Relative humidity and temperature modify the mechanical properties of isolated tomato fruit cuticles

Abstract

The mechanical properties of enzymatically isolated cuticular membrane (CM) from ripe tomato fruits were investigated at 10 to 45°C and relative humidity (RH) of 40 to wet. CM samples were stressed by uniaxial tension loads to determine their tensile modulus, E, breaking stress (strength), σ(max), and maximum elongation, ε(max). The CM stress-strain curves revealed a biphasic behavior when tested at RH values below wet conditions. In the first phase, CM responded to the loads by instantaneous extension with no further extension recorded until a further load was added: defined as pure elastic strain (E(e)). In the second phase, CM responded by instantaneous extension and by some additional time-dependent extension, defined as viscoelastic strain (E(v)). When CMs were submerged in aqueous solution (wet), the stress-strain curves were monophasic, with both elastic and viscoelastic strain. E(e) depended on RH and was higher than E(v), which was independent of RH. Temperature decreased E(e) and σ(max) of tomato fruit CM. Temperature response was not linear but consisted of two temperature-independent phases separated by a transition temperature. This transition zone has been related previously to the presence of a secondary phase transition in the cutin matrix of the tomato fruit CM.

Transcriptional Activity of the MADS Box ARLEQUIN/TOMATO AGAMOUS-LIKE1 Gene Is Required for Cuticle Development of Tomato Fruit

“…Mechanical properties of fruit cuticles were measured following the protocols already described by Matas et al (2005). Isolated cuticles were inspected with a microscope to confirm the absence of cracks; afterward, rectangular segments (3 mm 3 9 mm) were cut with the aid of a metal block.…”

“…Mechanical tests were performed as a transient creep test to determine changes in the length of a cuticle segment by maintaining samples in uniaxial tension, under a constant load, for 1,200 s, during which the longitudinal extension of each sample was recorded every 3 s by a computer system. Each sample was tested repeatedly using an ascending sequence of sustained tensile forces (from 0.098 N to the breaking point by 0.098 N load increments) without recovery time (Matas et al, 2005). The tensile force exerted along the sample was divided by the cross-sectional area of the sample in order to determine the stresses.…”

Transient Silencing of CHALCONE SYNTHASE during Fruit Ripening Modifies Tomato Epidermal Cells and Cuticle Properties

“…Rectangular uniform segments (3 mm 3 9 mm) of isolated cuticles were sectioned using a metal block and inspected microscopically to confirm the absence of small cracks before mechanical testing. Mechanical tests were performed as a transient creep test maintaining samples in uniaxial tension, under a constant load for 1,200 s, with the longitudinal extension being recorded every 3 s. Each sample was tested using an ascending sequence of sustained tensile forces (from 0.098 N to breaking point by 0.098 N load increments) without recovery time (Matas et al, 2005). The system was enclosed in an environment-controlled chamber that allowed the control of temperature and relative humidity.…”

Structure–function relationships of the plant cuticle and cuticular waxes — a smart material?

“…Temperature is an abiotic factor that also has a considerable effect on cuticular mechanics. Increased temperature regimes resulted in increased instantaneous extensibility and overall reduced stiffness and strength (Edelmann et al 2005;Matas et al 2005). These temperature-dependent effects can be as small as 1 • C and are likely to be related to secondary phase transitions of the semicrystalline cutin polymer matrix.…”