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Abstract
Low soil temperatures present a major limitation for direct-seeding many agronomic and horticultural crops. This limitation is particularly true for areas that have relatively short growing seasons, making it necessary to direct-seed into cool soils in the spring.
The Dept. of Horticulture changed its curriculum prior to 1992 to conform to the change from the quarter to the semester system that took place in Fall 1992. As a result of changes in our student body, their interests, and new accounting procedures for determining productivity in our college and the university, another revamping of our curriculum was accomplished beginning in Fall 1992 and our curriculum was changed again to take effect in Fall 1994. Our students now have a choice of a Landscape, Design, Construction Management option or Horticulture. Students all take a two-semester sequence of an Introductory Horticulture course—they must choose a production and management course from three out of four commodity areas (floriculture, landscape, pomology, or vegetable crops), and three out of five upper-division courses in applied physiology or genetics. They must also take a course in Greenhouse Structures and Management and a senior-level capstone course in Horticutural Management. This curriculum has broadened our students' exposure to horticulture to a much greater degree than was present in our old curriculum. In addition, they have about 20–21 credits (out of 120) for electives.
Some horticultural crops have very high respiration rates which makes it difficult to develop modified atmosphere packages that will prevent the product from being injured by high CO2 or from injury by low O2' or anaerobic conditions. Asparagus has a very high respiration rate and responds well to relatively high CO2. Oxygen concentration is less important providing that the asparagus does not go anaerobic.
This investigation reports the results of holding asparagus at 0 C in packages of 3 film thicknesses (1, 2 or 3 mil LDPE) and varying the number of holes from 0 to 16 per package. Five hundred grams of asparagus was held up to 4 weeks. Carbon dioxide and oxygen inside the packages was monitored as well as the quality of the asparagus.
Abstract
History. In 1897, Molisch first suggested the term that was translated as chilling injury to describe the injurious effects of low but non-freezing temperatures on certain plant species (40). More than 50 years were to pass, however, before it was recognized that a similar low-temperature injury might be sustained by germinating seeds. Earlier in this century, Kidd and West (32, 33) reported that soaking seeds of Phaseolus vulgaris L. at 10°C increased the amount of material leached from them and decreased germination compared with seeds soaked at 20°. In 1926, Kotowski (34) noted that the seeds of several warm-season vegetable crops would not germinate below 18°. During this period, it was generally acknowledged that reduced low-temperature germination as exhibited by seeds of most tropical and subtropical species was a consequence of seed infestation by soil-borne pathogens. For example, Leach (37) suggested that many soil organisms had lower optimum growth temperatures than the minimum temperature for seed germination. Thus, while seed germination was inhibited by low soil temperature, soil pathogens could readily grow, multiply and attack the seed.
A study of the ultrastructure of leaf tissues of Chinese mustard shows that there is a progressive degeneration of the membrane structure of the grana of the chloroplast accompanied with the appearance of globules of lipid material and loss of chlorophyll during leaf senescence. A controlled atmosphere of 5% CO2 plus 3% O2 maintained chloroplast grana membrane structure for up to 4 weeks storage at 10°C. Both 5% CO2 (in air) and 5% CO2 plus 3% O2 maintained the highest chlorophyll content compared to 3% O2 alone or in air (control).
In 1987, 1988, and 1989, the behavior of four different table grape varieties including Alden, Concord, Himrod, and Vanessa were studied during storage at 0°C.
The first objective of our study was to determine the behavior of table grapes in modified atmosphere packages in terms of general acceptance. After three years of experimenting with these three films we were able to obtain a modified atmosphere of about 3% O2 and 10-15% CO2 at 0°C using a 3 mil thickness LDPE.
Our second objective was to use moisture absorbents as a means of reducing the relative humidity inside the void volume of a package by the inclusion of different desiccants in the package to establish a desirable relative humidity.
Examining different storage characteristics, our data showed that `Himrod', `Vanessa', and `Concord' grape clusters stored in the presence of KNO3 and KCl had better quality compared to grape clusters stored in the presence of other sorption compounds or controls with no sorbants.
The grape variety `Himrod' under conventional storage practices has a short storage life while it has an excellent quality character.
To modify berry size and cluster compactness, different treatments are being used. Application of these cultural practices has pronounced effect on storage life of grapes. The cultural practices consist of different combinations of gibberellin application (two different concentrations), girdling and cluster thjnning.
Biophysical and biochemical evaluation of the grapes under two different modified storage conditions showed that treated grapes react differently during storage. Our results suggest that grapes that were only treated with gibberellin (20 ppm at shatter and 50 ppm postshatter) were better than control slid any other combined treatments and the worst was the case of only girdling application. Combination of these two treatments were intermediate in terms of biophysical evaluation.
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.
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.
Abstract
Excised onion (Allium cepa L.) shoot apices exposed directly to temperatures of 10 to 15°C grew more than those excised from similarly treated half or whole bulbs. The temperature pretreatments which promoted the greatest growth of excised onion shoots at 20° ranged from 5 to 12.5°. Exposure to 30° following a 10° treatment negated the promotive effect of the lower temperature.