Micromechanics of Plant Growth Under Healthy and Salt Stress Conditions for Bioinspired Design

Nature has offered much inspiration to design bio-inspired based efficient composites. Abstraction of the hidden cues of the hierarchical organization, principles and underlying structure-function relations are some of the critical approaches of bioinspired materials design. However, significant effort has been focused on rigid natural composites such as bone, wood, and bamboo for designing structures optimized for strength, toughness, and density. In this study, we investigate the vascular tissue of a fast-growing plant sunflower (Helianthus annuus) to gain insights into changes in cell wall mechanics from early stages with a soft pliable structure to later stages with tough lignified mass. Our focus lies on the cell wall as these components play a vital role in maintaining cell growth for structural integrity during development.<br/>To conduct the study, we grew sunflowers in the lab under healthy and salt-stressed conditions and compared the response from the early stages of 4 weeks to 12 weeks. We employed the depth-sensing nanoindentation technique (Hysitron T1 980) to map the elastic and viscous properties and Raman spectroscopy to analyze the composition changes and evaluated the structure mechanics and composition connected among the stages due to salt presence. Combining these results provided a comprehensive understanding of the micromechanics of cell-wall structure from primary to secondary growth. The results are presented in the context of functional composite design. Overall, this research sheds light on the importance of examining the mechanical properties of cell walls during different growth stages and provides valuable data for developing bioinspired materials with enhanced functionalities and optimized composite interfaces.