Studies on water transport through the sweet cherry fruit surface: IX. Comparing permeability in water uptake and transpiration

Abstract

Water uptake and transpiration were studied through the surface of intact sweet cherry (Prunus avium L.) fruit, exocarp segments (ES) and cuticular membranes (CM) excised from the cheek of sweet cherry fruit and astomatous CM isolated from Schefflera arboricola (Hayata) Hayata, Citrus aurantium L., and Stephanotis floribunda Brongn. leaves or from Lycopersicon esculentum Mill. and Capsicum annuum L. var. annuum Fasciculatum Group fruit. ES and CM were mounted in diffusion cells. Water (deionized) uptake into intact sweet cherry fruit, through ES or CM interfacing water as a donor and a polyethyleneglycol (PEG 6000, osmotic pressure 2.83 MPa)-containing receiver was determined gravimetrically. Transpiration was quantified by monitoring weight loss of a PEG 6000-containing donor (2.83 MPa) against dry silica as a receiver. The permeability coefficients for osmotic water uptake and transpiration were calculated from the amount of water taken up or transpired per unit surface area and time, and the driving force for transport. Permeability during osmotic water uptake was markedly higher than during transpiration in intact sweet cherry fruit (40.2-fold), excised ES of sweet cherry fruit (12.5- to 53.7-fold) and isolated astomatous fruit and leaf CM of a range of species (on average 23.0-fold). Partitioning water transport into stomatal and cuticular components revealed that permeability of the sweet cherry fruit cuticle for water uptake was 11.9-fold higher and that of stomata 56.8-fold higher than the respective permeability during transpiration. Increasing water vapor activity in the receiver from 0 to 1 increased permeability during transpiration across isolated sweet cherry fruit CM about 2.1-fold. Permeability for vapor uptake from saturated water vapor into a PEG 6000 receiver solution was markedly lower than from liquid water, but of similar magnitude to the permeability during self-diffusion of (3)H(2)O in the absence of osmotica. The energy of activation for self-diffusion of water across ES or CM was higher than for osmotic water uptake and decreased with increasing stomatal density. The data indicate that viscous flow along an aqueous continuum across the sweet cherry fruit exocarp and across the astomatous CM of selected species accounted for the higher permeability during water uptake as compared to self-diffusion or transpiration.

Localization of the Transpiration Barrier in the Epi- and Intracuticular Waxes of Eight Plant Species: Water Transport Resistances Are Associated with Fatty Acyl Rather Than Alicyclic Components

“…The first part of this model is based on the finding that the majority of water molecules are absorbed into and cross through the cuticular wax (as opposed to larger, polar solutes that pass through a limited number of aqueous channels extending from the epidermal cell wall to the tissue surface; Riederer and Schreiber, 2001;Schönherr and Schreiber, 2004;Beyer et al, 2005;Popp et al, 2005;Schreiber, 2005;Schönherr, 2006;Weichert and Knoche, 2006;Arand et al, 2010). The epicuticular wax film must consequently impose a resistance on water movement, and this resistance acts in series with the resistance(s) imposed on inner pathway sections.…”

Water Uptake Through the Surface of Fleshy Soft Fruit: Barriers, Mechanism, Factors, and Potential Role in Cracking

“…For a sweet cherry fruit having an osmotic potential of −2.8 MPa, the equilibrium humidity above which water vapor uptake would occur is about 98 % (Beyer et al 2005). Above this humidity, fruit will take up water from the vapor phase even though the surface is dry.…”

“…Above this humidity, fruit will take up water from the vapor phase even though the surface is dry. However, the rates of vapor uptake from a saturated atmosphere will be low and negligible compared to water uptake from the liquid phase (Beyer et al 2005). Moreover, air humidity rarely exceeds 99 % under field conditions (even in the rain; Nobel 1999).…”

“…The driving force equals the difference in water potential (ΔΨ in MPa) between the fruit (Ψ fruit in MPa) and that of the water on the surface (Ψ water in MPa; Eq. 11.2) (Beyer et al 2005). Because the water potential of the water adhering to the fruit surface is zero (Ψ water = 0 MPa), the water potential of the fruit drives uptake (ΔΨ = − Ψ fruit ; Eq.…”

“…The A of a fruit is usually estimated from measurements of either its volume or its orthogonal dimensions and assuming a simple geometric model (a sphere, ellipsoid, truncated cone, etc.). Under experimental conditions, the driving force can be standardized by incubating the fruit (or diffusion cell with epidermal segment or isolated cuticle) in a closed container at constant temperature and humidity (and low light intensity) above a water receiver such as dry silica gel or a saturated salt slurry (Beyer et al 2005;Knoche et al 2000;Wexler 1995). To minimize the inseries boundary layer (and so measure the pure skin property), the vapor phase should be vigorously stirred or the distance between the transpiring surface and the silica gel (or salt, etc.)…”