Length Of Photoperiod Research Articles

Light Flux Density and Photoperiod Affect Growth and Secondary Metabolism in Fully Expanded Basil Plants.

Indoor production of basil (Ocimum basilicum L.) is influenced by light spectrum, photosynthetic photon flux density (PPFD), and the photoperiod. To investigate the effects of different lighting on growth, chlorophyll content, and secondary metabolism, basil plants were grown from seedlings to fully expanded plants in microcosm devices under different light conditions: (a) white light at 250 and 380 μmol·m-2·s-1 under 16/8 h light/dark and (b) white light at 380 μmol·m-2·s-1 under 16/8 and 24/0 h light/dark. A higher yield was recorded under 380 μmol·m-2·s-1 compared to 250 μmol·m-2·s-1 (fresh and dry biomasses 260.6 ± 11.3 g vs. 144.9 ± 14.6 g and 34.1 ± 2.6 g vs. 13.2 ± 1.4 g, respectively), but not under longer photoperiods. No differences in plant height and chlorophyll content index were recorded, regardless of the PPFD level and photoperiod length. Almost the same volatile organic compounds (VOCs) were detected under the different lighting treatments, belonging to terpenes, aldehydes, alcohols, esters, and ketones. Linalool, eucalyptol, and eugenol were the main VOCs regardless of the lighting conditions. The multivariate data analysis showed a sharp separation of non-volatile metabolites in apical and middle leaves, but this was not related to different PPFD levels. Higher levels of sesquiterpenes and monoterpenes were detected in plants grown under 250 μmol·m-2·s-1 and 380 μmol·m-2·s-1, respectively. A low separation of non-volatile metabolites based on the photoperiod length and VOC overexpression under longer photoperiods were also highlighted.

The influence of photoperiod on development and population growth performance of the Phytoseiulus persimilis fed on Tetranychus urticae

ABSTRACT Environmental factors, such as photoperiod, can play an important role in the development of mites. The influence of photoperiod (L:D = 4:20, 8:16, 12:12, 16:8 and 20:4) on the development and population parameters of the predatory mite, Phytoseiulus persimilis Athias-Henriot fed on two-spotted spider mite, Tetranychus urticae Koch was examined under laboratory conditions. Pre-adult development decreased with increasing photoperiod until 12 h, after which the development period progressively increased. Longevity of both sexes demonstrated significant differences throughout photoperiods, with the longest at 20:4 L:D and the shortest at 8:16 L:D. The highest value of mean total fecundity was 13.62 egg/female at 12:12 L:D photoperiod. The net reproductive rate (R 0), the intrinsic rate of increase (r) and the finite rate of increase (λ), showed the highest value at 12:12 L:D. The R 0, r and λ for P. persimilis increased with increasing photoperiod from 4:20 to 12:12 L:D, but decreased sharply at the 16:8 and 20:4 L:D treatments. Our findings indicate that photoperiod has a significant role in advancing the rate of development, survival rate, and reproduction for commercial production of P. persimilis, with a 12:12 photoperiod length recognized as the ideal period for commercial production in culture.

Genetic Analyses of the Shape and Volume of Onion Bulbs and Daylength Effects on Bulbing

The formation of onion (Allium cepa) bulbs is affected by photoperiod length and onion germplasm is commonly classified as short- (SD), intermediate-, or long-day (LD) types. The objectives of this study were to develop a segregating family from a cross between doubled haploids (DHs) of LD and SD onions and complete genetic analyses of bulb shape and volume, as well as daylength effects on bulbing. DH parents and F1 and F2 progenies were grown in a greenhouse under lengthening days. The diameters of the neck constriction and pseudostems were measured weekly and their ratio was used as the determinant of bulbing. Bulbs were harvested when the foliage collapsed and the diameters and heights of individual bulbs were measured and used to calculate a shape index (diameter divided by height) and bulb volume. Single nucleotide polymorphisms (SNPs) were genotyped and a genetic map of 112 SNPs constructed. Genetic analysis revealed two highly significant quantitative trait loci (QTL) affected bulbing under increasing daylengths, and both QTL showed significant additive effects with no dominance. One highly significant QTL was detected for bulb-shape index and explained 30% of phenotypic variation for bulb shape. Three additional QTL were slightly above the significance threshold, and together these four QTL explained over 50% of the phenotypic variation for bulb shape. No significant QTL were detected for bulb volume. These results reveal that bulb-shape and daylength effects on bulbing are relatively simply inherited, and this research should facilitate introgression of traits between onion populations of different daylength sensitivities and efforts to modify bulb shape.

CRONOSOJA: a daily time-step hierarchical model predicting soybean development across maturity groups in the Southern Cone

Abstract Abstract. Accurate prediction of phenology is the most critical aspect for the development of models aimed at estimating seed yield, particularly in species that exhibit variable sensitivity to environmental factors throughout the cycle and among genotypes. With this purpose, we evaluated the phenology of 34 soybean varieties in field experiments located in Argentina, Uruguay and Paraguay. Experiments covered a broad range of maturity group (MG)s (2.2–6.8), sowing dates (SDs) (from spring to summer) and latitude range (24.9–35.6 °S), thus ensuring a wide range of thermo-photoperiodic conditions during the growing season. Based on the observed data, daily time-step models were developed and tested, first for each genotype, and then across MGs. We identified base temperatures specific for different developmental phases and an extra parameter for calculating the photoperiod effect after the R1 stage (flowering). Also, an optimum photoperiod length for each MG was found. Model selection showed that the determinants of phenology across MGs were mainly affecting the duration of vegetative and early reproductive phases. Even so, early phases of development were better predicted than later ones, particularly in locations with cool growing seasons, where the model tended to overestimate their duration. In summary, we have constructed a soybean phenology model that simulates phenology accurately across various geographic locations and sowing dates. The model’s process-based approach has resulted in root mean square errors ranging from 5.8 to 9.5 days for different developmental stages. The final model was made available at http://cronosoja.agro.uba.ar.

Effect of Photoperiod Duration on Efficiency of Low-Temperature Hardening of <i>Arabidopsis thaliana</i> Heynh. (L.)

The effect of photoperiod duration on efficiency of low-temperature hardening was investigated in Arabidopsis thaliana (L.) Heynh. plants, ecotype Col-0. Six-week-old plants were exposed to cold acclimation at a temperature of 2С during 1‒5 days at photoperiods of 0, 8, and 16 h (illuminance of 200 mol/(m2 s)). According to survival data and leakage of electrolytes after test freezing (6C, 24 h), the plants exposed to cold acclimation in the dark did not show frost resistance. The plants hardened in the light (irrespective of the length of photoperiod) considerably improved their frost resistance by the end of the cold-acclimation period. Net photosynthesis/dark respiration ratio in these plants was almost two times greater than in control material (without hardening). The plants exposed to a 16-h-long photoperiod surpassed the type of treatment with 8-h-long illumination both in the highest levels of accumulation of sugars (by almost 40%) and in the rate of reaching these levels in daily dynamics of hardening. It was shown that MDA content transiently rose during the first 24 h of hardening in the light and did not change in the dark, which may point to a signal role of lipid peroxidation products upon cold acclimation. It was discovered that the photoperiod duration affected the formation rate of frost resistance in A. thaliana plants. A more prolonged operation of A. thalianas photosynthetic apparatus at 16-h-long photoperiod considerably accelerated the accumulation of sugars upon cold acclimation and, therefore, hastened development of frost resistance as compared with an 8-h-long photoperiod. It was concluded that rapid formation of frost resistance in A. thaliana requires a combination of low above-zero temperature and 16-h-long photoperiod.

Potential of the worldwide-cultivated cyanobacterium Arthrospira platensis for CO2 mitigation: Impacts of photoperiod lengths and abiotic parameters on yield and efficiency

This study reports A. platensis capacity to capture and convert CO2 into biomass. The cyanobacterium was cultivated under controlled conditions with a 5 % v/v CO₂-enriched atmosphere at different photoperiods (light/dark): 12 h/12 h, 20 h/4 h, and 24 h (continuous light). The photoperiod influence on biomass growth and its effect on CO₂ uptake was evaluated by analyzing the supernatant dissolved inorganic carbon and nitrate concentration. The experimental dissolved inorganic carbon values were compared with numerical computations obtained from an established model. While the control without biomass stabilized at 36 ± 1.07 mgC/L of dissolved inorganic carbon, the A. platensis cultures stabilized at 675 ± 44.5 mgC/L on average. These results suggest that the alkalinity induced by photosynthesis and nitrate bio-assimilation enhances CO₂ dissolution in the culture medium. The photoperiod increase from 12 h/12 h to 24 h proved to boost the biomass productivity and CO₂ fixation rate from 0.05 to 0.13 g/L/d and 71.92 to 216.84 mgCO₂/L/d, respectively.

Molecular basis of polyglutamine-modulated ELF3 aggregation in Arabidopsis temperature response.

Some plants, like Arabidopsis thaliana, possess a molecular mechanism that allows them to sense changes in temperature and respond by modifying growth rate, photoperiod length and timing of flowering. Underlying this mechanism is a tripartite protein complex called the Evening Complex (EC) that functions as a DNA transcription repressor targeting growth-related genes. ELF3, a large disordered scaffolding protein, is the primary component of the EC. At low temperature ELF3 sits over DNA targets occluding transcription machinery and halting growth. Rising temperature promote ELF3 condensate formation as it becomes sequestered in large reversible nuclear condensates allowing DNA transcription and plant growth to proceed. A C-terminal prion-like domain (PrD) has been observed to be sufficient for ELF3 aggregation. Within this PrD region lies a poly-glutamine repeat of variable length, the size of which has been found to modulate the thermal responsiveness as measured by hypocotyl (stem) elongation and condensate formation. We use a polymer chain growth approach to build large ensembles and characterize monomeric ELF3-PrD at a range of polyQ lengths and temperatures. We then explore temperature-dependent dynamics of wild-type ELF3-PrD and a mutant, F527A, using chain growth structures as initial conformations for replica exchange (REST2) simulations. We find increased solvent accessibility of expanded polyQ tracts, promotion of temperature-sensitive helices adjacent to polyQ tracts, and exposure of a cluster of aromatic residues at increased temperature, all three of which promote inter-protein interaction. Protein condensate formation is a ubiquitous but poorly understood mechanism implicated in a range of biological functions and malfunction. Our computational approach to understanding the molecular basis for the temperature sensitivity of this system has wider implications on the understanding of phenomena regulating condensate formation more generally.

Longday Photoperiod Accelerates Flowering in Indonesian Non-Flowering Shallot Variety

The shallot flowering ability is essential to increase productivity by assembling superior varieties through the hybridization and botanical seed or true shallot seed (TSS). The photoperiod length greatly influences flowering in shallot, which plays a significant role in the flowering initiation. This research aims to study flowering responses with different photoperiods in shallots. Six shallot varieties: Lokananta, Bima Brebes, Rubaru, Palasa, Biru Lancor, and Batu Ijo, were grown in a greenhouse under a short-day photoperiod, 10 hours of natural condition photoperiod for 60 days. Furthermore, half of the plants are moved to long-day treatment. The temperature during plantation is around from 7-13°C (similar to Indonesia’s upland temperature). The results indicate that long-day photoperiod increased the shallot flowering response on the five shallot varieties tested, except Rubaru. Rubaru could not produce flowers under both photoperiod treatments 120 days after plantation (DAP). Lokananta variety is the most responsive variety to flower, even on short-day photoperiod. Palasa variety, which could not flower under Indonesian photoperiod conditions, could produce flowers on long-day treatment and underplanting conditions at low to moderate temperatures.

0196 Retinal responsivity is associated with circadian phase and circadian alignment but not sleep timing

Abstract Introduction Light entrains the central circadian clock, with projections from the retina to the SCN through melanopsin-containing retinal ganglion cells (ipRGCs). Altered responsivity to light reflects ipRGC functioning and may be a physiological vulnerability for disrupted photoentrainment. Understanding how retinal responsivity relates to sleep and circadian timing may inform who might most benefit from sleep and circadian interventions. Methods 64 participants (85 observations) ages 20-66 years old were recruited during winter (n=35) and summer months (n=50), and included individuals with seasonal depression (n=33) and nonseasonal, never depressed controls (n=31). The post-illumination pupil response (PIPR) to red and blue light was used to measure the responsivity of ipRGCs (average 1:30pm; 10am-7pm). Circadian phase was assessed using Dim Light Melatonin Onset (DLMO), collected every 30-minutes on Friday evenings. Midsleep timing was measured using actigraphy (average number nights=4), and circadian alignment was calculated as the DLMO-midsleep phase angle. We performed a multilevel regression to determine the relationship between PIPR and markers of sleep and circadian timing, accounting for repeated seasonal assessments with a random intercept of participant. Covariates included age, gender, diagnostic group, and circadian time of PIPR assessments. We ran sensitivity analyses including photoperiod length on the day of PIPR assessment to account for potential light exposure on the PIPR. Results Greater retinal responsivity was associated with later DLMO (b=4.45; partially standardized b=0.28; SE=1.84; p=0.03), and shorter DLMO-midsleep phase angle (b= -7.33; partially standardized b= -0.32; SE=2.51; p=0.004), but not midsleep (b= -3.44; partially standardized b= -0.14; SE=2.35; p>0.05). Individuals with later DLMO had PIPR assessments at earlier circadian times (b= -0.12; SE=0.04; p=0.01). Older participants (b= -0.04; SE=0.02; p=0.04) and controls (b= -0.95; SE=0.44; p=0.04) had earlier sleep midpoints, but covariates were not associated with circadian markers. The association between circadian timing and PIPR became nonsignificant (b=4.15; partially standardized b=0.26; SE=1.88; p=0.06) when including photoperiod. Conclusion Retinal responsivity was associated with circadian but not behavioral sleep timing, suggesting ipRGC functioning may have downstream effects on circadian entrainment. Assessing circadian variation of retinal responsivity remains a crucial next step prior to testing whether retinal responsivity impacts response to circadian-focused interventions. Support (If Any) NIMH K.A.R.MH103303

Bright as day and dark as night: light-dependant energy for lipid biosynthesis and production in microalgae.

Microalgae are photosynthetic organisms functioning as the green bio-factories for various pharmaceutical and biofuel products. To date, numerous attempts have been carried out to manipulate culture conditions to maximize the production of the desired metabolites. Because light is the energy source of microalgae for their growth and metabolites biosynthesis, it has been one of the most investigated variables emphasized on the deep understanding of how microalgae respond towards light changes as an external stimulus. This review discusses the effects of different light sources, light intensities, light wavelengths and length of photoperiod on various microalgae species, especially in terms of biomass and lipid productivity. Additionally, the relationship between photoregulation processes and lipid productivity of microalgae are also deliberated. The current available approaches of microalgae mass cultivation, including different types of open and closed systems are recapitulated with the intention to highlight the significant insights for the design of future photoreactors.

Long-term effect of elevated air humidity on seasonal variability in diurnal leaf conductance and gas exchange in silver birch

Environmental conditions and photoperiod length drive the seasonal variability of gas exchange in plants. Still, little is known about trees’ adaptation to climate change, expressed as a delay in decreasing photosynthetic capacity at the end of the growing season. We investigated the effect of elevated air humidity (RH) and sampling period (from July to September) on the variability of net photosynthesis (An), dark respiration (R), daytime (gl_day) and night-time (gl_night) leaf conductance, an index of leaf chlorophyll content (SPAD), and An:SPAD ratio in cut shoots of silver birch (Betula pendula Roth). Measurements of cut shoots were conducted in a climate chamber to eliminate the direct effect of field conditions. The An, An:SPAD ratio, and gl_day were higher in the humidification treatment (H) than in the control (C) (P < 0.05) in autumn. The R was higher in the control than in the humidification treatment across the study period. The gl_night increased considerably in September in both treatments (P < 0.05) and was significantly correlated with R. Our findings suggest that autumnal leaf conductance and gas exchange in silver birch are considerably influenced by long-term exposure to elevated RH and are probably related to a complex of leaf senescence processes, including nitrogen retranslocation.

Effect of seasonally changing aerial environment on testosterone in Karagouniko and Chios sheep

A well-established activity in Greece and other Mediterranean countries is sheep farming. Karagouniko and Chios sheep are promising breeds and targets for the reproductive physiologist’s attention. Under this context, part of the reproductive physiology of Karagouniko and Chios was investigated, taking into account the environment. Specifically, four time periods were considered; April-June (Long days, increasing photoperiod length), July-September (Long days, decreasing photoperiod length), October-December (Short days, decreasing photoperiod length), and January-March (Short days, increasing photoperiod length). The effect of the period on the concentration of the testosterone (main male hormone) in rams of the breeds above was studied, by using repeated measures analysis of variance, also taking into account the environmental variables air temperature, relative humidity, sunshine, rainfall, and photoperiod, in the Artificial Insemination Center of Karditsa (39°21’18’’N, 21°54’19’’E), Greece. The lowering of photoperiod from April-June to July-September (long days) and afterward, even more to October-December (short days) coincided with a progressive increase of testosterone in both breeds. Photoperiod seems to have a major role in the concentration of Karagouniko and Chios breeds' testosterone compared to the other environmental variables. When considering the whole experimental period, Chios sheep had significantly higher (P < 0.05) testosterone (1.95 ng/ml) than the Karagouniko one (1.55 ng/ml). Our findings could contribute towards the more rational exploitation of the examined sheep breeds.

Influence of the photoperiod duration on the biological properties of PGPR-bacteria of the soybean rhizosphere (Glycine max (L.) Merr.)

Physiological and biochemical properties of the PGPR-bacteria isolated from the rhizosphere of the soybean (Glycine max (L.) Merr), grown under different photoperiod duration were investigated. A short-day soybean cultivar Clark was selected for the study; it was exposed to a long natural day (16 hours – control) and a short day (9 hours – test). The short day was created by darkening the plants with light-tight chambers for three weeks from 5 p.m. to 9 a.m. the next day. The field experiment was carried out at the experimental site of the Department of Physiology and Biochemistry of Plants and Microorganisms of V.N. Karazin Kharkiv National University, located in the Botanical garden of the University. Soil samples from the soybean rhizosphere were taken at the budding phase; the bacteria were isolated in a nitrogen-depleted medium. We studied cultural characteristics of bacteria (Gram stain, bacterial morphology, mobility, type of respiration, oxidase and catalase positivity) and their physiological and biochemical properties (the capability of proteolysis and nitrate reduction). A greater variety of bacteria in terms of cultural properties was isolated from the rhizosphere of soybean grown under long-day conditions. Probably, this is due to the higher intensity of root exudate excretion (chemoattagative factors) during the long day which is caused by different metabolic intensities at various photoperiod lengths. The highest number of isolates with proteolytic activity was observed in bacteria under long-day conditions. This property is considered to have a significant impact on the mineral nutrition of plants. Analysis of literature data showed that the higher amount of protein is accumulated in soybean leaves during the long day as a result of intensification of nitrogen nutrition provided by bacteria capable of proteolysis. Under conditions of a short day, a higher number of isolates capable of nitrate reduction was observed. A decrease in the number of isolates capable of nitrate reduction under a long-day condition can be explained by the possible repression of assimilative nitrate reductase by a large amount of ammonium formed during the ammonification of organic substances. Thus, the obtained results suggest that the photoperiod duration can determine physiological and biochemical properties of the rhizosphere microbiota of the plants sensitive to this factor.

Critical Photoperiod and Optimal Quality of Night Interruption Light for Runner Induction in June-Bearing Strawberries

The optimal photoperiod and light quality for runner induction in strawberries ‘Sulhyang’ and ‘Maehyang’ were investigated. Two experiments were carried out in a semi-closed walk-in growth chamber with 25/15 °C day/night temperatures and a light intensity of 250 μmol·m–2·s–1photosynthetic photon flux density (PPFD) provided from white light-emitting diodes (LEDs). In the first experiment, plants were treated with a photoperiod of either 12, 14, 16, 18, 20, or 22 h In the second experiment, a total of 4 h of night interruption (NI) light at an intensity of 70 μmol·m–2·s–1PPFD provided from either red, blue, green, white, or far-red LED in addition to 11 h short day (SD). The results showed that both ‘Sulhyang’ and ‘Maehyang’ produced runners when a photoperiod was longer than 16 h, and the number of runners induced positively correlated with the length of photoperiod. However, the plant growth, contents of chlorophyll, sugar and starch, and Fv/Fo decreased in a 22 h photoperiod. All qualities of the NI light, especially red light, significantly increased the number of runners and daughter plants induced per plant as compared with those in the SD treatment in both cultivars. In a conclusion, a photoperiod between 16 and 20 h and NI light, especially red NI light, can be used for quality runner induction in both ‘Sulhyang’ and ‘Maehyang’.

Phytoplankton communities in temporary ponds under different climate scenarios

Temporary water bodies, especially vernal pools, are the most sensitive aquatic environments to climate change yet the least studied. Their functioning largely depends on their phytoplankton community structure. This study aimed to determine how temperature and photoperiod length (by simulating inundation in different parts of the year under five climate scenarios) affect the succession and structure of phytoplankton communities soon after inundation. Photoperiod was the most important factor affecting phytoplankton species richness, total abundance and the abundance of taxonomic groups in the course of succession. A long photoperiod (16 h) and a moderate temperature (16 °C) in vernal pool microcosms (late spring inundation after a warm snowless winter) were the most favourable conditions for phytoplankton growth (especially for the main taxonomic groups: chlorophytes and cryptophytes) and species richness. With short photoperiods (inundation in winter) and low temperatures, the communities transformed towards diatoms, euglenoids and cyanobacteria. In line with our predictions, a high temperature (25 °C) favoured a decline in phytoplankton species diversity. Our study shows that climate change will result in seasonal shifts in species abundance or even in their disappearance and, finally, in potential strong changes in the biodiversity and food webs of aquatic ecosystems in the future.

Growth and health status of Pangasionodon hypophthalmus reared under manipulated photoperiod conditions

Background: In general, the length of photoperiod affects the physiology of Pangasionodon hypophthalmus. This study aimed to understand the growth and health status of this fish reared under manipulated photoperiods. Methods: The study was conducted between June to August 2020[A1] . Three treatments were applied: control (natural photoperiod); 18 hours of darkness (18D6L; tanks were placed under a dark tarp tent for 18 hours); and 24 hours of darkness (24D0L; tanks were placed under a dark tarp tent continuously). Three replications were performed per treatment. At baseline, fish were approx. 7.5 cm [A2] total length (TL) and 4 g body weight (BW), and were reared in circular plastic tanks (100 L; 30 fish/tank) with aerators and filters, and fed with commercial fish feed pellet (2 times/day to satiation). Fish growth and survival were studied once/week, and blood and tissue samples were taken at the end of the experiment (8 th week). Tissue was formalin fixed and HE stained. Results: The survival of fish in all treatment was 100%. The fish reared in 24D0L and 18D6L grew better than control, achieving mean TL of 23 cm and BW of 98 g (control = 19 cm TL and 72 g BW). There was no difference in hematology condition or tissue structure between the three groups. Tissue structure of gill, kidney and liver were normal, but light abnormality due to parasites was present in the gill of fish reared in 24D0L. Blood samples for all three groups showed mean red blood cell count of 1,800,000 cells/ml and white blood cell (WBC) count of 55,200 cells/ml. WBC consisted of lymphocyte 65%, monocyte 24%, thrombocyte 6%, neutrophil 3%, eosinophil 1% and basophile 1%. Conclusion: Data obtained indicate that a short photoperiod improves the growth of P. hypophthalmus fish and does not negatively affects their health.

Growth and health status of Pangasionodon hypophthalmus reared under manipulated photoperiod conditions

Background: In general, the length of photoperiod affects the physiology of Pangasionodon hypophthalmus. This study aimed to understand the growth and health status of this fish reared under manipulated photoperiods. Methods: The study was conducted between June to August 2020[A1] . Three treatments were applied: control (natural photoperiod); 18 hours of darkness (18D6L; tanks were placed under a dark tarp tent for 18 hours); and 24 hours of darkness (24D0L; tanks were placed under a dark tarp tent continuously). Three replications were performed per treatment. At baseline, fish were approx. 7.5 cm [A2] total length (TL) and 4 g body weight (BW), and were reared in circular plastic tanks (100 L; 30 fish/tank) with aerators and filters, and fed with commercial fish feed pellet (2 times/day to satiation). Fish growth and survival were studied once/week, and blood and tissue samples were taken at the end of the experiment (8 th week). Tissue was formalin fixed and HE stained. Results: The survival of fish in all treatment was 100%. The fish reared in 24D0L and 18D6L grew better than control, achieving mean TL of 23 cm and BW of 98 g (control = 19 cm TL and 72 g BW). There was no difference in hematology condition or tissue structure between the three groups. Tissue structure of gill, kidney and liver were normal, but light abnormality due to parasites was present in the gill of fish reared in 24D0L. Blood samples for all three groups showed mean red blood cell count of 1,800,000 cells/ml and white blood cell (WBC) count of 55,200 cells/ml. WBC consisted of lymphocyte 65%, monocyte 24%, thrombocyte 6%, neutrophil 3%, eosinophil 1% and basophile 1%. Conclusion: Data obtained indicate that a short photoperiod improves the growth of P. hypophthalmus fish and does not negatively affects their health.

Nanda-Hamner Curves Show Huge Latitudinal Variation but No Circadian Components in Drosophila Montana Photoperiodism.

Insect species with a wide distribution offer a great opportunity to trace latitudinal variation in the photoperiodic regulation of traits important in reproduction and stress tolerances. We measured this variation in the photoperiodic time-measuring system underlying reproductive diapause in Drosophila montana, using a Nanda-Hamner (NH) protocol. None of the study strains showed diel rhythmicity in female diapause proportions under a constant day length (12 h) and varying night lengths in photoperiods ranging from 16 to 84 h at 16°C. In the northernmost strains (above 55°N), nearly all females entered diapause under all photoperiods and about half of them even in continuous darkness, while the females of the southern strains showed high diapause proportions only in the circadian 24 h photoperiod. Significant correlation between the strains’ mean diapause proportions in ≥ 24 h photoperiods and critical day length (CDL; half of the females enter diapause) suggests at least partial causal connection between the traits. Interestingly, females of the northern strains entered diapause even in ≤ 24 h photoperiods, where the night length was shorter than their critical night length (24 h - CDL), but where the females experienced a higher number of Light:Dark cycles than in 24 h photoperiods. NH experiments, performed on the control and selection lines in our previous selection experiment, and completed here, gave similar results and confirmed that selection for shorter, southern-type CDL decreases female diapausing rate in non-circadian photoperiods. Overall, our study shows that D. montana females measure night length quantitatively, that the photoperiodic counter may play a prominent but slightly different role in extra short and extra long photoperiods and that northern strains show high stability against perturbations in the photoperiod length and in the presence of LD cycles. These features are best explained by the quantitative versions of the damped external coincidence model.

Hematology of Pangasionodon hypopthalmus Reared Under Controlled Photoperiod

Manipulated photoperiod has been used to improve the growth of cultured Pangasionodon hypopthalmus. Photoperiod length affects the fish physiology in general and thus reflected in its hematological condition. The hematology of P. hypopthalmus reared in short photoperiod was studied in May–August 2020. There were three treatments applied, namely natural photoperiod (P-Nat, fish tanks were placed under clear plastic tent), 18 hours dark (P-18D, the tanks were placed under dark tarp tent for 18 hours) and 24 hours dark (P-24D, the tanks were placed under dark tarp tent continuously). The fish (3 inches TL, 4 grams BW) were reared in circular tanks ( 100 L) at a density of 30 fishes/tank and fed with commercial fish feed pellets twice a day,, ad libitum. Blood samples were obtained prior to the experiment and at the 8th week. Results showed no significant differences in hematological parameters of the fishes among treatments. The number of erythrocytes and leucocytes in the pre-treated fish was approximately 1,850,000 and 55,200 cells/ml, respectively. While those of the treated fish was 1,760,000 and 54,600 cells/ml (P-Nat); 1.760.000 and 55,000 cells/ml (P-18D) and 1,790,000 and 55,000 cells/ml (P-24D). In pre-treated fish as well as all treated fishes, hemoglobin was around 10 g/dL and glucose was around 110 mg/dL. The percentage of leucocyte type cells were as follows: lymphocyte 65%, monocyte 24%, thrombocyte 6%, neutrophil 3%, eosinophil 1% and basophile 1%. The value of hematological parameters indicate that the fish was in normal and healthy condition and thus it is proved that shortened photoperiod do not affects P. hypopthalmus health in general.

Growth and health status of Pangasionodon hypophthalmus reared under manipulated photoperiod conditions.

Background: In general, the length of photoperiod affects the physiology of Pangasionodon hypophthalmus. This study aimed to understand the growth and health status of this fish reared under manipulated photoperiods. Methods: The study was conducted between May and August 2020. Three treatments were applied: control (natural photoperiod); 18 hours of darkness (18D6L; tanks were placed under a dark tarp tent for 18 hours); and 24 hours of darkness (24D0L; tanks were placed under a dark tarp tent continuously). Three replications were performed per treatment. At baseline, fish were approx. 3 inch total length (TL) and 4 g body weight (BW), and were reared in circular plastic tanks (100 L; 30 fish/tank) with aerators and filters, and fed with commercial fish feed pellet (2 times/day to satiation). Fish growth and survival were studied once/week, and blood and tissue samples were taken at the end of the experiment (8 th week). Tissue was formalin fixed and HE stained. Results: The survival of fish in all treatment was 100%. The fish reared in 24D0L and 18D6L grew better than control, achieving a mean TL of 23 cm and BW of 98 g (control = 19 cm TL and 72 g BW). There was no difference in hematology condition or tissue structure between the three groups. Tissue structure of gill, kidney and liver were normal, but light abnormality due to parasites was present in the gill of fish reared in 24D0L. Blood samples for all three groups showed mean red blood cell count of 1,800,000 cells/ml and white blood cell (WBC) count of 55,200 cells/ml. WBC consisted of lymphocyte 65%, monocyte 24%, thrombocyte 6%, neutrophil 3%, eosinophil 1% and basophile 1%. Conclusion: Data obtained indicate that a short photoperiod improves the growth of P. hypophthalmus fish and does not negatively affects their health.