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

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.

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

HortScience ◽

10.21273/hortsci13270-18 ◽

2019 ◽

Vol 54 (1) ◽

pp. 95-99 ◽

Cited By ~ 2

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.

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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 ◽

10.21273/hortsci.46.2.217 ◽

2011 ◽

Vol 46 (2) ◽

pp. 217-221 ◽

Cited By ~ 41

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.

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

Plants ◽

10.3390/plants10112483 ◽

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.

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

HortTechnology ◽

10.21273/horttech04661-20 ◽

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.

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Evaluation of the Light Environment of a Plant Factory with Artificial Light by Using an Optical Simulation

Agronomy ◽

10.3390/agronomy10111663 ◽

2020 ◽

Vol 10 (11) ◽

pp. 1663

Author(s):

Kota Saito ◽

Yasuhiro Ishigami ◽

Eiji Goto

Keyword(s):

Light Emitting Diode ◽

Three Dimensional ◽

Photosynthetic Photon Flux Density ◽

Design Parameters ◽

Photon Flux ◽

Photon Flux Density ◽

Optical Simulation ◽

Artificial Light ◽

Light Emitting ◽

Three Dimensional Models

Good lighting designs can establish suitable light environments in plant factories with artificial light (PFALs). This study used optical simulations to investigate the effects of lighting designs in PFALs on the coefficient of variation of light absorption (Φp; CV) of individual plants and the coefficient of utilization for the lighting system (U). Three-dimensional models of canola plants were constructed using a scanner, and a 3D model of the cultivation shelf was also created. The photosynthetic photon flux density (PPFD) distribution in the cultivation spaces, with or without the canola plants, was estimated first. The PPFD on the canola leaves was then estimated when the lighting design parameters, such as number, distance, height, radiant flux, and light distribution of the light-emitting diode lamps, were modified. The optical simulation showed good accuracy when estimating the PPFD distributions on the cultivation shelf and the leaves of the canola plants. The results showed that while the PPFD distribution across the growing area was uniform, it was not on a plant canopy. By appropriately controlling the layout of the lamps and their directionality, lighting designs that reduce Φp; CV and improve U in PFAL could be possible, and optical simulations could help to develop them.

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Side Lighting Enhances Morphophysiology by Inducing More Branching and Flowering in Chrysanthemum Grown in Controlled Environment

International Journal of Molecular Sciences ◽

10.3390/ijms222112019 ◽

2021 ◽

Vol 22 (21) ◽

pp. 12019

Author(s):

Jingli Yang ◽

Byoung Ryong Jeong

Keyword(s):

Plant Growth ◽

Growth And Development ◽

Growth Parameters ◽

Photosynthetic Photon Flux Density ◽

Chrysanthemum Morifolium ◽

Photon Flux ◽

Photon Flux Density ◽

Light Emitting ◽

Closed Type ◽

Chrysanthemum Morifolium Ramat

Light is one of the most important factors that influence plant growth and development. This study was conducted to examine how lighting direction affects plant morphophysiology by investigating plant growth parameters, leaf anatomy, epidermal cell elongation, stomatal properties, chloroplast arrangement, and physiological changes. In closed-type plant factory units, the rooted cuttings of two chrysanthemum (Chrysanthemum morifolium Ramat.) cultivars, ‘Gaya Glory’ and ‘Pearl Egg’, were subjected to a 10 h photoperiod with a 300 μmol∙m−2∙s−1 photosynthetic photon flux density (PPFD) provided by light-emitting diodes (LEDs) from three directions relative to the plant including the top, side, and bottom. Compared to the top or bottom lighting, the side lighting greatly enhanced the plant growth, improved the leaf internal structure and chloroplast arrangement, induced small stomata with a higher density, and promoted stomatal opening, which is associated with an increased stomatal conductance and photosynthetic efficiency. It is worth noting that the side lighting significantly enhanced the induction of branching and flowering for both cultivars., The plants grown with side lighting consistently exhibited the greatest physiological performance. We conclude that the lighting direction had a profound effect on the morphophysiological characteristics of chrysanthemum, and that side lighting dramatically promoted their growth and development, especially in their branching and flowering.

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

HortScience ◽

10.21273/hortsci14925-20 ◽

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.

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

HortScience ◽

10.21273/hortsci13630-18 ◽

2019 ◽

Vol 54 (2) ◽

pp. 323-327 ◽

Cited By ~ 3

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.

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Light Emitting Diodes (LEDs) as Agricultural Lighting: Impact and Its Potential on Improving Physiology, Flowering, and Secondary Metabolites of Crops

Sustainability ◽

10.3390/su13041985 ◽

2021 ◽

Vol 13 (4) ◽

pp. 1985

Author(s):

Musa Al Murad ◽

Kaukab Razi ◽

Byoung Ryong Jeong ◽

Prakash Muthu Arjuna Samy ◽

Sowbiya Muneer

Keyword(s):

Crop Production ◽

Morphological Changes ◽

Light Emitting Diode ◽

Crop Productivity ◽

Photon Flux ◽

Flower Initiation ◽

Nutrient Metabolism ◽

Light Emitting ◽

Cultivation Systems ◽

Lighting Systems

A reduction in crop productivity in cultivable land and challenging environmental factors have directed advancement in indoor cultivation systems, such that the yield parameters are higher in outdoor cultivation systems. In wake of this situation, light emitting diode (LED) lighting has proved to be promising in the field of agricultural lighting. Properties such as energy efficiency, long lifetime, photon flux efficacy and flexibility in application make LEDs better suited for future agricultural lighting systems over traditional lighting systems. Different LED spectrums have varied effects on the morphogenesis and photosynthetic responses in plants. LEDs have a profound effect on plant growth and development and also control key physiological processes such as phototropism, the immigration of chloroplasts, day/night period control and the opening/closing of stomata. Moreover, the synthesis of bioactive compounds and antioxidants on exposure to LED spectrum also provides information on the possible regulation of antioxidative defense genes to protect the cells from oxidative damage. Similarly, LEDs are also seen to escalate the nutrient metabolism in plants and flower initiation, thus improving the quality of the crops as well. However, the complete management of the irradiance and wavelength is the key to maximize the economic efficacy of crop production, quality, and the nutrition potential of plants grown in controlled environments. This review aims to summarize the various advancements made in the area of LED technology in agriculture, focusing on key processes such as morphological changes, photosynthetic activity, nutrient metabolism, antioxidant capacity and flowering in plants. Emphasis is also made on the variation in activities of different LED spectra between different plant species. In addition, research gaps and future perspectives are also discussed of this emerging multidisciplinary field of research and its development.

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Different LED Light Wavelengths and Photosynthetic Photon Flux Density Effect on Colletotrichum acutatum Growth

Plants ◽

10.3390/plants11010143 ◽

2022 ◽

Vol 11 (1) ◽

pp. 143

Author(s):

Neringa Rasiukevičiūtė ◽

Aušra Brazaitytė ◽

Viktorija Vaštakaitė-Kairienė ◽

Alma Valiuškaitė

Keyword(s):

Flux Density ◽

Photosynthetic Photon Flux Density ◽

Growth Characteristics ◽

Colletotrichum Acutatum ◽

Photon Flux ◽

Photon Flux Density ◽

Photosynthetic Photon Flux ◽

Light Emitting ◽

Led Light ◽

Fungus Growth

The study aimed to evaluate the effect of different photon flux density (PFD) and light-emitting diodes (LED) wavelengths on strawberry Colletotrichum acutatum growth characteristics. The C. acutatum growth characteristics under the blue 450 nm (B), green 530 nm (G), red 660 nm (R), far-red 735 nm (FR), and white 5700 K (W) LEDs at PFD 50, 100 and 200 μmol m−2 s−1 were evaluated. The effect on C. acutatum mycelial growth evaluated by daily measuring until five days after inoculation (DAI). The presence of conidia and size (width and length) evaluated after 5 DAI. The results showed that the highest inhibition of fungus growth was achieved after 1 DAI under B and G at 50 μmol m−2 s−1 PFD. Additionally, after 1–4 DAI under B at 200 μmol m−2 s−1 PFD. The lowest conidia width was under FR at 50 μmol m−2 s−1 PFD and length under FR at 100 μmol m−2 s−1 PFD. Various LED light wavelengths influenced differences in C. acutatum colonies color. In conclusion, different photosynthetic photon flux densities and wavelengths influence C. acutatum growth characteristics. The changes in C. acutatum morphological and phenotypical characteristics could be related to its ability to spread and infect plant tissues. This study’s findings could potentially help to manage C. acutatum by LEDs in controlled environment conditions.

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