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Jakob Markvart, Eva Rosenqvist, Helle Sørensen, Carl-Otto Ottosen, and Jesper M. Aaslyng

during the darkest period of the year, but knowledge of its optimal use for plant production is lacking. Present greenhouse installations typically have limited supplemental light control options with a fixed intensity, so the main question is when to use

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Katrine Heinsvig Kjaer and Carl-Otto Ottosen

Protected plant production systems at northern latitudes largely rely on the use of supplemental light to extend the number of light hours during the day and subsequently the light integral ( Markvart et al., 2009 ). However, because the electricity

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Alexander G. Litvin, Christopher J. Currey, and Lester A. Wilson

phenlypropanoid pathways for secondary metabolites such as essential oils and flavonoids, our objective was to quantify the effect of supplemental light source and spectra on growth, gas exchange, and aroma and flavor of culinary herbs grown hydroponically in a

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

; Bula et al., 1991 ). Moreover, this technology is being adopted by the greenhouse tomato industry as an efficient alternative to high-pressure sodium fixtures commonly used to provide supplemental light during low-light periods of the year. LEDs are

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Seenithamby Lgogendra, Harry W. Janes, Harry Motto, and Gene Giacomelli

With the increasing establishment of greenhouses in conjunction with resource recovery projects (i.e., producing electricity by burning a low cost fuel), greenhouse facilities have access to low cost heat and in many cases electricity as well. In this regard we have been studying the production of spinach with the use of supplemental light.

The goal of the research was to establish the relationship between light and productivity and to also investigate the effects of light on tissue nitrate levels. The data indicate that an average daily PPF of 13-14 moles will provide enough energy to maximize the plant's relative growth rate. It was also found that supplemental HPS light with a PPF of 90 μmoles/m2/sec given over a 12h period will increase the total light received by a plant in mid-winter by about 50% and lead to a 10% decrease in leaf nitrate level.

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Dennis R. Decoteau and Heather H. Friend

The influence of end-of-day (EOD) supplemental light-priming on pepper (Capsicum annuum cv. Keystone Resistant Giant No. 3) transplants was investigated for possible residual growth effects on subsequent plant growth and fruit production. Greenhouse grown pepper transplants were fluorescent light-primed for one hour prior to dusk for three weeks in 1988 and four weeks in 1989 and then transplanted to the field. EOD fluorescent light-priming of pepper plants reduced the height, leaf area, dry weight, fruit number, and fruit weight as compared to non-treated plants prior to first harvest. EOD fluorescent light-priming of pepper transplants had little effect on early and total fruit production. These results suggest that EOD fluorescent light-priming of transplants that affect early pepper growth in the field have little residual influence on subsequent fruit production.

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B. Dansereau, Y. Zhang, S. Gagnon, and H.L. Xu

We examined effects of single-layer glass and double-layer antifog polyethylene films on growth and flowering of stock (Matthiola incana L.) and snapdragon (Antirrhinum majalis L.) in a 3-year period. Stock produced more buds/spike with shorter but thicker stems under single-layer glass and under antifog 3-year polyethylene, and showed higher photosynthetic capacity (P c) under single-layer glass than under other covers regardless of light regimes. Similarly, growth and flowering of snapdragon were significantly better under single-layer glass than in polyethylene houses. A supplemental light of 60 μmol·m-2·s-1 accelerated flowering by 20 to 25 days, improved flower quality, and eliminated differences in plant growth and quality of snapdragon between covering treatments. The P c of stock was lower under all polyethylene covers than under single-layer glass. Among the three antifog polyethylene films, a slightly higher P c was measured for plants under antifog 3-year polyethylene. However, there was no difference among covering treatments in the net photosynthetic rate (P N) at low light level (canopy level). Supplemental lighting reduced P c of stock leaves, especially under single-layer glass, and diminished differences in P c among covering treatments. Dry mass was more influenced by larger leaf area caused by higher leaf temperature than by P N. Overall, antifog 3-year polyethylene was a good covering material when both plant quality and energy saving were considered.

Open access

Geoffrey Weaver and Marc W. van Iersel

., 2019 ). Dimmable LED lights can be interfaced with quantum sensors and control systems, allowing for adaptive lighting control ( van Iersel and Gianino, 2017 ). With adaptive lighting, supplemental light is provided so that the PPFD of sunlight and

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Celina Gómez and Cary A. Mitchell

and yield of tomatoes Acta Hort. 148 547 554 Johnston, T.J. Pendleton, J.W. Peters, D.B. Hicks, D.R. 1969 Influence of supplemental light on apparent photosynthesis, yield and yield components of soybeans ( Glycine max L.) Crop Sci. 9 577 581 Jokinen

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Mohamed Badrane Erhioui, M. Dorais, A. Gosselin, and A.P. Papadopulos

Most experiments on the effects of cover materials on greenhouse crops have provided no real statistical replication for the cover materials. This study was conducted in Winter 1996 at the Harrow Research Centre (Ontario) in nine minihouses covered with glass (single-glass), D-poly (double inflated polyethylene film), and acrylic (rigid twin acrylic panel) offering a 3 × 3 latin square experimental design. Tomato plants (Lycopersicon esculentum L.) were grown in CO2-enriched atmosphere (1000 ppm) under three covering materials, and two light treatments (natural light, and supplemental light at 65 μmol·m–2·s–1) in order to determine the effects of supplemental light on growth, photosynthesis, reproductive carbon allocation, and evolution of carbohydrates synthesis in the diurnal cycles. Overall, the application of supplemental light increased photosynthesis rate, yields, harvest index, total chlorophyll content, and starch accumulation in all treatments, regardless of the type of cover materials. Early marketable yield in acrylic and D-poly houses was higher than in glasshouses. Plants grown under enhanced light intensity flowered earlier and produced 12% more marketable fruits than those grown under natural light. The photosynthetic rate of plants grown in acrylic houses was higher than that of plants grown in glasshouses and those grown in D-poly. The leaves of plants grown in acrylic and D-poly houses had higher dry mass contents and much higher specific leaf weight (>10%) than plants in glasshouses. The net photosynthesis dropped after 3 months of treatment, accompanied by a high accumulation of carbohydrates in the leaves. These results indicate that a photosynthetic acclimation occurs earlier during the growth period suggesting a limitations in carbon metabolism.