Browsing by Subject "LED"

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  • Reichel, Philipp; Munz, Sebastian; Hartung, Jens; Prager, Achim; Kotiranta, Stiina; Burgel, Lisa; Schober, Torsten; Graeff-Honninger, Simone (2021)
    Cannabis is one of the oldest cultivated plants, but plant breeding and cultivation are restricted by country specific regulations. Plant growth, morphology and metabolism can be manipulated by changing light quality and intensity. Three morphologically different strains were grown under three different light spectra with three real light repetitions. Light dispersion was included into the statistical evaluation. The light spectra considered had an influence on the morphology of the plant, especially the height. Here, the shade avoidance induced by the lower R:FR ratio under the ceramic metal halide lamp (CHD) was of particular interest. The sugar leaves seemed to be of elementary importance in the last growth phase for yield composition. Furthermore, the last four weeks of flowering were crucial to influence the yield composition of Cannabis sativa L. through light spectra. The dry flower yield was significantly higher under both LED treatments compared to the conventional CHD light source. Our results indicate that the plant morphology can be artificially manipulated by the choice of light treatment to create shorter plants with more lateral branches which seem to be beneficial for yield development. Furthermore, the choice of cultivar has to be taken into account when interpreting results of light studies, as Cannabis sativa L. subspecies and thus bred strains highly differ in their phenotypic characteristics.
  • Solala, Kari (Helsingfors universitet, 2009)
    The literature review of this thesis deals with light, different light sources and their properties. LED (Light Emitting Diode) light was specially taken into consideration, because the use of LED lights will increase in general illumination. The literature review also deals with the quality changes of dairy products and potatoes caused by exposure to light. The aim of this study was to search for such a spectral distribution of light which would cause only minor changes in the sensory quality of milk and the surface colour of potatoes. Objective was to also find out if there is a difference between the effects of fluorescent light and LED light on the quality of milk and greening of potatoes. Reduced (1,5 %) fat milk and new potatoes were used as testing materials. The milk in commercial carton board packages was exposed to six different light sources: white fluorescent lamp, white LED and LED of four different colours. The potatoes packed in transparent LDPE (Low Density Poly Ethylene) bags were stored under five different light sources: white fluorescent lamp, white LED and LED of three different colours. The light intensity at the surface of the packages was about 1000 lx in both studies. In the milk study, the effects of light were evaluated with a sensory method using descriptive analysis. In the potato study, the light effects were analysed with colour measurements (avalue) using a spectrophotometer and with surface temperature measurements using a laser thermometer. Sensory evaluation of milk there resulted in few statistically significant differences in the intensity of the attributes between the milks stored under different light sources. Light exposure caused a rapid greening of potatoes in every illumination. According to colour change percentage, the greening order under different lights was: white LED < yellow LED < green LED < turquoise LED < fluorescent light. The potatoes which were stored in dark had no change in their surface colour. The surface temperature of potatoes increased most under white LED and turquoise LED lights. A spectral distribution of light which would have caused less changes in sensory quality of milk than commonly used fluorescent light was not found in this study. The results showed, however, that in addition to blue light which has always been considered the most harmful for milk the red light also caused remarkable quality changes. Based on the results of this study, it could be suggested that under the LED lights the quality of packed milk retained its quality characteristics at least as well as under the fluorescent light. There were differences between the effects of different lights on the greening of potatoes. White and yellow LED light caused less greening of potatoes than the other lights. The strongest greening of potatoes was observed under the fluorescent light.
  • Kauste, Krista (Helsingfors universitet, 2012)
    The aim of this study was to compare warm white LED and High Pressure Sodium (HPS) -lamps in the greenhouse cultivation of lettuce. Two experiments were carried out in which lettuce growth and external quality was observed, the effect of lamps on leaf temperature was measured and the electricity consumption of LED- and HPS-lamps was compared. First experiment carried out with iceberg lettuce (´Frillice`) and second experiment with red oakleaf lettuce (´Rouxai´). In the second experiment, the effect of light treatment on the color of leaves was also investigated. The presence of tipburn was another measurement of external quality in both experiments. LED-lamp with DLC-sensor (Dynamic Light Control), which was designed to optimize the illumination according to the existing natural light, was also included in the experiments. Light quality or observed differences in temperatures or relative humidity did not significantly affect the fresh weight or external quality of ice berg lettuce. Oakleaf lettuces grown under LED-light were much smaller and they had more tipburn symptoms compared to HPS-treatment. No significant differences were found in the anthocyaninlevels of oakleaf lettuce grown under different lightning treatments. LED -lighting consumed about 22% less electricity than HPS-lamp in both experiments. However, energy efficiency of HPS- and LED-lamps cannot be directly compared, since HPS-lamps illuminated larger area than the LED- luminaires. DLCsensor was able to adjust illumination according to natural light and to reduce energy consumption, but it did not increase fresh weight accumulation in relation to power consumption compared to LED-luminaire without DLC.
  • Åman, Olli (Helsingfors universitet, 2014)
    Plant cells in plant cell cultures can be used for production of secondary metabolites and recombinant proteins. Producing the desired compounds can be problematic since cells grow slowly, yields can be low and sometimes plant cells do not produce the desired compounds. Yields can be increased by various methods, of which optimisation of growth conditions to favour growth and secondary metabolite biosynthesis is one of various strategies. Light quality is known to have an impact on growth of plants and on accumulation of secondary metabolites. Plants receive information of their environment with photoreceptors, which gives plants ability to alter their morphology and biochemistry to adapt to the prevailing conditions. One of the most important factors involved in controlling morphology and metabolism is activity of bZIP protein HY5, which levels are controlled by degradation by E3 ubiquitin ligase COP1. The photoreceptors are divided to three main groups. A group of Blue/UV-A photoreceptors consists of cryptochromes and phototropins. Phytochromes are photochrome photoreceptors of wavebands of red and far-red. UVR8 photoreceptors are specialized to sense UV-B wavebands. Activated photoreceptors reduce the activity of COP1 individually or inductively. Plant cells contain the same genetic information as intact plants. Object of this study is to investigate effects of different light spectra on plant cell mass pigment accumulation, lipid content and accumulation of secondary metabolites. Additionally, the obtained results can be utilized in designing new artificial light sources to enhance growth and nutritional value of horticultured plants grown under artificial light. VTT's callus cultures established from berries of Rubus (raspberry, cloudberry, arctic bramble) and Vaccinium (lingonberry, bilberry, cranberry) were used in this study. The cell cultures were grown in hormone balanced solid media. For this research Valoya provided four different LED light sources with different spectra, ranging between wavebands 400–800 nm. All berry callus cultures were grown for continuous period of 28–31 days under different light sources. Mass pigments, lipid composition, total phenolic concentration and anthocyanins were analysed from each cell cultures which received different light treatments. Samples were pooled and were by freeze dried and milled. Mass pigments were extracted with acetone and analysis was carried out with UPLC-DAD. Extraction of lipids was carried out with petroleum ether followed with transesterification of glycerolipids and silylation of free fatty acids. The lipid extracts were analysed with GC-MS. Phenolic compounds were extracted with methanol and the extracts were treated with Folin-Ciocalteu's reagent and then analysed with spectrophotometer. Anthocyanins were extracted with acidified methanol and a portion of the extracts were hydrolysed to qualify anthocyanidin moieties of anthocyanins. The extracts and the hydrolysed extract were analysed with UPLC-DAD. Analysis of volatile compounds from each light treated samples was carried out with SPME GC-MS. The obtained results were used to compare concentration differences of the analytes under different light treatments. Correlations between the concentrations of the analytes and different wavebands were possible to establish from the results. Activation of cryptochromes and phytochromes reduced certain lipids that are precursors in LOX-pathway which indicates to increased activity of the pathway. Same wavebands which activated the photoreceptors reduced accumulation of mass pigments, whereas, wavebands of far-red increased the concentrations of mass pigments. In some cases it was observed that small difference in light spectra reduced mass pigment accumulation significantly. The plant cell cultures produced mainly anthocyanins which anthocyanidin moieties were same as in intact plants. Cryptochrome and phytochrome activation increased accumulation of anthocyanins. Yields of anthocyanins can be increased significantly with certain spectra significantly. The effect of light spectra did not have as straightforward effect on total phenolic content. Specie- and linewise differences were observed in light conditions where the highest concentrations of total phenolics were obtained.
  • Kotiranta, Stiina (Helsingfors universitet, 2014)
    Plant growth and morphology can be manipulated with light. Previously light manipulation experiments were mostly conducted by modifying the solar spectrum with light absorbing filters. Today, research can be conducted with modern LED lighting techniques, which enables specific spectrum tailoring. Light can be tailored specifically for a species or a family, and the needs of the farmer can also be taken into consideration. In this study, tomato (Solanum lycopersicum L. cv ’Efialto’) seedlings were grown under six different spectra. Plant morphology, stomatal function and drought tolerance were measured. Growth measurements included stem height, plant fresh and dry weight, leaf -area and leaf number. In addition, the effect of light quality on leaf morphology was studied by measuring leaf blade and petiole length. All measurements were conducted on well-watered and water-stressed plants, in order to study the effect of drought on vegetative growth and drought tolerance. Stomata conductance was studied by measuring leaf temperature prior to and during water stress. Leaf surface temperature indicates transpiration rate; thus the higher the conductance the lower leaf temperature. In addition to leaf temperature measurements, photosynthesis and stomatal conductance were measured by leaf level infra-red gas analysis. R:FR ratio was the dominant factor for affecting plant morphology. However, the B:G ratio also played a key role; when the B:G ratio was low, it further enhanced the elongation growth, a response caused by low R:FR ratio. Irradiance in green and yellow wavebands regulated stomatal closure. During water stress, the light treatment with the highest green irradiance, induced more rapid stomatal closure which was evident as increased leaf temperature and decreased gas exchange. Light-depenedent stomatal closure and decreased transpiration could explain the improved performance of these seedlings during the drought period. Light spectral quality thus affected the drought tolerance of tomato plants through its effects on plant morphology and stomata function.