Short-term Heat Research Articles

Application of a coupled model of photosynthesis, stomatal conductance and transpiration for rice leaves and canopy

Physiological assumptions incorporated in crop models need improvement to more realistically represent responses to heat stress, rising CO2, and genetic diversity. Coupling of leaf-level photosynthesis and stomatal conductance sub-models within an energy balance has been proposed to improve gas exchange predictions underlying many of these responses. The purpose of this study was to calibrate model subcomponents, assess individual- and coupled- sub-model performance, integrate this methodology with the ORYZA rice model, and evaluate the ability of the original and modified model to accurately simulate responses at canopy level using soil–plant-atmosphere research (SPAR) chamber data, with respect to plant age, CO2 concentration, and short-term high heat exposure. Individual and coupled sub-models were more accurate for leaf rice photosynthesis (average R2 of 0.81) than stomatal conductance or transpiration (average R2 of 0.46 and 0.77 respectively) when averaged across all treatments and measurement dates. Photosynthetic parameter Vcmac25 linearly decreased over the growing season, while Jmax25 and Tp were relatively constant over time and between CO2 levels, until about 50% heading when declines between 25% and 45% were observed through the beginning of grain filling. Diurnal and daily canopy net photosynthesis estimates were closer to observed values (ambient CO2. R2 = 0.71, elevated CO2. R2 = 0.70, P < 0.001) using this coupled approach compared with the original ORYZA model (ambient CO2. R2 = 0.263, elevated CO2. R2 = 0.420, P < 0.01). Canopy transpiration results were similar between the two approaches at 28 °C, but the energy balance method showed more realistic responses to elevated CO2 and warming temperature. These results indicated the use of a coupled energy balance model can more accurately predict rice gas exchange processes compared to uncoupled photosynthesis/transpiration methods when simulating responses to different CO2 and temperature conditions, and thus may provide more realistic assessments of current and future climate impacts on rice production.

A 5-day Heat Acclimation Program Improves Heat Stress Indicators While Maintaining Exercise Capacity.

Wardenaar, FC, Ortega-Santos, CP, Vento, K, Beaumont, JS, Griffin, SC, Johnston, C, and Kavouras, SA. A 5-day heat acclimation program improves heat stress indicators while maintaining exercise capacity. J Strength Cond Res 35(5): 1279-1286, 2021-This study aimed to evaluate whether a daily 60 minutes isothermic biking protocol during a 5-day period could improve physiological heat acclimation and exercise performance capacity in partially acclimated subjects. A quasi-experimental study consisted of an intervention (INT, n = 7) and control (CON, n = 7) group completing 2 12 minutes Cooper tests (pre-CT on day 1 and post-CT on day 7) and a heat stress test (HST, on day 9). INT performed additional intensive exercise 1 hour per day on days 1-5, whereas CON did not. During CTs and HST, core temperature (Tc, telemetric capsule), skin temperature (Tsk, sensors at neck, right shoulder, left hand, and right shin), and heart rate (HR, chest strap) were continuously monitored and baseline, average, peak, and increment were calculated. During the HST, the INT group showed a smaller baseline-peak Tc increment (INT 0.88 ± 0.27 vs. CON 1.64 ± 0.90° C, p = 0.02), a lower HR peak (150.2 ± 12.6 vs. 173.0 ± 16.8 b·min-1, p = 0.02), and lower Tsk peak (36.47 ± 0.62 vs. 36.54 ± 0.46° C, p = 0.04). There was a nonsignificant, but practical difference based on a moderate effect size for change in pre-CT to post-CT performance of nearly +2.7 ± 12.3% in INT and -3.0 ± 8.5% in CON (p = 0.32 and d = 0.51), and HST distance covered resulting in a nonsignificant difference of 464 ± 849 m between INT and CON (p = 0.38 and d = 0.44). In conclusion a short-term 5-day heat acclimation program including 300 minutes of extra exercise resulted in positive physiological adaptions to heat stress, as indicated by lower core temperature and HR in comparison with a control group.

Leaf vein pattern response to heat and drought requires genes that influence PINFORMED1 localization and is mimicked by ABA treatment

The plasticity of plant development allows acclimation to environmental stresses such as heat and drought. For example, increased vein density with more vein meetings is proposed to provide more efficient and robust water delivery when water availability is reduced. We demonstrate that Arabidopsis leaves respond to short term heat or drought by increasing leaf vein density, which in heat includes a higher density of vein meetings. We find that a set of genes, UNHINGED, FORKED1, FORKED-LIKE1, 2 and 3, which influence PINFORMED1 localization and control vein meeting in developing leaves, is required for the vein pattern response to heat or drought. Comparison of δ13C (‰) and nitrogen (%) under different conditions suggests that while wild type and mutant genotypes enriched δ13C (‰) under drought conditions, only wild type increased total shoot nitrogen suggesting increased photosynthetic assimilation. One explanation is that the mutants’ open vein pattern fails to supply sufficient water to support increased photosynthesis. Finally, treatment with ABA caused changes to leaf vein pattern similar to heat or drought treatment, a response that was eliminated in the abscisic acid insensitive1 but not the forked1 genotype. This suggests that the vein pattern response to reduced water availability may in part be controlled by ABA.

Scrotal thermoregulation and sequential sperm abnormalities in buffalo bulls (Bubalus bubalis) under short-term heat stress.

Heat stress reduces the reproductive capacity of bulls raised in tropical climate. However, the reestablishment of scrotal thermoregulation and the dynamics of sperm defects emergence after stress are not completely known in buffaloes. Thus, the study aimed to evaluate the effect of short-term heat stress over scrotal thermoregulation and sperm attributes, relating them to spermatogenesis stages. Five buffalo bulls went through scrotal insulation during 48h (from day 0 to day 2). Semen samples were collected every 7 days (from day -7 to day 49) and analyzed about the progressive motility, viability, and sperm morphology. Heat stress significantly destabilized scrotal thermoregulation (P<0.001). Scrotal temperature was from 4.2 to 6.3°C lower than the core body temperature, except on insulation days (P<0.001), and returned to the basal condition five days after the removal of the stressing stimulus. More significant deleterious effects were observed in sperm morphology than in cell concentration, motility, and viability. The chronology of morphologic defects expression demonstrated tail defects (days 7-14), cytoplasmic droplets (days 14-28), and head defects (day 28), returning to pre-insulation condition 35 days after the thermal challenge. Thus, hyperthermia harmed more intensely spermatozoa in epididymal transit, elongated spermatids, and secondary spermatocytes. It is concluded that water buffalo bulls present a peculiar manifestation of sperm morphology after short-term stress, indicating an important difference related to the bovine species. Therefore, during the andrological evaluation of buffalo bulls, it is necessary to avoid the allometric extrapolation between these species.

Thermal characteristics of a long-term heat storage unit with sodium acetate trihydrate

Energy storage is a key technology to provide stable renewable energy supply to buildings. Latent heat energy storage system is a promising technique for domestic thermal energy storage systems due to its high thermal energy storage density and the ability to store heat for both short and long periods. The common domestic heat storage accumulators are designed for short-term storage, where heat can’t be stored for a long time. In this experiment investigation, a latent heat storage with 75 L water and 137.8 kg phase change material is tested. Sodium acetate trihydrate based composite with stable supercooling ability is used as the phase change material. The sensible heat of the storage is used for short-term heat storage, the latent heat is for long-term heat storage. The combination of short-term heat storage and long-term heat storage is attractive for heating systems with variable heat supply. In this experiment, thermal power and heat exchange capacity rates of the heat storage were analyzed. The stable supercooling success rate and hence the long-term heat storage was also investigated. The results showed that, under the test conditions, 21.7 kWh heat was stored in the tank during charging, 14.0 kWh heat was released during discharging of the sensible heat (short-term heat storage) and 7.6 kWh heat was discharged during discharging of the latent heat (long-term heat storage). The sodium acetate trihydrate remained stable supercooled in 66% of the test cycles. The storage had a relatively high heat exchange capacity rate of at least 340 W/K during charging.

RNA-Seq Highlights Molecular Events Associated With Impaired Pollen-Pistil Interactions Following Short-Term Heat Stress in Brassica napus.

The global climate change is leading to increased frequency of heatwaves with crops getting exposed to extreme temperature events. Such temperature spikes during the reproductive stage of plant development can harm crop fertility and productivity. Here we report the response of short-term heat stress events on the pollen and pistil tissues in a commercially grown cultivar of Brassica napus. Our data reveals that short-term temperature spikes not only affect pollen fitness but also impair the ability of the pistil to support pollen germination and pollen tube growth and that the heat stress sensitivity of pistil can have severe consequences for seed set and yield. Comparative transcriptome profiling of non-stressed and heat-stressed (40°C for 30 min) pollen and pistil (stigma + style) highlighted the underlying cellular mechanisms involved in heat stress response in these reproductive tissues. In pollen, cell wall organization and cellular transport-related genes possibly regulate pollen fitness under heat stress while the heat stress-induced repression of transcription factor encoding transcripts is a feature of the pistil response. Overall, high temperature altered the expression of genes involved in protein processing, regulation of transcription, pollen-pistil interactions, and misregulation of cellular organization, transport, and metabolism. Our results show that short episodes of high-temperature exposure in B. napus modulate key regulatory pathways disrupted reproductive processes, ultimately translating to yield loss. Further investigations on the genes and networks identified in the present study pave a way toward genetic improvement of the thermotolerance and reproductive performance of B. napus varieties.

Изменение структуры жаростойкого алюминидо-никелевого покрытия под воздействием теплового лазерного импульса

The regularities of changes in the structure and phase composition of the thermal protective aluminide-nickel coating (Ni — 45 %; Al — 14 %; Co — 22 %; Cr — 18.9 %; Fe — 0.15 %; Nb — 0.14 %; Y — 0.09 %; Ca — 0.06 %; Mn — 0.01 %; C — 0.15 %; Si — 0.15 %; S — 0.006 %) after exposure to short-term pulsed heat fluxes of various power, created by the radiation of a pulse-periodic laser LRS-150A with a radiation wavelength λ = 1.06 µm and a pulse duration τ = 12·10–3 s. The radiation energy was E = 5, 10, and 15 J. Microstructural analysis and the elemental composition of the resulting coating were carried out as well as analysis of the phase composition. X-ray microanalysis of the coating was also carried out. In the initial state and after irradiation of the coating with a heat flux of power P = 7·103 W/cm2, light microregions are observed in the micrographs of the surface. These regions do not have clearly defined external boundaries and consist of the NiAl phase and a small amount of the Ni3Al phase with the presence of inclusions of particles containing a solid solution of Ni – Co – Cr. After irradiation of the coating with heat fluxes of higher power (P = 1.7·104 W/cm2 and P = 2.2·104 W/cm2), large convex formations appeared on its surface, consisting mainly of Ni3Al and NiAl phases. On micrographs of the surface, they appear as white areas with well-defined outer boundaries. The content of the Ni3Al phase in them in comparison with the initial state increased, and the content of the NiAl phase decreased, while the particles of inclusions of Ni, Co, and Cr disappeared. It can be assumed that an increase in the Ni3Al content is associated with the dissolution of particles of a solid solution of Ni – Co and Cr in the melt and the subsequent diffusion of nickel into the NiAl phase. When exposed to a heat flux of power P = 2.2·104 W/cm2, microcracks appear on the areas of the coating surface covered with aluminum oxide.

Influence of a local short-term heat treatment on the formability of orbital formed functional components

Conventional processes like shearing dispose a lack in efficiency and formability to manufacture functional components with a high geometric variety. A possibility to allow the efficient and sustainable manufacturing is the application of innovative forming operations like orbital forming. Thus, a strain-hardened component with a load-adapted thickness profile can be manufactured in a single-stage process. Thereby, the control of the material flow could be identified as major challenge due to the three-dimensional stress and strain state. In order to reduce the parts weight and simultaneously guarantee the same level of performance, conventional steel is substituted by lightweight materials such as precipitation hardenable aluminum alloys. However, new challenges arise due to the reduced formability of aluminum compared to conventional steel. In recent research, the potential of a short-term heat treatment to enlarge the formability could be shown. The presented process locally reduces the materials strength, thus allowing a control of the material flow by the interaction between softened areas and areas, which offer the initial conditions. In this contribution, the influence on the formability of orbital formed components manufactured out of the precipitation hardenable aluminum alloy EN AW 6016 by a local short-term heat treatment is investigated. Different geometry-based heat treatment layouts are applied in order to maximize the thickening on different radial positions. The potential to enhance the formability is evaluated by comparing geometrical and mechanical properties of the components manufactured in the conventional process route and with a previous heat treatment. The analysis of radial cross-sections and the hardness distribution reveals the positive influence of the heat treatment but also points out the geometrical dependency of the effect due to the characteristic material flow in orbital forming.

Early life thermal stress modulates hepatic expression of thermotolerance related genes and physiological responses in two rabbit breeds

There are few data about early thermal conditioning (TC) and its effect on later life in rabbits. Therefore, the present study aimed to investigate the impact of exposing two rabbit breeds to early age short-term heat stress (EA-STHS) on physiological parameters and hepatic expression levels of some genes. Rabbits from New Zealand White (NZW) and Baladi Black (BB) rabbit breeds were reared in a controlled environmental chamber (28 ± 2 °C and 40 ± 2% RH). At 42 days of age, rabbits from both breeds were equally divided into two groups; control (untreated) and heat exposed groups (kept at 36 ± 1 °C and 62% RH for 6 h). At 13 weeks of age, rabbits of all groups were re-exposed to acute heat stress (36 ± 1 °C and 62% RH for 6 h). At 13 weeks of age, plasma CORT, plasma MDA, and hepatic MDA had significantly lower levels in the rabbits from the two breeds subjected to EA-STHS than untreated control groups. plasma TAC and the relative hepatic expression of all the studied genes like Hsp70, HspA9, Hsp90α and UCP2 had significantly higher levels in EA-STHS treated NZW and BB rabbits compared with the control groups. In conclusion, the results suggest that EA-STHS has a long-lasting effect on the later life response to acute heat stress in NZW and BB breeds, as indicated by the hepatic expression profile of several genes, corticosterone, and antioxidant parameters. Additionally, each breed had characteristic patterns for the tested parameters at each time point and treatment. HIGHLIGHTS Rabbits are susceptible to thermal stress, which is associated with adverse effects on production and reproduction traits. Early-age thermal conditioning is one of the suggested protective treatments to reduce the heat stress adverse effects. Early age short-term thermal stress may induce thermotolerance ability to later time heat exposure in both rabbit breeds.

Expression of Heat Shock Proteins in Response to Mild Short-term Heat Shock in Human Deciduous Dental Pulp Fibroblast-like Cells

Expression of Heat Shock Proteins in Response to Mild Short-term Heat Shock in Human Deciduous Dental Pulp Fibroblast-like Cells

Machine-learning-based multi-step heat demand forecasting in a district heating system

Short-term heat demand forecasting in district heating (DH) systems is essential for a sufficient heat supply and optimal operation of the DH. In this study, a machine learning based multi-step short-term heat demand forecasting approach using the data of the largest Slovenian DH system is considered. The proposed approach involved feature extraction and comparative analysis of different representative machine learning based forecasting models. Nonlinear models performed better than linear models, and the best forecasting results were obtained by Gaussian process regression (GPR), where the mean absolute normalized error was 2.94% of the maximum heating power of the DH system. The analysis confirmed the importance of accurate temperature forecasts but did not confirm the relevance of using future solar irradiation forecasts. The optimal length of training data is shown to be 3 years, and past data of up to 4 days can be used as input to increase the forecasting accuracy. The forecasting model (GPR) proposed in this study can be fitted to different DH systems. In the presented case study, it was selected to implement the online forecasting solution for the DH of Ljubljana and has been generating forecasts with a mean absolute normalized error of 2.70% since November 2019.

Effects of short-term heat acclimation on whole-body heat exchange and local nitric oxide synthase- and cyclooxygenase-dependent heat loss responses in exercising older men.

What is the central question of this study? Does short-term heat acclimation enhance whole-body evaporative heat loss and augment nitric oxide synthase (NOS)-dependent cutaneous vasodilatation and NOS- and cyclooxygenase (COX)-dependent sweating, in exercising older men? What is the main finding and its importance? Our preliminary data (n=8) demonstrated that short-term heat acclimation improved whole-body evaporative heat loss, but it did not influence the effects of NOS and/or COX inhibition on cutaneous vasodilatation or sweating in older men during an exercise-heat stress. These outcomes might imply that although short-term heat acclimation enhances heat dissipation in older men, it does not modulate NOS- and COX-dependent control of cutaneous vasodilatation or sweating on the forearm. Ageing is associated with decrements in whole-body heat loss (evaporative+dry heat exchange), which might stem from alterations in nitric oxide synthase (NOS)- and cyclooxygenase (COX)-dependent cutaneous vasodilatation and sweating. We evaluated whether short-term heat acclimation would (i) enhance whole-body heat loss primarily by increasing evaporative heat loss, and (ii) augment NOS-dependent cutaneous vasodilatation and NOS- and COX-dependent sweating, in exercising older men. Eight older men [mean (SD) age, 59(8)years] completed a calorimetry and microdialysis trial before and after 7days of exercise-heat acclimation. For the calorimetry trials, whole-body evaporative and dry heat exchange were assessed using direct calorimetry during 30min bouts of cycling at light, moderate and vigorous metabolic heat productions (150, 200 and 250W/m2 , respectively) in dry heat (40°C, 20% relative humidity). For the microdialysis trials, local cutaneous vascular conductance and sweat rate were assessed during 60min exercise in the heat (35°C, 20% relative humidity) at four dorsal forearm skin sites treated with lactated Ringer solution (control), NOS inhibitor, COX inhibitor or combined NOS and COX inhibitors, via microdialysis. Evaporative heat loss during moderate (P=0.036) and vigorous (P=0.021) exercise increased after acclimation. Inhibition of NOS alone reduced cutaneous vascular conductance to a similar extent before and after acclimation (P<0.040), whereas separate and combined NOS and COX inhibition had no significant effects on sweating relative to the control site (P=0.745). Our preliminary results might suggest that short-term heat acclimation improves evaporative heat loss, but does not significantly modulate the contributions of NOS or COX to cutaneous vasodilatation or sweating on the forearm in older men during an exercise-heat stress.

An ER–Golgi Tethering Factor SLOH4/MIP3 Is Involved in Long-Term Heat Tolerance of Arabidopsis

Plants are often exposed not only to short-term (S-) heat stress but also to diurnal long-term (L-) heat stress over several consecutive days. To reveal the mechanisms underlying L-heat stress tolerance, we here used a forward genetic screen for sensitive to long-term heat (sloh) mutants and isolated sloh4. The mutant was hypersensitive to L-heat stress but not to S-heat stress. The causal gene of sloh4 was identical to MIP3 encoding a member of the MAIGO2 (MAG2) tethering complex, which is composed of the MAG2, MIP1, MIP2 and MIP3 subunits and is localized at the endoplasmic reticulum (ER) membrane. Although sloh4/mip3 was hypersensitive to L-heat stress, the sensitivity of the mag2-3 and mip1-1 mutants was similar to that of the wild type (WT). Under L-heat stress, the ER stress and the following unfolded protein response (UPR) were more pronounced in sloh4 than in the WT. Transcript levels of bZIP60-regulated UPR genes were strongly increased in sloh4 under L-heat stress. Two processes known to be mediated by INOSITOL REQUIRING ENZYME1 (IRE1) - accumulation of the spliced bZIP60 transcript and a decrease in the transcript levels of PR4 and PRX34, encoding secretory proteins - were observed in sloh4 in response to L-heat stress. These findings suggest that misfolded proteins generated in sloh4 under L-heat stress may be recognized by IRE1 but not by bZIP28, resulting in the initiation of the UPR via activated bZIP60. Therefore, it would be possible that only MIP3 in the MAG2 complex has an additional function in L-heat tolerance, which is not related to the ER-Golgi vesicle tethering.

Coral Disease Time Series Highlight Size-Dependent Risk and Other Drivers of White Syndrome in a Multi-Species Model

Coral diseases contribute to the decline of reef communities, but factors that lead to disease are difficult to detect. In the present study, we develop a multi-species model of colony-scale risk for the class of coral diseases referred to as White Syndromes, investigating the role of current or past conditions, including both environmental stressors and biological drivers at the colony and community scales. Investigating 7 years of coral survey data at five sites in Guam we identify multiple environmental and ecological associations with White Syndrome, including a negative relationship between short-term heat stress and White Syndrome occurrence, and strong evidence of increasing size-dependent White Syndrome risk across coral species. Our findings result in a generalized model used to predict colony-scale White Syndrome risk for multiple species, highlighting the value of long-term monitoring efforts to detect drivers of coral disease.

High temperature sensitivity of kernel formation in different short periods around silking in maize

Anthesis stage has been proved a typically sensitive period to heat stress in maize (Zea mays L.), but effects of short–term heat stress around anthesis (tasseling–silking period) are not known. A temperature–controlled experiment was conducted using one heat–sensitive maize hybrid and two temperature levels, 40/30 °C (heat stress) and 32/22 °C (control) in eight different short–term episodes around silking (silking represented “0”) which were from 15 d before silking (BS) to 15 d after silking (AS) with 5–d (15–10, 10–5, 5–0 d BS and 0–5, 5–10, 10–15 d AS) and 15–d (15–0 d BS and 0–15 d AS) intervals. The yield losses under 15–d heat stress (average of –25.9 %) around silking were higher than 5–d (average of –16.1 %), and the post–silking time (average of –22.1 %) was more sensitive than pre–silking (average of –15.1 %). Wherein, the first 5 d post–silking short–term heat stress resulted in the largest yield loss (–28.1 %) as a function of kernel number reduction among the treatments with 5–d period heat stress, and yield reduced by 30.4 % in 15 d post–silking heat stress. Kernel number was more closely correlated with pollen shedding number (r = 0.58) than with pollen viability (r = 0.18) in heat stress. The decreased pollen shedding number was a result of suppressed anther dehiscence rather than pollen grain production. The damaged pollen morphology during development reduced pollen viability. Maize leaves maintained a stable photosynthesis at heat stress could be related to the increased stomatal conductance and transpiration, showing a higher heat stress tolerance. Thus, pollen shedding, pollination, pollen tube growth, and early kernel formation in the period shortly after silking are more sensitive to heat stress in maize. A proper crop management (i.e., slightly adjusting sowing date) that can avoid overlapping 5 d post–silking growth with heat stress is recommended. When selecting of or breeding for heat tolerant maize hybrids, the short growth phase from silking to kernel formation should be closely concerned.

Physiological, Transcriptomic, and Metabolic Responses of Ginkgo biloba L. to Drought, Salt, and Heat Stresses.

Ginkgo biloba L. is highly adaptable and resistant to a range of abiotic stressors, allowing its growth in various environments. However, it is unclear how G. biloba responds to common environmental stresses. We explored the physiological, transcriptomic, and metabolic responses of G. biloba to short-term drought, salt, and heat stresses. Proline, H2O2, and ABA contents, along with CAT activity, increased under all three types of stress. SOD activity increased under salt and heat stresses, while soluble protein and IAA contents decreased under drought and salt stresses. With respect to metabolites, D-glyceric acid increased in response to drought and salt stresses, whereas isomaltose 1, oxalamide, and threonine 2 increased under drought. Piceatannol 2,4-hydroxybutyrate and 1,3-diaminopropane increased under salt stress, whereas 4-aminobutyric acid 1 and galactonic acid increased in response to heat stress. Genes regulating nitrogen assimilation were upregulated only under drought, while the GRAS gene was upregulated under all three types of stressors. ARF genes were downregulated under heat stress, whereas genes encoding HSF and SPL were upregulated. Additionally, we predicted that miR156, miR160, miR172, and their target genes participate in stress responses. Our study provides valuable data for studying the multilevel response to drought, salinity, and heat in G. biloba.

Improved mitochondrial function in salmon (Salmo salar) following high temperature acclimation suggests that there are cracks in the proverbial \u2018ceiling\u2019

Mitochondrial function can provide key insights into how fish will respond to climate change, due to its important role in heart performance, energy metabolism and oxidative stress. However, whether warm acclimation can maintain or improve the energetic status of the fish heart when exposed to short-term heat stress is not well understood. We acclimated Atlantic salmon, a highly aerobic eurythermal species, to 12 and 20 °C, then measured cardiac mitochondrial functionality and integrity at 20 °C and at 24, 26 and 28 °C (this species’ critical thermal maximum ± 2 °C). Acclimation to 20 °C vs. 12 °C enhanced many aspects of mitochondrial respiratory capacity and efficiency up to 24 °C, and preserved outer mitochondrial membrane integrity up to 26 °C. Further, reactive oxygen species (ROS) production was dramatically decreased at all temperatures. These data suggest that salmon acclimated to ‘normal’ maximum summer temperatures are capable of surviving all but the most extreme ocean heat waves, and that there is no ‘tradeoff’ in heart mitochondrial function when Atlantic salmon are acclimated to high temperatures (i.e., increased oxidative phosphorylation does not result in heightened ROS production). This study suggests that fish species may show quite different acclimatory responses when exposed to prolonged high temperatures, and thus, susceptibility to climate warming.

Comparing responses of dairy cows to short-term and long-term heat stress in climate-controlled chambers

Heat stress (HS) in dairy cows can be classified into short-term heat stress (STHS) and long-term heat stress (LTHS) according to the number of consecutive days in HS. The comparative study of these 2 types of HS is limited in terms of their effects on the production and energy metabolism of cows. In this study, 4 lactating Holstein cows (102.5 ± 12 days in milk, 605 ± 22 kg of body weight, second parity) fitted with rumen fistulae were randomly assigned to 1 of 2 groups in a 2 × 2 crossover design and allocated to 1 of 2 climate-controlled chambers. This study contained 2 periods, each with a control phase and a HS phase. There was a recovery phase between 2 periods. The HS phase comprised either STHS (3 d) or LTHS (7 d) treatments. Data collected from the 3 d of STHS and the last 3 d of LTHS were compared. The chambers were set at thermal neutral conditions (20°C, 50% humidity) during the control and recovery phases or cyclical HS conditions (26-38°C, 50% humidity) during the HS phase. Compared with STHS, LTHS decreased milk yield by 17.2% and dry matter intake by 12.6%, indicating that LTHS caused a more severe decline in milk production and feed intake. In addition, LTHS decreased milk protein concentration by 6.8% and milk protein yield by 22.4%. In comparison with STHS, LTHS decreased rumen liquor volatile fatty acid (29.7%), blood glucose (11.6%), and nonesterified fatty acid (13.6%) concentrations, but increased milk urea nitrogen by 15.1%, blood urea nitrogen by 8.6%, and creatine concentrations by 15.4%. Our results suggest that although reduced feed intake may be mainly responsible for reduced milk production during STHS, impaired rumen metabolism and suppressed mobilization of adipose tissue could be the main reasons for further reduction in milk yield during LTHS.

Quantification and Impact of Cold Storage and Heat Exposure on Mass Rearing Program of Bactrocera dorsalis (Diptera:Tephritidae) Genetic Sexing Strain.

Simple SummaryStoring insects at low temperature has been an effective approach for mass rearing programs, which can increase the shelf-life of bioagents and flexibly manipulate their pre-release periods. However, introducing insects to temperatures outside of their accustomed range can lead to stress and thereby influence their quality and competitiveness in the field. Bactrocera dorsalis is an economically important pest can devastate many fruits and vegetables, and cold storage has been used in storing, packing and shipping of sterile B. dorsalis males to control the wild population, but the impact of cold storage on the quality of B. dorsalis has never been investigated. Here, we examined the impacts of pupal cold storage on developmental parameters and quality of B. dorsalis adults. Overall, we found that pupal cold storage has a negative effect on some biological parameters of B. dorsalis, especially in fecundity. Thus, heat exposure was further conducted on the post-storage adults, and our results show that short-term heat exposure could partially compensate for the loss in fecundity in B. dorsalis adults resulting from the pupal cold storage. Our findings indicate that the flexibility of the B. dorsalis mass rearing program could be improved by utilizing cold storage and heat exposure.Cold storage and heat exposure are crucial components of tephritid fruit fly mass-rearing programs, as they influence the development and fitness traits of produced flies. This work investigated the effects of cold storage on the pupal developmental parameters and quality of Bactrocera dorsalis (Hendel) genetic sexing strain (GSS) adults. Furthermore, the impact of short-term thermal exposure on the fecundity of B. dorsalis (GSS) that also underwent pupal cold storage was examined. Our results show that pupal development time, emergence rate, partial emergence rate, flight ability and fecundity were significantly affected by low temperature and pupal age and their interaction. Pupal cold storage did not pose negative impacts on the mating competition and response to methyl eugenol (ME) in the males. In addition, compared with the adults that were subjected to the same pupal storage protocol (five-day-old pupae stored at 13 °C), adult exposure to 41 °C for 1 h showed significant reparative effects on fecundity. In summary, the cold storage procedure of B. dorsalis (GSS) pupae has the potential to improve the flexibility and efficiency of mass-rearing schedules. Furthermore, short-term thermal exposure showed reparative effects on the fecundity costs induced by pupal cold storage in B. dorsalis (GSS).

Current rice models underestimate yield losses from short-term heat stresses.

Crop production will likely face enormous challenges against the occurrences of extreme climatic events projected under future climate change. Heat waves that occur at critical stages of the reproductive phase have detrimental impacts on the grain yield formation of rice (Oryza sativa). Accurate estimates of these impacts are essential to evaluate the effects of climate change on rice. However, the accuracy of these predictions by crop models has not been extensively tested. In this study, we evaluated 14 rice growth models against four year phytotron experiments with four levels of heat treatments imposed at different times after flowering. We found that all models greatly underestimated the negative effects of heat on grain yield, suggesting that yield projections with these models do not reflect food shocks that may occur under short-term extreme heat stress (SEHS). As a result, crop model ensembles do not help to provide accurate estimates of grain yield under heat stress. We examined the functions of grain-setting rate response to temperature (TRF_GS) used in eight models and showed that adjusting the effective periods of TRF_GS improved the model performance, especially for models simulating accumulative daily temperature effects. For TRF_GS which uses daily maximum temperature averaged for the effective period, the models provided better grain yield estimates by using maximum temperatures averaged only when daily maximum temperatures exceeded the base temperature (Tbase ). An alternative method based on heating-degree days and stage-dependent heat sensitivity parameters further decreased the prediction uncertainty of grain yield under heat stress, where stage-dependent heat sensitivity was more important than heat dose for model improvement under SEHS. These results suggest the limitation of the applicability of existing rice models to variable climatic conditions and the urgent need for an alternative grain-setting function accounting for the stage-dependent heat sensitivity.