Fulvic acid alleviates the stress of low nitrogen on maize by promoting root development and nitrogen metabolism.

The potential of fulvic acid (FA) to improve plant growth has been acknowledged, but its effect on plant growth and nutrient uptake under nutrient stress remains unclear. This study investigated the effects of different FA application rates on maize growth and nitrogen utilization under low nitrogen stress. The results showed that under low nitrogen stress, FA significantly stimulated maize growth, particularly root development, biomass, and nitrogen content. The enhanced activity levels of key enzymes in nitrogen metabolism were observed, along with differential gene expression in maize, which enriched nitrogen metabolism, amino acid metabolism and plant hormone metabolism. The application of FA regulated the hormones' level, reduced abscisic acid content in leaves and Me-JA content in roots, and increased auxin and zeatin ribose content in leaves. This study concludes that, by promoting root development, nitrogen metabolism, and hormone metabolism, an appropriate concentration of FA can enhance plant tolerance to low nitrogen conditions and improve nitrogen use efficiency.

Nematodes and their bacterial prey improve phosphorus acquisition by wheat.

Plant growth is greatly influenced by the rhizosphere microbiome, which has been traditionally investigated from a bottom-up perspective assessing how resources such as root exudates stimulate microbial growth and drive microbiome assembly. However, the importance of predation as top-down force on the soil microbiome remains largely underestimated. Here, we planted wheat both in natural and in sterilized soils inoculated with the key microbiome predators - bacterivorous nematodes - to assess how plant performance responds to top-down predation of the soil microbiome and specific plant growth-promoting bacteria, namely phosphate-solubilizing bacteria. We found that nematodes enriched certain groups (e.g. Actinobacteria, Chloroflexi, and Firmicutes) and strengthened microbial connectance (e.g. Actinobacteria and Proteobacteria). These changes in microbiome structure were associated with phosphate-solubilizing bacteria that facilitated phosphorus (P) cycling, leading to greater P uptake and biomass of wheat in both soils. However, the enhancement varied between nematode species, which may be attributed to the divergence of feeding behavior, as nematodes with weaker grazing intensity supported greater abundance of phosphate-solubilizing bacteria and better plant performance compared with nematodes with greater grazing intensity. These results confirmed the ecological importance of soil nematodes for ecosystem functions via microbial co-occurrence networks and suggested that the predation strength of nematodes determines the soil bacteria contribution to P biogeochemical cycling and plant growth.

Genome-Wide Identification and Functional Analysis of Nitrate Transporter Genes (NPF, NRT2 and NRT3) in Maize.

Nitrate is the primary form of nitrogen uptake in plants, mainly transported by nitrate transporters (NRTs), including NPF (NITRATE TRANSPORTER 1/PEPTIDE TRANSPORTER FAMILY), NRT2 and NRT3. In this study, we identified a total of 78 NPF, seven NRT2, and two NRT3 genes in maize. Phylogenetic analysis divided the NPF family into eight subgroups (NPF1-NPF8), consistent with the results in Arabidopsis thaliana and rice. The NRT2 family appears to have evolved more conservatively than the NPF family, as NRT2 genes contain fewer introns. The promoters of all NRTs are rich in cis-acting elements responding to biotic and abiotic stresses. The expression of NRTs varies in different tissues and developmental stages, with some NRTs only expressed in specific tissues or developmental stages. RNA-seq analysis using Xu178 revealed differential expression of NRTs in response to nitrogen starvation and nitrate resupply. Moreover, the expression patterns of six key NRTs genes (NPF6.6, NPF6.8, NRT2.1, NRT2.5 and NRT3.1A/B) varied in response to alterations in nitrogen levels across distinct maize inbred lines with different nitrogen uptake rates. This work enhances our understanding of the structure and expression of NRTs genes, and their roles in nitrate response, paving the way for improving maize nitrogen efficiency through molecular breeding.

Up-regulated 2-alkenal reductase expression improves low-nitrogen tolerance in maize by alleviating oxidative stress.

In plants, cellular lipid peroxidation is enhanced under low nitrogen (LN) stress; this increases the lipid-derived reactive carbonyl species (RCS) levels. The cellular toxicity of RCS can be reduced by various RCS-scavenging enzymes. However, the roles of these enzymes in alleviating oxidative stress and improving nutrient use efficiency (NUE) under nutrient stress remain unknown. Here, we overexpressed maize endogenous NADPH-dependent 2-alkenal reductase (ZmAER) in maize; it significantly increased the tolerance of transgenic plants (OX-AER) to LN stress. Under LN condition, the biomass, nitrogen accumulation, NUE, and leaf photosynthesis of the OX-AER plants were significantly higher than those of the wild-type (WT) plants. The leaf and root malondialdehyde and H2 O2 levels in the transgenic plants were significantly lower than those in WT. The expression of antioxidant enzyme-related genes ZmCAT3, ZmPOD5 and ZmPOD13 was significantly higher in the transgenic lines than in WT. Under LN stress, the nitrate reductase activity in the OX-AER leaves was significantly increased compared with that in the WT leaves. Furthermore, under LN stress, ZmNRT1.1 and ZmNRT2.5 expression was upregulated in the OX-AER plants compared with that in WT. Overall, up-regulated ZmAER expression could enhance maize's tolerance to LN stress by alleviating oxidative stress and improve NUE.

Soil nematode community and crop productivity in response to 5-year biochar and manure addition to yellow cinnamon soil.

BACKGROUND: Manure and biochar soil amendments have shown many benefits to soil quality and crop productivity. This study aimed to reveal the effects of biochar and manure applications on soil fertility improvement and crop productivity in yellow cinnamon soil. RESULTS: This study based on a 5-year field experiment. Four treatments were designed, included the control (CK), biochar amendment, manure amendment, and both biochar and manure amendment (BM). The results showed that: after five years, both biochar and manure treatment improved soil structure by increasing soil mean weight diameter (MWD), and soil water and nutrient supply was also increased by increasing the contents of water content, available potassium and available phosphorus. The productivity was also enhanced as wheat yield under the biochar, manure, and BM treatments increased by 3.59-11.32% compared with CK. In addition, biochar and manure treatment increased soil microbial biomass carbon (MBC) by > 15%, and soil total nematode abundance was significantly increased. Furthermore, the nematode community structure was significantly affected by biochar and manure treatment, dominant trophic group in CK was herbivores, but bacterivores were dominant in the biochar and manure treatments. The distribution of nematode genera was closely related to soil chemical properties and microbial biomass. Increases in the Shannon's diversity index, and decreases in the dominance index and summed maturity index after the 5-year treatment indicated a sustainable soil ecosystem after the biochar and manure applications. CONCLUSIONS: These findings indicate that biochar and manure result in better soil quality and increased productivity in yellow cinnamon soil.

The Stimulatory Effects of Nanochitin Whisker on Carbon and Nitrogen Metabolism and on the Enhancement of Grain Yield and Crude Protein of Winter Wheat.

Nanochitin whisker (NC) with a cationic nature could enhance plant photosynthesis, grain yield, and quality of wheat, but have not been systematically studied. This study was designed to investigate the stimulatory effects of NC on dry matter (DM) and nitrogen (N) accumulation and translocation, and on the metabolism of carbon (C) and N in later growth stages of winter wheat to reveal the enhancement mechanism of grain yield and crude protein concentration. Different parts of NC-treated plants from pot grown experiments were collected at the pre- and post-anthesis stages. The accumulation, translocation, and contributions of DM and N from pre-anthesis vegetation organs to grains, as well as key metabolic enzyme activities, including sucrose phosphate synthase (SPS) and phosphoenolpyruvate carboxylase (PEPC), were examined. The results showed that, at an application rate of 6 mg·kg-1 of NC in the soil, the accumulation of DM and N were significantly enhanced by 16.2% and 38.8% in pre-anthesis, and by 15.4% and 30.0% in post-anthesis, respectively. Translocation of N and DM in the post-anthesis periods were enhanced by 38.4% and 50.9%, respectively. NC could also stimulate enzyme activities, and increased 39.8% and 57.1% in flag leaves, and by 36.0% and 58.8% in spikes, respectively, at anthesis. SPS and PEPC increased by 28.2% and 45.1% in flag leaves, and by 42.2% and 56.5% in spikes, respectively, at 15 days after anthesis. The results indicated that the NC promoted N metabolism more than C metabolism, and resulted in the enhancement of grain yield by 27.56% and of crude protein concentration in grain by 13.26%, respectively.

Modeling framework for simulating concentrations of solute chemicals, nanoparticles, and solids in surface waters and sediments: WASP8 Advanced Toxicant Module.

Toxicant concentrations in surface waters are of environmental concern due to their potential impacts to humans and wildlife. Numerical models provide system insight, support management decisions, and provide scenario testing on the impacts of toxicants. The Water Quality Analysis Simulation Program (WASP) is a widely used framework for developing site-specific models for simulating toxicant concentrations in surface waters and sediments over a range of complexities and temporal and spatial scales. WASP8, with the Advanced Toxicant module, has been recently released, incorporating a complete architecture redesign for an increased number of state variables and different state variable types. WASP8 incorporates a new structure for simulating light intensity and photoreactions in the water column, including the distinction of 10 different wavelength bands, and nanoparticle heteroaggregation to solids. We present a hypothetical case study, using the Cape Fear River, North Carolina as a representative example for simulating solute chemicals, nanoparticles, and solids to demonstrate the new and updated capabilities of WASP8.

Reductive Dechlorination of Trichloroethene by Zero-valent Iron Nanoparticles: Reactivity Enhancement through Sulfidation Treatment.

Zero-valent iron nanoparticles (nZVI) synthesized in the presence of reduced sulfur compounds have been shown to degrade trichloroethene (TCE) at significantly higher rates. However, the applicability of sulfidation as a general means to enhance nZVI reactivity under different particle preparation conditions and the underlying cause for this enhancement effect are not well understood. In this study, the effects of sulfidation reagent, time point of sulfidation, and sulfur loading on the resultant particles were assessed through TCE degradation experiments. Up to 60-fold increase in TCE reaction rates was observed upon sulfidation treatment, with products being fully dechlorinated hydrocarbons. While the reactivity of these sulfur-treated nZVI (S-nZVI) was relatively unaffected by the sulfidation reagent (viz., sodium sulfide, dithionite, or thiosulfate) or the sequence of sulfidation relative to iron reduction, TCE reaction rates were found to depend strongly on sulfur to iron ratio. At a low sulfur loading, TCE degradation was accelerated with increasing sulfur dose. The rate constant reached a limiting value, however, as the sulfur to iron mole ratio was greater than 0.025. Different from previous propositions that iron sulfidation leads to more efficient TCE or tetrachloroethene (PCE) degradation by enabling depassivation of iron surface, affording catalytic pathways, or facilitating electron transfer, we show that the role of sulfur in nZVI lies essentially in its ability to poison hydrogen recombination, which drives surface reactions to favor reduction by atomic hydrogen. This implies that the reactivity of S-nZVI is contaminant-specific and is selective against the background reaction of water reduction. As the effect of sulfur manifests through surface processes, sulfidation represents a broadly applicable surface modification approach to modulate or increase the reactivity of nZVI for treating TCE and other related contaminants.

Reflectance and fluorescence characterization of maize species using field laboratory measurements and lidar remote sensing.

Laser-induced fluorescence is an important technique to study photosynthesis and plants. Information on chlorophyll and other pigments can be obtained. We have been using a mobile laboratory in a Chinese experimental farm setting to study maize (Zea mays L.) leaves by reflectance and fluorescence measurements and correlated the spectroscopic signals to the amount of fertilizer supplied. Further, we studied five different species of maize using the remote monitoring of the fluorescence signatures obtained with the same mobile laboratory, but now in a laser radar remote-sensing configuration. The system separation from the target area was 50 m, and 355 nm pulsed excitation using the frequency-tripled output from an Nd:YAG laser was employed. Principal component analysis and linear discriminant analysis were combined to identify the different maize species using their fluorescence spectra. Likewise, the spectral signatures in reflectance and fluorescence frequently allowed us to separate different fertilizer levels applied to plants of the same species.

Biodegradation of phenol-contaminated soil and plant growth promotion by Myroides xuanwuensis H13.

Physicochemical methods for remediating phenol-contaminated soils are costly and inefficient, making biodegradation an environmentally friendly alternative approach. This study aims to screen for potential phenol-degrading bacteria and to verify the removal capacities of a selected strain in a bioaugmentation experiment at the greenhouse level using Brassica chinensis L. (Chinese cabbage) as the model plant and phenol-contaminated soil. In parallel, pot experiments were conducted using a collaborative approach based on this model system. We found that Myroides xuanwuensis strain H13 showed a high degradation capability, with a 97.67% efficiency in degrading 100 mg/L phenol. Under shaking flask conditions, H13 facilitated the solubilization of tricalcium phosphate and potassium feldspar powder. Pot experiments suggested a phenol removal percentage of 89.22% and enhanced availability of soil phosphorus and potassium for plants with H13 inoculation. In this case, the abundance of soil microbes and the activity of soil enzymes significantly increased as well. Furthermore, both photosynthesis and the antioxidant system in Chinese cabbage were enhanced following H13 inoculation, resulting in its increased yield and quality. Partial least squares path modeling revealed that H13 can primarily affect plant root growth, with a secondary impact on photosynthesis. These findings highlight the potential of biodegradation from phenol-degrading bacteria as a promising strategy for efficient phenol removal from soil while promoting plant growth and health.IMPORTANCEThis study is significant for environmental remediation and agriculture by its exploration of a more environmentally friendly and cost-effective bio-strategy in treating phenol-contaminated soil. These findings have essential implications for environmental remediation efforts and sustainable agriculture. By utilizing the biodegradation capabilities of Myroides xuanwuensis strain H13, it is possible to remove phenol contaminants from the soil efficiently, reducing their negative effects. Furthermore, the enhanced growth and health of the Chinese cabbage plants indicate the potential of this approach to promote sustainable crop production.

Core microbial taxonomies that maintain high organic carbon content in upland soil.

The accumulation of soil carbon (C) is crucial for the productivity and ecological function of farmland ecosystems. The balance between microbial carbon dioxide (CO2) emission and fixation determines the sustained accumulation potential of C in soil. Microorganisms involved in this process are highly obscure, thus hindering identification and further application of microorganisms with fertile soil function. In this study, a series of typical upland farmland soils were collected from 29 regions and their microbial community structure and soil C fractions were analyzed. Additionally, the rates of CO2 emission and fixation in each soil were measured. The results showed that the correlation between soil CO2 emissions and the SOC concentration was logarithmic, while that between CO2 fixation and SOC was linear. Bacterial and fungal diversity showed an upward trend with increasing soil C, and their α diversity was significantly correlated with CO2 fixation, but not correlated with CO2 emission. Fungi were more associated with soil C than bacteria, and the strength of linkage with soil C varied among the different phyla of microorganisms. Furthermore, the core microbial taxa in soils with low, medium and high SOC levels were identified by discarding redundant amplicon sequence variants, and their community differentiation was significantly driven by soil CO2 emission and fixation based on Mantel analysis. The high abundance of Chloroflexi, Nitrospirota, Actinobacteria, and Mortierellomycota in core taxa might indicate a high level of SOC level. This study highlights that SOC fluctuations are mainly driven by the core microbial taxa, rather than all microbial taxa in the agricultural system. Our research sheds light on the targeted regulation of the soil microbial community structure in upland farmland for soil fertility enhancement.

Microbial species pool-mediated diazotrophic community assembly in crop microbiomes during plant development.

Plant-associated diazotrophs strongly relate to plant nitrogen (N) supply and growth. However, our knowledge of diazotrophic community assembly and microbial N metabolism in plant microbiomes is largely limited. Here we examined the assembly and temporal dynamics of diazotrophic communities across multiple compartments (soils, epiphytic and endophytic niches of root and leaf, and grain) of three cereal crops (maize, wheat, and barley) and identified the potential N-cycling pathways in phylloplane microbiomes. Our results demonstrated that the microbial species pool, influenced by site-specific environmental factors (e.g., edaphic factors), had a stronger effect than host selection (i.e., plant species and developmental stage) in shaping diazotrophic communities across the soil-plant continuum. Crop diazotrophic communities were dominated by a few taxa (~0.7% of diazotrophic phylotypes) which were mainly affiliated with Methylobacterium, Azospirillum, Bradyrhizobium, and Rhizobium. Furthermore, eight dominant taxa belonging to Azospirillum and Methylobacterium were identified as keystone diazotrophic taxa for three crops and were potentially associated with microbial network stability and crop yields. Metagenomic binning recovered 58 metagenome-assembled genomes (MAGs) from the phylloplane, and the majority of them were identified as novel species (37 MAGs) and harbored genes potentially related to multiple N metabolism processes (e.g., nitrate reduction). Notably, for the first time, a high-quality MAG harboring genes involved in the complete denitrification process was recovered in the phylloplane and showed high identity to Pseudomonas mendocina. Overall, these findings significantly expand our understanding of ecological drivers of crop diazotrophs and provide new insights into the potential microbial N metabolism in the phyllosphere.IMPORTANCEPlants harbor diverse nitrogen-fixing microorganisms (i.e., diazotrophic communities) in both belowground and aboveground tissues, which play a vital role in plant nitrogen supply and growth promotion. Understanding the assembly and temporal dynamics of crop diazotrophic communities is a prerequisite for harnessing them to promote plant growth. In this study, we show that the site-specific microbial species pool largely shapes the structure of diazotrophic communities in the leaves and roots of three cereal crops. We further identify keystone diazotrophic taxa in crop microbiomes and characterize potential microbial N metabolism pathways in the phyllosphere, which provides essential information for developing microbiome-based tools in future sustainable agricultural production.

Effects of tillage and biochar on soil physiochemical and microbial properties and its linkage with crop yield.

Vertisols are clayey soils with a high potential for improving production. Therefore, understanding the impact of tillage and fertilization on soil physicochemical properties and microbial community is essential for improving the vertisols with a high montmorillonite and smectite clay content. A 3-year field experiment was conducted to compare the effects of different tillage and fertilization practices at three depths of the vertisol under the wheat-maize cropping system in the North China Plain. The experimental treatments included rotary tillage without fertilization (R-CK), rotary tillage with chemical nitrogen (N), phosphorus (P), and potassium (K) fertilization (R-NPK), R-NPK plus biochar (R-NPKB), deep tillage without fertilization (D-CK), deep tillage with chemical N, P, and K fertilization (D-NPK), and D-NPK plus biochar (D-NPKB). The results showed that D-NPKB significantly improved winter wheat and summer maize yields by 14.4 and 3.8%, respectively, compared with R-NPK. The nitrate (NO3 --N) content of the deeper soil layer in D-NPKB was significantly higher than that in D-NPK. Meanwhile, biochar application increased the pH in the three layers. Compared with R-NPK, D-NPKB significantly increased the average content of available phosphorus (AP), soil organic carbon (SOC), and total nitrogen (TN) by 73.7, 18.5, and 19.0%, respectively. Meanwhile, Gaiellale, Sphingomonadaceae, and Nocardioidaceae were the predominant bacteria at the family level across all treatments, with a total relative proportion ranging from 14.1 to 23.6%. In addition, the abundance of Bacillaceae in deep tillage was 9.4% higher in the 20-30-cm soil layer than that in rotary tillage. Furthermore, the correlation analysis revealed a significant positive correlation between crop yield and chemical factors such as NO3 --N and the abundances of Gaiellalea, Sphingomonadaceae, and Nocardioidaceae. The findings collectively indicated that deep tillage combined with biochar application could increase the soil nutrients and modify the bacterial structure in the deeper soil layer and therefore will be beneficial for improving the productivity of the vertisols.

A numerical modeling framework for simulating the key in-stream fate processes of PAH decay in Muskeg River Watershed, Alberta, Canada.

Most previous water quality studies oversimplified in-stream processes for modeling the fate and transport of critical organic contaminants, such as Polycyclic Aromatic Hydrocarbons (PAHs). Taking four selected PAHs as representative organic contaminants, we developed a numerical modeling framework using a Water Quality Analysis Simulation Program 8 (WASP8) and a well-established watershed model, i.e., Soil and Water Assessment Tool (SWAT) to: (1) address the influence of in-stream processes, including direct photolysis, volatilization, partitioning of PAHs to suspended solids, and DOC complexation processes on PAH concentrations; and (2) establish relationships between spatiotemporal distribution of environmental factors (e.g., ice coverage, water temperature, wind, and light attenuation), in-stream processes, and PAH concentrations at a watershed scale. Using calibrated SWAT and WASP8 models, we evaluated the impacts of seasonal changes in environmental factors on in-stream processes in the Muskeg River watershed, which is part of the Athabasca Oil Sands Region (AOSR), the third-largest crude oil reserves of the world in western Canada. Among four selected PAHs, simulation results suggest that Naphthalene primarily decay in the water through volatilization or direct photolysis. For Phenanthrene, Pyrene, and Chrysene, DOC complexation, volatilization, and direct photolysis all contribute to their decay in the water, with a strong dependence on seasonality. Model simulations indicated that direct photolysis and volatilization rates are meager in cold seasons, mainly due to low river temperature and ice coverage. However, these processes gradually resume when entering the warm season. In summary, the model simulation results suggest that critical in-stream processes such as direct photolysis, volatilization, and partitioning and their relationship with environmental factors should be considered when simulating the fate and transport of organic contaminants in the river systems. Our results also reveal that the relationship between environmental factors and fate processes affecting PAH concentrations can vary across a watershed and in different seasons.

[Characteristics of acidification and the distribution of available phosphorus along soil depths in heavy clay soils in southern Henan Province, China]. / è±«å—é»æ¿åœŸå£¤åˆ†å±‚é ¸åŒ–å’Œè€•å±‚é€Ÿæ•ˆç£·åˆ†å¸ƒç‰¹å¾.

The acidification of agricultural soil in the southern part of the North China Plain has become more obvious, which is particularly true for the heavy clay soil types, such as yellow-cinnamon and lime concretion black soils. To understand the spatial variability of the pH value and nutrients on the vertical agricultural soil profile of heavy clay soils in this area, we measured pH values and available phosphorus (AP) in 63 farmland sample points from Xiping County in the southern Henan Province. Geostatistical methods and ArcGIS technology were used to map soil pH values along three soil depths (0-10, 10-20, and 20-30 cm) and the spatial distribution of soil AP in the tillage layer (0-20 cm). Furthermore, the correlation between pH and AP was analyzed. The results showed that mean pH values of typical yellow-cinnamon and typical fluvo-aquic soils from three soil layers were 4.98, 4.93, 5.31, and 5.46, 5.81, 6.26, respectively, which gradually increased with soil depths. However, there was no significant difference among the three soil layers. Mean pH values of typical lime concretion black soil from the three soil layers were 5.23, 5.43 and 6.03, respectively, and that of the 20-30 cm soil layer was significantly higher than that of the 0-10 cm (by 0.8-1 pH unit) and the 10-20 cm layers. The pH of the 20-30 cm soil layer of the calcareous lime concretion black and moist soils were also significantly higher than that of the 0-10 and 10-20 cm soil layers. The AP contents of the typical yellow-cinnamon, typical lime concretion black, moist, typical fluvo-aquic and calcareous lime concretion black soils in 0-20 cm soil layer were 8.85-54.75, 4.27-37.49, 8.22-51.80, 6.07-34.82, and 13.22-22.85 mg·kg-1, respectively. The results of the map indicated that the areas with low AP were distributed in the middle of the study area in blocks, and the areas with high AP were distributed around the study area in dots and flakes. The pH values of the typical yellow-cinnamon, typical lime concretion black, and moist soils positively correlated with the content of AP in the 0-20 cm soil layer. In conclusion, the heavy clay soil in southern Henan Province became stratified acidification, which slowed down along the soil depth. Soil AP contents in the tillage layer were distributed unevenly in the study area, and were affected by soil types and soil pH. These results would be useful for the improvement of heavy clay soil acidification in the southern part of the North China Plain.

The quality of compost was improved by low concentrations of fulvic acid owing to its optimization of the exceptional microbial structure.

The influence of different concentrations of fulvic acid at 0, 100, 200, and 400 mg/kg was evaluated during the course of composting with straw and mushroom residues as substrates. The optimal concentration of fulvic acid is 100 mg/Kg based on microbial characteristics, chemical parameters, and germination index testing. Nearly 80% of the microbial taxa responded significantly to fulvic acid over the composting period, with a dynamic change of the co-occurrence network from complex to simple and then to complex. Fulvic acid accelerated the progress of composting and reduced the emission of gases at the thermophilic phase. The optimal concentration of fulvic acid enriched the beneficial microorganisms Aeribacillus, Oceanobacillus, and Rhodospirillaceae, and decreased the abundances of pathogenic microorganisms Corynebacterium, Elizabethkingia, and Sarcocystidae. This study indicates a new strategy to optimize the composting process using the biostimulant fulvic acid.

Extraction optimization and quality evaluation of humic acids from lignite using the cell-free filtrate of Penicillium ortum MJ51.

Bio-solubilization of lignite is a promising technology to transform coal into humic acids (HAs) which are broadly used in agriculture. In this work, HAs were extracted from lignite using the cell-free filtrate (CFF) of Penicillium ortum MJ51. The extraction method was optimized using response surface methodology (RSM) based on the interactive effects of nitric acid concentrations, coal loading ratio, extraction temperature and time as input factors, and the absorbance of HAs at 450 nm wavelength as the output response. Under optimized conditions (lignite pretreated with 4.7 N HNO3, coal loading ratio of 4.9%, temperature of 77.3 °C and time of 8.6 hours), the absorbance at 450 nm peaked at 70.28, and the concentration and extraction yield of HAs were 31.3 g L-1 and 63.9%, respectively, which were dramatically higher than those observed for traditional biological methods (0.7 g L-1 and 14.1%, respectively). The qualities of HAs produced under optimized conditions were evaluated and compared with those extracted by the conventional chemical method. The optimized process resulted in better HA quality indices, including lower molecular mass; higher nitrogen; less aromatic carbon; more aliphatic and carboxylic carbon; and higher bioactivity for promoting plant growth. Moreover, the anti-flocculation ability was improved, thereby supporting its applicability in agriculture. Extraction of HAs from lignite using the CFF of P. ortum MJ51 provides a novel technological approach for the efficient conversion of lignite to bio-active HAs.

Plant developmental stage drives the differentiation in ecological role of the maize microbiome.

BACKGROUND: Plants live with diverse microbial communities which profoundly affect multiple facets of host performance, but if and how host development impacts the assembly, functions and microbial interactions of crop microbiomes are poorly understood. Here we examined both bacterial and fungal communities across soils, epiphytic and endophytic niches of leaf and root, and plastic leaf of fake plant (representing environment-originating microbes) at three developmental stages of maize at two contrasting sites, and further explored the potential function of phylloplane microbiomes based on metagenomics. RESULTS: Our results suggested that plant developmental stage had a much stronger influence on the microbial diversity, composition and interkingdom networks in plant compartments than in soils, with the strongest effect in the phylloplane. Phylloplane microbiomes were co-shaped by both plant growth and seasonal environmental factors, with the air (represented by fake plants) as its important source. Further, we found that bacterial communities in plant compartments were more strongly driven by deterministic processes at the early stage but a similar pattern was for fungal communities at the late stage. Moreover, bacterial taxa played a more important role in microbial interkingdom network and crop yield prediction at the early stage, while fungal taxa did so at the late stage. Metagenomic analyses further indicated that phylloplane microbiomes possessed higher functional diversity at the early stage than the late stage, with functional genes related to nutrient provision enriched at the early stage and N assimilation and C degradation enriched at the late stage. Coincidently, more abundant beneficial bacterial taxa like Actinobacteria, Burkholderiaceae and Rhizobiaceae in plant microbiomes were observed at the early stage, but more saprophytic fungi at the late stage. CONCLUSIONS: Our results suggest that host developmental stage profoundly influences plant microbiome assembly and functions, and the bacterial and fungal microbiomes take a differentiated ecological role at different stages of plant development. This study provides empirical evidence for host exerting strong effect on plant microbiomes by deterministic selection during plant growth and development. These findings have implications for the development of future tools to manipulate microbiome for sustainable increase in primary productivity. Video Abstract.

Reactions of chlorinated ethenes with surface-sulfidated iron materials: reactivity enhancement and inhibition effects.

Recent studies on the use of controlled sulfur amendment to improve the reactivity and selectivity of zerovalent iron (ZVI) in reductive dechlorination reactions have generated renewed interest in ZVI-based remediation materials. However, existing studies have focused on the reactions between trichloroethene (TCE) and lab-synthesized ZVI, and the applicability of sulfidation to ZVIs with different material characteristics for reductive dechlorination of chloroethenes such as tetrachloroethene (PCE) and cis-dichloroethene (cis-DCE) has not been systematically examined. In this study, four ZVI materials from commercial sources having different sizes and morphological and compositional characteristics were subjected to various sulfidation treatments and were assessed in batch reactions with PCE, TCE, or cis-DCE. Sulfur amendment induces modest increases in PCE degradation rates and steers reactions towards a cleaner pathway that has minimum accumulation of partially dechlorinated intermediates. In the case of cis-DCE, bifurcating outcomes were observed that include enhancement effects for two high-purity ZVIs and inhibitory effects for two ZVIs possessing low levels of metal impurities. Further investigations based on controlled metal dosing reveal that the trace metals commonly present in cast iron or recycled metal scraps, such as Cu and Ni, can act as adventitious catalysts for cis-DCE reduction. Sulfidation results in poisoning of these catalytic ingredients and accounts for the adverse effect observed with a subset of ZVIs. Collectively, this study confirms enhanced degradation of highly chlorinated ethenes (PCE and TCE) by sulfidation of ZVIs from diverse origins; nonetheless, the effects of sulfidation can be highly variable for the less chlorinated ethenes due to differences in the material characteristics of ZVI and the predominant dechlorination pathways.

High Potassium Application Rate Increased Grain Yield of Shading-Stressed Winter Wheat by Improving Photosynthesis and Photosynthate Translocation.

Wheat (Triticum aestivum L) production on the Huang-Huai Plain of China has substantially affected in the past 50 years as a result of the decreasing total solar radiation and sunshine hours. Potassium has a significant effect on improving leaf photosynthesis ability under stress conditions. Five potassium application rates (K), 0 (K0), 50 (K50), 100 (K100), 150 (K150), and 250 (K250) mg K2O kg-1 soil, combined with two shading levels, no shading (NS) and shading at early filling stage for 10 days (SE), were used to investigate the effects of K application on winter wheat growth under SE condition. Under NS condition, the parameters related to chlorophyll fluorescence characteristics, dry matter productivity and grain yields reached the maximum values at a middle K application rate (100 mg K2O kg-1 soil). Shading stress significantly reduced leaf SPAD value, showed negative effects on chlorophyll fluorescence characteristics and reduced grain yield of winter wheat. However, as the result of the interaction of K×S, compared to NS condition, higher K application rate (150 mg and 250 K2O kg-1 soil) was beneficial in terms of achieving a higher grain yield of winter wheat under SE by improving leaf SPAD value, alleviating the damage of SE on the winter wheat photosynthetic system, and increasing fructan content and dry matter translocation percentage.