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- Author or Editor: L. L. Morris x
Most, if not all, horticultural fruits, vegetables, and ornamentals of tropical origin are subject to physiological injury when subjected to temperatures below about 12.5°C but above their freezing temperature. This damage does not involve freezing and is commonly termed chilling injury. Chilling-sensitive plants, and plant parts, are subject to injury at all stages of their development, except in the dry-seed stage.
The past quarter century has been a “Golden Era” for the development of a multitude of vegetable cultivars. We have seen the development of tomatoes that can be mechanically harvested with only slight injury to the fruit; sweet corn that is “super-sweet” with an extremely tender pericarp; green beans that are stringless and peas tha-t are very determinate and adaptable to mechanical harvesting. Countless other breeding achievements have been made in vegetable quality and adaptability, not to mention the broad spectrum of disease and insect resistance that has been bred into nearly every vegetable species. We can be thankful for our highly competitive system for bringing about so many of these advances in such a short time.
Plants of head lettuce (Lactuca sativa L.) were rapidly regenerated in vitro using apex segments, expanded axial buds, and leaf sections. Shoot development occurred after 14 days on Miller’s medium plus 5.0 mg/liter 3-indoleacetic acid (IAA) and 0.5 mg/liter kinetin at 22.5°C. Root initiation was induced by transferring rootless plantlets to Miller’s medium plus 1 mg/liter indolebutyric acid (IBA) for 2 weeks. Plants were transplanted to pots 4 weeks after initial culturing, and to the field within an additional 3 to 5 weeks. Heads appeared similar to those propagated from seed and viable seed was produced.
The Las Vegas Valley receives most of its water from the Colorado River due to a static federal water allocation the remainder from pumping groundwater. The increased water demand due to the population rise in the Las Vegas Valley is expected to overtake its current water allocation in the next few years. Over 60% of the potable water used in the Las Vegas valley is used to irrigate urban landscapes. Poorly designed desert landscapes can ultimately use more water than traditional landscapes and increase residential energy costs. Most of the desert landscaping currently installed by homeowners either ignores principles that conserve water or conserve energy. The program was designed to be used with homeowner associations and commercial landscapers. The residential homeowner proved to be the most responsive to this type of program. The overall goal of this program is to teach residents how to convert a high water use landscape to lower water use and reduce dependence on potable water for irrigation and still maintain high quality landscapes. In 1995, a 7-week, hands-on, landscape design curriculum was developed and used to teach homeowners how to create desert landscape designs that conserve water and energy and compared its water use to traditional, turfgrass landscapes. Participants leave the course with a finished design of their making with information on how to install the landscape themselves or how to hire a professional to do the installation. In 1996-97 a Master Gardener was taught and mentored how to teach the class in Las Vegas using the existing curriculum. Since 1995, over 500 residents have been trained and water use savings documented by the existing water purveyors. This program is self-funded through class fees.
Postharvest discoloration of cultivated mushrooms (Agaricus.bisporus [Lange] Sing., ‘tan strain’) was significantly retarded by treatment with succinic acid-2,2-dimethylhydrazide (SADH). The optimum SADH concn was 100 ppm. The effect, however, lasted no longer than 3 days after which time all SADH treatments discolored at rates equal to or greater than controls. The decrease in discoloration was correlated with a decrease in o-diphenol oxidase (o-DPO) activity. Protease activity was higher in SADH treated mushrooms suggesting that reduction in browning was due to degradation of o-DPO rather than direct inhibition of o-DPO by SADH. In vitro SADH competes with proline for quinones produced by enzymatic or non-enzymatic oxidation of diphenols. It is proposed that in vivo SADH exerts a dual effect in reducing mushroom discoloration: first SADH induces degradation of o-DPO through an increase in proteolytic activity, and second it binds to quinones thereby removing intermediates which lead to pigment formation.
Storage of mushrooms (Agaricus bisporus, [Lange] Sing.) in 0% O2 reduced discoloration and o-diphenol oxidase (o-DPO) activity for up to 7 days. Levels of O2 above 0% had little or no effect in reducing discoloration and o–DPO activity compared to air controls. Concentrations of CO2 above 5% appeared to increase surface discoloration while markedly inhibiting o-DPO activity. After transfer to air, the effectiveness of the increased CO2 treatments in reducing o-DPO activity in mushrooms depended on storage time in CO2.
In vitro CO2 markedly inhibited o-DPO activity, with 50% inhibition at 25% CO2. Complete inhibition was never attained. The inhibition by CO2 was found to be competitive with respect to catechol and could not be overcome by increasing the O2 concentration above 20%. The action of CO2 in vivo in reducing o-DPO activity could be through a direct competitive inhibition or through the inhibitory effect of CO2 on mushroom maturation.
Fruits were collected on weekly intervals in 1980, beginning at fruit set (ovary shatter) and continuing through harvest. Additional samples collected at harvest in 1980 and veraison in 1981 were sorted into preveraison green, postveraison green, and ripening categories. Seed number per berry was directly related to accumulation of 14C-photosynthate, fresh weight, and dry weight. Seed number had little relationship with berry content of indoleacetic acid (IAA), abscisic acid (ABA) or percentage of acidity. Percentage of soluble solids was not affected by seed number prior to veraison, but after veraison, percentage of soluble solids and intensity of juice color were inversely related to seed number. Nonripe fruit at the time of harvest had fewer seeds per berry, and fruit containing an immature seed did not accumulate ABA or enter veraison. IAA levels were similar in ripening and nonripening fruit. IAA declined to basal levels by about 55 days after peak bloom. ABA began to increase after 65 days from peak bloom and berry changes associated with veraison occurred after 72 days.