Nutrient Availability Research Articles

Trophic cascades and top-down control: found at sea

This review investigates the current state of knowledge on trophic control and cascades in marine ecosystems. It critically examines claims that top-down control and trophic cascades are rarer in saltwater ecosystems than in their freshwater counterparts, that these phenomena are scarcer in the marine water column than in intertidal or benthic habitats, and that various abiotic and/or biotic factors explain the incidence of top-down control and trophic cascades in neritic and pelagic ecosystems. This review suggests that top-down control is more widespread in neritic and pelagic ecosystems than species-level trophic cascades, which in turn are more frequent than community-level cascades. The latter occur more often in marine benthic ecosystems than in their lacustrine and neritic counterparts and are least frequently found in pelagic ecosystems. These distinctions among ecosystem types likely derive from differences in the spatial dimensionality and scale of physical processes through their effects on nutrient availability and community composition. The incidence of community-level trophic cascades among neritic and pelagic ecosystems is inversely related to biodiversity and omnivory, which are in turn associated with temperature. Regional variability in benthic and neritic trophodynamics also results from differences in producer and consumer traits and food web structure. Fear of predators, rather than predation mortality itself, drives many marine trophic cascades and massive vertical migrations. Paradoxical and synergistic trophic interactions, as well as positive feedback loops derived from biological nutrient cycling, complicate the conventional dichotomy between top-down and bottom-up control. Finally, this review presents a set of ecological factors whose alternative states favor top-down or bottom-up control in marine ecosystems.

Enhanced Electrokinetic Remediation of Agricultural Soil: Assessment of Chromium (VI) Removal and Soil Property Alterations

ABSTRACT This study evaluated the efficiency of enhanced electrokinetics (EKR) in removing hexavalent chromium Cr (VI) from agricultural soil using three potent electrolyte solutions: citric acid (CA), EDTA, and Tween 80. Distilled water was used as a control experiment. Further, to understand the influence of the applied current across the soil column and the targeted areas, a length-wise as well as depth-wise distribution of Cr (VI) was analyzed. Additionally, the key properties of agricultural soil, such as organic matter, carbonate content and sulfate ions, were investigated to study both the effect of soil properties on the efficiency of EKR, and the alterations in soil properties due to the EKR treatment. The findings revealed that CA was the most effective enhancing agent in removing Cr (VI), with 37.5% removal, followed by EDTA (33.4%), distilled water (23.8%), and Tween 80 (22.8%). The chromate ions, Cr-EDTA complexes, and Cr-Cit complexes migrated toward the anode through electro-migration, resulting in higher Cr (VI) in analytes and S1 and S2 soil sections. The surfactant could not form a metal complex but caused the mobilization of organic matter and soil colloids, resulting in relatively lower removal rates. The depth-wise Cr (VI) distribution indicated higher Cr (VI) retention at the bottom and middle sections due to gravitational leaching and compact soil arrangement. EKR was effective in eliminating excess sulfate ions from the soil, while improving the availability of essential nutrients through organic matter mobilization. The application of CA-enhanced EKR over Cr (VI)-contaminated agricultural field can give promising remediation with minimum disturbance to the soil properties.

Microbial and Phytoremediation Strategies for Agricultural Soil Bioremediation: Mechanisms and Future Perspectives

Bioremediation is an eco-friendly approach that utilizes microbes and plants to effectively remove a wide range of pollutants from the soil. Various strategies—such as bioventing, biopiling, biostimulation, bioattenuation, and bioaugmentation—are employed to enhance biological processes, breaking down complex soil contaminants into simpler, non-toxic forms. These byproducts are absorbed by plants and microorganisms, contributing to a healthier environment. While extensive research exists on bioremediation techniques and microbial mechanisms, reports on their practical applications and proven benefits remain limited. Therefore, developing effective bioremediation strategies is crucial to degrade pollutants at scale, preserve nutrient availability, and optimize microbial populations and processes, including biodegradation, biosorption, biomineralization, bioaccumulation, and biotransformation, tailored to specific contaminants. This paper reviews various bioremediation approaches and their potential as viable solutions for addressing emerging environmental pollutants. With continued advancements, microbial and phytoremediation could mitigate pollution and promote long-term environmental health.

Co-inoculation of arbuscular mycorrhizal fungi and Bacillus subtilis enhances morphological traits, growth, and nutrient uptake in maize under limited phosphorus availability.

The use of beneficial microorganisms to enhance phosphate fertilizer use efficiency and solubilize residual phosphorus (P) is a promising strategy to improve soil P availability for plants. This study tested the hypothesis that inoculation with arbuscular mycorrhizal fungi, either alone or in combination with Bacillus subtilis, enhances maize growth and optimizes nutrient availability, particularly phosphorus. The experiment was conducted under greenhouse conditions with four replications, following an 8 × 3 factorial design. Treatments included individual inoculations with Bacillus subtilis (IPACC26), Rhizophagus clarus (RJN102A), Claroideoglomus etunicatum (SCT101A), and a commercial inoculant of Rhizophagus intraradices (Rootella BR ULTRA), as well as three co-inoculations (IPACC26 combined with each fungus) and a non-inoculated control. These treatments were combined with three levels of phosphate fertilization (0, 50, and 100% of the recommended P level). Mycorrhizal colonization improved root architecture and increased photosynthetic pigments and uptake of P and other nutrients, resulting in greater plant growth and biomass production. The most pronounced effects were observed in plants inoculated with R. clarus and C. etunicatum, either alone or in combination with B. subtilis, at the 0 and 50% P levels. At 0% P, inoculated plants accumulated significantly more biomass, with root and shoot dry mass up to 3,000% and 680% higher, respectively, than those of uninoculated plants; this effect was associated with a 1,700% increase in shoot P accumulation compared to the control. These findings highlight the potential of these inoculants as biofertilizers for more sustainable and efficient phosphorus management in maize cultivation.

Fate of Rhizosphere Microorganisms and Growth of Leguminous Plants in Cassava Mill Effluent Simulated Soil

Aims: The aim of this study was to determine the effect of cassava mill effluent in simulated soil on rhizosphere microorganisms and growth of leguminous plants. Methodology and Results: The fate of rhizosphere microbes and growth of leguminous plants in cassava mill effluent simulated soil was evaluated using standard physical, microbiological and biochemical techniques. The results showed that the number of buds, leaves and nodules formed fluctuated across the concentration. The fungal isolates from the cassava mill effluent simulated soil were virtually the same across the concentration gradients of 0%, 10%, 20%, 30%, 40%, 50% and 100%, the only difference was that different fungal genera were found in plots where different leguminous plants were used for the simulation experiment. C. mucunoides at cassava mill effluent (CME) impacted plots (0%-100%) had Saccharomyces sp. and Mucor indicus as it’s predominant fungal isolate while the C. pubescens from the same site had Fusarium sp. and Gliocladium sp. as its predominant fungal isolates. Cassava mill effluent (CME)-simulated soil (0%-100%) had Chromobacterium sp. and Corynebacterium sp as it’s predominant bacterial isolates from the Centrosema pubescens plots. Calopogonium mucunoides plots had Bacillus sp., Acinetobacter sp. and Escherichia coli as it bacterial isolates. Same nitrogen-fixing bacteria were isolated from all the cassava mill effluent simulated plots (0%-100%) irrespective of the legume planted for the phytoremediation exercise. The nitrogen-fixers isolated were: Azotobacter sp., Azospirillum sp., Frankia sp., Bradyrhizobium sp., Hebaspirillum sp., Cyanobacteria (or blue green algae) and Anabaena sp. Other isolates were Nostoc sp., Clostridium sp. and Rhizobium sp. Conclusion, Significance and Impact of Study: The simulation experiment analysis revealed that soil acidity influences many chemical and biological characteristics of soil including availability of nutrient and toxicity of metals which can also affect microbial community in many ways. It also revealed that acidic soils can significantly reduce nodulation and nodule function in leguminous plants.

Reverse microdialysis of sucrose stimulates soil fungal and bacterial growth at the microscale.

The rhizosphere is a critical microenvironment that plays key roles in plant nutrient availability, largely due to root interactions with rhizospheric microbes. However, we lack suitable methods that can elucidate mechanisms determining rhizospheric community structure and function within the context of a dynamic, undisturbed soil. Microdialysis has been used for low intrusive soil nutrient sampling at the scale of a fine root, with small probes that also enable release of defined compounds. We evaluated whether microdialysis could simulate exudation, by the release of sucrose, and stimulate changes in a soil microbial community, allowing us to determine the microbes that responded most to carbon release. Microdialysis successfully stimulated growth on probe surfaces of fungi and bacteria, which were extracted and sequenced for identification. Microbial growth was also visualized with scanning electron microscopy. The majority of the species stimulated were classified as fast growing or opportunistic, e.g. yeasts, moulds, proteobacteria and actinobacteriota, which are known to respond quickly (within days) to the release of simple sugars as exudates in the rhizosphere. The study demonstrates the potential of using microdialysis as a tool to investigate interactions between root exudation and soil microbial community composition, initially for individual compounds and in the future for more complex compositions.

Characterization of Saline Soil Rhizobacteria from Coastal Lands in Dissolving Phosphate, Nitrogen Fixing and Synthesizing IAA Growth Hormone

Saline soils are a major constraint to agricultural productivity, affecting nutrient availability and plant growth due to high salt concentrations. As global agricultural demands increase, sustainable strategies are needed to improve crop resilience and productivity in saline environments. Rhizobacteria, particularly those with the ability to solubilize phosphate, fix atmospheric nitrogen, and produce plant growth hormones such as indole-3-acetic acid (IAA), offer a promising solution. The study aimed to identify potential indigenous rhizobacteria extracted from the rhizosphere of saline soil in Southeast Sulawesi. The research was carried out in the Agronomy Laboratory, Faculty of Agriculture Halu Oleo University. The experimental design employed a completely randomized setup, involving ten different isolates. These isolates were assessed for their capacity to solubilize phosphate, fix nitrogen, and produce the growth hormone known as IAA. The findings revealed that all the rhizobacteria isolates exhibited the ability to fix nitrogen, and synthesize IAA, however, 2 isolates could not dissolve phosphate. Among them, the rhizobacteria labeled KLK-LS14 displayed the highest phosphate solubilization, with a halo diameter of up to 1.55 cm. As for nitrogen fixation, the isolates KDI-LS04, KNW-LS08, KLK-LS10, and KLK-LS14 demonstrated the highest levels. In terms of IAA hormone synthesis, the isolates KNW-LS08, KLK-LS14, and KDI-LS04 exhibited the greatest production, with respective contents of 47.44 µg/ml filtrate, 48.11 µg/ml filtrate, and 50 µg/ml filtrate. The most promising isolates, such as KLK-LS14 and KNW-LS08, exhibited high nitrogen fixation and IAA production, making them suitable candidates for agricultural bio-inoculants. These findings suggest practical applications in sustainable agriculture, particularly for reclaiming saline soils. Future work should focus on large-scale field trials and integrating these rhizobacteria into farming practices to improve crop yield, reduce dependency on chemical fertilizers, and support the development of environmentally friendly agricultural technologies. Keywords: Indigenous rhizobacteria, IAA, phosphate solvent, nitrogen fixer, saline soil, sustainable agriculture, Plant Growth-Promoting Rhizobacteria (PGPR).

Influence of farmyard manure compost and biochar in the amelioration of soil fertility and crop productivity under drought stress conditions.

Drought stress is a leading environmental concern which restricts plant growth and nutrients availability. A greenhouse pot experiment was designed to examine the impact of farmyard manure-based biochar (FMB) and compost (FMC) on soybean osmoprotectants, antioxidants, nutrient uptake, and soil biochemical characteristics under three different moisture levels of w100, 75, and w50. Results of the study revealed that drought stress significantly reduced plant's physiochemical and gaseous exchange attributes whilst combine treatment of FMB30 + FMC30 substantially improved soybean root growth, leaf area index, total chlorophyll content, and stomatal conductance by 37.41, 19.55, 32.59, and 27.61%, respectively, at W50 moisture level. Additionally, leave relative water content also boosted up to 18.62% at W50 moisture under FMB30 + FMC30 treatment. Additionally, leaves catalase, peroxide and superoxidase dismutase notably decreased up to 49.15, 41.64, and 76% respectively under the co-amendment of FMB and FMC. Moreover, soil MBC (22%), MBN (124%), MBP (97%), NO3-N (167%), NH4-N (158%), Olsen P (54%), K (23), and SOC (7.51%) increased remarkably under FMB30 + FMC30 treatment at w50 drought level. Overall, these results indicate that biochar and compost both are crucial amendments particularly in semi-arid and arid regions to get better crop yield.

Exploration of Plant Growth-promoting Traits of Diazotroph Isolates Obtained from Rhizospheric Soil

Rhizospheric diazotrophs play a pivotal role in sustainable agriculture by enhancing nutrient availability and promoting plant growth. The present study was conducted to explore native plant growth-promoting diazotrophic bacteria from the rhizosphere of different plants. 3 isolates (Hb1R 1, WhR 2, and GrR 1) were selected out of 24 as promising based on plant growth-promoting traits such as phosphate (P), potassium (K), and zinc (Zn) solubilization, as well as production of indole acetic acid (IAA) and ammonia (NH3). All three isolates exhibited quantitative P solubilization and NH3 production, ranging from 13.55 ± 1.20 to 300.3 ± 7.78 µg/ml and 1.074 ± 0.15 to 9.584 ± 0.165 mM/ml, respectively. Indole acetic acid (IAA) production of 85.6 ± 0.33 to 156.75 ± 1.62 µg/ml after 96 hours of incubation was demonstrated only by GrR 1. Maximum N fixation of 2.15 ± 0.22 mg/ml was exhibited by Hb1R 1, followed by GrR 1 (1.85 ± 0.1 mg N/ml) and WhR 2 (1.03 ± 0.09 mg N/ml). 16S rRNA gene sequencing identified isolates Hb1R 1, WhR 2, and GrR 1 as Enterobacter cloacae subsp. dissolvens strain Hb1R1, Enterobacter cloacae strain GrR1, and Enterobacter cloacae strain WhR2, respectively. These isolates show promise as bioinoculants for sustainable agriculture, warranting further studies on field application and adaptability to enhance crop productivity.

Global phylogeography and microdiversity of the marine diazotrophic photoautotrophs Trichodesmium and UCYN-A.

Photoautotrophic diazotrophs, specifically the genera Trichodesmium and UCYN-A, play a pivotal role in marine nitrogen cycling through their capacity for nitrogen fixation. Despite their global distribution, the microdiversity and environmental drivers of these diazotrophs remain underexplored. This study provides a comprehensive analysis of the global diversity and distribution of Trichodesmium and UCYN-A using the nitrogenase gene (nifH) as a genetic marker. We sequenced 954 samples from the Pacific, Atlantic, and Indian Oceans as part of the Bio-GO-SHIP project. Our results reveal significant phylogenetic and biogeographic differences between and within the two genera. Trichodesmium exhibited greater microdiversity compared to UCYN-A, with clades showing region-specific distribution. Trichodesmium clades were primarily influenced by temperature and nutrient availability. They were particularly frequent in regions of phosphorus stress. In contrast, UCYN-A was most frequently observed in regions experiencing iron stress. UCYN-A clades demonstrated more homogeneous distributions, with a single sequence variant within the UCYN-A1 clade dominating across varied environments. The biogeographic patterns and environmental correlations of Trichodesmium and UCYN-A highlight the role of microdiversity in their ecological adaptation and reflect their different ecological strategies. These findings underscore the importance of characterizing the global patterns of fine-scale genetic diversity to better understand the functional roles and distribution of marine nitrogen-fixing photoautotrophs.IMPORTANCEThis study provides insights into the global diversity and distribution of nitrogen-fixing photoautotrophs, specifically Trichodesmium and UCYN-A. We sequenced 954 oceanic samples of the nifH nitrogenase gene and uncovered significant differences in microdiversity and environmental associations between these genera. Trichodesmium showed high levels of sequence diversity and region-specific clades influenced by temperature and nutrient availability. In contrast, UCYN-A exhibited a more uniform distribution, thriving in iron-stressed regions. Quantifying these fine-scale genetic variations enhances our knowledge of their ecological roles and adaptations, emphasizing the need to characterize the genetic diversity of marine nitrogen-fixing prokaryotes.

Effects of liming on soil physical and chemical properties in Europe and North America: A review

Abstract Soil acidity is one of the major constraints limiting crop production worldwide. About 50% of the global arable land is acidic. Liming remains an effective strategy for soil acidity amelioration and improvement of soil fertility. The objective of this review was to summarize information on liming effects on soil physical and chemical properties in the North American and European contexts. We reviewed how different lime products influence soil pH and various soil processes that contribute to soil physical and chemical health. Our findings were that, when applied at appropriate rates, liming materials generally increased soil pH, cation exchange capacity (CEC), exchangeable calcium and magnesium, nutrient availability and reduced toxicities of aluminum (Al), manganese (Mn), and heavy metals. Many studies showed that liming modifies soil properties and processes both in the short‐ and long‐term. While most studies reported improvements in nutrient availability, there were some differences in liming impacts on phosphorus (P) and potassium (K), mostly due to differences in soil type and composition. Liming improves structural properties including aggregate stability, soil friability, porosity, and water infiltration. Knowledge about liming impacts on soil physical and chemical properties is essential for optimizing liming rates to enhance soil health and improve productivity. Future studies should explore liming effects on CEC, associations of P and K with cations supplied by liming (e.g., Ca2+), and use of some waste materials as lime alternatives.

Yeasts as Biofertilizers and Biocontrol Agents: Mechanisms and Applications.

Yeasts, a large and diverse group of microorganisms, are gaining increasing interest from both the scientific community and industry. Yeasts' natural association with plants has endowed them with a broad repertoire of mechanisms that facilitate a beneficial coexistence. Despite the ability of certain yeast species to enhance plant growth and demonstrate broad-spectrum antifungal activities, their commercialization remains limited. This mini-review focuses on recent insights into the mechanisms by which yeasts stimulate plant growth and protect plants from certain diseases. Yeast species support plant growth by increasing the supply or availability of essential nutrients or by producing phytohormones. The mode of action of yeasts as biological control agents includes competition for nutrients and space, mycoparasitism, formation of biofilms that inhibit pathogen growth, and production of killer toxins, hydrolytic enzymes, and volatile organic compounds. Additionally, yeasts can induce systemic resistance in host plants by enhancing defensive enzyme activity or upregulating pathogenesis-related gene expression. This mini-review explores the current and future applications of yeasts as biofertilizers and biocontrol agents, emphasizing the metabolic engineering of yeast strains and the engineering of plant microbiomes.

Potential distribution of the endangered Ballota adenophora, endemic to Saudi Arabia under climate change scenarios: toward conservation prioritization

Species distribution modeling, or SDM, is a useful tool for identifying species potential distribution and assessing how human-caused changes affect particular species in desert environments. The fact that such applications are still uncommon on plant species in the Arabian Peninsula may have to do with the fact that many dry lands and deserts throughout the world are located in hostile environments. The First Biennial Update Report (BUR1) - UNFCCC mentioned that as temperatures rise and precipitation patterns shift, Ballota adenophora, like many other species, faces increased stress from altered growing conditions and habitat loss. Over the past century, the Ballota adenophora’s population has drastically decreased throughout its geographic range. Changes in natural resources, such water and nutrient availability, brought on by ongoing climate change are linked to this decline. We examined how B. adenophora might respond to anticipated climate change over the coming decades using species distribution models (SDMs). We fitted ensemble SDMs using recently created climatic data based on more precise climate models and a variety of dispersal scenarios in order to lessen uncertainty and bias in our SDM predictions. Our Species Distribution Models (SDMs) revealed significant habitat suitability in Madinah, Tabuk, the Hisma range, Jabal Al Lauz, and Jabal Radua, north of Yanbu. Further, our models anticipated that the distribution range of B. adenophora will drop by more than 4% during the next few decades. Our findings advocate for immediate conservation action at the global and national levels to mitigate the effects of climate change on B. adenophora. This study can help shape policy and mitigation efforts to protect and preserve endemic species in the Arabian Peninsula. These hotspots should be focused on by policy makers and stakeholders and declared as protectorates in the region. The largest number of species per area would be protected by focusing primarily on the hotspots with high potential habitat suitability.

Non-growth substrate ethane perturbs core methanotrophy in obligate methanotroph Methylosinus trichosporium OB3b upon nutrient availability.

Type II methanotrophs present a dual advantage: mitigating methane emissions and producing bioproducts such as polyhydroxybutyrate (PHB). However, their full potential remains untapped, partly due to a limited understanding of how co-occurring gases influence their metabolism. Methane-rich emissions from both natural and anthropogenic sources are frequently accompanied by secondary gases, such as ethane, which create heterogeneous substrate conditions. This study reveals that ethane, a non-growth co-metabolic substrate, significantly modulates the metabolism of type II obligate methanotrophs, affecting microbial growth, methane oxidation, and PHB synthesis. These results advance our understanding of the metabolic plasticity of these organisms and also reveal new opportunities to leverage secondary substrates for selectively fine-tuning beneficial methanotrophic activities, such as biopolymer production.

Pengaruh Pemberian Abu Cangkang Kerang Laut dan Pupuk SP-36 Terhadap Pertumbuhan dan Hasil Tanaman Tomat Pada Tanah Gambut

The development of tomato plants on peat soils has problems including low soil pH and low nutrient availability. Efforts to overcome these problems require liming which aims to increase the pH of peat soil. The ameliorant material used is Sea Shell Ash to improve the biological, physical, and chemical properties of the soil, and the addition of SP-36 fertilizer to increase the growth and yield of tomato plants. This study aims to obtain the best dose of sea shell ash and SP-36 fertilizer for the growth and yield of tomato plants on peat soil. The research was conducted at Bengkayang Dormitory, Jalan Sepakat, from June to August. The design used was a complete randomized design (CRD) consisting of 2 factors, namely the Shell Ash factor (A) and SP-36 Fertilizer (P). The seashell ash factor is a1: with 100 g/polybag, a2: with 200 g/polybag, and a3; with 300 g/polybag. The SP-36 fertilizer factor is p1: with 2 g/polybag SP-36 fertilizer, p2: with 4 g/polybag SP-36 fertilizer, and p3: with 5 g/polybag SP-36 fertilizer. The observation variables in this study included: plant height (cm), root volume (cm3), plant dry weight (g), number of fruits per plant (fruit), fruit weight per plant (g), and weight per fruit (g). The results showed that SP-36 fertilizer had no effect on the yield of tomato plants, but cane ash did.

Changes in the bulk soil after fresh corn grown with organic and inorganic fertilizer application.

The effects of different fertilizer applications on crop growth, soil health, and microbial communities are critical for sustainable agriculture. Positive interactions between crop roots and their associated microbiomes are essential to improve nutrient availability and promote plant growth. Therefore, this study aimed to investigate the changes in bulk soil chemical properties and diversity of phosphate-solubilizing microorganisms after growing three fresh corn plants under the application of vermicompost, black soldier flies, and inorganic fertilizers. Fresh corn yield and soil samples were collected from purple waxy, pink waxy, and sweet corn grown under field conditions. The capacity to solubilize mineral phosphate and indole acetic acid was also determined using a spectrophotometer. The results showed that organic and inorganic fertilizers can maintain the ear-fresh weight of the three fresh corn varieties and tend to increase some soil chemicals after growth. Application of inorganic fertilizer and black soldier flies mixed with inorganic fertilizer resulted in the highest ear fresh weight, with 6,291.30 and 5,887.40 kg ha-1, respectively. Moreover, the soil pH, available phosphorus, and copper tended to increase, whereas zinc and chromium decreased. However, fertilizer management did not affect the diversity of the phosphate-solubilizing microorganisms. In addition, the three phosphate-solubilizing fungal isolates were similar to the type strain of Candida tropicalis. The phosphate-solubilizing fungi isolate potentials were not significantly different in AlPO4, and FePO4 solubilizing. Only two PSF isolates from purple waxy produced IAA hormone between 462.81-562.81 mg l-1.

Impact of different treatment methods and timings on soil microbial communities with transgenic maize straw return

Understanding the impact of genetically modified (GM) crop straw return on soil ecosystems is crucial as GM crops become more prevalent. This study assesses the effects of straw mulching and deep tillage on soil microbial communities from GM and non-GM maize, highlighting potential ecological impacts. Shotgun metagenomic sequencing was utilized to analyze the microbial community structure and functional genes in soil samples collected at different times (30, 180, and 270 days) after straw mulching and deep tillage treatments. The study included insect-resistant transgenic maize varieties 2A-7 and CM8101 and their non-transgenic counterparts B73 and Zheng58. Different treatment methods significantly affect soil microbial alpha-diversity and beta-diversity, with deep tillage resulting in higher alpha-diversity compared to mulching, and the 180-day mark exhibiting the highest alpha-diversity across all sampling times. Early straw treatment prompted a rapid microbial response to nutrient availability, with notable changes in diversity and function over time. Straw treatments notably altered soil microbial functions, especially in carbon cycling and nutrient metabolism. Interestingly, the microbial effects of GM versus non-GM maize straw were similar, suggesting crop residue type under consistent soil management practices might not significantly alter microbial community structures. The methods and timing of straw treatments have a significant impact on soil microbial communities, surpassing the differences between GM and non-GM straw. These findings highlight the importance of straw management practices for sustainable agricultural ecosystem management.

Genomic basis of adaptation to serpentine soil in two Alyssum species shows convergence with Arabidopsis across 20 million years of divergence.

Serpentine outcrops, characterized by low nutrient availability, high heavy metal concentrations, propensity to drought, and island-like distributions, offer valuable systems to study parallelisms in repeated adaptation to extreme environments. While shared phenotypic manifestation of adaptation to serpentine environments has been investigated in many species, it is still unclear whether there may be a common genetic basis underlying such responses. Here we assess local adaptation to serpentine soil and infer the parallel genetic signatures of local adaptation to serpentine environments in two thus far unexplored closely related species, Alyssum gmelinii and Alyssum spruneri (Brassicaceae). Then we measure gene- and function-level convergence with the previously explored Arabidopsis arenosa, to reveal candidate shared adaptive strategies within Brassicaceae. We tested for adaptation using a reciprocal substrate-transplant experiment in A. gmelinii. Then, after assembling a reference genome, we generated population-level sequencing data of four population pairs and performed genome scans for directional selection to infer serpentine adaptive candidate genes in Alyssum. Finally, we compared candidate gene lists with those inferred in similar experiments in Arabidopsis arenosa and used protein-protein interaction networks to discern functional convergence in serpentine adaptation. Independent colonization of serpentine environments by Alyssum populations is associated with footprints of selection on genes related to ion transport and homeostasis, nutrient and water uptake, and life-history traits related to germination and reproduction. Reciprocal transplant experiments demonstrated that adapted plants germinate sooner and exhibit better growth in serpentine conditions while excluding heavy metals and increasing Ca uptake in their tissues. Finally, a significant fraction of such genes and molecular pathways is shared with Arabidopsis arenosa. We show that genetic adaptation to the multi-factorial challenge imposed by serpentine environments involves key pathways that are shared not only between closely related species, but also between Brassicaceae tribes of ∼20 Mya divergence.

Ecophysiological Responses of Triterpene Glycosides in Buds of Aralia elata (Miq.) Seem. to Late Spring Frost with Soil-Mediated Effects

Late spring frost (LSF) poses a threat to temperate forest ecosystems; however, its combined effects with soil properties on triterpene glycosides in the buds of valuable shrubs are still unclear. In this study, natural Aralia elata (Miq.) Seem. populations were investigated in 15 counties in Heilongjiang and Jilin provinces in Northeast China. Buds were sampled in 3–5 cm length and used for determining triterpene glycosides (TGs) of Araloside VI, Araloside V, and 4-F8 (structural analogs) in spring of 2023. LSF in Heilongjiang showed longer days reaching 20 °C (CD20) (6.0 ± 2.5 d), LSF number (NLSF) (1.8 ± 0.5 times) and duration (DLSF) (21.5 ± 5.2 d), and days of temperature rise (DTR) (15.9 ± 3.8 d) compared to Jilin (4.4 ± 0.4 d, 1.2 ± 0.4 times, 17.4 ± 3.9 d, 12.0 ± 3.3 d, respectively). Araloside VI (0.30–0.59%) was positively driven by DLSF but negatively driven by DTR. Araloside V (0.04–0.17%) and 4-F8 (0.09–0.44%) were positively influenced by the lowest temperature, DTR, and CD20, negatively influenced by NLSF, and slightly influenced by organic matter. In LSF-prone regions, soil organic matter and nutrient availability do not need to be enriched, and soil pH should be higher than 5.7 if high TGs are the objective in A. elata buds.

A new phenotyping method for root growth studies in compacted soil validated by GWAS in barley

BackgroundSoil compaction is defined as the reduction of air-filled pore space affecting soil density, water conductivity and nutrient availability. These conditions negatively influence root morphology, root development and plant growth leading to yield loss. To date, the ability of roots to penetrate compacted soil has been investigated using high density agar or wax-petrolatum layers as a proxy for compaction. Nevertheless, these methods are not realistic and fail to account for the root-soil interaction that influences root growth ability.ResultsArtificially compacted soil lumps were prepared using natural field soil mixed with sand and vermiculite in a 1:1:0.2 ratio and adjusted to a final water content of 31%. A Genome Wide Association Study (GWAS) was performed to validate this new methodology, combining a panel of 139 barley cultivars with a Single Nucleotide Polymorphism (SNP) dataset of 5,317 polymorphic markers. The panel was evaluated at seedling stage for four traits: total root length, average of diameter width, seminal root number, shoot: root weight ratio and two novel Quantitative Trait Loci (QTLs) associated with total root length were identified on Chr 4 H and 5 H. Four genes (a Nitrate Transporter1 (NRT1)/Peptide Transporter (PTR) family protein 2.2, a Hedgehog-interacting-like protein, an expansin and a cyclic nucleotide-gated channel) were hypothesized as plausible candidates for further investigation, given their implication in root development. In addition, the new phenotyping method revealed an altered plagiogravitropism phenomenon in barley during root emergence in compact substrates. In uncompacted soil, only the primary root exhibits vertical gravitropic set-point angle while a variable number of embryonic seminal roots develop with a shallower growth angle. In contrast, in compacted substrate all roots developed vertically to restore the growth angle after reaching a length of 4–5 millimetres.ConclusionsA methodology based on root-soil interaction is presented as a new method for root growth evaluation and genomic studies in seedlings growing in compacted soil.