Spectral Lights Research Articles

Spectral lights influence growth and metabolic efficiency leading to enhanced phytochemical contents of Coriandrum sativum L.

Coriandrum sativum. L (coriander) is an aromatic herb containing valuable bioactive compounds. The current study aimed to understand the role of light quality influence on the metabolic performance of C. sativum. The study was conducted by integrating LED lights viz. red (100 R:0B), red: blue (50 R:50B); blue (0 R:100B), and warm white (WW, served as control). The fresh and dry biomass was highest under 0 R:100B spectral LED lights, whereas the photosynthetic performance was maximum under 50 R:50B LED lights. Among the major vitamins studied, ascorbic acid content was maximized under 50 R:50B spectral LED lights, while α-tocopherol content was highest under 0 R:100B light conditions. Luteolin and umbelliferone, the detected coumarins, exhibited their highest levels under 50 R:50B light spectral composition, however, chlorogenic acid demonstrated its maximum level under 0 R:100B spectral LED lights. C. sativum plants grown under 50 R:50B light displayed a relatively higher content of volatile compounds including, decanal, 2-decenal, 2,6,11-trimethyldodecane, 2-dodecenal, and (E)-tetradec-2-enal. Glucose, fructose, and sucrose identified as the major primary metabolites, were highest under 50 R:50B light. Moreover, the stem and leaf anatomy exhibited the greatest vascularization when influenced by 50 R:50B and 0 R:100B spectral LED lights. Histochemical studies further revealed an intense accumulation of metabolites under the 50 R:50B spectral light conditions. The study also demonstrated the influence of light quality on chloroplast ultrastructure, influencing starch accumulation and providing insights into plant cell metabolic activity through the observed association of chloroplasts with mitochondria. Taken together, the study suggests that 50 R:50B spectral combination could play an important role in augmenting the metabolic performance and phytonutrient outcomes of C. sativum.

Chromatic processing and receptive-field structure in neurons of the anterior optic tract of the honeybee brain.

Color vision in honeybees is a well-documented perceptual phenomenon including multiple behavioral tests of trichromaticity and color opponency. Data on the combined color/space properties of high order visual neurons in the bee brain is however limited. Here we fill this gap by analyzing the activity of neurons in the anterior optic tract (AOT), a high order brain region suggested to be involved in chromatic processing. The spectral response properties of 72 units were measured using UV, blue and green light stimuli presented in 266 positions of the visual field. The majority of these units comprise combined chromatic-spatial processing properties. We found eight different neuron categories in terms of their spectral, spatial and temporal response properties. Color-opponent neurons, the most abundant neural category in the AOT, present large receptive fields and activity patterns that were typically opponent between UV and blue or green, particularly during the on-tonic response phase. Receptive field shapes and activity patterns of these color processing neurons are more similar between blue and green, than between UV and blue or green. We also identified intricate spatial antagonism and double spectral opponency in some receptive fields of color-opponent units. Stimulation protocols with different color combinations applied to 21 AOT units allowed us to uncover additional levels of spectral antagonism and hidden inhibitory inputs, even in some units that were initially classified as broad-band neurons based in their responses to single spectral lights. The results are discussed in the context of floral color discrimination and celestial spectral gradients.

Invited Session III: Diversity in chromatic processing across the animal kingdom: Color vision in stomatopod crustaceans.

Stomatopod crustaceans, commonly known as mantis shrimp, have perhaps the most unusual color-vision systems of any animals. The uniqueness is possible because stomatopods have compound eyes. Here, each unit, or ommatidium, acts as an independent visual detector, with its own corneal lens, internal optics, and set of photoreceptors. Ommatidia tuned to different wavelengths can be individually placed in the eye to build unusual color systems. In mantis shrimps, the receptors responsible for color vision are limited to six parallel rows of ommatidia that together form an equatorial belt, called the midband. Various receptors in these ommatidia are tuned to eight narrow-band spectral channels in the visible spectrum plus up to four additional ultraviolet channels. Thus, there is a total of twelve different color receptors for color vision. How these color channels are analyzed in the complex set of optic lobes existing behind the retina is only partly understood. It appears that stomatopods use both opponent and labelled-line color channels. Oddly, these animals appear to have limited ability to discriminate between spectral lights, but they have outstanding color constancy. Color vision, and color processing, in stomatopods is probably unlike that of any other animal group.

Spectral Light Treatment Influenced Morpho-Physiological Properties and Carvacrol Accumulation in Indian Borage.

The online version contains supplementary material available at 10.1007/s00344-023-11028-6.

Fabrication of Hematite (α-Fe2O3) nanoparticles under different spectral lights transforms physio chemical, biological, and nanozymatic properties

Fabrication of iron oxide (Fe2O3) nanoparticles (NPs) with different spectral lights was carried out to unveil the effect of change in the wavelength of Photons. NPs were synthesized by co-precipitation technique exposed to different light regimes (dark environment, daylight, and colored lights (blue, green, yellow, and red) from light emitting diodes (LEDs) at room temperature. X-ray diffractogram (XRD) analysis revealed that the synthesized NPs were hematite (α-Fe2 O3) with rhombohedral structure while scanning electron microscopic (SEM) study demonstrate the spherical and nano-disk like surface morphology. An increase in the size of NPs from 20.61 nm to 28.87 nm was observed with the increase in the wavelength of light. The elemental composition and surface chemistry of NPs were studied from energy-dispersive x-ray diffractive (EDX) and Fourier transform infrared spectroscopy (FT-IR) spectra. Maximum free radical quenching activity and total antioxidant potential were found by red light synthesized NPs (13.72%, and 36.72 ± 1.06 µg AAE/mg, respectively). The dark environment synthesized NPs had the maximum reduction potential (20.20 ± 0.4 µg AAE/mg). The highest metal chelating and cation radical scavenging was observed by blue light (41.48%) and daylight (9.71%) synthesized NPs respectively. α-Fe2O3 NPs showed significant enzyme inhibitory effects on urease, lipase, and alpha-amylase. The NPs also exhibited intrinsic peroxidase-like activity. Green and red light synthesized α-Fe2O3 NPs displayed the strongest antibacterial activity (12 mm) against Methicillin-resistant Staphylococcus aureus, and Pseudomonas aeruginosa respectively. This study is considered a novel step toward the synthesis of hematite (α-Fe2O3) NPs under LEDs with specific physio-chemical and biological properties to be employed in biological, environmental, and agricultural fields.

A novel instrument to determine hue discrimination.

We report and verify a novel hue discrimination instrument. We also investigate its efficiency to determine hue discrimination in persons with normal color vision. Experimental and clinical investigation. The instrument setup comprises an optical unit and examination unit. The optical unit is composed of the same 2 spectrometers and their controllers, which enables the independent emission of different spectral lights. Two independent bundle fibers connect the optical unit and the examination unit. Two different wavelength lights are illuminated on the bipartite upper and lower circular objectives with a visual angle of 2 degrees in the examination unit. The examinee recognizes the difference in the spectral lights between the bipartite targets. Persons with normal color vision are examined and the findings are confirmed using the Ishihara Test for Colour Deficiency. The instrument could generate spectral light from 450 to 650 nm within 2-nm accuracy. The spectral light showed a different light intensity according to the spectral centroid, ranging from 450 to 650nm, but the difference could be adjusted and was negligible in terms of determination of hue discrimination using the power meter. Three width slits, 0.2mm, 0.5mm, and 1.0mm, to homogenize the light path were investigated. The half-width wavelength was accurate on each spectral centroid; however, the 0.5mm slit was suitable to generate an efficient light path. The hue discrimination differed among the study participants. In general, at short and long wavelength lights, the hue discrimination range was large: about 15nm at 450nm and about 10nm at 650nm. Between 470 and 620 nm, the hue discrimination showed good sensitivity and specificity between 8 and 2nm depending on the targeting wavelength lights. Intraindividual variation was small, ranging from 3 to 1nm, thus indicating good repeatability. The time to examine the hue discrimination was about 20min. This newly invented instrument using two independent spectrometer units enabled the determination of hue discrimination. The instrument's sensitivity and specificity including its repeatability were confirmed and indicated that the instrument could be a clinically applicable method.

Effect of light spectra on stem cutting rooting and lavender growth

French lavender (Lavandula dentata L.) is of great ornamental, medicinal, and aromatic interest. It is generally propagated vegetatively using stem cuttings. When using artificial lighting, a specific light composition can modify the entire plant phenology and is a factor that can be managed in controlled conditions. This study evaluated the rooting of stem cuttings and growth of lavender under four spectral LED lights. The LED lights used were: T0 (white LED, Roblan®), T1 (AP67 Milky, Valoya®), T2 (NS1, Valoya®), and T3 (AP673L Milky, Valoya®). The first phase evaluated the rooting of stem cuttings and initial development. The plants were then transferred to plastic pots to evaluate plant growth. In both rooting and growing phases, the plant morphological characteristics and water and light efficiencies were evaluated. Nutrient-uptake efficiencies were also evaluated after the growing phase. It was observed that cuttings rooted under the influence of T1 showed greater height. After the growing phase, plants under T3 showed better results in electricity use efficiency, water use efficiency, and nutrient-uptake efficiency and less nitrate leaching. They also presented more uniform growth with a compact canopy. Thus, T1 was better for the stem cuttings rooting phase, while T3 was better for growth and energy efficiency.

Effect of Wide-Spectrum Monochromatic Lights on Growth, Phytochemistry, Nutraceuticals, and Antioxidant Potential of In Vitro Callus Cultures of Moringa oleifera.

Moringa oleifera, also called miracle tree, is a pharmaceutically important plant with a multitude of nutritional, medicinal, and therapeutic attributes. In the current study, an in-vitro-based elicitation approach was used to enhance the commercially viable bioactive compounds in an in vitro callus culture of M. oleifera. The callus culture was established and exposed to different monochromatic lights to assess the potentially interactive effects on biomass productions, biosynthesis of pharmaceutically valuable secondary metabolites, and antioxidant activity. Optimum biomass production (16.7 g/L dry weight), total phenolic contents (TPC: 18.03 mg/g), and flavonoid contents (TFC: 15.02 mg/g) were recorded in callus cultures placed under continuous white light (24 h), and of other light treatments. The highest antioxidant activity, i.e., ABTS (550.69 TEAC µM) and FRAP (365.37 TEAC µM), were also noted under white light (24 h). The analysis of phytochemicals confirmed the significant impact of white light exposures on the enhanced biosynthesis of plant secondary metabolites. The enhanced levels of secondary metabolites, i.e., kaempferol (1016.04 µg/g DW), neochlorogenic acid (998.38 µg/g DW), quercetin (959.92 µg/g DW), and minor compounds including luteolin, apigenin, and p-coumaric acid were observed as being highest in continuous white light (24 h with respect to the control (photoperiod). Similarly, blue light enhanced the chlorogenic acid accumulation. This study shows that differential spectral lights demonstrate a good approach for the enhancement of nutraceuticals along with novel pharmacologically important metabolites and antioxidants in the in vitro callus culture of M. oleifera.

Dietary supplementation with Gracilaria gracilis by-products modulates the immune status and oxidative stress response of gilthead seabream (Sparus aurata) stimulated with Photobacterium damselae subsp. piscicida

This study evaluated the effects of agar waste (AW) dietary supplementation, obtained from the seaweed Gracilaria gracilis cultivated under two different spectral lights, neutral (NT) and blue (BL), on haematological parameters, inflammatory response, and antioxidant biomarkers of gilthead seabream (Sparus aurata). Three diets were prepared: i) a basal diet (CTR), ii) a diet supplemented with 2.5% NT, and iii) a diet supplemented with 2.5% BL. After 15 days of feeding, fish were injected with PBS (placebo) or inactivated Photobacterium damselae subsp. piscicida (stimulated) and sampled at 4 h and 24 h post-stimulus.Results indicated that fish fed NT and BL supplemented diets had lower Ht value and mean corpuscular volume (MCV) than fish fed the CTR diet, regardless of the stimulus and the sampling time. No differences in mean corpuscular haemoglobin (MCH) were found between fish fed the different diets, while the mean corpuscular haemoglobin concentration (MCHC) increased in fish fed AW supplemented diets compared to fish fed the CTR diet, regardless of the stimulus and the sampling time. In response to inflammation, fish fed the NT diet displayed higher neutrophils count in blood when compared to the CTR group, regardless of the stimulus and sampling time. Thrombocyte count was higher in fish fed NT and BL diets than in the CTR group, especially in the stimulated fish (Diet*injection (D*I), P = 0.004). An increase in plasma protease activity was detected in fish fed NT or BL diets in both placebo and stimulated fish regardless of the sampling time. Hepatic catalase activity was higher in fish fed the NT and BL than in the CTR group, particularly in the stimulated fish (D*I, P < 0.001). In addition, both stimulated and placebo fish that received the BL diet showed an increase in hepatic GR activity compared to the CTR group, regardless of the sampling time.Dietary supplementation with AW by-products obtained from G. gracilis cultured under NT and BL conditions showed to improve the inflammatory and antioxidant mechanisms in gilthead seabream in response to a UV-killed bacterial stimulus, having valuable applications for the sustainable use of seaweed toward improving the health and welfare of cultured fish.

Stress responses on the growth and mycotoxin biosynthesis of Fusarium proliferatum associated with stored poultry feeds

Animal and poultry feeds majorly constitutes of cereal grains and their by-products representing an excellent substrate for fungal colonization and mycotoxin contamination. Additionally, ecological factors play a crucial role in the process of fungal colonization in stored food/feed material. Here, we propose the physiological behavior of Fusarium proliferatum MYS9 in response to the combinational effects of different abiotic factors such as light, temperature, solutes and relative humidity. Red and blue spectral lights had stimulating effect on the growth and biomass and also Fumonisin B1 production recording 141.60 µg and 69.77 µg/g feed, respectively. The radial growth and biomass formation of F. proliferatum declined with the increasing ionic solute potential while the non-ionic solute potential showed an irregular pattern of growth and biomass. The room temperature (28 °C) showed maximum colony diameter (7.78 cm), biomass (1.32 g per 50 mL medium) and FB1 biosynthesis (913.25 µg/g feed). A significant radial growth was observed at 96% relative humidity and a high biomass of 0.82 g per 50 mL medium was observed at 98% humidity. A maximum growth of the fungus was observed at 28 °C in combination of -51.02 bars of osmotic pressure while the lower and higher temperature ranges with high osmotic pressures restricted the growth. The present study provides useful data facilitating a better understanding of the influence of ecological factors on fungal growth and toxin production in feeds and help to optimize storage measures and prevention strategies.

Synergistic influence of CuO nanoparticles and spectral lights transforms biomass, antioxidative response, and antioxidants in Brassica nigra

Some nanoparticles (NPs) have photocatalytic and photodynamic properties that change on variation in wavelength of light carrying different energies. To access photo-dynamic toxicity of CuO NPs, Brassica nigra seeds were in vitro grown on CuO NPs supplemented media under the exposure of five different spectral lights (white, blue, red, yellow and green). Light wavelength significantly affected shoot and root length and fresh weight of B. nigra and CuO NPs exerted different level of toxicity under these lights. Noteworthy variations were observed in free radical scavenging activity, total antioxidantive response and total reducing power potential when plants were grown in presence of NPs and spectral lights. Significant variations in total phenolics and flavonoids contents were observed in shoots as compared with roots. HPLC analysis presented variation in phenolics in shoots extracts under synergistic influence of NPs and light regime. The study shows that nanoparticles exert different level of toxicity under different wavelengths of lights. Resultantly plants show variations in morphological and biochemical responses. Consequently secondary metabolites produce in plants at varying concentrations to mitigate nanotoxicity under photodynamic response. Phenolics and flavonoid production enhance in plant grown in presence of CuO NPs and different wavelength of striking light.

Interactive Effect of Light and CdO Nanoparticles on Dodonaea viscosa Morphological, Antioxidant, and Phytochemical Properties.

Cadmium nanoparticles (NPs) used in semiconducting devices are photosensitive and optically active. The objective of this study was to investigate the interactive effect of different spectral lights and CdO NPs on morphological, antioxidant, and phytochemical characteristics of Dodonaea viscosa. The plants were grown on media in the presence of green and chemically synthesized CdO NPs and under red, yellow, green, blue, and white light intensities. Results illustrated that plant morphological parameters changed in the presence of different spectral lights and NPs behaved differentially under different spectral lights. Fresh and dry weights of plants decreased in the presence of NPs in the media; however, the concentration and route of synthesis of NPs have a significant effect on these parameters. The same was observed in the case of shoot and root lengths; however, green synthesized NPs were found to be less toxic under different spectral lights. The total antixodant response increased under yellow, blue, and white lights, while the total reducing potential of plant extracts significantly varied depending upon the NP concentration and light spectrum. Different spectral lights significantly influenced the syntheses of phenolics and flavonoids under CdO NP stress and light regimes. It is concluded that toxicity of NPs also depends upon the wavelength of striking light that varies the morphological, biochemical, and antioxidative response of the plants. Furthermore, the white light might have synergistic effects of different wavelengths.

ZnO NPs reveal distinction in toxicity under different spectral lights: An in vitro experiment on Brassica nigra (Linn.) Koch

Abstract Metallic nanoparticles (NPs) have been studied for their optimistic and pessimistic influence on plants growth and physiology under different light regimes. To investigate the influence of NPs under different light wavelengths, Brassica nigra (Linn.) Koch plants were grown on ZnO NPs supplemented media under the exposure of five different spectral lights (white, blue, red, yellow and green). ZnO NPs toxicity varied under different spectral lights. Difference in light wavelength significantly altered toxicity level of NPs on shoot root length and weight parameters of B. nigra. Free radical scavenging activity, total antioxidant response, and total reducing power potential also considerably varied in shoots and roots when plants were grown in presence of NPs and spectral lights. Concentration of total phenolics and flavonoids also changed in shoots and roots to combat NPs stress. HPLC analysis presented that chlorogenic acid upregulated under NPs influence in red and white light; while quercetin increased under NPs stress in blue light. The study shows that NPs have different toxicity response under different light wavelengths and plant behaves according to environmental conditions to mitigate NPs stress. However, detailed phytochemical and molecular studies are required to explain photodynamic toxicity of NPs.

Light-mediated biosynthesis of phenylpropanoid metabolites and antioxidant potential in callus cultures of purple basil (Ocimum basilicum L. var purpurascens)

Ocimum basilicum L. var purpurascens (purple basil) contains medicinally valuable metabolites. Light greatly influences the physiological processes, including biomass accumulation and secondary metabolites production in medicinal plants. Herein, we investigated the influence of different spectral lights on the biosynthesis of phenylpropanoid metabolites in purple basil callus cultures. Growth kinetics was ostudied for a total of 49 days, with 7 days of sampling time. Among the various treatments, blue light resulted in maximum biomass accumulation, total phenolic content (TPC), total flavonoid content (TFC) and antioxidant DPPH, FRAP and ABTS activities, as compared to controls. Moreover, blue light also encouraged higher superoxide dismutase activity while the red light was found effective for enhanced peroxidase activity. HPLC analysis revealed enhanced rosmarinic acid (87.62 mg/g DW) and anthocyanins (cyanidin: 0.15 mg/g DW and peonidin: 0.13 mg/g DW) contents under dark grown callus cultures which were almost 1.55, 1.25 and 1.18–fold greater than controls, respectively. Conversely, red light caused maximum production of cichoric acid (14.65 mg/g DW). Moreover, a positive correlation occurred among the accumulation of phenolic and flavonoids and antioxidant activities. These results suggest that light quality strongly influences medicinally valuable phenylpropanoid metabolites biosynthesis along with antioxidant potential in in vitro cultures of purple basil. Light-enhanced precious metabolites in callus of Basil.

Tunable spectrum resemblance of LED lights for improving the photosynthetic action of Chinese Cabbages

To increase efficiency, and reduce energy loss and waste, we propose to improve the photosynthetic action spectrum resemblance (SRPAS) of LED light with the absorption spectra of the fresh leaf, for accelerating the growth of Chinese Cabbages. Eight spectral LED lights were adopted to irradiate Chinese Cabbages under 150 μmol•m−2 s−1 for a 16 hd−1 photoperiod. Of these, under the irradiation of blue + broad red + more yellow (BRY2) light with high spectrum resemblance of 75%, the fresh weight and dry weight are 5.1times and 3.0 times, respectively, and the leaf area and leaf number are 1.7 times, as high as under the blue light. The results demonstrate that the optimized LED light can be presumed to have the highest spectrum resemblance (SRPAS) with the absorption spectra of Chinese Cabbages, and the highest energy-conversion efficiency. These conclusions may be of great benefit to further assess and find either an ideal light applied for plant growth or design of better light sources for growing different plants.

In vitro shoot growth and adventitious rooting of Wikstroemia gemmata depends on light quality

In vitro propagation of the ornamentally interesting species Wikstroemia gemmata is limited by the recalcitrance to form adventitious roots. In this article, two strategies to improve the rooting capacity of in vitro microcuttings are presented. Firstly, the effect of exogenous auxin was evaluated in both light and dark cultivated stem segments and also the sucrose-content of the medium was varied in order to determine better rooting conditions. Secondly, different spectral lights were evaluated and the effect on shoot growth and root induction demonstrated that the exact spectral composition of light is important for successful in vitro growth and development of Wikstroemia gemmata. We show that exogenous auxin cannot compensate for the poor rooting under unfavorable light conditions. Adapting the culture conditions is therefore paramount for successful industrial propagation of Wikstroemia gemmata.

Monochromatic lights-induced trends in antioxidant and antidiabetic polyphenol accumulation in in vitro callus cultures of Lepidium sativum L.

Lepidium sativum L. is an important edible, herbaceous plant with huge medicinal value as cardio-protective, hepatoprotective and antitumor agent. This study was designed and performed to investigate biosynthesis of plant's active ingredients in callus cultures of L. sativum in response to the exposure of multi spectral lights. Optimum biomass accumulation (15.36 g/L DW), total phenolic and flavonoid contents (TPC; 47.43 mg/g; TFC; 9.41 mg/g) were recorded in calli placed under white light (24 h) compared to rest of the treatments. Antioxidant enzymatic activities i.e. superoxide dismutase and peroxidase were found optimum in cultures exposed to green light (SOD; 0.054 nM/min/mg FW, POD; 0.501 nM/min/mg FW). Phytochemical analysis further confirmed the potential influence of white light exposure on enhanced production of plant's metabolites. Significant enhancement level of major metabolic compounds such as chlorogenic acid (7.20 mg/g DW), quercetin (22.08 mg/g DW), kaempferol (7.77 mg/g DW) and minor compounds including ferulic acid, sinapic acid, protocatechuic acid, vanillic acid and caffeic acid were recorded in white light compared to control (photoperiod), whereas blue light increased the p-coumaric acid accumulation. Moreover, callus cultures of this plant under white light (24 h) showed highest in vitro based anti-diabetic and antioxidant activities compared to other conditions. Finding of our current study revealed that multi spectral lights are proved to be an effective strategy for enhancing metabolic quantity of antioxidant and anti-diabetic bioactive compounds in callus cultures of L. sativum L.

Production of biomass and medicinal metabolites through adventitious roots in Ajuga bracteosa under different spectral lights

Ajuga bracteosa an important medicinal herb, is getting endangered worldwide due to destructive harvesting by pharmaceutical industries in its different habitats. It is in dire need for protection and demands conservation and sustainable utilization. In the present study, effects of α-naphthalene acetic acid (NAA) under different spectral lights were estimated on the growth, secondary metabolism and biosynthesis of phenolic acids in adventitious roots (AR) cultures of A. bracteosa. Among the different spectral lights, highest AR induction frequency (88%) and formation of biomass (72 g/L FW and 22 g/L DW) were recorded in explants incubated in the presence of 1.5 mg/L NAA under yellow light. Maximum production of poly phenols (TPC;44.2 mg) and flavonoids (TFC;2.51 mg) were recorded in the AR cultures grown in the presence of blue light. Further, highest total protein content of (401.6 μg) was detected in the AR in response to normal white light. Blue spectral light induced maximum superoxide dismutase (SOD; 2.5 nM) and peroxidase activity (POD;0.85 nM) respectively, in AR cultures. Compared with other monochromatic lights, red light significantly enhanced the antioxidant potential of the AR cultures. Analysis through High performance liquid chromatography (HPLC-DAD) revealed significant variations in the levels of important phenolic acids such as gallic acid, catechin, rutin, caffeic acid, myricetin and apigenin in the AR samples treated with the lights of different spectra.

Regulation of Visual Sensitivity Responses in Locusts Stimulated by Different Spectral Lights

Regulation of Visual Sensitivity Responses in Locusts Stimulated by Different Spectral Lights

Impacts of LED spectral quality on leafy vegetables: Productivity closely linked to photosynthetic performance or associated with leaf traits?

The success of growing vegetables indoors requires the most appropriate selection of lighting spectrum. This mini review discusses the impacts of LED spectral quality on different leafy vegetables with a focus on the studies of Chinese broccoli (Brassica alboglabra), ice plants (Mesembryanthem crystallinum) and lettuce (Lactuca sativa L. cv. Canasta). For each species, plants exposed to different spectral LED lights were all under the same light intensity and same photoperiod. Chinese broccoli grown under red(R):blue(B)-LED ratio of 84:16 (16B) had the highest light-saturated photosynthetic CO2 assimilation rate (Asat) and stomatal conductance (gs sat) compared to plants grown under other R:B-LED ratios. It was also shown that 16B is the most appropriate selection for Chinese broccoli to achieve the highest shoot productivity with a rapid leaf number and leaf area development. The highest concentrations of photosynthetic pigments, soluble and Rubisco protein on a leaf area basis were also observed in 16B plants. The results conclusively affirmed that the highest productivity of Chinese broccoli grown under 16B is closely linked to the highest photosynthetic performance on a leaf area basis. For ice plants grown under R:B-LED ratios of 90:10 (10B), they had the highest shoot biomass with a faster leaf development compared to plants grown under other RB-LED combinations. However, there were no differences in Asat, gs sat, photosynthetic pigments, soluble and Rubisco proteins on a leaf area basis. In the case of lettuce plants, it was a surprise to observe that plants grown under 0B and 20G (20% green (G)-LED and 80% R-LED) had the highest shoot biomass, and largest total leaf area and light interception area but the lowest net maximal photosynthetic rate on a leaf area basis, compared to other plants. The combined RB-LED enhanced other photosynthetic parameters while 0B and 20G conditions had inhibitory effects on maximum quantum efficiency of PS II with lower photosynthetic pigments, total soluble protein and Rubisco protein. These results suggest that impacts of LED light quality on productivity of lettuce (L. sativa L. cv. Canasta) is closely linked to leaf traits not associated with photosynthetic performance on a leaf area basis. Keywords: leafy vegetable, leaf traits, LED spectral quality, photosynthetic performance, productivity DOI: 10.25165/j.ijabe.20191206.5178 Citation: He J, Qin L, Chow W S. Impacts of LED spectral quality on leafy vegetables: Productivity closely linked to photosynthetic performance or associated with leaf traits? Int J Agric & Biol Eng, 2019; 12(6): 16–25.