Search Results (157)

Nitrogen (N) is the primary macronutrient that supports global agriculture. The Haber–Bosch process revolutionized the use of synthetic N fertilizers, enabling significant increases in crop yield. However, N losses from fertilization led to negative impacts on the environment. Improving crops’ N use efficiency (NUE) has been constrained by the limited understanding of N uptake and assimilation mechanisms, and the role of plant–microbe interactions. Among biological approaches, N fixation by cover crops and rhizobia symbioses represents a cornerstone strategy for improving NUE. The adoption of plant growth-promoting bacteria and arbuscular mycorrhizal fungi may enhance N acquisition by increasing root surface, modulating phytohormone levels, and facilitating nutrient transfer. Advances in plant molecular biology have identified key players and regulators of NUE (enzymes, transporters, and N-responsive transcription factors), which enhance N uptake and assimilation. Emerging biotechnological strategies include de novo domestication by genome editing of crop wild relatives to combine NUE traits and stress resilience back into domesticated cultivars. Additionally, novel fertilizers with controlled nutrient release and microbe-mediated nutrient mobilization, hold promise for synchronizing N availability with plant demand, reducing losses, and increasing NUE. Together, these strategies form a multidimensional framework to enhance NUE, mitigate environmental impacts, and facilitate the transition towards more sustainable agricultural systems. Full article

Global food security is challenged by population growth and the environmental toll of conventional fertilizers. Enhancing biological nitrogen fixation (BNF) in legumes like soybean (Glycine max) is a sustainable fertilization alternative. This study investigates a graphitic carbon nitride/iron oxide (Fe₂O₃/g–C₃N₄ or FC) nanocomposite as a dual–functional fertilizer to improve iron (Fe) nutrition and BNF in soybeans. A pot experiment was conducted using different FC concentrations (10, 100, and 200 mg kg⁻¹), alongside controls. Results showed that the 100 mg kg⁻¹ FC treatment (FC2) was most effective, significantly increasing soybean biomass, nodule number, and nodule fresh weight. The FC2 treatment also enhanced photosynthetic rates and chlorophyll content (SPAD values) while reducing stomatal conductance and transpiration, indicating improved water–use efficiency. Furthermore, FC application bolstered the plant’s antioxidant system by increasing the activity of superoxide dismutase (SOD) and peroxidase (POD). Elemental analysis confirmed that FC treatments significantly increased the uptake and translocation of Fe and nitrogen (N) in plant tissues. These findings demonstrate that the FC nanocomposite acts as a highly effective nanofertilizer, simultaneously addressing iron deficiency and boosting nitrogen fixation to promote soybean growth. This work highlights its potential as a sustainable solution to enhance crop productivity and nutrient use efficiency in modern agriculture. Full article

Drought represents a paramount constraint on global agricultural productivity, imposing severe limitations on crop yield and quality across diverse agroecosystems. Nitrogen (N), functioning as an indispensable macronutrient fundamental to plant architecture, metabolism, and stress acclimatization, exerts a pivotal influence in modulating plant resilience to water deficit. Substantial evidence accumulated in recent years underscores that optimal N nutrition significantly enhances plant adaptive capacity under drought by improving intrinsic water use efficiency (WUEi), optimizing photosynthetic performance, augmenting antioxidant defense systems, promoting advantageous root architectural modifications, and stabilizing biological N fixation (BNF) symbioses. This comprehensive review synthesizes current knowledge on the intricate physiological and molecular mechanisms underpinning N-mediated drought mitigation. We meticulously examine regulatory roles of N in water relations and hydraulic conductivity, photosynthetic apparatus protection and carbon assimilation efficiency, N metabolic flux and assimilation homeostasis, reactive oxygen species (ROS) scavenging and osmotic adjustment, root system development and resource foraging strategies, BNF system robustness under water stress, and the complex signaling networks integrating N and drought responses. Furthermore, we critically evaluate existing research consensus, identify persisting controversies and knowledge gaps, and delineate future research trajectories and translational challenges. The overarching objective is to furnish a robust theoretical foundation for devising precision N management strategies and advancing the breeding of drought-resilient, nutrient-efficient crop cultivars suited to arid and semi-arid regions facing escalating climate variability. Full article

Pollution from heavy metals represents one of the most important threats to crops. Among these, Nickel (Ni) represents a dangerous element, strictly related to anthropic activity and easily accumulated in plants. In this study, effects of high levels (1 mM) of Ni²⁺ were investigated in barley (Hordeum vulgare L. cv. Nure) grown hydroponically, inducing a severe reduction in plant growth, as well as genotoxic damage. Moreover, stress affects photosynthesis, inducing a decrease in Fv/Fm and ΦPSII and an increase in D1 protein and RuBisCO (RbcL) abundance to compensate for the loss of photosynthetic efficiency. Changes were observed in carbon metabolism, with increases in phosphofructokinase, glyceraldehyde-3P dehydrogenase-NAD⁺, and pyruvate kinase expression confirmed by increased proteins and activities. Notably, there was an evident rise in PEP carboxylase activity, presence, and expression. This increase boosts the TCA cycle (increased fumarase) and supports photorespiration. Evident rises were observed also for glucose-6P dehydrogenase activity and presence. Ni²⁺ stress induced an evident increase in enzymes involved in nitrogen metabolism: particularly, the chloroplastic GS2/Fd-GOGAT cycle and N assimilation through the cytosolic glutamate dehydrogenase reaction were enhanced. These results design a specific stress-responsive metabolism by diverting the synthesis of N-compounds through alternative C/N assimilation pathways to counteract the effects of Ni²⁺ toxicity. This study depicts a diversion of the main C/N metabolism network towards an increase in leaf N assimilation, using carbon skeletons from dark CO₂ fixation under high Ni²⁺ stress. These results may provide possible targets for the improvement of heavy metal tolerance in cereals. Full article

While root exudates play a crucial role in maintaining ecosystem balance and promoting plant growth, existing research primarily focuses on single ecosystems (e.g., field crops), with systematic investigations of their ecological functions in compound cropping systems, particularly nitrogen (N) cycling mechanisms in orchard multi-cropping systems, remaining limited. This review focuses on the N impact mechanisms mediated by plant root exudates in orchard ecosystems, emphasizing how root exudates optimize soil N activation, absorption, and utilization efficiency by modulating rhizosphere processes (e.g., nitrogen mineralization, root architecture remodeling). Studies indicate that the changes in orchard ecosystem function mediated by organic acids and flavonoids root exudates can significantly reduce nitrogen loss risks and increase the soil nitrogen turnover rate by lowering pH-activated nutrients, balancing the C:N ratio, and immobilizing microbial communities. This process also involves the coordinated regulation of nitrification, denitrification, and microbial fixation. Future research should prioritize investigating the interaction networks and regulatory mechanisms between root exudates of associated orchard crops and N-fixing microorganisms. This research direction will provide a scientific basis for improving the N use efficiency in orchard crops, optimizing fertilizer reduction techniques, and reducing chemical fertilizer usage, providing significant implications for achieving sustainable agricultural development. The theoretical support offers important scientific and practical value for advancing green and sustainable agriculture. Full article

Chinese ancient calligraphy and paintings, as priceless cultural heritage, face dual conservation challenges: cleaning accumulated contaminants and combating microbial deterioration. Addressing these issues, this study develops a multifunctional poly(vinyl alcohol)/poly(2-hydroxyethyl acrylate) (PVA/PHEAA)-based hydrogel system, including a basic robust hydrogel, an ethylene glycol (EG)-modified antifreeze version, and a polyhexamethylene biguanide (PHMB)-composite antibacterial hydrogel. By tuning interfacial adhesion energy at the molecular level, these hydrogels enable gentle yet effective cleaning of delicate substrates such as Xuan paper, efficiently removing surface and embedded dirt without mechanical damage. Molecular dynamics simulations revealed a “capture-and-fixation” dual-mode mechanism driven by hydrogen bonding and network reconfiguration, supporting the experimental findings. The EG-modified hydrogel retains elasticity at −20 °C, allowing conservation work in cold environments. Meanwhile, the PHMB-integrated hydrogel achieves a 99.6% antibacterial rate against E. coli and S. aureus, combining cleaning and long-term antimicrobial protection. Quantitative cleaning tests (n = 3) showed the PVA/PHEAA gel removed >90% of particulates, significantly outperforming traditional methods while leaving no detectable residues. Experimental results confirm the hydrogels’ compatibility with cultural materials and their multifunctionality in Xuan paper conservation. This study introduces a novel material solution for restoring traditional Chinese calligraphy and paintings, significantly advancing the application of functional hydrogels in cultural heritage preservation. By extending the lifespan of ancient artworks through a safe, residue-free, and reversible cleaning approach, it contributes to the enduring transmission of Chinese civilization. Full article

Nannochloropsis oceanica (Suda & Miyashita) R. E. Lee holds considerable potential for the production of high-value compounds, including pigments, lipids, and polyunsaturated fatty acids. Sodium acetate, a widely used carbon source in microbial cultivation, is both cost-effective and efficient. Although it has been reported to enhance biomass production in various microalgae, its effects on metabolic pathways differ substantially across species. In this study, we investigated the transcriptional responses of N. oceanica to sodium acetate supplementation using high-throughput mRNA sequencing. Sodium acetate significantly promoted growth but elicited a distinct metabolic reprogramming in contrast to patterns commonly observed in other microalgae. We identified 747 differentially expressed genes (399 upregulated and 348 downregulated), reflecting a substantial transcriptomic shift. Pathways related to lipid metabolism, carbon fixation, and photosynthesis were markedly suppressed. Notably, genes associated with photosynthesis were downregulated by 34–43 fold, suggesting a strategic reallocation of resources away from energy-intensive photosynthetic processes in the presence of an external organic carbon source. In sharp contrast to Chlamydomonas reinhardtii P. A. Dangear and Haematococcus pluvialis (Flotow) Wille, lipid metabolism in N. oceanica was not enhanced under sodium acetate supplementation. Instead, expression of lipid metabolism genes decreased by 5–14 fold, with most fatty acid- and lipase-related genes also downregulated (4–30 fold). Together, these findings reveal that N. oceanica adopts a unique adaptive strategy, channeling acetate-derived carbon primarily into rapid biomass accumulation rather than energy storage or high-value metabolite synthesis. This work provides new insights into the species-specific responses of microalgae to organic carbon sources. Full article

A diverse array of soil microorganisms exhibit plant growth-promoting (PGP) traits, many of which enhance root growth and development. These microorganisms include various taxa of bacteria, fungi, microalgae and yeasts—some of which are currently used in biofertilizers and biostimulant formulations. Recent studies have begun to unravel the complex communication between plant roots and beneficial microorganisms, revealing mechanisms that modulate root nitrogen (N) uptake beyond atmospheric N₂ fixation pathways. Root N uptake is tightly regulated by plants through multiple mechanisms. These include transcriptional and post-transcriptional control of plasma membrane-localized N transporters in the epidermis, endodermis, and xylem parenchyma. Additionally, N uptake efficiency is influenced by vacuolar N storage, assimilation of inorganic N into organic compounds, and the maintenance of electrochemical gradients across root cell membranes. Many of these processes are modulated by microbial signals. This review synthesizes current knowledge on how soil microorganisms influence root N uptake, with a focus on signaling molecules released by soil beneficial microbes. These signals include phytohormones, volatile organic compounds (VOCs), and various low-molecular-weight organic compounds that affect transporter expression, root architecture, and cellular homeostasis. Special attention is paid to the molecular and physiological pathways through which these microbial signals enhance plant N acquisition and overall nutrient use efficiency. Full article

Scientific nitrogen management is essential for maximizing crop growth potential while minimizing resource waste and environmental impacts. Alfalfa (Medicago sativa L.) is the most widely cultivated high-quality leguminous forage crop globally, and is capable of providing nitrogen through nitrogen fixation. However, there remains some disagreement regarding its nitrogen management strategies. This study conducted a three-year field experiment and calibrated the APSIM-Lucerne model. Based on the calibrated model, three typical precipitation year types (dry, normal, and wet years) were selected. Combining field experiments, eight nitrogen application scenarios (0, 80, 120, 140, 160, 180, 200, and 240 kg·ha⁻¹) were set up. With the objectives of increasing alfalfa yield, nitrogen partial productivity, and nitrogen agronomic efficiency, this study investigates the appropriate nitrogen application thresholds for alfalfa under different precipitation year types. The results showed the following: (1) Alfalfa yield increased first and then decreased with the increase in nitrogen application level. The annual yield of the N160 treatment was the highest (13.39 t·ha⁻¹), which was 5.15% to 32.39% higher than that of the other treatments. (2) The APSIM-Lucerne model could well reflect the growth process and yield of alfalfa under different precipitation year types. The R² and NRMSE between the simulated and observed values of the former were 0.85–0.91 and 5.33–7.44%, respectively. The R² and NRMSE between the simulated and measured values of the latter were 0.74–0.96 and 2.73–5.25%, respectively. (3) Under typical dry, normal, and wet years, the optimal nitrogen application rates for alfalfa yield increases were 120 kg·ha⁻¹, 140 kg·ha⁻¹, and 160 kg·ha⁻¹, respectively. This study can provide a basis for precise nitrogen management of alfalfa under different precipitation year types. Full article

This study aimed to examine how biochar and Acacia species would affect biological nitrogen fixation (BNF) and water use efficiency (WUE) of understorey Acacia species as well as soil carbon (C) and nitrogen (N) pools 15 months after biochar application in the suburban native forest of subtropical Australia. This experiment was established with wood biochar applied at 0, 5, and 10 t ha⁻¹ at 20 months after prescribed burning. We collected foliar and soil samples 15 months after biochar application and used N isotope composition (δ¹⁵N) and carbon isotope composition (δ¹³C) to assess the BNF and WUE of two understorey Acacia species (Acacia leiocalyx and Acacia disparrima). We also characterised soil C and N pools and their δ¹⁵N and δ¹³C. Biochar did not influence Acacia plant BNF and WUE 15 months after biochar application. However, the BNF of A. leiocalyx was significantly greater compared with that of A. disparrima. The soil under A. leiocalyx had greater NH₄⁺-N (i.e., 10–20 cm) but lower δ¹⁵N than A. disparrima. This study represents one of the few attempts to apply the ¹⁵N natural abundance (δ¹⁵N) techniques to quantify the soil–plant–microbe interactions for N cycling in a native forest ecosystem. Understorey A. leiocalyx was more effective in improving N recovery post-fire via BNF. Soil under A. leiocalyx had greater N availability with lower δ¹⁵N, influencing plant available N sources and δ¹⁵N. Thus, A. leiocalyx would be able to fix more N₂ from the air compared with that of A. disparrima in the suburban native forest ecosystem subject to periodical fuel reduction prescribed burning. Full article

Enzymatic CO₂ fixation offers great potential for the sustainable synthesis of value-added compounds. Malic enzyme (ME) catalyzes the reverse carboxylation of pyruvate to malate, enabling direct CO₂ conversion into C₄ compounds with broad biosynthetic applications. However, the reverse carboxylation activity of wild-type ME is insufficient, and conventional enzyme engineering strategies remain limited by the complexity of identifying distal functional sites. Here, we present a Structure–Sequence–SCANNER (3S) co-evolution strategy that integrates protein structural analysis, sequence conservation profiling, and co-evolutionary network analysis to enable systematic identification of functionally relevant hotspot residues. Using this approach, we engineered Escherichia coli ME (EcME) variants with enhanced CO₂ fixation activities. In total, 106 single-point variants were constructed and screened. Among these, variants A464S and D97E exhibited significantly improved reverse carboxylation activities, with 1.7-fold and 1.6-fold increases in catalytic activity and 1.5-fold and 1.8-fold improvements in catalytic efficiency (k_cat/K_m), respectively, compared to wild-type EcME. Their catalytic efficiencies (k_cat/K_m) improved by 1.5-fold and 1.8-fold, increasing from 80 mM⁻¹·min⁻¹ for the wild-type enzyme to 120 and 130 mM⁻¹·min⁻¹, respectively. Mechanistic analyses revealed that A464S introduces a stabilizing hydrogen bond with N462, enhancing NADPH binding, while D97E forms a new salt bridge network with K513, resulting in contraction of the substrate pocket entrance and increased pyruvate affinity. These findings demonstrate the effectiveness of the 3S strategy in reprogramming enzyme functions and highlight its potential for constructing efficient artificial CO₂ fixation systems. Full article

This study innovatively integrates ball-milled manganese dioxide nanozyme (MDMP) with the Streptomyces rochei ZY-2 inoculant in aerobic rice straw composting. The ZY-2 inoculant efficiently degrades the three major components to generate humus precursors such as phenols and quinones, while the MnO₂ nanozyme accelerates precursor polymerization into stable humic acid (HA) via oxygen vacancy-mediated catalytic activity. Simultaneously, this combination regulates microbial communities to reduce greenhouse gas emissions. The results show that the co-treatment group (ZY-2+ MnO₂ nanozyme) had an increased HA content by 30.8%, raised HA/FA ratio by 31.6%, and degradation rates of 30.75%, 31.39%, and 16.74% for cellulose, hemicellulose, and lignin, respectively. Additionally, cumulative emissions of CH₄, N₂O, and NH₃ were significantly reduced by 35.22%, 28.23%, and 25.67% compared to the control, attributed to the MnO₂ nanozyme’s inhibition of methanogens, enhanced nitrogen fixation, and ZY-2-driven microbial metabolic optimization. This study proposes a dual-effect strategy of “enhanced humification-synergistic greenhouse gas mitigation” for agricultural waste recycling, demonstrating significant practical value. Full article

Background/Objectives: Trochanteric femoral fractures pose significant surgical challenges, particularly in elderly patients. Intramedullary nailing (IMN) and plate fixation (PF) are the primary operative strategies, yet their comparative efficacy and safety remain debated. This meta-analysis synthesizes randomized controlled trials (RCTs) to evaluate clinical, functional, perioperative, and biomechanical outcomes of IMN versus PF specifically in trochanteric fractures. Methods: A systematic search of six databases was conducted up to 20 May 2024, to identify RCTs comparing IMN and PF in adult patients with trochanteric femoral fractures. Data extraction followed PRISMA guidelines, and outcomes were pooled using random-effects models. Subgroup analyses examined the influence of fracture stability, implant type, and patient age. Risk of bias was assessed using the Cochrane RoB 2.0 tool. Results: Fourteen RCTs (n = 4603 patients) were included. No significant differences were found in reoperation rates, union time, implant cut-out, or mortality. IMN was associated with significantly reduced operative time (MD = −5.18 min), fluoroscopy time (MD = −32.92 s), and perioperative blood loss (MD = −111.68 mL). It also had a lower risk of deep infection. Functional outcomes and anatomical results were comparable. Subgroup analyses revealed fracture stability and nail type significantly modified operative time, and compression screws were associated with higher reoperation rates than IMN. Conclusions: For trochanteric femoral fractures, IMN and PF yield comparable results for most clinical outcomes, with IMN offering some advantages in surgical efficiency and perioperative morbidity, though functional outcomes were comparable. Implant selection and fracture stability influence outcomes, supporting individualized surgical decision making. Full article

Mobile eye tracking is an important tool in psychology and human-centered interaction design for understanding how people process visual scenes and user interfaces. However, analyzing recordings from head-mounted eye trackers, which typically include an egocentric video of the scene and a gaze signal, is a time-consuming and largely manual process. To address this challenge, we develop eyeNotate, a web-based annotation tool that enables semi-automatic data annotation and learns to improve from corrective user feedback. Users can manually map fixation events to areas of interest (AOIs) in a video-editing-style interface (baseline version). Further, our tool can generate fixation-to-AOI mapping suggestions based on a few-shot image classification model (IML-support version). We conduct an expert study with trained annotators (n = 3) to compare the baseline and IML-support versions. We measure the perceived usability, annotations’ validity and reliability, and efficiency during a data annotation task. We asked our participants to re-annotate data from a single individual using an existing dataset (n = 48). Further, we conducted a semi-structured interview to understand how participants used the provided IML features and assessed our design decisions. In a post hoc experiment, we investigate the performance of three image classification models in annotating data of the remaining 47 individuals. Full article

Cereal/legume intercropping enhances legume nodulation and improves nitrogen use efficiency (NUE) in cereal crops. This facilitation of symbiotic nitrogen fixation (SNF) in intercropped legumes involves a complex eco-physiological mechanism driven by multiple factors. Among them, interspecific root interactions (IRIs) are a key factor influencing SNF in intercropped legumes. Currently, it remains unclear whether and how IRIs modulate SNF to affect NUE and yield formation in legume species. In this study, maize/pea intercropping with different types of root separation [no barrier (NB) and plastic barrier (PB)] and pea monocropping (IP) were simulated in a nitrogen (N)-free nutrient matrix in pots, and the SNF, N metabolism, and N partitioning were investigated. We demonstrated that IRIs optimize SNF performance. N assimilation is positively regulated following increases in enzyme activity and gene expression in intercropped roots and nodules. Furthermore, IRIs facilitate amino acid (AA) export from nodules to roots and shoots, which is followed by an increase in AA levels in leaves (source) and leaf exudates (sink). Overall, intensive SNF drives N metabolism and alters source-to-sink N partitioning, thereby increasing NUE (by 23%) and yield (by 15%) in intercropped pea. This study reveals the positive roles of IRIs to the NUE and yield and provides useful reference material for increasing N contents derived from SNF to maximize NUE and crop yields in intercropped legumes. Full article