Investigation of the Mechanical Properties of Flax Cell Walls during Plant Development: The Relation between Performance and Cell Wall Structure

Camille Goudenhooft,Olivier Sire,Alain Bourmaud,Christophe Baley,Olivier Arnould,David Siniscalco,Tatyana Gorshkova

doi:10.3390/fib6010006

Abstract

The development of flax (Linum usitatissimum L.) fibers was studied to obtain better insight on the progression of their high mechanical performances during plant growth. Fibers at two steps of plant development were studied, namely the end of the fast growth period and at plant maturity, each time at three plant heights. The indentation modulus of the fiber cell wall was characterized by atomic force microscopy (AFM) using peak-force quantitative nano-mechanical property mapping (PF-QNM). Changes in the cell wall modulus with the cell wall thickening were highlighted. For growing plants, fibers from top and middle heights show a loose inner Gn layer with a lower indentation modulus than mature fibers, which exhibit thickened homogeneous cell walls made only of a G layer. The influence of these changes in the fiber cell wall on the mechanical performances of extracted elementary fibers was also emphasized by tensile tests. In addition, Raman spectra were recorded on samples from both growing and mature plants. The results suggest that, for the fiber cell wall, the cellulose contribution increases with fiber maturity, leading to a greater cell wall modulus of flax fibers.

Highlights

Flax (Linum usitatissimum L.) has been cultivated as a fiber crop in order to produce textiles [1]
How does the cell wall development lead to the impressive geometrical and mechanical properties of flax fibers? This study investigates the characteristics of cell wall properties of flax fibers during plant development
Raman spectroscopy with a linear analysis was performed

Summary

Introduction

Flax (Linum usitatissimum L.) has been cultivated as a fiber crop in order to produce textiles [1]. Fiber flax is used in the clothing industry, as its technical fibers have been used as reinforcement for composite materials since the 1930s [2]. Flax technical fibers are composed of elementary fibers, whose average performances reach a longitudinal Young’s modulus of 52.47 ± 8.57 GPa, a tensile strength of 945 ± 200 MPa, and a strain at break of 2.07 ± 0.45%; their average specific mechanical properties were proven to compete with those of glass fibers [3]. Flax is a unique model for studying cell growth. Its fibers can reach a length of several tens of millimeters [4]. The cell wall thickness in fibers is impressively high, as it can reach more than 10 μm, while most cell walls are less than a few microns thick [5]

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Conclusion