A method was developed to measure transpiration rates and apparent water-vapor permeability coefficients (P'H2O) of detached fruit using an analytical balance equipped with a humidity chamber, wide-range humidity-generating and sensing devices, and a datalogger. The system was designed to monitor weight changes with time and, hence, weight loss of individual fruit during exposure to specific relative humidities (RHs) and temperatures. Weight loss was corrected for loss due to respiratory exchange of 02 and CO2 before calculating P'H2O. Values of P'H2O for tomatoes obtained using this method over periods of 5 minutes to 24 hours ranged from 3 to 12 nmol·cm-2·s-1·kPa-1 at 20C, depending on the experimental conditions. These values are similar to previously published values and to those obtained in a conventional weight-loss experiment, which involved intermittent weighing. P'H20 for tomatoes dropped ≈15% in 24 hours. P'H20 increased with a transient increase in RH; the extent of the increase was variable from fruit to fruit, ranging from 5% to 100% over 30% to 90% RH. The change was reversible in that P'H2O increased and decreased within minutes following shifts in RH. Similar changes were found for strawberry P'H20. The increase in P'H2O may be due, in part, to a direct effect of water vapor on the water transport properties of the cuticular polymer and surface temperature depression as a result of evaporative cooling. At 50% RH and 20C, water vapor diffuses from tomatoes 50 times faster than O2 enters on a molar basis. This information will be useful for modeling RH changes in modified-atmosphere packages.
Ahmad Shirazi and Arthur C. Cameron
Thomas L. Davenport, Thomas L. White, and Stanley P. Burg
U.S. regulations prevent importation of fresh horticultural commodities that have not received an approved quarantine treatment assuring 99.999% (Probit 9) mortality of potentially invasive insect pests. Because imported mangoes (Mangifera indica) are likely to be infested by the caribbean fruit fly (Anastrepha suspensa) and other tropical fruit flies in the Americas, such as the mexican fruit fly (A. ludens), guava fruit fly (A. striata), inga fruit fly (A. distincta), south american fruit fly (A. fraterculus), sapote fruit fly (A. serpentina), and the west indian fruit fly (A. obliqua), they must be hot-water treated prior to shipment in order to satisfy quarantine requirement. Hot water treatment often damages the fruit, especially if it is not fully mature. Hypobaric [low pressure (LP)] intermodal shipping containers developed by the VacuFresh Corp. preserve fresh commodities, such as horticulturally mature mangoes, far longer than is possible using other technologies. We tested the ability of caribbean fruit fly eggs and larvae to survive simulated optimal hypobaric conditions for shipment of mangoes [15 and 20 mm mercury (Hg), ≥98% relative humidity, 13 °C (the lowest, safe nonchilling temperature)]. Caribbean fruit fly eggs or larvae were maintained on agar media, flushed with one air change per hour at the storage pressure, and shielded with Mylar to prevent radiant heat uptake and limit evaporative cooling. Nearly 98% of the eggs and larvae were killed within 1 week at 15 and 20 mm Hg in nine replicated experiments. All eggs were killed by 11 days with a predicted kill of 99.999% of the eggs by 9.4 days in 15 mm Hg and 10.6 days in 20 mm Hg LP (based on Probit 9 statistical analysis), whereas a substantial number of eggs survived to 14 days at atmospheric pressure (760 mm Hg). Shipment of fresh produce using this technology promises to provide quarantine control while preserving the freshness of fully mature tropical fruits and vegetables.
Thayne Montague, Roger Kjelgren, and Larry Rupp
Growth of woody landscape plants is strongly affected by the underlying surface. In urban areas, plants are subjected to energy balance characteristics of a variety of surfaces. This research investigated energy balance properties of six common urban surfaces: Kentucky bluegrass, pine bark mulch, concrete, asphalt, lava rock mulch, and gravel rock mulch. Each summer over a 2-year period incoming global radiation (GW), relative humidity, and air temperature were measured over each surface, and surface reflectivity (AW), surface temperature (TS), soil temperature (TO), and soil heat flux (SF) were measured below each surface. Thermal conductivity (K) and emitted surface longwave radiation (LW) were also calculated. Surface property differences were determined by regression analysis. Incoming global radiation (independent variable) versus TS, TO, SF, LW data (dependent variable) were analyzed. Linear or quadratic curves were selected according to significance of each variable and the coefficient of determination (R2). Surface reflectivity was greatest for concrete and least for lava rock mulch, and K was greatest for asphalt and concrete and least for lava rock and pine bark mulch. Under maximum GW, regression data indicate that SF and TO would be greatest under asphalt and least under lava rock and pine bark mulch. Under similar circumstances, TS and LW would be greatest for pine bark mulch and least for Kentucky bluegrass. This research revealed that more energy was conducted into the soil below asphalt and concrete, and that a greater portion of GW was prevented from entering the soil below pine bark and lava rock mulch than below other surfaces. Due to these effects, and the lack of evaporative cooling, surface temperatures were greater, and more longwave radiation was emitted from, non-vegetative surfaces than from turf.
Dewayne L. Ingram, Charles R. Hall, and Joshua Knight
consolidated into full trays at the rate of 60 trays per person per 8-h day. One person would move graded trays 40 at a time on a cart into a delivery truck every 10 min. Water would be used for evaporative cooling through fan and pad systems operating 9 months
Joshua Knight, Dewayne L. Ingram, and Charles R. Hall
4 weeks, and grown for an additional 8 weeks before marketing ( Ingram et al., 2017b ). Both modeled facilities were closed systems, so the irrigation and misting caused no runoff from the greenhouses. Water would also be used for evaporative cooling
James M. Garner and Allan M. Armitage
, Ontario, Canada). Ventilation fans and an evaporative cooling system were used to maintain daytime temperatures. A computerized environmental control system (Q-Com, Irvine, CA) was used to regulate and integrate environmental control functions. Flowering
Susmitha Nambuthiri, Robert L. Geneve, Youping Sun, Xueni Wang, R. Thomas Fernandez, Genhua Niu, Guihong Bi, and Amy Fulcher
evaporative cooling from the porous sidewall material ( Table 2 ). Evaporative cooling also appears to be a factor in reducing substrate heat buildup in WP containers relative to both Plastic and KR containers, which are nonporous ( Table 2 ; Figs. 1 and 2
Brian Makeredza, Michael Schmeisser, Elmi Lötze, and Willem J. Steyn
evaporative cooling in the tree ( Van de Ende, 1999 ). However, little research has been conducted to relate plant water status to sunburn incidence and severity; the link between plant water status and sunburn seems to be based primarily on observations. In a
Bryan J. Peterson, Olivia Sanchez, Stephanie E. Burnett, and Darren J. Hayes
evaporative cooling from the leaf surface ( Hartmann et al., 2011 ). However, OM has potential drawbacks, including the use of large volumes of water, potentially unsanitary conditions created by persistent water films on leaves ( Preece, 2003 ), the potential
Richard C. Beeson Jr. and Jianjun Chen
outdoor conditions, and relative humidity was normally higher inside the greenhouse. Although there was no measurable wind, air movement occurred during most afternoons from early spring until late fall due to operation of evaporative cooling fans