Resume.-Les parois des fibres des tiges de lin qui produisent un textile et des etoffes exceptionnelles ont une architecture cellulosique, traditionnellement decrite avec trois regions "spirales" majeures (Sl, 82-Ires dominante a structure tendant a devenir axiale -, 83) dans lesquelles !'orientation des microfibrilles reste parallele et constante (unidirectionnelle). II est montre ici que les changements d'orientation, aux interfaces de ces formations dominantes, font intervenir des plans intermediaires constitues d'arcs emboites, accentuables par goniometrie, doni I' organisation est celle d'analogues cholesteriques (structures helico'idales temporaires multidirectionnelles). Une modelisation de ces parois dans le temps et dans l'espace est proposee ; les mecanismes possibles de Ia morphogenese sont discutes en prenant en compte une cooperation entre un assemblage dirige (via le plasmalemma) et un auto-assemblage de type cristal liquide (analogue cholesterique intermittent). La comparaison de cette structure parietale avec celle des sclerites isodiametriques, ou les helico'ides se developpent de lacon continue, indique que Ia forme cellulaire parait etre un element determinant dans !'expression de !'architecture cholesterique et done des proprietes mecaniques (tenacite) de Ia fibre.Summary.-The cell wall of stem fibers of flax shows the classical cellulosic architecture with three main domains with constant slope (Sl, 82-thickened and locked into an almost axial direction-, 83) within which the microfibril orientation remains parallel (unidirectionnal, the so-called "spiral texture"). The present paper focus on the fact that arced change of orientation occurs at the major wall layer interfaces. The nested arcs are cancelled or reversed by tilting of the goniometric stage at the electron microscopy level ; they are transient cholesteric analog (multidirectional helicoids). Structural models are provided giving unified picture of the flax fiber wall according space and time. Data are consistant with a possible dual mechanism controlling the cellulosic framework morphogenesis: cooperation between a directed assembly (via the plasmalemma) and a liquid crystal-like self assembly. The secondary cell wall of fibers with intermittent cholesteric pattern is compared to the secondary cell wall of isodiametric sclereid with continuous cholesteric pattern and cell shapes appear essential for the expression of such architecture and thus of the mechanical properties (tenacity) of the fiber.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.