Biomechanics and anatomy of Lycopersicon esculentum fruit peels and enzyme‐treated samples

Abstract

We report the biomechanics and anatomy of fruit wall peels (before and after cellulase/pectinase treatment) from two Lycopersicon esculentum cultivars (i.e., Inbred 10 and Sweet 100 cherry tomatoes). Samples were tested before and after enzyme treatment in uniaxial tension to determine their rate of creep, plastic and instantaneous elastic strains, breaking stress (strength), and work of fracture. The fruit peels of both cultivars exhibited pronounced viscoelastic and strain-hardening behavior, but differed significantly in their rheological behavior and magnitudes of material properties, e.g., Inbred 10 peels crept less rapidly and accumulated more plastic strains (but less rapidly), were stiffer and stronger, and had a larger work of fracture than Sweet 100 peels. The cuticular membrane (CM) also differed; e.g., Sweet 100 CM strain-softened at forces that caused Inbred 10 to strain-harden. The mechanical behavior of peels and their CM correlated with anatomical differences. The Inbred 10 CM develops in subepidermal cell layers, whereas the Sweet 100 CM is poorly developed below the epidermis. Based on these and other observations, we posit that strain-hardening involves the realignment of CM fibrillar elements and that this phenomenon is less pronounced for Sweet 100 because fewer cell walls contribute to its CM compared to Inbred 10.

A Reevaluation of the Key Factors That Influence Tomato Fruit Softening and Integrity

“…AC and DFD fruits have similar cuticle anatomies (Fig. 7, A-D), with substantial epidermal cell encasement, where several outer epidermal cell layers show cuticularization of the anticlinal and periclinal cell walls, as has been described in several tomato cultivars (Bargel and Neinhuis, 2004;Matas et al, 2004). Fruits of both cultivars also showed similar patterns of cellulosic cell wall ramification within the cuticular layer, as revealed by staining with toluidine blue (Fig.…”

“…The cuticle itself is also thought to have an important influence on the biomechanical properties of ripening fruit (Petracek and Bukovac, 1995;Bargel and Neinhuis, 2004;Matas et al, 2004;Bargel and Neinhuis, 2005;Edelmann et al, 2005) and studies with isolated tomato fruit cuticles suggest that their relative contribution to tissue strength increases markedly during ripening, an idea that was previously suggested by analyses of intact tomato fruits (Jackman and Stanley, 1994). Taken together, a growing body of evidence suggests that, as with cell wall metabolism, dynamic changes in the structure and composition of the fruit cuticle that lead to a reduction in fruit firmness are likely to be an integral and regulated part of ripening.…”

“…A minimum of eight samples from each ripening stage was tested in unaxial tension using a model 4502 Instron Testing machine (Instron) and a 2.0 mm s 21 strain rate (see Matas et al, 2004). Data were rejected from samples that broke near or at their clamped ends; visual inspection of specimens during testing and of the shape of force-deformation graphs was used to assess clamp failure.…”

Localization of polysaccharides in isolated and intact cuticles of eucalypt, poplar and pear leaves by enzyme-gold labelling

“…Although it was found that cellulose fibres are mainly randomly oriented in cuticles of mature and ripe tomato fruits and Agave Americana young leaves [9,10], the position and distinction between groups of polysaccharides cannot be ascertained by such analytical techniques. On the other hand, stains like osmium tetroxideuranyl acetate-lead citrate combination [12], calcofluor white [9], ruthenium red [13], periodic acid-thiosemicarbazide-silver proteinate tests [12,14] or chlor-zinc-iodine [15] have been used for detecting polysaccharides in cross-sections of isolated leaf and fruit cuticles by electron, optical and fluorescence microscopy. Nevertheless, the lack of specificity of the dyes, the potential degree of impregnation of polysaccharides with chiefly lipidic cuticular components, and the restrictions to observe stained tissues at higher magnifications by optical and fluorescence microscopy, pose an obstacle for elucidating the nature and location of polysaccharides in the cuticle.…”

Pleiotropic Phenotypes of the sticky peel Mutant Provide New Insight into the Role of CUTIN DEFICIENT2 in Epidermal Cell Function in Tomato

“…Tomato (Solanum lycopersicum) fruit also serve as a powerful system for investigating the physical properties and biosynthesis of the cuticle fostered in large part by the abundance of cuticular lipid deposited during fleshy fruit development, its astomatous nature, and relevance in fruit cracking and postharvest storage Scott, 1997, 1998;Matas et al, 2004;Bargel and Neinhuis, 2005). Genomics-and proteomics-based approaches have identified genes and proteins preferentially expressed in the fruit peel, and perturbation of several genes through mutagenesis has revealed altered fruit cuticle phenotypes (Vogg et al, 2004;Hovav et al, 2007;Mintz-Oron et al, 2008;Isaacson et al, 2009;Yeats et al, 2010;Matas et al, 2011).…”