Temperature Response Research Articles

Divergent impacts of soil desiccation on atmospheric water vapor–temperature responses regulated by evapotranspiration

Abstract Climate warming induces temporally varying atmospheric water vapor, yet the spatial distribution of opposing trends across global land remains elusive. Here we use monthly ERA5 dataset to discern the responses of water vapor changes to rising air temperatures from 1982 to 2020. Simultaneous increase in both water vapor and air temperature over approximately three-quarters of global land, with a median of 0.21 mm·K–1, particularly evident in tropics. Strong positive responses are primarily influenced by increasing trends in evapotranspiration and low-elevation areas. About one-fifth of global land shows a decline in water vapor with a median of –0.62 mm·K–1, predominantly in southeastern South America and southwestern North America. Negative responses are also driven by evapotranspiration trends, where strong evapotranspiration enhances these effects that are less pronounced at high-altitude regions. The prevalence of positive response is highest during September-October-November (81%), while negative response observed most in December-January-February (35%). The spatial distribution of negative responses generally aligns with soil desiccation patterns; soil desiccation exacerbates negative responses in humid regions due to evaporative cooling but mitigates them in arid regions due to intensified warming. This study enhances our comprehension regarding divergent responses of atmospheric water vapor towards global warming.

Air temperature and precipitation constraining the modelled wetland methane emissions in a boreal region in northern Europe

Abstract. Wetland methane responses to temperature and precipitation are studied in a boreal wetland-rich region in northern Europe using ecosystem process models. Six ecosystem models (JSBACH-HIMMELI, LPX-Bern, LPJ-GUESS, JULES, CLM4.5, and CLM5) are compared to multi-model means of ecosystem models and atmospheric inversions from the Global Carbon Project and upscaled eddy covariance flux results for their temperature and precipitation responses and seasonal cycles of the regional fluxes. Two models with contrasting response patterns, LPX-Bern and JSBACH-HIMMELI, are used as priors in atmospheric inversions with Carbon Tracker Europe–CH4 (CTE-CH4) in order to find out how the assimilation of atmospheric concentration data changes the flux estimates and how this alters the interpretation of the flux responses to temperature and precipitation. Inversion moves wetland emissions of both models towards co-limitation by temperature and precipitation. Between 2000 and 2018, periods of high temperature and/or high precipitation often resulted in increased emissions. However, the dry summer of 2018 did not result in increased emissions despite the high temperatures. The process models show strong temperature and strong precipitation responses for the region (51 %–91 % of the variance explained by both). The month with the highest emissions varies from May to September among the models. However, multi-model means, inversions, and upscaled eddy covariance flux observations agree on the month of maximum emissions and are co-limited by temperature and precipitation. The setup of different emission components (peatland emissions, mineral land fluxes) has an important role in building up the response patterns. Considering the significant differences among the models, it is essential to pay more attention to the regional representation of wet and dry mineral soils and periodic flooding which contribute to the seasonality and magnitude of methane fluxes. The realistic representation of temperature dependence of the peat soil fluxes is also important. Furthermore, it is important to use process-based descriptions for both mineral and peat soil fluxes to simulate the flux responses to climate drivers.

Reconstruction of Local Three-dimensional Temperature Field of Tumor Cells with Low-toxic Nanoscale Quantum-dot Thermometer and Cepstrum Spatial Localization Algorithm.

The optimal method for three-dimensional thermal imaging within cells involves collecting intracellular temperature responses while simultaneously obtaining corresponding 3D positional information. Current temperature measurement techniques based on the photothermal properties of quantum dots face several limitations, including high cytotoxicity and low fluorescence quantum yields. These issues affect the normal metabolic processes of tumor cells. This study synthesizes a low-toxicity cell membrane-targeted quantum dot temperature sensor by optimizing the synthesis method of CdTe/CdS/ZnS core-shell structured quantum dots. Compared to CdTe-targeted quantum dot temperature sensors, the cytotoxicity of CdTe/CdS/ZnS-targeted quantum dot temperature sensors is reduced by 40.79%. Additionally, a novel cepstrum-based spatial localization algorithm is proposed to achieve rapidly compute the three-dimensional positions of densely distributed quantum dot temperature sensors. Ultimately, both targeted and non-targeted CdTe/CdS/ZnS quantum dot temperature sensors were used simultaneously to label the internal and external regions of human osteosarcoma cells to obtain temperature data at these labeling positions. By combining this with the cepstrum-based spatial localization algorithm, the spatial coordinates of the quantum dot temperature sensors were obtained. Three-dimensional temperature field reconstruction of three local regions was achieved within a 12 μm axial range in living cells. The method described in this paper can be widely applied to the quantitative study of intracellular thermal responses.

Multi-Emitting Ratiometric Temperature Sensing and Tunable White Light Emitting Based on Effective Energy Transfer in a Lanthanide-Brønsted Acidic Ionic Liquid Coordination Polymer.

Isostructured lanthanide-Brønsted acidic ionic liquid coordination polymers, {[Ln(C7H7N2O4)(H2O)4]Cl2}n (LnIMDC(H2O)4, Ln = Eu3+, Gd3+, or Tb3+, C7H7N2O4 = [IMDC]-) and {[Eu0.5Tb0.5(C7H7N2O4)(H2O)4]Cl2}n (Eu0.5Tb0.5IMDC(H2O)4)), have been synthesized using 1,3-bis(carboxymethyl) imidazolium chloride ([H2IMDC]Cl) as linkers. LnIMDC(H2O)4 (Ln = Eu3+ or Tb3+) and Eu0.5Tb0.5IMDC(H2O)4 exhibit good temperature sensing performance over a wide temperature range with maximum sensitivities Sr of 2.73%·K-1 (392 K) and 2.74%·K-1 (362 K), and 2.21% K-1 (383 K), respectively. Meanwhile, the white light emission of Eu0.5Tb0.5IMDC(H2O)4 was achieved with Commission Internationale de l'Eclairage coordinates of (0.323, 0.328), a correlated color temperature of 5942 K, and a color rendering index (CRI) of 90. Moreover, the temperature response of the as-synthesized Eu0.5Tb0.5IMDC(H2O)4@PDMS film was monitored. The energy transfer efficiency and phosphorescence lifetime in the abovementioned coordination polymers were investigated to explore the energy transfer efficiency between [IMDC]- and Ln3+ as well as between Tb3+ and Eu3+.

Pressure and temperature response and phase transition path during small hole leakage in a near-industrial scale CO2 pipe

ABSTRACT As a large-scale CO2 migration method, pipelines play a crucial role in the CCUS industry chain. Small hole leakage caused by self defects, fatigue and corrosion, and natural disasters is a common accident in CO2 pipelines. When leaked CO2 is sprayed out through a small hole, the temperature inside the pipeline drops sharply under the Joule Thomson effect. This sudden temperature drop significantly reduces the toughness of the material, increases the risk of brittle fracture. In order to improve the CO2 pipeline release database, a new industrial scale CO2 pipeline has been built. The CO2 release experiments were carried out by using this experimental device. The experimental results showed that the pressure drop rate was fast under high pressure and then slowed down when the pressure dropped below the critical pressure, with the coexistence of gas and liquid. Rapid pressure drop and slight rebound occur during the leakage process, and low initial pressure leads to a more pronounced pressure plateau effect. Dense-phase CO2 leakage produced more dry ice than supercritical state, and the far field sublimation effect was more significant. In practice, particular attention should be paid to safety far from the leakage end.

Regulation of TADF by Internal and External Heavy Atom Effect in D-A MOF for Heterocrystal based Temperature-Compensated Photonic Device.

The application of temperature-compensated photonic device is hampered by poor accuracy and overly simplistic functions of propagation in photonic integrated circuits (PICs) field. Herein, we report a new library of donor-acceptor metal-organic framework (D-A MOF) with thermally activated delayed fluorescence (TADF) and the fabricating of temperature-compensated photonic device by virtue of the unique temperature response character of TADF emitters. Highly tunable through-space charge transfer (TSCT) of TADF was realized within the D-A MOFs through a novel strategy that synergistically combines the internal heavy atom effect (HAE) with an external HAE, induced by the incorporation of heavy atoms into different components, achieving the regulable photophysical indicators including adjustable PL wavelength (534 to 592 nm) and surging quantum yield (5.02%-47.39%). Further investigation of the impact of external HAE on TADF was conducted through crystal structures and Hirshfeld surface plots of four D-A regimes featuring substituent-based linkers. Notably, temperature-compensated photonic device based on heterocrystal was fabricated through integrating D-A MOFs with contrary temperature response. The emission signal output of the heterojunction remained nearly stable in 215 K to 295 K range, highlighting the promising potential application of TADF D-A MOF featuring sensitive temperature response in PICs field.

Transcriptomic Insights into Dual Temperature–Salinity Stress Response in “Shuike No. 1”, a Pioneering Rainbow Trout Strain Bred in China

Global warming poses a significant threat to aquaculture, particularly for cold-water species like rainbow trout (Oncorhynchus mykiss). Understanding the molecular mechanisms underlying stress responses is crucial for developing resilient strains. This study investigates the dual stress of salinity and temperature response of “Shuike No. 1” (SK), a pioneering commercially bred rainbow trout strain in China, using RNA-sequencing of gill, intestine, and liver tissues from fish exposed to four treatment combinations: freshwater at 16 °C, freshwater at 25 °C, saltwater (30‰) at 16 °C, and saltwater at 25 °C. Differential gene expression analysis identified a substantial number of DEGs, with the liver showing the most pronounced response and a clear synergistic effect observed under combined high-temperature and salinity stress. Weighted gene co-expression network analysis (WGCNA) revealed stress-responsive gene modules and identified hub genes, primarily associated with gene expression, endoplasmic reticulum (ER) function, disease immunity, energy metabolism, and substance transport. Key hub genes included klf9, fkbp5a, fkbp5b, ef2, cirbp, atp1b1, atp1b2, foxi3b, smoc1, and arf1. Functional enrichment analysis confirmed the prominent role of ER stress, particularly the pathway “protein processing in the endoplasmic reticulum.” Our results reveal complex, tissue-specific responses to dual stress, with high temperature exerting a stronger influence than salinity. These findings provide valuable insights into the molecular mechanisms underpinning dual stress responses in SK, informing future breeding programs for enhanced resilience in the face of climate change.

Construction of UCST-Responsive Claw-Like Polysulfobetaines for Efficient Capture of Cellulase.

The high cost of enzymatic glycolysis has seriously restricted the industrialization of lignocellulose-based sugar platform technology. Recovering and recycling cellulase can reduce the cost. Here, a thermo-responsive claw-type polysulfobetaine (PSPA) was constructed for hydrophobic grasping and efficient recycling of cellulase. Compared with the linear sulfobetaine homopolymer (PSPE), PSPA had more sensitive temperature response and strong cellulase recovery ability. PSPE-3 (Mw=355.1 kDa) was added to the hydrolysis system of corncob residue (CCR) (50 °C), at 0.4 mass ratio of PSPE-3 to cellulase, and after enzymatic hydrolysis, 50% of the cellulase was saved when cooling to 25 °C. But only 0.05 times PSPA-1 (Mw=30.0 kDa) was added to the CCR system, and 70% of the cellulase was saved when cooling to 25 °C. This work presents a claw shaped protein-capture agent, polysulfobetaine for capturing cellulase, which is of great significance to reduce the lignocellulosic hydrolysis cost, and efficiently separate enzyme proteins.

Tropical Glaciation and Glacio-Epochs: Their Tectonic Origin in Paleogeography

Precambrian tropical glaciation is an enigma of Earth’s climate. Overlooking fundamental difference of land/sea icelines, it was equated with a global frozen ocean, which is at odds with the sedimentary evidence of an active hydrological cycle, and its genesis via the runaway ice–albedo feedback conflicts with the mostly ice-free Proterozoic when its trigger threshold was well exceeded by the dimmer sun. In view of these shortfalls, I put forth two key hypotheses of the tropical glaciation: first, if seeded by mountain glaciers, the land ice would advance on sea level to be halted by above-freezing summer temperature, which thus abuts an open cozonal ocean; second, a tropical supercontinent would block the brighter tropical sun to cause the required cooling. To test these hypotheses, I formulate a minimal tropical/polar box model to examine the temperature response to a varying tropical land area and show that tropical glaciation is indeed plausible when the landmass is concentrated in the tropics despite uncertain model parameters. In addition, given the chronology of paleogeography, the model may explain the observed deep time climate to provide a unified account of the faint young Sun paradox, Precambrian tropical glaciations, and Phanerozoic glacio-epochs, reinforcing, therefore, the uniformitarian principle.

Double Metal Dots Configuration for Suppression of Spurious Responses in Temperature Compensated Surface Acoustic Wave Resonators on SiO2/LiNbO3 Structure

Double Metal Dots Configuration for Suppression of Spurious Responses in Temperature Compensated Surface Acoustic Wave Resonators on SiO₂/LiNbO₃ Structure

Analysis on thermomechanical characteristics of refractory brick structure with different material properties and structure parameters in incinerators

The service performance of refractory brick structure under high temperatures is critical to their life. A coupled thermal-stress model of refractory brick structure was established. Based on the model, the influence mechanisms of materials, brick number and brick thickness on the temperature and stress responses of the structure were revealed, which was aimed at providing guidance for optimizing the design of high-performance refractory brick structures. Results indicated that the maximum principal compressive stress in the center of the structure was significantly greater than the maximum principal tensile stress. Among corundum-mullite, andalusite and corundum-silicon carbide, corundum-silicon carbide had the strongest heat-transfer capability. At a maximum temperature of 1000 ℃, the peak compressive stresses were 198.37MPa, 182.13MPa and 117.24MPa for these three materials, respectively. The peak compressive stress decreased as the brick number increased, due to the relatively free expansion of the bricks resulting from gaps. And the three-brick structure exhibited the highest peak tensile stress. At 1000 ℃, the peak compressive stresses were 266.78MPa, 182.13MPa, and 165.89MPa for the single-brick, three-brick, and five-brick structures, respectively. In addition, the peak compressive stress decreased with the increase of brick thickness. At 1000 ℃, the peak compressive stresses decreased from 332.17MPa to 182.11MPa as the thickness increased from 60mm to 120mm. It is recommended to use corundum-silicon carbide as the material, with the brick thickness advised to be between 80 and 100mm.

A controlled co-assembly approach to tune temperature responsiveness of biomimetic proteins.

The controlled co-assembly of biomacromolecules through tuneable interactions offers a simple and fascinating opportunity to assemble multiple molecules into a single entity with enhanced complexity and unique properties. Herein, our study presents a dynamic co-assembled system using the multistimuli responsive intrinsically disordered protein Rec1-resilin and the adhesive hydrophilic protein silk sericin (SS). We utilized advanced characterization techniques including circular dichroism (CD) spectroscopy, dynamic light scattering (DLS), small-angle X-ray scattering (SAXS), and small/ultra-small angle neutron scattering (SANS/USANS) to elucidate the detailed co-assembly behavior of the system and its evolution over time and temperature. To achieve sufficient neutron contrast, we successfully biosynthesised deuterium-labeled Rec1-resilin (D-Rec1). Our research demonstrates that this co-assembly allows the formation of a robust entity with dynamic conformational assembly and disassembly, exhibiting both the upper critical solution temperature (UCST) and lower critical solution temperature (LCST) with reversibility. The assembly and disassembly dynamics of the co-assembled entity at UCST are very fast, while the process is kinetically controlled at LCST. This study provides significant new insights into the interplay of a hydrophilic, multi-responsive IDP and a highly hydrophilic protein, shaping the thermoresponsive and stable properties of the co-assembled entity.

Resposta do feijão-fava às altas temperaturas em ambiente natural e controlado

ABSTRACT Effects of abiotic stresses, such as high temperature, on plants are exacerbated by climate change. Lima beans exhibit higher tolerance to high temperatures than the common beans. Understanding the tolerance of lima bean landrace germplasm to high temperatures is important to improve their breeding. Therefore, in this study, we aimed to examine the high temperature responses of lima bean landrace varieties obtained from the Phaseolus Germplasm Bank at Universidade Federal do Piauí (BGP-UFPI, Brazil) in two environments. Five landraces showing the best performance in emission of flowers and number of pods formed (UFPI-945, UFPI1037, UFPI-876, UFPI-1036, and UFPI-1064) were evaluated in two cultivation environments, natural (29 ºC) and controlled (37 ºC), using a completely randomized design with four replications, with each plot consisting of a single plant. Analysis of variance and Tukey’s test (P < 0.05) were performed for 12 quantitative traits, followed by Pearson’s correlation analysis. Lima beans exhibited genetic variability in high temperature tolerance in both natural and controlled environments. Specifically, UFPI-1064 exhibited superior performance with higher pod thickness and width and number of flowers and lower flower and pod abortion than the other varieties in both natural and controlled environments. Pearson's correlation analysis revealed positive and strong correlations between the number of flowers and flower abortion in the natural environment and number of pods and seeds per pod in the controlled environment.

Strain selection and temperature responses of Ulva and Ulvaria (Chlorophyta) for application in land-based cultivation systems

Strain selection and temperature responses of Ulva and Ulvaria (Chlorophyta) for application in land-based cultivation systems

A Machine Learning-Enabled Real-Time temperature response system based on Polymer-Filler interactions for conductive network assembly

A Machine Learning-Enabled Real-Time temperature response system based on Polymer-Filler interactions for conductive network assembly

Embedment of Biosynthesised Silver Nanoparticles in PolyNIPAAm/Chitosan Hydrogel for Development of Proactive Smart Textiles.

A smart viscose fabric with temperature and pH responsiveness and proactive antibacterial and UV protection was developed. PNCS (poly-(N-isopropylakrylamide)/chitosan) hydrogel was used as the carrier of silver nanoparticles (Ag NPs), synthesised in an environmentally friendly manner using AgNO3 and a sumac leaf extract. PNCS hydrogel and Ag NPs were applied to the viscose fabric by either in situ synthesis of Ag NPs on the surface of viscose fibres previously modified with PNCS hydrogel, or by the direct immobilisation of Ag NPs by the dehydration/hydration of the PNCS hydrogel with the nanodispersion of Ag NPs in the sumac leaf extract and subsequent application to the viscose fibres. Compared to the pre-functionalised PNCS application method, the in situ functionalisation imparted much higher concentration of Ag NPs on the fibres, colouring the samples brown to brown-green. These samples showed more than 90% reduction in the test bacteria E. coli and S. aureus and provided excellent UV protection. In this case, the PNCS hydrogel acted as a reservoir for Ag NPs, whose release was based on a diffusion-controlled mechanism. Despite the Ag NPs decreasing the responsiveness of the PNCS hydrogel, the moisture management was still preserved in the modified samples. Accordingly, the PNCS hydrogel is a suitable carrier for biosynthesized Ag NPs to tailor the protective smart surface of viscose fibres.

Antibiotic legacies shape the temperature response of soil microbial communities.

Soil microbial communities are vulnerable to anthropogenic disturbances such as climate change and land management decisions, thus altering microbially-mediated ecosystem functions. Increasingly, multiple stressors are considered in investigations of ecological response to disturbances. Typically, these investigations involve concurrent stressors. Less studied is how historical stressors shape the response of microbial communities to contemporary stressors. Here we investigate how historical exposure to antibiotics drives soil microbial response to subsequent temperature change. Specifically, grassland plots were treated with 32-months of manure additions from cows either administered an antibiotic or control manure from cows not treated with an antibiotic. In-situ antibiotic exposure initially increased soil respiration however this effect diminished over time. Following the 32-month field portion, a subsequent incubation experiment showed that historical antibiotic exposure caused an acclimation-like response to increasing temperature (i.e., lower microbial biomass at higher temperatures; lower respiration and mass-specific respiration at intermediate temperatures). This response was likely driven by a differential response in the microbial community of antibiotic exposed soils, or due to indirect interactions between manure and soil microbial communities, or a combination of these factors. Microbial communities exposed to antibiotics tended to be dominated by slower-growing, oligotrophic taxa at higher temperatures. Therefore, historical exposure to one stressor is likely to influence the microbial community to subsequent stressors. To predict the response of soils to future stress, particularly increasing soil temperatures, historical context is necessary.

Core transcriptome network modulates temperature (heat and cold) and osmotic (drought, salinity, and waterlogging) stress responses in oil palm

Oil palm (Elaeis guineensis) yield is impacted by abiotic stresses, leading to significant economic losses. To understand the core abiotic stress transcriptome (CAST) of oil palm, we performed RNA-Seq analyses of oil palm leaves subjected to drought, salinity, waterlogging, heat, and cold stresses. A total of 19,834 differentially expressed genes (DEGs) were identified. Cold treatment induced the highest number of DEGs (5,300), followed by heat (4,114), drought (3,751), waterlogging (3,573), and, lastly, salinity (3096) stress. Subsequent analysis revealed the CAST of oil palm, comprising 588 DEGs commonly expressed under drought, salinity, waterlogging, heat, and cold stress conditions. Function annotation of these DEGs suggests their roles in signal transduction, transcription regulation, and abiotic stress responses including synthesis of osmolytes, secondary metabolites, and molecular chaperones. Moreover, we identified core DEGs encoding kinases, ERF, NAC TFs, heat shock proteins, E3 ubiquitin-protein ligase, terpineol synthase, and cytochrome P450. These core DEGs may be potential key modulators that interplay in triggering rapid abiotic stress responses to achieve delicate equilibrium between productivity and adaptation to abiotic stresses. This comprehensive study provides insights into the key modulators in the CAST of oil palm, and their potential applications as markers for selecting climate-resilient oil palms or opportunities to develop future climate resilient oil palm using genome editing.

Novel approach for modelling low enthalpy geothermal in deep sedimentary aquifers: a case study of 40 years of production data in the Dogger formation

Geothermal energy in the Paris urban area has been exploited since the early 1970s. Deep drilling in the Paris sedimentary basin has targeted hot brine in the Dogger formations from a mid-Jurassic carbonate rocks series. More than a hundred wells have been drilled to depths ranging from 1400 to 2000 m and decades of production and reinjection have resulted in variations in the aquifer pressure and temperature in some areas. The regional numerical model discussed herein is aimed at assessing the potential interactions between doublets and for assessing the impact of the addition of more wells in the future. While the integration of a 3D refined geological model into a large-scale reservoir model needs heavy computational resources, local models simplifying the main productive areas into one or two layers surrounded by impermeable units can be used to approximately assess the reservoir characteristics. The modelling of a semi-regional area of the Dogger reservoir in the Southern part of Paris (Cachan/Orly) has been performed, using a conventional double-layer approach to simulate the natural state and production history of the area using the simulator Waiwera, a fast parallel open-source geothermal simulator from the University of Auckland in New-Zealand. Calibration of a natural state model, which describes the conditions before any geothermal operations, has been performed, including an analysis of the impact of boundary condition values on the ability of the model to match the data available in the public domain. The temperature and pressure distributions, instead of being based on geostatistical mapping methods have been obtained from a calibrated natural state model. The implementation of a regional lateral cross flow observed from past studies proved to be essential for matching the measured temperatures and pressures along with variations in the deep heat flux. A calibrated model has been obtained from matching the available production data with mismatches of no more than 1.5 °C. The modelling results confirm the dominance of the shallower productive zone in the aquifers and give insights into the extent of the cooler areas created by the long-term operations. Thus we have used the Dogger reservoir, with multiple data sets available, as a case study for calibrating a semi regional numerical model of a deep sedimentary aquifer used for geothermal direct-use. Our modelling study accounts for the conceptual understanding of the sedimentary aquifer with its heterogeneities and calibrates the numerical model against the measured historical data. Based on the calibrated reservoir model, the pressure and temperature responses in deep productive areas can be determined enabling operators or decision makers to test future strategies for sustainably operating the geothermal resource.

7 days of L-citrulline supplementation does not improve running performance in the heat whilst in a hypohydrated state.

7days L-citrulline supplementation has been reported to improve blood pressure, O2 kinetics, gastrointestinal (GI) perfusion and endurance cycling performance through increasing arterial blood flow. In situations where blood volume is compromised (e.g., hyperthermia/hypohydration), L-citrulline may improve thermoregulation and exercise performance by redistributing blood flow to aid heat loss and/or muscle function. This study assessed 7days L-citrulline supplementation on running performance in the heat, whilst mildly hypohydrated. 13 endurance runners (2 female, 31 ± 8y, O2peak 60 ± 6mL/kg/min) participated in a randomised crossover study with 7days L-citrulline (CIT; 6g/d) or placebo (maltodextrin powder; PLA) supplementation. Participants completed a 50min running 'preload' at 65% O2peak (32°C, 50% relative humidity) to induce hyperthermia and hypohydration before a 3km running time trial (TT). Body mass and blood samples were collected at baseline, pre-preload, post-preload and post-TT, whilst core and skin temperature, heart rate and perceptual responses were collected periodically throughout. TT performance was not different between trials (CIT 865 ± 142s; PLA 892 ± 154s; P = 0.437). Core and skin temperature and heart rate (P ≥ 0.270), hydration (sweat rate, plasma volume, osmolality) indices (P ≥ 0.216), GI damage (P ≥ 0.260) and perceptual responses (P ≥ 0.610) were not different between trials during the preload and TT. 7days of L-citrulline supplementation had no effect on 3km running performance in the heat or any effects on thermoregulation or GI damage in trained runners in a hypohydrated state.