Non-mycorrhizal Plants Research Articles

Transfer of La, Ce, Sm and Yb to alfalfa and ryegrass from spiked soil and the role of Funneliformis mosseae.

Rare earth elements (REEs) are widely used in high-tech industries, and REE waste emissions have become a concern for ecosystems, food quality and human beings. Arbuscular mycorrhizal fungi (AMF) have repeatedly been reported to alleviate plant stress in metal-contaminated soils. To date, little information is available concerning the role of AMF in REE-contaminated soils. We recently showed that there was no transfer of Sm to alfalfa by Funneliformis mosseae, but only a single REE was examined, while light and heavy REEs are present in contaminated soils. To understand the role of AMF on the transfer of REEs to plants, we carried out an experiment using alfalfa (Medicago sativa) and ryegrass (Lolium perenne) in compartmented pots with separate bottom compartments that only were accessible by F. mosseae fungal hyphae. The bottom compartments contained a mixture of four REEs at equal concentrations (La, Ce, Sm and Yb). The concentration of REEs in plants was higher in roots than in shoots with higher REE soil-root than root-shoot transfer factors. Moreover, significantly higher light-REEs La and Ce were transferred to ryegrass shoots than Sm and the heavy-REE Yb, but this was not observed for alfalfa. Alfalfa dry weight was significantly increased by F. mosseae inoculation, but not ryegrass dry weight. For both plant species, there was significantly higher P uptake by the mycorrhizal plants than the nonmycorrhizal plants, but there was no significant transfer of La, Ce, Sm or Yb to alfalfa and ryegrass roots or shoots due to F. mosseae inoculation.

Long-Term Persistence of Arbuscular Mycorrhizal Fungi in the Rhizosphere and Bulk Soils of Non-host Brassica napus and Their Networks of Co-occurring Microbes.

Arbuscular mycorrhizal fungi (AMF) are obligate plant symbionts that improve the nutrition and health of their host. Most, but not all the crops form a symbiosis with AMF. It is the case for canola (Brassica napus), an important crop in the Canadian Prairies that is known to not form this association. From 2008 to 2018, an experiment was replicated at three locations of the Canadian Prairies and it was used to assess the impact of canola on the community of AMF naturally occurring in three cropping systems, canola monoculture, or canola in two different rotation systems (2-years, canola-wheat and 3-years, barley-pea-canola). We sampled canola rhizosphere and bulk soils to: (i) determine diversity and community structure of AMF, we expected that canola will negatively impact AMF communities in function of its frequency in crop rotations and (ii) wanted to assess how these AMF communities interact with other fungi and bacteria. We detected 49 AMF amplicon sequence variants (ASVs) in canola rhizosphere and bulk soils, confirming the persistence of a diversified AMF community in canola-planted soil, even after 10 years of canola monoculture, which was unexpected considering that canola is among non-mycorrhizal plants. Network analysis revealed a broad range of potential interactions between canola-associated AMF and some fungal and bacterial taxa. We report for the first time that two AMF, Funneliformis mosseae and Rhizophagus iranicus, shared their bacterial cohort almost entirely in bulk soil. Our results suggest the existence of non-species-specific AMF-bacteria or AMF-fungi relationships that could benefit AMF in absence of host plants. The persistence of an AMF community in canola rhizosphere and bulk soils brings a new light on AMF ecology and leads to new perspectives for further studies about AMF and soil microbes interactions and AMF subsistence without mycotrophic host plants.

Root Growth and Yield of Rice Plant Associated with Arbuscular Mycorrhizal Symbiosis Under Salt Stress

The presence of excessive salt around root system disrupts water and nutrient uptake by root, causes inhibition of plant growth resulting in low plant yield. Arbuscular mycorrhizal (AM) symbiosis known for its mutualism towards plant by enhancing plant root growth. This study examined how AM symbiosis improved root growth and yield of rice plant under different salinity levels. The experiment was conducted in the screenhouse of Faculty of Agriculture, Universitas Gadjah Mada which arranged in a Randomized Complete Block Design (RCBD) with two factors. The first factor was rice plant that applied with and without arbuscular mycorrhizal inoculum. The second factor was four salinity levels at 0 dS m-1 (non-saline), 2.5 dS m-1, 5 dS m-1, 7.5 dS m-1. The results showed that the increase of salinity level treatment was followed by increasing of root Na content, resulting in decreasing of root growth as well as plant yield. Higher colonization rate in mycorrhizal plant than non-mycorrhizal plant caused two-fold increase in root cation exchange capacity (CEC). Under salinity, roots of mycorrhizal plant became longer and thicker, also root fresh weight did not decrease compared to non-mycorrhizal plant. By having higher root CEC and more extensive root, mycorrhizal plant was able to alleviate yield loss under 7.5 dS m-1 salinity stress.

Stress-associated developmental reprogramming in moss protonemata by synthetic activation of the common symbiosis pathway

SummarySymbioses between angiosperms and rhizobia or arbuscular mycorrhizal fungi are controlled through a conserved signaling pathway. Microbe-derived, chitin-based elicitors activate plant cell surface receptors and trigger nuclear calcium oscillations, which are decoded by a calcium/calmodulin-dependent protein kinase (CCaMK) and its target transcription factor interacting protein of DMI3 (IPD3). Genes encoding CCaMK and IPD3 have been lost in multiple non-mycorrhizal plant lineages yet retained among non-mycorrhizal mosses. Here, we demonstrated that the moss Physcomitrium is equipped with a bona fide CCaMK that can functionally complement a Medicago loss-of-function mutant. Conservation of regulatory phosphosites allowed us to generate predicted hyperactive forms of Physcomitrium CCaMK and IPD3. Overexpression of synthetically activated CCaMK or IPD3 in Physcomitrium led to abscisic acid (ABA) accumulation and ectopic development of brood cells, which are asexual propagules that facilitate escape from local abiotic stresses. We therefore propose a functional role for Physcomitrium CCaMK-IPD3 in stress-associated developmental reprogramming

Arbuscular mycorrhizal fungi enhance nutrient acquisition and reduce aluminum toxicity in Lespedeza formosa under acid rain.

Lespedeza formosa is an economically important shrub in the agroecosystems of southern China, where acid rain (AR) is an increasingly serious environmental issue. However, the roles of arbuscular mycorrhizal fungi (AMF) in adapting the plants to AR stress are poorly understood. In this study, L. formosa seedlings were cultivated in a greenhouse, where the inoculated (colonization with Rhizophagus irregularis and Diversispora versiformis, alone and in combination) and non-inoculated plants were treated with three AR regimes (pH 5.6, 4.0, and 2.5) to evaluate the roles of AMF under acidic conditions. The results showed that AR individually suppressed plant growth by inhibiting photosynthetic parameters and induced Al phytotoxicity in non-mycorrhizal plants. However, mycorrhizal inoculation, especially in combination, significantly increased the total dry weight, photosynthetic capabilities, shoot nitrogen (N) concentration (average 15.8 and 16.7mgg-1 for non-mycorrhizal and mycorrhizal plants, respectively) and plant phosphorus (P) concentration (average 1.6 and 2.3mgg-1 for non-mycorrhizal and mycorrhizal plants, respectively) at pH 4.0, reduced N/P ratio (average 9.5 and 6.9for non-mycorrhizal and mycorrhizal plants, respectively) at pH 4.0, and protected roots against Al phytotoxicity (average 2.0 and 1.4mgg-1 for non-mycorrhizal and mycorrhizal roots, respectively), indicating that AMF could mitigate some of the detrimental effects of AR. Moreover, our findings suggest that AMF mainly benefited the plant through the combined effects of N concentrations and N/P ratios in shoots and Al3+ concentrations in roots under acidic conditions.

Mycorrhiza improves plant growth and photosynthetic characteristics of tea plants in response to drought stress

Tea plants are sensitive to soil moisture deficit, with the level of soil water being a critical factor affecting their growth and quality. Arbuscular mycorrhizal fungi (AMF) can improve water and nutrient absorption, but it is not clear whether AMF can improve the photosynthetic characteristics of tea plants. A potted study was conducted to determine the effects of Claroideoglomus etunicatum on plant growth, leaf water status, pigment content, gas exchange, and chlorophyll fluorescence parameters in Camellia sinensis cv. Fuding Dabaicha under well-watered (WW) and drought stress (DS) conditions. Root mycorrhizal colonization and soil hyphal length were significantly reduced by the eight-week DS treatment. AMF inoculation displayed a significant increase in shoot and root biomass production. The relative water content, leaf water potential, nitrogen balance index, pigment content, maximum photometric effect (Fv/Fm, QY_max), and steady-state photometric effect Y (II) (QY_Lss) decreased dramatically, while the leaf water saturation deficit and steady-state non-photochemical fluorescence quenching (NPQ_Lss) generally increased under DS conditions. Mycorrhizal treatment induced significantly higher relative water content, leaf water potential, nitrogen balance index, pigment (chlorophyll, flavonoid, and anthocyanin) content, net photosynthesis rate, transpiration rate, stomatal conductance, intercellular CO2 concentration, QY_max, and QY_Lss; however, it resulted in a lower leaf water saturation deficit and NPQ_Lss under both WW and DS conditions, as compared with non-mycorrhizal plants. These results imply that AMF promoted tea plant growth and alleviated negative effects of DS by promoting gas exchange, regulating the water status of leaves, and regulating photosynthetic parameters.

Allelopathy of Knotweeds as Invasive Plants.

Perennial herbaceous Fallopia is native to East Asia, and was introduced to Europe and North America in the 19th century as an ornamental plant. Fallopia has been spreading quickly and has naturalized in many countries. It is listed in the world’s 100 worst alien species. Fallopia often forms dense monospecies stands through the interruption of the regeneration process of indigenous plant species. Allelopathy of Japanese knotweed (Fallopia japonica), giant knotweed (Fallopia sachalinensis), and Bohemian knotweed (Fallopia x bohemica) has been reported to play an essential role in its invasion. The exudate from their roots and/or rhizomes, and their plant residues inhibited the germination and growth of some other plant species. These knotweeds, which are non-mycorrhizal plants, also suppressed the abundance and species richness of arbuscular mycorrhizal fungi (AMF) in the rhizosphere soil. Such suppression was critical for most territorial plants to form the mutualism with AMF, which enhances the nutrient and water uptake, and the tolerance against pathogens and stress conditions. Several allelochemicals such as flavanols, stilbenes, and quinones were identified in the extracts, residues, and rhizosphere soil of the knotweeds. The accumulated evidence suggests that some of those allelochemicals in knotweeds may be released into the rhizosphere soil through the decomposition process of their plant parts, and the exudation from their rhizomes and roots. Those allelochemicals may inhibit the germination and growth of native plants, and suppress the mycorrhizal colonization of native plants, which provides the knotweeds with a competitive advantage, and interrupts the regeneration processes of native plants. Therefore, allelopathy of knotweeds may contribute to establishing their new habitats in the introduced ranges as invasive plant species. It is the first review article focusing on the allelopathy of knotweeds.

The interaction of the mycorrhizae of the fungus Rhizophagus irregularis (Walker & Schüßler, 2010) (Glomerales: Glomeraceae) and the stem and bulb nematode (Ditylenchus dipsaci Kühn, 1857) (Tylenchida: Anguinidae) on the onion plant (Allium cepa L.) (Asparagales: Amaryllidaceae)

The stem and bulb nematode, Ditylenchus dipsaci, is a plant parasite that causes significant economic losses to growers of the main host plant, onion. Fungal mycorrhizae can increase plant growth and induce systemic resistance against many diseases and pests. However, no evidence of a detailed study was found regarding the relationship of mycorrhizae with D. dipsaci. In this study, the effects of the mycorrhizae of the fungus, Rhizophagus irregularis, on D. dipsaci, the stem and bulb nematode, on the onion plant, Allium cepa, were investigated. The mycorrhizae did not significantly reduce nematode penetration and multiplication on onion plant roots. Mean penetration rates for mycorrhizal and non-mycorrhizal plants were 13.5% and 7.5%, respectively. The multiplication rate was between 0.6 and 1.3 in a growth chamber and 0.7 and 3.6 in a greenhouse. Fresh plant weight was 0.9-2.2 g in the greenhouse. Since the mycorrhizae of R. irregularis increased the growth of the onion plant by increasing its tolerance to D. dipsaci, it would be beneficial to increase mycorrhizal levels in onion growing areas where D. dipsaci, the stem and bulb nematode, is present.

Mycorrhiza-Induced Alterations in Metabolome of Medicago lupulina Leaves during Symbiosis Development.

The present study is aimed at disclosing metabolic profile alterations in the leaves of the Medicago lupulina MlS-1 line that result from high-efficiency arbuscular mycorrhiza (AM) symbiosis formed with Rhizophagus irregularis under condition of a low phosphorus level in the substrate. A highly effective AM symbiosis was established in the period from the stooling to the shoot branching initiation stage (the efficiency in stem height exceeded 200%). Mycorrhization led to a more intensive accumulation of phosphates (glycerophosphoglycerol and inorganic phosphate) in M. lupulina leaves. Metabolic spectra were detected with GS-MS analysis. The application of complex mathematical analyses made it possible to identify the clustering of various groups of 320 metabolites and thus demonstrate the central importance of the carbohydrate and carboxylate-amino acid clusters. The results obtained indicate a delay in the metabolic development of mycorrhized plants. Thus, AM not only accelerates the transition between plant developmental stages but delays biochemical “maturation” mainly in the form of a lag of sugar accumulation in comparison with non-mycorrhized plants. Several methods of statistical modeling proved that, at least with respect to determining the metabolic status of host-plant leaves, stages of phenological development have priority over calendar age.

Growth-promoting effects of dark septate endophytes on the non-mycorrhizal plant Isatis indigotica under different water conditions

Growth-promoting effects of dark septate endophytes on the non-mycorrhizal plant Isatis indigotica under different water conditions

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.

Effect of mycorrhization and water stress on morphological parameters, concentration of phenolic compounds and antioxidant capacity of methanolic extract of Lupinus albus

Secondary metabolites and mycorrhizal symbiosis play important roles in the adaptation of plants to environmental conditions, but mycorrhizal symbiosis favours also accumulation of secondary metabolites. Our objective was to study effect of interaction between mycorrhization and water deficiency on morphological parameters, phenolic compound concentration in Lupinus albus and to perform an evaluation of the antioxidant potential of methanolic extract of this plant. Plants of L. albus were subjected to three levels of water defficiency (80, 50 and 30% of field capacity). Half of the plants in each treatment were inoculated with arbuscular mycorrhizal fungi. Total concentrations of polyphenols, flavonoids, and condensed tannins were measured, and antioxidant potential of methanolic extracts from leaves and roots of white lupin plants was evaluated. In general, mycorrhizal plants of L. albus had better growth indices in all watering regimes in comparison to non-mycorrhizal plants. The concentrations of phenolic compounds were maximal in the leaf extracts from L. albus plants inoculated with arbuscular mycorrhizal fungi grown under 30% of field capacity water regime, and in root extract of non-inoculated plants grown under 30% of field capacity. Methanolic extracts of all plants showed good antioxidant activity, with higher values in mycorrhizal drought-stressed plants.

Effect of High-Temperature Stress on Plant Physiological Traits and Mycorrhizal Symbiosis in Maize Plants.

Increasing high temperature (HT) has a deleterious effect on plant growth. Earlier works reported the protective role of arbuscular mycorrhizal fungi (AMF) under stress conditions, particularly influencing the physiological parameters. However, the protective role of AMF under high-temperature stress examining physiological parameters with characteristic phospholipid fatty acids (PLFA) of soil microbial communities including AMF has not been studied. This work aims to study how high-temperature stress affects photosynthetic and below-ground traits in maize plants with and without AMF. Photosynthetic parameters like quantum yield of photosystem (PS) II, PSI, electron transport, and fractions of open reaction centers decreased in HT exposed plants, but recovered in AMF + HT plants. AMF + HT plants had significantly higher AM-signature 16:1ω5cis neutral lipid fatty acid (NLFA), spore density in soil, and root colonization with lower lipid peroxidation than non-mycorrhizal HT plants. As a result, enriched plants had more active living biomass, which improved photosynthetic efficiency when exposed to heat. This study provides an understanding of how AM-mediated plants can tolerate high temperatures while maintaining the stability of their photosynthetic apparatus. This is the first study to combine above- and below-ground traits, which could lead to a new understanding of plant and rhizosphere stress.

Mycorrhiza Reduces Phosphorus Uptake from Struvite in Rye (Secale cereale L.) Plants

To reduce dependency on inorganic phosphorus (P) fertiliser, secondary P fertilisers such as struvite are becoming more important. However, the P uptake of these new fertilisers by plants is often not known and may be enhanced by plant associated microorganisms. We therefore investigated the effect of arbuscular mycorrhizae (AM) on P uptake in rye (Secale cereale L.), grown in the middle compartment of a box with chambers separated by a 30 µm mesh allowing fungal hyphae but not roots to penetrate. Plants with (AM) or without (control) mycorrhizae (Rhizophagus irregularis) were grown in a P limited sand medium for 72 days. After harvest, plants were analysed for mycorrhizal colonization, shoot and root development and nutrient (P, Ca, Mg) uptake. Further, pH was measured in each compartment. Shoot biomass of both treatments was not different, but root biomass was significantly lower in AM plants. Despite plants of the AM treatment being colonised by mycorrhizae, their P uptake was substantially lower compared to the control treatment, but root nutrient concentration was higher. Even though the pH in the mycorrhizal compartment of the AM treatment was significantly lower compared to the control, water- and CAL-extractable P were similar, indicating little P uptake from this compartment. Extractable P was reduced only in the root compartment of the control, which was associated with a lower pH compared to the AM treatment. In conclusion, mycorrhizae did not increase P uptake from struvite in rye plants. Non-mycorrhizal plants which invested more biomass into roots took up more P.Graphical abstract

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.

The Arbuscular Mycorrhizal Fungus Rhizophagus irregularis MUCL 41833 Modulates Metabolites Production of Anchusa officinalis L. Under Semi-Hydroponic Cultivation.

Anchusa officinalis is recognized for its therapeutic properties, which are attributed to the production of different metabolites. This plant interacts with various microorganisms, including the root symbiotic arbuscular mycorrhizal fungi (AMF). Whether these fungi play a role in the metabolism of A. officinalis is unknown. In the present study, two independent experiments, associating A. officinalis with the AMF Rhizophagus irregularis MUCL 41833, were conducted in a semi-hydroponic (S-H) cultivation system. The experiments were intended to investigate the primary and secondary metabolites (PMs and SMs, respectively) content of shoots, roots, and exudates of mycorrhized (M) and non-mycorrhized (NM) plants grown 9 (Exp. 1) or 30 (Exp. 2) days in the S-H cultivation system. Differences in the PMs and SMs were evaluated by an untargeted ultrahigh-performance liquid chromatography high-resolution mass spectrometry metabolomics approach combined with multivariate data analysis. Differences in metabolite production were shown in Exp. 1. Volcano-plots analysis revealed a strong upregulation of 10 PMs and 23 SMs. Conversely, in Exp. 2, no significant differences in PMs and SMs were found in shoots or roots between M and NM plants whereas the coumarin scoparone and the furanocoumarin byakangelicin, accumulated in the exudates of the M plants. In Exp. 1, we noticed an enhanced production of PMs, including organic acids and amino acids, with the potential to act as precursors of other amino acids and as building blocks for the production of macromolecules. Similarly, SMs production was significantly affected in Exp 1. In particular, the phenolic compounds derived from the phenylpropanoid pathway. Fifteen di-, tri-, and tetra-meric C6-C3 derivatives of caffeic acid were induced mainly in the roots of M plants, while four oleanane-types saponins were accumulated in the shoots of M plants. Two new salvianolic acid B derivatives and one new rosmarinic acid derivative, all presenting a common substitution pattern (methylation at C-9”' and C-9' and hydroxylation at C-8), were detected in the roots of M plants. The accumulation of diverse compounds observed in colonized plants suggested that AMF have the potential to affect specific plant biosynthetic pathways.

Reynoutria japonica invasion negatively affects arbuscular mycorrhizal fungi communities regardless of the season and soil conditions

Reynoutria japonica (Japanese knotweed) is one of the most potent global invasive plant species; however, there is still insufficient knowledge on the impact of its invasion on arbuscular mycorrhizal fungi (AMF, Glomeromycota). The aim of our study was to assess the condition of AMF communities under the influence of R. japonica and determine the temporal and site-dependent variability of this influence. We studied AMF spore number, species richness, and composition as well as biomass in pairs of adjacent plots encompassing R. japonica and resident plant species. We established these pairs of plots in different habitat conditions (light and heavier soil conditions), and we sampled them four times (two spring and two summer seasons) to check if the potential impact of the invader on AMF communities is soil- and/or season-dependent. We found that the invasion reduced AMF spore number, species richness, and biomass, but had no effect on AMF species composition. AMF parameters varied over time (spore number, species composition and biomass) and depended on soil condition (species richness), but were barely affected by interactions between the studied factors. The lower performance of AMF communities in R. japonica plots was probably due to the displacement of resident mycorrhizal plant species. This displacement was not complete as some mycorrhizal plants, especially spring ephemerals, managed to survive the invasion. These were probably responsible for the maintenance of AMF communities in the patches of R. japonica. In conclusion, AMF communities are negatively affected by the invasion, but R. japonica does not entirely eliminate AMF, which is optimistic from the viewpoint of restoring sites invaded by this non-mycorrhizal alien plant species.

Interactive Effects of Potassium and Mycorrhizal Fungi on Glomalin and Biochemical Responses of Sunflower Grown in a Pb and Zn Contaminated Soil

ABSTRACT It is well documented that sole application of potassium (K) or mycorrhizal fungi can alleviate heavy metal stress in plants. As an indicator of the efficient defense in the mycorrhizal fungi-plant system, glomalin synthesis in the rhizosphere can be determined. In this study, interactive effects of mycorrhizal fungi (MY) and K on glomalin content, heavy metal uptake and mycorrhizal properties of sunflower plants were examined with three soil K levels (0, 100, and 200 mg K kg−1 using K2SO4). The three levels of mycorrhization are: i) no mycorrhizal inoculation, ii) Rhizophagus irregularis inoculation, and iii) mixed mycorrhizal inoculum application. Joint application of potassium and mycorrhiza significantly increased the percentage of root colonization and easily extractable glomalin (EEG), showing 56% root colonization in the treatment of K100 + mixed mycorrhiza and 178 µg EEG g−1 in the treatment of K200 + mixed mycorrhiza. Joint application of MY and K significantly reduced the translocation of heavy metals to the shoot of the plants. The highest total uptake of Zn by plants per pot (2.01 mg pot −1) and Pb (0.78 mg pot −1) were found in non-mycorrhizal plants. The MY and K treatments also increased the chlorophyll content and leaf area index by 57%. This study concluded that application of potassium and mycorrhizal fungi enhanced glomalin production and increased plant resistance to heavy metal stress.

Arbuscular mycorrhizal fungi alleviate salinity stress and alter phenolic compounds of Moldavian balm

Mycorrhizal fungi are known to modulate the destructive effects of environmental stresses on plants. Arbuscular mycorrhizal fungi (AMF) symbiosis increases growth and stimulates the biosynthesis of bioactive compounds, thereby influencing polyphenolics content in medicinal plants under salt stress. The present study investigated the effects of AMF on growth traits, cell death, non-enzymatic antioxidants, and changes in the profile of phenolic compounds of Dracocephalum moldavica L. by HPLC analysis under different salinity concentrations. The experiment was performed as a factorial experiment based on a randomized complete block design including salinity treatment at four levels (0, 50, 100, and 150 mM NaCl) and mycorrhizal fungus treatment at three levels including non-inoculation and inoculated with Funneliformis mosseae and Claroideoglomus etunicatum with three replications. The experiment was performed in sterile controlled conditions in laboratory. The results showed that salinity reduced root colonization compared to the control conditions. Inoculation with AMF increased growth parameters and salinity tolerance of Deracocephalum Moldavica under all salinity levels. Through high-performance liquid chromatography, nine phenolic acids and flavonoids were analyzed in all treatments. Salinity and AMF inoculation altered the polyphenol profiles of Moldavian balm. F. mosseae inoculation increased most of the polyphenols at 50 and 150 mM NaCl, and C. etunicatum inoculation increased polyphenols at 100 mM NaCl more than F. mosseae. suggesting that F. mosseae and C. etunicatum mitigated the adverse effects of salinity, triggering non-enzymatic antioxidant activity by the accumulation of the flavonoid in roots and shoots and phenol in roots, enhancing growth parameters and reducing root cell death compared to non-mycorrhizal plants. As a positive point, salinity and mycorrhizal inoculation influenced the polyphenol content of D. moldavica and improved the production of phenolic compounds.