Effect of light quality on the growth and proximal composition of <Emphasis Type="Italic">Amphora</Emphasis> sp.

We determined the effects of various light spectra (white, blue, green, yellow, and Grolux) on the growth rate, proximate composition, pigment content, and cell size of the marine benthic diatom Amphora sp. during two growth phases of batch cultures. The growth rate was higher under green light and lowest with Grolux and yellow light. Cell size differed significantly between growth phases but remained unaffected by light spectra; the smallest cells were observed on the initial day of culture, whereas larger cells developed in the stationary phase under Grolux treatment. The proximate composition was modified by the light spectra and growth phase. In the exponential growth phase, the protein content was higher with yellow and white light, and lipid content peaked with Grolux. The pigment content (chlorophyll a, carotenoids) was also higher under yellow light. In the stationary growth phase, we noted a higher carbohydrate content under Grolux and yellow light. Our results show that light spectra and growth phase influence the metabolism of Amphora sp., changing its proximate composition, pigment content, growth rate, and cell size.     

The combined effects of blue light and dilution rate on lipid class and fatty acid composition of <Emphasis Type="Italic">Tisochrysis lutea</Emphasis>

The lipid class and the fatty acid compositions of microalgae highly influence bivalve larval and post-larval development. Light is an essential environmental factor for microalgal culture, and quantity and quality of light may induce changes in the biochemical composition of the algae. The objective of this study was to investigate the effect of light spectrum (blue vs. white light) on lipid class and fatty acid compositions of Tisochrysis lutea cultured in a chemostat. Two different dilution rates (D) were assayed for each light spectrum: 0.2 and 0.7 day^?1. Triacylglycerol (TAG), sterol, and hydrocarbon (HC) content increased sharply at low D. The proportion of alkenones was significantly reduced under blue light. Polyunsaturated fatty acids (PUFA), and particularly n-3 PUFA, content in phospholipids (PL) increased under blue light compared to white light at low D. Thus, blue light raised 22:6(n-3) levels in total lipids of T. lutea at low D. The cultivation of T. lutea in a chemostat at low D under blue light may improve nutritional value as feed for bivalve larvae by modifying the PUFA profile, especially increasing 22:6(n-3).     

Effects of light intensity,light quality,and illumination period on cell growth,TFA accumulation,and DHA production in <Emphasis Type="Italic">Crypthecodinium</Emphasis> sp. SUN

Crypthecodinium strains are ideal candidates for DHA production. In a previous study, light was found to be efficient in inducing total fatty acid accumulation in Crypthecodinium sp. SUN. In order to further analyze the light-inducing behavior of this microalga, experiments were conducted to elucidate the influence of different light intensities, light qualities, and illumination periods on DHA production. The results showed that an irradiance of 30 μmol photons m^?2 s^?1 was most suitable for DHA production. Compared to red light and blue light, green light was more efficient in elevating the total fatty acid content in the cells. It was also found that illumination at the first 24 h promoted cell growth, whereas it favored total fatty acid accumulation only during 48–96 h. This is the first systematic investigation of the influence of light on total fatty acid accumulation and DHA production in Crypthecodinium sp. SUN, providing a solid foundation for further research on DHA production.     

Transition from exponential to linear photoautotrophic growth changes the physiology of <Emphasis Type="Italic">Synechocystis</Emphasis> sp. PCC 6803

Phototrophic microorganisms like cyanobacteria show growth curves in batch culture that differ from the corresponding growth curves of chemotrophic bacteria. Instead of the usual three phases, i.e., lag-, log-, and stationary phase, phototrophs display four distinct phases. The extra growth phase is a phase of linear, light-limited growth that follows the exponential phase and is often ignored as being different. Results of this study demonstrate marked growth phase-dependent alterations in the photophysiology of the cyanobacterium Synechocystis sp. PCC 6803 between cells harvested from the exponential and the linear growth phase. Notable differences are a gradual shift in the energy transfer of the light-harvesting phycobilisomes to the photosystems and a distinct change in the redox state of the plastoquinone pool. These differences will likely affect the result of physiological studies and the efficiency of product formation of Synechocystis in biotechnological applications. Our study also demonstrates that the length of the period of exponential growth can be extended by a gradually stronger incident light intensity that matches the increase of the cell density of the culture.     

<Emphasis Type="Italic">In vitro</Emphasis> culture of <Emphasis Type="Italic">Drynaria fortunei</Emphasis>, a fern species source of Chinese medicine “Gu-Sui-Bu”

This study reports spore germination, early gametophyte development and change in the reproductive phase of Drynaria fortunei, a medicinal fern, in response to changes in pH and light spectra. Germination of D. fortunei spores occurred on a wide range of pH from 3.7 to 9.7. The highest germination (63.3%) occurred on ½ strength Murashige and Skoog basal medium supplemented with 2% sucrose at pH 7.7 under white light condition. Among the different light spectra tested, red, far-red, blue, and white light resulted in 71.3, 42.3, 52.7, and 71.0% spore germination, respectively. There were no morphological differences among gametophytes grown under white and blue light. Elongated or filamentous but multiseriate gametophytes developed under red light, whereas under far-red light gametophytes grew as uniseriate filaments consisting of mostly elongated cells. Different light spectra influenced development of antheridia and archegonia in the gametophytes. Gametophytes gave rise to new gametophytes and developed antheridia and archegonia after they were transferred to culture flasks. After these gametophytes were transferred to plastic tray cells with potting mix of tree fern trunk fiber mix (TFTF mix) and peatmoss the highest number of sporophytes was found. Sporophytes grown in pots developed rhizomes.     

Light Quality Regulates Lateral Root Development in Tobacco Seedlings by Shifting Auxin Distributions

Light is an important environmental regulator of diverse growth and developmental processes in plants. However, the mechanisms by which light quality regulates root growth are poorly understood. We analyzed lateral root (LR) growth of tobacco seedlings in response to three kinds of light qualities (red, white, and blue). Primary (1°) LR number and secondary (2°) LR density were elevated under red light (on days 9 and 12 of treatment) in comparison with white and blue lights. Higher IAA concentrations measured in roots and lower in leaves of plants treated with red light suggest that red light accelerated auxin transport from the leaves to roots (in comparison with other light qualities). Corroborative evidence for this suggestion was provided by elevated DR5::GUS expression levels at the shoot/root junction and in the 2° LR region. Applications of N-1-naphthylphthalamic acid (NPA) to red light-treated seedlings reduced both 1° LR number and 2° LR density to levels similar to those measured under white light; DR5::GUS expression levels were also similar between these light qualities after NPA application. Results were similar following exogenous auxin (NAA) application to blue light-treated seedlings. Direct [³H]IAA transport measurement indicated that the polar auxin transport from shoot to root was increased by red light. Red light promoted PIN3 expression levels and blue light reduced PIN1, 3–4 expression levels in the shoot/root junction and in the root, indicating that these genes play key roles in auxin transport regulation by red and blue lights. Overall, our findings suggest that three kinds of light qualities regulate LR formation in tobacco seedlings through modification of auxin polar transport.     

Blue light reduces photosynthetic efficiency of cyanobacteria through an imbalance between photosystems I and II

Several studies have described that cyanobacteria use blue light less efficiently for photosynthesis than most eukaryotic phototrophs, but comprehensive studies of this phenomenon are lacking. Here, we study the effect of blue (450 nm), orange (625 nm), and red (660 nm) light on growth of the model cyanobacterium Synechocystis sp. PCC 6803, the green alga Chlorella sorokiniana and other cyanobacteria containing phycocyanin or phycoerythrin. Our results demonstrate that specific growth rates of the cyanobacteria were similar in orange and red light, but much lower in blue light. Conversely, specific growth rates of the green alga C. sorokiniana were similar in blue and red light, but lower in orange light. Oxygen production rates of Synechocystis sp. PCC 6803 were five-fold lower in blue than in orange and red light at low light intensities but approached the same saturation level in all three colors at high light intensities. Measurements of 77 K fluorescence emission demonstrated a lower ratio of photosystem I to photosystem II (PSI:PSII ratio) and relatively more phycobilisomes associated with PSII (state 1) in blue light than in orange and red light. These results support the hypothesis that blue light, which is not absorbed by phycobilisomes, creates an imbalance between the two photosystems of cyanobacteria with an energy excess at PSI and a deficiency at the PSII-side of the photosynthetic electron transfer chain. Our results help to explain why phycobilisome-containing cyanobacteria use blue light less efficiently than species with chlorophyll-based light-harvesting antennae such as Prochlorococcus, green algae and terrestrial plants.     

Influence of light colours on growth and stress response of pearl gourami <Emphasis Type="Italic">Trichopodus leerii</Emphasis> under laboratory conditions

This study aimed to investigate the influence of illumination with different light spectra on growth and stress response in pearl gourami Trichopodus leerii Bleeker, 1852. Fish (6.35 ± 0.43 cm, 5.69 ± 0.67 g) were reared in 8 glass aquaria each with 25 fish under one of four different lighting conditions: yellow (max 546 nm), red (max 605 nm), blue (max 470 nm) and white (control). Experiments lasted for 90 days. The stress response was evaluated by measuring cortisol levels. No significant effect was observed on final body weight, length and specific growth rate of fish. However, best values for these characteristics were achieved for fish reared under yellow light. A significant higher weight gain, condition factor was found in fish reared under yellow light compared with fish reared under blue or red light. In contrast, a lower final body weight, specific growth rate and weight gain were achieved for fish reared under red light. Feed conversion ratio was significantly lower in fish under yellow light compared with red or blue light. Stressed fish showed lower cortisol levels under yellow light compared with other light exposures. The study indicates that, pearl gourami grows better under yellow light and that yellow light lowers the stress-induced cortisol response.     

Modified light spectral conditions prior to cryopreservation alter growth characteristics and cryopreservation success of potato (<Emphasis Type="Italic">Solanum tuberosum</Emphasis> L.) shoot tips in vitro

Light is one of the most important factors affecting growth and morphogenesis of plants. Light intensity, photoperiod and spectral composition greatly affect morphogenetic responses of in vitro plants. Modification of light spectra during recovery after cryopreservation improves survival and regeneration, but the effect of modified light conditions prior to cryopreservation are not known. Therefore, the aim of the present study was to follow the photomorphogenetic response of potato plants (Solanum tuberosum L.) under different light qualities i.e. cool white fluorescent (CW) used as control, warm white (HQI), white LEDs (W), blue LEDs (B), red LEDs (R) and a combination of red with 10?% of blue LEDs (RB) prior to cryopreservation, affecting recovery of cultivars Agrie Dzeltenie, Bintje, Maret, Anti and Désirée in vitro. Light spectral quality had a significant effect on growth characteristics of potato plants in vitro. Red light (R) promoted elongation growth but biomass accumulation remained low under monochromatic light treatments. Some of the pre-cryopreservation light treatments significantly affected post-cryopreservation success. Under blue LEDs, high early recovery was observed for all cultivars tested, whereas under red (R) or (HQI), lowest survival percentages were obtained 2–4 weeks after thawing. Specifically, during early recovery, blue light increased survival from 26 to 66?%, 4 to 31?% and 16 to 48?% for cultivars Agrie Dzeltenie, Anti, and Désirée, compared to illumination by red LEDs. Therefore, light spectral quality prior to cryopreservation can significantly affect the cryopreservation success of potato shoot tips.     

Red light and carbon dioxide differentially affect growth,lipid production,and quality in the microalga, <Emphasis Type="Italic">Ettlia oleoabundans</Emphasis>

Ettlia oleoabundans, a freshwater unicellular green microalga, was grown under different light qualities ± carbon dioxide-enriched air to determine the combined effects on growth and lipid production of this oleaginous species. Keeping total light intensity constant, when a portion of the cool white was replaced by red, volumetric lipid yield increased 2.8-fold mainly due to the greater yield of oleic acid, a desirable biodiesel precursor. Only 30 min of red light treatment was sufficient to increase lipid yield and quality to the same level as cultures provided red light for >14 days, indicating the potential role of red light in stimulating lipid production of this species. Carbon dioxide enrichment via air sparging enhanced exponential growth, carbon conversion efficiency, and nutrient consumption. Together, these results showed that light quality plays an important role in microalgal lipid production. Adjustment in light quality and gas delivery efficiency with carbon dioxide enrichment improved lipid yield and quality in this and possibly other oleaginous algal species.     

Effect of light and natural ventilation systems on the growth parameters and carvacrol content in the in vitro cultures of <Emphasis Type="Italic">Plectranthus amboinicus</Emphasis> (Lour.) Spreng

The aim of the current study is to investigate the influence of light intensity, quality of light and alternative membrane sytems on the growth and headspace-GC/MS chemical analysis of Plectranthus amboinicus cultivated in vitro. Nodal segments were grown under light intensities (26, 51, 69, 94 and 130 µmol m^?2 s^?1) provided by cool-white fluorescent lamps. Apical segments were grown under light-emitting diodes blue; red; 1 blue/2.5 red; 2.5 blue/1 red; 1 blue/1 red and white fluorescent lamps. Apical and nodal segments were grown under alternative membrane and membrane-free systems. One, two or four PTFE membranes were used on the lid of the culture vessel. The membranes provided natural ventilation and worked as filters. The results have shown significant differences in the growth and carvacrol content, as well as in the content of carvacrol precursors (γ-terpinene and p-cymene) in different treatments. Among all tested light intensities, the significant increase in the dry weight and in the carvacrol content of plantlets derived from the nodal segments was recorded at 69 µmol m^?2 s^?1. The monochromatic red led to greater shoot length and higher dry weight in plantlets derived from the apical segments, as well as to carvacrol accumulation greater than that provided by the fluorescent lamps. The culture vessel enclosure by one and two membranes led to higher dry weight in plantlets derived from the apical and nodal segments, respectively. They also showed higher carvacrol content. Thus, it is possible optimizing the growth and carvacrol content in P. amboinicus cultivated in vitro by adjusting these environmental parameters.     

Effects of different LED sources on the growth and nitrogen metabolism of lettuce

Using a light-emitting diode (LED) as the light source, the effects of eight different light treatments [white light (control, W), purple light (P), blue light (B), red light (R), green light (G), yellow light (Y), red–blue light in a 9:1 ratio (9R/1B), and red–blue light in a 4:1 ratio (4R/1B)] on the growth, quality and nitrogen metabolism of lettuce were studied. The results showed that compared with the white light, the purple light, blue light, red light, and the red-blue light combination could all increase the biomass of the aboveground part of lettuce to various degrees, while green light and yellow light inhibited lettuce growth. Under blue light, the contents of soluble protein and flavonoid in lettuce were the highest; under red light, the soluble sugar content was the highest, while the contents of soluble protein, free amino acids, and vitamin C (VC) were relatively higher under the 4R/1B light condition. Compared with white light, the sources of purple, blue, and red lights as well as the red–blue light combination all significantly reduced nitrate accumulation in lettuce, and the activities of the nitrogen (N) metabolism-related enzymes such as nitrate reductase, nitrite reductase, glutamine synthetase, glutamate synthase, and glutamate dehydrogenase were increased to varying degrees. In contrast, the contents of nitrate and ammonium N were significantly accumulated in lettuce under green light, and the activities of relative enzymes were significantly reduced. Therefore, the purple light, blue light, and red–blue combination light sources could promote N assimilation and improve the aboveground biomass accumulation in lettuce by improving the activity of the N metabolism-related enzymes in lettuce. Particularly under the 4R/1B light source, the biomass, soluble protein, VC, and total amino acid content were rather high in lettuce, which indicated that the 4R/1B light source could better effectively improve the nutritional quality and promote the growth of lettuce, while yellow light and green light are not suitable to serve as direct sources in a plant factory. These results provide a certain theoretical basis for the regulation of the light environment in cultivation facilities.     

Fluorescence change of <Emphasis Type="Italic">Fusobacterium nucleatum</Emphasis> due to <Emphasis Type="Italic">Porphyromonas gingivalis</Emphasis>

The aim of this study was to measure changes in the fluorescence of Fusobacterium nucleatum interacting with Porphyromonas gingivalis for excitation with blue light at 405-nm. P. gingivalis was mono- and co-cultivated in close proximity with F. nucleatum. The fluorescence of the bacterial colonies was photographed using a QLF-D (Quantitative Light-induced Fluorescence-Digital) Biluminator camera system with a 405 nm light source and a specific filter. The red, green and blue intensities of fluorescence images were analyzed using the image analysis software. A fluorescence spectrometer was used to detect porphyrin synthesized by each bacterium. F. nucleatum, which emitted green fluorescence in single cultures, showed intense red fluorescence when it was grown in close proximity with P. gingivalis. F. nucleatum co-cultivated with P. gingivalis showed the same pattern of fluorescence peaks as for protoporphyrin IX in the red part of the spectrum. We conclude that the green fluorescence of F. nucleatum can change to red fluorescence in the presence of adjacent co-cultured with P. gingivalis, indicating that the fluorescence character of each bacterium might depend on the presence of other bacteria.     

Mammalian <Emphasis Type="Italic">CYP2E1</Emphasis> gene triggered changes of relative ions fluxes,CaM content and genes expression profiles in <Emphasis Type="Italic">Petunia hybrida</Emphasis> cells to enhance resistance to formaldehyde

The influence of light quality and cytokinin content in media on growth, development, photosynthetic pigments and secondary metabolite content of Myrtus communis L. was evaluated in an in vitro culture. Various treatments with light emitting diodes (LEDs): 100% blue (B), a mix of 70% red and 30% blue (RB) and 100% red were applied and compared with a traditional fluorescent lamp as control. Axillary shoots were incubated on Murashige and Skoog medium with 30 g dm^?3 sucrose, 0.5% BioAgar, 0.5 μM 1-naphthaleneacetic acid and different concentrations of 6-benzyladenine (BA): 1, 2.5 and 5 µM. Cultures were maintained for 6 weeks in 23/21?±?1 °C (day/night), 80% relative humidity and 16/8 h photoperiod; photosynthetic photon flux density (PPFD) was 35 µmol m^?2 s^?1 in all treatments. Light spectra and BA content in media affected biometrical and phytochemical M. communis properties. Red LEDs and 5 µM BA resulted in the highest multiplication rate. The highest shoots were obtained under red LEDs, but with the lowest concentration of cytokinin in media. Fresh weight was greatest on LEDs containing blue light in the spectrum (B and RB); moreover, 5 µM BA increased dry weight. Photosynthetic pigment levels were lower under LED light compared to control lamps. Phenolic acids and flavonoids were identified in M. communis leaf extracts. Myricetin was the major constituent with highest concentration under red LEDs and highest BA level.     

Internally illuminated photobioreactor using a novel type of light-emitting diode (LED) bar for cultivation of <Emphasis Type="Italic">Arthrospira platensis</Emphasis>

The biochemical properties of Spirulina platensis in an internally illuminated photobioreactor (IlPBR) were investigated under different light-emitted diode (LED) wavelengths; blue (λ_max= 450 and 460 nm), green (λ_max= 525 nm), red (λ_max = 630 and 660 nm), and white (6,500K), with various light intensities (200, 500, 1,000, and 2,000 μmol/m²/sec) were examined. The highest specific growth rate, maximum biomass, and phycocyanin productivity occurred under the red LEDs (0.39/day, 0.10 g/L/day, and 0.14 g/g-cell/day, respectively) at 1,000 μmol/m²/sec; the lowest growth rate was obtained under blue LEDs. Indeed, the size of trichomes was changed into short form under blue LEDs at all light intensities or all LEDs at 2,000 μmol/m²/sec for the first 2 days after inoculation, and S. platensis did not grow in the IlPBR under the dark condition. These results provide a base for different approaches for designing the pilot scale photobioreactor and developing cost-effective light sources.     

Growth Promotion of Vegetative Gametophytes of <Emphasis Type="Italic">Undaria pinnatifida</Emphasis> by Blue Light

Through an acclimation period of 10 days, compared to white light, the maximal net photosynthetic rates were significantly higher for gametophytes of Undaria pinnatifida cultivated under blue light (400–500 nm), and were lower under red light (600–700 nm). Chlorophyll c and the carotenoid content of gametophytes were similar under blue light and red light but were much lower under white light. The growth rate of female gametophytes under blue light was higher than that under other lights, and the growth rate of male gametophytes showed little variation with respect to blue and white light. Male and female gametophytes were mixed together to form sporophytes under white, blue and red light. After approximately 5 days, 50% gametophytes became fertile under blue and white light, but remained vegetative under red light after 10 days.     

光质对湛江等鞭金藻生长和脂肪酸组成的影响

在气升式光生物反应器中研究不同光质光影响湛江等鞭金藻的生长。结果表明,藻细胞密度的大小顺序为：红光〉白光＋红光、白光〉白光＋蓝光＋红光〉白光＋蓝光〉蓝光。蓝光下多不饱和脂肪酸百分含量最高,占总脂肪酸的50．01％。白光下总单不饱和脂肪酸和总饱和脂肪酸含量最高,占总脂肪酸的24．19％和27．46％。多不饱和脂肪酸中C18：4。．3含量最高,占总脂肪酸的20．3％-23.3％,最高值出现在蓝光下;其次为C22：6n-3（DHA）,占总脂肪酸的10．2％-12．3％,在蓝光和白光＋蓝光中较高;而C18：2n-6和C18：3n-3均以红光下的为最高,分别达3．11％和8．04％。     

THE EFFECT OF LIGHT QUALITY ON THE CARBON METABOLISM AND EXTRACELLULAR RELEASE OF CHLAMYDOMONAS REINHARDTII DANGEARD1

The influence of red, blue, green, and white light on growth and photosynthetic rates, carbon metabolism, and rates of release of extracellular compounds in the freshwater alga Chlamydomonas reinhardtii Dangeard was examined. Relative growth constants were 0.28, 0.32, 0.40, and 0.41 in green, white, blue, and red light, respectively. Photosynthetic rates were higher in white, blue, or red than in green light of the same intensity. More than 66% of the ¹⁴CO₂ assimilated by cells grown under blue or green light was incorporated into the ethanol-insoluble fraction, compared with about 50% in cells grown under white or red light. The percentage of sugars in this fraction was significantly higher in cells grown under green or red light than in cells cultured in white or blue light, while the percentage of proteins was highest in blue light. Light quality also influenced the composition of the ethanol-soluble fraction. The percentage of organic acids was highest in cells grown in green and white light, while amino acids were highest in blue and green cultures. The percentage of ethanol-soluble sugars was greatest in cultures grown in blue and red light. The percentage release of dissolved organic carbon into the medium was highest in white light and lowest in blue or red light. The nature of the extracellular products varied according to the quality of light under which the cells were cultured, but had no consistent relation to the nature or concentration or components in the ethanol-soluble fraction.