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Martin J. Bukovac, Alicia Pastor, Royal G. Fader, and Moritz Knoche

Morphological and physical characteristics of the cuticular membrane (CM) of selected cultivars of sweet cherry (Prunus avium L.) fruit were studied relative to rain-induced cracking. Two characteristics of the CM may be determinants in rain-induced fruit cracking. The surface morphology and chemistry determine surface wettability and water retention, and the morphology and physicochemical characteristics its water permeability. The fruit epidermis as well as the guard cell walls adjacent to the outer vestibule and stomatal pore are covered by a thin lipoidal CM. Stomata were present at a frequency of 0.1 to 2 per mm2 depending on cultivar and fruit surface position. However, most appeared nonfunctional with many pores partially or completely occluded with wax-like material. There was no evidence of water (containing fluorescein or AgNO3) penetration into stomatal pores following surface application or submerging fruit for short periods. There was stomatal pore penetration when submerged fruit were infiltrated by reduced pressure in the presence of 0.1% L-77. Preferential sorption of AgNO3 and fluorescein by cuticular ledges and guard cells was noted. The epicuticular wax (ECW) had no significant fine-structure. The CM was isolated enzymatically (cellulase/pectinase) and found to be 1 to 2 μm thick with an area weight of 1.2 to 2.3 g·m–2, of which 25% to 40% was chloroform/methanol (1: 1by vol.) soluble. Fractionation of the chloroform/methanol fraction indicated the presence of four groups of nonpolar constituents. The fruit surface was moderately difficult to wet, forming contact angles of 85% to 105%, and with an estimated critical surface tension in the range of 16-24 mN·m–1. Fruit water loss (transpiration) and uptake on submersion was followed and found to be complex. Transpiration increased with an increase in temperature, and both rate of transpiration and water uptake increased after removal of the epicuticular and cuticular waxes. Pathways of water uptake and the significance of our findings to rain-induced fruit cracking will be discussed.

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Antonio J. Matas, Eward D. Cobb, Dominick J. Paolillo Jr., and Karl J. Niklas

The mechanical properties and anatomy of fruit wall peels and their enzyme-isolated cuticular membranes (CM) are reported for three cherry tomato (Lycopersicon esculentum Mill.) cultivars that are crack-resistant, crack-intermediate, and crack-prone (i.e., Inbred 10, Sweet 100, and Sausalito Cocktail, respectively). The resistant and intermediate fruit peels strain-hardened when extended progressively; those of the crack-prone cultivar did so only modestly. The CM of all cultivars strain-hardened when extended with small forces; the CM of the intermediate and crack-prone cultivars strain-softened under tensile forces that did not strain-soften the crack-resistant cultivar. The peels and CM of the resistant cultivar were stiffer, stronger, and required more energy to break than crack-prone peels. The CM of crack-resistant peels developed deeper within the subepidermis than in the crack-prone or crack-intermediate peels. The CM in the outer epidermal periclinal walls of the crack-resistant and crack-intermediate cultivars was thicker than that of crack-prone peels. These data indicate that CM thickness can be used to gauge crack susceptibility among cherry tomato fruit, which can be useful in breeding programs and would facilitate QTL mapping of the underlying genetic factors.

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Bishnu P. Khanal, Rejina Shrestha, Leonie Hückstädt, and Moritz Knoche

surface, they were all averaged. The mean of these scores was used in the subsequent correlative analyses ( Table 1 ). Table 1. Russeting susceptibility of 22 apple cultivars, mass of cuticular membrane (CM), dewaxed cuticular membrane (DCM) and wax

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Thanidchaya Puthmee, Kenji Takahashi, Midori Sugawara, Rieko Kawamata, Yoshie Motomura, Takashi Nishizawa, Toshiyuki Aikawa, and Wilawan Kumpoun

-permeable than cuticular membranes ( Lester, 1988 ). However, changes in the transpiration rate of cuticular membranes and net during fruit development have not yet been measured separately. The waterproofing ability of periderm tissue depends not only on its

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Moritz Knoche and Stefanie Peschel

The cuticular membrane (CM) covers all aboveground, primary surfaces of terrestrial plants. It serves as a protective barrier against water loss, infection with pathogens, and mechanical damage. Maintaining these functions throughout development

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Moritz Knoche, Bishnu P. Khanal, and Matej Stopar

in the cuticular membrane are the first detectable symptoms in russet development ( Faust and Shear, 1972a ; Hatch, 1975 ; Simons and Chu, 1978 ; Verner, 1938 ). A periderm is subsequently formed as a wound reaction that replaces the primary

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Stefanie Peschel and Moritz Knoche

/or 2) the mechanical constitution of the load-bearing peripheral structure, presumably the exocarp. Both groups of factors are mechanistically unrelated. The cuticular membrane plays an important role in cracking, because it represents the primary

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Bishnu P. Khanal and Moritz Knoche

minimize artifacts resulting from transpiration of the ES, tensile tests were performed and completed within 3 min of excision and preparation of the ES. Cuticular membranes were isolated from ES excised as described previously by incubating in 50 m m

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Moritz Knoche and Eckhard Grimm

cracks in the cuticular membrane (CM) when fruit surfaces were exposed to water or high humidity ( Knoche and Peschel, 2006 ). These cracks were limited to the CM, did not traverse epidermal or hypodermal cell layers, and were only detectable by

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Thomas O. Athoo, Andreas Winkler, and Moritz Knoche

significant factor in regulating pedicel transpiration. Pedicel transpiration obeyed fick’s law. Water movement through the cuticular membrane of the pedicel surface was the rate-limiting step in transpiration. The effects of various factors on transpiration