Hierarchical organization of mesocarp of Brazil nut (Bertholletia excelsa)Monday (19.03.2018) 15:00 - 15:20 Part of:
The dry and woody fruit of brazil nut (Bertholletia excelsa) protects the seeds from most predators in Amazon forest and is capable to resist a free fall from trees as high as 50 meters.(1) Therefore it has great potential as a source for bioinspiration of impact and puncture resistant materials. (2) This work aims at describing the macroscopic, cellular, fibrillar and molecular hierarchical levels of organization of the mesocarp layer of brazil nut fruit, which is responsible for the fruit’s mechanical performance. Mesocarp was characterized by chemical analysis, optical microscopy (OM), scanning electron microscopy (SEM) and microtomography (MicroCT). Mesocap is an orbicular and slightly flatten capsule with approximately 10 cm of diameter and wall thickness of 1 cm. It has a peduncle in one extremity and an opercular opening called pyxis, on the other extremity. On the cellular level, mesocarp is composed of sclerenchyma tissue (fibers and sclereid cells), xylem (tracheid cells) and phloem cells. The fibers are oriented from peduncle to pyxis in an inner region and randomly oriented in the most external regions of mesocarp. There are open channels throughout the structure, probably formed after the death of phloem cells, resulting in porosity of 3.6 %. The characterization of fibrillary level has shown that the fiber cell wall has microfibril angle of approximately 28°. Finally, in the molecular level, mesocarp is composed by approximately 58 % of lignin and more than 30 % of holocellulose. This structural characterization is important to understand the function of each hierarchical level of organization in the outstanding mechanical performance of brazil nut mesocarp, what may inspire new impact and puncture resistant materials.