Light Photoperiod Research Articles

An Interplay of Light and Smoke Compounds in Photoblastic Seeds.

Light increases the germinability of positively photoblastic seeds and inhibits the germination of negative ones. In an area where plant-generated smoke from fire is a periodically occurring environmental factor, smoke chemicals can affect the germination of seeds, including those that are photoblastically sensitive. Moreover, as smoke and its compounds, mostly karrikin 1, KAR1, have been used for priming the seeds of many species, including photoblastic ones, a systematic review of papers dealing with the phenomenon was conducted. The review indicates that the unification of experimental treatments (light spectrum, intensity and photoperiod, and KAR1 concentration within the species) could improve the quality of global research on the impact of smoke chemicals on photoblastic seeds, also at the molecular level. The review also reveals that the physiologically active concentration of KAR1 varies in different species. Moreover, the physiological window of KAR’s impact on germination can be narrow due to different depths of primary seed dormancy. Another concern is the mode of action of different smoke sources and formulations (aerosol smoke, smoke-saturated water), or pure smoke chemicals. The reason for this concern is the additive or synergetic effect of KARs, cyanohydrins, nitrates and other compounds, and the presence of a germination inhibitor, trimethylbutenolide (TMB) in smoke and its formulations. Obviously, environmental factors that are characteristic of the local environment need to be considered. From a practical perspective, seeds germinating faster in response to smoke chemicals can outcompete other seeds. Hence, a thorough understanding of this phenomenon can be useful in the restoration of plant habitats and the protection of rare species, as well as yielding an improvement in plants that are sown directly to the field. On the other hand, the application of smoke compounds can induce “suicidal germination” in the photoblastic seeds that are buried in the soil and deplete the soil seed bank of the local population of unwanted species.

Attached microalgae converting spent coffee ground into lipid for biodiesel production and sequestering atmospheric CO2 simultaneously

The impacts of simultaneous exposures of arbitrary light intensities and photoperiods on attached Chlorella vulgaris microalgal growth onto spent coffee ground (SCG) were studied, and subsequently optimized using Response Surface Methodology (RSM) tool. The statistical analysis revealed the optimum light intensity and photoperiod were achieved at 100 μmol/m2s and 20:4 dark:light hours/cycle, respectively, producing microalgal density of 0.358 g/g and lipid productivity of 16.8 mg/Lday. The biodiesel yielded from the optimum condition possessed high cetane number and oxidative stability due to the high saturated fatty acid methyl esters (FAME) content of 63.7 %. In fact, the major FAME compositions ranged within C16 to C18 which were favourable for quality biodiesel production. Furthermore, the viability of SCG to serve as a carbon source was also evidenced by the high productivities of microalgal protein and carbohydrate at 94 and 168 mg/L day, respectively. The capability of attached microalgal cultivation in sequestering atmospheric CO2 was finally unveiled, with high CO2 capture rate being recorded at 9.38 mg/L h. Accordingly, growing attached microalgae onto SCG was recognized as an alternative approach for sustainable CO2 reduction, while producing green diesel to assuage the global warming phenomenon.

Morpho-Metric and Specialized Metabolites Modulation of Parsley Microgreens through Selective LED Wavebands

Plant factories and high-tech greenhouses offer the opportunity to modulate plant growth, morphology and qualitative content through the management of artificial light (intensity, photoperiod and spectrum). In this study, three Light Emitting Diode (LED) lighting systems, with blue (B, 460 nm), red (R, 650 nm) and mixed red + green-yellow + blue (RGB) light were used to grow parsley microgreens to understand how light quality could change the phenotype and the profile of secondary metabolites. Plants showed altered morphological characteristics and higher amounts of secondary metabolites under RGB LEDs treatment. The results demonstrated that microgreens under red light showed the highest fresh yield, petiole length, coumaric acid content but also the highest nitrate content. Plants under RGB light showed the highest dry matter percentage and highest content of total and single polyphenols content, while blue light showed the highest ascorbic acid and ABTS antioxidant activity. Moreover, microgreens under red light showed more compact leaves with less intercellular spaces, while under blue and RGB light, the leaves displayed ticker spongy mesophyll with higher percentage of intercellular spaces. Therefore, the specific spectral band was able to modify not only the metabolic profile, but also it could modulate the differentiation of mesophyll cells. Light quality as a preharvest factor helps to shape the final parsley microgreens product as a whole, not only in terms of yield and quality, but also from a morpho-anatomical point of view.

Constant light exposure in early life induces m6A-mediated inhibition of IGF gene family in the chicken.

Insulin-like growth factor (IGF) family plays important roles in regulating the development of various organ systems through stimulating cell proliferation and differentiation. Photoperiod is an important factor affecting growth and development in the chicken, yet the effect of constant light exposure in early life on IGF1 and IGF2 expression in the chicken remains unclear. In this study, one-day-old chickens were kept in either constant light (24L:0D, LL) or natural photoperiod (12L:12D, LD) for the first week of life and then maintained in constant light from 8 to 21 d of age. Constant light exposure in early life reduced mRNA expression of IGF gene family, including mRNA expression of IGF1, IGF2, and IGF2 binding proteins, in the hippocampus, hypothalamus, and liver of chickens at both 7 and 21 d of age. Moreover, constant light exposure increased mRNA expression of genes involved in RNA methylation N6-methyladenosine (m6A) in a tissue-specific manner. Interestingly, higher m6A on 3'UTR of IGF2 mRNA coincides with lower IGF2 mRNA, indicating a possible role of m6A in the post-transcriptional regulation of IGF2 expression in the hippocampus, hypothalamus, and liver of chickens. These findings suggest a m6A-mediated gene regulation of IGF gene family in different organs of chicken and expand our knowledge on mechanism of gene regulation in response to early life experience.

Water Stress Inhibits Germination While Maintaining Embryo Viability of Subtropical Wetland Seeds: A Functional Approach With Phylogenetic Contrasts.

Wetland species commonly exhibit a range of strategies to cope with water stress, either through drought tolerance or through avoidance of the period of limited water availability. Natural populations provide a genetic resource for ecological remediation and may also have direct economic value. We investigated the effects of drought stress on the seed germination of wetland species. Nineteen species were germinated in four concentrations of polyethylene glycol 6000 (PEG) and were evaluated daily (12-h light photoperiod) or after 35 days (continuous darkness) to determine seed germination under water stress. Germination percentage decreased with an increase in polyethylene glycol 6000 (PEG) concentration, but species’ germination response to PEG concentration varied significantly. Seeds recovered their germinability after the alleviation of water stress, but the extent of recovery was species-dependent.

Effects of different light-emitting diode qualities on the growth and photosynthetic characteristics of Spathiphyllum floribundum

Spathiphyllum floribundum (Linden & André) N.E.Br. is an important indoor flower species. Thus, optimizing its growth by regulating the light quality under indoor low-light conditions may be critical for generating high-quality flowers. In this study, the effects of the following six light-quality treatments on peroxidase and superoxide dismutase activities in two S. floribundum cultivars (“Sweet Chico” and “Queen”) were analyzed: monochromatic light comprising 100% red (R, 657 nm) or 100% blue (B, 450 nm) light, a combination of R and B lights [80% R + 20% B (8:2), 70% R + 30% B (7:3), and 60% R + 40% B (6:4)], and white light. The light treatments were performed using light-emitting diodes. The light intensity and photoperiod were set to 45 ± 2 µmol·m−2·s−1 and 14 h·day−1, respectively. The results of this study revealed that an appropriate R:B light ratio may lead to increased pigment contents, thereby increasing the synthesis and accumulation of photosynthetic products, which will result in increased stress resistance and enhanced growth. These findings provide the basis for future investigations on the growth and production of S. floribundum and other indoor ornamental plants.

The Power of Far-Red Light at Night: Photomorphogenic, Physiological, and Yield Response in Pepper During Dynamic 24 Hour Lighting.

Supplemental light is needed during the winter months in high latitude regions to achieve the desired daily light integral (DLI) (photoperiod × intensity) for greenhouse pepper (Capsicum annuum) production. Peppers tend to have short internodes causing fruit stacking and higher labor time for plant maintenance when grown under supplemental light. Far-red light can increase internode length, and our previous study on tomatoes (Solanum lycopersicum) also discovered monochromatic blue light at night during continuous lighting (CL, 24 h) increased stem elongation. Furthermore, the use of low-intensity, long photoperiod lighting can reduce light fixture costs and overall electricity costs due to lower power prices during the night. Therefore, we investigated the use of blue and/or far-red light during the night period of CL to increase stem elongation. Three pepper cultivars with different internode lengths/growing characteristics (‘Maureno,’ ‘Gina,’ and ‘Eurix’) were used to investigate the effects on plant morphology in a short experiment, and one cultivar ‘Maureno’ was used in a long experiment to assess the impact on fruit yield. The five lighting treatments that were used are as follows: 16 h of white light during the day followed by either 8 h of darkness (16W – control), white light (24W), blue light only (16W + 8B), blue + far-red light (16W + 8BFR), or far-red light only (16W + 8FR). Calculated nighttime phytochrome photostationary state (PSS) was 0.833, 0.566, 0.315, and 0.186 for 24W, 16W + 8B, 16W + 8BFR, and 16W + 8FR respectively. All five treatments had the same DLI in photosynthetically active radiation (PAR) and far-red light. The 16W + 8BFR and 16W + 8FR treatments significantly increased internode length compared to 16W and 24W but neither was more impactful than the other. The 16W + 8B treatment also increased internode length but to a lesser extent than 16W + 8BFR and 16W + 8FR. This indicates that a nighttime PSS of 0.315 is sufficient to maximize stem elongation. Both 16W + 8B and 16W + 8BFR drove photosynthesis during the nighttime supporting a similar yield compared to 16W. Therefore, 16W + 8BFR is the most potential lighting strategy as it can lead to a greater reduction in the light fixture and electrical costs while maintaining yield and enhancing internode length.

Physiological and biochemical responses of Chinese cabbage (Brassica rapa var. chinensis) to different light treatments

BackgroundArtificial agriculture is promoted as an economically viable technology for developing plants under controlled conditions whereby light, water, and fertilizer intake are regulated in a controlled manner to produce maximum productivity with minimal resources. Artificial light has been used to produce high-quality vegetables because it can regulate plant growth and phytochemical production through light intensity, photoperiod, and spectrum modulation. This study aimed to compare the physiological and biochemical responses of Chinese cabbage (Brassica rapa var. chinensis) grown under artificial light with varying light intensities (75 and 150 µmol m−2 s−1), photoperiods (12:12 and 6:6:6:6 h), and wavelengths (blue, red, and magenta) to plants grown in a glasshouse under natural light. The novelty of this study lies in the manipulation of artificial LED lighting to achieve high-quality plant growth and phytochemical composition in B. rapa model vegetables for potential optimal productivity.ResultsThe analysis revealed that B. rapa grown under artificial lights produced more consistent biomass yield and had a higher chlorophyll content than B. rapa grown under natural light (control). Plants grown under artificial lights have also been shown to produce biochemical compositions derived primarily from fatty acids, whereas plants grown under natural light have a biochemical composition derived primarily from alkanes. Twenty compounds were found to be statistically different between light treatments out of a total of 31 compounds detected, indicating that they were synthesized in response to specific light conditions. Exposure to the full artificial light spectrum (white) resulted in the absence of compounds such as dodecane and 2,6,10-trimethyltridecane, which were present in B. rapa grown in natural light, whereas exposure to the blue spectrum specifically induced the production of tetracosane. Eicosane, neophytadiene, l-(+)-ascorbic acid 2,6-dihexadecanoate, and (Z,Z,Z)-9,12,15-octadecatrienoic acid were all prevalent compounds produced in B. rapa regardless of light conditions, and their absence may thus affect plant development and survival.ConclusionsThe results show that cultivation under artificial light produced consistent biomass, high chlorophyll content, and phytochemical content comparable to natural light conditions (control). These findings shed light on how artificial light could improve the production efficiency and organoleptic qualities of Chinese cabbage.Graphical

Kuluçka sırasında sıcağa alıştırma ve fotoperiyodik aydınlatmanın kuluçka performansı, kuluçka süresi, civciv kalitesi ve organ gelişimi üzerindeki etkisi

Objective: The objective of this study was to investigate the effects of thermal manipulation (TM) and photoperiodic lighting during the incubation on hatching performance, hatching time, chick quality and organ growth. Material and Methods: The study was composed of two consecutive experiments. The 1st experiment was application of TM, 1ºC higher eggshell temperature (EST, 38.8ºC ) for 6 h/day from 11 to 16 embryonic day, or optimal EST of 37.8ºC (Control) during the incubation. In second experiment, eggs were exposed to a photoperiodic lighting of 16h light and 8h darkness (16L: 8D) along with optimal EST (Light-Control) or TM (Light-Heated). Results: Thermal manipulation accelerated hatching time, reduced chick quality score, decreased relative bursa and tibia weights while heart and sternum weights increased with no effect on hatching performance. However, 16L: 8D photoperiodic lighting schedule along with TM significantly improved chick length at hatch indicating improved chick quality while other traits were not affected except for higher relative liver weight. Conclusion: It can be concluded that TM alone had negative effects on chick quality. However, photoperiodic lighting along with TM can be a positive approach towards better chick quality and post hatch performance as indicated by increased chick length and liver weight.

Enhanced Production of Phenylethanoids Mediated Through Synergistic Approach of Precursor Feeding and Light Regime in Cell Suspension Culture of Rhodiola imbricata (Edgew.).

Precursor feeding is a potential strategy for increasing specialized metabolite production in plant cell culture systems. In the present study, cell suspension cultures were developed and subsequently evaluated for precursor feeding investigations. Cell suspension cultures were established in Murashige and Skoog (MS) medium containing 0.5mg/L thidiazuron (TDZ) + 1mg/L α-naphthalene acetic acid (NAA). The growth biomass and metabolite pattern were analyzed to identify specific culture days required for prolific biomass production. The maximum cell dry weight (DW) was observed in leaf cell suspension (1.22g/100mL) and root cell suspension culture (1.12g/100mL) on day 21. Afterward, the effect of precursor concentrations (tyrosol; 0.5, 1, 2, and 3mM) along with two light regimes, photoperiod (16L/8D h, 70µmol/m2/s) and dark (24h), was evaluated for cell growth and metabolite accumulation. The results revealed that leaf cell suspension treated with 3mM tyrosol concentration detected maximum salidroside content (26.05mg/g DW) on day 15, incubated under photoperiod (16L/8D h) condition. Similarly, under photoperiod (16L/8D h), root cell suspension treated with 3mM tyrosol produced maximum salidroside content (26.62mg/g DW) on day 12. Moreover, the total phenolics content increased significantly (44.21mg/g DW) on day 12 in 3mM tyrosol treatment under photoperiod (16L/8D h). However, precursor concentrations did not influence the total flavonoids content. The present investigation suggests that the immediate pathway precursor, tyrosol, has a strong effect on enhanced production of salidroside, irrespective of explant type and light regimes.

Prediction of the Energy Consumption for Indoor Strawberry Cultivation in a Tropical Climate

This article addresses the lack of information for predicting the energy consumption of strawberry plantations inside plant factories located in tropical climate regions. This study aims to investigate the energy consumption of the cultivation of strawberries in the controlled environment room and to develop a TRNSYS computer model for the controlled environment room. Experiments were conducted in a 25 m3 controlled environment room. There are 180 strawberry trees inside the room. Light Emitting Diode (LED) grow light substitutes for natural sunlight. An air conditioner was used to regulate the indoor air condition. A computer model was developed using TRNSYS (TRaNsientSYStem simulation tool) and was validated using the collected data. There are three main components of the room heat load: transmission, lighting, and evapotranspiration. The lighting heat load shares more than 96% of the total heat load — the evapotranspiration load increases when the LED turns on. However, the lighting consumes only about 36% of total electricity consumption, while the air conditioner consumes 64%. Most of the electricity is used during the runner stage. Electricity consumption can be saved by 40% if the runners are grown outside the plant factory. Therefore, the high heat load is a feature in the plant factory. In this study, the lighting heat load is the most significant parameter. The strawberry light intensity requirement is the high lighting heat load. Consequently, the electricity for the air conditioner becomes high since the air conditioner removes the generated heat from the high light intensity. Therefore, the air conditioner electricity consumption is enormous in this study. Moreover, the required lighting intensity, photoperiod, and low air temperature factors affect electricity consumption. Therefore, the results from this study could provide strategies for energy cost reduction and plantation management for plant factories cultivation.

Light and Plant Growth Regulators on In Vitro Proliferation.

Plant tissue cultures depend entirely upon artificial light sources for illumination. The illumination should provide light in the appropriate regions of the electromagnetic spectrum for photomorphogenic responses and photosynthetic metabolism. Controlling light quality, irradiances and photoperiod enables the production of plants with desired characteristics. Moreover, significant money savings may be achieved using both more appropriate and less consuming energy lamps. In this review, the attention will be focused on the effects of light characteristics and plant growth regulators on shoot proliferation, the main process in in vitro propagation. The effects of the light spectrum on the balance of endogenous growth regulators will also be presented. For each light spectrum, the effects on proliferation but also on plantlet quality, i.e., shoot length, fresh and dry weight and photosynthesis, have been also analyzed. Even if a huge amount of literature is available on the effects of light on in vitro proliferation, the results are often conflicting. In fact, a lot of exogenous and endogenous factors, but also the lack of a common protocol, make it difficult to choose the most effective light spectrum for each of the large number of species. However, some general issues derived from the analysis of the literature are discussed.

Adaptation of Drosophila melanogaster to Long Photoperiods of High-Latitude Summers Is Facilitated by the ls-Timeless Allele.

Circadian clocks help animals to be active at the optimal time of the day whereby for most species the daily light-dark cycle is the most important zeitgeber for their circadian clock. In this respect, long arctic summer days are particularly challenging as light is present almost 24 h per day, and continuous light makes the circadian clocks of many animals arrhythmic. This is especially true for the fruit fly, Drosophila melanogaster, which possesses a very light-sensitive clock. The blue-light photoreceptor Cryptochrome (CRY) and the clock protein Timeless (TIM) are the light-sensitive components of the circadian clock and are responsible for constant light-induced arrhythmicity even at very low light intensities. Nevertheless, D. melanogaster was able to spread from its tropical origin and invade northern latitudes. Here, we tested whether a natural polymorphism at the timeless (tim) locus, s-tim and ls-tim, helped adaptation to very long photoperiods. The recently evolved natural allele, ls-tim, encodes a longer, less light sensitive form of TIM (L-TIM) in addition to the shorter (S-TIM) form, the only form encoded by the ancient s-tim allele. ls-tim has evolved in southeastern Italy and slowly spreads to higher latitudes. L-TIM is known to interact less efficiently with CRY as compared with S-TIM. Here, we studied the locomotor activity patterns of ~40 wild s-tim and ls-tim isofemale lines caught at different latitudes under simulated high-latitude summer light conditions (continuous light or long photoperiods with 20-h daily light). We found that the ls-tim lines were significantly more rhythmic under continuous light than the s-tim lines. Importantly, the ls-tim lines can delay their evening activity under long photoperiods, a behavioral adaptation that appears to be optimal under high-latitude conditions. Our observations suggest that the functional gain associated with ls-tim may drive the northern spread of this allele by directional selection.

From Embryo to Adult Life: Differential Expression of Visual Opsins in the Flatfish Solea senegalensis Under Different Light Spectra and Photoperiods

Visual photoreceptors in fish are usually adjusted to the light environment to ensure the highest efficiency and best adaptation. In the Senegalese sole, metamorphosis determines migration from pelagic to benthic habitats, with marked differences in both light intensity and spectrum. Here, we analysed the ontogeny of six visual photopigments, namely, rod opsin (rh1), short wavelength-sensitive (sws1 and sws2), medium wavelength-sensitive (rh2.3 and rh2.4), and long wavelength-sensitive (lws) cone opsins, in sole specimens maintained in light-dark cycles of white (LDW), blue (LDB), red (LDR), and continuous white (LL) lights by using RT-qPCR and in situ hybridisation. Most of the opsins displayed a similar developmental expression pattern under all tested conditions. However, lower transcripts were detected under LDR and LL compared to LDW and LDB. A significant increase in gene expression was detected before and after metamorphosis, reaching minimum transcript levels at hatching and during metamorphosis. Interestingly, green opsins (rh2.3 and rh2.4) displayed a significant increase only before metamorphosis, with their expression remaining low during and after metamorphosis. The rod opsin and short-, medium-, and long-wavelength sensitive cone opsins were detected in retinal photoreceptors of the sole from pre-metamorphic to adult stages by in situ hybridisation. In adults, the short-wavelength cone opsins (sws1 and sws2) were found in single cones, whereas the medium- (rh2.4) and long-wavelength (lws) cone opsins were present in double cones. The results obtained by in situ hybridisation in the retina of developing sole, in terms of number of positive cells and/or intensity of labelling, were consistent with the ontogenetic transcript patterns found by RT-qPCR, suggesting that most of the visual opsin expressions detected in the whole specimens could correspond to retinal expression. Taken together, our results pointed out that the ontogeny of the Senegalese sole is accompanied by remodelling in opsin gene expression, with the green-cone opsins being the most abundant photopigments in pre-metamorphosis and rod opsin the dominant visual photopigment from the completion of metamorphosis onwards. These results enlarge our knowledge of flatfish metamorphosis and ecology and provide useful information to develop light protocols adapted to different ontogenetic stages that could improve welfare and production in sole aquaculture.

Effects of light intensity and photoperiod on growth, lipid accumulation and fatty acid composition of Desmodesmus subspicatus LC172266 under photoautotrophic cultivation

Microalgae oil accumulation in their natural growing states hardly reaches the quantities needed to replace fossil-derived diesel. Therefore, for algae to be used as biofuel feedstock, their growths are manipulated with the aim of achieving high cell density and high lipid accumulation. Two major factors affecting microalgal biomass and lipid productivity are light intensity and photoperiod. In the present study, Desmodesmus subspicatus was grown photoautotrophically under varying light intensities and photoperiods with a view to assessing the growth, lipid accumulation potential and fatty acid composition. Whereas the optimal light intensity for biomass production of the microalga was 5000 lx, that for lipid productivity was 3500 lx. At 5000 lx and 18: 6 h light/dark cycle, biomass yield, lipid content and lipid productivity were highest, at values of 1.92 ± 0.03 g/L, 53% and 118.80 ± 2.04 mgL-1day -1 respectively. The major fatty acid of the alga was oleic acid irrespective of light changes. The quantities of lipid accumulated and the properties of the fatty acid methyl esters showed that Desmodesmus subspicatus LC172266 is an ideal feedstock for biodiesel production.

A CLINICAL STUDY ON DRY EYE AFTER CATARACT SURGERY.

Introduction: Dry eye as dened by the International Dry eye workshop is a multifactorial disease of the tears and ocular surfaces. Cataract surgery can cause dry eye as surgery can damage ocular surface. To nd out various factors Aims: responsible for dry eye after cataract surgery in presenile patients and the incidence of dry eye cases after cataract surgery. It was a Methods: prospective study on 100 patients Complete ocular examination and dry eye tests were done preoperatively and postoperatively. patients Results: who had longest tunnel incison, longer period of microscopic light exposure, vigorous irrigation, and eyedrops with preservatives had developed dry eye disease. As dry eye may develop after cataract surgery, so by decrea Conclusion: sing incision size of tunnel, minimizing microscopic light exposure and vigorous irrigation, using preservative free drops can decrease dry eye symptoms post operatively

The influence of LED light photoperiod on growth and mineral composition of Brassica microgreens indoors

The influence of LED light photoperiod on growth and mineral composition of <i>Brassica</i> microgreens indoors

Effects of light regime on circadian rhythmic behavior and reproductive parameters in native laying hens

The paper aimed to study the effects of light regime on circadian rhythmic behavior and reproductive parameters in a native laying hen, Beijing You Chicken (BYC) during 22 to 30 wk. A total of 630 19-wk-old BYC female chicken were allocated to 6 light regime groups with 3 replicates per group and 35 birds per replicate, reared in individually lit floor pens with separate outdoor areas. A 2 × 3 factorial experiment (2 lighting patterns: continuous and intermittent lighting; 3 photoperiods: 16 h, 14 h, 12 h) was arranged, including 16L:8D for group 1; 12L:2D:4L:6D for group 2; 14L:10D for group 3; 10L:2D:4L:8D for group 4; 12L:12D for group 5, and 8L:4D:4L:8D for group 6, respectively. The circadian rhythmic behavior of the hens, including feeding, egg-laying and sleeping behaviors were observed by scan sampling and target sampling method for consecutive 3 d every other week during 22 to 30 wk. Infrared cameras were set outside each pen to record the rhythmic behaviors of the birds every other hour (6:00–7:00;8:00–9:00;10:00–11:00;12:00–13:00;14:00–15:00;16:00–17:00;18:00–19:00;20:00–21:00;22:00–23:00;0:00–1:00;2:00–3:00;4:00–5:00). Theovarian weight, oviduct weight, oviduct length, the number of large yellow follicles (LYF), and small yellow follicles (SYF) were measured at the end of 30 wk. The egg-laying rate during 22 to 30 wk was measured. The results showed that the highest feeding frequency was given by the 16L:8D, and the lowest given by the 12L:12D (P < 0.05). The average feeding duration was the longest in the 8L:4D:4L:8D at 6:00 to 8:00 (18.67 min/hen) (P < 0.05), and the shortest in the 8L:4D:4L:8D at 18:00 to 20:00 (3.75 min/hen) (P < 0.05). The highest egg-laying frequency was given by the 8L:4D:4L:8D (0.28), the lowest given by the 10L:2D:4L:8D (0.21) (P < 0.05). The shortest egg-laying duration occurred at 6:00 to 8:00, was given by the 16L:8D (8 min/hen), and the longest egg-laying duration occurred at 18:00 to 20:00, was given by 16L:8D and 8L:4D:4L:8D (>20.5 min/hen) (P < 0.05). The highest sleeping frequency was given by the 12L:2D:4L:6D, the lowest was given by the 12L:12D (P < 0.05). At 6:00 to 8:00, the shortest sleeping duration was given by 12L:2D:4L:6D (1.5 s/hen), at 18:00 to 20:00, the longest given by 8L:4D:4L:8D (14.3 s/hen) (P < 0.05). Lighting pattern and photoperiod alone or in interaction had no effect on egg-laying rate during 22 to 30 wk (P > 0.05), but had significant effects on ovarian weight, oviduct weight, oviduct length, the number of LYF and SYF (P < 0.05), and the continuous groups were all significantly higher than the intermittent groups (P < 0.05). The present study indicated that light regimes affected the frequency and duration of circadian behavior in BYC laying hens, and the continuous light was more beneficial to the reproductive development than the intermittent light in the early laying period.

Light Intensity and Photoperiod Affect Growth and Nutritional Quality of Brassica Microgreens.

We explored the effects of different light intensities and photoperiods on the growth, nutritional quality and antioxidant properties of two Brassicaceae microgreens (cabbage Brassica oleracea L. and Chinese kale Brassica alboglabra Bailey). There were two experiments: (1) four photosynthetic photon flux densities (PPFD) of 30, 50, 70 or 90 μmoL·m−2·s−1 with red:blue:green = 1:1:1 light-emitting diodes (LEDs); (2) five photoperiods of 12, 14, 16, 18 or 20 h·d−1. With the increase of light intensity, the hypocotyl length of cabbage and Chinese kale microgreens shortened. PPFD of 90 μmol·m−2·s−1 was beneficial to improve the nutritional quality of cabbage microgreens, which had higher contents of chlorophyll, carotenoids, soluble sugar, soluble protein and vitamin C, as well as increased antioxidant capacity. The optimal PPFD for Chinese kale microgreens was 70 μmol·m−2·s−1. Increasing light intensity could increase the antioxidant capacity of cabbage and Chinese kale microgreens, while not significantly affecting glucosinolate (GS) content. The dry and fresh weight of cabbage and Chinese kale microgreens were maximized with a 14-h·d−1 photoperiod. The chlorophyll, carotenoid and soluble protein content in cabbage and Chinese kale microgreens were highest for a 16-h·d−1 photoperiod. The lowest total GS content was found in cabbage microgreens under a 12-h·d−1 photoperiod and in Chinese kale microgreens under 16-h·d−1 photoperiod. In conclusion, the photoperiod of 14~16 h·d−1, and 90 μmol·m−2·s−1 and 70 μmol·m−2·s−1 PPFD for cabbage and Chinese kale microgreens, respectively, were optimal for cultivation.

Effects of Continuous Light (LD24:0) Modulate the Expression of Lysozyme, Mucin and Peripheral Blood Cells in Rainbow Trout

Continuous photoperiod is extensively used in fish farming, to regulate the reproductive cycle, despite evidence suggesting that artificial photoperiods can act as a stressor and impair the immune system. We evaluated the potential effects of an artificial photoperiod on mucus components: lysozyme and mucin, in juvenile rainbow trout (Oncorhynchus mykiss) after exposure for one month to natural photoperiod (LD12:12) or constant light (LD24:0) artificial photoperiod. For each treatment, we assessed changes in peripheral blood cells (erythrocytes and leukocytes) and skin mucus component concentrations. Our results show a decrease in lysozyme concentration, while mucin levels are increased. Similarly, we find elevated monocytes and polymorphonuclears under constant light photoperiod. These findings suggest that LD24:0 regulates lysozyme, mucin, and leukocytes, implying that artificial photoperiods could be a stressful.