Effect of Light Treatment on Chemical Composition of Andrographis paniculata Seedlings.

Light quality consists of a spectrum of different bands, which not only affects plant, development, and primary metabolism but also affects the secondary metabolism of plants. It is an important factor affecting the content of active components of medicinal plants. The A. paniculata seedlings planted in the laboratory, as materials, were tested with red light, far red light, blue light, and ultraviolet light separately. The study assays the content of six main chemical components separately by LC-MS, observes the changes in the content, and analyzes the relationship between the light quality and the active ingredient of A. paniculata. Using the ointment yield and pH value, the fingerprint analysis method of A. paniculata standard decoction was established, and we discussed the selection of index components of A. paniculata standard decoction. It was suggested to select andrographolide as the index component. It will provide a theoretical basis for the large area cultivation of A. paniculata and optimize the quality of medicinal materials to ensure the quality of standard decoction.

Metabolic changes in cucumber leaves are enhanced by blue light but differentially affected by UV interactions with light signalling pathways in the visible spectrum.

Ultraviolet radiation (UV, 280-400 nm) as an environmental signal triggers metabolic acclimatory responses. However, how different light qualities affect UV acclimation during growth is poorly understood. Here, cucumber plants (Cucumis sativus) were grown under blue, green, red, or white light in combination with UV. Their effects on leaf metabolites were determined using untargeted metabolomics. Blue and white growth light triggered increased levels of compounds related to primary and secondary metabolism, including amino acids, phenolics, hormones, and compounds related to sugar metabolism and the TCA cycle. In contrast, supplementary UV in a blue or white light background decreased leaf content of amino acids, phenolics, sugars, and TCA-related compounds, without affecting abscisic acid, auxin, zeatin, or jasmonic acid levels. However, in plants grown under green light, UV induced increased levels of phenolics, hormones (auxin, zeatin, dihydrozeatin-7-N-dihydrozeatin, jasmonic acid), amino acids, sugars, and TCA cycle-related compounds. Plants grown under red light with UV mainly showed decreased sugar content. These findings highlight the importance of the blue light component for metabolite accumulation. Also, data on interactions of UV with green light on the one hand, and blue or white light on the other, further contributes to our understanding of light quality regulation of plant metabolism.

The Impact of LED Lighting Spectra in a Plant Factory on the Growth, Physiological Traits and Essential Oil Content of Lemon Balm (Melissa officinalis).

With the recent development of LED lighting systems for plant cultivation, the use of vertical farming under controlled conditions is attracting increased attention. This study investigated the impact of a number of LED light spectra (red, blue, green and white) on the growth, development and essential oil content of lemon balm (Melissa officinalis), a herb and pharmaceutical plant species used across the world. White light and red-rich light spectra gave the best outputs in terms of impact on the growth and yield. For blue-rich spectra, the development and yield was lower despite having a significant impact on the photosynthesis activity, including Fv/Fm and NDVI values. For the blue-rich spectra, a peak wavelength of 450 mn was better than that of 435 nm. The results have practical value in terms of increased yield and the reduction of electricity consumption under controlled environmental conditions for the commercial production of lemon balm.

Effects of Light on Secondary Metabolite Biosynthesis in Medicinal Plants.

Secondary metabolites (SMs) found in medicinal plants are one of main sources of drugs, cosmetics, and health products. With the increase in demand for these bioactive compounds, improving the content and yield of SMs in medicinal plants has become increasingly important. The content and distribution of SMs in medicinal plants are closely related to environmental factors, especially light. In recent years, artificial light sources have been used in controlled environments for the production and conservation of medicinal germplasm. Therefore, it is essential to elucidate how light affects the accumulation of SMs in different plant species. Here, we systematically summarize recent advances in our understanding of the regulatory roles of light quality, light intensity, and photoperiod in the biosynthesis of three main types of SMs (polyphenols, alkaloids, and terpenoids), and the underlying mechanisms. This article provides a detailed overview of the role of light signaling pathways in SM biosynthesis, which will further promote the application of artificial light sources in medicinal plant production.

Photosynthetic Efficiency and Yield of Cucumber (Cucumis sativus L.) Grown under HPS and LED Lighting in Autumn-Winter Cultivation.

The objective of this study was to evaluate the effect of the supplemental lighting of cucumber with sodium pressure lamps (HPSs) and light-emitting diodes (LEDs) on photosynthetic efficiency and yield in autumn-winter cultivation. Cucumber plants of the 'Svyatogor' F1 midi-cucumber parthenocarpic type cultivar were grown on mineral wool mats in three compartments, differing only in the type of light, i.e., (1) HPS top lighting (HPS) in the first compartment, (2) HPS top lighting and LED panel interlighting (HPS + LED) in the second compartment and (3) LED top lighting and inter-row LED panels (LED) in the third compartment. The photosynthetically active radiation was the same in each compartment. The study showed that the highest commercial yields of cucumber could be achieved under LED light (top and inter-row). The chlorophyll content in the leaf blade of younger leaves was higher in plants under LED lighting. This type of lighting also had a positive effect on the gas exchange of plants (net carbon assimilation, stomatal conductance, transpiration). LED and HPS + LED lighting increased the chlorophyll a fluorescence parameters, such as Fs, Fm' and vitality index (PI), in both younger and older leaves, which also increased the fruit yield in the tested combinations.

Plastic response to early shade avoidance cues has season-long effect on Beta vulgaris growth and development.

Early-emerging weeds are known to negatively affect crop growth but the mechanisms by which weeds reduce crop yield are not fully understood. In a 4-year study, we evaluated the effect of duration of weed-reflected light on sugar beet (Beta vulgaris L.) growth and development. The study included an early-season weed removal series and a late-season weed addition series of treatments arranged in a randomized complete block, and the study design minimized direct resource competition. If weeds were present from emergence until the two true-leaf sugar beet stage, sugar beet leaf area was reduced 22%, leaf biomass reduced 25%, and root biomass reduced 32% compared to sugar beet grown season-long without surrounding weeds. Leaf area, leaf biomass, and root biomass was similar whether weeds were removed at the two true-leaf stage (approximately 330 GDD after planting) or allowed to remain until sugar beet harvest (approximately 1,240 GDD after planting). Adding weeds at the two true-leaf stage and leaving them until harvest (~1,240 GDD) reduced sugar beet leaf and root biomass by 18% and 23%, respectively. This work suggests sugar beet responds early and near-irreversibly to weed presence and has implications for crop management genetic improvement.

Physiological and biochemical responses of green and red perilla to LED-based light.

BACKGROUND: Light-emitting diodes (LEDs) are widely used in closed-type plant production systems to improve biomass and accumulate bioactive compounds in plants. Perilla has been commonly used as herbal medicine because of its health-promoting effects. This study aimed to investigate the physiological and biochemical responses of green and red perilla under various visible-light spectra. RESULTS: Results showed that red (R) LEDs improved fresh weights of shoots and roots, plant height, internode length, node number and leaf area, as well as photosynthetic rate of green and red perilla plants compared to blue (B) LEDs and RB combined LEDs. Meanwhile, B resulted in higher stomatal conductance, transpiration rate and Fv/Fm compared to R. Supplementation of green (G) and far-red (FR) did not enhance perilla growth. Reduction or absence of B decreased leaf thickness, adaxial and abaxial epidermis, and palisade and spongy mesophyll. Total phenolic content, antioxidant capacity, rosmarinic acid content and caffeic acid content of green perilla were higher under R, R8B2 and RGB + FR, while greater values were obtained in red perilla under R. Accumulation of perillaldehyde, luteolin and apigenin presented different trends from those of rosmarinic and caffeic acids in both cultivars. CONCLUSIONS: Growth and accumulation of bioactive compounds in green perilla were greater than in red perilla under similar light quality, and R LEDs or a higher R ratio in combination treatments were suitable for cultivating high-quality green and red perilla plants in closed-type plant factories. © 2020 Society of Chemical Industry.

The Combination of Selenium and LED Light Quality Affects Growth and Nutritional Properties of Broccoli Sprouts.

Selenium (Se) supplement was combined with different LED light qualities to investigate mutual effects on the growth, nutritional quality, contents of glucosinolates and mineral elements in broccoli sprouts. There were five treatments: CK:1R1B1G, 1R1B1G+Se (100 µmol L-1 Na2SeO3), 1R1B+Se, 1R2B+Se, 2R1B+Se, 60 µmol m-2 s-1 PPFD, 12 h/12 h (light/dark). Sprouts under a combination of selenium and LED light quality treatment exhibited no remarkable change fresh weight, but had a shorter hypocotyl length, lower moisture content and heavier dry weight, especially with 1R2B+Se treatment. The contents of carotenoid, soluble protein, soluble sugar, vitamin C, total flavonoids, total polyphenol and contents of total glucosinolates and organic Se were dramatically improved through the combination of Se and LED light quality. Moreover, heat map and principal component analysis showed that broccoli sprouts under 1R2B+Se treatment had higher nutritional quality and health-promoting compound contents than other treatments. This suggests that the Se supplement under suitable LED lights might be beneficial to selenium-biofortified broccoli sprout production.

[Effects of light quality on growth and icariin flavonoid content of Epimedium pseudowushanense under different light intensity].

In this study, the growth index including plant height, compound leaf area, specific leaf area, leaf water content, number of branches, and leaf biomass per plant and the icariin flavonoids such as epimedin A, epimedin B, epimedin C and icariin of Epimedium pseudowushanense were determined on 30 d and 60 d under light intensity(18.2±2.5) µmol·m~(-2)·s~(-1)(L1) and(90.9 ±2.5) µmol·m~(-2)·s~(-1)(L2), and white light as control, red light, blue light and yellow light were used as three light quality treatments, to study the effect of light quality on the growth and flavonoids accumulation of E. pseudowushanense. The E. pseudowushanense was sui-table for growth under L1 light intensity, the blue light treatment significantly reduced the leaf area, but had little effect on the stem height, the red light treatment and the yellow light treatment had no obvious effect on the stem height and leaf area, but the yellow light treatment significantly increased the germination of new branches, and had a sustained promoting effect, and the biomass was significantly higher than the white light treatment at 60 d. The content of icariin flavonoids in red light, blue light and yellow light treatment was higher than that in white light treatment at 30 d and 60 d under L1 light intensity, while yellow light treatment promoted the synthesis of icariin flavonoids to the largest extent, which was 1.8 and 1.9 times of white light treatment(30 d and 60 d).Under L2 light intensity, the effect of strong light on promoting stem germination became the main factor, while the yellow light treatment showed no significant effect on promoting stem germination, and the red light treatment exhibited a significant effect on reducing leaf area. Icariin flavonoids under red light, blue light and yellow light treatment were all lower than that under white light treatment, that is, the effect of white light treatment on the synthesis of icariin flavonoids is better than red light, blue light and yellow light treatment. When the time of strong light treatment was longer, the degradation range of icariin flavonoids in other light treatment appeared, while red light treatment promotes the synthesis of icariin flavonoids. Therefore, the influence of light quality on E. pseudowushanense is quite different under different light intensity, no matter from growth index or flavonoid content index. The results support that the biomass and icariin flavonoid content can be increased by providing appropriate red and yellow light.

Blue and red light affects morphogenesis and 20-hydroxyecdisone content of in vitro Pfaffia glomerata accessions.

The combination of different colors from light-emitting diodes (LEDs) may influence growth and production of secondary metabolites in plants. In the present study, the effect of light quality on morphophysiology and content of 20-hydroxyecdysone (20E), a phytoecdysteroid, was evaluated in accessions of an endangered medicinal species, Pfaffia glomerata, grown in vitro. Two accessions (Ac22 and Ac43) were cultured in vitro under three different ratios of red (R) and blue (B) LEDs: (i) 1R:1B, (ii) 1R:3B, and (iii) 3R:1B. An equal ratio of red and blue light (1R:1B) increased biomass accumulation, anthocyanin content, and 20E production (by 30-40%). Moreover, 1R:1B treatment increased the size of vascular bundles and vessel elements, as well as strengthened xylem lignification and thickening of the cell wall of shoots. The 1R:3B treatment induced the highest photosynthetic and electron transport rates and enhanced the activity of oxidative stress-related enzymes. Total Chl content, Chl/Car ratio, and NPQ varied more by accession type than by light source. Spectral quality affected primary metabolism differently in each accession. Specifically, in Ac22 plants, fructose content was higher under 1R:1B and 1R:3B treatments, whereas starch accumulation was higher under 1R:3B, and sucrose under 3R:1B. In Ac43 plants, sugars were not influenced by light spectral quality, but starch content was higher under 3R:1B conditions. In conclusion, red and blue LEDs enhance biomass and 20E production in P. glomerata grown in vitro.

Effects of light quality on growth and icariin flavonoid content of Epimedium pseudowushanense under different light intensity / 中国中药杂志

In this study, the growth index including plant height, compound leaf area, specific leaf area, leaf water content, number of branches, and leaf biomass per plant and the icariin flavonoids such as epimedin A, epimedin B, epimedin C and icariin of Epimedium pseudowushanense were determined on 30 d and 60 d under light intensity(18.2±2.5) μmol·m~(-2)·s~(-1)(L1) and(90.9 ±2.5) μmol·m~(-2)·s~(-1)(L2), and white light as control, red light, blue light and yellow light were used as three light quality treatments, to study the effect of light quality on the growth and flavonoids accumulation of E. pseudowushanense. The E. pseudowushanense was sui-table for growth under L1 light intensity, the blue light treatment significantly reduced the leaf area, but had little effect on the stem height, the red light treatment and the yellow light treatment had no obvious effect on the stem height and leaf area, but the yellow light treatment significantly increased the germination of new branches, and had a sustained promoting effect, and the biomass was significantly higher than the white light treatment at 60 d. The content of icariin flavonoids in red light, blue light and yellow light treatment was higher than that in white light treatment at 30 d and 60 d under L1 light intensity, while yellow light treatment promoted the synthesis of icariin flavonoids to the largest extent, which was 1.8 and 1.9 times of white light treatment(30 d and 60 d).Under L2 light intensity, the effect of strong light on promoting stem germination became the main factor, while the yellow light treatment showed no significant effect on promoting stem germination, and the red light treatment exhibited a significant effect on reducing leaf area. Icariin flavonoids under red light, blue light and yellow light treatment were all lower than that under white light treatment, that is, the effect of white light treatment on the synthesis of icariin flavonoids is better than red light, blue light and yellow light treatment. When the time of strong light treatment was longer, the degradation range of icariin flavonoids in other light treatment appeared, while red light treatment promotes the synthesis of icariin flavonoids. Therefore, the influence of light quality on E. pseudowushanense is quite different under different light intensity, no matter from growth index or flavonoid content index. The results support that the biomass and icariin flavonoid content can be increased by providing appropriate red and yellow light.

Regulation of Growth and Flavonoid Formation of Tea Plants ( Camellia sinensis) by Blue and Green Light.

The effects of blue (BL) and green light (GL) treatment during the dark period were examined in Camellia sinensis as a first step to understanding the spectral effects of artificial BL and GL on plant secondary metabolism and light signaling interactions. BL could induce the expression of CRY2/3, SPAs, HY5, and R2R3-MYBs to promote the accumulation of anthocyanins and catechins in tea plants. GL, on the other hand, could stimulate the accumulation of several functional substances (e.g., procyanidin B2/B3 and l-ascorbate) and temper these BL responses via down-regulation of  CRY2/3 and PHOT2. Furthermore, the molecular events that triggered by BL and GL signals were partly overlapped with abiotic/biotic stress responses. We indicate the possibility of a targeted use of BL and GL to regulate the amount of functional metabolites to enhance tea quality and taste, and to potentially trigger defense mechanisms of tea plants.

Differential accumulation of silymarin induced by exposure of Silybum marianum L. callus cultures to several spectres of monochromatic lights.

Silybum marianum L. (Milk thistle) is one of the most extensively studied medicinal herbs with well-known hepatoprotective activity. Light is considered as a key abiotic elicitor influencing several physiological processes in plants, including the biosynthesis of secondary metabolites. In this study, we investigated the influence of light quality on morphological and biochemical aspects in in vitro grown leaf-derived callus cultures of S. marianum. Combination of 6-benzylaminopurine (BAP 2.5 mg/L) and α-naphthalene acetic acid (NAA 1.0 mg/L) resulted in optimum callogenic response (97%) when placed under cool-white light with 16 h light and 8 h dark. Red light significantly increased the total phenolic content (TPC), total flavonoid content (TFC), antioxidant and superoxide dismutase (SOD) activities while highest peroxidase (POD) activity was recorded for the dark grown cultures, followed by green light grown cultures. HPLC analysis revealed enhanced total silymarin content under red light (18.67 mg/g DW), which was almost double than control (9.17 mg/g DW). Individually, the level of silychristin, isosilychristin, silydianin, silybin A and silybin B were found greatest under red light, whereas green spectrum resulted in highest accumulation of isosilybin A and isosilybin B. Conversely, the amount of taxifolin was found maximum under continuous white light (0.480 mg/g DW) which was almost 8-fold greater than control (0.063 mg/g DW). A positive correlation was found between the TPC, TFC and antioxidant activities. This study will assist in comprehending the influence of light quality on production of valuable secondary metabolites in in vitro cultures of S. marianum L.

Influence of light quality on growth, secondary metabolites production and antioxidant activity in callus culture of Rhodiola imbricata Edgew.

Rhodiola imbricata is a rare medicinal herb well-known for its adaptogenic and antioxidant properties due to the presence of a diverse array of secondary metabolites, including phenylethanoids and phenylpropanoids. These secondary metabolites are generating considerable interest due to their potential applications in pharmaceutical and nutraceutical industries. The present study investigated the influence of light quality on growth, production of industrially important secondary metabolites and antioxidant activity in callus cultures of Rhodiola imbricata. Callus cultures of Rhodiola imbricata were established under different light conditions: 100% red, 100% blue, 100% green, RGB (40% red: 40% green: 20% blue) and 100% white (control). The results showed that the callus cultures grown under red light accumulated maximum amount of biomass (7.43 g/l) on day 21 of culture, as compared to other light conditions. Maximum specific growth rate (0.126 days-1) and doubling time (132.66 h) was observed in callus cultures grown under red light. Reverse phase-high performance liquid chromatographic (RP-HPLC) analysis revealed that the callus cultures exposed to blue light accumulated maximum amount of Salidroside (3.12 mg/g DW) on day 21 of culture, as compared to other light conditions. UV-Vis spectrophotometric analysis showed that the callus cultures exposed to blue light accumulated maximum amount of total phenolics (11.84 mg CHA/g DW) and total flavonoids (5.53 mg RE/g DW), as compared to other light conditions. Additionally, callus cultures grown under blue light displayed enhanced DPPH free radical scavenging activity (53.50%). Callus cultures grown under different light conditions showed no significant difference in ascorbic acid content (11.05-13.90 mg/g DW) and total antioxidant capacity (27.37-30.17 mg QE/g DW). The correlation analysis showed a positive correlation between total phenolic content and DPPH free radical scavenging activity in callus cultures (r = 0.85). Taken together, these results demonstrate the remarkable potential of light quality on biomass accumulation and production of industrially important secondary metabolites in callus cultures of Rhodiola imbricata. This study will open new avenues and perspectives towards abiotic elicitation strategies for sustainable growth and enhanced production of bioactive compounds in in-vitro cultures of Rhodiola imbricata.

Effect of light quality on total gypenosides accumulation and related key enzyme gene expression in Gynostemma pentaphyllum / 中草药·英文版

Objective: Light quality has effect on the accumulation of gypenosides in the medicinal plant Gynostemma pentaphyllum in the family Cucurbitaceae, while the squalene synthase (SS) and squalene epoxidase (SE) are the key enzymes for gypenoside biosynthesis. The objective of this study was to elucidate the relationship between light quality and biosynthesis key enzyme involving the regulation of gypenoside accumulation. Methods: The content of total gypenosides was measured by colorimetric method and the expression of SS and SE gene was determined by quantitative Real-time PCR in the seedlings of G. pentaphyllum which were grown with different light quality. Results: Light quality showed remarkable impacts on the accumulation of total gypenosides. The highest content of total gypenosides in the plant under red light condition was determined, followed by blue light and white light, while the lowest content was recorded under dark condition. qRT-PCR analysis proved that the expression levels of SS and SE genes were also affected by light quality. The high-level gene expressions of SS and SE were found in the plant under red light condition, followed by blue light, with the least content in darkness. The statistical analysis revealed that the total gypenosides were significantly different in different light treatment and the content of total gypenosides was positively related to the expression of SS and SE genes. Conclusions: Light quality regulates gypenoside accumulation via altering the expression of SS and SE in G. pentaphyllum.

[Effects of light quality on growth and internal quality of Whitmania pigra].

In this study, four light color treatments (red blue, white, natural light) were tested to determine effects of light spectrum on the growth of larval Whitmania pigra (30 days old) at the same intensity. The experiment lasted for 50 days. The specific growth rate (SGR) under blue light condition was significantly higher during 30 days to 40 days. At the end of the experiment, specific growth rate (SGR) and weight gain rate under red light condition were higher (P<0.05) than those under other groups. Meanwhile, the enzymes activities of digestive enzymes (protease, amylase and lipase) were higher under red light condition. However, the enzymes activities of antioxidant enzymes (SOD, CAT, ALP) were lower under white light condition compared with the other treatments（P＜0.05）. In addition, no significant changes were observed for water content, total ash, acid insoluble ash, pH and antithrombin activity in the all treatments. After 50 days, the digestive enzymes and growth rate were higher under red light condition but antioxidant enzymes were lower under white light condition. Furthermore, light spectrum has no significant effect on the internal quality of Wh. pigra.

Circadian and Light Regulated Expression of CBFs and their Upstream Signalling Genes in Barley.

CBF (C-repeat binding factor) transcription factors show high expression levels in response to cold; moreover, they play a key regulatory role in cold acclimation processes. Recently, however, more and more information has led to the conclusion that, apart from cold, light-including its spectra-also has a crucial role in regulating CBF expression. Earlier, studies established that the expression patterns of some of these regulatory genes follow circadian rhythms. To understand more of this complex acclimation process, we studied the expression patterns of the signal transducing pathways, including signal perception, the circadian clock and phospholipid signalling pathways, upstream of the CBF gene regulatory hub. To exclude the confounding effect of cold, experiments were carried out at 22 °C. Our results show that the expression of genes implicated in the phospholipid signalling pathway follow a circadian rhythm. We demonstrated that, from among the tested CBF genes expressed in Hordeumvulgare (Hv) under our conditions, only the members of the HvCBF4-phylogenetic subgroup showed a circadian pattern. We found that the HvCBF4-subgroup genes were expressed late in the afternoon or early in the night. We also determined the expression changes under supplemental far-red illumination and established that the transcript accumulation had appeared four hours earlier and more intensely in several cases. Based on our results, we propose a model to illustrate the effect of the circadian clock and the quality of the light on the elements of signalling pathways upstream of the HvCBFs, thus integrating the complex regulation of the early cellular responses, which finally lead to an elevated abiotic stress tolerance.

Growth, photosynthetic pigments and production of essential oil of long-pepper under different light conditions

ABSTRACT Piper hispidinervum C. DC. is popularly known as long-pepper and it owns a commercial value due to the essential oil it produces. Long-pepper oil is rich in safrole and eugenoln components that have insecticidal, fungicidal and bactericidal activity. It has been establish that to medicinal plants light influences not only growth but also essential oil production. The growth, the content of photosynthetic pigments and the essential oil production of Piper hispidinervum at greenhouses with different light conditions was evaluated. The treatments were characterized by cultivation of plants for 180 days under different light conditions, produced by shading greenhouses with 50% and 30% of natural incident irradiance, two colored shading nets red (RN) and blue (BN) both blocking 50% of the incident radiation and one treatment at full-sun (0% of shade). The results showed that the treatments of 50% shade and RN and BN were the ones which stimulated the greater growth. Blue and red light also had the best production of photosynthetic pigments. Essential oil yielded more under full sun therefore this is the most indicated condition to produce seedlings for the chemical and pharmaceutical industry.

Progress of effects of light on plant flavonoids / 中国中药杂志

As an important secondary metabolites of medicinal plant, flavonoids plays a very important role on itself including light protection and antioxidant. Light is one of the important environmental factors which impacts the secondary metabolites of plant and has a significant impact on biological synthesis of flavonoids. This paper reviews the recent progress of the effects of light on flavonoids on the plants focusing from light intensity and light quality, and summarizes briefly functions of the phenylalanine ammonia lyase (PAL) in plant secondary metabolism and the upstream key enzyme chalcone synthase (CHS) in flavonoid biosynthetic pathway.

Impact of pre-harvest light spectral properties on health- and sensory-related compounds in broccoli florets.

BACKGROUND: Plants grown at different latitudes experience differences in light spectral composition. Broccoli (Brassica oleracea L. var italica) plants were grown in climate-controlled chambers under supplemental wavelengths (red, far-red, red + far-red or blue) from light-emitting diodes (LEDs). The light treatments were combined with two cold climate temperatures (12 and 15 °C) during broccoli head formation to investigate the effects on morphology and content of health- and sensory-related compounds: glucosinolates, flavonols, ascorbic acid and soluble sugars. RESULTS: Supplemental far-red and red + far-red light led to elongated plants and the lowest total glucosinolate content in broccoli florets. The content of quercetin was highest with supplemental red light. Vitamin C was not significantly affected by the light treatments, but 12 °C gave a higher content than 15 °C. CONCLUSION: The effects of supplemental red and far-red light suggest an involvement of phytochromes in the regulation of glucosinolates and flavonols. A shift in red:far-red ratio could cause changes in their content besides altering the morphology. The sugar and vitamin C content appears to be unaffected by these light conditions. Supplemental blue light had little effect on plant morphology and content of the health- and sensory related compounds.