TY - JOUR

T1 - Pedicel Transpiration in Sweet Cherry Fruit

T2 - Mechanisms, Pathways, and Factors

AU - Athoo, Thomas O.

AU - Winkler, Andreas

AU - Knoche, Moritz

PY - 2015

Y1 - 2015

N2 - Pedicel appearance is a good indicator of freshness in sweet cherries (Prunus avium L.). Fruit with shriveled, discolored pedicels have reduced market value. Shriveled pedicels are thought to result from postharvest water loss due to transpiration. The objectives of our study were to 1) quantify the transpiration permeances of fruit and pedicel surfaces; 2) determine the role of the fruit in pedicel transpiration; and 3) identify the effects of selected factors on pedicel transpiration. Fruit with and without pedicels were incubated under controlled conditions [usually 22 8C, 75% relative humidity (RH)] and their mass losses determined gravimetrically. Pedicel transpiration was calculated by subtracting measured transpiration of fruit without pedicels from that of fruit with pedicels. Cumulative pedicel transpiration increased with time. Rates of pedicel transpiration were essentially constant over the first 0 to 1.5 hours but declined thereafter, approaching an asymptote over the subsequent period of 1.5 to 96 hours over whichmeasurements were made. Cumulative pedicel transpiration exceeded the amount of water in the pedicel, indicating that at least some of the transpired water originated from the fruit. There was no significant effect of steam girdling on pedicel transpiration suggesting that water moved from the fruit to the pedicel through the xylem (steaming prevents phloem conduction). Abrading the cuticular membrane (CM) from a pedicel surface or extracting the cuticular wax by dipping pedicels once or five times in chloroform/methanol (1:1 v/v) increased rates of transpiration 12-, 3-, and 5-fold, respectively. The water vapor permeance of the pedicel surface determined under steady-state conditions (8.7 ± 0.4x10-4m s-1) exceeded that of the fruit (2.1 ± 0.1x10-4 m s-1), possibly because of a more permeable CM and/or a higher stomatal density (38.5 ± 1.3 stomata/mm2 for pedicels vs. 1.1 ± 0.0 stomata/mm2 for fruit). Treatments known to affect stomatal opening (incubation in buffered abscisic acid at 0.1mMor inCO2- orN2-atmospheres) had no effects on pedicel transpiration. Rates of transpiration were negatively correlated with RH but positively with temperature. There was no effect of RH and/or temperature on the permeances of pedicel or fruit surfaces. From our results it is inferred that 1) pedicel transpiration is a physical process governed by Fick’s law of diffusion, where cuticle and wax in particular represent the major rate-limiting barriers; 2) the permeances of pedicel surfaces exceed those of fruit surfaces; and 3) pedicel transpiration can be minimized by minimizing the driving force (difference in water vapor concentration) during postharvest handling and storage.

AB - Pedicel appearance is a good indicator of freshness in sweet cherries (Prunus avium L.). Fruit with shriveled, discolored pedicels have reduced market value. Shriveled pedicels are thought to result from postharvest water loss due to transpiration. The objectives of our study were to 1) quantify the transpiration permeances of fruit and pedicel surfaces; 2) determine the role of the fruit in pedicel transpiration; and 3) identify the effects of selected factors on pedicel transpiration. Fruit with and without pedicels were incubated under controlled conditions [usually 22 8C, 75% relative humidity (RH)] and their mass losses determined gravimetrically. Pedicel transpiration was calculated by subtracting measured transpiration of fruit without pedicels from that of fruit with pedicels. Cumulative pedicel transpiration increased with time. Rates of pedicel transpiration were essentially constant over the first 0 to 1.5 hours but declined thereafter, approaching an asymptote over the subsequent period of 1.5 to 96 hours over whichmeasurements were made. Cumulative pedicel transpiration exceeded the amount of water in the pedicel, indicating that at least some of the transpired water originated from the fruit. There was no significant effect of steam girdling on pedicel transpiration suggesting that water moved from the fruit to the pedicel through the xylem (steaming prevents phloem conduction). Abrading the cuticular membrane (CM) from a pedicel surface or extracting the cuticular wax by dipping pedicels once or five times in chloroform/methanol (1:1 v/v) increased rates of transpiration 12-, 3-, and 5-fold, respectively. The water vapor permeance of the pedicel surface determined under steady-state conditions (8.7 ± 0.4x10-4m s-1) exceeded that of the fruit (2.1 ± 0.1x10-4 m s-1), possibly because of a more permeable CM and/or a higher stomatal density (38.5 ± 1.3 stomata/mm2 for pedicels vs. 1.1 ± 0.0 stomata/mm2 for fruit). Treatments known to affect stomatal opening (incubation in buffered abscisic acid at 0.1mMor inCO2- orN2-atmospheres) had no effects on pedicel transpiration. Rates of transpiration were negatively correlated with RH but positively with temperature. There was no effect of RH and/or temperature on the permeances of pedicel or fruit surfaces. From our results it is inferred that 1) pedicel transpiration is a physical process governed by Fick’s law of diffusion, where cuticle and wax in particular represent the major rate-limiting barriers; 2) the permeances of pedicel surfaces exceed those of fruit surfaces; and 3) pedicel transpiration can be minimized by minimizing the driving force (difference in water vapor concentration) during postharvest handling and storage.

UR - http://www.scopus.com/inward/record.url?scp=84927937304&partnerID=8YFLogxK

U2 - 10.21273/jashs.140.2.136

DO - 10.21273/jashs.140.2.136

M3 - Article

AN - SCOPUS:84927937304

VL - 140

SP - 136

EP - 143

JO - Journal of the American Society for Horticultural Science

JF - Journal of the American Society for Horticultural Science

SN - 0003-1062

IS - 2

ER -