title: Intracuticular wax fixes and restricts strain in leaf and fruit cuticles.
abstract: This paper investigates the effects of cuticular wax on the release of strain and on the tensile properties of enzymatically isolated cuticular membranes (CMs) taken from leaves of agave (Agave americana), bush lily (Clivia miniata), holly (Ilex aquifolium), and ivy (Hedera helix) and from fruit of apple (Malus × domestica), pear (Pyrus communis), and tomato (Lycopersicon esculentum). Biaxial strain release was quantified as the decrease in CM disc area following wax extraction. Stiffness, maximum strain and maximum force were determined in uniaxial tensile tests using strips of CM and dewaxed CMs (DCMs). Biaxial strain release, stiffness, and maximum strain, but not maximum force, were linearly related to the amount of wax extracted. Apple CM has the most wax and here the effect of wax extraction was substantially accounted for by the embedded cuticular wax. Heating apple CM to 80°C melted some wax constituents and produced an effect similar to, but smaller than, that resulting from wax extraction. Our results indicate that wax 'fixes' strain, effectively converting reversible elastic into irreversible plastic strain. A consequence of 'fixation' is increased cuticular stiffness.
authors.affiliation: Institute for Biological Production Systems, Leibniz-University Hannover, Herrenhäuser Straße 2, 30419, Hannover, Germany.
authors.forename: Bishnu Prasad
authors.initials: BP
authors.lastname: Khanal
authors.affiliation: Institute for Biological Production Systems, Leibniz-University Hannover, Herrenhäuser Straße 2, 30419, Hannover, Germany.
authors.forename: Eckhard
authors.initials: E
authors.lastname: Grimm
authors.affiliation: Institute of Chemistry, Martin-Luther-University Halle-Wittenberg, von-Danckelmann-Platz 4, 06120, Halle (Saale), Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Finger
authors.affiliation: Institute of Chemistry, Martin-Luther-University Halle-Wittenberg, von-Danckelmann-Platz 4, 06120, Halle (Saale), Germany.
authors.forename: Alfred
authors.initials: A
authors.lastname: Blume
authors.affiliation: Institute for Biological Production Systems, Leibniz-University Hannover, Herrenhäuser Straße 2, 30419, Hannover, Germany.
authors.forename: Moritz
authors.initials: M
authors.lastname: Knoche
mesh_terms: D027882:Agave; D005638:Fruit; D035981:Hedera; D030017:Ilex; D019668:Liliaceae; D018551:Solanum lycopersicum; D019684:Magnoliopsida; D027845:Malus; D019441:Plant Epidermis; D018515:Plant Leaves; D031989:Pyrus; D013718:Tensile Strength; D014885:Waxes
chemical_list: D014885:Waxes
keywords: crystallinity; cuticle; fracture; rheology; stiffness; stress