Fibers produced by the flax plant provide strength by being extensively cross-linked composites of cellulose, pectin, and protein in a long, tube-like architecture.

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Flax fiber has been used for millenia throughout the world for the production of linen textile. Its strength and desirable properties are a result of its microscopic structure and chemistry. Flax fibers are relatively long, tube-like composites (up to about 5 cm, or 2 inches) of cellulose supplemented by pectin and other polysaccharides, lined up in the direction of the tube, surrounded by concentric layers of cells forming a super-strong secondary wall. Extensive cross-linking, aided by the presence of several types of proteins, binds all the components into an intricate matrix. Edit Summary

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"[W]ith a large amount of unidirectional cellulose microfibrils, flax fibre is described as a good model of a tubular structure of high tensile strength and low elasticity. Such properties indicate a bearing role for fibres in the plant stem, providing mechanical support and protection against herbivore and sap-sucking insects" (Morvan et al. 2003:936-7)

[Flax fibres] "are long and multinucleate cells without septum or partition (average length 2–5 cm) and have a secondary wall of very large thickness (5–15 μm). Fibres are gathered in bundles of one to three dozen cells that encircle the vascular cylinder. The bundle cohesion is insured by pectins, accumulating in the primary wall and cell junctions...At maturity [the fibers contain]...5–15% non-cellulosic polysaccharides (NCPs). The chemical composition of NCPs depends on growth stage, indicating important cell wall remodelling, fibre position and variety...Glycine-rich proteins (GRPs) and arabinogalactan-proteins (AGPs)...may contribute to the cross-linking of pectins...cellulose microfibrils, tethered by cross-linking (galacto)glucomanans/glucans, are embedded in a pectic matrix." (Morvan et al. 2003:936)

"At maturity, flax fibres show thickened secondary cell wall with cellulose microfibrils locked into an almost axial direction...Apart from cellulose, flax fibres contain other polymers, which are highly negatively charged..."encrusting components"...these non-cellulosic polymers (NCPs) contain not only classical hemi-celluloses but also pectins...long chains of b1-4-D-galactan as the main encrusting component of ultimate fibres" (Morvan et al. 2003:939)

"[T]he pectic nature of the main NCPs of flax fibre secondary wall is now well established...they are progressively cross-linked within fibre cell wall during plant development" (Morvan et al. 2003:940)

"Glycine-rich proteins (GRPs) account for about 0.1–0.4% of the mass of ultimate fibre...they interact strongly with cellulose microfibrils...interaction between pectins and AGPs...Cellulose microfibrils, tethered by cross-linking polymers, are embedded in a NC matrix...Glucans including xyloglucans and [galacto]glucomanans are hydrogen-bound to cellulose in the primary wall...while xylans are the main cross-linking polymers in secondary wall...They may form an independent network as extensin in primary wall, and become cross-linked, for example, through ester linkages between glutamic acids and cellulose " (Morvan et al. 2003:941)

"[P]ectins constitute the principal matrix network in which lies embedded the frame-work of cellulose and cross-linking glycans" (Morvan et al. 2003:941-2)

"Galactose appears to be the predominant sugar of NCPs, and b-1-4-galactan together with RG-I and PGA become the most abundant tightly bound NCPs with plant development...The significant variations in sugars observed at different growth stage indicate important remodelling with structural impacts on the physical properties of fibres and consequently on their bearing role in the stem." (Morvan et al. 2003:942)

Journal article
Building flax fibres: more than one brick in the walls

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Journal article
Engineering flax and hemp for an alternative to cottonTrends in BiotechnologyJuly 26, 2002
Michel J.M Ebskamp

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Living System/s

Organism
Cultivated FlaxLinum usitatissimumSpecies

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