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Yves Desjardins, André Gosselin and Michel Lamarre

Asparagus (Asparagus officinalis L.) transplants and in vitro-cultured clones were grown and acclimatized under two photosynthetic photon flux (PPF) conditions (ambient and ambient + 80 μmol·s-1·m-2) and three atmospheric CO2 concentrations (330, 900, and 1500 ppm). Short- and long-term effects were measured in the greenhouse and after two seasons of growth in the field, respectively. In the greenhouse, CO2 enrichment (CE) and supplemental lighting (SL) increased root and fern dry weight by 196% and 336%, respectively, for transplants and by 335% and 229%, respectively, for clones. For these characteristics, a significant interaction was observed between SL and CE with tissue-cultured plantlets. In the absence of SL, CE did not significantly increase root or shoot dry weight. No interaction was observed between CE and SL for transplants, although these factors significantly improved growth. It was possible to reduce the nursery period by as much as 3 weeks with CE and SL and still obtain a plant size comparable to that of the control at the end of the experiment. Long-term effects of SL were observed after two seasons of growth in the field. Supplemental lighting improved survival of transplants and was particularly beneficial to in vitro plants. Clones grown under SL were of similar size as transplants after 2 years in the field.

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Badrane M. Erhioui, André Gosselin, Xiuming Hao, Athanasios P. Papadopoulos and Martine Dorais

A study was conducted in mini-greenhouses covered with single-glass (glass), double inflated polyethylene film (D-poly), or rigid twin acrylic panels (acrylic) to determine the effects of covering materials and supplemental lighting (SL) (65 μmol·m-2·s-1 at 1 m from the ground, providing a 16-hour photoperiod) on growth, yield, photosynthesis, and leaf carbohydrate concentration of `Trust' greenhouse tomato plants (Lycopersicon esculentum Mill.). Regardless of the light treatment, the marketable yield (kg·m-2) and the number of fruit per square meter in D-poly houses were higher (P ≤ 0.05) by 15% to 16% and 13% to 17%, respectively, than in glasshouses. Under supplemental lighting (SL), similar results were observed in acrylic houses compared to glasshouses. Covering materials had no significant effect on photosynthesis and leaf chlorophyll (chl) concentration. SL increased the number of leaves (March) by 15% (P ≤ 0.05) in glasshouses, marketable fruit yield by 23% (P ≤ 0.01) in acrylic houses, leaf specific weight by 19% to 33% (P ≤ 0.05) in all houses, total chl concentration by 10% to 14% (P ≤ 0.01) in acrylic houses, and photosynthetic rate (March) by 22% (P ≤ 0.01) in glasshouses. Under nonsupplemental lighting (nonSL, daily solar radiation of 8.42 MJ·m-2), plant height in acrylic houses was significantly higher (P ≤ 0.05) than in glasshouses. Neither covering materials nor SL affected (P ≤ 0.05) dry matter allocation to the fruit. Results suggest that D-poly and acrylic houses with SL provide the best environment for the early yield (February to March) under southwestern Ontario growing conditions. The photosynthetic rate decreased (P ≤ 0.05) by 18% in acrylic, and 15% in D-poly and glasshouses after 2 months of growth under nonSL. Conversely, the decrease in carbon exchange rate was not significant in D-poly houses and glasshouses under SL. As a result, the photosynthesis decline observed in the present study could not be explained by leaf starch accumulation in March.

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W. Garrett Owen and Roberto G. Lopez

Variability in outdoor daily temperatures and photosynthetic daily light integrals (DLIs) from early spring to late fall limits the ability of propagators to accurately control propagation environments to consistently callus, root, and yield compact herbaceous perennial rooted liners. We evaluated and compared the effects of sole-source lighting (SSL) delivered from red (R) and blue (B) light-emitting diodes (LEDs) to supplemental lighting (SL) provided by high-pressure sodium (HPS) lamps on herbaceous perennial cutting morphology, physiology, and growth during callusing and initial rhizogenesis. Cuttings of perennial sage (Salvia nemorosa L. ‘Lyrical Blues’) and wand flower (Gaura lindheimeri Engelm. and A. Gray ‘Siskiyou Pink’) were propagated in a walk-in growth chamber under multilayer SSL provided by LEDs with [R (660 nm)]:[B (460 nm)] light ratios (%) of 100:0 (R100:B0), 75:25 (R75:B25), 50:50 (R50:B50), or 0:100 (R0:B100) delivering 60 µmol·m−2·s–1 for 16 hours (total DLI of 3.4 mol·m−2·d−1). In a glass-glazed greenhouse (GH control), cuttings were propagated under ambient solar light and day-extension SL provided by HPS lamps delivering 40 µmol·m−2·s–1 to provide a 16-hour photoperiod (total DLI of 3.3 mol·m−2·d−1). At 10 days after sticking cuttings, callus diameter and rooting percentage were similar among all light-quality treatments. For instance, callus diameter, a measure of growth, of wand flower cuttings increased from an average 1.7 mm at stick (0 day) to a range of 2.7 to 2.9 mm at 10 days after sticking, regardless of lighting treatment. Relative leaf chlorophyll content was generally greater under SSL R75:B25 or R50:B50 than all other light-quality treatments. However, stem length of perennial sage and wand flower cuttings propagated under SSL R50:B50 at 10 days were 21% and 30% shorter and resulted in 50% and 8% greater root biomass, respectively, compared with those under SL. The herbaceous perennial cuttings propagated in this study under SSL R50:B50 were of similar quality or more compact compared with those under SL, indicating that callus induction and initial rooting can occur under LEDs in a multilayer SSL propagation system.

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Jennifer K. Boldt

Energy inputs are a major production cost for greenhouse-grown plants. Primary energy inputs include heating and supplemental lighting, and they are the third largest expense after labor and plant material ( United States Department of Agriculture

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Celina Gómez, Christopher J. Currey, Ryan W. Dickson, Hye-Ji Kim, Ricardo Hernández, Nadia C. Sabeh, Rosa E. Raudales, Robin G. Brumfield, Angela Laury-Shaw, Adam K. Wilke, Roberto G. Lopez and Stephanie E. Burnett

The recent increased market demand for locally grown produce is generating interest in the application of techniques developed for controlled environment agriculture (CEA) to urban agriculture (UA). Controlled environments have great potential to revolutionize urban food systems, as they offer unique opportunities for year-round production, optimizing resource-use efficiency, and for helping to overcome significant challenges associated with the high costs of production in urban settings. For urban growers to benefit from CEA, results from studies evaluating the application of controlled environments for commercial food production should be considered. This review includes a discussion of current and potential applications of CEA for UA, references discussing appropriate methods for selecting and controlling the physical plant production environment, resource management strategies, considerations to improve economic viability, opportunities to address food safety concerns, and the potential social benefits from applying CEA techniques to UA. Author’s viewpoints about the future of CEA for urban food production are presented at the end of this review.

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Donglin Zhang, Allan M. Armitage, James M. Affolter and Michael A. Dirr

Lysimachia congestiflora Wils. (Primulaceae) is a new crop for American nurseries and may be used as an annual in the north and a half-hardy perennial in the south. The purpose of this study was to investigate the influence of photoperiod, temperature, and irradiance on its flowering and growth. Three experiments were conducted with photoperiod of 8, 12, 16 hrs day-1, temperature of 10, 18, 26C, and irradiance of 100, 200, 300 μmol m-2s-1, respectively. Plant.9 given long day photoperiod (16 hours) flowered 21 and 34 days earlier, respectively, than plants at 12 sad 8 hour photoperiods. Plants under long day treatment produced more flowers than those at 8 and 12 hours. Plant dry weight did not differ between treatments, but plants grown in the long day treatment produced fewer but larger leaves. Total plant growth increased as temperature increased, but lower temperature (10C) decreased flower initiation and prevented flower development, while high temperature (26C) reduced the longevity of the open flowers. Flowering was accelerated and dry weight increased as plants were subjected to high irradiance levels. The results suggest that Lysimachia congestiflora is a quantitative long day plant. It should be grown under a photoperiod of at least 12 hours at a temperature of approximately 20C. Low light areas should be avoided and supplemental lighting to provide the long days may improve the plant quality.

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David S. de Villiers, Robert W. Langhans, A.J. Both, Louis D. Albright and Sue Sue Scholl

CO2 enrichment increases efficiency of light utilization and rate of growth, thereby reducing the need for supplemental lighting and potentially lowering cost of production. However, during warmer periods of the year, CO2 enrichment is only possible intermittently due to the need to vent for temperature control. Previous research investigated the separate and combined effects of daily light integral and continuous CO2 enrichment on biomass accumulation in lettuce. The current research was designed to look at the efficiency with which lettuce is able to utilize intermittent CO2 enrichment, test the accuracy with which growth can be predicted and controlled, and examine effects of varying CO2 enrichment and supplemental lighting on carbon assimilation and plant transpiration on a minute by minute basis. Experiments included application of various schedules of intermittent CO2 enrichment and gas exchange analysis to elucidate underlying physiological processes. Same-day and day-to-day adjustments in daily light integrals were made in response to occasional CO2 venting episodes, using an up-to-the-minute estimate of growth progress based on an integration of growth increments that were calculated from actual light levels and CO2 concentrations experienced by the plants. Results indicated lettuce integrates periods of intermittent CO2 enrichment well, achieving expected growth targets as measured by destructive sampling. The gas-exchange work quantified a pervasive impact of instantaneous light level and CO2 concentration on conductance and CO2 assimilation. Implications for when to apply supplemental lighting and CO2 enrichment to best advantage and methods for predicting and controlling growth under intermittent CO2 enrichment are discussed.

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O. Ayari, M. Dorais and A. Gosselin

Daily and seasonal variations of photosynthetic activity, chlorophyll a (Chl-a) fluorescence and foliar carbohydrate content were studied in situ on greenhouse tomato (Lycopersicon esculentum Mill. `Trust') plants grown under CO2 enrichment and supplemental lighting. The objective of this study was to assess the effect of seasonal variation of the photosynthetic photon flux (PPF) on photosynthetic efficiency of tomato plants and to determine the presence or absence of photosynthetic down-regulation under greenhouse growing conditions prevailing in northern latitudes. During winter, the fifth and the tenth leaves of tomato plants showed low, constant daily photosynthetic activity suggesting a source limitation under low PPF. In winter, the ratio of variable to maximum Chl-a fluorescence in dark adapted state (Fv/Fm) remained constant during the day indicating no photoinhibition occurred. In February, an increase in photosynthetic activity was followed by a decline during March, April, and May accompanied by an increase in sucrose and daily starch concentrations and constant but high hexose level. This accumulation was a long-term response to high PPF and CO2 enrichment which would be caused by a sink limitation. Thus, in spring we observed an in situ downregulation of photosynthesis. The ratio Fv/Fm decreased in spring compared to winter in response to increasing PPF. The daily decline of Fv/Fm was observed particularly as a midday depression followed by a recovery towards the end of the day. This indicated that tomato leaves were subject to a reversible inhibition in spring. Fv/Fm was lower in March than in April and May even though PPF was higher in April and May than in March. These results suggest that tomato plants develop an adaptive and protective strategy as PPF increases in spring.

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Brian R. Poel and Erik S. Runkle

treatment, whereas all others were statistically similar. Fig. 2. Dry shoot and root weights of seven seedling cultivars grown under ambient light and supplemental lighting from two high-pressure sodium (HPS) or four light-emitting diode (LED) treatments

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Hiroshi Hamamoto and Keisuke Yamazaki

buds were found in all plants grown in all three growth cabinets. The plants were then moved into a glasshouse. Fig. 1. ( A ) Daily photoperiods (white zones) and supplemental lighting periods (shaded zones) used in Expts. 1, 2, and 3 to study