Effect of calcium oxalate crystals on the micromechanical properties of sclerenchyma tissue from the pecan nutshell (Carya illinoinensis)

• Published in: Plant physiology and biochemistry 2022-01, Vol.170, p.249-254
• Main Authors: Arzate-Vázquez, I., Méndez-Méndez, J.V., Nicolás-Bermúdez, J., Chanona-Pérez, J.J., Domínguez-Fernández, R.N., Vélez-Rivera, N.
• Format: Article
• Language: English
• Subjects: Calcium Oxalate; Calcium oxalate crystals; Carya; Indentation test; Micromechanical properties; Pecan nutshell; Sclerenchyma
• ISSN: 0981-9428; 1873-2690
• DOI: 10.1016/j.plaphy.2021.12.011

The objective of this study was to evaluate the effect of the presence of calcium oxalate (CaOx) crystals on the micromechanical properties of sclerenchyma tissue from the pecan nutshell (Carya illinoinensis). The microstructure of the cross-section nutshell was examined using light microscopy (LM) and atomic force microscopy (AFM). Using an instrumented indentation system, indentation tests with maximum loads of 500 mN were made on the biological material where the variables studied were the number of crystals present in the evaluated area and the size of individual crystals. Microscopic analysis revealed that the pecan nutshell consists of sclerenchyma tissue with multiple CaOx crystals randomly distributed throughout the material, exhibiting prismatic shapes and various sizes. The results of the indentation tests showed that the examined areas where there were crystals (1, 2 or up to 3) presented values of hardness and elastic modulus significantly higher (P  0.05) between the values of the micromechanical properties of the areas evaluated as a function of the number of crystals. On the other hand, it was observed that the size of the crystals did not show a direct correlation with the mechanical properties evaluated as expected. In conclusion, the biomineralization phenomenon is a successful strategy designed by nature to improve the rigidity of the pecan nutshell, where the CaOx crystals strengthen the structure by increasing the micromechanical properties. •The effect of CaOx crystals on the micromechanical properties of the sclerenchyma from the pecan nutshell were evaluated by indentation tests.•The CaOx crystals increased the hardness (≈20%) and elastic modulus (≈13%) of the sclerenchyma tissue locally.•There were no significant differences between the values of the micromechanical properties evaluated as a function of the number of crystals.•The size of the crystals did not show a direct correlation with the mechanical properties.•CaOx crystals strengthen the structure of the pecan nutshell, demonstrating that they fulfill a mechanical function.