TY - JOUR

T1 - Studies on water transport through the sweet cherry fruit surface. 11. FeCl3 decreases water permeability of polar pathways

AU - Weichert, Holger

AU - Knoche, Moritz

PY - 2006/8/23

Y1 - 2006/8/23

N2 - The effect of FeCl3 (10 mM) on osmotic water uptake into detached sweet cherry fruit (Prunus avium L.) and on the 3H 2O permeability (Pd) of excised exocarp segments (ES) or enzymatically isolated cuticular membranes (CM) was investigated. ES or CM were mounted in an infinite dose diffusion system, where diffusion is monitored from a dilute donor solution through an interfacing ES or CM into a receiver solution under quasi steady-state conditions. In the absence of FeCl3, 3H2O diffusion through stomatous ES was linear over time, indicating that Pd was constant. Adding FeCl3 to the donor decreased Pd by about 60%. Pd remained at a decreased level when replacing the FeCl3 donor again by deionized water. The decrease in Pd was positively and linearly related to the stomatal density of the ES. There was no effect of FeCl3 on the Pd of astomatous sweet cherry fruit ES or CM regardless of the presence of wax (epicuticular or cuticular). FeCl3 decreased Pd when added to the donor (-63%) or receiver (-16%), but there was no effect when it was added to donor and receiver solutions simultaneously. The decrease in P d depended on the pH of the receiver and the presence of citrate buffer. There was no effect of FeCl3 with citrate buffer as a receiver regardless of pH (range 2.0-6.0). When using nonbuffered receiver solutions with pH adjusted to pH 2.0, 3.0, 4.5, or 6.0, FeCl3 markedly decreased 3H2O diffusion at pH ≥ 3 but had no effect at pH 2.0. FeCl3 increased the energy of activation (E a) for 3H2O diffusion (range 15-45°C) through stomatous ES but had no significant effect in astomatous CM. The increase in Ea by FeCl3 was positively related to stomatal density. FeCl3 decreased the Pd for 2-(1-naphthyl)[1- 14C]acetic acid (NAA) and 2,4-dichloro[U-14C]- phenoxyacetic acid (2,4-D) in stomatous ES. The magnitude of the effect depended on the degree of dissociation and was larger for the dissociated acids (pH 6.2) than for the nondissociated acids (pH 2.2). Incubating whole fruit in isotonic solutions of selected osmotica resulted in significant water uptake that was inversely related to the molecular weight of the osmotica and was consistently lower for fruit treated with FeCl3. The FeCl3 induced decrease in water fluxes was larger for osmotica having a low molecular weight than for those with a higher molecular weight. Our data indicate that FeCl 3 decreased the permeability of the stomatous sweet cherry exocarp to water and other polar substances by pH-dependent formation of precipitates that decrease transport along polar pathways. Decreasing the permeability of polar pathways by a precipitation reaction is a useful target in developing strategies against rain-induced fruit cracking.

AB - The effect of FeCl3 (10 mM) on osmotic water uptake into detached sweet cherry fruit (Prunus avium L.) and on the 3H 2O permeability (Pd) of excised exocarp segments (ES) or enzymatically isolated cuticular membranes (CM) was investigated. ES or CM were mounted in an infinite dose diffusion system, where diffusion is monitored from a dilute donor solution through an interfacing ES or CM into a receiver solution under quasi steady-state conditions. In the absence of FeCl3, 3H2O diffusion through stomatous ES was linear over time, indicating that Pd was constant. Adding FeCl3 to the donor decreased Pd by about 60%. Pd remained at a decreased level when replacing the FeCl3 donor again by deionized water. The decrease in Pd was positively and linearly related to the stomatal density of the ES. There was no effect of FeCl3 on the Pd of astomatous sweet cherry fruit ES or CM regardless of the presence of wax (epicuticular or cuticular). FeCl3 decreased Pd when added to the donor (-63%) or receiver (-16%), but there was no effect when it was added to donor and receiver solutions simultaneously. The decrease in P d depended on the pH of the receiver and the presence of citrate buffer. There was no effect of FeCl3 with citrate buffer as a receiver regardless of pH (range 2.0-6.0). When using nonbuffered receiver solutions with pH adjusted to pH 2.0, 3.0, 4.5, or 6.0, FeCl3 markedly decreased 3H2O diffusion at pH ≥ 3 but had no effect at pH 2.0. FeCl3 increased the energy of activation (E a) for 3H2O diffusion (range 15-45°C) through stomatous ES but had no significant effect in astomatous CM. The increase in Ea by FeCl3 was positively related to stomatal density. FeCl3 decreased the Pd for 2-(1-naphthyl)[1- 14C]acetic acid (NAA) and 2,4-dichloro[U-14C]- phenoxyacetic acid (2,4-D) in stomatous ES. The magnitude of the effect depended on the degree of dissociation and was larger for the dissociated acids (pH 6.2) than for the nondissociated acids (pH 2.2). Incubating whole fruit in isotonic solutions of selected osmotica resulted in significant water uptake that was inversely related to the molecular weight of the osmotica and was consistently lower for fruit treated with FeCl3. The FeCl3 induced decrease in water fluxes was larger for osmotica having a low molecular weight than for those with a higher molecular weight. Our data indicate that FeCl 3 decreased the permeability of the stomatous sweet cherry exocarp to water and other polar substances by pH-dependent formation of precipitates that decrease transport along polar pathways. Decreasing the permeability of polar pathways by a precipitation reaction is a useful target in developing strategies against rain-induced fruit cracking.

KW - Cuticle

KW - Ferric salts

KW - Fruit cracking

KW - Prunus avium L.

KW - Stomata

UR - http://www.scopus.com/inward/record.url?scp=33748575570&partnerID=8YFLogxK

U2 - 10.1021/jf061251f

DO - 10.1021/jf061251f

M3 - Article

C2 - 16910722

AN - SCOPUS:33748575570

VL - 54

SP - 6294

EP - 6302

JO - Journal of Agricultural and Food Chemistry

JF - Journal of Agricultural and Food Chemistry

SN - 0021-8561

IS - 17

ER -