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Nihal C. Rajapakse and John W. Kelly

The response of chrysanthemum plants to varying R:FR ratios and phytochrome photoequilibrium values (Ø = Pfr/Ptot) was evaluated by growing plants under 6%, or 40% CuSO4 and water spectral filters. Using a narrow band-width (R = 655-665 and FR = 725-735 nm) and a broad bandwidth (R = 600-700 and FR = 700-800 nm) for R:FR calculation, 6% CUSO4 filter transmitted light with greater R:FR (3.9) and grater Ø (0.81) than 40% CuSO4 or water filters. Light transmitted through 40% CuSO4 and water filters had a similar narrow band R:FR ratio (1.2), but the broad band R:FR ratio (2.1) of 40% CuSO4 filter was higher than water filter. Estimated Ø value was similar for both water and 40% CuSO4 filters. Final height of plants grown in CuSO4 chambers was about 30% less than the plants in control chambers. The results suggest that broad band R:FR ratio correlated more closely to plant response than the narrow band R:FR ratio.

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Toshio Shibuya, Ryosuke Endo, Yoshiaki Kitaya, and Saki Hayashi

), thereby improving tolerance to mechanical stress including wind damage ( Latimer and Mitchell, 1988 ). The reduction of shoot elongation is due to the R:FR of the filtered light, which is higher than that of sunlight due to the film’s selective absorption

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Janni Bjerregaard Lund, Theo J. Blom, and Jesper Mazanti Aaslyng

-red ratio (R:FR ratio)] have been shown to limit elongation growth ( Khattak and Pearson, 2006 ; Mortensen and Strømme, 1987 ; Rajapakse and Kelly, 1992 ). However, the effect of changes in light quality is not always positive. A decrease in the R:FR ratio

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Jasmine J. Mah, David Llewellyn, and Youbin Zheng

ratio (R:FR) at lower crop level because of the presence and growth of HBs. The photosynthetic photon flux ( PPF , μmol·m −2 ·s −1 between 400 and 700 nm), measured inside the greenhouses just above the HB level, were reduced by 40% to 53% relative to

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Kaori Itagaki, Toshio Shibuya, Motoaki Tojo, Ryosuke Endo, and Yoshiaki Kitaya

powdery mildew fungus ( P. xanthii ) was suppressed on cucumber ( C. sativus ) seedlings acclimatized to higher R:FR (>7.0) than that of natural light (R:FR ≈ 1.2) ( Shibuya et al., 2011 ). Structural properties of the cucumber leaves caused by

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Daedre S. Craig and Erik S. Runkle

absorption at 730 nm) absorbing form, P R and P FR , respectively ( Hayward, 1984 ; Sager et al., 1988 ). The R:FR incident on the plant influences the phytochrome photoequilibria (P FR /P R+FR ) within the plant. On absorbing R light, P R converts mainly

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Toshio Shibuya, Kaori Itagaki, Motoaki Tojo, Ryosuke Endo, and Yoshiaki Kitaya

., 2002 ; Khanam et al., 2005 ; Rahman et al., 2002 ; Schuerger and Brown, 1997 ; Wang et al., 2010 ). Here, we focused on the R:FR of typical commercial fluorescent lamps commonly used in CTPS. Cucumber seedlings grown under fluorescent lamps with a

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Mengzi Zhang and Erik S. Runkle

qualities on plant height. For example, poinsettias were grown under cladding materials of neutral density (control) (R:FR = 1.07) or FR, R, and blue (400–500 nm) plastic filters, creating an FR-deficient, R-deficient, and blue-deficient environment with an

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Toshio Shibuya, Ryosuke Endo, Yuki Kitamura, Yoshiaki Kitaya, and Nobuaki Hayashi

fluorescent lamps used in these systems have less shoot elongation than those grown under natural light ( Ohyama et al., 2003 ). The reduced shoot elongation seems to be the result of the high red to far-red ratios (R:FR) of typical commercial fluorescent

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Diego A. Mata and Javier F. Botto

correlates with the R/FR ratios in a wide range of light conditions ( Smith, 1981 ). Low R/FR ratios induce several responses in plants known as shade avoidance syndrome that include the promotion of elongation of internodes, petioles, and leaves; the