Combined Stress Research Articles

Impact of nitrogen on photosynthesis, remobilization, yield, and efficiency in winter wheat under heat and drought stress

Droughts and high temperatures often occur during the late reproductive periods of winter wheat, greatly threatening winter crop production. However, the potential of nitrogen (N) management to mitigate the adverse effects of heat and drought stress on winter wheat remains unclear. Therefore, a two-season wheat experiment was performed to examine the impacts of temperature, soil moisture, and N supply on the photosynthetic rate, N accumulation and remobilization efficiency, and water and N use efficiency. Drought and heat stress resulted in a significant reduction in gas exchange, which was exacerbated by combined stress. In the combined stress treatment (HD), the stomatal conductance and transpiration rate under low N (N1) application increased by approximately 20 % and 15 %, respectively, compared to those under high N (N3) application. The highest net photosynthetic rate and instantaneous water use efficiency were observed under medium N (N2) application. An appropriate reduction in N supply alleviated the impacts of combined stress on growth traits, with the aboveground dry mass and green leaf area under N1 application increasing by 8.49 % and 24.10 %, respectively, compared with those under N3. Drought and heat stress significantly reduced the mean grain-filling rate, grain N accumulation (GNA), and contribution to grain N by post-anthesis N uptake (CANU), especially under combined stress. Compared with that under N1, the GNA in the DH treatment under N2 increased by 7.16 %, whereas the CANU gradually decreased with increasing N supply. Compared with the control, combined stress slightly increased WUE-biomass but decreased WUE-yield, and 19.91 % and 10.77 % lower NUE-yield and NUE-biomass, respectively, were observed under combined stress. The yield, WUE-biomass, and NUE-biomass of the DH treatment with N1 application increased by 16.19 %, 9.27 %, and 6.97 %, respectively, compared with those of the N3 treatment, whereas the WUE-biomass and NUE-yield were greatest under the N2 treatment. Entropy-topsis analysis revealed that the DH treatment under the N1 supply had a greater composite evaluation index than did the N2 and N3 supplies. Reducing nitrogen application effectively mitigated yield suppression and improved water and nitrogen use efficiency in winter wheat under post-anthesis combined stress.

Transcriptome Profiles Reveal Key Regulatory Networks during Single and Multifactorial Stresses Coupled with Melatonin Treatment in Pitaya (Selenicereus undatus L.).

In response to evolving climatic conditions, plants frequently confront multiple abiotic stresses, necessitating robust adaptive mechanisms. This study focuses on the responses of Selenicereus undatus L. to both individual stresses (cadmium; Cd, salt; S, and drought; D) and their combined applications, with an emphasis on evaluating the mitigating effects of (M) melatonin. Through transcriptome analysis, this study identifies significant gene expression changes and regulatory network activations. The results show that stress decreases pitaya growth rates by 30%, reduces stem and cladode development by 40%, and increases Cd uptake under single and combined stresses by 50% and 70%, respectively. Under stress conditions, enhanced activities of H2O2, POD, CAT, APX, and SOD and elevated proline content indicate strong antioxidant defenses. We identified 141 common DEGs related to stress tolerance, most of which were related to AtCBP, ALA, and CBP pathways. Interestingly, the production of genes related to signal transduction and hormones, including abscisic acid and auxin, was also significantly induced. Several calcium-dependent protein kinase genes were regulated during M and stress treatments. Functional enrichment analysis showed that most of the DEGs were enriched during metabolism, MAPK signaling, and photosynthesis. In addition, weighted gene co-expression network analysis (WGCNA) identified critical transcription factors (WRKYs, MYBs, bZIPs, bHLHs, and NACs) associated with antioxidant activities, particularly within the salmon module. This study provides morpho-physiological and transcriptome insights into pitaya's stress responses and suggests molecular breeding techniques with which to enhance plant resistance.

Silicon weakens the outer apoplastic barrier in roots of rice and delays its formation, resulting in increased Na+ and Cl− fluxes to the shoot

In rice, silicon can mitigate abiotic and biotic stresses. We therefore investigated the effect of Si on key root traits related to soil flooding and salinity tolerance with emphasis on the outer apoplastic barrier and cortical aerenchyma. We tested the hypothesis that Si application alters the phenotypic response of these root traits by growing rice in nutrient solutions without or with Si, designed to mimic drained or flooded soils. We measured the barrier strength through resistance to O2 and water of the outer parts of adventitious roots along with cortical aerenchyma and other root structural traits. We found that Si delayed the barrier formation and caused lower amounts of inducible cortical aerenchyma. The delay in barrier formation resulted in higher xylem loading of Na+ and Cl-, i.e., the sap flux of both ions was significantly higher for plants with access to Si. The increased ion fluxes correlated with lower lignin and suberin deposition in the outer part of the root. Consequently, we do not recommend using Si application to alleviate combined stress of salinity and soil flooding in rice, since the barrier was more permeable to O2, and the aerenchyma formation was less pronounced in roots with Si.

Identification of genes involved in the tomato root response to Globodera rostochiensis parasitism under varied light conditions.

Understanding the intricate interplay between abiotic and biotic stresses is crucial for deciphering plant responses and developing resilient cultivars. Here, we investigate the combined effects of elevated light intensity and nematode infection on tomato seedlings. Chlorophyll fluorescence analysis revealed significant enhancements in PSII quantum yield and photochemical fluorescence quenching under high light conditions. qRT-PCR analysis of stress-related marker genes exhibited differential expression patterns in leaves and roots, indicating robust defense and antioxidant responses. Despite root protection from light, roots showed significant molecular changes, including downregulation of genes associated with oxidative stress and upregulation of genes involved in signaling pathways. Transcriptome analysis uncovered extensive gene expression alterations, with light exerting a dominant influence. Notably, light and nematode response synergistically induced more differentially expressed genes than individual stimuli. Functional categorization of differentially expressed genes upon double stimuli highlighted enrichment in metabolic pathways, biosynthesis of secondary metabolites, and amino acid metabolism, whereas the importance of specific pathogenesis-related pathways decreased. Overall, our study elucidates complex plant responses to combined stresses, emphasizing the importance of integrated approaches for developing stress-resilient crops in the face of changing environmental conditions.

Strengthening bioremediation potential: Enterobacter ludwigii ES2 for combined nicosulfuron and Cd contamination through whole genome and microbial diversity community analysis

Nicosulfuron and Cd are common pollutants that pose significant threats to the environment and human health, particularly under combined stress. This study is the first to remediate environmental nicosulfuron and Cd under combined stress using microbiological techniques. Enterobacter ludwigii ES2 was isolated, characterized, and demonstrated to degrade 93.80 % of nicosulfuron and remove 59.64 % of Cd within 4 d. Potential functional genes, including nicosulfuron degradation genes gstA, gstB, glnQ, glnP, mreB, and sixA, and Cd tolerance/removal-related genes mntA, mntB, mntH, dnaK, znuA, and zupt, were predicted by sequencing the whole genome of strain ES2, and their expression was verified by qRT-PCR. Strain ES2 managed oxidative stress induced by Cd through superoxide dismutase, glutathione, catalase, peroxidase, and malondialdehyde. Furthermore, to repair compound stress, up to 90.48 % of nicosulfuron and 67.74 % of Cd were removed. The community structure analysis indicated that Enterobacteriaceae, Sphingomonadaceae, and Gemmatimonadaceae were dominant populations, with ES2 stably colonizing and becoming the dominant bacterium. In summary, ES2 demonstrated significant potential in remediating nicosulfuron and Cd pollution from various perspectives, providing a solid theoretical foundation.

Nutrient content, osmolytes accumulation and antioxidative enzyme activities of sandalwood under drought and salt stresses

Sandalwood (Santalum album L.) has potential to grow into various types of soil under arid as well as semi-arid regions. To find out the sustainable host plant species for sandalwood grown under stress, an RBD experiment was conducted on sandalwood grown without a host and with five selected hosts (Alternanthera sp., Azadirachata indica, Dalbergia sissoo, Melia dubia, and Aquilaria malaccensis) based on prior studies. After 6 weeks of establishment, individual and combine water and salinity stresses were applied and maintained for up to 180 days to investigate their impact on the nutrient content, concentration of osmolytes, and activities of antioxidative enzymes in sandalwood. Haustoria formation showed significant reduction under individual and combined water deficit and salinity stress. Sandalwood grown with Dalbergia sissoo and Melia dubia showed relatively higher nutrients content such as N, P, Ca, Mg, Zn, Fe, and S, which were dramatically reduced under individual and combined water deficit and salinity stress. Osmolytes concentration (proline, soluble sugars, and soluble proteins) increased with intensified stress and sandalwood accumulated higher osmolytes when grown with Dalbergia sissoo and Melia dubia. The activities of antioxidant enzymes showed a significant increase under water deficit, salinity, and combined stress compared to the control, but sandalwood grown with Dalbergia sissoo and Melia dubia exhibited higher activities. Results signify the importance of hosts i.e. Dalbergia sissoo and Melia dubia which provide suitable growth and nutrition to growing sandalwood by maintaining ion homeostasis, ROS balance, and nutrient content under water deficit, salinity, and interactive stress. Results highlighted the significance of D. sissoo and M. dubia, which may be good long-lasting host species for sandalwood production in sub-tropical climates to adapt to changing environmental conditions.

Dynamics of physiological and biochemical effects of heat, drought and combined stress on potato seedlings

BackgroundHeat and drought stresses usually occur together in nature, and both are expected to increase in frequency and intensity as a result of climate change. The synergistic impacts of these compound climate extremes on potatoes are far from the effects of individual stresses. However, the dynamics of the effects of combined heat and drought stresses on potato physiology and biochemistry have yet to be thoroughly assessed. To elucidate this point, we set up a pot experiment using ‘Atlantic’ potato seedlings as test material. A total of six treatments were set up: CK (normal growth conditions: 21 ℃, 0 PEG), A1B1 (31 ℃, 20% PEG), A1B2 (31 ℃, 10% PEG), A1B3 (31 ℃, 0 PEG), A2B1 (21 ℃, 20% PEG), and A2B2 (21 ℃, 10% PEG), and 15 physiological indices were determined with the stress time of 0, 6, 12 and 18 days.ResultsAfter 18 days of stress, the phenotype of potato seedlings was significantly different. Compared with CK, the thickness of potato leaves and palisade tissue increased under heat and drought stress, and the combined stress reduced the photosynthetic efficiency of potato leaves. In all treatments except CK, the chlorophyll content decreased significantly, the antioxidant enzyme activity increased first and then decreased, and the relative conductivity and malondialdehyde content increased significantly. The heat and combined treatment made the content of the osmotic regulator first increase and then decrease, while the treatment of 21 ℃ had no significant change. According to the correlation, principal component and interaction analysis, both heat and drought treatment had significant effects on each index, and the longer the stress time, the greater the effect, and the effect of combined stress was greater than that of single stress. However, after 6 days of stress, the activity of antioxidant enzymes and the content of transparent regulatory substances increased.ConclusionsIn conclusion, potato can cope with heat, drought and combined stress by adjusting leaf tissue structure, antioxidant enzyme activity and osmotic regulatory substances in a short time.Graphical

Proteomic dynamics revealed sex-biased responses to combined heat-drought stress in Marchantia.

Recent studies have documented plant responses to climate change extensively, particularly to single-stress exposures. However, critical factors for stress survival, such as sexual differentiation, are not often considered. The dioicous Marchantia polymorpha stands as an evolutionary milestone, potentially preserving ancestral traits from the early colonizers. In this study, we employed proteomic analyses complemented with physiological monitoring to investigate combined heat and drought responses in Tak-1 (male) and Tak-2 (female) accessions of this liverwort. Additionally, targeted transcriptomics was conducted using different natural populations from contrasting environments. Our findings revealed sex-biased dynamics among natural accessions, particularly evident under control conditions and during early stress responses. Although Tak-2 exhibited greater diversity than Tak-1 under control conditions, male accession demonstrated distinct and more rapid stress sensing and signaling. These differences in stress response appeared to be strongly related to sex-specific plasticity influenced by geoclimatic origin. Furthermore, we established distinct protein gene ages and genomic distribution trends, underscoring the importance of protein diversification over time. This study provides an evolutionary perspective on sexual divergence and stress emergence employing a systems biology approach, which allowed for the establishment of global and sex-specific interaction networks in the stress response.

Shear Performance of Prefabricated Steel Ultra-High-Performance Concrete (UHPC) Composite Beams under Combined Tensile and Shear Loads: Single Embedded Nut Bolts vs. Studs

Ultra-high-performance concrete (UHPC) is widely used in precast concrete-steel composite beams because of its beneficial properties, including reduced structural weight, higher flexural rigidity, and reduced tensile crack formation. In comparison to conventional steel-concrete composite beams, steel-UHPC composite beams exhibit superior characteristics, including reduced structural deadweight, enhanced flexural stiffness, and the capacity to withstand tensile cracking. One successful attempt at meeting the current demands for expedited girder engineering is the development of steel-UHPC composite beams with full-depth precast slabs as key components affecting the overall structural performance using dismountable single embedded nut bolts (SENBs) and widely used studs as competitive alternatives. In contrast, shear connectors are exposed to a combined tensile and shear stress in service life rather than shear only. The corresponding scientific problem is the problem of combined effects under stress in practical applications, but there is currently no relevant research. The shear performance of SENBs in precast steel-UHPC composite beams under tension and shear loads remains unclear. For this purpose, ten push-out specimens and theoretical analyses were performed in this paper, considering the influence of the connector’s type and tensile-to-shear ratio. However, ten specimens were conducted to investigate the tensile-to-shear ratio, and the connector’s type on shear performance is limited. In the future, an increasing number of specimens and test parameters should be considered to investigate the shear performance of precast steel-UHPC composite beams. An increase in the tension-to-shear ratio resulted in a substantial reduction in the ultimate shear capacity, initial shear stiffness, and ductility of the studs. The increase in the tensile-shear ratio from 0 to 0.47 resulted in a 16.9% decline in the ultimate shear capacity, a 30.4% reduction in the initial shear stiffness, and a 21.7% decrease in the ductility of the Series I samples. However, an increase in the tensile-to-shear ratio of the Series II samples from 0 to 0.47 resulted in a 31.3% decline in ultimate shear strength, a 33.2% decline in initial shear stiffness, and a 41.9% decline in ductility. The SENBs demonstrated minimal deviations in ultimate shear capacity compared to their stud counterparts, despite exhibiting notable differences in shear stiffness, and ductility. A lower tensile-to-shear ratio was recommended in practical engineering, which might achieve a larger ultimate shear capacity, stiffness, and ductility. The design-oriented models with enhanced applicability were developed to predict the tension-shear relationship and the load-slip curve of SENBs in prefabricated steel-UHPC composite beams subjected to combined tensile and shear loads. For a tensile-shear relationship model, the point error range was 0 to 0.08, with an average error of 0.03. The square coefficient (R2) was 0.99 for a load-slip curve model. The study findings could offer a credible reference for the shear mechanism of such economical and environmentally friendly precast steel-UHPC composite beams in accelerated bridge construction.

Nonlinear impacts of temperature on antibiotic resistance in Escherichia coli

The increase in bacterial antibiotic resistance poses a significant threat to the effectiveness of antibiotics, and there is growing evidence suggesting that global warming may speed up this process. However, the direct influence of temperature on the development of antibiotic resistance and the underlying mechanisms is not yet fully understood. Here we show that antibiotic resistance exhibits a nonlinear response to elevated temperatures under the combined stress of temperatures and antibiotics. We find that the effectiveness of gatifloxacin against Escherichia coli significantly diminishes at 42 °C, while resistance increases 256-fold at 27 °C. Additionally, the increased transcription levels of genes such as marA, ygfA, and ibpB with rising temperatures, along with gene mutations at different sites, explain the observed variability in resistance patterns. These findings highlight the complexity of antibiotic resistance evolution and the urgent need for comprehensive studies to understand and mitigate the effects of global warming on antibiotic resistance.

Nitrite and sulfide stress affects physiological and metabolic functions of gills in crab Eriocheir sinensis

Nitrite and sulfide are environmental factors that affect crabs survival and immunity. Gills are important respiratory and immune organs of Chinese mitten crabs Eriocheir sinensis, and both nitrite and sulfide can affect the physiological function stability of gill tissues. The present study investigated the acute toxicity of 10 mg/L nitrite and 5 mg/L sulfide, single and in combination, on the morphological, immune, osmoregulatory, and metabolic functions of the gill tissues of Chinese mitten crab. Both single and combined stressors were observed to disrupt the structural integrity of gill tissues. Oxidative stress-related indicators, including MDA, H2O2, and ·O2− content, exhibited an increase in all stress groups. The activities of antioxidant enzymes such as CAT and SOD and the expression levels of antioxidant genes fluctuated to varying degrees in all stress groups. The expression levels of osmotic regulating genes such as aqp, vatp, and nhe increased, as did the expression levels of lipid metabolism-related genes such as pparγ, rxr, fabp1, gyk, and dgat1. Furthermore, nitrite and sulfide stress affected the functions of metabolic pathways related to arachidonic acid, linoleic acid, D-amino acids, phenylalanine, and other substances in Chinese mitten crabs gill tissues. Additionally, the study identified 18 potential biomarkers related to stress responses. The nitrite and sulfide stressors disrupt the structure of crab gill tissues, cause osmoregulation disturbances, immune dysfunction, induce amino acid and lipid metabolic changes in gill tissue.

Unravelling the impact of drought and salt stresses on Thymus pannonicus: Morpho-physiological and biochemical insights

This research assesses the effects of drought and salt stresses applied individually or in combination on Thymus pannonicus, a resilient perennial herb native to the Pannonian vegetation region. Our experiment aimed to comprehensively evaluate morphological, physiological, and biochemical parameters of the thyme subjected to two levels of soil water capacity (SWC) - 70 % (control and salt stress) and 40 % (drought stress and combined stresses) - along with two salinity levels, 0 mM NaCl (control and drought stress) and 60 mM NaCl (salt stress and combined stresses). The plants exhibited significant responses to all the studied parameters under 40 % SWC in both treatments, demonstrating notable reductions in shoot and root parameters. In contrast, salt treatment at 60 mM had a minimal impact on growth. A stability in photosynthetic pigment composition was observed in all treatment, whereas a notable decrease (p < 0.05) in relative water content was seen in drought-stressed treatments compared to the to the control. Essential oil contents were higher in the control (0.91 ml/100g DW) but significantly declined (p < 0.05) under drought stress and combined stresses conditions (0.49 ml/100g DW and 0.53 ml/100g DW respectively). Particularly, the GC-MS analysis revealed a significant decrease (p < 0.05) in thymol and carvacrol content for the drought-stressed treatments. Substantial reductions were evident for the total polyphenol concentration and antioxidant capacity under the combined stress treatment, measuring 101.49 mg GAE/g DW and 106.57 AAE/g DW, respectively. Interestingly, the HPLC analysis indicated the highest levels of rosmarinic acid and caffeic acid in the drought-stressed treatment, while the lowest ones were recorded in the combined stress treatment. These findings indicated the responses of Thymus pannonicus to environmental stressors, emphasizing the need for further investigations for a comprehensive understanding of salinity effects.

Insights into the responses of Akabare chili landraces to drought, heat, and their combined stress during pre-flowering and fruiting stages

Drought, heat, and their combined stress have increasingly become common phenomena in horticulture, significantly reducing chili production worldwide. The current study aimed to phenotype Akabare chili landraces (Capsicum spp.) in climate chambers subjected to drought and heat treatments during their early generative stage, focusing on PSII efficacy (Fv/Fm), net photosynthetic rate (PN), stomatal conductance (gs), leaf cooling, and biomass production. Six landraces were examined under heat and control conditions at 40/32 °C for 4 days and at 30/22 °C under drought and control conditions followed by a 5-day recovery under control conditions (30/22 °C, irrigated). Two landraces with higher (>0.77) and two with lower (<0.763) Fv/Fm during the stress treatments were later evaluated in the field under 55-day-long drought stress at the fruiting stage. In both treatments, stress-tolerant landraces maintained high Fv/Fm, PN, and better leaf cooling leading to improved biomass compared to the sensitive landraces. Agro-morpho-physiological responses of the tolerant and sensitive landraces during the early generative stage echoed those during the fruiting stage in the field. A climate chamber experiment revealed a 13.9 % decrease in total biomass under heat stress, a further 21.5 % reduction under drought stress, and a substantial 38.7 % decline under combine stress. In field conditions, drought stress reduced total biomass by 28.1 % and total fruit dry weight by 26.2 %. Tolerant landraces showed higher Fv/Fm, demonstrated better wilting scores, displayed a higher chlorophyll content index (CCI), and accumulated more biomass. This study validated lab-based results through field trials and identified two landraces, C44 and DKT77, as potential stress-tolerant genotypes. It recommends Fv/Fm, PN, and CCI as physiological markers for the early detection of stress tolerance.

Moderating Effect of General Self-Efficacy on the Relationship between Pregnancy Stress, Daily Hassles Stress, and Preterm Birth Risk in Women Experiencing Preterm Labor: A Cross-Sectional Study.

This study investigated the moderating role of general self-efficacy (GSE) on how stress caused by pregnancy and daily hassle affect the risk of preterm birth (PTB) in women experiencing preterm labor. This cross-sectional study included 196 pregnant women experiencing preterm labor before 37 weeks of gestation. We used IBM SPSS Statistics 27 and employed Hayes process macro version 4 (model 1) and hierarchical regression to analyze the moderating effect of GSE on the relationship between pregnancy stress, daily hassle stress, and PTB risk. Stress caused by pregnancy and daily hassle was positively correlated to PTB risk (r = .54, p < .001; r = .25, p < .001, respectively). While GSE did not significantly correlate with pregnancy stress, it negatively correlated with daily hassle stress (r = - .19, p = .009). GSE significantly moderated the relationship between combined stressors and PTB risk. As GSE levels increased, escalation in PTB risk in response to increasing stress levels was a more pronounced, highlighting a complex interaction between higher GSE levels and response to escalating stress levels. This model accounted for 39.5% of the variance in the PTB risk. Higher GSE may amplify the impact of stress on PTB risk, rather than mitigate it, which suggests a more nuanced role of GSE in the stress response of pregnant women at risk of preterm labor. GSE should be considered in care strategies, and managing its impact on stress perception and responses in pregnant women is crucial.

The ectomycorrhizal fungus Paxillus involutus positively modulates Castanea sativa Miller (var. Marsol) responses to heat and drought co-exposure

Castanea sativa Miller, a high-valuable crop for Mediterranean countries, is facing frequent and prolonged periods of heat and drought, severely affecting chestnut production. Aiming to tackle this problem, this study unraveled the influence of mycorrhizal association with the fungi Paxillus involutus (Batsch) on young chestnut plants' responses to combined heat (42 °C; 4 h/day) and drought (no irrigation until soil moisture reached 25%) over 21 days of stress exposure. Heat stress had no harmful effects on growth, photosynthesis, nor induced oxidative stress in either mycorrhizal (MR) or non-mycorrhizal (NMR) chestnut plants. However, drought (alone or combined) reduced the growth of NMR plants, affecting water content, leaf production, and foliar area, while also hampering net CO2 assimilation and carbon relations. The mycorrhizal association, however, mitigated the detrimental effects of both stresses, resulting in less susceptibility and fewer growth limitations in MR chestnut plants, which were capable of ensuring a proper carbon flow. Evaluation of the oxidative metabolism revealed increased lipid peroxidation and hydrogen peroxide levels in NMR plants under water scarcity, supporting their higher susceptibility to stress. Conversely, MR plants activated defense mechanisms by accumulating antioxidant metabolites (ascorbate, proline and glutathione), preventing oxidative damage, especially under the combined stress. Overall, drought was the most detrimental condition for chestnut growth, with heat exacerbating stress susceptibility. Moreover, mycorrhizal association with P. involutus substantially alleviated these effects by improving growth, water relations, photosynthesis, and activating defense mechanisms. Thus, this research highlights mycorrhization's potential to enhance C. sativa resilience against climate change, especially at early developmental stages.

Impact of high temperature and drought stress on the microbial community in wolf spiders

High temperatures and drought present significant abiotic challenges that can limit the survival of many arthropods, including wolf spiders, which are ectothermic and play a crucial role in controlling pest populations. However, the impact of these stress factors on the microbiota of spiders remains poorly understood. In this study, we utilized 16 S rRNA gene sequencing to explore the diversity and composition of bacterial communities within Pardosa pseudoannulata under conditions of high temperature and drought stress. We found that Firmicutes, Bacteroidetes, and Proteobacteria were the predominant bacterial phyla present. Analyses of alpha diversity indicated an increase in bacterial diversity under combined stress conditions, as reflected by various diversity indices such as Ace, Chao1, Shannon, and Simpson. Furthermore, co-occurrence network analysis highlighted intricate interactions among the microbial taxa (e.g., Enterobacter, Chitinophaga, and Eubacterium), revealing the adaptive complexity of the spider's microbiome to environmental stress. Functional prediction analysis suggested that combined stress conditions might enhance key metabolic pathways, particularly those related to oxidative phosphorylation and amino acid metabolism. Using Random Forest analysis, we determined that changes in three heat shock proteins were largely attributed to variations in bacterial communities, with Firmicutes being notably influential. Collectively, this in-depth analysis offers novel insights into the responses of microbial communities within spider microbiomes to combined abiotic stresses, providing valuable information for understanding extreme climate impacts and informing ecological management strategies.

The effect of Arbuscular Mycorrhizal fungal species Funneliformis mosseae and biochar against Verticillium dahliae in pepper plants under salt stress

Both biotic and abiotic stress factors play an important role in reducing the growth and productivity of many crops. In this study, the effects of arbuscular mycorrhizal (AM) fungi and biochar (Bc) were investigated against Verticillium dahliae (Vd) disease in pepper plants grown under salt stress. These effects were evaluated on enzyme activities, salt tolerance, disease severity, plant growth and physiological characteristics. In this study, pepper was treated with 2% biochar, Funneliformis mosseae (Fm), Vd and different concentrations of salt (0 mM, 50 mM, 100 mM, 150 mM). The interaction of Fm and 2% Bc significantly increased the morphological parameters of the plant and the plant tolerated salt and Vd under combined high stress conditions of biotic (Vd) and abiotic (salt) stresses. It was also shown that Fm had a different effect than Bc on the membrane injury index (MII; %) and had a significant effect on leaf relative water content (LRWC; %). In addition, Vd increased mycorrhizal reliance, with the higher spore density of AMF higher disease severity observed in treatments involving Fm and Fm + Bc. Furthermore, phenol and antioxidant values were altered in Vd treatments, while Fm decreased CAT enzyme activation. Therefore, this study supports that AMF + biochar used in sustainable agriculture increases plant resistance to the soil pathogen (V. dahliae) and the salt stresses.

Theoretical investigation of threshold pressure gradient in hydrate-bearing clayey-silty sediments under combined stress and local thermal stimulation conditions

Due to the characteristics of smaller grain size and higher clay mineral content, the threshold pressure gradient (TPG) exists in multi-phase flow within hydrate-bearing clayey-silty sediments (HBCSS), which significantly affects the gas production from hydrate reservoirs. However, multi-phase flow through HBCSS relates to thermal-hydrological-mechanical coupling, leading to the understanding of TPG in HBCSS with complex pore structures and hydrate distribution is unclear. In this study, a theoretical TPG model of HBCSS is developed by considering the combined influences of effective stress, temperature increase, pore structures, hydrate saturation and its growth patterns. The proposed TPG model has been thoroughly validated using available experimental data. Moreover, the parameter sensitivity analysis is conducted based on this derived model, revealing a positive correlation between TPG and both effective stress and temperature increase. While TPG generally increases with higher hydrate saturation when other parameters are held constant, the relationship between TPG and hydrate saturation is non-monotonic. This observation suggests that TPG is impacted not only by hydrate saturation but also by other factors, including hydrate growth patterns and pore structures. The findings of this study establish a theoretical foundation for characterizing the nonlinear flow behavior during hydrate exploitation.

Blue light as an important factor increasing plant tolerance to acute photooxidative stress

Previous studies have confirmed the stimulating effect of blue light on phenolic compound accumulation and emphasized that sufficient dose of blue light is essential for biosynthesis of B-dihydroxylated flavonoids with enhanced antioxidant properties (under UV-lacking conditions). This study investigates the importance of blue light and complex role of phenolic compounds in plant tolerance against acute photooxidative stress. Hordeum vulgare (L. Cv. Bojos) seedlings were acclimated to different light spectra (blue, green:red 1:1, and white composed of blue:green:red 1:1:1) at total irradiance 400 µmol.m−2.s−1. Subsequently, they were subjected to a 3-hour combined stress induced by high photosynthetically active (850–950 µmol.m−2.s−1) and UV-B (2.0–2.5 W.m−2) radiation. Content of flavonoids, expression of genes involved in their biosynthesis (phenylalanine ammonia-lyase, chalcone synthase, flavonoid 3′-hydroxylase), and antioxidant activity of plant extracts were significantly highest in plants acclimated to blue light. As an indicator of reactive oxygen species interaction with biomolecules, the content of lipid hydroperoxides was estimated. It was demonstrated that plants acclimated to blue light revealed significantly lower extent of lipid peroxidation compared to those acclimated to white or green:red light. Plants exposed to combined light-induced stress for 3 hours exhibited pronounced disruption of PSII function: FV/FM tended to decrease proportionally with decreasing amount of blue photons in the treatments. Additionally, stress exposure upregulated the expression of genes related to phenolic compounds but not genes encoding antioxidant enzymes. We confirmed higher resistance of plants acclimated to blue light and presume that phenolic compounds are significantly involved in protection during the acute phase of stress.

Insight into response mechanism of aerobic granular sludge to combined nanoparticle stress: Nitrogen removal, microbial community and heavy metal resistance genes

Multiple nanoparticles presented in wastewater treatment plants can produce comprehensive ecotoxicity. In this study, copper oxide nanoparticles (nCuO) and zinc oxide nanoparticles (nZnO) were investigated for their co-toxicity to aerobic granular sludge (AGS) systems. The combined stress of nCuO and nZnO performed significant antagonistic effects on nitrogen removal both under acute and chronic stress. Under chronic stress, nCuO and nZnO co-existence performed significant antagonistic effects on cell membrane, adenosine triphosphate (ATP) activity and microbial community structure. PICRUSt analysis indicated that nCuO (15 mg/L) co-existence alleviated nZnO (10 mg/L) inhibition on energy production and membrane transport metabolic pathways. In addition, nCuO addition to single nZnO weakened the toxicity of nZnO to nitrogen metabolism, glucose metabolism, and electron transfer genes, contributing to an alleviation in nitrogen removal inhibition. As compared with individual stress, combined stress decreased Cu(II) release from nCuO, but increased Zn(II) release from nZnO. The combination of nCuO and nZnO increased zinc resistance gene amplification and czcC gene proportion, and promoted Zn(II) efferent from cells, also with AGS resistance.