TY - JOUR T1 - Water Movement through the Surfaces of the Grape Berry and Its Stem JF - American Journal of Enology and Viticulture JO - Am. J. Enol. Vitic. DO - 10.5344/ajev.2011.10056 SP - ajev.2011.10056 AU - Tobias Becker AU - Moritz Knoche Y1 - 2011/03/08 UR - http://www.ajevonline.org/content/early/2011/03/08/ajev.2011.10056.abstract N2 - Water uptake and transpiration of detached grape berries (Vitis vinifera L. cv. Chardonnay, Müller-Thurgau, Riesling) were determined gravimetrically. Water movement was linearly related to time. Abrading the cuticle from the berry surface increased rates of uptake and transpiration 73- and 7-fold, respectively. Restricting water movement to the berry surface by sealing the stem including the stem/fruit juncture decreased rates of uptake (−76%) and transpiration (−16%). Rates of uptake were weakly those of transpiration were closely related to the surface area of the berry. Transpiration rates were higher in the stylar (+44%) than the cheek region. The water potential of developing Riesling berries (Ψfruit) was approximately constant between 20 and 76 days after full bloom (DAFB) ranging from −0.52 (± 0.18) to −0.58 (± 0.15) MPa and decreased thereafter to −1.56 (± 0.04) MPa at 131 DAFB when the solute potential was −3.66 (± 0.01) MPa. The permeability of the cuticle of Riesling berries to water uptake decreased from 43.3 (± 7.0) nm/s to 4.1 (± 1.2) nm/s between 28 and 131 DAFB, respectively, that for transpiration from 7.3 (± 0.3) nm/s to 1.6 (± 0.0) nm/s. Water uptake was not affected by NaCl, KCl, CaCl2, FeCl3 or AlCl3 (all at 1 to 100 mM). Only MgCl2 slightly increased water uptake. Increasing temperature from 2 to 35°C increased rates of water uptake in Riesling and Müller-Thurgau berries 2.2-fold [equiv. energy of activation 19.6 (± 3.3) kJ/mol]. Flow rates, fluxes and permeabilities of stem and berry surfaces in water uptake and transpiration are discussed and a water balance for vascular and surface transport of water in a Riesling berry under hypothetical weather conditions is estimated. ER -