Department of Mechanical Engineering, Texas A&M University, USA.
Department of Soil and Crop Sciences, Faculty of Molecular and Environmental Plant Sciences, Texas A&M University, USA.
J Mech Behav Biomed Mater. 2020 Jun;106:103731. doi: 10.1016/j.jmbbm.2020.103731. Epub 2020 Mar 23.
Grasses represent the most productive and widely grown crop family across the globe but are susceptible to structural failure (lodging) during growth (e.g., from wind). The mechanisms that contribute to structural failure in grass stems are poorly understood due to a lack of systematic studies of their biomechanical behavior. To this end, this study examines the biomechanical properties of sweet sorghum (Sorghum bicolor (L.) Moench), focusing on the time-dependent behavior of the stems. Specifically, we conducted uniaxial compression tests under ramp and creep loading on pith and stem specimens of the sorghum cultivar Della. The tests demonstrated significantly nonlinear and time-dependent stress-strain behavior in all samples. We surmise that this behavior arises from a combination of poroelasticity due to migration of water through the plant and viscoelasticity due to rearrangement of macromolecular networks, such as cellulose microfibrils and lignin matrices. Overall, our measurements demonstrate that sorghum is not a simple reversible elastic material. As such, a complete understanding of the conditions that lead to stem lodging will require knowledge of sorghum's time-dependent biomechanical properties. Of practical importance, the time-dependent biomechanical properties of the stem influence its mechanical stability under various loading conditions during growth in the field (e.g., different wind speeds).
草类在全球范围内是最具生产力和广泛种植的作物家族，但在生长过程中（例如，由于风）容易发生结构失效（倒伏）。由于对其生物力学行为缺乏系统研究，导致人们对导致草茎结构失效的机制了解甚少。为此，本研究考察了甜高粱（Sorghum bicolor (L.) Moench）的生物力学特性，重点研究了茎的时变行为。具体来说，我们对高粱品种 Della 的髓心和茎标本进行了 ramp 和 creep 加载下的单轴压缩测试。测试表明，所有样本均表现出明显的非线性和时变应力-应变行为。我们推测，这种行为是由于水通过植物迁移引起的多孔弹性和大分子网络（如纤维素微纤维和木质素基质）重新排列引起的粘弹性的共同作用。总的来说，我们的测量结果表明，高粱不是一种简单的可逆弹性材料。因此，要全面了解导致茎倒伏的条件，就需要了解高粱的时变生物力学特性。从实际重要性来看，茎的时变生物力学特性会影响其在田间生长过程中在各种加载条件下的机械稳定性（例如，不同的风速）。
