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B. Todd Bunnell, Lambert B. McCarty, and Hoke S. Hill

Creeping bentgrass (Agrostis palustris Huds.) is used on putting greens for its fine-leaf texture, consistent speed, smooth ball roll, and year-round color. In recent years bentgrass use has extended into the warmer climates of the southern United States. Being a C3 plant, bentgrass is not well adapted to extended hot and humid environmental conditions. Subsurface air movement systems are now commercially available that can transport air through the root zone to alter soil conditions and potentially improve bentgrass survival. This research investigated the effects of subsurface air movement on the composition of soil gases, matric potential, temperature, and growth response of a sand-based creeping bentgrass golf green. Treatments included: air movement direction (evacuate, inject, and no air) and duration of air movement (0400-0600 hr, 1000-1800 hr, and 24 hours). Treatment combinations were imposed for 13 days. Subsurface air movement reduced CO2 at the 9-cm depth to values <0.0033 mol·mol-1 when evacuating or injecting air, depending upon duration. Soil matric potentials at a 9-cm depth were decreased by a maximum of 96% when evacuating air for 24-hour duration compared to no-air plots. Soil temperatures at 9 cm were decreased ≈1 to 1.5 °C when injecting air from 1000 to 1800 hr and 24-hour treatments and increased ≈0.75 °C when evacuating air from 1000 to 1800 hr. Subsurface air movement did not improve creeping bentgrass turf quality or rooting. Although not effective in improving the growth response of creeping bentgrass, subsurface air movement may be a useful tool to improve soil gas composition, reduce excess soil moisture, and potentially reduce soil temperature(s) of heat-stressed creeping bentgrass golf greens.

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Celia M. Cantín, Carlos H. Crisosto, and Kevin R. Day

) or low oxygen (O 2 ) levels may accelerate the production of “off flavor” ( Golias and Bottcher, 2003 ; Kader et al., 1989 ). To the best of our knowledge, few or no MAP studies on plum postharvest performance have been conducted; therefore, the aim

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Ling Li, Takashi Watanabe, Atsuko Uragami, Hiroaki Kitazawa, and Xiangyou Wang

To control asparagus harvest timing, we investigated the effects of short-term low (5%) oxygen (O2) treatment in the cultivation area on asparagus growth and yield using a closed cultivation system. During 120 days of cultivation, low O2 treatments were initiated at 0 to 4, 20 to 24, and 40 to 44 days after planting (DAP). The sprouting spears and control crown yield gradually decreased with increasing DAP. However, low O2 treatment at 0 to 4 DAP significantly delayed the decrease until 80 DAP, although the total yield did not change during cultivation. In contrast, low O2 treatments at 20 to 24 and 40 to 44 DAP did not affect yield performance. Taken together, short-term low O2 treatment immediately after planting can change the harvest timing of white asparagus and can be used for effective asparagus culturing in a closed system, such as a plant factory.

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Jim Hancock, Pete Callow, Sedat Serçe, Eric Hanson, and Randy Beaudry

Controlled-atmosphere storage had little effect on the quality of fruit of eight cultivars held under 2 kPa oxygen (O2) and 8 kPa carbon dioxide (CO2) versus ambient air. ‘Elliott’ fruit harvested from bushes with only 30% ripe fruit had significantly better storage quality than fruit picked later; however, there was no significant difference in the storage life of fruit that was stored fully blue versus partially green. Fruit from the first harvest of four cultivars had superior storage quality to that of the second. In one comparison of the long-term storability of nine cultivars, ‘Bluegold’, ‘Brigitta’, and ‘Legacy’ performed the best, storing for 4 to 7 weeks. In another postharvest trial of 17 cultivars, ‘Brigitta’ stored the longest (8 weeks) followed by ‘Aurora’ and ‘Draper’ (7 weeks). The most resistant genotypes to Alternaria spp. were ‘Brigitta’, ‘Aurora’, ‘Elliott’, and ‘Draper’, whereas the most resistant genotypes to Colletotrichum spp. were ‘Elliott’, ‘Brigitta’, ‘Toro’, ‘Draper’, and ‘Bluejay’.

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S.R. Drake, D.C. Elfving, M.A. Drake, T.A. Eisele, S.L. Drake, and D.B. Visser

This study was conducted over two crop seasons using `Scarletspur Delicious' and `Gale Gala' apple trees (Malus ×domestica). The bioregulators aminoethoxyvinylglycine (AVG), ethephon (ETH), and 1-methylcyclopropene (MCP) were applied at various times before or after harvest. Fruit response was evaluated at harvest and after regular atmosphere (RA) and controlled atmosphere (CA) storage [2.0% oxygen (O2) and <2.0% carbon dioxide (CO2) at 0 °C] and quality of whole and juice apple products evaluated. AVG reduced starch loss and ethylene production, enhanced firmness, and reduced cracking in `Gale Gala,' but reduced sensory acceptance of apples and apple juice. ETH intensified starch loss, ethylene production, and reduced firmness, but did not affect `Gale Gala' fruit cracking. AVG followed by ETH reduced starch loss, ethylene production, and cracking and maintained firmness. This combination also aided in sensory acceptance of apples but reduced sensory preference of apple juice. Exposure to postharvest MCP improved flesh firmness retention and reduced ethylene production after both RA and CA storage. MCP either favored or reduced sensory acceptance of whole apples, depending on the particular season, but reduced sensory preference of apple juice. Sensory scores for `Scarletspur Delicious' apples were more strongly modified by bioregulators than were `Gale Gala' apples.

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S.R. Drake, E.A. Mielke, and D.C. Elfving

`Concorde' pears from three plantings were harvested at various maturities, stored in regular (RA) or controlled atmosphere (CA) storage and their quality evaluated. Starting at a firmness of 57.0 N (12.81 lbf), `Concorde' pears can be harvested over a period of 14 days with no loss in quality and be good candidates for either RA or CA storage. A 14-day delay in harvest resulted in a one box size increase. Regardless of the time of harvest, `Concorde' pears can be stored in RA for periods not to exceed 90 days. RA storage beyond 90 days resulted in reduced appearance, poor pedicel condition, and enhanced internal breakdown. Early harvest should be considered when RA storage is expected to exceed 90 days; however astringency may develop. Regardless of harvest, `Concorde' pears can be stored for 180 days in CA with no quality loss, particularly if the CA composition is 1.5% oxygen (O2) and 1.0% carbon dioxide (CO2). Internal breakdown can be a problem in CA if the CO2 exceeds 1.0%. Low O2 (<1.5%) CA is not recommended for `Concorde' pears.

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Shiow Y. Wang and Hongjun Jiao

The effect of blackberries (Rubus sp.) genotypes on antioxidant activities against superoxide radicals (O2 ), hydrogen peroxide (H2O2), hydroxyl radicals (OH), and singlet oxygen (O,), was evaluated. The results were expressed as percent inhibition of active oxygen species production in the presence of fruit juice. The active oxygen radical absorbance capacity (ORAC) value referred to the net protection in the presence of fruit juice, and was expressed as micromoles of α-tocopherol, ascorbate, α-tocopherol, and β-carotene equivalents per 10 g of fresh weight for O2 , H2O2, OH, and O2, respectively. Among the different cultivars, juice of Hull' blackberry had the highest oxygen species, superoxide radicals (O2 ), hydrogen peroxide (H2O2), hydroxyl radicals (OH), and singlet oxygen (O2,) scavenging capacity. Different antioxidants have their functional scavenging capacity against active oxygen species. There were interesting and marked differences among the different antioxidants in their abilities to inhibit the different active oxygen species. β-carotene had by far the highest scavenging activity against O2 but had absolutely no effect on H2O2. Ascorbic acid was the best at inhibiting H2O2 free radical activity. For OH, there was a wide range of scavenging capacities with α-tocopherol the highest and ascorbic acid the lowest. Glutathione had higher O2 scavenging capacity compared to the other antioxidants.

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O.I. Padilla-Zakour, K.S. Tandon, and J.M. Wargo

`Hedelfingen' and `Lapins' sweet cherries (Prunus avium) were stored in air or in two types of modified atmosphere (MA) bags (LifeSpan 204 and 208) at 3 °C (37.4 °F) and 90% relative humidity for 4 weeks. Various analytical and quality measurements were conducted weekly on `Hedelfingen' cherries, whereas on `Lapins' these were done initially and at the end of 4 weeks. For `Hedelfingen' cherries, there were differences in carbon dioxide (CO2) and oxygen (O2) composition within the MA bags, depending on the bag used. This resulted in slightly better cherry quality for the bag with lower O2 permeability (L204), which equilibrated at 4% to 5% O2 and 7% to 8% CO2. For `Lapins', the two MA bags showed concentrations of 9% to 10% O2 and 8% to 9% CO2 and similar final fruit quality. There was a significant weight loss for the control treatments over time (6% to 13%), whereas the MA treatments showed minimal losses. A higher incidence of cracking and decay was observed in MA treatments of `Hedelfingen' but not in `Lapins'. Control cherries had significant shriveling and browning of stems; MA-stored cherries had green and healthy stems after 4 weeks. No significant differences were observed in pH, acidity, soluble solids, firmness, and hue angle among the storage treatments. MA packaged cherries seemed to maintain better color than control cherries over time. Similarly, MA cherries had better appearance and eating quality after 4 weeks when compared to control cherries.

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Chuanjiu He, Fred Davies*, Ronald Lacey, and Que Ngo

Elevated levels of ethylene occur in enclosed crop production systems and in space-flight environments—leading to adverse plant growth and sterility. There are engineering advantages in growing plants at hypobaric (reduced atmospheric pressure) conditions in biomass production for extraterrestrial base or spaceflight environments. Objectives of this research were to characterize the influence of hypobaria on gas exchange and ethylene evolution of lettuce (Lactuca sativa L. cv. Buttercrunch). Lettuce was grown under variable total gas pressures [50 and 101 kPa (ambient)]. The six chambered, modular low plant growth (LPPG) system has a Rosemount industrial process gas chromatograph (GC) for determining gas concentrations of oxygen (O2), carbon dioxide (CO2) and nitrogen (N). With the LPPG system, changes in CO2 can be tracked during the light and dark periods on a whole canopy basis, and transpirate collected as a measurement of transpiration. During short growth periods of up to seven days, growth was comparable between low and ambient pressure. However, there was a tendency for leaf tip burn under ambient pressure, in part because of higher ethylene levels. Tip burn increased under high light (600 vs. 300 μmol·m-1·s-1) and high CO2 (600 vs. 100 Pa). The CO2 assimilation rate and dark respiration tended to be higher under ambient conditions. High humidity (100%) reduced CO2 assimilation rate compared to 70% RH. Ethylene was increased by high light (600 vs. 300 μmol·m-1·s-1) and high CO2 (600 vs. 100 Pa). Ethylene was higher under ambient than low pressure. Enhanced plant growth under low pressure may be attributed to reduced ethylene production and decreased dark respiration (lower night consumption of metabolites).

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John M. DeLong, Robert K. Prange, Jerry C. Leyte, and Peter A. Harrison

HarvestWatch is a new chlorophyll fluorescence (F)-based technology that identifies the low-oxygen threshold for apple (Malus × domestica) fruit in dynamic low-O controlled atmosphere (DLOCA) storage environments [e.g., <1% oxygen (O2)]. Immediately following harvest, `Cortland', `Delicious', `Golden Delicious', `Honeycrisp', `Jonagold' and `McIntosh' fruit were cooled and loaded into 0.34 m3 (12.0 ft3) storage cabinets. A static controlled atmosphere (CA) regime of 1.5% O2, 1.5% carbon dioxide (CO2) and 3 °C (37.4 °F) [0 °C (32.0 °F) for `Delicious' and `Golden Delicious'] was established for the control fruit, while the low-O2 threshold was identified by a spike in the fluorescence parameter, Fα, as the O2 levels in the DLOCA cabinets were lowered below 1%. The DLOCA storages were then maintained at O2 levels of 0.1% to 0.2% above the threshold value for each cultivar, which returned Fα to prethreshold signatures. Quality measurements following 5 to 9 months of storage and a 7-day shelf life of 20 °C (68.0 °F), showed that the HarvestWatch fruit were generally firmer, had no incidence of superficial scald in `Cortland' and `Delicious' apples, and did not accumulate fermentative volatile compounds. The HarvestWatch system permits rapid, real-time measurements of the status of stored apple fruit in ultra low-O2 environments without the inconvenience of breaking the room's atmosphere. Our results indicate that HarvestWatch facilitates what may be the highest possible level of fruit quality retention in long-term, low-O2 apple storage without the use of scald-controlling or other chemicals before storage.