Photosynthetic efficiency, growth and secondary metabolism of common buckwheat (Fagopyrum esculentum Moench) in different controlled-environment production systems.

Light-emitting diodes (LEDs) and high-pressure sodium lamps (HPS) are among the most commonly used light sources for plant cultivation. The objective of this study was to evaluate the effect of two controlled-environment production systems differing in light sources on growth, photosynthetic activity, and secondary metabolism of common buckwheat. We hypothesized that LED light with the majority of red and blue waves would increase physiological and biochemical parameters compared to sunlight supplemented with HPS lamps. The experiment was performed in a phytotronic chamber (LEDs) and in a greenhouse (solar radiation supplemented with HPS lamps as a control). The effects were analyzed at the flowering phase with biometric measurements, leaf chlorophyll index, the kinetics of chlorophyll a fluorescence, content of soluble carbohydrates and phenolics in the leaves. Applied LED light decreased the biomass but stimulated the production of phenolics compared to control plants. In control plants, a positive correlation between flavonoid content and energy dissipation from photosystem II (DIo/CSm) was found, while in plants under LEDs total pool of phenolic content correlated with this parameter and the quantum yield of electron transport (φ Ro and ψ Ro) was lower than that of the control, probably affecting buckwheat biomass.

Effect of Light and Dark on the Phenolic Compound Accumulation in Tartary Buckwheat Hairy Roots Overexpressing ZmLC.

Fagopyrum tataricum 'Hokkai T10' is a buckwheat cultivar capable of producing large amounts of phenolic compounds, including flavonoids (anthocyanins), phenolic acids, and catechin, which have antioxidant, anticancer, and anti-inflammatory properties. In the present study, we revealed that the maize transcription factor Lc increased the accumulation of phenolic compounds, including sinapic acid, 4-hydroxybenzonate, t-cinnamic acid, and rutin, in Hokkai T10 hairy roots cultured under long-photoperiod (16 h light and 8 h dark) conditions. The transcription factor upregulated phenylpropanoid and flavonoid biosynthesis pathway genes, yielding total phenolic contents reaching 27.0 ± 3.30 mg g-1 dry weight, 163% greater than the total flavonoid content produced by a GUS-overexpressing line (control). In contrast, when cultured under continuous darkness, the phenolic accumulation was not significantly different between the ZmLC-overexpressing hairy roots and the control. These findings suggest that the transcription factor (ZmLC) activity may be light-responsive in the ZmLC-overexpressing hairy roots of F. tataricum, triggering activation of the phenylpropanoid and flavonoid biosynthesis pathways. Further studies are required on the optimization of light intensity in ZmLC-overexpressing hairy roots of F. tataricum to enhance the production of phenolic compounds.

Ultrasound Treatment of Buckwheat Grains Impacts Important Functional Properties of Resulting Flour.

The benefit of not containing the gluten complex protein also provides problems with the achievement of typical and proper texture, especially in bakery products. Ultrasound (US) treatment has been previously studied on buckwheat as assistance treatment facilitating the release of antioxidant compounds. However, there is no study regarding the changes occurring in US-treated buckwheat grains regarding the structure-creating capacity, like water absorption, gelling, and pasting. The aim of this study is to the impact of US-treatment of buckwheat grains at 1:10, 1:5, and 1:2.5 solid: liquid ratio (in water). The particle size distribution, water absorption index (WAI), water solubility index (WSI), swelling power (SP), pasting characteristics, color, soluble, insoluble and total polyphenols content (SPC, IPC, TPC) and antioxidant activity (DPPH) were assessed in resulting flours. US-treatment caused specific agglomeration, resulting in bigger particles for 1:5, and 1:2.5 ratio treated samples, while higher dilution (1:10) increased smaller particle size fractions. The WAI and SP were the highest for the1:5 solid: liquid ratio sample, and the same sample revealed the highest peak viscosity, breakdown, and setback values. The ultrasound treatment increased the WSI, which was positively correlated with insoluble polyphenols content. The soluble polyphenols content decreased, and insoluble polyphenols content increased in all ultrasound treated samples. The DPPH scavenging activity remaining in grain after US treatment was lowered compared to the control sample. The relocation of pigments resulted in a redness and yellowish increase in all treated samples, while lightness was also increased but was most pronounced for a 1:10 ratio treated sample. The results suggest that ultrasound treatment of grain can improve the essential functional properties of buckwheat flour.

The light-induced transcription factor FtMYB116 promotes accumulation of rutin in Fagopyrum tataricum.

Tartary buckwheat (Fagopyrum tataricum) not only provides a supplement to primary grain crops in China but also has high medicinal value, by virtue of its rich content of flavonoids possessing antioxidant, anti-inflammatory, and anticancer properties. Light is an important environmental factor that can regulate the synthesis of plant secondary metabolites. In this study, we treated tartary buckwheat seedlings with different wavelengths of light and found that red and blue light could increase the content of flavonoids and the expression of genes involved in flavonoid synthesis pathways. Through coexpression analysis, we identified a new MYB transcription factor (FtMYB116) that can be induced by red and blue light. Yeast one-hybrid assays and an electrophoretic mobility shift assay showed that FtMYB116 binds directly to the promoter region of flavonoid-3'-hydroxylase (F3'H), and a transient luciferase activity assay indicated that FtMYB116 can induce F3'H expression. After transforming FtMYB116 into the hairy roots of tartary buckwheat, we observed significant increases in the content of rutin and quercetin. Collectively, our results indicate that red and blue light promote an increase in flavonoid content in tartary buckwheat seedlings; we also identified a new MYB transcription factor, FtMYB116, that promotes the accumulation of rutin via direct activation of F3'H expression.

[Influence of light on gene expression of key synthesis enzyme genes FtANR and FtLAR about proanthocyanidin in seeds of homologous plant of food and medicine Fagopyrum tataricum].

Tartary buckwheat Fagopyrum tataricum is an important medicinal and functional herb due to its rich content of flavonoids in the seeds. F.tataricum exhibited good functions for free radicals scavenging， anti-oxidation， anti-aging activities. Although much genetic knowledge of the synthesis， regulation， accumulation of rutin， the genetic basis of proanthocyanidins(PAs) in tartary buckwheat and their related gene expression changes under different lights(blue， red， far red， ultraviolet light) remain largely unexplored. In this study， we cloned one anthocyanidin reductase gene(ANR) and two leucocyanidin reductase gene(LAR) named FtANR，FtLAR1，FtLAR3 involved in formation of(+)-catechin and(-)-epicatechin precusor proanthocyanidin by digging out F. tataricum seed transcriptome data. The expression data showed that the opposite influence of red light on these gene transcript level compared to others lights. The expression levels of FtANR and FtLAR1 decreased and FtLAR3 appeared increment after exposed in the red light， while the expression levels of those genes appeared opposite result after exposed in the blue and far red light.

Calcium oxalate druses affect leaf optical properties in selenium-treated Fagopyrum tataricum.

Plants of the genus Fagopyrum contain high levels of crystalline calcium oxalate (CaOx) deposits, or druses, that can affect the leaf optical properties. As selenium has been shown to modify the uptake and accumulation of metabolically important elements such as calcium, we hypothesised that the numbers of druses can be altered by selenium treatment, and this would affect the leaf optical properties. Tartary buckwheat (Fagopyrum tataricum Gaertn.) was grown outdoors in an experimental field. At the beginning of flowering, plants were foliarly sprayed with sodium selenate solution at 10 mg selenium L-1 or only with water. Plant morphological, biochemical, physiological and optical properties were examined, along with leaf elemental composition and content. Se spraying did not affect leaf biochemical and functional properties. However, it increased leaf thickness and the contents of Se in the leaves, and decreased the density of calcium oxalate druses in the leaves. Except Se content, Se spraying did not affect contents of other elements in leaves, including total calcium per dry mass of leaf tissue. Redundancy analysis showed that of all parameters tested, only the calcium oxalate druses parameters were significant in explaining the variability of the leaf reflectance and transmittance spectra. The density of CaOx druses positively correlated with the reflectance in the blue, green, yellow and UV-B regions of the spectrum, while the area of CaOx druses per mm2 of leaf transection area positively correlated with the transmittance in the green and yellow regions of the spectrum.

UV-B radiation increases anthocyanin levels in cotyledons and inhibits the growth of common buckwheat seedlings.

The impact of short-term UV-B treatment on the content of individual flavonoids and photosynthetic pigments in cotyledons and the growth of common buckwheat (Fagopyrum esculentum Moench) seedlings was investigated. Seeds of four common buckwheat cultivars were germinated in darkness over a period of 4 days and acclimatized for 2 days under a 16/8 h light/dark photoperiod at 24/18 °C day/night, and exposure to 100-120 µmol ∙ m-2 ∙ s-1 of photosynthetically active radiation (PAR). Seedlings were divided into three batches, including two batches subjected to different doses of UV-B (5 W ∙ m-2 and 10 W ∙ m-2, one hour per day) for 5 days, and a control group exposed to PAR only. Exposure to UV-B increased anthocyanin levels in the cotyledons of all examined cultivars, it inhibited hypocotyl elongation, but did not affect the content of photosynthetic pigments. Flavone concentrations increased in cv. Red Corolla and Kora, remained constant in cv. Panda and decreased in cv. Hruszowska. Exposure to UV-B decreased rutin levels in cv. Hruszowska, but not in the remaining cultivars. Cultivars Hruszowska, Panda and Kora appeared to be less resistant to UV-B than Red Corolla. Higher resistance to UV-B radiation in Red Corolla can probably be attributed to its higher content of anthocyanins and rutin in comparison with the remaining cultivars.

Fagopyrins and Protofagopyrins: Detection, Analysis, and Potential Phototoxicity in Buckwheat.

Buckwheat contains many healthy nutrients, and its consumption is therefore increasing. Buckwheat also contains fluorescent phototoxic fagopyrins. A systematic review of fagopyrins and the phototoxicity of buckwheat found that reliable quantitative data on fagopyrin toxicity are not yet available. Generally, buckwheat seeds, flour, and teas are safe in normal amounts. Diets extensively composed of buckwheat sprouts, herbs, and particularly flowers or of fagopyrin-rich buckwheat extracts may cause fagopyrism. A reference standard is needed, as it would enable the accurate evaluation of fagopyrin content in buckwheat products and would allow proper testing of their as yet unknown physical, chemical, and biological characteristics.

Phenylalanine and LED lights enhance phenolic compound production in Tartary buckwheat sprouts.

The present study aimed to investigate the effects of different l-phenylalanine (l-Phe) concentrations and various light-emitting diodes (LEDs) on the accumulation of phenolic compounds (chlorogenic acid, vitexin, rutin, quercetin, cyanidin 3-O-glucoside, and cyanidin 3-O-rutinoside) in Tartary buckwheat sprouts. We found that 5mM was the optimum l-Phe concentration for the synthesis of total and individual phenolic compounds. The highest rutin (53.09 mg/g DW) and chlorogenic acid (5.62 mg/g DW) content was observed with Red+Blue and white lights. Comprehensive differences in total and individual anthocyanin content were observed between different lights; however, the total anthocyanin content (9.12 mg/g DW) was 1.5-fold higher in blue light. The expression levels of regulatory genes, such as FtDFR and FtANS, were 7.1-fold higher with l-Phe treatment. Gene expression results showed that the phenolic compounds in Tartary buckwheat sprouts increased with the use of l-Phe and LED lights.

Effects of light-emitting diodes on expression of phenylpropanoid biosynthetic genes and accumulation of phenylpropanoids in Fagopyrum tataricum sprouts.

Buckwheat sprouts are a popular food item in many countries. The effects of light-emitting diodes (LEDs) on sprout growth and development, changes in mRNA transcription, and accumulation of phenylpropanoid compounds were studied in tartary buckwheat 'Hokkai T8' sprouts. The highest transcript levels were observed after 2 days of LED exposure for all genes, especially FtPAL and FtF3'H, which showed higher expression in sprouts grown under blue and white light than in those grown under red light. Catechin content in sprouts grown under red light increased dramatically throughout the 10 day time course. Maximum rutin content (43.37 mg/g dry weight (DW)) was observed in sprouts at 4 days after exposure (DAE) to blue light. Similarly, the highest cyanidin 3-O-rutinoside content (0.85 mg/g DW) was detected at 10 DAE to blue light. On the basis of these results, blue LED light is recommended as a light source for enhancing the content of phenolic compounds in tartary buckwheat sprouts.

Isolation, analysis and structures of phototoxic fagopyrins from buckwheat.

Buckwheat products are commonly used in health foods and food supplements. However, public awareness regarding the presence of photodynamic naphthodianthrones fagopyrins that can cause photosensitization is low. At least two additional compounds with structures similar to that of fagopyrin are known to exist; however, the structures of these compounds have never been determined. In this work, we improved the extraction procedure and the chromatographic analysis of fagopyrins by developing a simple, sensitive and high-resolution high performance liquid chromatography (HPLC) analytical method using fluorescence detection. We observed at least six fagopyrin derivatives, which were isolated and characterized via UV-Vis absorption, NMR spectroscopy and mass spectrometry. We determined the structures of two new derivatives (fagopyrin A and fagopyrin E) and proved the existence of protofagopyrins that can transform into fagopyrins upon light exposure. Our methods complement the existing knowledge regarding fagopyrins and will allow for their further analysis, isolation and investigation of their biological activity.

Effects of white, blue, and red light-emitting diodes on carotenoid biosynthetic gene expression levels and carotenoid accumulation in sprouts of tartary buckwheat (Fagopyrum tataricum Gaertn.).

In this study, the optimum wavelengths of light required for carotenoid biosynthesis were determined by investigating the expression levels of carotenoid biosynthetic genes and carotenoid accumulation in sprouts of tartary buckwheat (Fagopyrum tataricum Gaertn.) exposed to white, blue, and red light-emitting diodes (LEDs). Most carotenoid biosynthetic genes showed higher expression in sprouts irradiated with white light at 8 days after sowing than in those irradiated with blue and red lights. The dominant carotenoids in tartary buckwheat sprouts were lutein and ß-carotene. The richest accumulation of total carotenoids was observed in sprouts grown under white light (1282.63 µg g(-1) dry weight), which was relatively higher than that in sprouts grown under blue and red lights (940.86 and 985.54 µg g(-1), respectively). This study might establish an effective strategy for maximizing the production of carotenoids and other important secondary metabolites in tartary buckwheat sprouts by using LED technology.

Seedling development in buckwheat and the discovery of the photomorphogenic shade-avoidance response.

Numerous botanists of the early 19th century investigated the effect of sunlight on plant development, but no clear picture developed. One hundred and fifty years ago, Julius Sachs (1863) systematically analysed the light-plant relationships, using developing garden nasturtium (Tropaeolum majus) and seedlings of buckwheat (Fagopyron esculentum) as experimental material. From these studies, Sachs elucidated the phenomenon of photomorphogenesis (plant development under the influence of daylight) and the associated 'shade-avoidance response'. We have reproduced the classical buckwheat experiments of Sachs (1863) and document the original shade-avoidance syndrome with reference to hypocotyl elongation and cotyledon development in darkness (skotomorphogenesis), white light and shade induced by a canopy of green leaves. In subsequent publications, Sachs elaborated his concepts of 1863 and postulated the occurrence of 'flower-inducing substances'. In addition, he argued that the shade-avoidance response in cereals, such as wheat and maize, is responsible for lodging in crowded plant communities. We discuss these processes with respect to the red- to far-red light/phytochrome B relationships. Finally, we summarise the phytochrome B-phytohormone (auxin, brassinosteroids) connection within the cells of shaded Arabidopsis plants, and present a simple model to illustrate the shade-avoidance syndrome. In addition, we address the relationship between plant density and health of the corresponding population, a topic that was raised for the first time by Sachs (1863) in his seminal paper and elaborated in his textbooks.

Molecular characterisation and the light-dark regulation of carotenoid biosynthesis in sprouts of tartary buckwheat (Fagopyrum tataricum Gaertn.).

Seven partial-length cDNAs and 1 full-length cDNA that were involved in carotenoid biosynthesis and 2 partial-length cDNAs that encoded carotenoid cleavage dioxygenases were first isolated and characterised in 2 tartary buckwheat cultivars (Fagopyrum tataricum Gaertn.), Hokkai T8 and Hokkai T10. They were constitutively expressed at high levels in the leaves and flowers, where carotenoids are mostly distributed. During the seed development of tartary buckwheat, an inverse correlation between transcription level of carotenoid cleavage dioxygenase and carotenoid content was observed. The light-grown sprouts exhibited higher levels of expression of carotenoid biosynthetic genes in T10 and carotenoid content in both T8 and T10 compared to the dark-grown sprouts. The predominant carotenoids in tartary buckwheat were lutein and ß-carotene, and very abundant amounts of these carotenoids were found in light-grown sprouts. This study might broaden our understanding of the molecular mechanisms involved in carotenoid biosynthesis and indicates targets for increasing the production of carotenoids in tartary buckwheat.

Effects of UV-B irradiation on the levels of anthocyanin, rutin and radical scavenging activity of buckwheat sprouts.

The effects of various light compositions on the levels of anthocyanin, rutin and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity in buckwheat (Fagopyrum esculentum Moench) sprouts were evaluated. Dark-grown 6-day-old buckwheat sprouts were irradiated with different sources of visible and ultraviolet (UV) light. Particularly, we examined the effect of UV-B at wavelengths of 260-320 nm, 280-320 nm, and 300-320 nm on the production of flavonoid compounds, using multiple fluorescent lights and cylinders that filter out certain portions of the UV-B. The results showed that irradiation with UV-B>300 nm increased the levels of anthocyanin and rutin, as well as the DPPH radical scavenging activity. When sprouts were irradiated with UV-B light at wavelengths of 260-300 nm, yellowing or withering occurred within 24h of irradiation, indicating that wavelengths in this range are detrimental to the growth of buckwheat sprouts.

Accumulation of phenylpropanoids and correlated gene expression during the development of tartary buckwheat sprouts.

Buckwheat sprouts are considered an excellent dietary source of phenolic compounds. The time duration and amount of light for sprouting strongly affect the nutritional quality of sprouts. In this study, these two factors were investigated in two cultivars of tartary buckwheat sprouts: Hokkai T8 and T10. The transcriptional levels of flavonoid biosynthetic genes were investigated in light/dark- and dark-treated sprouts. Among the main flavonoid biosynthesis structural genes, FtPAL, Ft4CL, FtF3H, FtDFR, and FtANS exhibited higher transcriptional levels than others as compared to that of a housekeeping gene (histone H3) during sprouting; FtF3'H1, FtF3'H2, FtFLS2, and FtANS were substantially upregulated at 2, 4, and 6 days in light/dark-treated T10 sprouts than in dark-treated ones. However, FtDFR was downregulated in 8 and 10 day old light/dark-treated sprouts of both cultivars. High-performance liquid chromatography (HPLC) analysis revealed that increasing the culture time did not affect the accumulation of flavonoids or anthocyanins. However, light contributed the production of anthocyanins in Hokkai T10 sprouts. The anthocyanins included cyanidin 3-O-glucoside, cyanidin 3-O-rutinoside, and delphinidin-3-O-coumarylglucoside, which were identified by HPLC and electrospray ionization-tandem mass spectrometry. Instead of anthocyanins, Hokkai T8 sprouts produced large amounts of 4 flavonoid C-glycosylflavone compounds in both light/dark and dark conditions: orientin, isoorientin, vitexin, and isovitexin. These results indicate that these two types of tartary buckwheat sprouts have different mechanisms for flavonoid and anthocyanin biosynthesis that also vary in light/dark and dark conditions.

[Influences of enhanced UV-B radiation and drought stress on biomass accumulation and allocation of Fagopyrum dibotrys].

OBJECTIVE: To study the influences of enhanced UV-B radiation and drought stress on the biomass accumulation and allocation of Fagopyrum dibotrys, and so as to provide a theoretical basis for the cultivation, the protection and use of F. dibotrys. METHOD: By experiment of potted plant, the biomass accumulation and allocation of F. dibotrys were measured under different drought stresses and UV-B radiations. RESULT: In conditions of adequate water, enhanced UV-B radiation significantly reduced biomass accumulation to root, biomass accumulation to leaves, total biomass accumulation and biomass allocation to root in F. dibotrys, while it could increase biomass allocation to stem. In conditions of moderate drought stress, enhanced UV-B radiation increased biomass accumulation to root, biomass accumulation to stem and biomass accumulation to root. In the conditions of severe drought stress, enhanced UV-B radiation increased biomass accumulation to root, it also could lead in a certain increase to biomass accumulation to stem. Biomass allocation to root, stem and leaves was not sensitive to enhanced UV-B radiation. CONCLUSION: The influences of enhanced UV-B radiation in simulation and drought stress on the biomass accumulation and allocation of F. dibotrys were determined by water conditions and different apparatus. Overall, we verified that enhanced UV-B radiation would reduce the influences of biomass accumulation of F. dibotrys by drought.

Light stimulation triggered expression of genes coding for vacuolar proton-pump enzymes V-ATPase and V-PPase in buckwheat.

Although coloration in plants is ascribable to both the accumulation of anthocyanin pigments in vacuoles and to the acidification of vacuolar pH, the environmental factors causing the decrease in vacuolar pH are unknown. We found that blue-light irradiation of buckwheat seedlings using light-emitting diodes caused reddening on the surface of the hypocotyls. It has also been reported that light stimulation induces an accumulation of anthocyanin pigments. However, here we confirmed for the first time on the basis of real-time PCR analysis that light stimulation simultaneously triggers expression of the genes coding for subunit A of vacuolar H+-ATPase (V-ATPase) and vacuolar H(+)-pyrophosphatase (V-PPase).

Morphology of nectaries and biology of nectar production in the distylous species Fagopyrum esculentum.

BACKGROUND AND AIMS: The mechanisms of floral nectar production in buckwheat (Fagopyrum esculentum, Polygonaceae), a distylous pseudo-cereal, have received relatively little attention, prompting an investigation of the factors that regulate this process. The aim was to perform a refined study of the structures that secrete nectar and of the internal and external parameters influencing nectar volumes and sugar concentrations. METHODS: In order to control environmental parameters, plants were cultivated in growth rooms under controlled conditions. The structure of nectaries was studied based on histological sections from flowers and flower buds. Nectar was extracted using glass micropipettes and the sugar concentration was measured with a hand refractometer. Sugar concentration in the phloem sap was measured using the anthrone method. To test the influence of photosynthesis on nectar production, different light and defoliation treatments were applied. KEY RESULTS: Unicellular trichomes were located in the epidermis at the ventral part of eight nectary glands situated on the flower receptacle alternately with stamens. Vascular bundles consisting of both phloem and xylem were identified at the boundary between a multilayered nectary parenchyma and a sub-nectary parenchyma with chloroplasts. A higher volume of nectar in thrum morphs was observed. No other difference was found in morphology or in sugar supply to inflorescences between morphs. Nectar secretion was strongly influenced by plant age and inflorescence position. Nectar volumes were higher in the upper inflorescences and during the flowering peak. Light had a dual role, (1) acting directly on reproductive structures to trigger flower opening, which conditions nectar secretion, and (2) stimulating photosynthetic activity, which regulates nectar accumulation in open flowers. CONCLUSIONS: In buckwheat, nectar is secreted by trichomes and probably proceeds, at least in part, from phloem sap. Nectar secretion is strongly influenced by floral morph type, plant age, inflorescence position and light.

Antioxidative enzymes in the response of buckwheat (Fagopyrum esculentum moench) to ultraviolet B radiation.

The behavior of the enzymatic antioxidant defense system was studied in buckwheat leaves and seedlings subjected to short-term enhanced UV-B radiation. The effects of UV-B action were monitored immediately after irradiation as well as after recovery. The applied dose induced an increase in lipid peroxidation and total flavonoid content, a decrease in chlorophyll content, and a change in enzymatic digestibility of extracted DNA. The activity of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase, and soluble peroxidase, as well as the isoelectric focusing (IEF) pattern of peroxidase isoforms, was analyzed. In treated as well as recovered seedlings, soluble and ascorbate peroxidase activities were increased. The activity of SOD was not altered, whereas CAT activity was decreased. In contrast to seedlings, only CAT activity was increased in treated and recovered leaves.