Structure of epidermis wall, cuticle and cuticular microcracks in nectarine fruit

Abstract

Summary ― The fine structure of the epidermis of the nectarine fruit ("Tasty-fruit" cultivar) has been investigated. The work was mainly focussed on cuticular microcracks which occur on the ripe fruit. The outer wall of the epidermal cell is thick and is composed of different layers which exhibit various textures. A layer that could be interpreted as a cutinized, dense network of polysaccharidic fibrils, clearly appears at the junction between the cuticle and the wall. Cracks result in an abrupt interruption of the cuticle, but the layer at the junction of the cuticle and the wall and in some instances the waxes remain at the surface of the cell wall. The wall itself shows the same aspect in the cracks and under the normal cuticle. The susceptibility of cracks to the penetration by phytopathogenic fungi is discussed.nectarine / cuticle / cell-wall / epidermis Résumé ― Structure de microfissures cuticulaires dans la paroi épidermique de nectarine. La structure fine de l'épiderme de nectarine (cultivar "Tasty-fruit") a été étudiée en microscopie optique et en microscopie électronique à transmission. Le travail a été principalement orienté sur des microfissures cuticulaires qui surviennent sur les fruits mûrs. En microscopie optique (fig 1-4 (fig 10-11), mais la paroi présente le même aspect dans les fissures et sous la cuticule normale. La couche constituant la jonction entre la paroi et la cuticule, et dans certains cas des cires, subsistent à la surface de la paroi cellulaire (fig 12). Dans les fissures s'étendant sur plusieurs cellules épidermiques, des crevasses profondes ont été observées à la jonction entre 2 cellules adjacentes (fig 14) bien que plus généralement l'interface entre cellules semble renforcée par une structure cuticulaire (fig 15). La texture de la paroi épidermique (c'est-à-dire la disposition des fibrilles de cellulose) a été étudiée sur des échantillons traités par la méthylamine afin d'extraire la matrice amorphe de la paroi. La paroi externe des cellules épidermiques est constituée de couches de textures variées (fig 17-24). La texture des parois situées sous la cuticule normale ne paraît pas différente de celle des parois situées sous les fissures cuticulaires. La sensibilité des fissures à la pénétration par des champignons phytopathogènes est discutée.nectarine / cuticule / paroi cellulaire / épiderme

Effect of Hydroxypropyl Methylcellulose‐Lipid Edible Composite Coatings on Plum (cv. Autumn giant) Quality During Storage

“…Storey and Price (1999) studied the microstructure of the skin of 'd'Agen' plums, observing that the epicuticular wax was a closely packed granular structure overlying a more amorphous layer, which was more than 5 m thick. In addition, these authors observed very few cuticular fractures over the surface of 'd'Agen' plums apart from those associated with stoma, contrary to the epicuticular wax of other fruits, such as apple, pear, and nectarines, which frequently fracture during fruit growth (Knuth and Stosser 1987;Kovás and others 1994;Nguyen-The 1991). This wax layer of d'Angen plums was supposed to be responsible for the high resistance to water movement across the cuticle during drying (Price and others 2000).…”

Modelling the effect of cuticular crack surface area and inoculum density on the probability of nectarine fruit infection by Monilinia laxa

“…Direct penetration of M. laxa conidia through an intact cuticle has never been observed [Nguyen‐The, 1991; Fourie & Holz, 2003a (nectarine), 2003b (plum)]. Conidial infection has been described occurring through stomata, lenticels, wounds (mainly caused by insects and birds) or cuticular cracks (Byrde & Willetts, 1977; Xu & Robinson, 2000; Xu et al , 2001b).…”

“…Conidial infection has been described occurring through stomata, lenticels, wounds (mainly caused by insects and birds) or cuticular cracks (Byrde & Willetts, 1977; Xu & Robinson, 2000; Xu et al , 2001b). Cuticular cracks are likely to play a major role in fungal infection (Nguyen‐The, 1991; Fourie & Holz, 2003a). Cuticular cracks occur when the fruit growth rate is maximal, a few weeks before harvest, although they can also result from fruit‐to‐fruit, fruit‐to‐leaf or fruit‐to‐twig contact (Michailides & Morgan, 1993, 1997).…”

Cuticular Cracking on Nectarine Fruit Surface: Spatial Distribution and Development in Relation to Irrigation and Thinning

“…Cuticular cracks may be defined as the physical failure of the fruit skin (Milad and Shackel, 1992). They form shallow or deeper oblong wounds on fruit (Nguyen-The, 1991;Sekse, 1998). In addition to having a negative affect on fruit appearance, they may also influence organoleptic quality, particularly by accelerating softening due to water loss (Beyer et al, 2002;Glenn and Poovaiah, 1989).…”