Abstract
The tracheary system of plant leaves is composed of a cellulose skeleton with diverse hierarchical structures. It is built of polygonally bent helical microfilaments of cellulose-based nanostructures coated by different layers, which provide them high compression resistance, elasticity, and roughness. Their function includes the transport of water and nutrients from the roots to the leaves. Unveiling details about local interactions of tracheary elements with surrounding material, which varies between plants due to adaptation to different environments, is crucial for understanding ascending fluid transport and for tracheary mechanical strength relevant to potential applications. Here we show that plant tracheary microfilaments, collected from Agapanthus africanus and Ornithogalum thyrsoides leaves, have different surface morphologies, revealed by nematic liquid crystal droplets. This results in diverse interactions among microfilaments and with the environment; the differences translate to diverse mechanical properties of entangled microfilaments and their potential applications. The presented study also introduces routes for accurate characterization of plants' microfilaments.
Highlights
Morphology of Helical Tracheary MicrofilamentsHelical tracheary elements extracted from plants belonging to the same Asparagales order, A. africanus (Fig. 1A) and O. thyrsoides (Fig. 1B), were chosen
The isolated microfilaments isolated from each plant were glued onto glass microscopic slide bars using two-sided glue tape
Filaments collected from A. africanus and O. thyrsoides leaves by simple breaking of the leaves, similar to the method described in ref. 6, were suspended in 1-cm2 frames and treated with NaOH 5% wt/wt solution for 1 h to access the nanostructures cellulose skeletons as shown in Fig. 1 H and I and SI Appendix, Fig. S1 D–F and Fig. 3D
Summary
Helical tracheary elements extracted from plants belonging to the same Asparagales order, A. africanus (Fig. 1A) and O. thyrsoides (Fig. 1B), were chosen. The untreated microfilaments extracted from leaves of both plants A. africanus and O. thyrsoides were thoroughly investigated by SEM (Fig. 2 A1–D1 and A2–D2, respectively) Both microfilaments exhibit similar diameters, and elbows appear along the helical shapes when stretched. After removing the external layers of the microfilament, dispersed droplets with homeotropic anchoring at the droplet–air surface display a similar texture for both A. africanus and O. thyrsoides (Fig. 3E) This texture is completely different from the textures observed for the previous pierced nematic droplets in “dressed” microfilaments. 2C2 and 3 A, Inset) and ellipsoidal fringes from A. africanus (Fig. 2C1) to a similar rapidly varying texture observed near the microfilaments’ main axis (Fig. 3E), which gives evidence of the variation of the nanostructure particle orientation from axial to out of plane and back, seen by SEM. Macroscopic properties, the mechanical properties of single filaments and bundles of tracheary microfilaments were investigated
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