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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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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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Toshio Shibuya, Junki Komuro, Norio Hirai, Yoshiko Sakamoto, Ryosuke Endo, and Yoshiaki Kitaya

in these systems have shorter shoots than those grown under natural light ( Ohyama et al., 2003 ). The reduced shoot elongation is due to the high R:FR ratio of typical commercial FLs, which emit little FR irradiation. Thus, increasing the FR content

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David Llewellyn, Youbin Zheng, and Mike Dixon

preferential absorption of red light by the upper plant canopy. It has been postulated, by various growers, that reductions in plant quality when grown below HB crops are due to a combination of insufficient PAR and reductions in the R:FR at the lower crop

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James E. Faust, Pamela C. Korczynski, and Uttara C. Samarakoon

length, and reduces lateral branching ( Runkle and Heins, 2001 ; Smith, 1982 ). Hypothetically, plants grown in hanging baskets will reduce the DLI and the R:FR environment for the crop underneath, thus increasing stem elongation and decreasing crop

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Libertad Mascarini, Gabriel A. Lorenzo, and Fernando Vilella

In roses (Rosa ×hybrida L.), the bending of branches is a technique that modifies the canopy of the plant and could affect such parameters as the leaf area index (LAI), the quality of reflected light, and the water index (WI) of the plant. The measurement of spectral reflectance with remote sensors is a nondestructive, quick, and simple method to study these parameters. The aim of this paper is to quantify the modification of reflected radiation quality, the LAI and the water index of the plant with different canopies, and its impact on flowering and the number and quality of flowers produced. In R. ×hybrida `Terracotta', using the spectral crop reflectance, the red: far red ratio [red (R) = 680 nm; far red (FR) = 730 nm], percentage of blue light of reflected radiation, and vegetation indices [normalized difference vegetation index (NDVI), simple ratio index (SRI), water index (WI)] were calculated in two architectural managements: traditional (upright hedge) and bent shoot. NDVI had a greater correlation with LAI than SRI (r2 = 0.98 and 0.85, respectively), but SRI was more reliable for LAI values of 1 to 3.5. The bent shoot system compared to the traditional one decreased the R:FR ratio of reflected radiation and increased LAI and plant water content. These changes were related to a higher commercial quality of the flowers (longer flowering shoots with a larger stem diameter and fresh weight), although there was no significant difference in the number of flowers harvested. The period that showed the largest difference in the quality of the flower using the bent shoot system had a LAI of 2.8 vs. 1.8 with traditional management and a marked reduction in the R:FR of the light reflected by bent plants. The bent shoot system advanced the peak production by 1 month at the end of winter and improved the flowers at a time when sun radiation is limiting factor for production.

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Jasmine Jenji Mah, David Llewellyn, and Youbin Zheng

substantial photomorphological effects. For example, the red [R (600–700 nm)] to far red [FR (700–800 nm)] photon flux ratio (R:FR) can dramatically affect plant morphology in sole-source lighting scenarios ( Carvalho and Folta, 2014 ; Demotes-Mainard et al

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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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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