Changes in strain and deposition of cuticle in developing sweet cherry fruit

Abstract

Changes in surface area, deposition and elastic strain of the cuticular membrane (CM) were monitored during development of sweet cherry (Prunus avium L.) fruit. Fruit mass and surface area ('Sam') increased in a sigmoidal pattern between 16 and 85 days after full bloom (DAFB) with maximum rates of 0.35 g day(-1) and 0.62 cm(2) day(-1), respectively. Rates of total area strain, namely the sum of elastic plus plastic strain, were highest in cheek and stem cavity regions followed by stylar and suture regions. Rates of total uniaxial strain were higher in transverse, namely perpendicular to the stem/stylar axis, than in longitudinal direction, namely parallel to the stem/stylar axis. On a whole fruit basis CM mass remained essentially constant during fruit development. Mass of CM, dewaxed CM and wax per unit surface area decreased during development, particularly between 43 and 71 DAFB. There was no change in wax content of isolated CM. Up to 43 DAFB the surface area of isolated CM was similar to the area prior to excision indicating little elastic strain, but markedly decreased thereafter. Calculating elastic and plastic components of total strain of the CM revealed, that initial deformation up to 22 to 43 DAFB was mostly plastic. Thereafter, elastic strain was evident and both, elastic and plastic deformation, increased linearly with an increase in total strain. There was no consistent difference in the relative contribution of elastic strain to total strain between transverse and longitudinal directions, but both total and elastic strain were larger in the transverse direction. Abrading the CM had only little effect on fruit turgor. However, turgor decreased when the exocarp was cut indicating that the exocarp provided a significant structural shell of a mature sweet cherry fruit ('Regina'). Our data demonstrate, that (1) surface area expansion in sweet cherry fruit causes elastic and plastic strain of the CM, and (2) the onset of elastic strain coincided with the cessation of CM formation.

Morphological, Histological and Ultrastructural Changes in Fruit Epidermis of Apple Malus Domestica cv. Ligol (Rosaceae) at Fruit Set, Maturity and Storage

“…Maguire et al (1999) and Curry (2009) reported similar observations. Roy et al (1994) and Knoche et al (2004) suggested that the microcracks occur on apple fruits as a result of their intensive growth and in particular the enlargement of their volume and surface area, while the mass of the cuticular membrane per fruit remains constant. The deepening of microcracks results from shrinkage of the fruits during storage, associated with water loss from their cells.…”

Transcriptional analysis of cell wall and cuticle related genes during fruit development of two sweet cherry cultivars with contrasting levels of cracking tolerance

“…Examples include Prunus species and Vitis vinifera L. (Knoche et al, 2004;Becker and Knoche, 2012). As mentioned above, during cherry fruit growth there are two phases that involve a significant increase in fruit size and therefore expansion of the cuticle.…”

“…Cracking index is one of the most common laboratory tests that have been used to assess the degree of tolerance among cultivars avoiding the effect of environmental conditions (Christensen, 1972;Lane et al, 2000;Moing et al, 2004). Although differences in cracking tolerance levels have not been fully explained, a recent approach suggests that these could be related to the dynamics of the stages of fruit growth, with the properties of the cuticle being some of the most important factors involved in the onset of this problem (Knoche et al, 2004).…”

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

“…The mechanical performance of a fruit surface affects fruit appearance, handling and storage, but also plays a prominent role in fruit cracking. It is therefore not surprising that several studies were carried out to analyse fruit cracking symptoms of important crops such as tomato or sweet cherry (Prunus avium L.) fruit (Bargel et al 2004a(Bargel et al , 2004b and references therein; Knoche et al 2004). Only recently, Matas et al (2004b) reported a correlation between CM thickness, mechanical properties and resistance to cracking of cherry tomato fruit.…”