Light Reflected from Colored Mulches to Growing Turnip Leaves Affects Glucosinolate and Sugar Contents of Edible Roots

Abstract— Plastic mulches are widely used to conserve water and control weeds with less applied herbicides in production of food crops. Both yield and quality are important and can be affected by reflected blue (B), red (R) and far-red (FR) light combinations received during growth and development. Photosynthate allocation among growing plant parts and flavor of edible roots were studied in turnip ( Brassica rapa L.) grown in trickle-irrigated field plots with blue, green and white mulches. The blue and green mulches reflected different amounts of B, but they both reflected FR/R ratios higher than the ratio in incoming sunlight. The white mulch reflected more photosyn-thetic light and a lower FR/R ratio than the blue or green mulches. Plants grown with blue and green mulches did not differ significantly in leaf length, root size and shoot/ root biomass ratio. Those grown with white had shorter leaves and larger roots. Taste testers found that plants grown with blue mulch developed roots with a sharp flavor, and roots from plants grown with green mulch had a mild flavor. Those grown with white had a less distinct flavor. Roots grown with blue mulch had the greatest concentrations of total glucosinolates (GSL) and ascorbic acid. Reducing sugar concentrations were higher in roots grown with green than in those grown with blue mulches. The comparison of chemical composition of roots from plants grown with blue versus green mulches is important because the main difference was the amount of reflected B, suggesting that B influenced an enzyme involved in the pathway from glucose to GSL. We conclude that the spectrum of light reflected from mulch on the soil surface can influence not only shoot/root biomass ratio but also flavor-related chemical composition of field-grown food crop plants.     

Photodynamic Inactivation of <Emphasis Type="BoldItalic">E. coli</Emphasis> PTCC 1276 Using Light Emitting Diodes: Application of Rose Bengal and Methylene Blue as Two Simple Models

The lack of a comparative study about potential of high-power light emitting diodes (LEDs) for photodynamic inactivation (PDI) of pathogenic microorganisms has remained as a challenging issue for researchers. Therefore, the aim of this study is to fill this gap through introduction of an efficient model for in vitro PDI in an aqueous medium. For this purpose, two individual 30 mW/cm² irradiation systems were designed using suitable sets of green and red LEDs. At another work, Methylene blue (MB) and Rose bengal (RB) as two simple models in the range of 5–150 μM were used in order to compare PDI of E. coli PTCC 1276 using red and green LED systems. Our results showed that a first-order mathematical model has the strength to describe the temporal variation of survival curves. Based on our results, when concentration of photosensitizer increased, the rate of inactivation for RB increased while MB depicted a maximum rate value at 25 μM. In a comparative study, optimum inactivation of E. coli PTCC 1276 obtained during 2- and 10-min irradiation of the LED systems using RB and MB at 150 and 25 μM, respectively. With regard to lower value of inactivation time and higher rate of inactivation for RB, use of simultaneous green high-power LEDs and RB is proposed as an efficient approach for PDI of pathogenic bacteria in future industrial applications.     

Heteroblastic Development and Shade-avoidance in Response to Blue and Red Light Signals in Acacia implexa

Information from blue (400–500 nm) and red (660–730 nm) wavelengths is used by plants to determine proximity of neighbors or actual shading. Plants undergo trait changes in order to out-compete neighbors or accommodate shading. Heteroblasty, the dramatic shift from one leaf type to another during juvenility, can be influenced by the light environment although it is unknown whether cues from blue or red (or both) are driving the developmental process. Seedlings of three populations of Acacia implexa (Mimosaceae) collected from low, medium and high rainfall habitats were grown in a factorial design of high/low blue and red light to determine how light signals affect heteroblasty and patterns of biomass allocation. Low blue light significantly delayed heteroblasty in the low rainfall population and low red light significantly delayed in the low and high rainfall populations. Low blue light increased stem elongation and decreased root biomass whereas low red light induced a strong shade-avoidance response. These results were consistent across populations although the low rainfall population showed greater trait variability in response to red light signals. We conclude that red light conveys a greater information signal than blue light that affects heteroblasty and seedling development in A. implexa .     

Nonlinear dynamics of intracellular methylene blue during light activation of cell cultures

Methylene blue (MB+) is a well-known dye in medicine and has been discussed as an easily applicable drug for topical treatment in photodynamic therapy (PDT). Methylene blue can potentially be used as a redox indicator to detect the important redox reactions that are induced during PDT. The kinetics of this process was analyzed on a subcellular level with confocal laser scanning microscopy. BKEz-7 endothelial cells were incubated 4 h with 1 microM MB+. The fluorescence dynamics of MB+ during irradiation with 633 nm light was observed with subcellular resolution. Images were acquired at 0.5 s intervals (frame rate 1 image/0.5 s). Fluorescence was observed in the red channel of the laser scanning microscope. Synchronously, the phase-contrast image was visualized with the green channel. Morphological changes could therefore be correlated with the dynamics of MB+. In addition, the light-dose-dependent phototoxicity at 633 nm irradiation was determined by viable cell counting. After an induction period (phase I), fast fluorescent spikes could be observed in the whole cytoplasm, which decayed with a time constant of about 20 s (phase II), followed by a period of nearly constant fluorescence intensity (phase III) and exponential photobleaching (phase IV). Phase II exhibits highly nonlinear kinetics, which is hypothesized to correlate probably with a nonlinear quantal production of reactive oxygen species (ROS). Morphological cell changes were not observed during phase II. During phase III, a pycnotic cell nucleus developed. From the determination of viable cells we can conclude that a light dose applied within phase II was only sublethal in correlation with morphological observations. Overproduction of ROS leading finally to cell killing during phases III and IV is discussed.     

High red,green, and blue color purity electroluminescence from MEH‐PPV and polyalkyfluorenes‐based bright white polymer light emitting displays

A series of white polymer light emitting displays (PLEDs) based on a polymer blend of polyalkylfluorenes and poly(2‐methoxy‐5,2′‐ethyl‐hexyloxy‐1,4‐phenylene vinylene) (MEH‐PPV) was developed. MEH‐PPV or red light emitting alkyfluorene copolymer (PFR) was blended with blue light emitting alkyfluorene copolymer (PFB), and MEH‐PPV was blended with both green light emitting alkyfluorene copolymer (PFG) and PFB to generate white light emission PLEDs. Low turn on voltage (2.7 V), high brightness (12,149 nits), high efficiency (4.0 cd/A, 4.0 lm/W), and good color purity (Commission Internationale de L'Eclairage (CIE_x,y) co‐ordinates (0.32, 0.34)) were obtained for the white PLEDs based on the PFB and MEH‐PPV polymer blend. Exciplex formation in the interface between PFR and PFB induced a new green emission peak for these two components based white PLEDs. As a result, strong white emission (4078 nits) was obtained by mixing the red, green, and blue (RGB) three primary colors. High color purity of blue (CIE, x = 0.14, y = 0.08), green (CIE, x = 0.32, y = 0.64) and red (CIE, x = 0.67, y = 0.33) emissions was achieved for white PLEDs combining with dielectric interference color‐filters. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 330–341, 2007     

Effect of light quality on the accumulation of photosynthetic pigments, proteins and mycosporine-like amino acids in the red alga Porphyra leucosticta (Bangiales, Rhodophyta)

The effect of different light qualities (white, blue, green, yellow and red light) on photosynthesis, measured as chlorophyll fluorescence, and the accumulation of photosynthetic pigments, proteins and the UV-absorbing mycosporine-like amino acids (MAAs) was studied in the red alga Porphyra leucosticta. Blue light promoted the highest accumulation of nitrogen metabolism derived compounds i.e., MAAs, phycoerythrin and proteins in previously N-starved algae after seven days culture in ammonium enriched medium. Similar results were observed in the culture under white light. In contrast, the lowest photosynthetic capacity i.e., lowest electron transport rate and lowest photosynthetic efficiency as well as the growth rate were found under blue light, while higher values were found in red and white lights. Blue light favored the accumulation of the MAAs porphyra-334, palythine and asterina-330 in P. leucosticta. However, white, green, yellow and red lights favored the accumulation of shinorine. The increase of porphyra-334, palythine and asterina-330 occurred in blue light simultaneous to a decrease in shinorine. The accumulation of MAAs and other nitrogenous compounds in P. leucosticta under blue light could not be attributed to photosynthesis and the action of a non-photosynthetic blue light photoreceptor is suggested. A non-photosynthetic photoreceptor could be also involved in the MAAs interconversion pathways in P. leucosticta.     

Enhanced wavelength-sensitivity of volume holographic grating with dual-photoinitiation system in polymer-dispersed liquid crystal

We propose a method to improve the wavelength-sensitivity of a volume holographic grating by mixing dual-photoinitiation dopants, namely, rose bengal (RB)/N-phenylglycine (NPG) system and methylene blue (MB)/p-toluenesulfonic acid (PTSA) system, which enable the fabrication of gratings upon both green and red light illumination. The RB/NPG green light photoinitiation system is chosen in combination with the red-active MB/PTSA system because RB and MB absorb light near 567 and 665 nm independently. In this case, the holographic gratings, recorded in polymer-dispersed liquid crystal, can be fabricated simultaneously by two different visible laser lights with an output wavelength of 532 and 632.8 nm. The electro-optical performances of the gratings exposed upon 532 and 632.8 nm have been implemented: the diffraction efficiencies (DE) are 75% and 57% respectively when the exposure time is optimised to 2 min and 17 min; the threshold voltage is approximately 2.9 V/μm. The enhanced wavelength-sensitivity of holographic gratings allows for the storage of three-dimensional (3D) images on the same hologram plate, and these 3D images are easily reconstructed by both red and green light.     

Enhancement of the Modulation Response of Quantum-Dot-Based Down-Converted Light through Surface Plasmon Coupling

In this paper, we first elaborate on the effects of surface plasmon (SP) coupling on the modulation responses of the emission of a light-emitting diode (LED) and its down-converted lights through colloidal quantum dots (QDs). The results of our past efforts for this subject are briefly discussed. The discussions lay the foundation for the presentation of the new experimental data of such down-converted lights in this paper. In particular, the enhancement of the modulation bandwidth (MB) of a QD-based converted light through SP coupling is demonstrated. By linking green-emitting QDs (GQDs) and/or red-emitting QDs (RQDs) with synthesized Ag nano-plates via surface modifications and placing them on a blue-emitting LED, the MBs of the converted green and red emissions are significantly increased through the induced SP coupling of the Ag nano-plates. When both GQD and RQD exist and are closely spaced in a sample, the energy transfer processes of emission-reabsorption and Förster resonance energy transfer from GQD into RQD occur, leading to the increase (decrease) in the MB of green (red) light. With SP coupling, the MB of a mixed light is significantly enhanced.     

Efficient White‐Light Generation from Ionically Self‐Assembled Triply‐Fluorescent Organic Nanoparticles

Low cost, simple, and environmentally friendly strategies for white‐light generation which do not require rare‐earth phosphors or other toxic or elementally scare species remain an essentially unmet challenge. Progress in the area of all‐organic approaches is highly sought, single molecular systems remaining a particular challenge. Taking inspiration from the designer nature of ionic‐liquid chemistry, we now introduce a new strategy toward white‐light emission based on the facile generation of nanoparticles comprising three different fluorophores assembled in a well‐defined stoichiometry purely through electrostatic interactions. The building blocks consist of the fluorophores aminopyrene, fluorescein, and rhodamine 6G which represent blue, green, and red‐emitting species, respectively. Spherical nanoparticles 16(±5) nm in size were prepared which display bright white‐light emission with high fluorescence quantum efficiency (26 %) and color coordinate at (0.29, 0.38) which lie in close proximity to pure white light (0.33, 0.33). It is noteworthy that this same fluorophore mixture in free solution yields only blue emission. Density functional theory calculations reveal H‐bond and ground‐state proton transfer mediated absolute non‐parallel orientation of the constituent units which result in frustrated energy transfer, giving rise to emission from the individual centers and concomitant white‐light emission.     

KINETICS OF PHOTOSYNTHETIC APPARATUS ADAPTATION IN Scenedesmus obliquus TO CHANGE IN IRRADIANCE AND LIGHT QUALITY

Abstract— Cells of the unicellular green alga Scenedesmus obliquus grown under high (20 W m^-2) or low (5 W m^-2) irradiancies of white light show all characteristics of sun or shade plants, respectively. When transferred to alternate light conditions, the cells adapt within 6 h. When cells grown under high irradiance of white light are transferred to red (683 nm) or blue (424 nm) light, they show characteristics similar to cells adapted to low or high irradiancies of white light, respectively. This adaptation to different wavelengths takes about 12 h. The underlying changes in the photosynthetic apparatus are discussed.     

Effects of Light Exposure and Use of Intraocular Lens on Retinal Pigment Epithelial Cells In Vitro

To investigate the effect of a blue light-filtering intraocular lens (IOL) and a UV-absorbing IOL on light-induced damage to retinal pigment epithelial (RPE) cells laden with the lipofuscin fluorophore N -retinylidene- N -retinylethanolamine (A2E), A2E-laden RPE cells were exposed to white light which was filtered by either a blue light-filtering IOL or a UV-absorbing IOL. After 30 min of illumination the cell viability and the level of reactive oxygen species (ROS), free glutathione (GSH), vascular endothelial growth factor (VEGF) and pigment epithelium-derived factor (PEDF) were determined. In the absence of an IOL, the white light exposure decreased cell viability to 37.2% of the nonirradiated control. The UV-absorbing IOL tended to reduce light-induced cell death; however, the decrease was not significant. The blue light-filtering IOL significantly attenuated light-induced cell damage, increasing cell viability to 79.5% of the nonirradiated control. The presence of the blue light-filtering IOL significantly increased GSH and PEDF levels, and decreased ROS and VEGF levels. This study suggests that a blue light-filtering IOL may be more protective against A2E-induced light damage and inhibit more light-induced ROS and VEGF production than a conventional UV-absorbing IOL.     

LIGHT REQUIREMENTS FOR THE ENHANCED SYNTHESIS OF A PLASTID mRNA DURING SPIRODELA GREENING

A plastid mRNA (5 × 10⁵ mol wt) appears as a burst 3 h after white light greening of steady state dark grown plants of Spirodela oligorrhiza. In this species, chlorophyll synthesis begins after 12 h. The light requirement is different from the pulse of far-red reversible red light required to abolish the lag of chlorophyll synthesis in many species, including Spirodela. Continuous high energy far-red is not stimulatory. When the illumination is not continued throughout the time of incorporation, the stimulation is minimal. Low energy blue and red light are stimulatory, and green and far-red light are ineffectual. Blue light was > 5 times as effective as red light at many dose levels. Illumination with 3 × 10¹⁷ quanta/m²/s (50pEm/cm²/s) blue light at 476 nm gave about half maximum stimulation.     

RELATIONSHIP BETWEEN LIGHT QUALITY DEPENDENCE AND IRRADIANCE ADAPTATION OF PHOTOSYNTHESIS IN Acetabularia mediterranea*

Characteristic differences in the light intensity curves of photosynthesis after growth of cells of Acetabularia mediterranea Lamour. (A. acetabulum (L.) Silva) in weak and strong white light were similar to those for red and blue light-treated cells, respectively. This indicated that responses to white light quantity and those to light quality might be causally related. Small differences in the thylakoid polypeptide composition of cells grown in high and low intensities of white light were not significant and thus did not help to clarify whether the adaptations to blue or red light, respectively, were the same. When the red to blue-light ratio was varied, keeping the total photon fluence rate constant, the photosynthetic capacity (red light saturated O₂-production) was dependent on blue light irradiance in a logarithmic fashion. The specific influence of red light was not detectable, indicating that only blue light was effective for light irradiance adaptation in Acetabularia. The situation was different, at least for a transient period, when adaptation to light irradiance was allowed to proceed from a low photosynthetic activity after preirradiation of the cells with prolonged red light. The effect of low white light irradiances was pronounced, causing a maximum increase of photosynthetic activity within 3 days. The response to blue light was enhanced as well, and a very low photon irradiance added to continuous red light caused a change of the same order as that produced by high irradiances of blue light alone. This elevated action of low intensity white and blue light is most likely due to increased metabolite supply derived from the degradation of starch enhanced by this light quality. Therefore, photosynthetic effectiveness in Acetabularia is regulated by the irradiance of blue light and by feedback via photosynthetic products.     

MODE OF COACTION BETWEEN UV-A AND LIGHT ABSORBED BY PHYTOCHROME IN CONTROL OF APPEARANCE OF RIBULOSE-1.5-BISPHOSPHATE CARBOXYLASE IN THE SHOOT OF MILO (Sorghum vulgare Pers.)

Abstract— In shoots of milo ( Sorghum vulgare Pers.) appearance of ribulosebisphosphate carboxylase (RuBPCase) and of translatable mRNA for its small subunit is stimulated strongly by red light (R, operating through phytochrome) and UV-A light (UV-A). Ultraviolet-A is more effective than R.
The mode of coaction between phytochrome and light absorbed by the blue/UV-A light photoreceptor ('cryptochrome') was analyzed in detail in case of enzyme appearance. Fluence rate dependencies, lagphases and the time course of the response are compatible with the view that UV-A intensifies a process which is occurring in R alone albeit at a lower rate.
With both light qualities the light effect is fully reversible by far-red light up to 1 h. This means that during this period only phytochrome (P_fr) controls the terminal response, i.e. the actual appearance of RuBPCase. During this 1 h period after the onset of light UV-A or R have no effect on the level of translatable mRNA for the small subunit of RuBPCase indicating that it requires more than 1 h for the light signal to affect gene expression.
When R and UV-A are given longer onset of escape from full reversibility is observed at the same time for both light qualities in the case of RuBPCase appearance. The extent of the reversible response is greater after UV-A pretreatment than after a R pretreatment.
It is argued that the data are consistent with the concept that phytochrome (P_fr) controls the terminal photoresponse, in the present case appearance of RuBPCase, while light absorbed via cryptochrome leads to an increase in responsiveness of the RuBPCase producing machinery towards P_fr.     

Light quality influences indigo precursors production and seed germination in Isatis tinctoria L. and Isatis indigotica Fort

Isatis tinctoria L. and Isatis indigotica Fort. are biennial herbaceous plants belonging to the family of Cruciferae that are used as a source of natural indigo and show several morphological and genetic differences. Production of indigo (indigotin) precursors, indican (indoxyl beta-D glucoside) and isatan B (indoxyl ketogluconate), together with seed germination ability were compared in Isatis tinctoria and Isatis indigotica grown under six different light conditions (darkness, white, red, far red, blue, yellow light) at 25 degrees C. Light quality influenced both germination and production of indigo precursors in the two Isatis species. Different responsiveness to far red and blue light was observed. Indeed, a detrimental effect on germination by blue and far red light was found in I. tinctoria only. Different amounts of isatan B were produced under red and far red light in the two Isatis species. In I. tinctoria, the level of main indigo precursor isatan B was maximal under red light and minimal under far red light. Whereas in I. indigotica far red light promoted a large accumulation of isatan B. The photon fluence rate dependency for white and yellow light responses showed that the accumulation of indigo precursors was differently influenced in the two Isatis species. In particular, both white and yellow light enhanced above 40 micromol m(-2) s(-1) the production of isatan B in I. indigotica while only white light showed a photon fluence dependency in I. tinctoria. These results suggest a different role played by the labile and stable phytochrome species (phyA and phyB) in the isatan B production in I. tinctoria and I. indigotica. I. indigotica, whose germination percentage was not influenced by light quality, demonstrated higher germination capability compared with I. tinctoria. In fact, I. tinctoria showed high frequency of germination in darkness and under light sources that establish high phytochrome photoequilibrium (red, white and yellow light). Germination in I. tinctoria was negatively affected by far red and blue light. I. indigotica seeds appear to be indifferent to canopy-like light (far red). Our results provide further insights on the distinct behaviour of I. tinctoria and I. indigotica that belong to two different genetic clusters and different original environments.     

Effects of Light‐emitting Diode Radiations on Human Retinal Pigment Epithelial Cells In Vitro

Human visual system is exposed to high levels of natural and artificial lights of different spectra and intensities along lifetime. Light‐emitting diodes (LEDs) are the basic lighting components in screens of PCs, phones and TV sets; hence it is so important to know the implications of LED radiations on the human visual system. The aim of this study was to investigate the effect of LEDs radiations on human retinal pigment epithelial cells (HRPEpiC). They were exposed to three light–darkness (12 h/12 h) cycles, using blue‐468 nm, green‐525 nm, red‐616 nm and white light. Cellular viability of HRPEpiC was evaluated by labeling all nuclei with DAPI; Production of reactive oxygen species (ROS) was determined by H2DCFDA staining; mitochondrial membrane potential was quantified by TMRM staining; DNA damage was determined by H2AX histone activation, and apoptosis was evaluated by caspases‐3,‐7 activation. It is shown that LED radiations decrease 75–99% cellular viability, and increase 66–89% cellular apoptosis. They also increase ROS production and DNA damage. Fluorescence intensity of apoptosis was 3.7% in nonirradiated cells and 88.8%, 86.1%, 83.9% and 65.5% in cells exposed to white, blue, green or red light, respectively. This study indicates three light–darkness (12 h/12 h) cycles of exposure to LED lighting affect in vitro HRPEpiC.     

Effects of Supplementary Blue and UV-A LED Lights on Morphology and Phytochemicals of Brassicaceae Baby-Leaves

Brassicaceae baby-leaves are good source of functional phytochemicals. To investigate how Chinese kale and pak-choi baby-leaves in response to different wavebands of blue (430 nm and 465 nm) and UV-A (380 nm and 400 nm) LED, the plant growth, glucosinolates, antioxidants, and minerals were determined. Both agronomy traits and phytochemical contents were significantly affected. Blue and UV-A light played a predominant role in increasing the plant biomass and morphology, as well as the contents of antioxidant compounds (vitamin C, vitamin E, phenolics, and individual flavonols), the antioxidant activity (DPPH and FRAP), and the total glucosinolates accumulation. In particular, four light wavebands significantly decreased the content of progoitrin, while 400 nm UV-A light and 430 nm blue light were efficient in elevating the contents of sinigrin and glucobrassicin in Chinese kale. Meanwhile, 400 nm UV-A light was able to increase the contents of glucoraphanin, sinigrin, and glucobrassicin in pak-choi. From the global view of heatmap, blue lights were more efficient in increasing the yield and phytochemical levels of two baby-leaves.     

Molecular Engineering Approaches Towards All-Organic White Light Emitting Materials

White light emitting (WLE) materials are of increasing interest owing to their promising applications in artificial lighting, display devices, molecular sensors, and switches. In this context, organic WLE materials cater to the interest of the scientific community owing to their promising features like color purity, long-term stability, solution processability, cost-effectiveness, and low toxicity. The typical method for the generation of white light is to combine three primary (red, green, and blue) or the two complementary (e.g., yellow and blue or red and cyan) emissive units covering the whole visible spectral window (400–800 nm). The judicious choice of molecular building blocks and connecting them through either strong covalent bonds or assembling through weak noncovalent interactions are the key to achieve enhanced emission spanning the entire visible region. In the present review article, molecular engineering approaches for the development of all-organic WLE materials are analyzed in view of different photophysical processes like fluorescence resonance energy transfer (FRET), excited-state intramolecular proton transfer (ESIPT), charge transfer (CT), monomer-excimer emission, triplet-state harvesting, etc. The key aspect of tuning the molecular fluorescence under the influence of pH, heat, and host–guest interactions is also discussed. The white light emission obtained from small organic molecules to supramolecular assemblies is presented, including polymers, micelles, and also employing covalent organic frameworks. The state-of-the-art knowledge in the field of organic WLE materials, challenges, and future scope are delineated.     

Designing Tunable White‐Light Emission from an Aurophilic CuI/AuI Coordination Polymer with Thioether Ligands

White‐light emitters have attracted considerable attention due to their importance in current and future technologies. By incorporating molecular fragments that independently emit in the blue, green/yellow, and red visible regions, specifically Cu‐NC, Au???Au interactions, and Cu‐SR₂, respectively, into a single material, new white‐light‐emitting systems have been targeted. With this goal, three new Cu^I/thioether‐based coordination polymers containing bridging [Au(CN)₂]^? units have been synthesized and structurally characterized, and their photoluminescence properties (at room and low temperatures) have been delineated. Using this approach, white‐light emission (tunable from slightly yellow to slightly blue, depending on λ_ex) is generated from Cu(Me₂S)[Au(CN)₂], a feature uncommon in such simple coordination compounds.