scholarly journals Regulating Flowering and Extension Growth of Poinsettia Using Red and Far-red Light-emitting Diodes for End-of-day Lighting

HortScience ◽  
2019 ◽  
Vol 54 (2) ◽  
pp. 323-327 ◽  
Author(s):  
Mengzi Zhang ◽  
Erik S. Runkle
Keyword(s):  
Light Emitting Diode ◽  
Red Light ◽  
Extension Growth ◽  
Moderate Intensity ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Light Emitting ◽  
Potential Alternative ◽  
Ornamental Crops ◽  
The Impact

Manipulating light quality is a potential alternative method of regulating plant height in the commercial production of ornamental crops. In particular, end-of-day (EOD) lighting with a high red (R; 600–700 nm) to far-red (FR; 700–800 nm) ratio (R:FR) can suppress extension growth, whereas a low R:FR can promote it. We investigated the effects of the R:FR and duration of EOD lighting in regulating extension growth and flowering of two poinsettia cultivars, White Glitter and Marble Star. Plants were grown at 20 °C under 9-hour days with or without EOD lighting provided by two types of light-emitting diode bulbs: R+white+FR (subsequently referred to as R+FR) and FR only. The R:FR ratios were 0.73 and 0.04, respectively, and the photon flux density between 400 and 800 nm was adjusted to 2 to 3 μmol·m−2·s–1 at plant canopy. The six EOD lighting treatments were R+FR or FR for 2 or 4 hours, 2 hours of R+FR followed by 2 hours of FR, and 4 hours of R+FR followed by 2 hours of FR. We also investigated the impact of a 4-hour moderate-intensity (13 μmol·m−2·s–1) EOD FR treatment in the second replication. EOD lighting generally increased poinsettia extension growth, with the greatest promotion under the longest lighting periods. There were no differences in days to first bract color and days to anthesis when the 9-hour day was extended by 2 hours, but flowering was delayed under 4- or 6-hour EOD treatments, except for the 2-hour R+FR + 2-hour FR and 4-hour FR treatments. Four hours of moderate-intensity EOD FR greatly promoted extension growth and delayed or prevented bract coloration in both cultivars. We conclude that EOD lighting promotes extension growth of poinsettia, and specifically, EOD FR at a low intensity (2–3 μmol·m−2·s–1) is not perceived as long-day signal, whereas a higher intensity (13 μmol·m−2·s–1) of FR delays flowering.

scholarly journals LightCue: An Innovative Far-Red Light Emitter for Locally Modifying the Spectral Cue in Outdoor Conditions with Global Consequences on Plant Architecture

Plants ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 2483
Author(s):  
Alain Fortineau ◽  
Didier Combes ◽  
Céline Richard-Molard ◽  
Ela Frak ◽  
Alexandra Jullien
Keyword(s):  
Plant Architecture ◽  
Light Emitting Diode ◽  
Red Light ◽  
Inhibitory Effect ◽  
Photosynthetic Photon Flux Density ◽  
High Irradiance ◽  
Light Signal ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Light Emitting

Plasticity of plant architecture is a promising lever to increase crop resilience to biotic and abiotic damage. Among the main drivers of its regulation are the spectral signals which occur via photomorphogenesis processes. In particular, branching, one of the yield components, is responsive to photosynthetic photon flux density (PPFD) and to red to far-red ratio (R:FR), both signals whose effects are tricky to decorrelate in the field. Here, we developed a device consisting of far-red light emitting diode (LED) rings. It can reduce the R:FR ratio to 0.14 in the vicinity of an organ without changing the PPFD in outdoor high irradiance fluctuating conditions, which is a breakthrough as LEDs have been mostly used in non-fluctuant controlled conditions at low irradiance over short periods of time. Applied at the base of rapeseed stems during the whole bolting-reproductive phase, LightCue induced an expected significant inhibitory effect on two basal targeted axillary buds and a strong unexpected stimulatory effect on the overall plant aerial architecture. It increased shoot/root ratio while not modifying the carbon balance. LightCue therefore represents a promising device for progress in the understanding of light signal regulation in the field.

scholarly journals Supplemental Far-red Light-emitting Diode Light Increases Growth of Foxglove Seedlings Under Sole-source Lighting

2020 ◽  
Vol 30 (5) ◽  
pp. 564-569
Author(s):  
Claudia Elkins ◽  
Marc W. van Iersel
Keyword(s):  
Flux Density ◽  
Plant Height ◽  
Light Emitting Diode ◽  
Red Light ◽  
Dry Weight ◽  
Sole Source ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Light Emitting ◽  
Light Intensities

Seedlings may be grown indoors where environmental conditions can be precisely controlled to ensure consistent and reliable production. The optimal spectrum for production under sole-source lighting is currently unknown. Far-red light (λ = 700–800 nm) typically is not a significant part of the spectrum of light-emitting diode (LED) grow lights. However, far-red light is photosynthetically active and can enhance leaf elongation, which may result in larger leaves and increased light interception. We hypothesized that adding far-red light to sole-source lighting would increase the growth of ‘Dalmatian Peach’ foxglove (Digitalis purpurea) seedlings grown under white LED lights, potentially shortening production times. Our objective was to evaluate the effect of far-red light intensities, ranging from 4.0 to 68.8 µmol·m−2·s−1, on the growth and morphology of foxglove seedlings. Foxglove seedlings were grown in a growth chamber with a photosynthetic photon flux density (PPFD) of 186 ± 6.4 μmol·m−2·s−1 and supplemental far-red light intensities ranging from 4.0 to 68.8 µmol·m−2·s−1. As far-red light increased, shoot dry weight, root dry weight, plant height, and plant height/number of leaves increased by 38% (P = 0.004), 20% (P = 0.029), 38% (P = 0.025), and 34% (P = 0.024), respectively, while root weight fraction decreased 16% (P = 0.034). Although we expected supplemental far-red light to induce leaf and/or stem expansion, specific leaf area and compactness (two measures of morphology) were unaffected. Because a 37% increase in total photon flux density (PPFD plus far-red light) resulted in a 34.5% increase in total plant dry weight, the increased growth likely was due to increased photosynthesis rather than a shade-acclimation response. The growth response was linear across the 4.0 to 68.8 µmol·m−2·s−1 range of far-fed light tested, so we were unable to determine a saturating far-red photon flux density.

scholarly journals Growth and Appearance Quality of Four Microgreen Species under Light-emitting Diode Lights with Different Spectral Combinations

HortScience ◽  
2020 ◽  
Vol 55 (9) ◽  
pp. 1399-1405
Author(s):  
Qinglu Ying ◽  
Yun Kong ◽  
Youbin Zheng
Keyword(s):  
Plant Height ◽  
High Intensity ◽  
Light Emitting Diode ◽  
Red Light ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Light Emitting ◽  
Led Light ◽  
Red Led ◽  
Dry Biomass

To investigate plant growth and quality responses to different light spectral combinations, cabbage (Brassica oleracea L. var. capitata f. rubra), kale (Brassica napus L. ‘Red Russian’), arugula (Eruca sativa L.), and mustard (Brassica juncea L. ‘Ruby steak’) microgreens were grown in a controlled environment using sole-source light with six different spectra: 1) FL: cool white fluorescent light; 2) BR: 15% blue and 85% red light-emitting diode (LED); 3) BRFRL: 15% blue, 85% red, and 15.5 µmol·m−2·s−1 far-red (FR) LED; 4) BRFRH: 15% blue, 85% red, and 155 µmol·m−2·s−1 FR LED; 5) BGLR: 9% blue, 6% green, and 85% red LED; and 6) BGHR: 5% blue, 10% green, and 85% red LED. For all the light treatments, the total photosynthetic photon flux density (PPFD) was set at ≈330 µmol·m−2·s−1 under a 17-hour photoperiod, and the air temperature was ≈21 °C with 73% relative humidity (RH). At harvest, BR vs. FL increased plant height for all the tested species except arugula, and enlarged cotyledon area for kale and arugula. Adding high-intensity FR light to blue and red light (i.e., BRFRH) further increased plant height for all species, and cotyledon area for mustard, but it did not affect the fresh or dry biomass for any species. Also, BRFRH vs. BR increased cotyledon greenness for green-leafed species (i.e., arugula, cabbage, and kale), and reduced cotyledon redness for red-leafed mustard. However, BGLR, BGHR, and BRFRL, compared with BR, did not affect plant height, cotyledon area, or fresh or dry biomass. These results suggest that the combination of 15% blue and 85% red LED light can potentially replace FL as the sole light source for indoor production of the tested microgreen species. Combining high-intensity FR light, rather than low-level (≤10%) green light, with blue and red light could be taken into consideration for the optimization of LED light spectral quality in microgreen production under environmental conditions similar to this experiment.

scholarly journals Critical Photoperiod and Optimal Quality of Night Interruption Light for Runner Induction in June-Bearing Strawberries

Agronomy ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1996
Author(s):  
Yali Li ◽  
Jie Xiao ◽  
Jiangtao Hu ◽  
Byoung Ryong Jeong
Keyword(s):  
Red Light ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Light Emitting ◽  
Red Led ◽  
Critical Photoperiod ◽  
Closed Walk ◽  
White Light Emitting Diodes ◽  
Optimal Quality

The optimal photoperiod and light quality for runner induction in strawberries ‘Sulhyang’ and ‘Maehyang’ were investigated. Two experiments were carried out in a semi-closed walk-in growth chamber with 25/15 °C day/night temperatures and a light intensity of 250 μmol·m–2·s–1photosynthetic photon flux density (PPFD) provided from white light-emitting diodes (LEDs). In the first experiment, plants were treated with a photoperiod of either 12, 14, 16, 18, 20, or 22 h In the second experiment, a total of 4 h of night interruption (NI) light at an intensity of 70 μmol·m–2·s–1PPFD provided from either red, blue, green, white, or far-red LED in addition to 11 h short day (SD). The results showed that both ‘Sulhyang’ and ‘Maehyang’ produced runners when a photoperiod was longer than 16 h, and the number of runners induced positively correlated with the length of photoperiod. However, the plant growth, contents of chlorophyll, sugar and starch, and Fv/Fo decreased in a 22 h photoperiod. All qualities of the NI light, especially red light, significantly increased the number of runners and daughter plants induced per plant as compared with those in the SD treatment in both cultivars. In a conclusion, a photoperiod between 16 and 20 h and NI light, especially red NI light, can be used for quality runner induction in both ‘Sulhyang’ and ‘Maehyang’.

scholarly journals Morphological Response of Soybean (Glycine max (L.) Merr.) Cultivars to Light Intensity and Red to Far-Red Ratio

Agronomy ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 428 ◽  
Author(s):  
Tina Hitz ◽  
Jens Hartung ◽  
Simone Graeff-Hönninger ◽  
Sebastian Munz
Keyword(s):  
Cropping Systems ◽  
Light Emitting Diode ◽  
Red Light ◽  
Photosynthetic Photon Flux Density ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Shade Avoidance ◽  
Internode Elongation ◽  
Morphological Response ◽  
Petiole Elongation

In soybean production, the shade avoidance response can affect yield negatively in both mono- and inter-cropping systems due to increased heterogeneity of the crop and lodging. This is mainly regulated by photoreceptors responding to the ratio between red and far-red light (R:FR) and photosynthetic photon flux density (PPFD). In this study, three soybean cultivars were grown under different R:FR and PPFD in a light emitting diode (LED) climate chamber to disentangle the effect of each on morphology and dry matter. Results showed that plant organs were influenced differently and indicated an interaction with the increase in assimilates at high PPFD. Internode elongation was mainly influenced by low PPFD with an additive effect from low R:FR, whereas petiole elongation responded strongly under low R:FR. Hence, petiole elongation can be seen as the main response to the threat of shade (high PPFD and low R:FR) and both petiole and internode elongation as a response to true shade (low PPFD and low R:FR). Interactions between cultivar and light treatment were found for internode length and diameter and leaf mass ratio, which may be unique properties for specific cropping systems.

scholarly journals Light-emitting Diodes Can Replace High-pressure Sodium Lighting for Cut Gerbera Production

HortScience ◽  
2019 ◽  
Vol 54 (1) ◽  
pp. 95-99 ◽  
Author(s):  
Dave Llewellyn ◽  
Katherine Schiestel ◽  
Youbin Zheng
Keyword(s):  
High Pressure ◽  
Treatment Effects ◽  
Light Emitting Diode ◽  
Photosynthetic Photon Flux Density ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Vase Life ◽  
Light Emitting ◽  
Greenhouse Study ◽  
Flower Diameter

A greenhouse study was undertaken to investigate whether light-emitting diode (LED) technology can be used to replace high-pressure sodium (HPS) lighting for cut gerbera production during Canada’s traditional supplemental lighting (SL) season (November to March). The study was carried out at the University of Guelph’s research greenhouse, using concurrent replications of SL treatments within the same growing environment. LED (85% red, 15% blue) and HPS treatment plots were set up to provide equal amounts of supplemental photosynthetically active radiation (PAR) at bench level. This setup was used to assess the production of three cultivars of cut gerbera (Gerbera jamesonii H. Bolus ex Hook.f): Acapulco, Heatwave, and Terra Saffier. There were no treatment differences in SL intensity, with average SL photosynthetic photon flux density (PPFD) and daily light integral (DLI) of 55.9 µmol·m−2·s−1 and 2.3 mol·m−2·d−1, respectively. Flowers harvested from the LED treatment had a 1.9% larger flower diameter in ‘Acapulco’; 4.2% shorter and 3.8% longer stems in ‘Heatwave’ and ‘Terra Saffier’, respectively; and 7.7% and 8.6% higher fresh weights for ‘Acapulco’ and ‘Terra Saffier’, respectively, compared with flowers harvested from the HPS treatment. There were no differences in accumulated total or marketable flower harvests for any of the cultivars. The vase life of ‘Acapulco’ flowers grown under the LED treatment was 2.7 d longer than those grown under the HPS treatment, but there were no SL treatment effects on water uptake for any of the cultivars during the vase life trials. There were no SL treatment effects on specific leaf area for any of the cultivars. There were only minimal treatment differences in leaf, soil, and air temperatures. Cut gerbera crops grown with under LED SL had equivalent or better production and crop quality metrics compared with crops grown under HPS SL.

scholarly journals Regulation of Chloroplast Ultrastructure, Cross-section Anatomy of Leaves, and Morphology of Stomata of Cherry Tomato by Different Light Irradiations of Light-emitting Diodes

HortScience ◽  
2011 ◽  
Vol 46 (2) ◽  
pp. 217-221 ◽  
Author(s):  
Liu XiaoYing ◽  
Guo ShiRong ◽  
Xu ZhiGang ◽  
Jiao XueLei ◽  
Takafumi Tezuka
Keyword(s):  
Light Emitting Diode ◽  
Photosynthetic Apparatus ◽  
Chloroplast Ultrastructure ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Starch Granules ◽  
Cherry Tomato ◽  
Spongy Tissue ◽  
Light Emitting ◽  
Tissue Cells

The chloroplast structural alteration and the photosynthetic apparatus activity of cherry tomato seedlings were investigated under dysprosium lamp [white light control (C)] and six light-emitting diode (LED) light treatments designated as red (R), blue (B), orange (O), green (G), red and blue (RB), and red, blue, and green (RBG) with the same photosynthetic photon flux density (PPFD) (≈320 μmol·m−2·s−1) for 30 days. Compared with C treatment, net photosynthesis of cherry tomato leaves was increased significantly under the light treatments of B, RB, and RBG and reduced under R, O, and G. Chloroplasts of the leaves under the RB treatment were rich in grana and starch granules. Moreover, chloroplasts in leaves under RB seemed to be a distinct boundary between granathylakoid and stromathylakoid. Granathylakoid under treatment B developed normally, but the chloroplasts had few starch granules. Chloroplasts under RBG were similar to those under C. Chloroplasts under R and G were relatively rich in starch granules. However, the distinction between granathylakoid and stromathylakoid under R and G was obscure. Chloroplasts under O were dysplastic. Palisade tissue cells in leaves under RB were especially well-developed and spongy tissue cells under the same treatment were localized in an orderly fashion. However, palisade and spongy tissue cells in leaves under R, O, and G were dysplastic. Stomatal numbers per mm2 were significantly increased under B, RB, and RBG. The current results suggested blue light seemed to be an essential factor for the growth of cherry tomato plants.

scholarly journals Growth of Impatiens, Petunia, Salvia, and Tomato Seedlings under Blue, Green, and Red Light-emitting Diodes

HortScience ◽  
2014 ◽  
Vol 49 (6) ◽  
pp. 734-740 ◽  
Author(s):  
Heidi Marie Wollaeger ◽  
Erik S. Runkle
Keyword(s):  
Light Quality ◽  
Light Emitting Diode ◽  
Red Light ◽  
Morphological Characteristics ◽  
Photon Flux ◽  
Fluorescent Light ◽  
Flower Bud ◽  
Specialty Crops ◽  
Light Emitting ◽  
Shoot Weight

Plant growth and architecture are regulated in part by light quality. We performed experiments to better understand how young plants acclimate to blue (B), green (G), and red (R) light and how those responses can be used to produce plants with desirable morphological characteristics. We grew seedlings of impatiens (Impatiens walleriana), salvia (Salvia splendens), petunia (Petunia ×hybrida), and tomato (Solanum lycopersicum) under six sole-source light-emitting diode (LED) treatments or one cool-white fluorescent treatment that each delivered a photosynthetic photon flux (PPF) of 160 µmol·m−2·s–1 for 18 h·d−1. Leaf number was similar among treatments, but plants grown under 25% or greater B light were 41% to 57% shorter than those under only R light. Plants under R light had 47% to 130% greater leaf area and 48% to 112% greater fresh shoot weight than plants grown under treatments with 25% or greater B. Plants grown under only R had a fresh shoot weight similar to that of those grown under fluorescent light for all species except tomato. In impatiens, flower bud number at harvest generally increased with B light, whereas in tomato, the number of leaflets with intumescences decreased with B light. This research discusses how light quality can be manipulated for desired growth characteristics of young plants, which is important in the production of specialty crops such as ornamentals, herbs, and microgreens.

scholarly journals Flowering, Stem Extension Growth, and Cutting Yield of Foliage Annuals in Response to Photoperiod

HortScience ◽  
2019 ◽  
Vol 54 (4) ◽  
pp. 661-666
Author(s):  
Kellie J. Walters ◽  
Allison A. Hurt ◽  
Roberto G. Lopez
Keyword(s):  
Growth And Development ◽  
Light Emitting Diode ◽  
Stem Elongation ◽  
Growth Index ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Stock Plant ◽  
Light Emitting ◽  
Flowering Stem ◽  
The Aesthetic

Foliage annuals are primarily grown for the aesthetic appeal of their brightly colored, variegated, or patterned leaves rather than for their flowers. Once foliage annuals become reproductive, vegetative growth of many species diminishes or completely ceases and plants can become unappealing. Therefore, the objectives of this study were to quantify how growth and development during production and stock plant cutting yield of bloodleaf (Iresine herbstii), Joseph’s coat (Alternanthera sp.) ‘Brazilian Red Hots’ and ‘Red Threads’, Persian shield (Strobilanthes dyerianus), and variegated potato vine (Solanum jasminoides) are influenced by photoperiod and night interruption (NI) lighting with or without far-red (FR) radiation. Photoperiods consisted of a 9-hour short day (SD) or a 9-hour SD extended to 10, 12, 13, 14, or 16 hours with red (R):white (W):FR light-emitting diode (LED) lamps (R:FR = 0.8) providing a total photon flux density (TPFD) of ≈2 µmol·m−2·s–1 of radiation. In addition, two treatments consisted of a 9-hour SD with a 4-hour NI from lamps containing the same R:W:FR or R:W LEDs (R:FR = 37.4). Bloodleaf plant and Joseph’s coat ‘Brazilian Red Hots’ and ‘Red Threads’ developed inflorescences or flowers under photoperiods ≤12 to 13 hours and were classified as obligate SD plants. Under LEDs providing R:W:FR radiation, stem elongation of reproductive bloodleaf and Joseph’s coat ‘Brazilian Red Hots’ and ‘Red Threads’ increased as photoperiod increased from 9 to 12 hours. In addition, stem elongation of bloodleaf, Joseph’s coat ‘Brazilian Red Hots’ and ‘Red Threads’, and Persian shield and growth index (GI = {plant height + [(diameter 1 + diameter 2)/2]}/2) of bloodleaf and Persian shield was significantly greater under NI with FR radiation than without FR radiation. Fewer or no cuttings were harvested from Joseph’s coat ‘Brazilian Red Hots’ and ‘Red Threads’ under photoperiods ≤12 or ≤13 hours, respectively. To prevent unwanted flowering of bloodleaf plant and Joseph’s coat, a photoperiod ≥14 hours or 4-hour NI must be maintained with LEDs providing either R:W or R:W:FR radiation, however; stem elongation is significantly reduced under R:W LEDs.

scholarly journals Blue Light Monochromatic Irradiation for 12 Hours in Lighting Pattern with Combinations of Blue and Red Light Elongates Young Cos Lettuce Leaves and Promotes Growth under High Daily Light Integral

HortScience ◽  
2021 ◽  
pp. 1-6
Author(s):  
Tomohiro Jishi ◽  
Ryo Matsuda ◽  
Kazuhiro Fujiwara
Keyword(s):  
Flux Density ◽  
Blue Light ◽  
Light Emitting Diode ◽  
Red Light ◽  
Dry Weight ◽  
Photosynthetic Photon Flux Density ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Photosynthetic Photon Flux ◽  
Leaf Elongation

Cos lettuce was grown under different spectral photon flux density distribution (SPFD) change patterns with blue- and/or red light-emitting diode (LED) irradiation with a 24-hour cycle. Twelve treatments were designed with a combination of four relative SPFD (RSPFD) change patterns and three photosynthetic photon flux density (PPFD) levels. The RSPFD change patterns were as follows: BR/BR, simultaneous blue- and red-light irradiation (BR) for 24 h; R/BR, red-light monochromatic irradiation (R) for 12 h followed by 12 hours of BR; B/BR, blue-light monochromatic irradiation (B) for 12 hours followed by 12 hours of BR; and B/R, 12 hours of B followed by 12 hours of R. Each RSPFD change pattern was conducted at three daily average photosynthetic photon flux densities (PPFDave) of 50, 100, and 200 µmol·m−2·s−1. The RSPFD change patterns that included B (B/BR and B/R) resulted in elongated leaves. A low ratio of active phytochrome to total phytochrome under B was considered the reason for leaf elongation. Shoot dry weight was significantly greater under the RSPFD change patterns that included B when the PPFDave was 200 µmol·m−2·s−1. The leaf elongation caused by B would have increased the amount of light received and thereby promoted growth. However, excessive leaf elongation caused the plants to fall, and growth was not promoted under the RSPFD change patterns that included B when the PPFDave was 50 µmol·m−2·s−1. Thus, 12-hour B promoted growth under conditions in which leaf elongation leads to increases in the amount of light received.

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