Long-term Heat Research Articles

Long-Term Heat Tolerance and Accelerated Metamorphosis: Hot Spring Adaptations of Buergeria japonica.

Extreme temperatures are a major threat to the survival of ectotherms such as amphibians. The tree frogs belonging to the genus Buergeria have accomplished a latitudinal distribution and a wide range of thermal adaptations. In particular, Buergeria japonica, referred to as the "hot spring frog", has been reported to tolerate extremely high temperatures. However, it is unclear how the heat tolerance and metamorphic strategies of this species vary among populations at different temperatures. We therefore conducted long-term heat tolerance experiments on multiple populations of B. japonica tadpoles and their congenic species to determine their survivability and development speed. We observed heat tolerance differences between B. japonica/Buergeria choui and Buergeria buergeri. Buergeria japonica exhibited the highest tolerance among all species, and the Seranma hot spring population showed the highest survival rate and accelerated development speed. However, at temperatures higher than 35°C, they could not survive until the completion of metamorphosis, contrary to previous field observations. Our behavioral experiment showed attenuation of the high temperature preference of B. japonica tadpoles associated with developmental stages, suggesting that they can tolerate extreme temperatures for a limited time window during their development until metamorphosis.

Effects of Heat and Drought Stress on Sustainable Agriculture and Future Food Security in Türkiye

This review investigates the effects of heat and drought stress on future food security of Turkish agriculture. Temperature average is expected to rise to 3.2°C at the end of the current century while annual precipitation will decline more than 10% in the west and south and rise by 20% in the north of Türkiye, implying that climate change will affect ecosystem sustainability. It is therefore crucial to develop strategies to mitigate and adapt to climate change such as adjusting the planting schedule, reduced tillage, fertiliser microdosing, pre-sowing seed treatment, and the application of growth promoting bacteria to improve tolerance to stress by comprehending how plants respond physiologically and biochemically under these stress conditions. Long-term heat stress may hinder photosynthetic electron transport, decreasing the plant's ability to make use of energy for photosynthesis. The immediate response of plants under drought stress involves closing stomatal openings to reduce water loss through stomatal conductance. Combined heat and drought stress have a greater adverse effect on plant development and production than their effects in isolation. Plant phenotyping can play a major role in “climate-proofing” Turkish agriculture through the identification and development of crop varities with improved prouctivity, climate resilience and input requirements. Digital agriculture will also improve the efficiency of Turkish agricultural systems as the adapt to a hotter drier climate. To ensure future food security and the viability of the agro-economic system in Türkiye steps must be taken to make Turkish agriculture more robust in preparation for the impacts of climate change.

Cost-Effective Control of Hybrid Ground Source Heat Pump (GSHP) System Coupled with District Heating

Hybrid ground source heat pump systems (GSHP) offer energy flexibility in operation. For hybrid GSHP systems coupled with district heating, limited studies investigated control strategies for reducing system energy costs from the perspective of building owners. This study proposed a cost-effective control strategy for a hybrid GSHP system integrated with district heating, investigating how power limits of district heating/GSHP, COP value for control (COPctrl), and control time horizon impact the system annual energy cost, CO2 emissions, and long-term borehole heat exchanger system performance. The simulations were performed using the dynamic building simulation tool IDA ICE 4.8. The results indicate that to realize both the energy cost savings and the long-term operation safety, it is essential to limit the heating power of district heating/GSHP and select an appropriate COPctrl. The control time horizon insignificantly affected the annual energy cost and long-term borehole heat exchanger system performance. The recommended COPctrl was 3.6, which is near the GSHP seasonal performance factor. Eventually, the cost-effective control reduced the system’s annual energy cost by 2.2% compared to the GSHP-prioritized control. However, the proposed control increased the CO2 emissions of the hybrid GSHP system due to the higher CO2 emissions from district heating.

Experimental investigation of two-stage NH3–H2O resorption heat storage system with solution concentration difference

Widespread application of solar energy is severely restricted to its instability in time and space. Heat storage system is considered to be one of the most effective pathways to achieve long-term heat supply. Among all the heat storage technologies, solution concentration difference storage technologies stand out for low heat loss and high energy density. By substituting condenser and evaporator in conventional absorption cycle with a high-pressure absorber and low-pressure generator, a resorption cycle could be established. Compared with absorption heat storage cycle, working pressure of resorption heat cycle is lower, making it possible to utilize low-pressure heat source. Two-stage heat source cycle is further proposed to lower working pressure and upgrading supply water temperature. Resorption energy storage cycle with solution concentration difference is established and studied. A prototype based on two-stage ammonia-water resorption heat storage cycle was set up and tested. The result shows that the constraint relation between ambient temperature and heat source temperature of the proposed system. In single-stage mode, the lowest working ambient temperature is 5 °C when heat source temperature is 90 °C. The lowest working ambient temperature could be declined to 0 °C when heat source temperature rises to 120 °C. In two-stage mode, the lowest working ambient temperature is 0 °C when heat source temperature is only 110 °C, which proves the adaptability of two-stage cycle. The highest ESCOP appears in the 15 °C–120 °C single-stage mode, which is 0.742. The highest COP is 1.324 under the same condition. The highest energy density occurs in two-stage mode, which is 467.07 kJ/kg when ambient and heat source is set as 15 °C, 120 °C. The advantage that two-stage mode could enlarge solution concentration difference is verified.

Intraspecific variation in responses to extreme and moderate temperature stress in the wild species, Solanum carolinense (Solanaceae).

Adaptation or acclimation to local temperature regimes has often been used as a proxy for predicting how plant populations will respond to impending novel conditions driven by human-caused climate change. To understand how plants may successfully respond to increasing air temperatures (extreme and moderate) in the future, we explored how temperature tolerance traits differ in populations of Solanum carolinense from northern (MN) and southern (TX) regions of the continental USA in a two-experiment study. In the first experiment, we compared the heat and cold tolerance in vegetative (sporophyte) and reproductive (male gametophyte) traits. In the second experiment, we studied if long-term heat influences plant development by examining how development in moderate heat affected reproductive structures and reproductive success. We found that temperature sensitivity differed between southern populations, which regularly experience extreme heat, and northern populations which do not. In contrast to our expectations, northern populations appeared more heat-tolerant than southern populations for vegetative traits such as chlorophyll stability and reproductive traits such as pollen germination. Our results are consistent with a heat-avoidance, rather than tolerance mechanism to mitigate extreme heat during pollen germination. In the second experiment, plants developing under the moderate heat treatment had significantly smaller reproductive structures and reduced seed production (27% fewer seeds on average than in the control treatment). Reproductive structures that developed in moderate heat were also reduced in size, particularly in the northern populations relative to populations from the south. We conclude that rising temperatures have the potential to incur substantial negative consequences for the reproductive success of individuals in this species and that some populations already mitigate stressful temperature conditions through phenotypic plasticity.

The effects of vitamin C and vitamin B12 on improving spermatogenesis in mice subjected to long-term scrotal heat stress.

Scrotal hyperthermia poses a significant threat to spermatogenesis and fertility in mammalian species. This study investigated the effects of vitamin B12 and vitamin C on spermatogenesis in adult male mice subjected to long-term scrotal hyperthermia. The rationale is based on the sensitivity of germ cells and epididymal sperm to increased scrotal temperatures. While various factors, both internal and external, can raise the testicular temperature, this study focused on the potential therapeutic roles of vitamins B12 and C. After inducing scrotal hyperthermia in mice, vitamin B12 and vitamin C were administered for 35 days. We assessed sperm parameters, serum testosterone levels, stereological parameters, the percentage of apoptotic cells, reactive oxygen species (ROS) levels, and glutathione (GSH) levels. Additionally, real-time polymerase chain reaction was used to analyze the expression of the c-kit, stimulated by retinoic acid gene 8 (Stra8), and proliferating cell nuclear antigen (Pcna) genes. Vitamin C was more effective than vitamin B12 in improving sperm parameters and enhancing stereological parameters. The study showed a significant decrease in apoptotic cells and a beneficial modulation of ROS and GSH levels following vitamin administration. Moreover, both vitamins positively affected the expression levels of the c-kit, Stra8, and Pcna genes. This research deepens our understanding of the combined impact of vitamins B12 and C in mitigating the effects of scrotal hyperthermia, providing insights into potential therapeutic strategies for heat stress-related infertility. The findings highlight the importance of considering vitamin supplementation as a practical approach to counter the detrimental effects of elevated scrotal temperatures on male reproductive health.

Machine-learning-assisted long-term G functions for bidirectional aquifer thermal energy storage system operation

Optimization of aquifer thermal energy storage (ATES) performance in a building system is an important topic for maximizing the seasonal offset between energy demand and supply and minimizing the building's primary energy consumption. To evaluate ATES performance with bidirectional operation, this study develops an analytical solution-based model to simulate the spatiotemporal thermal response in an aquifer. The model consists of three temperature response functions, similar to the G functions in borehole thermal energy storage (BTES), to estimate the transient temperature profile in the aquifer during seasonally varying injection and extraction of hot/cold water. Applying machine learning (ML) based data classification and regression techniques to the results of a series of finite element (FE) benchmark simulations of typical ATES configurations, model input parameters are linked to the subsurface thermal, hydrogeological, and ATES operational properties. Compared to the benchmark simulation results, the errors of the proposed model in estimating the annual energy storage and locating the thermally affected area are about 3 % and 1 %, respectively. The model was applied to a previous short-term case study, and the error in the transient production temperature estimation is about 1 %. The long-term heat recovery ratio estimated from the model also compares well to those calculated from the previous study and the validated numerical model. Because of its fast computation, the proposed model can be coupled with the individual building system simulation and used for preliminary ATES design, and this will allow for greater exploration of ATES operational space and, therefore, better choices of ATES operating conditions. The proposed model can also be coupled with the district heating and cooling network simulation for computationally efficient city-scale long-term ATES potential assessment.

Changes in characteristics of spermatogonial stem cells in response to heat stress in stallions

Spermatogonial stem cells (SSCs) are essential for the maintenance of male fertility and survival of species. Environmental conditions, notably heat stress, have been identified as important causes of male infertility and have a negative impact on SSCs. Animals with cryptorchid testes (CT) are optimal models for the study of long-term heat stress-related changes in germ cells. The effect of heat stress on germ cells differs depending on the spermatogenesis stage. Thus, verifying whether the specific phase of spermatogenesis is dependent or independent of heat stress in stallions is important. We evaluated the heat stress-related response of SSCs by comparing the relative abundance of mRNA transcripts and expression patterns of the undifferentiated embryonic cell transcription factor 1 (UTF-1) and deleted in azoospermia-like (DAZL) in the seminiferous tubules of CT and normal testes (NT) of stallions using reverse transcription-quantitative polymerase chain reaction (RT-qPCR), immunofluorescence, and western blotting. We also analyzed the relative abundance of mRNA of different proliferative markers, including minichromosome maintenance 2 (MCM2), marker of proliferation Ki-67 (MKI-67), and proliferating cell nuclear antigen (PCNA). Testicular tissues from four Thoroughbred unilateral cryptorchid postpubertal stallions were used in this study during the breeding season. The relative abundance of the mRNA transcripts of UTF-1 and MCM2 was significantly upregulated in the CT group than that of those in the NT group. In contrast, the relative abundance of the mRNA transcripts of DAZL was significantly downregulated in the CT group than that of those in the NT group. Western blot quantification showed that the relative intensity of UTF-1 protein bands was significantly higher, while that of DAZL protein bands was significantly lower in the CT group than in the NT group. Immunofluorescence studies showed that the number of germ cells immunostained with UTF-1 was significantly higher while immunostained with DAZL was significantly lower in the CT group than that in the NT group. The higher expression level of UTF-1 in the CT group shows that undifferentiated SSCs are not affected by long-term exposure to heat stress. These results also indicate that germ cells after differentiation phase are directly affected by heat-stress conditions, such as cryptorchidism, in stallions.

Long-term thermal stress induces hepatic injury and alters the thermotolerance response in Hong Kong catfish (Clarias fuscus)

Global climate change has a significant impact on fish survival and the aquaculture industry. Even highly adaptable organisms like Siluriformes fish are susceptible to these effects. This study investigates the consequences of extreme high temperature on Hong Kong catfish (Clarias fuscus), a species known for its long-term habitation in tropical and subtropical regions. In this study, C. fuscus were cultivated for 90 days at high temperature (HT, 34 °C) and normal temperature (NT, 26 °C), followed by subjecting the two groups to high temperature stress (34 °C) and temperature recovery (26 °C). The hepatic histology, biochemical, and transcriptomic characteristics of the species were examined before acute high temperature stress (NT-C, HT-C), after acute high temperature stress (NT-T, HT-T), and after temperature recovery (NT-R, HT-R). The histological analysis revealed that long-term heat stress damaged the liver tissue of C. fuscus. Furthermore, significant damage was observed in the liver tissues of the NT group under acute high temperature stress, while no further damage was observed in the HT group. The biochemical analysis showed that 90 days of heat stress altered the body's immune and oxidative balance, resulting in an increase in alkaline phosphatase (ALP), alanine aminotransferase (ALT), catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPX) activities, and a decrease in malondialdehyde (MDA) content. Upon acute heat stress, the liver function of the NT group was disordered and unable to produce enough total-bilirubin (T-BIL), while the aspartate aminotransferase (AST) activity of the HT group was more susceptible to being affected. Long-term heat stress led to significant changes in gene expression, with the NT group showing three times more differentially expressed genes (DEGs) identified in the liver compared to the HT group under acute heat stress conditions. Analysis of DEG enrichment during the same treatment period in both groups revealed significant differences in amino acid metabolism and lipid metabolism pathways. These results suggest that long-term heat stress caused liver tissue damage in C. fuscus, altering immune and oxidative balance, enzyme activity sensitivity, as well as the body's response to acute heat stress pathways and intensity. This study lays the groundwork for future investigations into fish adaptability to sudden temperature changes and aquaculture strategies to mitigate heat stress in fish facing extreme temperatures.

Simplified method and numerical simulation analysis of pipe-group long-term heat transfer in deep-ground heat exchangers

Deep-buried pipe-group heat transfer is a primary form of utilizing geothermal energy in the middle and deep ground layers. This study introduces a methodology to simplify the heat transfer process of a pipe-group into a single borehole within a finite computational domain. The proposed methodology allows for rapid and accurate assessment of the heat transfer performance of the pipe-group with coaxial deep-ground heat exchangers (C-DGHEs). The feasibility of this simplified method is supported by numerical validation. Consequently, a 20-year numerical computation is performed for pipe-group models with spacings of 15, 20, 30, and 40 m, alongside a comparative study on the heat transfer of a single borehole C-DGHE with a computational domain radius of 200 m. For a pipe-group spacing of 15 m, the results demonstrated that the heat transfer boundary is exceeded in the first year of heat extraction but stabilized into a steady decline. For a spacing of 40 m, the decrease in heat transfer over 20 years was less than 15 % compared to the single C-DGHE. This research effectively evaluates the heat transfer performance of pipe groups, providing theoretical support and technical guidance to develop and promote the applications of deep geothermal energy.

Transient simulation of conjugate heat transfer of kerosene with thermal oxidative and surface coking reactions at a supercritical pressure

The regenerative cooling technology in aerospace applications often involves supercritical-pressure heat transfer of a hydrocarbon fuel, in which thermal oxidative reactions of the fuel would lead to surface coke accumulation on the cooling channel wall. In this paper, the long-term transient conjugate heat transfer of kerosene has been numerically investigated in a circular mini tube at a supercritical pressure of 3 MPa. The modified chemical mechanism and kinetics of thermal oxidative and surface coking reactions of kerosene are proposed, which, with an additional surface reaction, are capable of treating large coke deposition in regions with sharp temperature gradients. Transient surface coke accumulation and its effect on heat transfer are handled by a dynamic mesh technique. A series of numerical studies are conducted to elucidate the influences of surface heat flux, dissolved oxygen mass fraction, inlet fuel mass flow rate, and coke layer thermal conductivity on the supercritical-pressure heat transfer and thermal oxidative reactions. The effects of different reaction pathways on surface coke accumulation are analyzed comprehensively, and it is revealed that the oxygen-consuming surface coke deposition is initiated only at the high fuel temperature at around 590 K. The present numerical results would enhance fundamental understanding of the long-term transient heat transfer process of a hydrocarbon fuel at supercritical pressures in the regenerative cooling applications.

Revealing the injustice and factors that affect the resilience responses of residents in the full period of heat waves

Due to the influence of global warming and the urban heat island effect, heat wave resilience is particularly important for residents. In this study, we constructed a full-period evaluation system for heat wave resilience comprising three phases of preparation, resistance, and recovery from the social level in order to assess the phenomenon of heat injustice in heat waves and provide feasible heat action strategies. The results obtained by clustering, variance, and correlation analyses of the data showed the following. (1) Inequality was found in the resilience of residents with different social attributes in each phase of the heat waves. (2) The social attributes of vulnerable groups were heterogeneous in various phases of heat waves. (3) Environmental perception factors that affected resilience were heterogeneous in different phases of heat waves. Therefore, policies should focus on vulnerable groups in each phase of heat waves, and the roles of governments, neighborhoods, and individuals in heat action programs need to be clarified. The results obtained in this study provide useful evidence for developing long-term heat management and heat injustice mitigation strategies.

Exploring heat risk adaptation governance: A case study of the UK

Rising temperatures exacerbated by climate change are a growing concern in the UK. This paper assesses the state of heat risk governance in the country through an analysis of the Adverse Weather and Health Plan (AWHP) launched in 2023, which replaces the former Heatwave Plan (HWP) for England — the prominent policy for addressing heatwaves in the UK. Through 17 semi-structured interviews with key stakeholders, the paper assesses the perceived effectiveness of the new plan in addressing heat risk. The findings demonstrate that AWHP has been positively received and is considered to have well-functioning institutional arrangements and strategies tailored to manage immediate heat risks. However, areas for improvement are identified: the need to enhance public communication and broaden the cross-sectoral understanding of heat impacts beyond the domain of ‘health’. Further, the research reveals gaps in leadership, institutional structure, delineation of roles and responsibilities, and funding and resources for addressing long-term heat risk and preparedness in the UK. The paper explores these and highlights the need for strengthening governance and capacity to tackle the multi-dimensional climate risk, i.e., heat, effectively.

Integrated analysis of transcriptome and small RNAome reveals regulatory network of rapid and long-term response to heat stress in Rhododendron moulmainense

Main conclusionThe post-transcriptional gene regulatory pathway and small RNA pathway play important roles in regulating the rapid and long-term response of Rhododendron moulmainense to high-temperature stress.The Rhododendron plays an important role in maintaining ecological balance. However, it is difficult to domesticate for use in urban ecosystems due to their strict optimum growth temperature condition, and its evolution and adaptation are little known. Here, we combined transcriptome and small RNAome to reveal the rapid response and long-term adaptability regulation strategies in Rhododendron moulmainense under high-temperature stress. The post-transcriptional gene regulatory pathway plays important roles in stress response, in which the protein folding pathway is rapidly induced at 4 h after heat stress, and alternative splicing plays an important role in regulating gene expression at 7 days after heat stress. The chloroplasts oxidative damage is the main factor inhibiting photosynthesis efficiency. Through WGCNA analysis, we identified gene association patterns and potential key regulatory genes responsible for maintaining the ROS steady-state under heat stress. Finally, we found that the sRNA synthesis pathway is induced under heat stress. Combined with small RNAome, we found that more miRNAs are significantly changed under long-term heat stress. Furthermore, MYBs might play a central role in target gene interaction network of differentially expressed miRNAs in R. moulmainense under heat stress. MYBs are closely related to ABA, consistently, ABA synthesis and signaling pathways are significantly inhibited, and the change in stomatal aperture is not obvious under heat stress. Taken together, we gained valuable insights into the transplantation and long-term conservation domestication of Rhododendron, and provide genetic resources for genetic modification and molecular breeding to improve heat resistance in Rhododendron.

Nutritional, Utility, and Sensory Quality and Safety of Sunflower Oil on the Central European Market

In the quality monitoring of 18 sunflower oil samples from the EU market, 14 were refined and 4 were cold-pressed. They demonstrated high quality of technological processing with low values of trans-unsaturated fatty acids, acid value, and peroxide value and also met the limits set by legislation in the content of process contaminants 3-monochloropropane-1,2-diol (3-MCPD) esters and glycidyl esters. Measurements of oxidative stability showed a difference in utility value. The average induction period of the oils from the traditional varieties was 2.6 h, predisposing them to cold cooking or short-term frying, while the 11.8 h of the four high oleic sunflower oils (HOSO) indicates the possibility of long-term heat stress. The nutritional benefit is the average vitamin E content of 663 mg/kg oil. The overall sensory quality of the samples was evaluated by a 12-member panel of trained assessors. On the seven-point category scale, the oils were of good to exceptional quality. The cold-pressed oils (CPOs) differed in having, on average, lower trans-unsaturated fatty acid content, process contaminants at unmeasurable levels, and, on average, higher vitamin E concentrations. The specific organoleptic properties of the CPOs were characterized by a pleasant nutty and sunflower seed flavor.

Investigation on heat transfer performance of energy diaphragm walls under groundwater flow condition

The flow of groundwater affects the transport of heat, subsequently impacting the heat transfer performance of energy diaphragm walls. To investigate the effect of groundwater flow on the thermal performance of energy diaphragm walls in the actual project, a three-dimensional finite element model of the thermo-hydro coupling was established. This model's accuracy was confirmed using in-situ experimental data. Subsequent analyses explored the influence of groundwater flow velocity on the long-term heat transfer efficiency of energy diaphragm walls and the temperature field distribution in both the wall and adjacent soil during winter/summer cyclical operations. Studies have shown that the increase of groundwater flow velocity can promote the migration of heat accumulated in the wall and in the soil around the wall to a position farther away from the wall along the flow direction, thereby promoting the long-term heat exchange efficiency of the thermo-active diaphragm walls. Moreover, as winter and summer operating conditions transition, the previously accumulated heat in the wall and surrounding soil aids in boosting the current mode's heat exchange efficiency. In addition, groundwater flow also facilitates the movement of heat accumulated at the bottom of the excavation face, allowing the ground's temperature field to stabilize faster. This indirectly bolsters the heat exchange efficiency of the energy diaphragm walls. The research results may enrich the understanding of the heat transfer behavior of energy diaphragm walls under actual working conditions.

Bubbling triggered crystallization of xylitol phase change material for controllable heat retrieval: The subcooling effect

Towards long-term seasonal latent heat storage, the PCMs with strong supercooling are recommended as the heat storage medium. Nevertheless, the suitable techniques activating latent heat release is also of significance in the period of heat supply. The present work investigated the N2 bubbling triggered crystallization of supercooled xylitol. Special attention was paid to the subcooling effect. The N2 bubbling was identified to be a potential technique to trigger crystallization of xylitol at moderate degrees of subcooling. It was found that efficient crystallization issues were obtained with degrees of subcooling from 40 °C to 60 °C, while uncrystallization was obtained with both lower and higher subcooling. The recorded temperature history curves show that subcooling effect has strong influence on the crystallization behavior. The crystallization points tend to decline from 51.9 °C to 42.3 °C with degree of subcooling rising from 40 °C to 50 °C. The crystallization durations extend with subcooling effect enhancing. Fortunately, bubbling technique has slight influence on the properties of formed xylitol crystals. Moreover, the subcooling significantly influences the transportation behavior of bubbles. Particularly, The specific growth rates of bubbles are determined to be as low as 0.005 mm/min with the lowest degree of subcooling 10 °C, and continue to rise over 20 times when the subcooling reaches to 60 °C. The interfaces of bubbles as potential nucleation sites were deemed to be one of the important issues to activate heterogeneous nucleation, thus trigger crystallization. The present investigation is helpful to understand the fundamentals of bubbling effect on crystallization with broad range of subcooling.

Bacteria undergo significant shifts while archaea maintain stability in Pocillopora damicornis under sustained heat stress

Global warming reportedly poses a critical risk to coral reef ecosystems. Bacteria and archaea are crucial components of the coral holobiont. The response of archaea associated with warming is less well understood than that of the bacterial community in corals. Also, there have been few studies on the dynamics of the microbial community in the coral holobiont under long-term heat stress. In order to track the dynamic alternations in the microbial communities within the heat-stressed coral holobiont, three-week heat-stress monitoring was carried out on the coral Pocillopora damicornis. The findings demonstrate that the corals were stressed at 32 °C, and showed a gradual decrease in Symbiodiniaceae density with increasing duration of heat stress. The archaeal community in the coral holobiont remained relatively unaltered by the increasing temperature, whereas the bacterial community was considerably altered. Sustained heat stress exacerbated the dissimilarities among parallel samples of the bacterial community, confirming the Anna Karenina Principle in animal microbiomes. Heat stress leads to more complex and unstable microbial networks, characterized by an increased average degree and decreased modularity, respectively. With the extension of heat stress duration, the relative abundances of the gene (nifH) and genus (Tistlia) associated with nitrogen fixation increased in coral samples, as well as the potential pathogenic bacteria (Flavobacteriales) and opportunistic bacteria (Bacteroides). Hence, our findings suggest that coral hosts might recruit nitrogen-fixing bacteria during the initial stages of suffering heat stress. An environment that is conducive to the colonization and development of opportunistic and pathogenic bacteria when the coral host becomes more susceptible as heat stress duration increases.

Inverse Estimation of Dynamic Heat Flux Using Proportional Integral Derivative Control

To improve long-term dynamic heat flux prediction using an embedded thermocouple, a novel inverse estimation approach using a proportional integral derivative (PID) control scheme is proposed. A feedforward model of the discrete integer-order transfer function was identified from a one-dimensional dynamic heat-flux sensor using the calibrated heat flux with varying amplitudes of the pseudo-random binary sequence and its single-temperature response data. Using the model and unit-step temperature response as the controlled plant and reference input signal, the PID controller with a low-pass filter was designed. Using the on-site temperature measurement data as the reference signal instead of the unit-step temperature, the time-history control output values, that is, the inverse estimated dynamic heat flux of the designed PID controller, were obtained. The comparison of the test results and the discussion indicate that 1) the proposed inverse method avoids the impact of the thermal inertia of the thermocouple and significantly alleviates the effects of measurement noise, and 2) in addition to high identification efficiency and measurement fidelity, further improvement in the effective measuring time of the dynamic heat flux was observed.

Heat Treatments at Varying Ambient Temperatures and Durations Differentially Affect Plant Defense to Blumeria hordei in a Resistant and a Susceptible Hordeum vulgare Line.

Our previous research showed that a powdery mildew resistant barley line (MvHV07-17) maintains its resistance to Blumeria hordei (Bh) even if plants are exposed to a long-term high temperature of 35°C for 120 h before Bh inoculation, whereas such high temperature pretreatment further increases susceptibility to infection in the susceptible barley line MvHV118-17. In the present study, we extended this approach using short-term high-temperature water treatment (49°C for 30 s) to determine how it affects powdery mildew resistance in these barley lines. We found that this short-term heat shock (HS) impaired plant defense responses, as reflected by development of Bh colonies and visible necrotic spots on leaves of MvHV07-17, which does not develop visible symptoms upon Bh inoculation under optimal growth conditions. In contrast, both HS and long-term heat stress enhanced susceptibility to Bh in MvHV118-17 plants. These results were supported by the measurement of Bh biomass using a qPCR method. Furthermore, microscopic examinations showed that HS elevated the rate of successful Bh penetration events and the spread of cell death in the surrounding mesophyll area and allowed for colony formation and sporulation in resistant barley, whereas early and effective plant defense responses, such as papilla formation and single-cell epidermal hypersensitive response, were significantly reduced. Furthermore, we found that the accumulation of hydrogen peroxide in both resistant and susceptible barley was correlated with susceptibility induced by HS and long-term heat-stress. This study may contribute to a better understanding of plant defense responses to Bh in barley exposed to heat. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.