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

and carotenoids. We also included a consumer sensory panel in Expt. 2 to gauge how ratios of red, blue, and far red light affect the sensory attributes of greenhouse-grown tomatoes. Materials and Methods Plant materials and growing conditions. For Expt

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Dave Hawley, Thomas Graham, Michael Stasiak, and Mike Dixon

., 2017 ; Stasiak et al., 1998 ). The objectives of this study were to evaluate bud yield, and cannabinoid and terpene contents when plants were grown with no SCL (control), Red-Blue SCL, or RGB SCL. Two crop cycles are presented; the results of the first

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Hiroshi Hamamoto and Keisuke Yamazaki

We investigated the reproductive responses of three cultivars of short-day plants to day-extension and night-break treatment with red, blue, and green light-emitting diodes (LEDs). The plants examined were all Malvaceae species: two cultivars of okra [Abelmoschus esculentus (L.) Moench.] and a cultivar of native rosella [Abelmoschus moschatus ssp. tuberosus (Span.) Borss.]. To create day extension or night break, we provided supplemental light from LED panels with peak photon emissions of 470 (blue), 520 (green), or 650 (red) nm. Day-extension treatment using red or blue LEDs inhibited flower and bud appearances; the response was especially pronounced with red LEDs. Night-break treatment with red LEDs also delayed flower bud appearance, but night break with blue LEDs did not produce a clear effect. Night break with green light delayed flowering more strongly than blue light but a little less than red light. We concluded that the dark period-regulated reproductive processes of these plants are most sensitive to disruption by red light, closely followed by green light, but that they are insensitive to blue light, especially when the exposure period is short.

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Lie Li, Yu-xin Tong, Jun-ling Lu, Yang-mei Li, and Qi-chang Yang

the lower canopy and deep leaves of plants, especially those with overlapping leaves, such as lettuce ( Sun et al., 1998 ). Moreover, the nitrate concentration was decreased under short-term continuous combinations of red, blue, and green LEDs ( Bian

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Haijie Dou, Genhua Niu, Mengmeng Gu, and Joseph Masabni

lettuce HortScience 45 1809 1814 Kang, W.H. Park, J.S. Park, K.S. Son, J.E. 2016 Leaf photosynthetic rate, growth, and morphology of lettuce under different fractions of red, blue, and green light from light-emitting diodes (LEDs) Hort. Environ. Biotechnol

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Zhong-Hua Bian, Rui-Feng Cheng, Qi-Chang Yang, Jun Wang, and Chungui Lu

Light-emitting diodes (LEDs) have shown great potential for plant growth and development, with higher luminous efficiency and more flexible and feasible spectral control compared with other artificial lighting. The combined effects of red and blue (RB) LED with or without green (G) LED light and white LED light on lettuce (Lactuca sativa L.) growth and physiology, including nitrate content, chlorophyll fluorescence, and phytochemical concentration before harvest, were investigated. Continuous light exposure at preharvest can effectively reduce nitrate accumulation and increase phytochemical concentrations in lettuce plants. Nitrate accumulation is dependent on the spectral composition and duration of treatment: lettuce exposed to continuous RB (with or without G) LED light with a photosynthetic photon flux (PPF) of 200 µmol·m−2·s−1 exhibited a remarkable decrease in nitrate content at 24 hour compared with white LED light treatment at the same PPF. In addition, RB LED light (R:B = 4:1) was more effective than white LED light at the same PPF in facilitating lettuce growth. Moreover, continuous LED light for 24 hours significantly enhanced free-radical scavenging activity and increased phenolic compound concentrations. We suggest that 24 hours continuous RB LED with G light exposure can be used to decrease nitrate content and enhance lettuce quality.

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Wesley C. Randall and Roberto G. Lopez

80 μmol·m −2 ·s –1 of varying proportions of red and blue light from LEDs, stem elongation, but not dry mass, could be manipulated. As blue light increased from 0 to 32 μmol·m −2 ·s –1 and red light was reduced from 80 to 48 μmol·m −2 ·s –1 (red:blue

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W. Garrett Owen and Roberto G. Lopez

’ (red leaf) and ‘Grand Rapid TBR’ (green leaf), whereas 100:0 red:blue SSL LEDs to influence lettuce morphology and growth. Thus, the use of LEDs for lettuce growth, development, and spectrum-dependent plant photo-physiological responses is well

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W. Garrett Owen and Roberto G. Lopez

responsible for the red, blue, or purple pigmentation in reproductive and vegetative tissues ( Chalker-Scott, 1990 ). The concentration of anthocyanins in foliage is influenced by environmental conditions such as light quality, light intensity, and temperature

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Christopher J. Currey and Roberto G. Lopez

2200 hr ( Table 2 ). Supplemental light was delivered from a 150-W HPS lamp (PL2000; P.L. Lights, Beamsville, Ontario, Canada) or one of three LED arrays (Orbital Technologies Corporation, Madison, WI) varying in the proportion (%) of red:blue light