Light Regimes Research Articles

Effects of surface geometry on light exposure, photoacclimation and photosynthetic energy acquisition in zooxanthellate corals.

Symbiotic corals display a great array of morphologies, each of which has unique effects on light interception and the photosynthetic performance of in hospite zooxanthellae. Changes in light availability elicit photoacclimation responses to optimize the energy balances in primary producers, extensively documented for corals exposed to contrasting light regimes along depth gradients. Yet, response variation driven by coral colony geometry and its energetic implications on colonies with contrasting morphologies remain largely unknown. In this study, we assessed the effect of the inclination angle of coral surface on light availability, short- and long-term photoacclimation responses, and potential photosynthetic usable energy. Increasing surface inclination angle resulted in an order of magnitude reduction of light availability, following a linear relationship explained by the cosine law and relative changes in the direct and diffuse components of irradiance. The light gradient induced by surface geometry triggered photoacclimation responses comparable to those observed along depth gradients: changes in the quantum yield of photosystem II, photosynthetic parameters, and optical properties and pigmentation of the coral tissue. Differences in light availability and photoacclimation driven by surface inclination led to contrasting energetic performance. Horizontally and vertically oriented coral surfaces experienced the largest reductions in photosynthetic usable energy as a result of excessive irradiance and light-limiting conditions, respectively. This pattern is predicted to change with depth or local water optical properties. Our study concludes that colony geometry plays an essential role in shaping the energy balance and determining the light niche of zooxanthellate corals.

ФОТОСИНТЕТИЧЕСКАЯ ПРОДУКТИВНОСТЬ ИСКУССТВЕННО СОЗДАННЫХ ФИТОЦЕНОЗОВ С ПРИМЕНЕНИЕМ ОСАДКА СТОЧНЫХ ВОД

The results of studies on the use of sewage sludge (SS) as an unconventional chemical meliorant for the formation of antierosion vegetation cover on sand pits of technogenic origin are presented. Two variants of applying SS on the surface of the technogrunt were studied: 1 - fragmentally with a layer of 2-3 cm, 2 - with a continuous layer of 5-10 cm. In experimental variants with SS, the indicators of biological productivity for the 4th year of life were greater than in the control: plant height - by 3,5-4,5 times; reserves of aboveground phytomass - by 29 and 56 times. It is shown that long-term SS, which has undergone the processes of humification and leaching, is a promising and inexpensive meliorant suitable for increasing the fertility of sandy industrial soil and creating highly productive stable phytocenoses on them. Festuca rubra L. (the dominant species of perennial grasses) was chosen to assess the degree of SS influence on the state of artificially created phytocenoses. The efficiency of the photosynthetic apparatus (FA) of this species was estimated by the following informative indicators: the content of plastid pigments, the intensity of photosynthesis, and the chlorophyll index. It was revealed that the highest absolute indicators of aboveground phytomass and chlorophyll content are typical for plants in the experimental variant with continuous application of SS. However, the calculated indicators of the efficiency of the FA showed that the productivity of the chlorophyll unit is higher in the experimental variant with fragmentary application of SS. The maximum values of the FA performance indicators of Festuca rubra in the experimental variants were noted in the first half of the growing season. At the end of the season, due to the strong thickening of the cover and changes in the light regime, a sharp decrease in the photosynthetic activity of assimilating organs was noted. Thus, the state of artificially created stable phytocenoses, based on the estimate of photosynthetic productivity, confirms the most promising use of fragmentary application of SS during restoration activities.

In Vitro Propagation of "Salsaparrilha" [Herreria salsaparrilha Mart. (Asparagaceae)]: An Antisyphilitic Medicinal Species.

An efficient procedure for in vitro propagation of Herreria salsaparrilha Martius was established from single-node explants (fourth and fifth nodes from apex to the base) derived from donor plants maintained under shading-house conditions. After surface sterilization, explants are inoculated in test tubes containing 15mL of Murashige and Skoog (MS) medium without growth regulators. Cultures are maintained under 35μmolm-2s-1 irradiance, a 16/8-h light/dark light regime, at 26±2°C. The subcultures are carried out under the same conditions, adding 6-benzyladenine 1.0mg/L and Phytagel® 2.8g/L. Shoots are elongated and rooted by transferring individual shoots to half-strength MS medium without growth regulators. After 25-30days, elongated rooted shoots are transferred to plastic pots containing 25-30mL of sterile distilled water, covered with a transparent plastic bag, and kept under the same growth room conditions for 2days. Plants are transferred to cups containing autoclaved and washed sand and kept in a shading house (50% light interception) for acclimatization. True-to-type adult plants were successfully recovered under ex vitro conditions.

Lipid Profile of Parr and Smolts of Atlantic Salmon (Salmo salar L.) Reared in Aquaculture Under Various Lighting Regimes

Lipid Profile of Parr and Smolts of Atlantic Salmon (Salmo salar L.) Reared in Aquaculture Under Various Lighting Regimes

Expression of Muscle-Specific Genes in Aquacultured Atlantic Salmon (Salmo salar L.) Fingerlings under Conditions of Different Lighting and Feeding Regimes

Expression of Muscle-Specific Genes in Aquacultured Atlantic Salmon (Salmo salar L.) Fingerlings under Conditions of Different Lighting and Feeding Regimes

ЦИРКАДНЫЙ РИТМ В ЯЙЦЕКЛАДКЕ КУР

The paper is devoted to poultry motor activity circadian rhythms and these rhythms influence on layer production. The time of egg forming in layer oviduct is proved to be constant, that is, 24 hours. It doesn’t depend on egg laying cycle longevity. Egg laying time is determined with ovulation time. The signal to production rhythms synchronization is the time light switching on in poultry house. When light in poultry house is being switched on at the same time the ovulation beginning phase is moving towards morning hours and resulting in egg laying pause. Some egg laying rhythm asynchrony is characteristic for low productive layers. New light regimes introduction with layers biological rhythms accounting helps to increase egg production.

Improvement of technology in the cultivation of strawberries hybrid Soraya F1 during a vegetative trial

The Strawberry (Fragaria x ananassa Duch.) is a favorite dessert crop, which is in great demand and ranks first among fruit and berry crops. The principle of growing strawberries directly from seeds gives the advantages of obtaining clean, reliable plant material and improving phytosanitary conditions. The aim of the research was to introduce innovations in the technology of growing high-quality planting material of garden strawberries (Fragaria x ananassa Duch.) of the Superelite class based on healthy hybrid seeds of the first generation of strawberry hybrid Soraya F1 under artificial lighting conditions in hydroponic culture. As a result, innovations in the artificial lighting regime, hydroponic culture conditions, substrate composition, irrigation regime and composition of the nutrient solution for root nutrition of plants were introduced, the flow of phytohormones, phytosanitary condition and quality of strawberry crop were analyzed.

SCIENTIFIC SUBSTANTIATION OF THE PRODUCTIVITY OF SOWING ALFALFA DEPENDING ON SOIL AND CLIMATIC CONDITIONS OF THE FOREST-STEPPE OF UKRAINE

The article presents a review of literature sources on the study of alfalfa productivity depending on the influence of sowing dates, mineral phosphorus-potassium nutrition, soil liming, pre-sowing seed treatment with bacterial preparations and modes of grass stand use when grown for fodder purposes. It was found that the change of photoperiod in the year of sowing was a signal in alfalfa plants to pass through the microstages of growth and development, which was determined by the length of daylight hours and sowing dates, regardless of hydrothermal resources. Observations showed that the crop reached the beginning of flowering phase (code 61-62 of the BBSN) at daylight hours of 14:53-16:12 h, while at 12:48 h it reached the budding phase (code 49 of the BBSN). Regardless of climate change, which has been observed for more than a decade, sowing alfalfa provided the highest productivity indicators with early spring sowing and long-term use of the grass stand. Over the three years of vegetation, its leaf mass yield averaged 47.03 t/ha, dry matter yield was 11.09 and 2.07 t/ha of crude protein, and gross and metabolizable energy were 204.72 and 104.52 GJ/ha, respectively. At the same time, with the recommended summer sowing date (20 July), the indicators decreased by 9.1, 11.5, 13.1, 12.2 and 11.7%, respectively. Analysing the agro-ecological resources of Ukraine, given the natural soil fertility, moisture, temperature and light conditions, they are quite favourable for the maximum realisation of the biological potential of the fodder productivity of sowing alfalfa within the yield of fodder units of 10-12 t/ha and 1.8-2.2 t/ha of digestible protein. Among the elements of intensifying the cultivation of seed alfalfa for the production of plant raw materials and harvesting of various types of fodder, fertilisation is the most effective factor influencing their quantity and quality. To calculate the amount of mineral fertiliser, we take into account the biological characteristics of the crop, its cyclical growth and development during the growing season, the method of sowing and the duration of grassland use. Regardless of the geographical origin of the seed alfalfa, for two years of using the grass stand and observing technological measures of cultivation (lime, phosphorus-potassium mineral fertilisers, seed inoculation), alfalfa provided the highest yield of crude protein of 5.83-5.97 t/ha when mowing the first mowing in the flowering phase, the second - at the beginning of flowering and the third in the budding phase. Mowing of three mowings of sowing alfalfa at the beginning of the flowering phase contributes to the effective use of the light regime of the growing season as the main factor in increasing productivity. Innovative technologies for growing seed alfalfa use growth-regulating agents of various origins, microfertilisers and biological seed treatment products to increase yields and dry matter quality for foliar feeding. The complex application of these preparations provides an increase in the yield of leaf mass by 16.6-18.2%. Thus, in the context of modern agricultural development, alfalfa is one of the components of reducing the anthropogenic load on the agro-ecological system and increasing the production of environmentally friendly high-protein feed and livestock products for the purpose of efficient use of hydrothermal resources and environmental protection.

The role of supplemental lighting during late fall and winter on photosynthetic and non-photosynthetic pigments biosynthesis of cut rose flower (Rosa hybrida cv. ‘Dolce Vita’)

ABSTRACT Low levels of natural light within the late fall and winter periods are main restricting factors for greenhouse-cut rose flower production in northern countries. Here, the effects of supplemental lighting on photosynthetic and non-photosynthetic pigments and the morphological response of cut rose flower cv. ‘Dolce Vita’ were investigated. Four different supplemental lighting regimes, including 85, 170, 255, and 340 μmol·m−2·s−1 PPFD using a high-pressure sodium lamp for a six-hour day extension started at sunset were applied to rose plants during late fall and winter. With increasing light intensity to 255 μmol·m−2·s−1 PPFD, the content of chlorophyll a, total chlorophyll, carotenoid content, and the ratio of chlorophylls a/b as well as amount of anthocyanins greatly improved. The highest phenol content and total antioxidant capacity was observed in 170 μmol·m−2·s−1 PPFD. Moreover, extending of daylength by light intensity of 255 μmol·m−2·s−1 PPFD had a significant affirmative effect on traits of growth, including flower stem length (P < 0.01), leaf number (P < 0.05), renewal bud formation (P < 0.05), time of harvesting (P < 0.05), and vase life of cut flowers (P < 0.01). Considering physiological and morphological improvement, extending of daylength from 10-h to 16-h by supplemental light of 255 μmol·m−2·s−1 PPFD would be the best choice to cultivate cut rose flower cv. ‘Dolce Vita’.

Harnessing diurnal dynamics: Deciphering the interplay of light cycles on algal-bacterial membrane bioreactors

Light profoundly modulates the algal-bacterial membrane bioreactor (algal-bacterial MBR) performance. Yet, its outdoor deployment grapples with the inherent diurnal cycle of sunlight, engendering suboptimal light conditions. The adaptability of such systems to these fluctuating light conditions and their implications for practical outdoor applications remained an under-explored frontier. In response, this study meticulously scrutinized two laboratory-scale algal-bacterial MBRs under varying light regimes: a 24-h continuous and a 12-h cyclic illumination. Over 70 days, continuous illumination was observed to yield superior biomass production and total nitrogen and total phosphorus removal efficiencies compared to its cyclic counterpart. Contrarily, when focusing on membrane fouling, the 12-h cyclic illumination exhibited lower membrane fouling. The spectral analyses coupled with adhesion ability evaluation, traced the enhanced membrane fouling under continuous illumination to the elevated organics and heightened adhesive properties of the flocs. Given the tangible benefits of reduced membrane fouling and the potential harnessing of solar radiation, the 12-h cyclic illumination emerges as an economically astute operational paradigm for algal-bacterial MBRs. The significance of this study is to promote the application of algal-bacterial MBR in sewage treatment and provide robust support for the development of green technology in the future.

Excitation and control of level populations in rectangular quantum wells by unipolar half-cycle attosecond pulses

Unipolar and quasi-unipolar half-cycle pulses represent the limit of the pulse shortening in a given spectral range. So far such pulses have become a subject of active research due to their potential in the ultrafast optics and study of new regimes of light–matter interactions with subcycle resolution. Here, we show the possibility of the effective ultrafast control of the level populations in 1D rectangular quantum wells (such a model is used for modeling semiconductor nanostructures and nanoparticles) by the half-cycle unipolar attosecond light pulses in comparison to the single-cycle ones. It is shown that the population dynamics is determined by the electric pulse area divided into its characteristic “scale,” which is given by the quantum well width when pulse duration is smaller than the orbital period of electrons in the ground state. Both the selective excitation of quantum states and the feasibility of the population inversion by subcycle unipolar pulses are demonstrated.

Biochemical repercussions of light spectra on nitrogen metabolism in spinach (Spinacia oleracea) under a controlled environment.

Selecting appropriate light spectra of light-emitting diodes (LEDs) and optimal nutrient composition fertilizers has become integral to commercial controlled environment agriculture (CEA) platforms. This study explored the impact of three LED light regimes (BR: Blue17%, Green 4%, Red 63%, Far-Red 13% and infrared 3%, BGR; Blue 20%, Green 23%, Red 47%, Far-Red 8% and infrared 2%; and GR; Blue 25%, Green 41%, Red 32%, and Far-Red 2%) and nitrogen levels (3.6 and 14.3 mM N) on spinach (Spinacea oleracea). Under limited nitrogen (3.6 mM), BGR light increased the fresh shoot (32%) and root (39%) biomass than BR, suggesting additional green light's impact on assimilating photosynthates under suboptimal nitrogen availability. Reduced chlorophyll (a and b) and carotenoid accumulation, electron transport rate (ETR), and higher oxalates under limited nitrogen availability highlighted the adverse effects of red light (BR) on spinach productivity. Increased activities of nitrogen-associated enzymes (GOGAT; Glutamate synthase, GDH; NADH-Glutamate dehydrogenase, NR; Nitrate reductase, and GS; Glutamine synthetase) in spinach plants under BGR light further validated the significance of green light in nitrogen assimilation. Amino acid distributions remained unchanged across the light spectra, although limited nitrogen availability significantly decreased the percent distribution of glutamine and aspartic acid. Overall, this study demonstrated the favorable impacts of additional green light on spinach productivity, as demonstrated under BGR, than GR alone in response to nitrogen perturbation. However, the exact mechanisms underlying these impacts still need to be unveiled. Nevertheless, these outcomes provided new insights into our understanding of light spectra on spinach nitrogen metabolism.

The growing profile of Diplotaxis tenuifolia (L.) DC. under different LED lighting

The growth of rocket Diplotaxis tenuifolia (L.) DC. profiles was studied during 30 days of growing in the chamber under different lighting regimes; T5_ peak at 630 nm, LED1_ peak at 545 nm and LED2_ peak at 599 nm. There were no significant differences in dry weight after 15 days, however, from day 15 to 30, the increase in dry weight was significantly biggest under LED2. This agrees well with estimated average leaf area (LA) per plant (43.83 cm2 ), the increase of LA (39.70 cm2 ) and total fresh weight (7.898 g per plant). The regression analysis revealed the strongest correlation between the dry weight and PPFD_R light intensity (0.792**), showing the positive effect of additional LED lighting in comparison with standard T5 light.

Hopping from the heat: The locomotory activity patterns of the Lesser Egyptian Jerboa (Jaculus jaculus)

Arid-dwelling mammals are exposed to extreme daily temperatures, which puts these mammals at risk of overheating and dehydration, particularly while active, these risks are increased as the body size is reduced. Consequently, these small mammals often show strict nocturnality, confining their locomotor activity to the dark period of the day. One such animal is the Lesser Egyptian Jerboa (Jaculus jaculus), which occurs in the hyper-arid central regions of the Arabian Peninsula. In this study, twelve male J. jaculus were subjected to different light regimes. All the animals exhibited entrainment of their activity to the dark phase of each respective light regime. However, unlike other small arid dwelling mammals, J. jaculus confined most of its activity during the last few hours of the night rather than the initial hours of the night, a pattern which is consistent even under constant DD conditions. The last few hours of the night correlate to the coolest experienced temperatures in summer in the wild and, therefore, the ideal time for a very small mammal to be active. Larger small mammals, which may be less at risk of overheating, can afford to be active during the warmer periods of the night, namely the initial hours.

High daily light integral positively regulate photosynthetic capacity through mediating nitrogen partitioning and leaf anatomical characteristic in flowering Chinese cabbage

In controlled environment agriculture, optimization of lighting regimes, i.e. daily light integral (DLI, photosynthetic photon flux density (PPFD) x photoperiod duration), plays vital roles to maximize harvestable yield and reduce lighting costs. Regulating PPFD or photoperiod have been widely used for energy-efficient cultivation, while the mechanisms of multiple DLI contributing to photosynthesis capacity are poorly understood. Hence, the treatment of 16/8 h light/dark compared with 24 h continuous lighting (CL), at 200 and 300 μmol m−2 s−1 PPFD, with the DLI from 11.52 to 25.92 mol m−2 d−1, were conducted in flowering Chinese cabbage respectively. The results showed that higher DLI significantly promoted relative growth rate and dry matter accumulation, irrespective of the combination of PPFD and photoperiod, consequently facilitated faster harvest compared to the lower DLI of 11.52 mol m−2 d−1 treatment. Under higher DLI, the increase in Rubisco content was the primary factor accelerating photosynthetic capacity, followed by the increases in gm. Additionally, the enhancement of Rubisco was ascribed to the increased allocation of nitrogen to the carboxy system. Furthermore, the increase of gm under higher DLI was largely resulted from the increase in Sm/S and Sc/S caused by increased accumulation of soluble sugar and starch. Unexpectedly, at the same DLI of 17.28 mol m−2 d−1, extending photoperiod from 16 to 24 h d−1 had no influence on photosynthetic capacity, although 24 h 200 μmol m−2 s−1 treatment reduced the abaxial stomatal density and light-saturated stomatal conductance, and increased the thickness of cell walls and the contents of chlorophyll and Rubisco, compared with 16 h 300 μmol m−2 s−1 treatment. To summarize, plant growth and ripening were promoted as the DLI increased. And optimized nitrogen allocation accounted for the promotion of photosynthetic capacity. Increasing photoperiod at the same DLI had no promotion on photosynthetic capacity.

Modulating Effect of Extremely High-Frequency Low-Intensity Electromagnetic Radiation on Tissue Oxidative Metabolism and Skin Microhemodynamics

We set out to examine the indicators of microhemodynamics and tissue oxidative metabolism in rats after their tenfold exposure to extremely high-frequency low-intensity electromagnetic radiation (EHF EMR). The aim was to elucidate the specifics of skin microcirculation and tissue oxidative metabolism following exposure to tenfold electromagnetic radiation of extremely high frequency. The experiment was carried out on 40 mature male Wistar rats weighing 200–220 g, which were kept in standard vivarium conditions under natural light regimen. The animals were divided into two groups with 20 rats each. The animals in the first group were biological controls and were exposed to false EHF EMR (placebo); the animals in the second group were exposed to mm-exposure in the morning, 10 sessions daily. On the 10th day of EMR exposure, the indicators of skin tissue fluorescence on the tail base were recorded. Tenfold exposure to low-intensity EHF EMR was shown to increase the concentration and intensity of NADH fluorescence, as well as the FAD and redox ratio. This indicates an increased cellular demand for ATP and the predominance of oxidative phosphorylation over other processes, thus demonstrating the activation of the respiratory chain. At the same time, an increase in endothelium-dependent vasodilation, a decrease in peripheral resistance, an increase in blood flow to the nutritive microvascular bed, and an improvement in venular outflow were observed in the microcirculatory bed. The conclusion is made that the modulating effect of EHF EMR is manifested in the rearrangements of correlations. Thus, the coefficient of variation comes to the fore – the final calculated indicator of microcirculation, which has strong negative associations with all indicators of tissue metabolism (FAD, NADH, RR). In addition, the amplitudes of endothelial rhythms associated with periodic releasing of nitric oxide by the endothelium show a strong negative association with FAD.

Optimizing supplemental light spectrum improves growth and yield of cut roses

During the seasons with limited light intensity, reductions in growth, yield, and quality are challenging for commercial cut rose production in greenhouses. Using artificial supplemental light is recommended for maintaining commercial production in regions with limited light intensity. Nowadays, replacing traditional lighting sources with LEDs attracted lots of attention. Since red (R) and blue (B) light spectra present the important wavelengths for photosynthesis and growth, in the present study, different ratios of supplemental R and B lights, including 90% R: B 10% (R90B10), 80% R: 20% B (R80B20), 70% R: 30% B (R70B30) with an intensity of 150 µmol m−2 s−1 together with natural light and without supplemental light (control) were applied on two commercial rose cultivars. According to the obtained results, supplemental light improved growth, carbohydrate levels, photosynthesis capacity, and yield compared to the control. R90B10 in both cultivars reduced the time required for flowering compared to the control treatment. R90B10 and R80B20 obtained the highest number of harvested flower stems in both cultivars. Chlorophyll and carotenoid levels were the highest under control. They had a higher ratio of B light, while carbohydrate and anthocyanin contents increased by having a high ratio of R light in the supplemental light. Analysis of chlorophyll fluorescence was indicative of better photosynthetic performance under a high ratio of R light in the supplemental light. In conclusion, the R90B10 light regime is recommended as a suitable supplemental light recipe to improve growth and photosynthesis, accelerate flowering, and improve the yield and quality of cut roses.

Activities of Energy Metabolism Enzymes in Atlantic Salmon Salmo salar L. Smolts and Parr Grown under Different Light Regimens.

Activities of enzymes of energy and carbohydrate metabolism in muscles and the liver were studied in Atlantic salmon Salmo salar L. smolts and parr grown under continuous or natural lighting and different feeding regimens in autumn followed by a short photoperiod in winter. Enzyme activities were found to differ between test and control salmon groups and between parr and smolts sampled at the end of the winter period. Smolts grown under continuous lighting and round-the-clock feeding differed from other groups by having higher cytochrome c oxidase (COX) activity and lower aldolase activity in muscles. Differences in aerobic metabolism in muscles between parr and smolts were found to be the same in all experimental groups, COX and aldolase activities being relatively higher in smolts. The pattern of changes in enzyme activities in the liver from parr to smolts differed between different experimental groups. Based on the results, the photoperiod was assumed to affect the activities of energy metabolism enzymes in salmon juveniles and may eventually affect the completion of smoltification.

Digital Automation of Energy-Efficient In Vitro Irradiation of Orchard Plum Micro Cuttings

The yield and efficiency of cultivation of any crop depends on the quality of the planting material. The most promising method of modern horticulture, which makes it possible to significantly increase its environmental sustainability, is to obtain planting material, improved by culture of isolated tissues in vitro. There is blue honeysuckle, raspberries, garden strawberries, steppe cherries, domestic plums, and other crops studied in vitro in the Udmurt Federal Research Centre of the Ural Branch of the Russian Academy of Sciences (Udmurt FRC UB RAS). The light regime has a great influence on plant growth under in vitro conditions. A review of specialized literature showed the energy efficiency of the pulsed mode of plants irradiation as significantly reducing power consumption compared to stationary (continuous) one with the same quality of the grown products. In the Udmurt FRC UB RAS, pulsed irradiation of garden strawberry explants in vitro made it possible to increase their rooting by 10 %. The mode of irradiation in modern illuminators with LEDs under in vitro conditions can be changed by means of digital automated control systems. This makes it possible to implement an energy-saving pulsed irradiation mode that allows efficient electricity use. The purpose of this work was to develop a digital system for automated control of the operation of the irradiator with LEDs for the implementation of an energy-efficient pulsed mode of plant irradiation in vitro and its experimental testing. Experiments conducted with it on plum micro-cuttings showed that the largest leaf area (119 %) compared to the control was obtained using light pulses with a duration of 0.8 s, which confirms the feasibility of using a pulsed irradiation mode and optimizes its parameters for these conditions.

Phytoplankton and Its Role in the Formation of the Underwater Light Regime in Artificial Reservoirs

Phytoplankton and Its Role in the Formation of the Underwater Light Regime in Artificial Reservoirs