Combination Of Light Intensity Research Articles

Foliar Phenotypic Plasticity Reflects Adaptation to Environmental Variability.

Arabidopsis thaliana ecotypes adapted to native habitats with different daylengths, temperatures, and precipitation were grown experimentally under seven combinations of light intensity and leaf temperature to assess their acclimatory phenotypic plasticity in foliar structure and function. There were no differences among ecotypes when plants developed under moderate conditions of 400 µmol photons m-2 s-1 and 25 °C. However, in response to more extreme light or temperature regimes, ecotypes that evolved in habitats with pronounced differences in either the magnitude of changes in daylength or temperature or in precipitation level exhibited pronounced adjustments in photosynthesis and transpiration, as well as anatomical traits supporting these functions. Specifically, when grown under extremes of light intensity (100 versus 1000 µmol photons m-2 s-1) or temperature (8 °C versus 35 °C), ecotypes from sites with the greatest range of daylengths and temperature over the growing season exhibited the greatest differences in functional and structural features related to photosynthesis (light- and CO2-saturated capacity of oxygen evolution, leaf dry mass per area or thickness, phloem cells per minor vein, and water-use efficiency of CO2 uptake). On the other hand, the ecotype from the habitat with the lowest precipitation showed the greatest plasticity in features related to water transport and loss (vein density, ratio of water to sugar conduits in foliar minor veins, and transpiration rate). Despite these differences, common structure-function relationships existed across all ecotypes and growth conditions, with significant positive, linear correlations (i) between photosynthetic capacity (ranging from 10 to 110 µmol O2 m-2 s-1) and leaf dry mass per area (from 10 to 75 g m-2), leaf thickness (from 170 to 500 µm), and carbohydrate-export infrastructure (from 6 to 14 sieve elements per minor vein, from 2.5 to 8 µm2 cross-sectional area per sieve element, and from 16 to 82 µm2 cross-sectional area of sieve elements per minor vein); (ii) between transpiration rate (from 1 to 17 mmol H2O m-2 s-1) and water-transport infrastructure (from 3.5 to 8 tracheary elements per minor vein, from 13.5 to 28 µm2 cross-sectional area per tracheary element, and from 55 to 200 µm2 cross-sectional area of tracheary elements per minor vein); (iii) between the ratio of transpirational water loss to CO2 fixation (from 0.2 to 0.7 mol H2O to mmol-1 CO2) and the ratio of water to sugar conduits in minor veins (from 0.4 to 1.1 tracheary to sieve elements, from 4 to 6 µm2 cross-sectional area of tracheary to sieve elements, and from 2 to 6 µm2 cross-sectional area of tracheary elements to sieve elements per minor vein); (iv) between sugar conduits and sugar-loading cells; and (v) between water conducting and sugar conducting cells. Additionally, the proportion of water conduits to sugar conduits was greater for all ecotypes grown experimentally under warm-to-hot versus cold temperature. Thus, developmental acclimation to the growth environment included ecotype-dependent foliar structural and functional adjustments resulting in multiple common structural and functional relationships.

Effects of Led Light Intensity and Carbon Dioxide Concentration on the Growth of Spinach (Spinacia oleracea L.) in a Plant Factory

This research aimed to investigate the effects of light intensity and the carbon dioxide (CO2) concentration on spinach’s growth during vegetative stage in plant factory (PF). Two experiments were conducted with different CO2 concentration in closed chamber (500 ppm and 800 ppm). In each experiment, plants were hydroponically grown under three light intensities of 115, 140 and 160 µmol.m-2s-1. Growth’s parameters were determined at different growth stages (T30, T37 and T44 respectively to 30, 37 and 44 days after sowing). ANOVA analysis and non-parametric Kruskal analysis of variance were used to evaluate the statistical significance of the treatment effects. The results showed that, before 30 days old, the increase of light intensity was not significantly effected to the growth of plant. During later growing periods (30 days old afterward), the increase of light intensity remarkably boost up yield’s related traits such as leaf number, fresh mass and dry mass under 500ppm CO2 concentration. The combination of light intensity and CO2concentration at 800ppm showed the plant growth indicators increased significantly at the T37 and T44 stages (after 30 days old), especially at the last week of growth period, fresh weight and dry weight of plants were significantly different at the light treatment L2, increased 37% and 57.6%, respectively as compared to light treament only. The results suggested that, during latest growing period, the average light intensity of 140 µmol.m-2s-1combining with elevating CO2 concentration is an alternatively way to enhance spinach growth. The findings of this study could be helpful for growers to improve growing conditions for a better development of spinach in the indoor farming (PF)

Optimization of light intensity and color temperature in the cultivation of Chlorella vulgaris culture using the Surface Response Method

Microalgae have an important role as a source of biomass in producing energy. One type of microalgae that has the potential to be developed is Chlorella vulgaris. Several factors that affect the growth and biomass production of Chlorella vulgaris microalgae are color temperature and light intensity because they play an important role in the photosynthesis process. This study aims to influence the effect of light and color temperature and optimize these parameters using Response Surface Methodology (RSM). Two independent variables were varied: light intensity 200, 400, 600, 800, 1000 lux and color temperature 3000, 4000, 5000, and 6000 K. The results showed that the average value of Chlorella vulgaris growth was higher along with higher light intensity. At a color temperature of 4000 K, the highest biomass yield and the most negligible biomass production were found at 6000 K. At a color temperature of 4000 K, it is feasible to apply it as an alternative lighting source in the production of Chlorella vulgaris. The combination of light intensity and color temperature shows that the specific growth rate and doubling time have opposite trends where high values produce low values and vice versa. Growth in dark conditions, the specific growth rate was 0.0026 day-1, and the optimal light intensity at 600 lux treatment. ANOVA evaluation showed that color temperature greatly affected growth. Based on the optimization, the optimal specific growth rate of 00751day-1 with the conditions of light intensity and color temperature of 556 lux and 4152 K, respectively.

Morphological and Physiological Responses of Cucumber Seedlings to Different Combinations of Light Intensity and Photoperiod with the Same Daily Light Integral

Lighting strategies for morphological and physiological characteristics of horticultural crops often focus on the proper daily light integral (DLI); however, a suitable combination of photosynthetic photon flux density (PPFD) and photoperiod at the same DLI is conducive to optimize the light environment management in vegetable seedling production. In the present study, cucumber seedlings (Cucumis sativus L. cv. Tianjiao No. 5) were grown for 21 days under six different combinations of PPFD and photoperiod at a constant DLI of 11.5 mol⋅m−2⋅d−1, corresponding to a photoperiod of 7, 10, 13, 16, 19, and 22 h⋅d−1 provided by white light-emitting diodes (LEDs) under a controlled environment. Results showed that plant height, hypocotyl length, and specific leaf area of cucumber seedlings decreased quadratically with increasing photoperiod, and the opposite trend was observed in seedling quality index of cucumber seedlings. In general, pigment content and fresh and dry weight of cucumber seedlings increased as photoperiod increased from 7 to 16 h⋅d−1, and no significant differences were found in fresh and dry weight of shoot and root as photoperiod increased from 16 to 22 h⋅d−1. Sucrose and starch content of cucumber leaves increased by 50.6% and 32.3%, respectively, as photoperiod extended from 7 to 16 h⋅d−1. A longer photoperiod also led to higher cellulose content of cucumber seedlings, thus improving the mechanical strength of cucumber seedlings for transplanting. CsCesA1 relative expression level showed a trend similar to cellulose content. We propose that CsCesA1 is the key gene in the response to cellulose biosynthesis in cucumber seedlings grown under different combinations of PPFD and photoperiod. In summary, prolonging the photoperiod and lowering PPFD at the same DLI increased the quality of cucumber seedlings. An adaptive lighting strategy could be applied to increase seedling quality associated with the reduction of capital cost in cucumber seedling production.

Temperature Rise at the Pulp-Dentin Junction for a Multi-Layered Composite Restoration using the Finite Element Method

Objectives: During the light-curing process of composite restoration, excessive heat can be produced, which can potentially lead to pulp necrosis (death). In this study, we aimed, based on the Finite Element Method (FEM), to assess the risk of pulp damage during the light-curing process by investigating the influence of light-curing devices, under various irradiation regimes, on the temperature increase at the pulp-dentin junction, during a one-layer or multi-layered deep composite restoration. Methods: A Three-dimensional finite element method model of typical geometry and material properties, as commonly reported in the literature, was employed in COMSOL Multiphysics simulations in order to determine the temperature increase in the pulp. Various combinations of light intensities, durations, and irradiation regimes were investigated for the two cases, of shallow and deep multi-layered composite restoration. Results: Results of light-curing composite resins within enamel; indicate that the temperature rise during the curing process was within the safety margins. Results of light-curing composite resin restorations closer to the pulp with thin remaining dentin, indicate a temperature increase that could be sufficient to cause thermal injury in the pulp. Modulating the light output marginally, reduced the temperature rise while reducing the intensity and increasing the curing duration which was consistently more effective in this respect. Conclusion: The results clearly demonstrate that with currently adopted standard procedures, there exists a risk of thermal injury during multi-layered composite restorations with thin remaining dentin; it is thus important to establish appropriate curing regimes that would lead to minimal temperature increase during deep composite restorations and hence reduce the risk of thermal injury to the pulp.

Plant Factories Are Heating Up: Hunting for the Best Combination of Light Intensity, Air Temperature and Root-Zone Temperature in Lettuce Production.

This study analyzed interactions among photon flux density (PPFD), air temperature, root-zone temperature for growth of lettuce with non-limiting water, nutrient, and CO2 concentration. We measured growth parameters in 48 combinations of a PPFD of 200, 400, and 750 μmol m–2 s–1 (16 h daylength), with air and root-zone temperatures of 20, 24, 28, and 32°C. Lettuce (Lactuca sativa cv. Batavia Othilie) was grown for four cycles (29 days after transplanting). Eight combinations with low root-zone (20 and 24°C), high air temperature (28 and 32°C) and high PPFD (400 and 750 μmol m–2 s–1) resulted in an excessive incidence of tip-burn and were not included in further analysis. Dry mass increased with increasing photon flux to a PPFD of 750 μmol m–2 s–1. The photon conversion efficiency (both dry and fresh weight) decreased with increasing photon flux: 29, 27, and 21 g FW shoot and 1.01, 0.87, and 0.76 g DW shoot per mol incident light at 200, 400, and 750 μmol m–2 s–1, respectively, averaged over all temperature combinations, following a concurrent decrease in specific leaf area (SLA). The highest efficiency was achieved at 200 μmol m–2 s–1, 24°C air temperature and 28°C root-zone temperature: 44 g FW and 1.23 g DW per mol incident light. The effect of air temperature on fresh yield was linked to all leaf expansion processes. SLA, shoot mass allocation and water content of leaves showed the same trend for air temperature with a maximum around 24°C. The effect of root temperature was less prominent with an optimum around 28°C in nearly all conditions. With this combination of temperatures, market size (fresh weight shoot = 250 g) was achieved in 26, 20, and 18 days, at 200, 400, and 750 μmol m–2 s–1, respectively, with a corresponding shoot dry matter content of 2.6, 3.8, and 4.2%. In conclusion, three factors determine the “optimal” PPFD: capital and operational costs of light intensity vs the value of reducing cropping time, and the market value of higher dry matter contents.

Effects of light intensity and co-inoculation of arbuscular mycorrhizal fungi and rhizobium on root growth and nodulation of Indigofera tinctoria

<p class="Default"><em>Indigofera tinctoria</em> is a legume that is cultivated as a source of natural indigo dyes. As a legume, <em>Indigofera tinctoria</em> is capable of symbiosis with soil microbes. This study evaluates the effects of light intensity and microbial inoculation on root growth and nodulation. The study used a complete randomized block design with a split-plot pattern. Light intensity was the main plot with four levels of light intensity 100%, 50%, 25%, and 10%. Microbial inoculation was a subplot with four levels without inoculation, mycorrhizae inoculation, rhizobium inoculation, and double inoculation with both mycorrhizae and rhizobium. The results obtained show that light intensity and microbial inoculation affected root length, root fresh weight, root biomass, and the number of nodules. 50% light intensity was optimum for root length, while 100% light intensity was optimum for root fresh weight, root biomass, and a number of nodules. Root growth and nodulation were further increased with double inoculation. The combination of light intensity and microbial inoculation affected root biomass and nodulation. The combination of 100% light intensity and double inoculation resulted in the highest root biomass and nodule numbers. Mycorrhizae and rhizobium have a synergistic relationship to nodulation and root growth. Double inoculation with mycorrhizae and rhizobium efficiently increased root biomass and the number of nodules under low or high light intensity.</p>

Chlorella Vulgaris Surface-Mount Photobioreactor with Vision-Based Growth Signature Prediction Optimized by Electromagnetism-Like Mechanism

ndustrial waste disrupts the natural production of microalgae cultures. Cultivation of microalgae in a controlled environment highly results to biomass with lower contamination necessary as high-valued economic product. In response to the emerging challenges of sustainable energy production, the integration of computational intelligence and biosystems engineering is considered as an open research area. In this study, Chlorella vulgaris microalgae were cultivated in BG-11 growth medium on three customized surface-mount light bioreactors that are equipped with digital camera for growth monitoring in terms of accumulated biomass surface area and color reflectance intensity via IoT. Feature-based machine learning models predicted microalgae growth area in terms of water temperature, pH level and turbidity, and light intensity. Microalgae cultures were exposed to combinations of white artificial light source of 2000 ± 1000 lux and water temperature of 27 ± 5°C using Peltier plate to discriminate biomass growth within a 30-day cultivation period. A total of nine environmental conditions were employed to clearly discriminate the impacts of environmental stressors to microalgae growth. Combined neighborhood component analysis and ReliefF was used to select high impact color features of C, Ye, M, H, and S with biomass area. Electromagnetism-like mechanism optimized-RBNN bested RNN and generalized processing regression with R2 of 0.985 and RMSE of 6.262. There is also considerable growth in biomass surface area for certain combinations of light intensity and water temperature (2125 ± 625 lux and 28.75 ± 3.25°C), and turbidity and water pH concentrations (3.85 ± 0.15 NTU and 8.025 ± 0.775). However, the photobioreactor with 27°C and 2000 lux exposure is considered having the exact optimum controlled environment condition in cultivating Chlorella vulgaris based on the generated growth in biomass surface area of 38.314%. This developed intelligent system is scalable for seamless microalgae production of any strands for renewable energy resource.

Light Intensity and Biofertilizers Effect on Natural Indigo Production and Nutrient Uptake of Indigofera tinctoria L.

This research investigated the effect of light intensity and biofertilizer on the yield, which includes the production of indigo compounds and plant nutrient uptake. The study used a randomized complete block design with a split plot design with 4 levels of light intensity as the main plots and 4 levels of biofertilizer as a sub plots with 3 replications. The combination of light intensity and biofertilizer affects fresh weight, biomass and tissue nitrogen. The highest fresh weight and biomass was found at 100% light intensity with double inoculation of mycorrhizae and rhizobium. Whereas the highest tissue nitrogen was at 10% light intensity with double inoculation of mycorrhizae and rhizobium. The production of indigo affected by light intensity, ie at 10% light intensity indicates the highest indigo. Mycorrhizae and rhizobium have a synergistic relationship as biofertilizer in increasing plant yields and nutrient uptakes in 100% light intensity.

Effects of Light on Secondary Metabolites in Selected Leafy Greens: A Review.

In contrast to the primary metabolism, responsible for essential synthesis mechanisms and mass balance in plants, the secondary metabolism is not of particular importance for each cell but for the plant organism as its whole. Most of these metabolites show antioxidant properties and are beneficial for human health. In order to affect accumulation of those metabolites, light is an essential factor. It is possible to select various combinations of light intensity and light quality to address corresponding photoreceptors and synthesis. However, the plethora of additional variables considering environmental conditions such as temperature, relative humidity or cultivation method complicate defining specific “light recipes”. This review summarizes experiments dealing with consumable leafy greens such as lettuce or basil and the enhancement of three selected metabolites – anthocyanins, carotenoids and flavonols.

Nutritional quality, mineral and antioxidant content in lettuce affected by interaction of light intensity and nutrient solution concentration

Light and nutrient are important factors for vegetable production in plant factory or greenhouse. The total 12 treatments which contained the combination of four light intensity (150, 250, 350 and 450 μmol · m−2 · s−1) and three nutrient solution concentration (NSC) (1/4, 1/2, 3/4 strength NSC) were established for investigation of lettuce growth and quality in a growth chamber. The combination of light intensity and NSC exhibited significant effects on photosynthetic pigment, nutritional quality, mineral content and antioxidant capacity. That a higher light intensity were readily accessible to higher chlorophyll a/b showed in lettuce of treatment of 350 μmol · m−2 · s−1 × 3/4NSC and 450 μmol · m−2 · s−1 × 1/4NSC. Lower total N contents, higher content of soluble protein, vitamin C, soluble sugar and free amino acid exhibited in lettuce under treatment of 250 and 350 μmol · m−2 · s−1 × 1/4NSC or 3/4NSC. With increasing NSC and LED irradiance, the content of total P and K in lettuce increased and decreased, respectively. The highest and lowest total Ca content were found in treatment of 150 μmol · m−2 · s−1 × 1/4NSC and 450 μmol · m−2 · s−1 × 1/4NSC, respectively, and higher content of total Mg and Zn was observed under 250 μmol m−2 s−1 × 1/4NSC and 150 μmol · m−2 · s−1 × 3/4NSC, respectively. The antioxidant contents generally decreased with increasing NSC level. The higher antioxidant content and capacity occurred in lettuce of 350 μmol · m−2 · s−1 × 1/4NSC treatment. The interaction of 350 μmol · m−2 · s−1 × 1/4NSC might be the optimal condition for lettuce growth in plant factory.

Immobile Rhodobium Marinum for Enhancing Hydrogen Excitation: Optimization of Environmental Factors [light intensity, pH and agitation

Optimization of an environmental factor (pH, light intensity and agitation) for Hydrogen gas production using immobilized bacteria photosynthetic of Rhodobium marinum through facultative-photo-fermentation was studied. The experiment was conducted by using CRD (completely random design) to understand the effect of each selected parameter and their combination. The result shows that the combination of light intensity, pH and agitation were significantly affected the hydrogen production. Further data analyses gave information that light intensity and pH treatments were regulating the substrate consumption, i.e. accelerating the glucose digestion, which was, enhance the hydrogen gas production. The highest production of hydrogen gas from the experiment was in the range of 1055 - 1200 mL/L, at glucose, contain 10 g/L in the substrate. The optimizations of the photo-fermentation adaptive processes for bioproduction hydrogen gas are a necessary step to find the optimum condition of hydrogen rate and yield, in a certain period. Hydrogen gas is one of the powerful energy carriers that easy to be converting into energy form dailies such as electricity, fuel, heat or storage battery.

Effects of light intensity and plant growth regulators on callus proliferation and shoot regeneration in the ornamental succulent Haworthia

BackgroundHaworthia are desert succulents belonging to the Asphodelaceae family. Haworthia species are cultivated commercially as ornamentals and some rare species are quite valuable at retail market but growth slowly and difficult to propagation. However, an efficient micropropagation protocol was remained insufficient.ResultsThe organogenic cultures obtained from inflorescence explants were cultured on Murashige and Skoog (MS) medium supplemented with various combinations of 6-benzylaminopurine (BA) and α-naphthalene acetic acid (NAA) under a light intensity of 10 μmol m−2 s−1 or 45 μmol m−2 s−1. The highest callus proliferation index (93.15%) with 1.0 mg L−1 BA + 0.1 mg L−1 NAA under a light intensity of 10 μmol m−2 s−1. The best shoot proliferation rates were on media with either 1 mg L−1 BA + 0–0.4 mg L−1 NAA (65.57–81.01%) under a light intensity of 45 μmol m−2 s−1. The highest root length (15.57 mm) and the highest rooting frequency (17 roots per shoot) were obtained when adventitious shoots were inoculated on MS medium with 0.4 mg L−1 NAA + 0.4 mg L−1 IBA. The survival rate of the transplanted plantlets was about 100%. The efficient micropropagation protocol proliferated Haworthia regenerate plants from inflorescence within 11 weeks.ConclusionsThe present study determined the best combination of light intensity and plant growth regulators (PGRs) for improved organogenesis of Haworthia during propagation by tissue culture. This optimized protocol showed light intensity is an important factor for efficient callus or shoot regeneration. These results indicate that it will be useful to optimize the light conditions for future commercial cultivation, germplasm conservation, genetic engineering and molecular biology research of this ornamental plant.

Effects of cyclin-dependent kinase activity on the coordination of growth and the cell cycle in green algae at different temperatures.

The progression of the cell cycle in green algae dividing by multiple fission is, under otherwise unlimited conditions, affected by the growth rate, set by a combination of light intensity and temperature. In this study, we compared the cell cycle characteristics of Desmodesmus quadricauda at 20 °C or 30 °C and upon shifts between these two temperatures. The duration of the cell cycle in cells grown under continuous illumination at 20 °C was more than double that at 30 °C, suggesting that it was set directly by the growth rate. Similarly, the amounts of DNA, RNA, and bulk protein content per cell at 20 °C were approximately double those of cells grown at the higher temperature. For the shift experiments, cells grown at either 20 °C or 30 °C were transferred to darkness to prevent further growth, and then cultivated at the same or the other temperature. Upon transfer to the lower temperature, fewer nuclei and daughter cells were produced, and not all cells were able to finish the cell cycle by division, remaining multinuclear. Correspondingly, cells placed in the dark at the higher temperature divided faster into more daughter cells than the control cells. These differences correlated with shifts in the preceding cyclin-dependent kinase activity, suggesting that cell cycle progression was not related to growth rate or cell biomass but correlated with cyclin-dependent kinase activity.

Variations of dominant free-floating Ulva species in the source area for the world’s largest macroalgal blooms, China: Differences of ecological tolerance

Species composition and seasonal variations of free-floating Ulva species were investigated in the source area of the world’s largest macroalgal blooms during 2009–2015. Based on a combination of a morphological analysis and sequences of nuclear-encoded ITS and 5S rDNA spacer regions, the dominant species in the free-floating Ulva community at the early stage of green tides were Ulva compressa, Ulva flexuosa, and Ulva linza. The first appearance of Ulva prolifera on the sea surface was in mid-May and it dominated the floating Ulva community in June from 2009 to 2011. From 2012–2015, U. prolifera was not only the first species to appear on the sea surface but also the dominant species during the whole early stage of green tides. To explain the successional mechanism, the effects of environmental factors on the growth of four Ulva species were examined in the laboratory under different combinations of light intensity and temperature. It was found that the highest growth rate of U. prolifera was 44.9%/d, which was much higher than the other three Ulva species. The strong tolerance of U. prolifera to extreme conditions also helps it survive and bloom in the Yellow Sea.

Interaction effects of light intensity and nitrogen concentration on growth, photosynthetic characteristics and quality of lettuce (Lactuca sativa L. Var. youmaicai)

Light intensity and nitrogen concentration of nutrient solution are considered crucial for the contents of vitamin C and nitrate in cultivated leaf vegetables. We here investigated the effects of various combinations of light intensity (60, 140 and 220μmolm−2s−1) and nitrogen concentration (7, 15 and 23mmolL−1) of the solution on the growth, photosynthetic characteristics, vitamin C and nitrate content of lettuce. Our results demonstrate that the lettuce had the largest dry biomass at the high illumination of 220μmolm−2s−1 and low nitrogen of 7mmolL−1. The higher light and low nitrogen also contributed to the accumulation of vitamin C and decrease of nitrate in lettuce leaves. The effect of nitrogen supply on chlorophyll concentrations was more efficient under low light than high illumination. Our results reveal that there was an obvious interaction between light intensity and nitrogen available for the photosynthesis, yield and quality of lettuce. This study provides valuable insights into the combinational regulation of light intensity and nitrogen supply for improving growth and nutritional quality of vegetables grown in greenhouse and plant factory.

Correlation between Strawberry (Fragaria ananassa Duch.) Productivity and Photosynthesis-Related Parameters under Various Growth Conditions.

In the present study, we investigated changes in chlorophyll fluorescence, photosynthetic parameters and fruit yields, as well as fruit phytochemical accumulation of strawberry (Fragaria ananassa Duch.) that had been cultivated in a greenhouse under different combinations of light intensity and temperature. In plants grown with low light (LL) photosystem II chlorophyll fluorescence was found to increase as compared with those grown under high light (HL). When strawberry plants were grown with temperature higher than 5°C in addition to LL, they showed decrease in non-photochemical quenching (NPQ), photochemical quenching (qP), as well as chlorophyll fluorescence decrease ratio (RFd) when compared with other combinations of light and temperature. Moreover, fruit yield of strawberry was closely correlated with chlorophyll fluorescence-related parameters such as NPQ, qP, and RFd, but not with the maximum efficiency of PS II (Fv/Fm). Although plant groups grown under different combinations of light and temperature showed almost comparable levels of photosynthesis rates (Pr) when irradiated with low-intensity light, they displayed clear differences when measured with higher irradiances. Plants grown under HL with temperature above 10°C showed the highest Pr, in contrast to the plants grown under LL with temperature above 5°C. When the stomatal conductance and the transpiration rate were measured, plants of each treatment showed clear differences even when analyzed with lower irradiances. We also found that fruit production during winter season was more strongly influenced by growth temperature than light intensity. We suggest that fruit productivity of strawberry is closely associated with chlorophyll fluorescence and photosynthesis-related parameters during cultivation under different regimes of temperature and light.

UMG n-type Cz-silicon: Influencing Factors of the Light-induced Degradation and its Suitability for PV Production

Due to boron being present in compensated n-type silicon, minority carrier lifetime degrades under illumination. Lifetime reduction by light-induced degradation up to a factor of 16 was observed for illumination with 100 mW/cm2. In contrast to p-type, the degradation process in n-type does not follow a simple exponential trend. So this degradation process is time dependently investigated in this contribution. It is known that this process depends on a combination of light intensity and sample temperature, hence degradation is investigated independently and a separation of the influences was possible: a relation between light intensity and saturation value of normalized Cz defect concentration Nt*, and between sample temperature during illumination and defect generation rate will be presented. Furthermore it is shown that due to degradation the diffusion length of compensated n-type silicon in the degraded state is as low as in degraded p-type silicon. Finally it is shown that solar cells made from a compensated n-type crystal suffer from efficiency degradation.

Reduction of open circuit voltage loss in a polymer photovoltaic cell via interfacial molecular design: Insertion of a molecular spacer

Loss to the open circuit voltage (Voc) in organic photovoltaic cells is a critical bottleneck to achieving high power conversion efficiency. We demonstrate that the insertion of multilayers of a poly(phenylene ethynylene) spacer into the planar heterojunction between poly(3-hexylthiophene) and phenyl-C61-butyric acid methyl ester incrementally escalates the Voc of a polymer solar cell from 0.43 V to 0.9 V. Through a combination of light intensity and temperature dependent measurements, we show that this control over the molecular structure local to the interface increases Voc by raising the polaron pair energy and by suppressing the dark-diode current.

Migratory Responses of Benthic Diatoms to Light and Temperature Monitored by Chlorophyll Fluorescence

As an important adaptation for survival in the sediments of intertidal flats, benthic diatoms move up and down in response to a wide range of environmental stimuli. We investigated the vertical migration of two diatoms—Cylindrotheca closterium (Agradh) Kutzing (B-25) and Nitzschia sp. (B-3)—under different combinations of light intensity and temperature conditions. An imaging pulse amplitude modulated (PAM) fluorometer was used to measure the minimum fluorescence (F0) in order to monitor variations in diatom biomass in surface sediments. Rapid light curves (RLCs) were applied to assess their photosynthetic activities. Both species had increased motility under higher temperatures, with the longer valved C. closterium being twice as fast as the shorter valved Nitzschia sp. The former was also influenced by exposure to light intensities of 100 or 250 μmol m−2 s−1, whereas the latter was not. Consequently, no light/temperature interaction effect was associated with the vertical migration of Nitzschia sp., perhaps because of its lower photosynthetic capacity and smaller cell size. Therefore, we conclude that motile benthic diatoms exhibit species-specific responses to light and temperature due to differences in their photosynthetic capability and morphological characteristics.