Search Results (4,058)

Common bean grain yield is strongly influenced by nitrogen availability and can be improved through biological nitrogen fixation (BNF), which among cultivars and Rhizobium strains. This study evaluated the BNF ability of 15 common bean cultivars and their symbiotic performance with three Rhizobium strains, including a strain authorized by the Brazilian Ministry of Agriculture, to identify variability for breeding strategies and select promising inoculants. A greenhouse experiment was carried out, and data were subjected to variance analysis, with means compared by the Scott–Knott test at 5% probability. A partial diallel analysis was also performed to estimate general and specific combining ability. Based on these results, seven cultivars and two strains (UFLA 02-100 and CIAT 899) were selected for field evaluation. BNF was influenced by genotype, strain, and genotype × strain interaction, and traits related to BNF were controlled by both additive and non-additive genetic effects. Inoculation with Rhizobium promoted grain yield comparable to nitrogen fertilization. The cultivar BRSMG Zape showed superior grain yield and high general combining ability, indicating its potential for breeding programs aimed at improving BNF. The strain UFLA 02-100 resulted in higher grain yield than the reference strain CIAT 899, suggesting its potential as a recommended inoculant for common bean production. Full article

Phosphorus (P) limitation is prevalent in terrestrial ecosystems. Plants can improve soil P availability through the exudation of organic acids and symbiotic interactions with microorganisms. However, associations between different plant functional groups and phosphorus cycling in P limited karst ecosystems remain poorly understood. To investigate this, the exudation rates of oxalic, citric and acetic acids from fine roots, the contents of carbon, nitrogen, and P in leaves and fine roots, and the contents of oxalic, citric and acetic acids, total P, available P (AP), and microbial biomass P in rhizosphere soils were measured across different plant functional groups in a karst ecosystem in southwestern China. Additionally, the activities of acid and alkaline phosphatases were also analyzed, as well as the relative abundance, community structure, diversity, and co-occurrence network patterns of arbuscular mycorrhizal fungi (AMF) and alkaline phosphatase-encoding (phoD) gene-harboring bacteria. The results showed that both the exudation rates and the contents of organic acids and AP were highest in the tree group, followed by the shrub and grass groups. The AP content of the legume group was significantly higher than that of the non-legume group. The exudation rates of oxalic acid were significantly greater than those of citric and acetic acids. AMF diversities were highest in the shrub and legume groups. The diversities of phoD-harboring bacteria decreased from the tree group to the shrub group and then to the grass group, yet there were no significant differences between the legume and non-legume groups. The communities of both AMF and phoD-harboring bacteria exhibited significant differences among these plant functional groups. The prevalent genera of phoD-harboring bacteria across all groups were Pseudomonas and Halomonas, with Halomonas being particularly prevalent in the legume group. The AMF community was dominated by Glomus, which attained its highest relative abundance in the tree and legume groups. Furthermore, the increased exudation rate and content of oxalic acid were associated with higher relative abundances of Glomus in AMF and Pseudomonas and Bacillus among phoD-harboring bacteria. Structural Equation Model (SEM) analysis demonstrated that plant-exuded organic acids, especially oxalic acid, were positively associated with P availability indirectly through their linkages with the diversity and abundance of AMF and phoD-harboring bacteria. The crucial role of oxalic acid was particularly prominent in the tree and legume groups. Our findings suggest that screening AMF and phoD-harboring bacteria with highly efficient P transformation activity and inoculating them into the rhizosphere of plants with high oxalic acid exudation could help improve plant resilience to P limitation and support sustainable restoration in karst ecosystems. Full article

Drought stress severely restricts agricultural productivity. Effective drought mitigation requires both improved rhizosphere water retention and enhanced nutrient availability. Poly-γ-glutamic acid (PGA) was expected to enhance water retention, while residue after evaporation (RAE) of 2-keto-L-gulonic acid fermentation was expected to supply labile carbon and promote nutrient mobilization. We hypothesized that their combined application would synergistically optimize the rhizosphere environment and enhance maize seedlings’ resistance to drought. A pot experiment was conducted to evaluate the growth of maize under simulated drought conditions, containing four treatments: control (C), RAE alone (R), PGA alone (P), and their combination (M). Results demonstrated that the M treatment synergistically promoted maize seedling growth, increasing the seedling growth index by 125% compared to the control. Co-application also synergistically enhanced the accumulation of osmotic adjustment substances (proline, soluble proteins, and soluble sugars) and ascorbic acid content, while reducing malondialdehyde (MDA) level. Furthermore, the M treatment markedly increased soil ammonium nitrogen and total organic carbon, thereby improving soil moisture and optimizing the rhizosphere conditions. Mantel analysis revealed that the M treatment restructured soil bacterial communities and enzyme activities by enhancing nutrient and organic carbon availability, which subsequently improved overall soil properties. These findings suggest that co-application of PGA and RAE improves maize seedling drought resilience and soil nutrient supply, offering a promising and economically viable strategy for sustainable agriculture in drought-prone regions by valorizing industrial by-products. Full article

Root exudates are key drivers of rhizosphere microbial assembly, yet their effects across coexisting plant species with different functional roles remain unclear. We examined the effects of root exudates from five desert steppe species in Inner Mongolia: one constructive species, two dominant species, and two accompanying species. Exudates were collected hydroponically and applied to bulk soil in a three-week incubation experiment. Microbial communities were analyzed using high-throughput sequencing, functional prediction, and co-occurrence network analysis. Exudate addition significantly altered bacterial community composition, reducing bacterial richness, while fungal communities showed weaker responses. Exudates from constructive and dominant species enriched Actinobacteria, including Rubrobacter, Arthrobacter, and Solirubrobacter, and increased functional groups linked to chemoheterotrophy and nitrogen transformation. In contrast, exudates from accompanying species induced distinct microbial assemblages without promoting Actinobacteria dominance. Exudate addition also increased bacterial network complexity, suggesting enhanced microbial interactions. Soil pH decreased and available nitrogen and phosphorus increased, strongly correlating with bacterial community shifts. Overall, root exudates mediate species-specific microbial assembly and functional reorganization in desert steppe soils, driven mainly by plant functional roles rather than taxonomic relatedness. This study provides new insights into how plant-derived substrates regulate microbial communities and nutrient cycling in arid ecosystems. Full article

Protected cultivation of pepper in southern China’s red soil region often leads to soil degradation and continuous cropping obstacles. To investigate whether biochar can alleviate these problems by regulating the soil microenvironment, pot and incubation experiments were conducted from 2021 to 2023 with biochar application rates of 0~10% (w/w). The results showed that appropriate biochar application significantly improved pepper yield and soil quality. Under the 6% biochar treatment, pepper yield and dry matter accumulation increased by 89.05% and 36.79%, respectively, compared to the control. Soil bacterial and fungal abundances increased by 346.61% and 107.37%, and their OTU numbers rose by 64.13% and 35.15%, respectively. Biochar application also elevated soil pH, organic matter, available potassium, and total nitrogen contents, improved aggregate stability, and enhanced the activities of urease, catalase, sucrase, and acid phosphatase. Furthermore, biochar altered the rhizosphere microbial community structure and increased bacterial diversity. These findings demonstrate that biochar can promote pepper growth by improving soil physicochemical properties, enzyme activities, and microbial community structure, providing a viable strategy for mitigating continuous cropping obstacles in protected cultivation. Full article

This review proposes a “phenomenon–mechanism–regulation” framework for understanding nitrogen immobilization during the conversion of green waste into growing media. Nitrogen immobilization acts as a double-edged sword: intense short-term immobilization, typically occurring within the first 1–2 weeks after substrate establishment, can rapidly deplete mineral nitrogen and induce plant nitrogen deficiency, whereas the immobilized nitrogen is subsequently incorporated into microbial biomass and lignin-associated organic pools, forming a slow-release reservoir that enhances nitrogen retention and reduces leaching losses. Owing to its extremely high C/N ratio (often >100) and the coexistence of labile carbon fractions and recalcitrant compounds (e.g., lignin and phenolics), green waste exhibits substantially stronger immobilization potential than conventional media. Empirical evidence indicates that nitrogen immobilization can reach 10–115 mg N·L⁻¹ within a few days in wood-derived substrates, and additional fertilization of up to 100 mg N·L⁻¹ may be required to maintain crop growth. Mechanistically, nitrogen immobilization is governed by the coupling of microbial assimilation—driven by stoichiometric C/N imbalance (typically triggered when C/N > 20–25)—and abiotic chemical fixation, including reactions between NH₄⁺/NO₂⁻ and lignin-derived phenolics forming stable organic nitrogen compounds. The relative dominance of these pathways is jointly regulated by carbon quality, nitrogen form, and pH. Based on these mechanisms, regulatory strategies are summarized at multiple scales, including feedstock pretreatment to reduce labile carbon availability, substrate formulation to optimize C/N balance, and model-assisted intelligent fertigation to synchronize nitrogen supply with crop demand. Overall, this study provides a theoretical basis for improving green waste valorization and promoting sustainable horticultural production. Full article

Aluminum (Al) toxicity constrains plant performance in acidic volcanic soils, yet nitrogen (N) fertilization may influence Al availability and plant responses. This study evaluated the effects of N source and rate under contrasting soil liming conditions on vegetative growth, mineral nutrition, and physiological performance of non-bearing northern highbush blueberry (Vaccinium corymbosum L. cv. Blue Ribbon^®) plants. A split–split-plot experiment was conducted in southern Chile using urea or potassium nitrate applied at 0, 20, or 40 kg N ha⁻¹ to plants grown in unlimed soil or soil amended with calcium carbonate or magnesium oxide. Vegetative growth, tissue mineral composition, stomatal conductance, chlorophyll fluorescence, and leaf chlorophyll were monitored during the first season. Growth responded primarily to soil liming rather than N supply, indicating low N demand and substantial soil N mineralization under the experimental conditions. Foliar N increased from 1.36 to 1.70% with increasing N rates. Urea nutrition reduced foliar Al concentration by 12% compared with nitrate. Under unlimed conditions, representing maximal soil Al availability, urea fertilization was associated with 70% higher Al retention in roots relative to nitrate. Chlorophyll content was consistently higher under urea supply, while the maximum photochemical efficiency of photosystem II remained unaffected. These findings indicate that N form influences plant Al partitioning independently of growth responses. Although the underlying mechanisms were not directly assessed, the observed patterns suggest that urea fertilization may reduce Al translocation to shoots under conditions of high Al availability. Full article

Soil nutrient loss and infertility in rocky desertification areas severely constrain ecological restoration. Exploring the impacts of external field remediation technologies on soil quality in these regions may offer novel strategies for soil enhancement and ecosystem recovery. This study conducted a three-month experiment to investigate the impact of continuous electric (ET, 20 V) and magnetic (MT, 200 mT) field treatments on soil nutrients, enzyme activities, and bacterial communities in simulated moderate and severe rocky desertification soils. Results showed that although an overall declining trends in total contents of key soil nutrients (Total nitrogen, total phosphorus, and total potassium), both electric and magnetic field treatments effectively mitigated the decreases of total nitrogen and potassium content (with the exception of total phosphorus) in rocky desertification soils, while improving their available contents compared to the control (CK). Electric field application significantly reduced the pH of moderate and severe rocky desertification soils through electrolysis, shifting the soil from alkaline (pH 7.69 and 7.73, respectively) to slightly acidic (pH 6.71 and 6.37, respectively); Both electric and magnetic field treatments enhanced urease and sucrase activities in moderately and severely rocky desertified soils. Compared to the CK, the increases were 21.92%, 4.46%, 5.70%, and 66.43% in moderately rocky desertified soil, and 10.06%, 42.15%, 20.66%, and 0.93% in severely rocky desertified soil, respectively. Their effects on phosphatase and catalase activities varied with the degree of rocky desertification. However, in severely rocky desertified soil, both treatments significantly increased phosphatase and catalase activities by 19.55%, 24.63%, 61.07%, and 38.05% compared to the CK, respectively. Furthermore, both electric and magnetic treatments significantly reduced bacterial α-diversity (chao1, ACE, Shannon, Simpson, and Pielou J indices) but optimized community structure by enriching dominant phyla with specific ecological functions, such as Pseudomonadota (7.63–41.10%), Bacteroidota (13.52–69.29%), and Verrucomicrobiota (38.26–104.81%). Functional prediction revealed that the abundances of dominant pathways (such as chemoheterotrophy, aerobic chemoheterotrophy, and nitrogen fixation) was enhanced following both treatments. Mantel analysis further indicated strengthened correlations among soil nutrients, enzyme activities, and bacterial communities, particularly under magnetic field treatment. These findings demonstrate that electric and magnetic field applications effectively facilitate nutrient cycling, stimulate enzyme activities, and optimize microbial community structure, thereby improving soil ecological functions and overall quality in rocky desertification regions, highlighting their potential for ecological restoration in karst areas. Full article

Microplastics (MPs), particularly low-density polyethylene (LDPE), are widespread pollutants in aquatic environments and may affect cyanobacterial physiology. This study investigated the concentration-dependent effects of LDPE-MPs on the physiology and transcriptomic responses of Arthrospira platensis. Cultures were exposed to 10–5000 mg/L LDPE-MPs (nominal size ≤ 500 µm) for 16 days. Low to moderate concentrations (10–1000 mg/L) produced minimal effects on growth, biomass accumulation, or pigment contents. In contrast, higher concentrations (3000–5000 mg/L) were associated with reduced growth and biomass, accompanied by declines in chlorophyll a (Chl a) and phycobiliproteins over time. By day 16 at 5000 mg/L, biomass and Chl a decreased to 1.47 ± 0.03 g/L and 8.39 ± 0.24 µg/mL, respectively, compared with 1.64 ± 0.04 g/L and 10.81 ± 0.52 µg/mL in the control (p < 0.05). Accordingly, Chl a yield decreased by 13%. Field-emission scanning electron microscopy revealed adhesion of LDPE particles to filament surfaces and the formation of extracellular polymeric substance (EPS)-rich aggregates, which may influence light availability and nutrient exchange. Transcriptomic analysis indicated changes in several metabolic pathways, including nitrogen assimilation, photosynthetic electron transport, carbon metabolism, and metal homeostasis, together with differential expression of genes related to stress responses and EPS biosynthesis. Overall, these findings suggest that relatively high concentrations of LDPE microplastics may influence physiological and metabolic processes in A. platensis. Full article

Aquatic–terrestrial ecotones are highly dynamic biogeochemical hotspots where hydrological fluctuations profoundly influence microbial community structure and ecosystem functioning. However, the mechanisms underlying microbial community responses across hydrological gradients remain insufficiently understood. In this study, 16S rRNA gene sequencing was used to comparatively analyze bacterial communities in the waterward and landward zones of the drawdown area of the Danjiangkou Reservoir. The results showed that bacterial community composition differed significantly between the two zones, and waterlogging markedly increased bacterial α-diversity. Community variation was primarily associated with key environmental factors, including total phosphorus (TP), soil moisture content (SMC), and nitrate nitrogen (NO₃⁻-N). Compared with the landward zone, stochastic processes contributed more to community assembly in the waterward zone, which also exhibited higher network complexity and topological stability. In addition, several keystone taxa were identified, suggesting their potential roles in maintaining network structure and ecological stability. Functional prediction further revealed distinct metabolic potentials between zones, with enhanced anaerobic and redox-related functions in the waterward zone and predominantly aerobic metabolism in the landward zone. These findings suggest that hydrological fluctuations reshape bacterial community structure and potential ecological functions by jointly regulating water availability and nutrient dynamics. This study provides new insights into microbial ecological processes in reservoir riparian zones and offers a scientific basis for the management of aquatic–terrestrial ecotone ecosystems. Full article

Wheat productivity and grain quality are strongly influenced by nutrient management and soil moisture availability. Nitrogen (N) and potassium (K) regulate biomass production, physiological stability and grain protein development. However, their efficiency varies under water-limited conditions. This study aimed to evaluate how soil moisture modulates nitrogen–potassium efficiency, nutrient partitioning, physiological responses and grain quality development in wheat. The current experiment was planned to assess the impact of varying but combined levels of N and K fertilizers on wheat crop growth and yield components as well as nutrient uptake and grain quality under different irrigation levels (i.e., normal irrigation Field Capacity (FC) 100%, partial water deficit FC75%, moderate water deficit FC50%, severe water deficit FC25%). The results of the study showed that increasing N-K supply enhanced biomass, chlorophyll contents, nutrient accumulation and grain quality under full irrigation, with N2K2 showing the highest growth, yield and quality traits. Under moderate deficit, N2K1 maintained a relatively stable yield and physiological performance, whereas severe moisture limitation markedly reduced nutrient uptake, grain development and fertilizer efficiency despite a higher NK application. Progressive reductions in irrigation also altered nutrient distribution among leaves, straw and grain, indicating moisture-regulated remobilization during grain filling. Maximum increments in values for plant height (27%), total biomass (108%), grain yield (183%), grain NPK content (38%, 6.3%, 26%), grain protein (38%) and wet gluten (38%) were noted in the N2K2 treatment at FC100%, but these parameters showed up to 80% reduction under the same treatment of N-K at FC25%. It is concluded that wheat response to N–K fertilization was moisture dependent and fertilizer rate alone did not ensure productivity under severe water deficit. Therefore, integrating nutrient supply with irrigation management is essential to sustain productivity and grain quality. Full article

The transport sector is a major contributor to urban air pollution and greenhouse gas emissions in Pakistan, posing significant challenges to sustainable development and climate commitments. This study develops the first technology-resolved, high-resolution, multi-pollutant emission inventory and scenario analysis for Pakistan’s transport sector, addressing key gaps in previous studies that lacked integrated multi-pollutant assessments, comprehensive coverage of non-road sources, and long-term scenario comparisons. The analysis integrates road and non-road transport sources within the Greenhouse Gas–Air Pollution Interactions and Synergies (GAINS) modeling framework. Emissions are projected for 2024–2050 under a business-as-usual (BAU) scenario and three mitigation pathways: an Electric Vehicle Transition (EVT) emphasizing transport electrification, a Euro-VI scenario focusing on stringent fuel and vehicle emission standards, and an integrated nationally determined contribution strategy (NDC+) scenario combining electrification, regulatory improvements, and structural transport reforms. In 2024, transport-related emissions are estimated at approximately 22 kt of fine particulate matter (PM_2.5), over 300 kt of nitrogen oxides (NO_x), and nearly 39 Mt of carbon dioxide (CO₂), alongside substantial emissions of other gaseous pollutants and short-lived climate forcers. By 2050, the NDC+ scenario achieves the largest reductions relative to business-as-usual, demonstrating that coordinated electrification and emission control strategies can simultaneously reduce air pollution and greenhouse gas emissions. The results demonstrate strong synergies between climate mitigation and air quality improvement, showing that integrated strategies combining electrification with stringent emission standards can simultaneously reduce greenhouse gas emissions and major air pollutants while advancing cleaner and more sustainable mobility. This analysis provides a consistent and policy-relevant evidence base derived from best-available data and modeling tools to support Pakistan’s NDC implementation, sustainable mobility planning, and integrated air quality and climate strategies, with lessons transferable to other rapidly developing economies. Full article

Systematic comparisons of how plants with contrasting ecological strategies respond to extremely wide nutrient availability gradients remain limited. We investigated the physiological, photosynthetic, and growth adaptations of four plant species representing distinct ecological strategies: Triticum aestivum L. (C3 annual crop), Zea mays L. (C4 annual crop), Ipomoea aquatica Forssk. (C3 annual/perennial aquatic vegetable), and Canna glauca L. (C3 perennial wetland ornamental). Plants were grown hydroponically under nitrogen (N), phosphorus (P), and potassium (K) gradients ranging from 0% to 500% of standard Hoagland nutrient solution. The study results showed that all measured plant traits exhibited characteristic unimodal dose–response patterns. Optimal performance mostly occurred at 100–150% nutrient availability gradients. Severe inhibition or mortality occurred at extreme gradients. Simultaneously, different plant species displayed markedly varying response amplitudes and nutrient-specific sensitivities. Z. mays showed the highest nutrient use efficiency and broadest optimal ranges, particularly for N and K. C. glauca exhibited extraordinary N responsiveness (32-fold increase in photosynthetic rate) but narrow optimal ranges (e.g., 1.01 ± 0.15 μmol CO₂/(m²·s) at the 1% N treatment vs. 32.52 ± 3.33 μmol CO₂/(m²·s) at the 150% N treatment). I. aquatica showed pronounced P limitation with broad tolerance to supra-optimal N and K. T. aestivum displayed moderate responses with clear sensitivity to N limitation. Root–shoot ratios declined systematically with increasing nutrient availability across all plant species, following negative exponential functions. The results of data analyses revealed significant effects of N, P, and K availability on all the determined plant traits. Correlation analyses demonstrated tight coupling effects among physiological, photosynthetic, and growth traits, indicating integrated whole-plant responses to nutrient variations. These findings reveal that plant ecological strategy systematically modulates nutrient response patterns and provide a quantitative framework for species-specific nutrient management. This study provides a theoretical basis for precision fertilization of aquatic vegetables and wetland plants, and more broadly support species-specific nutrient management in controlled-environment agriculture. Full article

Mediterranean-type ecosystems (METs) occur on five continents and represent some of the most climatically constrained yet biologically rich regions on Earth. In these environments, legumes and their nitrogen-fixing rhizobial symbionts—including widely distributed genera such as Rhizobium, Bradyrhizobium, and Ensifer—play a pivotal role in sustaining plant productivity, nutrient cycling, and ecosystem resilience. This review synthesizes current knowledge on the environmental regulation of legume–Rhizobium symbiosis specifically within Mediterranean-type ecosystems, focusing on how nitrogen (N) and phosphorus (P) availability, light conditions, and carbon allocation trade-offs shape symbiotic performance across the five Mediterranean-type regions of the world (California, central Chile, the Cape Region of South Africa, southwestern Australia, and the Mediterranean Basin). By integrating physiological, ecological, and biogeochemical perspectives, we highlight how the shared features of these regions—strong seasonal drought, chronic nutrient limitation (particularly P in southwestern Australia and the Cape Region), recurrent fires, and exceptionally high plant diversity—constrain and, at the same time, favor the ecological success of symbiotic legumes. Throughout the review, we use case studies from key legume genera such as Lupinus in Chile and southwestern Australia, Virgilia and other Cape legumes in South Africa, Acacia in Australian kwongan and woodlands, and Medicago and Cytisus in the Mediterranean Basin and California to illustrate how general principles of legume–Rhizobium ecology manifest under Mediterranean-type climatic and edaphic constraints. Beyond summarizing established mechanisms, we critically examine the limitations of current metagenomic approaches, which often provide descriptive inventories of soil microbial communities without linking microbial composition to functional outcomes. We argue that advancing the field requires integrated, hypothesis-driven research that combines multi-omic tools with plant eco-physiology, soil nutrient dynamics, and temporal replication. Finally, we outline key priorities for future research, including the integration of functional ‘omics’, the study of microbiome interactions beyond rhizobia, the development of predictive models for Mediterranean-type ecosystems under climate change, and the application of symbiotic principles to restoration and agroecological management. By bridging molecular, physiological, and ecosystem perspectives, this review provides a conceptual framework for understanding and enhancing legume–Rhizobium symbiosis across five continents in a rapidly changing world. Full article

Rice is a globally important food crop, and its production is often affected by extreme climates such as drought and high temperatures. This study investigated how drought applied at different growth stages affects cadmium (Cd) uptake and accumulation in rice, as well as the underlying mechanisms. The results showed that drought treatments generally increased soil organic matter and alkali-hydrolyzed nitrogen content but decreased pH and available phosphorus content. The available Cd content in soil under the grain-filling stage drought treatment was lower than that under other treatments. Speciation analysis showed that under grain-filling stage drought, exchangeable Cd decreased by 3.04%, and residual Cd increased by 2.67%. Furthermore, drought treatments significantly enhanced soil urease and sucrase activities. Rice plant height and yield were significantly affected by the timing of drought, with the grain-filling stage drought treatment yielding the highest, while full growth stage and tillering stage drought treatments resulted in significantly lower yields. Cd content in various organs followed the order: root > stem > leaf > brown rice, with the brown rice Cd content being the lowest under grain-filling stage drought. In conclusion, drought treatment during the grain-filling stage had the least effect on Cd content in various rice tissues while maintaining a relatively high yield, providing a theoretical basis for water management in Cd-contaminated paddy fields. Full article