Influence of the morphology characters of the stem on the lodging resistance of Marylin flax

• The lodging resistance of Marylin flax was studied.
• The stem structure and the elementary fibres mechanical properties were analysed.
• The number of fibres is maximal at medium height of the plant.
• The fibres’ diameter decreases with the stem height because of the growth mechanisms.
• The Young’s modulus of elementary fibres was obtained by flexural tests on stems.

Flax fibres are widely used for composites reinforcement. Within the plant, these fibres have a mechanical support role for the stem, participating especially in the resistance against lodging. Flax stems (Linum usitatissimum) of the Marylin variety were cultivated in the same geographical zone over 4 successive years. Various parameters influencing the stem stiffness were analysed: the height and the diameter of the stems, their internal organization including the proportion of fibre bundles, the diameter and mechanical properties of elementary fibres. It was shown that the fibre yield and number of fibres increased with the height of the plants, the number of fibres being maximal at medium height. In addition, the fibres’ diameter decreases with the height of the stem because of the growth mechanisms. No correlation was found between the fibres’ mechanical properties and the height of the plants. Lastly, flexural tests on stems made it possible to correlate their stiffness with the Young modulus of the elementary fibres as well as their internal organization. This result confirmed the crucial role of fibres in the support of the plant and in particular in the lodging behaviour.