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Optimal red: Blue ratio in led lighting for nutraceutical indoor horticulture
... The temperature of the nutrient solution can impact precipitation, co-precipitation, and complexation processes [85]. Maintaining an optimal temperature range of 18-27 • C [29,33,59,63,64,79] is crucial to prevent nutrient insolubility and ensure availability for plants. ...
... Even a minor change in pH has an apparent physiological response [81]. A pH range of 5-7.5 is generally recommended for most plant species in hydroponics [15,33,34,51,64]. ...
... Light conditions significantly influence the nutritional and sensory qualities of plants [7,63,65]. For instance, lettuce shows optimal growth under artificial lighting with a photosynthetic photon flux density (PPFD) of 150-250 µmolm −2 s −1 [7,62,64,93]. Hydroponics utilizes artificial illumination to supplement light requirements for the process of photosynthesis, a photochemical reaction that is crucial for converting CO 2 into carbohydrates [10,65]. Plant photoreceptors absorb this radiation and are responsible for the morphology and growth of the plant [7]. ...
Hydroponics is a soilless farming technique that has emerged as a sustainable alternative. However, new technologies such as Industry 4.0, the internet of things (IoT), and artificial intelligence are needed to keep up with issues related to economics, automation, and social challenges in hydroponics farming. One significant issue is optimizing growth parameters to identify the best conditions for growing fruits and vegetables. These parameters include pH, total dissolved solids (TDS), electrical conductivity (EC), light intensity, daily light integral (DLI), and nutrient solution/ambient temperature and humidity. To address these challenges, a systematic literature review was conducted aiming to answer research questions regarding the optimal growth parameters for leafy green vegetables and herbs and spices grown in hydroponic systems. The review selected a total of 131 papers related to indoor farming, hydroponics, and aquaponics. The review selected a total of 123 papers related to indoor farming, hydroponics, and aquaponics. The majority of the articles focused on technology description (38.5%), artificial illumination (26.2%), and nutrient solution composition/parameters (13.8%). Additionally, remaining 10.7% articles focused on the application of sensors, slope, environment and economy. This comprehensive review provides valuable information on optimized growth parameters for smart hydroponic systems and explores future prospects and the application of digital technologies in this field.
... Plants are characterized by their ability to respond to different wavelengths since they have different photoreceptors, phytochromes for red and far red light (Franklin and Quail, 2010), cryptochromes, phototropins and zeitlupes for blue light (Demarsy and Fankhauser, 2009;Lin and Shalitin, 2003) and UVR8 for ultraviolet b light (Rizzini et al., 2011). Use of Light-Emitting Diodes (LED) technology as supplementary light has become usual in different crops (Dlugosz-Grochowska et al. 2016;Tewolde et al. 2016;Piovene et al., 2015), due to advances in recent years that have allowed reduced cost since they are more efficient than conventional light (Goto et al., 2014). The peak wavelength of LED used in horticulture ranges from blue (450 nm) to far red (730 nm) (Yeh and Chung, 2009). ...
... The plant response to light is very specific, it varies between crops and even cultivars (Mizuno et al., 2011), could be influenced by a variety of factors (Ouzounis et al., 2015) and is still poorly studied. Previous studies on LED lights used during strawberry growing reported differences in content of functional compounds, thus have been described an increase of anthocyanins (Choi et al. 2013;Kadomura-Ishikawa et al., 2013 andZhang et al. 2018), phenolic compounds (Choi et al., 2015) and flavonoids concentration (Piovene et al., 2015). As well differences in some parameter related with organoleptic quality have been described, for example an increase in content of fructose (Choi et al. 2013), organic acids (Choi et al., 2015) and color (Nadalinii et al., 2017). ...
... The higher α-amylase inhibition in vitro was obtained at red light treatment with 10 lights per lineal meter and blue light treatment with 5 lights per lineal meter, the rest of the combinations tested did not show statistically significant differences compared with control ( Fig. 1). (Choi et al. 2015;Paparozzi et al., 2018) or not differences between red and blue light compared to control (Piovene et al., 2015). ...
Strawberries are a widely consumed fruit that are increasingly popular due to the perceived health benefits associated with their consumption. Fruit quality is highly dependent on the growing environment where light is one of the most significant environmental factors influencing plant physiology and metabolism. In the present work we sought to test the hypothesis that manipulation of the light environment in a commercial growing environment would influence fruit yield and quality. Fruit were grown with supplemental light-emitting diodes in the red (623 nm), far-red (727 nm) and blue (470 nm) regions of the spectrum at three different densities. The majority of light treatments resulted in increased fruit yield. All treatments also significantly enhanced contents of anthocyanins and polyphenols. Furthermore fruit exhibited enhanced antioxidant activity. Individual strawberry sugars showed differences depending on sampling date whereas Brix, acidity and ascorbic acid was not affected by the LED lights. Strawberry fruit extracts from all treatments exhibited the capacity to inhibit the digestive enzymes pancreatic lipase and α-amylase activity in vitro, extract from fruit grown under supplemental lighting had a greater inhibitory capacity. These data suggest that strawberry fruit grown in the presence of supplemental light may impart health benefits via enhanced functional compounds and by limiting calorific assimilation. The findings of this study provide the first evidence that the use of light-emitting diodes increase the inhibitory effects of polyphenols on digestive enzymes in strawberry.
... Fresh and dry weights of plants under red light were higher than other treatments, similar to Chen et al. (2016) and Johkan et al. (2010). Piovene et al. (2015) reported that basil leaf fresh weight was consistently reduced by blue light; however, red light contributed to a 1.5-fold increase in fresh weight. This is consistent with the current research findings. ...
... In another study, orange light increased tomato dry matter at the EoD rather than blue light (Matsuda et al., 2016). Although different light regimes are required for different crops, the optimal ratio of blue to red light reportedly depended on crop yield (Piovene et al., 2015). Light quality usually affects photosynthesis and plant morphology, ultimately leading to changes in yield and dry weight percentages. ...
... (2010), chlorophyll a and b contents increased in strawberries under red light treatment. However, Piovene et al. (2015) indicated that areas covered by the red light spectrum largely affect photosynthesis. Johkan et al. (2010) also observed that total chlorophyll in the lettuce was lowered by red and blue lights rather than fluorescent light. ...
Article type: Increasing day length during the short photoperiod in fall and winter is a beneficial method of increasing biomass production and altering plant morphology and phytochemistry. The objective of this study was to examine the effects of light quality at the end of the day (EoD) on the growth and phytochemical characteristics of lemon balm. During short-day photoperiods in autumn, lemon balm (Melissa officinalis L.) seedlings were exposed to red, blue, and combined red/blue light using light-emitting diodes for 2 hours at the EoD. The results showed that exposure to red light significantly increased biomass. Plants grown under blue light yielded the highest percentage of dry matter and their leaves had the highest chlorophyll content and flavonoids. The highest carotenoid content was found in plants irradiated with blue light and later with red+blue light. The highest levels of total phenols, anthocyanins, and antioxidant activity were found in plants grown under red light. In addition, light quality had a significant effect on essential oil content. The highest essential oil content was obtained in the red and red+blue light treatments. The light quality at the EoD significantly changed the essential oil composition. The blue light significantly increased the citronellal content but decreased the geranial and linalool content. This study provided insights into the effects of Eo D light quality on plant growth and metabolite accumulation in lemon balm with a short photoperiod. In conclusion, supplemental light at the EoD can effectively improve plant growth and secondary metabolite quality in medicinal plants.
... They found that supplemental RB light improved the growth and photosynthesis of seedlings grown inside an incubator and in plastic pots. In sweet basil (Ocinum basilicum) and strawberry (Fragaria × Ananassa), it was found that LED lighting improves yield, energy use efficiency (EUE), antioxidants, and phenolics, while it reduces nitrate concentration; the optimum LED R/B ratio was 0.7, with B light being predominant [15]. Later, it was found that an R/B ratio of 3 (red 70%/blue 23%) was optimal for the sustainable indoor growing of sweet basil, scoring the highest yield, quality, resource (water and energy) use efficiency and antioxidant activity. ...
... Water-use efficiency was defined as a plant's fresh weight per total amount of water supplied to the culture tanks and absorbed by plants (g Fw L −1 H 2 O) [15]. ...
... Energy-use efficiency, respectively, was calculated as the ratio between total yield and total electricity consumption [15]. In order to determine the electrical energy consumption, own measurements, based on energy data logger, as well as the manufacturer's information of the rated power, were used. ...
By applying three different LED light treatments designated as Blue (B), Red(R)/Blue(B), Red(R) and White (W) light as well as the control, the effect on Diplotaxis tenuifolia phenotype (yield and quality), physiological, biochemical, molecular status as well as growing systems’ resources use efficiency, was examined. We observed that basic leaf characteristics such as leaf area, leaf num-ber, relative chlorophyll content as well as root characteristics such as total root length and root architecture remain unaffected by different LEDs. Yield expressed in fresh weight is slightly low-er in LED lights than in the control (1113 gr m−2), with R light producing the least (679 gr m−2). However, total soluble solids were significantly affected (highest, 5.5° Brix, in R light) and FRAP was improved in all LED lights (highest, 191.8 μg/g FW, in B) in comparison to the control while nitrate content was less (lowest, 949.2 μg/g FW, in R). Differential gene expression showed that B LED light affects more genes in comparison to R and R/B lights. Although total phenolic content was improved under all LED lights (highest, 1.05 mg/g FW, in R/B) we did not detect a signifi-cant amount of DEGs in the phenylpropanoid pathway. R light positively impacts the expression of the genes encoding for photosynthesis components. On the other hand, the positive impact of R light on SSC was possibly since the expression of key genes such as SUS1 was induced. In summary, this research is an integrative and innovative study where the exploration of the effect of different LED lights on rocket growing under protected cultivation, in a closed chamber cultivation system, is performed in multiple levels.
... There was only a minor difference between the means of A and B1. B2 had a slightly lower mean R/B value, indicating a less than 10% shift in the spectral peak ratios at low irradiance, but this difference is negligible considering the broad light response sensitivity range of plants [34]. ...
... An important assumption of this study was that the quality of light is constant in all cultivation trays. Although the R/B ratio of B2 was statistically different from the groups A and B1, the difference was minor compared with the spectral sensitivity of plant growth traits measured by various research groups for different species [22,24,34]. The statistically significant differences in R/B ratios may be attributed to a slight shift in the emission spectrum of the luminaires at low power or to the increased portion of wall reflections in the low end of the R/B distribution, especially on the extreme dark zone of tray B2, as indicated by the dark blue colors in Figure 5a. ...
Differences in individual plant growth are affected by the spatial variation of light intensity, reducing the homogeneity of microgreen crops. Identifying the tradeoffs between light uniformity and crop quality is challenging due to the confounding effect of nonuniform illuminance with other noise factors. This study presents the results of hydroponic pea (Pisum sativum, L) growth experiments aimed at quantifying the effect of photon irradiance variations. By adjusting the power of LED luminaires, we established one uniformly illuminated zone and two non-uniformly illuminated zones. Germinated seeds with 6 cm-long radicles were transplanted to cultivation trays with known light intensity in predetermined positions. Plants were cut 12 days after the start of light treatment and measured for fresh weight and shoot height. Our findings revealed no significant difference between the crop yield on trays having the same average PPFD but different light uniformity. However, correlation analysis of individual measurement data showed that local PPFD differences explained 31% of the fresh weight variation, and the rest was attributed to noise in the germination and growth processes. We also discuss the implications of our findings for the design and optimization of vertical farms.
... In this context, light-emitting diodes (LED) have many advantages with respect to fluorescent and HPS (high-pressure sodium) lamps, since LEDs are more energy efficient and economical [13,14]. LEDs also have a longer operational lifetime (30,000-50,000 h) than fluorescent (20,000 h) or incandescent lights (1000 h), and the limited emission of radiant heat allows their placement near the plant canopy [15]. ...
... However, defining tailored light recipes for specific plant species is not so easy, according to the literature, and other works should consolidate the knowledge in this field. In fact, the optimal light recipe depends not only on the plant species, but also on other factors like the growth stages or the objectives of the growth, e.g., flowering, vegetative growth, fruit, and even postharvest quality management [14,18]. In addition, environmental variables, such as humidity and temperature, must be taken into strong consideration. ...
The modern agriculture system based on open-field crops requires a lot of energy and resources in terms of soil, water, and chemicals. Vertical farming (VF) systems could be a viable alternative for some types of cultivation that are receiving interest thanks to their high modularity, optimized water and nutrients use, and LEDs employment as an energy-efficient light source. However, VF design and installation are expensive and require well-tailored optimization depending on the specific crop to increase its competitiveness. This work analyzed the effects of different combinations of NPK (nitrogen-phosphorus-potassium) slow-release fertilizers and LED-based light recipes on the growth of baby leaf lettuce (Lactuca sativa L.), taking advantage of the Design of Experiments (DoE) methodology. The type of slow-release fertilizer, its quantity measured as the number of aggregates from 0 to 6, and the type of light recipe were considered as input factors, and their possible influence on the growth of lettuce (in terms of morphological parameters) in a controlled indoor farming system was measured. Results suggest that using higher fertilizer inputs equal to six aggregates leads to an increase of average leaf area equal to 46% (from 13.00 cm 2 to 19.00 cm 2), while the fresh weight of lettuce increases by 65% (from 1.79 g to 2.96 g). However, the height of plants also depends on the combination of the light recipes. In particular, the separate coupling of higher inputs of two fertilizers and light recipes leads to an increase in the height of lettuce equal to 33% (from 6.00 cm to 8.00 cm).
... LEDs increased carotenoid concentrations in edible flowers opened a broad room for further investigations of their usage (Kopsell et al., 2016). In contrast, aromatic herbs exhibit increased accumulation of phenols, anthocyanins and carotenoids when subjected to various LED recipes (Piovene et al., 2015). Furthermore, an indoor chamber or glasshouse equipped with LED's not only provides the best suited photosynthetic active radiation (PAR) but also ensures better control of temperature, humidity and water availability for the plant to display a better growth and overall production. ...
... Owing to the harmful effects of nitrates on the human body, foods with less nitrates are preferred in the diet and a European regulation (EU: 1258/2011) exists to regulate the nitrate content of foods. Leafy vegetables such as tatsoi (Simanavi cius and Vir sil _ e, 2018), basil (Piovene et al., 2015), spinach (Ohashi-Kaneko et al., 2007), rocket (Signore et al., 2020), and lettuce (Bian et al., 2020) have been shown to contain less nitrate when exposed to LED lights. The continuous LED treatment in this experiment has shown a startling reduction but the pulsed LED and control treatments both had significantly greater nitrate concentrations. ...
Photoperiod, light intensity, and spectral quantum distribution (SPD) affect plant development and physiology. Light determines morphological signals, influences plant behavior and regulates metabolism in addition to providing energy for photosynthesis. In this experiment, lettuce (Lactuca sativa) was grown in an indoor LED-equipped chamber, operated in a pulsed and continuous mode, with an average photosynthetic photon flux density (PPFD) at a seedling level of 150 µmole s¯¹ m¯², photoperiod of 16 h for growing cycle of 30 days. The primary aim of this study was to observe the effects of varying LED on the growth and quality of the produce. Regardless of the treatments, in both continuous and pulsed LED, an increment in the yield, leaf length and leaf width of lettuce was recorded in comparison to the control, which was managed in a glasshouse under controlled environmental conditions using a winter cropping cycle. In-vitro physiological analysis of lettuce revealed the outperformance of the continuous LED treatment over the pulsed LED as well as the control in terms of total sugars, chlorophyll concentration, carotenoids, phenolic index, and sucrose accumulation. Continuous LED treatment has also resulted in a significant reduction in nitrate content, a commercially vital parameter, making it the most advantageous and effective of all the treatments performed. However, the production of anthocyanins, an antioxidant released during stress, was enhanced under pulsed LED which requires further investigation and improvements to achieve an improved metabolite profile of lettuce with a minimal energy usage and cost.
... Energy Use Efficiency (EUE), Water Use Efficiency (WUE), and Light Use Efficiency (LUE) were measured both on PFAL and greenhouse. The energy use efficiency was calculated based on the energy consumption and yield of rocket expressed by the equation as the ratio between total yield and total electricity consumption [27]. ...
... The water use efficiency was expressed as a plant's fresh weight per total amount of water supplied to the culture tanks and absorbed by plants [27]. ...
Wild rocket is a leafy vegetable with economic interest as a consequence of baby leaf ready-to-eat salads. The climate crisis is expected to influence wild rocket production, but these effects could be confronted with cultivation in greenhouses and plant factories with artificial lighting (PFALs). Climate responses are related to growing seasons. Our objective was to test the impact of two growing seasons, winter and summer, on the growth and physiology of wild rocket baby leaves in different controlled environment systems (greenhouse and PFAL). The growth cycle was reduced by 27% in the PFAL compared to the greenhouse during winter. Summer yield was greater in the greenhouse, but leaf number and area were greater in the PFAL. The lowest water use efficiency was recorded in the greenhouse during summer. Energy use efficiency was lower in PFAL compared to the greenhouse. Land use efficiency was not affected by the growing system, but in PFALs it is able to increase it by growing in vertical layers. Relative chlorophyll content and total soluble solids were enhanced in the greenhouse. The photosynthetic efficiency evaluation showed considerable stress in summer-grown plants in the greenhouse, as shown by PIABS and φP0. In general, the production was similar in the PFAL regardless of seasons.
... Plants 2023,12, 2056 ...
... Plants 2023, 12, 2056 ...
Recently, LEDs with various light qualities have been used in closed plant factories, and they are known to have different effects on the growth and quality of crops. Therefore, this study was conducted to investigate the change in growth and quality in mini red romaine lettuce using LEDs with various light qualities. Wide red spectrum (WRS)-LEDs, blue (B)-LEDs, blue + red (BR)-LEDs, red (R)-LEDs, and white (W)-LEDs were used as the artificial light sources. Regarding growth, the R-LED treatment showed the most positive effect, but the leaf shape was not normal and the Hunter b* value was not suitable because it was higher than that of the other treatments. The Hunter a*, SPAD, and NDVI values of the B- and BR-LED treatments were effective, but this was not the case for those of the R- and W-LED treatments. The anthocyanin reflectance index 1 (ARI1) was 20 times higher in the B-LED treatment than in the R-LED treatment, and the ascorbic acid content was the highest in the WRS-LED treatment. In the sensory evaluation, bitterness and sweetness showed opposite tendencies. Regarding the overall preference, the BR-LED treatment received the highest score. Correlation analysis showed that the bitterness was closely correlated with the anthocyanin content and leaf color. Taken together, BR-LEDs provided a good top fresh weight, dark red leaves, and high anthocyanin and ascorbic acid contents, with the highest overall preference; therefore, BR-LEDs were the most suitable for the cultivation of mini red romaine lettuce.
... Supplemental blue LED light also seems to accelerate the growth rate of certain plants, such as strawberries [68] and azalea [69], yet they still require red light wavelength in order to maintain their physical and nutritional quality. Spinach also displays a similar reaction to supplemental blue light, with researchers proving that cold white LEDs-LEDs with very high photon radiance on the 445 nm wavelength-advance the development of spinach plants by a full week, yet the research did not investigate what effect that has on the nutritional quality of the spinach plants [28] [33]. ...
... For example, the combination of red and blue light wavelength greatly increases both the size and the weight of peppers, while it offers easy modulation of capsaicinoids and carotenoids, as well as control over the fruit's color [26]. Basil and strawberries perhaps the most prominent example, with researchers identifying that the combination of red and blue LED light increases both the leaf yield and the nutritional quality of the plant [68]. There are also studies concluding that monochromatic or duochromatic LED light have poor results on the yield of certain plants, such as radish [33], suggesting that other wavelength and/or intensity combinations need to be investigated. ...
As energy gradually becomes a more valuable commodity, the desire for reduced energy losses strengthens. Lighting is a critical field on this matter, as it accounts for a large percentage of the global electricity consumption and modern lighting systems are greatly more efficient than incandescent, discharge, and fluorescent lights. Previous research has proven that plants do not require the entire visible spectrum but react only to specific wavelengths, making it possible to control their growth and yield via artificial lighting. The flexibility of control of Light Emitting Diode (LED) lights allows for the combination of great energy losses reduction and controlled plant growth, achieving the improvement of two major parameters in a single action. This review paper summarizes the current research on the effect different light wavelengths have on specific plant species and discusses the applications of LED lighting for horticulture, yield storage, and disease protection.
... Regarding the adjustment of the R:B ratio, the study in [94] investigated various ratios for different cultivars, including both fruit and vegetative plants, specifically strawberry and basil. The control treatment used fluorescent light. ...
Indoor farming in controlled greenhouses is becoming increasingly widespread due to the urgent global need for food and its ability to address challenges posed by climate change and extreme environmental conditions. However, it requires costly, energy-intensive supplemental lighting, raising concerns about economic feasibility and increased energy demand from power systems. To address these concerns, recent studies have explored lighting strategies that manipulate different lighting factors, such as light quantity and spectra, aiming to reduce costs, increase energy efficiency, and optimize plant growth and productivity. This review highlights these lighting strategies while reporting on both positive and negative effects on plant growth, as well as resultant cost and implications for indoor greenhouses. The reviewed studies indicate that advanced lighting strategies can reduce energy consumption and costs without negatively affecting plant health, achieving reductions of up to 52% in settings with no natural light and up to 92% when sunlight is incorporated. Additionally, we propose a novel taxonomy for mapping different lighting strategies to distributed energy resources, thus positioning indoor greenhouses as microgrids to improve energy management. This taxonomy serves as a foundation for reviewing previous studies that making this review a valuable reference for comparing a broad range of lighting strategies. Furthermore, the proposed mapping aids in translating plant requirements into power system concepts. This framework supports the development of advanced lighting strategies and opens up new research avenues of research that address the needs of the power and agricultural sectors.
... Due to the difference in metabolic plasticity of tested cultivars, red lettuce possibly experienced pulsed LED as a stress, resulting in a reduced nitrate reductase (NR) expression, that led to an enhanced nitrate accumulation. Numerous research in the past on leafy vegetables such as basil, spinach, rocket, green lettuce and tatsoi clearly showed that LED in general is responsible for containing less nitrate in vegetables (Piovene et al., 2015;Ohashi-Kaneko et al., 2007;Signore et al., 2020;Bian et al., 2020;Simanavičius and Viršilė, 2018). Moreover, RB LED is known to enhance the vital metabolic and physiological activities of plants. ...
Light manipulation for plant cultivation is a critical area of study in controlled environment agriculture (CEA), where a variety of artificial lighting conditions are often employed in plant factories, growth chambers and greenhouses. With this aim of manipulation, two lettuce cultivars, green and red, were treated with two different LED treatments: a continuous LED in which an average photosynthetic photon flux density (PPFD) at the seedling level was maintained at 228 µmole s‾ 1 m‾ 2 , a photoperiod of 16 h was set for a growing cycle of 30 days, and a dynamic mode pulsed LED treatment with a pulsed frequency set at 1 kHz with a duty cycle of 50 % along with the PPFD at 228 µmole s‾ 1 m‾ 2 , a 16-hour photoperiod, and a growing cycle of 30 days. Sampling for quality assessment was done at harvesting (T0) and the effect of pre-harvest LED application was analyzed after 7 days of cold storage (T7). A significant reduction in the average fresh weight of both cultivars was seen under pulsed LED while a significant increase in leaf length was noticed among the treatments in red lettuce. Both treatments resulted in non-significant variations for photosynthetic pigments: total chlorophyll and carotenoids, while no significant differences were seen in terms of phenolic index and anthocyanin production in green lettuce. Red lettuce, however, yielded a significantly higher phenolic index for continuous LED at T0, which significantly declined at T7. In green lettuce, nitrate production underwent no significant differences under both treatments and time points; however, pulsed LED in red lettuce yielded significantly higher nitrate than continuous LED at T0. At both timepoints, no marked changes were seen in terms of total sugars in green lettuce, while a significant reduction in sugar was recorded under pulsed LED treatment. On the other hand, a significant decline in total sugars was noticed between the timepoints for red lettuce under continuous LED treatment, while no such variations were seen in red lettuce. Similarly, at T0 both green and red lettuce showed no remarkable increment or decline for sucrose, while it significantly declined between timepoints for red lettuce. Non-destructive analysis was carried out to investigate the health status of lettuce plants where the green lettuce under pulsed LED accumulated higher anthocyanins at both T0 and T7 and higher chlorophyll at T7 than red lettuce under the same LED application. Significantly higher anthocyanins were also seen at T7 between the two treatments in green lettuce. Non-significant differences, however, were found between the treatments and timepoints for both the photochemical maximum quantum efficiency of photosystem II (Fv/Fm ratio) and the overall performance index (PI) of leaves. This research demonstrated the significance of artificial light modification from continuous to pulsed LED to save energy costs and a step forward towards retaining the quality of the produce in this dynamic mode.
... impact on the quantity and caliber of agricultural output [13,16,17]. Plants' photosynthetic activity spectra (PAS) make it abundantly evident that the pigments involved in photosynthesis, chlorophylls and carotenoids, are capable of efficiently absorbing red (600-700 nm) and blue (400-500 nm) light. ...
Phosphites are being recognized as the new emerging candidates for luminescence in the modern era. In the proposed research article, Ce³⁺/Eu²⁺ co-activated NaBa(PO3)3 phosphite phosphors synthesized utilizing sol-gel technique. Through the use of XRD and Rietveld refinement, the phase identity and crystal structure of produced phosphor are examined. SEM is employed to analyze the morphology and elemental composition of the prepared sample. The sample shows blue emission enhancement in the phosphor on energy transfer with the Ce³⁺ ion by 6 times. This highly instance blue emitting phosphor has color purity of 98.49%. These all results confirm that the prepared phosphor is potential candidate for WLEDs, display applications and blue emitting phosphor for plant cultivation applications.
... The most challenging part of LED lights is to supply sufficient or optimum quantity and quality of light to the plants (Samuolienė et al., 2013;Dong et al., 2014). The effects of different light compositions on strawberry growth, yield and fruit quality have been studied by several researchers (Piovene et al., 2015;Choi et al., 2015;Naznin et al., 2016). However, the inconsistency of the reports might be due to different sources of light that often influence plant growth and flower production of strawberry plants. ...
The growth and production of strawberries in a plant factory are highly affected by environmental factors such as light and temperature. Recent interest in plant factory production of strawberries in soilless substrates has raised concerns about the potential effects of root zone temperature (RZT) and light intensity on plant growth and fruit yields. The hypothesis suggests that RZT and light intensity can improve plant growth and affect flower production. This study aimed to investigate the effects of RZT and light intensity on the growth and reproductive performance of strawberries. The root zone of the 'Festival' strawberry plants was subjected to a temperature of 15°C during the night for root zone cooling (RZC) treatment meanwhile without RZT as the control, under two different light intensities: 200 mmolm-2 s -1 and 300 mmolm-2 s -1 . From the result, the root and crown temperatures in the RZC treatment were maintained at 15-21°C. The number of leaves was significantly affected by the interaction between RZT and light intensity. The crown diameter in the RZC treatment group (13.27 cm) was higher than in the control group (12.06 cm). Higher light intensity (356.9 mmolm-2 s -1 ) significantly increased the chlorophyll content. Flower production in the RZC treatment was 52% higher than in the control group. The enumeration of growth organs and flowers increased in the RZC treatment, suggesting the induction of reproductive growth by the low root zone temperature. However, the light intensity received by the plants and the interaction between RZC and light intensity did not have any effect on flower production. Fruit size, fruit pH, fruit firmness and total soluble solids: titratable acidity were not affected by RZT, light intensity, or the interaction between RZT and light intensity. The increase in flower production can be attributed to the lower plant temperature, specifically at the crown, which was at 10-12°C. In conclusion, RZC can induce growth and reproductive performance, ultimately increasing the fruit yield of hydroponically cultivated strawberries in a plant factory.
... LEDs can also be used in various horticultural lighting applications, such as tissue culture, controlled environment research, and supplemental and photoperiod lighting for greenhouses [2]. Te application of LEDs in agricultural cultivation increases yield, quality [1,7], photosynthesis efciency [8][9][10], and the content of secondary metabolite compounds [11][12][13] in agricultural commodities, especially horticultural commodities. However, the efect of LEDs on plant growth and quality is species-specifc, and the efect is infuenced by cultivation conditions [6]. ...
Currently, light-emitting diode (LED) technology has produced a more energy-efficient and versatile technology as an artificial lighting system that can be applied in the agricultural sector. Artificial lighting technology has been proven to be effective in increasing the production of agricultural products, especially horticultural commodities. As one of the primary horticulture commodities, tomatoes are the most common crop produced in controlled environments with LED artificial lighting. The focus of this study is to describe the application of LED lights in tomato cultivation and postharvest. We provide an amalgamation of the recent research achievements on the impact of LED lighting on photosynthesis, vegetative growth, flowering, production, and postharvest of tomatoes. Red-blue (RB) lighting induces photosynthesis; increases the content of chlorophyll a, chlorophyll b, and carotenoids in tomato leaves; regulates vegetative growth in tomatoes; and increases the production of tomatoes. In postharvest tomatoes, blue LED lighting treatment can slowly change the color of the tomato skin to red, maintain hardness, and increase shelf life. Future research may be carried out on the effect of LED artificial lighting on tomatoes’ phytochemical, antioxidant and other crucial nutritional content. Different LED wavelengths can be explored to enhance various bioactive compounds and health-promoting components.
... The second wavelength range is used to accelerate the growth of leaves and stems by providing light that is suitable for photosynthesis. In this range, the wavelength of blue light (450 nm) and red light (660 nm) is incorporated with far-red light 790 nm at a ratio of 50:50 [19,[23][24][25][26]. The final wavelength range is designed for the flowering and propagation stage. ...
... These results demonstrate the importance of blue light in photosynthesis and the subsequent biomass production (Piovene et al. 2015), which is driven by photosynthetic activity (Gerovac et al. 2016). ...
Campomanesia pubescens (gabiroba) is a fruit tree that is native to the Cerrado and that has commercial potential and medicinal properties. It has recalcitrant seeds that do not tolerate desiccation and storage. Here, C. pubescens plants were grown in vitro under different light qualities. Light-emitting diodes (LEDs) were used at wavelengths for white (W) and blue in combination with red in the proportions BR (1:1), BR (1:3) and BR (3:1), at 100 ± 5 μmol m-2 s-1 over a 16-hour photoperiod. The leaf anatomy, chlorophyll a fluorescence, chloroplast pigments and malondialdehyde (MDA) content were evaluated. Studies on Cerrado plants grown in vitro focusing on light quality and its effects on plant development and growth are scarce. Records of anatomical and physiological C. pubescens characteristics when grown in vitro under different lighting qualities using LEDs are nonexistent. In this context, the aim of this study was to analyze the anatomical and physiological responses of C. pubescens seedlings from in vitro cultivation under different light qualities, to support future studies on the propagation and conservation of this species. This work is a pioneer for this species. When the plants were cultivated in combinations of blue/red LEDs 1:1 and 3:1, they yielded higher biomass, presenting higher epidermis and chlorenchyma values with greater stomatal density and functionality, better photosynthetic efficiency, higher Y(II) values, qP and higher total chlorophyll concentrations, and thus these lights did not cause oxidative damage compared to the white (control) LEDs. This study contributed to a better understanding of the anatomical and physiological changes in C. pubescens plants grown in vitro under different light qualities. C. pubescens plants exhibited varied anatomical and physiological characteristics depending on the spectrum of light used here. The combinations of BR (1:1) or BR (3:1) LEDs are promising for the propagation of the species, given their positive influence on most of the studied traits.
... The amount of energy needed to develop lettuce crops under red and blue LED lighting (95 percent red and 5 percent blue) was 50 percent lower than the amount of energy needed to grow the same amount of dry biomass under conventional light sources (Poulet et al., 2014). When treated with LEDs with the highest energy use efficiency compared to conventional fluorescent lamps, it was found that the plants displayed improved nutraceutical properties and increased biomass, fruit yield, antioxidant content and reduced nitrate content in an experiment on the indoor cultivation of basil and strawberries (Piovene et al., 2015). The literature analysis found that microgreens treated with a red and blue LED combination exhibited the highest levels of photosynthetic activity; however, it is not immediately evident what exact ratio of blue and red-light combination produced the results. ...
... However, HPS lamps have a low efficiency of only 25%-30%, which not only requires considerable energy but also induces light stress in plants (Randall et al., 2014). Light-emitting diodes (LEDs) are solid-state, semiconducting diodes that can generate light in the 250 to 1000 nm wavelength range (Piovene et al., 2015). Compared with traditional HPS lamps lighting, LEDs offer a longer life period, greater spectrum specificity, and consume less energy to produce light (D'Souza et al., 2015;Dayani et al., 2016). ...
Background
Light is a critical factor in plant growth and development, particularly in controlled environments. Light-emitting diodes (LEDs) have become a reliable alternative to conventional high pressure sodium (HSP) lamps because they are more efficient and versatile in light sources. In contrast to well-known specialized LED light spectra for vegetables, the appropriate LED lights for crops such as cotton remain unknown.
Results
In this growth chamber study, we selected and compared four LED lights with varying percentages (26.44%–68.68%) of red light (R, 600–700 nm), combined with other lights, for their effects on growth, leaf anatomy, and photosynthesis of cotton seedlings, using HSP lamp as a control. The total photosynthetic photon flux density (PPFD) was (215 ± 2) μmol·m ⁻² ·s ⁻¹ for all LEDs and HSP lamp. The results showed significant differences in all tested parameters among lights, and the percentage of far red (FR, 701–780 nm) within the range of 3.03%–11.86% was positively correlated with plant growth (characterized by leaf number and area, plant height, stem diameter, and total biomass), palisade layer thickness, photosynthesis rate ( P n ), and stomatal conductance ( G s ). The ratio of R/FR (4.445–11.497) negatively influenced the growth of cotton seedlings, and blue light (B) suppressed stem elongation but increased palisade cell length, chlorophyll content, and P n .
Conclusion
The LED 2 was superior to other LED lights and HSP lamp. It had the highest ratio of FR within the total PPFD (11.86%) and the lowest ratio of R/FR (4.445). LED 2 may therefore be used to replace HPS lamp under controlled environments for the study of cotton at the seedling stage.
... Calculations of WUEi have recently been improved to embed the impact of mesophyll conductance on CO 2 diffusion in leaf cells (Stangl et al. 2019;Vernay et al. 2020). The results of this experiment show that the use of red and a combination of red and blue lightemitting diodes as light sources affects photosynthesis and stomata parameters may be by increasing chlorophyll absorption, which has also been reported by other researchers (Piovene et al., 2015;Kang et al., 2016). Of all the parameters affecting plant growth, light is an important environmental parameter affecting stomatal conductance Kang et al., 2016). ...
Artificial light source is one of the most important factors for high quality and quantity vegetable production in a plant factory. Aiming to investigate the role of light spectra on growth, chlorophyll fluorescence, photosynthesis and stomata parameters in lettuce plants grown in a plant factory, a factorial experiment was conducted based on a completely randomized design with two lettuce cultivars (Lollo Rossa and Lollo Bionda) and four spectra LED illumination red (656 nm), red/blue (3:1) (656 nm), blue (450 nm) and white (449 nm). The results showed that the combination of red and blue LED light had the greatest effect on stomatal conductance (gs), number of stomata, length and width of stomata in both lettuce cultivars. On the other hand, the maximum substomatal CO2 concentration (Ci) was observed in both lettuce cultivars when they were treated with red LED light. The results also showed that the maximum CO2 assimilation rate (PN) was observed in Rossa variety under white LED and in Bionda cultivar under blue LED light. Contrary to the results related to some of photosynthetic parameters, the highest values of vegetative traits (plant height, dry and fresh mass of shoots and roots, leaf number and leaf area) of plants were observed in the treatment of red and blue light combination. It is concluded that plant growth, chlorophyll fluorescence characteristics, photosynthetic and stomatal properties can be affected by different spectra and cultivars of lettuce, so that the choice of proper lighting is a fundamental requirement for the cultivation of this plant.
... The amount of energy needed to develop lettuce crops under red and blue LED lighting (95 percent red and 5 percent blue) was 50 percent lower than the amount of energy needed to grow the same amount of dry biomass under conventional light sources (Poulet et al., 2014). When treated with LEDs with the highest energy use efficiency compared to conventional fluorescent lamps, it was found that the plants displayed improved nutraceutical properties and increased biomass, fruit yield, antioxidant content and reduced nitrate content in an experiment on the indoor cultivation of basil and strawberries (Piovene et al., 2015). The literature analysis found that microgreens treated with a red and blue LED combination exhibited the highest levels of photosynthetic activity; however, it is not immediately evident what exact ratio of blue and red-light combination produced the results. ...
... In this study, lower nitrates as well as high total sugars were found in the plants of both LED and LED+IR treatments which confirmed that LED is beneficial in lowering the nitrates and elevating the sugar levels in spearmint. Similar findings were previously reported in leafy vegetables such as tatsoi (Simanavičius and Viršilė, 2018), basil (Piovene et al., 2015), spinach (Ohashi-kaneko, 2007), rocket (Signore et al., 2020), and lettuce (Bian et al., 2020). Soluble sugars serve various functions in plant cells, including critical components of energy and biosynthetic processes. ...
Indoor agriculture is becoming more relevant as a result of artificial lighting, which makes it possible to increase productivity, improve quality and cultivate where natural light is insufficient. The present study was conducted by growing spearmint inside a glasshouse under light emitting diode (LED), high pressure sodium (HPS), and light emitting diode assisted infrared (LED+IR) light treatments, while the control plants were grown outside the glasshouse under natural sunlight. Morphological analyses revealed that LED supplemental light performed better in terms of plant height, number of stems per plant, and fresh weight of the produce than all other tested light treatments, whereas HPS favored increased internode spacing. The analytical determinations revealed the outperformance of LED in terms of total carotenoids, total anthocyanins, and total sugar accumulation in spearmint leaves. Plants grown under both LED and LED+IR accumulated less nitrate than plants grown under HPS. HPS treated spearmint plants also showed a reduction in the total carotenoids and total sugar levels. Moreover, no significant changes were observed in lipid peroxidation (as measured by the thiobarbituric acid reactive substances, TBARS assay) among all treatments. On the other hand, control plants showed the highest phenolic index relative to the other light treatments which provided a brief overview of the effects of the light spectrum of artificial lighting, such as LED, HPS, LED+IR, and natural sunlight on spearmint growth, oxidative stress, and secondary metabolite production
... In terms of light quality effects on plant traits, Samuolienė et al. [6] demonstrated that a 7:1 red-to-blue spectrum promoted larger strawberry fruits and higher sugar content, but at the same time, inhibited flowering [7]. Piovene et al. [8] experimentally observed that the best strawberry growth and fruit quality was achieved with a red-to-blue light ratio of 7:10, but the best strawberry growth rate was obtained with a 34% blue light content [9]. In addition, red and blue light can have a significant effect on the roots, stems, and leaves of plants [10][11][12]. ...
In crop cultivation, particularly in controlled environmental agriculture, light quality is one of the most critical factors affecting crop growth and harvest. Many scholars have studied the effects of light quality on strawberry traits, but they have used relatively simple light components and considered only a small number of light qualities and traits in each experiment, and the results were not complete or objective. In order to comprehensively investigate the effects of different light qualities from 350 nm to 1000 nm on strawberry traits to better predict the future growth trend of strawberries under different light qualities, we proposed a new approach. We introduced Spearman’s rank correlation coefficient to handle complex light quality variations and multiple traits, preprocessed the cultivation data through the CEEDMAN method, and predicted them using the Informer network. We took 500 strawberry plants as samples and cultivated them in 72 groups of dynamically changing light qualities. Then, we recorded the growth changes and formed training and testing sets. Finally, we discussed the correlation between light quality and plant trait changes in consistency with current studies, and the proposed prediction model achieved the best performance in the prediction task of nine plant traits compared with the comparison models. Thus, the validity of the proposed method and model was demonstrated.
... Light quality not only affects plant growth and development, but also regulates the accumulation of secondary metabolites. The phenolic content and antioxidant activity of pea sprouts treated with different light qualities were significantly higher than those grown in the dark (Fig. 2), agreement with the results on buckwheat malt (Lee et al., 2014) and basil (Piovene et al., 2015). This phenomenon may be because light can promote the production of malonyl-CoA and coumaroyl-CoA (involved in the biosynthesis of phenolic compounds) by enhancing photosynthesis (Kim et al., 2006), thereby increasing the phenolic content of plants. ...
Light, as an energy source and environmental signal, can significantly impact plant growth, development, and metabolism. This study explored three aspects of light environment, including light quality (different red and blue combination), intensity (9–90 μmol/m2/s), and photoperiod (4–20 h/d) to identify and utilize the optimal light conditions for promoting morphogenesis and the accumulation of phenolic compounds in pea (Pisum sativum L.) sprouts of variety Taiwanxiaobaihua. The results showed that dark conditions and red light promoted the longitudinal growth of pea sprouts, while blue light had an inhibitory effect. The appropriate ratio of red and blue light could positively affect the morphological establishment of pea sprouts, promoting the accumulation of total phenolic and total flavonoid contents and improving the antioxidant properties. Within a certain light range, the total flavonoid content and total flavonoid yield of pea sprouts showed an increasing trend with the light intensity increase and the photoperiod extension. Precise estimation of optimal light parameters was achieved using regression models, the total flavonoid content, total flavonoid yield, and dry matter mass of pea sprouts reached an optimal amount at red/blue light ratios of 0.33, 0.46, and 0.71, at 105.86, 90.00, and 9.00 μmol/m2/s of light intensity and at 32.33, 23.28 and 8.23 h/d of photoperiod, respectively. Specifically, increasing dry matter mass by 1 mg decrease in total flavonoid content by 0.78 mg in pea sprouts under these conditions. The scientifically guided light regulation technologies can improve the yield and quality of sprouts and provide a scientific basis for the sustainable development of the sprout industry.
... As the application of indoor farming technologies takes place in several regions of the world-mainly in Asian (42%), European (30%) and North American (21%) countries-the market is expected to reach a global value of 5.80 billion USD by 2022 (Pennisi, Sanyé-Mengual, et al., 2019). From a production perspective, indoor farming systems allow for increasing yields (up to 23-fold, as compared to traditional agriculture (Cicekli & Barlas, 2014), improved food quality (Piovene et al., 2015), and greater production stability due to enhanced resilience to climatic events as compared with traditional agricultural systems (Kozai et al., 2015). The potential for reducing land use for agriculture is associated with both the possibility to explore the vertical dimension allowed by the use of artificial lighting (Kozai et al., 2015), the possibilities offered for year-round production (Kozai et al., 2015), and the potential reconversion of abandoned or unused buildings into agricultural systems (Gasperi et al., 2016). ...
The global megatrends of decreasing water supply, increasing population, urbanization, and unabated climate change have contributed to globally decreasing stocks of arable land per person. Under these circumstances, the sustainability of the traditional farming model based on large rural farms is likely to come under threat in coming decades. One approach for engaging with this challenging problem is vertical farming, which is based on controlled-environment agriculture. Aim of this this article was to find out the environmental sustainability through control environment agriculture for future food production. This study was conducted based on secondary sources as literature survey. Controlled environment agriculture (CEA) is a technology for plant production in environmentally controlled structures such as high tunnels, greenhouses, growth chambers, or indoor vertical farming warehouse farming. The potential benefits of vertical farming include a sustainable food-production model with all-year-round crop production, higher yields by an order of magnitude, and freedom from droughts, floods, and pests. The environmental benefits are significant, including providing healthy organic food not contaminated from chemicals. No pollution or exceptionally low pollution due to no use of pesticide, chemical fertilizer, and minimum use of water. More research is also needed that carefully assesses and confirms this environmental benefit at different locations and scales for a specific crop.
... However, HPS have a low e ciency of only 25-30%, which not only requires considerable energy but also induces light stress in plants (Randall and Lopez, 2014). Light emitting diodes (LEDs) are solid-state, semiconducting diodes that can generate light in the 250 to 1000 nm wavelength range (Piovene et al., 2015). They have a longer life period and greater spectrum speci city than traditional HPS lighting (D'Souza et al., 2015). ...
Light is a critical factor of plant growth and development, particularly in controlled environments. Light-emitting diodes (LEDs) have become a reliable alternative to conventional high pressure sodium (HSP) lamps because they are more efficient and versatile light sources. In contrast to well-known specialized LED light spectrums for vegetables, the appropriate LED lights for crops such as cotton remain unknown. In this growth chamber study, we selected and compared four LED lights with varying percentages (26.44-68.68%) of red light (R, 600-700 nm), combined with other lights, for their effects on growth, leaf anatomy and photosynthesis of cotton seedlings, using HSP as a control. The total photosynthetic photon flux density (PPFD) was 215±2 μ mol/m ² ·s for all LEDs and HSP. The results showed significant differences in all tested parameters among lights, and the percentage of far red (FR, 701-780 nm) within the range of 3.03-11.86% was positively correlated with plant growth (characterized by leaf number and area, plant height and diameter, and total biomass), palisade layer thickness, photosynthesis rate (Pn) and stomatal conductance (Gs). The ratio of R/FR (4.445-11.497) negatively influenced the growth of cotton seedlings, and blue light (B) suppressed stem elongation but increased palisade cell length, chlorophyll content and Pn. The LED 2 was superior to other LED lights and HSP. It had the highest ratio of FR within the total PPFD (11.86%) and the lowest ratio of R/FR (4.445); LED 2 may therefore be used to replace HPS under controlled environments for the study of cotton at the seedling stage.
... Recent research on crop responses to supplemental LED lighting under controlled environments mainly focused on optimization of light spectra and photon flux density (e.g. [19,[28][29][30][31][32][33][34][35][36]). However, fewer studies investigated the interactions of supplemental lighting with other environmental factors such as air temperature, fertilizer concentration and growing season under controlled environments [37][38][39][40]. ...
There is an increasing interest in alternatives to peat in growing media due to environmental constraints. However, plants grown in peat substitutes often show impaired growth compared to plants grown in peat-based media. Hence, it would be interesting to know whether these deficiencies can be compensated by supplementing other growth factors, e.g. light. The present study aims to investigate the interactive nature between growing media and supplemental lighting on plant growth and morphology, and to examine whether supplemental light emitting diode (LED) lighting may compensate adverse growing media effects. Basil (Ocimum basilicum L.) and Chinese cabbage (Brassica rapa subsp. pekinensis) were grown in different growing media consisting of peat, green compost, coconut pulp, wood fibre, perlite and sphagnum moss under blue, red and far-red supplemental LED lighting. We found significant interactions between growing media and supplemental photosynthetically active radiation (PAR) on plant growth, morphology and development. At low light intensities, peat-based and substituted growing media performed similarly, whereas with increasing light intensities the peat-based growing media significantly outperformed their alternatives. The substrate choice determines the required amount of supplemental light to compensate for adverse growing media effects and the amount varies depending on plant species and season. Thereby, it was indicated that red light alleviates adverse growing media effects best. We also found that far-red light is not effective when background PAR is low and becomes more effective under high background PAR. The implications and prospects of the results are discussed.
... Bantis et al. (2016) reported that two basil cultivars showed high total phenolic content under an LED light with blue, red, green, and UV wavelengths. Piovene et al. (2015) observed an increase in antioxidant compounds of the horticultural crop species under different red and blue LED light ratios. Similarly, Wojciechowska et al. (2015) observed the highest concentration of total phenols and radical detoxifying capacity in lamb's lettuce supplemented with red and blue light in a ratio of 9:1. ...
The light spectrum plays a major role in regulating plant growth and development, influencing photosynthesis and photo-morphogenesis. The objective was to evaluate the weight and antioxidant activity of ‘Lavinia’ lettuce (Lactuca sativa L. var. capitata L.) plants under LED lights with different red:blue ratios (R:B) used as a supplement to ambient light in a greenhouse at different seasons. Five LED light supplemented treatments were used, white (W, as control, ratio blue:green:red:far-red (B:G:R:Fr) = 30:45:20:5; 0.7:1.0), blue (B = 50:20:20:10; R:B = 0.4:1.0), white-r (Wr = 25:30:40:5; 1.6:1.0), white-R (WR = 15:15:63:7; 4.2:1.0) and red (R = 10:10:75:5; 7.5:1.0) were applied in early autumn, late autumn and winter. Immediately after transplant into the hydroponic system, lettuces plants with 3-4 true leaves (5-6 cm root length) were treated with light treatments for 14 d and harvested. In early autumn, late autumn, and winter, the PAR range applied in ambient light and supplemental lights was between 361 to 495, 222 to 304, and 297 to 407 µmol m-2 s-1, respectively. Lettuce showed the highest fresh leaf mass in early autumn compared to late autumn and winter due to the highest leaf number. In early autumn, only lettuce under the highest R:B (7.5:1.0) had a lower weight among the light treatments. Overall, lettuces supplemented with R:B between 1.6 (Wr) to 4.2 (WR) had significantly higher DM than the control (0.7:1.0). Total phenolic contents (TPC) and antioxidant capacity (AC) were highest in early autumn, followed by winter and late autumn. Light with the highest R:B (7.5:1.0) diminished TPC and AC in all growing season. This study showed that the quality of ‘Lavinia’ lettuce plants grown in early autumn under R:B between 1.6 and 4.2 improved DM, and higher red component decreased the antioxidant activity.
... 27 Similarly, in cyclamen it was shown that blue added to red light improved flower induction, the number of flower buds and open flowers. 28 Studying different ratios of R:B light and comparing it with fluorescent light 29 reported that basil and strawberry reached their highest leaf fresh weight when grown under R:B ratios of 0.7 and 1.5, respectively. These authors also indicated that in general, LED lights were superior in energy use efficiency when compared to fluorescent light. ...
Light-emitting diodes (LEDs) offer the potential for physiological control of flowering and vegetative growth of ornamental potted plants such as African violet ( Saintpaulia ionantha Wendl.). In this experiment, we investigated the flowering and vegetative traits of African violet under 6 months of artificial illumination of four different spectra: monochromatic red, monochromatic blue, mixed red 75% plus blue 25%, and fluorescent light under 118 μmol m ⁻² s ⁻¹ ± 6 μmol m ⁻² s ⁻¹ photon flux for 12 h per day. Results showed that the number of days to the open flower stage was significantly influenced by irradiance. Although the blue-illuminated plants appeared to be significantly smaller and compact, they were superior in their most flowering qualities as they induced a pronounced effect on the flowering in terms of earliness, uniformity, consistency, the number of flowers, and the percentage of canopy covered with the flowers. We concluded that LEDs can be used as an effective tool to manipulate plant visual qualities without any further need for the application of conventional plant regulator chemicals, which are mostly identified as hazardous substances.
... This is unexpected as red light is absorbed by chlorophyll and therefore used for photosynthesis (Zhu et al., 2008) and is seen to activate the aperture of stomata (Ogawa, 1981) associated with a higher photosynthesis rate (Nautiyal et al., 1994). Possible explanations might be the modification of B:R ratio as for Ocimum basilicum biomass accumulation, decreased as a result of increasing shares of red light (Piovene et al., 2015). However, other studies with other plants reported not the same and the effect of B:R ratio seems therefore to be species-specific. ...
Abstract
Several Asian herbaceous plants with an importance for the consumption in Europe, were investigated in greenhouse and climate chambers. For further studies were selected Persicaria odorata fam. Polygonaceae and Perilla frutescens var. crispa (Thunb.) H. Deane, fam. Lamiaceae. The aim was to investigate the effect of different light conditions on yield and nutritional value of both species for indoor cultivation. The main light sources were fluorescent light tubes (FT). Daylight integral (DLI), provided by fluorescent tubes, was modified in two groups one chamber 4.68 and another 9.06 mol m-2 d-1. Whereby the daylight integral was the same by one variant and the respective control but differed between variants, that means values can just be compared between them and not between different variants. The light spectrum was adjusted for cultivation of Persicaria odorata by additional monochromatic LEDs: blue (443 nm) 11 μmol m-2 s-1, green (515 nm) 7 μmol m-2 s-1, and red (629 nm) 12 μmol m-2 s-1. In experiments with Perilla frutescens the control variant (FT) grew with two different light conditions 123.29 or 177.33 μmol m-2 s-1, by adding of LED with blue (443 nm) and red (629 nm) for the test plants (FT+bLEDs) under 125.62 or (FT+rLEDs) under 197.31 μmol m-2 s-1, respectively. The increase in light intensity correlated positively with an increase in biomass in both plants (+0.56% +1% increased light intensity for P. odorata, +1.92% for P. frutescens) and resulted in higher flavonoid levels. The levels of polyphenols and anthocyanins (detectable only in P. frutescens) decreased. Modifying the light spectrum by adding LED lighting gave different results: blue LED light increased biomass and decreased polyphenol content in both plants. Red LED light decreased biomass in P. odorata and increased flavonoid content in P. frutescens. Green LED light applied to P. odorata affected polyphenol and flavonoid contents positively (but not significantly). Study proved that Asian herbaceous plants are suitable for indoor farming. By adjusting light conditions (intensity and spectrum), significant increases of yield and nutritional value can be achieved. However, it is to consider the plant species and which of the phytonutrients is of importance, e.g., flavonoids, polyphenols or anthocyanins. Therefore, light conditions should be chosen carefully under consideration of all relevant growth or quality parameters.
Keywords: Perilla frutescens, Persicaria odorata, light spectrum, light intensity, polyphenols, flavonoids
... The combination of red and blue LED boosted total phenolics and antioxidant capacity of the plant. This result is in consistence with previous reports from several other plants (Son and Oh 2013;Piovene et al. 2015;Yeow et al. 2020). This outcome is much rational as phenolics are enriched with free radical scavenging properties (Velika and Kron 2012). ...
Unlabelled:
Light emitting diodes (LEDs) as an alternative light source for plants had shown to enhance the plant material quality. Indian borage or Plectranthus amboinicus (Lour.) Spreng, a medicinal herb produces carvacrol as the major volatile organic compound (VOC). Histolocalization of VOCs and expression pattern of the terpenoid biosynthesis genes after spectral light treatment is not yet reported in P. amboinicus. This work investigated the morpho-physiological, biochemical and transcriptional responses towards red, green, blue, warm white and red-blue (RB, 1:1) LEDs treatment at 40 ± 5 μmol m-2 s-1 light intensity after 40 days. Maximal growth index (GI), leaf fresh weight and dry weight were obtained in RB (1:1) treated plants. There was one-fold increase in phenolics content and 2.5-fold increase in antioxidant activity in comparison to warm white. High quantity of terpenes and phenolics deposition were observed in the glandular trichomes of RB (1:1). Maximum carvacrol accumulation (14.45 µmol g-1 FW) was also detected in RB (1:1). The transcript levels of early terpene biosynthesis genes PaDXS, PaDXR, PaHMGR and cytochrome P450 monooxygenase genes, PaCYP1 and PaCYP9 were highly upregulated in RB (1:1) and green. The overall results suggest RB (1:1) as the better lighting option amongst the studied spectral lights for obtaining maximum phytochemicals in P. amboinicus. Work is being continued with different spectral ratios of red and blue LED lights to maximize phytochemical accumulation, the outcome of which will be reported elsewhere in near future.
Supplementary information:
The online version contains supplementary material available at 10.1007/s00344-023-11028-6.
... The chlorophyll present in the plant leaves are known to absorb light in the range between 650 and 750 nm (red region) while carotenoids and other accessory pigments mostly absorb wavelength between 450 and 500 nm (blue region) [7]. Several researchers have investigated the application of red and blue LEDs on the growth behaviour and photosynthetic activity of indoor plants [8][9][10]. It also involves studies related to physiological, biochemical, molecular and ultrastructural behaviour of plants as blue light is known to enhance biosynthesis of chlorophyll. ...
The study presented a comprehensive documentation of different operating parameters influencing bioelectricity generation potential of PMFCs with Chlorella sorokiniana-based microalgal bio-cathode. An optimum duration of light-dark period is highly essential for growth of both plants and microalgae. The study demonstrated that 12/12 h light-dark phase was optimum to extract maximum performance from PMFCs without creating operational stress. The effect of different light sources on growth of indoor plants Philodendron erubescens and Epipremnum aureum as well as microalgae was studied. White light proved to be superior among all light source for plant growth and chlorophyll concentration at the bio-cathode. The obtained power density of 26.42 mW m⁻² under white light was 72%, 54% and 15% higher than red, blue and red-blue mix lights, respectively. Also, the addition of novel plant growth media can influence plant growth resulting in 31% increased power generation. The configuration of PMFC setup and placement of electrodes and membranes are highly important criteria affecting PMFC performance. Anode position at A2 at 7 cm below soil, being closer to membranes proved to enhance transmembrane ion transport with an increase in power density up to 2.2 times. Three-chamber PMFC with narrow bottom anode chamber helps in creating favourable anaerobic environment with 26% decrease in O2 concentration and increasing power generation up to 31.40 mW m⁻² which was 15.44% higher as compared to two-chamber PMFC. Additionally, the internal resistance was found to decrease from 270 to 190 Ω.
... Higher WUE values are associated with higher PPFD or ambient CO 2 concentrations, while instantaneous WUE measurement depends on many environmental factors such as light and drought conditions (Piovene et al., 2015;Leakey et al., 2019). Furthermore, A n measurements from individual leaves or time points in a treatment group may not have a good correlation with crop yield (Wang et al., 2015). ...
Light-emitting diodes (LEDs) enhance plant production in vertical farms by regulating photosynthetic rate and phytochemistry. Specific light recipes can be formulated using LEDs for high output by fine-tuning spectral composition and irradiance. In this study, the growth, development, and nutritional quality of three kale cultivars (‘Toscano’, ‘Redbor’, and ‘Winterbor’) were examined under different blue peak emission wavelengths (λpeak). Photosynthetic photon flux density (PPFD) was maintained at 200 ± 10% μmol m − 2 s − 1 over a 16-hr photoperiod. The LED light treatments had blue λpeak centered at 400, 420, and 450 nm wavelengths, all with spectral ratios of 20% blue, 20% green, 60% red in the visible light region, and 15% of total PPFD in the far-red region. The control light was cool-white fluorescent (CWF) light with blue λpeak at 436 nm and a slightly higher amount of PPFD in the blue region (23%). The biomass yield and leaf physical characteristics were largely unaffected by the light treatments with different blue λpeak. However, the concentration of carotenoids and chlorophylls in kale leaves was influenced by the type and amount of blue light during growth. Future research should investigate the effect of different blue light percentages in pre- and post-harvest LED treatments (continuous or pulsed) on high-value, nutritious crops.
... Although blue light is very effective for chlorophyll biosynthesis and stomata opening, many studies showed that blue light was less effective than red light for driving photosynthesis [31−33] . The reason is that blue light can be absorbed by lower-efficiency pigments such as carotenoids or inactive pigments such as anthocyanins leading to a reduction in blue light energy that absorbed by the chlorophyll pigments [34] . Shimizu et al. [31] reported that plant biomass and photosynthesis rate had similar response to Volatile oil concentration and growth of thyme plants monochromatic blue and red light. ...
The objective of this study was to evaluate the growth and volatile oil concentrations of thyme (Thymus vulgaris L.) plants under different red to blue light ratios of 4:1 (R4B1), 2:1 (R2B1), 1:1 (R1B1), and 1:2 (R1B2) with light-emitting diodes (LEDs) and fluorescent light (FL) in a plant factory. Thyme plants were sampled at three intervals of 12, 24, and 36 d after treatment. The results showed that the growth and medicinal components accumulation of thyme plants were significantly affected by different light qualities. The significant higher biomass, leaf area, and volatile oil concentrations of thyme plants were obtained under treatment R4B1 compared with treatment FL, regardless of the cultivation period. When analyzing the volatile oil constituents of thyme plants, thymol, γ-terpinene, p-cymene and α-terpinene were detected as the main constituents. However, the response of these different constituents varied with different light qualities. The above results indicated that the targeted constituent concentrations could be manipulated by employing different light qualities according to various purposes. Based on the above results, R4B1 can be considered as the optimal light treatment for thyme plants growth and volatile oil production in a closed production system with LEDs.
... Pennisi et al. studied the optimal PPFD (photosynthetic Photon Flux Density) for the indoor cultivation of basil, ranging from 100 to 300 μmol m −2 s −1 with a constant photoperiod of 16h d −1 , using red and blue light in a fixed ratio (Red/Blue = 3), finding that the optimized radiation intensity was 250 μmol m −2 s −1 [23]. Regarding the specific light recipe, the great majority of works are devoted to monochromatic LED lights and only a few have studied interactions between different wavelengths, among them: Piovene et al. investigated the physiological and phytochemical variations of basil in response to different ratios of blue and red light, finding that a Red/Blue ratio equal to 0.7 guaranteed the best results [24]; Jensen et al. demonstrated that spectral manipulation of the grow light can produce relevant effects on postcultivation performance of chilling sensitive plants, and a ratio between Red and Green LEDs equal to 80:20 was suggested [25]. ...
Indoor farms are a promising way to obtain vegetables in standard quantity and quality. As opposed to previous studies, this study attempts to calculate optimized LED light conditions for different growth stages (five-days time step) of basil (Ocimum basilicum) to enhance its indoor growth through a statistical approach. Design of Experiments (DoE) was used to plan a limited number of experiments (20) and to calculate quantitatively the effect of different light recipes on four responses: the number of plants, their height, the Leaf Area Index, and the amount of water used. Different proportions (from 25% to 77%) of Hyper Red (660 nm) and Deep Blue (451 nm), intensities in terms of LEDs-plant distance (60, 70 and 80 cm), and the addition of Warm White (3000 K) LEDs were considered as independent variables. The obtained models suggest that a light recipe tailored for every growth step in the plant's life is beneficial. Appropriate LEDs must be carefully chosen at the beginning of growth, whereas distance becomes relevant at the end. This is confirmed by the results analysis carried out at the end of an additional growth test where the optimal light recipe extracted from the DoE's results were used.
... [35], [36]. A red to blue ratio of 4:3 was selected as the most suitable spectra for the selected crop based on previous works [37], [38]. The light plan for the time scheduled system (System 1) was selected to represent the traditional on-off method used by growers for comparison of energy consumption and plant health properties. ...
This paper presents an intelligent horticulture lighting and monitoring system to achieve energy-efficient supplemental lighting while maintaining the light quality and intensity at desired levels in the photosynthesis spectrum. Energy-efficiency is achieved through delivering only the required net light intensity, consisting of sunlight and supplemental LED light, using an intelligent controller that does not depend on the lighting system model. To this end, an online neural-network learning control system is developed, comprised of low-cost light sensors for measuring the photosynthetic photon flux density (PPFD), dimmable LED light fixtures, cameras, and internet-of-things (IoT)-enabled firmware used for crop monitoring and performance evaluation. Experiments performed in a research greenhouse facility on the lettuce crop are presented which indicate that the system can deliver the desired Daily Light Integrals (DLIs) to the plants in the presence of changing daylight conditions. The proposed method can thus deliver the exact amount of light to a specific crop based on the required light recipes during different growth phases. The control performance is further compared with a conventional on-off time-scheduling method in terms of plant health, growth, and energy requirements. The experiments indicate that the proposed solution can reduce energy consumption per unit dry mass of lettuce by 28% when compared to existing time-scheduling methods.
Amidst the ongoing urbanization process, the significance of urban agriculture has garnered increasing attention. With the expansion of urban population, the urban landscape broadens, and agriculture becomes more commercialized, the...
The cultivation of medical cannabis (Cannabis sativa L.) is expanding in controlled environments, driven by evolving governmental regulations for healthcare supply. Increasing inflorescence weight and plant specialized metabolite (PSM) concentrations is critical, alongside maintaining product consistency. Medical cannabis is grown under different spectra and photosynthetic photon flux densities (PPFD), the interaction between spectrum and PPFD on inflorescence weight and PSM attracts attention by both industrialists and scientists. Plants were grown in climate-controlled rooms without solar light, where four spectra were applied: two low-white spectra (7B-20G-73R/Narrow and 6B-19G-75R/2Peaks), and two high-white (15B-42G-43R/Narrow and 17B-40G-43R/Broad) spectra. The low-white spectra differed in red wavelength peaks (100% 660 nm, versus 50:50% of 640:660 nm), the high-white spectra differed in spectrum broadness. All four spectra were applied at 600 and 1200 μmol m⁻² s⁻¹. Irrespective of PPFD, white light with a dual red peak of 640 and 660 nm (6B-19G-75R/2Peaks) increased inflorescence weight, compared to white light with a single red peak of 660 nm (7B-20G-73R/Narrow) (tested at P = 0.1); this was associated with higher total plant dry matter production and a more open plant architecture, which likely enhanced light capture. At high PPFD, increasing white fraction and spectrum broadness (17B-40G-43R/Broad) produced similar inflorescence weights compared to white light with a dual red peak of 640 and 660 nm (6B-19G-75R/2Peaks). This was caused by an increase of both plant dry matter production and dry matter partitioning to the inflorescences. No spectrum or PPFD effects on cannabinoid concentrations were observed, although at high PPFD white light with a dual red peak of 640 and 660 nm (6B-19G-75R/2Peaks) increased terpenoid concentrations compared to the other spectra. At low PPFD, the combination of white light with 640 and 660 nm increased photosynthetic efficiency compared with white light with a single red peak of 660nm, indicating potential benefits in light use efficiency and promoting plant dry matter production. These results indicate that the interaction between spectrum and PPFD influences plant dry matter production. Dividing the light energy in the red waveband over both 640 and 660 nm equally shows potential in enhancing photosynthesis and plant dry matter production.
In smart greenhouse farming, the impact of light qualities on plant growth and development is crucial but lacks systematic identification of optimal combinations. This study addresses this gap by analysing various light properties’ effects (photoperiod, intensity, ratio, light–dark order) on Arabidopsis thaliana growth using days-to-flower (DTF) and hypocotyl length as proxies to measure plant growth and development. After establishing suitable ranges through a comprehensive literature review, these properties varied within those ranges. Compared to white light, a 16-h cycle of blue light reduces DTF and hypocotyl length by 12 % and 3 %, respectively. Interestingly, similar results can be achieved using a shorter photoperiod of 14-h light (composed of 8 h of a mixture of 66.7 μmol m−2s−1 red and 800 μmol m−2s−1 blue lights (i.e. blue:red ratio of 12:1) followed by 6 h of monochromatic red light and 10-h dark. These findings offer potential for efficient growth light recipes in smart greenhouse farming, optimizing productivity while minimizing energy consumption.
Cây Húng quế là một loại rau gia vị và dược liệu được trồng phổ biến ở Việt Nam, các hợp chất tạo mùi vị của cây này như phenolics và flavonoid được quan tâm. Nghiên cứu so sánh việc tăng trưởng của cây Húng quế in vitro dưới ánh sáng xanh lơ gồm LED 440, 450 hoặc 460nm với đèn huỳnh quang để tìm hiểu sự thay đổi hình thái, sinh khối cây, trao đổi khí trong quang hợp, hàm lượng sắc tố, đường, tinh bột và tích lũy flavonoid ở lá sau 4 tuần. Kết quả, các cây tăng trưởng dưới đèn huỳnh quang hoặc LED 450nm có lóng thân ngắn, nhưng số lá và tổng diện tích lá cao hơn so với cây tăng trưởng dưới LED 440 hay 460nm; sinh khối khô tích lũy ở rễ của tất cả các cây dưới LED xanh đều giảm so với đối chứng. Ánh sáng LED 440 hay 460nm thúc đẩy gia tăng sinh khối khô của thân, trong khi ánh sáng xanh 450nm lại giúp tích lũy sinh khối trong lá. Cường độ quang hợp của lá, hàm lượng chlorophyll a, đường, tinh bột và hàm lượng hợp chất phenol trong lá các cây dưới ánh sáng xanh lơ (440, 450 và 460nm) đều giảm so với đối chứng. Tuy nhiên, ánh sáng 450nm giúp duy trì tỷ lệ chlorophyll a/b, carotenoid và flavonoid trong lá khá cao tương đương so với đối chứng.
Từ khóa: Flavonoid, hợp chất phenol, LED xanh, Ocimum basilicum L, quang hợp.
Light quality (spectral arrangement) and quantity (photoperiod and intensity) influence plant growth and metabolism and also interact with several factors including environmental parameters in defining the plant behavior. The Light Emitting Diode (LED) lights are extensively utilized in the cultivation of several plant species , especially horticultural plants due to their lower power consumption and higher luminous efficiency compared to the conventional fluorescent lights. The aim of this review paper is to examine the potential of LED technology as it relates to plant lighting in greenhouses and other horticultural environments. It also desires to give an in-depth study of the advantages of LED lighting on plant development, yield, the production of secondary metabolites, and defense mechanisms. Horticultural lighting might undergo a revolution because LEDs are used in solid-state lighting, which would be a tremendous advancement after decades of research. LEDs may be used in a variety of horticulture lighting applications, such as tissue culture lighting, controlled environment research lighting, supplementary lighting, and photoperiod lighting for greenhouses. The primary impacts of light colors on plant performance are shown by the spectrum effects of LEDs as an independent source of light, together with the diverse sensitivity of many plant species and alternatives. LED light influences performance of enzyme, gene expression, cell wall formation, plant defense and postharvest quality. The spectrum reactions are mediated by the ambient lighting in a greenhouse, which also indicates a strong relationship between the additional supplementary lighting and changing environmental factors. LEDs are growing further to become cost-effective for even large-scale horticulture lighting applications as light output increases and device expenditures decrease.
Intensive cultivation is one of the strategies for developing Porang commodities to increase production by using LED lights as optimum lighting for Porang cultivation. Porang bulbil was germinated and planted in a growth chamber with 100% red, 100% blue, 100% white, and 67%:20%:13% red:blue:white lighting. Compared to other LED treatments and sunlight, red:blue:white LED had the best effect on Porang plant germination parameters in the first 30 days, with 100% of germination parameters (GP %), 17.2 days of mean germination time (MGT), 6.33%/day of germination rate index (GRI), 5.81% of germination velocity coefficient (CVG), and 138.0 of germination index (GI). For the next 30 days, red:blue:white LED had the best effect on Porang plant vegetative growth, with 29.64 cm plant height, 11.43 cm crown diameter, 21.96 cm root length, 17.342 g fresh weight, 1.368 g dry weight, and 57.53 leaf green index. The plant height prediction model is used to predict crop yield, with the coefficient of determination (R²), root means square deviation (RMSE), mean absolute error (MAE), and average absolute percentage error (MAPE) values up to 0.9854, 0,6894, 1,2623, and 3,9413, respectively, under model validation of the combination of LED.
This paper presents development of a low-cost sensor to measure the light intensity for plant growth, referred to as photosynthetic photon flux density (PPFD), which is a quantum light measurement unit for horticultural LED lighting. The total PPFD is comprised of daylight and supplemental LED lights in the red and blue photosynthesis wavebands with peak wavelengths at 660 nm and 457 nm, respectively. To this end, a multi-waveband spectral light sensor is utilized along with an accurate spectroradiometer reference sensor for calibration. A comparative study of machine learning-based methods is presented to obtain the sensor coefficients for measuring the PPFD, indicating that the decision tree and random forest models exhibit low mean absolute percentage errors (MAPEs) of 0.01%-0.88% for red and blue channels, respectively; but may lead to data over-fitting in real-time applications because of their complexity. However, the simple multi-linear regression method yields MAPEs of 0.98% and 0.84% for red and blue channels, respectively, which may be better suited for real-time applications. As a use-case scenario, the calibrated PPFD sensor was experimentally tested on a hydroponic testbed located inside a greenhouse facility. The system was exposed to natural and supplemental LED lighting, in the blue and red light spectra, under a daylighting feedback control scheme. Experiments demonstrate that daily light integral values with less than 20% tracking errors can be achieved on the blue and red channels using the calibrated sensors.
To enhance the transplants' growth and reduce energy use efficiency, Eggplant (Solanum melongena L.) transplants (cv. Jingqie 21) were cultivated in a plant factory laboratory under different LED light spectrums. The experimental treatments included white plus blue LED lights (R: B=0.5, WB0.5), white LED lights (R: B=0.9, W0.9), white plus red LED lights (R: B=2.7, WR2.7), white plus red plus UV lights (R: B=3.8, WRUV3.8), and red plus blue plus green LED lights (R: B=5.4, RBG5.4). The transplants were grown for 30 d under a light intensity of 250 μmol/m2·s and a photoperiod of 16 h/d. The morphological indicators and biomass accumulation of eggplant transplants were significantly higher in the W0.9 treatment compared to the other experimental treatments. The photosynthetic quantum yield in the W0.9 treatment exhibited an increase of over 22% compared to that in the WR2.7 treatment. The shoot dry weight of the W0.9 treatment reached (381±41) mg/plant and the leaf area was (113.3±8.9) cm2, indicating a higher health index compared to the other treatments. However, there were no significant differences in the net photosynthetic rate of the leaves among all treatments. The energy yield (EY) of the W0.9 treatment was (37.7±1.8) g/kW·h, which was higher than others. Therefore, considering the high quality of transplants and the maximization of energy use efficiency, the LED light spectrum in the eggplant transplants production was recommended to the white LED light with an R: B ratio of 0.9. Keywords: eggplant transplants, LED light spectrum, growth, energy use efficiency DOI: Citation: Yang H, Wang T, Ji F, Zhou Q, Wang J F. Effects of LED light spectrum on the growth and energy use efficiency of eggplant transplants. Int J Agric & Biol Eng, 2023; 16(3): 23–29.
The spectral quality of supplemental greenhouse lighting can directly influence aroma volatiles and secondary metabolic resource allocation (i.e., specific compounds and classes of compounds). Research is needed to determine species-specific secondary metabolic responses to supplemental lighting (SL) sources with an emphasis on variations in spectral quality. The primary objective of this experiment was to determine the impact of supplemental narrowband blue (B) and red (R) LED lighting ratios and discrete wavelengths on flavor volatiles in hydroponic basil (Ocimum basilicum var. Italian Large Leaf). A natural light (NL) control and different broadband lighting sources were also evaluated to establish the impact of adding discrete and broadband supplements to the ambient solar spectrum. Each SL treatment provided 8.64 mol . m-2. d⁻¹ (100 µmol . m-2. s⁻¹, 24 h . d⁻¹) photon flux. The daily light integral (DLI) of the NL control averaged 11.75 mol . m-2.d⁻¹ during the growth period (ranging from 4 to 20 mol . m-2.d⁻¹). Basil plants were harvested 45 d after seeding. Using GC-MS, we explored, identified, and quantified several important volatile organic compounds (VOCs) with known influence on sensory perception and/or plant physiological processes of sweet basil. We found that the spectral quality from SL sources, in addition to changes in the spectra and DLI of ambient sunlight across growing seasons, directly influence basil aroma volatile concentrations. Further, we found that specific ratios of narrowband B/R wavelengths, combinations of discrete narrowband wavelengths, and broadband wavelengths directly and differentially influence the overall aroma profile as well as specific compounds. Based on the results of this study, we recommend supplemental 450 and 660 nm (± 20 nm) wavelengths at a ratio of approximately 10B/90R at 100-200 µmol . m-2.s⁻¹, 12-24 h . d⁻¹ for sweet basil grown under standard greenhouse conditions, with direct consideration of the natural solar spectrum and DLI provided for any given location and growing season. This experiment demonstrates the ability to use discrete narrowband wavelengths to augment the natural solar spectrum to provide an optimal light environment across variable growing seasons. Future experiments should investigate SL spectral quality for the optimization of sensory compounds in other high-value specialty crops.
Indoor farming of basil (Ocimum basilicum L.) under artificial lighting to support year-round produce demand is an area of increasing interest. Literature data indicate that diverse light regimes differently affect downstream metabolic pathways which influence basil growth, development and metabolism. In this study, basil was grown from seedlings to fully developed plants in a microcosm, an innovative device aimed at growing plants indoor as in natural conditions. Specifically, the effects of white (W) and blue-red (BR) light under a photosynthetic photon flux density of 255 μmol m−2 s−1 on plant growth, photochemistry, soluble nutrient concentration and secondary metabolism were investigated. Plants grew taller (41.8 ± 5.0 vs. 28.4 ± 2.5 cm) and produced greater biomass (150.3 ± 24.2/14.7 ± 2.0 g vs. 116.2 ± 28.3/12.3 ± 2.5 g fresh/dry biomass) under W light compared to BR light. The two lighting conditions differently influenced the soluble nutrient concentration and the translocation rate. No photosynthetic stress was observed under the two lighting regimes, but leaves grown under W light displayed higher levels of maximum quantum yield of PSII and electron transport rate. Sharp differences in metabolic patterns under the two lighting regimes were detected with higher concentrations of phenolic compounds under the BR light.
We studied the effects of cultivar, nutrient solution strength and light intensity on daily variation of nitrate content in basil (Ocimum basilicum L.) leaves. A glasshouse experiment was carried out in Naples (Portici, Italy) from the 26th of May to the 5th of July 2005. Plants of two basil cultivars ('Napoletano' and 'Genovese') were cultivated on floating system with aerated nutrient solution replaced every week. Two nutrient solutions were compared: single strength Hoagland (H) and double strength Hoagland (2H). Thirty days after transplanting (DAT), the plants grown in the 2H solution were divided into two different shading treatments: 0% (control) and 50% shading obtained by using a 50% cut-off screen. On the 29th of June (34 DAT), leaf nitrate content was measured five times during the day (at 6:30am, 10:30am, 1:00pm, 4:00pm and 6:30pm) on 'Genovese' and 'Napoletano' plants grown in H and 2H solution. On the 5th of July (40 DAT), the leaf nitrate content was measured on plants grown at full sun light and 50% shading, only in 2H solution. Nutrient solution strength affected leaf nitrate content, which was higher in leaves of plants grown in the 2H solution. Plants at 50% shading showed higher leaf nitrate content compared to the control. Leaf nitrate content decreased during the day in response to light intensity. Plants of the cultivar 'Napoletano' showed the largest leaf area and the lowest leaf dry matter percentage, nevertheless no significant differences were observed in terms of nitrate contents between the two cultivars.
Microgreens are a very specific type of vegetables and are considered to be in the group of “functional foods” which are products that process particular health promoting or disease preventing properties that are additional to their normal nutritional value. The aim of this study was to evaluate the impact of supplementary short-term red LEDs lighting on the antioxidant properties of microgreens. Different species of red and green leaf microgreens (amaranth, basil, mustard, spinach, broccoli, borage, beet, kale, parsley, pea) were grown to harvest time in a greenhouse in a peat substrate under daylight with supplementary lighting provided by standard high-pressure sodium lamps (HPS). At pre-harvest stage of 3 days, HPS lamps were supplemented by 638 nm LEDs, whereas reference plants continued staying under lighting conditions identical to those of growth. PPFD generated by illuminator was 170 µmol m-2 s-1 and net PPFD generated by the illuminator in combination with HPS lamps - 300 µmol m-2 s-1 (16-h; 19-22/15-18°C). Due to the increased activity of the metabolic system for the protection from a mild photooxidative stress antioxidant properties of microgreens were changed. Natural antioxidant compounds were in order: pea>broccoli>borage>mustard=amaranth> basil=kale>beet=parsley>tatsoi. Total phenols concentration increased with supplemental red in all microgreens from 9.1% in mustard to 40.8% in tatsoi, except of amaranth, where decrease of 14.8% was observed. Ascorbic acid content increased in amaranth (79.5%), pea (65.2%), kale (60.6%), broccoli (59.1%) and mustard (25.0%), but decreased in basil (53.9%) and borage (46.9%), and had no significant effect in tatsoi, beet and parsley. Total anthocyanins significant increased in broccoli (45.1%), kale (44.0%), amaranth (38.0%), tatsoi (34.5%), parsley (27.0%) and pea (14.6%), significant decrease was detected in borage (51.8%), mustard (45.1%) and beet (43.3%) and was not significantly affected in basil.
Photosynthesis rates under HPS light were measured on various plant species. Euphorbia pulcherrima, Plectranthus scutellarioides and Lactuca sativa were selected for more detailed experiments under natural light and artificial light provided by HPS lamps or LEDs under controlled environment conditions. Comparisons have been made between gas exchange characteristics including the light compensation point and the slope of light response curves under practicalrelevant light intensities. Light compensation points under light qualities with input of red LEDs were between 13-15 μmol m-2 s-1 in all three model plants. Average photosynthetic rates at 100 and 200 μmol m-2 s-1 PPF red and blue/red LED light were above other calculated values for the other light qualities. The photosynthetic rates under blue/green/red LED light declined considerably less, than the purely energetic consideration would anticipate. Accordingly the green component in the spectrum contributed noteworthy to the photosynthetic performance of plants.
The experiments were carried out in 2009 in phytotron chambers and commercial greenhouses of the Lithuanian Institute of Horticulture. The frigo plants of 'Elkat' strawberries (Fragaria x ananassa Duch.) were investigated. The frigo sprouts were grown in a phytotron chamber for a month under different light-emitting diode (LED) treatment: sole red (640 nm) light, photosynthetic photon flux density (PPFD) beside leaves of strawberries – 200 µmol m -2 s -1 ; combination of red (640 nm) with blue (455 nm) light, maintained PPFD was 174.5 and 25.5 µmol m -2 s -1 , respectively. The photoperiod of 16 hours and 21/16ºC day/night temperature in the phytotron chamber were maintained. After LED treatment, strawberry sprouts were transplanted to a bed mulched by white film in the polythene greenhouse. The spectral quality of light influenced the morphogenesis and diverse physiological responses of frigo plants of 'Elkat' strawberry. Development was improved, carbohydrate accumulation and pigment ratio of plants was increased in strawberries grown under red and blue LEDs. Whereas, red LED induced elongation of flowering stem and all plant, and resulted in 1.8 times higher shoot/root ratio. The positive influence of red and blue light treatment on the formation of runners, inflorescence and crown was observed. The fruiting of frigo strawberries ended after 40 days after planting. The treatment of sole red light or combination of red and blue LEDs had no persistent effect on the harvest of frigo strawberries. However, red LED treatment resulted in a smaller size of fruits. It confirms that a mixture of red and blue LED spectral components is necessary for the development of frigo strawberries, likewise for normal plants.
Data from field experiments carried out in three consecutive years under contrasting N supply and radiation environment altered by artificial shading were used to identify (a) the relationship between N concentration and organ size under conditions of unrestricted N supply and (b) critical levels of soil nitrate (Nmincrit), where nitrogen concentration of cauliflower organs begin to decline because of N limitations. The decline of N concentrations in cauliflower was analysed at different levels of morphological aggregation, i.e., the whole shoot level, the organ level (leaves, stem, and curd), and within different leaf groups within the canopy. Nmincrit values (0–60 cm soil depth) for total nitrogen concentration of cauliflower organs leaves, stem and curd were estimated at 85, 93 and 28 kg N ha–1, respectively. Within the canopy, Nmincrit values for total N of leaves increased from the top to the bottom from 44 to 188 kg N ha–1. Nmincrit values for protein N in leaves from different layers of the canopy were much lower at around 30 kg N ha–1, without a gradient within the canopy. It is discussed that these differences in Nmincrit values are most likely a consequence of N redistribution associated with nitrogen deficiency. The decline of average shoot nitrogen concentrations, [Nm] (%N DM), with shoot dry matter, W
sh, (t ha–1) under conditions of optimal N supply was [Nm]= 4.84 (0.071) W
sh
–0.089( 0.011), r
2=0.67 (S.E.). The reduction of radiation intensity by artificial shading (60% of control) had no significant influence on total nitrogen concentrations of leaves and only a small influence on protein nitrogen concentrations in lower layers of the canopy. The leaf nitrate nitrogen fraction of nitrogen, f
nitr (–), within the canopy decreased linearly with increased average incident irradiance in different canopy layers (I
av, W PAR m–2) (f
Nitr. = 0.2456(0.0188) – 0.0023(0.0004)I
av, r
2 = 0.67.
The prospects for genetic manipulation of photosynthesis are assessed with an emphasis on the biochemical and morphological
aspects of light capture. The connection between different parts of the photosynthetic process is considered together with
the influence of environmental factors, development and acclimation, and metabolic regulation. The sites of real and potential
photosynthetic losses are identified, using tropical rice as a case study. The important interaction between photosynthetic
capacity, acclimation to the light environment, nitrogen accumulation and canopy architecture are discussed. The possibility
of genetic intervention to increase both biomass accumulation and improve nitrogen economy simultaneously are considered.
Finally, the numerous procedures for genetic manipulation of light harvesting are also discussed, with a view to improving
radiation‐use efficiency in crops.
Cryptochromes are blue light photoreceptors found in plants, bacteria, and animals. In Arabidopsis, cryptochrome 2 (cry2) is involved primarily in the control of flowering time and in photomorphogenesis under low-fluence light. No data on the function of cry2 are available in plants, apart from Arabidopsis (Arabidopsis thaliana). Expression of the tomato (Solanum lycopersicum) CRY2 gene was altered through a combination of transgenic overexpression and virus-induced gene silencing. Tomato CRY2 overexpressors show phenotypes similar to but distinct from their Arabidopsis counterparts (hypocotyl and internode shortening under both low- and high-fluence blue light), but also several novel ones, including a high-pigment phenotype, resulting in overproduction of anthocyanins and chlorophyll in leaves and of flavonoids and lycopene in fruits. The accumulation of lycopene in fruits is accompanied by the decreased expression of lycopene beta-cyclase genes. CRY2 overexpression causes an unexpected delay in flowering, observed under both short- and long-day conditions, and an increased outgrowth of axillary branches. Virus-induced gene silencing of CRY2 results in a reversion of leaf anthocyanin accumulation, of internode shortening, and of late flowering in CRY2-overexpressing plants, whereas in wild-type plants it causes a minor internode elongation.
In this study the impact of achenes on polyphenolic compounds, ascorbic acids, and antioxidant activities in strawberry purees at production and after storage at 6 and 22 degrees C for 8 and 16 weeks was investigated. Strawberry purees were made from flesh, berry, and achene-enriched homogenate and contained 0, 1.2, and 2.9% achenes, respectively. At production, strawberry purees made from flesh contained more anthocyanins, p-coumaroyl glycosides, and ascorbic acids, whereas increasing achene levels caused increasing levels of ellagic acid derivatives, proanthocyanidins, flavonols, total phenolics (TP), and antioxidant activities. In addition, the anthocyanins, TP, and ferric reducing ability power (FRAP) in purees with more achenes were better retained during storage. Ascorbic acids and anthocyanins declined rapidly during storage, whereas other polyphenols and antioxidant activities were more stable; that is, the contributions from anthocyanins and ascorbic acids to TP and antioxidant activities decreased. The findings that achenes contributed significantly to polyphenol content and stability of strawberry purees may be interesting in a nutritional and, thus, commercial, perspective.
The use of light emitting diodes (LEDs) for supplemental lighting in greenhouses is a major interest. Overnight lighting with LEDs is expected to increase the crop yield and quality with less cost. Growth chamber experiments were carried out to investigate the effect of overnight supplemental lighting by LEDs with four different spectral qualities (blue, green, red, and far-red light) on the growth of three cultivars each of lettuce, garland chrysanthemum, Chinese mustard, and Welsh onion. Plants transplanted in 7.5 cm plastic pots were placed in the growth chambers at the 4-6 true-leaf stage and were grown under different spectral light treatments for three to five weeks. The originally installed cool white fluorescent lamps were used during the day (10 h) period. The photosynthetic photon flux (PPF, 400-700 nm) at the top of plants was adjusted to 100 μmol m-2 s-1. During the night (14 h) period, overnight lighting by LEDs was provided at a PPF level of 50 μmol m-2 s-1. The day and night air temperatures were maintained at 25 and 20°C, respectively. The relative humidity was maintained at 70% throughout the two periods. The results showed that the growth of most plant species was affected by the light quality of the overnight lighting. Particularly, the shoot fresh weights of lettuce under blue and red light were 22 and 38% greater, respectively than in the control without overnight lighting. Blue and red light showed a similar effect on the shoot fresh weight of garland chrysanthemum. Blue light promoted the elongation of stem and leaves of both crops.
Recent developments show that Light Emitting Diodes (LED) can most likely not replace High Pressure Sodium (HPS) lights for full production cycles. However, the typical discrete spectral properties of LEDs make them highly suitable for (1) steering plant or flower development at specific growth stages and (2) providing optimal light at close distances to the plant, e.g., in multi-layered systems. We explored this potential to steer flowering induction in the Ghent azalea (Rhodondendron simsii). We developed an optimal light recipe for multi-layered forcing. Rhododendron simsii cultivation necessitates a forcing period in order to obtain intense flower colors and uniform flowering. Forcing requires three weeks 21°C, 70-80% RH and 91 μmol m-2 s-1 light intensity. This means extreme high energy input in winter. HPS lights have a high degree of heat radiation preventing their use in multi-layered systems. Since LEDs seems suitable, to determine the optimal wavelength composition and intensities we compared four LED-units equipped with different amounts of Red, Far-Red and Blue light with conventional HPS lamps and a control. Except for the control, none of the lighting treatments received external sunlight to mimic multi-layered conditions. The experiment was repeated eight times. Measurements indicated increased flower size under additional lighting. All three wavelengths are necessary for optimal flower quality, although red light is of far greater importance then blue light. Light intensities of 91 μmol m-2 s-1 with LED give comparable or even better results than HPS. With LED, the necessary lighting period can be reduced compared to HPS lights. Our results show potential for the use of LED in multi-layered systems for the forcing of azalea, with potential to reduce energy cost remarkably.
The artificial light plays an important role in crop growth, and LED as a new light source has broad prospects in the development of supplementary lighting system. According to the deficiency of fixed light intensity and light spectrums, this paper presented a self-adaptive and precise supplementary lighting system with comprehensive consideration of crop characteristics, effective photosynthesis light intensity and environment temperature. The system monitored the environment temperature and light intensity of specific light spectrums, and calculated the amount of supplementary light accurately. Based on two PWM signals, both red and blue light intensity were adjusted to meet different demands of quantitative supplementation of light in different stages and conditions. Experiments were made in actual production. The results showed that the system was stable, reliable and accurate, and could avoid the lacking or excess supplementation of light in different stages of crops.
We studied the effects of light quality and light period on the flowering of everbearing strawberry plants (Fragaria × ananassa Duch. 'HS138') during the nursery period, to increase the fruit production efficiency of transgenic strawberry plants in a closed plant production system. The plants were grown under a 16-h light period versus continuous lighting illuminated by white fluorescent lamps, blue LEDs, or red LEDs. Flowering was significantly earlier in plants grown under (1) blue LEDs compared to red LEDs, irrespective of light period, and (2) continuous lighting compared to the 16-h light period, irrespective of light quality. The results show that blue light advances the flowering of everbearing strawberry plants compared to red light. While continuous lighting by blue LEDs advanced flowering and shortened the vegetative growth period, the fruit yield of plants grown under continuous lighting by blue LEDs was higher than that of plants grown under our standard cultivation conditions (i.e., 16-h light period by white fluorescent lamp). In conclusion, shortening the nursery period by adjusting light quality and light period increased fruit production efficiency compared to standard cultivation conditions.
Plant factories where leafy vegetables are cultivated until harvest in closed systems with artificial lighting were proposed, developed, and implemented in Japan during the 1980s. During the 1990s, the products from these factories received high evaluations by the food service industry, to which they primarily catered. During the 2000s, commercial production of nursery plants of fruits and vegetables was initiated in plant factories. Since the late 2000s, plant factory technology has been introduced worldwide, particularly to Asian countries. Plant factories also provide good cultivation systems for the production of medicinal plants and genetically modified crops for pharmaceutical use. In late 2000s, light-emitting diodes (LEDs) were introduced to plant factories as a more efficient light source. LEDs are expected to reduce the electricity costs of lighting and cooling because they have a higher efficiency of converting electric power to light power and exert lower cooling loads than conventional light sources. To achieve plant production in plant factories by using LEDs, more achievement of plant research is required taking engineering and plant physiological approaches, in areas such as the creation of optimal LED lighting systems, promotion of photosynthesis, control of gene expression, photomorphogenesis, and synthesis of secondary metabolites. This study reviews recent research status and achievements regarding plant production in plant factories with artificial lighting and introduces plant research topics related to LEDs utilization.
Especially in an open crop (e.g., young plants) morphological responses to light quality can affect light interception, crop photosynthesis and growth. Earlier work showed a substantial morphology related biomass increase for young cucumber plants grown under 100% artificial sunlight (ASL) compared with 100% high pressure sodium light (HPS). Here, ASL is used to investigate the effect of HPS and LEDs compared with ASL, when applied supplemental to an ASL background. Tomato plants were grown in a climate room under 17 h ASL (50% of in total 200 μmol PAR m-2 s-1) supplemented with 50% HPS, light emitting diodes LEDs (red/blue), or ASL. The 100% ASL-grown plants produced 32-45% more dry weight, due to a more efficient light interception. As ASL lamps are not energy-efficient enough for commercial production we tried to simplify the solar spectrum while retaining enhanced crop productivity in greenhouses. Red/blue/far-red LEDs, at a ratio inducing the same phytochrome photostationary state (PSS) as natural sunlight, and sulphur-plasma lamps, emitting a continuous spectrum in the PAR-region, were tested and compared with supplemental red/blue LEDs, HPS and ASL in a greenhouse experiment. Red/blue/far-red LEDs resulted in a visual appearance similar to the ASL-plants, while red/blue LEDs produced the most compact morphology. Red/blue/far-red LEDs enhanced dry weight for cucumber (+21%) and tomato (+15%) compared with HPS. Dry weight and compactness were intermediate for sulphur-plasma. The differences were attributable to effects of leaf orientation and positioning on light interception, and not to photosynthesis per unit leaf area. The PSS appears to be a key-factor to control crop morphology, providing a tool to induce ‘sunlight’ crop characteristics to enhance productivity.
High-power (HP) light emitting diodes (LEDs) offer exciting opportunities for plant lighting research. LED technology now provides intensity levels and wavelengths potentially well suited to study plant growth and development under 'realistic', or specific artificially manipulated radiation environments. However, while the ability offered by LEDs to specify precisely the spectral composition provides greater flexibility than conventional broad-spectrum lighting, it also presents significant challenges in characterising what might constitute an 'optimum' light spectrum for plant growth. Plant growth and development under customdesigned HP LED arrays, capable of supporting up to 700 LEDs and as many as 10 spectral peaks, were studied within the controlled environment rooms at the New Zealand Controlled Environment Laboratory (NZCEL). White-based and red-blue (RB) based LED spectra, consisting of multitude peaks between 400 and 740 nm, were examined for their potential as sole-source lighting rigs for growing Arabidopsis thaliana. Development rates and biomass were measured from germination to seed set under 200 and 400 μmol m -2 s-1 photosynthetically active radiation (PAR), provided by HP LED arrays or the standard high pressure discharge (HID) metal halide and tungsten halogen lighting rig used within NZCEL. Development rate was comparable under the two light sources, but greater biomass obtained under LED suggests an additional potential benefit of LEDs over conventional HID lighting.
Supplemental lighting is proven to increase transplant growth and quality in vegetable nursery greenhouses. To evaluate plant responses to supplemental LED light quality, tomato seedlings ('Komeett') were grown in a greenhouse (Tucson, AZ, USA) until the second true leaf stage with 55.5±1.4 μmol m-2 s-1 photosynthetic photon flux of supplemental LED lighting (18-hour photoperiod). Treatments consisted of different red:blue photon flux ratios (1) 100% red:0% blue, (2) 96% red:4% blue, (3) 84% red:16% blue and a control without supplemental lighting. These ratios were evaluated under low and high daily solar light integrals (DLI) (8.9±0.9 and 19.4±1.9 mol m-2 d-1, respectively) created by different shade screens deployed in the greenhouse. Growth and morphological parameters including dry shoot mass, leaf count, stem diameter, hypocotyl length, leaf area, and chlorophyll concentration indicated the benefit of supplemental light, especially under low DLI, but there were no significant differences among different red:blue ratios regardless of DLI. The seedlings also exhibited the same high photosynthetic capacity measured under 1000 μmol m-2 s-1 PPF, ambient temperature and CO2 concentration regardless of the red:blue ratios. From this preliminary study it seems that for 'Komeett' tomato seedlings grown in greenhouse, use of 100% red LED supplemental lighting was sufficient and no additional blue light was required regardless of DLI.
Recently developed high-brightness light-emitting diodes (LEDs) offer new opportunities in the future plant lighting technologies. Application of the newgeneration of light sources provide remarkable conditions for the control of photomorphogenesis in plants, accelerating the breeding cycles, improving food quality, and energy saving. LEDs appear to be powerful instruments for light spectrum manipulation for crop growth regulation. Combinatorial lighting technologies will emerge on the basis of LED application: variable-spectrum lighting modules could be designed using various combinations of high-power monochromatic (narrow-band) LEDs. In our experiments, we studied application of LEDs with the narrow-bandwidth wavelength emissions in the photocontrol of basic physiological processes in several vegetable and ornamental crops. Plants were grown in controlled environment. PPF was provided by LED panels which were composed of blue and red light LEDs with the peak wavelengths at 460, 635, and 660 nm, respectively. Various spectral photon distribution in the long-wave region was provided using 635 and 660 nm LEDs separately or in combination. Changes in plant growth responses, phase transitions, pigment accumulation were observed in various light environments. Experimental data show that different LED systems with discrete wavelength ranges peaking at blue and red spectral regions can be used effectively both for basic research of plant photomorphogenesis and for the fine tuning of physiological processes in plants and optimization of the species/cultivar light regimes.
The effects of light quality on biomass and internal quality of leaf lettuce, spinach and komatsuna were examined. The plants were grown hydroponically in an environmentally controlled room with a 12-h light period and under a light/dark temperature of 20 ± 1°C/18 ± 1°C and a photosynthetic photon flux density (PPFD) of 300 μmol m-2 s-1 under four light quality treatments, i.e., red light from red fluorescent lamps (R) or blue light from blue fluorescent lamps (B) or a mixture of R and B (RB) or white light from white fluorescent lamps (W). The irradiation of R compared with W increased shoot dry weight in komatsuna and decreased the nitrate content in spinach. Irradiation of B or RB compared with W increased the L-ascorbic acid content in leaf lettuce and komatsuna and decreased the nitrate content in leaf lettuce. Irradiation of B was not suitable for the spinach cultivation due to an extremely decreased shoot dry weight although the carotenoid content was slightly increased. Our data show that controlling light quality is useful to achieve higher productivity or higher nutritional quality of the commercial crops even under limited light intensity in controlled-environment agricultural facilities although the effective light quality treatment differs depending on the plant species.
The effects of an increase in ultraviolet-B radiation (UV-B, 280–320 nm)
on growth, photosynthesis and photoinhibition of a UV-B sensitive variety of
cucumber (Cucumis sativus L. cv. Poinsett) were
investigated at four levels of applied nitrogen (N, 0.5, 2.0, 5.0 and 10.0 mol
m-3). Plants were grown for 33 days in a UV-B
transparent greenhouse at ambient and ambient +25% biologically
effective UV-B radiation (UV-BBE). A modulated lamp
system controlled supplemental UV-B levels; average doses of
UV-BBE were 2.5 ± 0.8 (ambient) and 3.1 ±
1.0 (ambient +25%) kJ m-2
d-1. The doses are comparable to the expected change in
UV-BBE between 1979 and 1999 under similar weather
conditions at this latitude. Plant biomass, height, and leaf N, chlorophyll
and leaf carbon content increased with increasing amounts of applied N. At the
highest level of N application, supplemental levels of UV-B caused a near
identical decrease in leaf area (20%), height (28%) and total
biomass (20%) compared with plants grown under ambient UV-B conditions.
There was no such effect when N stress was imposed. Apparent quantum yield
(&phis;app), dark respiration and photosynthetic rate
were unaffected by the supplemental UV-B and photodestruction of reaction
centres was not evident. However, there was a significant increase in
photoinhibition at midday in the N-replete plants. In leaves with N content
<3%, supplemental levels of UV-B caused the concentration of UV-B
absorbing compounds to increase significantly (72% at the lowest level
of applied N). The epidermis was thicker at all levels of N under supplemental
UV-B. The stress response to low N may confer secondary protection against
UV-B damage and changes in N status due to fertilisers or pollution may lead
to changes in UV-B sensitivity.
The effect of light quality on cell size and cell cycle, growth rate, productivity, photosynthetic efficiency and biomass composition of the marine prasinophyte Tetraselmis suecica F&M-M33 grown in 2-L flat panel photobioreactors illuminated with light emitting diodes (LEDs) of different colors was investigated. Biomass productivity and photosynthetic efficiency were comparable between white and red light, while under blue and green light productivity decreased to less than half and photosynthetic efficiency to about one third. Differences in cell size and number correlated with the cell cycle phase. Under red light cells were smaller and more motile. Chlorophyll content was strongly reduced with red and enhanced with blue light, while carotenoids and gross biomass composition were not affected by light quality. The eicosapentaenoic acid content increased under red light. Red light can substitute white light without affecting productivity of T. suecica F&M-M33, leading to smaller and more motile cells and increased eicosapentaenoic acid content. Red LEDs can thus be profitably used for the production of this microalga for aquaculture. Biotechnol. Bioeng. © 2013 Wiley Periodicals, Inc.
The role of UV radiation in the accumulation of anthocyanin in 'Gros Colman' (Vitis vinifera L.), a light-sensitive cultivar, was examined by using berry sections prepared from the softened green berries at veraison. The sections were exposed to diffuse sunlight under covering materials such as glass plate, polyolefin film (PO), polyvinyl chloride film (PVC), UV-proof PVC, ethylenetetrafluoroethylene (ETFE), polycarbonate resin plate (PC), fiber-reinforced acrylic resin plate (FRA) for 72 hr. The accumulation of anthocyanin in the berry skins under diffuse sunlight was greatly reduced with the covering materials which prevent the penetration of UV light. Artificial irradiation with an UV lamp (peak wavelength: 352nm) greatly promoted the accumulation of anthocyanin. With increasing light intensity in the UV-A region (320-400 nm) up to 0.4 W · m-2, the anthocyanin content markedly increased, reached a plateau and then levelled off at 2.3 W · m-2. Increasing the intensity of white light up to 8.5 W · m-2 induced a gradual accumulation of anthocyanin. When UV irradiation was combined with white light at about 4.1 W · m-2, the accumulation of anthocyanin was further enhanced. These results suggest that UV light is involved in the accumulation of anthocyanin in 'Gros Colman' grapes. Hence, UV permeability of covering materials in the protected culture should be considered.
This paper reviews the published methods of nitrate‐nitrogen (NO3‐N) determination with the objective to assess their applicability to soil and plant tissue anarysis. The methods are separated into three categories on the basis of the analytical approach utilized for NO3‐N determination. Strengths and weaknesses of the methods are discussed. The first analytical approach utilitizes direct measurement of NO3‐N by the following methods: (a) colorimetric (after a color producing reaction with NO3‐N), (b) potentiometric, (c) absorption of UV radiation by NO3‐N in a complex matrix, (d) transnitration of salicylic acid, and (e) chromatographic (separation and measurement of NO3‐N) methods. The second approach is based on the reduction of NO3‐N to nitrite‐nitrogen (NO2‐N), ammonium‐nitrogen (NH4‐N), or nitric oxide and measurement of the reduction product. When NO3‐N is reduced to NO2‐N, the measurement may be achieved by (a) colorimetric, (b) fluorimetric, (c) coulometric, and (d) catalytic kinetic methods. When NO3‐N is reduced to NH4‐N, the measurement is done by (a) colorimetric (after a color producing reaction with NH4), (b) potentiometric, (c) steam distillation, and (d) gas diffussion conductimetric methods. A chemiluminescence detection method is utilized when NO3‐N is reduced to nitric oxide. The third approach determines NO3‐N concentration by measuring the change in the concentration of the chemical species that react with NO3‐N and form a complex.
Carotenoids are secondary plant metabolites that serve antioxidant functions in plant photosynthetic processes, as well as in actions of disease reduction in mammalian systems. The production of antioxidant compounds within plants can increase, or decrease in response to environmental stress. Plant secondary metabolites, such as carotenoids, serve functional roles to overcome the negative consequences to plant growth caused by a stressful environment. Carotenoid accumulation appears to be shaped by a plant species' physiological, genetic, and biochemical attributes, as well as environmental growth factors such as air temperature, light intensity, and photoperiod. Significant genetic variation for carotenoid accumulations has been documented for many vegetable crop species. Further, potential exists for genetic manipulation of carotenoid biosynthesis. Cultural management will influence phytochemical (carotenoid) concentrations in crops, which may affect nutritional values.
Using UV-A, blue (B), green (G), red (R), and far-red (FR) light-emitting diodes (LEDs), we investigated the effects of different supplemental light qualities on phytochemicals and growth of ‘Red Cross’ baby leaf lettuce (Lactuca sativa L.) grown at a high planting density under white fluorescent lamps as the main light source inside a growth chamber. Photon flux added by supplemental LEDs for UV-A, B, G, R and FR were 18, 130, 130, 130 and 160μmolm−2s−1, respectively. Photosynthetic photon flux (PPF, 400–700nm), photoperiod, and air temperature (day/night) was 300μmolm−2s−1, 16h, and 25°C/20°C in all treatments including white light control. After 12 days of light quality treatment (22 days after germination), phytochemical concentration and growth of lettuce plants were significant affected by light treatments. Anthocyanins concentration increased by 11% and 31% with supplemental UV-A and B, respectively, carotenoids concentration increased by 12% with supplemental B, phenolics concentration increased by 6% with supplemental R while supplemental FR decreased anthocyanins, carotenoids and chlorophyll concentration by 40%, 11% and 14%, respectively, compared to those in the white light control. The fresh weight, dry weight, stem length, leaf length and leaf width significantly increased by 28%, 15%, 14%, 44% and 15%, respectively, with supplemental FR light compare to white light, presumably due to enhanced light interception by enlarged leaf area under supplemental FR light. Although the mechanisms of changes in phytochemicals under different supplemental light quality are not well known, the results demonstrated that supplemental light quality could be strategically used to enhance nutritional value and growth of baby leaf lettuce grown under white light.
The growth and production of anthocyanin, flavonoid and phenolic compounds were evaluated in Lollo Rosso lettuce ‘Revolution’ grown continuously under films varying in their ability to transmit UV radiation (completely transparent to UV, transparent above 320, 350, 370 and 380 nm and completely opaque to UV radiation). Plants were grown from seed under UV transparent and UV blocking films and destructively harvested 3–4 weeks after transplanting. Plants under a complete UV blocking film (UV400) produced up to 2.2 times more total above ground dry weight than plants under the UV transparent film. In contrast, anthocyanin content in plants under the UV blocking film was approximately eight times lower than in plants under a UV transparent film. Furthermore, there was a curvilinear relationship between the anthocyanin content and UV wavelength cutoff such that above 370 nm there was no further reduction in anthocyanin content. Fluorescence measurements indicated that photosynthetic performance index was 15% higher under the presence of UVB and UVA (UV280) than under the presence of UVA (UV320) and 53% higher than in the absence of UV radiation suggesting protection of the photosynthetic apparatus possibly by phenolic compounds. These findings are of particular importance as the potential of UV transmitting films to increase secondary compounds may offer the opportunity to produce plants commercially with increased health benefits compared to those grown under conventional films.
A full-length cDNA encoding glutamine synthetase (GS) was cloned from a gt10 library of tobacco leaf RNA, and the nucleotide sequence was determined. An open reading frame accounting for a primary translation product consisting of 432 amino acids has been localized on the cDNA. The calculated molecular mass of the encoded protein is 47.2 kDa. The predicted amino acid sequence of this precursor shows higher homology to GS-2 protein sequences from other species than to a leaf GS-1 polypeptide sequence, indicating that the cDNA isolated encodes the chloroplastic isoform (GS-2) of tobacco GS. The presence of C-and N-terminal extensions which are characteristic of GS-2 proteins supports this conclusion. Genomic Southern blot analysis indicated that GS-2 is encoded by a single gene in the diploid genomes of both tomato and Nicotiana sylvestris, while two GS-2 genes are very likely present in the amphidiploid tobacco genome. Western blot analysis indicated that in etiolated and in green tomato cotyledons GS-2 subunits are represented by polypeptides of similar size, while in green tomato leaves an additional GS-2 polypeptide of higher apparent molecular weight is detectable. In contrast, tobacco GS-2 is composed of subunits of identical size in all organs examined. GS-2 transcripts and GS-2 proteins could be detected at high levels in the leaves of both tobacco or tomato. Lower amounts of GS-2 mRNA were detected in stems, corolla, and roots of tomato, but not in non-green organs of tobacco. The GS-2 transcript abundance exhibited a diurnal fluctuation in tomato leaves but not in tobacco leaves. White or red light stimulated the accumulation of GS-2 transcripts and GS-2 protein in etiolated tomato cotyledons. Far-red light cancelled this stimulation. The red light response of the GS-2 gene was reduced in etiolated seedlings of the phytochrome-deficient aurea mutant of tomato. These results indicate a phytochrome-mediated light stimulation of GS-2 gene expression during greening in tomato.
Biosynthesis of phenolic compounds is known to be sensitive to light environments, which reflects the possible role of these compounds for photoprotection in plants. Herein, the effects of UV and visible light on biosynthesis of flavonoids was investigated, i.e., proanthocyanidins (PAs) and flavonols, in young berry skins of a red-wine grape, Vitis vinifera cv. Cabernet Sauvignon. Shading with light-proof boxes from the flowering stage until 49 days after treatment (DAT) partially decreased PA concentrations, and completely decreased flavonol concentrations in the berry skins. Shading decreased the transcript abundance of a flavonol-related gene more remarkably than those of PA-related genes. In addition, light exclusion influenced the composition of PAs, such as the decrease in the proportion of trihydroxylated subunits and the mean degree of polymerization (mDP) within PAs. However, solar UV exclusion did not affect the concentration and composition of PAs, whereas this exclusion remarkably decreased the flavonol concentration. Consistently, UV exclusion did not influence the transcript levels of PA-related genes, whereas it dramatically decreased that of flavonol-related genes. These findings indicated a different light regulation of the biosynthesis of these flavonoids in young berry skins of wine grape. Visible light primarily induces biosynthesis of PAs and affects their composition, whereas UV light specifically induces biosynthesis of flavonols. Distinct roles of members of a MYB transcription factor family for light regulation of flavonoid biosynthesis were proposed.
Flavonoid content of mulberry leaves of 19 varieties of species, determined spectrophotometrically in terms of rutin equivalent, varied from 11.7 to 26.6 mg g−1 in spring leaves and 9.84 to 29.6 mg g−1 in autumn leaves. Fresh leaves gave more extract than air-dried or oven-dried ones. HPLC showed that mulberry leaves contain at least four flavonoids, two of which are rutin and quercetin. The percentage superoxide ion scavenged by extracts of mulberry leaves, mulberry tender leaves, mulberry branches and mulberry bark were 46.5, 55.5, 67.5 and 85·5%, respectively, at a concentration of 5 μg ml−1. The scavenging effects of most mulberry extracts were greater than those of rutin (52.0%).
• The differential accumulation of various polyphenols, particularly of flavonoids and hydroxycinnamates, was studied in leaves of
Ligustrum vulgare exposed to increasing sunlight under well watered or drought-stress conditions.
• Light- and drought-induced changes in leaf polyphenol concentrations were normalized to the CO2 assimilation rate. The functional roles of flavonoids and hydroxycinnamates were analysed through tissue localization using multispectral fluorescence microimaging, and through efficiencies to scavenge superoxide radicals (O2–) and to screen UV wavelengths.
• Clear effects of light and water treatments on leaf polyphenol concentrations were not observed, as the CO2 assimilation rate varied according to sunlight and water availability. However, biosynthesis of quercetin 3-O-rutinoside, luteolin 7-O-glucoside and echinacoside, which were efficient O2–scavengers, increased sharply in response to solar radiation. By contrast, carbon for the synthesis of p-coumaric acid and monohydroxyflavones, efficient UV screeners but poor O2–scavengers, did not vary depending on light treatments. Flavonoids accumulated in both the adaxial epidermis and the palisade tissue because of sunlight irradiance, whereas echinacoside occurred largely in abaxial tissues.
• We hypothesize that flavonoids may serve antioxidant functions in response to excess light and drought stress, and that a coordinate control system between hydroxycinnamate and flavonoid pathways operated in L. vulgare exposed to excess light.