Arbuscular Mycorrhizal Fungi Contribute to Phosphorous Uptake and Allocation Strategies of Solidago canadensis in a Phosphorous-Deficient Environment

Contribution of arbuscular mycorrhiza and exoenzymes to nitrogen acquisition of sorghum under drought

Introduction

For low-fertile and degraded soils of sub-Saharan Africa, nitrogen (N) is often the most growth-limiting factor restricting crop yields. The often-suggested exploitation of advantageous rhizosphere traits such as enzyme secretion and/or the symbiosis with arbuscular mycorrhizal fungi (AMF) remains to be validated as a potential strategy to overcome N limitation, especially when N deficiency co-occurs with further abiotic stresses such as water scarcity.

Methods

Three sorghum genotypes were cultivated in soil mesocosms with a root-exclusion compartment, where only AMF could scavenge for nutrients under drought and optimal conditions. Plant carbon (C) investment into the rhizosphere and N uptake were tracked by 15N application coupled with 13CO2 labeling.

Results

Under drought, uptake of mineral 15N by AMF from the root-exclusion compartment increased 4-12 times compared to well-watered conditions. In addition, water stress enhanced below-ground allocation of recently assimilated C into microbial biomass. Drought reduced the enzymatic potential (Vmax) of chitinase while increasing leucine aminopeptidase (LAP) activity. This suggests that N acquisition via protein mineralization in soil was relatively enhanced compared to that of chitin following moisture limitation. LAP substrate affinity (Km) was reduced by drought compared to that of chitinase with genotype-specific shifts in the rhizosphere enzyme systems observed.

Conclusion

Our findings suggest that below-ground C allocation activated AMF symbiosis and its associated microbiome. This not only led to a shift in enzyme-driven exploitation of distinct organic N sources but also induced a strong increase in AMF-based mineral N acquisition from the mycosphere. This trait plasticity in response to drought may be harnessed to stabilize food production from low-fertile soil under the increasingly negative impacts of droughts due to climate change.

Symbiotic synergy: How Arbuscular Mycorrhizal Fungi enhance nutrient uptake, stress tolerance, and soil health through molecular mechanisms and hormonal regulation

Arbuscular Mycorrhizal (AM) symbiosis is integral to sustainable agriculture and enhances plant resilience to abiotic and biotic stressors. Through their symbiotic association with plant roots, AM improves nutrient and water uptake, activates antioxidant defenses, and facilitates hormonal regulation, contributing to improved plant health and productivity. Plants release strigolactones, which trigger AM spore germination and hyphal branching, a process regulated by genes, such as D27, CCD7, CCD8, and MAX1. AM recognition by plants is mediated by receptor-like kinases (RLKs) and LysM domains, leading to the formation of arbuscules that optimize nutrient exchange. Hormonal regulation plays a pivotal role in this symbiosis; cytokinins enhance AM colonization, auxins support arbuscule formation, and brassinosteroids regulate root growth. Other hormones, such as salicylic acid, gibberellins, ethylene, jasmonic acid, and abscisic acid, also influence AM colonization and stress responses, further bolstering plant resilience. In addition to plant health, AM enhances soil health by improving microbial diversity, soil structure, nutrient cycling, and carbon sequestration. This symbiosis supports soil pH regulation and pathogen suppression, offering a sustainable alternative to chemical fertilizers and improving soil fertility. To maximize AM 's potential of AM in agriculture, future research should focus on refining inoculation strategies, enhancing compatibility with different crops, and assessing the long-term ecological and economic benefits. Optimizing AM applications is critical for improving agricultural resilience, food security, and sustainable farming practices.

Exploring agro-ecological significance, knowledge gaps, and research priorities in arbuscular mycorrhizal fungi

This systematic review examines the global agricultural relevance and practical environmental implications of arbuscular mycorrhizal fungi (AMF) within the phylum Glomeromycota. Following PRISMA guidelines, ensuring a comprehensive and unbiased literature review, a literature search was conducted, focusing on the functional roles of AMF in enhancing crop productivity, nutrient uptake, and soil health. Key findings reveal that AMF contribute significantly to sustainable agriculture by reducing the need for chemical fertilizers and increasing plant resilience to environmental stressors like drought, salinity, or pest resistance. The review highlights the importance of AMF in forming symbiotic relationships with plants, which enhance nutrient absorption and improve soil structure, showcasing long-term benefits such as reduced erosion or improved water retention. However, the current literature lacks in-depth exploration of the taxonomy and evolutionary aspects of AMF, as well as the specific functional roles they play in different agricultural contexts, e.g., understanding evolution could enhance strain selection for specific crops. This review identifies several urgent research gaps, including a need for a more refined understanding of AMF community dynamics under varying land management practices. For example, there are gaps in and a critical evaluation of advanced molecular techniques. Such techniques are essential for studying these interactions. Addressing these gaps will enhance the integration of AMF into sustainable agricultural systems and improve ecosystem management practices across different geographical regions. Future research should prioritize developing precise molecular imaging techniques and optimizing AMF applications for different crops and soil types to maximize their ecological and agricultural benefits. This could be practical through interdisciplinary collaboration (e.g., involving molecular biologists, agronomists, etc.). In conclusion, this review advances the practical application of AMF in agriculture and its contribution to biodiversity conservation in agroecosystems. Integrating these findings into policy frameworks could encourage sustainable farming practices, promote the adoption of AMF inoculants, and foster incentives for environmentally friendly land management strategies.

Systematic review registration

https://www.bmj.com/content/372/bmj.n71.

Evaluating Sorghum bicolor resistance to Solidago canadensis invasion under different nitrogen scenarios

Ecosystem exposure to a biological invasion such as plant invasion could contribute to the extinction of native species and loss of productivity and ecosystem balance. Solidago canadensis (S. canadensis) is a highly invasive species that has formed monocultures in China, Europe, Asia, Australia, and New Zealand. It was designated as a notorious invasive species by the Chinese government. It has adversely affected the agroecosystem's ability to germinate various plant seeds, including wheat, lettuce, and pepper, which could lead to food insecurity. This study was conducted to control the invasive species S. canadensis by utilizing a competitive species, Sorghum bicolor (S. bicolor) as a cover plant. Sorghum bicolor exudes allelochemicals such as sorgoleone from its roots which suppress the photosystem II activity of nearby plants. The synthesis of sorgoleone depends on a supply of nitrogen. The present study involved the cultivation of S. bicolor alongside the invasive species S. canadensis, with three different invasion levels (high, medium, and low) and three different nitrogen forms (ammonical, nitrate, and combined ammonical and nitrate nitrogen) applied as a modified Hogland solution. S. bicolor expressed higher performance over the invasive species under ammonical and combined nitrogen forms under low and medium invasion levels. Furthermore, even at greater levels of invasion, S. bicolor was not suppressed by S. canadensis. However, the plant height and dry biomass of S. bicolor were significantly high across both nitrogen forms. Leaf area, CO2 uptake, and photosystem II activity of S. canadensis were unable to sustain its growth under the low invasion condition. The plant biomass of S. canadensis was suppressed by up to 80% and the relative dominance index of S. bicolor was 5.22 over S. canadensis. There was a strong correlation between CO2 uptake, leaf area, and plant biomass. Principal component analysis showed that the first four components had a total variance of 96.89%, with principal component 1 (PC1) having the highest eigenvalue at 18.65. These promising findings suggested that S. bicolor, whose high intensity might be employed to control the invasion process for environmental safety, might be able to recover the barren ground that S. canadensis had invaded.

Enhanced Soil Fertility and Carbon Dynamics in Organic Farming Systems: The Role of Arbuscular Mycorrhizal Fungal Abundance

Arbuscular mycorrhizal fungi (AMF) are critical for soil ecosystem services as they enhance plant growth and soil quality via nutrient cycling and carbon storage. Considering the growing emphasis on sustainable agricultural practices, this study investigated the effects of conventional and organic farming practices on AMF diversity, abundance, and ecological functions in maize, pepper, and potato-cultivated soils. Using next-generation sequencing and quantitative PCR, we assessed AMF diversity and abundance in addition to soil health indicators such as phosphorus content, total nitrogen, and soil organic carbon. Our findings revealed that, while no significant differences in soil physicochemical parameters or AMF diversity were observed across farming systems when all crop data were combined, organic farming significantly enhances AMF abundance and fosters beneficial microbial ecosystems. These ecosystems play vital roles in nutrient cycling and carbon storage, underscoring the importance of organic practices in promoting robust AMF communities that support ecosystem services. This study not only deepens our understanding of AMF's ecological roles but also highlights the potential of organic farming to leverage these benefits for improving sustainability in agricultural practices.

Functionality of arbuscular mycorrhizal fungi varies across different growth stages of maize under drought conditions

Physio-biochemical regulations governing crop growth period are pivotal for drought adaptation. Yet, the extent to which functionality of arbuscular mycorrhizal fungi (AM fungi) varies across different stages of maize growth under drought conditions remains uncertain. Therefore, periodic functionality of two different AM fungi i.e., Rhizophagus irregularis SUN16 and Glomus monosporum WUM11 were assessed at jointing, silking, and pre-harvest stages of maize subjected to different soil moisture gradients i.e., well-watered (80% SMC (soil moisture contents)), moderate drought (60% SMC), and severe drought (40% SMC). The study found that AM fungi significantly (p < 0.05) affected various morpho-physiological and biochemical parameters at different growth stages of maize under drought. As the plants matured, AM fungi enhanced root colonization, glomalin contents, and microbial biomass, leading to increased nutrient uptake and antioxidant activity. This boosted AM fungal activity ultimately improved photosynthetic efficiency, evident in increased photosynthetic pigments and photosynthesis. Notably, R. irregularis and G. monosporum improved water use efficiency and mycorrhizal dependency at critical growth stages like silking and pre-harvest, indicating their potential for drought resilience to stabilize yield. The principal component analysis highlighted distinct plant responses to drought across growth stages and AM fungi, emphasizing the importance of early-stage sensitivity. These findings underscore the potential of incorporating AM fungi into agricultural management practices to enhance physiological and biochemical responses, ultimately improving drought tolerance and yield in dryland maize cultivation.

Expanded trade: tripartite interactions in the mycorrhizosphere

Interactions between arbuscular mycorrhizal fungi (AMF), plants, and the soil microbial community have the potential to increase the availability and uptake of phosphorus (P) and nitrogen (N) in agricultural systems. Nutrient exchange between plant roots, AMF, and the adjacent soil microbes occurs at the interface between roots colonized by mycorrhizal fungi and soil, referred to as the mycorrhizosphere. Research on the P exchange focuses on plant-AMF or AMF-microbe interactions, lacking a holistic view of P exchange between the plants, AMF, and other microbes. Recently, N exchange at both interfaces revealed the synergistic role of AMF and bacterial community in N uptake by the host plant. Here, we highlight work carried out on each interface and build upon it by emphasizing research involving all members of the tripartite network. Both nutrient systems are challenging to study due to the complex chemical and biological nature of the mycorrhizosphere. We discuss some of the effective methods to identify important nutrient processes and the tripartite members involved in these processes. The extrapolation of in vitro studies into the field is often fraught with contradiction and noise. Therefore, we also suggest some approaches that can potentially bridge the gap between laboratory-generated data and their extrapolation to the field, improving the applicability and contextual relevance of data within the field of mycorrhizosphere interactions. Overall, we argue that the research community needs to adopt a holistic tripartite approach and that we have the means to increase the applicability and accuracy of in vitro data in the field.

Trichoderma viride improves phosphorus uptake and the growth of Chloris virgata under phosphorus-deficient conditions

Introduction

Phosphorus (P) readily forms insoluble complexes in soil, thereby inhibiting the absorption and utilization of this essential nutrient by plants. Phosphorus deficiency can significantly impede the growth of forage grass. While Trichoderma viride (T. viride) has been recognized for promoting the assimilation of otherwise unobtainable nutrients, its impact on P uptake remains understudied. Consequently, it is imperative to gain a more comprehensive insight into the role of T. viride in facilitating the uptake and utilization of insoluble P in forage grass.

Methods

This research explored the influence of T. viride inoculation on P absorption and the growth of Chloris virgata (C. virgata) across various P sources. We treated plants with control P (P), tricalcium phosphate (TCP), calcium phytate (PHY), and low P (LP), with and without T. viride inoculation (P+T, TCP+T, PHY+T, LP+T). We analyzed photosynthesis parameters, growth indices, pigment accumulation, P content, leaf acid phosphatase activity.

Results

Results demonstrated that T. viride inoculation alleviated inhibition of photosynthesis, reduced leaf acid phosphatase activity, and enhanced growth of C. virgata in the presence of insoluble P sources. Additionally, T. viride inoculation enabled the plants to extract more available P from insoluble P sources, as evidenced by a substantial increase in P content: shoot P content surged by 58.23 to 59.08%, and root P content rose by 55.13 to 55.2%. Biomass P-use efficiency (PUE) declined by 38% upon inoculation with T. viride compared to the non-inoculated insoluble P sources, paralleled by a reduction in photosynthetic P-use efficiency (PPUE) by 26 to 29%. Inoculation under insoluble P sources further triggered a lower allocation to root biomass (25 to 26%) and a higher investment in shoot biomass (74 to 75%). However, its application under low P condition curtailed the growth of C. virgata.

Discussion

Our results suggest that T. viride inoculation represents an innovative approach for plants to acquire available P from insoluble P sources, thereby promoting growth amid environmental P limitations. This insight is crucial for comprehending the synergy among forage grass, P, and T. viride.

Impacts of Arbuscular Mycorrhizal Fungi on Metabolites of an Invasive Weed Wedelia trilobata

The invasive plant Wedelia trilobata benefits in various aspects, such as nutrient absorption and environmental adaptability, by establishing a close symbiotic relationship with arbuscular mycorrhizal fungi (AMF). However, our understanding of whether AMF can benefit W. trilobata by influencing its metabolic profile remains limited. In this study, Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was conducted to analyze the metabolites of W. trilobata under AMF inoculation. Metabolomic analysis identified 119 differentially expressed metabolites (DEMs) between the groups inoculated with AMF and those not inoculated with AMF. Compared to plants with no AMF inoculation, plants inoculated with AMF showed upregulation in the relative expression of 69 metabolites and downregulation in the relative expression of 50 metabolites. AMF significantly increased levels of various primary and secondary metabolites in plants, including amino acids, organic acids, plant hormones, flavonoids, and others, with amino acids being the most abundant among the identified substances. The identified DEMs mapped 53 metabolic pathways, with 7 pathways strongly influenced by AMF, particularly the phenylalanine metabolism pathway. Moreover, we also observed a high colonization level of AMF in the roots of W. trilobata, significantly promoting the shoot growth of this plant. These changes in metabolites and metabolic pathways significantly affect multiple physiological and biochemical processes in plants, such as free radical scavenging, osmotic regulation, cell structure stability, and material synthesis. In summary, AMF reprogrammed the metabolic pathways of W. trilobata, leading to changes in both primary and secondary metabolomes, thereby benefiting the growth of W. trilobata and enhancing its ability to respond to various biotic and abiotic stressors. These findings elucidate the molecular regulatory role of AMF in the invasive plant W. trilobata and provide new insights into the study of its competitive and stress resistance mechanisms.

Isolation and Identification of Acer truncatum Endophytic Fungus Talaromyces verruculosus and Evaluation of Its Effects on Insoluble Phosphorus Absorption Capacity and Growth of Cucumber Seedlings

The symbiosis between endophytic fungi and plants can promote the absorption of potassium, nitrogen, phosphorus, and other nutrients by plants. Phosphorus is one of the indispensable nutrient elements for plant growth and development. However, the content of available phosphorus in soil is very low, which limits the growth of plants. Phosphorus-soluble microorganisms can improve the utilization rate of insoluble phosphorus. In this study, Talaromyces verruculosus (T. verruculosus), a potential phosphorus-soluble fungus, was isolated from Acer truncatum, a plant with strong stress resistance, and its phosphorus-soluble ability in relation to cucumber seedlings under different treatment conditions was determined. In addition, the morphological, physiological, and biochemical indexes of the cucumber seedlings were assessed. The results show that T. verruculosus could solubilize tricalcium phosphate (TCP) and lecithin, and the solubilization effect of lecithin was higher than that of TCP. After the application of T. verruclosus, the leaf photosynthetic index increased significantly. The photosynthetic system damage caused by low phosphorus stress was alleviated, and the root morphological indexes of cucumber seedlings were increased. The plant height, stem diameter, and leaf area of cucumber seedlings treated with T. verruculosus were also significantly higher than those without treatment. Therefore, it was shown that T. verruculosus is a beneficial endophytic fungus that can promote plant growth and improve plant stress resistance. This study will provide a useful reference for further research on endophytic fungi to promote growth and improve plant stress resistance.

Diversity, Distribution, and applications of arbuscular mycorrhizal fungi in the Arabian Peninsula

Investigations of arbuscular mycorrhizal fungi (AMF) received extreme interests among scientist including agronomists and environmental scientists. This interest is linked to advantages provided by AMF in enhancing the nutrients of their hosts via improving photosynthetic pigments and antioxidant production. Further, it also positively alters the production of plant hormones. AMF through its associations with plants obtain carbon while in exchange, provide nutrients. AMF have been reported to improve the growth of Tageteserecta, Zea mays, Panicum turgidum, Arachis hypogaea, Triticum aestivum and others. This review further documented the occurrence, diversity, distribution, and agricultural applications of AMF species reported in the Arabian Peninsula. Overall, we documented 20 genera and 61 species of Glomeromycota in the Arabian Peninsula representing 46.51 % of genera and 17.88 % of species of AMF known so far. Funneliformis mosseae has found to be the most widely distributed species followed by Claroideoglomus etuicatum. There are 35 research articles focused on Arabian Peninsula where the stress conditions like drought, salinity and pollutants are prevailed. Only one group studied the influence of AMF on disease resistance, while salinity, drought, and cadmium stresses were investigated in 18, 6, and 4 investigations, respectively. The genus Glomus was the focus of most studies. The conducted research in the Arabian Peninsula is not enough to understand AMF taxonomy and their functional role in plant growth. Expanding the scope of detection of AMF, especially in coastal areas is essential. Future studies on biodiversity of AMF are essential.

Unlocking dynamic root phenotypes for simultaneous enhancement of water and phosphorus uptake

Phosphorus (P) and water are crucial for plant growth, but their availability is challenged by climate change, leading to reduced crop production and global food security. In many agricultural soils, crop productivity is confronted by both water and P limitations. The diminished soil moisture decreases available P due to reduced P diffusion, and inadequate P availability diminishes tissue water status through modifications in stomatal conductance and a decrease in root hydraulic conductance. P and water display contrasting distributions in the soil, with P being concentrated in the topsoil and water in the subsoil. Plants adapt to water- and P-limited environments by efficiently exploring localized resource hotspots of P and water through the adaptation of their root system. Thus, developing cultivars with improved root architecture is crucial for accessing and utilizing P and water from arid and P-deficient soils. To meet this goal, breeding towards multiple advantageous root traits can lead to better cultivars for water- and P-limited environments. This review discusses the interplay of P and water availability and highlights specific root traits that enhance the exploration and exploitation of optimal resource-rich soil strata while reducing metabolic costs. We propose root ideotype models, including 'topsoil foraging', 'subsoil foraging', and 'topsoil/subsoil foraging' for maize (monocot) and common bean (dicot). These models integrate beneficial root traits and guide the development of water- and P-efficient cultivars for challenging environments.

Strong Invasive Mechanism of Wedelia trilobata via Growth and Physiological Traits under Nitrogen Stress Condition

Nitrogen (N) is one of the most crucial elements for plant growth. However, a deficiency of N affects plant growth and development. Wedelia trilobata is a notorious invasive plant species that exhibits superior tolerance to adapt to environmental stresses. Yet, research on the growth and antioxidant defensive system of invasive Wedelia under low N stress, which could contribute to understanding invasion mechanisms, is still limited. Therefore, this study aims to investigate and compare the tolerance capability of invasive and native Wedelia under low and normal N conditions. Native and invasive Wedelia species were grown in normal and low-N conditions using a hydroponic nutrient solution for 8 weeks to assess the photosynthetic parameters, antioxidant activity, and localization of reactive oxygen species (ROS). The growth and biomass of W. trilobata were significantly (p < 0.05) higher than W. chinensis under low N. The leaves of W. trilobata resulted in a significant increase in chlorophyll a, chlorophyll b, and total chlorophyll content by 40.2, 56.2, and 46%, respectively, compared with W. chinensis. W. trilobata significantly enhanced antioxidant defense systems through catalase, peroxidase, and superoxide dismutase by 18.6%, 20%, and 36.3%, respectively, providing a positive response to oxidative stress caused by low N. The PCA analysis showed that W. trilobata was 95.3% correlated with physiological traits by Dim1 (79.1%) and Dim2 (16.3%). This study provides positive feedback on W. trilobata with respect to its comprehensive invasion mechanism to improve agricultural systems via eco-friendly approaches in N deficit conditions, thereby contributing to the reclamation of barren land.

Influence of plant species, mycorrhizal inoculant, and soil phosphorus level on arbuscular mycorrhizal communities in onion and carrot roots

Arbuscular mycorrhizal fungi (AMF) are ancient and ecologically important symbionts that colonize plant roots. These symbionts assist in the uptake of water and nutrients, particularly phosphorus, from the soil. This important role has led to the development of AMF inoculants for use as biofertilizers in agriculture. Commercial mycorrhizal inoculants are increasingly popular to produce onion and carrot, but their specific effects on native mycorrhizal communities under field conditions are not known. Furthermore, adequate availability of nutrients in soils, specifically phosphorus, can reduce the diversity and abundance of AMF communities in the roots. The type of crop grown can also influence the composition of AMF communities colonizing the plant roots. This study aimed to investigate how AMF inoculants, soil phosphorus levels, and plant species influence the diversity of AMF communities that colonize the roots of onion and carrot plants. Field trials were conducted on high organic matter (muck) soil in the Holland Marsh, Ontario, Canada. The treatments included AMF-coated seeds (three to five propagules of Rhizophagus irregularis per seed) and non-treated onion and carrot seeds grown in soil with low (~46 ppm) and high (~78 ppm) phosphorus levels. The mycorrhizal communities colonizing the onion and carrot roots were identified by Illumina sequencing. Five genera, Diversispora, Claroideoglomus, Funneliformis, Rhizophagus, and Glomus, were identified in roots of both plant species. AMF communities colonizing carrot roots were more diverse and richer than those colonizing onion roots. Diversispora and Funneliformis had a 1.3-fold and 2.9-fold greater abundance, respectively, in onion roots compared to carrots. Claroideoglomus was 1.4-fold more abundant in carrot roots than in onions. Inoculation with R. irregularis increased the abundance and richness of Rhizophagus in AMF communities of onion roots but not in carrot roots. The soil phosphorus level had no effect on the richness and diversity of AMF in the roots of either crop. In summary, AMF inoculant and soil phosphorus levels influenced the composition of AMF communities colonizing the roots of onion and carrot plants, but the effects varied between plant species.

Mycorrhizal fungus Serendipita indica-associated acid phosphatase rescues the phosphate nutrition with reduced arsenic uptake in the host plant under arsenic stress

Symbiotic interactions play a vital role in maintaining the phosphate (Pi) nutrient status of host plants and providing resilience during biotic and abiotic stresses. Serendipita indica, a mycorrhiza-like fungus, supports plant growth by transporting Pi to the plant. Despite the competitive behaviour of arsenate (AsV) with Pi, the association with S. indica promotes plant growth under arsenic (As) stress by reducing As bioavailability through adsorption, accumulation, and precipitation within the fungus. However, the capacity of S. indica to enhance Pi accumulation and utilization under As stress remains unexplored. Axenic studies revealed that As supply significantly reduces intracellular ACPase activity in S. indica, while extracellular ACPase remains unaffected. Further investigations using Native PAGE and gene expression studies confirmed that intracellular ACPase (isoform2) is sensitive to As, whereas extracellular ACPase (isoform1) is As-insensitive. Biochemical analysis showed that ACPase (isoform1) has a Km of 0.5977 µM and Vmax of 0.1945 Unit/min. In hydroponically cultured tomato seedlings, simultaneous inoculation of S. indica with As on the 14thday after seed germination led to hyper-colonization, increased root/shoot length, biomass, and induction of ACPase expression and secretion under As stress. Arsenic-treated S. indica colonized groups (13.33 µM As+Si and 26.67 µM As+Si) exhibited 8.28-19.14 and 1.71-3.45-fold activation of ACPase in both rhizospheric media and root samples, respectively, thereby enhancing Pi availability in the surrounding medium under As stress. Moreover, S. indica (13.33 µM As+Si and 26.67 µM As+Si) significantly improved Pi accumulation in roots by 7.26 and 9.46 times and in shoots by 4.36 and 8.85 times compared to the control. Additionally, S. indica induced the expression of SiPT under As stress, further improving Pi mobilization. Notably, fungal colonization also restricted As mobilization from the hydroponic medium to the shoot, with a higher amount of As (191.01 ppm As in the 26.67 µM As+Si group) accumulating in the plant's roots. The study demonstrates the performance of S. indica under As stress in enhancing Pi mobilization while limiting As uptake in the host plant. These findings provide the first evidence of the As-Pi interaction in the AM-like fungus S. indica, indicating reduced As uptake and regulation of PHO genes (ACPase and SiPT genes) to increase Pi acquisition. These data also lay the foundation for the rational use of S. indica in agricultural practices.

Dose dependent effect of nitrogen on the phyto extractability of Cd in metal contaminated soil using Wedelia trilobata

Cadmium (Cd) is one of the toxic heavy metal that negatively affect plant growth and compromise food safety for human consumption. Nitrogen (N) is an essential macronutrient for plant growth and development. It may enhance Cd tolerance of invasive plant species by maintaining biochemical and physiological characteristics during phytoextraction of Cd. A comparative study was conducted to evaluate the phenotypical and physiological responses of invasive W. trilobata and native W. chinensis under low Cd (10 µM) and high Cd (80 µM) stress, along with different N levels (i.e., normal 91.05 mg kg-1 and low 0.9105 mg kg-1). Under low-N and Cd stress, the growth of leaves, stem and roots in W. trilobata was significantly increased by 35-23%, 25-28%, and 35-35%, respectively, compared to W. chinensis. Wedelia trilobata exhibited heightened antioxidant activities of catalase and peroxidase were significantly increased under Cd stress to alleviate oxidative stress. Similarly, flavonoid content was significantly increased by 40-50% in W. trilobata to promote Cd tolerance via activation of the secondary metabolites. An adverse effect of Cd in the leaves of W. chinensis was further verified by a novel hyperspectral imaging technology in the form of normalized differential vegetation index (NDVI) and photochemical reflectance index (PRI) compared to W. trilobata. Additionally, W. trilobata increased the Cd tolerance by regulating Cd accumulation in the shoots and roots, bolstering its potential for phytoextraction potential. This study demonstrated that W. trilobata positively responds to Cd with enhanced growth and antioxidant capabilities, providing a new platform for phytoremediation in agricultural lands to protect the environment from heavy metals pollution.

The Invasion of Galinsoga quadriradiata into High Elevations Is Shaped by Variation in AMF Communities

Mountain ranges have been previously suggested to act as natural barriers to plant invasion due to extreme environmental conditions. However, how arbuscular mycorrhizal fungi (AMF) affect invasion into these systems has been less explored. Here, we investigated how changes in AMF communities affect the performance of Galinsoga quadriradiata in mountain ranges. We performed a greenhouse experiment to study the impact of inoculations of AMF from different elevations on the performance and reproduction of invaders and how competition with native plants changes the effects of invader-AMF interactions. We found strong evidence for a nuanced role of AMF associations in the invasion trajectory of G. quadriradiata, with facilitative effects at low elevations and inhibitory effects at high elevations. Galinsoga quadriradiata performed best when grown with inoculum collected from the same elevation but performed worst when grown with inoculum collected from beyond its currently invaded range, suggesting that AMF communities can help deter invasion at high elevations. Finally, the invasive plants grown alone experienced negative effects from AMF, while those grown in competition experienced positive effects, regardless of the AMF source. This suggests that G. quadriradiata lowers its partnerships with AMF in stressful environments unless native plants are present, in which case it overpowers native plants to obtain AMF support during invasion. Finally, our results indicate that invader-AMF interactions can inhibit invasive range expansion at high elevations, and biotic interactions, in addition to harsh environmental conditions, make high-elevation mountain ranges natural barriers against continued invasion.

Effect of Trichoderma viride on insoluble phosphorus absorption ability and growth of Melilotus officinalis

Phosphorus (Pi) deficiency is a major factor of limiting plant growth. Using Phosphate-solubilizing microorganism (PSM) in synergy with plant root system which supply soluble Pi to plants is an environmentally friendly and efficient way to utilize Pi. Trichoderma viride (T. viride) is a biocontrol agent which able to solubilize soil nutrients, but little is known about its Pi solubilizing properties. The study used T. viride to inoculate Melilotus officinalis (M. officinalis) under different Pi levels and in order to investigate the effect on Pi absorption and growth of seedlings. The results found that T. viride could not only solubilizate insoluble inorganic Pi but also mineralize insoluble organic Pi. In addition, the ability of mineralization to insoluble organic Pi is more stronger. Under different Pi levels, inoculation of T. viride showed that promoted the growth of aboveground parts of seedlings and regulated the morphology of roots, thus increasing the dry weight of seedlings. The effect of T. viride on seedling growth was also reflected the increasing of chlorophyll fluorescence parameters and photosynthetic pigment content. Moreover, compared to the uninoculated treatments, inoculation of T. viride also enhanced Pi content in seedlings. Thus, the T. viride was a beneficial fungus for synergistic the plant Pi uptake and growth.

Effects of Septoglomus constrictum and Bacillus cereus on the competitive growth of Ageratina adenophora

Beneficial microorganisms play a pivotal role in the invasion process of exotic plants, including arbuscular mycorrhizal fungi (AMF) and Bacillus. However, limited research exists on the synergistic influence of AMF and Bacillus on the competition between both invasive and native plants. In this study, pot cultures of Ageratina adenophora monoculture, Rabdosia amethystoides monoculture, and A. adenophora and R. amethystoides mixture were used to investigate the effects of dominant AMF (Septoglomus constrictum, SC) and Bacillus cereus (BC), and the co-inoculation of BC and SC on the competitive growth of A. adenophora. The results showed that inoculation with BC, SC, and BC + SC significantly increased the biomass of A. adenophora by 14.77, 112.07, and 197.74%, respectively, in the competitive growth between A. adenophora and R. amethystoides. Additionally, inoculation with BC increased the biomass of R. amethystoides by 185.07%, while inoculation with SC or BC + SC decreased R. amethystoides biomass by 37.31 and 59.70% compared to the uninoculated treatment. Inoculation with BC significantly increased the nutrient contents in the rhizosphere soil of both plants and promoted their growth. Inoculation with SC or SC + BC notably increased the nitrogen and phosphorus contents of A. adenophora, therefore enhancing its competitiveness. Compared with single inoculation, dual inoculation with SC and BC increased AMF colonization rate and Bacillus density, indicating that SC and BC can form a synergistic effect to further enhance the growth and competitiveness of A. adenophora. This study reveals the distinct role of S. constrictum and B. cereus during the invasion of A. adenophora, and provide new clues to the underlying mechanisms of interaction between invasive plant, AMF and Bacillus.

Invasive Plant Alternanthera philoxeroides Benefits More Competition Advantage from Rhizosphere Bacteria Regardless of the Host Source

The rhizosphere plays a vital role in the exchange of materials in the soil-plant ecosystem, and rhizosphere microorganisms are crucial for plant growth and development. In this study, we isolated two strains of Pantoea rhizosphere bacteria separately from invasive Alternanthera philoxeroides and native A. sessilis. We conducted a control experiment to test the effects of these bacteria on the growth and competition of the two plant species using sterile seedlings. Our findings showed that the rhizobacteria strain isolated from A. sessilis significantly promoted the growth of invasive A. philoxeroides in monoculture compared to native A. sessilis. Both strains significantly enhanced the growth and competitiveness of invasive A. philoxeroides under competition conditions, regardless of their host source. Our study suggests that rhizosphere bacteria, including those from different host sources, can contribute to the invasion of A. philoxeroides by significantly enhancing its competitiveness.

Soil phosphorus form affects the advantages that arbuscular mycorrhizal fungi confer on the invasive plant species, Solidago canadensis, over its congener

Interactions between plants and arbuscular mycorrhizal fungi (AMF) are strongly affected by soil phosphorus (P) availability. However, how P forms impact rhizosphere AMF diversity, community composition, and the co-occurrence network associated with native and invasive plants, and whether these changes in turn influence the invasiveness of alien species remain unclear. In this work, we performed a greenhouse experiment with the invasive species Solidago canadensis and its native congener S. decurrens to investigate how different forms of P altered the AMF community and evaluate how these changes were linked with the growth advantage of S. canadensis relative to S. decurrens. Plants were subjected to five different P treatments: no P addition (control), simple inorganic P (sodium dihydrogen phosphate, NaP), complex inorganic P (hydroxyapatite, CaP), simple organic P (adenosine monophosphate, AMP) and complex organic P (myo-inositol hexakisphosphate, PA). Overall, invasive S. canadensis grew larger than native S. decurrens across all P treatments, and this growth advantage was strengthened when these species were grown in CaP and AMP treatments. The two Solidago species harbored divergent AMF communities, and soil P treatments significantly shifted AMF community composition. In particular, the differences in AMF diversity, community composition, topological features and keystone taxa of the co-occurrence networks between S. canadensis and S. decurrens were amplified when the dominant form of soil P was altered. Despite significant correlations between AMF alpha diversity, community structure, co-occurrence network composition and plant performance, we found that alpha diversity and keystone taxa of the AMF co-occurrence networks were the primary factors influencing plant growth and the growth advantage of invasive S. canadensis between soil P treatments. These results suggest that AMF could confer invasive plants with greater advantages over native congeners, depending on the forms of P in the soil, and emphasize the important roles of multiple AMF traits in plant invasion.

A response of biomass and nutrient allocation to the combined effects of soil nutrient, arbuscular mycorrhizal, and root-knot nematode in cherry tomato

Introduction

The biomass and nutrient allocation strategies in plants are fundamental for predicting carbon storage and mineral and nutrient cycles in terrestrial ecosystems. However, our knowledge regarding the effects of multiple environmental factors on biomass and nutrient allocation remains limited.

Methods

Here we manipulated soil composition (three levels), arbuscular mycorrhizal fungi inoculation (AMF, five levels), and root-knot nematode inoculation (RKN, two levels) using random block design to reveal the effects of these factors on biomass and nutrient allocation strategies of cherry tomato.

Results and Discussion

Our results showed that biomass and nutrient allocation were affected by soil composition, AMF and RKN individually or interactively. The biomass and nutrient allocation in cherry tomato shows different adaptation strategies responded to the joint action of three factors. The reduction of soil nutrients increased belowground biomass allocation, and aboveground nitrogen and phosphorus concentration. AMF colonization increased aboveground biomass allocation and reproductive investment and promoted aboveground nitrogen and phosphorus inputs. Cherry tomato can mitigate the stress of RKN infection by investing more biomass and nutrients into belowground organs. Our study showed that plants can adjust their survival strategies by changing biomass and nutrient allocation to adapt to variation in soil abiotic and biotic factors. These findings contribute to our understanding of the adaptive processes of plant biomass and nutrient allocation strategies under multiple environmental factors.

Effect of arbuscular mycorrhizal fungi on the responses of Ageratina adenophora to Aphis gossypii herbivory

The invasive weed Ageratina adenophora can form a positive symbiotic relationship with native arbuscular mycorrhizal fungi (AMF) to promote its invasion ability. However, the function of AMF during the feeding of Aphis gossypii in A. adenophora was poorly understand. This study aimed to investigate the effects of two dominant AMF (Claroideoglomus etunicatum and Septoglomus constrictum) on A. adenophora in response to the feeding of the generalist herbivore A. gossypii. The results showed that A. gossypii infestation could significantly reduce the biomass, nutrient and proline contents of A. adenophora, and increase the antioxidant enzyme activities, defense hormone and secondary metabolite contents of the weed. Compared with the A. gossypii infested A. adenophora, inoculation C. etunicatum and S. constrictum could significantly promote the growth ability and enhanced the resistance of A. adenophora to A. gossypii infestation, and the aboveground biomass of A. adenophora increased by 317.21% and 114.73%, the root biomass increased by 347.33% and 120.58%, the polyphenol oxidase activity heightened by 57.85% and 12.62%, the jasmonic acid content raised by 13.49% and 4.92%, the flavonoid content increased by 27.29% and 11.92%, respectively. The survival rate of A. gossypii and density of nymphs were significantly inhibited by AMF inoculation, and the effect of C. etunicatum was significantly greater than that of S. constrictum. This study provides clarified evidence that AMF in the rhizosphere of A. adenophora are effective in the development of tolerance and chemical defense under the feeding pressure of insect herbivory, and offer references for the management of the A. adenophora from the perspective of soil microorganisms.

Parametarhizium hingganense, a Novel Ectomycorrhizal Fungal Species, Promotes the Growth of Mung Beans and Enhances Resistance to Disease Induced by Rhizoctonia solani

The mutualistic interactions between mycorrhizae and plants first occurred along with the terrestrialization of plants. The majority of vascular plants are in symbiosis with mycorrhizal fungi. Due to their importance to the economy and ecology, arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) fungi emerge as the most popular ones. However, the mechanism underlying the beneficial function of ECM fungi is not as clear as AM fungi. Here, the interaction between Parametarhizium hingganense, a novel fungal species isolated from forest litter, and mung bean (Vigna radiata) was studied. P. hingganense demonstrated P solubilization ability in vitro. Treatment of P. hingganense on the seeds resulted in promoted growth with enhanced P content. The hyphae of green fluorescence protein (GFP)-tagged P. hingganense were found to surround the roots and develop between cells, suggesting the establishment of an ectomycorrhizal symbiosis. Upon symbiosis with P. hingganense, the levels of jasmonic acid (JA) and gibberellin (GA₁) and total phenolic and flavonoid content elevated. Meanwhile, damping off caused by Rhizoctonia solani in mycorrhizal plants was alleviated. Taken together, the above findings suggested that symbiosis with P. hingganense conferred growth promotion and priming of defense responses to host plants which should be associated with facilitated P uptake and increased JA and GA₁ levels.

Impact of the Arbuscular Mycorrhizal Fungus Funneliformis mosseae on the Physiological and Defence Responses of Canna indica to Copper Oxide Nanoparticles Stress

Copper oxide nanoparticles (nano-CuO) are recognized as an emerging pollutant. Arbuscular mycorrhizal fungi (AMF) can mitigate the adverse impacts of various pollutants on host plants. However, AMF's mechanism for alleviating nano-CuO phytotoxicity remains unclear. The goal of this study was to evaluate how AMF inoculations affect the physiological features of Canna indica seedlings exposed to nano-CuO stress. Compared with the non-AMF inoculated treatment, AMF inoculations noticeably improved plant biomass, mycorrhizal colonization, leaf chlorophyll contents, and the photosynthetic parameters of C. indica under nano-CuO treatments. Moreover, AMF inoculation was able to significantly mitigate nano-CuO stress by enhancing antioxidant enzyme activities and decreasing ROS levels in the leaves and roots of C. indica, thus increasing the expression of genes involved in the antioxidant response. In addition, AMF inoculation reduced the level of Cu in seedlings and was associated with an increased expression of Cu transport genes and metallothionein genes. Furthermore, AMF inoculations increased the expression levels of organic acid metabolism-associated genes while facilitating organic acid secretion, thus reducing the accumulation of Cu. The data demonstrate that AMF-plant symbiosis is a feasible biocontrol approach to remediate nano-CuO pollution.