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Liang Zheng, Huaming He and Weitang Song

., 2013 ; Jiao et al., 2007 ). Changes in light quality, intensity, and duration cause responses at anatomical, physiological, and biochemical levels and, thus, influence plant morphology and functioning ( Haliapas et al., 2008 ). The development of LED

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Ki-Ho Son, Jin-Hui Lee, Youngjae Oh, Daeil Kim, Myung-Min Oh and Byung-Chun In

systems, can generate optimal light conditions for improving crop yield because of their reduced energy consumption and control of light quality, intensity, and period ( Massa et al., 2008 ). The production of phytochemicals, which are considered major

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Po-Lung Chia and Chieri Kubota

both allow easier grafting and reduce the risk of scion exposure. Also, the authors are aware that commercial propagators often encounter inconsistencies in seedling morphology, possibly as a result of changes in light quality during twilight hours or

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Kui Lin, Zhi Huang and Yong Xu

-related functions ( Lee et al., 2009 ; Nicolle et al., 2004 ; Park et al., 2008 ; Zao et al., 2004 ). In recent years, it has become one of the main vegetable species grown under soilless facility cultivation. Varying effects of light quality on the biomass

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Keun H. Cho, Veronica Y. Laux, Nathan Wallace-Springer, David G. Clark, Kevin M. Folta and Thomas A. Colquhoun

apex basipetally transports down the plant stem and accumulates at the base of cuttings to initiate adventitious roots ( Christiaens et al., 2016 ). Perception of light quality by plants can induce changes in gene expression and hormonal regulation

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

possibility that wavelength selection may also play a significant role in secondary metabolite production ( Lefsrud et al., 2008 ). In a separate study, Li and Kubota (2009) evaluated the impact of light quality on the phytochemical content of baby leaf

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Aisu Gu, Wenfang Liu, Chao Ma, Jin Cui, Richard J. Henny and Jianjun Chen

( Beyramizade et al., 2008 ; Gantait and Mandal, 2010 ; Vargas et al., 2004 ). Additionally, little information is available regarding the effects of light quality on rooting and growth of regenerated adventitious shoots. Light quality has a pronounced effect

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Nihal C. Rajapakse and John W. Kelly

The use of light quality as an alternate method for controlling ornamental plant growth was evaluated using copper sulfate solutions as optical filters, The light passed through CuSO4 solutions had high red/far-red (R/FR) ratio. Plant height and average internode length were significantly reduced by high R/FR light. Plants grown under high R/FR light had smaller leaves and a lower total leaf area but had thicker leaves, as indicated by specific leaf weight, than the control plants. Fresh and dry weights of leaves, stems and roots were reduced by high R/FR light. Dry matter accumulation in leaves was increased by high R/FR light while it was reduced in stems. Exogenous gibberellic acid (GA) application partially overcame the height reduction under high R/FR light indicating that GA biosynthesis maybe affected by light treatment. Results suggests alteration of light quality could be used in controlling ornamental plant growth as an alternate method to conventional chemical growth regulator applications.

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Meriam Karlssonl and Jarle Nilsen

`Ultra Rose Star' petunia plants were germinated and grown at 21C. The study was initiated 26 days after seeding and the photoperiod was 15 h of light and 9 h of darkness. During the initial or ending 90 min of the light period, the plants were exposed to a light quality of a higher (≈2.0) or lower (≈0.8) red (R, 660 nm) to far red (FR, 730 nm) ratio than daylight (R: FR, ≈1.1). Flowering occurred within 65 days from seeding for plants in all treatments. Plants receiving a low R: FR during the initial 90 min of the day had similar internode lengths as those plants receiving a high R: FR at the end of the day. The average internode length of the main stem at flowering was 0.6 ± 0.08 cm for plants receiving a low R: FR in the morning or a high R: FR at the end of the day. In addition, the internodes of those plants exposed to a low R: FR in the morning were longer than on plants receiving a low R: FR at night or a high R: FR in the morning. The average internode length at flowering was 0.4 ± 0.08 cm for plants with an ending low R: FR or a beginning high R: FR light quality of the day.

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Giuliana Mulas and Lyle E. Craker

Variation in light quality is known to modify plant morphology, growth, and chemical constituency in plants. In the present study, the effect of light quality on growth and essential oil composition in rosemary (Rosmarinus officinalis L.) was investigated by comparing plants receiving supplemental red (660 nm) and far-red (730 nm) with each other and with control plants not receiving supplemental light. Except for the supplemental light treatments, all plants were grown under natural light conditions in a greenhouse and received full daylight, averaging 9.23 h/day during the study. The red and far-red light treatments, given as day extensions, started daily 15 min before sunset and continued for 4 h each evening for 4 weeks. No significant differences were observed in biomass yield from the different light treatments, but far-red light caused elongation of internodes and a reduction in the number of leaves in comparison with control and red-light treated plants. Essential oil production was highest in plants grown under far-red light treatments.