Daily Light Research Articles

Daily rhythms of locomotor activity and transcript levels of non-visual opsins in the brain of the blind Mexican cavefish (Astyanax mexicanus)

Most organisms possess endogenous circadian clocks that synchronise their physiology and behaviour with environmental cycles, with the light-dark (LD) cycle being the most potent synchronising signal. Consequently, it can be hypothesised that animals that have evolved in the dark, as in caves or deep sea, may no longer possess a functional light-entrained biological clock. In this research, the blind cavefish Astyanax mexicanus was selected as a model organism to investigate the potential effects of daily light conditions on the circadian timekeeping mechanisms. First, we focused on describing behavioural photic entrainment and the presence of a circadian endogenous rhythmicity by recording locomotor activity rhythms under different lighting regimes: LD 12:12, after a 6-h shift of LD, constant darkness (DD), and constant dim light (LLdim). Secondly, we aimed at characterising the mechanisms of photodetection by analysing the daily rhythms of expression of selected non-visual extraocular opsins (exo-rhod, opn3, rgra, rgrb, tmt1a and tmt1b) in the brain of this blind species using real-time quantitative PCR. Our results revealed that blind Mexican cavefish activity rhythms were entrained to the LD cycle, with a diurnal activity pattern that persisted in a circadian fashion under constant lighting conditions. Additionally, statistically significant daily variations and/or rhythms were observed in three out of the six non-visual opsin genes analysed (opn3, rgra and tmt1b), all of them displaying nocturnal acrophases. These findings suggest that daily rhythms in extraretinal non-visual opsins may be transducing daily photic cycles and contributing to the entrainment of locomotor activity and other light-synchronised rhythms in blind cavefish species.

Hyperspectral Imaging Reveals Differential Carotenoid and Chlorophyll Temporal Dynamics and Spatial Patterns in Scots Pine Under Water Stress.

Drought-related die-off events have been observed throughout Europe in Scots pine (Pinus sylvestris L.). Such events are exacerbated by carbon starvation that is, an imbalance of photosynthetic productivity and resource usage. Recent evidence suggests that optically measurable photosynthetic pigments such as chlorophylls and carotenoids respond to water stress (WS). However, there is a lack of measurements using imaging spectroscopy, and the mechanisms linking xanthophyll-related changes in reflectance captured by the photochemical reflectance index (PRI) and chlorophyll changes in red edge position (REP) to WS are not understood. To probe this, we conducted a greenhouse experiment where 3-year-old Pinus sylvestris saplings were subjected to water limitation and followed using hyperspectral imaging (HSI) spectroscopy, water status and photosynthetic measurements. Carotenoids (e.g., xanthophyll cycle) and chlorophylls responded to WS, which was observed using the HSI-derived indices PRI and REP respectively. The spatial-temporal response in these two pigment-reflectance groupings differed. The spatial distribution of PRI represented the light intensity around the time of the measurement, whereas REP reflected the daily averaged light intensity over the experimental course. A further difference was noted upon rewatering, where the carotenoid-related PRI partially recovered but the chlorophyll-related REP did not.

Duration of Light Exposure Using White Light-Emitting Diode (LED) on the Performance of White Oyster Mushroom (Pleurotus ostreatus L.)

Background: In the dynamic world of mushroom cultivation, optimizing growth conditions is paramount for maximizing yield and quality. This research sought to evaluate the influence of varying hours of exposure to white light through light-emitting diodes (LED) on growth and yield performance of white oyster mushroom (Pleurotus ostreatus L.). Its aim was to determine the most effective light exposure duration for enhancing mushroom growth and yield. Research Design: Using a completely randomized design (CRD), the study used four treatments: 8 hours of lighting (T1), 12 hours of lighting (T2), 16 hours of lighting (T3), and a control group that received natural light (T4). The study was conducted in Palayamanan (8° 27’ 5.3118" N and 126° 9’ 59.7739" E) area at North Eastern Mindanao State University’s -Tagbina Campus from July 2023 to November 2023. Results: Results from the study provided interesting insights into the indirect nature of the relationship between light exposure and mushroom development. The findings of the study indicate that the duration of light exposure significantly affects the growth and yield of white oyster mushrooms. Both mycelium growth (29.80 days) and fruiting body formation (7.83 days), as well as harvesting time (10.87 days), were improved by 12 hours of lighting, while the control group consistently showed poor performance. Conclusion: Based from the analysis, it is evident that 12 hours of lighting consistently performed very well, with the exception of a minor under-performance in the case of yield per harvest, suggesting that 12 hours might be the ideal duration. Hence, 16 hours of lighting also demonstrated some advantages in certain variables, indicating potential for further study.

The Effect of LED Lighting Durations on Growth, Yield and Quality of Mustard (Brassica juncea L.) under Greenhouse Condition

Light-emitting diodes (LEDs) show promise as a radiation source for intensive crop cultivation systems, especially for vegetables in the greenhouse. Regarding mustard greens, most studies have investigated the effects of LED lights at the seedling stage under chamber conditions for microgreens not addressed throughout their growing period up to harvest. Therefore, this study is focused to evaluate the effect of additional LED lighting time from 6 pm on the growth, yield and quality of mustard greens under a greenhouse in Kien Giang province as a typical tropical region. The experiment was arranged in a completely randomized design with 3 replications, from August 1st to September 18th, 2023. Four treatments: AL0, AL2, AL4 and AL6 correspond to lighting durations of 0, 2, 4 and 6 h of LED light, which includes a combination of 3 white lights: 1 pink light, 58 μmol·m−2·s−1 PPFD, and a Blue (18 %): Green (41 %): Red (41 %) ratio. Results showed that AL4 had the most significant positive impact on mustard plant growth, with higher dry and fresh weight, plant height, leaf width and length. However, AL6 inhibited most parameters except leaf number. Additionally, under AL4 conditions, mustard allocated more biomass to leaves, while those under AL6 conditions allocated more biomass to stems. In terms of quality, LED lighting duration negatively influenced protein content. For instance, AL0 showed the significantly greatest protein value (2.87 ± 0.08 g·kg−1) compared to others. Apart from AL0, AL6 had a considerably higher value of protein content (2.58 ± 0.2 g·kg−1) compared to AL2 (1.74 ± 0.04 g·kg−1) and AL4 (2.17 ± 0.07 g·kg−1). The additional durations of LED lighting influenced mature mustard greens’ morphology, physiology and quality, providing valuable scientific information for improving vegetable quality and quantity in tropical zones. HIGHLIGHTS 4 hours of additional LED light had the most significant positive impact on mustard plant growth, with higher dry and fresh weight, plant height, leaf width, and length. Additionally, leaf number increased under 6 hours of additional LED light. Under 4 hours of additional LED light, mustard allocated more biomass to leaves, while those under 6 hours of additional LED light allocated more biomass to stems. Lighting with LED resulted in a lower protein value, and different durations of LED lighting resulted in varying protein content values. GRAPHICAL ABSTRACT

Daily Light Integral and Far-Red Radiation Influence Morphology and Quality of Liners and Subsequent Flowering and Development of Petunia in Controlled Greenhouses

Petunia stands as the top-selling bedding plant in the U.S., and improved lighting control in greenhouses holds the potential to reduce crop production time and optimize crop quality. This study investigated the impact of four distinct daily light integral (DLI) conditions with and without supplemental far-red (FR) radiation on the growth of petunia liners and subsequent development of finish plants. Two experiments were conducted in spring (9 April to 18 June 2021) and winter (28 October 2021 to 6 January 2022). Petunia cuttings were rooted in a common environment and then transferred to four greenhouse sections with different DLI treatments: 6, 9, 12, and 15 mol·m−2·d−1 for four weeks. Within each DLI condition, half of the plants were exposed to 28 μmol·m−2·s−1 supplemental FR radiation for 16 h daily (equivalent to 1.61 mol·m−2·d−1 light integral). The number of flower buds and open flowers were tracked daily. Representative liners were destructively harvested and evaluated after four weeks of lighting treatments. The remaining plants were transplanted and moved to a common DLI condition of 15 mol·m−2·d−1 for an additional three weeks before being destructively harvested and evaluated as finish plants. The primary finding reveals the promoting effect of DLI on flowering, branching, morphology, and biomass accumulation of petunia liners, with many effects persisting into the finish stage. A threshold DLI of 9 mol·m−2·d−1 was identified, as lower DLI (6 mol·m−2·d−1) resulted in extensive stem elongation, rendering the plants unmarketable. Higher DLI levels were found to be optimal in terms of flowering and morphology. Supplemental FR accelerated flowering by up to three days in the summer experiment and up to 12 days in the winter experiment. However, FR had limited impact on the number of flower buds and open flowers, branching, and shoot and root weight of the finish plants. Interactions between DLI and FR were observed on some parameters, whereby FR effects were more pronounced under lower DLI. Overall, both higher DLI and supplemental FR exhibited beneficial effects, but DLI had a more pronounced effect. Thus, DLI during petunia liner production appears more important than adding FR. This study well simulated the commercial propagation and production of petunia plants, providing practical insights for decision-making regarding lighting strategies.

Trait component analysis of lettuce in response to daily light integrals at two growth stages

AbstractLittle is known about the relative impact of lighting duration and light intensity on lettuce production, as well as whether daily light integrals (DLIs) play a significant role during different plant growth stages. Four DLIs were tested: 8.64, 11.52, 12.96, and 17.28 mol m−2 day−1 as supplemental lighting, which were obtained from a combination of supplemental light intensities at 200 and 300 µmol m−2 day−1 for 12 and 16 h. Sunlight was used as control. A direct correlation was observed between DLIs and yield, total fresh weight, and total dry weight. Under supplemental lighting, relative growth rate (RGR) increased due to an increase in net assimilation rate (NAR) rather than in leaf area ratio (LAR). Plants in the seedling stage were more sensitive to an elevation in DLI than in the head stage. This was confirmed by a greater increase in NAR compared to their corresponding control under the same DLI. Increasing DLI also improved lettuce quality via reducing nitrate and increasing protein content. Higher DLIs (12.96 and 17.28 mol m−2 day−1) led to a decrease in maximum quantum yield of photosystem II and an increase in performance index. In conclusion, manipulating RGR through NAR adjustments proved to be more effective than changes in LAR, and adjusting supplemental DLI at each stage was necessary to achieve a larger NAR and, consequently, a larger RGR.

Growth, phytochemical, and phytohormonal responses of basil to different light durations and intensities under constant daily light integral

Horticulture in controlled environments has been increasingly used to tackle limitations on crop production. As a crucial environmental factor, light regulate plant growth and metabolism. In the present study, basil plants were subjected to different light durations and intensities considering constant daily light integral (DLI). The lighting environment included 200, 300, and 400 µmol m− 2 s− 1 intensities for 18, 12, and 9 h, respectively. DLI amounted to 12.96 mol m− 2 d− 1 among all light treatments (LI200 for 18 h, LI300 for 12 h, and LI400 for 9 h). Half of the plants under each light treatment were exposed to 30 µmol m− 2 s− 1 of far-red light. The results indicated the general negative impact of LI400/9 on the growth of basils. Exposure to far-red light hurt the growth of the shoot, while it enhanced stem and petiole elongation. This effect was due to higher gibberellin accumulation, which resulted in shade avoidance responses. Exposure to far-red light also reduced anthocyanin and flavonoid contents, as two important nutritional components. Soluble carbohydrates increased, while storage carbohydrates decreased by increasing lighting duration/decreasing light intensity or by far-red light inclusion. The lowest antioxidant activity was detected in LI400/9. In the LI200/18, the highest level of auxin and the lowest level of cytokinin were detected, while the LI300/12 exhibited the highest level of gibberellin hormone. Low light intensity and long photoperiod enhanced plant biomass and phytochemical production and are recommended for basil production in controlled environments.

Sinusoidal LED light recipes can improve rocket edible biomass and reduce electricity costs in indoor growth environments.

Accumulation of edible biomass by crop plants relies on maintenance of a high photosynthetic rates across the photoperiod, with assimilation rate (A) generally responding to increasing light intensity in a hyperbolic fashion. In natural environments light fluctuates greatly over the course of the day, however in Controlled Environmental Agricultural (CEA) systems, light intensity can be supplemented or precisely controlled using LEDs to create near optimum conditions. In such indoor growth environments light is often delivered as a square wave and recommendations to horticulturalists are given in the form of Daily Light Integrals (DLI). However, this does not take into account the slow photosynthetic induction at the start of the photoperiod and the decline of A towards the end of the photoperiod, which has been demonstrated by several previous studies. Square wave light regimes therefore potentially cause suboptimal photosynthetic utilization of the applied lighting and waste electricity. Here we have adapted light recipes to gradually increase and decrease in intensity to take account of these findings. We demonstrate that, utilising a sinusoidal light regime capped at 250 μmol m-2 s-1, it is possible to increase edible biomass of rocket (by ca. 20%) compared to square wave delivered at 250 at the same DLI. Additionally, this can be achieved using less electricity (0.6%), therefore reducing energy costs and improving profitability. We suggest that capping maximum light intensity at 250 µmol m-2 s-1 improves the operating efficiency of PSII photochemistry (Fq'/Fm') also known as the photosynthetic efficiency by maintaining A later in the photoperiod. We show that a higher electron transfer rate (ETR) is maintained in these treatments over the photoperiod compared to higher light intensity caps, resulting in a greater Daily Photochemical Integral (DPI). We attribute this to less NPQ due to a greater sink capacity for the end products of electron transport, ATP and NADPH, as A is kept high for longer.

INFLUENCE OF MIXOTROPHY ON CELL CYCLE PHASE DURATION AND CORRELATION OF KARLOTOXIN SYNTHESIS WITH LIGHT AND G1 PHASE IN KARLODINIUM VENEFICUM: Influence of mixotrophy on cell cycle and toxicity in Karlodinium veneficum

Karlodinium veneficum forms fish killing blooms in estuaries worldwide. The toxicity of these blooms is variable and thought to be connected to bloom stage and in situ growth rates. Methods for measuring in situ growth rates rely on the assumption that cell cycle progression is phased to the diel photocycle, which is true for phototrophically-growing K. veneficum cultures where G1 phase occurs during light and S and G2 + M phases occur during darkness. However, K. veneficum is a facultative mixotroph that also phagocytizes microalgal prey, and the effects of this mixotrophy on its cell cycle synchrony are unknown. Furthermore, toxicity in laboratory cultures is inversely related to growth rate and is light dependent, suggesting synchrony between the cell cycle (G1 phase) and karlotoxin synthesis. To test this, the cell cycle phase distribution and cellular toxin content for phototrophic and mixotrophic cultures of K. veneficum were monitored hourly for a full diel cycle. The results demonstrated that mixotrophic cultures maintained a synchronized cell cycle, despite increased growth rates. The faster growth rates were attributed to a shortened duration of G1 phase in mixotrophic cultures compared to phototrophic cultures (30.8 ± 9.2 hours vs 69.4 ± 21.5 hours, respectively). Meanwhile, toxin production was observed only during light hours, consistent with synthesis initiating with the photorespiratory byproduct glycolate. Cellular toxin content had a significant positive correlation with the percentage of G1 phase cells and a significant negative correlation with the percentage of S phase cells. These results indicate a clear role in mixotrophy increasing growth rates of K. veneficum and of the diel photocycle in synchronizing the cell and karlotoxin synthetic cycles.

Design, development and experimental evaluation of a concentrator agrivoltaic system with integrated spectrally splitting Fresnel lens

The main aim of this research is to develop and evaluate a cost-effective, innovative agrivoltaic system that optimizes land use by simultaneously producing agricultural products and generating electricity on the same land. In this regard, a highly transparent concentrator agrivoltaic system that utilizes the spectral splitting property is developed. The system consists of a Fresnel lens coated with a dichroic thin film and a receiver made of silicon solar cells. In this system, the sunlight is first focused by a Fresnel lens and then split into two spectral ranges by the dichroic film: (i) photosynthetically active radiation (PAR), which passes through the film and can be utilized by the plants, and (ii) the remaining spectrum, which is reflected to the receiver to generate electricity. Cherry tomatoes and mint were planted under the system. The results showed that the receiver reduces the intensity of the focused radiation by almost 3.28 times. The optical efficiency of the receiver is 83.1% and the electricity generated is up to 18.1 watts. The photosynthetic photon flux density (PPFD) under the agrivoltaic system ranges from 229 to 778 μmol/m2. s, while the daily light integral (DLI) varies between 13.5 and 27 mol/m2.d. Cherry tomatoes grown in the shade of the agrivoltaic system are larger, heavier and have a deeper red hue, while the mint plants have larger, greener, and longer leaves. In addition, the agrivoltaic system provides cooler soil temperatures, ranging from 3.66°C to 9.53°C, and retains 5.7% to 8.4% more moisture, resulting in less water consumption. The total initial cost of the system was USD 587 and included the agricultural and photovoltaic components and maintenance. Over a period of ten years, the cumulative costs are likely to amount to USD 1,165. However, the system has strong economic potential, starting at an annual income of USD 27 and expected to exceed USD 15,000. This analysis indicates a favorable return on investment that should pay for itself within six years.

Response to Addition of Lighting Duration and Electrical Induction in Lettuce (Lactuca sativa L.) Plant on the Uptake of Nitrogen, Phosphors, Potassium and Yield

Background: The impact of excessive use of chemical fertilizers and pesticides causes problems of land degradation, low fertility levels and reduced cation exchange capacity. To increase nutrient uptake and yield of lettuce plants, cultivation techniques using induction and additional lighting are needed. The aim is to increase nutrient absorption and plant yields. Methods: The research design used a split plot with Factorial Randomized Groups. Factor 1 Lighting duration (P) for 4 and 8 hours per day and Factor 2, induction with DC (Direct Current) current (S). Induction 1 time per day (S1); The treatment in this study was repeated 4 times. Induction 2 times per day (S2) and Induction 3 times per day (S3). Result: The combination P2S2 showed good results regarding the uptake of Nitrogen (20.1 Kg.Ha-1), Phosphorus (2.71 Kg.Ha-1) and Potassium (67.23 Kg.Ha-1) in plant leaves. The P1S2 treatment showed a leaf area of (1652.19 cm2). The adding 4 hours of light and an induction interval of 2 times per day gave good results on the uptake of Nitrogen, Phosphorus and Potassium in the leaf of lettuce plants.

The Health and Nutritional Benefits of Fruits and Vegetables to Reduce the Risk of Obesity and High Blood Lipids

Background: Vegetables and fruits are an important part of a healthy diet and help with growth and support body functions and physical, mental, and social well-being at all ages. They can also help prevent all forms of malnutrition, such as undernutrition, micronutrient deficiencies, obesity, and overweight, and reduce the risk of non-communicable diseases. World Health Organization consumption of at least 400 grams of fruits and vegetables per day, or five servings of 80 grams each, and the reasons for the sad fact that most people do not eat enough of them to maintain a healthy life for the sake of obesity treatment and weight reduction. Objectives: The aim of the study was to investigate the effects of increasing fruit and vegetable intake rich in antioxidants and vitamins on people at risk of obesity and high levels of blood fat and to provide education about its benefits and the amount of daily rations. Methods: This a descriptive cross-sectional study, 160 obese women underwent to Aspetar ospital in Misurata city during The period (October–December 2022) and they were divided into two groups of 80 women per group. The first group was presented with a weight-loss diet devoid of vegetables and fruits. The second group was given a weight-loss diet rich in vegetables, including cucumber, lettuce, tomato, and fruits (kiwi, apple, and orange). For three consecutive months. Results: The findings were a decrease in weight with an average of 8 kg per woman for the first group and 15 kg per woman for the second group, and the average cholesterol and triglycerides were 280 mg/100 dL of blood and 230 mg/100 dL of blood, respectively, for the women of the first group. While it was 150 mg/100 dL blood and 90 mg/100 dL blood for the women of the second group, with some daily light exercise for all women in the two groups. Conclusion: This study indicates that consumption of three to five portions/day of fruit and vegetables is highly associated with prevention and a low risk of obesity, high blood fat, cholesterol, and cardiovascular disease. Therefore, we recommend relying on eating vegetables and fruits daily to reduce weight and blood fats, improve health, and nourish the body.

Vertical farming goes dynamic: optimizing resource use efficiency, product quality, and energy costs

Vertical farming is considered to be a key enabler for transforming agrifood systems, especially in or nearby urbanized areas. Vertical farming systems (VFS) are advanced indoor cropping systems that allow for highly intensified and standardized plant production. The close control of environmental parameters makes crop production stable and repeatable, ensuring year-round uniform product quality and quantity irrespective of location. However, due to continuous changes in plant physiology and development, as well as frequent changes in electricity prices, the optimum conditions for crop production and its associated costs can change within days or even minutes. This makes it beneficial to dynamically adjust setpoints for light (intensity, spectrum, pattern, and daylength), CO2, temperature, humidity, air flow, and water and nutrient availability. In this review, we highlight the beneficial effects that dynamic growth conditions can have on key plant processes, including improvements in photosynthetic gas exchange, transpiration, organ growth, development, light interception, flowering, and product quality. Our novel findings based on modeling and experimentation demonstrate that a dynamic daily light intensity pattern that responds to frequent changes in electricity prices can save costs without reducing biomass. Further, we argue that a smart, dynamic VFS climate management requires feedback mechanisms: several mobile and immobile sensors could work in combination to continuously monitor the crop, generating data that feeds into crop growth models, which, in turn, generate climate setpoints. In addition, we posit that breeding for the VFS environment is at a very early stage and highlight traits for breeding for this specialized environment. We envision a continuous feedback loop between dynamic crop management, crop monitoring, and trait selection for genotypes that are specialized for these conditions.

Germination responses of carob (Ceratonia siliqua L.) seeds to salinity and water stresses: Implications for the restoration of Mediterranean marginal lands

The iconic Mediterranean tree, Ceratonia siliqua L., holds substantial potential for restoring arid and semi-arid marginal lands. However, there is limited knowledge about the interaction of various abiotic factors and environmental stressors on seed germination of C. siliqua. Therefore, we examined the influence of salinity levels (0, 75, 150, 225 mM) and water stress using PEG6000 (−0.4, −0.8, −1.2 MPa) on C. siliqua seed germination under varying thermoperiods (15/25 °C and 25/35 °C) and photoperiods (12 hours of light and complete darkness). Our findings indicate that higher temperatures (25/35 °C) significantly reduced germination of seeds compared to lower temperatures (15/25 °C). However, the photoperiods showed no significant impact, especially under minimal salinity stress and low osmotic potentials (75 mM NaCl and −0.4 MPa PEG). In general, C. siliqua seeds exhibited enhanced performance in darkness at higher osmotic potentials, while increased stress prolonged the germination period. The dry weight of seedlings decreased with higher osmotic potential, although 75 mM NaCl promoted seedling biomass production. Our results confirm C. siliqua resilience to high salinity and moderate drought, offering practical applications for its successful reintroduction and cultivation in challenging Mediterranean environmental conditions.

291 Isoenergetic reduction of dietary macronutrients changes body composition and physical activity in cats, regardless of body condition, when fed to maintenance

Abstract Commercial extruded cat foods deviate noticeably from the natural diet of wild cats and contain greater carbohydrate and less protein. This alteration in macronutrient distribution is postulated as a potential factor in feline obesity, yet the precise role of carbohydrates in either predisposing to, or treating, obesity in cats remains inconclusive. This study explored the effects of diets differing in protein, fat, and carbohydrates (NFE) on physical activity and body composition when fed to adult male cats to maintain body weight (BW). Three extruded diets were formulated for adult maintenance according to AAFCO in an isoenergetic approach using the same ingredients in varying proportions: low-protein (LP; protein 28% of metabolizable energy [ME], fat 40% ME, NFE 32% ME), low-fat (LF; protein 42% ME, fat 30% ME, NFE 30% ME), or low-carbohydrate (LC; protein 36% ME, fat 41%ME, NFE 23% ME). Lean (n = 9) and obese (n = 9) adult male neutered cats were fed each diet for 4-wk in a 3 x 3 Latin square design. Physical activity was measured via actigraphy on d 15 to 21 of each period. On d 23 total tissue mass (TTM), body fat mass (BFM), lean soft tissue mass (LSTM), and bone mineral content (BMC) were assessed by dual energy x-ray absorptiometry. Daily food intake and weekly BW were recorded. Data were statistically analyzed in SAS Studio via the GLIMMIX procedure with diet and body condition (bc) as fixed effects and cat as subject. A Tukey post-hoc analysis was performed to assess multiple comparisons when significant (P < 0.05). Body weight (Pbc < 0.0001), TTM (Pbc < 0.0001), BFM (Pbc < 0.0001), LSTM (Pbc < 0.0001), and BMC (Pbc = 0.004) were greater in obese compared with lean cats. Regardless of body condition, LSTM was greater in cats consuming the LF diet (P = 0.010). Daily physical activity was similar between lean and obese cats; however, activity as a ratio of light:dark activity was greater for lean cats compared with obese (Pbc = 0.027). Additionally, cats were more active during dark hours when fed LC and LF (Pdiet = 0.016), though no difference was observed for activity during light hours (P = 0.452). These findings support previous observations regarding body composition disparities between lean and obese cats. Contrary to previous reports, no discernible distinctions in voluntary physical activity were noted between lean and obese cats. In previous studies, both high-carbohydrate and high-fat diets reduced voluntary physical activity when fed to maintain BW which was attributed to a potential alteration in mood and energy levels seen in other species. An increase in physical activity in cats consuming the LF diet could suggest a similar pattern. Future research should explore the metabolic implications of varied macronutrient distributions to expand upon the physiological insights presented herein. Funding for this study was provided by Champion Petfoods, Mitacs Accelerate, and the Natural Sciences and Engineering Council of Canada.

Modifying the Ambient Light Spectrum Using LED Lamps Alters the Phenolic Profile of Hydroponically Grown Greenhouse Lettuce Plants without Affecting Their Agronomic Characteristics.

The growth and development of green lettuce plants can be modulated by the prevailing light conditions around them. The aim of this study was to evaluate the effect of ambient light enrichment with different LED light spectra on agronomic characteristics, polyphenol concentration and relative gene expression of enzymes associated with polyphenol formation in 'Levistro' lettuce grown hydroponically in a Nutrient Film Technique (NFT) system for 28 days in a greenhouse. The spectra (blue:green:red:far-red) and red:blue (R:B) ratios obtained by enriching ambient light with Blue (B), White (W), Blue-Red (BR) and Red (R) LED light were B: 47:22:21:10, 0.5:1; W: 30:38:23:9, 0.8:1; BR: 33:15:44:8, 1.3:1 and R: 16:16:60:8, 3.8:1, respectively, and photosynthetically active radiation (PAR) under the different treatments, measured at midday, ranged from 328 to 336 µmoles m-2 s-1. The resulting daily light integral (DLI) was between 9.1 and 9.6 mol m-2 day-1. The photoperiod for all enrichment treatments was 12 h of light. The control was ambient greenhouse light (25:30:30:15; R:B = 1.2:1; PAR = 702 µmoles m-2 s-1; DLI = 16.9 mol m-2 day-1; photoperiod = 14.2 h of light). Fresh weight (FW) and dried weight percentage (DWP) were similar among the enrichment treatments and the control. The leaf number increased significantly under BR and R compared to B lights. The relative index of chlorophyll concentration (RIC) increased as plants grew and was similar among the enrichment treatments and the control. On the other hand, the concentration of chlorogenic acid and chicoric acid increased under BR and B lights, which was consistent with the higher relative expression of the coumarate 3-hydroxylase enzyme gene. In view of the results, it is inferred that half of the PAR or DLI is sufficient to achieve normal growth and development of 'Levistro' lettuce plants, suggesting a more efficient use of light energy under the light enrichment treatments. On the other hand, the blue and combined blue-red lights promoted the accumulation of phenolic compounds in the leaves of 'Levistro' lettuce plants.

Improving Bioelectricity by Optimizing the Use of Electrodes in Photosynthetic Microbial Fuel Cells Based on the Algae Scenedesmus sp. and Shrimp Cultivation Waste

Abstract Rapid economic growth and increasing electrical energy consumption have raised significant challenges to the provision of sustainable electrical energy. This research aims to examine the effect of variations in the population density of microalgae and the type of electrode (graphite and nickel) on the electrical voltage produced. This research was carried out experimentally using a randomized block design (RAK) consisting of 5 treatments and 3 repetitions. Electrical voltage data was taken every 60 minutes for 12 hours (6 hours of light and 6 hours of dark) for all treatments. The results showed that the use of different types of electrodes in the PMFC circuit did not affect the electrical voltage produced because both electrodes produced voltage electricity with a difference that is not much different, namely for graphite electrodes between 38.1 mV – 135.6 mV in the light phase and between 16.7 mV – 144.1 mV in the dark phase, while for nickel electrodes it is between 18.2 mV – 135.4 mV in the light phase and between 18.3 mV – 156 mV in the dark phase. Variations in population density of the microalgae Scenedesmus sp. used in the PMFC circuit have a significant effect (P<0.05) on the electrical voltage produced, namely in the light phase of treatment (P4) 2×107 it is 131.53 ± 25.12 mV for graphite electrodes and 137.90 ± 17.26 mV for nickel electrodes, while in the dark phase treatment (P3) 2×106 it was 168.70 ± 18.55 mV for graphite electrodes and 139.70 ± 27.35 mV for nickel electrodes.

Electricity Consumption Profile of Urban Households in Nsukka, Enugu State

In recent times, the uncontrollably rising global energy consumption has become a global problem with its attendant socio-economic and environmental consequences. Hence, this study utilized linear regression model to examine how households’ socio-economic attributes and use of appliances together determine electricity consumption and savings in Nsukka metropolis, Enugu state, Nigeria. Socio-economic variables found to have positive and significant effect on electricity consumption were age of working-class respondents, being married, household size, household active members, unemployed household members, prepaid and estimated electricity billing system, monthly income and high electricity supply hours. In terms of electrical appliances, high hours of electronics’ use per week, incandescent and LED bulbs usage, high number of bulbs, cooling hours of 9 and above per week, lighting hours of 16 and above and weekly heating hours were positively related to electricity consumption and statistically significant. We suggest that the creation of energy efficiency awareness at the household and educational institution levels should be vigorously pursued. Government should subsidize the prices of energy efficient appliances to encourage purchases by low-income earners. Constant overbilling of estimated and postpaid electricity users, as lamented by respondents in the survey, should be discouraged by electricity users. This will enable users to conserve energy and not waste energy as revenge tactics for overbilling. The promotion and full deployment of prepaid meters in the study area by electricity providers would go a long way in complementing the efforts for clean development mechanism in Nigeria.

The influence of lighting and thermal environments on sleep and cognitive function in older adults

Recent research has demonstrated the significant influence of lighting and thermal conditions on cognitive performance and sleep quality. However, a notable gap exists in understanding how these factors impact older adults within their living environments. This study examined the relationship between daily lighting and thermal exposures with cognitive performance and sleep quality in older adults. Eighteen older adults, with a mean age of 75 (SD = 7.7, female = 13), participated in a three-day study. Throughout the protocol, their indoor lighting and thermal conditions were monitored using environmental sensors. Participants were instructed to complete a series of cognitive tasks twice a day. Additionally, they wore a smartwatch-type actigraph and a wearable light tracker to monitor their sleep/wake patterns and daily light exposure. The findings showed that appropriate nighttime lighting correlated with improved evening cognitive performance. Higher nighttime indoor lighting intensity positively correlated with cognitive measures, while nighttime correlated color temperature (CCT) exposure had negative correlations. Daytime melanopic equivalent daylight illuminance (MEDI) exposure significantly predicted total sleep time, with increased circadian-effective light exposure reducing sleep fragmentation. Conversely, higher nighttime lighting intensity was linked to decreased sleep efficiency. Higher bedroom temperatures were associated with improved sleep efficiency and reduced fragmentation. These findings highlight the importance of optimizing lighting conditions and maintaining comfortable temperatures in residential environments to promote cognitive performance and sleep quality among older adults.

A Systematic Literature Review on Parameters Optimization for Smart Hydroponic Systems

Hydroponics is a soilless farming technique that has emerged as a sustainable alternative. However, new technologies such as Industry 4.0, the internet of things (IoT), and artificial intelligence are needed to keep up with issues related to economics, automation, and social challenges in hydroponics farming. One significant issue is optimizing growth parameters to identify the best conditions for growing fruits and vegetables. These parameters include pH, total dissolved solids (TDS), electrical conductivity (EC), light intensity, daily light integral (DLI), and nutrient solution/ambient temperature and humidity. To address these challenges, a systematic literature review was conducted aiming to answer research questions regarding the optimal growth parameters for leafy green vegetables and herbs and spices grown in hydroponic systems. The review selected a total of 131 papers related to indoor farming, hydroponics, and aquaponics. The review selected a total of 123 papers related to indoor farming, hydroponics, and aquaponics. The majority of the articles focused on technology description (38.5%), artificial illumination (26.2%), and nutrient solution composition/parameters (13.8%). Additionally, remaining 10.7% articles focused on the application of sensors, slope, environment and economy. This comprehensive review provides valuable information on optimized growth parameters for smart hydroponic systems and explores future prospects and the application of digital technologies in this field.