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... For basil there has not been a consensus on the optimal light spectrum for improved growth. Pennisi et al. (2019) found the optimal R:B ratio to be 3 (i.e. with 23% blue light), whereas Piovene et al. (2015) found 0.7 (i.e. with 37 % blue light) to be optimal. However, Lim and Kim (2021) did not find a clear effect of solely red and of R:B ratio ranging from 1.1 to 3 (from 20 to 27 % blue light) on basil growth or morphology. ...
... Light intensity and spectrum can affect the content of phenolic acids, flavonoids and anthocyanins. In particular blue light (400-500 nm) has been found to stimulate the biosynthesis of compounds from the phenylpropanoid pathway such as flavonoid and anthocyanin content in a number of crops: in fruit and leaves of strawberry (Piovene et al., 2015;Zhang et al., 2018), lettuce (Samuoliene et al., 2013) and Arabidopsis (Chen et al., 2006). Blue light has also been found to stimulate the biosynthesis of rosmarinic acid, chicoric acid, chlorogenic acid, p-OH-cinnamic acid derivative, 2-O-feruloyl tartaric acid and quercetin rhamnoside in green basil (Taulavuori et al., 2013(Taulavuori et al., , 2016, and phenolic acids in red lettuce (Ouzounis et al., 2015). ...
... Findings by Pennisi et al. (2019) indicated an optimum at 23 % blue light resulting in the highest total flavonoids content while 58 % and 19 % blue light resulted in the lowest total flavonoid content in green basil. In contrast, Piovene et al. (2015) found that a range of blue light from 10 to 40 % did not increase the total flavonoid content in basil. In red lettuce 47 % blue light gave the highest content of flavonoids whereas 59 % blue light yielded the highest content in green lettuce (Son and Oh, 2013). ...
... locusta L.) [55], strawberry fruits (F. ananassa) [56], strawberry leaves [56], green lettuce (Lactuca sativa L.) [57], red lettuce (Lactuca sativa L.) [57], and sweet basil (Ocimum basilicum L.) [56]) with quantitative assessments of multiple secondary metabolites between two experimental conditions (control (without LED illumination) vs. treatment (with LED)). Overall, this revealed higher flavonoid content under LED in half of the antioxidant and estimates 50% of six studies and only one of the phenolic studies ( Figure 3). ...
... locusta L.) [55], strawberry fruits (F. ananassa) [56], strawberry leaves [56], green lettuce (Lactuca sativa L.) [57], red lettuce (Lactuca sativa L.) [57], and sweet basil (Ocimum basilicum L.) [56]) with quantitative assessments of multiple secondary metabolites between two experimental conditions (control (without LED illumination) vs. treatment (with LED)). Overall, this revealed higher flavonoid content under LED in half of the antioxidant and estimates 50% of six studies and only one of the phenolic studies ( Figure 3). ...
... locusta L.) [55], strawberry fruits (F. ananassa) [56], strawberry leaves [56], green lettuce (Lactuca sativa L.) [57], red lettuce (Lactuca sativa L.) [57], and sweet basil (Ocimum basilicum L.) [56]) with quantitative assessments of multiple secondary metabolites between two experimental conditions (control (without LED illumination) vs. treatment (with LED)). Overall, this revealed higher flavonoid content under LED in half of the antioxidant and estimates 50% of six studies and only one of the phenolic studies ( Figure 3). ...
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Vegetables and herbs play a central role in the human diet due to their low fat and calory content and essential antioxidant, phytochemicals, and fiber. It is well known that the manipulation of light wavelengths illuminating the crops can enhance their growth rate and nutrient contents. To date, it has not been easy to generalize the effects of LED illumination because of the differences in the plant species investigated, the measured traits, the way wavelengths have been manipulated, and the plants’ growing environments. In order to address this gap, we undertook a quantitative review of LED manipulation in relation to plant traits, focusing on vegetables and herbs. Here, we use standardized measurements of biomass, antioxidant, and other quantitative characteristics together with the whole range of the photosynthetic photon flux density (PPFD). Overall, our review revealed support for the claims that the red and blue LED illumination is more reliable and efficient than full spectrum illumination and increases the plant’s biomass and nutritional value by enhancing the photosynthetic activity, antioxidant properties, phenolic, and flavonoids contents. Although LED illumination provides an efficient way to improve yield and modify plant properties, this study also highlights the broad range of responses among species, varieties traits, and the age of plant material.
... Specifically, the use of red and blue together seems to be preferable; however, the optimal proportions may vary. In fact, depending on several factors, the employment of blue light must be preponderant over red or vice versa, with the possible addition of green or white LED light [22][23][24][25]. These variations are mainly due to thedifferent environmental conditions applied during the tests, such as the light surrounding the experiments' area (e.g., into the dark or into a greenhouse) or time of exposure (varying from 21 to 64 days) or daily photoperiod (from 12 to 18 h). ...
... The different age of collection and analysis of the growth parameters may be one of the other factors leading to the different influence of light. Thus, if the results of some studies lead to the hypothesis that in the first weeks of plant life, blue light is more important than red, other studies refuse it [22]. In addition, in general, the influence of LED lights on the germination phase is ignored. ...
... Prior to scanning, leaves were cut at certain points to extend their full area on the paper and to better assess their area. Following these measurements, the LAI (Leaf Area Index), given by the ratio of Average Leaf Area to the area of the pot in which the plants had grown, and the SLA (Specific Leaf Area) index, given by the ratio of Average Leaf Area to Average Leaf Dry Mass, were also calculated [22,38]. ...
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This study aims to optimize the conditions for “Genovese” basil (Ocimum Basilicum) germination and growth in an indoor environment suitable for horticulture, through a synergic effect of light and fertilizers addition. In fact, several studies determined that specific light conditions are capable to enhance basil growth, but this effect is highly dependent on the environmental conditions. In this study, the effect of different light sources was determined employing a soil with a negligible amount of fertilizer, demonstrating substantial improvement when LED lights (hyper red and deep blue in different combinations) were applied with respect to daylight (Plants height: + 30%, Total fresh mass: + 50 %). Thereafter, a design of experiment approach has been implemented to calculate the specific combination of LED lights and fertilizer useful to optimize the basil growth. A con-trolled-release fertilizer based on nitrogen, phosphorus and potassium (NPK) derived from agro-residues, and a soil enriched in macronutrients were compared. Results demonstrate signifi-cant improvements for the growth parameters with the employment of the controlled-release NPK, with respect to enriched soil, combined with a ratio of hyper red and deep blue LED light equal to 1:3 (Total fresh mass: +100 %, Leaves number: + 20 %).
... Neither the supplementation of warm-white light with blue or red LEDs (50 µ mol m −2 s −1 ) was effective for increasing the biomass in baby-leaf lettuce [26]. Furthermore, even the combination of red/blue light may require supplemental broad-spectral energy of 500-600 nm (red-blue-white lighting) to increase the biomass in leafy crops, as the works of Lin et al. and Piovene et al. [27,28] suggest. However, other works found a positive effect for baby-leaf crops growing under these light regions, especially if high proportions of red lighting (>75%) were supplemented with blue LEDs at optimal ratios, instead of using monochromatic lighting [29,30]. ...
... Neither the supplementation of warm-white light with blue or red LEDs (50 µmol m −2 s −1 ) was effective for increasing the biomass in baby-leaf lettuce [26]. Furthermore, even the combination of red/blue light may require supplemental broadspectral energy of 500-600 nm (red-blue-white lighting) to increase the biomass in leafy [27,28] suggest. However, other works found a positive effect for baby-leaf crops growing under these light regions, especially if high proportions of red lighting (>75%) were supplemented with blue LEDs at optimal ratios, instead of using monochromatic lighting [29,30]. ...
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This work studies the enhancement of glucosinolates (GSLs) in mustard sprouts as health promoters. Sprouts of Sinapis alba, Brassica nigra, and B. carinata were grown under broad-spectrum, monochromatic blue or red light-emitting diode (LED) lamps, irrigated with 0–100 mM sodium chloride (NaCl), and sprayed with 0–250 µM methyl jasmonate (MeJA) as elicitor. The use of LEDs did not result in increased sprout biomass in any case. The effect of the applied treatments on the GSLs depended on the species and were restricted to Brassica spp. The red LEDs produced an overall increase in GSLs over 500% in B. carinata (from 12 to 81 mg 100 g−1 F.W.), compared to the white broad-spectrum lights, although the highest increase in content was obtained in treated sprouts with 250 µM MeJA (104 an 105 mg 101 g−1 F.W., under the red and blue LEDs, respectively). The combination of blue LEDs, 100 mM NaCl, and 250 µM MeJA enhanced the levels of GLSs in B. nigra to the maximum (81 mg 100 g−1 F.W.). Overall, these results indicate that by modifying the growing conditions for a given sprout, enhancement in the accumulation of GSLs as health promoters is possible. The use of these treatments is a sustainable alternative to genetic modification when looking for bioactive-enriched foods, delivering natural plant foods rich in bioactive ingredients (e.g., glucosinolates). Nevertheless, the response to the treatments varies among species, indicating that treatments will require adjustment across sprouts. Further research continues with producing cruciferous sprouts to obtain GSL-enriched formulas for further studying the effects of their bioavailability and bioactivity on health-promotion.
... For light spectra, 3 different R:B ratios, 3:7, 7:3, and 9:1 (hereafter indicated by RB3:7, RB7:3, and RB9:1, respectively), were used. The proportion of red light was calculated by defining the relative areas of the spectrum within the red light region [36]. The light was provided by dimmable red and blue LED lamps (GreenPower research modules, Philips, NL). ...
... However, the net photosynthetic rate and chlorophyll fluorescence parameters were not affected by the different R:B ratios significantly ( Table 4). The photosynthetic rate in basil and strawberry (blue light percentage from 7.3 to 37.7%) [36] and the chlorophyll fluorescence parameters (Fv/Fm, PhiPSII, and Fv/Fm-PhiPSII) in cucumber (blue light percentage from 0 to 100%) [40] were significantly affected by R:B ratios when the proportion of blue light was below 10%. In the present study, the proportion of blue light is equal to or greater than 10%, which may be a possible factor leading to these results. ...
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Quantitative nutrient management has advantages, such as saving resources and improving nutrient utilization, compared with the conventional electrical conductivity management method. The growth and nutrient utilization of vegetables are affected by the integrated environmental conditions such as nutrient supply and light spectrum. This study investigated the effects of applied nutrient quantity (ANQ) (0.5, 1, 2, and 4 times (T) the absorption quantity of nutrients determined in the preliminary experiment, indicated by 0.5T, 1T, 2T, and 4T, respectively) in nutrient solution and red:blue ratio (R:B = 3:7, 7:3, and 9:1, indicated by RB3:7, RB7:3, and RB9:1, respectively) on the growth and nutrient utilization of basil plants in a plant factory with artificial lighting. Results demonstrated that the nutrient use efficiency (NUE) and the nutrient absorption efficiency (NAE) were significantly increased by the ANQ of 0.5T compared with the treatments of 1T, 2T, and 4T, irrespective of R:B ratios. Furthermore, under the ANQ of 0.5T, RB7:3 significantly increased the yield and the absorption of N and K of the basil plant compared with other R:B ratios. Therefore, the ANQ of 0.5T combined with RB7:3 was considered the optimal combination to improve the yield, NUE, and NAE of basil plants in the present study.
... The need to cultivate where natural light is insufficient (e.g., northern latitudes and indoor cultivation) and the quest for techniques that enhance vegetable quality has led to a surge in interest for the use of artificial lighting. The introduction of light-emitting diodes (LEDs) has in this respect facilitated considerable progress (Piovene et al., 2015). Considering that plants can respond to changes in light quality through different types of photoreceptors, the use of LED technologies with highly defined and modifiable spectral properties (250-1000 nm) renders this application even more interesting (Lin et al., 2021). ...
... Another quality aspect strongly influenced by the R:B spectral ratios is nitrate content. Piovene et al. (2015) observed that the nitrate content in sweet basil cultivated under R:B= 0.7 was significantly lower (635 mg kg -1 FW) than that obtained with R:B= 5.5 (1015 mg kg -1 FW). Although the range of visible radiation (400-700 nm) is commonly considered the most important for photosynthetic activity, photoreceptors in plants can detect and respond to shorter and longer wavelengths outside the photosynthetically active radiation range (Holopainen et al., 2018). ...
Article
Combining health-promoting nutrition with gastronomic novelty is a major trend currently driving the agri-food sector. Basil (Ocimum basilicum L.) is a genetically diverse aromatic vegetable crop that combines rich phytochemical composition and enticing sensory profile. The current review examines how genetic variation underlies the phytochemical composition, nutrient composition, and volatile aromatic compounds of basil. It further provides a critical assessment of preharvest factors that configure product quality, including nutrient modulation, controlled stress, biofortification, biostimulant and light management applications. Appropriate genotype selection may facilitate sustainable production of improved quality, whereas targeted preharvest applications combined with optimized light intensity and spectral quality may effectively increase the content of essential phytochemicals and micronutrients, while suppressing the accumulation of anti-nutritive agents. The application of biostimulants may further underpin the sustainability factor in basil production, especially under growth-limiting conditions. The current review constitutes a critical synopsis of all available scientific literature investigating key factors configuring the composition of basil in minerals, bioactive secondary metabolites, micronutrients and volatile aromatic compounds from 1996 to 2022. Topics warranting further research are highlighted, with emphasis placed in identifying optimal combinations within the genotype-environment-management interaction nexus that tap the physiological and molecular mechanisms responsible for improving plant performance and functional-sensory quality in basil. LINK: https://authors.elsevier.com/a/1e-wU3AAyUFv1P
... Light intensity and spectrum can affect the content of phenolic acids, flavonoids, and anthocyanins. In particular, blue light (400-500 nm) has been found to stimulate the biosynthesis of compounds from the phenylpropanoid pathway such as flavonoid and anthocyanin content in several crops: in fruit and leaves of strawberry (Piovene et al., 2015;Zhang et al., 2018), lettuce (Samuoliene et al., 2013), and Arabidopsis (Chen et al., 2006). Blue light has also been found to stimulate the biosynthesis of rosmarinic acid, chicoric acid, chlorogenic acid, p-OH-cinnamic acid derivative, 2-O-feruloyl tartaric acid, and quercetin rhamnoside in green basil (Taulavuori et al., 2013(Taulavuori et al., , 2016, and phenolic acids in red lettuce (Ouzounis et al., 2015). ...
... Findings by Pennisi et al. (2019) indicated an optimum at 23% blue light resulting in the highest total flavonoids content while 58% and 19% blue light resulted in the lowest total flavonoid content in green basil. In contrast, Piovene et al. (2015) found that a range of blue light from 10 to 40% did not increase the total flavonoid content in basil. In red lettuce, 47% blue light gave the highest content of flavonoids whereas 59% blue light yielded the highest content in green lettuce (Son and Oh, 2013). ...
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Blue light, measuring from 400 to 500 nm, is generally assumed to increase the content of antioxidants in plants independent of the species. Blue light stimulates the biosynthesis of phenolic compounds such as flavonoids and their subclass anthocyanins from the phenylpropanoid pathway. Flavonoids, anthocyanins, and phenolic acids are strong reactive oxygen species (ROS) scavengers and may lessen the symptoms of abiotic stresses such as chilling. We tested the hypothesis that a high percentage of blue light induces the accumulation of antioxidants and that this effect depends on the photosynthetic photon flux density (PPFD, 400–700 nm). The effect may be more pronounced at a lower PPFD. We investigated the changes in primary and secondary metabolites of basil in response to the percentage of blue light (9, 33, 65, and 100%) applied either as a 5-day End-Of-Production (EOP) treatment or continuous throughout the growth cycle in the green cv. Dolly. We also studied if the response to the percentage of blue light (9 or 90%) was dependent on the total PPFD (100 or 300 μmol m –2 s –1 PPFD) when applied as a 5-day EOP treatment in the green cv. Dolly and the purple cv. Rosie. For both green and purple basil, it was found that the percentage of blue light had little effect on the levels of antioxidants (rosmarinic acid, total ascorbic acid, total flavonoids, and total anthocyanins) at harvest and no interactive effect with PPFD was found. Antioxidants generally decreased during postharvest storage, wherein the decrease was more pronounced at 4 than at 12°C. Chilling injury, as judged from a decrease in F v /F m values and from the occurrence of black necrotic areas, was not affected by the percentage of blue light. Particularly, chilling tolerance in the purple cultivar was increased in plants grown under higher PPFD. This may be related to the increased levels of soluble sugar and starch in leaves from high PPFD treated plants.
... Light intensity and spectrum can affect the content of phenolic acids, flavonoids, and anthocyanins. In particular, blue light (400-500 nm) has been found to stimulate the biosynthesis of compounds from the phenylpropanoid pathway such as flavonoid and anthocyanin content in several crops: in fruit and leaves of strawberry (Piovene et al., 2015;Zhang et al., 2018), lettuce (Samuoliene et al., 2013), and Arabidopsis (Chen et al., 2006). Blue light has also been found to stimulate the biosynthesis of rosmarinic acid, chicoric acid, chlorogenic acid, p-OH-cinnamic acid derivative, 2-O-feruloyl tartaric acid, and quercetin rhamnoside in green basil (Taulavuori et al., 2013(Taulavuori et al., , 2016, and phenolic acids in red lettuce (Ouzounis et al., 2015). ...
... Findings by Pennisi et al. (2019) indicated an optimum at 23% blue light resulting in the highest total flavonoids content while 58% and 19% blue light resulted in the lowest total flavonoid content in green basil. In contrast, Piovene et al. (2015) found that a range of blue light from 10 to 40% did not increase the total flavonoid content in basil. In red lettuce, 47% blue light gave the highest content of flavonoids whereas 59% blue light yielded the highest content in green lettuce (Son and Oh, 2013). ...
... [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. ...
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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.
... While these general trends hold true and reliably allow for R:B ratios to be determined to best suit desired crop performance and characteristics, there are some additional factors to consider. For instance, in fruit-bearing crops such as strawberry (Fragaria ×ananassa) and sweet pepper (Capsicum annuum), higher rates of photosynthesis were observed under lower R:B (higher blue), however higher fruit yield was found under higher R:B (higher red) (Naznin et al. 2019;Piovene et al. 2015). The decrease in fruit yield despite high photosynthesis in plants grown in a high compared with low R:B ratio may be due to greater partitioning of assimilates to leaves instead of the fruits, which can also occur in crops grown under high light intensity (Trouwborst et al. 2011). ...
Article
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For many growers, established and newcomers, the determination of the optimal light spectrum for growing crops can be challenging and highly dependent on crop species and variety. With the increased popularity of LED lighting, the capability to fine-tune a light spectrum has never been greater. Here, we break down the fundamental roles of the major spectral regions (ultraviolet, blue, green, red, and far-red) and explain the effect on plant growth, yield, and crop quality (i.e., greenness, coloration, flavor) when applied in isolation or combination. The first part of this review examines plant responses to light stimuli and the potential benefits for growers. We also discuss how LED lighting can be used to manipulate plant growth and development to improve crop productivity and/or value. We suggest some basic LED light "recipes" that could be used by growers to deliver specific growth effects and provide an easy-to-use visual reference guide. The second part of this review explores the impact of light treatments on crop productivity. Increased productivity is weighed against the ongoing costs associated with various light treatments, modeled in the context of UK electricity pricing. Light is an essential resource for all plants, providing the energy necessary for photosyn-thesis, the process that enables plants to grow. However, light also plays a major role in influencing plant morphology and physiology, which is dependent not just on light intensity but also the spectral quality (color) of light. The effects of intensity and quality on plant performance and morphology are discussed in this review, with emphasis on how light can be used to improve the quality and quantity of crop yield.
... The effect of B light in regulating crop yield has been addressed in a range of recent reports, although with conflicting results [31]. Increasing the B light fraction inhibits cell division and cell expansion, and thus decreases the leaf area [32]. ...
Article
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Leafy greens are increasingly being produced indoors with electric lighting from light-emitting diodes (LEDs). Red (R) and blue (B) LEDs are commonly used to ensure healthy plant growth, but biofortification techniques can potentially maximise nutritional quality. The aim of the study was to evaluate the effects of B (peak = 450 nm) and R (peak = 665 nm) light ratios (R:B) of 9:1, 3:1, and 1:3 on growth, metabolic response, and the accumulation of mineral nutrients in spinach ‘Corvair F1’ and ‘Space F1’ grown in hydroponic solutions with different iron (Fe) concentrations (2, 5, and 15 mg L−1). Plant biomass and leaf length, width, and number generally decreased as the R:B decreased, leading to a high concentration of Fe in the solution. A higher Fe dose increased the contents of some other minerals but depended on the R:B and cultivar. For example, Zn generally increased with increasing Fe but Cu content decreased, especially in ‘Space F1’. There were less-profound effects of the R:B and Fe dose on metabolites or antioxidant capacity. The research findings suggest that the overall nutritional quality of spinach could improve with lighting and Fe biofortification strategies and thus increase the sustainability of indoor crop production.
... Ngcobo et al. (2020a) demonstrated that on-plant illumination of cherry tomatoes with red light, targeting trusses, enhanced the fruit carotenoid concentration and overall fruit quality. Piovene et al. (2015) examined physiological and phytochemical plant responses to LED lights, at different ratios, in indoor cultivated leafy vegetable and fruit crops [(sweet basil (Ocimum basilicum L) and strawberry (Fragaria × ananassa)]. The authors concluded that a spectral red:blue (R:B) ratio of 0.7 improved plant development and nutraceutical properties in both crops. ...
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In this research, the combined effect of red and blue LED lights on tomato plants and fruit was investigated. Selected tomato plants were illuminated with a combination of red light (RL) and blue light (BL) at a ratio of (1:1) with a combined pho-tosynthetic photon flux density (PPFD) of 138 ± 5 µmol m −2 s −1. This illumination was installed above the plants and was terminated at different stages of plant growth, namely, at 50% flowering (FLW) and when fruit were mature green (MG). The plants were allowed to receive natural light during the day and were exposed to the light treatments 3 h after sunset and 3 h before sunrise. Control plants received only natural light. Growth, yield, and quality parameters were assessed. Both light treatments, whether terminated at FLW or MG, significantly enhanced plant height, number of leaves, and branching, with light treatment until the MG stage having a lesser, but nonetheless significant, effect. Plants that were treated with additional light until fruit were MG had a significantly increased total fruit mass compared with other treatments. Surprisingly , plants treated until FLW showed a significant increase in number of fruit per plant. Both treatments did not have a significant effect on colour parameters, while light treatments, particularly treatment until MG, were able to significantly enhance chlorophyll degradation in fruit. In addition, both light treatments resulted in a significant increase in fruit lycopene, the most important carotenoid in red tomato, while also potentially increasing the concentration of β-carotene, as well as total soluble solids (TSS), phenolics, and vitamin C. Treating tomato plants with a combination of LED light sources only until FLW was sufficient to enhance growth, yield, and antioxidant phytonutrients in tomatoes with no additional increase with further light treatment.
... Recently, LEDs are extensively used in plant factories compared to fluorescent lamps due to their extended life, decreased heat output, and lower power consumption. Due to lower prices and improved performance, light-emitting diodes (LEDs) have been used as artificial lighting for crop cultivation for the past decade (Piovene et al., 2015;Kang et al., 2016). ...
Article
Red and blue light-emitting diodes (LEDs) are widely used as light sources in plant factories. Plants grown under red and blue light only produces purplish-gray light environment where plant leaves look purplish-gray. Under that light condition, it makes difficulty to check health status of plants specially insect and disease infected leaves by human naked eye. But the leaf color turns green when inspected under full spectrum of light environment. In this regard, the use of green light to red and blue create a white light environment which is congenial for the grower. Likewise, CO2 assimilation of green light is usually lower compared to red and blue light because of its lower absorptance under low PPFD. But at higher PPFD (≥500 µmol m⁻² s⁻¹), green light shows higher CO2 assimilation rate compared to red and blue light through uniform distribution of full spectrum (red, green and blue) of light into the plant canopy and the lower leaves. In this study, optimal intensity of green light supplementation to the red and blue LEDs was evaluated for better growth, yield, and quality of lettuce. In experiment I and II, green light was added with red and blue light where total photosynthetic photon flux density (PPFD) was increased for the additional green light. In experiment III, 0, 10, 20, 30, 40, 50, 60, 70, 80 µmol m⁻² s⁻¹ green (G) light was supplemented to 235 µmol m⁻² s⁻¹ red (R) and 59 µmol m⁻² s⁻¹ blue (B) light maintaining 294 µmol m⁻² s⁻¹ total PPFD. Lettuce plants were cultivated hydroponically in three-step vertical grow beds using half-strength of Enshi nutrient solution. The temperature was maintained at 20 ± 2 °C at day and night and the day length was 16 h. In experiment I and II, the fresh mass of lettuce grown under the combination of R, B and G LEDs was found higher than those cultivated under R and B LEDs only. In experiment III, lettuce plants produced high fresh masses when 30 µmol m⁻² s⁻¹ of G light was supplemented with R and B lights maintaining the ratio 211:30:53 (R:G:B). By supplementing excessive G light (≥50 µmol m⁻² s⁻¹) with R and B lights, lettuce shoot fresh mass declined. The various combinations of irradiation of R, G and B LED did not significantly affect the contents of ascorbic acid and mineral nutrients. It is recommended to supplement 30 µmol m⁻² s⁻¹ of green light to red and blue light for a higher yield of lettuce. Therefore, the suitable LED (R:G:B) combination would be 72% of red, 10% of green and 18% of blue for lettuce cultivation following recycled hydroponics in plant factories.
... Pennisi et al. [40] investigated that with R:B ratio increasing from 0.5 to 3.0, the light electricity consumption of lettuce production based on leaf fresh weight increased by 44%. A similar result was found in basil whose light electricity consumption based on fresh weight decreased from 83.0 to 23.2 g/kW when the R:B ratio increased from 0.7 to 5.5 [41] . Consistent with the previous researches, when the cultivation lighting environment was offered by lower R:B ratio treatments, better yield, and energy use efficiency of hydroponic pakchoi were detected compared with the outcomes of the other treatments. ...
... Additionally, breeding specifically for higher quality will produce highly desirable products with high market value. Light spectrum, temperature, humidity and nutrient supply can be managed so as to alter the accumulation of target compounds in leaves and fruits [54,55] and increase the nutritional value of crops, including proteins (quantity and quality), vitamins A, C and E, carotenoids, flavonoids, minerals, glycosides and anthocyanins [12]. For instance, naturally occurring mutations (in grapevine) and gene editing (in kiwifruit) have been used to modify plant architecture, which will be useful for indoor growing in restricted spaces. ...
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Protected cropping offers a way to bolster food production in the face of climate change and deliver healthy food sustainably with fewer resources. However, to make this way of farming economically viable, we need to consider the status of protected cropping in the context of available technologies and corresponding target horticultural crops. This review outlines existing opportunities and challenges that must be addressed by ongoing research and innovation in this exciting but complex field in Australia. Indoor farm facilities are broadly categorised into the following three levels of technological advancement: low-, medium- and high-tech with corresponding challenges that require innovative solutions. Furthermore, limitations on indoor plant growth and protected cropping systems (e.g., high energy costs) have restricted the use of indoor agriculture to relatively few, high value crops. Hence, we need to develop new crop cultivars suitable for indoor agriculture that may differ from those required for open field production. In addition, protected cropping requires high start-up costs, expensive skilled labour, high energy consumption, and significant pest and disease management and quality control. Overall, protected cropping offers promising solutions for food security, while reducing the carbon footprint of food production. However, for indoor cropping production to have a substantial positive impact on global food security and nutritional security, the economical production of diverse crops will be essential.
... However, plant yield can reach a plateau or decrease when the blue light proportion in the spectrum reaches a threshold, which varies among species [29]. In conclusion, the response to blue-red lighting is species-dependent, which has also been shown in other studies [28,30,31]. ...
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Microgreens are becoming increasingly popular both as horticultural crops and as vegetables consumed by humans. They are classified as foods of high nutritional value. Twenty-eight microgreens crops were grown in a growth chamber under fully controlled conditions in order to determine how different light treatments affected their growth rate. The plants were grown under three light sources emitting red/blue ratios of about 6.7, 0.6, and 1.6 units (Red light, Blue light, and R + B light, respectively). Apart from that, the spectrum contained 10% yellow and orange light and 10% green light. The fresh weight of the plants ranged from 8 (perilla) to 1052 mg (nasturtium), whereas the length ranged for the same plants from 2.0 to 26.2 cm. The nasturtium was particularly strongly distinguished from the other species by the high values of its biometric parameters. The fresh mass of most of the other microgreens ranged from 20 to 100 mg, whereas their height ranged from 5 to 8 cm. Red light caused a significant increase in the fresh and dry weights of more than half of the species. The light spectrum had a lesser influence on the length of the plants. The research results showed considerable differences in the dynamics of growth of commonly cultivated microgreens.
... Light is the driving force for plants photo-morphogenetic response. Traditional light sources are not well fitted to limit spectral emissions only within the photosynthetically active radiation (PAR,, and this reduces their efficiency in transforming electricity into light, therefore leading to higher energy consumption (Piovene et al., 2015). In contrast, different studies suggest that LEDs (light emitting diodes) are a viable alternative to traditional lighting systems, due to the ability to set the desired spectral combination, their low electrical input requirement and limited heat emissions. ...
... Furthermore, within the PAR, red (R) and blue (B) wavebands are considered the most important energy sources for photosynthetic CO2 assimilation (Lin et al., 2013). Thanks to LED technology, it is possible to specifically target certain spectral regions and successfully operate changes in the red:blue (RB) ratio in order to supply the appropriate balance for plant growth and development (Piovene et al., 2015). To date, most of the studies about the optimal indoor light composition concern lettuce and basil, but only a few studies are available for other species. ...
... Lamiaceae) is among the most interesting plants for indoor cultivation mainly due to its worldwide use as a culinary and medicinal herb, thanks to essential oils (Ch et al., 2015;Khaki et al., 2011;Prinsi et al., 2020;Tenore et al., 2017) and phenolic compounds, such as flavonoids and phenylpropanoids (Jayasinghe et al., 2003;Prinsi et al., 2020) extracted from leaves and flowers, but also thanks to its little size and short growing period, that make basil a perfect candidate for intensive agricultural approaches. Basil metabolic profile, markedly its essential oil profile, is clearly affected by light spectra, light intensity and fertilizer application (Aldarkazali et al., 2019;Amaki et al., 2011;Avgoustaki, 2019;Bantis et al., 2016;Dou et al., 2018Dou et al., , 2019Frąszczak et al., 2014;Hosseini et al., 2019;Ioannidis et al., 2002;Johnson et al., 1999, Johnson at al., 2019Litvin et al., 2020;Lobiuc et al., 2017;Matysiak and Kowalsky, 2019;Meng and Runkle, 2019;Milenković et al., 2019;Mosadegh et al., 2018;Naiji and Souri, 2018;Naznin et al., 2019;Pennisi et al., 2019Pennisi et al., , 2020Piovene et al., 2015;Samuoliene et al., 2012;Schenkels et al., 2020;Shiga et al., 2009;Tarakanov et al., 2012;Taulavuori et al., 2016) as well as by successive harvest (Corrado et al., 2020), however results from literature are difficult to compare due to different experimental designs, including different set-ups, cultivation methods, root substrates and light supply. Thus, no definitive lighting protocols are so far available for basil indoor growers and further studies are needed to establish reliable lighting protocols for commercial cultivation. ...
Article
To simulate a typical market-oriented cultivation in laboratory, plants of basil (Ocimum basilicum L.) were grown from seedling to flowering stages in a new-concept microcosm device that enables roots and aerial parts to grow as under real crop conditions. To test the device efficacy, two microcosms were used with the same lighting architecture, temperature and photoperiodic conditions and with two different light spectra, white (W) or blue-red (BR), displaying a similar spectral power in the blue region. Plant growth, biomass yield, photosynthetic efficiency and nutrient uptake were determined. An innovative analytical approach for secondary metabolic profile was also developed to determine basil quality. The plants grew vigorous and healthy for the whole cultivation period and under both the lighting regimes, giving a biomass yield similar to those of basil grown under conventional greenhouse and field conditions. The two lighting regimes differently affected plant growth and yield, with the BR light, that was characterized by a higher photosynthetic photon flux density (PPFD), associated to higher plants, earlier flowering and greater yield. In the average, fresh and dry aerial biomasses per plant were about 250 g and 41 g under BR and about 114 g and 9 g under W light. Higher concentrations of major nutrients were detected in plants under W light, thus indicating that yield levels and major nutrient concentrations are not necessarily related to each other. Similar Fv/Fm (0.76–0.78) and ETR values were observed under the two light regimes , possibly indicating that plants under long lasting cultivation can adapt to different light regimes to reach similar photosynthetic efficiency levels. Different secondary metabolic profiles were detected in tissues sampled at the end of cultivation period and previously unreported profiles for basil were also recorded, possibly indicating that the extent of plant growth affects secondary metabolism in basil, in addition to light spectrum and PPFD level. This is the first report of basil grown under microcosm conditions from seedlings to adult plants. Our results indicate that the microcosm based-technology is effective in simulating a typical market-oriented cultivation and that long lasting cultivation emphasizes the effects of different environmental conditions on plant growth and metabolism.
... The research to deliver improvements in shelf life, sensory traits and nutritional density is continuing as evidenced by the several Innovate UKRI funded projects (IUK 105141, 49078, 55310, 509898, 511273 etc) but the ability to fully control the environment opens up other avenues to be explored to facility productivity and efficiency gains. Accessing a wider range of germplasm for the CEA/VF systems allows for a broader range of options to be developed for crop nutrition and nutritional density, health beneficial compound and unique sensory profiles (Piovene et al., 2015;Hasan et al., 2017). A deep dive review of this was undertaken recently by Kozai et al (2019) in their book reviewing the area. ...
Technical Report
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This report presents summary findings of a study looking at how the UK’s food production can align to enable development of a food system that better meets requirements for a healthy diet and a sustainable environment. The COVID-19 pandemic and post- EU exit recoveries present an opportunity to realign the food system with human health needs and sustainable, decarbonised production systems. Research uses four plausible scenarios (Scenarios for UK Food and Nutrition Security in the wake of the COVID-19 Pandemic) to explore the range of possible options using land use change, agroecological approaches, use of legumes and new cultivation technology e.g. vertical farming. This report is part of a series from the ESRC 'UK food and nutrition security during and after the COVID-9 pandemic (Grant ES/V004433/1).
... In O. basilicum, however, which is probably one of the most studied species under indoor conditions including LED lights, previous reports showed conflicting results. For example, blue light was reported to affect stem elongation and leaf expansion either positively [41,42] or negatively [43]. These discrepancies demonstrate the difficulty of comparing phenotypic studies performed in different laboratories where cultivation set-ups vary, and strengthen the interest in using an LED color gradient to change light quality with all other environmental parameters being constant. ...
Article
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Background The increasing demand for local food production is fueling high interest in the development of controlled environment agriculture. In particular, LED technology brings energy-saving advantages together with the possibility of manipulating plant phenotypes through light quality control. However, optimizing light quality is required for each cultivated plant and specific purpose. Findings This article shows that the combination of LED gradient set-ups with imaging-based non-destructive plant phenotyping constitutes an interesting new screening tool with the potential to improve speed, logistics, and information output. To validate this concept, an experiment was performed to evaluate the effects of a complete range of red:blue ratios on 7 plant species: Arabidopsis thaliana, Brachypodium distachyon, Euphorbia peplus, Ocimum basilicum, Oryza sativa, Solanum lycopersicum, and Setaria viridis. Plants were exposed during 30 days to the light gradient and showed significant, but species-dependent, responses in terms of dimension, shape, and color. A time-series analysis of phenotypic descriptors highlighted growth changes but also transient responses of plant shapes to the red:blue ratio. Conclusion This approach, which generated a large reusable dataset, can be adapted for addressing specific needs in crop production or fundamental questions in photobiology.
... Subsequent declines of LED prices have led to commercial crop cultivation in closed, environmentally controlled facilities known as vertical farms Benke and Tomkins, 2017;O Sullivan et al., 2019 and plant factories with artificial lighting Kozai, 2013;Kozai et al., 2020 , which use numerous LEDs as light sources to drive photosynthesis, resulting in overwhelmingly high planting density, high growth rates, and high crop quality Orsini et al., 2020 . Field and greenhouse cultivations also use LEDs for purposes such as supplemental lighting for photosynthesis support Deram et al., 2014;Hikosaka et al., 2013 , photomorphogenesis modification Cope andBugbee, 2013;Jeong et al., 2014 , metabolite synthesis activation Kitazaki et al., 2018;Kopsell et al., 2014;Piovene et al., 2015 , andpest management Cochard et al., 2019;Stukenberg et al., 2015 . In addition to visible light of the 400 -700 nm wavelength range required for maintenance of the basic physiology of plants, far-red Shibuya et al., 2019;Zhang and Runkle, 2019 for photomorphogenesis and ultraviolet light Huché-Thélier et al., 2016 for metabolite synthesis are wavelength bands that improve crop quality. ...
Article
This study investigated a light sensor function of light-emitting diodes (LEDs), the use of which is expanding in plant cultivations. Unimodal spectral LEDs of four types with respective emission peak wavelengths of 464, 501, 634, and 849 nm, and a white LED with a bimodal spectrum with 455-nm primary and 574-nm secondary peaks were used for this study. Open circuit voltage (VOC) of up to 1-2 V was induced in the LEDs when they were irradiated with sunlight. The VOC value of the 634 nm LED saturated with a low photon flux density can be used for binary discrimination between daylight and night. Each LED had a VOC inducible threshold wavelength of incident light. By virtue of the wavelength threshold feature, existence of a plant leaf between a light source and the LEDs is detectable by comparing the VOC values of blue-green range LEDs (464 nm, 501 nm) and near-infrared (NIR) LEDs (849 nm). Under leaf shadow, the NIR LED VOC exceeded those of the blue-green range LEDs. Under natural incident sunlight, the VOCs of the blue-green range LEDs were greater than that of the NIR LED. Another function of LEDs in agricultural use has been demonstrated.
... However, the response to red light appears less uniform across species. Compared to monochromatic or high percentage blue light, high proportions (≥50%) of red light reduced basil yield by restricting leaf area and biomass (Carvalho et al., 2016;Piovene et al., 2015), while decreases in blue proportions restricted tomato stomatal conductance (Lanoue et al., 2017), but had no effect on shoot biomass of either basil (Pennisi et al., 2019) or tomato (Solanum lycopersicum) (Hernández et al., 2016). Thus, the ratio of blue to red light affects leaf physiology and overall growth in complex ways. ...
Article
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With increasing urbanisation and consumer concerns over food miles, indoor urban plant factories are gaining popularity. These offer precise regulation of the crop environment, but optimal light requirements vary between species and according to grower specifications. Here we introduce a novel assessment framework to optimise light quality in urban plant factories accounting for yield, resource use efficiency and flavour, factors that have only been studied separately in previous research. Yield, water and energy use efficiency and flavour of sweet basil (Ocimum basilicum cv. Genovese) and tomato (Solanum lycopersicum cv. Micro-Tom) were determined for plants grown supplied with 100% blue, 66% blue + 33% red, 33% blue + 66% red, or 100% red lighting. In both species, 66% red and 100% red optimised water use efficiency and energy use respectively. For basil, 100% blue light maximised leaf biomass, while 66% red enhanced leaf flavouring volatiles. In Micro-Tom, all treatments produced similar fruit biomass, but 100% red light enhanced flavour-related volatiles in foliage. By considering trade-offs between yield, efficiency and flavour, growers can select bespoke lighting treatments to optimise their product according to specific market demands and minimise environmental impacts.
... Сочетание красных и синих СДО наиболее часто применяется для обеспечения роста и развития многих растений, особенно зеленных культур (10,11). Использование этих светодиодных облучателей положительно сказывается на повышении скорости фотосинтеза и накоплении биомассы растений (12,13). Красный диапазон спектра (КС) важен для нормального роста и развития растений, формирования фотосинтетического аппарата и его дальнейшей активности, синтеза и накопления фотоассимилятов (6,14,15). ...
... The possibility of modulating the biochemical composition and antioxidant capacity of plants through the adoption of different management strategies, for example, by changing the irrigation regime used in an aquaponics system, should merit attention, because, in this way, there is the possibility of producing a crop with an added value (Piovene et al., 2015;Rodrigues et al., 2020). Therefore, this study aimed to evaluate the production of total phenolic compounds and antioxidant activity in S. ambigua cultivated in an aquaponics system with Pacific white shrimp (Litopenaeus vannamei) under different regimes of continuous irrigation, in addition to evaluating water quality, shrimp and plant growth performance and nitrogen recovery. ...
Article
This study aimed to evaluate the production of phenolic compounds, antioxidant activity and growth performance of Sarcocornia ambigua exposed to different periods of continuous irrigation in an aquaponics system with Litopenaeus vannamei reared in a biofloc technology (BFT) system, in addition to possible effects on shrimp growth performance, nitrogen recovery and water quality. Four treatments were evaluated as follows: 6, 12, 18 and 24 h of continuous irrigation per day, all set up in triplicate. Plants from the 12 and 24 h of irrigation treatments exhibited significantly higher values of phenolic compounds, 48.4 ± 1.8 and 47.7 ± 1.6 mg Gallic acid equivalent (GAE) 100 g−1 FW (fresh weight), respectively, when compared with the 6 and 18 h treatments, 42.6 ± 1.1 and 42.6 ± 1.3 mg GAE 100 g−1 FW, respectively (p < 0.05). Antioxidant activity also differed significantly between treatments (p < 0.05). The highest concentrations were found in treatments of 12 and 24 h of irrigation, which presented 41.3 ± 0.6 and 42.7 ± 0.8 μmol Trolox Equivalent Antioxidant Capacity (TEAC) 100 g−1 FW, respectively. For treatments of 6 and 18 h of irrigation, the concentrations were 29.9 ± 0.8 and 31.1 ± 1.5 μmol TEAC 100 g−1 FW. No significant differences between treatments were observed for plant and shrimp growth performance (p ≥ 0.05). There was also no significant effect of the different irrigation periods on water quality (p ≥ 0.05). The overall mean nitrogen recovery was 29.3% for all treatments. In conclusion, S. ambigua cultivated under 12 and 24 h of continuous irrigation exhibited higher production of bioactive compounds and antioxidant activity.
... Recently, the evaluation of LUE and EUE based on fresh biomass has attracted increasing attention from growers, and in previous studies has been reported to have a close correlation with both the specific LED spectra and plant cultivars. The EUE of basil leaves decreased with increased R ratio in the RB treatment in [48], while Poulet et al. found that the energy use of the W LED group was similar to that of the RB treatment [49]. Son et al. reported a lower power consumption with the highest EUE in the lettuce group grown under the light source containing the highest proportion of W LEDs [25]. ...
... Recently, the evaluation of LUE and EUE based on fresh biomass has attracted increasing attention from growers, and in previous studies has been reported to have a close correlation with both the specific LED spectra and plant cultivars. The EUE of basil leaves decreased with increased R ratio in the RB treatment in [48], while Poulet et al. found that the energy use of the W LED group was similar to that of the RB treatment [49]. Son et al. reported a lower power consumption with the highest EUE in the lettuce group grown under the light source containing the highest proportion of W LEDs [25]. ...
Article
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White (W) light-emitting diode (LED) light has been used as an efficient light source for commercial plant cultivation in vertical farming. This study aimed to examine the effect of W LED light sources on the growth and quality of butterhead and romaine lettuce. Three W LED light sources including normal W light (NWL) which has 450 nm as its pumping wavelength and two specific W lights (SWL1 and SWL2) with shorter blue peak wavelength (437 nm) were used to grow lettuce in comparison to a red (R) and blue (B) LED combination. As a result, SWL1 and SWL2 treatments with the same electrical power or photosynthetic photon flux density (PPFD) resulted in more growth of both lettuce cultivars compared to RB treatment. Some phenolic and flavonol contents were increased in the RB treatment, whereas SWL2 treatment stimulated the accumulation of other phenolic and flavonol compounds. Meanwhile, neither NWL nor SWL1 treatments increased the individual phenolic and flavonol contents in either cultivar (except for some flavonols in romaine lettuce in the SWL1 group). In addition, light and energy use efficiencies were also highest in the SWL1 and SWL2 treatments. These results illustrate the positive effects of specific W LED light on lettuce growth and quality, and suggest that the specific W LED light sources, especially SWL2, could be preferably used in vertical farming.
... Prior to scanning, leaves were cut at certain points to extend their full area on the paper and to better assess their area. Following these measurements, the LAI (Leaf Area Index), given by the ratio of Average leaf area to the area of the pot in which the plants had grown, and the SLA (Specific Leaf Area) index, given by the ratio of Average leaf area to Average leaf dry mass, were also calculated [4,16]. ...
Article
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This study aims to optimize artificial LEDs light conditions, for “Genovese” basil germination and growth in an indoor environment suitable for horticulture. Following a previous study on the synergic effect of LEDs light and a tailored fertilizer, in this study, the effect of white LED in combination with hyper red and deep blue, as well the plants–lights distance, was correlated to 14 growth and germination parameters, such as height, number of plants, etc. A design of experiments approach was implemented, aiming to derive mathematical models with predictive power, employing a restrained number of tests. Results demonstrated that for the germination phase, it is not possible to derive reliable mathematical models because almost the same results were found for all the experiments in terms of a fruitful germination. On the contrary, for the growth phase, the statistical analysis indicates that the distance among plants and lights is the most significant parameter. Nevertheless, correlations with LED light type emerged, indicating that white LEDs should be employed only to enhance specific growth parameters (e.g., to reduce water consumption). The tailored models derived in this study can be exploited to further enhance the desired property of interest in the growth of basil in horticulture.
... Conventional light sources, such as high-pressure sodium (HPS), have a high operating temperature, low electrical efficiency, and limited controllability [1,10]. In contrast, light-emitting diodes (LEDs) provide tremendous potential for horticultural lighting in modern agriculture compared to conventional horticultural light sources due to their long functional life [26], lower heat production [25], spectral configuration flexibility [27], and high photosynthetically active radiation efficiency [28]. HPS lamps have been replaced by LED lamps in controlled agricultural environments, such as in growth chambers and greenhouses, in recent years [29,30]. ...
Article
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Insufficient light in autumn–winter may prolong the production periods and reduce the quality of plug seedlings grown in greenhouses. Additionally, there is no optimal protocol for supplementary light strategies when providing the same amount of light for plug seedling production. This study was conducted to determine the influences of combinations of supplementary light intensity and light duration with the same daily light integral (DLI) on the morphological and physiological properties of cucumber seedlings (Cucumis sativus L. cv. Tianjiao No. 5) grown in a greenhouse. A supplementary light with the same DLI of 6.0 mol m−2 d−1 was applied with the light duration set to 6, 8, 10, or 12 h d−1 provided by light-emitting diodes (LEDs), and cucumber seedlings grown with sunlight only were set as the control. The results indicated that increasing DLI using supplementary light promoted the growth and development of cucumber seedlings over those grown without supplementary light; however, opposite trends were observed in the superoxide dismutase (SOD) and catalase (CAT) activities. Under equal DLI, increasing the supplementary light duration from 6 to 10 h d−1 increased the root surface area (66.8%), shoot dry weight (24.0%), seedling quality index (237.0%), root activity (60.0%), and stem firmness (27.2%) of the cucumber seedlings. The specific leaf area of the cucumber seedlings decreased quadratically with an increase in supplementary light duration, and an opposite trend was exhibited for the stem diameter of the cucumber seedlings. In summary, increased DLI or longer light duration combined with lower light intensity with equal DLI provided by supplementary light in insufficient sunlight seasons improved the quality of the cucumber seedlings through the modification of the root architecture and stem firmness, increasing the mechanical strength of the cucumber seedlings for transplanting.
... In addition, LED lights may allow to manipulate the spectral composition of light by furnishing only some of the spectra of which the visible light is composed (Goto, 2012). All these aspects, individually or altogether, have shifted the interest of growers from traditional HPS and fluorescent lamps to LED lights (Piovene et al., 2015). However, different species may behave in different ways with respect to utilized spectra, thus species-specific studies are needed to tailor the LED spectra to species and growers' needs: some authors reported a positive effect, on lettuce, of the addition of LED lights to the fluorescent lamps instead of using monochromatic spectrum (Chen et al., 2014), while others observed that some wavelengths may improve the nutritional characteristics of "adult" vegetables and baby leaf (Li and Kubota, 2009;Bian et al., 2015;Kopsell et al., 2015;Qian et al., 2016) or microgreens (Samuoliene et al., 2013;Brazaitytė et al., 2015;Meas et al., 2020) and may even help to reduce some anti-nutritional compounds (Samuoliene et al., 2012;Wojciechowska et al., 2016;Signore et al., 2020). ...
... For example, it is possible to use LEDs of different wavelengths like 450 nm (blue light), 530 nm (green light), and 650 nm (red light) apart from white light to create an optimized lighting system in respect to growth, biomass, and plant development. Currently, additional light applications in horticultural production and scientific research are mainly limited to the addition of red and blue light (Agarwal & Gupta, 2016;Kaiser, Ouzounis, et al., 2019;Kaiser, Weerheim, et al., 2019;Piovene et al., 2015;Thoma et al., 2020). Since natural UVB radiation in greenhouses is low because of the UV-impermeable glass, artificial broad-band UVB radiation is usually applied with fluorescent light sources, e.g. ...
Article
Ultraviolet B (UVB) radiation in low but ecological-relevant doses acts as a regulator in the plant's secondary metabolism. This study investigates the effect of UVB radiation from light-emitting diodes (LEDs) [peak wavelength of (290 ± 2) nm] on the biosynthesis of health-promoting secondary plant metabolites (carotenoids, phenolic compounds, and glucosinolates) of green and red leafy vegetables of Lactuca sativa, Brassica campestris, and Brassica juncea followed by evaluation of potential adverse effects in a human liver cell model. UVB radiation led to a significant increase in individual secondary plant metabolites, especially of phenolic compounds and glucosinolates, e.g. alkenyl glucosinolate content. Kaempferol und quercetin glycoside concentrations were also significantly increased compared to untreated plants. The plant extracts from Lactuca sativa, Brassica campestris, and Brassica juncea were used to assess cytotoxicity (WST-1 assay and trypan blue staining), genotoxicity (comet assay), and production of reactive oxygen species (EPR) using metabolically competent human-derived HepG2 liver cells. No adverse effects in terms of cytotoxicity, genotoxicity, or oxidative stress were detected in an extract concentration ranging from 3.125 to 100 μg ml⁻¹. Notably, only at very high concentrations were marginal cytostatic effects observed in extracts from UVB-treated as well as untreated plants. In conclusion, the application of UVB radiation from LEDs changes structure-specific health-promoting secondary plant metabolites without damaging the plants. The treatment did not result in adverse effects at the human cell level. Based on these findings, UVB LEDs are a future alternative, promising light source to replace currently commonly used high-pressure sodium lamps in greenhouses.
... Buildings can also be made more energy efficient, for example by using the heat generated by the light for heating (Butturini and Marcelis, 2019). High-tech infrastructure including lights can create improved food quality (Piovene et al., 2015), consistent, year around production , and employment in an otherwise highly seasonal business. It provides greater production stability due to enhanced resilience to climatic events and increasing yields compared to traditional agricultural systems (Kozai, 2016). ...
Article
Basil (Ocimum basilicum L.) is a popular crop worldwide among farmers; it is relatively easy to grow and is well adapted to hydroponic and Controlled Environment Agriculture (CEA) systems having a high profitability margin. Several studies investigated the effect of the environmental factors on the qualitative and quantitative factors of basil: the effect of light is crucial for development, nutritional properties and sensory characteristics. The principles of sustainability, profitability and resource-effectiveness all encourages farmers to use energy-efficient LED light sources. These tools easily allow for the modification of spectral distribution and light intensity; numerous suggestions have been made for developing goal-driven light recipes for maximum cost-effectiveness and for reducing carbon footprint. Here, the results of several studies are summarized for providing a solid base for light recipe utilization of basil production in terms of light intensity, duration, and spectral distribution. Experimental results related to the impact of light treatments on vegetative parameters, phytonutrient content and sensory properties of basil are discussed, and optimal ranges of light parameters are summarized. Due to the increasing number of promising specialized research the wider application of purpose-driven high-tech production systems is expected in future basil growing.
... Positive effect of red-light irradiation (635-700 nm, 200 µmol m −2 s −1 , LED lighting sources) was observed also on basil leaves, in which the antioxidant capacity, the total phenolics, and the flavonoid concentration increased by 14, 30, and 52%, respectively [138]. In the same study, however, it was reported that the red-light treatment did not affect phenolics content and antioxidant capacity of strawberry (Fragaria × ananassa) fruit, even leading to a decreased flavonoid content. ...
Article
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Plants continuously rely on light as an energy source and as the driver of many processes in their lifetimes. The ability to perceive different light radiations involves several photoreceptors, which in turn activate complex signalling cascades that ultimately lead to a rearrangement in plant metabolism as an adaptation strategy towards specific light conditions. This review, after a brief summary of the structure and mode of action of the different photoreceptors, introduces the main classes of secondary metabolites and specifically focuses on the influence played by the different wavelengths on the content of these compounds in agricultural plants, because of their recognised roles as nutraceuticals.
... The current study used 50 μmol m −2 s −1 as the background fluence rate because it is the fluence rate provided by the white light sources currently installed in our plant tissue room. The light environments tested were enriched in B and R light, two regions that are typically present in high proportions in indoor settings Piovene et al. 2015). A ratio of 1:1 did not show any significant differences compared to white light. ...
Article
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Guayusa (Ilex guayusa) is an endemic plant from the Amazon with potential medicinal applications. Indigenous people are familiar with such applications and use guayusa based on ancestral knowledge. There is a growing interest in guayusa-based products in urban areas of Ecuador and internationally. The supply cannot meet the demand. Currently, traditional practices are used for guayusa growth and the potential use of the protected forest is foreseen. This work describes a protocol for the in vitro propagation of guayusa, a sustainable solution to generate high quality plants in reduced space. Stakes obtained from stems were used as explants. Chemical sterilization with ethanol and sodium hypochlorite resulted in 100% surface-sterilized stakes. The growth medium mWPM resulted in favorable outcomes regarding shoot development and elongation, as well as rooting. Supplementation with activated charcoal resulted in reduced browning, only 10% of the shoots presented necrosis during the elongation phase. More than two thirds of shoots were able to develop roots spontaneously. Medium supplementation with the auxin indole-3-butyric acid, IBA, may be considered when rooting does not occur spontaneously. Acclimatization was performed in soil. The protocol was tested under different light spectra, revealing that guayusa growth is affected by light quality. The photobiology of this shade tolerant plant requires further characterization, but the data uncovered a potential role for green and far-red light in root development.
... A current study by Hernandez et al. (2020) confirms the corresponding increase in biomass efficacy of LEDs, as their LED treatment led to a 2.4 to 3.1 times greater biomass efficacy than HPS, which matches our findings [60]. Another study in which LED and FL treatments were compared, reported a biomass efficacy three to five times higher under LED than under FL lighting [61]. In contrast, the LED system used in this current study greatly exceeds their findings, as the LED enabled a biomass efficacy 6 to 10 times higher than the FL system (Table 4) under our experimental conditions. ...
Article
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A light-emitting diode (LED) system covering plant-receptive wavebands from ultraviolet to far-red radiation (360 to 760 nm, “white” light spectrum) was investigated for greenhouse productions of Thymus vulgaris L. Biomass yields and amounts of terpenoids were examined, and the lights’ productivity and electrical efficiency were determined. All results were compared to two conventionally used light fixture types (high-pressure sodium lamps (HPS) and fluorescent lights (FL)) under naturally low irradiation conditions during fall and winter in Berlin, Germany. Under LED, development of Thymus vulgaris L. was highly accelerated resulting in distinct fresh yield increases per square meter by 43% and 82.4% compared to HPS and FL, respectively. Dry yields per square meter also increased by 43.1% and 88.6% under LED compared to the HPS and FL lighting systems. While composition of terpenoids remained unaffected, their quantity per gram of leaf dry matter significantly increased under LED and HPS as compared to FL. Further, the power consumption calculations revealed energy savings of 31.3% and 20.1% for LED and FL, respectively, compared to HPS. In conclusion, the implementation of a broad-spectrum LED system has tremendous potential for increasing quantity and quality of Thymus vulgaris L. during naturally insufficient light conditions while significantly reducing energy consumption.
... LED light sources not only provide energy for photosynthesis, but also are a versatile technology used to easily modulate light quality to induce specific traits in crops, like the biosynthesis of functional compounds [19][20][21][22][23][24][25][26]. Many studies have shown that increased levels of flavonoids are detected in plants growing under red and blue wavelengths [27][28][29]. Most of these studies have been conducted on higher plants, whereas only a few information is available on sprouts, which are usually cultivated in the dark or under limiting light conditions. ...
Article
Sprouts are nutritious food, easy to produce even in extra-terrestrial platforms, where the exposure to ionising radiation can alter their morpho-anatomical traits and phytochemical content. The aim of this study was to evaluate whether sprout production under specific light wavelengths can mitigate the negative effects of radiation and/or stimulate the induction of hormesis. Germinated seeds, with actively proliferating cells, of mung bean were irradiated with increasing X-ray doses (0–20 Gy) and then incubated in controlled conditions under four different light regimes: dark (D), white light (W), red light (R), red-blue light (RB). Morpho-anatomical development of the sprouts was investigated through light-microscopy and their content of flavonoids and isoflavones was quantified by HPLC. Two significant conclusions emerged: 1) RB wavelength induces hormesis by stimulating the production of antioxidant compounds; 2) R wavelength offsets the harmful effects of radiation on morpho-anatomical traits, even at the highest X-ray dose.
... Most studies on indoor systems seem to focus on the total accumulation of phytochemicals while individual compounds are ignored. [10][11][12] Aside from comparing cultivation systems and highlighting their characteristics, the innovative aspect of this research is therefore an in-depth analysis of the relations between different classes of bioactive compounds and specific herbs, building upon other similar studies. [13][14][15] Finally, small plants have been selected as the object of the study because they are the most likely to be cultivated by users of indoor chambers like the one on hand for the present investigation. ...
Article
Background Aromatic herbs are an important source of bioactive compounds. Different cultivation systems should give each plant a specific amount and quality of those compounds. In this study, the effects of three cultivation systems (indoor, greenhouse, and organic field) on the composition of bioactive compounds in parsley (Petroselinum crispum cv. ‘Flat Leaf’), green basil (Ocimum basilicum var. minimum cv. ‘Greek’), and purple basil (Ocimum basilicum cv. ‘Red Rubin’) were evaluated. Results β‐carotene and lutein were the carotenoids with the highest concentration in the three plants in all cultivation systems. Overall, parsley proved to be a source of flavonoids. The major phenolic compound found in basil plants was rosmarinic acid, while most anthocyanins were derived from cyanidin aglycone. Among the three plants studied, the highest content of vitamin C was found in parsley from the field, 2.6 and 5.4 times higher than the indoor and greenhouse cultivation, respectively. Conclusion The results suggest that different cultivation systems influence and modulate the concentration of bioactive compounds in plants differently, varying according to their class, and that, above all, indoor system is an effective cultivation system for the production of bioactive compounds. This article is protected by copyright. All rights reserved.
... Son and Oh (2013) found a decrease in growth rate in lettuce cultivars with the increase in B and UV-A light, while Wang et al. (2016) reported that leaf photosynthetic capacity and photosynthetic rate increased with decreasing R:B ratio, along with promoted shoot dry weight (Table 1). In sweet basil and strawberry, the R:B ratio of 0.7 was found to be optimal based on a range of analyses (morphological, physiological and biochemical elements), among 5 LEDs ratios (0.7, 1.2, 1.5, 5.5) and compared to white fluorescent light as a control (Piovene et al. 2015; Tables 1 and 2), whereas previously Folta and Childers (2008) had observed the greatest growth rate of strawberry plants under 34% B-66% R, among 4 different B:R ratios (100-0, 66-34, 34-66, 0-100%). In greenhouse production, Kaiser et al. (2019) supplied tomato with different R:B ratios (0, 6, 12 and 24%) in integration to sunlight, which resulted in an increase in total biomass and fruit number until the optimum of 12% (Table 2). ...
Article
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Mesembryanthemum crystallinum is an annual succulent plant that is being used as an emerging healthy leafy vegetable. To investigate the growth and physiological response of M. crystallinum to artificial lighting, five different light treatments were applied at 150 µmol(photon) m-2 s-1, which were white (W), different rations of red/blue (B) (15, 40, and 70%B), and blue (100%B), respectively. Our results showed that plants could gain as much as edible leaf area and dry mass with a certain ratio of blue (40%) in comparison with W. Plants grown under 100%B resulted in reduced photosynthetic rate, leaf area, and fresh mass compared with W. Adding blue fraction in the light regime enhanced the photosynthetic performance by influencing the amount of chlorophyll (Chl), Chl a/b, and specific leaf area. Under red/blue treatments, the electron transport rate and effective quantum yield of both PSII and PSI increased, while the nitrate content was reduced and flavonoids and total antioxidant capacity were unaffected.
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Green bean (Phaseolus vulgaris L.) is one of the most important sources of vegetable proteins in the world and it is cultivated all year round, but the light availability, during the dark season, limited its growth. Nevertheless, recent studies conducted on greenhouse horticulture demonstrated that, with the application of light emitting diodes (LEDs) as supplementary light (SL) technology, it is possible to overcome this limitation. Consequently, during the experiment conducted, two cultivars of green bean (‘Saporro’ and ‘Maestrale’) were grown with a soilless system in a cold greenhouse during the fall-winter period. To increase the photoperiod and the daily light integral (DLI), early in the morning, four hours of red (R), blue (B) and red+blue (R+B) supplementary light were supplied by LEDs at 180 μmol·m−2·s−1 (PPFD) at plants level. Plants grown under LEDs improved the yield and the gas exchange system compared with the plants grown under natural light; when B light was supplied as a sole source of SL, it increased the dry matter content and the brightness (L*) of the pods. Between the cultivars, ‘Maestrale’ produced 20 g∙plant−1 of pods more than ‘Saporro’ but the latter’s colour was brighter (L*) and greener (a*), and ‘Saporro’ also showed the highest photosynthetic efficiency (ΦPSII). In conclusion, ‘Maestrale’ and ‘Saporro’ obtained encouraging out-of-season yields under different LED spectra, but among those B light seems to improve overall crop performances and pods quality.
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Studying the positive role of applying organic mulch and different colors of LEDs light, on the growth and yield of green bean plants, were carried out during 2019/2020 and 2020/2021 seasons, at a privet farm within Suez Governorate. Seedlings of Bronco cultivar were transplanted at the 15th of October of both seasons. Two types of organic mulch i.e., chopped maize straw and chopped rice straw, addition to bare soil (control) were tested as a soil mulch treatment (factor 1). In addition, LEDs light colors i.e., red, blue and "red + blue" and without LED light were also tested (factor 2). Finally, interaction between both studied factors was also studied. Studied factors were arranged in split plot design with three replicates. Organic soil mulches were arranged in the main plots. However, LEDs light colors were arranged within the sub main plots. Vegetative growth parameters i.e., plant height, number of leaves/plant, stem diameter, number of branches/plant, fresh and dry weight of plants were measured. Moreover, percentages of nitrogen, phosphorus and potassium contents in leaves, as well as, chlorophyll reading (SPAD) were also measured. In addition, pod characteristics i.e., number of pods/plant, average pod weight and fiber content in pods, were studied as well. Finally, both early and total yield of green bean were studied. Changes in soil temperature under organic mulch treatments, as well as, bare soil were daily measured during the growing seasons. Results indicated that, in general, applying tested types of organic mulch modified soil temperature. Moreover, both tested factors were enhanced measured characters of vegetative growth, leaves content of nitrogen, phosphorus and potassium, as well as yield and its components. Furthermore, both treatments of chopped maize straw and "red + blue" LEDs light, as well as the interaction between both treatments were the most suitable for increasing productivity and quality of green bean plants.
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Artificial light has proved useful for optimal and consistent production of high-quality plants and plant produce. Among artificial light sources, light-emitting diodes (LED) offer advantages for indoor cultivation including narrow and customizable light spectra, lower heat production and higher energy efficiency. With the aim to improve both productivity and nutritional quality of Hydrocotyl bonariensis Lam. (largeleaf pennywort), phenotypical and phytochemical responses were assayed for plants grown under natural light and under four different spectral compositions of LED lighting: (1) red and blue (R : B = 83 : 35), (2) red and blue with a higher blue irradiance (R : B = 83 : 65), (3) red, blue and green (R : B : G = 83 : 35 : 12), and (4) red, blue and ultraviolet A (R : B : U = 83 : 35 : 10). Results show that the ratio of red to blue light has a substantial influence on plant growth and leaf biomass in H. bonariensis. Plants grown under the system with a higher level of blue irradiance showed the highest leaf number, total leaf area, leaf biomass, plant height, total antioxidant content, total phenol and total flavonoid content compared to plants grown under natural light in a greenhouse or the other LED conditions. The addition of green LED had a neutral effect on plant growth and on total antioxidant, phenol and flavonoid content while the addition of ultraviolet A LED had a negative effect on plant growth and on total antioxidant and phenol content. These findings provide fundamental information for the design of light sources, which will be useful for sustainable indoor cultivation of H. bonariensis and other pennywort species.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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.
Article
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%).