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Bernard H. Zandstra, Sylvia Morse, Rodney V. Tocco, and Jarrod J. Morrice

Asparagus is a perennial crop that normally is established from one-year-old crowns and maintained for 12 to 20 years until the yield declines beyond profitability ( Zandstra et al., 1992 ). Before introduction of all-male hybrids, volunteer

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Sven Verlinden, Silvanda M. Silva, Robert C. Herner, and Randolph M. Beaudry

( Irving and Hurst, 1993 ). As the level of carbohydrates in the spear declines, the transcription of genes related to senescence increases ( Davies et al., 1996 ; Irving et al., 2001 ; King et al., 1995 ). The tip section of asparagus spears is comprised

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A.R. Gonzalez, T. Wang, D.J. Makus, and A. Mauromoustakos

Respiration and quality changes were measured in white and green asparagus stored at 20°C. Green asparagus had a higher respiration rate and weight loss than white. Respiration rates decreased and stabilized after 2 days storage in both green and white asparagus. Total phenolics and pulp pH were higher in green than in white asparagus. No significant difference was observed in titratable acidity. Total phenolics and pH decreased while titratable acidity increased during storage of both types of asparagus. Ascorbic acid levels were higher in green spears but soluble solids were higher in white spears. Both ascorbic acid and soluble solids decline during storage. Total chlorophyll content of green asparagus decreased during storage. White asparagus had little chlorophyll. Green color, measured by CDM –a values, followed the same pattern as total chlorophyll.

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Dong Sik Yang, Svoboda V. Pennisi, Ki-Cheol Son, and Stanley J. Kays

sequence: ( A ) Hemigraphis alternata , Tradescantia pallida , Hedera helix , Fittonia argyroneura , Asparagus densiflorus , and Hoya carnosa ; ( B ) H. alternata , T. pallida , H. helix , A. densiflorus , H. carnosa , and F. argyroneura ; ( C

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S.M. Silva, R.C. Herner, and R.M. Beaudry

To help elucidate of the relationship between decline in sugar (especially sucrose) and senescence in asparagus (Asparagus officinallis L.), spears with or without tips were treated with 6-benzylaminopurine (6-BAP) and stored during 25 days at 0°C. 6-BAP was applied using a cheesecloth soaked with 100 ppm solution (30-s contact) immediately after harvesting to the tip or to the cut surface for spears that had 2 cm of the tip removed. Time-dependent profile of fluorescence, chlorophyll content, amount of fructose, glucose, and sucrose were measured for four segments from tip to the base of the spears over. Respiration rate and general visual quality were also evaluated for the whole spear on a daily basis. Three replications were used for all evaluations. 6-BAP reduced respiration rate of spears with intact tips, slowed the decline in fluorescence, and slowed chlorophyll degradation for the tip during 25 days of storage at 0°C. Respiration rate was higher in spears that had the tip removed, regardless the use of 6-BAP; however, the decline of fluorescence and chlorophyll degradation were lower in 6-BAP-treated spears. Application of 6-BAP also slowed the decline in sucrose content. 6-BAP effects were more marked when comparing with spears lacking their tip. The visual quality was higher in spears with tips that were treated with 6-BAP.

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Robert J. Dufault

The objective of this study was to determine the effect of forcing summer asparagus (May to October) and age at first harvest after transplanting on yield and quality. Ten-week-old `UC 157 F1' asparagus seedlings were field-planted on Sept. 1986 and forced to emerge from 1988 to 1992 by mowing fern in separate replicated plots in May, June, July, August, September, or October. Forcing treatments were not spring-harvested. Forced yields were compared to normal spring harvests (emerging from January to April). Harvesting began for the first time ≈18 or 30 months after transplanting. Spring 1988 yields were greatest of all, but declined yearly for 5 years. Summer forcing in either July or August maintained acceptable yields through 1992. The warmer climate during summer forcing caused most plants to reach the prescribed cutting pressure (eight spears per plant) within a standard 6-week harvest season. Cooler temperatures during spring harvest seasons slowed spear emergence and prevented the plants from reaching prescribed cutting pressure. Forcing in May and June was too stressful to plant recovery after the harvest season by reducing fern regrowth and increasing plant death. Cooler temperatures during October forcing inhibited spear emergence. Forcing in September yielded less than forcing in July and August, but September asparagus would command higher market prices. There was no advantage at any harvest time to delay first harvests from 18 to 30 months after transplanting. Forcing in July through September has potential as an alternative enterprise in coastal South Carolina.

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Silvanda Silva, Sven Verlinden, Robert Herner, and Randolph Beaudry

Base-to-tip profiles of sucrose, glucose, fructose, and respiration rate were measured for asparagus (Asparagus officinalis L.) spears stored at 0C. Fructose content was ≈3-fold and 4-fold higher than glucose and sucrose, respectively. The highest level of fructose was found in the base and was ≈15-fold higher than the tip. The changes in asparagus metabolism were characterized by loss of sucrose and a high rate of respiration within the first hours after harvest. Sucrose was more rapidly lost than the other sugars during this period. The respiration rate was measured along the length of intact spears at 0.5, 1, 2, and 3 h after harvest. Subsequent measurements were taken after larger time intervals for 23 days. The respiration rate declined rapidly to ≈60% of the initial rate within 12 h, decreasing more slowly thereafter. Initially, the respiration rate of the tip was about four times that of the base, but, after 23 days, the respiration rate of the tip was only twice that of the base. Sucrose content and respiration rates were closely correlated.

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Silvanda Silva, Sven Verlinden, Robert Herner, and Randolph Beaudry

Asparagus spears (Asparagus officinalis L.) were placed in solutions of six different concentrations of sucrose (0%, 1%, 2%, 4%, 8%, and 16%) plus citric acid at 0C for 24 h following harvest. The profiles of sucrose, fructose, glucose, and respiration rate along the length of the spear were evaluated throughout storage. The effect of carbohydrate loading on the rate of respiration, sucrose loss, and the shelf life of asparagus was determined. For all treatments, sugars decreased and respiration rate increased from the butt to the tip. The 4% sucrose treatment enhanced the sugar level in the tip ≈5-fold relative to the control. For the 8% and 16% treatments, sucrose tended to accumulate in the base. Spears loaded with higher sucrose concentrations had higher respiration rates than controls up to 3 h after loading. After this time, no significant differences were observed between treatments. For all treatments, respiration rates declined rapidly following harvest, stabilizing in ≈24 h. Weight gain and growth increased as the treatment sucrose concentration decreased. Solution uptake was enhanced by loading at lower humidity levels.

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Arthur Loughton, Randy Baker, and O. Brian Allen

Five between-row spacings of asparagus ranging from 60 to 120 cm were combined with five planting depths ranging from 15 to 30 cm, in a central composite rotatable design. After seven harvest seasons, the accumulated yields (kg·ha–1) declined linearly by 108 (+18) kg·ha–1 for each increase of 1 cm of depth. Accumulated yield also declined linearly by 6.6 (+4.5) kg·ha–1 with each increase of 1 cm in row width. Depth and row width did not interact. Effects of treatment on average spear weight were negligible. When the experiment was terminated, the final depth of all crowns, regardless of original planting depth, had floated to about 11.3 cm.

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S.M. Silva, R.C. Herner, and R.M. Beaudry

The purpose of this work was to investigate the influence of O2 and CO2 partial pressures on glycolytic carbon flux, phosphorylated intermediates, phosphate, pyrophosphate, and phosporylated nucleotides in asparagus spears tips stores at 1 °C. The effects of CO2 (0, 5, 10, and 20 kPa) combined with O2 pressures ranging from 0.1 to 16 kPa (1% O2 = 1.013 kPa O2 at 1 atm) were investigated. Spears were enclosed within a low-density polyethylene (LDPE) package (for the 5-, 10-, and 20-kPa CO2 treatments) having a surface area of 462 cm2 and enclosed in 1.95-L glass jars. Low O2 enhanced the interconversion of phosphoenolpyruvate (PEP) to pyruvate (PYR) and F6P to F1,6P2 relative to high O2. When spears tips at 16 kPa O2 were compared to those at harvest, little change occurred in the adenylate or phosphate pools. PPi and ATP contents decreased as the O2 partial pressure declined below 16 kPa O2. In general, as CO2 increased, PPi and ATP decreased, while Pi, ADP, and AMP increased. The adenylate energy charge (AEC) declined with a decline in the O2 partial pressure, declining most rapidly below 2 kPa O2. Low O2 reduced AEC relative to high O2. Increasing CO2 partial pressure reduced AEC, an effect not evident at lower O2. The data suggest low O2 and elevated CO2 impair oxidative phosphorylation and induce nonsustaining carbon metabolism, which may limit asparagus spear survival under O2-deficient conditions.