Elevated Temperature Stress Research Articles

Quantitatively characterize the response of the hybrid grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂) under elevated temperature stress

Global warming may affect the health of marine species. However, the collected information on quantitative assessment of response in fish under elevated temperature is poorly defined. The present study aimed to quantitatively evaluate the effects of the hybrid grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂) under elevated temperature (33 °C and 36 °C, ET1 and ET2) stress for 14 days. As endpoints, we examined changes in body growth, hemato-immunological parameters, liver oxidative stress markers, as well as changes of the stomach digestive enzymes. Compared to the control, the body weight was significantly decreased in ET2 group for 14 d exposure, and a remarkable change of differential leukocyte counts of the fish was observed in ET1 group at 3 d and in ET2 group at 14 d. The respiratory burst activity of the hybrid grouper leukocytes markedly decreased in the treatment groups after 14-d exposure. Overall, the antioxidant enzyme activities and transcriptional levels of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), and glutathione peroxidase (GSH-PX) were markedly inhibited in the liver for 3-d and 14-d exposure. The expression levels of nf-κb mRNA were significantly inhibited while the expression levels of atp2b1 mRNA were significantly induced after 14-d exposure. The activities of pepsin and lipase in the stomach were significantly reduced. In addition, an innovative hazard classification system (ET-HCS) was developed to quantitatively characterize the stress response of the fish following elevated temperature treatments. The stress level of ET2 group for 14-d exposure was ranked as level IV (high stress), and the other treatments were ranked as level II (low stress). Taken together, the findings of this study further extend our understanding of quantitative assessment of response in fish under high-temperature stress, which provides valuable information for improving countermeasures of mariculture industry.

Transcriptomic Analysis Provides New Insights into the Tolerance Mechanisms of Green Macroalgae Ulva prolifera to High Temperature and Light Stress.

Our research focused on understanding the genetic mechanisms that contribute to the tolerance of Ulva prolifera (Chlorophyta), a marine macroalgae, to the combined stress of high temperature and high light intensity. At the mRNA level, the up-regulated DEGs showed enrichment in pathways related to ribosomes, proteasomes, and peroxisomes. The spliceosome pathway genes were found to be vital for U. prolifera's ability to adapt to various challenging situations in all the comparison groups. In response to elevated temperature and light intensity stress, there was a significant increase in genes and pathways related to ribosomes, proteasomes, and peroxisomes, whereas autophagy showed an increase in response to stress after 24 h, but not after 48 h. These findings provide novel insights into how U. prolifera adapts to elevated temperature and light stress.

Development and validation of stability-indicating method of etrasimod by HPLC/DAD/MS/MS technique with greenness profiling

Etrasimod, a novel selective sphingosine-1-phosphate receptor modulator, was recently approved by the U.S. Food and Drug Administration and the European Medicinal Agency for the treatment of moderately to severely active ulcerative colitis in adults. In this research, the forced degradation study as an integral part of drug product and packaging development, which generates data on degradation mechanisms, is published. The development and validation of the stability-indicating method using a superior high-performance liquid chromatography technique coupled with a diode array detector and tandem mass spectrometer was performed to support the forced degradation study and monitor the formation of degradation products. Etrasimod demonstrated good stability under elevated temperature and basic stress conditions, while acidic hydrolysis, oxidative, and photolytic degradation produced eight degradation products. The knowledge of degradation products will be useful in the long-term stability study for establishing the acceptance criteria of etrasimod as a drug substance and dosage form during quality control and stability assessment. The eco-friendliness of the developed forced degradation procedure was evaluated using various greenness appraisal tools. The green metric tools showed that the forced degradation procedure obeys eco-friendly conditions.

Analysis of converter transformer pressboard insulation degradation under surge using mathematical morphology

Nowadays, with the significant expansion of industrial growth, the bulk power requirement can only be satisfied through high-voltage direct current HVDC transmission. The converter transformer is the utmost vital part of the HVDC transmission. Pressboard insulation is most commonly used as inter-disc insulation in converter transformers. During working conditions due to elevated temperature and different operational stresses, insulation material gets deteriorated. It may cause a risk to the life of the converter transformer. The effects of elevated temperatures as well as frequency on pressboard insulation of the converter transformer are examined in this study. The condition evaluation and morphological changes in pressboard insulation at elevated temperatures can evaluate with the help of frequency domain spectroscopy (FDS) and atomic force microscopy (AFM) techniques. The impact of elevated temperatures on insulation material can be analyzed based on surface roughness and dielectric parameters. In MATLAB Simulink environment, a dual winding single-phase converter transformers valve side star winding 60 discs model is constructed for impulse test. Based upon arrival time and velocity of traveling wave, insulation degradation location can be identified by using mathematical morphology. The simulation results demonstrate that the suggested method can notably located degradation across disc winding.

Increasing the cross-link density in a dual dissociative and associative polythiourethane covalent adaptable network improves both creep resistance and extrudability

There have been significant, recent reports of the effects of cross-link density on the relaxation dynamics and processability of exclusively associative covalent adaptable networks (CANs), also called vitrimers. Similar characterization is lacking for the substantial number of CANs that exhibit dual associative and dissociative dynamic covalent chemistries. Polythiourethane (PTU), which is a thiol-based analogue of polyurethane, is one such polymer class that exhibits both dissociative and associative dynamic chemistries. Here, we tune the cross-link density of PTU CANs by systematic incorporation of long-chain and short-chain thiols. As would be commonly expected, relative to networks with lower cross-link density, PTU networks with higher cross-link density exhibit improved creep resistance at 60 °C and 100 °C. However, we also observe faster elevated-temperature stress relaxation with increasing cross-link density, which is attributable to the dual nature of the PTU dynamic chemistry, with the associative dynamic mechanism being increasingly favored and becoming increasingly more rapid with increasing cross-link density. Because of this shift, our PTU CAN with the highest cross-link density undergoes facile melt extrusion at 150 °C; in contrast, our PTU CAN of lowest cross-link density cannot be melt extruded. Overall, this work highlights the significance of cross-link density in networks exhibiting two or more dynamic chemistries and how that may lead to otherwise unexpected outcomes, e.g., better processability at higher cross-link density.

Elevated Temperature Stress Analysis of Cobalt-Based Composite Cladding by Microwave Process on Gas Turbine Rotor Blade Using FEA

Elevated Temperature Stress Analysis of Cobalt-Based Composite Cladding by Microwave Process on Gas Turbine Rotor Blade Using FEA

Environmental Effects during Early Life-History Stages and Seed Development on Seed Functional Traits of an Australian Native Legume Species.

Understanding how seed functional traits interact with environmental factors to determine seedling recruitment is critical to assess the impact of climate change on ecosystem restoration. This study focused on the effects of environmental factors on the mother plant during early plant life history stages and during seed development. Desmodium brachypodum A. Gray (large tick trefoil, Fabaceae) was used as a model species. Firstly, this study analyzed seed germination traits in response to temperature and moisture stress. Secondly, it investigated how seed burial depth interacts with temperature and soil moisture to influence seedling emergence traits. Finally, it determined if contrasting levels of post-anthesis soil moisture could result in changes in D. brachypodum reproductive biology and seed and seedling functional traits. The results showed that elevated temperature and moisture stress interacted to significantly reduce the seed germination and seedling emergence (each by >50%), while the seed burial improved the seedling emergence. Post-anthesis soil moisture stress negatively impacted the plant traits, reducing the duration of the reproductive phenology stage (by 9 days) and seed production (by almost 50%). Unexpectedly, soil moisture stress did not affect most seed or seedling traits. In conclusion, elevated temperatures combined with low soil moisture caused significant declines in seed germination and seedling emergence. On the other hand, the reproductive output of D. brachypodum had low seed variability under soil moisture stress, which might be useful when sourcing seeds from climates with high variability. Even so, a reduction in seed quantity under maternal moisture stress can impact the long-term survival of restored plant populations.

Evaluating the Present and Future Heat Stress Conditions in the Grand Duchy of Luxembourg

The impact of elevated air temperature and heat stress on human health is a global concern. It not only affects our well-being directly, but also reduces our physical work capacity, leading to negative effects on society and economic productivity. Climate change has already affected the climate in Luxembourg and, based on the results of regional climate models, extreme heat events will become more frequent and intense in the future. To assess historical conditions, the micro-scaleRayManPro 3.1 model was used to simulate the thermal stress levels for different genders and age classes based on hourly input data spanning the last two decades. For the assessment of future conditions, with a special emphasis on heat waves, a multi-model ensemble of regional climate models for different emission scenarios taken from the Coordinated Regional Climate Downscaling Experiment (CORDEX) was used. For both, the past and future conditions in Luxemburg, an increase in the heat stress levels was observed. Small differences for different age groups and genders became obvious. In addition to the increase in the absolute number of heat waves, an intensification of higher temperatures and longer durations were also detected. Although some indications of the adaptation to rising air temperatures can be observed for high-income countries, our results underscore the likelihood of escalating heat-related adverse effects on human health and economic productivity unless more investments are made in research and risk management strategies.

Physiological impact of heat stress and their alleviation measures in agriculture: A review

Abiotic stresses are becoming more prevalent in modern agriculture as a result of shifting climate scenarios. Elevated temperature stress is one of the most important abiotic stresses to address since it has detrimental consequences for plant physiology, molecular structure, and phenology. The morphological impact occurs in the form of reduced germination, poor emergence, poor seedling vigor, abnormal seedling. Heat stress also results in the closure of stomata, reduced leaf size and consequent increase in stomatal density. One of the major physiological impacts of heat stress is on the fluidity of the membrane structure of the plant cell. Heat stress leads to increased fluidity of the thylakoid membrane and disruption of metabolic functions, which either deliver or accept electrons from PSII and, thus, cause dislodging of PSII from thylakoid membrane. The respiration generally increases in the temperature range of 0-35/ 40⁰C, reaches plateau at 40-50⁰C and decreases beyond 50⁰C due to damage to the respiratory mechanism. Elevated temperature directly impacts the cellular water content and indirectly through the increased water depletion rate from the soil. In order to design the appropriate corrective actions, it is crucial to research all the factors leading to heat stress thoroughly. The traditional agronomic and breeding interventions are crucial, but the rising food demand and the intensifying heat stress call for some cutting-edge biotechnological interventions, such as transgenics, genome editing, and CRISPR/cas9, to induce genome-level heat tolerance. The present review deals in detail with each of the previously listed aspects.

Physiological and Biochemical Effect of Elevated Night Temperature Stress on Bread Wheat (Triticum aestivum L.)

A laboratory experimentation was done in the Department of Plant Physiology, Institute of Agricultural Sciences, Banaras Hindu University to evaluate elevated night temperature effect in wheat (Triticum aestivum L.) to see the response in some antioxidant and biochemical parameters in two wheat cultivars viz. HUW-234 (comparatively tolerant to heat stress) and sonalika (comparatively susceptible to heat stress). A significance difference was recorded in the parameters pertaining to antioxidant system includes catalase, SOD and APX activity were found to increase substantially when the plants kept under stress conditions (250C/ 240C day and night temperature) than the plants kept under controlled condition (250C/150C day and night temperature). The percent increase in the antioxidant enzyme activity was found to be more in the tolerant genotype (HUW-234) than in the susceptible genotype (Sonalika). There was 23.52 % increase was reported in the catalase activity by tolerant genotype when kept under stress conditions than those kept under control. Significant reductions were reported in most of the photosynthetic and membrane parameters viz., chlorophyll ‘a’, chlorophyll ‘b’ and membrane thermostability index. Similar percent reduction was reported with respect to biochemical parameters (total protein content, starch content and soluble sugar content) in the susceptible variety kept under high night temperature regime. Based on the pooled data of two-year experimentation it can be concluded that variety HUW-234 was found to be more tolerant than variety sonalika to HNT stress.
 Key Words: High night temperature, Wheat, Catalase activity, Anti-oxidant system.

Infliximab aggregates produced in severe and mild elevated temperature stress conditions induce an extended specific CD4 T-cell response

Aggregation has been widely described as a factor contributing to therapeutic antibody immunogenicity. Although production of high-affinity anti-drug antibodies depends on the activation of CD4 T lymphocytes, little is known about the T-cell response induced by antibody aggregates, especially for aggregates produced in mild conditions resulting from minor handling errors of vials. Large insoluble infliximab (IFX) aggregates produced in severe elevated temperature stress conditions have been previously shown to induce human monocyte-derived dendritic cell (moDC) maturation. We here showed that large IFX aggregates recruit in vitro a significantly higher number of CD4 T-cells compared to native IFX. Moreover, a larger array of T-cell epitopes encompassing the entire variable regions was evidenced compared to the native antibody. We then compared the responses of moDCs to different types of aggregates generated by submitting IFX to mild conditions of various times of incubation at an elevated temperature. Decreasing stress duration reduced aggregate size and quantity, and subsequently altered moDC activation. Of importance, IFX aggregates generated in mild conditions and not altering moDC phenotype generated an in vitro T-cell response with a higher frequency of CD4 T cells compared to native IFX. Moreover, cross-reactivity studies of aggregate-specific T cells showed that some T cells could recognize both native and aggregated IFX, while others responded only to IFX aggregates. Taken together, our results suggest that aggregation of antibodies in mild elevated temperature stress conditions is sufficient to alter moDC phenotype in a dose-dependent manner and to increase T-cell response.

Co-occurring elevated temperature and drought stress inhibit cotton pollen fertility by disturbing anther carbohydrate and energy metabolism

The effects of individually applied heat or drought stress on cotton’s pollen fertility, and consequently on yield formation, have been extensively studied. In contrast, the effects of their compound stress have received minimal attention. To address this, a pond experiment was conducted using a cotton cultivar, Yuzaomian 9110 and the treatments consisted of control (CK), drought stress (DS), elevated temperature (ET), and the combination of elevated temperature and drought stress (ET+DS). Results revealed that ET+DS resulted in larger decreases in cottonseed number per boll and boll weight than DS or ET, which were attributed to the lower pollen fertility under the combined stress compared to either single stress. The decreases in pollen fertility under all stress conditions were further associated with disturbances in anther carbohydrate and energy metabolism. Pollen viability was negatively correlated with sucrose content, but was positively correlated with starch and ATP contents under different conditions. Specifically, DS increased anther sucrose content by increasing sucrose phosphate synthetase (SPS) activity to enhance sucrose synthesis, and by decreasing sucrose synthetase (SuSy) and acid/alkaline INV activities to restrict sucrose hydrolysis to fructose and glucose. Similar to DS, ET+DS increased anther sucrose content, which was attributed to the restricted sucrose hydrolysis, due to the reduced activities of SuSy and acid/alkaline INV, and acid INV activity even was lower under ET+DS than DS. However, ET enhanced acid invertase (INV) activity to promote sucrose hydrolysis, and down-regulated the expression of GhSUT3A/D (sucrose transporter gene), GhSUT4 (sucrose transporter gene) and GhSWEET55 (encoding Sugars Will Eventually Be Exported Transporters proteins) to inhibit sucrose transport into anthers, so the anther sucrose content was decreased. Furthermore, ET, DS and ET+DS treatments significantly decreased starch synthesis by down-regulating the expression of GhAGP, GhGBSS and GhSSS; however, the ET+DS treatment had a lower GhSSS expression than any single stress, which further inhibited amylopectin synthesis and resulted in lower anther starch content compared to CK and either of the individual stresses. In addition, significant reductions were observed in anther pyruvate content under all stress conditions, which inhibited the ATP production in the tricarboxylic acid cycle. Nevertheless, different pathways were involved in the response of energy metabolism to single and combined stresses. In particular, single ET or DS down-regulated GhHK1 and GhPK to decrease pyruvate formation, while the downregulation of GhHK1 and GhPGK were responsible for the decreased pyruvate content under combined stress. Additionally, either single stress resulted in the upregulation and downregulation of GhATP α subunit and GhATP β subunit of ATP synthase, respectively, the opposite was observed under the condition of combined stress, indicating that differential response mechanisms of ATP synthase are activated between the combined stress and any individual stresses. All these confirmed that elevated temperature combined with drought stress have a unique effect on carbohydrate and energy metabolism of anthers, resulting in larger decreases in pollen fertility, cottonseed number per boll and boll weight than either of the stresses alone.

Accelerated aging of tire and road wear particles by elevated temperature, artificial sunlight and mechanical stress — A laboratory study on particle properties, extractables and leachables

Tire and road wear particles (TRWP) are generated in large quantity by automobile traffic on roads but their way of degradation in the environment is largely unclear. Laboratory experiments were performed on the effect of elevated temperature (simulating 2–3 years), sunlight exposure (simulating 0.5 years) and mechanical stress on the physical properties and chemical composition of TRWP and of cryo-milled tire tread (CMTT). No significant effects were observed of the applied mechanical stress on mean properties of pristine particles. After sunlight exposure up to 40 % in mass were lost from the TRWP, likely due to the loss of mineral incrustations from their surface. The chemical composition of TRWP and CMTT was characterized by determining 27 compounds, antioxidants (phenylene diamines), vulcanization agents (benzothiazoles and guanidines) and their transformation products (TPs). Extractables of TRWP (580–850 μg/g) were dominated by TPs, namely benzothiazolesulfonic acid (BTSA). CMTT showed much higher amounts of extractables (4600 μg/g) which were dominated by parent chemicals such as N-(1,3-dimethylbutyl)-N′-phenyl-1,4-phenylenediamine (6-PPD), diphenylguanidine (DPG) and mercaptobenzothiazole (MBT). Sunlight exposure affected the amount of extractables more strongly than elevated temperature, for TRWP (−45 % vs −20 %) and CMTT (−80 % vs −25 %) and provoked a clear shift from parent compounds to their TPs. After sunlight exposure extractables of TRWP were dominated by BTSA and DPG. Sunlight exposure drastically reduced the 6-PPD amount extracted from both, TRWP and CMTT (−93 %, −98 %), while its quinone (6-PPDQ) increased by around 1 % of the 6-PPD decrease, only. For many TPs, concentration in leachates were higher than in extracts, indicating ongoing transformation of their parent compounds during leaching. These results highlight that abiotic aging of TRWP leads to strong changes in their chemical composition which affect their particle properties and are of relevance for the environmental exposure to tire-related chemicals.

Regulatory network of rice in response to heat stress and its potential application in breeding strategy.

The rapid development of global industrialization has led to serious environmental problems, among which global warming has become one of the major concerns. The gradual rise in global temperature resulted in the loss of food production, and hence a serious threat to world food security. Rice is the main crop for approximately half of the world's population, and its geographic distribution, yield, and quality are frequently reduced due to elevated temperature stress, and breeding rice varieties with tolerance to heat stress is of immense significance. Therefore, it is critical to study the molecular mechanism of rice in response to heat stress. In the last decades, large amounts of studies have been conducted focusing on rice heat stress response. Valuable information has been obtained, which not only sheds light on the regulatory network underlying this physiological process but also provides some candidate genes for improved heat tolerance breeding in rice. In this review, we summarized the studies in this field. Hopefully, it will provide some new insights into the mechanisms of rice under high temperature stress and clues for future engineering breeding of improved heat tolerance rice.

Electro-thermo-mechanical instability study of fiber-reinforced bimorph convex dielectric elastomer

ABSTRACT Intelligent electroactive polymer-based dielectric elastomer actuators (DEAs) are capable of geometrical disorientation. These actuators are susceptible to electro-thermo-mechanical instability due to their ability to be electrically powered at various stresses and temperatures. This proposed work provides mathematical derivations for the study of instability in coupled electro-thermo-mechanical anisotropic bimorph convex DEAs. The equilibrium equations are formulated assuming the taper ratio because of the convex structure and the ply angles due to anisotropy. MATLAB is employed to numerically solve the complicated equations for critical stretch, nominal electric field, and entropy under a variety of mechanical, electrical, and thermal loads. The observations indicate that under conditions of , and , an increase in nominal stress from to leads to a corresponding increase in the peak point of the nominal electric field, specifically from to for axial stretch values of 2.107 and 2.159, respectively. When the nominal electric field is reported against nominal electric displacement, it enhances with the rise in temperature and reduces with the hike in nominal stress and taper ratio. When the fibers are arranged parallel to the axial stretch direction then the failure point of stretch is least, compared to that oriented in a perpendicular direction. The present study demonstrates that elevated temperature and nominal stress result in an increase in entropy, leading to a corresponding increase in system disorder. Furthermore, the perpendicular alignment of fibers with respect to axial stretch is found to decrease the degree of system randomness.

Differential photo-physiological responses of two giant clam species to elevated temperature stress from Rodrigues Island, Western Indian Ocean

Abstract. Ramah S, Kaullysing D, Soondur M, Taleb-Hossenkhan N, Bhagooli R. 2023. Differential photo-physiological responses of two giant clam species to elevated temperature stress from Rodrigues Island, Western Indian Ocean. Indo Pac J Ocean Life 7: 64-70. Bleaching events leading to mass mortality of coral reef and its associated symbiotic organisms have become an alarming issue worldwide. However, as compared to corals, little has been documented regarding giant clams’ (Tridacnines) thermal photo-physiological susceptibility. Triplicate specimens of the small giant clam Tridacna maxima and the fluted giant clam T. squamosa collected from the lagoon of Rodrigues Island, Western Indian Ocean were exposed at two temperatures, 29°C and 32°C, under a constant low light intensity of approximately 200 µmol quanta m-2 s-1 over a 12-hour duration. The photo-physiological parameters namely, effective quantum yield of photosystem II (?PSII), relative maximum Electron Transport Rate (rETRmax) and maximum Non-Photochemical Quenching (NPQmax) were determined using a Diving Pulse-Amplitude-Modulated (D-PAM) fluorometer prior to and after 3 and 12 hours of exposures. At 29°C the photo-physiological parameters did not vary significantly for both species. At 32°C, T. squamosa and T. maxima exhibited significant declines in ?PSII as at 3 and 12 hours, respectively. The rETRmax of T. squamosa showed a significant decrease at 3 hours while both species showed a significant reduction in their NPQmax functioning as from 3 hours. The experiment also recorded the disintegration of the mantle tissue in T. squamosa after 12 hours. These findings indicate that T. squamosa is thermally more susceptible than T. maxima. Further in-depth investigations on symbionts genetic types and antioxidant responses of both the Tridacna host and symbionts are required to thoroughly understand giant clams’ variable heat stress responses in the era of ocean warming.

Sweetpotato cultivars responses to interactive effects of warming, drought, and elevated carbon dioxide.

Plants are sensitive to changes projected in climates, such as elevated carbon dioxide (eCO2), high temperature (T), and drought stress (DS), which affect crop growth, development, and yield. These stresses, either alone or in combination, affect all aspects of sweetpotato plant growth and development, including storage root development and yield. We tested three sweetpotato cultivars (Beauregard, Hatteras, and LA1188) responses to eight treatments (Control, DS, T, eCO2, DS + T, T + eCO2, DS + eCO2, DS + T + eCO2). All treatments were imposed 36days after transplanting (DAP) and continued for 47days. Treatments substantially affected gas exchange, photosynthetic pigments, growth, and storage root components. Cultivars differed considerably for many of the measured parameters. The most significant negative impact of DS was recorded for the shoot and root weights. The combination of DS + T had a significant negative effect on storage root parameters. eCO2 alleviated some of the damaging effects of DS and high T in sweetpotato. For instance, eCO2 alone or combined with DS increased the storage root weights by 22% or 42% across all three cultivars, respectively. Based on the stress response index, cultivar "Hatteras" was most tolerant to individual and interactive stresses, and "LA 1188" was sensitive. Our findings suggest that eCO2 negates the negative impact of T or DS on the growth and yield of sweetpotato. We identified a set of individual and interactive stress-tolerant traits that can help select stress cultivars or breed new lines for future environments.

Combined effect of elevated temperature and drought stress on carbohydrate metabolism of cotton (Gossypium hirsutum L.) subtending leaves.

High temperatures and drought are expected to become more frequent in the future and last longer than ever before. To investigate their combined effect on cotton subtending leaves (LSCB), an experiment was conducted from 2016 to 2018 using a non-heat-tolerant cotton cultivar and a heat-tolerant cultivar. Two temperature regimes with ambient temperature (AT, 31.0/26.4 °C) and elevated temperature (ET, 33.4/28.9 °C, 2.5 °C higher than AT) and three drought treatments with a soil relative water content (SRWC) of 75 ± 5%, 60 ± 5%, and 45 ± 5% were established repeatedly. ET decreased Pn, initial rubisco activity (4.1.1.39, RuBP) and cy-FBPase (3.1.3.11) activity, upregulated GhSuSyA, and GhSuSyD expressions, and increased SuSy (2.4.1.13) activity, which led to the decline of the final starch and sucrose contents. Moreover, RuBP, Pn, and starch content all decreased with drop in SRWC levels, but the cy-FBPase and SPS (2.4.1.14) activity increased, which in turn increased sucrose content. Under combined stresses, when the changing trends of ET and drought effects were the same, the decrease of Pn, RuBP, and starch content was greater than under single stress exposure. However, when the changing trends of ET and drought effects were adverse, the combined effects on indicators such as cy-FBPase, SuSy, sucrose content were mostly similar to drought stress. These results indicate that the effect of drought on carbohydrate metabolism in LSCB is more prominent than ET. Thus, the drought effect for carbohydrate metabolism in LSCB may need more attention than ET under combined heat and drought stress. This article is protected by copyright. All rights reserved.

Co-occurring elevated temperature and drought stresses during cotton fiber thickening stage inhibit fiber biomass accumulation and cellulose synthesis

In order to investigate the effect of simultaneous elevated temperature and drought on Gossypium hirsutum fiber development under the background of global climate change, cotton (cv. Sumian 15 and cv. PHY370WR) plants were grown under ambient temperature (AT) or elevated temperature (ET, 2.5–2.7 °C higher than AT) conditions from 2016 to 2018. Meanwhile, three soil relative water content (SRWC) levels including (75 ± 5) % (optimum soil moisture), (60 ± 5) % (moderate drought) and (45 ± 5) % (severe drought) were established under each temperature condition. Results showed that elevated temperature combined with drought more negatively impacted the theoretical maximum of fiber biomass by further reducing the duration of rapid increase and the average increase rate of fiber biomass than any single stress. Elevated temperature and drought had opposite effects on sucrose synthesis in fibers by differently altering sucrose phosphate synthase (SPS) activity and GhSPS isoforms (GhSPS-1, GhSPS-2, and GhSPS-3) expressions, and the two stresses had an antagonistic effect on SPS activity when they were coupled. However, lower sucrose content was observed under all single and coupled stresses, meaning that less carbon was available for cellulose synthesis. Elevated temperature or drought alone also limited cellulose synthesis by decreasing the activities of sucrose synthase (SuSy), soluble acid invertase (VIN) and alkaline invertase (CIN) involved in sucrose degradation. The decrease of SuSy activity should be the result of down-regulation of GhSuSyA, GhSuSyB and GhSuSyC expressions, and the decrease of VIN activity should be the result of down-regulation of GhInv-1 and GhInv-2 expressions under high temperature or drought alone. The combination of the two stresses had more negatively effects on SuSy activity by further down-regulating the iso-forms GhSuSyA and GhSuSyB expressions, on VIN activity by further decreasing GhInv-1 and GhInv-2 expressions, and on CIN activity than any single stress, which would further inhibit sucrose degradation to form UDPG for cellulose synthesis. Moreover, elevated temperature or drought alone enhanced callose accumulation by highly up-regulating GhCalS-5 expression and down-regulating β-1,3-glucanase expression, and the combined stress further increased the callose accumulation, suggesting that more UDPG from sucrose decomposition was allocated to callose synthesis rather than cellulose synthesis. All these confirmed that elevated temperature combined with drought exhibited synergistic negative effects on cotton fiber biomass accumulation and cellulose synthesis during fiber thickening.

Mechanisms of Kale (Brassica oleracea var. acephala) Tolerance to Individual and Combined Stresses of Drought and Elevated Temperature.

Rising temperatures and pronounced drought are significantly affecting biodiversity worldwide and reducing yields and quality of Brassica crops. To elucidate the mechanisms of tolerance, 33 kale accessions (B. oleracea var. acephala) were evaluated for individual (osmotic and elevated temperature stress) and combined stress (osmotic + temperature). Using root growth, biomass and proline content as reliable markers, accessions were evaluated for stress responses. Four representatives were selected for further investigation (photosynthetic performance, biochemical markers, sugar content, specialized metabolites, transcription level of transcription factors NAC, HSF, DREB and expression of heat shock proteins HSP70 and HSP90): very sensitive (392), moderately sensitive (395), tolerant (404) and most tolerant (411). Accessions more tolerant to stress conditions were characterized by higher basal content of proline, total sugars, glucosinolates and higher transcription of NAC and DREB. Under all stress conditions, 392 was characterized by a significant decrease in biomass, root growth, photosynthesis performance, fructan content, especially under osmotic and combined stress, a significant increase in HSF transcription and HSP accumulation under temperature stress and a significant decrease in NAC transcription under all stresses. The most tolerant accession under all applied stresses, 411 showed the least changes in all analyzed parameters compared with the other accessions.