Conventional or greenhouse cultivation of flax: What influence on the number and quality of flax fibers?

Flax fibers (Linum usitatissimum L.) are of great interest for textile and composite applications. Thus, their use for industrial purposes requires increasing quantities and constant quality. In general, plants can change their morphology and mechanical properties when submitted to stress, particularly in the case of the reaction of plants to wind, a phenomenon known as seismomorphogenesis. In this paper, the influence of greenhouse or field cultivation on plant architecture and anatomy as well as the fiber yield and mechanical performances of flax fibers are investigated. The results highlight the development of much taller plants under greenhouse conditions, but similar fiber length and number of fibers per plant with both types of cultivation. Finally, the bending stiffness of stems is estimated by three-point bending tests and fiber performances are measured by tensile tests; in terms of mechanical properties at the stem level but also at the fiber scale, there are no statistically significant differences between greenhouse and field cultivated plants. In conclusion, despite the increased plant height under greenhouse conditions (44% increase in total height), fiber yield and properties are unchanged compared to field cultivation. Hence, the greenhouse cultivation of flax does not appear to favor higher fiber yields or quality, but nevertheless maintains compliance with these essential criteria.