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G. Yelenosky, D. Hutchison and H. Barrett

Ten-month-old seedlings, grown from seed extracted from 22 individual pummelo [Citrus grandis (L.) Osbeck] × trifoliate orange [Poncirus trifoliata (L.) Raf.] citrus hybrid trees that survived -15C freezes near Monticello, Fla., were cold-acclimated in controlled-environment rooms and freeze-tested at -6.7C for 4 h. Freeze damage to open-pollinated progeny was ranked by the number of uninjured seedlings and percentage of leaves killed and wood dieback. Morphological segregation was not associated with differences in freeze survival, and the dominant trifoliate gene was readily evident. Progeny from one tree, identified as 98-71, are considered the most likely candidates for further study in developing cold-hardy citrus trees.

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Chieri Kubota, Michael A. McClure, Nancy Kokalis-Burelle, Michael G. Bausher and Erin N. Rosskopf

duration of transportation or disease epidemic could result in a long-term impact on plant growth and yield. New controlled environment technology. One critical item necessary for successful grafted seedling production is uniformity of seedlings

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Weixing Cao and Theodore W. Tibbitts

Plants of the potato (Solanum tuberosum L.) cultivars Denali, Norland, Haig, and Kennebec were grown for 42 days under three temperature cycling periods (thermoperiods) with continuous irradiation in two repeated experiments to help determine if temperature cycling might be varied to optimize tuber development of potatoes in controlled environments. Thermoperiods of 6/6 hours, 12/12 hours and 24/24 hours were established with the same temperature change of 22/14C and same controlled vapor pressure deficit of 0.60 kPa. The thermoperiod of 24/24 hours significantly promoted tuber initiation but slowed tuber enlargement in all four cultivars, compared to the thermoperiods of 6/6 hours and 12/12 hours. `Denali' produced the highest tuber and total dry weights under the 6/6 hours thermoperiod. `Kennebec' produced the highest tuber dry weight under the 12/12 hours thermoperiod. Thermoperiods had no significant effect on shoot and root dry weights of any cultivars. The major effect of thermoperiod was on initiation and enlargement of tubers.

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R.M. Wheeler, K.A. Corey, B.A. Vieux, S.W. Mosakowski, J.C. Sager and W.M Knott

Ethylene concentrations were monitored using gas chromatography (GC/PID) throughout growth and development of wheat, soybean, and lettuce stands grown hydroponically inside a large, closed growth chamber (20 m2 area, 113 m3 vol.). For wheat (cv. Yecora Rojo), ethylene concentration increased from < 10 ppb to about 120 ppb at about 28 days after planting (pre-anthesis) and then declined sharply over the next 4 weeks to a plateau of about 10 ppb during canopy maturation and senescence. A similar pattern of evolution was measured for soybean stands (cv. McCall), with peak concentrations of 40 to 70 ppb occurring near 50 days after planting. Unlike wheat, a slight increase in ethylene was noted in the latter stages of soybean stand senescence. For lettuce stands (cv. Waldmann's Green), ethylene increased slowly to 10 to 15 ppb by 24 days after planting, and then rose sharply to 40 ppb by 28 days, when plants were harvested. Data will be used to define ranges for phytotoxicity studies and to project atmospheric contaminant control needs for tightly closed plant growth systems.

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Youbin Zheng, Ping Zhang and Mike Dixon

To evaluate the performance of four newly developed high-intensity-discharge lamp types on plant growth and production, tomato (Lycopersicon esculentum cv. Tradiro F1) plants were grown indoors under 100% artificial lighting for 17 weeks. The four lamp types were: high-pressure sodium high output [HPS(HO)], high-pressure sodium standard [HPS(STD)], metal halide warm deluxe [MH(WDX)] and metal halide cool deluxe [MH(CDX)]. All the lamps tested were 1000 W. HPS(HO) had the highest electrical energy use efficiency (EUE) (0.98 μmol·m–2·s–1·W–1 at 40 cm directly under the lamp); HPS(STD), MH(WDX) and MH(CDX) had 93%, 72% and 61% of the EUE of the HPS(HO), respectively. The photosynthetically active radiation (PAR) outputs of different lamp types had the following order: HPS(HO) > HPS(STD) > MH(WDX) > MH(CDX). The percentage red of PAR of the four tested lamp types had the same order as above, but the percentage blue of PAR of these lamp types had exactly the opposite order. As a result, plants growing under the two HPS lamp types were taller and flowered and fruited earlier than plants under the two MH lamp types. Chlorophyll content index was generally greater in leaves under MH lamps than in leaves under HPS lamps. We recommend that the HPS lamp be used for flowering and fruiting crops and the MH lamp would be better used for foliar and compact crops.

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Gary W. Stutte

NASA has investigated the use of recirculating nutrient film technique (NFT) systems to grow higher plants on long-duration space missions for many years and has demonstrated the feasibility of using recirculating systems on numerous crop species. A long duration (418-day) experiment was conducted at Kennedy Space Center, Fla., to evaluate the feasibility of using recirculating hydroponics for the continuous production of Solanum tuberosum L. `Norland'. The productivity of four sequential batch plantings was compared to staggered harvest and plantings. The accumulation of bioactive organic compounds in the nutrient solution resulted in reduced plant height, induced early tuber formation, and increased harvest index of the crops in both production systems. The changes in crop development were managed by increasing planting density and reducing cycle time to sustain production efficiency.

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Greg Schlick and David Bubenheim

Chenopodium quinoa is being considered as a “new” crop for Contolled Ecological Life Support Systems(CELSS) due to the unique protein composition and high mineral values of the seeds and leaves. Quinoa is known to have very high protein levels (12-185 reported from field trials), with desirable amino acid proportions, and mineral concentrations suitable for a balanced human diet. Contolled environment, hydroponic culture has increased the nutritional value and has the potential of increasing the yield. Protein and mineral values have increased substantially and will be discussed in more depth. The high concentration of protein, unique amino acid profile, high mineral values, versatility in preparation and the potential for increased yields make quinoa a useful crop for CELSS and long-term space missions

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R.M. Wheeler, C.L. Mackowiak, J.C. Sager, N.C. Yorio, W.M. Knott and W.L. Berry

Two studies were conducted in which `Waldmann's Green' lettuce (Lactuca sativa L.) was grown hydroponically from seed to harvest in a large (20-m2), atmospherically closed growth chamber for the National Aeronautics and Space Administration's controlled ecological life support system (CELSS) program. The first study used metal-halide (MH) lamps [280 μmol·m-2·s-1 photosynthetic photon flux (PPF)], whereas the second used high-pressure sodium (HPS) lamps (293 μmol·m-2·s-1). Both studies used a 16-hour photoperiod, a constant air temperature (22 to 23C), and 1000 μmol·mol-1 CO2 during the light period. In each study, canopy photosynthesis and evapotranspiration (ET) rates were highly correlated to canopy cover, with absolute rates peaking at harvest (28 days after planting) at 17 μmol CO2/m2 per sec and 4 liters·m-2·day-1, respectively. When normalized for actual canopy cover, photosynthesis and ET rates per unit canopy area decreased with age (between 15 and 28 days after planting). Canopy cover increased earlier during the study with HPS lamps, and final shoot yields averaged 183 g fresh mass (FM)/plant and 8.8 g dry mass (DM)/plant. Shoot yields in the first study with MH lamps averaged 129 g FM/plant and 6.8 g DM/plant. Analysis of leaf tissue showed that ash levels from both studies averaged 22% and K levels ranged from 15% to 17% of tissue DM. Results suggest that lettuce should be easily adaptable to a CELSS with moderate lighting and that plant spacing or transplant schemes are needed to maximize canopy light interception and sustain efficient CO2 removal and water production.

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Desmond G. Mortley, Douglas R. Hileman, Conrad K. Bonsi, Walter A. Hill and Carlton E. Morris

little data on the decreased performance and the tolerance limits of crop plants exposed to the unique perturbations that occur in closed, controlled environments. Failures are characterized by short-term, acute stress. Cumulative experience in controlled