Increasing H2O2 Concentration Research Articles

Exogenous application of gibberellic acid reduces antioxidant capacity of leaves, resulting in increased Tipburn damages in Lisianthus cultivars

Tipburn (calcium (Ca) deficiency disorder of new leaf tips) is a severe problem in horticultural crop production. Studies have focused on the fact that tipburn commonly occurs during bolting and shown that plants exhibited greater tipburn damage than the control when bolting was induced using exogenous gibberellic acid (GA). However, why exogenous GA application enhances tipburn damage and why tipburn occurs during bolting remains unclear. To address this knowledge gap, we investigated the occurrence of tipburn, Ca concentrations in each organ, antioxidant capacity (superoxide dismutase (SOD) and catalase activity), and gene expression in three lisianthus cultivars (‘Umihonoka’ (UH), ‘Reina White’ (RW), and ‘Voyage Peach’ (VP)), where bolting was induced through exogenous active GA application (GA treatment) and discussed the cause of tipburn occurring during bolting. The incidence and severity of tipburn in the GA treatment were significantly higher than those in the control group in all cultivars. The Ca concentrations in the top leaves of the GA treatment were similar to or higher than those in the control treatment for all cultivars. In contrast, SOD activity in VP was significantly lower in GA treatment than that in the control, which was consistent with the results of SOD-CuZn expression. Additionally, significantly lower catalase activity at GA treatment were detected in the UH and RW than at the control. Recent studies have reported that reactive oxygen species and antioxidants significantly affect the appearance of blossom-end rot. Therefore, exogenous GA application decreased the antioxidant capacity of the upper leaves, resulting in increased tipburn damage. In addition, it is known that a decrease in antioxidant capacity and an increase in H2O2 concentration in leaves of Arabidopsis is a trigger for the initiation of bolting. Our findings provide important insight into the causes and ecological implications of tipburn during bolting.

Congo red dye degradation using Fe-containing mineral as a reactive material derived from waste foundry dust

This study investigated the applicability of industrial waste. The high affinity of Fe-based products is widely used for industrial effluents because of their capability to oxidize contaminants. Waste foundry dust (WFD) is an Fe oxide that has been investigated as a potential reactive material that causes the generation of reactive oxidants. We aimed to investigate the physicochemical properties of WFD and the feasibility in the Fenton oxidation process. The WFD was used as a catalyst for removing Congo red (CR), to evaluate the generation of •OH and dissolution of Fe during the oxidation process. The linkage of •OH generation by WFD with eluted Fe(II) through the Fe dissolution was found. The Fenton oxidation reaction, CR degradation was affected by H2O2 concentration, initial pH, WFD dosage, initial CR concentration, and coexisting anions. The CR degradation efficiency increased with an increase in H2O2 concentration and WFD dosage. In addition, chloride and sulfate in solution promoted CR degradation, whereas carbonate had a negative effect on the Fenton oxidation process. The elution of Fe promotes CR degradation, over three reuse cycles, the degradation performance of the CR decreased from 100 to 81.1%. For the Fenton oxidation process, •OH generation is linked to Fe redox cycling, the surface passivation and Fe complexes interrupted the release of reactive oxidants, which resulted in the degradation of the CR decreased. This study proposed that WFD can serve as catalysts for the removal of CR.

Efficiency of Hydrogen Peroxide and Fenton Reagent for Polycyclic Aromatic Hydrocarbon Degradation in Contaminated Soil: Insights from Experimental and Predictive Modeling

This study investigates the degradation kinetics of polycyclic aromatic hydrocarbons (PAHs) in contaminated soil using hydrogen peroxide (H2O2) and the Fenton process (H2O2/Fe2+). The effect of oxidant concentration and the Fenton molar ratio on PAH decomposition efficiency is examined. Results reveal that increasing H2O2 concentration above 25 mmol/samples leads to a slight increase in the rate constants for both first- and second-order reactions. The Fenton process demonstrates higher efficiency in PAH degradation compared to H2O2 alone, achieving decomposition yields ranging from 84.7% to 99.9%. pH evolution during the oxidation process influences PAH degradation, with alkaline conditions favoring lower elimination rates. Fourier-transform infrared (FTIR) spectroscopy analysis indicates significant elimination of PAHs after treatment, with both oxidants showing comparable efficacy in complete hydrocarbon degradation. The mechanisms of PAH degradation by H2O2 and the Fenton process involve hydroxyl radical formation, with the latter exhibiting greater efficiency due to Fe2+ catalysis. Gaussian process regression (GPR) modeling accurately predicts reduced concentration, with optimized ARD-Exponential kernel function demonstrating superior performance. The Improved Grey Wolf Optimizer algorithm facilitates optimization of reaction conditions, yielding a high degree of agreement between experimental and predicted values. A MATLAB 2022b interface is developed for efficient optimization and prediction of C/C0, a critical parameter in PAH degradation studies. This integrated approach offers insights into optimizing the efficiency of oxidant-based PAH remediation techniques, with potential applications in contaminated soil remediation.

Effects of radiation dose and dose rate on alginate and the use of radiation degraded alginate for peanut

Aqueous solutions of alginate (4 %) with or without hydrogen peroxide (0–2 % H2O2) were irradiated under a gamma Co-60 source. The effect of dose rate on the radiation scission yield (Gs) of resulting irradiated alginate was determined. At the dose of 20 kGy, the G(s) value of irradiated alginate decreased with the increase dose rate, suggesting that the irradiation at a suitable dose rate could further improve the radiation chemical yield of degradation. For the alginate irradiated at the same dose rate, G(s) value increased with the increase of H2O2 concentration. Average molecular weight (Mw) and polydispersity index (PI) of irradiated alginate rapidly decreased with the increase in dose and further decreased by addition of H2O2. The oligoalginate with Mw ~ 9800 g/mol was obtained by radiation degradation of 4 % alginate solution containing 2 % H2O2 at dose of 20 kGy. Radiation scission of glycoside bonds and formation of carbonyl groups (C=O) were indicated in UV and FTIR spectra of irradiated alginate. Peanut seedlings were fertilized with alginate and oligoalginate solutions, and the results showed that all growth parameters of the treated plants were better than those of the control. Furthermore, the oligoalginate prepared by gamma irradiation can be applied as a plant growth promoter for agriculture production.

Comprehensive analysis of MAPK gene family in upland cotton (Gossypium hirsutum) and functional characterization of GhMPK31 in regulating defense response to insect infestation

Key messageThe transcriptomic, phenotypic and metabolomic analysis of transgenic plants overexpressing GhMPK31 in upland cotton revealed the regulation of H2O2 burst and the synthesis of defensive metabolites by GhMPK31.Mitogen-activated protein kinases (MAPKs) are a crucial class of protein kinases, which play an essential role in various biological processes in plants. Upland cotton (G. hirsutum) is the most widely cultivated cotton species with high economic value. To gain a better understanding of the role of the MAPK gene family, we conducted a comprehensive analysis of the MAPK gene family in cotton. In this study, a total of 55 GhMPK genes were identified from the whole genome of G. hirsutum. Through an investigation of the expression patterns under diverse stress conditions, we discovered that the majority of GhMPK family members demonstrated robust responses to abiotic stress, pathogen stress and pest stress. Furthermore, the overexpression of GhMPK31 in cotton leaves led to a hypersensitive response (HR)-like cell death phenotype and impaired the defense capability of cotton against herbivorous insects. Transcriptome and metabolomics data analysis showed that overexpression of GhMPK31 enhanced the expression of H2O2-related genes and reduced the accumulation of defensive related metabolites. The direct evidence of GhMPK31 interacting with GhRBOHB (H2O2-generating protein) were found by Y2H, BiFC, and LCI. Therefore, we propose that the increase of H2O2 content caused by overexpression of GhMPK31 resulted in HR-like cell death in cotton leaves while reducing the accumulation of defensive metabolites, ultimately leading to a decrease in the defense ability of cotton against herbivorous insects. This study provides valuable insights into the function of MAPK genes in plant resistance to herbivorous insects.

Enzyme-Empowered "Two Birds with One Stone" Strategy for Amplifying Tumor Apoptosis and Metabolic Clearance.

Nanomedicine has reshaped the landscape of cancer treatment. However, its efficacy is still hampered by innate tumor defense systems that rely on adenosine triphosphate (ATP) for fuel, including damage repair, apoptosis resistance, and immune evasion. Inspired by the naturally enzymatic reaction of glucose oxidase (GOx) with glucose, here a novel "two birds with one stone" technique for amplifying enzyme-mediated tumor apoptosis and enzyme-promoted metabolic clearance is proposed and achieved using GOx-functionalized rhenium nanoclusters-doped polypyrrole (Re@ReP-G). Re@ReP-G reduces ATP production while increasing H2O2 concentrations in the tumor microenvironment through GOx-induced enzymatic oxidation, which in turn results in the downregulation of defense (HSP70 and HSP90) and anti-apoptotic Bcl-2 proteins, the upregulation of pro-apoptotic Bax, and the release of cytochrome c. These processes are further facilitated by laser-induced hyperthermia effect, ultimately leading to severe tumor apoptosis. As an enzymatic byproduct, H2O2 catalyzes the conversion of rhenium nanoclusters in Re@ReP-G nanostructures into rhenate from the outside in, which accelerates their metabolic clearance in vivo. This Re@ReP-G-based "two birds with one stone" therapeutic strategy provides an effective tool for amplifying tumor apoptosis and safe metabolic mechanisms.

Complex Formation between the Transcription Factor WRKY53 and Antioxidative Enzymes Leads to Reciprocal Inhibition.

The transcription factor WRKY53 of the model plant Arabidopsis thaliana is an important regulator of leaf senescence. Its expression, activity and degradation are tightly controlled by various mechanisms and feedback loops. Hydrogen peroxide is one of the inducing agents for WRKY53 expression, and a long-lasting intracellular increase in H2O2 content accompanies the upregulation of WRKY53 at the onset of leaf senescence. We have identified different antioxidative enzymes, including catalases (CATs), superoxide dismutases (SODs) and ascorbate peroxidases (APXs), as protein interaction partners of WRKY53 in a WRKY53-pulldown experiment at different developmental stages. The interaction of WRKY53 with these enzymes was confirmed in vivo by bimolecular fluorescence complementation assays (BiFC) in Arabidopsis protoplasts and transiently transformed tobacco leaves. The interaction with WRKY53 inhibited the activity of the enzyme isoforms CAT2, CAT3, APX1, Cu/ZuSOD1 and FeSOD1 (and vice versa), while the function of WRKY53 as a transcription factor was also inhibited by these complex formations. Other WRKY factors like WRKY18 or WRKY25 had no or only mild inhibitory effects on the enzyme activities, indicating that WRKY53 has a central position in this crosstalk. Taken together, we identified a new additional and unexpected feedback regulation between H2O2, the antioxidative enzymes and the transcription factor WRKY53.

MiR408 balances plant growth and heat response in rice

MicroRNAs are small noncoding RNAs that regulate gene expression by targeting complementary mRNA molecules. Among them, microRNA408 (miR408) is an ancient microRNA influencing plant growth and aiding in abiotic stress adaptation. We proved that miR408 sliced uclacyanin7 (UCL7) directly by degradome sequencing. However, the mechanisms underlying the balance between growth and stress response of rice (Oryza sativa L.) controlled by miR408 remain unclear. We conducted a study comparing Nipponbare (wild-type, WT) plants with miR408–3p-overexpression (miR408–3p-OX) and UCL7-overexpression (UCL7-OX) plants under normal and heat stress conditions. Through RNA-sequencing, physiological measurements, and phenotype examination, we observed that miR408 overexpression resulted in increased dry weight and grain yield, higher levels of ATP and non-structural carbohydrates (NSC), improved photosynthesis, and reduced H2O2 content, antioxidant enzyme activity, and ATPase activity in seedling plants compared to UCL7-OX plants. Additionally, the application of H2O2 scavengers, such as ascorbic acid (ASA) and dimethylthiourea (DMTU), further enhanced dry weight and photosynthesis by reducing H2O2 levels. Under heat stress conditions, miR408 overexpression sharply increased H2O2 content, antioxidant enzyme activity, ATP levels, and ATPase activity compared to UCL7-OX plants, thereby enhancing heat tolerance in rice seedlings. These findings suggest that miR408 and its target gene UCL7 participate in regulating energy homeostasis to achieve a balance between growth and heat response. This regulation involves modulating H2O2 levels and optimizing the relationship between the target of rapamycin (TOR) and SNF1-related protein kinase 1 (SnRK1) in rice.

Salt stress responses of microalgae biofilm communities under controlled microcosm conditions

Algal biofilms play an essential role in ecosystem functioning, but their physiological and biochemical changes during salt stress remain poorly understood. This study aimed at investigating how biofilm communities react to different salinity in a microcosm experiment and to offer insights into the potential effects of future freshwater salinization. Biofilm samples collected from Iriri River (Drâa basin, Southern Morocco) were exposed to water gradually enriched with sodium chloride to obtain three final concentrations (1, 10, and 30 g/L) over 14 days, and the changes were compared with control. Several biofilm responses were analyzed throughout the experiment, including biofilm biomass, changes in community structure and composition via eDNA metabarcoding, physiological feedback, biochemical parameters, antioxidant activities, non-enzymatic salt stress markers, osmoprotection indicators, and nitrogen assimilation. High salt concentrations significantly altered biofilm communities' composition, structure, and function, leading to an overall decrease in alpha diversity and a decrease in diatom and cyanobacterial biomass, while green algae remained unchanged. Chlorophyll a content increased in biofilm exposed to low salt concentration (1 g/L) and decreased at high salt concentrations while carotenoid significantly increased even at high salinity (10 g/L). Biofilm also showed an increase in carbohydrates and a decrease in protein content under high salinities (10 and 30 g/L). In addition, salt stress-induced ROS generation in the biofilm, with an increase in H2O2 content, caused oxidative damage and lipid peroxidation with an increase in MDA levels. To prevent this damage, elevated proline content was recorded, and additionally, the biofilm exhibited antioxidant defense mechanisms by rising activity of ROS-scavenger enzymes such as SOD, CAT, and POD. Our experimental results highlighted the salinity effect on algal biofilm as well as physiological and biochemical responses. This study could help predict the consequences of freshwater salinization on river biofilms and its potential impact at the ecosystem level.

Foliar treatment with MSB (menadione sodium bisulphite) to increase artemisinin content in Artemisia annua plants

Artemisinin is a sesquiterpene lactone endoperoxide, recognized for its application as a treatment for malaria. Besides, it has activity against several types of cancers, as well as anti-viral and anti-inflammatory properties. The chemical synthesis of artemisinin is quite complex and economically unfeasible. Hence, artemisinin is typically obtained from Artemisia annua plants in low quantities in relation to the biomass. A strategy to increase the biosynthesis of secondary metabolites would be the application of elicitors. In this work, the effect of treating A. annua plants with menadione sodium bisulphite (MSB) is studied. An initial dose-optimization was conducted by treating the plants with different MBS concentrations (0, 0.2, 0.8, 1, 2, 3 and 4 mM) and artemisinin was quantified 48 h after treatment. The highest artemisinin content (3.71 mg artemisinin g−1 DW) was obtained with 1 mM of MSB. Then, harvesting time was optimised (24, 48 and 72 h after treatment application) with 1 mM of MSB. The largest increase in artemisinin content was observed at 48 h with an increment of 62.37 % over the control. The treatment increased H2O2 content, as well as the activity of superoxide dismutase (SOD) and ascorbate peroxidase (APX). Besides, MSB up-regulated HMGR (the gene for 3-hydroxy-3-methylglutaryl-CoA reductase) and DXS (the gene for 1-deoxy-D-xylulose-5-phosphate synthase) 24 h after treatment. Both genes are involved in the MVA (mevalonate) and MEP (2C-methylerythritol 4-phosphate) pathways, respectively. These pathways represent the initiation of artemisinin biosynthesis. Thus, MSB application and the consequent up-regulation of early biosynthetic pathway genes along with the triggered oxidative stress may have been contributed to the observed increase in artemisinin production.

High temporal resolution of hydrogen peroxide (H2O2) dynamics during heat stress does not support a causative role in coral bleaching

Human-induced climate change is causing ocean warming that triggers the breakdown of the coral–algal symbiosis. The proximate cause of this phenomenon, known as coral bleaching, is commonly attributed to the overproduction of reactive oxygen species (ROS) by the thermally stressed photosynthetic algal symbionts. However, direct evidence that algal ROS production (e.g., in the form of H2O2) and coral physiological stress are the ultimate cause of bleaching remains ambiguous. Here, we investigated the temporal dynamics of H2O2 and oxygen (O2) concentrations during thermally induced coral bleaching to disentangle cause from consequence. Microsensors at the tissue interface of Pocillopora damicornis measured H2O2 and O2 concentrations while exposing single nubbins to baseline temperatures (30 °C) and to minor (33 °C), moderate (36 °C), and high (39 °C) levels of acute heat stress using the Coral Bleaching Automated Stress System (CBASS). We show that a temporary decline in O2 concentration, accompanied by a declining photosynthetic efficiency and loss of Symbiodiniaceae and pigmentation, is the initial response to moderate thermal stress. This response was neither provoked nor followed by an increased H2O2 concentration at the coral tissue interface. A steady light-independent increase of H2O2 was only detected during high heat stress, resulting in the complete and permanent loss of photosynthetic activity. Our findings do not support a direct connection between algal photodamage and an increase in H2O2 concentration during thermally induced bleaching and suggest that more research on the function of H2O2 is warranted. This notion is further substantiated by the observation of an additional source of H2O2, likely oxidative bursts, that were common at the baseline temperature and under minor heat stress, while their occurrence decreased at moderate and high heat stress. Resolving the multifaceted and dynamic roles of H2O2 in coral bleaching is critical to better understand the response of the coral holobiont to thermal stress and identifying the processes underlying the breakdown of the coral–algal symbiosis.

Insight into the biodegradation behavior of pure molybdenum under simulated inflammatory condition

The study explores the impact of simulated inflammation on the corrosion behavior of pure Mo, a potential biodegradable metal for biomedical applications for the first time. Under simulated inflammatory conditions, Mo exhibits altered electrochemical properties, such as increased open circuit potential, higher corrosion rates, and reduced impedance as H2O2 concentration rises. Immersion test confirm the higher corrosion rates with increases in H2O2 concentration. Interestingly, pure Mo exhibit uniform corrosion behavior under aggressive simulated inflammation which is beneficial to maintain biomedical devices’ mechanical integrity. Furthermore, the underlying biodegradation mechanism and the mechanism of inflammatory cell-released inflammation species induced corrosion were discussed.

SmRAV1, an AP2 and B3 Transcription Factor, Positively Regulates Eggplant's Response to Salt Stress.

Salt stress is a lethal abiotic stress threatening global food security on a consistent basis. In this study, we identified an AP2 and B3 domain-containing transcription factor (TF) named SmRAV1, and its expression levels were significantly up-regulated by NaCl, abscisic acid (ABA), and hydrogen peroxide (H2O2) treatment. High expression of SmRAV1 was observed in the roots and sepal of mature plants. The transient expression assay in Nicotiana benthamiana leaves revealed that SmRAV1 was localized in the nucleus. Silencing of SmRAV1 via virus-induced gene silencing (VIGS) decreased the tolerance of eggplant to salt stress. Significant down-regulation of salt stress marker genes, including SmGSTU10 and SmNCED1, was observed. Additionally, increased H2O2 content and decreased catalase (CAT) enzyme activity were recorded in the SmRAV1-silenced plants compared to the TRV:00 plants. Our findings elucidate the functions of SmRAV1 and provide opportunities for generating salt-tolerant lines of eggplant.

Effects of Hydrogen Peroxide on the Hydrogen Bonding Structure and Dynamics of Water and Its Influence on the Aqueous Solvation of the Insulin Monomer.

The hydrogen bond structure and dynamics of water and hydrogen peroxide (H2O2) in their binary mixtures have been studied at 298 K by classical molecular dynamics simulations. Twelve different concentrations of aqueous-H2O2 solutions are considered for this study. We have analyzed the interactions between water and H2O2 by site-site pair correlation functions and observed that the probability of formation of OW···HP hydrogen bonds are higher compared to OP···HW. The second solvation shell of water is strongly affected by increasing H2O2 concentrations (XP > 0.50), which signifies the destruction of the tetrahedral network structure of water. The translational and rotational dynamics of water and H2O2 do not significantly change up to 25% of H2O2 in aqueous mixtures. The hydrogen bond lifetime of water-water, water-H2O2, and H2O2-H2O2 in the aqueous-H2O2 solutions shows a very minimal change with increasing H2O2 concentrations. In addition to this, we also investigated the effect of H2O2 on the insulin monomer and observed that higher concentrations of H2O2 (XP = 0.10) change the secondary structure. The influence of H2O2 is more on chain-B than that on chain-A in the insulin monomer. The H2O2 occupancy at the protein surface is higher for negatively charged (GLU) and polar (ASN and THR) amino acid residues compared with that for positively charged and neutral residues in the solutions.

Genome-wide identification of ascorbate peroxidase (APX) gene family and the function of SmAPX2 under high temperature stress in eggplant

Ascorbate peroxidase (APX) plays pivotal roles in regulating diverse biological processes in plants against biotic and abiotic stresses by eliminating hydrogen peroxide (H2O2). However, the function and information of APX gene family members in eggplant's response to high temperature stress remain largely unclear. Herein, we have identified nine APXs in the eggplant genome (SmAPXs), which were classified into three clades and the members of each clade exhibited similar gene structures and motifs. SmAPXs were distributed on seven chromosomes and contained phytohormone responsiveness-, defense and stress-related, and transcription factors binding cis-elements within their promoters. Transcript expressions of some SmAPXs, especially SmAPX2 that localize in cytomembrane and cytoplasm, were up-regulated by high temperature and ABA treatment. SmAPX2 exhibits APX enzyme activity, which enables to catalyze oxidation of ascorbic acid by H2O2in vitro and alleviate the H2O2 accumulation under high temperature stress by SmAPX2 transient expression in vivo. SmAPX2 silencing decreased eggplant's tolerance to high temperature stress, accompanied by transcript expression down-regulation of high temperature defense-related and ABA-response-related genes, reduction of APX enzyme activity, and increase of H2O2 content. These data provide comprehensive overview of SmAPX gene family, and indicate that SmAPX2 positively functions in eggplant response to high temperature stress.

Genome-Wide Identification of Catalase Gene Family and the Function of SmCAT4 in Eggplant Response to Salt Stress

Salinity is an important abiotic stress, damaging plant tissues by causing a burst of reactive oxygen species (ROS). Catalase (CAT) enzyme coded by Catalase (CAT) genes are potent in reducing harmful ROS and hydrogen peroxide (H2O2) produced. Herein, we performed bioinformatics and functional characterization of four SmCAT genes, retrieved from the eggplant genome database. Evolutionary analysis CAT genes revealed that they are divided into subgroups I and II. The RT-qPCR analysis of SmCAT displayed a differential expression pattern in response to abiotic stresses. All the CAT proteins of eggplant were localized in the peroxisome, except for SmCAT4, which localized in the cytomembrane and nucleus. Silencing of SmCAT4 compromised the tolerance of eggplant to salt stress. Suppressed expression levels of salt stress defense related genes SmTAS14 and SmDHN1, as well as increase of H2O2 content and decrease of CAT enzyme activity was observed in the SmCAT4 silenced eggplants. Our data provided insightful knowledge of CAT gene family in eggplant. Positive regulation of eggplant response to salinity by SmCAT4 provides resource for future breeding programs.

The effect of spermine on Tetranychus urticae-Cucumis sativus interaction

BackgroundTwo spotted spider mite, Tetranychus urticae (Acari: Tetranychidae) is one of the most important plant pests in the world. Due to increased resistance of mites to acaricides, it is necessary to use other methods such as inducing resistance in plants by natural compounds for pests' management. Polyamins such as spermine are effective in increasing plant resistance to biotic and abiotic stressors. In this research, the effect of spermine treatments in cucumber plants on life table parameters of T. urticae was investigated. Also, top-down effect of spermine and T. urticae on cucumber biochemical parameters was measured. In the experiments, 1, 2 and 3 mM spermine concentrations were used.ResultsAmongst the spermine treatments, those mites that fed on cucumbers which received 1 mM spermine showed the shortest protonymphal period and higher ovipositon period, fecundity, gross and net reproductive rates and life expectancy compare to control. Treatment with 2 mM spermine lead to the longest teleochrysalis period and shortest range of age-stage-specific fecundity period. In addition, 2 mM spermine lowered intrinsic and finite rate of population increase in T. urticae. The longest larval period of T. urticae was observed in 3 mM spermine. Feeding of T. urticae from cucumber plants increased hydrogen peroxide (H2O2), malondialdehyde (MDA) content, electrolyte leakage (EL) level and ascorbate peroxidase (APX) activity but inhibited catalase (CAT) activity in this plant. Infested cucumber plants treated with 2 mM spermine showed lower H2O2 and MDA content and highest activity of APX and CAT on day 1 and 3 compare to the others. The 3 mM spermine increased H2O2 content in infested plants during the whole experiment as well as non-infested plants in day 5 and 9 only. This treatment induced the highest MDA content and lowest catalase activity on day1, 3 and 5 of experiment in infested plants.ConclusionThis study showed that 2 mM spermine was the only effective concentration that reduce cucumber sensitivity to T. urticae. The trend of changes in biochemical parameters, especially H2O2, in 3 mM spermine was abnormal, and this concentration could be considered toxic.

The Growth, Leaf Antioxidant Enzymes and Amino Acid Content of Tomato as Affected by Grafting on Wild Tomato Rootstocks 1 (S. Pimpinellifolium and S. Habrochaites) Under Salt Stress

Salinity in soil or water is a serious threat to plant growth, which reduces yields and threatens food security. It is possible to reduce the negative effects of salinity on tomato scions through grafting. To evaluate the effects of salt stress on graft combinations in hydroponic conditions, SP3, SP4, SP5 (S. pimpinellifolium), SH1, SH3, SH5 (S. habrochaites) and two hybrids L × SP5 (S. lycopersicum L. × S. pimpinellifolium) and L × SH3 (S. lycopersicum L. × S. habrochaites) were used as rootstock and two varieties Galaxy and H2274 (S. lycopersicum L.) were used as scion. Plants were evaluated in terms of biomass parameters and antioxidant enzyme activities and amino acid contents in leaf tissues under control and salt stress conditions. Salt stress decreased the fresh weight of shoots and roots by 68.71 and 23.59, respectively, and increased H2O2 content (93.90 %) and MDA content (63.71 %). In addition, salt stress in leaf tissues POD (204.49 %), CAT (83.87 %), SOD (204.49 %), GR (88.23 %), GST (100.16 %), G6PD (32.85 %), 6GPD (46.19 %), APX (157.29 %) caused an increase in enzymes and total amino acid content (160.57 %). In salt stress conditions, SH5/Galaxy and L × SP5/Galaxy are the graft combinations with the highest fresh shoot and root weight, leaf number and root volume. These graft combinations contain the most isoleucine, proline lysine, alanine arginine, sucrosine leucine, methionine, hydroxyproline glutamate, glutamine and histidine amino acids in leaf tissues and have the lowest MDA content. Ungrafted H2274 and Galaxy plants have the highest MDA and content under salt stress conditions, these ungrafted plants have the least other amino acids and enzymes other than theonine amino acid in their leaf tissues. Furthermore, ungrafted plants under saline conditions had the lowest shoot and root fresh weight, leaf number and root volume. MDA content correlated negatively with shoot and root fresh weight, leaf number and root volume. H2O2 correlated positively with CAT, SOD, GST and peroxidase enzymes and negatively with APX, GR and G6PD enzymes. It seems that the antioxidant enzyme activity and amino acid content in leaf tissues influence salinity response and the appropriate rootstock/scion combination could be a viable method for tomato cultivation in saline conditions.

MD simulation of chemically enhanced polishing of 6H-SiC in aqueous H2O2

Chemical enhanced polishing (CEP) is a widely employed final process for achieving precise surface shaping and planarization of semiconductor wafers. However, determining the chemical effect involved in material removal through experimental means is extremely challenging. In this study, we conducted reactive force field (ReaxFF) molecular dynamics (MD) simulations to gain insight into the chemical effects of CEP using an aqueous hydrogen peroxide (H2O2) diamond suspension as a polishing medium for 6H-SiC single crystals. The inclusion of aqueous H2O2 resulted in the formation of SiOH and COH species, which are comparatively easier to remove through mechanical abrasion. Furthermore, an increase in H2O2 concentration was found to enhance the material removal. The MD simulations also revealed that the chemical effects on the Si-face of 6H-SiC were more pronounced than those on the C-face due to the generation of a greater number of SiO species and the favourable atomic structure of the Si-face for chemical removal. The results showed that the material remove rate on the Si-face is greater than that on the C-face during polishing, aligning with the findings from MD simulation. Furthermore, a systematic experimental study was carried out to examine the influence of various conditions on material removal rate and surface quality in both polishing and lapping processes.

Synergistic effects of hydrogen peroxide and phosphate on uranium(VI) immobilization: implications for the remediation of groundwater at decommissioned in situ leaching uranium mine.

The processes of acid in situ leaching (ISL) uranium (U) mines cause the pollution of groundwater. Phosphate (PO43-) has the potential to immobilize U in groundwater through forming highly insoluble phosphate minerals, but the performance is highly restricted by low pH and high sulfate concentration. In this study, hydrogen peroxide (H2O2) and PO43- were synergistically used for immobilizing U based on the specific properties of groundwater from a decommissioned acid ISL U mine. The removal mechanisms of U and the stability of U on the formed minerals were elucidated by employing X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and kinetic experiments. Our results indicated that the removal of U by simultaneously adding H2O2 and PO43- was significantly higher than the removal of U by individually adding H2O2 or PO43-. The removal of U increased with increasing PO43- concentration from 20 to 200 mg L-1 while decreased with increasing H2O2 concentration from 0.003 to 0.3%. Specifically, the removal efficiency of U from groundwater reached 98% after the application of 0.003% H2O2 and 200 mg L-1 PO43-. Amorphous iron phosphate that preferentially formed at low H2O2 and high PO43- concentrations played a dominant role in U removal, while the formations of schwertmannite and crystalline iron phosphates may be also contributed to the removal of U. This was significantly different from the immobilization mechanism of U through the formation of uranyl phosphate minerals after adding phosphate. The kinetic experimental results suggested that the immobilized U had a good stability. Our research may provide a promising method for in situ remediating U-contaminated groundwater at the decommissioned acid ISL U mines.