Chemical and structural analysis of Eucalyptus globulus and E. camaldulensis leaf cuticles: a lipidized cell wall region

Abstract

The plant cuticle has traditionally been conceived as an independent hydrophobic layer that covers the external epidermal cell wall. Due to its complexity, the existing relationship between cuticle chemical composition and ultra-structure remains unclear to date. This study aimed to examine the link between chemical composition and structure of isolated, adaxial leaf cuticles of Eucalyptus camaldulensis and E. globulus by the gradual extraction and identification of lipid constituents (cutin and soluble lipids), coupled to spectroscopic and microscopic analyses. The soluble compounds and cutin monomers identified could not be assigned to a concrete internal cuticle ultra-structure. After cutin depolymerization, a cellulose network resembling the cell wall was observed, with different structural patterns in the regions ascribed to the cuticle proper and cuticular layer, respectively. Our results suggest that the current cuticle model should be revised, stressing the presence and major role of cell wall polysaccharides. It is concluded that the cuticle may be interpreted as a modified cell wall region which contains additional lipids. The major heterogeneity of the plant cuticle makes it difficult to establish a direct link between cuticle chemistry and structure with the existing methodologies.

Assembly of tomato fruit cuticles: a cross‐talk between the cutin polyester and cell wall polysaccharides

“…While the 1094 cm −1 signal was constant, a gradient corresponding to the crystalline cellulose was observed, highlighting a higher signal in the most external part of the exocarp in agreement with immunolabeling and NMR (Fig ). High crystallinity of cutin‐associated cellulose is in accordance with the fibrillar films observed by transmission electron microscopy after chemical hydrolysis of the cutin of Eucalyptus leaves (Guzman et al , ). Interestingly, extraction of cellulose from tomato peels after chemical hydrolysis showed a high yield in crystalline cellulose (Jiang & Hsieh, ).…”

Effects of methyl jasmonate on plant growth and leaf properties

“…For all the plant species, application of MeJA had no marked effects on cuticle compositions. The only exception was at the highest MeJA concentration (2.5 mM), with the relative content of phenolic compounds, cutin, or cutan (corresponding to the bond at 1600 cm −1 ) increasing while the relative content of polysaccharides decreased (corresponding to the bond at approximately 1020 cm −1 ; Guzmán et al, ; Heredia‐Guerrero et al, ) (Fig. ).…”

“…Although the cuticle is usually considered to be separate from the underlying epidermal cell walls, recent studies have suggested that the cuticle is simply an extension of the cell wall region that contains additional lipids ( Yeats and Rose , ; Guzmán et al, ). Therefore, in the present study we referred to cuticle thickness as the combined thickness of the epidermal cell wall and cuticle (Fig.…”

“…These tissues were digested overnight at room temperature before being washed twice using deionised water. Samples were examined using light microscopy to ensure that the underlying tissues were completely removed before being air dried and then the four replicates of each treatment were mixed evenly and analysed using FTIR ( Guzmán et al, ).…”

The use of laser light to enhance the uptake of foliar‐applied substances into citrus (Citrus sinensis) leaves

“…Although the primary functions of these protective layers are to prevent water loss and to act as a defense from pathogens and pests (Kerstiens, 1996), these surface properties also make foliar applications of agrichemicals (e.g., foliar nutrients, pesticides) difficult. The movement of substances across the cuticle and into leaves is most feasible through the stomatal openings (Burkhardt et al, 2012) found almost exclusively on the abaxial leaf surface in Citrus L. leaves (Reed and Hirano, 1931), through the polysaccharide matrix (Guzmán et al, 2014), and through occasional cracks in the cuticle itself. Stomata significantly contribute to the overall exchange of hydrophilic substances across leaf surfaces (Eichert et al, 2008); nevertheless, the collective area of stomatal openings that would allow for penetration of externally supplied solutions into the leaf is still reduced, even under optimum circumstances, because: (1) stomata often close under a variety of biotic and abiotic conditions (Daszkowska-Golec and Szarejko, 2013), (2) only a small percentage of the opened stomata participate in the uptake process (Eichert and Burkhardt, 2001), and (3) the entire stomata opening is not available to the movement of aqueous solutions because stomates are protected against infiltration by their geometry and pore walls (Schönherr and Bukovac, 1972).…”