Morphogenesis of plant cell walls at the supramolecular level: Internal geometry and versatility of helicoidal expression

Summary The concept of the cell wall organized in a helicoidal pattern was outlined. When studied in transmission electron microscopy, the observed textures appear as a deceptive figure,i.e., as a trompe l'oeil. Difficulties—both technological and visual in the reconstitution of the actual geometry (exposure of the microfibrillar framework, 3-dimensional and 4-dimensional restoration), and the interest of simple modelling to understand the changes in cellulose orientation according to space and time are emphasized.The morphogenesis of helicoidal walls presents two main characteristics: it is both very defined and flexible, thus adaptable to varied programs of differentiation and to different environmental conditions. The observations of various cell examples and of responses to experimental treatments, lead to the following considerations: a) the shift of cellulose occurs continuously with time through a constant mutual angle. The wall seems to be built up as an indefinite continuum and forms a monotonous oscillatory system (unvarying motion); b) the shift of cellulose occurs through a mutual angle variable with time (varying motion, change from monotonous helicoid to bimodal helicoid, or sporadic bursts with arrested motion).The helicoidal wall appears as a fibrous composite with multifunctional possibilities ranging from fluidity to stiffness. The helicoidal assembly is remarkably adaptable to different physiological conditions of growth and specialization.