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  • Author or Editor: Robert W. Langhans x
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Luminares are the vehicle used to reflect and direct the light energy from the lamps to the desired area. There many companies manufacturing luminares and many different designs. The efficiency of the luminare can vary greatly from one design to another. We attempted to measure the efficiency of a selected group of luminares. The results were confusing as we will show and further investigations into this problem uncovered the major reasons for the discrepancies and difficulties in coming to a simple recommendation.

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Easter liliy (Lilium longiflorum Thunb. `Nellie White') bulbs were stored in moist peatmoss for up to 85 days at – 1.0 or 4.5C. Bulbs were periodically removed from storage and analyzed to determine levels of soluble carbohydrates and starch. Storage at – 1.0C induced large accumulations of sucrose, mannose, fructose, and oligosaccharide in both mother and daughter scales. Starch concentration declined substantially during this period. Storage at 4.5C resulted in less dramatic alterations in bulb carbohydrates, although trends toward increased soluble carbohydrates and reduced starch levels were seen. The accumulation of mannose suggests that glucomannan, a secondary storage carbohydrate, was also degraded during – 1.0C storage.

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With the primary objective of assuring food safety at the production level, a HACCP (Hazard Analysis and Critical Control Point) plan was developed and implemented in an 8000-ft2 greenhouse producing 1000 heads of lettuce per day in Ithaca, N.Y. The plan was developed following the HACCP principles and application guidelines published by the National Advisory Committee on Microbiological Criteria for Foods (1997). The CEA glass greenhouse uses both artificial high-pressure sodium lamps and a shade curtain for light control. Temperature is controlled via evaporative cooling and water heating. Lettuce plants are grown in a hydroponic pond system and are harvested on day 35 from day of seeding. Known and reasonable risks from chemical, physical, and microbiological hazards were defined during the hazard analysis phase. Critical control points were identified in the maintenance of the pond water, the operation of evaporative coolers, shade curtains, and during harvesting and storage. Appropriate prerequisite programs were implemented before the HACCP plan as a baseline for achieving minimum working conditions. Proper critical limits for some potential hazards were established and monitoring programs set up to control them. Postharvest handling was setup in an adjacent head house that was adapted as a food manufacturing facility according to New York State Dept. of Agriculture and Markets standards. Potential applications will be discussed.

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Abstract

Environmental variation within a growth chamber was measured both physically and biologically. Experimental designs are suggested to increase precision in research studies.

Open Access

The release of latent buds (adaptive reiteration) and aerial shoot architecture of the rhizomatous calla lily plant has been researched for pot production. Rhizome mapping has explicitly shown vegetative and floral bud positioning in relation to tissue growth and expansion. Floral initiation normally occurred only on the mother portion of rhizomes. Gibberellic acid (GA3) application enhanced this phenomenon and caused initiation on daughter ramets. Bud excision performed at planting through Day 16 microscopically revealed lack of floral initiation in dissected meristems prior to planting, transition by Day 4, elongation beginning at Day 8 and `small to medium sized spadixes present by Day 12 and 16. Floral development was similar in treated and untreated primary buds, but delayed in secondary and tertiary buds with elongation occurring by Day 16. Pretreatment of GA3 prior to planting revealed spadix presence at Day 0. Floral development correlated with ramet size showed most flowers on largest ramets but formation on all sizes with GA3 treatment. GA3 also caused increased vegetative bud formation on rhizomes.

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The objective of this study was to determine the dry weight, height, and leaf area growth responses of impatiens (Impatiens walerana Hook. f.) plug seedlings to air temperatures ranging from 18 to 29C. The conditions maintained in the controlled-environment growth rooms (CEGR) were ambient C02 levels, 24-h lighting, and photosynthetic photon flux (PPF) ranging from ≈215; to 335 μmol·m-2·s-1. Mean daily temperatures of the plug medium ranged from 19.6 to 27.7C. At the higher PPF level, shoot dry weight decreased at plug medium temperatures (PMT) > 25C; at lower PPF levels (<300 μmol·m-2·s-1), shoot dry weight continued to increase with PMT > 25C. The mean relative growth rate (MRGR) of shoot dry weight was positively correlated with PMT during the initial growth period (up to 14 days from sowing) and was negatively correlated thereafter. The maximum MRGR was predicted to occur at 11.7 days from sowing for a PMT of 19.6C, at 10.8 days for a PMT of 21.6C, and at 9.7 days for a PMT of 23.6C. Linear regression coefficients of shoot height as a function of PMT were substantially higher for seedlings grown at lower PPF than those for seedlings from the highest PPF level. Seedling leaf area consistently increased with increasing temperature. Net assimilation rate (NAR) decreased with increasing seedling age NAR increased with increasing PPF. A decrease in NAR was apparent at 29C relative to values at the lower temperatures. Leaf area ratio (LAR) declined with increasing seedling age and PPF; a quadratic relationship of LAR as a function of PMT indicates a minimum LAR at 22.5C. The seedlings grown at 29C were excessively tall, had thin succulent leaves, and were judged unacceptable for shipping and transplanting. Maximum quality indices (i.e., dry weight per height) were found at PMT of 24.3 to 25.OC for 10- to 14-day-old seedlings and at PMT of 23.0 to 24.OC for 16- to 20-day-old seedlings.

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Uniformity of growth response of impatiens (Impatiems wallerana Hook. f.) plug seedlings was examined in four identical growth rooms. Differences among growth rooms for dry weight, height, and leaf area of 10- to 24-day-old seedlings were generally not significant. During six experiments over 6 months, an individual growth room was maintained under contant baseline environmental conditions. Differences in growth response over time appear to be related to nutrition and irradiance levels. For three experiments with nearly identical irradiance, temperature, and nutrition levels, dry weight and height growth differences over time were only rarely significant. These results illustrate that rather unsophisticated growth rooms can provide consistent growth response over time among experimental units.

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Constructed wetlands have been used to treat many types of aqueous wastes. This innovative plant-based technology is ideally suited for use in the greenhouse horticulture industry given high levels of nutrients in irrigational runoff and drainage and the horticultural experience of greenhouse managers. Use of small-scale systems under controlled environment conditions could provide efficient and reliable year-round drainage remediation at minimal cost. Four identical 0.5m2 recirculating wetland tanks planted with Iris pseudacorus were used to treat simulated greenhouse drainage high in nitrate and other salts. Percent removal for batch-wise treatment was measured by determining concentration changes for ions in a constant volume. Nitrogen removal ranged from 87.3 to 96.7% with 7 day retention times for plant uptake experiments. Greater than 90% removal of phosphorus and potassium was achieved with 1 day and 5 day retention times, respectively. Sodium removal ranged from 13 to 60%. aluminum, boron, calcium, iron, magnesium, manganese, sulfur, and zinc were reduced appreciably within 7 days of recirculation. Treatment efficacy did not decrease over the 10 month study. Denitrification experiments using sucrose to induce anaerobic conditions showed greater than 90% nitrogen removal within 24 hours. Overall, the results were encouraging for the use of this technology in treating horticultural drainage.

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A production system for lettuce seedlings aimed at uniformity and repeatability for transplanting into a hydroponic system has been researched. Parameters for the initial 24 hr. germination period include low light levels (85 μmols), 20°C temperature to avoid thermodormancy, and no fertilizer in the media or nutrient solution to avoid imbibition and osmotic problems from salts. The 10 day nursery environment begins at 24 hrs. with 250 μmols of constant fluorescent light, 25°C and addition of 1/2 strength fertilizer. A sample size of 24 seedlings for dry weights at Day 7 and 11 (transplant) has established a growth curve for experimental comparison. Selection on Day 6 for uniformity at transplant eliminates small and large seedlings based on size and unfolding of first true leaf. Medias researched include oasis, rockwool, Metro Mix 360, peat-vermiculite and `rubber dirt'. Container type, cell size and transplanting techniques have proven plastic cells with peat-vermiculite optimum. Fertilizer has been incorporated into the media or added at 0, 24, 48 or 72 hrs. after germination with 24 hrs. proving optimum. Dry weights and growth chamber uniformity were compared.

Free access

Abstract

Media, nutrition, light and temperature studies were conducted with several species of Cactaceae and Crassulaceae to develop systems for propagating and growing succulents from seed or cuttings in the cool climates and low light irradiances found at northern latitudes. A peat-perlite (1:1 by volume) medium was suitable for rooting and growth. Nitrate nitrogen applied at the rate of 100 ppm with every watering appears optimal for various species at all stages of propagation and development. Most species grew equally well when grown at 10° or 17ºC night temperature. Acceptable germination percentages were obtained with an irradiance of 220 µE·m−2s−1 and a medium temperature of 24°C.

Open Access