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Jakob Markvart, Eva Rosenqvist, Helle Sørensen, Carl-Otto Ottosen, and Jesper M. Aaslyng

-plant producers reduced their use of energy for heating per square meter greenhouses by 23% from 2000 to 2006, whereas their use of electricity per square meter greenhouses, mainly used as supplemental growth light, increased by 30% in the same period ( Møllenberg

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Katrine Heinsvig Kjaer and Carl-Otto Ottosen

Protected plant production systems at northern latitudes largely rely on the use of supplemental light to extend the number of light hours during the day and subsequently the light integral ( Markvart et al., 2009 ). However, because the electricity

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Claudia Elkins and Marc W. van Iersel

and van Iersel, 2017 ), but not for growth responses. Our objective was to evaluate 18 intensities of supplemental far-red light, ranging from 4.0 to 68.8 µmol·m −2 ·s −1 , on the growth and morphology of ‘Dalmatian Peach’ foxglove ( Digitalis purpurea

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Shuyang Zhen and Marc W. van Iersel

use of supplemental light. Supplemental light use efficiency can be improved by implementing energy-efficient lights, such as light-emitting diodes (LEDs) ( Nelson and Bugbee, 2014 ). In addition to the efficiency of the lights, the overall efficiency

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Alexander G. Litvin, Christopher J. Currey, and Lester A. Wilson

., 2006 ), air temperature ( Chang et al., 2005 ), and light intensity and duration ( Beaman et al., 2009 ; Chang et al., 2008 ). Traditionally, broad-spectrum lamps such as HPS or metal halide have been used for supplemental greenhouse lighting, but

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Paul Deram, Mark G. Lefsrud, and Valérie Orsat

latitudes must compensate for the attenuation in total light availability (from prolonged winter with short daylight hours), and supplemental artificial lighting is required to maintain a consistent crop yield throughout the Canadian winters. Conventional

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Marc W. van Iersel and David Gianino

, for efficient year-round production in greenhouses, supplemental light is often needed from late fall through early spring ( Clausen et al., 2015 ; Gómez et al., 2013 ). High-pressure sodium (HPS) lamps are still the most commonly used lamp for

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Michael P. Dzakovich, Celina Gómez, Mario G. Ferruzzi, and Cary A. Mitchell

; Bula et al., 1991 ). Moreover, this technology is being adopted by the greenhouse tomato industry as an efficient alternative to high-pressure sodium fixtures commonly used to provide supplemental light during low-light periods of the year. LEDs are

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Michael P. Dzakovich, Celina Gómez, and Cary A. Mitchell

locally grown, fresh tomatoes during the off-season, greenhouse tomato growers in northern climates increasingly rely on supplemental lighting to compensate for the naturally low solar daily light integral (DLI), or the daily amount of photosynthetically

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Celina Gómez, Robert C. Morrow, C. Michael Bourget, Gioia D. Massa, and Cary A. Mitchell

supplemental photosynthetic light to sustain steady supplies of high-quality produce during the off-season. Most greenhouse growers who use supplemental lighting rely on overhead high-pressure sodium lamps because of their capability to deliver adequate