Non-mycorrhizal Research Articles

Rhizophagus intraradices mediated mitigation of arsenic toxicity in wheat involves differential distribution of arsenic in subcellular fractions and modulated expression of Phts and ABCCs

Biomagnification of arsenic in food chain through wheat consumption poses a serious threat to human health. Therefore, it is necessary to elucidate mechanism of arsenic tolerance and detoxification in wheat. The study aimed to unravel the strategies adopted by arbuscular mycorrhizal fungi to alleviate arsenic toxicity in wheat. To accomplish this, independent and interactive effects of arsenic and Rhizophagus intraradices were assessed. Colonization by R. intraradices resulted in lower expression of high-affinity phosphate transporters (Phts) in comparison with non-mycorrhizal (NM) plants, thereby lowering arsenic concentrations in mycorrhizal (M) plants. Additionally, the subcellular fractionation analysis indicated differential distribution of arsenic. In NM plants, arsenic accumulated primarily in cell wall and organelle fractions. Conversely, in M plants arsenic was more concentrated in the cell wall and vacuolar fractions. This was related to higher levels of hydroxyl and aldehyde groups in cell wall fraction of root along with increased expression of C-type ATP-binding cassette transporters in root and leaves. These factors enabled effective sequestration of arsenic in the cell wall and vacuoles of M plants, thereby reducing its toxicity. Furthermore, the proportion of inorganic arsenic was lower in M plant, as it transformed it into less toxic organic forms.

Mycorrhizal and non-mycorrhizal perennial ryegrass roots exhibit differential regulation of lipid and Ca2+ signaling pathways in response to low and high temperature stresses

Lipids and Ca2+ are involved as intermediate messengers in temperature-sensing signaling pathways. Arbuscular mycorrhizal (AM) symbiosis is a mutualistic symbiosis between fungi and terrestrial plants that helps host plants cope with adverse environmental conditions. Nonetheless, the regulatory mechanisms of lipid- and Ca2+-mediated signaling pathways in mycorrhizal plants under cold and heat stress have not been determined. The present work focused on investigating the lipid- and Ca2+-mediated signaling pathways in arbuscular mycorrhizal (AM) and non-mycorrhizal (NM) roots under temperature stress and determining the role of Ca2+ levels in AM symbiosis and temperature stress tolerance in perennial ryegrass (Lolium perenne L.) Compared with NM plants, AM symbiosis increased phosphatidic acid (PA) and Ca2+ signaling in the roots of perennial ryegrass, increasing the expression of genes associated with low temperature (LT) stress, including LpICE1, LpCBF3, LpCOR27, LpCOR47, LpIRI, and LpAFP, and high temperature (HT) stress, including LpHSFC1b, LpHSFC2b, LpsHSP17.8, LpHSP22, LpHSP70, and LpHSP90, under LT and HT conditions. These effects result in modulated antioxidant enzyme activities, reduced lipid peroxidation, and suppressed growth inhibition caused by LT and HT stresses. Furthermore, exogenous Ca2+ application enhanced AM symbiosis, leading to the upregulation of Ca2+ signaling pathway genes in roots and ultimately promoting the growth of perennial ryegrass under LT and HT stresses. These findings shed light on lipid and Ca2+ signal transduction in AM-associated plants under LT and HT stresses, emphasizing that Ca2+ enhances cold and heat tolerance in mycorrhizal plants.

Differential Strategies of Two Arbuscular Mycorrhizal Fungi Varieties in the Protection of Lycium ruthenicum under Saline-Alkaline Stress.

To delve into the growth and physiological adaptations exhibited by the economically vital black wolfberry (Lycium ruthenicum) upon inoculation with arbuscular mycorrhizal fungi (AMF) under varying levels of saline-alkaline stress A series of pot experiments were conducted in a gradient saline-alkaline environment (0, 200, 400 mM NaCl: NaHCO3 = 1:1). One-year-old cuttings of black wolfberry, inoculated with two AMF species-Funneliformis mosseae (Fm) and Rhizophagus intraradices (Ri)-served as the experimental material, enabling a comprehensive analysis of seedling biomass, chlorophyll content, antioxidant enzyme activities, and other crucial physiological parameters. This study demonstrated that both Fm and Ri could form a symbiotic relationship with the root of Lycium ruthenicum. Notably, Fm inoculation significantly bolstered the growth of the underground parts, while exhibiting a remarkable capacity to scavenge reactive oxygen species (ROS), thereby effectively mitigating membrane oxidative damage induced by stress. Additionally, Fm promoted the accumulation of abscisic acid (ABA) in both leaves and roots, facilitating the exclusion of excess sodium ions from cells. Ri Inoculation primarily contributed to an enhancement in the chlorophyll b (Chlb) content, vital for sustaining photosynthesis processes. Furthermore, Ri's ability to enhance phosphorus (P) absorption under stressful conditions ensured a steady influx of essential nutrients. These findings point to different strategies employed for Fm and Ri inoculation. To holistically assess the saline-alkaline tolerance of each treatment group, a membership function analysis was employed, ultimately ranking the salt tolerance as Fm > Ri > non-mycorrhizal (NM) control. This finding holds paramount importance for the screening of highly resilient Lycium ruthenicum strains and offers invaluable theoretical underpinnings and technical guidance for the remediation of saline-alkaline soils, fostering sustainable agricultural practices in challenging environments.

The ectomycorrhizal fungus Paxillus involutus positively modulates Castanea sativa Miller (var. Marsol) responses to heat and drought co-exposure

Castanea sativa Miller, a high-valuable crop for Mediterranean countries, is facing frequent and prolonged periods of heat and drought, severely affecting chestnut production. Aiming to tackle this problem, this study unraveled the influence of mycorrhizal association with the fungi Paxillus involutus (Batsch) on young chestnut plants' responses to combined heat (42 °C; 4 h/day) and drought (no irrigation until soil moisture reached 25%) over 21 days of stress exposure. Heat stress had no harmful effects on growth, photosynthesis, nor induced oxidative stress in either mycorrhizal (MR) or non-mycorrhizal (NMR) chestnut plants. However, drought (alone or combined) reduced the growth of NMR plants, affecting water content, leaf production, and foliar area, while also hampering net CO2 assimilation and carbon relations. The mycorrhizal association, however, mitigated the detrimental effects of both stresses, resulting in less susceptibility and fewer growth limitations in MR chestnut plants, which were capable of ensuring a proper carbon flow. Evaluation of the oxidative metabolism revealed increased lipid peroxidation and hydrogen peroxide levels in NMR plants under water scarcity, supporting their higher susceptibility to stress. Conversely, MR plants activated defense mechanisms by accumulating antioxidant metabolites (ascorbate, proline and glutathione), preventing oxidative damage, especially under the combined stress. Overall, drought was the most detrimental condition for chestnut growth, with heat exacerbating stress susceptibility. Moreover, mycorrhizal association with P. involutus substantially alleviated these effects by improving growth, water relations, photosynthesis, and activating defense mechanisms. Thus, this research highlights mycorrhization's potential to enhance C. sativa resilience against climate change, especially at early developmental stages.

Unraveling the diversity of hyphal explorative traits among Rhizophagus irregularis genotypes

Differences in functioning among various genotypes of arbuscular mycorrhizal (AM) fungi can determine their fitness under specific environmental conditions, although knowledge of the underlying mechanisms still is very fragmented. Here we compared seven homokaryotic isolates (genotypes) of Rhizophagus irregularis, aiming to characterize the range of intraspecific variability with respect to hyphal exploration of organic nitrogen (N) resources, and N supply to plants. To this end we established two experiments (one in vitro and one in open pots) and used 15N-chitin as the isotopically labeled organic N source. In Experiment 1 (in vitro), mycelium of all AM fungal genotypes transferred a higher amount of 15N to the plants than the passive transfer of 15N measured in the non-mycorrhizal (NM) controls. Noticeably, certain genotypes (e.g., LPA9) showed higher extraradical mycelium biomass production but not necessarily greater 15N acquisition than the others. Experiment 2 (in pots) highlighted that some of the AM fungal genotypes (e.g., MA2, STSI) exhibited higher rates of targeted hyphal exploration of chitin-enriched zones, indicative of distinct N exploration patterns from the other genotypes. Importantly, there was a high congruence of hyphal exploration patterns between the two experiments (isolate STSI always showing highest efficiency of hyphal exploration and isolate L23/1 being consistently the lowest), despite very different (micro) environmental conditions in the two experiments. This study suggests possible strategies that AM fungal genotypes employ for efficient N acquisition, and how to measure them. Implications of such traits for local mycorrhizal community assembly still need to be understood.

Transcriptome Analysis Reveals the Impact of Arbuscular Mycorrhizal Symbiosis on Toona ciliata var. pubescens Seedlings

Toona ciliata var. pubescens, known as “Chinese mahogany”, has high commercial value and is classified as a level II priority protected wild plant in China. However, due to overexploitation and its poor natural regeneration capacity, natural T. ciliata var. pubescens forests show varying degrees of decline in habitat adaptability. Arbuscular mycorrhizal fungi (AMF) symbiosis presents a potential strategy to enhance its regeneration. In this study, T. ciliata var. pubescens seedlings were inoculated with Septoglomus viscosum, followed by RNA-Seq analysis to compare gene expression differences between AMF-inoculated (AMI) and non-mycorrhizal (NM) treatments three months post-inoculation. A total of 16,163 differentially expressed genes (DEGs) were upregulated by AMF colonization, constituting 96.46% of the total DEGs. Specifically, 14,420 DEGs were exclusively expressed in the AMI treatment, while 35 DEGs were completely silenced. Most of the upregulated DEGs were located on the cell membrane, nucleus, and cytoskeleton and functioned in protein binding, S-adenosylmethionine-dependent methyltransferase activity, and lipid binding during cellular/macromolecule/protein localization, intracellular/protein transport, the cell cycle, and signal transduction. Additionally, lots of key genes related to oxidative stress responses, nutrient transport, and small GTPase-mediated signal transduction were found to be upregulated. These results suggest that AMF inoculation may enhance root cell growth by activating genes involved in nutrient uptake, stress responses, signal transduction, and substance transportation. This study elucidates the molecular mechanisms underlying the growth promotion of T. ciliata var. pubescens through AMF symbiosis, laying a foundation for the future application of AMF in its natural forest regeneration.

Benefits in plant N uptake via the mycorrhizal pathway in ample soil moisture persist under severe drought

Under global change, drought is a threat of increasing importance to plant growth and nutrition. We employed isotopic labeling on potted tomatoes (Solanum lycopersicum, cv. ‘Micro Tom’) to investigate the role of an arbuscular mycorrhizal fungus (AMF – Rhizophagus irregularis) in plant uptake of nitrogen (N) from either inorganic (15NH4Cl) or organic source (15N-labeled clover biomass) along a soil moisture gradient. 15N was provided into root-excluding mesh bags inserted in pots with mycorrhizal (M) and nonmycorrhizal (NM) plants. After labeling, a substrate moisture gradient ranging from ample moisture to the wilting point was maintained for the terminal 4 weeks.M plants acquired strikingly more 15N derived from either the inorganic or organic source than their NM counterparts. The advantage of M plants in 15N uptake was manifested across the entire moisture range, although a declining trend was observed toward the drought extreme. M plants exploited up to threefold more 15N if it was provided in the inorganic form than in the organic form, probably due to faster availability of ammonium dissolved from 15NH4Cl and adsorbed on soil particles as compared to ammonium ions derived from clover biomass via mineralization. Interestingly, NM plants received more 15N from the organic than from the inorganic source. Mycorrhiza caused a fourfold increase in N acquisition from mineral sources but only by twofold from organic sources. We speculate that this was partly caused by higher rates of N transformation of ammonium ions released by mineralization to more mobile forms (nitrification) that happened inside mesh bags with the clover biomass, and we discuss possible mechanisms responsible for such increased mobility.

Role of melatonin in enhancing arbuscular mycorrhizal symbiosis and mitigating cold stress in perennial ryegrass (Lolium perenne L.).

Melatonin is a biomolecule that affects plant development and is involved in protecting plants from environmental stress. However, the mechanisms of melatonin's impact on arbuscular mycorrhizal (AM) symbiosis and cold tolerance in plants are still unclear. In this research, AM fungi inoculation and exogenous melatonin (MT) were applied to perennial ryegrass (Lolium perenne L.) seedlings alone or in combination to investigate their effect on cold tolerance. The study was conducted in two parts. The initial trial examined two variables, AM inoculation, and cold stress, to investigate the involvement of the AM fungus Rhizophagus irregularis in endogenous melatonin accumulation and the transcriptional levels of its synthesis genes in the root system of perennial ryegrass under cold stress. The subsequent trial was designed as a three-factor analysis, encompassing AM inoculation, cold stress, and melatonin application, to explore the effects of exogenous melatonin application on plant growth, AM symbiosis, antioxidant activity, and protective molecules in perennial ryegrass subjected to cold stress. The results of the study showed that compared to non-mycorrhizal (NM) plants, cold stress promoted an increase in the accumulation of melatonin in the AM-colonized counterparts. Acetylserotonin methyltransferase (ASMT) catalyzed the final enzymatic reaction in melatonin production. Melatonin accumulation was associated with the level of expression of the genes, LpASMT1 and LpASMT3. Treatment with melatonin can improve the colonization of AM fungi in plants. Simultaneous utilization of AM inoculation and melatonin treatment enhanced the growth, antioxidant activity, and phenylalanine ammonia-lyase (PAL) activity, while simultaneously reducing polyphenol oxidase (PPO) activity and altering osmotic regulation in the roots. These effects are expected to aid in the mitigation of cold stress in Lolium perenne. Overall, melatonin treatment would help Lolium perenne to improve growth by promoting AM symbiosis, improving the accumulation of protective molecules, and triggering in antioxidant activity under cold stress.

Arbuscular mycorrhiza differentially adjusts central carbon metabolism in two contrasting genotypes of Vigna radiata (L.) Wilczek in response to salt stress

The study aimed at investigating Arbuscular Mycorrhiza (AM) mediated metabolic changes in two genotypes of mungbean (Vigna radiata) differing in their salt tolerance in presence of salt stress (100 mM NaCl). Colonisation by Claroideoglomus etunicatum resulted in higher growth, photosynthetic efficiency, total protein content, and lower levels of stress markers, indicating alleviation of stress in mungbean plants. AM differentially upregulated the components of Tricarboxylic acid (TCA) cycle in salt tolerant (ST) and salt sensitive (SS) genotypes that could be correlated to AM-mediated moderation in nutrient uptake. Under salt stress, while maximum increase in the activity of α-ketoglutarate dehydrogenase (65%) was observed in mycorrhizal (M)-ST; the increase in isocitrate dehydrogenase (79%) and fumarase (133%) activities was maximum in M-SS plants over their non-mycorrhizal (NM) counterparts. Apart from TCA, AM also affected gamma-aminobutyric acid (GABA) and glyoxylate pathways. Activities of enzymes implicated in GABA shunt increased in both the genotypes under stress resulting in increase in GABA concentration (46%). Notably, glyoxylate pathway was induced by AM in SS only, wherein M-SS exhibited significantly higher isocitrate lyase (49%) and malate synthase (104%) activities, reflected in higher malic acid concentration (84%), than NM under stress. The results suggest that AM moderates the central carbon metabolism and strategizes towards boosting the formation of stress-alleviating metabolites such as GABA and malic acid, especially in SS, bypassing the steps catalysed by salt-sensitive enzymes in TCA cycle. The study, therefore, advances the understanding on mechanisms by which AM ameliorates salt stress.

Arbuscular mycorrhiza fungus alleviates arsenic mediated disturbances in tricarboxylic acid cycle and nitrogen metabolism in Triticum aestivum L.

Utilization of arbuscular mycorrhizal (AM) fungi (AMF) as a sustainable strategy in redeeming arsenic (As) toxicity in plants is a promising approach. Low As accumulation, restoration of physiological processes, and As tolerance by AMF have been documented in crop plants. However, to comprehend AM-mediated As tolerance in plants, understanding the biochemical responses of host to the symbiont is crucial. The study evaluated the effect of an AM fungus, Rhizophagus intraradices on tricarboxylic acid cycle (TCA) and nitrogen metabolism of Triticum aestivum under three As concentrations (0, 25, and 50 mg As kg−1 soil). Results showed that TCA cycle and nitrogen metabolism were severely impaired by As that resulted into a higher C/N ratio. However, colonization by R. intraradices attenuated As mediated alterations in TCA cycle by augmenting the activity of pyruvate dehydrogenase that provided sufficient substrate for the TCA cycle. Furthermore, mycorrhizal (M) plants reinstated the activities of isocitrate dehydrogenase, succinate dehydrogenase, fumarase, and malate dehydrogenase even under high As level. Although citrate synthase and oxoglutarate dehydrogenase activities declined upon As exposure in M-plants, these were nevertheless higher than their non-mycorrhizal (NM) counterparts, ensuring higher levels of citric acid and succinic acid in M-plants. AM colonization also moderated the As-mediated disturbances in nitrogen assimilation by augmenting the activity of nitrate reductase, nitrite reductase, glutamine synthase, and glutamine-2-oxoglutarate amino transferase. Overall findings of the study point out that colonization by R. intraradices favourably regulated the TCA cycle and nitrogen metabolism and confronted As-mediated alterations in C/N ratio.

Arbuscular mycorrhizal symbiosis enhances perennial ryegrass growth during temperature stress through the modulation of antioxidant defense and hormone levels

Perennial ryegrass (Lolium perenne L.) refers to a vital species of grass grown extensively as a biofuel and biochemical production across temperate regions. However, both low temperature (LT) and high temperature (HT) conditions are unfavorable for the development of this species, causing reduced forage yield. Arbuscular mycorrhizal (AM) fungi are recognized for promoting host plants’ resistance to abiotic stresses via different mechanisms. However, the mechanism underlying the alleviation of plant damage induced by high-temperature stress and low-temperature stress by AM fungi remains to be elucidated so far. Therefore, the current work attempted to explore how the symbiosis with AM fungus Rhizophagus irregularis (R. irregularis) affects the antioxidant activity and hormone levels in ryegrass under LT and HT stresses and reveals the molecular mechanisms. In addition, the contents of non-enzymatic antioxidants, and hydrogen peroxide (H2O2), the activities of antioxidant enzymes, the genes encoding antioxidant enzymes, and the endogenous hormone-related genes in the perennial ryegrass inoculated with or without R. irregularis were analyzed upon exposure to LT and HT stresses. The results showed that inoculating AM plants with R. irregularis alleviated growth inhibition caused by LT and HT stress, as evidenced by significantly higher plant height, shoot and root dry weight, leaf chlorophyll and carotenoid content, net photosynthesis rate, and photochemical efficiency (Fv/Fm) in comparison to non- mycorrhizal (NM) plants under LT and HT stress. Under LT and HT conditions, AM symbiosis decreased electrolyte leakage (EL), malondialdehyde (MDA), H2O2, and abscisic acid (ABA) contents while significantly increasing the activities of our analyzed enzymes (with the exception of peroxidase (POD) in shoots and ascorbate peroxidase (APX) in roots), AsA/DHA and GSH/GSSG ratio, gibberellic acid 3 (GA3), jasmonic acid (JA) and indoleacetic acid (IAA) contents in shoots and roots. R. irregularis inoculation significantly upregulated almost all genes encoding antioxidant enzyme we tested (except for LpGPX1, LpGPX3, and LpGR in shoots, which were unaffected by AM symbiosis in 3d LT treatment) and some related genes in JA biosynthetic pathway, gibberellin synthesis as well as auxin transport and signaling while down-regulated the biosynthesis and signaling genes involved in ABA.In general, the findings suggested that AM symbiosis regulated the antioxidant defense and the hormone levels in ryegrass, which consequently alleviated the temperature stress-induced plant inhibition.

Azoxystrobin alters the dynamics of short‐term phosphorus uptake of mycorrhizal potato plants associated to Rhizophagus irregularis

AbstractBackgroundAzoxystrobin is widely used in crops against several fungal diseases, but may have potential negative effects on soil microorganisms beneficial to plants such as arbuscular mycorrhizal (AM) fungi. To date, the impact of azoxystrobin has been studied on the growth and healing capacity of AM fungi, but not on the inorganic phosphorus (Pi) uptake dynamics.AimsThe aim of the study was to investigate the impact of azoxystrobin on the dynamics of Pi uptake by potato plants associated or not to Rhizophagus irregularis. Additionally, fungal root colonization, plant growth, and P accumulation were assessed.MethodsA semi‐hydroponic cultivation system was used using mycorrhizal (M) and nonmycorrhizal (NM) plants growing in presence/absence of azoxystrobin. The percentage of Pi depletion in the nutrient solution was determined by inductively coupled plasma atomic emission spectroscopy after 30 and 60 days of circulation.ResultsWhatever the presence/absence of the AM fungus, azoxystrobin decreased Pi uptake by plants after 30 days of growth. Conversely, after 60 days in absence of azoxystrobin, a larger Pi uptake was measured in the M plants, while the reverse was noticed in presence of azoxystrobin.ConclusionsThe M plants were more affected by azoxystrobin than those growing in absence of the fungicide, suggesting a direct effect of azoxystrobin on the AM fungus and an indirect effect on the plant–fungus associates via a potential imbalance in the transfer of nutrients. Although it is difficult to extrapolate our results to field, fungicide toxicity on crops inoculated with selected AM fungi deserves to be explored.

The effects of natural enemies on herb diversity in a temperate forest depend on species traits and neighbouring tree composition

Abstract There is mounting evidence that top‐down control by natural enemies helps maintain plant diversity in natural ecosystems. Previous work has concentrated on either forest trees or grassland herbs. Our knowledge of how natural enemies affect herb diversity in forests is limited. We used fungicides and insecticide to experimentally examine the effects of fungi and insects on herb abundance and diversity at the community‐wide scale and within groups of species with certain traits. We also assessed how the effects of fungi and insects on herb assemblages were modified by neighbouring tree diversity and composition in an old‐growth temperate forest. We found that fungicides increased overall herb abundance by 7% while decreasing herb diversity by 5%. This effect of fungicides on both herb abundance and diversity weakened with the increase of neighbouring tree diversity. Insecticide did not affect either herb abundance or diversity noticeably, except in areas dominated by deciduous trees where insecticide application reduced herb diversity. Fungicides and insecticide decreased the diversity of relatively less defended species (i.e. thin‐leaved and non‐clonal) but had no effect on the diversity of herbs with stronger defensive traits (i.e. thick‐leaved and clonal). Fungicides increased the abundance of non‐mycorrhizal (NM) species but not arbuscular‐mycorrhizal (AM) species, although the effect of fungicides on herb diversity was unrelated to species' mycorrhizal association. Insecticide had stronger effects on the abundance and diversity of NM species than AM species. Synthesis. We conclude that fungi and insect herbivores are critical to regulating herb abundance and diversity in this temperate forest, with their effects dependent on species' traits and neighbouring tree diversity and composition. Our results highlight the importance of top‐down control of understory herb communities by natural enemies in temperate forests, advancing our understanding of the processes shaping plant diversity in natural ecosystems.

Regulation of Phosphorus and Zinc Uptake in Relation to Arbuscular Mycorrhizal Fungi for Better Maize Growth

Zinc (Zn) is an important micronutrient for plants, whose deficiency in alkaline soils creates hurdles in the achievement of optimum crop growth. Moreover, overuse of phosphorus (P) fertilizers often causes Zn immobilization in the soil. The employment of arbuscular mycorrhizal fungi (AMF) could be potentially environmentally friendly technology in this regard. Therefore, a pot experiment was conducted to assess the beneficial role of AMF (Glomus species) on maize under low and high P and Zn levels. Seven levels of Zn (0, 20, 40, 60, 80, 100 and 120 mg Zn kg−1 soil ZnSO4·7H2O) and three levels of P (0, 14.5, 29 and 58 kg ac−1 as single superphosphate) were applied with (M+) and without AMF (M−). The results showed that a high application rate of Zn (100 and 120 mg Zn kg−1 soil) restricted P translocation in plants and vice versa. Moreover, the nutritional status of mycorrhizal plants (AM) was better than non-mycorrhizal (NM) plants. AM plants showed a maximum positive response at 20 mg Zn kg−1 soil, or 29 kg P ac−1. In response to 20 mg Zn kg−1 soil, root colonization was maximum, which enhanced the maize nutrient concentration in shoots. In conclusion, AMF inoculation (M+) with P (29 kg ac−1) and Zn (20 mg kg−1) is efficacious for improving maize’s growth and nutrition. More investigations are suggested at the field level under different agroclimatic zones to ascertain whether P (29 kg ac−1) or Zn (20 mg kg−1) with AMF is the best treatment for maize growth optimization.

Elevational distribution and occurrence of arbuscular mycorrhizal fungi in non-host Carex capillacea.

Little is known about Arbuscular mycorrhizal (AM) fungal colonization and community composition in non-mycorrhizal (NM) plants, especially along elevational gradients. This study explores this question using a NM plant, Carex capillacea, at Mount Segrila, Tibet. Here, C. capillacea, its rhizosphere soil, and the neighboring mycotrophic plant Poa annua were sampled at four elevations to evaluate and compare their AM fungi colonization and communities. The results showed that AM fungal colonization density of C. capillacea was negatively correlated with elevation and biomass of total NM plants per quadrat. AM fungal diversity and community composition between C. capillacea and P. annua showed a similar pattern. In addition, elevation and soil did not significantly influence the AM community in C. capillacea, while they were important abiotic factors for assemblages in rhizosphere soil and P. annua. These findings support that a broad array of AM fungi colonize the root of C. capillacea, and a mycelial network from a co-occurring host plant might shape the AM fungal communities in C. capillacea along the elevation gradient. The co-occurrence patterns of AM fungi associated with non-mycotrophic species and adjacent mycotrophic species have important implications for understanding AM fungal distribution patterns and plant-AM interactions.

Mycorrhizal types influence island biogeography of plants

Plant colonization of islands may be limited by the availability of symbionts, particularly arbuscular mycorrhizal (AM) fungi, which have limited dispersal ability compared to ectomycorrhizal and ericoid (EEM) as well as orchid mycorrhizal (ORC) fungi. We tested for such differential island colonization within contemporary angiosperm floras worldwide. We found evidence that AM plants experience a stronger mycorrhizal filter than other mycorrhizal or non-mycorrhizal (NM) plant species, with decreased proportions of native AM plant species on islands relative to mainlands. This effect intensified with island isolation, particularly for non-endemic plant species. The proportion of endemic AM plant species increased with island isolation, consistent with diversification filling niches left open by the mycorrhizal filter. We further found evidence of humans overcoming the initial mycorrhizal filter. Naturalized floras showed higher proportions of AM plant species than native floras, a pattern that increased with increasing isolation and land-use intensity. This work provides evidence that mycorrhizal fungal symbionts shape plant colonization of islands and subsequent diversification.

Stoichiometry of Carbon, Nitrogen and Phosphorus in Shrub Organs Linked Closely With Mycorrhizal Strategy in Northern China.

Mycorrhizal strategies include mycorrhizal statuses and mycorrhizal types, which are important reflections of the functional characteristics of ecosystems. The stoichiometry of carbon, nitrogen, and phosphorus in plant organs is an important part of ecosystem functions, which has an important impact on the nutrient cycle of the ecosystem. The concentration of carbon, nitrogen, and phosphorus played a crucial role in ecosystem functioning and dynamics. The purpose of this study is to provide theoretical basis and data support for improving the properties of global terrestrial ecosystems by exploring the impact of mycorrhizal strategies on the stoichiometry of C, N, and P in different shrub organs. In this study, stoichiometric patterns of carbon (C), nitrogen (N) and phosphorus (P) in different shrub organs under different mycorrhizal status or types were analyzed at 725 samples across Northern China. Results showed that in different mycorrhizal status, the highest carbon concentration in shrub organs appeared in the facultatively mycorrhizal (FM) mycorrhizal status, and the highest nitrogen concentration appeared in the Non-mycorrhizal (NM) mycorrhizal status. Under different mycorrhizal types, the nitrogen concentration in the shrub organs under the arbuscular mycorrhiza (AM) mycorrhizal type was the highest, and the phosphorus concentration under the ecto-mycorrhiza (ECM) mycorrhizal type was the highest. In the OM or FM mycorrhizal status, the concentrations of C, N, and P in the stems and leaves increase with the increase of the concentrations of C, N, and P in the roots. In the NM mycorrhizal status, the N concentration in the stems and leaves increases with the increase of the N concentration in the roots. Under AM, AM+ECM, and ECM mycorrhizal type, the concentrations of C, N, and P are closely related in roots, stems and leaves. The content of plant nutrients in different organs is closely related. It turned out that mycorrhizal statuses or types are able to alter the allocation of C, N, and P in different organs, and the relationships of C, N, and P among different organs are able to present different trend with the varying of mycorrhizal statuses or types.

The effect of arbuscular mycorrhizal fungi on the phenolic compounds profile, antioxidant activity and grain yields in wheat cultivars growing under hydric stress.

Hydric stress affects the production of wheat (Triticum aestivum L.) worldwide, making some tools necessary to cope with the decrease in rainfall. A sustainable alternative is the use of arbuscular mycorrhizal fungi (AMF) as biofertilisers. Here, we analysed the effects of AMF strains adapted or non-adapted to hyper-arid conditions on the phenolic profiles and antioxidant activities of wheat grains from two cultivars with contrasting tolerance to osmotic stress (Ilustre, moderately tolerant; and Maxi, tolerant) grown with and without hydric stress. Eight phenolic compounds were detected, apigenin-C-pentoside-C-hexoside I being the most abundant and showing an increase of 80.5% when inoculated with the fungus Funneliformis mosseae (FM) obtained from Atacama Desert under normal irrigation with respect to non-mycorrhizal (NM) plants. NM treatments were associated with higher grain yields. FM showed a noticeable effect on most phenolic compounds, with an increase up to 30.2% in apigenin-C-pentoside-C-hexoside III concentration under hydric stress with respect to normal irrigation, being also responsible for high antioxidant activities such as ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) and DPPH (2,2-diphenyl-1-picrylhydrazyl) activities. Inoculation with FM adapted to hydric stress produced improvements in phenolics composition and antioxidant activities in grains from wheat plants growing under hydric stress conditions, improving their food quality and supporting the development of further studies to determine whether the use of adapted AMF could be a realistic tool to improve grain quality in a scenario of increasing hydric stress conditions. © 2021 Society of Chemical Industry.

Lime-rich and lime-poor coastal dunes: Natural blowout activity differs with sensitivity to high N deposition through differences in P availability to the vegetation

In industrialized countries, biodiversity is threatened by high atmospheric N deposition. In coastal dunes, blowouts can mitigate this through deposition of fresh sand, but lime-rich and lime-poor dunes may differ in blowout activity. We studied natural blowout activity and explanatory factors in 2000 and 2014 in up to 51 sites along the Dutch coast, representative for other parts of Europe. We further analyzed plant and soil characteristics related to P nutrition in seven sites in 2019 and found that blowout activity was intrinsically linked to interactions between the geosphere, pedosphere and biosphere. Blowout activity was higher in lime-rich than in lime-poor dunes, especially in 2014. This difference could not be explained by wind velocity and only partly by position in the landscape, but was associated with pH, critical N load and rabbit density. At high pH, P availability to the vegetation was low. Arbuscular mycorrhizal (AM) plant species thus predominated, which belong to the most characteristic dune plants and may provide rabbit food of better quality than nonmycorrhizal (NM) or ericoid mycorrhizal (ErM) plants. Root biomass was also low at high pH, which may reduce cohesion of the sand and increase blowout activity, especially in areas with high rabbit density. At low pH, P availability increased, which favored NM and ErM rather than AM plants, and root biomass increased, which increased stability of the blowouts. As a restoration measure, (re)activation of blowouts may improve buffer capacity, characteristic biodiversity and conservation status of coastal dune grasslands. However, lime-poor dunes are more vulnerable to acidification, increase in P availability and blowout stabilization than lime-rich dunes. In extremely lime-poor dunes, it may even be better to let vegetation develop towards Dune heathlands, which are also EU priority habitats.

Distribution of plant mycorrhizal traits along an elevational gradient does not fully mirror the latitudinal gradient.

The influence of mycorrhizal symbiosis on ecosystem processes depends on the mycorrhizal type and status of plants. Early research hypothesized that the proportion of arbuscular mycorrhizal (AM) species decreases and of ectomycorrhizal (ECM) and ericoid mycorrhizal (ERM) species increases along increasing elevations and latitudes. However, there is very scarce information about this pattern along elevation gradients. We aimed to test this hypothesis and to describe the trends in plant mycorrhizal status by examining the Pyrenean mountain range (from 400 to 3400m asl). The distribution of plant mycorrhizal types: AM, ECM, ERM, and non-mycorrhizal (NM) and status (obligately, OM, or facultatively, FM mycorrhizal plants, FM) were identified based on the Pyrenean Floristic Atlas and analyzed for climatic and edaphic drivers. The proportion of AM plants decreased slightly with elevation, while ECM species peaked at 1000m asl. The proportion of ERM and NM plant species rose with increasing elevation. The proportion of FM species increased, and OM species decreased with increasing elevation. The change of AM and ECM species, and OM and FM species, along the elevational gradient, corresponds broadly to changes along the latitudinal gradient, driven by a combination of climatic and edaphic factors. Differently, the elevational occurrence of NM plant species is mainly driven only by climatic factors (low temperature) and that of ERM species by only edaphic factors (low pH). Large-scale macroecological studies (≥50km grid cell) well reflect the effects of climate on the distribution of plant mycorrhizal traits, but local data (≤1km grid cell) are needed to understand the effects of soil conditions and land use.