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Claudia Elkins and Marc W. van Iersel

album L. by shadelight: The effect of light quality (total fluence rate) and light quality (red:far-red ratio) New Phytol. 88 239 248 Park, Y. Runkle, E.S. 2016 Investigating the merit of including far-red radiation in the production of ornamental

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M.R. Evans and G. Li

The annual bedding plants `Dazzler Rose Star' impatiens (Impatiens wallerana), `Cooler Blush' vinca (Catharanthus roseus), `Orbit Cardinal' geranium (Pelargonium × hotorum), `Janie Bright Yellow' marigold (Tagetes patula) and `Bingo Azure' pansy (Viola tricolor) were grown on germination papers treated with deionized water (DI), 2500 or 5000 mg·L-1 (ppm) humic acid (HA) or nutrient control (NC) solutions. Seedlings grown on HA-treated germination papers had higher dry root weights than those grown on DI or NC-treated germination papers. Except for impatiens, seedlings germinated on HA-treated germination papers had higher lateral root numbers and higher total lateral root lengths than those grown on DI and NC-treated germination papers. Impatiens grown on NC-treated germination papers had higher lateral root numbers than those grown on DI or HA-treated germination papers. Overall, lateral root numbers for impatiens were higher for seedlings germinated on HA-treated papers than DI or NC-treated papers and highest lateral root numbers occurred on those impatiens germinated on papers treated with 5000 mg·L-1 HA. Except for geranium, seedlings grown in HA-amended sphagnum-peat-based substrates had similar dry root and dry shoot weights as those grown in unamended substrates. Geranium seedlings grown in HA-amended sphagnum peat-based substrates had significantly higher dry root weights than those grown in unamended substrates. However, dry shoot weights of geranium grown in HA-amended sphagnum peat-based substrates were similar to those grown in unamended substrates.

Open access

Claudia Elkins and Marc W. van Iersel

Supplemental light can increase growth and accelerate production of greenhouse crops, but it can be expensive if not provided in a way that promotes efficient use of the light. Dimmable light-emitting diode (LED) fixtures have the potential to reduce lighting costs because the output can be precisely controlled to meet crop needs. Because light is used more efficiently to drive photosynthesis at lower photosynthetic photon flux densities (PPFDs), we hypothesized that providing Rudbeckia fulgida var. sullivantii ‘Goldsturm’ seedlings with the same daily light integral (DLI), spread out over a longer photoperiod and at lower PPFDs, should improve growth. A DLI of 12 mol·m−2·d−1 was provided in a greenhouse over 12, 15, 18, or 21-hour photoperiods from a combination of sunlight and supplemental light from LEDs, using adaptive lighting control. Plants grown without supplemental light had an ≈12-hour photoperiod and received an average DLI of 5 mol·m−2·d−1, ≈58% less light than the four lighting treatments. Lengthening the photoperiod from 12 to 21 hours increased shoot dry mass (30%), root dry mass (24%), plant height (14%), leaf area (16%), and chlorophyll content index (48%), and decreased specific leaf area (26%). There was no significant effect of photoperiod on root mass fraction or compactness. Growth parameters of plants without supplemental light were 26% to 90% smaller compared with those in the 12-hour photoperiod treatment. Treatment effects on canopy size, seen as early as 2 weeks into the study, were correlated with final shoot dry mass. Longer photoperiods did not induce a shade-avoidance response, based on specific leaf area and compactness data. The 24% increase in root dry mass for the plants in the 21-hour photoperiod suggests that cropping cycles can be shortened by 1 to 2 weeks compared with the 12-hour photoperiod. This could result in more crop turns per year and increased profits. In addition, fewer lights would be needed for adequate growth, reducing the capital cost of the lighting system.

Open access

John L. Griffis Jr.

session ended with trainees removing germinated ornamental seedlings (zinnia) from day 1 and planting some of them up in small plastic bags filled with soil. Participants were encouraged to take the rest of the seedlings home (each student started with ≈25

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Joshua K. Craver, Jennifer K. Boldt, and Roberto G. Lopez

influence quality and flowering in petunia and pansy HortScience 45 1332 1337 Park, Y. Runkle, E.S. 2016 Investigating the merit of including far-red radiation in the production of ornamental seedlings grown under sole-source lighting Acta Hort. 1134 259 266

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Jeremy R. Pinto, Rhiannon A. Chandler, and R. Kasten Dumroese

-irrigated seedlings, similar to results with vegetable and ornamental seedlings ( Ahmed et al., 2000 ; Argo and Biernbaum, 1995 ; Kang et al., 2004 ; Morvant et al., 2001 ; Santamaria et al., 2003 ; Wilson et al., 2003 ). Our data show that subirrigated

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W. Garrett Owen and Roberto G. Lopez

vitro callus formation and growth. There is little known about the effects of light quality from SSL on callus formation and growth and on initial ARF during vegetative propagation of herbaceous perennials. The recent interest in SSL LEDs for ornamental

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Rhuanito Soranz Ferrarezi, Geoffrey Matthew Weaver, Marc W. van Iersel, and Roberto Testezlaf

-and-flow benches for ornamental seedling and plant production. Photo courtesy of Midwest GRO Master Inc. (St. Charles, IL). (B) Small swimming pools adapted for large deciduous seedling production in containers ( Schmal et al., 2007 ). © 2007 by the Board of

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Joshua K. Craver, Krishna S. Nemali, and Roberto G. Lopez

developmental responses to light quality in a horticultural context Acta Hort. 956 131 139 Wollaeger, H.M. Runkle, E.S. 2014 Producing commercial-quality ornamental seedlings under sole-source LED lighting Acta Hort. 1037 269 276 Yorio, N.C. Goins, G.D. Kagie, H