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Kevin R. Cope and Bruce Bugbee

crop shown is radish on the day of harvest. Note the differences in plant form across treatments, which are arranged (left to right) warm, neutral, and cool white LEDs. LED = light-emitting diode. Light treatments. Warm, neutral, and cool white LEDs

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Devdutt Kamath, Yun Kong, Chevonne Dayboll, and Youbin Zheng

, there is a lack of information on their use for the production and maintenance of stock plants for cutting production. Light-emitting diodes (LEDs) are replacing traditional light sources (e.g., high-pressure sodium and fluorescent lights) as SSL in

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Joshua K. Craver, Jennifer K. Boldt, and Roberto G. Lopez

.R. Peters, Inc., Allentown, PA) providing 100 mg·L −1 nitrogen (N). Fig. 1. Spectral quality from 400 to 700 nm delivered from light-emitting diode (LED) fixtures or high-pressure sodium (HPS) lamps providing a photosynthetic photon flux density ( PPFD ) of

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Christopher J. Currey and Roberto G. Lopez

root development of Impatiens , Pelargonium , and Petunia grown under ambient daylight supplemented with ≈70 μmol·m −2 ·s −1 , respectively, delivered from high-pressure sodium (HPS) lamps or light-emitting diodes with varying proportions of red

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Chase Jones-Baumgardt, David Llewellyn, and Youbin Zheng

Gosselin, 2002 ; Dorais et al., 2017 ). High-pressure sodium (HPS) fixtures have been commonly used in greenhouses for SL ( Hemming, 2011 ; Ouzounis et al., 2015 ). Recently, light-emitting diodes (LEDs) have been increasingly used as an alternative to

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Joshua K. Craver, Jennifer K. Boldt, and Roberto G. Lopez

., 2017 ). One alternative to traditional greenhouse production is multilayer or vertical production indoors in repurposed shipping containers, warehouses, or chambers under sole-source lighting (SSL) provided by light-emitting diodes (LEDs). While SSL

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Dean A. Kopsell and Carl E. Sams

were measured at the beginning and confirmed at the end of each experimental run. Fig. 1. Spectroradiometer photon flux distribution for the light treatments of: ( A ) red and blue light-emitting diode (LED) treatment of 627 nm and 470 nm, respectively

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W. Garrett Owen and Roberto G. Lopez

grass ( Pennisetum × advena ) plants. Fig. 1. ( A – H ) Spectral quality of 4.5 µmol·m −2 ·s −1 delivered from day-extension low-intensity light-emitting diode (LED) lamps. ( A ) 7:11:33:49 blue:green:red:far-red light ratio (%); control, ( B ) 70 µmol

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M.E. Hoenecke, R.J. Bula, and T.W. Tibbitts

Light-emitting diodes (LEDs) with high-intensity output are being studied as a photosynthetic light source for plants. High-output LEDs have peak emission at ≈660 nm concentrated in a waveband of ±30 nm. Lettuce (Lactuca sativa `Grand Rapids') seedlings developed extended hypocotyls and elongated cotyledons when grown under these LEDs as a sole source of irradiance. This extension and elongation was prevented when the red LED radiation was supplemented with more than 15 μmol·m-2·s-1 of 400- to 500-nm photons from blue fluorescent lamps. Blue radiation effects were independent of the photon level of the red radiation.

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N.C. Yorio, M. Sanwo, and C.S. Brown

Light-emitting diodes (LEDs) are a potential light source for growing plants in space flight systems because of their superior safety and reliability, small mass and volume, electrical efficiency, and longevity. To determine the influence of narrow-spectrum LEDs on plant growth and metabolism, wheat (Triticum aestivum L. `Superdwarf') plants were grown under red LEDs (peak emission 660 nm) and compared to plants grown under daylight fluorescent, red LEDs + 1% blue fluorescent light (BL), and red LEDs + 10% BL. Plants were taller, had longer flag leaves, and delayed seed development when grown under red LEDs or red LEDs + 1% BL compared to those grown with 10% BL or under daylight fluorescent. Viable seeds (290% germination) were produced in all plants regardless of the light treatment. Total dry matter (DM), head DM, and seed DM were similar in the plants grown under the four light regimes, and there were no differences in the starch content of the seeds. Starch levels were 4-times greater and sucrose levels were 2.5-times greater in leaves of plants grown under the red LEDs compared to daylight fluorescent. Daylight fluorescent leaves showed a 1.8-fold increase in sucrose phosphate synthase (SPS) activity, a regulatory enzyme of sucrose synthesis. These results indicate that wheat can be grown successfully under red LEDs, but there are differences in carbohydrate concentration and metabolism in photosynthetic tissue.