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Matthew G. Blanchard and Erik S. Runkle

were grown at five lateral distances from under a stationary high-pressure sodium (HPS) lamp with an oscillating parabolic reflector (rotating HPS) or under incandescent (INC) lamps. INC lamps operated continuously for the entire NI (CONT INC) or for 6

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Wesley C. Randall and Roberto G. Lopez

(HID) lights. High-pressure sodium (HPS) lamps are the most commonly used HID light sources, and several characteristics contribute to their use. However, HPS lamps primarily emit light in the spectral range of 565 to 700 nm, which is primarily yellow

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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

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Brian R. Poel and Erik S. Runkle

flowering of Celosia, Impatiens, Salvia, Tagetes , and Viola HortScience 40 1336 1339 Randall, W.C. Lopez, R.G. 2014 Comparisons of supplemental lighting from high-pressure sodium lamps and light-emitting diodes during bedding plant seedling production

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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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Wesley C. Randall and Roberto G. Lopez

overhead SL ( Oh et al., 2010 ; Randall and Lopez, 2014 ; Sherrard, 2003 ). High-intensity discharge lamps, such as HPS and metal halide lamps, have traditionally been used for SL to increase greenhouse DLI. High-pressure sodium lamps have long been the

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

We thank Dale Brabham, Philips Lighting Corp., for providing the HPS SON-Agro lamps for testing; Lisa Ruffe for horticultural assistance in conducting these studies; and Joe Martinez and Joe Benjamin for growth chamber maintenance. Mention

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David L. Bubenheim, Raman Sargis, and David Wilson

Electronic dimming of high intensity discharge lamps offers control of photosynthetic photon flux (PPF) but is often characterized as causing significant spectral changes. Growth chambers with 400 W metal halide (MH) and high pressure sodium (HPS) lamps were equipped with a dimmer system using silicon controlled rectifiers (SCR) as high speed switches. Phase control operation turned the line power off for some period of the AC cycle. At full power the electrical input to HPS and MH lamps was 480 W (RMS) and could be decreased to 267 W and 428 W, respectively, before the arc was extinguished. Concomitant with this decrease in input power, PPF decreased by 60% in HPS and 50% in MH. The HPS lamp has characteristic spectral peaks at 589 and 595 nm. As power to the HPS lamps was decreased the 589 nm peak remained constant while the 595 nm peak decreased, equalling the 589 nm peak at 345 W input, and was almost absent at 270 W input. The MH lamp has a broader spectral output but also has a peak at 589 nm and another, smaller peak, at 545 nm. As input power to the MH lamps decreased the 589 nm peak diminished to equal the 545 nm peak. As input power approached 428 W the 589 nm peak shifted to 570 nm. While a spectral change was observed as input power was decreased in both MH and HPS lamps, the phytochrome equilibrium ratio (Pfr/Ptot) remain unchanged for both lamp types.

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David L. Bubenheim, Raman Sargis, and David Wilson

Electronic dimming of high-intensity discharge lamps offers control of photosynthetic photon flux (PPF) but is often characterized as causing significant spectral changes. Growth chambers with 400-W metal halide (MH) and high-pressure sodium (HPS) lamps were equipped with a dimmer system using silicon-controlled rectifiers (SCR) as high-speed switches. Phase control operation turned the line power off for some period of the alternating current cycle. At full power, the electrical input to HPS and MH lamps was 480 W (root mean squared) and could be decreased to 267 W and 428 W, respectively, before the arc was extinguished. Concomitant with this decrease in input power, PPF decreased by 60% in HPS and 50% in MH. The HPS lamp has characteristic spectral peaks at 589 and 595 nm. As power to the HPS lamps was decreased, the 589-nm peak remained constant while the 595-nm peak decreased, equaling the 589-nm peak at 345-W input, and the 589-nm peak was almost absent at 270-W input. The MH lamp has a broader spectral output but also has a peak at 589 nm and another smaller peak at 545 nm. As input power to the MH lamps decreased, the peak at 589 diminished to equal the 545-nm peak. As input power approached 428 W, the 589-nm peak shifted to 570 nm. While the spectrum changed as input power was decreased in the MH and HPS lamps, the phytochrome equilibrium ratio (Pfr: Ptot) remains unchanged for both lamp types.