Natural Temperature Conditions Research Articles

A comparison of consistent UV treatment versus inconsistent UV treatment in horticultural production of lettuce

UV radiation is an underrated radiation currently missing in many horticultural production systems of vegetables in protected cultivation. It can be added e.g., in LED light sources. Using lettuce as a model plant, this study determined whether the use of UVB LEDs is suitable (1) for use in consistent systems (indoor farming) or (2) inconsistent systems (greenhouse). Blue and red LEDs were selected as additional artificial lighting to UVB LEDs. Both approaches led to a reproducible increase of desired flavonol glycosides, such as quercetin-3-O-(6′′-O-malonyl)-glucoside or quercetin-3-O-glucuronide and the anthocyanin cyanidin-3-O-(6′′-O-malonyl)-glucoside in lettuce. The impact of the consistent UVB treatment is higher with up to tenfold changes than that of the inconsistent UVB treatment in the greenhouse. Varying natural light and temperature conditions in greenhouses might affect the efficiency of the artificial UVB treatment. Here, UVB LEDs have been tested and can be recommended for further development of lighting systems in indoor farming and greenhouse approaches.

Analysis of Landscape Patterns Changes and Driving Factors of the Guangdong Chaoan Fenghuangdancong Tea Cultural System in China

Guangdong Chaoan Fenghuangdancong Tea (GCFT) Cultural System is the second batch of China’s Nationally Important Agricultural Heritage Systems (China-NIAHS), identified by the Ministry of Agriculture and Rural Affairs in 2014 as having rich biodiversity, valuable knowledge of indigenous technology, and unique ecological and cultural landscape. Under the dual background of rapid urbanization and agricultural industry structure transformation, China-NIAHS-GCFT is facing the reality of structural changes in land use/cover and landscape patterns. Therefore, it is important to systematically portray land use/land cover (LULC) changes in China-NIAHS-GCFT sites and clarify the spatial pattern differences due to the impact of China-NIAHS-GCFT recognition on tea garden areas and the tea industry. This study was conducted in Chaozhou City, Guangdong Province, where GCFT is located, to compare and analyze the LULC characteristics of the core area of the heritage site (Chaoan, Chaozhou) and the control area (Raoping, Chaozhou) before and after recognition. We assessed the spatial variation in tea garden area and the intrinsic driving mechanisms of the change by integrating social factors, such as China-NIAHS-GCFT recognition, and natural factors, such as elevation, precipitation, and temperature. The results show that: (1) Around 2010, the change in LULC of the core and control areas progressed from slight changes to dramatic changes, mainly shifting from natural to anthropogenic landscapes. The decrease in the cropland and grassland and the increase in built-up land in the core area were obviously larger than those in the control area. (2) Before and after GCFT was recognized as China-NIAHS in 2014, the changing pattern of tea garden shifts from “basically stable and small growth” to a trend of “substantial expansion”. Specifically, the recognition brought about tea garden area expansion and tea industry development in the core area, especially Fenghuang. Meanwhile, a radiating effect extends to the control area, especially the townships adjacent to Fenghuang. (3) Similar natural climatic conditions of temperature and precipitation in the two regions provide a basic growing environment for tea trees; however, elevation was the key natural resource condition affecting the distribution of tea gardens. The elevation conditions of the core area are more suitable for growth of tea trees compared to the control area.

Molecular Docking and In Vitro Studies of Ochratoxin A (OTA) Biodetoxification Testing Three Endopeptidases.

Ochratoxin A (OTA) is considered one of the main mycotoxins responsible for health problems and considerable economic losses in the feed industry. The aim was to study OTA's detoxifying potential of commercial protease enzymes: (i) Ananas comosus bromelain cysteine-protease, (ii) bovine trypsin serine-protease and (iii) Bacillus subtilis neutral metalloendopeptidase. In silico studies were performed with reference ligands and T-2 toxin as control, and in vitro experiments. In silico study results showed that tested toxins interacted near the catalytic triad, similar to how the reference ligands behave in all tested proteases. Likewise, based on the proximity of the amino acids in the most stable poses, the chemical reaction mechanisms for the transformation of OTA were proposed. In vitro experiments showed that while bromelain reduced OTA's concentration in 7.64% at pH 4.6; trypsin at 10.69% and the neutral metalloendopeptidase in 8.2%, 14.44%, 45.26% at pH 4.6, 5 and 7, respectively (p < 0.05). The less harmful α-ochratoxin was confirmed with trypsin and the metalloendopeptidase. This study is the first attempt to demonstrate that: (i) bromelain and trypsin can hydrolyse OTA in acidic pH conditions with low efficiency and (ii) the metalloendopeptidase was an effective OTA bio-detoxifier. This study confirmed α-ochratoxin as a final product of the enzymatic reactions in real-time practical information on OTA degradation rate, since in vitro experiments simulated the time that food spends in poultry intestines, as well as their natural pH and temperature conditions.

Instrumentation complex for measuring the thermophysical properties of rocks in natural occurrence temperature conditions

A schematic diagram and an operation algorithm of an instrumentation complex for measuring the thermal conductivity and thermal diffusivity of rocks by the non-stationary method of a linear source under natural occurrence temperature conditions up to 200 °C are proposed. Thermocouples are used to measure the temperature of the probes. The complex contains two linear (needle) probes, which are placed in a rock sample at a certain distance r from each other. One probe, containing a linear heater and a thermocouple, radiates heat, the other one, containing a thermocouple, is a measuring probe. The cold junction temperature of thermocouples is measured by a semiconductor sensor. To calculate the voltage of the cold junction from the value of its temperature, a direct conversion of thermoEMF by a power polynomial is used. To calculate the temperature of the hot junction of the probe, an inverse transformation by a power polynomial of the voltage values of the hot junction of thermocouples into temperature was applied. In direct and inverse transformations, the degree of polynomials is 10. To reduce the temperature measurement error, digital filtering of signals from thermocouples was used. A digital-to-analogue converter is included in the heater circuit of the radiating probe for flexible heating control. The results of measuring the thermal conductivity and thermal diffusivity of dry and wet sand samples are consistent with the literature data on the temperature dependence.

Exogenous melatonin improves the chilling tolerance and preharvest fruit shelf life in eggplant by affecting ROS- and senescence-related processes

Low temperature is the most common abiotic stress factors during the eggplant cultivation in solar greenhouses. Melatonin plays important roles in plant resistance to low temperature. However, the role of melatonin in regulating chilling tolerance and extending the preharvest shelf life of eggplant fruits is still unknown. In this study, we investigated the effects of exogenous melatonin on eggplant plants and fruits in response to low temperature. Under simulated low-temperature conditions, exogenous melatonin significantly relieved the chilling symptoms of seedlings by reducing reactive oxygen species (ROS) and malondialdehyde (MDA) levels and relative leakage rates. These reductions were caused by higher superoxide dismutase (SOD) and catalase (CAT) activities and increased endogenous polyamine and melatonin levels compared with those in untreated seedlings. Notably, the expression levels of SOD, CAT1/2, and polyamine synthesis genes (ADC and ODC) were also increased by 100 μmol · L−1 melatonin, as well as those of genes involved in melatonin synthesis (TDC, T5H, SNAT, ASMT, and COMT) and cold regulation (COR1, CBFa/b, and ZAT2/6/12). To further investigate the effects of melatonin on eggplant leaves and fruits under natural low temperature conditions, 100 μmol · L−1 melatonin was sprayed on the functional leaves at three days before commodity maturation. Melatonin significantly alleviated chilling injury in the leaves and pericarp and extended the preharvest shelf life of the fruit by increasing the expression of COR1, CBF, ZAT2/6/12, and API5 and decreasing the expression of senescence-related genes (NCED1/2 and SAG12). Therefore, 100 μmol · L−1 melatonin improved chilling tolerance and fruit shelf life by upregulating ZAT2/6/12 to affect ROS- and senescence-related processes, which provides a reference for alleviating cold stress and extending the preharvest fruit shelf life in eggplant.

Flexible energy-saving strategies in female temperate-zone bats

Torpor is characterized by an extreme reduction in metabolism and a common energy-saving strategy of heterothermic animals. Torpor is often associated with cold temperatures, but in the last decades, more diverse and flexible forms of torpor have been described. For example, tropical bat species maintain a low metabolism and heart rate at high ambient and body temperatures. We investigated whether bats (Nyctalus noctula) from the cooler temperate European regions also show this form of torpor with metabolic inhibition at high body temperatures, and whether this would be as pronounced in reproductive as in non-reproductive bats. We simultaneously measured metabolic rate, heart rate, and skin temperature in non-reproductive and pregnant females at a range of ambient temperatures. We found that they can decouple metabolic rate and heart rate from body temperature: they maintained an extremely low metabolism and heart rate when exposed to ambient temperatures changing from 0 to 32.5 °C, irrespective of reproductive status. When we simulated natural temperature conditions, all non-reproductive bats used torpor throughout the experiment. Pregnant bats used variable strategies from torpor, to maintaining normothermy, or a combination of both. Even a short torpor bout during the day saved up to 33% of the bats' total energy expenditure. Especially at higher temperatures, heart rate was a much better predictor of metabolic rate than skin temperature. We suggest that the capability to flexibly save energy across a range of ambient temperatures within and between reproductive states may be an important ability of these bats and possibly other temperate-zone heterotherms.

Weak effects on growth and cannibalism under fluctuating temperatures in damselfly larvae

The Earth’s climate is changing with a trend towards higher mean temperatures and increased temperature fluctuations. Little attention has been paid to the effects of thermal variation on competition within species. Understanding the temperature-dependence of competition is important since it might affect dynamics within and between populations. In a laboratory experiment we investigated the effects of thermal variation on growth and cannibalism in larvae of a damselfly. The temperature treatments included three amplitudes between 20 and 26 °C with an average of 23 °C, and a constant control at 23 °C. Larvae were also raised at five constant temperatures for an estimation of the thermal performance curve, which showed that the thermal optimum for growth was 26.9 °C. Cannibalism was significantly positively correlated with initial body size variance. There was neither a difference among the temperature variation treatments, nor between the constant and the variation treatments in growth and cannibalism. Hence, positive and negative effects of temperature variation within the linear range of a species thermal performance curve might cancel each other out. Since our study mimicked natural temperature conditions, we suggest that the increase in temperature variation predicted by climate models will not necessarily differ from the effects without an increase in variation.

Thermo-mechanically coupled constitutive equations for soft elastomers with arbitrary initial states

It is a long-standing challenge to predict the thermo-mechanically coupled behaviors of initially stressed soft elastomers since most of the existing theories ignore the influences of thermoelastic deformation histories. The constitutive equations may be completely different even for the same initial stresses, if the latter is originated from isothermal and adiabatic deformations, respectively. In this paper, we establish a general framework for deriving constitutive equations for soft elastomers with arbitrary initial states. Instead of using the virtual stress-free configuration, we define the natural state by imposing the stress-free condition and the natural temperature condition. The derivations are based on a new proposed intrinsic embedding method of initial states, in which an additive decomposition of material strains is employed and the material coordinates can be properly defined. Once the natural-state-based free energy density and internal constraint are specified, the required constitutive equations can be accordingly obtained. We then derive the explicit formulations of the Cauchy stress and the entropy by linearization. On this basis, the embedding of initial states in Saint Venant–Kirchhoff, Blatz–Ko, Mooney–Rivlin, Neo-Hookean, Gent, and exponential form elastomers are detailed discussed. The influences brought by the initial stresses, the initial temperature, and the internal constraint on the elastic coefficients are analyzed separately. The new proposed constitutive equations show quantitative agreement with the classical theories under isothermal circumstances and fill a theoretical blank in this field under non-isothermal circumstances. Our approaches significantly improve the current constitutive theory of soft materials and may shed some light on the theoretical modeling of multi-field coupling problems.

Response of Source-Sink Characteristics and Rice Quality to High Natural Field Temperature During Reproductive Stage in Irrigated Rice System.

Global warming greatly affects the development of rice at different growth stages, thereby deteriorating rice quality. However, the effect of high natural field temperature during reproductive stages on rice quality is unclear. Thus, grain filling dynamics, source-sink characteristics and quality-related traits were compared between two contrasting natural field temperature conditions namely normal (low temperature) (LRT) and hot (high temperature) growth season (HRT) during reproductive stage. Compared with LRT, HRT significantly increased chalky grain rate (about 1.6–3.1%), chalkiness level (about 4.7–22.4%), protein content (about 0.93–1.07%), pasting temperature, setback, and consistence, and decreased total starch content (about 4.6–6.2%). Moreover, HRT significantly reduced the leaf area index (LAI, about 0.54–1.11 m2 m–2), specific leaf weight (SLW, about 1.27–1.44 mg cm–2) and source-sink ratio (leaf-sink ratio and/or stem-sink ratio), shortened the active grain filling period by 3.1–3.2 days, and reduced the rations of dry matter translocation to grain (RDMs). In conclusion, we suggested that significant reduction in assimilate translocation after flowering, resulting in the reduced active grain-filling duration and the poor rice quality (high chalkiness and the poor eating and cooking quality), modulated by source-sink characteristics in response to high natural field temperature during reproductive stage. These results enriched the study of high temperature-stressed rice and served as an important reference for selecting high-quality, heat-tolerant varieties and protecting rice quality under high-temperature conditions.

Multi-factor sensitivity analysis of chloride ingression: A case study for Hangzhou Bay Bridge

The transport of chloride into concrete is affected by many factors, including temperature, relative humidity, load cracks, and material properties. The purpose of this paper is to analyze the influence of various factors on the chloride ingression process through a case study for Hangzhou Bay Bridge located in marine environment. Firstly, based on the concentration of free chloride in pore solution, a porous media diffusion model is derived, considering the chloride adsorption term. Then, chloride adsorption isotherm, time-varying diffusion coefficient, temperature, relative humidity, and macroscopic cracks are simulated respectively by the porous media diffusion model. The main conclusions are as follows: (1) The chloride adsorption effect and time-varying diffusion coefficient have a great influence on the numerical results, which cannot be ignored in any case. (2) The natural temperature and relative humidity conditions of the case have a small effect on the simulation results. (3) Under the marine atmospheric environment, the macroscopic load cracks have a small influence on chloride ingression in the long term.

Grain micronutrient composition and yield components in field‐grown wheat are negatively impacted by high night‐time temperature

AbstractBackground and objectivesWheat (Triticum aestivum L.) is highly vulnerable to heat stress during sensitive growth and developmental stages, including grain‐filling. The impact of high daytime heat stress on wheat yield and quality losses has been extensively investigated, while information related to high night‐time temperature (HNT) is limited. The major objective was to ascertain the changes in wheat grain macro‐ and micro‐nutrient composition and yield‐related parameters on exposure to HNT during grain‐filling. Twelve diverse genotypes were grown in field‐based custom‐built heat tents that allowed natural light and temperature conditions during the day and imposed stress overnight.FindingsThe field‐tents imposed a 3.2°C higher night‐time temperature compared to ambient conditions throughout the grain‐filling period. HNT stress reduced 200 grain weight by 1.9%, grain yield by 3.1%, seed starch content by 2.5%, and seed protein content by 3.6% per °C increase in HNT.ConclusionsHNT had significant negative effect on grain macro‐ and micro‐nutrient content. However, starch and protein concentrations were differentially correlated with grain nutrients, with starch negatively correlated with many of the micronutrients under control and HNT.Significance and noveltyThis negative correlation highlights the imperative balance of seed micronutrient composition that needs to be maintained as efforts are intensified to enhance grain yield under favorable and warming environments.

Micropropagation and Acclimatization of Common Oregano (&amp;lt;i&amp;gt;Origanum vulgare&amp;lt;/i&amp;gt; L. Subsp. &amp;lt;i&amp;gt;vulgare&amp;lt;/i&amp;gt;) by Shoot Tip Culture

Origanum vulgare L. is a commercially valued species with remarkable biological properties. It is subject to over-exploitation practices that seriously threaten its sustainability for future generations. Thus, micropropagation serves as a tool for the protection and domestication of this species. In this study, we established an in vitro vegetative propagation protocol for Origanum vulgare. This is done through the axillary bud technique by carrying out various tests. Six culture media (MS, MSm, N30K, SD, SH and B5) were tested. Therefore, SD was chosen for the following experiments. Seven cytokinins (adenine (Ad), N6-(2-isopentenyl) (2ip), zeatin (Zeat), kinetin (Kin), benzyladenine (BAP), 1,3-diphenylurea (DPU) and thidiazuron (TDZ) at 5 concentrations (0.44, 1.33, 2.22, 3.11 and 4.44 μM/L) were evaluated. Thus, Kin at 3.11 μM allowed high regeneration of vitroplants, optimal elongation, total rooting of explants, maximum bud multiplication, and absence of hyperhydric explants. In fact, the integration of auxins (indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), and 1-naphthaleneacetic acid (NAA)) into the culture medium and their combinations with 3.11 μM Kinetin contributed to the optimization of the root part. Thus, it was improved in particular in the case of 3.11 μM Kin and 6.27 μM IBA. Three polyamines (Putrescine, Spermidine and Spermine) at different concentrations (1.134, 3.402, 5.67, 7.938 and 11.34 μM/L) combined at 3.11 μM Kin and 6.27 μM IBA were tested. In fact, 1.304 μM putrescine was considered to be the most suitable for in vitro culture of explants, since it allowed optimal propagation of buds and roots, also a high rate of regeneration and rhizogenesis. GA3 at 1.15 μM combined with 3.11 μM Kin and 6.27 μM IBA permitted maximum bud multiplication. The acclimatization was carried out successfully using vitroplants showing good foliar and root development. Thus, three months after acclimatization, the seedlings were transferred into large pots under natural light and temperature conditions. Almost all acclimatized plants developed flowers in the first year between May and July.

Supplemental irrigation frequencies effects on the morphological and yield parameters of mung bean [Vigna radiata (L.) R. Wilczek] in Burkina Faso

Mung bean (Vigna radiata) is grown throughout the world thanks to its short cycle, its great adaptability to climatic conditions and its good digestibility. In Burkina Faso, agriculture is faced with irregular rainfalls, resulting in water stress on plants causing growth and yields reduction. This study aims at identifying supplemental irrigation frequencies that help good mung bean plant to grow and yield. So, four watering schemes were applied to plants aged 26 days, grown in pots on a sandy and silty substrate, in natural conditions of light and temperature during the wet season. The watering regimes concerned a batch of plants watered only by rain (0 day scheme) and three other batches, each watered with tap water in the absence of rain respectively every 5 days, every 10 days and every 15 days. A completely randomized three-replicate block system was set up and agro-morphology parameters were measured. The study showed that the 5 days diet resulted in plants with better growth and good pod yields compared to other watering schemes. These results confirm that supplemental irrigation applied early during drought po0063kets is resilience to the irregularity of rains in the wet season, which is accentuated by climate change.

Heat Stress Affects Seed Set and Grain Quality of Vietnamese Rice Cultivars during Heading and Grain Filling Period

Environmental stress trigger a variety of rice plant response, ranging from alters seed set, grain yield and grain quality during flowering and grain filling stage. Efforts are required to improve our understanding of the impact of heat stress on rice production, which are essential strategies in rice cultivation. This article investigated the seed set, yield components and grain yield of Vietnamese rice cultivars (Indica germplasm) under high temperature environment during the flowering and grain filling stage. Six rice cultivars, including popular cultivars and new cultivars of Cuu Long Delta Rice Research Institute, and one popular extraneous cultivar with differences in maturing time, were grown in pots at high temperature (HT) and natural temperature condition as control (CT). All rice cultivars were subjected to the high temperature starting from the heading stage to the harvest maturity, applied by greenhouse effect. The greenhouse has about 25 cm window opening on 3 sides for air ventilation. The seed set rate of the heat-sensitive rice genotypes decreased significantly under HT, leading to a significant reduction in grain yield. The lowest seed set was recorded in “OM4900” (44.3%) and “OM18” (39.9%) under high temperature environment. The lower yield in all rice cultivars at an elevated temperature resulted in a dramatic decrease of filled grains and contributed to a loss of 1000-grain weight. ‘“OM892” is a potential rice cultivar for heat tolerant breeding program due to the seed set percentage was above 80% in both HT and CT conditions. High temperature during the grain filling stage resulted in a decreased amylose and increased chalkiness for all OM cultivars.

Stability of Oxygen Nanobubbles under Freshwater Conditions

The use of nanobubbles (NBs) has gained significant attention in various applications (e.g., aeration in biological water treatment, water disinfection, membrane defouling, and ground water and sediment remediation) in recent decades because of their superior characteristics such as the improved mass transfer at the gas-liquid interfaces, their lifetime up to a couple of weeks, the formation of reactive oxygen species (ROS) with high oxidative potential. However, there is a lack of information about the effect of various factors on the stability of NBs for a long storage period under freshwater conditions. In this study, a comprehensive investigation was conducted to systematically examine the stability of oxygen NBs in water under various conditions which are closely related to a typical freshwater or the drinking water treatment. The oxygen NB stability in water was evaluated by monitoring the change in the bubble concentrations, size distribution, average diameter, and zeta potential for 60 days of storage time under different pH, hardness, ionic strength, natural organic matter (NOM), chlorine, and temperature conditions. In addition, the formation of hydroxyl radical (•OH) was investigated using disodium terephthalate which form fluorescent adducts with •OH in the presence of oxygen NBs. Among the parameters investigated, the impacts of cations, low pH, and high SUVA254 NOM on the stability of oxygen NBs were more significant than other conditions. The half-lives of oxygen NBs under various conditions follow the order Ca2+ < Na+ < pH 3 < high SUVA254 NOM < pH 5 < 30 °C. Oxygen NBs were more stable in softwater than hardwater. Oxygen NBs were relatively stable for 3 days regardless of pH. For a longer storage period, oxygen NBs disappeared faster at pH 3 than at high pH. High SUVA254 NOM destabilized NBs more than low SUVA254 NOM, indicating the impact of hydrophobicity on the NB stability. The temperature effect on the NB stability was negligible for a short storage time, while higher temperature destabilized oxygen NBs for a longer storage time. One of the main disappearance pathway of oxygen NBs in water was found to be coalescing, rising, and leaving the container, which would be promoted greatly by cations, low pH and NOM with high aromaticity. The formation of hydroxyl radical in NB solutions was detected at pH 3 by a florescent probe molecule. When oxygen NBs are released in water bodies, high calcium, high SUVA254 NOM, and low pH would significantly reduce the availability of NBs and their residence time in freshwater.

Biogeochemical thallium cycling during a mesocosm phytoplankton spring bloom: Biotic versus abiotic drivers

Thallium (Tl) is classified as a non-(bio)-essential and highly toxic element in the marine environment. Despite its active and passive involvement in bio-cycling processes, it is considered a conservative type element in open ocean settings. Previous studies on the Tl-behavior in the coastal waters of the southern North Sea, however, documented non-conservative Tl-behavior in seasonal and tidal patterns. As drivers for the non-conservative depletion, Tl-fixation in redox stratified adjacent sediments as well as its complexation with algae-bloom derived organic matter were suggested. Due to superimposition by resuspended lithogenic particles, it was not possible to distinguish whether the Tl concentration pattern was induced by biotic or abiotic processes. The main motivation of the present study was to investigate the non-conservative Tl-behavior during a phytoplankton bloom in coastal ocean water masses and to identify potential key drivers. We conducted an indoor mesocosm experiment where artificial seawater was inoculated with a natural phytoplankton and bacteria community from the southern North Sea and incubated under natural light and temperature conditions, mimicking a neritic North Sea water column. The incubation of six weeks covered the different stages of two distinct phytoplankton bloom events as well as a subsequent bacteria bloom. Our results reveal a non-conservative Tl-depletion, which seemed to be primarily caused by the coupling to algae bloom derived OM-cycling. The extent of Tl-depletion was dependent on the amount and the composition of organic matter. While the first phytoplankton bloom, dominated by Diatom-species, did not induce significant deviations of Tl from theoretical conservative behavior, especially the colonial stage (hydrogel formation) of the secondary occurring Phaeocystis sp. bloom induced significant depletions of dissolved Tl with rates up to ~27% d-1. Global extrapolations of potential algae-induced deficits in dissolved Tl and its potential export Tl from the open water column have shown that the processes identified for Tl removal in this study could be responsible for a flux in the range of 4–20% of the total removal previously assumed in Tl mass balances. Our study emphasizes that although Tl is classified as a conservative-type element, biological processes have an impact on the global Tl budget and thus must be considered in the respective oceanographic models.

Sexual maturation in Atlantic salmon male parr may be triggered both in late summer and early spring under standard farming conditions

Male Atlantic salmon (Salmo salar) display different sexual strategies, maturing either as parr during the freshwater phase (as sneaky spawners), or as post smolts following one or several years at sea. First sexual maturation (puberty) occurs at different times depending on environmental and genetic factors. To improve our knowledge on the timing (age and season) of first sexual maturation in Atlantic salmon male parr, we investigated pubertal activation in second generation farmed salmon from the Norwegian river Figgjo, reared under natural conditions of photoperiod and water temperature. Histological analysis, in combination with morphometric measurements, plasma androgen levels and pituitary gonadotropin gene expression analysis revealed that, as previously reported, some male parr initiated early sexual maturation in spring at one year of age. Interestingly, some male parr were observed to initiate sexual maturation already in autumn, six months after hatching (under-yearlings), much earlier than reported in previous studies. One-year old maturing males showed a low induction in gonadotropin levels, while under-yearling maturing males displayed a significant increase in fshb transcripts as compared to immature/early-maturing fish. Plasma testosterone, detectable also in immature/early-maturing males, increased constantly during testes development, while 11-ketotestosterone, undetectable in immature/early-maturing and early maturing males, increased during more advanced stages of maturation. A mild feminization of the testes (ovotestes) was detected in a subset of samples. This study brings new knowledge on the little investigated field of sexually maturing under-yearlings in Atlantic salmon. This is also the first study comparing the physiology of under-yearling vs one-year old maturing male parr, thus bringing new insights to the remarkable plasticity of Atlantic salmon puberty.

The role of salt stress on laboratory cultivation of green macroalga Enteromorpha compressa and its antioxidant activity

Cultivation of the green seaweed Enteromorpha compressa was performed under natural laboratory spring environmental conditions of temperature, light intensity and photoperiod to study the salinity tolerance of this intertidal green macroalga. Cultivation was carried out under artificial seawater (ASW) of different concentrations (18, 35, 53 and 106 g/l sea salt) compared to the control using natural seawater (NSW). Growth rate and pigment content of the cultivated alga were recorded at regular intervals during the experimental duration. Antioxidant activity of the crude ethanolic extract and its fractions (petroleum ether, chloroform, ethyl acetate and acetone) was performed against DPPH radical scavenging assay and compared to the standard synthetic antioxidant butylated hydroxy-toluene (BHT). The finding showed that enhancement of algal growth rate under ASW concentrations of 35, 53 and to a lesser extent at 106 g/L during the first 15 days of cultivation were due to the increased pigment biosynthesis, photosynthetic and metabolic activities and followed by gradual retardation due to the impact of prolonged salt stress. Antioxidant activity of alga was found to be concentration, type of extract and incubation time dependent. Acetone fraction of all salt concentrations showed higher antioxidant activity compared to other fractions. Pronounced activity was recorded at higher seawater conc. (106g/l).

Influence of water availability and temperature on estimates of microbial extracellular enzyme activity.

Soils are highly heterogeneous and support highly diverse microbial communities. Microbial extracellular enzymes breakdown complex polymers into small assimilable molecules representing the limiting step of soil organic matter mineralization. This process occurs on to soil particles although currently it is typically estimated in laboratory aqueous solutions. Herein, estimates of microbial extracellular enzyme activity were obtained over a broad range of temperatures and water availabilities frequently observed at soil upper layers. A Pseudomonas strain presented optimum extracellular enzyme activities at high water activity whereas a desiccation resistant bacterium (Deinococcus) and a soil thermophilic isolate (Parageobacillus) showed optimum extracellular enzyme activity under dried (i.e., water activities ranging 0.5–0.8) rather that wet conditions. Different unamended soils presented a distinctive response of extracellular enzyme activity as a function of temperature and water availability. This study presents a procedure to obtain realistic estimates of microbial extracellular enzyme activity under natural soil conditions of extreme water availability and temperature. Improving estimates of microbial extracellular enzyme activity contribute to better understand the role of microorganisms in soils.

Activity budget of zoo-housed Dolichotis patagonum mates

Captive conditions differ widely from an animal’s natural environment and risk making them prone to reduced behavioural flexibility and sometimes impaired reproduction. The Patagonian mara Dolichotis patagonum, a near threatened species, is a large rodent endemic to Argentina with a singular social organisation that combines monogamy with communal breeding. The aim of this study was to learn more about the activity budget and behavioural synchrony between mates of zoo-housed D. patagonum and thus contribute to research and conservation programmes at modern zoos worldwide. The study implicated 28 animals housed at Cordoba Zoo (Argentina) under natural photoperiod and temperature conditions. Behaviour was recorded once a week every hour from 0800–1800 for a 28-day period and the total offspring at the end of the spring-summer season were counted. The recorded activity budget was: resting (43%), feeding (25%) and alert (13%), the remaining categories accounting for less than 10%. Resting, feeding and alert were the only categories associated with hourly changes. There was 48% behavioural synchrony between mates (both sexes engaging in the same behaviour at the same time) and a total of 23 offspring were counted, corresponding to one litter each reproducing female. The similarity between the behavioural response of these zoo-housed individuals and available data on the behaviour of D. patagonum in the wild indicates that zoo-housed D. patagonum behavioural activities can be considered positive responses, providing useful information for the future development of reintroduction programmes.