Severe Heat Stress Research Articles

Heat-stress induced sesquiterpenes of Chrysanthemum nankingense attract herbivores but repel herbivore feeding

Plants are frequently exposed to heat stress as a result of global warming. Heat stress leads to a series of physiological responses including stress volatile elicitation, but how heat stress-induced volatile cues affect the behavior of herbivores is poorly understood. In this study, the polyphagous herbivore Spodoptera litura (tobacco cutworm, TCW) and Chrysanthemum nankingense were selected as the model to elucidate the interactions between herbivore behavior and heat stress-induced plant physiological changes. Photosynthetic characteristics and volatile emissions were measured in C. nankingense control plants (25 °C for 3 h), in C. nankingense exposed to moderate (35 °C for 3 h), and severe (45 °C for 3 h) heat stresses. Net photosynthetic rate (An) decreased by more than two-fold after exposure to 45 °C due to non-stomatal inhibition of photosynthesis. 45 °C treatment induced emissions of the camphor and (E)-β-caryophyllene. Exposure to 35 °C had minor effects on photosynthetic characteristics and did not induce terpene emissions. Using dual-choice olfactometer bioassays, we found that 45 °C treatment enhanced the attractiveness of the plants to TCW. Moreover, the leaf concentrations of nine sesquiterpenes were increased and the feeding of TCW was strongly inhibited after 45 °C treatment compared with control plants. Taken together, our study highlights the impact of heat stress on the behavior of the herbivore mediated by the accumulation and emission of sesquiterpenes and suggests altered pest-host interactions under future warmer climates. Modulation of terpenoid emissions and contents should be considered in developing future ecological pest control strategies in agricultural fields.

Genotype by environment interaction due to heat stress in Brown Swiss cattle

Due to its geographical position and a highly variable orography, Italy is characterized by several climatic areas and thus, by many different dairy cow farming systems. Brown Swiss cattle, in this context, are a very appreciated genetic resource for their adaptability and low metabolic requirement. The significant heterogeneity in farming systems may consist of genotype by environment (G × E) interactions with neglected changes in animals' rank position. The objective of this study was to investigate G × E for heat tolerance in Brown Swiss cattle for several production traits (milk, fat, and protein yield in kilograms; fat, protein, and cheese yield in percentage) and 2 derivate traits (fat-corrected milk and energy-corrected milk). We used the daily maximum temperature-humidity index (THI) range, calculated according to weather stations' data from 2008 to 2018 in Italy, and 202,776 test-day records from 23,396 Brown Swiss cows from 639 herds. Two different methodologies were applied to estimate the effect of the environmental variable (THI) on genetic parameters: (1) the reaction norm model, which uses a continuous random covariate to estimate the animal additive effect, and (2) the multitrait model, which splits each production pattern as a distinct and correlated trait according to the first (a thermal comfort condition), third (a moderate heat stress condition), and fifth (a severe heat stress condition) mean THI value quintile. The results from the reaction norm model showed a descending trend of the additive genetic effect until THI reached the value of 80. Then we recorded an increase with high extreme THI values (THI 90). Permanent environmental variance at increasing THI values revealed an opposite trend: The plot of heritability and the ratio of animal permanent environmental variance to phenotypic variance showed that when the environmental condition worsens, the additive genetic and permanent environmental component for production traits play a growing role. The negative additive genetic correlation between slope and linear random coefficient indicates no linear relationship between the production traits or under heat stress conditions, except for milk yield and protein yield. In tridimensional wireframe plots, the extreme margin decreases until a minimum of ∼0.90 of genetic correlation in the ECM trait, showing that the magnitude of G × E interaction is greater than the other traits. Genetic correlation values in Brown Swiss suggest the possibility of moderate changes in animals' estimated breeding value in heat stress conditions. Results indicated a moderate G × E interaction but significant variability in sire response related to their production level.

Delineating the impacts of air temperature and humidity for endurance exercise.

What is the central question of this study? What are the independent effects of air temperature and humidity on performance, physiological and perceptual responses during endurance exercise? What is the main finding and its importance? When examined independently, elevated air temperature increased heat strain and impaired aerobic exercise performance, but to a lesser extent than has been reported previously. These findings highlight the importance of absolute humidity relative to temperature when exercising or working under severe heat stress. Many studies have reported that ambient heat stress increases physiological and perceptual strain and impairs endurance exercise, but effects of air temperature per se remain almost unexamined. Most studies have used matched relative humidity, thereby exponentially increasing absolute humidity (water content in air) concurrently with temperature. Absolute (not relative) humidity governs evaporative rate and is more important at higher work rates and air temperatures. Therefore, we examined the independent effects of air temperature and humidity on performance, thermal, cardiovascular and perceptual measures during endurance exercise. Utilizing a crossover design, 14 trained participants (7 females) completed 45min fixed-intensity cycling (70% ) followed by a 20-km time trial in each of four environments: three air temperatures at matched absolute humidity (Cool, 18°C; Moderate, 27°C; and Hot, 36°C; at 1.96kPa, air velocity ∼4.5m/s), and one at elevated humidity (Hot Humid, 36°C at 3.92kPa). Warmer air caused warmer skin (0.5°C/°C; P<0.001), higher heart rate (1bpm/°C; P<0.001), sweat rate (0.04l/h/°C; P<0.001) and thermal perceptions during fixed-intensity exercise, but minimally affected core temperature (<0.01°C/°C; P=0.053). Time-trial performance was comparable between Cool and Moderate (95% CI: -1.4, 5.9%; P=0.263), but 3.6-6% slower in Hot (95% CI: ±2.4%; P≤0.006). Elevated humidity increased core temperature (P<0.001), perceived temperature and discomfort but not skin temperature or heart rate, and reduced mean blood pressure (P=0.046) during fixed-intensity exercise. Elevated humidity impaired time-trial performance by 3.4% (95% CI: ±2.2%; P=0.006). In conclusion, these findings quantify the importance of absolute humidity alongside air temperature when exercising under severe heat stress.

Disentangling the effects of microalgal diversity and thermal history on freshwater phototrophic biofilms facing heat stress: A thermal dose approach

Abstract The increase in heatwave intensity and duration is challenging microalgal photosynthesis in shallow waters. In particular, the extent of photosynthesis impairment or limitation due to short extreme heat stress events occurring during a heatwave remains unknown. In this study, we investigated the importance of microalgal diversity and thermal history in response of phototrophic biofilms to severe heat stress. We exposed isolated microalgal strains, synthetic communities previously acclimated at three temperatures, and natural phototrophic biofilms sampled at different seasons to several temperature/duration pairs (from 31 to 44°C for 30, 60, 120 or 180 min). Microalgal photosynthetic activity (FV/FM) was measured after each heat stress and was shown to be a function of thermal dose, defined as the product of time and an exponential function of temperature. It appeared that the thermal history plays an important role in tolerance to heat stress, with synthetic communities acclimated at highest temperature being more tolerant. However, the responsiveness (i.e. the strength of the response) to heat stress was driven by the microalgal diversity of the community. Synthesis. Our analysis showed that although photosynthetic activity was negatively impacted by heat stress, gross primary productivity was even more strongly and rapidly impacted, highlighting the fact that in situ, even moderate heat stress can significantly impair primary productivity in shallow waters.

A behavior and physiology-based decision support tool to predict thermal comfort and stress in non-pregnant, mid-gestation, and late-gestation sows.

Although thermal indices have been proposed for swine, none to our knowledge differentiate by reproductive stage or predict thermal comfort using behavioral and physiological data. The study objective was to develop a behavior and physiology-based decision support tool to predict thermal comfort and stress in multiparous (3.28 ± 0.81) non-pregnant (n = 11), mid-gestation (n = 13), and late-gestation (n = 12) sows. Regression analyses were performed using PROC MIXED in SAS 9.4 to determine the optimal environmental indicator [dry bulb temperature (TDB) and dew point] of heat stress (HS) in non-pregnant, mid-gestation, and late-gestation sows with respiration rate (RR) and body temperature (TB) successively used as the dependent variable in a cubic function. A linear relationship was observed for skin temperature (TS) indicating that TDB rather than the sow HS response impacted TS and so TS was excluded from further analyses. Reproductive stage was significant for all analyses (P < 0.05). Heat stress thresholds for each reproductive stage were calculated using the inflections points of RR for mild HS and TB for moderate and severe HS. Mild HS inflection points differed for non-pregnant, mid-gestation, and late gestation sows and occurred at 25.5, 25.1, and 24.0°C, respectively. Moderate HS inflection points differed for non-pregnant, mid-gestation, and late gestation sows and occurred at 28.1, 27.8, and 25.5°C, respectively. Severe HS inflection points were similar for non-pregnant and mid-gestation sows (32.9°C) but differed for late-gestation sows (30.8°C). These data were integrated with previously collected behavioral thermal preference data to estimate the TDB that non-pregnant, mid-gestation, and late-gestation sows found to be cool (TDB < TDB preference range), comfortable (TDB = TDB preference range), and warm (TDB preference range < TDB < mild HS). The results of thisstudy provide valuable information about thermal comfort and thermal stress thresholds in sows at three reproductive stages. The development of a behavior and physiology-based decision support tool to predict thermal comfort and stress in non-pregnant, mid-gestation, and late-gestation sows is expected to provide swine producers with a more accurate means of managing sow environments.

Thermoregulatory response and oxidative stress indices of rabbit bucks administered ascorbic acid and sodium bicarbonate in a humid tropical environment

Abstract Background This study aimed to assess the effect of ascorbic acid and sodium bicarbonate on thermoregulatory response and oxidative stress markers of rabbit bucks during highest temperature-humidity index in a humid tropical environment as a mitigation strategy against impact of high ambient temperature on the animals. Twenty-eight exotic rabbit bucks of 9 months old weighing 2.54 ± 0.23 kg were randomly allotted to four treatments consisting of T1 (Control-2 ml of sterile water), T2 (2 ml of 300 ppm ascorbic acid), T3 (2 ml of 0.30% sodium bicarbonate) and T4 (2 ml mixture of 150 ppm ascorbic acid + 0.15% sodium bicarbonate, administered orally at 48 h interval for 12 weeks. After a month of administration, rectal temperature, ear temperature, respiratory rate and pulse rate were monitored twice daily (8:00 am and 4:00 pm). Semen samples were collected from all bucks weekly for seminal lipid peroxidation and total antioxidant activity assay. Blood samples were collected from all bucks and serum obtained using standard procedure to assay for lipid peroxidation and total antioxidant activity. Results The result revealed that the rabbits were exposed to very severe heat stress for greater part of the day. At week 5, bucks on T2, T3 and T4 had increased respiratory rate at 8 am than those on T1, similar trend was observed at week 4 and 6. At 4 pm, the pulse rate was significantly (p &lt; 0.05) different among the treatments at weeks 11, bucks on T2, T3 and T4 had significantly lowered (p &lt; 0.05) pulse rate than those on T1. The administration of ascorbic acid, sodium bicarbonate and its combination did not significantly (p &gt; 0.05) influence the ear and rectal temperature of the bucks. At week 11, seminal total antioxidant activity of bucks on T1, T2 and T3 was significantly (p &lt; 0.05) lower than bucks on control T4. Lipid peroxidation level was significantly (p &lt; 0.05) lower in bucks on T2, T3 and T4 than those bucks on the control. Conclusion The administration of ascorbic acid, sodium bicarbonate and its combination had enhanced seminal total antioxidant and reduced lipid peroxidation in heat-stressed bucks.

Mutation of the polyadenylation complex subunit CstF77 reveals that mRNA 3' end formation and HSP101 levels are critical for a robust heat stress response.

Heat shock protein 101 (HSP101) in plants, and bacterial and yeast orthologs, is essential for thermotolerance. To investigate thermotolerance mechanisms involving HSP101, we performed a suppressor screen in Arabidopsis thaliana of a missense HSP101 allele (hot1-4). hot1-4 plants are sensitive to acclimation heat treatments that are otherwise permissive for HSP101 null mutants, indicating that the hot1-4 protein is toxic. We report one suppressor (shot2, suppressor of hot1-4 2) has a missense mutation of a conserved residue in CLEAVAGE STIMULATION FACTOR77 (CstF77), a subunit of the polyadenylation complex critical for mRNA 3' end maturation. We performed ribosomal RNA depletion RNA-Seq and captured transcriptional readthrough with a custom bioinformatics pipeline. Acclimation heat treatment caused transcriptional readthrough in hot1-4 shot2, with more readthrough in heat-induced genes, reducing the levels of toxic hot1-4 protein and suppressing hot1-4 heat sensitivity. Although shot2 mutants develop like the wild type in the absence of stress and survive mild heat stress, reduction of heat-induced genes and decreased HSP accumulation makes shot2 in HSP101 null and wild-type backgrounds sensitive to severe heat stress. Our study reveals the critical function of CstF77 for 3' end formation of mRNA and the dominant role of HSP101 in dictating the outcome of severe heat stress.

The protective effect of aqueous orange peel extract against severe heat stress on reproductive efficiency, milk yield, and antioxidant status of female rabbits

Heat stress in rabbits negatively affects their reproductive ability and milk yield. Aqueous orange peel extract (AOPE) is high in potential natural antioxidants that help avoid free radical damage and is a good source of phytochemicals. Based on these benefits, it was hypothesized that oral administration of AOPE could overcome the negative impacts of severe heat stress on reproductive and lactation performance, physiological parameters, and antioxidant status. To determine the protective effect of AOPE, 36 female rabbits (six-months-old, average body weight of 2.67 ± 0.03 kg) were given 1.50 mL water (control), and 2.50 or 5.00 mL AOPE every two days for four months. Oral AOPE administration significantly reduced the respiration rate (RR) and rectal temperature (RT) during pregnancy and lactation. The reproductive performance (litter size) and productive performance (litter weight and litter weight gain) were significantly increased by AOPE treatment, compared with the control. The highest milk yield was recorded in 5.00 mL AOPE treatment (5.00 mL). AOPE treatments significantly increased serum superoxide dismutase (SOD) and catalase (CAT), and AOPE treatment (5.00 mL) lowered serum thiobarbituric acid reactive substances (TBARs) of heat-stressed rabbits. Serum total antioxidant capacity (TAC) was not affected by AOPE treatment. The addition of AOPE improved reproductive performance, physiological parameters, and antioxidant status, but did not have a beneficial effect on conception rate of female rabbits under severe heat stress.

Physiological responses of several beef cattle breeds based on environmental conditions in Beef Cattle Research Station

Physiological conditions were one factors that can affect the growth of cattle. The study aimed to determine the physiological responses of several beef cattle breeds that are reared in Beef Cattle Research Station (BCRS), Grati District, Pasuruan Regency, East Java Indonesia, was carried out by measure temperature, humidity, Temperature Humidity Index (THI), rectal temperature, respiration frequency, body temperature, Head Tolerance Coefficient (HTC) and heart rate of 159 cows consisting of Bali, Madura, Jabres, Galekan, Rambon, Peranakan Ongole (PO), Belgian Blue x PO cross, PO x Bali cross (POBA) which were observed during 4 months in pens. Data were analysed descriptively. The result of the study were ambient temperature and relative humidity of the pen ranged from 25-34.12°C and 54.88-84.27%, THI ranged from 74.92-84.97, body temperature ranged from 35.06-38.53°C, respiration frequency ranged from 20-54 times/minute, HTC ranged from 1.81-3.34, and heart rate ranged from 65-92 times/minute. It was concluded that several breeds of beef cattle in BCRS have mild to severe heat stress, high heat tolerance, respiration rate and heart rate. This condition does not cause production problem in several beef cattle, but in BB x PO cross it has potential to low productivity.

Near-term regional climate change in East Africa

In the coming few decades, projected increases in global temperature and humidity are generally expected to exacerbate human exposure to climate extremes (e.g., humid-heat and rainfall extremes). Despite the growing risk of humid-heat stress (measured by wet-bulb temperature), it has received less attention in East Africa, where arid and semi-arid climatic conditions prevail. Moreover, no consensus has yet been reached across models regarding future changes in rainfall over this region. Here, we screen Global Climate Models (GCMs) from CMIP5 and CMIP6 and use, for boundary conditions, simulations from only those GCMs that simulate successfully recent climatic trends. Based on these GCMs and Regional Climate Model (RCM) simulations, we project that annual mean temperature is likely to rise by 2 ℃ toward midcentury (2021–2050) ​at a faster rate than the global average (about 1.5 ℃), under the RCP8.5 and SSP5-8.5 scenarios, associated with more frequent and severe climate extremes. In particular, low-lying regions in East Africa will be vulnerable to severe heat stress, with an extreme wet-bulb temperature approaching or exceeding the US National Weather Service’s extreme danger threshold of 31 ℃. On the other hand, population centers in the highlands of Ethiopia will receive significantly more precipitation during the autumn season and will see more extreme rainfall events, with implications for flooding and agriculture. The robustness of these results across all GCM and RCM simulations, and for both of CMIP5 and CMIP6 frameworks (CMIP: Coupled Model Inter-comparison Project) supports the reliability of these future projections. Our simulations of near-term climate change impacts are designed to inform the development of sound adaptation strategies for the region.

Fine-scale heterogeneity reveals disproportionate thermal stress and coral mortality in thermally variable reef habitats during a marine heatwave.

The online version contains supplementary material available at 10.1007/s00338-022-02328-6.

Physiological responses of Holstein calves and heifers carrying the SLICK1 allele to heat stress in California and Florida dairy farms.

Inheritance of the SLICK1 allele of the prolactin receptor gene improves thermotolerance of lactating Holstein cows under humid heat stress conditions. The aim of this study was to investigate whether pre- and postweaning Holstein heifers carrying the SLICK1 allele would show physiological responses indicative of higher tolerance to heat stress in high- and low-humidity climates. A total of 101 heifer calves of two age groups heterozygous for the SLICK1 allele and 103 wild-type half-siblings were evaluated during July 2020 in 3 dairy farms in central California and 2 in south Florida. Dry bulb temperature and relative humidity data were recorded during evaluation and used to calculate the temperature-humidity index (THI). Physiological measurements were obtained between 1600 and 1900 h in California, and 1200 and 1400 h in Florida and included rectal temperature, respiration rate, skin temperature, and sweating rate. Data were analyzed via Generalized Linear Mixed Models including the main effects of genotype, state, group, sire, farm within state, and interactions, with THI included as a covariate. The correlations between THI and dependent variables were analyzed via linear regression. The average 24-h THI was higher in Florida compared with California (90 vs. 72, respectively); the main driver of the higher THI in Florida was the high relative humidity (average 85.6% in Florida vs. 36.7% in California). In Florida, the rectal temperature of slick calves was 0.4°C lower than non-slick calves (39.5 ± 0.1 vs 39.9 ± 0.1°C); no differences were detected between slick and non-slick calves in California. Regardless of genotype, heifer calves in Florida had higher respiration rate, higher rectal and skin temperatures, and lower sweating rate than in California. This study is the first to evaluate physiological responses of calves carrying the SLICK1 allele under heat stress conditions in different climates. Our findings demonstrate that the presence of this allele is associated with lower rectal temperatures in pre- and post-weaning Holstein females. According to the physiological parameters evaluated, calves raised in Florida appeared to be under more severe heat stress; in those conditions, the SLICK1 allele was advantageous to confer thermotolerance as evidenced by lower rectal temperature in slick animals.

Evaluation of thermo-adaptability between Tharparkar (Bos indicus) and crossbred (Bos indicus X Bos taurus) calves in a controlled environment

The global warming driven climate change has increased the susceptibility of livestock around the globe to heat stress (HS), which reduces animal productivity and threatens the sustainability of marginal farmers. The objective of this investigation was to evaluate thermo-adaptability between Tharparkar calves (TC), an indigenous milch breed of India and crossbred calves (CC) during induced heat stress in controlled environment. For this purpose, 12 apparently healthy male calves (six in each group) aged 5–6 months, were selected. The experiment was conducted at physiologically comfortable temperature (25 °C), moderate HS (31 °C) and severe HS (37 °C) for 21 days each in a psychrometric chamber. In each experimental day, the calves were exposed to 6 h of heat. There were 7 days of acclimatization period before experiment and 10 days of recovery period at ambient temperature between each 21 day exposure period. During experimental period, the blood was collected at 1st, 6th, 11th, 16th, 21st day and among ten-day recovery period the blood was collected at 5th day. Physiological responses, serum electrolytes, metabolic enzymes profiles, antioxidant capacity, oxidative stress status and general endocrine milieu were studied. Relative mRNA expression study of Heat Shock Protein (HSP) 70, HSP90, induced Nitric Oxide Synthase (iNOS) and endothelial NOS (eNOS) were carried out by qPCR. There was significant (p < 0.05) change in the displacement in rectal temperature, respiration rate, serum alanine aminotransferase level between two breeds at moderate and severe HS. Similar change was observed in total antioxidant capacity, superoxide dismutase, and endocrinological parameters. The comparatively lower mRNA expression of HSP70 and higher expression of HSP90 in TC than CC point the better thermo-adaptability of the same. The results of the experiment indicated that TC are more thermo-adaptable than CC at different modality of stress in controlled temperature conditions.

Negative effects of heat stress on maize yield were compensated by increasing thermal time and declining cold stress in northeast China.

Northeast China (NEC), an important maize region located at high northern latitudes, is undergoing pronounced climate warming. This warming highlights the importance of taking the effects of brief extreme high and low temperature events into account when addressing the impacts of climate warming on crop yields. The spatiotemporal variability of heat and cold stress and their impact on yield were determined by combining climate data, maize phenological observations and yield records from 1981 to 2018 for 17 counties in the major maize cropping area of NEC. Spatially, more severe heat stress during the vegetative phase occurred in the western border and cold stress occurred in the central regions. Both stresses during the reproductive phase and growing degree days (GDD) showed a northeast-southwest gradient. Temporally, we found overall increased (0.5°C•d/yr) heat stress during the vegetative phase, which was predominantly more than five times that during the reproductive phase. The cold stress during the vegetative phase was alleviated by an average of -1.3°C•d/yr, particularly in the central regions. In contrast, exposure to a cold environment during the reproductive phase was intensified, with an average of 0.3°C•d/yr, though a few downward trends mainly occurred near the borders of three provinces. The increasing trend in GDDr was 3.6°C•d/yr, almost twice as high as that in the vegetative phase. The impact of increased heat stress contributed an average yield loss of 0.10 t/ha/10a, while reduced cold stress during the vegetative phase coupled with increased GDD increased yield by 0.42 t/ha/10a. Although cold stress during the reproductive phase had an insignificant impact on yield, its intensity together with the increase in heat stress, especially in the vegetative phase, should be considered when developing appropriate adaptations to increase maize yield in the face of ongoing warming.

Reproductive performance and milk yield of rabbits fed diets supplemented with garden cress (Lepidium sativum) seed

Recently, phytochemicals in plants have evoked interest as sources of naturally beneficial substances and as alternatives to antimicrobials. Based on these benefits, it was hypothesized that garden cress (GC; Lepidium sativum) supplementation could overcome the negative impacts of severe heat stress on the reproductive and lactation performance, physiological parameters, and antioxidant status of rabbits. Twenty-four mature V-line does (6 months old) with an average body weight of 3.65 ± 0.54 kg were randomly assigned into four homogenously equal groups (n = 6) according to the level of supplemented GC seeds. Rabbits in the control group were fed a basal diet without GC seeds (GC 0), the other three treatment groups (GC 3, GC 4.5, and GC 6) were fed a basal diet supplemented with GC seeds at levels 3, 4.5 and 6%, respectively. Investigations revealed that the inclusion of 3% GC enhanced the litter weight of heat-stressed rabbits on the 7th, 14th, and 21st days. Furthermore, treatment with 3% and 6% GC seeds increased the milk yield on the 28th day. the most of lipid profile parameters, such as cholesterol, triglyceride, high-density lipoprotein (HDL), low-density lipoprotein (LDL), serum urea levels, and antioxidant status improved in rabbits supplemented with 6% GC. In conclusion, the dietary supplemention of GC seed at 6% increased milk yield at 28th day “weaning age”, consequently, improved the blood lipid profile and antioxidant status. Further studies should be conducted to commercialize theusage of garden cress seeds as a supplement in rabbits.

Identification of Glu-D1 Alleles and Novel Marker-Trait Associations for Flour Quality and Grain Yield Traits under Heat-Stress Environments in Wheat Lines Derived from Diverse Accessions of Aegilops tauschii.

Heat stress during grain filling is considered one of the major abiotic factors influencing wheat grain yield and quality in arid and semi-arid regions. We studied the effect of heat stress on flour quality and grain yield at moderate and continuous heat stress under natural field conditions using 147 lines of wheat multiple synthetic derivatives (MSD) containing Aegilops tauschii introgressions. The study aimed to identify the marker–trait associations (MTAs) for the quality traits and grain yield under heat-stress conditions and identify stress-resilient germplasm-combining traits for good flour quality and grain yield. The MSD lines showed considerable genetic variation for quality traits and grain yield under heat-stress conditions; some lines performed better than the recurrent parent, Norin 61. We identified two MSD lines that consistently maintained relative performance (RP) values above 100% for grain yield and dough strength. We found the presence of three high-molecular-weight glutenin subunits (HMW-GSs) at the Glu-D1 locus derived from Ae. tauschii, which were associated with stable dough strength across the four environments used in this study. These HMW-GSs could be potentially useful in applications for future improvements of end-use quality traits targeting wheat under severe heat stress. A total of 19,155 high-quality SNP markers were used for the genome-wide association analysis and 251 MTAs were identified, most of them on the D genome, confirming the power of the MSD panel as a platform for mining and exploring the genes of Ae. tauschii. We identified the MTAs for dough strength under heat stress, which simultaneously control grain yield and relative performance for dough strength under heat-stress/optimum conditions. This study proved that Ae. tauschii is an inexhaustible resource for genetic mining, and the identified lines and pleiotropic MTAs reported in this study are considered a good resource for the development of resilient wheat cultivars that combine both good flour quality and grain yield under stress conditions using marker-assisted selection.

Heat and drought priming induce tolerance to subsequent heat and drought stress by regulating leaf photosynthesis, root morphology, and antioxidant defense in maize seedlings

Novel stress tolerance strategies, such as heat and drought priming, are widely used in plants to increase tolerance to subsequent stresses. To date, it is still not known whether heat, drought, and combined stress priming can improve the tolerance of maize plants to heat, drought, and combined stresses by improving the morphology and distribution of roots and antioxidant defense mechanisms in maize seedlings. Here, seedlings of maize were firstly twice exposed to heat, drought, and combined stress at 33 °C/25 °C and 50–60% of soil water holding capacity (SWHC) followed by temperature and water recovery, and then subjected to more severe heat, drought, and combined stress at 36 °C/28 °C and 45–55% of SWHC. Under individual heat or drought stress, healthy values of gas exchange and chlorophyll fluorescence parameters, leaf relative water content, leaf water potential, and leaf cooling were significantly reduced, while superoxide anion and MDA contents in roots were significantly increased. Combined heat and drought stress usually exhibit a typical superimposed effect for the abovementioned parameters. Plants with heat, drought, and combined stress priming improved the redox balance of maize roots by enhancing the activities of superoxide dismutase, peroxidase, and catalase, initiated increases in root vitality as well as osmoregulatory substance contents as evidenced by increased soluble sugar, soluble protein, and proline contents. Principal component analysis revealed a strong correlation between antioxidant enzyme activities and osmoregulatory substance contents in roots. The combined stress priming effectively increased total root length, total root surface area, total root volume, and total root dry weight when compared with no priming. Combined stress priming optimized root distribution, leading to an increase in root length density and root dry weight density in the 12–18, 18–24, and 24–30 cm soil layers. Additionally, a strong positive correlation was observed between leaf relative water content, leaf water potential, and leaf cooling, indicating that better leaf water relations in the primed plants were conducive to the improvement of leaf cooling capacity, which provides good conditions for the increase in photosynthetic rate to maintain the integrity of the maize plant. The significant increases in leaf area, specific leaf weight, aboveground dry mass, and a significant reduction in leaf rolling in combined stress-primed plants indicated that the negative effects of heat and drought stress can be effectively mitigated. The current data indicated that the beneficial stress memory induced by priming in maize seedlings developed their defense systems to trigger more effective clearance mechanisms against subsequent combined heat and drought stress. These findings provided evidence that heat, drought, and combined stress priming enhanced maize adaptability to subsequent heat, drought, and combined stress by improving the morphology, distribution, and antioxidant capacity of the root system. • The effects of combined heat and drought stress on leaf water relations, photosynthesis, , and root physiological activities were studied. • Combined stress-primed plants acquired a stress imprint. • The enhanced tolerance of primed plants to heat and drought stress may be attributed to improved physiological activities in roots.

Intestinal metabolomics of juvenile lenok (Brachymystax lenok) in response to heat stress.

Changes in the metabolic profile within the intestine of lenok (Brachymystax lenok) when challenged to acute and lethal heat stress (HS) are studied using no-target HPLC-MS/MS metabonomic analysis. A total of 51 differentially expressed metabolites (VIP > 1, P < 0.05) were identified in response to HS, and 34 occurred in the positive ion mode and 17 in negative ion mode, respectively. After heat stress, changes in metabolites related to glycolysis (i.e., alpha-D-glucose, stachyose, and L-lactate) were identified. The metabolites (acetyl carnitine, palmitoylcarnitine, carnitine, and erucic acid) related to fatty acid β-oxidation accumulated significantly, and many amino acids (L-tryptophan, D-proline, L-leucine, L-phenylalanine, L-aspartate, L-tyrosine, L-methionine, L-histidine, and L-glutamine) were significantly decreased in HS-treated lenok. The mitochondrial β-oxidation pathway might be inhibited, while severe heat stress might activate the anaerobic glycolysis and catabolism of amino acid for energy expenditure. Oxidative damage in HS-treated lenok was indicated by the decreased glycerophospholipid metabolites (i.e., glycerophosphocholine, 1-palmitoyl-2-hydroxy-sn-glycero-3-phosphoethanolamine, 1-palmitoyl-sn-glycero-3-phosphocholine, 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine, and 1, 2-dioleoyl-sn-glycero-3-phosphatidylcholine) and the increased oxylipin production (12-HETE and 9R, 10S-EpOME). The minor oxidative pathways (omega-oxidation and peroxisomal beta-oxidation) were likely to be induced in HS-treated lenok.

Wearable cooling and dehumidifying system for personal protective equipment (PPE)

While PPE prevents the health care personnel from exposing to the harmful surroundings, it creates a barrier to the dissipation of body heat and perspiration, leading to severe heat stress during prolonged exposure. Here, we report a lightweight wearable cooling and dehumidifying system capable of extracting 51.7 W heat and 26.3 g/hour moisture within protective coverall without compromising the protection. The system could continuously operate for 6 h without taking off the PPE. Compared with the available commercial cooling garments with different cooling methods, the system could provide about 3.2 ∼ 5.0 times mean cooling power per unit weight in a prolonged working condition. In a simulated hospital environment, the optimum cooling effect was equivalent to 3.5 °C drop in ambient temperature and 6 % decrease in ambient relative humidity. It will not only enhance user’s comfort and performance but potentially reduce the heating, ventilation and air conditioning (HVAC) energy consumption by 12 % ∼ 30 % in building environments.

Rhizobium inoculation and exogenous melatonin synergistically increased thermotolerance by improving antioxidant defense, photosynthetic efficiency, and nitro-oxidative homeostasis in Medicago truncatula

Global warming negatively affects plant growth due to the detrimental effects of high temperature-induced heat stress. Rhizobium inoculation (RI) and exogenous melatonin (MT) have shown a positive role in resisting abiotic stress. However, their synergistic effect on avoiding heat-induced damages in Medicago truncatula has not been studied yet. Hence, the objective of the present study was to evaluate the impact of these amendments (RI and MT) to ameliorate the heat damages in Medicago truncatula. The study was comprised of two factors: (1) heat-induced stress: (i) optimum temperature (26 ± 1°C): (23 ± 1°C) (day: night), (ii) moderate heat (35 ± 1°C): (28 ± 1°C), and (iii) severe heat (41 ± 1°C): (35 ± 1°C) for 72 h, and (2) amendments: (i) no RI + no MT (NRI + NMT), (ii) Rhizobium inoculation (RI), (iii) 60 μM melatonin (MT), and (iii) RI + MT. Results showed that the combined application of RI and MT was better than their individual applications, as it prevented heat-induced membrane damages by declining the hydrogen peroxide (34.22% and 29.78%), superoxide anion radical (29.49% and 26.71%), malondialdehyde contents (26.43% and 21.96%), and lipoxygenase activity (44.75% and 25.51%) at both heat stress levels as compared to NRI + NMT. Moreover, RI + MT treated plants showed higher antioxidative and methylglyoxal detoxification enzymes (Gly I and Gly II) activities under heat stress. While, NRI + NMT treated plants showed a higher level of methylglyoxal contents (47.99% and 46.71%) under both levels of heat stress. Relative to NRI + NMT plants, RI + MT pretreated plants exhibited improved heat tolerance as indicated by higher chlorophyll (37.42% and 43.52%), carotenoid contents (32.41% and 47.08%), and photosynthetic rate (42.62% and 64.63%), under moderate and severe heat stress, respectively. Furthermore, RI + MT pretreated plants had considerably higher indole-3 acetic acid and abscisic acid concentrations under moderate (54.02% and 53.92%) and severe (68.36% and 64.61%) heat stress conditions. Similarly, plant dry biomass, NPK uptake, nitric oxide, and nitrate reductase activity were high in RI + MT treated plants, under both levels of stress. Therefore, this study advocates the positive synergistic effect of RI and MT pretreatment against moderate and severe heat-induced stress and for possible maintenance of plant growth under changing scenarios of global warming.