New Insights into the Properties of Pubescent Surfaces: Peach Fruit as a Model (original) (raw)
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Plant …, 2011
The surface of peach (Prunus persica 'Calrico') is covered by a dense indumentum, which may serve various protective purposes. With the aim of relating structure to function, the chemical composition, morphology, and hydrophobicity of the peach skin was assessed as a model for a pubescent plant surface. Distinct physicochemical features were observed for trichomes versus isolated cuticles. Peach cuticles were composed of 53% cutan, 27% waxes, 23% cutin, and 1% hydroxycinnamic acid derivatives (mainly ferulic and p-coumaric acids). Trichomes were covered by a thin cuticular layer containing 15% waxes and 19% cutin and were filled by polysaccharide material (63%) containing hydroxycinnamic acid derivatives and flavonoids. The surface free energy, polarity, and work of adhesion of intact and shaved peach surfaces were calculated from contact angle measurements of water, glycerol, and diiodomethane. The removal of the trichomes from the surface increased polarity from 3.8% (intact surface) to 23.6% and decreased the total surface free energy chiefly due to a decrease on its nonpolar component. The extraction of waxes and the removal of trichomes led to higher fruit dehydration rates. However, trichomes were found to have a higher water sorption capacity as compared with isolated cuticles. The results show that the peach surface is composed of two different materials that establish a polarity gradient: the trichome network, which has a higher surface free energy and a higher dispersive component, and the cuticle underneath, which has a lower surface free energy and higher surface polarity. The significance of the data concerning water-plant surface interactions is discussed within a physiological context.
698 PB 306 Wettability and Surface Tension of Fruit Surfaces
HortScience, 1994
Nettability is an important factor to be considered in postharvest treatments such as washing, aqueous dippings, coatings, etc. Pome fruits (ten apple and four pear cultivars) and stone fruits (nectarine and plums) were evaluated for wetting behavior and surface tension at room temperature. Nettability was assessed by measuring contact angles of water. Surface tension was calculated by measuring contact angles of methylene iodide and water or by a series of pure surfactants using Zisman's method. Wetting behavior on apple fruits depended on cultivar, with water contact angles ranging from 75° to 131°. For pear fruits, wetting also depended on cultivar. Calculated surface tensions of pear fruits were in general higher than most apple cultivars tested. In stone fruits, plums presented a high water-repellency with a contact angle of 137°. The wetting of fruit surfaces seems to be governed by the nature of the chemical groups exposed on the surface of the cuticle and also by the sur...
Epidermal segments: a useful model system for studying water transport through fruit surfaces
HortScience, 2003
Water conductance of the cuticle of mature fruit of apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf., 'Golden Delicious Reinders/'Malling 9 (M.9)], sweet cherry (Prunus avium L., 'Sam /'Alkavo), grape (Vitis vinifera L.), pepper (Capsicum annuum L. var. annuum Fasciculatum Group, 'Jive), and tomato (Lycopersicon esculentum Mill.) was de ter mined using excised epi der mal segments (consisting of epi der mis, hy po der mis, and some cell layers of parenchyma) and enzymatically isolated cuticular mem branes (CM) from the same sample of fruit. Segments or CM were mounted in diffusion cells and transpiration was monitored gravi met ri cal ly. Conductance (m•s-1) was cal cu lat ed by dividing the flux of water per unit segment or CM area (kg•m-2 •s-1) by the dif fer ence in water vapor concentration (kg•m-3) across segments or CM. Transpiration through segments and through CM increased with time. Conductance of segments was consistently lower than that of newly isolated CM (3 days or less). Conductance decreased with increasing time after isolation for apple, grape, or sweet cherry CM, and for sweet cherry CM with increasing temperature during storage (5 to 33 °C for 4 days). There was no significant effect of duration of storage of CM on conductance in pepper or tomato fruit. Following storage of CM for more than 30 days, differences in con duc tance between isolated CM and excised seg ments decreased in apple, grape, and sweet cherry, but not in pepper or tomato. Use of metabolic inhibitors (1 mM NaN 3 or 0.1 mM CCCP), or pretreatment of segments by freez ing (-19 °C for 18 hours), or vacuum infiltration with water, had no effect on conductance of apple fruit segments. Our results suggest that living cells present on excised segments do not affect conductance and that epidermal seg ments provide a useful model system for quan ti fy ing conductance without the need for iso lat ing the CM. Chemical names used: sodium azide (NaN 3); carbonylcyanide m-chlorophenylhydrazone (CCCP).
Journal of Agricultural and Food Chemistry, 2002
Rain-induced cracking of sweet cherry (Prunus avium L.) fruit is thought to be related to water absorption through the fruit surface. Conductance for water uptake (g tot. uptake ) through the fruit surface of 'Sam' sweet cherry was studied gravimetrically by monitoring water penetration from a donor solution of deionized water through segments of the outer pericarp into a polyethyleneglycol (PEG) containing receiver solution. Segments consisting of cuticle plus five to eight cell layers of epidermal and hypodermal tissue were mounted in stainless steel diffusion cells. Conductance was calculated from flow rates of water across the segment and the difference in osmotic potential between donor and receiver solution. Flow rates were constant up to 12 hours and decreased thereafter. A log normal distribution of g tot. uptake was observed with a median of 0.97 × 10 -7 m·s -1 . Further, g tot. uptake was not affected by storage duration (up to 71 days) of fruit used as a source of segments, thickness of segments (range 0.1 to 4.8 mm), or segment area exposed in the diffusion cell. Osmolality of the receiver solution in the range from 1140 to 3400 mmol·kg -1 had no effect on g tot. uptake (1.45 ± 0.42 × 10 -7 m·s -1 ), but g tot. uptake increased by 301% (4.37 ± 0.46 × 10 -7 m·s -1 ) at 300 mmol·kg -1 . g tot. uptake was highest in the stylar scar region of the fruit (1.44 ± 0.16 × 10 -7 m·s -1 ) followed by cheek (1.02 ± 0.21 × 10 -7 m·s -1 ), suture (0.57 ± 0.17 × 10 -7 m·s -1 ) and pedicel cavity regions (0.22 ± 0.09 × 10 -7 m·s -1 ).
Journal of the American Society For Horticultural Science, 2012
Water uptake through the exocarp of intact sweet cherry [Prunus avium (L.)] fruit was determined gravimetrically in an immersion assay (25 °C). Fruit with sealed pedicel/fruit juncture were incubated in water during the fi rst interval (0 to 0.75 hour) and in 10 mM salt solutions of selected cations during the second (0.75 to 1.5 hours) and third interval (1.5 to 2.25 hours) of an experiment. Rates of water uptake (F) were calculated for fi rst, second and third intervals (F I , F II and F III , respectively) and salt effects indexed by the ratios F II /F I and F III /F I . AgNO 3 (F II /F I = 0.65), NaCl (0.70), BaCl 2 (0.67), CdCl 2 (0.69), CuCl 2 (0.42), HgCl 2 (0.58), and SrCl 2 (0.69), and the salts of trivalent cations AlCl 3 (0.50), EuCl 3 (0.58), and FeCl 3 (0.49), signifi cantly decreased water uptake into mature ʻSamʼ fruit as compared to the water control (0.87). KCl (0.82), NH 4 Cl (0.85), CaCl 2 (0.75), MgCl 2 (0.88), MnCl 2 (0.81), and ZnCl 2 (0.72) had no effect, LiCl (1.00) increased uptake. Similar data were obtained for F III /F I . The effect of FeCl 3 on water uptake was independent of the presence of CaCl 2 , AlCl 3 , or CuCl 2 , as sequential or simultaneous treatment with these salts reduced water uptake to the same extent as with FeCl 3 alone. Increasing FeCl 3 concentration up to 1 mM decreased uptake, higher concentrations had no further effect. FeCl 3 and CaCl 2 to a smaller extent decreased water uptake in developing ʻReginaʼ sweet cherry fruit (55 to 91 days after full bloom). FeCl 3 had no signifi cant effect on water uptake along the pedicel/fruit juncture, but markedly reduced uptake through the exocarp of all cultivars investigated (ʻBurlatʼ, ʻEarly Riversʼ, ʻHedelfi ngerʼ, ʻKnauffsʼ, ʻReginaʼ, ʻSamʼ, ʻSummitʼ, and ʻVanʼ). Effects of CaCl 2 on water uptake were limited to ʻBurlatʼ, ʻEarly Riversʼ, and ʻHedelfi ngerʼ. CaCl 2 and FeCl 3 both decreased fruit cracking, but FeCl 3 was more effective. The mode of action of mineral salts in decreasing water uptake and fruit cracking and their potential for fi eld use are discussed.
Water on the surface aggravates microscopic cracking of the sweet cherry fruit cuticle
Journal of the American Society For Horticultural Science, 2006
The effect of surface water on the frequency of microcracks in the cuticular membrane (CM) of exocarp segments (ES) of developing sweet cherry fruit (Prunus avium L.) was studied. Strain of CM and ES on the fruit surface was preserved by mounting a stainless steel washer on the fruit surface in the cheek region using an ethyl-cyanacrylate adhesive. ES were excised by tangentially cutting underneath the washer. Frequency of microcracks in the CM of ES was determined following infi ltration for 10 minutes with a 0.1% acridine orange solution by fl uorescence microscopy before and after exposure to deionized water (generally 48 hours). Exposing the surface of ES of mature 'Burlat' sweet cherry fruit to water resulted in a rapid increase in microcracks in the CM that approached an asymptote at about 30 microcracks/cm 2 within 24 hours. There was no change in microcracks in the CM when the surface of the ES remained dry. Incubating ES in polyethylene glycol solution that was isotonic to fruit juice extracted from the same batch of fruit resulted in a greater increase in frequency of microcracks as compared to incubation in deionized water. The waterinduced increase in microcracks was closely related to strain of the CM across different developmental stages within a cultivar [between 45 and 94 days after full bloom (DAFB); r 2 = 0.96, P ≤ 0.001, n = 9] or across different cultivars at maturity (r 2 = 0.92, P ≤ 0.0022, n = 6). Incubating ES of developing fruit in enzyme solution containing pectinase and cellulase such that the outer surface remained dry resulted in complete rupture and failure of the ES. Time to rupture and percentage of ruptured ES were closely related to the strain of the CM (r 2 = 0.92, P ≤ 0.001, n = 9 and r 2 = 0.68, P ≤ 0.0063, n = 9, respectively). Removal of epicuticular wax had no effect on frequency of water-induced microcracks. Also, temperature had no effect on frequency of water-induced microcracks, but frequency of microcracks increased exponentially when exposing the outer surface of ES to relative humidities above 75%. At 100% humidity the increase in frequency of microcracks did not differ from that induced by liquid water. Local wetting the surface of intact fruit in the pedicel cavity or stylar end region resulted in formation of macroscopically visible cracks despite of a net water loss of fruit. Uniaxiale tensile tests using dry and fully hydrated CM strips isolated from mature 'Sam' sweet cherry fruit established that hydration increased fracture strain, but decreased fracture stress and moduli of elasticity. Our data demonstrate that exposure of the fruit surface to liquid water or high concentrations of water vapor resulted in formation of microcracks in the CM.
Studies on Water Transport through the Sweet Cherry Fruit Surface: V. Conductance for Water Uptake
Journal of the American Society For Horticultural Science, 2002
Rain-induced cracking of sweet cherry (Prunus avium L.) fruit is thought to be related to water absorption through the fruit surface. Conductance for water uptake (g tot. uptake ) through the fruit surface of 'Sam' sweet cherry was studied gravimetrically by monitoring water penetration from a donor solution of deionized water through segments of the outer pericarp into a polyethyleneglycol (PEG) containing receiver solution. Segments consisting of cuticle plus five to eight cell layers of epidermal and hypodermal tissue were mounted in stainless steel diffusion cells. Conductance was calculated from flow rates of water across the segment and the difference in osmotic potential between donor and receiver solution. Flow rates were constant up to 12 hours and decreased thereafter. A log normal distribution of g tot. uptake was observed with a median of 0.97 × 10 -7 m·s -1 . Further, g tot. uptake was not affected by storage duration (up to 71 days) of fruit used as a source of segments, thickness of segments (range 0.1 to 4.8 mm), or segment area exposed in the diffusion cell. Osmolality of the receiver solution in the range from 1140 to 3400 mmol·kg -1 had no effect on g tot. uptake (1.45 ± 0.42 × 10 -7 m·s -1 ), but g tot. uptake increased by 301% (4.37 ± 0.46 × 10 -7 m·s -1 ) at 300 mmol·kg -1 . g tot. uptake was highest in the stylar scar region of the fruit (1.44 ± 0.16 × 10 -7 m·s -1 ) followed by cheek (1.02 ± 0.21 × 10 -7 m·s -1 ), suture (0.57 ± 0.17 × 10 -7 m·s -1 ) and pedicel cavity regions (0.22 ± 0.09 × 10 -7 m·s -1 ).
Planta, 2000
Water conductance of the cuticular membrane (CM) of sweet cherry (Prunus avium L. cv. Sam) fruit during stages II and III (31±78 days after full bloom, DAFB) was investigated by gravimetrically monitoring water loss through segments of the exocarp. Segments were mounted in stainless-steel diusion cells, ®lled with 0.5 ml of deionized water and incubated for 8 h at 252°C over dry silica. Conductance was calculated by dividing the amount of water transpired per unit surface area and time by the dierence in water vapor concentration across the segment (23.07 g m ±3 at 25°C). Fruit mass and fruit surface area increased 4.9-and 2.8-fold between 31 and 78 DAFB, respectively. However, CM mass per unit area decreased from 3.9 to 1.5 g m ±2 , and percentage of total wax content remained constant at about 31%. Stomatal density decreased from 0.8 to 0.2 mm ±2 (31±78 DAFB). Total conductance of the CM on the fruit cheek (g tot. ) remained constant during stage II of development (approx. 1.38´10 ±4 m s ±1 from 31 to 37 DAFB), increased to 1.73´10 ±4 m s ±1 during early stage III of fruit growth (43±64 DAFB) then decreased to 0.95´10 ±4 m s ±1 at maturity (78 DAFB). Partitioning g tot. into cuticular (g cut. ) and stomatal conductance (g sto. ) revealed that the relative contribution of g cut. to g tot. increased linearly from 30% to 87% of g tot. between 31 and 78 DAFB, respectively. On a whole-fruit basis, g tot. and g cut. consistently increased up to 64 DAFB, and decreased thereafter. A signi®cant negative linear relationship was obtained between g cut. and CM thickness, but not between the permeability coecient (p) and CM thickness. Further, p was positively related to strain rate, suggesting that strain associated with expansion of the fruit surface increased p.
Functional Plant Biology, 2010
Investigations on ''natural'' cuticular cracks were conducted on nectarine fruit [Prunus persica (L.) Batsch var. nucipersica (Suckow) C.K. Schneid.]. A method for quantifying the cuticular crack surface area on a whole fruit basis was proposed. By using a stratified sampling design, the spatial distribution of the cuticular cracks over three regions (stylar end, peduncle, and cheek), their morphology, and the estimation of the total proportion of cuticular cracks on the fruit were studied. These features were examined during fruit development and in response to several fruit growing conditions corresponding to various crop loads and irrigation regimes. Cuticular cracks on nectarine fruit occurred during the final rapid fruit growth stage. Larger fruit presented higher cuticular crack densities in the apical regions than in the cheek regions. Thin and larger cuticular cracks occurred continuously during fruit development. Cuticular cracks represented 10% to 12.5% of the fruit surface area for well irrigated or low crop load trees, whereas they covered less than 4.5% for the heavy crop load and water deficit treatments. Cheek regions largely contributed to the total cuticular crack surface area (>60%), regardless of the fruit growing conditions. After irrigation was restricted, cuticular crack development was limited. A positive relationship was established between the cuticular crack surface area per fruit surface area and the fruit fresh weight.