Search Results

You are looking at 1 - 10 of 27 items for

  • Author or Editor: Robert Langhans x
Clear All Modify Search

This research explored cool crop production in various climate zones using CEA facilities and hydroponics ponds to control growth rate and quality through root zone temperature control. The precise controls were used to vary air and water temperatures to study the temperature gradient between root and shoot zones. Effect of this gradient was measured by growth rates and final harvest dry weights. Lactuca sativa L. cv. Ostinata seedlings were germinated and grown 11 days in a growth chamber and moved to greenhouse ponds. Air temperatures chosen were 17, 24, and 31°C. These were constant for the 24 days that lettuce grew in the ponds with a 5°C decrease for 14 hours. during the night. Water temperatures of the three ponds in the greenhouse were set and maintained at 17, 24, and 31°C. Maximum final harvest weights were obtained at 24°C air/water 24°C. Final weights for the 17 and 31°C water setpoint were comparable at 24°C air. The 31 °C air /water inhibited quality and final dry weight, while 17 and 24°C water produced equivalent dry weights at 31°C air. At 31°C air heads were tighter at 17 than at 24°C, and loose at 31°C. At air 17 °C maximum weight was at 24°C water and minimum at 31°C water. At 17°C air, the 24°C water plants were of good quality, with thicker leaves but visibly smaller than the 31°C water crop. Significant differences in harvest dry weights were shown at each 7-day harvest beginning on day 14, due to both air and water setpoint factors and there was significant interaction between them.

Free access

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.

Free access

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.

Free access

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.

Free 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.

Free access

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

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.

Free access

Abstract

The effects of reduced irradiance on dry weight partitioning in Easter lilies was examined by forcing vernalized bulbs of Lilium longiflorum Thumb. ‘Nellie White’ during two growing seasons. Forcing commenced in a glasshouse under standard growing conditions; immediately following flower bud initiation (FBI), plants were transferred to a range of irradiance reduction treatments (0%, 20%, 50%, or 85% reduction) in the greenhouse or to complete darkness in a growth chamber. Greenhouse irradiance reduction treatments resulted in alterations in whole-plant source-sink relationships. Total plant dry weight and overall plant quality were reduced in shaded plants. The depletion rate of mother bulb dry matter was not affected by reduced irradiance, whereas daughter bulb reserve loss was increased by irradiance reduction treatments. There was no daughter bulb reserve remobilization in plants grown in complete darkness after FBI. Flower bud and open flower dry weights were progressively reduced as irradiance was reduced. With an 85% irradiance reduction, plants forced from 17.5-cm bulbs had 63% bud abortion, whereas, with 20.0-cm bulbs, only 12% of the buds aborted. Plants grown in complete darkness after FBI became etiolated, and flowers failed to open. These results demonstrate differences in the ability of various morphological regions of the bulb to respond to reductions in greenhouse irradiance. Since the daughter bulb response to reduced irradiance was relatively slow, additional remobilization of dry matter from the daughter bulb is probably of minimal benefit during short periods of reduced irradiance in commercial greenhouses.

Open Access

Abstract

Changes in carbohydrate types and quantities in the bulbs, stems, leaves, and buds of Easter lilies (Lilium longiflorum Thunb. ‘Nellie White’) forced under ambient or reduced irradiance conditions were investigated. Analysis by high-performance liquid chromatography (HPLC) revealed that sucrose is the dominant soluble carbohydrate in bulb tissues, with glucose, fructose, and mannose present at significantly lower concentrations. During growth of the flowering shoot, mother bulb reserves are preferentially used regardless of greenhouse irradiance. Beginning 40 days after planting, there was a steady decrease in mother bulb starch concentration until anthesis, 70 days later. Increased bulb sucrose, glucose, mannose, and fructose concentrations were correlated with the induction of starch breakdown and carbohydrate export. Under natural greenhouse irradiance conditions, daughter bulb carbohydrate reserves were not used, as starch and soluble carbohydrate concentrations remained constant. Irradiance reductions of 50% to 85% significantly reduced total carbohydrate concentration in leaves and floral buds and induced export from the daughter bulb, as evidenced by elevated levels of daughter bulb soluble carbohydrates and reductions in starch concentration. Dark-grown plants exhibited similar daughter bulb carbohydrate metabolism patterns as plants grown in full sun: starch was not hydrolyzed and soluble carbohydrates did not increase in concentration. Collectively, these results suggest 1) bulb export metabolism is characterized by elevated soluble carbohydrate concentrations, 2) there is a minimum irradiance requirement for carbohydrate export processes from the daughter bulb, and 3) reductions in greenhouse irradiance result in reduced carbohydrate levels in Easter lily leaves and flower buds.

Open Access

Protein is an important and essential dietary component. Common bean, a major source of vegetable protein in the Americas, was chosen for study in controlled environments with a view to its potential for use in space colonies. Eighteen 0.58-m2 stands of the cranberry type of bean, `Etna', were grown in the greenhouse at plant densities of 7, 15, and 28 plants/m2 in a recirculating ebb-and-flow system. Duration of photoperiod and thermoperiod was 16 h. Day/night temperatures settings were 25/20 °C. Daily light integral was matched across greenhouse sections by means of supplemental lighting; it averaged 17 mol/m2 per day. Crop cycle was 70 days from seed to harvest. At harvest, plants were dismembered so that dry weights of leaf, branch, stem, pod, and bean yields could be separately measured by node of origin. Internode lengths were recorded, and all loose trash recovered. The relationship between yield and plant density followed the form expected. Yield of edible biomass at 7 plants/m2 (284 g/m2) was 88% of that at 28 plants/m2 (324 g/m2), a significant difference. At 15 plants/m2 it was 97%. The trend suggests that further gains (but only very small) in yield can be expected with increased density in this cultivar. Productivity and quantum yield at 28 plants/m2 were 4.69 g/m2 per day and 0.27 g/mol, respectively. The coefficient of variation for plants grown at 28 plants/m2 was three times that of plants grown at 7 plants/m2 (0.88 vs. 0.26). Yield component analysis, harvest index, and plant morphology at the different planting densities are discussed.

Free access