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Namiko Yamori, Yoriko Matsushima, and Wataru Yamori

sufficient. Previously, the use of conventional light sources such as fluorescent lamps entails high electricity costs. The introduction of LEDs into plant cultivation in the 2000s reduced the costs of both lighting and cooling because high-intensity LED

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W. Garrett Owen and Roberto G. Lopez

increase the DLI in the greenhouse. High-intensity LEDs are a promising new SL technology that offer many benefits over the commercially available lamps commonly used in horticulture for SL ( Gómez et al., 2013 ; Morrow, 2008 ). They are solid

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Joshua K. Craver, Joshua R. Gerovac, Roberto G. Lopez, and Dean A. Kopsell

, 2012 ). The development of LED technology has further progressed this form of production due to the higher electrical efficiency, lower output of radiant heat, and spectral control this lighting strategy provides. In addition, the development of these

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Gary W. Stutte

Light-emitting diodes (LEDs) are solid-state semiconductor devices that produce narrow spectrum light when voltage is applied. The use of LEDs in photobiology research was reported in the 1980s and the concept of using LEDs for plant lighting was

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Cinthia Nájera and Miguel Urrestarazu

in a soilless system and in closed and controlled structures under LED lights ( Johkan et al., 2012 ; Urrestarazu et al., 2016 ). This advance in agriculture can be beneficial for the reduction of nitrate levels in plants that accumulate the most and

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Heidi Marie Wollaeger and Erik S. Runkle

Light-emitting diodes are well suited for commercial plant production because of their high energy efficiency and spectral specificity ( Mitchell et al., 2012 ). When operated at favorable temperatures, well-constructed LEDs have an operating

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Ying-Chun Chen, Chen Chang, and Huey-Ling Lin

well documented. Using light-emitting diodes (LEDs) as the light source has been found to have positive effects on in vitro shoot and root development of various species, resulting in improved adaptability and growth after transfer to soil ( Gupta and

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Fumiko Kohyama, Catherine Whitman, and Erik S. Runkle

FR light generates an intermediate P FR /P R+FR that is most promotive for flowering in LDP ( Craig and Runkle, 2012 ; Thomas and Vince-Prue, 1997 ). LEDs are replacing INC lamps because LEDs are much more energy efficient, have a much longer

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Miguel Urrestarazu, Cinthia Nájera, and María del Mar Gea

Fluorescent lamps are widely used in horticulture, particularly in in vitro culture. However, LED lighting systems have several beneficial properties, including their spectral composition, durability, long operating lifetime, wavelength specificity

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Gioia D. Massa, Jeffery C. Emmerich, Robert C. Morrow, C. Michael Bourget, and Cary A. Mitchell

Electrical cost, primarily for lighting, is one of the largest factors inhibiting the development of “warehouse-based” controlled environment agriculture (CEA). In a jointly sponsored collaboration, we have developed a reconfigurable LED lighting array aimed at reducing the electrical energy needed to grow crops in controlled environments. The lighting system uses LED “engines” that can operate at variable power and that emit radiation only at wavelengths with high photosynthetic activity. These light engines are mounted on supports that can be arranged either as individual intracanopy “lightsicles” or in an overhead plane of lights. Heat is removed from the light engines using air flow through the hollow LED strip mounts, allowing the strips to be placed in close proximity to leaves. Different lighting configurations depend on the growth habit of the crops of interest, with intracanopy lighting designed for planophile crops that close their canopy, and close overhead lighting intended for erectophile and rosette crops. Tests have been performed with cowpea, a planophile dry bean crop, growing with intracanopy LED lighting compared to overhead LED lighting. When crops are grown using intracanopy lighting, more biomass is produced, and a higher index of biomass per kW-h is obtained than when overhead LEDs are used. In addition, the oldest leaves on intracanopy-grown plants are retained throughout stand development, while plants lit from overhead drop inner-canopy leaves due to mutual shading after the leaf canopy closes. Research is underway to increase the energy efficiency and automation of this lighting system. This work was supported in part by NASA: NAG5-12686.