Presence Of Arbuscular Mycorrhizal Fungi Research Articles

Soil compaction reversed the effect of arbuscular mycorrhizal fungi on soil hydraulic properties.

Arbuscular mycorrhizal fungi (AMF) typically provide a wide range of nutritional benefits to their host plants, and their role in plant water uptake, although still controversial, is often cited as one of the hallmarks of this symbiosis. Less attention has been dedicated to other effects relating to water dynamics that the presence of AMF in soils may have. Evidence that AMF can affect soil hydraulic properties is only beginning to emerge. In one of our recent experiments with dwarf tomato plants, we serendipitously found that the arbuscular mycorrhizal fungus (Rhizophagus irregularis 'PH5') can slightly but significantly reduce water holding capacity (WHC) of the substrate (a sand-zeolite-soil mixture). This was further investigated in a subsequent experiment, but there we found exactly the opposite effect as mycorrhizal substrate retained more water than did the non-mycorrhizal substrate. Because the same substrate was used and other conditions were mostly comparable in the two experiments, we explain the contrasting results by different substrate compaction, most likely caused by different pot shapes. It seems that in compacted substrates, AMF may have no effect upon or even decrease the substrates' WHC. On the other hand, the AMF hyphae interweaving the pores of less compacted substrates may increase the capillary movement of water throughout such substrates and cause slightly more water to remain in the pores after the free water has drained. We believe that this phenomenon is worthy of mycorrhizologists' attention and merits further investigation as to the role of AMF in soil hydraulic properties.

Computer vision models enable mixed linear modeling to predict arbuscular mycorrhizal fungal colonization using fungal morphology

The presence of Arbuscular Mycorrhizal Fungi (AMF) in vascular land plant roots is one of the most ancient of symbioses supporting nitrogen and phosphorus exchange for photosynthetically derived carbon. Here we provide a multi-scale modeling approach to predict AMF colonization of a worldwide crop from a Recombinant Inbred Line (RIL) population derived from Sorghum bicolor and S. propinquum. The high-throughput phenotyping methods of fungal structures here rely on a Mask Region-based Convolutional Neural Network (Mask R-CNN) in computer vision for pixel-wise fungal structure segmentations and mixed linear models to explore the relations of AMF colonization, root niche, and fungal structure allocation. Models proposed capture over 95% of the variation in AMF colonization as a function of root niche and relative abundance of fungal structures in each plant. Arbuscule allocation is a significant predictor of AMF colonization among sibling plants. Arbuscules and extraradical hyphae implicated in nutrient exchange predict highest AMF colonization in the top root section. Our work demonstrates that deep learning can be used by the community for the high-throughput phenotyping of AMF in plant roots. Mixed linear modeling provides a framework for testing hypotheses about AMF colonization phenotypes as a function of root niche and fungal structure allocations.

Arbuscular mycorrhizal fungi reduce soil N2O emissions by altering root traits and soil denitrifier community composition

Arbuscular mycorrhizal fungi (AMF) increase the ability of plants to obtain nitrogen (N) from the soil, and thus can affect emissions of nitrous oxide (N2O), a long-lived potent greenhouse gas. However, the mechanisms underlying the effects of AMF on N2O emissions are still poorly understood, particularly in agroecosystems with different forms of N fertilizer inputs. Utilizing a mesocosm experiment in field, we examined the effects of AMF on N2O emissions via their influence on maize root traits and denitrifying microorganisms under ammonia and nitrate fertilizer input using 15N isotope tracer. Here we show that the presence of AMF alone or both maize roots and AMF increased maize biomass and their 15N uptake, root length, root surface area, and root volume, but led to a reduction in N2O emissions under both N input forms. Random forest model showed that root length and surface area were the most important predictors of N2O emissions. Additionally, the presence of AMF reduced the (nirK + nirS)/nosZ ratio by increasing the relative abundance of nirS-Bradyrhizobium and Rubrivivax with ammonia input, but reducing nosZ-Azospirillum, Cupriavidus and Rhodopseudomonas under both fertilizer input. Further, N2O emissions were significantly and positively correlated with the nosZ-type Azospirillum, Cupriavidus and Rhodopseudomonas, but negatively correlated with the nirS-type Bradyrhizobium and Rubrivivax. These results indicate that AMF reduce N2O emissions by increasing root length to explore N nutrients and altering the community composition of denitrifiers, suggesting that effective management of N fertilizer forms interacting with the rhizosphere microbiome may help mitigate N2O emissions under future N input scenarios.

Improving plant adaptation to soil antimony contamination: the synergistic contribution of arbuscular mycorrhizal fungus and olive mill waste

BackgroundThis study aimed to investigate the alterations in biochemical and physiological responses of oat plants exposed to antimony (Sb) contamination in soil. Specifically, we evaluated the effectiveness of an arbuscular mycorrhizal fungus (AMF) and olive mill waste (OMW) in mitigating the effects of Sb contamination. The soil was treated with a commercial strain of AMF (Rhizophagus irregularis) and OMW (4% w/w) under two different levels of Sb (0 and 1500 mg kg−1 soil).ResultsThe combined treatment (OMW + AMF) enhanced the photosynthetic rate (+ 40%) and chlorophyll a (+ 91%) and chlorophyll b (+ 50%) content under Sb condition, which in turn induced more biomass production (+ 67–78%) compared to the contaminated control plants. More photosynthesis in OMW + AMF-treated plants gives a route for phenylalanine amino acid synthesis (+ 69%), which is used as a precursor for the biosynthesis of secondary metabolites, including flavonoids (+ 110%), polyphenols (+ 26%), and anthocyanins (+ 63%) compared to control plants. More activation of phenylalanine ammonia-lyase (+ 38%) and chalcone synthase (+ 26%) enzymes in OMW + AMF-treated plants under Sb stress indicated the activation of phenylpropanoid pathways in antioxidant metabolites biosynthesis. There was also improved shifting of antioxidant enzyme activities in the ASC/GSH and catalytic pathways in plants in response to OMW + AMF and Sb contamination, remarkably reducing oxidative damage markers.ConclusionsWhile individual applications of OMW and AMF also demonstrated some degree of plant tolerance induction, the combined presence of AMF with OMW supplementation significantly enhanced plant biomass production and adaptability to oxidative stress induced by soil Sb contamination.

Tripartite interactions among free‐living, N‐fixing bacteria, arbuscular mycorrhizal fungi, and plants: Mutualistic benefits and community response to co‐inoculation

AbstractInteractions between arbuscular mycorrhizal (AM) fungi and free‐living nitrogen fixers (FLNF) occur in the rhizosphere where they can enhance plant nutrient acquisition, impact plant growth, and affect soil processes. Tripartite mutualism commonly occurs between nodule‐forming plants, symbiotic diazotrophs, and AM fungi, and can occur between non‐nodulating plants, FLNF, and AM fungi. However, information on the extent of, and controls on, tripartite mutualism in non‐nodulating plant systems is limited to a small number of crop plants and culturable microbial inoculum, mostly in greenhouse growing conditions. We conducted a systematic literature review to synthesize the current understanding of the responses of plants, AM fungi, and FLNF to co‐inoculation, as well as the conditions affecting tripartite mutualism and the magnitude and range of benefits conferred. Our review shows that plants generally benefit from co‐inoculation with AM fungi and FLNF taxa, but benefits are highly variable and context dependent, ranging from 94% reduction in plant shoot biomass to 255% increase in total plant biomass. Additionally, the presence of AM fungi can increase abundance of FLNF and the presence of FLNF can increase AM fungal root colonization, but these responses also vary widely. Major factors influencing variation in response to co‐inoculation by all organisms include plant phenology/age, soil type and nutrient availability, and partner pairing. There is potential for leveraging these tripartite mutualisms to improve plant productivity and soil microbial function, but successful application is more likely with a thorough understanding of the environmental and mechanistic controls on these relationships and testing of field‐scale implementation.

Effect of Arbuscular Mycorrhizal Fungi and Rock Phosphate on Growth, Physiology, and Biochemistry of Carob under Water Stress and after Rehydration in Vermicompost-Amended Soil.

In the Mediterranean region, reforestation programs record failures following successive drought periods. The use of different plant-growth-promoting amendments and the understanding of drought-induced physiological and biochemical responses of carob will contribute to the reforestation program's success. In this study, the effects of arbuscular-mycorrhizal-fungi (AMF), vermicompost (VC), and rock phosphate (RP) on carob seedlings under drought stress (DS) and recovery (REC) conditions were evaluated. A greenhouse experiment was conducted with carob seedlings grown in the presence of AMF, VC, and RP, applied alone or in combination under well-watered (WW), DS (by stopping irrigation for 12 days), and recovery (REC) conditions. The obtained results indicated that the triple combination (AMF + VC + RP) presented the highest improvement in water potential, photosynthetic pigment content, stomatal conductance, and chlorophyll fluorescence compared to the controls under DS and after REC. In addition, this combination resulted in improved tolerance of carob seedlings to DS and a high potential for rapid recovery after rehydration due to a high accumulation of sugars, proteins, and antioxidant enzymes. In summary, the results underline the importance of inoculating carob with AMF in combination with (in)-organic amendments in improving its tolerance to DS and its recovery performances.

Mycorrhizosphere bacteria inhibit chromium uptake and phytotoxicity by regulating proline metabolism, antioxidant defense system, and aquaporin gene expression in tomato.

Chromium (Cr) contamination in soil-plant systems poses a pressing environmental challenge due to its detrimental impacts on plant growth and human health. Results exhibited that Cr stress decreased shoot biomass, root biomass, leaf relative water content, and plant height. However, single and co-application of Bacillus subtilis (BS) and arbuscular mycorrhizal fungi (AMF) considerably enhanced shoot biomass (+ 21%), root biomass (+ 2%), leaf relative water content (+ 26%), and plant height (+ 13) under Cr stress. The frequency of mycorrhizal (F) association (+ 5%), mycorrhizal colonization (+ 13%), and abundance of arbuscules (+ 5%) in the non-stressed soil was enhanced when inoculated with combined BS and AMF as compared to Cr-stressed soil. The co-inoculation with BS and AMF considerably enhanced total chlorophyll, carotenoids, and proline content in Cr-stressed plants. Cr-stressed plants resulted in attenuated response in SOD, POD, CAT, and GR activities when inoculated with BS and AMF consortia by altering oxidative stress biomarkers (H2O2 and MDA). In Cr-stressed plants, the combined application of BS and AMF considerably enhanced proline metabolism, for instance, P5CR (+ 17%), P5CS (+ 28%), OAT (- 22%), and ProDH (- 113%) as compared to control. Sole inoculation with AMF downregulated the expression of SIPIP2;1, SIPIP2;5, and SIPIP2;7 in Cr-stressed plants. However, the expression of NCED1 was downregulated with the application of sole AMF. In contrast, the relative expression of Le4 was upregulated in the presence of AMF and BS combination in Cr-stressed plants. Therefore, it is concluded that co-application of BS and AMF enhanced Cr tolerance by enhancing proline metabolism, antioxidant enzymes, and aquaporin gene expression. Future study might concentrate on elucidating the molecular processes behind the synergistic benefits of BS and AMF, as well as affirming their effectiveness in field experiments under a variety of environmental situations. Long-term research on the effect of microbial inoculation on soil health and plant production might also help to design sustainable chromium remediation solutions.

A Critical Review of the Effectiveness of Biochar Coupled with Arbuscular Mycorrhizal Fungi in Soil Cadmium Immobilization.

Cadmium-contaminated soil significantly threatens global food security and human health. This scenario gives rise to significant worries regarding widespread environmental pollution. Biochar and arbuscular mycorrhizal fungi (AMF) can effectively immobilize cadmium in the soil in an environmentally friendly way. Existing studies have separately focused on the feasibility of each in remediating polluted soil. However, their association during the remediation of cadmium-polluted soils remains unclear. This review paper aims to elucidate the potential of biochar, in conjunction with AMF, as a strategy to remediate soil contaminated with cadmium. This paper comprehensively analyzes the current understanding of the processes in cadmium immobilization in the soil environment by examining the synergistic interactions between biochar and AMF. Key factors influencing the efficacy of this approach, such as biochar properties, AMF species, and soil conditions, are discussed. The influences of biochar-AMF interactions on plant growth, nutrient uptake, and overall ecosystem health in cadmium-contaminated environments are highlighted. This review indicates that combining biochar and AMF can improve cadmium immobilization. The presence of AMF in the soil can create numerous binding sites on biochar for cadmium ions, effectively immobilizing them in the soil. Insights from this review contribute to a deeper understanding of sustainable and eco-friendly approaches to remediate cadmium-contaminated soils, offering potential applications in agriculture and environmental management.

A survey on the composition and occurrence frequency of arbuscular mycorrhizal fungi in rhizospheric soils and roots of vegetables grown in Ho Chi Minh city

The study aimed to determine the presence and composition of arbuscular mycorrhizal fungi (AMF) in the rhizospheric soils and roots of vegetable plants (14 species of leafy vegetables) grown in Hoc Mon, Cu Chi, and Binh Chanh districts, Ho Chi Minh city. The results of the isolation of AMF spores based on the wet sieving method showed the presence of AMF in the rhizospheric soils of vegetables with an average spore density of 87.6 spores/50 g of soil. For the symbiotic ratio of AMF to the root tissues, there was no symbiosis in 4 vegetable crops, including amaranth, mustard green, leaf mustard, and bok choy. Still, there was symbiosis in the remaining 10 plants, with an average symbiotic rate of 6.6%. Identification of AMF spores based on the morphological characteristics recorded in all the soil samples appeared spore phenotypes of 5 fungal genera including Glomus, Acaulospora, Gigaspora, Scutellospora, and Sclerocystis. However, 3 morphological types were not yet identified. From the obtained results, two genera, Glomus and Acaulospora, have the highest frequency at 43.9 and 39.6%, respectively.

Effects of microplastic polystyrene, simulated acid rain and arbuscular mycorrhizal fungi on Trifolium repens growth and soil microbial community composition

Microplastic pollution is a global and ubiquitous environmental problem in the oceans as well as in the terrestrial environment. We examined the fate of polystyrene (PS) beads in experimental soil in the presence and absence of symbiotic arbuscular mycorrhizal fungi (AMF) and simulated acid rain to determine whether combinations of these three factors interact to alter growth of the white clover Trifolium repens. We found that PS, simulated acid rain or AMF added singly to soil did not alter T. repens growth or yields. In contrast, PS and AMF together significantly reduced shoot biomass while simulated acid rain and PS together significantly reduced available soil phosphorus independent of AMF presence. PS, AMF and simulated acid rain together significantly reduced soil NO3–-N. AMF added singly also enriched for beneficial soil bacteria of the genus Solirubrobacter while PS combined with AMF significantly enriched the potential plant pathogenic fungus Spiromastix spp. AMF innoculated with PS increased the abundance of soil hydrocarbon degraders independent of the presence of simulated acid rain. In addition, the abundance of soil nitrate reducers was increased by the presence of PS especially in the presence of AMF and simulated acid rain. Moreover, the latter increased the abundance of soil pathogens within the fungal community including antibiotic producers. These findings indicate that the coexistence of microplastics, acid rain and AMF may exacerbate the adverse effects of microplastics on soil and plant health.

Nutrient-dependent cross-kingdom interactions in the hyphosphere of an arbuscular mycorrhizal fungus.

The hyphosphere of arbuscular mycorrhizal (AM) fungi is teeming with microbial life. Yet, the influence of nutrient availability or nutrient forms on the hyphosphere microbiomes is still poorly understood. Here, we examined how the microbial community (prokaryotic, fungal, protistan) was affected by the presence of the AM fungus Rhizophagus irregularis in the rhizosphere and the root-free zone, and how different nitrogen (N) and phosphorus (P) supplements into the root-free compartment influenced the communities. The presence of AM fungus greatly affected microbial communities both in the rhizosphere and the root-free zone, with prokaryotic communities being affected the most. Protists were the only group of microbes whose richness and diversity were significantly reduced by the presence of the AM fungus. Our results showed that the type of nutrients AM fungi encounter in localized patches modulate the structure of hyphosphere microbial communities. In contrast we did not observe any effects of the AM fungus on (non-mycorrhizal) fungal community composition. Compared to the non-mycorrhizal control, the root-free zone with the AM fungus (i.e., the AM fungal hyphosphere) was enriched with Alphaproteobacteria, some micropredatory and copiotroph bacterial taxa (e.g., Xanthomonadaceae and Bacteroidota), and the poorly characterized and not yet cultured Acidobacteriota subgroup GP17, especially when phytate was added. Ammonia-oxidizing Nitrosomonas and nitrite-oxidizing Nitrospira were significantly suppressed in the presence of the AM fungus in the root-free compartment, especially upon addition of inorganic N. Co-occurrence network analyses revealed that microbial communities in the root-free compartment were complex and interconnected with more keystone species when AM fungus was present, especially when the root-free compartment was amended with phytate. Our study showed that the form of nutrients is an important driver of prokaryotic and eukaryotic community assembly in the AM fungal hyphosphere, despite the assumed presence of a stable and specific AM fungal hyphoplane microbiome. Predictable responses of specific microbial taxa will open the possibility of using them as co-inoculants with AM fungi, e.g., to improve crop performance.

Evaluating the Interaction between Arbuscular Mycorrhizal Fungi (AMF) and Plant Pathogens

The presence of arbuscular mycorrhizal fungi (AMF) in the rhizosphere has been shown to exert a substantial influence on plant disease resistance. The colonization of AMF induces a cascade of defense responses in plants, resulting in heightened resistance to pathogen invasion. The current study unveils the essential role of AMF in initiating systemic defense responses in plants. When plants undergo colonization by AMF, they initiate a variety of molecular and biochemical mechanisms that enhance their immune system. These systemic defense responses equip the plant with the ability to both withstand invading pathogens and ready neighboring uninfected tissues for potential future attacks. In addition, the establishment of AMF in the roots can induce physical alterations in the root architecture, thereby increasing the difficulty for pathogens to infiltrate and infect plants. While there have been notable advancements in understanding the overall impact of AMF colonization on plant disease resistance, further investigation is needed. Future investigations should delve into the mechanisms of AMF colonization on plant disease resistance, with a particular emphasis on elucidating the signaling pathways and biochemical factors that trigger systemic defense responses. This will offer valuable insights into the molecular foundation of plant immunity and aid in the development of precise disease management strategies. AMF can also serve as biocontrol agents for sustainable management of plant diseases, thereby decreasing dependency on chemical pesticides and encouraging environmentally-conscious practices. The efficiency of AMF colonization and the expression of plant defense responses can be significantly altered by environmental factors, such as soil conditions and nutrient availability. Comprehending these factors will facilitate the formulation of efficient management tactics to enhance biotic interactions in agricultural systems.

Soil Physicochemical Characteristics and Spore Density of Indigenous Arbuscular Mycorrhizal Fungi (AMF) in Different Vegetation Patches of a Marginal Upland in Central Philippines

To show the importance of plant-microbe association in stressed tropical landscapes, the study evaluated the physicochemical characteristics and indigenous arbuscular mycorrhizal fungi (AMF) spore density in selected vegetation patches of marginal upland soils in Central Philippines. Five quadrats were used in the study, namely Andropogon aciculatus (control plot), Imperata cylindrica, Chromolaena odorata, Melastoma malabathricum and mixed vegetation patch. Results showed that soils in the studied vegetation patches had different physicochemical characteristics and AMF spore density. Although all patches had clay soil texture and comparable water-holding capacity, mixed vegetation patch had moderate compaction (1.33 g cm-3) and higher porosity (50.31%) compared with the other patches, which had extreme compaction (1.37-1.65 g cm-3) and lower porosity (37.74-48.76%). In terms of chemical properties, soils in different patches had moderate (5.69) to strongly acidic pH (5.13), moderate organic matter (2.69-2.91%) levels, low P (2.67-3.94 ppm) content and above critical K levels (0.2-1.2 cmol+ kg-1). Results also revealed that C. odorata patch had the highest spore density count (11.33 spores 100 g-1), followed by mixed vegetation (9 spores 100 g-1), M. malabathricum (8.33 spores 100 g-1), and A. aciculatus patch having the lowest spore density count (4 spores 100 g-1). The significant spore density variability was attributed to the differences in soil’s physicochemical characteristics among the different vegetation patches and AMF host specificity. Spores detection, therefore, indicated AMF presence and helped the adaptation mechanism of the natural vegetation in this degraded upland.

Divergent response of maize and soybean rhizosphere to arbuscular mycorrhiza

Maize and soybean are capable of forming symbiotic relationship with arbuscular mycorrhizal fungi (AMF), which enables the plants to overcome P limitations and resist drought effects. The results indicate that the activities of β-glucosidase, chitinase and acid phosphatase in the rhizosphere were double those in the bulk soil, regardless of plant species. Both soybean and maize demonstrated a decrease in β-glucosidase activity. However, chitinase activity displayed a divergent pattern between the two plant species under AMF influence, with a notable 18.5% increase in maize compared to a substantial 44.8% decrease in soybean. The presence of AMF resulted in a 50% reduction in rhizosphere microbial biomass phosphorus (MBP) in soybean, whereas this effect was not observed in maize. The distinct nutrient demands of each plant species appear to regulate the impact of AMF on the characteristics of microbial activities in the rhizosphere.

Pioneer plants of calcareous land in its early succession and the existence of Arbuscular Mycorrhizal Fungi

Abstract. Suharno, Sufaati S, Wulandari D, Alfarabbi MB, Maulani S, Ruhani AA. 2023. Pioneer plants of calcareous land in its early succession and the existence of Arbuscular Mycorrhizal Fungi. Biodiversitas 24: 6209-6217. Calcareous land is characterized with the high presence of calcium carbonate and classified as marginal land because it does not have the quality to support plant growth. The soil quality in calcareous land is poor physically, chemically, and biologically. Nonetheless, certain plants and Arbuscular Mycorrhizal Fungi (AMF) thrive in this area. This research aims to determine plant diversity and the existence of AMF on calcareous land in Jayapura City, Papua, Indonesia. Data were collected through field observations in former limestone mining areas for a year. The results show that 41 types of plants were found at the study site. Based on the important value index, the most important plants were Bidens pilosa, Borreria sp., Piper aduncum, Pteris vittata, Polystichum sp., Axonopus compressus, Muntingia calabura, Pteris cretica, Cynodon sp., and Eleusine indica. Family with the largest number of species were Poaceae followed by Fabaceae, Pteridaceae, Moraceae, and Asteraceae. Based on plant habitus, 14.64% were ferns, 34.15% grasses, 39.62% herbaceous plants, and 12.20% trees. Plants sampled for the presence of AMF included B. pilosa, M. calabura, and P. aduncum. These plant species had level of AMF colonization of 71.2, 71.4, and 63.3%, respectively. There were 13 morphospecies of AMF belonging to the genera Glomus (46.15%), Claroideoglomus (7.69%), Acaulospora (38.46%), and Scutellospora (7.69%). The mutually beneficial symbiotic relationship between plants and AMF can be capitalized for managing the revegetation of former mining land with calcareous soil.

Mycorrhizal fungal communities associated with three metal accumulator plants growing in an abandoned Pb smelting factory.

Plants associated with mycorrhizal fungi has the ability to establish on metal-contaminated soils playing an important role in phytoremediation programs. The objective of this study was to examine the presence of arbuscular mycorrhizal fungi (AMF) (spores density, diversity, indicator species, and root colonization) and dark septate endophytic fungi (DSE fungal root colonization) in three metal accumulator plants (Sorghum halepense, Bidens pilosa, and Tagetes minuta) growing in soils with high Pb content. The Pb content in AMF spores and plant biomass were also assessed. Rhizosphere soil samples were taken from the three dominant plant species at six study sites surrounding the abandoned Pb smelter and one uncontaminated site. The three studied plants were colonized by AMF and DSE fungi. A total of 24 AMF morphospecies were present in the Pb-contaminated areas. The AMF indicator species in the control site (non-contaminated area) was Funneliformis mosseae and in the most contaminated site were Gigaspora decipiens and Denticustata biornata. There was an increase in mycorrhizal variables such as the number of AMF vesicles, spore number, Pb content in AMF spores and plant biomass and DSE colonization (in Sorghum) with increasing soil Pb contamination, but a decrease in AMF diversity and richness was found. For upcoming soil restoration projects, it is crucial to understand the mycorrhizal fungi as well as the plant community that has adapted to the highly contaminated environment.

Functions of arbuscular mycorrhizal fungi in regulating endangered species Heptacodium miconioides growth and drought stress tolerance.

The important values of AMF in regulating endangered species Heptacodium miconioides growth and drought stress tolerance. The wild endangered tree Heptacodium miconioides is distributed sporadically in mountainous areas and often subjected to various abiotic stresses, such as drought. The mutualistic association between plants and arbuscular mycorrhizal fungi (AMF) is known to have a significant impact on plant growth and their ability to withstand drought conditions. However, the role of AMF in H. miconioides seedlings in regulating drought tolerance remains unknown. This study investigated the ability of AMF symbionts to mitigate drought and their underlying mechanism on H. miconioides leaves. The results showed that drought stress dramatically decreased the leaf biomass and damaged the chloroplast structure in seedlings. Conversely, inoculation with AMF noticeably alleviated the deleterious effects of drought stress by restoring leaf morphology and improving the photosynthetic capacity. Moreover, plants inoculated with AMF enhanced the proportion of palisade tissue to spongy tissue in the leaves and the size of starch grains and number of plastoglobules in the chloroplast ultrastructure. A transcriptomic analysis showed that 2157 genes (691 upregulated and 1466 downregulated) were differentially expressed between drought stress with AMF inoculation and drought treatment. Further examination demonstrated that the genes exhibiting differential expression were predominantly associated with the advancement of photosynthesis, sucrose and starch metabolism, nitrogen metabolism, chloroplast development, and phenylpropanoid biosynthetic pathways, and the key potential genes were screened. These findings conclusively provided the physiological and molecular mechanisms that underlie improved drought resistance in H. miconioides in the presence of AMF, which could contribute to improving the survival and species conservation of H. miconioides.

Effects of arbuscular mycorrhizal fungi on plant invasion success driven by nitrogen fluctuations

Abstract Both enemies and mutualists play crucial roles in shaping plant invasion processes. Recent studies have suggested that resource fluctuations could indirectly promote plant invasion through higher trophic levels, such as enemies. However, the influence of mutualists like arbuscular mycorrhizal fungi (AMF) on plant invasion under nitrogen fluctuations remains untested. We conducted a pot mesocosm experiment using a three‐factorial experimental design to assess the individual and interactive effects of nitrogen availability, nitrogen fluctuation and AMF on invasive success of alien plants. We grew nine invasive alien species alongside five different native communities in pot mesocosms. These were then subjected to varied nitrogen availabilities (low vs. high), nitrogen fluctuations (constant vs. pulsed) and AMF presence or absence within a sterile substrate. We found that pulsed nitrogen supply increased the dominance of invasive alien species in low nitrogen availability, regardless of the presence or absence of AMF inoculation. However, in high nitrogen availability, pulsed nitrogen supply only enhanced this dominance in pots without AMF inoculation. This was tentatively evidenced by the three‐way interaction among nitrogen‐availability, nitrogen‐fluctuation and AMF‐inoculation treatments. Furthermore, the dominance promotion by nitrogen addition was greater than that by AMF inoculation. Synthesis and applications. Our findings present, for the first time, evidence that AMF may play a crucial role in mediating the promotion effects of nitrogen fluctuations on alien plant invasion. To better understand the invasion process of alien plants and evaluate their impact on native communities, future research should integrate abiotic and biotic drivers into a single framework. Furthermore, our findings underscore the importance of prioritizing habitats with higher nutrient availability and variability for protection against alien plant invasions.

The Role of Lignin in the Compartmentalization of Cadmium in Maize Roots Is Enhanced by Mycorrhiza.

In nature, arbuscular mycorrhizal fungi (AMF) play a crucial role in the root systems of plants. They can help enhance the resistance of host plants by improving the compartmentalization of toxic metal contaminants in the cell walls (CWs). However, the functions and responses of various CW subfractions to mycorrhizal colonization under Cd exposure remain unknown. Here we conducted a study to investigate how Cd is stored in the cell walls of maize roots colonized by Funneliformis mosseae. Our findings indicate that inoculating the roots with AMF significantly lowers the amount of Cd in the maize shoots (63.6 ± 6.54 mg kg-1 vs. 45.3 ± 2.19 mg kg-1, p < 0.05) by retaining more Cd in the mycorrhized roots (224.0 ± 17.13 mg kg-1 vs. 289.5 ± 8.75 mg kg-1, p < 0.01). This reduces the adverse effects of excessive Cd on the maize plant. Additional research on the subcellular distribution of Cd showed that AMF colonization significantly improves the compartmentalization of 88.2% of Cd in the cell walls of maize roots, compared to the 80.8% of Cd associated with cell walls in the non-mycorrhizal controls. We observed that the presence of AMF did not increase the amount of Cd in pectin, a primary binding site for cell walls; however, it significantly enhanced the content of lignin and the proportion of Cd in the total root cell walls. This finding is consistent with the increased activity of lignin-related enzymes, such as PAL, 4CL, and laccase, which were also positively impacted by mycorrhizal colonization. Fourier transform infrared spectroscopy (FTIR) results revealed that AMF increased the number and types of functional groups, including -OH/-NH and carboxylate, which chelate Cd in the lignin. Our research shows that AMF can improve the ability of maize plants to tolerate Cd by reducing the amount of Cd transferred from the roots to the shoots. This is achieved by increasing the amount of lignin in the cell walls, which binds with Cd and prevents it from moving through the plant. This is accomplished by activating enzymes related to lignin synthesis and increasing the exposure of Cd-binding functional groups of lignin. However, more direct evidence on the immobilization of Cd in the mycorrhiza-altered cell wall subfractions is needed.

Arbuscular mycorrhizal fungi reduce N2O emissions from degraded residue patches

Nitrous oxide (N2O) is a potent greenhouse gas, and agricultural soils represent a major anthropogenic source. Crop residues provide nutrients for plants but also act as hotspots of N2O production. The hyphae of arbuscular mycorrhizal fungi (AMF) could proliferate in organic patches, utilize released N from the organic patches, and potentially mitigate N2O emissions. However, the effect of AMF on N2O emissions in degraded residue patches and the possible microbial mechanism remain uncertain. Here, a mesocosm experiment was conducted to investigate the impact of AMF (Funneliformis mosseae) inoculation on N2O emissions, availabilities of carbon and nitrogen, extracellular enzyme activities, and the abundance of key N-cycling genes in degraded residue patches. Our results showed that AMF hyphae significantly reduced N2O emissions from degraded residue patches. Quantitative PCR analysis of key functional genes involved in N2O production (amoA, nirK, nirS) and consumption (nosZ) showed that AMF significantly reduced the abundance of the bacterial amoA and nirS genes. NH4+, NO3−, total dissolved nitrogen (TDN), total nitrogen (TN), and dissolved organic carbon (DOC) contents decreased drastically in the presence of AMF. In addition, the activities of all tested extracellular enzymes were significantly decreased by AMF and positively correlated with DOC content. Multiple stepwise regression analysis demonstrated that the abundance of the nirS gene primarily influenced N2O emissions and was positively correlated with DOC content in degraded residue patches. Our findings indicate that AMF suppressed N2O producers, particularly nirS-type denitrifiers, by slowing down the release of C and N from degraded residues, thereby leading to a cascade effect on the decrease of N2O emissions. This study provides a promising approach to mitigate N2O emissions by enhancing AMF in the agroecosystems.