Leaf anatomy and fiber types of Curaua (Ananas comosus var. erectifolius)

This study investigated the variability in the morphological, physiological, mechanical, thermal, and crystallographic properties of fiber types of Curaua (Ananas comosus var. erectifolius) extracted from different leaf regions. Initially, histological sections of cross-sectional leaves were prepared and a classification of vascular, primary, and secondary types were carried out with an optical microscope. Then, bundles were extracted from the leaves, separated into fiber classes (vascular fibers—VF, primary fibers—PF, and secondary fiber—SF). Finally, the morphological, mechanical, thermal, and chemical properties of these different types of fibers were determined by microscopy, the tensile test, thermogravimetry, and X-ray diffraction techniques, respectively. The results showed no statistical differences for the tensile strength (300 MPa), Young's modulus (13 GPa), and elongation (2.3) between the three fiber classes. PF and SF showed superior mechanical performance than VF, which can be attributed to leaf morphology and plant physiology, as SF and PF types are responsible for the leaf structural function. In addition, different results were found for PF, SF, and VF for the aspect ratio (270, 269, and 135) and crystalline cellulose contents (74, 75 and 66%) and crystal sizes (26, 28 and 21 Å), respectively. The thermal behavior and the contents of cellulose, hemicellulose, and lignin did not vary among the fiber types.