Light Regimes Research Articles

Effect of photoperiod during incubation on embryonic temperature, hatch traits, and performance of 2 commercial broiler strains

Provision of light during incubation has shown the potential to enhance hatching traits and affect posthatch productivity, physiology, and behavior. In this study, 2 repeated trials were conducted to investigate the effect of photoperiod and strain on the embryo temperature, hatching traits and posthatch growth performance of 2 commercial strains of broilers (Ross 308 and Cobb 500). In each trial, hatching eggs were randomly distributed into 6 incubators with 3 photoperiod treatments: blue LED light for 12 h d-1 (12L:12D) or 18 h d-1 (18L:6D) during entire incubation were compared with no illumination condition (DARK). Data were analyzed as a 3×2 factorial arrangement with the trial as the blocking factor. Embryos incubated under 12L:12D and 18L:6D had lower air cell temperature (P < 0.05) than the DARK embryos from d 13 of incubation onward except on the day of candling. The response of air cell temperature to periodic illumination differed between 2 strains. Cobb embryos had lower air cell temperature in 12L:12D than those incubated with 18L:6D from d 16 of incubation onward, whereas lower air cell temperature was found in Ross embryos when illuminated with 18L:6D photoperiod compared to those under 12L:12D. The 12L:12D treatment was associated with improved (P < 0.05) navel closure condition of hatchlings. There were no differences in hatchability, embryo mortality, body weight, or length at hatch among photoperiod groups or its combination with strain. No differences in production parameters were found between DARK and illuminated groups. However, 12L:12D had heavier (P < 0.05) body weight on d 14 of age and higher (P < 0.05) body weight gain than 18L:6D from d 7 to 14 of age. The results of this study indicate that providing blue LED light up to 18 h d-1 has no detrimental effect on production of broilers, however, 12L:12D light regime improved chick quality at hatch compared to DARK and resulted in heavier birds by d 14 compared to 18L:6D.

How the Distribution of Photon Delivery Impacts Crops in Indoor Plant Environments: A Review

Indoor plant production allows for increased controllability over plant growth, particularly with the employment of specific lighting regimes. This article reviews research investigating the influence of various light regimes that provide crops with the same light spectrum and daily light integral (DLI), yet with different lighting schedules and intensities. The structure of these light regimes includes changing photoperiod duration and light intensity, cyclic lighting schedules (increased number of light/dark cycles over 24 h, same total illuminated time and intensity), and intermittent and fluctuating lighting (with intervals ranging from 60 s to 60 min). The most common crops investigated were leafy greens, although some fruiting, ornamental, and model crop Arabidopsis are included. Under constant DLI, extending photoperiod and reducing light intensity generally increased the total amount of biomass accumulation and increased light interception. Increases in the number of shortened light/dark cycles contributed to decreased yield, leaf area, and photosynthetic rate, compared to the more standard single light/dark cycle. Intermittent and fluctuating lighting regimes generally reduced biomass accumulation and light interception. These results indicate that the total amount of light delivered to crops is important, but how that light is delivered can influence crop growth. This review will be useful for growers and researchers when designing lighting systems and regimes to produce horticultural crops in indoor plant environment systems.

Quantifying the impact of management on the three-dimensional structure of boreal forests

Forest management practices modify the composition and three-dimensional structure of boreal forests. Such changes affect light regimes, microclimate and habitat availability in forests, thus contributing to the regulation of ecosystem functioning and biodiversity. Compared to traditional even-aged forestry, prevalent in Fennoscandia since the mid-20th century, uneven-aged forestry has emerged as an alternative approach that may lead to more diverse and resilient forests, as well as a more sustainable provision of ecosystem services. However, the biophysical impacts of uneven-aged strategies have not yet been robustly quantified. Here, we present a detailed assessment of the structural characteristics of even-aged and uneven-aged boreal forest stands in southern Finland, aiming to clarify how these different management approaches regulate three-dimensional forest structure. Using terrestrial laser scanning, we derived and compared several structural traits closely linked to forest functioning. We found that, although different management types result in similar patterns in total plant material, they differ significantly on how plant material is allocated within vertical strata. Moreover, we demonstrated that commonly used structural diversity metrics cannot not capture the morphological intricacies arising from the three-dimensional dispersion of plant material inside the forest stand. Our results highlight the dynamic nature of even-aged forests, where the structural characteristics change with the rotation, whereas uneven-aged forest structures are more stable over time. Precise quantification of forest structure will help to understand which attributes impact the environmental functions and conditions that modify ecosystem services, and how these are altered with forest management.

Plant-Growth Promoting Microbes Change the Photosynthetic Response to Light Quality in Spinach.

In this study, the combined effect of plant growth under different light quality and the application of plant-growth-promoting microbes (PGPM) was considered on spinach (Spinacia oleracea L.) to assess the influence of these factors on the photosynthetic performance. To pursue this goal, spinach plants were grown in a growth chamber at two different light quality regimes, full-spectrum white light (W) and red-blue light (RB), with (I) or without (NI) PGPM-based inoculants. Photosynthesis-light response curves (LRC) and photosynthesis-CO2 response curves (CRC) were performed for the four growth conditions (W-NI, RB-NI, W-I, and RB-I). At each step of LRC and CRC, net photosynthesis (PN), stomatal conductance (gs), Ci/Ca ratio, water use efficiency (WUEi), and fluorescence indexes were calculated. Moreover, parameters derived from the fitting of LRC, such as light-saturated net photosynthesis (PNmax), apparent light efficiency (Qpp), and dark respiration (Rd), as well as the Rubisco large subunit amount, were also determined. In not-inoculated plants, the growth under RB- regime improved PN compared to W-light because it increased stomatal conductance and favored the Rubisco synthesis. Furthermore, the RB regime also stimulates the processes of light conversion into chemical energy through chloroplasts, as indicated by the higher values of Qpp and PNmax in RB compared to W plants. On the contrary, in inoculated plants, the PN enhancement was significantly higher in W (30%) than in RB plants (17%), which showed the highest Rubisco content among all treatments. Our results indicate that the plant-growth-promoting microbes alter the photosynthetic response to light quality. This issue must be considered when PGPMs are used to improve plant growth performance in a controlled environment using artificial lighting.

A Network‐Scale Modeling Framework for Stream Metabolism, Ecosystem Efficiency, and Their Response to Climate Change

AbstractClimate change and the predicted warmer temperatures and more extreme hydrological regimes could affect freshwater ecosystems and their energy pathways. To appreciate the complex spatial and temporal interactions of carbon cycling in flowing waters, ecosystem metabolism (gross primary production [GPP] and ecosystem respiration [ER]) must be resolved at the scale of an entire river network. Here, we propose a meta‐ecosystem framework that couples light and temperature regimes with a reach‐scale ecosystem model and integrates network structure, catchment land cover, and the hydrologic regime. The model simulates the distributed functioning of dissolved and particulate organic carbon, autotrophic biomass, and thus ecosystem metabolism, and reproduces fairly well the metabolic regimes observed in 12 reaches of the Ybbs River network, Austria. Results show that the annual network–scale metabolism was heterotrophic, yet with a clear peak of autotrophy in spring. Autochthonous energy sources contributed 43% of the total ER. We further investigated the effect of altered thermal and hydrologic regimes on metabolism and ecosystem efficiency. We predicted that an increase of 2.5°C in average stream water temperature could boost ER and GPP by 31% (24%–57%) and 28% (5%–57%), respectively. The effect of flashier hydrologic regimes is more complex and depends on autotrophic biomass density. The analysis shows the complex interactions between environmental conditions and biota in shaping stream metabolism and highlights the existing knowledge gaps for reliable predictions of the effects of climate change in these ecosystems.

The Influence of Different Lighting and Feeding Regime on the Activity of Energy Metabolism Enzymes in Farmed Atlantic Salmon Fingerlings

The effect of constant and natural lighting modes in combination with different feeding regimes on the activity of energy and carbohydrate metabolism enzymes in the muscles and liver of salmon under-yearlings artificially grown in aquaculture in the southern region of Russia was investigated. The revealed differences in the activity of the studied enzymes in under-yearlings indicate changes in the level of energy metabolism and the use of carbohydrates in the processes of ATP synthesis and other biosynthesis pathways in muscles and liver, depending on lighting conditions and in combination with the feeding regime. The high level of aerobic metabolism in the muscles and the increased use of carbohydrates in glycolysis in the liver in salmon fingerlings raised under constant light corresponded to their highest average weight gain. In individuals from all experimental groups, changes in the activity of the studied enzymes were found in dependence on the time after the start of the experiment, that indicated an increase in the levels of aerobic and anaerobic metabolism in muscles and glycolysis in the liver, necessary for the biosynthesis processes during growth.

PHOSPHOLIPID COMPOSITION OF FINGERLINGS OF ATLANTIC SALMON &lt;i&gt;SALMO SALAR&lt;/i&gt; DURING GROWTH AND DEVELOPMENT IN AQUACULTURE: THE EFFECT OF DIFFERENT LIGHTING AND FEEDING REGIMES

The effect of different modes of feeding and lighting (natural and continuous) on the phospholipid composition of Atlantic salmon fingerlings reared under commercial aquaculture in the summer-autumn period in North Ossetia-Alania was studied. Qualitative and quantitative determination of phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, lysophosphatidylcholine, sphingomyelin was carried out by high performance liquid chromatography. A decrease (September-November) The content of the studied phospholipids in fingerlings decreased, which should be considered primarily as a biochemical adaptation of development, preparation of juveniles for the upcoming smoltification. The effects of lighting and feeding regime on phospholipid composition were found mainly in fish reared under constant lighting and 24/7 feeding and fish reared under natural light and feeding during daylight hours, however, the observed changes were not specific to a particular experimental group of fish in the framework of this study.

Distribution, species composition and bioecology of autotrophic weeds in potato and vegetable crops

Increasing the gross yield and quality of the potato and vegetable crops is of great importance in meeting the food needs of the population in the world. In many countries of the world, including China, weeding and herbicides are applied together with potato and vegetable planting, or during the growing season. This research intends to to determine the current state of the distribution and damage caused by the types of weeds and flower parasites in the fields of potato and vegetable crops in the conditions of irrigated typical and meadow gray soils of the Tashkent region. In this research, laboratory, field experiments in research works, phenological observations, biometric measurements were done using “Methods of conducting field experiments”, the number of weeds were studied according to A.M. Tulikov’s methodological manuals, and determination of grain suppression, statistical analysis of research results was done in accordance with A.B. Dospekhov. The results showed that among the biological groups, the group of spring weeds was dominant, accounted for 48% of the species composition. This group consisted of 14 rounds, whereas the overwintering biogroup consisted of 6 species (21%), followed by 4 species of rhizomatous weeds (14%), 3 species of taproots (11%), 1 species each of taproots and nodules (3%). According to the experiments, 45 % of the species recorded in beet fields were adapted to grow among mowed crops. This pattern was apparently related to more favorable heat, light, and nutrient regime conditions created in mowed crop fields for weed growth and development.

Research Progress and Effects of Light on Poultry Circadian Rhythm Regulation Based on CiteSpace

Light is not only an important environmental regulation factor in poultry growth and development, but it is also a key factor affecting circadian rhythm. To explore research frontiers between light and circadian rhythm, this study analyzes related literature in the field of light and circadian rhythm from the Web of Science core database and draws a knowledge graph using CiteSpace, presenting the subject distribution and research frontiers. This study also focuses on the regulation of light in the circadian rhythm of poultry, explores the effects of light on the growth and immunity of poultry, and analyzes the regulatory effect of light on melatonin levels. In summary, the current research frontiers of light and circadian rhythm are lighting, hepatocytes, the suprachiasmatic nucleus (SCN), blue light, and immune function. Light regimes played important roles in poultry welfare, yield, growth and development and affected the circadian rhythm in poultry by regulating melatonin levels. The exploration of the relationships between clock genes and circadian rhythm was important for the application of light regulation in poultry.

Application of point cloud data to assess edge effects on rainforest structural characteristics in tropical Sumatra, Indonesia

ContextIn forestry, edge zones created by forest degradation and fragmentation are more susceptible to disturbances and extreme weather events. The increase in light regime near the edge can greatly alter forest microclimate and forest structure in the long term. In this context, understanding edge effects and their impact on forest structure could help to identify risks, facilitate forest management decisions or prioritise areas for conservation.ObjectiveIn this paper, we focus on the application of airborne laser scanning (ALS) data to assess the impact of edge effects on forest structural metrics in degraded rainforests in Sumatra, Indonesia. Changes in structural heterogeneity with respect to distance from an edge were also quantified.MethodsWe used 22 ALS structural metrics extracted from 105 plots in secondary forests adjacent to oil palm plantations and analysed the change in canopy structure across edge-to-interior transects. In addition, 91 plots taken from less disturbed areas were used as reference for comparison with the near-to-edge plots.ResultsOur analysis found strong evidence of degradation in the secondary forests studied, with multiple edge interactions resulting in a non-diminishing effect even at long distances from the forest edge. On average, we observed a large decrease of about 40% in all metrics of canopy height and about 25% in some metrics of canopy structure across all distances from an edge when compared to the interior forest conditions. Thus, in our forests, canopy height and structure were more susceptible to edge effects than metrics related to canopy gaps. Finally, the degraded forest in our study exhibited lower structural complexity, both at patch and landscape levels, suggesting that disturbances can greatly alter structural complexity in tropical rainforests.ConclusionOur study confirms the potential of ALS-derived vegetation metrics to study and understand the effects of forest edges and the associated changes in structural complexity over large areas in tropical rainforests. The approach followed here is transferrable to similarly fragmented landscapes in the tropics.

EFFECTS OF VARIOUS LIGHT INTENSITIES ON PHYCOCYANIN COMPOSITION OF CYANOBACTERIUM LIMNOSPIRA FUSIFORMIS (VORONICHIN) NOWICKA-KRAWCZYK, MÜHLSTEINOVÁ &amp; HAUER

Phycocyanin denotes a photosynthetic pigment discovered in Rhodophyta and cyanobacteria, which has been used in medical, industrial, and agricultural applications. In general, phycocyanin production by cyanobacteria depends on many environmental conditions, mainly light during the cultivation period. The goal of this research was to see how various light intensities of 47, 52, as well as 60 µmol m-2 s-1, affected the Phycocyanin production of cyanobacterium Limnospira fusiformis cultured in Zarrouk medium with a maximum temperature of 28°C. The outcomes revealed that with mild light intensity (52 µmol m-2 s-1), increased phycocyanin production of 11.94 ng/mg took place. With regard to greater light intensity (60 µmol m-2 s-1), the lesser phycocyanin production of 0.57 ng/mg took place. These results give a good impression that moderate lighting increases phycocyanin production, but high light intensity inhibits it. The statistical analysis results also showed that there are significant differences between the light intensities used in the study at a level of p&lt;0.05. Therefore, this study concluded that phycocyanin was affected by light intensity. Light regime optimization gives a good yield of this pigment. In this study, high phycocyanin production by cyanobacterium Limnospira fusiformis occurred in mild light intensity (52 µmol m-2 s-1).

The effect of temperature and salinity on DMSP production in Gephyrocapsa oceanica (Isochrysidales, Coccolithophyceae)

ABSTRACT A subtropical clone of Gephyrocapsa oceanica was grown over the temperature and salinity range 10–30°C and 20‰–45‰ respectively. Cellular DMSP increased with increasing salinity, compatible with the hypothesis that DMSP is a compatible osmolyte. Cellular DMSP content was highest at colder temperatures and decreased as temperature increased. Net DMSP production rate also depended on cell size and growth rate was greatest about 2°C below the optimum growth temperature of 20°C for this clone. This resulted in a unimodal response of net DMSP production to increasing temperature: net DMSP production increased with increasing temperature when the cells were growing at temperatures below optimum for growth. At and above optimum growth temperature, further warming decreased net DMSP production. For the effect of temperature alone, in the subtropical oceans, where G. oceanica is growing at or above its optimum, further warming due to climate change will result in decreased net DMSP production and so a probable decrease in the flux of DMS to the atmosphere and sulphate aerosol production. Inasmuch as these aerosols modulate cloud albedo and longevity then these too will both decrease, resulting in a positive feedback response for temperature. The reverse effect may occur in higher latitude oceans where growth temperature is below optimum. The exact response in both regions is complicated because warming will also enhance water column stratification and may reduce mixed layer depths, affecting both nutrient and light regimes, as well as possible species succession effects. Further work is required to investigate these other indirect temperature effects.

Molecular structures reveal the origin of spectral variation in cryptophyte light harvesting antenna proteins.

In addition to their membrane-bound chlorophyll a/c light-harvesting antenna, the cryptophyte algae have evolved a unique phycobiliprotein antenna system located in the thylakoid lumen. The basic unit of this antenna consists of two copies of an αβ protomer where the α and β subunits scaffold different combinations of a limited number of linear tetrapyrrole chromophores. While the β subunit is highly conserved, encoded by a single plastid gene, the nuclear-encoded α subunits have evolved diversified multigene families. It is still unclear how this sequence diversity results in the spectral diversity of the mature proteins. By careful examination of three newly determined crystal structures in comparison with three previously obtained, we show how the α subunit amino acid sequences control chromophore conformations and hence spectral properties even when the chromophores are identical. Previously we have shown that α subunits control the quaternary structure of the mature αβ.αβ complex (either open or closed), however, each species appeared to only harbor a single quaternary form. Here we show that species of the Hemiselmis genus contain expressed α subunit genes that encode both distinct quaternary structures. Finally, we have discovered a common single-copy gene (expressed into protein) consisting of tandem copies of a small α subunit that could potentially scaffold pairs of light harvesting units. Together, our results show how the diversity of the multigene α subunit family produces a range of mature cryptophyte antenna proteins with differing spectral properties, and the potential for minor forms that could contribute to acclimation to varying light regimes.

Theoretical growth rate of microalgae under high/low-flashing light

Dynamic light regimes strongly impact microalgal photosynthesis efficiency. Finding the optimal way to supply light is then a tricky problem, especially when the growth rate is inhibited by overexposition to light and, at the same time, there is a lack of light in the deepest part of the culture. In this paper, we use the Han model to study the theoretical microalgal growth rate by applying periodically two different light intensities. Two approaches are considered depending on the period of the light pattern. For a large light period, we demonstrate that the average photosynthetic rate can be improved under some conditions. Moreover, we can also enhance the growth rate at steady state as given by the PI-curve. Although, these conditions change through the depth of a bioreactor. This theoretical improvement in the range of 10-15% is due to a recovery of photoinhibited cells during the high irradiance phase. We give a minimal value of the duty cycle for which the optimal irradiance is perceived by the algae culture under flashing light regime.

Analysis of Discrete-Time Queues with Branching Arrivals

We consider a discrete-time single server queueing system, where arrivals stem from a multi-type Galton–Watson branching process with migration. This branching-type arrival process exhibits intricate correlation, and the performance of the corresponding queueing process can be assessed analytically. We find closed-form expressions for various moments of both the queue content and packet delay. Close inspection of the arrival process at hand, however, reveals that sample paths consist of large independent bursts of arrivals followed by geometrically distributed periods without arrivals. Allowing for non-geometric periods without arrivals, and correlated bursts, we apply π-thinning on the arrival process. As no closed-form expressions can be obtained for the performance of the corresponding queueing system, we focus on approximations of the main performance measures in the light and heavy traffic regimes.

Adaptive photoperiod interpretation modulates phenological timing in Atlantic salmon

Photoperiod, the portion of 24-h cycle during which an organism is exposed to illumination, is an important phenological cue in many animals. However, despite its influence on critical biological processes, there remain many unknowns regarding how variations in light intensity translate into perceived photoperiod. This experiment examined how light intensity variations affect perceived photoperiod in Atlantic salmon (Salmo salar) to determine whether photoperiod interpretation is, a) fixed such that anything above a minimum detection threshold is regarded as ‘illumination’, or b) adaptive and varies with recent light exposure. To do this we compared the frequency of smoltification and sexual maturation between groups of male parr which were exposed to one of eight light regimes on a 12:12 cycling regime (12-hour day/12-hour night). The eight regimes were divided into two treatments, four with ‘High’ daytime light intensity and four with ‘Low’ daytime light intensity. The ‘High' and ‘Low' intensity treatments were each sub-divided into four groups for which the subjective ‘night’ light intensity was 100%, 10%, 1% and 0% of the daytime light intensity, with four replicate tanks of each treatment. The results show that above a minimum detection threshold, Atlantic salmon have adaptive photoperiod interpretation which varies with recent light exposure, and that adaptive photoperiod interpretation modulates the timing of the parr-smolt transformation and sexual maturation. Further, we show that photoperiod interpretation varies between closely related families. Given the influence of phenological timing on species survival, our results reveal a critical role for integration of photoperiod interpretation in attempts to understand how geographically shifting thermal niches due to climate change will affect future populations.

Light prevents pathogen-induced aqueous microenvironments via potentiation of salicylic acid signaling

Many plant pathogens induce water-soaked lesions in infected tissues. In the case of Pseudomonas syringae (Pst), water-soaking effectors stimulate abscisic acid (ABA) production and signaling, resulting in stomatal closure. This reduces transpiration, increases water accumulation, and induces an apoplastic microenvironment favorable for bacterial growth. Stomata are sensitive to environmental conditions, including light. Here, we show that a period of darkness is required for water-soaking, and that a constant light regime abrogates stomatal closure by Pst. We find that constant light induces resistance to Pst, and that this effect requires salicylic acid (SA). Constant light did not alter effector-induced accumulation of ABA, but induced greater SA production, promoting stomatal opening despite the presence of ABA. Furthermore, application of a SA analog was sufficient to prevent pathogen-induced stomatal closure and water-soaking. Our results suggest potential approaches for interfering with a common virulence strategy, as well as providing a physiological mechanism by which SA functions in defense against pathogens.

Photoinhibition and Photoprotective Responses of a Brown Marine Macroalga Acclimated to Different Light and Nutrient Regimes.

Plants and brown algae avoid photoinhibition (decline in photosystem II efficiency, Fv/Fm) caused by excess light energy and oxidative stress through several photoprotective mechanisms, such as antioxidant xanthophyll production and heat dissipation. The heat dissipation can be measured as non-photochemical quenching (NPQ) and is strongly driven by de-epoxidation of xanthophyll cycle pigments (XCP). Although NPQ is known to increase under high light acclimation and nutrient-deficient conditions, a few studies have investigated the combined effects of the conditions on both NPQ and associated xanthophyll-to-chlorophyll (Chl) a ratio. The present study investigated the photosynthetic parameters of the brown alga Sargassum fusiforme acclimated to three irradiance levels combined with three nutrient levels. Elevated irradiance decreased Fv/Fm but increased NPQ, XCP/Chl a ratio, and fucoxanthin/Chl a ratio, suggesting the photoprotective role of antioxidant fucoxanthin in brown algae. Reduced nutrient availability increased NPQ but had no effect on the other variables, including XCP/Chl a ratio and its de-epoxidation state. The results indicate that NPQ can be used as a sensitive stress marker for nutrient deficiency, but cannot be used to estimate XCP pool size and state.

Need for speed: a breakthrough speed breeding protocol for hemp

Need for speed: a breakthrough speed breeding protocol for hemp

Quantifying binding kinetics with fluorescence microscopy.

Many processes crucial to life are regulated by the binding and unbinding of key molecules, such as target molecules to allosteric protein sites or transcription factors to gene loci. Capturing such binding events in living systems is often accomplished using fluorescence based methods. However, accurately determining assembly and disassembly rates from fluorescence data is challenging on account of the photophysical behavior of the fluorescent labels such as blinking and photobleaching. Here we present a Bayesian method that can simultaneously learn binding and unbinding rates while correcting for photophysical artifacts. We show that our method is robust across low light regimes relevant to in vivo experiments. We benchmark our method on both simulated and experimental data.