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Agriculture
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Impact of Light on Horticultural Crops
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Impact of Light on Horticultural Crops

A special issue of Agriculture (ISSN 2077-0472). This special issue belongs to the section "Crop Production".

Deadline for manuscript submissions: closed (20 September 2022) | Viewed by 37740

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Dr. Athanasios Koukounaras

E-Mail Website
Guest Editor
Department of Horticulture, Aristotle University, 54124 Thessaloniki, Greece
Interests: cultivation techniques for vegetable production; quality of vegetable products; hydroponic vegetable production; postharvest physiology of vegetables; role of light on vegetables’ growth; quality of seedlings; quality and seed germination; vegetable grafting; innovative forms of vegetable products; organic cultivation of vegetables
Special Issues, Collections and Topics in MDPI journals
Dr. Filippos Bantis

E-Mail Website
Guest Editor
Department of Horticulture, Aristotle University, 54124 Thessaloniki, Greece
Interests: horticulture;plant photobiology;controlled environment agriculture;plant physiology;vegetable grafting
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Light is an essential factor for the growth and quality of horticultural plants and its effects depend upon parameters such as duration, intensity and quality. It is an energy source for photosynthesis as well as a signal triggering plant photomorphogenesis and physiological, biochemical and molecular responses. However, solar light strongly differs between winter and summer conditions, with excess light in open field cultivations imposing severe stress on plants, especially during summer months, while supplementary light sources are implemented in greenhouse crop production to complement natural light when it is insufficient. On the other hand, artificial lighting is used as the sole lighting source in plant factories and nurseries (i.e., healing chambers, plant tissue culture). In order to enhance sustainability and profitability, light must be studied and efficiently applied within horticultural crop production. Novel technologies such as light-emitting diodes, new transparent greenhouse covering materials, photoselective nettings, growth chambers and plant factories showcase the critical role of light interacting with plants from the level of seed germination to growth rate, product quality and postharvest storage.

This Special Issue focuses on recent findings in horticultural crops with regard to light characteristics (i.e., quality, quantity etc.) presented as research papers, short communications and review articles.

Dr. Athanasios Koukounaras
Dr. Filippos Bantis
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Agriculture is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Light quantity and quality
  • Light-emitting diodes (LEDs)
  • Plant factory with artificial lighting (PFAL)
  • Physiology
  • Photomorphogenesis
  • Photosynthesis
  • Plant growth and quality
  • Postharvest storage
  • Climate change
  • Shade net house

Published Papers (12 papers)

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Editorial

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4 pages, 184 KiB  
Editorial
Impact of Light on Horticultural Crops
by Filippos Bantis and Athanasios Koukounaras
Agriculture 2023, 13(4), 828; https://0-doi-org.brum.beds.ac.uk/10.3390/agriculture13040828 - 04 Apr 2023
Cited by 1 | Viewed by 1959
Abstract
Light is an essential factor for the growth and quality of horticultural plants and its effects depend upon parameters such as duration, intensity and quality [...] Full article
(This article belongs to the Special Issue Impact of Light on Horticultural Crops)

Research

Jump to: Editorial

13 pages, 708 KiB  
Article
Ultraviolet Radiation Management in Greenhouse to Improve Red Lettuce Quality and Yield
by Ioannis Lycoskoufis, Angeliki Kavga, Georgios Koubouris and Dimitrios Karamousantas
Agriculture 2022, 12(10), 1620; https://0-doi-org.brum.beds.ac.uk/10.3390/agriculture12101620 - 06 Oct 2022
Cited by 4 | Viewed by 1996
Abstract
The intensity of ultraviolet (UV) radiation affects the yield and quality of red lettuce. The current study aimed to develop a UV management system in a greenhouse to achieve high yield and quality in red lettuce production. The study consisted of two experiments. [...] Read more.
The intensity of ultraviolet (UV) radiation affects the yield and quality of red lettuce. The current study aimed to develop a UV management system in a greenhouse to achieve high yield and quality in red lettuce production. The study consisted of two experiments. In the first experiment, the effects of the different UV transparencies of the plastic materials covering the greenhouse on plant growth and the concentration of antioxidants in red lettuce were studied. For this purpose, two greenhouses were covered with polyethene of different transparencies to UV radiation. One greenhouse was covered with a common type of polyethene transparent in a large spectrum of UV radiation (UV-open), while the second greenhouse was covered with polyethene untransparent to ultraviolet radiation (UV-block). The plants were grown in a deep flotation hydroponic system. At the end of the cultivation, plant growth measurements, leaf colour measurements, and the determination of antioxidant components’ concentration were carried out. Red lettuce plants harvested 42 days after planting had an average head weight 42% greater in the UV-block greenhouse compared to plants grown in the UV-open greenhouse. However, the red leaf colour of plants in the UV-block greenhouse lagged significantly compared to that in the UV-open greenhouse. Moreover, the total phenolic content, the total flavonoid content, and the antioxidant capacity of the lettuce leaves in the UV-block greenhouse were significantly lower compared to the corresponding values of the plants in the UV-open greenhouse. During the second experiment, a new cultivation system of red lettuce, which combined a UV-block polyethene film as a greenhouse cover and a pre-harvested supplemental UV light, was tested. For this purpose, various doses of supplemental UV lighting were tested in the UV-block greenhouse for ten days prior to harvest. From these tests, it emerged that applying supplemental UV lighting with a dose of 425 kJ m−2 d−1 for ten days before harvest produces red lettuces of the same quality as those produced in a UV-open greenhouse. This technique of growing red lettuce increases its yield by 30% without a negative effect on the quality of the product. Full article
(This article belongs to the Special Issue Impact of Light on Horticultural Crops)
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14 pages, 1017 KiB  
Article
Influence of Lighting and Laser Irradiation on the Germination of Caper Seeds
by María Laura Foschi, Mariano Juan, Bernardo Pascual and Nuria Pascual-Seva
Agriculture 2022, 12(10), 1612; https://0-doi-org.brum.beds.ac.uk/10.3390/agriculture12101612 - 04 Oct 2022
Cited by 6 | Viewed by 1613
Abstract
Caper seeds present difficulties in their germination, which has been studied by several research teams. It is known that light can release dormancy in some seeds, but its effect on caper seed germination has not yet been deeply studied. The main aim of [...] Read more.
Caper seeds present difficulties in their germination, which has been studied by several research teams. It is known that light can release dormancy in some seeds, but its effect on caper seed germination has not yet been deeply studied. The main aim of this study was to analyze the response of caper seeds germination to light exposure. The study analyzed the germination response of seeds to lighting with different wavelengths (white, red, blue, red + blue and darkness) and to the He-Ne laser light, using both dry seeds and seeds that had been previously soaked in water. Overall, it could be stated that caper seeds are insensitive to light during the germination process. Thus, germination could be carried out in lightness or darkness, so germination in nurseries could be carried out in the darkness, leading to substantial energy savings. Caper seed irradiation with a He-Ne laser during short exposure times improved the germination percentage for the seeds previously soaked in water, germinating all viable seeds. However, applying a solution of gibberellic acid was always required in all the cases studied. Full article
(This article belongs to the Special Issue Impact of Light on Horticultural Crops)
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14 pages, 1625 KiB  
Article
The Combinations of White, Blue, and UV-A Light Provided by Supplementary Light-Emitting Diodes Promoted the Quality of Greenhouse-Grown Cucumber Seedlings
by Zhengnan Yan, Chunling Wang, Long Wang, Xin Li, Guanjie Wang and Yanjie Yang
Agriculture 2022, 12(10), 1593; https://0-doi-org.brum.beds.ac.uk/10.3390/agriculture12101593 - 02 Oct 2022
Cited by 2 | Viewed by 1569
Abstract
Insufficient solar light in winter inside the greenhouse may lead to a lower quality of vegetable seedlings, and supplemental light is an effective technique to solve this problem. This study evaluated the impacts of supplementary white (W)-light-emitting diodes (LEDs), ultraviolet A LEDs (UV-A), [...] Read more.
Insufficient solar light in winter inside the greenhouse may lead to a lower quality of vegetable seedlings, and supplemental light is an effective technique to solve this problem. This study evaluated the impacts of supplementary white (W)-light-emitting diodes (LEDs), ultraviolet A LEDs (UV-A), white and blue LEDs (WB), the combinations of white and UV-A LEDs (W-UVA), and white, blue, and UV-A LEDs (WB-UVA) on the leaf morphology, photosynthetic traits, biomass accumulation, root architecture, and hormone content of cucumber (Cucumis sativus L. cv. Tianjiao No. 5) seedlings grown in the greenhouse. The results indicated that supplementary LED lighting led to a decreased plant height, shorter hypocotyl length, bigger leaf area, and thicker leaf compared with those grown with solar light only, regardless of light quality. The shoot fresh weight, root fresh weight, and seedling quality index of cucumber seedlings grown under the combinations of white, blue, and UVA radiations increased by 30.8%, 3.2-fold, and 1.8-fold, respectively, compared with those grown with natural light only. However, no significant differences were exhibited in the biomass accumulation of greenhouse-grown cucumber seedlings between the control and the UVA treatment. The cellulose content and stem firmness of greenhouse-grown cucumber seedlings grown under the combinations of white, blue, and UVA radiations increased by 49.9% and 13.1%, respectively, compared with those grown under white light only. Additionally, the cytokinin content of cucumber seedlings was promoted by over 36.7% by applying supplementary light. In summary, the combinations of white, blue, and UVA radiations led to compact morphological characteristics, superior mechanical properties, and preferable growth performance, which could be applied as an available lighting strategy to obtain the desired morphological and quality properties of vegetable seedlings. Full article
(This article belongs to the Special Issue Impact of Light on Horticultural Crops)
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10 pages, 1635 KiB  
Article
A Light Recipe including Far-Red Wavelength during Healing of Grafted Watermelon Seedlings Enhances the Floral Development and Yield Earliness
by Filippos Bantis, Anna Gkotzamani, Christodoulos Dangitsis and Athanasios Koukounaras
Agriculture 2022, 12(7), 982; https://0-doi-org.brum.beds.ac.uk/10.3390/agriculture12070982 - 07 Jul 2022
Cited by 5 | Viewed by 1535
Abstract
Watermelon is widely propagated through grafting, after which seedlings are subjected to healing under controlled conditions including artificial lighting. Light wavelengths, such as blue, red, and far-red, impose considerable effects on seedlings, which possibly carry on to the mature plants. The aim of [...] Read more.
Watermelon is widely propagated through grafting, after which seedlings are subjected to healing under controlled conditions including artificial lighting. Light wavelengths, such as blue, red, and far-red, impose considerable effects on seedlings, which possibly carry on to the mature plants. The aim of the present study is to examine whether different light wavelengths during healing of grafted watermelon seedlings impose variable effects during field cultivation. After grafting, seedlings were healed in an environmentally controlled healing chamber under fluorescent (FL) lamps and light-emitting diodes, providing 100% red (R), 100% blue (B), 88/12% R/B (12B), and 12B including 5% far-red (12B + FR). After acclimatization, seedlings were transplanted in the field. Vegetative growth until floral initiation was enhanced by 12B and 12B + FR, as shown by stem diameter and leaf number measurements. Flowering was mainly accelerated by 12B + FR and considerably decelerated by FL and B. The same pattern was followed by fruit yield, which was similar for all treatments at the end of the experiment. Nevertheless, fruit quality was not affected by any of the light treatments. It is concluded that a light recipe, including red, blue and far-red, wavelengths during healing of grafted seedlings enhances the overall growth, and flowering and yield earliness of watermelon crops. Full article
(This article belongs to the Special Issue Impact of Light on Horticultural Crops)
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12 pages, 1114 KiB  
Article
Proposed Light Wavelengths during Healing of Grafted Tomato Seedlings Enhance Their Adaptation to Transplant Shock
by Christos Melissas, Filippos Bantis, Christodoulos Dangitsis, Stefanos Kostas and Athanasios Koukounaras
Agriculture 2022, 12(6), 797; https://0-doi-org.brum.beds.ac.uk/10.3390/agriculture12060797 - 31 May 2022
Cited by 2 | Viewed by 1977
Abstract
Tomato, which is mainly established with grafted seedlings, is one of the most popular vegetables worldwide with a high nutritional value,. Market demand for grafted seedlings is high in specific seasons; thus, commercial nurseries face a problem of limited space availability during the [...] Read more.
Tomato, which is mainly established with grafted seedlings, is one of the most popular vegetables worldwide with a high nutritional value,. Market demand for grafted seedlings is high in specific seasons; thus, commercial nurseries face a problem of limited space availability during the healing stage. Light quality is an essential parameter during healing that can adjust seedling development towards desirable traits and lead to time and space saving during seedling production. Moreover, transplant shock constitutes another challenge that could limit crop yield. The objective of this study was to evaluate the overall quality of grafted tomato seedlings and their potential adjustment to transplant shock as affected by different light spectra during healing in a chamber. Evaluations were conducted immediately after exiting the healing chamber and after transplantation into pots. Light wavelengths were used from fluorescent lamps (FL) or light-emitting diodes with red (R), blue (B), red–blue combinations with 12 and 24% blue (12B and 24B), and white (W) emitting 11% blue. W enhanced the dry shoot biomass and the root architecture before and after transplantation. 24B led to an increased stem diameter, root development, and phenolic and antioxidant accumulation at both phases of the experiment. 12B enhanced the leaf area before transplantation and root development after transplantation. FL, R and B induced inferior seedling growth compared to the red–blue-containing LEDs, with B performing poorly in almost all tested parameters. Overall, red, including 11–24% blue, provides the optimum light conditions during the healing stage for the production of high-quality grafted tomato seedlings, with advanced capabilities of abiotic stress adaptation to transplant shock. Full article
(This article belongs to the Special Issue Impact of Light on Horticultural Crops)
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31 pages, 4696 KiB  
Article
Enabling Year-round Cultivation in the Nordics-Agrivoltaics and Adaptive LED Lighting Control of Daily Light Integral
by Marco Hernandez Velasco
Agriculture 2021, 11(12), 1255; https://0-doi-org.brum.beds.ac.uk/10.3390/agriculture11121255 - 11 Dec 2021
Cited by 7 | Viewed by 3201
Abstract
High efficacy LED lamps combined with adaptive lighting control and greenhouse integrated photovoltaics (PV) could enable the concept of year-round cultivation. This concept can be especially useful for increasing the production in the Nordic countries of crops like herbaceous perennials, forest seedlings, and [...] Read more.
High efficacy LED lamps combined with adaptive lighting control and greenhouse integrated photovoltaics (PV) could enable the concept of year-round cultivation. This concept can be especially useful for increasing the production in the Nordic countries of crops like herbaceous perennials, forest seedlings, and other potted plants not native of the region, which are grown more than one season in this harsh climate. Meteorological satellite data of this region was analyzed in a parametric study to evaluate the potential of these technologies. The generated maps showed monthly average temperatures fluctuating from −20 °C to 20 °C throughout the year. The natural photoperiod and light intensity also changed drastically, resulting in monthly average daily light integral (DLI) levels ranging from 45–50 mol·m−2·d−1 in summer and contrasting with 0–5 mol·m−2·d−1 during winter. To compensate, growth room cultivation that is independent of outdoor conditions could be used in winter. Depending on the efficacy of the lamps, the electricity required for sole-source lighting at an intensity of 300 µmol·m−2·s−1 for 16 h would be between 1.4 and 2.4 kWh·m−2·d−1. Greenhouses with supplementary lighting could help start the cultivation earlier in spring and extend it further into autumn. The energy required for lighting highly depends on several factors such as the natural light transmittance, the light threshold settings, and the lighting control protocol, resulting in electric demands between 0.6 and 2.4 kWh·m−2·d−1. Integrating PV on the roof or wall structures of the greenhouse could offset some of this electricity, with specific energy yields ranging from 400 to 1120 kWh·kW−1·yr−1 depending on the region and system design. Full article
(This article belongs to the Special Issue Impact of Light on Horticultural Crops)
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15 pages, 1211 KiB  
Article
The Impact of LED Light Spectrum on the Growth, Morphological Traits, and Nutritional Status of ‘Elizium’ Romaine Lettuce Grown in an Indoor Controlled Environment
by Bożena Matysiak, Stanisław Kaniszewski, Jacek Dyśko, Waldemar Kowalczyk, Artur Kowalski and Maria Grzegorzewska
Agriculture 2021, 11(11), 1133; https://0-doi-org.brum.beds.ac.uk/10.3390/agriculture11111133 - 12 Nov 2021
Cited by 15 | Viewed by 5268
Abstract
The study examined the influence of light quality on the growth and nutritional status of romaine lettuce grown in deep water culture with a floating raft system using two different nutrient solutions. Four spectra of LED light were used with different ratios of [...] Read more.
The study examined the influence of light quality on the growth and nutritional status of romaine lettuce grown in deep water culture with a floating raft system using two different nutrient solutions. Four spectra of LED light were used with different ratios of R, G, and B lights (80:10:10, 70:10:20, 60:10:30, and 70:18:12). Two nutrient solutions with a low (A) and moderately high (B) nutrient content were used. Regardless of the nutrient solution, the RGB 70:18:12 light promoted the production of leaf biomass as well as inhibited the accumulation of K and Mg in the leaves. Moreover, those plants were characterized by a low Nitrogen Balance Index (NBI) and a high flavonol index. In the last week of cultivation, there was a strong decrease in K, P, and nitrates in the nutrient solution, and an increase in Ca. In the final stage of growth, symptoms of withering of the tips of young leaves (tipburn) were observed on the plants. The most damage was observed on the plants growing under 70:10:20, 70:18:12, and with the higher concentration of minerals in the solution (B). Full article
(This article belongs to the Special Issue Impact of Light on Horticultural Crops)
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14 pages, 3104 KiB  
Article
Growth and Energy Use Efficiency of Grafted Tomato Transplants as Affected by LED Light Quality and Photon Flux Density
by Jianfeng Zheng, Peidian Gan, Fang Ji, Dongxian He and Po Yang
Agriculture 2021, 11(9), 816; https://0-doi-org.brum.beds.ac.uk/10.3390/agriculture11090816 - 27 Aug 2021
Cited by 13 | Viewed by 2745
Abstract
This study was conducted to compare the effects of broad spectrum during the whole seedling period and photon flux density (PFD) in the healing stage on the growth and energy use efficiency of grafted tomato (Lycopersicon esculentum Mill.) transplants in a plant [...] Read more.
This study was conducted to compare the effects of broad spectrum during the whole seedling period and photon flux density (PFD) in the healing stage on the growth and energy use efficiency of grafted tomato (Lycopersicon esculentum Mill.) transplants in a plant factory. Fluorescent lights, white LED lights, and white plus red LED lights were applied at the growth processes of grafted tomato transplants from germination of rootstock and scion to post-grafting. Three levels of PFD (50, 100, 150 μmol m−2 s−1) were set in the healing stage under each kind of light quality. The results indicated that the growth and quality of grafted tomato transplants under different broad spectrums were influenced by the ratio of red to blue light (R/B ratio) and the ratio of red to far-red light (R/FR ratio). A higher R/B ratio was beneficial to total dry matter accumulation, but excessive red light had a negative effect on the root to shoot ratio and the seedling quality index. The higher blue light and R/FR ratio suppressed stem extension synergistically. The LED lights had good abilities to promote plant compactness and leaf thickness in comparison with fluorescent lights. The plant compactness and leaf thickness increased with the increase in daily light integral in the healing stage within a range from 2.5 to 7.5 mol m−2 d−1 (PFD, 50 to 150 μmol m−2 s−1). Compared to fluorescent lights, the LED lights showed more than 110% electrical energy saving for lighting during the whole seedling period. Higher PFD in the healing stage did not significantly increase the consumption of electric power for lighting. White plus red LED lights with an R/B ratio of 1.2 and R/FR ratio of 16 were suggested to replace fluorescent lights for grafted tomato transplants production considering the high quality of transplants and electrical energy saving, and PFD in the healing stage was recommended to be set to 150 μmol m−2 s−1. Full article
(This article belongs to the Special Issue Impact of Light on Horticultural Crops)
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9 pages, 1269 KiB  
Article
Enhancing Growth and Glucosinolate Accumulation in Watercress (Nasturtium officinale L.) by Regulating Light Intensity and Photoperiod in Plant Factories
by Vu Phong Lam, Jaeyun Choi and Jongseok Park
Agriculture 2021, 11(8), 723; https://0-doi-org.brum.beds.ac.uk/10.3390/agriculture11080723 - 30 Jul 2021
Cited by 5 | Viewed by 2796
Abstract
Recent advancements in light-emitting diode technology provide an opportunity to evaluate the correlation between different light sources and plant growth as well as their secondary metabolites. The aim of this study was to determine the optimal light intensity and photoperiod for increasing plant [...] Read more.
Recent advancements in light-emitting diode technology provide an opportunity to evaluate the correlation between different light sources and plant growth as well as their secondary metabolites. The aim of this study was to determine the optimal light intensity and photoperiod for increasing plant growth and glucosinolate concentration and content in watercress. Two-week-old seedlings were transplanted in a semi-deep flow technique system of a plant factory for 28 days under four photoperiod–light intensity treatments (12 h—266 µmol·m−2·s−1, 16 h—200 µmol·m−2·s−1, 20 h—160 µmol·m−2·s−1, and 24 h—133 µmol·m−2·s−1) with the same daily light integral. The mean values of shoot fresh and dry weights were the highest under the 20 h—160 µmol·m−2·s−1 treatment, although there was no significant difference. Net photosynthesis and stomatal conductance gradually decreased with decreasing light intensity and increasing photoperiod. However, total glucosinolate concentration was significantly higher under 20 h—160 µmol·m−2·s−1 and 24 h—133 µmol·m−2·s−1 compared with 12 h—266 µmol·m−2·s−1 and 16 h—200 µmol·m−2·s−1. The total glucosinolate content was the greatest under 20 h—160 µmol·m−2·s−1 treatment. These data suggest that the 20 h—160 µmol·m−2·s−1 treatment promoted the maximum shoot biomass and glucosinolate content in watercress. This study supplies the optimal light strategies for the future industrial large-watercress cultivation. Full article
(This article belongs to the Special Issue Impact of Light on Horticultural Crops)
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12 pages, 3262 KiB  
Article
Effect of Colour of Light on Rooting Cuttings and Subsequent Growth of Chrysanthemum (Chrysanthemum × grandiflorum Ramat./Kitam.)
by Anita Schroeter-Zakrzewska and Faisal Anggi Pradita
Agriculture 2021, 11(7), 671; https://0-doi-org.brum.beds.ac.uk/10.3390/agriculture11070671 - 15 Jul 2021
Cited by 8 | Viewed by 3325
Abstract
A closed system for plant production with artificial light is an innovative method of plant cultivation. The objective of this study was to investigate the effect of light colour on rooting cuttings and subsequent growth of chrysanthemum (Chrysanthemum × grandiflorum Ramat./Kitam.) During [...] Read more.
A closed system for plant production with artificial light is an innovative method of plant cultivation. The objective of this study was to investigate the effect of light colour on rooting cuttings and subsequent growth of chrysanthemum (Chrysanthemum × grandiflorum Ramat./Kitam.) During the experiments, the following conditions were maintained: photoperiod 16 h or 10 h, temperature 22 °C, relative humidity of 65–70%. LED lamps emitted the following light colours: white, blue, white + blue (50:50), and red + blue (75:25). For all light spectra, the photosynthetic photon flux density (PPFD) was 50 μmol m−2 s−1. The effectiveness of exposure to different light colours was measured with parameters: cutting weight (g), cutting length (cm), length of roots, and index of leaf greenness (SPAD). The measurements referred to plant features determining plant quality, i.e., the number of flower buds and flower head, the diameter of the flower head, height of plants, index of leaf greenness (SPAD), the number of leaves, and the fresh and dry weights of aboveground parts of plants. The rooting of cuttings and subsequent growth are integral processes in the cultivation of potted chrysanthemums. Both were differently affected by the colour of light from LED lamps. The exposure to red + blue light resulted in the highest leaf greenness index (SPAD) value and the shortest cuttings with the longest roots. White + blue light significantly influenced most of the growth parameters, except the height of the plants and the number of leaves. Full article
(This article belongs to the Special Issue Impact of Light on Horticultural Crops)
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16 pages, 4962 KiB  
Article
Comparative Assessment of Hydroponic Lettuce Production Either under Artificial Lighting, or in a Mediterranean Greenhouse during Wintertime
by Orfeas Voutsinos, Maria Mastoraki, Georgia Ntatsi, Georgios Liakopoulos and Dimitrios Savvas
Agriculture 2021, 11(6), 503; https://0-doi-org.brum.beds.ac.uk/10.3390/agriculture11060503 - 29 May 2021
Cited by 15 | Viewed by 6290
Abstract
Butterhead lettuce was grown hydroponically in a vertical farm under high (HLI) and low (LLI) light intensity (310, and 188 μmol m−2 s−1, respectively) and compared to hydroponically grown lettuce in a greenhouse (GT) during wintertime in Athens, Greece (144 [...] Read more.
Butterhead lettuce was grown hydroponically in a vertical farm under high (HLI) and low (LLI) light intensity (310, and 188 μmol m−2 s−1, respectively) and compared to hydroponically grown lettuce in a greenhouse (GT) during wintertime in Athens, Greece (144 μmol m−2 s−1). The highest plant biomass was recorded in the HLI treatment, whereas LLI and GT produced similar plant biomass. However, the LLI produced vortex-like plants, which were non-marketable, while the plants in the GT were normal-shaped and saleable. Net photosynthesis was highest in the HLI and higher in the LLI than in the GT, thereby indicating that light intensity was the dominant factor affecting photosynthetic performance. Nevertheless, the unsatisfactory performance of the LLI is ascribed, not only to reduced light intensity, but also to reduced light uniformity as the LED lamps were closer to the plants than in the HLI. Furthermore, the large solar irradiance variability in the GT resulted in substantially higher adaptation to the increased light intensity compared to LLI, as indicated by chlorophyll fluorescence measurements. Light intensity and photoperiod are believed to be the primary reasons for increased nitrate content in the GT than in the vertical farming treatments. Full article
(This article belongs to the Special Issue Impact of Light on Horticultural Crops)
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