, Everitt Nicola M
Centre for Plant Integrative Biology, School of Biosciences, University of Nottingham, England LE12 5RD.
Phys Rev E Stat Nonlin Soft Matter Phys. 2012 Feb;85(2 Pt 1):021916. doi: 10.1103/PhysRevE.85.021916. Epub 2012 Feb 21.
The knowledge of mechanical properties of root cell walls is vital to understand how these properties interact with relevant genetic and physiological processes to bring about growth. Expansion of cell walls is an essential component of growth, and the regulation of cell wall expansion is one of the ways in which the mechanics of growth is controlled, managed and directed. In this study, the inherent surface mechanical properties of living Arabidopsis thaliana whole-root epidermal cells were studied at the nanoscale using the technique of atomic force microscopy (AFM). A novel methodology was successfully developed to adapt AFM to live plant roots. Force-Indentation (F-I) experiments were conducted to investigate the mechanical properties along the length of the root. F-I curves for epidermal cells of roots were also generated by varying turgor pressure. The F-I curves displayed a variety of features due to the heterogeneity of the surface. Hysteresis is observed. Application of conventional models to living biological systems such as cell walls in nanometer regimes tends to increase error margins to a large extent. Hence information from the F-I curves were used in a preliminary semiquantitative analysis to infer material properties and calculate two parameters. The work done in the loading and unloading phases (hysteresis) of the force measurements were determined separately and were expressed in terms of "Index of Plasticity" (η), which characterized the elasticity properties of roots as a viscoelastic response. Scaling approaches were used to find the ratio of hardness to reduced modulus (H/E(*)).
了解根细胞壁的力学特性对于理解这些特性如何与相关的遗传和生理过程相互作用以实现生长至关重要。细胞壁的扩张是生长的一个重要组成部分，而细胞壁扩张的调节是控制、管理和引导生长力学的方式之一。在本研究中，使用原子力显微镜（AFM）技术在纳米尺度上研究了活的拟南芥全根表皮细胞的固有表面力学特性。成功开发了一种新颖的方法，使AFM适用于活的植物根系。进行了力压痕（F-I）实验以研究沿根长度的力学特性。还通过改变膨压生成了根表皮细胞的F-I曲线。由于表面的异质性，F-I曲线呈现出多种特征。观察到滞后现象。将传统模型应用于纳米尺度的活生物系统（如细胞壁）往往会在很大程度上增加误差范围。因此，F-I曲线的信息被用于初步的半定量分析，以推断材料特性并计算两个参数。分别确定了力测量的加载和卸载阶段（滞后）所做的功，并以“可塑性指数”（η）表示，该指数表征了根作为粘弹性响应的弹性特性。使用标度方法来找到硬度与折合模量的比值（H/E(*)）。
