In this study, we present an on-chip analytical method using a microfluidic device to characterize the mechanical properties in growing roots. Roots are essential organs for plants and grow under heterogeneous conditions in soil. Especially, the mechanical impedance in soil significantly affects root growth. Understanding the mechanical properties of roots and the physical interactions between roots and soil is important in plant science and agriculture. However, an effective method for directly evaluating the mechanical properties of growing roots has not been established. To overcome this technical issue, we developed a polydimethylsiloxane (PDMS) microfluidic device integrated with a cantilevered sensing pillar for measuring the protrusive force generated by the growing roots. Using the developed device, we analyzed the mechanical properties of the roots in a model plant, Arabidopsis thaliana. The root growth behavior and the mechanical interaction with the sensing pillar were recorded using a time-lapse microscopy system. We successfully quantified the mechanical properties of growing roots including the protrusive force and apparent Young's modulus based on a simple physical model considering the root morphology. (c) 2025 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

This study used triaxial tests to examine the impact of the root diameter of Cunninghamia lanceolata (Chinese fir) on the mechanical behavior of sand, including stress-strain development, strength, volumetric strain, and failure envelope. It also revealed the reinforcement mechanisms of roots with different diameters based on root-soil interactions. The results showed the following: (1) The addition of roots significantly enhanced sand strength and reduced volumetric deformation. The average peak strength increased by 31.8%, while the average peak volumetric strain decreased by 34.3%. (2) Roots provided additional cohesion and increased the friction angle of the sand, causing the failure envelope to shift upward and deflect. (3) Smaller-diameter roots improved the mechanical properties of sand more significantly, leading to higher peak strength, shear strength parameters, and smaller volumetric deformation. As the root diameter increased from 1 mm to 5 mm, the peak strength ratio decreased from 1.78 to 1.13, and the peak volumetric strain increased from 0.48 to 0.79. (4) Smaller-diameter roots, which form denser networks, allowing more roots to resist loads, and have a higher elastic modulus providing greater tensile stress, also possess higher tensile strength and critical sliding tensile stress, making them less likely to fail, thereby making the mechanical reinforcement of sand more significant.

Understanding the pore water pressure distribution in unsaturated soil is crucial in predicting shallow landslides triggered by rainfall, mainly when dealing with different temporal patterns of rainfall intensity. However, the hydrological response of vegetated slopes, especially three-dimensional (3D) slopes covered with shrubs, under different rainfall patterns remains unclear and requires further investigation. To address this issue, this study adopts a novel 3D numerical model for simulating hydraulic interactions between the root system of the shrub and the surrounding soil. Three series of numerical parametric studies are conducted to investigate the influences of slope inclination, rainfall pattern and rainfall duration. Four rainfall patterns (advanced, bimodal, delayed, and uniform) and two rainfall durations (4h intense and 168-h mild rainfall) are considered to study the hydrological response of the slope. The computed results show that 17% higher transpiration-induced suction is found for a steeper slope, which remains even after a short, intense rainfall with a 100-year return period. The extreme rainfalls with advanced (PA), bimodal (PB) and uniform (PU) rainfall patterns need to be considered for the short rainfall duration (4 h), while the delayed (PD) and uniform (PU) rainfall patterns are highly recommended for long rainfall durations (168 h). The presence of plants can improve slope stability markedly under extreme rainfall with a short duration (4 h). For the long duration (168 h), the benefit of the plant in preserving pore-water pressure (PWP) and slope stability may not be sufficient.