Mycorrhizal Root Systems Research Articles

Effect of harvest dates, mycorrhiza, and some biostimulants on some vegetative growth properties and yield of volatile oil for sweet scented geranium plant (Pelargonium graveolens L.Herit.)

The experiment was carried out in one of the fields of Research Station B in the College of Agricultural Engineering Sciences / University of Baghdad - Al-Jadiriya on the fragrant plant for the spring season 2021 in order to study the effect of harvest date, mycorrhiza, bio-stimulants and the interaction among them on some characteristics of vegetative growth and the essential oil yield of sweet-scented geranium plants. The experiment used a randomized complete block design (RCBD) with a split-plot design with three replications. The experiment included three factors, as the factor of harvest dates represents the main panels with two harvest dates, which are 60 and 90 after planting and symbolized by H1 and H2. In contrast, the secondary panels include the treatment of the mycorrhizal fungal vaccine by two treatments, namely, not adding the mycorrhizal fungal vaccine to the root system and adding it with symbols M1 and M2 As for the sub-secondary panels, the treatments include four stimulating factors: the measurement treatment and the spraying of the vegetative mass with the amino acid phenylalanine at a concentration of 300 mg l ̄¹. The treatment of spraying the foliage with moringa leaf extract at a concentration of 10 gm L ̄¹ and the treatment of spraying the foliage with licorice root powder extract at a concentration of 10gm L ̄¹symbolized by B1, B2, B3, and B4 respectively. The results showed the superiority of the H2 treatment in most indicators of vegetative growth, as well as the increase in the percentages of each of the nutrients and volatile oil in the dried leaves and the volatile oil yield in the dried leaves. Treatment M2 significantly increased all vegetative growth characteristics as well as the percentages of nutrients and volatile oil in dried leaves and volatile oil yield in dried leaves. In contrast, treatment B3 showed an increase in the number of main branches, total number of leaves, total leaf area, fresh and dry weight of leaf yield in the plant and the content of The dried leaves of total chlorophyll as well as the percentages of nutrients and volatile oil in the dried leaves of the plant and the yield of volatile oil in the dried leaves. In contrast, treatment B2 had a significant effect in increasing the plant height rate, the number of main branches and the fresh weight of the leaves. It is one of the most prominent triple interaction treatments recorded. The largest increase in all the traits studied above is the triple interaction H2M2B3 treatment, which was characterized by an Bionatura http://dx.doi.org/10.21931/RB/CSS/2023.08.04.69 2 increase in most vegetative growth characteristics, especially the wet and dry weight of leaves and the percentages of nutrients as well as the percentage of volatile oil and volatile oil yield in the leaves. The triple interaction treatment H2M2B4 was also characterized by its recording of Remarkable superiority in both plant height and leaf content of Total chlorophyll and potassium percentage. Keywords: Sweet-scented geranium plant, Harvest date, Mycorrhizae, Biostimulants, vegetative growth, volatile oil.

Facilitation of plant water uptake by an arbuscular mycorrhizal fungus: a Gordian knot of roots and hyphae.

Arbuscular mycorrhizal (AM) fungi play a positive role in plant water relations, and the AM symbiosis is often cited as beneficial for overcoming drought stress of host plants. Nevertheless, water uptake via mycorrhizal hyphal networks has been little addressed experimentally, especially so through isotope tracing. In a greenhouse study conducted in two-compartment rhizoboxes, Medicago truncatula was planted in the primary compartment (PC), either inoculated with Rhizophagus irregularis or left uninoculated. Plant roots were either allowed to enter the secondary compartment (SC) or were restricted to the PC by root-excluding mesh. Substrate moisture was manipulated in the PC such that the plants were grown either in high moisture (15% of gravimetric water content, GWC) or low moisture (8% GWC). Meanwhile, the SC was maintained at 15% GWC throughout and served as a water source accessible (or not) by roots and/or hyphae. Water in the SC was labeled with deuterium (D) to quantify water uptake by the plants from the SC. Significantly, increased D incorporation into plants indicated higher water uptake by mycorrhizal plants when roots had access to the D source, but this was mainly explained by generally larger mycorrhizal root systems in proximity to the D source. On the other hand, AM fungal hyphae with access to the D source increased D incorporation into plants more than twofold compared to non-mycorrhizal plants. Despite this strong effect, water transport via AM fungal hyphae was low compared to the transpiration demand of the plants.

A Whole-Plant Culture Method to Study Structural and Functional Traits of Extraradical Mycelium.

An in vivo whole-plant bi-dimensional experimental system has been devised and tested with different host plants, in order to obtain extraradical mycelium (ERM) produced by different arbuscular mycorrhizal fungi (AMF). In this system, a host plant germling is inoculated with AMF to establish mycorrhizal symbiosis, and, after colonization, newly formed extraradical hyphae and spores are removed. Then the mycorrhizal root system is wrapped in a nylon net and placed between membranes in a Petri dish, allowing ERM to grow on the membrane surface. Such extraradical hyphae may be used for in situ morphometric analyses or collected for molecular or biochemical assays: in the latter case, the plant with its root sandwich may be reassembled to renew mycelium production. In this experimental system, which was tested with diverse host plant species and lines, values of explored membrane surface areas and densities of ERM showed wide ranges of variation, and its length ranged from 9.7±2.0 to 48.8±9.9m per plant, depending on host and AMF identity. Across the different plant-AMF combinations tested, the whole-plant system produced 2.0±0.6 to 5.3±0.3mg of ERM fresh biomass per plant per harvest. This experimental system can be used for a wide range of AMF and host plants species, either establishing arbuscular mycorrhizas or other mycorrhizal interactions. ERM produced and collected in the whole-plant system is suitable for morphological, physiological, and molecular analyses, facilitating studies on the different aspects of mycorrhizal symbiotic interactions.

Nutrient foraging by mycorrhizas: From species functional traits to ecosystem processes

Abstract Plant roots and the associated mycorrhizal fungal hyphae often selectively proliferate into patchily distributed soil nutrient hotspots, but interactions between these two components of a mycorrhizal root system are usually ignored or experimentally isolated in nutrient foraging studies. From studies in which both roots and mycorrhizal hyphae had access to nutrient hotspots, we compiled data on root foraging precision (increase in roots in nutrient hotspots relative to outside hotspots) of plant species from different ecosystems, ranging from temperate grasslands to subtropical forests. We found that root foraging precision across the wide range of plant species was strongly influenced by root morphology and mycorrhizal type. The precision of root nutrient foraging, as a plant functional trait, may coordinate with other root traits that are related to the economics of nutrient acquisition. High foraging precision is expected to associate with the strategy of fast return on the investment in roots, such as low construction cost, high metabolic rate and rapid turnover. Nutrient foraging by mycorrhizal fungi alone may be influenced by functional traits such as hyphal exploration distance, hyphal turnover, and hyphal uptake capacity and efficiency, but such data are limited to a small portion of mycorrhizal fungal species. We propose a conceptual framework in which to simulate nitrogen and phosphorus acquisition from both nutrient hotspots and outside hotspots in mixed‐species plant communities. Simulation outputs suggest that plant species with varying root morphology and mycorrhizal type can be adaptive to a range of nutrient heterogeneity. Although there are still knowledge gaps related to nutrient foraging, as well as many unexplored plant and fungal species, we suggest that scaling nutrient foraging from individual plants to communities would advance understanding of plant species interactions and below‐ground ecosystem function. A plain language summary is available for this article.

Impact of drought and stand edge on mycorrhizal density on the fine roots of Norway spruce

This paper evaluates the mycorrhizal status and root system of Norway spruce (Picea abies (L.) Karst.) with respect to trees’ position within the stand and artificially induced drought stress. Root systems were sampled during autumn of 2008, 2009 and 2013 from spruces exposed to varying conditions (totalling 18 trees, 47 samples). The experiment involved six groups of 3 spruces each. Three groups were growing within the stand and three groups at the stand’s edge. One tree from each group (total 6) was exposed to artificial drought using shelters deflecting rainfall away from the root system. For each sample, the number of active and non-active mycorrhizae on 20 root segments about 5 cm long was assessed. The densities of active and non-active mycorrhizae, proportion of active mycorrhizae, and root dry biomass weight were assessed. Factors’ significances were determined using ANOVA and the Tukey-Kramer test or the Kruskal-Wallis and Dunn’s tests. Samples from outside the sheltered area were characterized by higher numbers of active mycorrhizae than were those sampled within the sheltered area. Induced drought stress significantly influenced active mycorrhizae density. Significantly higher root dry biomass (roots <1 mm in diameter) was found at the stand’s interior versus its edge.

Elucidating mechanisms of mycorrhiza-induced resistance against Thielaviopsis basicola via targeted transcript analysis of Petunia hybrida genes

One important function of the arbuscular mycorrhizal (AM) symbiosis is the protection of plants against pathogenic microorganisms, but little is known of the molecular background of mycorrhiza-induced resistance (MIR) in roots. Here, we investigated possible mechanisms responsible for reduced disease development in Funneliformis mosseae–colonized roots of Petunia hybrida after infection with the root rot pathogen Thielaviopsis basicola. Monitoring of the pathogenic fungus revealed that reduced symptoms in mycorrhizal root systems are not primarily based on increased disease tolerance, but rather on induced resistance. The presence of T. basicola did not affect mycorrhiza development immediately (24 and 36 h after pathogen inoculation) but showed a slight negative influence after one week. AM induction of P. hybrida genes coding for nutrient transporters and defence-related genes was reduced by pathogen infection for some, but not all and only transiently, indicating that mycorrhiza functioning was maintained on the whole in pathogen-infected roots. In transcript profiling of 15 defence-related plant genes partially regulated by salicylic acid (SA) or jasmonate (JA) pathways, none showed expression resembling the phenomenon of priming usually accompanying JA-induced systemic resistance; several SA-regulated genes were down-regulated, when mycorrhizal roots were challenged with the pathogen. It is therefore proposed that mycorrhiza-intrinsic plant defence responses could establish a local barrier against root pathogens in mycorrhizal tissues. Expression patterns indicated a role of a basic endochitinase in these mycorrhiza-preformed barriers. Moreover, results suggested other oxilipins than jasmonate could be involved in signalling during interactions between the AM fungus and the pathogen in roots.

Overcoming Salinity Barriers to Crop Production Using Traditional Methods

Salinity is a major problem in arid and semi-arid regions, where irrigation is essential for crop production. Major sources of salinity in these regions are salt-rich irrigation water and improper irrigation management. The effects of salinity on crops include inhibition of growth and production, and ultimately, death. There are two main approaches to alleviating the adverse effects of salinity on agricultural crops: (i) development of salt-tolerant cultivars by screening, conventional breeding or genetic engineering, and (ii) the traditional approach dealing with treatments and management of the soil, plants, irrigation water, and plant environment. The success of the first approach is limited under commercial growing conditions, because salt-tolerance traits in plants are complex. The present paper reviews, analyzes, and discusses the following traditional approaches: (i) improving the plant environment, (ii) exploiting interactions between plant roots and bacteria and fungi, and (iii) treating the plant directly. With respect to improving the plant environment, we review the possibilities of decreasing salt content and concentration and improving the nutrient composition and concentration in the root zone, and controlling the plant's aerial environment. The interactions between salt-tolerant bacteria or mycorrhizal fungi and root systems, and their effects on salt-tolerance, are demonstrated and discussed. Discussed treatments aimed at alleviating salinity hazard by treating the plant directly include priming of seeds and young seedlings, using proper seed size, grafting onto tolerant rootstocks, applying non-enzymatic antioxidants, plant growth regulators or compatible solutes, and foliar application of nutrients. It can be concluded from the present review that the traditional approaches provide promising means for alleviating the adverse effects of salinity on agricultural crops.

Local and systemic mycorrhiza-induced protection against the ectoparasitic nematode Xiphinema index involves priming of defence gene responses in grapevine

The ectoparasitic dagger nematode (Xiphinema index), vector of Grapevine fanleaf virus (GFLV), provokes gall formation and can cause severe damage to the root system of grapevines. Mycorrhiza formation by Glomus (syn. Rhizophagus) intraradices BEG141 reduced both gall formation on roots of the grapevine rootstock SO4 (Vitis berlandieri×V. riparia) and nematode number in the surrounding soil. Suppressive effects increased with time and were greater when the nematode was post-inoculated rather than co-inoculated with the arbuscular mycorrhizal (AM) fungus. Using a split-root system, decreased X. index development was shown in mycorrhizal and non-mycorrhizal parts of mycorrhizal root systems, indicating that both local and systemic induced bioprotection mechanisms were active against the ectoparasitic nematode. Expression analyses of ESTs (expressed sequence tags) generated in an SSH (subtractive suppressive hybridization) library, representing plant genes up-regulated during mycorrhiza-induced control of X. index, and of described grapevine defence genes showed activation of chitinase 1b, pathogenesis-related 10, glutathione S-transferase, stilbene synthase 1, 5-enolpyruvyl shikimate-3-phosphate synthase, and a heat shock proein 70-interacting protein in association with the observed local and/or systemic induced bioprotection against the nematode. Overall, the data suggest priming of grapevine defence responses by the AM fungus and transmission of a plant-mediated signal to non-mycorrhizal tissues. Grapevine gene responses during AM-induced local and systemic bioprotection against X. index point to biological processes that are related either to direct effects on the nematode or to protection against nematode-imposed stress to maintain root tissue integrity.

Arbuscular mycorrhizas reduce nitrogen loss via leaching.

The capacity of mycorrhizal and non-mycorrhizal root systems to reduce nitrate (NO3 −) and ammonium (NH4 +) loss from soils via leaching was investigated in a microcosm-based study. A mycorrhiza defective tomato mutant and its mycorrhizal wildtype progenitor were used in this experiment in order to avoid the indirect effects of establishing non-mycorrhizal control treatments on soil nitrogen cycling and the wider soil biota. Mycorrhizal root systems dramatically reduced nitrate loss (almost 40 times less) via leaching, compared to their non-mycorrhizal counterparts, following a pulse application of ammonium nitrate to experimental microcosms. The capacity of AM to reduce nutrient loss via leaching has received relatively little attention, but as demonstrated here, can be significant. Taken together, these data highlight the need to consider the potential benefits of AM beyond improvements in plant nutrition alone.

Arbuscular mycorrhizas enhance plant interception of leached nutrients

Arbuscular mycorrhizal fungi (AMF) can increase plant growth and nutrition. However, their capacity to reduce the leaching of nutrients through the soil profile is less well understood. Here we present results of an experiment in which the effects of forming arbuscular mycorrhizas (AM) on plant growth and nutrition, nutrient depletion from soil, and nutrient leaching, were investigated in microcosms containing the grass Phalaris aquatica L. Mycorrhizal and non-mycorrhizal plants were grown in a mixture of riparian soil and sand under glasshouse conditions. The formation of AM by P. aquatica significantly increased plant growth and nutrient uptake. Lower levels of NO3-, NH4+ and plant available P in both soil and leachate were observed in columns containing mycorrhizal root systems. These differences in nutrient interception were proportionally greater than the increase in root biomass of the mycorrhizal plants, compared with their non-mycorrhizal counterparts. Taken together, these data indicate that mycorrhizal root systems have an important, but previously little considered, role to play reducing the net loss of nutrients via leaching.

Temperature‐Respiration Relationships Differ in Mycorrhizal and Non‐Mycorrhizal Root Systems of Picea abies (L.) Karst.

Root respiration has been shown to increase with temperature, but less is known about how this relationship is affected by the fungal partner in mycorrhizal root systems. In order to test respiratory temperature dependence, in particular Q (10) of mycorrhizal and non-mycorrhizal root systems, seedlings of PICEA ABIES (L.) Karst. (Norway spruce) were inoculated with the ectomycorrhizal fungus PILODERMA CROCEUM (Eriksson and Hjortstam, SR430; synonym: PILODERMA FALLAX: [Libert] Stalpers) and planted in soil respiration cuvettes (mycocosms). Temperature dependence of hyphal respiration in sterile cultures was determined and compared with respiration of mycorrhizal roots. Respiration rates of mycorrhizal and non-mycorrhizal root systems as well as sterile cultures were sensitive to temperature. Q (10) of mycorrhizal root systems of 3.0 +/- 0.1 was significantly higher than that of non-mycorrhizal systems (2.5 +/- 0.2). Q (10) of P. CROCEUM in sterile cultures (older than 2 months) was similar to that of mycorrhizal root systems, suggesting that mycorrhizae may have a large influence on the temperature sensitivity of roots in spite of their small biomass. Our results stress the importance of considering mycorrhization when modeling the temperature sensitivity of spruce roots.

Arbuscular mycorrhizal symbiosis is accompanied by local and systemic alterations in gene expression and an increase in disease resistance in the shoots

In natural ecosystems, the roots of many plants exist in association with arbuscular mycorrhizal (AM) fungi, and the resulting symbiosis has profound effects on the plant. The most frequently documented response is an increase in phosphorus nutrition; however, other effects have been noted, including increased resistance to abiotic and biotic stresses. Here we used a 16,000-feature oligonucleotide array and real-time quantitative RT-PCR to explore transcriptional changes triggered in Medicago truncatula roots and shoots as a result of AM symbiosis. By controlling the experimental conditions, phosphorus-related effects were minimized, and both local and systemic transcriptional responses to the AM fungus were revealed. The transcriptional response of the roots and shoots differed in both the magnitude of gene induction and the predicted functional categories of the mycorrhiza-regulated genes. In the roots, genes regulated in response to three different AM fungi were identified, and, through split-root experiments, an additional layer of regulation, in the colonized or non-colonized sections of the mycorrhizal root system, was uncovered. Transcript profiles of the shoots of mycorrhizal plants indicated the systemic induction of many genes predicted to be involved in stress or defense responses, and suggested that mycorrhizal plants might display enhanced disease resistance. Experimental evidence supports this prediction, and mycorrhizal M. truncatula plants showed increased resistance to a virulent bacterial pathogen, Xanthomonas campestris. Thus, the symbiosis is accompanied by a complex pattern of local and systemic changes in gene expression, including the induction of a functional defense response.

The conserved arbuscular mycorrhiza-specific transcription of the secretory lectin MtLec5 is mediated by a short upstream sequence containing specific protein binding sites

In Medicago truncatula a family of mycorrhiza-specific expressed lectins has been identified recently, but the function and regulation of these lectins during the arbuscular mycorrhiza symbiosis are still unknown. In order to characterize a first member of this protein family, MtLec5 was analyzed concerning its localization and regulation. Confocal laser scanning microscopy showed that MtLec5 is a secretory protein indicating a role as a vegetative storage protein, which is specifically expressed in mycorrhizal root systems. To study the molecular mechanisms leading to the mycorrhiza-specific transcription, deletion studies of pMtLec5 were done using reporter gene fusions. Potential cis-acting elements could be narrowed down to a 150 bp fragment that was located approximately at -300/-150 according to the transcription start, suggesting the binding of positive regulators to this area. Similar expression pattern of the reporter gene was found after transforming roots of the non-legume Nicotiana tabacum with the heterologous promoter-reporter fusions. This indicated that the observed mycorrhiza-specific transcriptional induction is not legume-specific. Electrophoretic mobility shift assays showed that several factors which were exclusively present in mycorrhizal roots bind within the 150 bp promoter area. This strengthens the hypothesis of positive regulators mediating the AM-specific gene expression.

The auxin‐inducible GH3 homologue Pp‐GH3.16 is downregulated in Pinus pinaster root systems on ectomycorrhizal symbiosis establishment

In an attempt to determine whether auxin-regulated plant genes play a role in ectomycorrhizal symbiosis establishment, we screened a Pinus pinaster root cDNA library for auxin-upregulated genes. This allowed the identification of a cDNA, Pp-GH3.16, which encodes a polypeptide sharing extensive homologies with GH3 proteins of different plants. Pp-GH3.16 was specifically upregulated by auxins and was not affected by cytokinin, gibberellin, abscisic acid or ethylene, or by heat shock, water stress or anoxia. Pp-GH3.16 mRNAs were quantified in pine roots inoculated with two ectomycorrhizal fungi, Hebeloma cylindrosporum and Rhizopogon roseolus. Surprisingly, Pp-GH3.16 was downregulated following inoculation with both fungal species. The downregulation was most rapid on establishment of symbiosis with an indole-3-acetic acid (IAA)-overproducing mutant of H. cylindrosporum, which overproduced mycorrhizas characterized by a hypertrophic Hartig net. This indicates that, despite being auxin-inducible, Pp-GH3.16 can be downregulated on establishment of symbiosis with a fungus that releases auxin. By contrast, Pp-GH3.16 was not downregulated in pine root systems inoculated with a nonmycorrhizal mutant of H. cylindrosporum, suggesting that the downregulation we observed in mycorrhizal root systems was a component of the molecular cross-talk between symbiotic partners at the origin of differentiation of symbiotic structures.

Effect of the arbuscular mycorrhizal fungus Glomus intraradices on expression of cytoskeletal proteins in tomato roots

The expression patterns of the cytoskeletal proteins α-, β-, and γ-tubulin, actin, and myosin were investigated in young tomato roots and older roots at different intensities of mycorrhizal colonization. The relative level of cytoskeletal proteins was estimated by protein blotting and immunostaining. The contribution of plant α-, β-, and γ-tubulin to the total protein pool was higher in uncolonized 2-week-old roots than in 10-week-old roots, whereas the contribution of actin remained constant. The level of plant tubulin expression was clearly higher in mycorrhizal root systems than in uncolonized older root systems. These results indicate that tubulins are more involved in plant cell differentiation than actin. Myosin of approximately 230 kDa was expressed in the roots of 10-week-old wild-type tomato but not in young or mycorrhizal tomatoes. In contrast, a smaller ca. 170 kDa myosin was consistently present in all root samples. Indirect immunofluorescence microscopy showed that plant myosin was located particularly along the periarbuscular membranes surrounding the arbuscule branches. In uncolonized roots, myosin was associated mainly with membranes adjacent to plant cell walls. These data provide novel evidence that myosin expression and localization in root cells responds to mycorrhizal colonization.Key words: actin, myosin, arbuscular mycorrhizal fungi, protein expression, tubulin.

Fire effects on mycorrhizal symbiosis and root system architecture in southern African savanna grasses

AbstractMycorrhizal symbiosis is a key factor influencing aspects of grassland and savanna structure and functioning including plant growth, competition, population and community dynamics, and responses to fire and herbivory. This study assessed the effects of fire on mycorrhizal symbiosis and root system architecture (RSA) in South African savanna grasses. Eighteen grass species were sampled across contrasting fire frequency treatments in the Kruger National Park experimental burn plots. All eighteen species studied were highly colonized by arbuscular mycorrhizal fungi (AMF). Both mycorrhizal symbiosis and RSA were strongly affected by fire, with an increase in AMF colonization and a decrease in root branching and fine root development with decreasing fire frequency. Greater water limitation in frequently burned savanna may result in greater fine root development, thus reducing plant dependency on AMF for acquisition of soil resources. Reduced mycorrhizal colonization in frequently burned savanna may also be driven by higher phosphorus : nitrogen ratios, or indirect effects related to higher grazing intensities in frequently burned sites.

The fungus does not transfer carbon to or between roots in an arbuscular mycorrhizal symbiosis.

• Carbon transfer from fungus to plant in the arbuscular mycorrhizal (AM) symbiosis has been reported, but its significance and even its existence have been called into question and the issue remains controversial. We investigated carbon movement from fungus to plant and from one mycorrhizal root system to another via a common AM fungal network in monoxenic cultures to avoid limitations of some previous studies. • 13 C and 14 C labeled substrates were supplied to functioning in vitro AM mycorrhizas between Ri T-DNA transformed carrot (Daucus carota) roots and Glomus intraradices to follow carbon movement into and between host and fungal metabolite pools. • Fungal triacylglycerol and trehalose were labeled when permeant substrates were supplied to the extraradical mycelium (ERM), but host-specific compounds in the roots did not become labeled. When labeled glucose was provided to a donor root system, label moved to recipient roots via a common AM fungal network but remained in fungal compounds. • We conclude that carbon flow in the AM symbiosis is normally unidirectional from plant to fungus and that while carbon is translocated by the fungus from one metabolically active root system to another, it remains within the intraradical mycelium (IRM).

Abundance, diversity, and vitality of mycorrhizae of Scots pine (Pinus sylvestris L.) in lignite recultivation sites.

Scots pine (Pinus sylvestris L.) stands cover large areas in the Lusatian and the Middle German lignite mining districts. Due to adverse chemical substrate conditions, the root systems of the trees are restricted to the ameliorated top-spoil and the organic forest floor layers. To investigate functioning of fine root systems under the prevailing site factors, we studied mycorrhizal colonization rate and frequency as well as mycorrhizal diversity, vitality and growth phases in Scots pine ecosystems along a chronosequence in both mining districts. Mycorrhizal rate was close to 100% in both districts. Mycorrhizal abundance was higher in the organic forest floor layer than the mineral soil layer. In total, 25 morphotypes were recorded. Diversity differed between the districts. The mycorrhizae of Amphinema byssoides, Tuber puberulum, Pinirhiza discolor, Pinirhiza cf. bicolorata and E-type were present in both mining areas. These morphotypes are typical of nutrient-rich soils with high pH values. Compared with the undisturbed sites, vitality of mycorrhizae was very high at the test sites on spoil substrate, correlating with the high growth dynamics of mycorrhizae at recultivation sites. A relatively high carbon flow to the mycorrhizal root systems at these sites seems likely. Thus, mycorrhizal root systems are able to cope with the ameliorated top-spoil and the organic layer. The main reason for the adaptation is the large number of ectomycorrhizal fungal species available in this area where Pinus sylvestris is indigenous.

Locally accumulated extractable compounds in mycorrhizal parts of maize roots suppress the growth ofHyphae ofGlomus intraradices

Extracts from mycorrhizal roots, non-mycorrhizal roots obtained from mycorrhizal root systems, and non-inoculated maize roots were fractionated by gel chromatography and their effects on the hyphal growth of arbuscular mycorrhizal fungusGlomus intraradices were studied under aseptic conditions. Low-molecular (MW lower than 3000) extracts obtained from mycorrhizal roots contained the fraction that most rapidly suppresses the hyphae growth. This was not observed for the fastest fraction obtained from non-mycorrhizal roots. The increased content of some inorganic ions, mainly potassium, was recorded in the fastest fraction of the mycorrhizal root extracts. At the same time, higher contents of two unidentified major organic compounds were revealed in this fraction of the mycorrhizal root extract compared to the non-mycorrhizal one. Some of these compounds, which are locally accumulated in the mycorrhizal parts of the root, are probably responsible for the effect observed. Potassium alone, even at a high concentration, cannot be responsible for the supression observed.

The root–microbe–soil interface: new tools for sustainable plant production

The root–microbe–soil interface: new tools for sustainable plant production