scholarly journals Relation between Changes in Photosynthetic Rate and Changes in Canopy Level Chlorophyll Fluorescence Generated by Light Excitation of Different Led Colours in Various Background Light

2019 ◽  
Vol 11 (4) ◽  
pp. 434 ◽  
Author(s):  
Linnéa Ahlman ◽  
Daniel Bånkestad ◽  
Torsten Wik
Keyword(s):  
Steady State ◽  
Light Quality ◽  
Incident Light ◽  
Red Light ◽  
Intensity Level ◽  
Potential Candidate ◽  
Light Emitting ◽  
Background Light ◽  
Light Regimes ◽  
The Difference

Using light emitting diodes (LEDs) for greenhouse illumination enables the use of automatic control, since both light quality and quantity can be tuned. Potential candidate signals when using biological feedback for light optimisation are steady-state chlorophyll a fluorescence gains at 740 nm, defined as the difference in steady-state fluorescence at 740 nm divided by the difference in incident light quanta caused by (a small) excitation of different LED colours. In this study, experiments were conducted under various background light (quality and quantity) to evaluate if these fluorescence gains change relative to each other. The light regimes investigated were intensities in the range 160–1000 μ mol   m − 2   s − 1 , and a spectral distribution ranging from 50% to 100% red light. No significant changes in the mutual relation of the fluorescence gains for the investigated LED colours (400, 420, 450, 530, 630 and 660 nm), could be observed when the background light quality was changed. However, changes were noticed as function of light quantity. When passing the photosynthesis saturate intensity level, no further changes in the mutual fluorescence gains could be observed.

scholarly journals The Role of Leaves in Photocontrol of Flower Bud Abscission in Hibiscus rosa-sinensis L. `Nairobi'

2000 ◽  
Vol 125 (1) ◽  
pp. 31-35 ◽  
Author(s):  
Uulke van Meeteren ◽  
Annie van Gelder
Keyword(s):  
Light Quality ◽  
Light Exposure ◽  
Red Light ◽  
Light Conditions ◽  
Flower Bud ◽  
Light Emitting ◽  
Hibiscus Rosa Sinensis ◽  
Number Of Leaves ◽  
Whole Plants

When compared with exposure to darkness, exposing Hibiscus rosa-sinensis L. `Nairobi' plants to red light (635 to 685 nm, 2.9 μmol·m-2·s-1) delayed flower bud abscission, while exposure to far-red light (705 to 755 nm, 1.7 μmol·m-2·s-1) accelerated this process. Flower bud abscission in response to light quality appears to be controlled partly by the presence of leaves. The delay of bud abscission was positively correlated to the number of leaves being exposed to red light. Excluding the flower buds from exposure to red or far-red light, while exposing the remaining parts of the plants to these light conditions, did not influence the effects of the light exposure on bud abscission. Exposing only the buds to red light by the use of red light-emitting diodes (0.8 μmol·m-2·s-1) did not prevent dark-induced flower bud abscission. Exposing the whole plants, darkness or far-red light could only induce flower bud abscission when leaves were present; bud abscission was totally absent when all leaves were removed. To prevent flower bud abscission, leaves had to be removed before, or at the start of, the far-red light treatment. These results suggest that in darkness or far-red light, a flower bud abscission-promoting signal from the leaves may be involved.

scholarly journals Growth and Bioactive Compound Synthesis in Cultivated Lettuce Subject to Light-quality Changes

HortScience ◽  
2017 ◽  
Vol 52 (4) ◽  
pp. 584-591 ◽  
Author(s):  
Ki-Ho Son ◽  
Jin-Hui Lee ◽  
Youngjae Oh ◽  
Daeil Kim ◽  
Myung-Min Oh ◽  
...  
Keyword(s):  
Blue Light ◽  
Bioactive Compounds ◽  
Light Quality ◽  
Red Light ◽  
Monochromatic Light ◽  
Bioactive Compound ◽  
Light Emitting ◽  
Compound Synthesis ◽  
Plant Factory ◽  
Ferulic Acids

This study aimed to determine the effect of changes in light quality on the improvement of growth and bioactive compound synthesis in red-leaf lettuce (Lactuca sativa L. ‘Sunmang’) grown in a plant factory with electrical lighting. Lettuce seedlings were subjected to 12 light treatments combining five lighting sources: red (R; 655 nm), blue (B; 456 nm), and different ratios of red and blue light combined with three light-emitting diodes [LEDs (R9B1, R8B2, and R6B4)]. Treatments were divided into control (continuous irradiation of each light source for 4 weeks), monochromatic (changing from R to B at 1, 2, or 3 weeks after the onset of the experiments), and combined (changing from R9B1 to R8B2 or R6B4 at 2 or 3 weeks after the onset of the experiments). Growth and photosynthetic rates of lettuce increased with increasing ratios of red light, whereas chlorophyll and antioxidant phenolic content decreased with increasing ratios of red light. Individual phenolic compounds, including chlorogenic, caffeic, chicoric, and ferulic acids, and kaempferol, showed a similar trend to that of total phenolics. Moreover, transcript levels of phenylalanine ammonia-lyase (PAL) and chalcone synthase (CHS) genes were rapidly upregulated by changing light quality from red to blue. Although the concentration of bioactive compounds in lettuce leaves enhanced with blue light, their contents per lettuce plant were more directly affected by red light, suggesting that biomass as well as bioactive compounds’ accumulation should be considered to enhance phytochemical production. In addition, results suggested that growth and antioxidant phenolic compound synthesis were more sensitive to monochromatic light than to combined light variations. In conclusion, the adjustment of light quality at a specific growth stage should be considered as a strategic tool for improving crop yield, nutritional quality, or both in a plant factory with electrical lighting.

scholarly journals Luminescence properties of novel red-emitting phosphor InNb1-xPxO4:Eu3+ for white light emitting-diodes

2015 ◽  
Vol 33 (2) ◽  
pp. 331-334 ◽  
Author(s):  
An Tang ◽  
Tao Ma ◽  
Liduo Gu ◽  
Yongtao Zhao ◽  
Junhui Zhang ◽  
...  
Keyword(s):  
White Light ◽  
Luminescence Intensity ◽  
Light Emitting Diodes ◽  
Red Light ◽  
Emission Spectra ◽  
Luminescence Properties ◽  
Potential Candidate ◽  
Light Emitting ◽  
Near Ultraviolet ◽  
White Light Emitting Diodes

AbstractInNb1-xPxO4:Eu3+ red phosphors were synthesized by solid-state reaction and their luminescence properties were also studied through photoluminescence spectra. The excitation and emission spectra make it clear that the as-prepared phosphors can be effectively excited by near-ultraviolet (UV) 394 nm light and blue 466 nm light to emit strong red light located at 612 nm, due to the Eu3+ transition of 5D0 → 7F2. The luminescence intensity is dependent on phosphorus content, and it achieves the maximum at x = 0.4. Excessive phosphorus in the phosphors can result in reduction of luminescence intensity owing to concentration quenching.With the increasing content of phosphorus, the phosphors are prone to emit pure red light. This shows that the InNb1.6P0.4O4:0.04Eu3+ phosphor may be a potential candidate as a red component for white light emitting-diodes.

scholarly journals Analysis on light quantity and quality based on diverse cloud conditions

2014 ◽  
Vol XL-7 ◽  
pp. 203-208
Author(s):  
M. Yamashita ◽  
M. Yoshimura
Keyword(s):  
Cloud Cover ◽  
Light Quality ◽  
Incident Light ◽  
Ground Surface ◽  
Light Environment ◽  
The Sun ◽  
Spectral Components ◽  
Light Quantity ◽  
The Difference ◽  
Light Components

Photosynthetic active radiation (PAR) is the source of incident light energy for the photosynthetic activity of plants. PAR additionally characterizes the light environment on the surface of the Earth. The light environment is an important factor for estimating quantities such as carbon exchange and the productivities of forests and agriculture. The incident PAR on the ground surface has the characteristics of light quantity consists of direct and diffuse components, and of light quality consists of spectral components such blue, green and red lights. These light quantity and quality are also important light environmental factors in the photosynthetic activities of plants under the natural environment. However, the light environment including direct and diffuse components and spectral components is easily affected by cloud conditions especially cloud cover and its movements. <br><br> In this paper, we focus on the characteristics of the light quantity and quality under diverse cloud conditions, and analyse the observational data, which are the global- and diffuse- spectral irradiances from 400 to 700 nm with quantum and energy units and the cloud conditions derived from whole-sky images taken during summer in Kyoto city. <br><br> As for the comparisons with light quality and cloud conditions, we use the Normalized Difference PAR Spectral Index (NDPSI) which shows the difference of red- and blue-light components and we use cloud cover and the Sun appearance ratio derived from the wholesky images to define the cloud conditions. <br><br> As the results of these analyses, we confirmed that there are the clear relationships between cloud cover and diffuse ratio, between the Sun appearance ratio and the normalized global PAR as the light quantity, between cloud cover and NDPSI in diffuse component, and between the Sun appearance ratio and NDPSI in direct component as the light quality.

scholarly journals Growth of Impatiens, Petunia, Salvia, and Tomato Seedlings under Blue, Green, and Red Light-emitting Diodes

HortScience ◽  
2014 ◽  
Vol 49 (6) ◽  
pp. 734-740 ◽  
Author(s):  
Heidi Marie Wollaeger ◽  
Erik S. Runkle
Keyword(s):  
Light Quality ◽  
Light Emitting Diode ◽  
Red Light ◽  
Morphological Characteristics ◽  
Photon Flux ◽  
Fluorescent Light ◽  
Flower Bud ◽  
Specialty Crops ◽  
Light Emitting ◽  
Shoot Weight

Plant growth and architecture are regulated in part by light quality. We performed experiments to better understand how young plants acclimate to blue (B), green (G), and red (R) light and how those responses can be used to produce plants with desirable morphological characteristics. We grew seedlings of impatiens (Impatiens walleriana), salvia (Salvia splendens), petunia (Petunia ×hybrida), and tomato (Solanum lycopersicum) under six sole-source light-emitting diode (LED) treatments or one cool-white fluorescent treatment that each delivered a photosynthetic photon flux (PPF) of 160 µmol·m−2·s–1 for 18 h·d−1. Leaf number was similar among treatments, but plants grown under 25% or greater B light were 41% to 57% shorter than those under only R light. Plants under R light had 47% to 130% greater leaf area and 48% to 112% greater fresh shoot weight than plants grown under treatments with 25% or greater B. Plants grown under only R had a fresh shoot weight similar to that of those grown under fluorescent light for all species except tomato. In impatiens, flower bud number at harvest generally increased with B light, whereas in tomato, the number of leaflets with intumescences decreased with B light. This research discusses how light quality can be manipulated for desired growth characteristics of young plants, which is important in the production of specialty crops such as ornamentals, herbs, and microgreens.

ANALYSE DER PHOTOSYNTHESE MIT BLITZLICHT

1964 ◽  
Vol 19 (8) ◽  
pp. 693-707 ◽  
Author(s):  
B. Rumberg ◽  
H. T. Witt
Keyword(s):  
Chlorophyll A ◽  
Red Light ◽  
Difference Spectrum ◽  
Reaction Scheme ◽  
Back Reaction ◽  
Absorption Bands ◽  
Light Reaction ◽  
Background Light ◽  
Light Product ◽  
The Difference

The primary reactions of photosynthesis are fast reactions. To get detailed informations we developed three different methods. 1. sensitive flash photometry 38, 2. periodically chemical relaxation51, 26a, 3. manometry in flashing light groups 26b. With the method of flash photometry fast absorption changes in suspensions of chlorella and spinach chloroplasts were studied. 7 different types of absorption changes have been separated and analysed (Fig. 2). Older results 28-49lead to a reaction scheme published in l. c. 13. This scheme was refined (s. Fig. 3) by results published in l. c. 14-26. In the following 6 papers these investigations are described in detail and supplement by new results.Separation of the difference-spectrum of chlorophyll-al (P 700) in 5 ways. Under “normal” conditions (exciting Hill - active chloroplasts with blue light between 380 and 480 mμ or with red light between 620 and 720 mµ) mixed changes of absorption can be observed between 400 and 800 mµ (Fig. 4, this difference-spectrum does not include the changes with τ<10-3 sec, s. Fig. 2). Out of this overall difference-spectrum one component with changes of absorption at 430 and 703 mμ could be separated by using the following different systems: a) aged chloroplasts reactivated by addition of reduced DPIP or reduced PMS (ascorbate in excess) (Fig. 5), b) plastoquinone-extracted chloroplasts [extraction with petroleumether] (Fig. 6), c) digitonin-treated chloroplasts reactivated by addition of reduced PMS [ascorbate in excess] (Fig. 7), d) chloroplasts at -150°C with addition of reduced PMS [ascorbate in excess] (Fig. 8), e) chloroplasts under the influence of far-red background-light [728 mµ] (Fig. 9).Kinetics. During the flash the absorption at 430 and 703 mµ decreases very fast (<10-5 sec). In the dark the back reaction takes place in ≈10-2 sec at 20°C (s. Fig. 10). This reaction time is always observable in the presents of far redbackground light λ>700 mμ. (The detecting light at 703 mµ can act already as far red background light.) At very low itensities of far red background light the backreaction takes place however in <10-4 sec (details s. l. c. 25a).Identification of chlorophyll-al. The upper results (5 equal spectra under different conditions) suggest that the changes of absorption at 430 and 703 mμ are caused by one substance. This was additionally proved by comparing the magnitude and the kinetic of both changes in reactivated aged or digitonin-treated chloroplasts under different conditions. The ratio of the amplitudes and the halflifes are identical at 430 and 703 mµ at different values of pH (Fig. 11 and Fig. 12) and also at different concentrations of added reduced PMS (Fig. 13). Decreases of absorption just within the two absorption bands of chlorophyll-a indicate that very probably a chlorophyll-a (Chl-aI-430-703) is in action. From the magnitude of the changes of absorption at 703 mμ it follows, that Chl-al has a concentration of 0,1% of the bulk of chlorophyll.Oxidation of Chl-ai. The decreases of absorption indicate an oxidation of Chl-al in the light. This is proved by the fact, that in aged or digitonin-treated chloroplasts reduced PMS can be directly coupled to the light product. This is demonstrated by the strong acceleration of the back reaction with increasing concentrations of reduced PMS (Fig. 13 and Fig. 15) and by the demonstration of a first order back reaction (Fig. 14 and Fig. 15). The experimental results are theoretically explained. It is proved, that the light product Chl-aI⨁ reacts with PMSH⊖ [compare measuring points and theoretical curve in Fig. 12] [s. scheme (1)]. From the measurements it follows a reaction constant of 1,5·107 l/Mol·sec (Fig. 15) and an energy of activation of 3,8 kcal/Mol (Fig. 16) for the reaction of Chl-aI⨁ with PMSH⊖.Chl-aI-oxidation as a primary act. The fact, that Chl-ai⊕ is built up within <10-5 sec (20°C) [Fig. 10] and that Chl-aI⨂ could be trapped at -150°C (Fig. 8 and Fig. 17) give evidence, that this oxidation is a primary act. The electron acceptor of Chl-ai is called Ζ. Ζ⊖ reduces via intermediary products TPN. Under the reported conditions a - e one light reaction cycle (I) of the overall electron transport system of photosynthesis has been isolated [s. scheme (1) and (2)].

Bright and persistent green and red light-emitting fine fibers: A potential candidate for smart textiles

2020 ◽  
pp. 117760
Author(s):  
Raul Barbosa ◽  
Santosh K. Gupta ◽  
Bhupendra B. Srivastava ◽  
Alexa Villarreal ◽  
Heriberto De Leon ◽  
...  
Keyword(s):  
Red Light ◽  
Potential Candidate ◽  
Smart Textiles ◽  
Light Emitting

scholarly journals Effect of light quality and quantity on productivity and phycoerythrin concentration in the cryptophyte Rhodomonas sp.

2021 ◽  
Author(s):  
Christos Latsos ◽  
Jasper van Houcke ◽  
Lander Blommaert ◽  
Gabrielle P. Verbeeke ◽  
Jacco Kromkamp ◽  
...  
Keyword(s):  
Light Quality ◽  
Incident Light ◽  
Red Light ◽  
Green Light ◽  
Dry Weight ◽  
Continuous Illumination ◽  
Light Illumination ◽  
Initial Growth ◽  
Light Conditions ◽  
Significant Difference

AbstractThe cryptophyte Rhodomonas sp. is a potential feed source for aquaculture live feed and resource for phycoerythrin (PE) production. This research investigates the influence of light, both quality and quantity, on the biomass productivity, composition and growth rate of Rhodomonas sp. The incident light intensity used in the experiments was 50 μmolphotons m−2 s−1, irrespective of the colour of the light, and cultivation took place in lab-scale flat-panel photobioreactors in turbidostat mode. The highest productivity in volumetric biomass (0.20 gdry weight L−1 day−1), measured under continuous illumination, was observed under green light conditions. Blue and red light illumination resulted in lower productivities, 0.11 gdry weight L−1 day−1 and 0.02 g L−1 day−1 respectively. The differences in production are ascribed to increased absorption of green and blue wavelength by phycoerythrin, chlorophyll and carotenoids, causing higher photosynthetically usable radiation (PUR) from equal photosynthetically absorbed irradiance (PAR). Moreover, phycoerythrin concentration (281.16 mg gDW−1) was stimulated under red light illumination. Because photosystem II (PSII) absorbs poorly red light, the algae had to induce more pigments in order to negate the lower absorption per unit pigment of the incident available photons. The results of this study indicate that green light can be used in the initial growth of Rhodomonas sp. to produce more biomass and, at a later stage, red light could be implemented to stimulate the synthesis of PE. Fourier-transform infrared spectroscopy (FTIR) analysis demonstrated a significant difference between the cells under different light quality, with higher contents of proteins for samples of Rhodomonas sp. cultivated under green light conditions. In comparison, higher carbohydrate contents were observed for cells that were grown under red and blue light.

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