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Katherine Kreuser, William C. Kreuser, Gautam Sarath and Keenan L. Amundsen

treatment effects on water permeability of the bur. The intent was to gain a deeper physiological understanding of seed dormancy in this important amenity grass. Materials and Methods Hormone profiling study. Seed hormone concentration and germination

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Yuliya A. Salanenka and Alan G. Taylor

), and the systemic insecticide phorate in mustard ( Sinapis alba ) ( Bardner, 1964 ). These collective results provide evidence that seedcoat permeability differed by crop and by compound. However, the same compound was not tested on several vegetable

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Randolph M. Beaudry and Niti Dube

The dynamic physiological processes of CO2 production, O2 uptake and ethylene synthesis for ripening tomato (Lycopersicon esculentum L.) and banana (M usa sp. cv `Valery') fruit were measured using a novel approach. Fruit were sealed in low density polyethylene pouches of known permeability to O2, CO2 and C2H4. The flux of these gases during the climacteric was closely tracked by their respective partial pressure in the headspace of the pouches. Some limitations in application exist due to modification of the atmosphere (primarily O2) within the pouch, however, the system provides some distinct advantages. These include the absence of gas handling equipment, measurement of O2 uptake despite high background levels of O2, measurement of the respiratory quotient, and measurement of low rates of ethylene production. Compared to low-flow, flow-through respirometers, this type of respirometer has the potential to permit the accumulation of several-fold higher levels of some gases due to the property of differential gas permeabilities possessed by polymer films.

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Robert D. Hagenmaier and Philip E. Shaw

The permeability to O2, CO2, C2H4, and water vapor was determined for 19 commercial fruit wax coatings, four ingredients thereof, and one shrink-wrap film. For the commercial coatings, the O2permeability at 50% relative humidity and 30C ranged from 470 to 22,000 ml (STP) × mil/(m2 × day × atm) (1 mil = 0.0254 mm) with CO)2. permeability two to eight times as high. Permeability to noncondensable gases tended to be higher for coatings made from carnauba wax than for those made from shellac and rosin. Commercial fruit wax had sufficiently low noncondensable gas permeability to account for large reductions in the respiration rate of coated fruit. Wax coatings could be improved if permeability were controlled:

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Stefanie Peschel and Moritz Knoche

focused on CM characteristics such as the CM and wax mass, the (elastic) strain of the CM, the densities of stomata and of microcracks in the exocarp, and the permeability of the exocarp to water transport in transpiration and in osmotic water uptake

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Eric W. Gay and Randolph M. Beaudry

O2 and CO2 permeabilities were determined for experimental polyethylene polymers (Dow Plastics, Freeport, Texas) in relation to low-density polyethylene (LDPE) films for the packaging of horticultural commodities. A stainless steel flow-through permeability cell was used to determine O2 and CO2 permeabilities at 0, 5, 10, 15, 20 and 25C for the polymers. Data were fitted to the Arrhenius' relationship and the Arrhenius' constant and energy of activation were determined. In addition, flow-through containers of sealed cherry tomatoes at room temperature were used to determine ethylene permeability of the polymers. The new polymers were several times more permeable than LDPE to O2, CO2, and ethylene. The results were incorporated into a model for predicting O2 concentrations over a temperature range for sliced apple fruit. The greater permeability of the new polymers will improve control of O2 and CO2 in modified atmosphere packages and enhance flexibility of package design.

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Sannai Gong and Kenneth A. Corey

A rapid steady state method for measurement of gas permeability of polymeric films was developed. Films were sealed between two equal volume chambers with pure O2 and pure N2 flowing through opposite sides. Oxygen concentration in the N2 cell was measured over time until steady state was reached. The method was used to determine oxygen permeability of two different films. Results from four replications on each film indicated excellent repeatability with coefficients of variation less than 3%. The time required to reach steady state oxygen concentration was dependent upon film type, flow rate, and temperature. The higher the N2 flow rate the shorter the time to reach steady state O2 concentrations. The slowest measurement at the lowest flow rate of 27 ml/min took less than 3 hours to collect the data necessary to achieve steady state. Increasing temperature from 10°C to 20°C resulted in an approximately 40% increase in O2 permeability for both films tested. The technique will be a valuable tool for measuring permeabilities of new films and the same film at different temperatures, and for selecting the appropriate material for modified atmosphere packaging of fresh produce.

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Yuliya A. Salanenka, Martin C. Goffinet and Alan G. Taylor

Cucumber is a species whose seeds have a semipermeable barrier restricting transport of solutes. A thin membrane beneath the testa, the perisperm–endosperm (PE) envelope, acts as a barrier to apoplastic permeability of cucumber and other

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Anwar A. Khan and James D. Maguire

Recently we have shown that the performance of vegetable seeds can be enhanced by matriconditioning in the presence of fixed amounts of chemically inert carriers, such as Micro-Cel™E and Zonolite™ Vermiculite, and water (Khan et al. National Symp. Stand Estab. Hort. Crops, p.19, 1990). This procedure, however, does not allow separation of seeds from the carrier during seed conditioning. This problem has been overcome by enclosing the seed in a semi-permeable membrane and placing the seed-membrane system in contact with the carrier and water (or test solution). By this means, the equilibrium moisture content, needed for seed conditioning is attained readily. This procedure allows conditioning of large amounts of seeds and eliminates the contamination of seeds from the carrier. The application of this procedure in seed enhancement within the seed industry will be discussed.

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Holger Weichert, Stefanie Peschel, Moritz Knoche and Dieter Neumann

, the most information is available on FeCl 3 . The data demonstrated that decreased water uptake is related to decreased permeability of the polar pathways ( Weichert and Knoche, 2006b ), which most likely results from a pH-dependent precipitation in