Cell/Development/Systems

Abstract

CS -15-3 - Tear resistance of plant tissues: how cell geometry in the leaf epidermis affects the failure pattern upon mechanical stress

Monday, July 16
1:43 PM - 2:03 PM

The epidermis forms the interface of plants with the environment and is expected to resist pathogen invasion and mechanical tear. We used onion epidermis to investigate how cell shape and orientation affect the failure behavior of the epidermis. Upon stretching, a pre-applied tear administered along the cell growth axis grows following a relatively straight path in many cases passing through the middle lamella. The tear trajectory initiated perpendicular to the cells’ growth axis, on the other hand, tends to deviate and eventually align with cells’ axes. Fluorescence imaging of S4B labeled samples suggests that the initial shift of the tear path in perpendicularly notched specimens may result from the cellulose orientation in the cell wall. We hypothesize that in addition to the cell wall material, cell geometry plays a strong role in the tearing pattern of the tissue. To investigate this, we engraved epidermal cell shapes on polymethylmethacrylate (PMMA) sheets using a laser engraver. Two types of cell geometry were engraved: onion epidermal cells with relatively straight anticlinal walls and interlocking cells of the Arabidopsis cotyledon. The removal of material by laser was intended to mimic the tendency of the middle lamella to fail and guide the cracks. Fracture tests indicated that engraved cell borders not aligned with the crack path increase the tearing force required for the crack to proceed. In samples with interlocking cells patterns, the cracks propagated intermittently in the interface and through the cells. The trajectory seemed to depend on the angle of the cell walls with respect to the crack path. In all cases, the work of fracture was increased compared with the control (PMMA sheet without engraving) or PMMA with onion-like pattern aligned with the crack. Together, the results indicate that waviness of the cell borders can increase the energy to tear the epidermis.

Co-Authors

Bara Altartouri – PhD Student, Institut de Recherche en Biologie Végétale, Département de sciences biologiques, Université de Montréal Shafayet Zamil – Postdoctoral fellow, Plant Science, McGill University Frédérick P. Gosselin – Associate Professor, Laboratoire de mécanique multi-échelles, Département de génie mécanique, École Polytechnique de Montréal Anja Geitmann – Professor and Dean, Plant Science, McGill University

Amir J. Bidhendi

PhD Candidate
Université de Montréal

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CS -15-3 - Tear resistance of plant tissues: how cell geometry in the leaf epidermis affects the failure pattern upon mechanical stress



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