Hyphal in vitro growth of the arbuscular mycorrhizal fungus Glomus mosseae is affected by chitinase but not by β-1,3-glucanase

Purified basic chitinase or #-1,3-glucanase or a combination of the two enzymes were applied to hyphae of the arbuscular mycorrhizal fungus Glomus mosseae grown in vitro. Chitinase applied to the hyphal tip produced an inhibition of hyphal extension, lysis of the apex and alterations of the growth pattern of the fungus. No effect was observed, however, when chitinase was applied to subapical parts of the hyphae or when glucanase was applied to any part of the hyphae. Application of a combination of the two enzymes to the hyphal tip produced an effect similar to that of chitinase alone.     

Phialophora graminicola, a dark septate fungus, is a beneficial associate of the grass Vulpia ciliata ssp. ambigua

The influence of three organic compounds and bakers' dry yeast on growth of external mycelium and phosphorus uptake of the arbuscular mycorrhizal fungus Glomus intraradices Schenck & Smith (BEG 87) was examined. Two experiments were carried out in compartmentalized growth systems with root-free sand or soil compartments. The sand and soil in the root-free compartments were left untreated or uniformly mixed with one of the following substrates (0.5 mg g⁻¹ soil): bakers' dry yeast, bovine serum albumin, starch or cellulose. Effects of the organic substrates on biomass and hyphal length density of the arbuscular mycorrhizal fungus were examined by using specific fatty acid signatures in combination with direct microscopy. Micro-organisms other than the arbuscular mycorrhizal fungus were measured by fatty acid signatures, and radioactive ³³P labelling of the root-free soil was used to determine arbuscular mycorrhizal hyphal phosphorus uptake. In general, hyphal growth of G. intraradices was enhanced by yeast and bovine serum albumin, whereas the carbon sources, starch and cellulose, depressed fungal growth. By analysing the fatty acid 16:1ω5 from phospholipids (indicating mycelium) and neutral lipids (indicating storage structures) it was shown that increased fungal growth due to yeast was mainly in vegetative hyphae and less in storage structures. Arbuscular mycorrhizal hyphal phosphorus uptake was decreased by cellulose, but unaffected by the other substrates compared with the control. This means that both growth and phosphorus transport by the arbuscular mycorrhizal fungus were decreased under cellulose treatment. However, the composition of the microbial community varied under different substrate conditions indicating a possible interactive component with arbuscular mycorrhizal hyphal growth and phosphorus uptake.     

An intact microtubule cytoskeleton is not necessary for interfacial matrix formation in orchid protocorm mycorrhizas

 This paper reports the changes that occur in the microtubule cytoskeleton of cells of orchid protocorms during infection by a compatible mycorrhizal fungus. In cells of protocorms uninfected by a mycorrhizal fungus, microtubules occurred in regular arrays. In contrast, the cells of orchid protocorms with established mycorrhizas appeared to contain irregularly arranged microtubules. Double labelling with anti-β-tubulin and rhodamine-labelled wheat-germ agglutinin demonstrated that these irregularly arranged microtubules occurred only inside fungal hyphae and that microtubules were absent from host cells containing mycorrhizal fungi. Microtubule depolymerisation was shown to occur at the early stages of fungal infection. There was neither loss of nor obvious organisational change in microtubules in cells adjacent to others containing fungal hyphae. Electron microscopy confirmed the presence of an interfacial matrix between the host plasma membrane and the hyphal wall. The loss of microtubules from cells infected by mycorrhizal fungi suggests that an intact host microtubule cytoskeleton is not necessary for the formation of the interfacial matrix in mycorrhizas of orchid protocorms. Accepted: 9 November 1995     

Cryopreservation of in vitro-produced Rhizophagus species has minor effects on their morphology, physiology, and genetic stability

Cryogenic storage is considered to be the most convenient method to maintain phenotypic and genetic stability of organisms. A cryopreservation technique based on encapsulation-drying of in vitro-produced arbuscular mycorrhizal fungi has been developed at the Glomeromycota In Vitro Collection. In this study, we investigated fungal morphology (i.e., number and size of spores, number of branched absorbing structures (BAS), hyphal length, and number of anastomosis per hyphal length), activity of acid phosphatase and alkaline phosphatase in extraradical hyphae, and variation in amplified fragment length polymorphism (AFLP) profiles of in vitro-produced isolates of five Rhizophagus species maintained by cryopreservation for 6 months at ?130 °C and compared to the same isolates preserved at 27 °C. Isolates were stable after 6 months cryopreservation. Comparing isolates, the number of BAS increased significantly in one isolate, and hyphal length decreased significantly in another isolate. No other morphological variable was impacted by the mode of preservation. Phosphatase activities in extraradical hyphae and AFLP profiles were not influenced by cryopreservation. These findings indicate that cryopreservation at ?130 °C of encapsulated-dried and in vitro-produced Rhizophagus isolates (i.e., Rhizophagus irregularis, Rhizophagus fasciculatus, Rhizophagus diaphanous, and two undefined isolates) is a suitable alternative for their long-term preservation.     

Aggregation of surface mine soil by interaction between VAM fungi and lignin degradation products of lespedeza

Summary The external mycelium of a vesicular-arbuscular mycorrhizal (VAM) fungus was effective in aggregating a sandy loam minesoil. The polysaccharide nature of the soil binding agent on hyphal surfaces and on the surfaces of sand particles in contact with the hyphae within the aggregate was demonstrated with the periodic acid-Schiff reagent staining reaction. A possible stabilizing mechanism for macroaggregates was proposed that involves a coupling reaction between glucosamines in the hyphal walls of the fungus with phenolic compounds released during lignin degradation of sericea lespedeza root tissue.     

Vegetative compatibility and anastomosis formation within and among individual germlings of tropical isolates of arbuscular mycorrhizal fungi (Glomeromycota)

Hyphal anastomoses which play a key role in the formation of interconnected mycorrhizal networks and in genetic exchange among compatible individuals have been studied in a limited number of species and isolates of arbuscular mycorrhizal fungi (AMF), mainly in symbiotic mycelium. In this work, the occurrence and frequency of anastomosis between hyphae of the same and different germlings were assessed in tropical isolates belonging to Acaulospora, Claroideoglomus, Gigaspora, Glomus, Rhizophagus and Scutellospora. Germlings belonging to Acaulospora, Claroideoglomus, Glomus and Rhizophagus formed perfect hyphal fusions, with frequencies ranging from 9.29?±?3.01 to 79.84?±?4.39 % within the same germling and from 14.02?±?7.36 to 91.41?±?3.92 % between different germlings. Rare fusions, occurring within the same hypha, were detected in Gigaspora species, and no anastomoses were observed in Scutellospora species. The consistent detection of nuclei in perfect fusions suggests that nuclear migration is active both within and between germlings. Present data on anastomosis formation, nuclear migration and germling viability in tropical isolates of AMF widen our knowledge on the extensive and consistent occurrence of successful hyphal fusions in this group of beneficial symbionts. The ability to anastomose and establish protoplasm flow, fundamental for the maintenance of physiological and genetic continuity, may produce important fitness consequences for the obligately biotrophic AMF.     

Spatial distribution and turnover of root-derived carbon in alfalfa rhizosphere depending on top- and subsoil properties and mycorrhization

Aims

This study analyzed the extent to which root exudates diffuse from the root surface towards the soil depending on topsoil and subsoil properties and the effect of arbuscular mycorrhizal fungal hyphae on root-derived C distribution in the rhizosphere.

Methods

Alfalfa was grown in three-compartment pots. Nylon gauze prevented either roots alone or roots and arbuscular mycorrhizal fungal hyphae from penetrating into the rhizosphere compartments. ¹⁴CO₂ pulse labeling enabled the measurement of ¹⁴C-labeled exudates in dissolved (DOC) and total organic carbon (TOC) in the rhizosphere, distributed either by diffusion alone or by diffusion, root hair and hyphal transport.

Results

Root exudation and microbial decomposition of exudates was higher in the rhizosphere with topsoil compared to subsoil properties. Exudates extended over 28 mm (DOC) and 20 mm (TOC). Different soil properties and mycorrhization, likely caused by the low arbuscular mycorrhizal colonization of roots (13?±?4 % (topsoil properties) and 18?±?5 % (subsoil properties)), had no effect.

Conclusions

Higher microbial decomposition compensated for higher root exudation into the rhizosphere with topsoil properties, which resulted in equal exudate extent when compared to the rhizosphere with subsoil properties. Higher ¹⁴C activity used for labeling compared with previous studies enabled the detection of low exudate concentrations at longer distances from the root surface.     

Atomic Force Microscopy of the fungi-mineral interface: applications in mineral dissolution, weathering and biogeochemistry

The interaction between mycorrhizal fungi and minerals is of fundamental importance in affecting the geochemical carbon cycle and CO(2) concentration in the atmosphere, alongside roles in soil creation and the release of nutrients. The symbiosis between the fungi and the plant, supported by photosynthesis in the host plant, has as one of its key features the interfacial zone where mineral and fungi come into contact. At this interface, the organism exudes a complex mixture of organic acids, chelating molecules, protons, and extracellular polysaccharide. In this review, examples will be given of recent Atomic Force Microscopy experiments to monitor the colonization of phyllosilicate minerals in sterile controlled microcosm environments containing only tree seedlings, mineral chips and mycorrhizal fungi. The surface activity of the colonizing fungal hyphae is extensive and complex. In complementary experiments involving exposure of minerals surfaces to single organic acids, it has been possible to monitor dissolution at the unit cell level and to extract activation energies for specific dissolution processes, for example 49kJmol(-1) for 100mM oxalic acid acting upon a biotite sample. The link between these simpler model experiments and the whole microcosm studies is illustrated partly by observations of fungal-colonized mineral surfaces from microcosms after careful removal of the organism and biolayer. These mineral surfaces give clear indications of basal plane modification and fungal weathering.     

Nitrogen Uptake by Trees and Mycorrhizal Fungi in a Successional Northern Temperate Forest: Insights from Multiple Isotopic Methods

Forest succession may cause changes in nitrogen (N) availability, vegetation and fungal community composition that affect N uptake by trees and their mycorrhizal symbionts. Understanding how these changes affect the functioning of the mycorrhizal symbiosis is of interest to ecosystem ecology because of the fundamental roles mycorrhizae play in providing nutrition to trees and structuring forest ecosystems. We investigated changes in tree and mycorrhizal fungal community composition, the availability and uptake of N by trees and mycorrhizal fungi in a forest undergoing a successional transition (age-related loss of early successional tree taxa). In this system, 82–96% of mycorrhizal hyphae were ectomycorrhizal (EM). As biomass production of arbuscular mycorrhizal (AM) trees increased, AM hyphae comprised a significantly greater proportion of total fungal hyphae, and the EM contribution to the N requirement of EM-associated tree taxa declined from greater than 75% to less than 60%. Increasing N availability was associated with lower EM hyphal foraging and ¹⁵N tracer uptake, yet the EM-associated later-successional species Quercus rubra was nonetheless a stronger competitor for ¹⁵N than AM-associated Acer rubrum, likely due to the more extensive nature of the persistent EM hyphal network. These results indicate that successional increases in N availability and co-dominance by AM-associated trees have increased the importance of AM fungi in the mycorrhizal community, while down-regulating EM N acquisition and transfer processes. This work advances understanding of linkages between tree and fungal community composition, and indicates that successional changes in N availability may affect competition between tree taxa with divergent resource acquisition strategies.     

Interactions between biochar and mycorrhizal fungi in a water-stressed agricultural soil

Biochar may alleviate plant water stress in association with arbuscular mycorrhizal (AM) fungi but research has not been conclusive. Therefore, a glasshouse experiment was conducted to understand how interactions between AM fungi and plants respond to biochar application under water-stressed conditions. A twin chamber pot system was used to determine whether a woody biochar increased root colonisation by a natural AM fungal population in a pasture soil (‘field’ chamber) and whether this was associated with increased growth of extraradical AM fungal hyphae detected by plants growing in an adjacent (‘bait’) chamber containing irradiated soil. The two chambers were separated by a mesh that excluded roots. Subterranean clover was grown with and without water stress and harvested after 35, 49 and 63 days from each chamber. When biochar was applied to the field chamber under water-stressed conditions, shoot mass increased in parallel with mycorrhizal colonisation, extraradical hyphal length and shoot phosphorus concentration. AM fungal colonisation of roots in the bait chamber indicated an increase in extraradical mycorrhizal hyphae in the field chamber. Biochar had little effect on AM fungi or plant growth under well-watered conditions. The biochar-induced increase in mycorrhizal colonisation was associated with increased growth of extraradical AM fungal hyphae in the pasture soil under water-stressed conditions.     

Tip growth of <Emphasis Type="Italic">Neurospora crassa</Emphasis> upon resource shortage: Disturbances of the coordination of elongation,branching, and septation

The characteristics of elongation, branching, septation, and nuclear morphology in hyphal tips (of ~400 μm in length) of the mycelial fungus Neurospora crassa isolated from the mycelium and cultivated for several hours have been investigated using intracellular fluorescent markers. The newly formed branches had the following characteristic features: (1) the predefined orientation was conserved, whereas the diameter decreased (from 10–20 to 6.5 ± 0.4 μm), as did the elongation rate (from 24 ± 1 to 6.7 ± 0.5 μm/min); (2) a disturbed branching pattern with abnormally large internodal distances (up to 1471 μm) and developmental arrest of part of the buds of lateral branches; and (3) a conserved septation pattern and a relatively constant length of hyphal segments (68 ± 2 μm). The size of the nucleus-free zone at the tip (5–33 μm) and the distance between the first septum and the growth point (210 ± 15 μm) in the daughter branches of the isolated fragments were almost the same as in hyphae connected to the mycelium, whereas the average distance between the growth point and the first lateral branch (492 ± 127 μm) and the variability of this parameter were higher in the isolated fragments. The morphology of the nuclei and the size of the nucleus-free zone near the growth point did not differ from those reported for normal vegetative hyphae of N. crassa. The experimental model developed may be used for the elucidation of details of molecular genetic mechanisms that underlie the regulation of interactions between the intracellular structures that provide tip growth of the hyphae in N. crassa.     

Mutations Affecting Hyphal Colonization and Pyoverdine Production in Pseudomonads Antagonistic toward Phytophthora parasitica

In previous studies, Pseudomonas putida 06909 and Pseudomonas fluorescens 09906 suppressed populations of Phytophthora parasitica in the citrus rhizosphere, suggesting that these bacteria may be useful in biological control of citrus root rot. In this study we investigated the mechanisms of antagonism between the bacteria and the fungus. Both bacteria colonized Phytophthora hyphae and inhibited the fungus on agar media. A hyphal column assay was developed to measure the colonization of bacteria on fungal hyphae and to enrich for colonization-deficient mutants. In this way we identified Tn5 mutants of each pseudomonad that were not able to colonize the hyphae and inhibit fungal growth in vitro. Colonization-deficient mutants were nonmotile and lacked flagella. Survival of nonmotile mutants in a citrus soil was similar to survival of a random Tn5 mutant over a 52-day period. Additional screening of random Tn5 mutants of both pseudomonads for loss of fungal inhibition in vitro yielded two distinct types of mutants. Mutants of the first type were deficient in production of pyoverdines and in inhibition of the fungus in vitro, although they still colonized fungal hyphae. Mutants of the second type lacked flagella and were not able to colonize the hyphae or inhibit fungal growth. No role was found for antibiotic production by the two bacteria in the inhibition of the fungus. Our results suggest that both hyphal colonization and pyoverdine production are important in the inhibition of Phytophthora parasitica by P. fluorescens and P. putida in vitro.     

Calcium homeostasis is required for contact-dependent helical and sinusoidal tip growth in Candida albicans hyphae

Hyphae of the dimorphic fungus, Candida albicans , exhibit directional tip responses when grown in contact with surfaces. On hard surfaces or in liquid media, the trajectory of hyphal growth is typically linear, with tip re-orientation events limited to encounters with topographical features (thigmotropism). In contrast, when grown on semisolid surfaces, the tips of C. albicans hyphae grow in an oscillatory manner to form regular two-dimensional sinusoidal curves and three-dimensional helices. We show that, like thigmotropism, initiation of directional tip oscillation in C. albicans hyphae is severely attenuated when Ca²⁺ homeostasis is perturbed. Chelation of extracellular Ca²⁺ or deletion of the Ca²⁺ transporters that modulate cytosolic [Ca²⁺] (Mid1, Cch1 or Pmr1) did not affect hyphal length but curve formation was severely reduced in mid1 Δ and cch1 Δ and abolished in pmr1 Δ. Sinusoidal hypha morphology was altered in the mid1 Δ, chs3 Δ and heterozygous pmr1 Δ/ PMR1 strains. Treatments that affect cell wall integrity, changes in surface mannosylation or the provision of additional carbon sources had significant but less pronounced effects on oscillatory growth. The induction of two- and three-dimensional sinusoidal growth in wild-type C. albicans hyphae is therefore the consequence of mechanisms that involve Ca²⁺ influx and signalling rather than gross changes in the cell wall architecture.     

Anatomy and mycotrophy of the achlorophyllous Afrothismia winkleri

Afrothismia winkleri develops fleshy rhizomes, densely covered with small root tubercles, narrowing to filiform roots with age. The exclusively intracellular mycorrhizal fungus has distinct morphologies in different tissues of the plant. In the filiform root the hyphae grow straight and vesicles are borne on short hyphal stalks. The straight hyphae are present in the epidermis of the root tubercles, but change to loosely coiled and swollen hyphae in the rhizome tissue. No penetration from epidermis to root cortex was found. From the rhizome, a separating cell layer permits only one or rarely two hyphal penetrations into the cortex of each root tubercle. The hyphae proceed apically within the root hypodermis in a spiral row of distinctively coiled hyphae, branches of which colonize the inner root cortex. In the inner root cortex the hyphal coils degenerate to amorphous clumps. In older roots the cortex itself also deteriorates, but epidermis, hypodermis, endodermis and central cylinder persist. The mycorrhizal pattern in A. winkleri is interpreted as an elaborate exploitation system whereby the fungus provides carbon and nutrients to the plant and, simultaneously but spatially distinct, its hyphae are used to translocate and store the matter within the plant. Several features indicate that the endophyte is an arbuscular mycorrhizal fungus.     

Mycorrhizal mediation of plant N acquisition and residue decomposition: Impact of mineral N inputs

Mycorrhizas are ubiquitous plant–fungus mutualists in terrestrial ecosystems and play important roles in plant resource capture and nutrient cycling. Sporadic evidence suggests that anthropogenic nitrogen (N) input may impact the development and the functioning of arbuscular mycorrhizal (AM) fungi, potentially altering host plant growth and soil carbon (C) dynamics. In this study, we examined how mineral N inputs affected mycorrhizal mediation of plant N acquisition and residue decomposition in a microcosm system. Each microcosm unit was separated into HOST and TEST compartments by a replaceable mesh screen that either prevented or allowed AM fungal hyphae but not plant roots to grow into the TEST compartments. Wild oat (Avena fatua L.) was planted in the HOST compartments that had been inoculated with either a single species of AM fungus, Glomus etunicatum, or a mixture of AM fungi including G. etunicatum. Mycorrhizal contributions to plant N acquisition and residue decomposition were directly assessed by introducing a mineral ¹⁵N tracer and ¹³C‐rich residues of a C₄ plant to the TEST compartments. Results from ¹⁵N tracer measurements showed that AM fungal hyphae directly transported N from the TEST soil to the host plant. Compared with the control with no penetration of AM fungal hyphae, AM hyphal penetration led to a 125% increase in biomass ¹⁵N of host plants and a 20% reduction in extractable inorganic N in the TEST soil. Mineral N inputs to the HOST compartments (equivalent to 5.0 g N m^?2 yr^?1) increased oat biomass and total root length colonized by mycorrhizal fungi by 189% and 285%, respectively, as compared with the no‐N control. Mineral N inputs to the HOST plants also reduced extractable inorganic N and particulate residue C proportion by 58% and 12%, respectively, in the corresponding TEST soils as compared to the no‐N control, by stimulating AM fungal growth and activities. The species mixture of mycorrhizal fungi was more effective in facilitating N transport and residue decomposition than the single AM species. These findings indicate that low‐level mineral N inputs may significantly enhance nutrient cycling and plant resource capture in terrestrial ecosystems via stimulation of root growth, mycorrhizal functioning, and residue decomposition. The long‐term effects of these observed alterations on soil C dynamics remain to be investigated.     

Arbuscular mycorrhizal phosphate transport under monoxenic conditions using radio-labelled inorganic and organic phosphate

Compartmented monoxenic cultures of Ri T-DNA transformed carrot roots and a symbiotic arbuscular mycorrhizal fungus demonstrated for the first time that phosphate in an organic form (³²P-labelled AMP) may be hydrolysed by extra-radical mycorrhizal hyphae in the absence of other organisms, and subsequently utilized as a mineral nutrient source by the host plant after fungal transport.     

The role of the motile tubular vacuole system in mycorrhizal fungi

Mycorrhizal fungi, to be effective for the plant, must be able to transfer mineral nutrient elements from sites of uptake at hyphal tips across various distances to the exchange region in the mycorrhiza. Vacuoles are likely to be important in this transport, since they contain elements of nutritional significance in abundance. In tip cells of hyphae of most fungi –- known to include three ectomycorrhizal basidiomycetes, an ericoid mycobiont, and two arbuscular mycorrhizal fungi –- the vacuoles form a motile tubular reticulum. The vacuoles are most active in hyphal tips, but non-motile vacuoles at a distance from the tip can be induced to become motile by environmental changes. Neither the tubular vacuolar reticulum nor its contents are properly preserved by conventional fixation and embedding. Vacuolar tubules are readily shown in vivo with fluorescent tracers, throughout the extramatrical mycelium and in outer hyphae of the sheath in eucalypt mycorrhizas synthesised with Pisolithus sp., but they have proved harder to label in field-collected ectomycorrhizas and ericoid mycorrhizas. Freeze-substitution does preserve the structure of vacuoles and vacuolar tubules, and careful anhydrous techniques allow them to be microanalysed, indicating high content of K and P in vacuoles of hyphal tips, and also in sheath and Hartig net of ectomycorrhizas. Vacuoles contain polyphosphate in diffuse, non-granular form. Polyphosphate is present right up to the tip region of hyphae as well as in sheath and Hartig net: thus important mineral nutrient elements are present at both ends of the long hyphal transport pathway. Exactly what happens in between, however, remains to be elucidated.     

Different levels of hyphal self-incompatibility modulate interconnectedness of mycorrhizal networks in three arbuscular mycorrhizal fungi within the Glomeraceae

Arbuscular mycorrhizal fungi (AMF) live in symbiosis with most plant species and produce underground extraradical hyphal networks functional in the uptake and translocation of mineral nutrients from the soil to host plants. This work investigated whether fungal genotype can affect patterns of interconnections and structural traits of extraradical mycelium (ERM), by comparing three Glomeraceae species growing in symbiosis with five plant hosts. An isolate of Funneliformis coronatus consistently showed low ability to form interconnected ERM and self-incompatibility that represented up to 21 % of hyphal contacts. The frequency of post-fusion self-incompatible interactions, never detected before in AMF extraradical networks, was 8.9 %. In F. coronatus ERM, the percentage of hyphal contacts leading to perfect hyphal fusions was 1.2–7.7, while it ranged from 25.8–48 to 35.6–53.6 in Rhizophagus intraradices and Funneliformis mosseae, respectively. Low interconnectedness of F. coronatus ERM resulted also from a very high number of non-interacting contacts (83.2 %). Such findings show that AMF genotypes in Glomeraceae can differ significantly in anastomosis behaviour and that ERM interconnectedness is modulated by the fungal symbiont, as F. coronatus consistently formed poorly interconnected networks when growing in symbiosis with five different host plants and in the asymbiotic stage. Structural traits, such as extent, density and hyphal self-compatibility/incompatibility, may represent key factors for the differential performance of AMF, by affecting fungal absorbing surface and foraging ability and thus nutrient flow from soil to host roots.     

Resolving the ‘nitrogen paradox’ of arbuscular mycorrhizas: fertilization with organic matter brings considerable benefits for plant nutrition and growth

Arbuscular mycorrhizal fungi (AMF) can transfer nitrogen (N) to host plants, but the ecological relevance is debated, as total plant N and biomass do not generally increase. The extent to which the symbiosis is mutually beneficial is thought to rely on the stoichiometry of N, phosphorus (P) and carbon (C) availability. While inorganic N fertilization has been shown to elicit strong mutualism, characterized by improved plant and fungal growth and mineral nutrition, similar responses following organic N addition are lacking. Using a compartmented microcosm experiment, we determined the significance to a mycorrhizal plant of placing a ¹⁵N‐labelled, nitrogen‐rich patch of organic matter in a compartment to which only AMF hyphae had access. Control microcosms denied AMF hyphal access to the patch compartment. When permitted access to the patch compartment, the fungus proliferated extensively in the patch and transferred substantial quantities of N to the plant. Moreover, our data demonstrate that allowing hyphal access to an organic matter patch enhanced total plant N and P contents, with a simultaneous and substantial increase in plant biomass. Furthermore, we demonstrate that organic matter fertilization of arbuscular mycorrhizal plants can foster a mutually beneficial symbiosis based on nitrogen transfer, a phenomenon previously thought irrelevant.