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The limitation of water and unfavorable soil conditions for plant's nutrient absorption present a hurdle to the growth and yield of red beans under drought stress conditions. Micronutrients, particularly zinc and molybdenum, show promise in mitigating drought effects. Various irrigation levels (100% and 70% of field capacity) and nutrient application methods were tested in the field (two locations) and the greenhouse in 2022. Parameters such as photosynthesis, gas exchange, root characteristics, nitrate reductase, antioxidant enzymes, and yield were evaluated. The combination of nano zinc priming (NZnP 150 mg L−1) and foliar spraying of nano zinc (FSNZn 0.04 mg L−1) at 100% field capacity resulted in the highest photosynthesis, gas exchange, and yield. Water stress increased the activity of antioxidant enzymes. In greenhouse test, NZnP (150 mg L−1) + FSNZn (0.04 mg L−1) at 100% field capacity promoted maximum root length and nitrate reductase activity. Overall, NZnP + FSNZn at 100% field capacity proved most effective for morphological and biochemical root characteristics and yield. Drought stress reduced red bean yield, but NZnP + FSNZn mitigated some adverse effects. Nano forms of zinc and molybdenum were more effective in mitigating drought stress. Location significantly influenced plant development, with lower temperatures delaying reproductive phase transition, leading to better vegetative and reproductive traits compared to the location with higher temperature. [ABSTRACT FROM AUTHOR]

Summary Transcription factors of the CYCLING DOF FACTOR (CDF) family activate in potato the SP6A FT tuberization signal in leaves. In modern cultivars, truncated StCDF1.2 alleles override strict SD control by stabilizing the StCDF1 protein, which leads to StCOL1 suppression and impaired activation of the antagonic SP5G paralog. By using DAP‐seq and RNA‐seq studies, we here show that StCDF1 not only acts as an upstream regulator of the day length pathway but also directly regulates several N assimilation and transport genes. StCDF1 directly represses expression of NITRATE REDUCTASE (NR/NIA), which catalyses the first reduction step in nitrate assimilation, and is encoded by a single potato locus. StCDF1 knock‐down lines performed better in N‐limiting conditions, and this phenotype correlated with derepressed StNR expression. Also, deletion of the StNR DAP‐seq region abolished repression by StCDF1, while it did not affect NLP7‐dependent activation of the StNR promoter. We identified multiple nucleotide polymorphisms in the DAP‐seq region in potato cultivars with early StCDF1 alleles, suggesting that this genetic variation was selected as compensatory mechanism to the negative impact of StCDF1 stabilization. Thereby, directed modification of the StCDF1‐recognition elements emerges as a promising strategy to enhance limiting StNR activity in potato. [ABSTRACT FROM AUTHOR]

Improving vegetable yield and optimizing its quality through nutrient management have long been central to plant nutrition and horticultural science. Copper (Cu) is recognized as an essential trace element that promotes plant growth and development. However, the mechanisms by which Cu influences nitrogen (N) metabolism remain largely unknown, with limited studies exploring the interaction between Cu and varying nitrate-to-ammonium (nitrate/ammonium) ratios. In this study, Chinese cabbage was exposed to two Cu concentrations (0 and 0.02 mg L-1) in combination with three nitrate/ammonium ratios (10/90, 50/50, and 90/10) under hydroponic conditions. The results showed that Cu application increased plant biomass, nitrate reductase (NR) and glutamine synthetase (GS) enzyme activities, the expression of NR (NIA) and GS2 (Gln2) genes, and N content in both shoots and roots. Additionally, Cu treatment decreased nitrate and free amino acid contents, as well as the expression of nitrate transporters NRT1.1 and NRT2.1 in roots while increasing these four parameters in shoots. Additionally, these effects were significantly modulated by the nitrate/ammonium ratios. In conclusion, Cu may facilitate nitrate transportation, enhance nitrate reduction, promote ammonium assimilation, and influence the transformation of organic N compounds, highlighting its potential role in improving N metabolism in Chinese cabbage. [ABSTRACT FROM AUTHOR]

Tobacco, a warm-season crop originating from the Americas, is highly susceptible to cold stress. The utilization of symbiotic fungi as a means to bolster crops' resilience against abiotic stresses has been proven to be a potent strategy. In this study, we investigated the effect of endophytic fungus Piriformospora indica on the cold resistance of tobacco. When exposed to cold stress, the colonization of P.indica in tobacco roots effectively stimulates the activity of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX). This, in turn, reduces the accumulation of reactive oxygen species (ROS), thereby mitigating oxidative damage. Additionally, P. indica elevates the levels of osmolytes, such as soluble sugars, proline, and soluble proteins, thus facilitating the restoration of osmotic balance. Under cold stress conditions, P. indica also induces the expression of cold-responsive genes. Furthermore, this fungus not only enhances photosynthesis in tobacco by stimulating the synthesis of photosynthetic pigments, strengthening Rubisco activity, and elevating PSII efficiency, but also fortifies tobacco's nitrogen assimilation by inducing the expression of nitrate transporter gene and activating enzymes related to nitrogen assimilation. Consequently, this synergistic optimization of nitrogen and carbon assimilation provides a solid material and energetic foundation for tobacco plants to withstand cold stress. Our study demonstrates that a mycorrhizal association between P. indica and tobacco seedlings provides multifaceted protection to tobacco plants against low-temperature stress and offers a valuable insight into how P. indica enhances the cold tolerance of tobacco. [ABSTRACT FROM AUTHOR]

Summary Nitrate (NO3−) serves as the primary inorganic nitrogen source assimilated by most terrestrial plants. The acquisition of nitrate from the soil is facilitated by NITRATE TRANSPORTERS (NRTs), with NRT2.1 being the key high‐affinity nitrate transporter. The activity of NRT2.1, which has multiple potential phosphorylation sites, is intricately regulated under various physiological conditions. Here, we discovered that CALCIUM‐DEPENDENT PROTEIN KINASE 28 (CPK28) positively regulates nitrate uptake under nitrogen deprivation conditions. We found CPK28 as the kinase targeted by immunoprecipitation followed by mass spectrometry and examined the in‐planta phosphorylation status of NRT2.1 in cpk28 mutant plants by employing quantitative MS‐based phosphoproteomics. Through a combination of in vitro phosphorylation experiment and immunoblotting using phospho‐specific antibody, we successfully demonstrated that CPK28 specifically phosphorylates NRT2.1 at Ser21. Functional analysis conducted in Xenopus oocytes revealed that co‐expression of CPK28 significantly enhanced high‐affinity nitrate uptake of NRT2.1. Further investigation using transgenic plants showed that the phosphomimic variant NRT2.1S21E, but not the nonphosphorylatable variant NRT2.1S21A, fully restored high‐affinity 15NO3− uptake ability in both nrt2.1 and cpk28 mutant backgrounds. This study clarifies that the kinase activity of CPK28 is promoted during nitrogen deprivation conditions. These significant findings provide valuable insights into the intricate regulatory mechanisms that govern nitrate‐demand adaptation. [ABSTRACT FROM AUTHOR]

This work was conducted to evaluate the effect of N source (NH4+/NO3-) and the implication of NH4+-induced acidification on plant development in Arabidopsis thaliana. seedlings were hydroponically cultivated during 21 days under three ratios of NO3−/NH4+ (mM); 2.5/0.0; 1.25/1.25, and 0.0/2.5. For each ratio, plants were cultivated under not controlled pH and adjusted pH at 6.2. Ammonium-fed plants (0.0/2.5) showed chlorosis if cultivated under uncontrolled pH. This symptom was associated with suppressions in plant growth, chlorophyll and iron contents as well as shoots hydration and nutrient concentration. Growth was limited with increasing NH4+ medium-concentration. At pH 6.2, plants receiving only NH4+ produced the same biomass as NO3-fed ones. The mineral disturbances in plants grown on strictly NH4+-medium (0.0/2.5) were alleviated under controlled pH. The activities of nitrate reductase (NR) and nitrite reductase (NIR) were lower in plants amended only with NH4+ under uncontrolled pH. At adjusted pH, the NR activity was ameliorated but that of NIR was not ameliorated, suggesting hence that NR activity depended on medium pH but that of NIR was related only to the pool of NO2-. In conclusion, this work demonstrated that the adjustment of pH at 6.2 mitigated significantly the toxic effects of ammonium to A. thaliana. [ABSTRACT FROM AUTHOR]

It is not known whether both reducing tiller-fertilizer and increasing panicle-fertilizer can significantly increase grain yield under mechanical deep placement. The two-year field experiment was conducted to access the effects of optimal nitrogen fertilization including reducing tiller-fertilizer, increasing panicle-fertilizer, with the method of mechanical deep placement on grain yield and its physiological traits of rice, in 2019 and 2020. The experimental materials were selected with hybrid rice Wufengyou615 (WFY615) and inbred rice Yuxiangyouzhan (YXYZ). There were six experiment treatments, i.e., no any fertilization (H1); traditional surface broadcast fertilization (SB) (90 kg N ha−1 as basal fertilization (BF) and 60 kg N ha−1 as tillering fertilizer (TF), namely, BF 90 kg N (SB) + TF 60 kg N (SB), (H2); BF 90 kg N (SB) + TF 45 kg N (DP, deep placement) + FF (flowering fertilizer) 7.5 kg N (SB), (H3); BF 90 kg (SB) + TF 45 kg N (DF) + FF 15 kg N (SB), (H4); BF 90 kg N(SB) + TF 30 kg N (DP) + FF 7.5 kg N (SB), (H5); BF 90 kg N (SB) + TF 30 kg N (DP) + FF 15 kg N (SB), (H6). The results showed that mean grain yield of WFY615 and YXYZ for H4 was 10.57 t ha−1 and 10.42 t ha−1, which was 14.58% and 7.49% higher than H2, respectively. The main reason was due to the increase of productive panicle per ha, spikelet per panicle and grain filling percentage. The highest total dry matter of WFY615 and YXYZ at heading (HS) and mature stages (MS) was for H4, which was 9.24, 15.97, 11.65, and 14.71 t ha−1, respectively. There was 31.09, 25.96, 41.73, and 20.58% higher total dry matter material of WFY615 and YXYZ for H4 than H2 at HS and MS, respectively. The largest leaf area index of H4 was also found at HS and fifteen days after HS for two rice cultivars, which was 6.24, 8.79, 6.09, and 8.29, respectively. The H4 treatment had the largest net photosynthetic rate, followed by H3 and H2, while the least net photosynthetic rate was recorded for H1. In addition, significant improvements were also founded in chlorophyll content, glutamate synthase, and nitrate reductase activities of sword leaves at HS for H4. Therefore, the fertilizer management can be regarded as one of high-efficiency fertilization method with 90 kg N ha−1 basal fertilizer by surface broadcast plus 45 kg N ha−1 tillering fertilizer under mechanical deep placement and 15 kg N ha−1 flowering fertilizer by surface broadcast. [ABSTRACT FROM AUTHOR]

The research on carbon materials and plants primarily focuses on their use in soil, showing variable effects. However, significant gaps exist regarding their impact under stress conditions (such as drought, salinity, etc.) and their interactions with plant physiological processes. Long-term effects on plant health and ecosystems are understudied, as are their interactions with other biofertilizers like algae extracts and plant growth-promoting rhizobacteria (PGPR). The aim of the present study was to evaluate the effects of seaweed extracts and PGPR on plant growth and some physio-biochemical properties of soft wheat (Triticum aestivum L.) and faba bean (Vicia faba L.). Two concentrations of aqueous extract from two seaweeds, Fucus spiralis (F) and Ulva rigida (U), and the PGPR bacillus strain solution S48 (S48S) were used either individually or in combination. All treatments were applied as foliar sprays. The findings showed that the combined application of Fucus spiralis extract [25%] (F), Ulva rigida extract [50%] (U), along with the PGPR S48 bacillus strain solution (S48S) promoted plant growth (50.93 cm for faba bean) and root development (17.90 cm for wheat). This treatment also resulted in increased chlorophyll content (3.25 mg/g Fresh Weight (FW) in soft wheat and 3.93 mg/g FW in faba bean), proteins (14.66 µg/mg FW in soft wheat and 23.79 µg/mg FW in faba bean), amino acids (0.46 mg/g FW in soft wheat and 0.56 mg/g FW in faba bean), and total carbohydrates (529.8 µg/ml in soft wheat and 340.7 µg/ml in faba bean) as compared to controls. On the other hand, the nitrate reductase activity was enhanced by seaweed extract application in both crops. Phosphorus (P) uptake by soft wheat and faba bean was significantly improved following the application of Ulva rigida extract [50%] (U), the PGPR S48 bacillus strain solution (S48S), and the co-treatment of Fucus spiralis extract [25%] (F) with the PGPR S48 bacillus strain solution (S48S). The findings suggest that the combined application of Fucus spiralis extract (F) and Ulva rigida extract (U) with the PGPR S48 bacillus strain solution (S48S) can significantly improve plant growth and nutrient absorption in durum wheat and faba bean. This offers a sustainable alternative to chemical fertilizers, reducing pollution and promoting healthier ecosystems. Furthermore, these biological treatments enhance plant resilience to abiotic stresses, potentially increasing yields in challenging conditions. By reducing reliance on chemical fertilizers, these practices can save money for farmers and advance sustainable agriculture. [ABSTRACT FROM AUTHOR]

Introduction: This study investigated the combined effects of molybdenum (Mo) and nitrogen (N) fertilization on N metabolism and amino acid content in the leaves of flue-cured tobacco (Nicotiana tabacum L.) during its mature stage through a pot experiment. Methods: Different application levels of Mo (0, 0.15, 0.30 mg/kg soil) and N (0.06, 0.24, 0.42 g/kg soil) were set to observe and analyze changes in leaf quality, N, and amino acid content in the tobacco plants. Results: The results revealed that the N fertilizer application level exhibited a primary effect on regulating the total nitrogen, nitrate nitrogen, soluble protein, and amino acid nitrogen concentrations within tobacco leaves, while the effectiveness of Mo fertilization was influenced by the level of N applied. Specifically, under the conditions of 0.24 g/kg soil N and 0.30 mg/kg soil Mo application, the N content, N accumulation, and dry matter mass of the tobacco plants increased significantly by 110%, 204%, and 48%, respectively. Concurrently, nitrate reductase activity increased by 107-fold, and the nitrate nitrogen content was relatively low, contributing to enhanced tobacco yield and safety. Moreover, this treatment led to a notable (170%) increase in free amino acid nitrogen content, with minimal impact on total amino acids and soluble proteins. Notably, it effectively increased the content of free amino acids beneficial to the sensory quality of tobacco (such as histidine, arginine, aspartic acid, isoleucine, and glutamic acid) without reducing the total amino acid content, while simultaneously reducing other amino acids that might affect quality. Therefore, the combined application of 0.30 mg/kg soil Mo and 0.24 g/kg soil N specifically optimized the amino acid composition in tobacco leaves, positively impacting overall quality and market competitiveness. Discussion: This study provides a theoretical basis for the rational application of Mo fertilizer in Mo-deficient areas to improve the yield and quality of fluecured tobacco. [ABSTRACT FROM AUTHOR]

Introduction: Changes in the rhizosphere microbiome and metabolites resulting from crop intercropping can significantly enhance crop growth. While there has been an increasing number of studies on various crop combinations, research on the intercropping of tobacco and maize at seedling stage remains limited. Methods: This study is the first to explore rhizosphere effects of intercropping between tobacco and maize seedling stages, we analyzed the nitrogen, phosphorus and potassium nutrients in the soil, and revealed the important effects on soil microbial community composition and metabolite profiles, thereby regulating crop growth and improving soil balance. Results and discussion: Compared with mono-cropping, intercropping increased the biomass of the two crops and promoted the nutrient absorption of nitrogen, phosphorus and potassium. Under intercropping conditions, the activities of sucrase, catalase and nitrate reductase in tobacco rhizosphere soil and the content of available potassium, the activities of nitrate reductase and acid phosphatase in maize rhizosphere soil were significantly increasing. Rhizosphere soil bacterial and fungal communities such as Sphingomonas, Massilia, Humicola and Penicillium respond differently to crop planting patterns, and soil dominant microbial communities are regulated by environmental factors such as pH, Organic Matter, Available Potassium, Nitrate Reductase, and Urease Enzyme. Network analysis showed that soil microbial communities were more complex after intercropping, and the reciprocal relationship between bacteria and fungi was enhanced. The difference of metabolites in soil between intercropping and monocropping system was mainly concentrated in galactose metabolism, starch and sucrose metabolism pathway, and the content of carbohydrate metabolites was significantly higher than that of monocropping soil. Key metabolites such as D-Sucrose, D-Fructose-6-Phosphate, D-Glucose-1-Phosphatel significantly influence the composition of dominant microbial communities such as Sphingomonas and Penicillium. This study explained the effects of intercropping between flue-cured tobacco and maize on the content of soil metabolites and soil microbial composition in rhizosphere soil, and deepened the understanding that intercropping system can improve the growth of flue-cured crops seedlings through rhizosphere effects. [ABSTRACT FROM AUTHOR]

Waxy corn is a special type of maize primarily consumed as a fresh vegetable by humans. Nitrogen (N) plays an essential role in regulating the growth progression, maturation, yield, and quality of waxy maize. A reasonable N application rate is vital for boosting the accumulation of both N and carbon (C) in the grains, thereby synergistically enhancing the grain quality. However, the impact of varying N levels on the dynamic changes in N metabolism, carbohydrate formation, and anthocyanin synthesis in purple waxy corn kernels, as well as the regulatory relationships among these processes, remains unclear. To explore the effects of varying N application rates on the N metabolism, carbohydrate formation, and anthocyanin synthesis in kernels during grain filling, a two-year field experiment was carried out using the purple waxy maize variety Jinnuo20 (JN20). This study examined the different N levels, specifically 0 (N0), 120 (N1), 240 (N2), and 360 (N3) kg N ha−1. The results of the analysis revealed that, for nearly all traits measured, the N application rate of N2 was the most suitable. Compared to the N0 treatment, the accumulation and content of anthocyanins, total nitrogen, soluble sugars, amylopectin, and C/N ratio in grains increased by an average of 35.62%, 11.49%, 12.84%, 23.74%, 13.00%, and 1.87% under N2 treatment over five filling stages within two years, respectively, while the harmful compound nitrite content only increased by an average of 30.2%. Correspondingly, the activities of related enzymes also significantly increased and were maintained under N2 treatment compared to N0 treatment. Regression and correlation analysis results revealed that the amount of anthocyanin accumulation was highly positively correlated with the activities of phenylalanine ammonia-lyase (PAL) and flavanone 3-hydroxylase (F3H), but negatively correlated with anthocyanidin synthase (ANS) and UDP-glycose: flavonoid-3-O-glycosyltransferase (UFGT) activity, nitrate reductase (NR), and glutamine synthetase (GS) showed significant positive correlations with the total nitrogen content and lysine content, and a significant negative correlation with nitrite, while soluble sugars were negatively with ADP-glucose pyrophosphorylase (AGPase) activity, and amylopectin content was positively correlated with the activities of soluble starch synthase (SSS), starch branching enzyme (SBE), and starch debranching enzyme (SDBE), respectively. Furthermore, there were positive or negative correlations among the detected traits. Hence, a reasonable N application rate improves purple waxy corn kernel nutritional quality by regulating N metabolism, as well as carbohydrate and anthocyanin biosynthesis. [ABSTRACT FROM AUTHOR]

Improving vegetable yield and optimizing its quality through nutrient management have long been central to plant nutrition and horticultural science. Copper (Cu) is recognized as an essential trace element that promotes plant growth and development. However, the mechanisms by which Cu influences nitrogen (N) metabolism remain largely unknown, with limited studies exploring the interaction between Cu and varying nitrate-to-ammonium (nitrate/ammonium) ratios. In this study, Chinese cabbage was exposed to two Cu concentrations (0 and 0.02 mg L-1) in combination with three nitrate/ammonium ratios (10/90, 50/50, and 90/10) under hydroponic conditions. The results showed that Cu application increased plant biomass, nitrate reductase (NR) and glutamine synthetase (GS) enzyme activities, the expression of NR (NIA) and GS2 (Gln2) genes, and N content in both shoots and roots. Additionally, Cu treatment decreased nitrate and free amino acid contents, as well as the expression of nitrate transporters NRT1.1 and NRT2.1 in roots while increasing these four parameters in shoots. Additionally, these effects were significantly modulated by the nitrate/ammonium ratios. In conclusion, Cu may facilitate nitrate transportation, enhance nitrate reduction, promote ammonium assimilation, and influence the transformation of organic N compounds, highlighting its potential role in improving N metabolism in Chinese cabbage. [ABSTRACT FROM AUTHOR]

Semi‐artificial photosynthetic system (SAPS) that combines enzymes or cellular organisms with light‐absorbing semiconductors, has emerged as an attractive approach for nitrogen conversion, yet faces the challenge of reaction pathway regulation. Herein, we find that photoelectrons can transfer from the −C≡N groups at the edge of cyano‐rich carbon nitride (g‐C3N4‐CN) to nitrate reductase (NarGH), while the direct electron transfer to nitrite reductase (cd1NiR) is inhibited due to the physiological distance limit of active sites (>14 Å). By means of the directional electron transfer between g‐C3N4‐CN and extracted biological enzymes, the product of the denitrification reaction was switched from inert N2 to usable nitrite with an unprecedented selectivity of up to 95.3 %. The converted nitrite could be further utilized by anammox microbiota and dissimilatory nitrate reduction to ammonia (DNRA) microorganisms, doubling the efficiency of total nitrogen removal (96.5±2.3 %) for biological nitrogen removal and ammonia generation (12.6 mg NH4+‐N L−1 h−1), respectively. Thus, our work paves an appealing way for the sustainable treatment and utilization of nitrate for ammonia fuel production by strategically regulating the electron transfer pathway across the biotic‐abiotic interface. [ABSTRACT FROM AUTHOR]

This review discusses the eco-friendly and cost-effective biosynthesis of gold nanoparticles (AuNPs) in viable microorganisms, focusing on microbes-mediated AuNP biosynthesis. This process suits agricultural, environmental, and biomedical applications, offering renewable, eco-friendly, non-toxic, sustainable, and time-efficient methods. Microorganisms are increasingly used in green technology, nanotechnology, and RNAi technology, but several microorganisms have not been fully identified and characterized. Bio-nanotechnology offers eco-friendly and sustainable solutions for nanomedicine, with microbe-mediated nanoparticle biosynthesis producing AuNPs with anti-oxidation activity, stability, and biocompatibility. Ultrasmall AuNPs offer rapid distribution, renal clearance, and enhanced permeability in biomedical applications. The review explores nano-size dependent biosynthesis of AuNPs by bacteria, fungi, and viruses revealing their non-toxic, non-genotoxic, and non-oxidative properties on human cells. AuNPs with varying sizes and shapes, from nitrate reductase enzymes, have shown potential as a promising nano-catalyst. The synthesized AuNPs, with negative charge capping molecules, have demonstrated antibacterial activity against drug-resistant Pseudomonas aeruginosa, and Acinetobacter baumannii strains, and were non-toxic to Vero cell lines, indicating potential antibiotic resistance treatments. A green chemical method for the biosynthesis of AuNPs using reducing chloroauric acid and Rhizopus oryzae protein extract has been described, demonstrating excellent stability and strong catalytic activity. AuNPs are eco-friendly, non-toxic, and time-efficient, making them ideal for biomedical applications due to their antioxidant, antidiabetic, and antibacterial properties. In addition to the biomedical application, the review also highlights the role of microbially synthesized AuNPs in sustainable management of plant diseases, and environmental bioremediation. [ABSTRACT FROM AUTHOR]

Backgroud: The present experiment was conducted to investigate the effects of in situ jaggery based biofloc on bio growth performance, physiological immune response, digestive enzyme activity, nutrient composition and disease resistance of Etroplus suratensis. Methods: The fingerlings of pearlspot, E. suratensis with an average body weight of 5.67±0.08 g was stocked at the rate of 150/m3 in treatment and control system. The insitu biofloc was produced in 2.4-ton capacity outdoor tanks using jaggery as carbon source at two different C:N ratio viz, 10: 1 (B1) and 20:1 (B2), where clear brackishwater system and without carbon sources as control. Result: The levels of ammonia nitrogen, nitrite-nitrogen and nitrate-nitrogen were reduced in the in situ biofloc compared to control while TSS and TS were increased significantly in all in situ biofloc compared to control. The physiological immune responses such as respiratory burst test, myeloperoxidase, serum lysozyme and antioxidant enzymes activity, superoxide dismutase and catalase were found to be significantly higher in B2 at end of the trial. Stress parameters glucose and cortisol were significantly lower in jaggery based biofloc system especially in (B2) C: N 20:1 compared to control. The fishes from the jaggery based biofloc groups possessed significantly (P<0.05) higher immune status as compared to control. The digestive enzymes activity such as amylase protease and lipase, of fish was higher in biofloc treatment and lower in control. Compared to control the nutrient composition of E. suratensis was significantly higher in the treatment groups. Moreover, jaggery based in situ fishes showed lower cumulative mortality rate and enhanced relative levels of protection after experimental challenge with A. hydrophila compared to control. [ABSTRACT FROM AUTHOR]

Global climate change and agricultural practices have increased atmospheric nitrogen (N) deposition, significantly affecting the nitrogen cycling process in grasslands. The impact of different N forms on key soil enzyme activities involved in N nitrification, particularly in the saline‐alkali grasslands of the Hexi Corridor, using natural grassland as a control (CK) and adding three N treatments: inorganic N (IN), organic N (ON) and a mixed N treatment (MN, with a 4:6 ratio of organic to inorganic N). Our study assessed the effects of these N forms on soil properties and enzyme activities crucial for N cycling. The findings indicate that different N forms significantly enhance soil mineral N content, with ON treatment leading to the highest increases in nitrate and ammonium content 92.44% and 35.6%, respectively, compared to CK. Both IN and ON treatments significantly boosted soil nitrate reductase and urease activities (p < 0.05), while MN treatment decreased nitrate reductase activity, with ON treatment showing the greatest sensitivity to enzyme activity changes. Soil pH slightly increased with N addition, but soil nitrite reductase activity remained relatively unchanged (0.372–0.385 mg g−1). Correlation analysis revealed that soil mineral N content and pH are key regulators of enzyme activities in saline‐alkaline grasslands. These results suggest that different N forms should be considered in nutrient cycling models, with organic N addition potentially enhancing soil N conversion and mitigating nutrient limitations in grassland ecosystems. [ABSTRACT FROM AUTHOR]

Melon damping off, which has a negative impact on melon quality and yield, can be safely and effectively managed with Trichoderma. Melon cultivar 'Longtian No. 1' was evaluated at both the adult and seedling stages in a pot experiment. The Rs and PD liquids were utilized as CK1 and CK2, respectively. Trichoderma viride Tv286 treatments T1B, T2B, T3B, and T4B were used based on Rs at concentrations of 104, 105, 106, and 107 CFU·g−1, respectively. The impact of several treatments on the antioxidant system and seedling quality of melon were assessed at 15, 25, and 35 days after sowing. We examined the effects of several treatments on melon quality, yield attributes, and physiological and biochemical markers during the adult stage at 10, 20, and 30 days after pollination. The effects of several treatments on melon damping off were also studied. Applying T. viride Tv286 at different rates effectively increased the activities of enzymes, including catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), ascorbate peroxidase (APX), and polyphenol oxidase (PPO), in the leaves of melon seedlings, significantly reduced the malondialdehyde (MDA) content, and improved the root–shoot ratio and seedling strength index. In terms of its influence on promoting the effect of antioxidant system indicators, T3B performed well. Melon seedlings treated with T3B showed higher CAT, POD, SOD, APX, and PPO activities in their leaves 35 days after sowing compared to CK1 (189.74, 169.61, 175.36, 224.20, and 477.39%, respectively). The strong seedling index and root–shoot ratio showed improvements of 130.43 and 79.71%, respectively, and the MDA content dropped by 35.66% at 35 days after sowing compared to CK1. Varying the rates at which T. viride Tv286 was applied increased the nitrate reductase (NR) activity and nitrate nitrogen, proline (Pro), chlorophyll, soluble sugar, and soluble protein contents in mature melon leaves, increasing melon quality and yield. T3B is the most effective marketing campaign. Compared to CK1, mature T3B leaves had higher NR activity, nitrate nitrogen content, chlorophyll content, soluble sugar content, soluble protein content, and Pro content 30 days after melon pollination (100.40, 135.17, 68.59, 93.65, 158.13, and 238.67%, respectively). The soluble solids, soluble protein, soluble sugar, vitamin C contents, and yield of melon fruit increased by 50.07, 126.82, 60.62, 70.79, and 61.45%, respectively, at 30 days after melon pollination compared to CK1. Optimal management of melon damping off can be accomplished with the application of T. viride Tv286 at different concentrations, with T3B exhibiting the best effect. The control effects reached 90.48 and 72.99% at the seedling and adult stages, respectively. Overall, T. viride Tv286 improved seedling quality, damping off control efficacy, melon yield and quality, and the antioxidant system during the seedling stage and enhanced physiological and biochemical characteristics during the adult stage. This study indicates the potential of T. viride Tv286 conidia as a biological control agent because it can prevent plant disease, increase yield, and improve quality. [ABSTRACT FROM AUTHOR]

The "knallgas" bacterium Cupriavidus necator is attracting interest due to its extremely versatile metabolism. C. necator can use hydrogen or formic acid as an energy source, fixes CO2 via the Calvin-Benson-Bassham (CBB) cycle, and grows on organic acids and sugars. Its tripartite genome is notable for its size and duplications of key genes (CBB cycle, hydrogenases, and nitrate reductases). Little is known about which of these isoenzymes and their cofactors are actually utilized for growth on different substrates. Here, we investigated the energy metabolism of C. necator H16 by growing a barcoded transposon knockout library on succinate, fructose, hydrogen (H2/CO2), and formic acid. The fitness contribution of each gene was determined from enrichment or depletion of the corresponding mutants. Fitness analysis revealed that (i) some, but not all, molybdenum cofactor biosynthesis genes were essential for growth on formate and nitrate respiration. (ii) Soluble formate dehydrogenase (FDH) was the dominant enzyme for formate oxidation, not membrane-bound FDH. (iii) For hydrogenases, both soluble and membrane-bound enzymes were utilized for lithoautotrophic growth. (iv) Of the six terminal respiratory complexes in C. necator H16, only some are utilized, and utilization depends on the energy source. (v) Deletion of hydrogenase-related genes boosted heterotrophic growth, and we show that the relief from associated protein cost is responsible for this phenomenon. This study evaluates the contribution of each of C. necator's genes to fitness in biotechnologically relevant growth regimes. Our results illustrate the genomic redundancy of this generalist bacterium and inspire future engineering strategies. IMPORTANCE The soil bacterium Cupriavidus necator can grow on gas mixtures of CO2, H2, and O2. It also consumes formic acid as carbon and energy source and various other substrates. This metabolic flexibility comes at a price, for example, a comparatively large genome (6.6 Mb) and a significant background expression of lowly utilized genes. In this study, we mutated every non-essential gene in C. necator using barcoded transposons in order to determine their effect on fitness. We grew the mutant library in various trophic conditions including hydrogen and formate as the sole energy source. Fitness analysis revealed which of the various energy-generating iso-enzymes are actually utilized in which condition. For example, only a few of the six terminal respiratory complexes are used, and utilization depends on the substrate. We also show that the protein cost for the various lowly utilized enzymes represents a significant growth disadvantage in s pecific conditions, offering a route to rational engineering of the genome. All fitness data are available in an interactive app at https://m-jahn.shinyapps.io/ShinyLib/. [ABSTRACT FROM AUTHOR]

Drawing inspiration from the nitrate reductase enzymes, which catalyze nitrate to nitrite in nature, here a bio‐inspired, reduced molybdenum oxide (MoOx) shell is introduced that is grown on top of a dendritic nickel foam core (NiNF). The resulting MoOx/NiNF material is prepared via a facile, two‐step electrodeposition strategy using commercially available, low‐cost precursors. This catalytic material displays a remarkable faradaic efficiency (FE) of 99% at −0.5 V versus RHE and a high ammonia (NH3) yield rate of up to 4.29 mmol h−1 cm−2 at −1.0 V versus RHE in neutral media. Most importantly, MoOx/NiNF exhibits exceptional stability for the nitrate reduction reaction (NO3RR), maintaining operation for over 3100 h at a high current density of −650 mA cm−2, with a yield rate of 2.6 mmol h−1 cm−2 and a stable average NH3 FE of ≈83%. Through combined XPS and in situ Raman spectroscopy it is shown that the pronounced affinity of MoOx/NiNF for nitrate is associated with a substantial presence of oxygen vacancies within the material. [ABSTRACT FROM AUTHOR]

The global ocean is undergoing gradual acidification and eutrophication which may have significant impacts on macroalgal communities. However, little is known regarding the interactive effects of ocean acidification (OA) and nitrate on Ulva lactuca, a primary producer widely distributed in coastal waters. This study focuses on the possible interactive effects of OA and elevated nitrate levels on physiological parameters of U. lactuca. Higher nitrate levels may increase growth, photosynthesis, respiration, pigment synthesis, Fv/Fm and Effective Quantum Yield, whereas CO2 enrichment may result in a reduction in photosynthesis, pigment content, Fv/Fm and Effective Quantum Yield. Higher nitrate levels increase NO3- uptake rate and nitrate reductase activity, which are further amplified by elevated CO2 levels. However, the stimulation of high nitrate towards pigment synthesis and photosynthesis is negatively affected by elevated CO2 levels. Our results suggest that U. lactuca could potentially increase its biomass in coastal eutrophic waters, and OA in the future is not expected to promote the growth of U. lactuca, but it can enhance its potential biofiltration to remove nitrate from coastal ecosystems. [ABSTRACT FROM AUTHOR]

Serotonin is a well-known animal hormone and ubiquitous monoamine. In recent years, its presence in plants has attracted the attention of many researchers. In plants, serotonin as signaling hormone plays a pivotal role in hormonal crosstalk, regulating antioxidant metabolism and developmental processes under abiotic stresses. Among abiotic stresses, salt stress considerably influences Guizotia abyssinica growth and physio-chemical functions. The effect of exogenous serotonin was assessed to ameliorate the harmful effect of salinity stress at different levels. All the growth parameters, chlorophyll pigments, gas exchange indicators, and nitrate reductase activity were decreased under all salinity levels while 2-thiobarbituric acid reactive substances (TBARS), proline, and antioxidant activities were increased. Serotonin improved the length of roots and shoots, basal diameter, leaf number, area, width and length, root dry matter, stem dry matter, leaves dry matter, chlorophyll a, chlorophyll b, chlorophyll fluorescence, transpiration rate, stomatal conductance, photosynthetic rate, relative water content, water use efficiency, and nitrate reductase under salt stress condition. Moreover, the upregulation of antioxidant enzymes evoked by the salt stress was further enhanced. Taken together, salt stress inhibited the growth and performance of G. abyssinica, however, exogenous application of serotonin fortified its tolerance by mitigating membrane damage and improving assimilatory functions, plant water status and plant defense metabolism, thereby lowering the adverse effects of salt stress on various plant growth performance and physio-biochemical functions. [ABSTRACT FROM AUTHOR]

Utilizing ammonium in wastewater is a prospective way to reduce costs for bioproduction by photosynthetic organisms. A model cyanobacterium Synechocystis sp. PCC 6803 takes advantage of tolerance to ammonium compared to other microalgae. However, in this study, we report that Synechocystis growth was inhibited when cultured in a medium containing ammonium. This may be due to the pH decreasing below 6 caused by consuming ammonium. Transcriptomic analysis by RNA-seq revealed that the expression of the genes for proteases, chaperones, and antioxidant-scavenging enzymes was induced, but photosynthetic components were repressed. Although these regulations are similar to the previous studies on acidic stress in nitrate-containing culture, the expression of genes such as sigD , slr0042 , slr0373 , slr0374 , and slr1501 was different, indicating that these phenomena are not simply identical to the known responses to acidic stress. The expression of the genes for photosynthesis, gluconeogenesis, and nitrogen assimilation was repressed, and glycolysis and the tricarboxylic acid cycle were induced. Despite the up-regulation of the carbon catabolism and down-regulation of nitrogen assimilation, the 2-oxoglutarate content in the ammonium-grown cells was lower than that in the nitrate-grown cells, and the contents of the major amino acids, such as Glu, Ala, Asp, and Gly were decreased, while the minor amino acids were the same or increased, especially Arg, Lys, Val, and Ile. These results demonstrated that the acidic stress induced by the consumption of ammonium ions differs from the sudden pH drop, and the Synechocystis cell manages amino acid levels to endure carbon limitation under the stress. [ABSTRACT FROM AUTHOR]

Nitrogen (N) is a macronutrient essential for plant growth and development; insufficient N availability has an extensive impact on the overall plant metabolism and productivity. Polyamines, short aliphatic amino-containing compounds naturally produced by living cells, have been widely reported to be beneficial for plant performance under several unfavorable conditions. In this work, the role of polyamine spermine (Spm) as a priming agent for wheat growing under N deficit was investigated. Wheat seeds were primed with 0.1 mM Spm for 3 h, germinated for 48 h, and then grown in N-sufficient or N-deficient media for 8 d. Spm treatment anticipated seed germination and, though priming with Spm did not result in any stimulatory effect on plants developed under an N-sufficient medium, under N limitation many of the studied traits improved compared with control plants. Under N deficit, wheat seedlings originated from Spm-primed seeds showed increased root length, developed the third leaf earlier, and maintained higher total N and protein contents and higher nitrate reductase (NR) and glutamine synthetase (GS) activities in their leaves, compared to control plants. Likewise, total amino acids increased in the roots of primed seedlings, and carbohydrates enhanced both in roots and leaves. Our findings indicate that seed priming with Spm promotes wheat germination and early seedling growth under N limitation, mainly by promoting root elongation and N allocation to the aerial part. [ABSTRACT FROM AUTHOR]

The unique positioning of mangrove ecosystems between land and sea makes them vital in the nitrogen cycle. The role of nitrification in the nitrogen cycle is important to provide nitrogen compounds readily absorbed by mangrove plants. Nevertheless, the nitrification process and nitrifying bacteria in mangrove areas have yet to be comprehensively understood. The primary objective of this study is to provide comprehensive analysis of nitrifying bacteria in mangrove sediments by conducting a systematic review. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses method is used as a guide to help report reviews systematically and has a flow chart to show the process of selecting relevant studies. Data collection was carried out by utilizing 6 databases and journal search engines including Scopus, PubMed, ResearchGate, Google Scholar, and Springer in order to achieve more comprehensive findings. This study employed the widely recognized and commonly used technique of defining the review's scope in a focused manner by first identifying the population, intervention, comparison, and outcome. This study identified 358 studies, and 31 studies were included in the review after screening. Based on the screening results, research on nitrifying bacteria in mangrove sediments is geographically limited to several countries such as Indonesia, Vietnam, Thailand, China, Mexico, the United States, India, and Saudi Arabia. This study vealed that there is a high level of diversity among nitrifying bacteria in mangrove sediment, with five distinct groups identified: ammonia oxidizing bacteria, nitrite oxidizing bacteria, anammox bacteria, and comammox bacteria, a recently identified group. In carrying out changes in nitrogen compounds, nitrifying bacteria use functional genes from different steps of the nitrification process, such as nitrogenase, ammonia monooxygenase subunit A, nitrite oxidoreductase alpha subunit, nitrate reductase alpha chain, nitrite reductase, nitric oxide reductase, nitrous oxide reductase, hydrazine synthase, hydrazine oxidoreductase and hydroxylamine oxidoreductase genes. Ammonia-oxidizing bacteria were the predominant group in general, but various nitrifying bacteria groups were distributed diversely across different mangrove environments. This study also indicated the vegetation type and the distribution of nitrifying bacteria in mangrove sediments. The depth of these sediments typically varies from 0 to 60 centimeters, with most samples taken at a depth of 0 to 20 centimeters. The type of vegetation at the sampling location is dominated by species of Kandelia candel, Avicennia marina, Kandelia obovata, and Rhizophora mangle. Limitations regarding research on nitrifying bacteria in mangrove sediments provide opportunities for in-depth study. This comprehensive review provides an in-depth overview of the variety and spread of nitrifying bacteria, highlighting their role in nitrogen cycling and emphasizing the potential for discovering new nitrifying bacteria in mangrove sediments. [ABSTRACT FROM AUTHOR]

This study investigates the impact of various molecular weights (MWs) of fulvic acid (FA) on maize growth, grain yield, and nutrient uptake under different nitrogen levels (NLs). A 2 × 3 balanced design was employed, with high (0.2 g N/kg) and low (0.05 g N/kg) NLs, and three FA MW ranges (W1 = 3 000 D, 3 000 < W2 = 10 000 D, W3 > 10 000 D) were applied at 25 mg/kg in soil. Significant interactions between NLs and FA MWs were observed in chlorophyll a/b ratio, nitrate reductase and glutamate dehydrogenase activities, nitrogen content, and nitrogen uptake efficiency. Overall, under different NLs, FA application reduced chlorophyll a/b ratio, increased nitrogen metabolism enzyme activities, promoted maize growth, and thereby improved grain yield and nitrogen fertiliser uptake efficiency. Additionally, the promotion effect of low MW FA on these indicators outweighed that of high MW FA, yet the latter exhibited a more pronounced effect on increasing grain nitrogen concentration. Structural equation model analysis revealed direct effects of chlorophyll content, nitrogen accumulation, nitrogen uptake efficiency, NLs and FA MWs on maize grain yield, with FA MWs negatively impacting yield. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to evaluate the impact of peanut straw mulching on the N change and the functional genes in Camellia oleifera intercropping systems. Methods: A field experiment with different types of straw mulch treatments (conventional tillage, whole, and crushed) and timing was (50 d and 150 d) established between 2018–2022; the soil N fractions, N transformation rates, the abundance and dominant species compositions of ammonia-oxidizing archaea (AOA), nirK, and nirS-harboring genes were investigated. Results: The whole peanut straw mulching of 150 d significantly improved (P < 0.05) the content of soil microbial biomass N (MBN), ammonia N (NH4+), and nitrate N (NO3-). The soil nitrification and ammonification rates increased by 96.8% and 132% in the 150 d of peanut crushed and whole straw mulching, respectively. Notably, the peanut straw mulching of 50 d mainly affects the diversity and relative abundance of AOA while the soil nirK and nirS-harboring genes were affected by 150 d crushed and whole peanut straw mulching, respectively. Redundancy analysis showed that crushed and whole peanut straw mulching affects nitrate reductase as the primary factor in regulating the soil N cycle via functional genes and soil variables. Conclusions: Long-term whole peanut straw or whole and crushed mixed straw mulching could hence be recommended to dryland farming communities to increase the soil N cycle and crop productivity in the C.oleifera-peanut intercropping system. [ABSTRACT FROM AUTHOR]

Cardiovascular functions in diabetes greatly depend on constitutive NOS (cNOS) activity. A comparative study of the effects of a steroid hormone ecdysterone and enalapril, an ACE inhibitor widely used to treat cardiac disorders on cNOS, inducible NOS (iNOS), xanthine oxidoreductase (XOR) activity, RNS, ROS, and lipid peroxidation in heart tissue in experimental diabetes was conducted. The rat model of diabetes was established by streptozotocin injection. NOS activity, NO2−, NO3−, uric acid, nitrosothiols, hydroperoxide, superoxide, and diene conjugate formation were studied spectrophotomerically. In diabetes, cNOS downregulation correlated with a dramatic fall of NO2− production and ~4.5-fold elevation of nitrosothiols, which agreed with a steep rise of iNOS activity, while NO3− remained close to control. Dramatic activation of XOR was observed, which correlated with the elevation of both superoxide production and nitrate reductase activity and resulted in strong lipid peroxidation. Ecdysterone and enalapril differently affected RNS metabolism. Ecdysterone moderately restored cNOS but strongly suppressed iNOS, which resulted in the reduction of NO3−, but full restoration of NO2− production. Enalapril better restored cNOS but less effectively suppressed iNOS, which promoted NO3− formation. Both drugs similarly inhibited XOR, which equally alleviated oxidative stress and lipid peroxidation. The synergistic action of iNOS and XOR was a plausible explanation for strong lipid peroxidation, abolished by the inhibition of iNOS and XOR by ecdysterone or enalapril. Complementary effects of ecdysterone and enalapril on cNOS, iNOS, and RNS are a promising basis for their combined use in the treatment of cardiovascular disorders caused by cNOS dysfunction in diabetes. [ABSTRACT FROM AUTHOR]

Denitrification is a crucial process in the global nitrogen cycle, in which two functionally equivalent genes, nirS and nirK, catalyse the critical reaction and are usually used as marker genes. The nirK gene can function independently, whereas nirS requires additional genes to encode nitrite reductase and is more sensitive to environmental factors than nirK. However, the ecological differentiation mechanisms of those denitrifying microbial communities and their adaptation strategies to environmental stresses remain unclear. Here, we conducted metagenomic analysis for sediments and bioreactor samples from Lake Donghu, China. We found that nirS‐type denitrifying communities had a significantly lower horizontal gene transfer frequency than that of nirK‐type denitrifying communities, and nirS gene phylogeny was more congruent with taxonomy than that of nirK gene. Metabolic reconstruction of metagenome‐assembled genomes further revealed that nirS‐type denitrifying communities have robust metabolic systems for energy conservation, enabling them to survive under environmental stresses. Nevertheless, nirK‐type denitrifying communities seemed to adapt to oxygen‐limited environments with the ability to utilize various carbon and nitrogen compounds. Thus, this study provides novel insights into the ecological differentiation mechanism of nirS and nirK‐type denitrifying communities, as well as the regulation of the global nitrogen cycle and greenhouse gas emissions. [ABSTRACT FROM AUTHOR]

Molybdenum (Mo) is an essential micronutrient across all kingdoms of life, where it functions as a key component of the active centers of molybdenum-dependent enzymes. For these enzymes to gain catalytic activity, Mo must be complexed with a pterin scaffold to form the molybdenum cofactor (Moco). The final step of Moco biosynthesis is catalyzed by the enzyme Mo-insertase. This review focuses on eukaryotic Mo-insertases, with an emphasis on those found in plants and mammals, which have been instrumental in advancing the understanding of Mo biochemistry. Additionally, a historical perspective is provided, tracing the discovery of Mo-insertase from the early 1960s to the detailed characterization of its reaction mechanism in 2021. This review also highlights key milestones in the study of Mo-insertase, including mutant characterization, gene cloning, structural elucidation at the atomic level, functional domain assignment, and the spatial organization of the enzyme within cellular protein networks. [ABSTRACT FROM AUTHOR]

The transmembrane nitrate reductase (Nar) is the first enzyme in the dissimilatory alternate anaerobic nitrate respiratory chain in denitrifying bacteria. To date, there has been no real-time method to determine its specific activity embedded in its native membrane; here, we describe such a new method, which is useful with the inside-out membranes of Paracoccus denitrificans and other denitrifying bacteria. This new method takes advantage of the native coupling of the endogenous NADH dehydrogenase or Complex I with the reduction of nitrate by Nar through the quinone pool of the inner membranes of P. denitrificans. This is achieved under previously reached anaerobic conditions. Inner controls confirming the specific Nar activity determined by this new method were made by the total inhibition of the Nar enzyme by sodium azide and cyanide, well-known Nar inhibitors. The estimation of the Michaelis–Menten affinity of Nar for NO3− using this so-called Nar-JJ assay gave a Km of 70.4 μM, similar to previously determined values. This new Nar-JJ assay is a suitable, low-cost, and reproducible method to determine in real-time the endogenous Nar activity not only in P. denitrificans, but in other denitrifying bacteria such as Brucella canis, and potentially in other entero-pathogenic bacteria. [ABSTRACT FROM AUTHOR]

Annona emarginata is a native Brazilian species capable of producing at least ten alkaloids of ecological, agronomic, and pharmacological importance. Some studies have explored the effect of external phytoregulators on the production of alkaloids, including the effect of auxins, which, like alkaloids, derive from the shikimic acid pathway. Thus, this study aimed to evaluate how indole acetic acid (IAA) and its inhibitor 2,3,5-triiodobenzoic acid (TIBA) impact the production of alkaloids and the primary metabolism of A. emarginata, which brings advances in the understanding of the mechanisms of alkaloid synthesis and can aid in the bioprospection of molecules of interest in Annonaceae. The design was completely randomized, with three treatments (control, IAA [10−6 M] and TIBA [10−6 M]) and five collection times (12, 36, 84, 156, and 324 h). The following variables were analyzed: total alkaloids, alkaloid profile, nitrate reductase activity, gas exchange in photosynthesis, chlorophyll a fluorescence, sugars, starch, and antioxidant activity. Of the twelve alkaloids analyzed, discretine and xylopine were not detected in the control plants; however, both were detected when IAA was applied (in roots and leaves) and xylopine (in roots) when the inhibitor was applied. The alkaloid asimilobine was not detected with the use of TIBA. Variations in alkaloid concentrations occurred in a punctual manner, without significant variations in photosynthesis and nitrate reductase activity, but with variations in the antioxidant system and sugar concentrations, mainly at 156 h, when the highest alkaloid concentrations were observed with the use of TIBA. It could be concluded that IAA is capable of selectively modulating the production of alkaloids in A. emarginata, either due to an external source or by the application of its inhibitor (TIBA). [ABSTRACT FROM AUTHOR]

In sweet potato, rational nitrogen (N) assimilation and distribution are conducive to inhibiting vine overgrowth. Nitrate (NO3-) is the main N form absorbed by roots, and cultivar is an important factor affecting N utilization. Herein, a hydroponic experiment was conducted that included four NO3- concentrations of 0 (N0), 4 (N1), 8 (N2) and 16 (N3) mmol L-1 with two cultivars of Jishu26 (J26, N-sensitive) and Xushu32 (X32, N-tolerant). For J26, with increasing NO3- concentrations, the root length and root surface area significantly decreased. However, no significant differences were observed in these parameters for X32. Higher NO3- concentrations upregulated the expression levels of the genes that encode nitrate reductase (NR2), nitrite reductase (NiR2) and nitrate transporter (NRT1.1) in roots for both cultivars. The trends in the activities of NR and NiR were subject to regulation of NR2 and NiR2 transcription, respectively. For both cultivars, N2 increased the N accumulated in leaves, growth points and roots. For J26, N3 further increased the N accumulation in these organs. Under higher NO3- nutrition, compared with X32, J26 exhibited higher expression levels of the NiR2, NR2 and NRT1.1 genes, a higher influx NO3- rate in roots, and higher activities of NR and NiR in leaves and roots. Conclusively, the regulated effects of NO3- supplies on root growth and NO3- utilization were more significant for J26. Under high NO3- conditions, J26 exhibited higher capacities of NO3- absorption and distributed more N in leaves and in growth points, which may contribute to higher growth potential in shoots and more easily cause vine overgrowth. [ABSTRACT FROM AUTHOR]

AbstractIn hydroponics, preferring a higher nitrate to ammonia ratio can lead to nitrate accumulation in plant tissues. Reducing nitrate application and substituting nitrate-based fertilizers with ammonium or urea can help solve this issue. Additionally, adding molybdenum (Mo) can decrease nitrate accumulation by stimulating nitrate reductase activity. This study was carried out in a factorial design within a completely randomized experimental setup to investigate the effects of varying nitrate, ammonium, and urea ratios, as well as Mo concentration in the nutrient solution, on vegetative growth and biochemical parameters in hydroponically grown Jenovise basil. The treatments included different ratios of nitrate: ammonium: urea (75:25:0, 50:25:25, 25:25:50, 0:25:75, 50:0:50, 25:0:75, 0:0:100, or 100:0:0) and three Mo levels (0.001, 0.01, 0.1 mg. L−1) in a modified Hoagland solution. The results indicated that growth-associated characteristics improved when nitrate was partially substituted with ammonium and urea in the nutrient solution. The highest total phenolics (2.61 mg. g−1 DW) and flavonoids (2500.36 mg. g−1 DW) were observed at a nitrate: ammonium: urea ratio of 75:25:0 with 0.1 mg. L−1 Mo. Plants treated with a nutrient solution containing a nitrate: ammonium: urea ratio of 0:25:75 and 0.01 mg L−1 Mo showed a significant increase in chlorophyll b concentration, reaching 0.22 mg.g−1 FW, which was higher than all other treatments. In conclusion, our findings demonstrated that optimizing the combined nitrate, ammonium, and urea ratios along with Mo in the nutrient solution regulated nitrate accumulation and growth in hydroponically grown basil. [ABSTRACT FROM AUTHOR]

This article presents the genome sequence of a strain of Methylomonas sp. AM2-LC, a methanotrophic bacterial species found in a Finnish lake. Methanotrophic bacteria are important for reducing methane emissions and have potential for biotechnological applications. The genome sequence can be used for comparative analysis and understanding the metabolic capabilities of methanotrophs. The article also discusses the isolation and DNA extraction process, as well as bioinformatic services provided by a sequencing facility. The document is a list of references related to methanotrophic bacteria, providing a comprehensive overview of current research in the field. It includes references to three scientific articles that cover microbial variant detection, methane-dependent mineral reduction, and the discovery of a new type of methanotroph. These articles are valuable resources for library patrons conducting research in microbiology. [Extracted from the article]

The phosphate solubilizing properties of Lysinibacillus macroides ST-30, Pseudomonas pelleroniana N-26, and Bacillus cereus ST-6 were tested for the chickpea crop of the Tarai region of Uttarakhand. These microbially inoculated plants have shown significant (p > 0.05) improvement in the plant health and crop health parameters, viz., root length, shoot length, fresh weight, dry weight, nodule number, nodule fresh weight, nodule dry weight, chlorophyll content, and nitrate reductase. The highest shoot length (46.10 cm) and chlorophyll content (0.57 mg g-1 fresh weight) were observed in ST-30 at 75 DAS with 20 kg P2O5/ha. Similarly, for plant P content, an increase of 90.12% over control was recorded in the same treatment. Treatments consisting of Lysinibacillus macroides ST-30 along with 20 kg/ha P2O5 were found to be most suitable as phosphatic fertilizer. Conclusively, sustainable agriculture practices in the Tarai as well as the field region may be developed based on a strategy of exploring microbial inoculants from the pristine region of the Western Himalayas. The presence and abundance of bacterial inoculants were confirmed through qRT-PCT. We conclude that the effective plant growth-promoting bacterium Lysinibacillus macroides ST-30 broadens the spectrum of phosphate solubilizers available for field applications and might be used together with 20 Kg/ha P2O5. [ABSTRACT FROM AUTHOR]

Introduction: Salinity negatively affects maize productivity. However, calcium lignosulfonate (CLS) could improve soil properties and maize productivity. Methods: In this study, we evaluated the effects of CLS application on soil chemical properties, plant physiology and grain quality of maize under salinity stress. Thus, this experiment was conducted using three CLS application rates, CLS0, CLS5, and CLS10, corresponding to 0%, 5%, and 10% of soil mass, for three irrigation water salinity (WS) levels WS0.5, WS2.5, and WS5.5 corresponding to 0.5 and 2.5 and 5.5 dS/m, respectively. Results and discussion: Results show that the WS0.5 × CLS10 combination increased potassium (K 0.167 g/kg), and calcium (Ca, 0.39 g/kg) values while reducing the sodium (Na, 0.23 g/kg) content in soil. However, the treatment WS5.5 × CLS0 decreased K (0.120 g/kg), and Ca (0.15 g/kg) values while increasing Na (0.75 g/kg) content in soil. The root activity was larger in WS0.5 × CLS10 than in WS5.5 × CLS0, as the former combination enlarged K and Ca contents in the root while the latter decreased their values. The leaf glutamine synthetase (953.9 µmol/(g.h)) and nitrate reductase (40.39 µg/(g.h)) were higher in WS0.5 × CLS10 than in WS5.5 × CLS0 at 573.4 µmol/(g.h) and 20.76 µg/(g.h), leading to the improvement in cell progression cycle, as revealed by lower malonaldehyde level (6.57 µmol/g). The K and Ca contents in the leaf (881, 278 mg/plant), stem (1314, 731 mg/plant), and grains (1330, 1117 mg/plant) were greater in WS0.5 × CLS10 than in WS5.5 × CLS0 at (146, 21 mg/plant), (201, 159 mg/plant) and (206, 157 mg/plant), respectively. Therefore, the maize was more resistance to salt stress under the CLS10 level, as a 7.34% decline in yield was noticed when salinity surpassed the threshold value (5.96 dS/m). The protein (13.6 %) and starch (89.2 %) contents were greater in WS0.5 × CLS10 than in WS5.5 × CLS0 (6.1 %) and (67.0 %), respectively. This study reveals that CLS addition can alleviate the adverse impacts of salinity on soil quality and maize productivity. Thus, CLS application could be used as an effective soil amendment when irrigating with saline water for sustainable maize production. [ABSTRACT FROM AUTHOR]

Ginseng, from the roots of Panax ginseng C. A. Meyer, is a widely used herbal medicine in Asian countries, known for its excellent therapeutic properties. The growth of P. ginseng is depend on specific and strict environments, with a preference for wetness but intolerance for flooding. Under excessive soil moisture, some irregular rust-like substances are deposited on the root epidermis, causing ginseng rusty symptoms (GRS). This condition leads to a significant reduce in yield and quality, resulting in substantial economic loses. However, there is less knowledge on the cause of GRS and there are no effective treatments available for its treatment once it occurs. Unsuitable environments lead to the generation of large amounts of reactive oxygen species (ROS). We investigated the key indicators associated with the stress response during different physiological stages of GRS development. We observed a significant change in ROS level, MDA contents, antioxidant enzymes activities, and non-enzymatic antioxidants contents prior to the GRS. Through the analysis of soil features with an abundance of moisture, we further determined the source of ROS. The levels of nitrate reductase (NR) and nitric oxide synthase (NOS) activities in the inter-root soil of ginseng with GRS were significantly elevated compared to those of healthy ginseng. These enzymes boost nitric oxide (NO) levels, which in turn showed a favorable correlation with the GRS. The activities of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase first rose and then decreased as GRS developed. Excess soil moisture causes a decrease in oxygen levels. This activated NR and NOS in the soil, resulting in a production of excess NO. The NO then diffused into the ginseng root and triggered a burst of ROS through NADPH located on the cell membrane. Additionally, Fe2+ in soil was oxidized to red Fe3+, and finally led to GRS. This conclusion was also verified by the Sodium Nitroprusside (SNP), a precursor compound producing NO. The presence of NO from NR and NOS in water-saturated soil is responsible for the generation of ROS. Among these, NO is the main component that contribute to the occurrence of GRS. [ABSTRACT FROM AUTHOR]

To analyse the effect of nutrient management on the growth, physiology, energy utilization, production and quality of black gram, a field trial on black gram was conducted at eastern Indian Gangetic alluvium during the autumn of 2020 and 2021. Treatments were two soil applications of cobalt (Co) and foliar spray of potassium (K) and boron (B) in five combinations. All treatments were arranged in a split-plot design and repeated three times. Two soil applications of cobalt (Co) were assigned in the main plots and foliar spray of potassium (K) and boron (B) in five combinations were assigned in sub-plots. Applications of Co in soil and foliar K+B facilitated significantly higher (p≤0.05) values for aerial dry matter (ADM), leaf area index (LAI), nodules per plant, total chlorophyll, net photosynthetic rate and nitrate reductase content in both 2020 and 2021, with a greater realization of photosynthetically active radiation interception, and use efficiency (IPAR and PARUE respectively), seed yield, seed nutrients and protein contents. Differences in LAI exhibited positive and linear correlation with IPAR explaining more than 60% variations in different growth stages. The innovative combination of soil Co (beneficial nutrient) application at 4 kg ha−1 combined with foliar 1.25% K (macronutrient) + 0.2% B (micronutrient) spray is a potential agronomic management schedule for the farmers to sustain optimum production of autumn black gram through substantial upgradation of growth, physiology, energy utilization, production and quality in Indian subtropics. [ABSTRACT FROM AUTHOR]

[Objectives] The paper aimed to study the effects of four kinds of different plant growth-promoting rhizobacteria(PGPR)on the rhizosphere environment change, growth and physiology of Isatis indigotica, in order to provide theoretical reference for the production of I. indigotica. [Methods] The four kinds of PGPR, which were named Enterobacter sp. GS-22, Bacillus sp. GS-27, Sphingobacterium sp. GS-72 and Acinetobacter sp. GS-103, were applied in pot experiment. In order to evaluate the growth promotion effect of PGPR on I. indigotica, the relevant indicators were determined, including soil physical and chemical properties, growth traits, photosynthetic parameters, nutrient and related enzyme activities, active components, and so on. [Results] The four kinds of PGPR had different effects on soil physicochemical properties. GS-22 and GS-72 could increase soil total nitrogen content, GS-22 and GS-103 significantly increased soil available phosphorus content, and soil organic matter content in all treatment groups significantly increased. Compared with not inoculated with soil rhizosphere bacteria(CK), the activities of soil urease, soil alkaline phosphatase and soil sucrase increased by 33. 78%-73. 70%, 49. 51%-83. 93% and 8. 10%-186. 26%, respectively. Four rhizosphere bacteria promoted the growth of I. indigotica, and increased plant height, taproot diameter, dry weight, fresh weight, and so on, and GS-22 had the most significant effect on the growth traits of I. indigotica. PGPR also had significant effects on physiology of I. indigotica. The activities of nitrate reductase, sucrose synthetase and acid phosphatase increased by 53. 81%-125. 19%, 57. 64%-76. 54% and 7. 87%-22. 78% compared with CK, respectively. Four rhizosphere bacteria were beneficial to the accumulation of nutrients, like soluble sugars, free amino acids, and active components, like total flavonoids, indigo and indirubin of I. indigotica, in which GS-22 and GS-27 especially increased the contents of total flavonoids, indigo and indirubin. [Conclusions] The rhizosphere bacteria GS-22, GS-27, GS-72 and GS-103 had the ability to promote plant growth in I. indigotica, improve the soil environment, and promote the growth and physiological processes of I. indigotica. Among them, GS-27 had the best comprehensive capability. The screened strains provided strategies for developing specialized microbial fertilizer for I. indigotica and achieving increased yield and efficiency of Chinese herbs. [ABSTRACT FROM AUTHOR]

Sorghum is a plant that mainly requires chemical nitrogen fertilization. There are organic fertilizers that can provide nutrients to plants with great benefits to the soil, such as chicken manure. To determine the influence of organic fertilization on nitrate reductase (NR), glutamine synthetase (GS), and the amount of chlorophyll, sorghum plants were grown using the following four treatments: soil (T1), soil + chicken manure 100 kg ha−1 of nitrogen (N) (T2), soil + chicken manure 200 kg ha−1 N (T3), and soil + ammonium sulfate 100 kg ha−1 N (T4). Leaves were sampled in the vegetative stage (VS), the reproductive stage (RS), and the maturation stage (MS). The highest NR activity occurred in plants with T2 and T3 in the VS. The highest GS activity was in T3 and T4 in the RS. The amount of chlorophyll a was the same in all phenological stages. However, the amount of chlorophyll b was influenced by the type of fertilization at different phenological stages. Organic fertilizers (OF) produced the highest NR activity. On the other hand, GS activity was higher with chemical fertilization (T4), which was equal to the second dose of organic fertilization (T3). Finally, chlorophyll a and b were influenced by both types of fertilization, and was different from T1. [ABSTRACT FROM AUTHOR]

Background: PGZ, a peroxisome proliferator-activated receptor γ agonist, possesses anti-inflammatory and antioxidant actions. The current study investigated an alternative molecular target of pioglitazone (PGZ) to protect against inflammatory bowel disease development. Methods: Rats were allocated into 4 groups: normal control (NC), acetic acid (AA), PGZ (25 mg/kg intraperitoneal (i.p) and PGZ+ EX527 (a sirtuin1 inhibitor) (5mg/kg, i.p) groups. Results: PGZ attenuated ulcerative colitis severity evident by decreased disease activity index, colon weight/ length ratio, gross damage, histological disruption and myeloperoxidase activity. PGZ suppressed oxidative stress by inhibition of lipid peroxidation and nitrite/nitrate content and enhancing glutathione level and antioxidant enzyme activities. PGZ reduction of colon injury was accompanied by suppressed inflammatory response as evidenced by decreased proinflammatory cytokines and IFN-γ- inducible protein 10 (CXCL 10) with restored interleukin-10. PGZ repaired the mucosal barrier integrity evident by increased claudin1expression. PGZ upregulated mRNA and protein expressions of SIRT1 (Silent information regulator 2 homologue 1) and p-IκBα (phosphory lated inhibitor kappa Balpha) protein expression. PGZ down regulated NOX4 (nicotinamide adenine dinucleotide phosphate oxidase 4), TLR4 (toll like receptor4), IKKβ kinase and p65 subunit mRNA expressions. Additionally, in RAW264.7 cells, PGZ suppressed protein expressions of H3K9ac (histone H3 lysine acetylation), NOX4 and inducible nitric oxide synthase, upregulated SIRT1 and arginase-1protein expressions. EX527 co-treatment reversed all effects of PGZ. Conclusions: Our findings indicated the beneficial effects of PGZ in UC via modulation of SIRT1/NOX4 signaling besides suppression of TLR4/NF-κB cascades and M1-M2 macrophage polarization. [ABSTRACT FROM AUTHOR]

Biomass pyrolysis by-products, such as biochar (BC) and wood vinegar (WV), are widely used as soil conditioners and efficiency enhancers in agriculture. A pot experiment was conducted to examine the effects of WV, both alone and in combination with BC, on soil properties in mildly saline soil and on cotton stress tolerance. The results demonstrated that BC and WV application, either individually or together, increased soil nutrient content. The combined application was more effective than the individual applications, resulting in a 5.18–20.12% increase in organic matter, a 2.65–15.04% increase in hydrolysable nitrogen, a 2.23–58.05% increase in effective phosphorus, and a 2.71–29.38% increase in quick-acting potassium. Additionally, the combined application of WV and BC led to greater improvements in cotton plant height, net photosynthetic rate (Pn), leaf nitrate reductase (NR), superoxide dismutase (SOD), and catalase (CAT) activities compared to the application of BC or WV alone. The enhancements in this study varied across different parameters. Plant height showed an increase of 14.32–21.90%. Net photosynthetic rate improved by 13.56–17.60%. Leaf nitrate reductase increased by 5.47–37.79%. Superoxide dismutase and catalase showed improvements of 5.82–64.95% and 10.36–71.40%, respectively (p < 0.05). Moreover, the combined treatment outperformed the individual applications of WV and BC, resulting in a significant decrease in MDA levels by 2.47–51.72% over the experimental period. This combined treatment ultimately enhanced cotton stress tolerance. Using the entropy weight method to analyze the results, it was concluded that the combined application of WV and BC could enhance soil properties in mildly saline soils, increase cotton resistance, and hold significant potential for widespread application. [ABSTRACT FROM AUTHOR]

Drought is a prominent abiotic stress that is exacerbated by climate change. The application of plant growth regulators (PGRs) and plant growth-promoting rhizobacteria (PGPR) has been considered an effective approach to mitigate adverse effects of drought stress. This study aimed to evaluate the effect of paclobutrazol (PBZ) and three rhizobacterial strains on various physiological parameters of wheat under drought stress. Experimental treatments consisted of three irrigation levels as the first main plot, and PBZ application at three levels as the second main plot. Furthermore, PGPR was applied at five levels as subplot. Results revealed that drought stress decreased relative water content (34%), chlorophyll fluorescence parameters, water use efficiency (WUE) (49%), Rubisco activity (40%), and increased antioxidant enzymes and malondialdehyde (52%), whereas PBZ treatment increased relative water content (RWC) (44%), and grain yield (WUEgy) (14%) compared to control treatment. Furthermore, the PGPR combination improved florescence parameters (by an average of 27%), catalase (34%), superoxide dismutase (22%), and nitrate reductase (34%) compared with control treatment. Moreover, grain yield correlated positively and significantly with chlorophyll content, and Rubisco and nitrate reductase activity, while it negatively correlated with malondialdehyde. In light of these findings, it is evident that a combination of PBZ and PGPR treatments emerges as a highly recommended approach for mitigating the adverse effects of water deficits, especially in the context of escalating climate change challenges. [ABSTRACT FROM AUTHOR]

This study investigated the effects of exogenous nitric oxide (NO) on growth, antioxidant enzymes, and key nitrogen metabolism enzymes in pepper seedlings under high-temperature stress. In addition, targeted metabolomics was used to study the differential accumulation of amino acid metabolites, thereby providing theoretical support for the use of exogenous substances to mitigate high-temperature stress damage in plants. The results showed that high-temperature stress increased soluble sugar, soluble protein, amino acids, proline, malondialdehyde (MDA), and hydrogen peroxide (H2O2) content, electrolyte leakage, and superoxide anion (O2·-) production rate while altering the activities of antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX)] and key nitrogen metabolism enzymes [nitrate reductase (NR), glutamine synthetase (GS), glutamate dehydrogenase (GDH), and nitric oxide synthase (NOS)]. c-PTIO (2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide, an NO scavenger) exacerbates oxidative stress and further reduces NO content and enzyme activities. However, exogenous SNP (sodium nitroprusside, an NO donor) effectively alleviated these adverse effects by enhancing antioxidant defense mechanisms, increasing NO content, and normalizing amino acid metabolite levels (kynurenine, N-acetyl-L-tyrosine, L-methionine, urea, and creatine), thereby maintaining normal plant growth. These findings suggest that SNP can enhance stress tolerance in pepper seedlings by improving osmotic regulation, antioxidant capacity, and nitrogen metabolism, effectively mitigating the damage caused by high-temperature stress. [ABSTRACT FROM AUTHOR]

Biological soil crusts (BSCs) serve important functions in conserving biodiversity and ecological service in arid and semi-arid regions. Afforestation on shifting sand dunes can induce the formation of BSC on topsoil, which can accelerate the restoration of a degraded ecosystem. However, the studies on microbial community succession along BSC development under sand-fixation plantations in desertification areas are limited. This paper investigated the soil properties, enzymatic activities, and bacterial and fungal community structures across an age sequence (0-, 10-, 22-, and 37-year-old) of BSCs under Caragana microphylla sand-fixation plantations in Horqin Sandy Land, Northeast China. The dynamics in the diversities and structures of soil bacterial and fungal communities were detected via the high-throughput sequencing of the 16S and ITS rRNA genes, respectively. The soil nutrients and enzymatic activities all linearly increased with the development of BSC; furthermore, soil enzymatic activity was more sensitive to BSC development than soil nutrients. The diversities of the bacterial and fungal communities gradually increased along BSC development. There was a significant difference in the structure of the bacterial/fungal communities of the moving sand dune and BSC sites, and similar microbial compositions among different BSC sites were found. The successions of microbial communities in the BSC were characterized as a sequential process consisting of an initial phase of the faster recoveries of dominant taxa, a subsequent slower development phase, and a final stable phase. The quantitative response to BSC development varied with the dominant taxa. The secondary successions of the microbial communities of the BSC were affected by soil factors, and soil moisture, available nutrients, nitrate reductase, and polyphenol oxidase were the main influencing factors. [ABSTRACT FROM AUTHOR]

Abstract In sweet potato, rational nitrogen (N) assimilation and distribution are conducive to inhibiting vine overgrowth. Nitrate (NO3 -) is the main N form absorbed by roots, and cultivar is an important factor affecting N utilization. Herein, a hydroponic experiment was conducted that included four NO3 - concentrations of 0 (N0), 4 (N1), 8 (N2) and 16 (N3) mmol L-1 with two cultivars of Jishu26 (J26, N-sensitive) and Xushu32 (X32, N-tolerant). For J26, with increasing NO3 - concentrations, the root length and root surface area significantly decreased. However, no significant differences were observed in these parameters for X32. Higher NO3 - concentrations upregulated the expression levels of the genes that encode nitrate reductase (NR2), nitrite reductase (NiR2) and nitrate transporter (NRT1.1) in roots for both cultivars. The trends in the activities of NR and NiR were subject to regulation of NR2 and NiR2 transcription, respectively. For both cultivars, N2 increased the N accumulated in leaves, growth points and roots. For J26, N3 further increased the N accumulation in these organs. Under higher NO3 - nutrition, compared with X32, J26 exhibited higher expression levels of the NiR2, NR2 and NRT1.1 genes, a higher influx NO3 - rate in roots, and higher activities of NR and NiR in leaves and roots. Conclusively, the regulated effects of NO3 - supplies on root growth and NO3 - utilization were more significant for J26. Under high NO3 - conditions, J26 exhibited higher capacities of NO3 - absorption and distributed more N in leaves and in growth points, which may contribute to higher growth potential in shoots and more easily cause vine overgrowth.

Heavy metals, such as chromium (Cr), are continuously introduced into the environment through human activities, notably from the excessive use of pesticides, synthetic fertilizers, and irrigation with sewage and industrial wastewater. These substances induce oxidative stress in plants, disrupting crucial morphological and biochemical processes. Seed germination and early plant development are vital stages in the life cycle of plants, heavily reliant on nitrogen metabolism and associated biochemical pathways for energy accumulation. This study aimed to assess the phytotoxic effects of chromium on the growth and biochemical parameters of germinating seedlings from two maize varieties, Pak-Afgoi and Neelem Desi. The findings revealed significant suppression caused by chromium, leading to reduced seed germination rates, embryonic growth, vigor index, and biomass. Nitrogen and protein levels, as well as nitrate reductase activity, were notably affected, with Pak-Afgoi showing lower decreases compared to Neelem. Carbohydrate mobilization and total sugar content also decreased with rising chromium concentrations, although Pak-Afgoi exhibited better nitrogen and carbohydrate utilization rates. Furthermore, oxidative stress markers like hydrogen peroxide (H2O2) and malondialdehyde (MDA) indicated damage to growth and biochemical attributes in maize. Interestingly, proline levels increased with higher chromium concentrations, suggesting a protective role in maintaining seedling viability during metabolic disruptions. These results underscore the detrimental impact of chromium on maize growth by altering plant nitrogen and carbohydrate metabolisms and inducing oxidative stress. [ABSTRACT FROM AUTHOR]

The fixation and transfer of biological nitrogen from peanuts to maize in maize–peanut intercropping systems play a pivotal role in maintaining the soil nutrient balance. However, the mechanisms through which root interactions regulate biological nitrogen fixation and transfer remain unclear. This study employed a 15N isotope labelling method to quantify nitrogen fixation and transfer from peanuts to maize, concurrently elucidating key microorganisms and genera in the nitrogen cycle through metagenomic sequencing. The results revealed that biological nitrogen fixation in peanut was 50 mg and transfer to maize was 230 mg when the roots interacted. Moreover, root interactions significantly increased nitrogen content and the activities of protease, dehydrogenase (DHO) and nitrate reductase in the rhizosphere soil. Metagenomic analyses and structural equation modelling indicated that nrfC and nirA genes played important roles in regulating nitrogen fixation and transfer. Bradyrhizobium was affected by soil nitrogen content and DHO, indirectly influencing the efficiency of nitrogen fixation and transfer. Overall, our study identified key bacterial genera and genes associated with nitrogen fixation and transfer, thus advancing our understanding of interspecific interactions and highlighting the pivotal role of soil microorganisms and functional genes in maintaining soil ecosystem stability from a molecular ecological perspective. Summary Statement: The metagenomic analyses and structural equation modelling indicated that Bradyrhizobium significantly affected the nitrogen fixation, whereas the nrfC and nirA influenced the nitrogen transfer. Overall, our study identified key bacterial genus and genes associated with nitrogen fixation and transfer, thus advancing our understanding of interspecific interactions and highlighting the pivotal role of soil microorganisms and functional genes in maintaining soil ecosystem stability from a molecular ecological perspective. [ABSTRACT FROM AUTHOR]