Low Stress Conditions Research Articles

Exploring Stable Low Soil Phosphorous Stress Tolerance in Rice Using Novel Allele Recombination From Oryza rufipogon

ABSTRACTAdvent of changing climatic conditions along with nutrient deficient soils adversely affects the environment for the rice production. Wild introgression lines derived from KMR3 and Oryza rufipogon population were evaluated in six environments, including optimum and low phosphorus stress condition. Significant differences among the introgression lines were observed for plant height, tiller number, biomass, grain yield per plant, days to 50% flowering and harvest index across the environments. Based on grain yield observed under optimum phosphorus and limited phosphorus (P stress condition), eight stress tolerance indices were calculated and found STI and GMP are the better indices to discriminate among tolerant and susceptible genotypes, and correlation studies also confirmed the significant association between STI and GMP. Cluster analysis based on stress tolerance indices revealed three different clusters distinguishing genotypes based on their stable performance on yield related traits. AMMI and GGE biplot analysis to identify the stable performance across environments revealed NSR60, NSR101, NSR105, NSR85 and NSR86 as high grain yielders, whereas NSR135, NSR5 and NSR88 as stable performers. WAASBY‐based stability analysis on multiple traits (MTSI) showed NSR135, NSR79 and NSR18 with lowest MTSI, indicating their high stability and high mean performance compared with parent KMR3. Further genotyping for low P tolerance gene (PSTOL1) and grain yield genes (Gn1a, SPIKE, TGW6, DEP1 and OsSPL14) using allele specific markers showed that the desirable alleles of SPIKE, Gn1a and TGW6 were derived from wild parent O. rufipogon. Low P tolerance allele PSTOL1 was absent in recurrent parent KMR3; however, the introgression lines harboured desirable alleles, which were derived from O. rufipogon. Further mapping studies will help to identify a significant potential QTLs/gene for low P tolerance from O. rufipogon. Wild introgression lines, NSR85, NSR124, NSR80, NSR54, NSR86 and NSR88, were found as the high yielding and nutrient stress tolerant genotypes, which can be used as potential donors in future breeding programmes for low P stress tolerance.

A FRACTAL PORE-SCALE MODEL OF STRESS-DEPENDENT THERMAL CONDUCTIVITY IN A RECTANGULAR CROSS-SECTION TREE-LIKE MICROFRACTURE NETWORK

Stress is an important external element influencing effective thermal conductivity (ETC). However, previous theoretical investigations of stress-dependent effective thermal conductivity have used a simplified parallel plate model, overlooking the complex structure of rock fracture networks. Therefore, this paper establishes a new fractal model for the stress-dependent ETC of a rectangular cross-section tree-like microfracture network. The model derives a constitutive equation between the stress-dependent ETC and the microscopic geometry structural parameters of the microfracture network. The model’s validity is confirmed by the error of less than 0.291% between the theoretical predictions and the experimental data. The influence of geometry structural parameters of the microfracture network (length ratio, width ratio, height ratio, angle, total number of branches and ratios of soft part, hard part, etc.) on the ETC under the low-stress state has been analyzed. It was discovered that the soft part of the rock microfracture network has the most impact on ETC. The fractal pore-scale model clarifies heat transfer mechanism in rock microfracture network under effective stress, with each parameter physically defined and independent of empirical constants.

Acidic Stress Induces Cytosolic Free Calcium Oscillation, and an Appropriate Low pH Helps Maintain the Circadian Clock in Arabidopsis

Acidic stress is a formidable environmental factor that exerts adverse effects on plant growth and development, ultimately leading to a potential reduction in agricultural productivity. A low pH triggers Ca2+ influx across the plasma membrane (PM), eliciting distinct responses under various acidic pH levels. However, the underlying mechanisms by which Arabidopsis plant cells generate stimulus-specific Ca2+ signals in response to acidic stress remain largely unexplored. The experimentally induced stimulus may elicit spikes in cytosolic free Ca2+ concentration ([Ca2+]i) spikes or complex [Ca2+]i oscillations that persist for 20 min over a long-term of 24 h or even several days within the plant cytosol and chloroplast. This study investigated the increase in [Ca2+]i under a gradient of low pH stress ranging from pH 3.0 to 6.0. Notably, the peak of [Ca2+]i elevation was lower at pH 4.0 than at pH 3.0 during the initial 8 h, while other pH levels did not significantly increase [Ca2+]i compared to low acidic stress conditions. Lanthanum chloride (LaCl3) can effectively suppress the influx of [Ca2+]i from the apoplastic to the cytoplasm in plants under acid stress, with no discernible difference in intracellular calcium levels observed in Arabidopsis. Following 8 h of acid treatment in the darkness, the intracellular baseline Ca2+ levels in Arabidopsis were significantly elevated when exposed to low pH stress. A moderately low pH, specifically 4.0, may function as a spatial-temporal input into the circadian clock system. These findings suggest that acid stimulation can exert a continuous influence on intracellular calcium levels, as well as plant growth and development.

Effect of Cr:C ratio on open three-body wear resistance of squeeze cast high chromium cast iron

A series of high chromium white cast iron (HCCI) alloys with varying Cr:C ratios were designed and fabricated through the squeeze casting process. This study investigates the effect of the Cr:C ratio on the mechanical properties, microstructure, phase diagram, and both low-stress and high-stress abrasion performance of HCCIs. Alloys with a very high Cr:C ratio exhibited better impact toughness but poorer hardness. Scanning electron microscopy (SEM) and phase diagram calculations elucidated the influence of the Cr:C ratio on microstructure, carbide volume fraction, and carbide type. Abrasion resistance was evaluated using impact abrasive wear (high-stress) and rubber-wheel (low-stress) abrasion on quartzite in open three-body wear. Comprehensive assessments under impact abrasive wear and rubber-wheel abrasive wear conditions suggest that the alloy achieves optimal abrasion resistance with a Cr:C ratio ranging from 8 to 11. Post-wear analysis reveals that surface damage varies between high-stress and low-stress conditions. The microstructure of squeeze HCCIs is significantly influenced by the Cr:C ratio, resulting in diverse operative wear mechanisms, including micro-cutting and micro-fracture. Successful adjustment of the Cr:C ratio led to the attainment of a nearly eutectic HCCIs composition suitable for squeeze casting.

Using a virtual reality game to train biofeedback-based regulation under stress conditions.

Physiological regulation strategies can be effective in reducing anxiety. However, while these strategies are often learned and practised under low-stress conditions, they are more likely to be required under conditions of high stress. We created virtual reality (VR) biofeedback games to both teach participants a breathing technique and then practise that technique under stress. We present two studies: the first provides a proof of concept, demonstrating that participants can apply the breathing technique during stress, with a significant lowering of both respiration rate and increase in heart rate variability (HRV) under stress (p < .001). The second study explicitly evaluated the effectiveness of training by comparing trained and untrained groups. Training was associated with a significantly greater HRV (p = .008) under stress. In within-group comparisons of HRV during stress compared to a baseline stressor presented before training, the trained group showed a significantly greater increase compared to untrained controls (p = .025). Our results show the feasibility and potential effectiveness of VR-based games for biofeedback training under experimentally applied stress. This may offer the opportunity for clinical techniques to more closely reflect the circumstances under which those techniques will be required.

Preparation and properties of ZTA/alloyed high manganese steel composites

In the long-term use of high manganese steels, it is not desirable to achieve wear resistance by austenite deformation strengthening alone. The wear resistance of high manganese steel is much lower than that of ordinary wear-resistant steel under medium and low stress conditions. Improving the instability of wear resistance caused by defects in high manganese steels is an important problem to be solved in current industrial production. In this study, a new type of high manganese alloy with high hardness and high wear resistance was prepared by multi-alloying with Cr-W-Mo elements on the basis of 20Mn1.2C. ZTA ceramic particles reinforced high manganese steel composites were prepared by selecting high manganese steel materials with excellent mechanical properties as the metal matrix of ceramic reinforced metal matrix composites. The Cr-W-Mo multi-alloyed high manganese alloys are mainly composed of a mixed austenite and ferrite matrix, M3C-type cementite and M6C-type carbides. The Cr2W6Mo6 sample has the best overall mechanical properties. Its hardness reached 49.8 HRC, which is 1.20 times higher than that of the Cr2 sample. The mass loss was 0.2571 g, which is 79.92% of the Cr16 sample (0.3217 g). The ZTA ceramic particles were well composited with the alloyed high manganese steel matrix, and the thickness of the interfacial layer was 20-30 μm, with the formation of Mn2AlO4 and (Fe, Mn)2SiO4, and (Al, Cr)2O3 in the interfacial layer. The best abrasion resistance was obtained at a ZTA content of 40 vol.%. The mass loss was 0.1669 g, which is 51.88% of the Cr16 material (0.3217 g).

Identifying crucial financial markets in the flows of cross-border capital – evidence from China's financial risk network

With the increasing openness of China's financial markets, it is important to address cross-border capital risks. This paper first calculates the stress indicators of financial markets by 24 variables, and then utilizes the Diebold-Yilmaz connectedness approach to examine the spillover effects among the volatility of cross-border capital and the stress indicators of various financial markets. We show both the real estate and stock market are crucial for cross-border capital flow. Using the rolling window method, we find significant time-varying spillovers between cross-border capital and financial markets, which peak during the periods with significant events such as the global financial crisis, the COVID-19 epidemic, and the shift in currency regime. This paper further applies the Markov-switching autoregressive model to identify three different states for the synthetic financial stress. After re-analyzing the subsample data, we observe that stock and real estate markets play significant roles in the low-stress state, foreign exchange and real estate markets in the medium-stress state, and stock and money markets in the high-stress state.

Use of light response curve parameters to estimate gross primary production capacity from chlorophyll indices of global observation satellite and flux data

The photosynthetic rate has a nonlinear relationship with PAR during the day. We previously developed an algorithm for estimating GPP capacity, which is defined GPP under low-stress condition, using light response curves (LRCs). In this study, we studied the characteristics of LRC parameters of the initial slope and the maximum gross photosynthesis rate (Pmax), and formulas to calculate Pmax from the relationship between the chlorophyll index of the green and near-infrared (NIR) bands (CIgreen) and the GPP capacity at PAR = 2000 μmol m−2 s−1 (GP2000) for nine vegetation types spanning tropical to subarctic climates on the Eurasian and North American continents using eddy covariance flux measurements and Moderate Resolution Imaging Spectrometer (MODIS) data. The slope of the relationship between CIgreen and GP2000 was highest for sites dominated by herbaceous plants such as open shrubland, savanna, and cropland (rice paddy); it was lower at sites dominated by woody plants. The yearly GPP/GPP capacity ratio was close to one in flux data. When the method was applied to satellite data, the daily GPP capacity exhibited a similar seasonal pattern to that of the Flux GPP and MODIS GPP products. Under high dryness conditions, Flux GPP showed the drop from the GPP capacity estimated from CIgreen and diurnal PAR data around noon, and they were nearly identical during the early morning and late afternoon. The instantaneous GPP capacity could be considered the baseline of the instantaneous GPP with stress-free conditions and important for quantifying midday depression at the sub-day scale.

Effects of Environmental Enrichment on the Growth, Gonadal Development, and Welfare of the Chinese Hooksnout Carp (Opsariichthys bidens)

To investigate the effects of environmental enrichment on the growth and welfare level of the Chinese hooksnout carp (Opsariichthys bidens), an experiment was carried out for 56 d with four types of enrichment environments: low-density physical enrichment, high-density physical enrichment, low-density social enrichment, and high-density social enrichment. The experimental results revealed that both physical and social enrichment treatments positively affected the growth and gonadal development of O. bidens. The physical enrichment treatment was found to increase the antioxidants’ content, such as CAT, SOD, and GSH, in the liver of O. bidens. Moreover, this treatment was able to lead to a reduction in MDA content and enhancement of the fish’s antioxidant capabilities. Behavioral observations, cortisol level analysis, and pcna gene expression analysis indicated that the physical enrichment treatment redused the clustering, aggression, and stress behaviors of O. bidens, maintaining them in a low-stress state. In most respects, the high-density physical enrichment has more positive effects than the low-density one. In contrast, the social enrichment treatments resulted in higher stress levels for O. bidens.

Twins and β0 precipitation effects on the lamellar degradation in TNM alloy during creep

In this paper, the microstructure instability of the TNM alloy during creep at 800 °C under 150 MPa and 250 MPa was investigated. The results indicate that, both β0 precipitation (inside lamellae) and primary γ twins formation are initiated during the second stage of creep. Compared to low creep stress conditions (150 MPa), high creep stress conditions (250 MPa) accelerate the initiation of the third stage of creep, inducing the precipitation of ω0 phase and secondary twins. The nanoscale ω0 particles formed inside β0 or at the interface of the β0/β0. The intersection of secondary γ twins and α2 lamellae leads to stress concentration and dislocation accumulation, providing nucleation points for β0 phase and promoting the precipitation of β0 within α2 lamellae. The precipitation of the secondary γ twin introduces a unit dislocation of 1/3 [111]γ in the (111) atomic planes, promoting the movement of adjacent atomic planes within the (111) atomic planes. The 1/3 [111]γ dislocations will dissociate into two partial dislocations via 1/3 [111]γ→1/4 [11 1‾]γT +1/9 [0 1‾1]γM. The adjacent atomic planes of the γ matrix and secondary γ twin can transformation to β0 through shear along 1/9 [0 1‾1]γM and 1/4 [11 1‾]γT, respectively. The size and content of β0 phase significantly increase in the third stage of high creep stress, accelerating the decomposition and fragmentation of the α2 lamellae, leading to rapid creep failure.

Damage deformation properties and acoustic emission characteristics of hard-brittle rock under constant amplitude cyclic loading

In order to study the deformation and damage characteristics of the limestone specimens with high strength and brittleness under constant amplitude cyclic loading, the deformation and the acoustic emission (AE) characteristics were analysed, and the relationship between them was sought. The damage variables under different amplitude cyclic loading were defined by AE counts. The results showed that the radial deformation of the limestone specimens was more sensitive and unstable than the axial deformation. The concept of apparent residual strain was proposed to describe the specimen deformation characteristics, and it resulted that the radial apparent residual strain produced at higher stress state would recover at lower stress state. The limestone specimens showed obvious Kaiser effect and Felicity effect under cyclic loading. When the upper limit of the cyclic loading was close to the peak stress of the specimen, the AE counts generated in unloading sections were almost the same as that in the loading sections. The damage was increased as the amplitude and the stress level increased and the unloading process at higher stress level would also lead to the aggravation of damages. Specimens would absorb more energy under cyclic loading than under uniaxial loading. Reasonable driving parameters should be controlled in underground excavation practice, to ensure that the stress level of surrounding rock mass in a periodic stress state is located before peak stress and such that to limit the occurrence of rock burst to a certain extent.

A stress-induced source of phonon bursts and quasiparticle poisoning

The performance of superconducting qubits is degraded by a poorly characterized set of energy sources breaking the Cooper pairs responsible for superconductivity, creating a condition often called “quasiparticle poisoning”. Both superconducting qubits and low threshold dark matter calorimeters have observed excess bursts of quasiparticles or phonons that decrease in rate with time. Here, we show that a silicon crystal glued to its holder exhibits a rate of low-energy phonon events that is more than two orders of magnitude larger than in a functionally identical crystal suspended from its holder in a low-stress state. The excess phonon event rate in the glued crystal decreases with time since cooldown, consistent with a source of phonon bursts which contributes to quasiparticle poisoning in quantum circuits and the low-energy events observed in cryogenic calorimeters. We argue that relaxation of thermally induced stress between the glue and crystal is the source of these events.

Combined salt and low nitrate stress conditions lead to morphophysiological changes and tissue-specific transcriptome reprogramming in tomato

Despite intense research towards the understanding of abiotic stress adaptation in tomato, the physiological adjustments and transcriptome modulation induced by combined salt and low nitrate (low N) conditions remain largely unknown. Here, three traditional tomato genotypes were grown under long-term single and combined stresses throughout a complete growth cycle. Physiological, molecular, and growth measurements showed extensive morphophysiological modifications under combined stress compared to the control, and single stress conditions, resulting in the highest penalty in yield and fruit size.The mRNA sequencing performed on both roots and leaves of genotype TRPO0040 indicated that the transcriptomic signature in leaves under combined stress conditions largely overlapped that of the low N treatment, whereas root transcriptomes were highly sensitive to salt stress. Differentially expressed genes were functionally interpreted using GO and KEGG enrichment analysis, which confirmed the stress and the tissue-specific changes. We also disclosed a set of genes underlying the specific response to combined conditions, including ribosome components and nitrate transporters, in leaves, and several genes involved in transport and response to stress in roots. Altogether, our results provide a comprehensive understanding of above- and below-ground physiological and molecular responses of tomato to salt stress and low N treatment, alone or in combination.

Mining key genes associated with phosphorus deficiency through genome-wide identification and characterization of cucumber SPX family genes

BackgroundProteins harboring the SPX domain are crucial for the regulation of phosphate (Pi) homeostasis in plants. This study aimed to identify and analyze the entire SPX gene family within the cucumber genome.ResultsThe cucumber genome encompassed 16 SPX domain-containing genes, which were distributed across six chromosomes and categorized into four distinct subfamilies: SPX, SPX-MFS, SPX-EXS and SPX-RING, based on their structure characteristics. Additionally, gene duplications and synteny analysis were conducted for CsSPXs, revealing that their promoter regions were enriched with a variety of hormone-responsive, biotic/abiotic stress and typical P1BS-related elements. Tissue expression profiling of CsSPX genes revealed that certain members were specifically expressed in particular organs, suggesting essential roles in cucumber growth and development. Under low Pi stress, CsSPX1 and CsSPX2 exhibited a particularly strong response to Pi starvation. It was observed that the cucumber cultivar Xintaimici displayed greater tolerance to low Pi compared to black-spined cucumber under low Pi stress conditions. Protein interaction networks for the 16 CsSPX proteins were predicted, and yeast two-hybrid assay revealed that CsPHR1 interacted with CsSPX2, CsSPX3, CsSPX4 and CsSPX5, implying their involvement in the Pi signaling pathway in conjunction with CsPHR1.ConclusionThis research lays the foundation for further exploration of the function of the CsSPX genes in response to low Pi stress and for elucidating the underlying mechanism.

Failure Analysis of Dissimilar Metal Welds between Ferritic Heat Resistant Steels and Austenitic Stainless Steels in Power Plant

This study analysed the failure of dissimilar metal welds (DMWs) between ferritic heat resistant steels and austenitic stainless steels and investigated its influencing factors by means of numerical simulation, microstructure characterization and mechanical property test. Under the long-term high-temperature service condition in practical power plant, the DMW failure mode was along the interface between nickel-based weld metal (WM) and ferritic heat resistant steel, and the failure mechanism was stress/strain concentration, microstructure degradation and oxidation coupling acting on the interface. The numerical simulation results show that interface stress/strain concentration was due to the differences in coefficient of thermal expansion and creep strength, and the degree of stress/strain concentration was related to service time. The ferrite band formed at the WM/ferritic steel interface was prone to cracking, attracting the fracture along the interface. The interface crack allowed oxidation to develop along the WM/ferritic steel interface. During long-term service, the interface stress/strain concentration, microstructure and oxidation all evolved, which synergistically promoted interface failure of DMW. However, only under the long-term service of low stress conditions could trigger the interface failure of DMW. Meanwhile, long-term service would reduce the mechanical strength and plasticity of DMW.

Evaluation of arsenic phytoremediation potential in Azolla filiculoides Lam. plants under low pH stress conditions

The Azolla filiculoides plants were challenged with different arsenic (As) concentration under low pH stress conditions. The growth rate and doubling time of the plants were severely affected by higher As treatments at pH 5.00 when compared with stress pH 4.75 treatments. Hence, pH 5.00 was considered for further studies. In 10–30 μM As treated cultures, after 6 days, the relative growth rate (RGR) of Azolla plants was significantly reduced and in higher concentration of As, the RGR was negatively regulated. The root trait parameters were also significantly affected by increasing concentrations of As. Further, photosynthetic performance indicators also show significant decline with increasing As stress. Overall, the plants treated with 40 and 50 μM of As displayed stress phenotypes like negative RGR, reduced doubling time and root growth, browning of leaves and root withering. The total proline, H2O2, POD and Catalase activities were significantly affected by As treatments. Meantime, 30 μM of As treated cultures displayed 15 μg/g/Fw As accumulation and moderate growth rate. Thus, the Azolla plants are suitable for the phytoremediation of As (up to 30 μM concentration) in the aquatic environment under low pH conditions (5.00). Furthermore, the transcriptome studies on revealed that the importance of positively regulated transporters like ACR3, AceTr family, ABC transporter super family in As (10 μM) stress tolerance, uptake and accumulation. The transporters like CPA1, sugar transporters, PiT were highly down-regulated. Further, expression analysis showed that the MATE1, CIP31, HAC1 and ACR3 were highly altered during the As stress conditions.

Derailment is associated with increased depressed mood at lower levels of stress: An experimental approach

BackgroundAs an emergent developmental construct, derailment – an individual difference hallmarked by a temporal discordance of the self – has been positively associated with depressive features, though less is known about the role of stress in this relationship. The aim of the present study was to explore the interaction between derailment and subjective stress on depressed mood. Methods265 adults recruited through Prolific – a crowd sourcing platform were first tasked with completing baseline measures, then were randomly assigned to a low stress or high stress condition. We utilized an adapted version of the Online Trier Stress Test to manipulate stress levels. Next, depressed mood and post-test perceived stress were measured. We analyzed data through STATA using a two-tailed independent samples t-test and multiple linear regression. ResultsFindings suggested the experimental manipulation increased subjective stress within the high stress condition compared to the low stress condition (Mdiff = 36.14, SE = 4.4, t = 8.21, p < .001). Further, we found the interaction between derailment and stress conditions was associated with increased depressed mood (β = −0.11, SE = 0.05, p = .038, R2 = 0.5). Notably, we found significant between-condition differences in depressed mood for those who endorsed either low (d = 0.22, SE = 0.07, p = .003) or moderate levels of derailment (d = 0.11, SE = 0.05, p = .033), but not for those who endorsed high levels of derailment (d = 0.01, SE = 0.07, p = .92). LimitationsThis study utilized self-report measures, which may be susceptible to biased responses. ConclusionsDerailment may play a role in the persistence of depressed mood regardless of varying contexts of stress.

Numerical simulation of blasting behavior of rock mass with cavity under high in-situ stress

With the shift of coal seam mining to the deep, the in-situ stress of coal and rock mass increases gradually. High ground stress can limit the generation of rock cracks caused by blasting, and blasting usually shows different crushing states than low stress conditions. In order to study the blasting expansion rule of rock mass with cavity under high ground stress and the rock mass fracture state under different side stress coefficients. In this paper, the effective range of blasting and the stress distribution under blasting load are analyzed theoretically. The RHT (Riedel-Hiermaier-Thoma) model is used to numerically simulate the blasting process of rock mass with cavity under different ground stress, and the influence of ground stress and lateral pressure coefficient on the crack growth of rock mass is studied. The results show that when there is no ground stress, the damage cracks in rock mass are more concentrated in the horizontal direction and the fracture development tends to the direction where the holes are located, which confirms the guiding effect and stress concentration effect of the holes in rock mass, which helps to promote the crack penetration between the hole and the hole. The length difference of horizontal and vertical damage cracks in rock mass increases with the increase of horizontal and vertical stress difference. Under the same lateral stress coefficient, the larger the horizontal and vertical stress difference is, the stronger the inhibition effect on crack formation is. For blasting of rock mass with high ground stress, the crack formation length between gun holes decreases with the increase of stress level, and the crack extends preferentially in the direction of higher stress. Therefore, the placement of gun holes along the direction of greater stress and the shortening of hole spacing are conducive to the penetration of cracks between gun holes and empty holes. The research can provide reference for rock breaking behavior of deep rock mass blasting.

Thermal effects of organic porous media on absorption and desorption behaviors of carbon dioxide

As a result of global warming, people are increasingly concerned about greenhouse gas emissions, particularly carbon dioxide (CO2). Many countries have been promoting carbon capture, storage (CCS) projects in order to alleviate climate degradation and achieve net zero carbon emissions. To study the thermal effects of organic porous media on CO2 absorption and desorption, molecular dynamics coupled with Monte Carlo (MDMC) were used in this study. A part of the CO2 molecules will be trapped within kerogen matrix due to its complex porous structure. The affinity of kerogen to CO2 facilitates CO2′s adsorption within the kerogen porous media, resulting in a heterogeneous distribution of CO2. The kerogen forms high potential energy peaks and low potential energy wells in the matrix, which provide preferred adsorption sites for CO2 in the porous space. The low stress state of CO2 also indicates that it prefers adsorption in the matrix as CO2 performs a lower potential energy state in the kerogen matrix than in the bulk phase. This study examines different thermal effects of kerogen, and results indicate that increasing CO2 thermal motion facilitates its absorption, while a high temperature matrix promotes CO2 desorption. Adsorbed layer provides resistance for CO2′s diffusion behaviors. The free energy of CO2′s diffusion is analyzed in relation to its mechanism, revealing that irregular thermal motion causes uncertainty in the adsorption capacity.

Phosphate solubilizing Aspergillus Niger PH1 ameliorates growth and alleviates lead stress in maize through improved photosynthetic and antioxidant response

Among the several threats to humanity by anthropogenic activities, contamination of the environment by heavy metals is of great concern. Upon entry into the food chain, these metals cause serious hazards to plants and other organisms including humans. Use of microbes for bioremediation of the soil and stress mitigation in plants are among the preferred strategies to provide an efficient, cost-effective, eco-friendly solution of the problem. The current investigation is an attempt in this direction where fungal strain PH1 was isolated from the rhizosphere of Parthenium hysterophorus which was identified as Aspergillus niger by sequence homology of the ITS 1 and ITS 4 regions of the rRNA. The strain was tested for its effect on growth and biochemical parameters as reflection of its potential to mitigate Pb stress in Zea mays exposed to 100, 200 and 500 µg of Pb/g of soil. In the initial screening, it was revealed that the strain has the ability to tolerate lead stress, solubilize insoluble phosphate and produce plant growth promoting hormones (IAA and SA) and other metabolites like phenolics, flavonoids, sugar, protein and lipids. Under 500 µg of Pb/g of soil, Z. mays exhibited significant growth retardation with a reduction of 31% in root length, 30.5% in shoot length, 57.5% in fresh weight and 45.2% in dry weight as compared to control plants. Inoculation of A. niger to Pb treated plants not only restored root and shoot length, rather promoted it to a level significantly higher than the control plants. Association of the strain modulated the physio-hormonal attributes of maize plants that resulted in their better growth which indicated a state of low stress. Additionally, the strain boosted the antioxidant defence system of the maize there by causing a significant reduction in the ascorbic acid peroxidase (1.5%), catalase (19%) and 1,1-diphenyl-2 picrylhydrazyl (DPPH) radical scavenging activity (33.3%), indicating a lower stress condition as compared to their non-inoculated stressed plants. Based on current evidence, this strain can potentially be used as a biofertilizer for Pb-contaminated sites where it will improve overall plant health with the hope of achieving better biological and agricultural yields.