| Abstract: | Sorghum [Sorghum bicolor (L.)] is a tropical grass that often suffers from structural failure (lodging) when subjected to mechanical loadings from wind, rain, and hail. During lodging, excessive lateral deflection occurs, which inherently correlates with the biomechanical and anatomical properties of the stem. Mechanical stimulation from lateral bending during plant growth and development alters phytohormones and expression of the transcriptome via mechanisms that may include epigenetic modifications. These modifications result in changes in the morpho-anatomical-biomechanical traits of plant stems, which can potentially enhance the stem resistance to lodging from lateral forces (bending). As such, a fundamental understanding of sorghum's biomechanical behavior is required to mitigate its propensity for lodging. This study first investigates changes in morpho-anatomical traits and biomechanical properties of bioenergy sorghum stems under mechanical stimulation during their growth and development. Based on statistical analysis, we discover that considerable differences exist between the stimulated and non-stimulated stems in terms of both their morpho-anatomical and mechanical properties. The mechanical stimulation produces shorter internodes with slightly larger diameters, as well as softer (more compliant) and stronger stems. The mechanical stimulation alters the cell wall thicknesses of the rind, vascular bundle, and pith tissues. We also investigate the different mechanical properties of the rind and pith and their effects on the overall deformation of stems, which is crucial in understanding stem lodging. Finally, we study the effect of microstructural geometries and mechanical properties of cell walls on the overall tensile and compressive behavior of different tissues in the stems. The electronic version of this dissertation is accessible from https://hdl.handle.net/1969.1/198727 |
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