Editorial

3 pages, 200 KiB

Open AccessEditorial

The Effects of LED Light Spectra and Intensities on Plant Growth

by Valeria Cavallaro and Rosario Muleo

Plants 2022, 11(15), 1911; https://doi.org/10.3390/plants11151911 - 23 Jul 2022

Cited by 5 | Viewed by 2735

Light is an electromagnetic radiation that occurs in a narrow range of over an extremely wide range of wavelengths, from gamma rays with wavelengths to radio waves measured in meters [...] Full article

(This article belongs to the Special Issue The Effects of LED Light Spectra and Intensities on Plant Growth)

Research

Jump to: Editorial, Review

18 pages, 3740 KiB

Open AccessArticle

Effect of Light Intensity on Morphology, Photosynthesis and Carbon Metabolism of Alfalfa (Medicago sativa) Seedlings

by Wei Tang, Haipeng Guo, Carol C. Baskin, Wangdan Xiong, Chao Yang, Zhenyi Li, Hui Song, Tingru Wang, Jianing Yin, Xueli Wu, Fuhong Miao, Shangzhi Zhong, Qibo Tao, Yiran Zhao and Juan Sun

Plants 2022, 11(13), 1688; https://doi.org/10.3390/plants11131688 - 25 Jun 2022

Cited by 31 | Viewed by 7493

Abstract

To understand how light intensity influences plant morphology and photosynthesis in the forage crop alfalfa (Medicago sativa L. cv. Zhongmu 1), we investigated changes in leaf angle orientation, chlorophyll fluorescence, parameters of photosynthesis and expression of genes related to enzymes involved in [...] Read more.

To understand how light intensity influences plant morphology and photosynthesis in the forage crop alfalfa (Medicago sativa L. cv. Zhongmu 1), we investigated changes in leaf angle orientation, chlorophyll fluorescence, parameters of photosynthesis and expression of genes related to enzymes involved in photosynthesis, the Calvin cycle and carbon metabolism in alfalfa seedlings exposed to five light intensities (100, 200, 300, 400 and 500 μmol m⁻² s⁻¹) under hydroponic conditions. Seedlings grown under low light intensities had significantly increased plant height, leaf hyponasty, specific leaf area, photosynthetic pigments, leaf nitrogen content and maximal PSII quantum yield, but the increased light-capturing capacity generated a carbon resource cost (e.g., decreased carbohydrates and biomass accumulation). Increased light intensity significantly improved leaf orientation toward the sun and upregulated the genes for Calvin cycle enzymes, thereby increasing photosynthetic capacity. Furthermore, high light (400 and 500 μmol m⁻² s⁻¹) significantly enhanced carbohydrate accumulation, accompanied by gene upregulation and increased activity of sucrose and starch-synthesis-related enzymes and those involved in carbon metabolism. Together, these results advance our understanding of morphological and physiological regulation in shade avoidance in alfalfa, which would guide the identification of suitable spatial planting patterns in the agricultural system. Full article

(This article belongs to the Special Issue The Effects of LED Light Spectra and Intensities on Plant Growth)

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16 pages, 4438 KiB

Open AccessArticle

Effects of Light Spectral Quality on Photosynthetic Activity, Biomass Production, and Carbon Isotope Fractionation in Lettuce, Lactuca sativa L., Plants

by Ivan G. Tarakanov, Daria A. Tovstyko, Maxim P. Lomakin, Alexander S. Shmakov, Nikolay N. Sleptsov, Alexander N. Shmarev, Vladimir A. Litvinskiy and Alexander A. Ivlev

Plants 2022, 11(3), 441; https://doi.org/10.3390/plants11030441 - 05 Feb 2022

Cited by 22 | Viewed by 3591

Abstract

The optimization of plant-specific LED lighting protocols for indoor plant growing systems needs both basic and applied research. Experiments with lettuce, Lactuca sativa L., plants using artificial lighting based on narrow-band LEDs were carried out in a controlled environment. We investigated plant responses [...] Read more.

The optimization of plant-specific LED lighting protocols for indoor plant growing systems needs both basic and applied research. Experiments with lettuce, Lactuca sativa L., plants using artificial lighting based on narrow-band LEDs were carried out in a controlled environment. We investigated plant responses to the exclusion of certain spectral ranges of light in the region of photosynthetically active radiation (PAR); in comparison, the responses to quasimonochromatic radiation in the red and blue regions were studied separately. The data on plant phenotyping, photosynthetic activity determination, and PAM fluorometry, indicating plant functional activity and stress responses to anomalous light environments, are presented. The study on carbon isotopic composition of photoassimilates in the diel cycle made it possible to characterize the balance of carboxylation and photorespiration processes in the leaves, using a previously developed oscillatory model of photosynthesis. Thus, the share of plant photorespiration (related to plant biomass enrichment with ¹³C) increased in response to red-light action, while blue light accelerated carboxylation (related to ¹²C enrichment). Blue light also reduced water use efficiency. These data are supported by the observations from the light environments missing distinct PAR spectrum regions. The fact that light of different wavelengths affects the isotopic composition of total carbon allowed us to elucidate the nature of its action on the organization of plant metabolism. Full article

(This article belongs to the Special Issue The Effects of LED Light Spectra and Intensities on Plant Growth)

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17 pages, 2144 KiB

Open AccessArticle

Daytime or Edge-of-Daytime Intra-Canopy Illumination Improves the Fruit Set of Bell Pepper at Passive Conditions in the Winter

by Vivekanand Tiwari, Itzhak Kamara, Kira Ratner, Yair Many, Victor Lukyanov, Carmit Ziv, Ziva Gilad, Itzhak Esquira and Dana Charuvi

Plants 2022, 11(3), 424; https://doi.org/10.3390/plants11030424 - 04 Feb 2022

Cited by 2 | Viewed by 1909

Abstract

Optimal light conditions ensure the availability of sufficient photosynthetic assimilates for supporting the survival and growth of fruit organs in crops. One of the growing uses of light-emitting diodes (LEDs) in horticulture is intra-canopy illumination or LED-interlighting, providing supplemental light for intensively cultivated [...] Read more.

Optimal light conditions ensure the availability of sufficient photosynthetic assimilates for supporting the survival and growth of fruit organs in crops. One of the growing uses of light-emitting diodes (LEDs) in horticulture is intra-canopy illumination or LED-interlighting, providing supplemental light for intensively cultivated crops directly within their canopies. Originally developed and applied in environmentally controlled greenhouses in northern latitude countries, this technique is nowadays also being tested and studied in other regions of the world such as the Mediterranean region. In the present work, we applied intra-canopy illumination for bell pepper grown in passive high tunnels in the Jordan Valley using a commercial LED product providing cool-white light. The study included testing of daytime (‘LED-D’) and edge-of-daytime (‘LED-N’) illumination, as well as a detailed characterization of fruit set and fruit survival throughout the growth season. We found that both light regimes significantly improved the fruit set and survival during winter, with some benefit of LED-N illumination. Notably, we found that western-facing plants of illuminated sections had a higher contribution toward the increased winter fruit set and spring yield than that of illuminated eastern-facing plants. Greater plant height and fresh weight of western-facing plants of the illuminated sections support the yield results. The differences likely reflect higher photosynthetic assimilation of western-facing plants as compared to eastern-facing ones, due to the higher daily light integral and higher canopy temperature of the former. This study provides important implications for the use of intra-canopy lighting for crops grown at passive winter conditions and exemplifies the significance of geographical positioning, opening additional avenues of investigation for optimization of its use for improving fruit yield under variable conditions. Full article

(This article belongs to the Special Issue The Effects of LED Light Spectra and Intensities on Plant Growth)

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23 pages, 17842 KiB

Open AccessArticle

Development and Implementation of an IoT-Enabled Optimal and Predictive Lighting Control Strategy in Greenhouses

by Shirin Afzali, Sahand Mosharafian, Marc W. van Iersel and Javad Mohammadpour Velni

Plants 2021, 10(12), 2652; https://doi.org/10.3390/plants10122652 - 02 Dec 2021

Cited by 12 | Viewed by 5492

Abstract

Global population growth has increased food production challenges and pushed agricultural systems to deploy the Internet of Things (IoT) instead of using conventional approaches. Controlling the environmental parameters, including light, in greenhouses increases the crop yield; nonetheless, the electricity cost of supplemental lighting [...] Read more.

Global population growth has increased food production challenges and pushed agricultural systems to deploy the Internet of Things (IoT) instead of using conventional approaches. Controlling the environmental parameters, including light, in greenhouses increases the crop yield; nonetheless, the electricity cost of supplemental lighting can be high, and hence, the importance of applying cost-effective lighting methods arises. In this research paper, a new optimal supplemental lighting approach was developed and implemented in a research greenhouse by adopting IoT technology. The proposed approach minimizes electricity cost by leveraging a Markov-based sunlight prediction, plant light needs, and a variable electricity price profile. Two experimental studies were conducted inside a greenhouse with “Green Towers” lettuce (Lactuca sativa) during winter and spring in Athens, GA, USA. The experimental results showed that compared to a heuristic method that provides light to reach a predetermined threshold at each time step, our strategy reduced the cost by 4.16% and 33.85% during the winter and spring study, respectively. A paired t-test was performed on the growth parameter measurements; it was determined that the two methods did not have different results in terms of growth. In conclusion, the proposed lighting approach reduced electricity cost while maintaining crop growth. Full article

(This article belongs to the Special Issue The Effects of LED Light Spectra and Intensities on Plant Growth)

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22 pages, 5751 KiB

Open AccessFeature PaperArticle

Monochromic Radiations Provided by Light Emitted Diode (LED) Modulate Infection and Defense Response to Fire Blight in Pear Trees

by Tiziana Sgamma, Ivano Forgione, Francesca Luziatelli, Calogero Iacona, Roberto Mancinelli, Brian Thomas, Maurizio Ruzzi and Rosario Muleo

Plants 2021, 10(9), 1886; https://doi.org/10.3390/plants10091886 - 12 Sep 2021

Cited by 5 | Viewed by 2456

Abstract

Pathogenesis-related (PR) proteins are part of the systemic signaling network that perceives pathogens and activates defenses in the plant. Eukaryotic and bacterial species have a 24-h ‘body clock’ known as the circadian rhythm. This rhythm regulates an organism’s life, modulating the activity of [...] Read more.

Pathogenesis-related (PR) proteins are part of the systemic signaling network that perceives pathogens and activates defenses in the plant. Eukaryotic and bacterial species have a 24-h ‘body clock’ known as the circadian rhythm. This rhythm regulates an organism’s life, modulating the activity of the phytochromes (phys) and cryptochromes (crys) and the accumulation of the corresponding mRNAs, which results in the synchronization of the internal clock and works as zeitgeber molecules. Salicylic acid accumulation is also under light control and upregulates the PR genes expression, increasing plants’ resistance to pathogens. Erwinia amylovora causes fire blight disease in pear trees. In this work, four bacterial transcripts (erw1-4), expressed in asymptomatic E. amylovora-infected pear plantlets, were isolated. The research aimed to understand how the circadian clock, light quality, and related photoreceptors regulate PR and erw genes expression using transgenic pear lines overexpressing PHYB and CRY1 as a model system. Plantlets were exposed to different circadian conditions, and continuous monochromic radiations (Blue, Red, and Far-Red) were provided by light-emitting diodes (LED). Results showed a circadian oscillation of PR10 gene expression, while PR1 was expressed without clear evidence of circadian regulation. Bacterial growth was regulated by monochromatic light: the growth of bacteria exposed to Far-Red did not differ from that detected in darkness; instead, it was mildly stimulated under Red, while it was significantly inhibited under Blue. In this regulatory framework, the active form of phytochrome enhances the expression of PR1 five to 15 fold. An ultradian rhythm was observed fitting the zeitgeber role played by CRY1. These results also highlight a regulating role of photoreceptors on the expression of PRs genes in non-infected and infected plantlets, which influenced the expression of erw genes. Data are discussed concerning the regulatory role of photoreceptors during photoperiod and pathogen attacks. Full article

(This article belongs to the Special Issue The Effects of LED Light Spectra and Intensities on Plant Growth)

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23 pages, 3833 KiB

Open AccessArticle

Light Spectra and Root Stocks Affect Response of Greenhouse Tomatoes to Long Photoperiod of Supplemental Lighting

by Jason Lanoue, Alyssa Thibodeau, Celeste Little, Jingming Zheng, Bernard Grodzinski and Xiuming Hao

Plants 2021, 10(8), 1674; https://doi.org/10.3390/plants10081674 - 14 Aug 2021

Cited by 11 | Viewed by 2712

Abstract

Plant biomass and yield are largely dictated by the total amount of light intercepted by the plant (daily light integral (DLI)—intensity × photoperiod). It is more economical to supply the desired DLI with a long photoperiod of low-intensity light because it uses fewer [...] Read more.

Plant biomass and yield are largely dictated by the total amount of light intercepted by the plant (daily light integral (DLI)—intensity × photoperiod). It is more economical to supply the desired DLI with a long photoperiod of low-intensity light because it uses fewer light fixtures, reducing capital costs. Furthermore, heat released by the light fixtures under a long photoperiod extended well into the night helps to meet the heating requirement during the night. However, extending the photoperiod beyond a critical length (>17 h) may be detrimental to production and lead to leaf chlorosis and a reduction in leaf growth and plant vigor in greenhouse tomato production. It is known that red light can increase leaf growth and plant vigor, as can certain rootstocks, which could compensate for the loss in plant vigor and leaf growth from long photoperiods. Therefore, this study investigated the response of tomatoes grafted onto different rootstocks to a long photoperiod of lighting under red and other light spectra. Tomato plants ‘Trovanzo’ grafted onto ‘Emperator’ or ‘Kaiser’ were subjected to two spectral compositions—100% red or a mix of red (75%), blue (20%), and green (5%) light for 17 h or 23 h. The four treatments supplied similar DLI. Leaf chlorosis appeared in all plants under 23 h lighting regardless of spectral compositions between 20 and 54 days into the treatment. The yield for 23 h mixed lighting treatment was lower than both 17 h lighting treatments. However, the 23 h red lighting treatment resulted in less leaf chlorosis and the plants grafted onto ‘Emperator’ produced a similar yield as both 17 h lighting treatments. Therefore, both spectral compositions and rootstocks affected the response of greenhouse tomatoes to long photoperiods of lighting. With red light and proper rootstock, the negative yield impact from long photoperiod lighting can be eliminated. Full article

(This article belongs to the Special Issue The Effects of LED Light Spectra and Intensities on Plant Growth)

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18 pages, 2851 KiB

Open AccessArticle

Effects of Different Light Spectra on Final Biomass Production and Nutritional Quality of Two Microgreens

by Stefania Toscano, Valeria Cavallaro, Antonio Ferrante, Daniela Romano and Cristina Patané

Plants 2021, 10(8), 1584; https://doi.org/10.3390/plants10081584 - 31 Jul 2021

Cited by 20 | Viewed by 3736

Abstract

To improve microgreen yield and nutritional quality, suitable light spectra can be used. Two species—amaranth (Amaranthus tricolor L.) and turnip greens (Brassica rapa L. subsp. oleifera (DC.) Metzg)—were studied. The experiment was performed in a controlled LED environment growth chamber (day/night [...] Read more.

To improve microgreen yield and nutritional quality, suitable light spectra can be used. Two species—amaranth (Amaranthus tricolor L.) and turnip greens (Brassica rapa L. subsp. oleifera (DC.) Metzg)—were studied. The experiment was performed in a controlled LED environment growth chamber (day/night temperatures of 24 ± 2 °C, 16 h photoperiod, and 50/60% relative humidity). Three emission wavelengths of a light-emitting diode (LED) were adopted for microgreen lighting: (1) white LED (W); (2) blue LED (B), and (3) red LED (R); the photosynthetic photon flux densities were 200 ± 5 µmol for all light spectra. The response to light spectra was often species-specific, and the interaction effects were significant. Morphobiometric parameters were influenced by species, light, and their interaction; at harvest, in both species, the fresh weight was significantly greater under B. In amaranth, Chl a was maximized in B, whereas it did not change with light in turnip greens. Sugar content varied with the species but not with the light spectra. Nitrate content of shoots greatly varied with the species; in amaranth, more nitrates were measured in R, while no difference in turnip greens was registered for the light spectrum effect. Polyphenols were maximized under B in both species, while R depressed the polyphenol content in amaranth. Full article

(This article belongs to the Special Issue The Effects of LED Light Spectra and Intensities on Plant Growth)

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12 pages, 3134 KiB

Open AccessArticle

Single Wavelengths of LED Light Supplement Promote the Biosynthesis of Major Cyclic Monoterpenes in Japanese Mint

by Takahiro Ueda, Miki Murata and Ken Yokawa

Plants 2021, 10(7), 1420; https://doi.org/10.3390/plants10071420 - 12 Jul 2021

Cited by 10 | Viewed by 3052

Abstract

Environmental light conditions influence the biosynthesis of monoterpenes in the mint plant. Cyclic terpenes, such as menthol, menthone, pulegone, and menthofuran, are major odor components synthesized in mint leaves. However, it is unclear how light for cultivation affects the contents of these compounds. [...] Read more.

Environmental light conditions influence the biosynthesis of monoterpenes in the mint plant. Cyclic terpenes, such as menthol, menthone, pulegone, and menthofuran, are major odor components synthesized in mint leaves. However, it is unclear how light for cultivation affects the contents of these compounds. Artificial lighting using light-emitting diodes (LEDs) for plant cultivation has the advantage of preferential wavelength control. Here, we monitored monoterpene contents in hydroponically cultivated Japanese mint leaves under blue, red, or far-red wavelengths of LED light supplements. Volatile cyclic monoterpenes, pulegone, menthone, menthol, and menthofuran were quantified using the head-space solid phase microextraction method. As a result, all light wavelengths promoted the biosynthesis of the compounds. Remarkably, two weeks of blue-light supplement increased all compounds: pulegone (362% increase compared to the control), menthofuran (285%), menthone (223%), and menthol (389%). Red light slightly promoted pulegone (256%), menthofuran (178%), and menthol (197%). Interestingly, the accumulation of menthone (229%) or menthofuran (339%) was observed with far-red light treatment. The quantification of glandular trichomes density revealed that no increase under light supplement was confirmed. Blue light treatment even suppressed the glandular trichome formation. No promotion of photosynthesis was observed by pulse-amplitude-modulation (PAM) fluorometry. The present result indicates that light supplements directly promoted the biosynthetic pathways of cyclic monoterpenes. Full article

(This article belongs to the Special Issue The Effects of LED Light Spectra and Intensities on Plant Growth)

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14 pages, 3634 KiB

Open AccessArticle

Morpho-Physiological Responses of Arabidopsis thaliana L. to the LED-Sourced CoeLux^® System

by Peter Beatrice, Mattia Terzaghi, Donato Chiatante, Gabriella Stefania Scippa and Antonio Montagnoli

Plants 2021, 10(7), 1310; https://doi.org/10.3390/plants10071310 - 28 Jun 2021

Cited by 4 | Viewed by 2066

Abstract

The CoeLux^® lighting system reproduces the true effect of natural sunlight entering through an opening in the ceiling, with a realistic sun perceived at an infinite distance surrounded by a clear blue sky. It has already been demonstrated that this new lighting [...] Read more.

The CoeLux^® lighting system reproduces the true effect of natural sunlight entering through an opening in the ceiling, with a realistic sun perceived at an infinite distance surrounded by a clear blue sky. It has already been demonstrated that this new lighting system generates long-term positive effects on human beings; however, there are no investigations so far concerning the plant responses to CoeLux^® lighting. To fill this gap, the model plant Arabidopsis thaliana L. was grown at four different distances from the light source, corresponding to four different light intensities (120, 70, 30, 20 μmol m⁻² s⁻¹). High-pressure sodium lamps were used as control light. Plant phenology and morpho-physiological traits were monitored to assess for the first time the ability of plants to grow and develop under the light spectrum and intensity of the CoeLux^® system. Plants grown at the lower light intensities showed a delayed life cycle and were significantly smaller than plants grown with more light. Furthermore, plants grown under the CoeLux^® light type showed an additional deficit when compared to control plants. Overall, our results show that both the light spectrum and intensity of the CoeLux^® system had a strong impact on A. thaliana growth performance. Full article

(This article belongs to the Special Issue The Effects of LED Light Spectra and Intensities on Plant Growth)

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14 pages, 2245 KiB

Open AccessArticle

The Effect of Plant Growth Compensation by Adding Silicon-Containing Fertilizer under Light Stress Conditions

by Natalya A. Semenova, Alexandr A. Smirnov, Andrey A. Grishin, Roman Y. Pishchalnikov, Denis D. Chesalin, Sergey V. Gudkov, Narek O. Chilingaryan, Anastasia N. Skorokhodova, Alexey S. Dorokhov and Andrey Y. Izmailov

Plants 2021, 10(7), 1287; https://doi.org/10.3390/plants10071287 - 24 Jun 2021

Cited by 18 | Viewed by 3389

Abstract

The effects of different spectral compositions of light-emitting diode (LED) sources and fertilizer containing biologically active silicon (Si) in the nutrient solution on morphological and physiological plant response were studied. Qualitative indicators and the productivity of plants of a red-leaved and a green-leaved [...] Read more.

The effects of different spectral compositions of light-emitting diode (LED) sources and fertilizer containing biologically active silicon (Si) in the nutrient solution on morphological and physiological plant response were studied. Qualitative indicators and the productivity of plants of a red-leaved and a green-leaved lettuce were estimated. Lettuce was grown applying low-volume hydroponics in closed artificial agroecosystems. The positive effect of Si fertilizer used as a microadditive in the nutrient solution on the freshly harvested biomass was established on the thirtieth day of vegetation under LEDs. Increase in productivity of the red-leaved lettuce for freshly harvested biomass was 26.6%, while for the green-leaved lettuce no loss of dry matter was observed. However, being grown under sodium lamps, a negative impact of Si fertilizer on productivity of both types of plants was observed: the amount of harvested biomass decreased by 22.6% and 30.3% for the green- and red-leaved lettuces, respectively. The effect of using Si fertilizer dramatically changed during the total growing period: up to the fifteenth day of cultivation, a sharp inhibition of the growth of both types of lettuce was observed; then, by the thirtieth day of LED lighting, Si fertilizer showed a stress-protective effect and had a positive influence on the plants. However, by the period of ripening there was no effect of using the fertilizer. Therefore, we can conclude that the use of Si fertilizers is preferable only when LED irradiation is applied throughout the active plant growth period. Full article

(This article belongs to the Special Issue The Effects of LED Light Spectra and Intensities on Plant Growth)

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16 pages, 1866 KiB

Open AccessFeature PaperArticle

Increased Plant Quality, Greenhouse Productivity and Energy Efficiency with Broad-Spectrum LED Systems: A Case Study for Thyme (Thymus vulgaris L.)

by Jenny Manuela Tabbert, Hartwig Schulz and Andrea Krähmer

Plants 2021, 10(5), 960; https://doi.org/10.3390/plants10050960 - 12 May 2021

Cited by 3 | Viewed by 2885

Abstract

A light-emitting diode (LED) system covering plant-receptive wavebands from ultraviolet to far-red radiation (360 to 760 nm, “white” light spectrum) was investigated for greenhouse productions of Thymus vulgaris L. Biomass yields and amounts of terpenoids were examined, and the lights’ productivity and electrical [...] Read more.

A light-emitting diode (LED) system covering plant-receptive wavebands from ultraviolet to far-red radiation (360 to 760 nm, “white” light spectrum) was investigated for greenhouse productions of Thymus vulgaris L. Biomass yields and amounts of terpenoids were examined, and the lights’ productivity and electrical efficiency were determined. All results were compared to two conventionally used light fixture types (high-pressure sodium lamps (HPS) and fluorescent lights (FL)) under naturally low irradiation conditions during fall and winter in Berlin, Germany. Under LED, development of Thymus vulgaris L. was highly accelerated resulting in distinct fresh yield increases per square meter by 43% and 82.4% compared to HPS and FL, respectively. Dry yields per square meter also increased by 43.1% and 88.6% under LED compared to the HPS and FL lighting systems. While composition of terpenoids remained unaffected, their quantity per gram of leaf dry matter significantly increased under LED and HPS as compared to FL. Further, the power consumption calculations revealed energy savings of 31.3% and 20.1% for LED and FL, respectively, compared to HPS. In conclusion, the implementation of a broad-spectrum LED system has tremendous potential for increasing quantity and quality of Thymus vulgaris L. during naturally insufficient light conditions while significantly reducing energy consumption. Full article

(This article belongs to the Special Issue The Effects of LED Light Spectra and Intensities on Plant Growth)

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9 pages, 1882 KiB

Open AccessCommunication

Metabolic Analysis of Root, Stem, and Leaf of Scutellaria baicalensis Plantlets Treated with Different LED Lights

by Hyeon-Ji Yeo, Chang-Ha Park, Soo-Yun Park, Sun-Ok Chung, Jae-Kwang Kim and Sang-Un Park

Plants 2021, 10(5), 940; https://doi.org/10.3390/plants10050940 - 08 May 2021

Cited by 8 | Viewed by 2631

Abstract

Light emitting diodes (LEDs) have recently been considered an efficient artificial light source in plant factories for enhancing plant growth and nutritional quality. Accordingly, this study aimed to review blue, red, and white LED light sources for efficiency and length of the growing [...] Read more.

Light emitting diodes (LEDs) have recently been considered an efficient artificial light source in plant factories for enhancing plant growth and nutritional quality. Accordingly, this study aimed to review blue, red, and white LED light sources for efficiency and length of the growing period to produce seedlings of Scutellaria baicalensis with high nutritional value. The roots, stems, and leaves of S. baicalensis seedlings were grown under different LED lights and harvested after two and four weeks, and analyzed using high-performance liquid chromatography and gas chromatography time-of-flight mass spectrometry to identify and quantify primary and secondary metabolites. Roots, particularly in the seedlings treated with white LEDs were determined to contain the greatest concentrations of the representative compounds present in S. baicalensis: baicalin, baicalein, and wogonin, which show highly strong biological properties compared to the other plant organs. A total of 50 metabolites (amino acids, sugars, sugar alcohols, organic acids, phenolic acids, and amines) were detected in the roots, stems, and leaves of S. baicalensis seedlings, and the concentrations of primary and secondary metabolites were generally decreased with the increasing duration of LED illumination. Therefore, this study suggests that white LED light and a 2-week growing period are the most efficient conditions for the production of baicalin, baicalein, and wogonin. Full article

(This article belongs to the Special Issue The Effects of LED Light Spectra and Intensities on Plant Growth)

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18 pages, 2578 KiB

Open AccessArticle

Green Light Improves Photosystem Stoichiometry in Cucumber Seedlings (Cucumis sativus) Compared to Monochromatic Red Light

by Nicholas B. Claypool and J. Heinrich Lieth

Plants 2021, 10(5), 824; https://doi.org/10.3390/plants10050824 - 21 Apr 2021

Cited by 8 | Viewed by 2798

Abstract

It has been shown that monochromatic red and blue light influence photosynthesis and morphology in cucumber. It is less clear how green light impacts photosynthetic performance or morphology, either alone or in concert with other wavelengths. In this study, cucumber (Cucumis sativus [...] Read more.

It has been shown that monochromatic red and blue light influence photosynthesis and morphology in cucumber. It is less clear how green light impacts photosynthetic performance or morphology, either alone or in concert with other wavelengths. In this study, cucumber (Cucumis sativus) was grown under monochromatic blue, green, and red light, dichromatic blue–green, red–blue, and red–green light, as well as light containing red, green, and blue wavelengths, with or without supplemental far-red light. Photosynthetic data collected under treatment spectra at light-limiting conditions showed that both red and green light enhance photosynthesis. However, photosynthetic data collected with a 90% red, 10% blue, 1000 µmol photons m⁻² s⁻¹, saturating light show significantly lower photosynthesis in the green, red, and red–green treatments, indicating a blue light enhancement due to photosystem stoichiometric differences. The red–green and green light treatments show improved photosynthetic capacity relative to red light, indicating partial remediation by green light. Despite a lower quantum efficiency and the lowest ambient photosynthesis levels, the monochromatic blue treatment produced among the tallest, most massive plants with the greatest leaf area and thickest stems. Full article

(This article belongs to the Special Issue The Effects of LED Light Spectra and Intensities on Plant Growth)

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14 pages, 2700 KiB

Open AccessArticle

Canopy Size and Light Use Efficiency Explain Growth Differences between Lettuce and Mizuna in Vertical Farms

by Theekshana C. Jayalath and Marc W. van Iersel

Plants 2021, 10(4), 704; https://doi.org/10.3390/plants10040704 - 06 Apr 2021

Cited by 16 | Viewed by 4827

Abstract

Vertical farming is increasingly popular due to high yields obtained from a small land area. However, the energy cost associated with lighting of vertical farms is high. To reduce this cost, more energy efficient (biomass/energy use) crops are required. To understand how efficiently [...] Read more.

Vertical farming is increasingly popular due to high yields obtained from a small land area. However, the energy cost associated with lighting of vertical farms is high. To reduce this cost, more energy efficient (biomass/energy use) crops are required. To understand how efficiently crops use light energy to produce biomass, we determined the morphological and physiological differences between mizuna (Brassica rapa var. japonica) and lettuce (Lactuca sativa ‘Green Salad Bowl’). To do so, we measured the projected canopy size (PCS, a morphological measure) of the plants throughout the growing cycle to determine the total amount of incident light the plants received. Total incident light was used together with the final dry weight to calculate the light use efficiency (LUE, g of dry weight/mol of incident light), a physiological measure. Plants were grown under six photosynthetic photon flux densities (PPFD), from 50 to 425 µmol m⁻² s⁻¹, for 16 h d⁻¹. Mizuna and lettuce were harvested 27 and 28 days after seeding, respectively. Mizuna had greater dry weight than lettuce (p < 0.0001), especially at higher PPFDs (PPFD ≥ 125 µmol m⁻² s⁻¹), partly because of differences in the projected canopy size (PCS). Mizuna had greater PCS than lettuce at PPFDs ≥ 125 µmol m⁻² s⁻¹ and therefore, the total incident light over the growing period was also greater. Mizuna also had a higher LUE than lettuce at all six PPFDs. This difference in LUE was associated with higher chlorophyll content index and higher quantum yield of photosystem II in mizuna. The combined effects of these two factors resulted in higher photosynthetic rates in mizuna than in lettuce (p = 0.01). In conclusion, the faster growth of mizuna is the result of both a larger PCS and higher LUE compared to lettuce. Understanding the basic determinants of crop growth is important when screening for rapidly growing crops and increasing the efficiency of vertical farms. Full article

(This article belongs to the Special Issue The Effects of LED Light Spectra and Intensities on Plant Growth)

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13 pages, 1757 KiB

Open AccessArticle

LED Illumination Spectrum Manipulation for Increasing the Yield of Sweet Basil (Ocimum basilicum L.)

by Md Momtazur Rahman, Mikhail Vasiliev and Kamal Alameh

Plants 2021, 10(2), 344; https://doi.org/10.3390/plants10020344 - 11 Feb 2021

Cited by 22 | Viewed by 4033

Abstract

Manipulation of the LED illumination spectrum can enhance plant growth rate and development in grow tents. We report on the identification of the illumination spectrum required to significantly enhance the growth rate of sweet basil (Ocimum basilicum L.) plants in grow tent [...] Read more.

Manipulation of the LED illumination spectrum can enhance plant growth rate and development in grow tents. We report on the identification of the illumination spectrum required to significantly enhance the growth rate of sweet basil (Ocimum basilicum L.) plants in grow tent environments by controlling the LED wavebands illuminating the plants. Since the optimal illumination spectrum depends on the plant type, this work focuses on identifying the illumination spectrum that achieves significant basil biomass improvement compared to improvements reported in prior studies. To be able to optimize the illumination spectrum, several steps must be achieved, namely, understanding plant biology, conducting several trial-and-error experiments, iteratively refining experimental conditions, and undertaking accurate statistical analyses. In this study, basil plants are grown in three grow tents with three LED illumination treatments, namely, only white LED illumination (denoted W*), the combination of red (R) and blue (B) LED illumination (denoted BR*) (relative red (R) and blue (B) intensities are 84% and 16%, respectively) and a combination of red (R), blue (B) and far-red (F) LED illumination (denoted BRF*) (relative red (R), blue (B) and far-red (F) intensities are 79%, 11%, and 10%, respectively). The photosynthetic photon flux density (PPFD) was set at 155 µmol m⁻² s⁻¹ for all illumination treatments, and the photoperiod was 20 h per day. Experimental results show that a combination of blue (B), red (R), and far-red (F) LED illumination leads to a one-fold increase in the yield of a sweet basil plant in comparison with only white LED illumination (W*). On the other hand, the use of blue (B) and red (R) LED illumination results in a half-fold increase in plant yield. Understanding the effects of LED illumination spectrum on the growth of plant sweet basil plants through basic horticulture research enables farmers to significantly improve their production yield, thus food security and profitability. Full article

(This article belongs to the Special Issue The Effects of LED Light Spectra and Intensities on Plant Growth)

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18 pages, 8059 KiB

Open AccessArticle

Modelling of Soybean (Glycine max (L.) Merr.) Response to Blue Light Intensity in Controlled Environments

by Tina Hitz, Simone Graeff-Hönninger and Sebastian Munz

Plants 2020, 9(12), 1757; https://doi.org/10.3390/plants9121757 - 11 Dec 2020

Cited by 7 | Viewed by 2260

Abstract

Low photosynthetic photon flux density (PPFD) under shade is associated with low blue photon flux density (BPFD), which independent from PPFD can induce shade responses, e.g., elongation growth. In this study, the response of soybean to six levels of BPFD under constant PPFD [...] Read more.

Low photosynthetic photon flux density (PPFD) under shade is associated with low blue photon flux density (BPFD), which independent from PPFD can induce shade responses, e.g., elongation growth. In this study, the response of soybean to six levels of BPFD under constant PPFD from LED lighting was investigated with regard to morphology, biomass and photosynthesis to increase the knowledge for optimizing the intensity of BPFD for a speed breeding system. The results showed that low BPFD increased plant height, leaf area and biomass and decreased leaf mass ratio. Photosynthetic rate and internode diameter were not influenced. A functional structural plant model of soybean was calibrated with the experimental data. A response function for internode length to the perceived BPFD by the internodes was derived from simulations and integrated into the model. With the aim to optimize lighting for a speed breeding system, simulations with alternative lighting scenarios indicated that decreasing BPFD during the growth period and using different chamber material with a higher reflectance could reduce energy consumption by 7% compared to the experimental setup, while inducing short soybean plants. Full article

(This article belongs to the Special Issue The Effects of LED Light Spectra and Intensities on Plant Growth)

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11 pages, 2406 KiB

Open AccessArticle

How Supplementary or Night-Interrupting Low-Intensity Blue Light Affects the Flower Induction in Chrysanthemum, A Qualitative Short-Day Plant

by Yoo Gyeong Park and Byoung Ryong Jeong

Plants 2020, 9(12), 1694; https://doi.org/10.3390/plants9121694 - 02 Dec 2020

Cited by 21 | Viewed by 4460

Abstract

This research examined the effects of the supplementary or night-interrupting (NI) blue (B) light supplied at a low intensity on the flowering, gene expression, and morphogenesis of chrysanthemum, a qualitative short-day plant. White (W) light-emitting diodes (LEDs) were used to provide light with [...] Read more.

This research examined the effects of the supplementary or night-interrupting (NI) blue (B) light supplied at a low intensity on the flowering, gene expression, and morphogenesis of chrysanthemum, a qualitative short-day plant. White (W) light-emitting diodes (LEDs) were used to provide light with a photosynthetic photon flux density (PPFD) of 180 μmol·m⁻²·s⁻¹ during the photoperiod to grow the plants in a plant factory. The control group was constructed with plants that were exposed to a 10-h short day (SD10) treatment without any blue light. The B light in this research was used for 4 h to either (1) extend the photoperiod for plants at the end of a 9-h short day (SD) treatment as the sole light source (SD9 + 4B), (2) provide night interruption (NI) to plants in the 13-h long-day (LD) treatment (LD13 + NI − 4B), (3) provide NI to plants in the 10-h SD treatment (SD10 + NI − 4B), or (4) supplement the W LEDs at the end of a 13-h LD treatment (LD13 + 4B). Blue LEDs were used to provide the supplementary/NI light at 10 μmol·m⁻²·s⁻¹ PPFD. The LD13 + NI − 4B treatment resulted in the greatest plant height, followed by LD13 + 4B. Plants in all treatments flowered. It is noteworthy that despite the fact that chrysanthemum is a qualitative SD plant, chrysanthemum plants flowered when grown in the LD13 + 4B and LD13 + NI − 4B treatments. Plants grown in the LD13 + 4B had the greatest number of flowers. Plants grown in the LD13 + 4B treatment had the highest expression levels of the cryptochrome 1, phytochrome A, and phytochrome B genes. The results of this study indicate that a 4-h supplementation of B light during the photoperiod increases flower bud formation and promotes flowering, and presents a possibility as an alternative method to using blackout curtains in LD seasons to practically induce flowering. The B light application methods to induce flowering in SD plants requires further research. Full article

(This article belongs to the Special Issue The Effects of LED Light Spectra and Intensities on Plant Growth)

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15 pages, 2234 KiB

Open AccessArticle

Changes in Beneficial C-glycosylflavones and Policosanol Content in Wheat and Barley Sprouts Subjected to Differential LED Light Conditions

by Muthusamy Muthusamy, Jong Hee Kim, Suk Hee Kim, Joo Yeol Kim, Jeong Wook Heo, HanGyeol Lee, Kwang-Sik Lee, Woo Duck Seo, Soyoung Park, Jin A Kim and Soo In Lee

Plants 2020, 9(11), 1502; https://doi.org/10.3390/plants9111502 - 06 Nov 2020

Cited by 8 | Viewed by 2321

Abstract

The spectral quality and intensity of light, photoperiodism, and other environmental factors have profound impacts on the metabolic composition of light-dependent higher plants. Hence, we investigate the effects of fluorescent light (96 μmol m⁻²s⁻¹) and white (100 μmol m [...] Read more.

The spectral quality and intensity of light, photoperiodism, and other environmental factors have profound impacts on the metabolic composition of light-dependent higher plants. Hence, we investigate the effects of fluorescent light (96 μmol m⁻²s⁻¹) and white (100 μmol m⁻²s⁻¹), blue (100 μmol m⁻²s⁻¹), and red (93 μmol m⁻²s⁻¹) light-emitting diode (LED) light irradiation on the C-glycosylflavone and policosanol contents in young seedlings of wheat and barley. Ultra-high-performance liquid chromatography (UHPLC) analyses of C-glycosylflavone contents in barley reveal that the saponarin content is significantly enhanced under blue LED light irradiation. Under similar conditions, isoorientin and isoschaftoside contents are improved in wheat seedlings. The contents of these C-glycosylflavones differed along with the light quality and growth period. The highest accumulation was observed in sprouts after three days under blue LED light irradiation. GC/MS analyses of policosanol contents showed that 1-hexacosanol (C26:o–OH) in barley and 1-octacosanol (C28:o–OH) in wheat seedlings were reduced under LED light irradiation, compared to seedlings under fluorescent light conditions. Nonetheless, the policosanol contents gradually improved with the extension of growth times and treatments, irrespective of the light quality. Additionally, a positive correlation was observed between the expression pattern of biosynthesis-related genes and the respective metabolite content in barley. This study demonstrates that blue LED light irradiation is useful in maximizing the C-glycosylflavone content in barley and wheat sprouts. Full article

(This article belongs to the Special Issue The Effects of LED Light Spectra and Intensities on Plant Growth)

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15 pages, 1851 KiB

Open AccessArticle

LED Lights Affecting Morphogenesis and Isosteroidal Alkaloid Contents in Fritillaria cirrhosa D. Don—An Important Chinese Medicinal Herb

by Chia-Chen Chen, Maw-Rong Lee, Chi-Rei Wu, Hsin-Ju Ke, Hui-Min Xie, Hsin-Sheng Tsay, Dinesh Chandra Agrawal and Hung-Chi Chang

Plants 2020, 9(10), 1351; https://doi.org/10.3390/plants9101351 - 13 Oct 2020

Cited by 12 | Viewed by 2758

Abstract

Investigations were carried out to study the effects of light-emitting diode (LED) lights on growth and development of isosteroidal alkaloids in embryogenic calli of Fritillaria cirrhosa D. Don, an important traditional Chinese medicine herb. Calli were cultured in glass bottles, each containing 100 [...] Read more.

Investigations were carried out to study the effects of light-emitting diode (LED) lights on growth and development of isosteroidal alkaloids in embryogenic calli of Fritillaria cirrhosa D. Don, an important traditional Chinese medicine herb. Calli were cultured in glass bottles, each containing 100 mL of Murashige and Skoog’s basal medium supplemented with 2% sucrose and 0.4% gellan gum powder, a gelling agent. These bottles were incubated in a specially designed plant growth chamber equipped with eight different LED lights consisting of single or combinations of four different light spectra emitting blue (450 nm), green (525 nm), red (660 nm), and far-red (730 nm) light. After three months of incubation, morphological changes in embryogenic calli were recorded, and LC-MS/MS analysis of cultures was carried out for peimisine, sipeimine, peiminine, and peimine. The highest number of somatic embryos and the maximum fresh weight was recorded in calli incubated under red (9R), infrared (9IR), and a combination of red+blue+infrared (3R3B3IR), respectively, in decreasing order. The highest contents of peimisine, peiminine, and peimine were recorded under red (9R) and infrared (9IR) lights, respectively. Eight LED lights had significant effects on the morphogenesis of embryogenic calli of F. cirrhosa D. Don and contents of isosteroidal alkaloids. Full article

(This article belongs to the Special Issue The Effects of LED Light Spectra and Intensities on Plant Growth)

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Review

Jump to: Editorial, Research

45 pages, 965 KiB

Open AccessReview

Light and Plant Growth Regulators on In Vitro Proliferation

by Valeria Cavallaro, Alessandra Pellegrino, Rosario Muleo and Ivano Forgione

Plants 2022, 11(7), 844; https://doi.org/10.3390/plants11070844 - 22 Mar 2022

Cited by 30 | Viewed by 5569

Abstract

Plant tissue cultures depend entirely upon artificial light sources for illumination. The illumination should provide light in the appropriate regions of the electromagnetic spectrum for photomorphogenic responses and photosynthetic metabolism. Controlling light quality, irradiances and photoperiod enables the production of plants with desired [...] Read more.

Plant tissue cultures depend entirely upon artificial light sources for illumination. The illumination should provide light in the appropriate regions of the electromagnetic spectrum for photomorphogenic responses and photosynthetic metabolism. Controlling light quality, irradiances and photoperiod enables the production of plants with desired characteristics. Moreover, significant money savings may be achieved using both more appropriate and less consuming energy lamps. In this review, the attention will be focused on the effects of light characteristics and plant growth regulators on shoot proliferation, the main process in in vitro propagation. The effects of the light spectrum on the balance of endogenous growth regulators will also be presented. For each light spectrum, the effects on proliferation but also on plantlet quality, i.e., shoot length, fresh and dry weight and photosynthesis, have been also analyzed. Even if a huge amount of literature is available on the effects of light on in vitro proliferation, the results are often conflicting. In fact, a lot of exogenous and endogenous factors, but also the lack of a common protocol, make it difficult to choose the most effective light spectrum for each of the large number of species. However, some general issues derived from the analysis of the literature are discussed. Full article

(This article belongs to the Special Issue The Effects of LED Light Spectra and Intensities on Plant Growth)

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18 pages, 1767 KiB

Open AccessReview

Comparative Effects of Different Light Sources on the Production of Key Secondary Metabolites in Plants In Vitro Cultures

by Mariam Hashim, Bushra Ahmad, Samantha Drouet, Christophe Hano, Bilal Haider Abbasi and Sumaira Anjum

Plants 2021, 10(8), 1521; https://doi.org/10.3390/plants10081521 - 26 Jul 2021

Cited by 38 | Viewed by 6217

Abstract

Plant secondary metabolites are known to have a variety of biological activities beneficial to human health. They are becoming more popular as a result of their unique features and account for a major portion of the pharmacological industry. However, obtaining secondary metabolites directly [...] Read more.

Plant secondary metabolites are known to have a variety of biological activities beneficial to human health. They are becoming more popular as a result of their unique features and account for a major portion of the pharmacological industry. However, obtaining secondary metabolites directly from wild plants has substantial drawbacks, such as taking a long time, posing a risk of species extinction owing to over-exploitation, and producing a limited quantity. Thus, there is a paradigm shift towards the employment of plant tissue culture techniques for the production of key secondary metabolites in vitro. Elicitation appears to be a viable method for increasing phytochemical content and improving the quality of medicinal plants and fruits and vegetables. In vitro culture elicitation activates the plant’s defense response and increases the synthesis of secondary metabolites in larger proportions, which are helpful for therapeutic purposes. In this respect, light has emerged as a unique and efficient elicitor for enhancing the in vitro production of pharmacologically important secondary metabolites. Various types of light (UV, fluorescent, and LEDs) have been found as elicitors of secondary metabolites, which are described in this review. Full article

(This article belongs to the Special Issue The Effects of LED Light Spectra and Intensities on Plant Growth)

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