Evidence for yellow light suppression of lettuce growth

Researchers studying plant growth under different lamp types often attribute differences in growth to a blue light response. Lettuce plants were grown in six blue light treatments comprising five blue light fractions (0, 2, 6% from high-pressure sodium [HPS] lamps and 6, 12, 26% from metal halide [MH] lamps). Lettuce chlorophyll concentration, dry mass, leaf area and specific leaf area under the HPS and MH 6% blue were significantly different, suggesting wavelengths other than blue and red affected plant growth. Results were reproducible in two replicate studies at each of two photosynthetic photon fluxes, 200 and 500 mumol m-2 s-1. We graphed the data against absolute blue light, phytochrome photoequilibrium, phototropic blue, UV, red:far red, blue:red, blue: far red and 'yellow' light fraction. Only the 'yellow' wavelength range (580-600 nm) explained the differences between the two lamp types.     

Photobiological Interactions of Blue Light and Photosynthetic Photon Flux: Effects of Monochromatic and Broad‐Spectrum Light Sources

Photosynthesis (Pn) and photomorphogenesis (Pm) are affected by light quality, light intensity and photoperiod. Although blue light (BL) is necessary for normal development, it is less efficient in driving Pn than other wavelengths of photosynthetically active radiation. The effects of BL on Pm are highly species dependent. Here we report the interacting effects of BL and photosynthetic photon flux (PPF) on growth and development of lettuce, radish and pepper. We used light‐emitting diode (LED) arrays to provide BL fractions from 11% to 28% under broad‐spectrum white LEDs, and from 0.3% to 92% under monochromatic LEDs. All treatments were replicated three times at each of two PPFs (200 and 500 μmol m^?2 s^?1). Other than light quality, environmental conditions were uniformly maintained across chambers. Regardless of PPF, BL was necessary to prevent shade‐avoidance responses in radish and lettuce. For lettuce and radish, increasing BL reduced stem length, and for both species, there were significant interactions of BL with PPF for leaf expansion. Increasing BL reduced petiole length in radish and flower number in pepper. BL minimally affected pepper growth and other developmental parameters. Pepper seedlings were more photobiologically sensitive than older plants. Surprisingly, there were few interactions between monochromatic and broad‐spectrum light sources.     

Supplementary Far-Red and Blue Lights Influence the Biomass and Phytochemical Profiles of Two Lettuce Cultivars in Plant Factory

Three different LED spectra (W: White light; WFR: W + far-red light; WB: W + blue light) with similar photosynthetic photon flux density (PPFD) were designed to explore the effects of supplementary far-red and blue lights on leaf color, biomass and phytochemicals of two cultivars of red-leaf lettuce (“Yanzhi” and “Red Butter”) in an artificial lighting plant factory. Lettuce plants under WB had redder leaf color and significantly higher contents of pigments, such as chlorophyll a, chlorophyll b, chlorophyll (a + b) and anthocyanins. The accumulation of health-promoting compounds, such as vitamin C, vitamin A, total phenolic compounds, total flavonoids and anthocyanins in the two lettuce cultivars were obviously enhanced by WB. Lettuce under WFR showed remarkable increase in fresh weight and dry weight; meanwhile, significant decreases of pigments, total phenolic compounds, total flavonoids and vitamin C were found. Thus, in the plant factory system, the application of WB can improve the coloration and quality of red leaf lettuce while WFR was encouraged for the purpose of elevating the yield of lettuce.     

Bilirubin- and light induced cell death in a murine lymphoma cell line

Cells from the mouse lymphoma cell line L5178Y-R were exposed to blue light from phototherapy lamps in the presence of solutions of 160 microM bilirubin supplemented with serum albumin. HPLC analysis showed that the bilirubin solution was photooxidised as a function of increasing light dose. The cells were stained with trypan blue to score necrosis, and apoptosis was assayed by the terminal deoxynucleotide transferase assay (TdT) or by studying the nuclear structure in cells stained with propidium iodide. A rapidly developing apoptosis was observed after light doses killing 60-80% of the cells as judged from the trypan blue exclusion test. The fraction of apoptotic cells was smaller than the fraction of necrotic cells. Exposure of the cells to fractions of light at a high dose rate was compared to the effect of the same total dose at a lower dose rate given as a single fraction. No large differences were found, however, there was a tendency of a higher degree of necrosis as well as apoptosis in the cells receiving the light in fractions at a high dose rate.     

Plant responses to current solar ultraviolet-B radiation and to supplemented solar ultraviolet-B radiation simulating ozone depletion: an experimental comparison

Field experiments assessing UV-B effects on plants have been conducted using two contrasting techniques: supplementation of solar UV-B with radiation from fluorescent UV lamps and the exclusion of solar UV-B with filters. We compared these two approaches by growing lettuce and oat simultaneously under three conditions: UV-B exclusion, near-ambient UV-B (control) and UV-B supplementation (simulating a 30% ozone depletion). This permitted computation of "solar UV-B" and "supplemental UV-B" effects. Microclimate and photosynthetically active radiation were the same under the two treatments and the control. Excluding UV-B changed total UV-B radiation more than did supplementing UV-B, but the UV-B supplementation contained more "biologically effective" shortwave radiation. For oat, solar UV-B had a greater effect than supplemental UV-B on main shoot leaf area and main shoot mass, but supplemental UV-B had a greater effect on leaf and tiller number and UV-B-absorbing compounds. For lettuce, growth and stomatal density generally responded similarly to both solar UV-B and supplemented UV-B radiation, but UV-absorbing compounds responded more to supplemental UV-B, as in oat. Because of the marked spectral differences between the techniques, experiments using UV-B exclusion are most suited to assessing effects of present-day UV-B radiation, whereas UV-B supplementation experiments are most appropriate for addressing the ozone depletion issue.     

Application of very small force measurements in monitoring the response of sunflower to weak blue light

A diaheliotropic response of sunflower, Helianthus annuus, following a short pulse of low intensity blue light to a small area of leaf surface was examined with the application of the very low-force-measurements technique (the order of magnitude of 10(-5) N). One leaf from a pair was illuminated with a low intensity blue-light-pulse and the force was recorded, generated by the stem of the plant tending to bend. A very low phototropic effect in response to blue light alone was observed which could be considerably enhanced by the application of background illumination with red light. Microelectrode measurements of the membrane potential of the mesophyll cells of the sunflower leaf showed hyperpolarization in response to a blue light pulse, observed very clearly under application of the red light background illumination. The hyperpolarization of the membrane potential was accompanied by acidification of extracellular compartments as monitored with a miniature pH-sensitive electrode, placed in the epidermis of the stem. The relatively short lag period between the hyperpolarization of the membrane potential and the decrease in pH suggests that the hyperpolarization is a direct effect of the blue light-induced proton extrusion. The acidification correlates with the light response, which suggests that acidification-induced stem wall loosening is responsible for the blue light-induced bending. The examined mechanisms are discussed in terms of sun tracking by a sunflower.     

Kinetic separation of phototropism from blue-light inhibition of stem elongation

These experiments tested the hypothesis that phototropic bending arises when a light gradient across the stem differentially inhibits cell elongation because of direct inhibition of cell elongation by light (the Blaauw hypothesis). Continuous irradiation of dark-grown cucumber seedlings (Cucumis sativus L.) with unilateral blue light inhibited hypocotyl elongation within 30 s, but did not induce phototropic curvature until 4.5 h after the start of irradiation. Marking experiments showed that curvature began simultaneously at the top and bottom of the growing region. In situ measurements of the light gradient across the stem with a glass fiber optic indicated that a 5- to 6-fold difference in fluence rate was established on the two sides of the stem. The light gradient established at the start of irradiation was the same as that after 6 h of irradiation. Changes in gravitropic responsiveness during this period were also ruled out. Calculations show that the light gradient should have caused curvature which would be detectable within 30 to 60 min and which would extrapolate to the start of irradiation--if the Blaauw hypothesis were correct. The long lag for phototropism in this case indicates that rapid inhibition of cell elongation by blue light does not cause the asymmetrical growth of phototropism. Rather, phototropism is superimposed upon this separate light growth response.     

THE EFFECT OF LIGHT QUALITY IN Prunus cerasus. I. PHOTORECEPTORS INVOLVED IN INTERNODE ELONGATION AND LEAF EXPANSION IN JUVENILE PLANTS

Evidence is presented to suggest that stem elongation in this woody species is controlled not only by phytochrome as previously suggested for other woody species, but also by a specific blue absorbing pigment (BAP). In contrast, the BAP seems to have no role to play in the development of total leaf area in these juvenile specimens.     

高性能光催化降解聚乙烯薄膜的研究

利用酸性蓝BGA染料敏化的纳米TiO2作为光催化剂, 与低密度聚乙烯(LDPE)树脂复合制备了具有可见光催化降解性能的复合塑料薄膜. 采用SEM、FTIR、VHX-100数码显微镜和高温凝胶渗透色谱(HTGPC)等分析技术系统地研究了该塑料薄膜在紫外光和太阳光照射下的降解性能. 探讨了塑料薄膜在光辐照前后的力学性能、质量和分子量变化规律. 研究结果表明, 该薄膜在经紫外线照射5 d后质量损失达到17.6％, 数均分子量由21800降低为5900; 经太阳光照射48 d后质量损失达到12.5％, 分子量降为8100. 辐照后薄膜拉伸强度和断裂伸长率显著降低, 羰基含量升高.     

Changes in Endogenous Phytohormones of Gerbera jamesonii Axillary Shoots Multiplied under Different Light Emitting Diodes Light Quality

Light quality is essential in in vitro cultures for morphogenesis process. Light emitting diodes system (LED) allows adjustment as desired and the most appropriate light spectrum. The study analyzed the influence of different LED light quality on the balance of endogenous phytohormones and related compounds (PhRC) in in vitro multiplied axillary shoots of Gerbera jamesonii. Over a duration of 40 days, the shoots were exposed to 100% red light, 100% blue light, red and blue light at a 7:3 ratio with control fluorescent lamps. Every 10 days plant tissues were tested for their PhRC content with the use of an ultra-high performance liquid chromatography (UHPLC). Shoots’ morphometric features were analyzed after a multiplication cycle. We identified 35 PhRC including twelve cytokinins, seven auxins, nine gibberellins, and seven stress-related phytohormones. Compounds content varied from 0.00052 nmol/g to 168.15 nmol/g of dry weight (DW). The most abundant group were stress-related phytohormones (particularly benzoic and salicylic acids), and the least abundant were cytokinins (about 370 times smaller content). LED light did not disturb the endogenous phytohormone balance, and more effectively mitigated the stress experienced by in vitro grown plants than the fluorescent lamps. The stress was most effectively reduced under the red LED. Red and red:blue light lowered tissue auxin levels. Blue LED light lowered the shoot multiplication rate and their height, and induced the highest content of gibberellins at the last stage of the culture.     

PHOTOREGULATION OF ROOT: SHOOT RATIO IN SOYBEAN SEEDLINGS*

Abstract— The partitioning of plant growth between shoot and root has the potential to affect diverse physiological processes including water and nutrient uptake, nitrogen fixation, light interception, and interactions between plant and soil microorganisms. Root: shoot ratio is determined both by genetics and developmental status as well as by availability of water, nutrients and light. It is shown here that relative root growth was modulated by photomorphogenetic treatments designed to affect phytochrome (supplemental far-red radiation given either as an end-of-day treatment or continuously during the photoperiod) or blue light photoreceptors (blue light-deficient low pressure sodium lamps ± low irradiances of supplemental blue [i.e. 5% of total photon flux: 25 μ.mol m^?2 s^?1]). Photomorphogenetic control of root: shoot ratio was apparent within1–2 days when light treatments were initiated at emergence, and did not necessarily involve changes in net seedling growth. On the other hand, shortened daylength inhibited early seedling growth but had little effect on partitioning. Changes in relative root dry matter induced by supplemental far red radiation or blue light deficiency were similar to those caused by low irradiances, suggesting that phytochrome or blue light photoreceptors may be involved in regulating the partitioning of growth between shoot and root as a part of adaptation to vegetation shade. The influence of spectral quality on root: shoot ratio should be considered when comparing plants grown under different types of lighting or with different spacing.     

Photoluminescence spectral reliance on aggregation order of 1,1-Bis(2'-thienyl)-2,3,4,5-tetraphenylsilole

1,1-Bis(2'-thienyl)-2,3,4,5-tetraphenylsilole (1) was prepared and characterized crystallographically. Silole 1 exhibited aggregation-induced emission (AIE) behavior like other 2,3,4,5-tetraphenylsiloles. Unexpectedly, aggregates formed in water/acetone (6:4 by volume) mixture emitted a blue light that peaked at 474 nm, while aggregates formed in the mixtures with higher water fractions emitted green light that peaked at 500 nm. Transmission electron microscopy demonstrated that the aggregates formed in the mixture with water fraction of 60% were single crystals, while aggregates that formed in the mixture with water fraction of 90% were irregular and poorly ordered particles. The unusual PL spectral reliance on aggregation order was further confirmed by PL emissions of macroscopic crystal powders and amorphous powders of the silole in the dry state. PL spectral blue shifting was observed upon aging of the poorly ordered aggregates formed in mixtures with water fractions of 70-90%, and they finally exhibited the same blue emission as the crystalline aggregates. The as-deposited thin solid film was amorphous and it could be transformed to a transparent crystalline film upon treatment in the vapor of an ethanol/water (1:1 by volume) mixture, along with PL spectral blue shifting due to changing of aggregation order. It was also found that the crystalline film showed a blue-shifted absorption spectrum relative to the amorphous film and the shift of the absorption edge of the spectra could match that of corresponding PL spectra. The FT-IR spectrum of crystal powders of 1 displayed more vibration modes compared with that of amorphous powders, suggesting the existence of different pi-overlaps or different molecular conformations. The crystals of 1-methyl-1,2,3,4,5-pentaphenylsilole and hexaphenylsilole also showed blue-shifted PL emissions of their amorphous solids, with a comparable PL spectral shift of 1. Developing of a silole solution on a TLC plate readily brought about an amorphous thin layer. Our results suggest that crystalline films of AIE-active siloles are potential emissive layers for efficient blue OLEDs with stable color and long lifetime.     

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 .     

High-power blue/UV light-emitting diodes as excitation sources for sensitive detection

With advances in III-V nitride manufacturing processes, high-power light-emitting diode (LED) chips in the blue and UV wavelengths are now commercially available at reasonable cost and can be used as excitation sources in optical sensing. We describe the use of these high-power blue and UV LEDs for sensitive fluorescence detection, including chip-based flow cytometry, capillary electrophoresis (CE), and single-molecule imaging. By using a blue LED with a focusable power of approximately 40 mW as the excitation source for fluorescent beads, we demonstrate a simple chip-based bead sorter capable of enriching the concentration of green fluorescent beads from 63% to 95%. In CE experiments, we show that a mixture of analyte solution containing 30 nM 6-carboxyrhodamine 6G and 10 nM fluorescein can be separated and detected with excellent signal-to-noise ratio (approximately 17 for 10 nM fluorescein) using the collimated emission from a blue LED; the estimated mass detection limit was approximately 200 zmol for fluorescein. We also demonstrated ultrasensitive fluorescence imaging of single rhodamine 123 molecules and individual lambda-DNA molecules. At a small fraction of the cost of an Ar+ laser, high-power blue and UV LEDs are effective alternatives for lasers and arc lamps in fluorescence applications that demand portability, low cost, and convenience.     

螺旋藻蛋白色素的稳定性研究

本文考察了螺旋藻蛋白色素（SP）的干粉和溶液的稳定性。SP干粉在暗处和室内自然光下较稳定，直射光下稍差。SP溶液在PH6～7时色泽呈蓝色，Cu2+对其稳定性有破坏作用，EDTA和柠檬酸可增强SP溶液稳定性，而明胶对其无影响，山梨酸对SP溶液色泽有良好的保护作用，SP在10％乙醇溶液或50％甘油溶液中较稳定。     

BLUE AND WHITE LIGHT EFFECTS ON CHLOROPLAST DEVELOPMENT IN A SOYBEAN MUTANT

Phenotypic difference for chloroplast development between the normal green (CL1) and the Cy₉y₉ soybean mutant was observed when the plants were grown under 18W m^?2 white or blue light. Under these conditions the mutant soybean accumulated less Chi b, neoxanthin, carotene and less total pigment than the CL1 genotype. Chloroplasts of the Cy₉y₉ line were deficient in the LHP complex relative to that of chloroplasts from the normal soybean. Specific differences were noted between chloroplasts from plants grown under blue and white light. Accumulations of a 34 kD (PSII) and a 16–17 kD (PSI) membrane polypeptide were decreased by blue light in both soybean genotypes. Blue light induced a greater accumulation of a 32 kD (PSII) polypeptide than white light. Blue light reduced granal thylakoid stacking and increased the proportion of stroma thylakoids compared to those that developed under white light. PSI electron transport activity was stimulated by the blue light treatment more than that of PSII.     

Isolation of herbicidal compounds,quercetin and β-caryophyllene,from Digera muricata

Synthetic herbicides are available to control weeds but these herbicides have many concerns. Eco-friendly herbicides obtained from plants is a better alternative to synthetic ones. Despite that the herbicidal activity of Digera muricata extracts have been reported but there are no studies regarding the isolation and identification of herbicidal compounds from D. muricata. Herein, we are reporting the identification of two herbicidal compounds from chloroform extract obtained from D. muricata. The chloroform extract was initially tested on the germination and early growth of two weeds; Avena fatua and Melilotus indicus as well as wheat where a significant decline in % age germination and growth of both weeds was observed. Among the 8 different fractions obtained using different chromatographic techniques, fractions 2 and 7 were found to be phytotoxic to both test weeds. The herbicidal efficacy was tested at 200, 150, 100, 50, 25 μg/ml. These two fractions were further purified on Reversed Phase High Pressure Liquid Chromatography (RP-HPLC). Fraction 2 yielded 3 sub-fractions (2A, 2B & 2C), while fraction 7 yielded 2 sub-fractions (7A, 7B). Fraction 2B caused 43%, 53%, and 57% decline in seed germination, shoot dry weight, and root dry weight of A. fatua, while these values against M. indicus were 50%, 81% and 84%, respectively. Fraction 7A caused 25%, 36%, and 42% decline in seed germination, shoot dry weight, and root dry weight of A. fatua, while these values against M. indicus were 35%, 62% and 69%, respectively, at 200 μg/ml conc. Cyanazine caused 61% and 50% reduction in seed germination of A. fatua and M. indicus, respectively. The herbicidal effects of these two fractions were found nonsignificant against wheat. Fourier Transform Infrared Spectroscopy (FT-IR), elemental analysis (C,H) and Nuclear Magnetic Resonanace (NMR) analyses of these two fractions depicted the presence of quercetin (Fraction 2B) and β-caryophyllene (Fraction 7A). In post emergence bioassays, the isolated compounds caused significant decrease in the biomass of both weeds. Plasma membrane integrity assays revealed electrolyte leakage in treated leaf discs of both weeds. It was concluded that quercetin and β-caryophyllene isolated from D. muricata exhibited toxicity towards both test weeds without harming wheat.     

Subcellular and molecular localization of rare earth elements and structural characterization of yttrium bound chlorophyll a in naturally grown fern Dicranopteris dichotoma

A rare earth element (REE) hyperaccumulator, Dicranopteris dichotoma, sampled from an REE mining area in South-Jiangxi region, was chosen for analysis of 15 REEs at subcellular and molecular levels by inductively coupled plasma-mass spectrometry (ICP-MS). The sum of the concentrations of 15 REEs (∑REEs) of D. dichotoma leaf was about 0.1% dry mass. Results indicated that the ∑REEs of different subcellular fractions of D. dichotoma leaf were cell walls>organelles>the ‘soluble’ fraction (i.e., cytosol and vacuoles)>cell membranes. ICP-MS results also showed that REEs existed in chlorophylls and lutein, though REE concentrations in carotene and pheophytin were both lower than the procedural blank levels. The ∑REEs of crude lipopolysaccharide and Ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) obtained from D. dichotoma leaf were 1200 and 343 mg/kg, respectively. The extended X-ray absorption fine structure (EXAFS) study of D. dichotoma chlorophyll a indicated that yttrium was bound to the porphyrin ring of chlorophyll a, and one yttrium atom was surrounded by four nitrogen atoms with the average yttrium-nitrogen bond length being 0.236 nm. These data might be useful for understanding of the physiological role of REEs in hyperaccumulator D. dichotoma.     

UV-B-INDUCED INCREASE IN SPECIFIC LEAF WEIGHT OF CUCUMBER AS A CONSEQUENCE OF INCREASED STARCH CONTENT

Abstract Specific leaf weight (SLW), the ratio of leaf dry matter to area, often increases in plants exposed to elevated UV-B radiation (280–315 nm). Increased SLW can result from greater leaf thickness or increased leaf density ( e.g . accumulation of high density substances in cells). The basis for large increases in SLW was examined in the first and third leaves of cucumber differing in developmental stage at the start of UV treatment. Leaf 1 was approximately 50% fully expanded, while leaf 3 had just unfolded. It is shown here that up to 80% of the UV-generated change in SLW in leaf 1 was caused by accumulation of nonstructural carbohydrates, especially starch (increasing from 13 to 23% of total dry weight). Leaf 3 contained a much smaller proportion of nonstructural carbohydrates (less than 8%) and the effect on SLW was correspondingly less. As shown in the previous paper, UV-B inhibition of growth in leaf 3 was reversed by supplemental blue light (BL) in a fluence-dependent manner between 0.23 to 2.68 mol m ² perday. Fluence-response curves revealed that supplemental BL reversed both the UV-induced accumulation of starch and increase in SLW in leaf 1 over the same range. The data are consistent with a back-up of photosynthate into leaf 1 as a result of UV-B inhibition of growth in leaf 3. The data also demonstrate that increases in SLW cannot be assumed to represent increases in leaf thickness.     

RESEARCH NOTE

Abstract— The endogenous levels of indole-3-acetic acid (IAA), abscisic acid (ABA) and gibberellins (GA) were examined by gas chromatography-mass spectrometry in Prunus cerasus plantlets grown under different light conditions in relation to previous work on the photocontrol of stem elongation. The endogenous levels of free and conjugated IAA in the apical sections of red-grown shoots were about two-fold higher than those in the blue-treated plants, and these corresponded with maximum shoot elongation. By contrast, greater concentrations of ABA and GA were found in blue-grown plants compared to red with intermediate shoot growth. When blue was combined with red or far red, lower levels of IAA, ABA and GA correlated with less growth. These results suggest that the regulation of stem elongation by phytochrome and a blue-absorbing pigment may, at least in part, occur through a modulation of hormone levels.