Extraradical Hyphae Of Arbuscular Mycorrhizal Fungi Research Articles

Soil patch heterogeneity improves plant productivity and nutrients regulated by arbuscular mycorrhizal fungi

AbstractThe interlacing and mosaic distribution of karst soil and rock result in the high spatial heterogeneity of the natural karst habitat. Karst plants are suffered from spatially heterogeneous microhabitats with different‐sized patches. Arbuscular mycorrhizal (AM) fungi are crucial in regulating plant productivity and nutrients in heterogeneous karst environments. However, how spatial patch heterogeneity influences plant productivity and nutrient utilization by AM fungi regulation in karst soil remains unclear. A simulated heterogeneity experiment regarding soil grid patches was conducted by planting Bidens pilosa into a microcosm of a square device. Experimental treatments included the mycorrhizal fungus treatments inoculation with (M+) or non‐inoculation with (M−) Glomus etunicatum fungus, and the spatial heterogeneity treatments involved homogeneous patches (HO), heterogeneity‐small patches (HS), and heterogeneity‐large patches (HL). The growth and nutritional traits of plants were analyzed. The results showed that AM fungus promoted the productivity and nutrient uptake of B. pilosa by substantial increases in biomass, nitrogen (N) accumulation, phosphorus (P) accumulation, and N/P ratio. The spatial heterogeneity promoted the biomass and N and P accumulations of B. pilosa when inoculating with AM fungus. The mycorrhizal colonization rate and hyphae length were greater in HS than in HO and HL under the M+ treatment, with a greater response ratio of biomass, N and P under HS conditions. These indicated that the heterogeneous small patches had a greater promotion of the biomass production and nutrients of B. pilosa with inoculation of AM fungus because extensive fungal hyphae can acquire soil resources in more distant patches outside the root zone with more economical metabolic costs compared to roots. We thus conclude that patch heterogeneity contributes to plant productivity and nutrient utilization regulated by AM fungi in karst soil, and the broader nutrient capture induced by extraradical hyphae of AM fungi may be an adaptive mechanism for karst plants to cope with heterogeneous environmental conditions.

Parasitic plants indirectly regulate decomposition of soil organic matter

Abstract Parasitic plants have been shown to affect soil‐organic‐matter (SOM) decomposition, but the mechanism is unknown. As arbuscular mycorrhizal fungi (AMF) can affect decomposition and compete with parasitic plants for carbon, we hypothesized that parasitic plants can indirectly regulate SOM decomposition by suppressing the effects of AMF on decomposition. To test this hypothesis, we conducted two container experiments in which the herbaceous plant Bidens pilosa was inoculated with the AMF Rhizophagus intraradices or not, and Cuscuta australis or not. In one experiment, we provided SOM within hyphae‐in‐growth bags as 13C‐/15 N‐labelled maize leaves and in the other experiment as phytate‐P. We assessed growth and nutrient uptake of B. pilosa, growth of C. australis, the SOM remaining in the hyphae‐in‐growth bags, and the bacterial communities. Parasitization increased the 13C and decreased the organic P remaining in the bags, but only in the presence of the extraradical AMF hyphae. AMF decreased the 13C and increased the organic P remaining in the absence of the parasite, but not in the presence of the parasite. Our results demonstrate that parasitic plants can regulate the decomposition of organic materials indirectly by suppressing the effect of the extraradical AMF hyphae on decomposition. In other words, parasitic plants can regulate SOM decomposition indirectly via a multitrophic cascading effect. Our study helps to unravel the mechanisms of a sophisticated hidden ecological process, and is an important step forward in elucidating the roles of parasitic plants in soil nutrient cycling. Read the free Plain Language Summary for this article on the Journal blog.

Arbuscular mycorrhizal fungi outcompete fine roots in determining soil multifunctionality and microbial diversity in a desert ecosystem

Fine roots and mycorrhizal fungi play a crucial role in soil nutrient cycling and microbial processes. However, the importance of the symbioses between fine roots and arbuscular mycorrhizal fungi (AMF) in different plant functional groups to maintain soil multifunctionality (the ability to provide multiple functions and services) and microbial diversity remains unclear, especially in desert ecosystems. In this study, we conducted an ingrowth core experiment on three vegetation types, namely shrub-dominated, grass-dominated, and mixed vegetation communities, in the Mu Us Desert, northern China, to investigate the importance of fine roots and mycorrhizal fungi in shaping soil nutrient composition and microbiome. Furthermore, we detected the relationships among AMF-related inputs [extraradical AMF hyphae and glomalin-related soil protein (GRSP)], soil multifunctionality, and soil microbial diversity. We found that most of the soil properties associated with nutrient cycling and microbial community composition and diversity varied among the three vegetation types, but were not significantly different between distinct ingrowth core treatments with fine root and hyphal access. AMF-related inputs, especially the easily extractable GRSP, were the most important determinants of soil multifunctionality and microbial community diversity across the shrub and grass communities, while the changes in soil multifunctionality and microbial diversity were inconsistent with the trend of fine root biomass. Moreover, AMF-related inputs were positively correlated with soil nutrients, particularly soil organic carbon (SOC). In contrast to the minimal negative correlation between SOC and soil microbial richness, soil multifunctionality was positively correlated with SOC. These findings support the role of AMF in shaping soil multifunctionality and microbial diversity by stabilizing SOC in a desert ecosystem, regardless of the fine root accessibility of plant functional groups. Therefore, this study improved our understanding of plant-derived carbon in the soil and its effects on the induction of soil abiotic and biotic processes in resource-limited ecosystems.

Metabolite profiling of the hyphal exudates of Rhizophagus clarus and Rhizophagus irregularis under phosphorus deficiency.

Arbuscular mycorrhizal (AM) fungal extraradical hyphae exude their metabolites into the soil. Root exudate metabolites are affected by plant species and P status. However, the effect of P status on AM hyphal exudate metabolites has been unknown. This study aimed to examine hyphal exudate metabolite composition of two AM fungal species and their response to P deficiency through metabolite profiling. Rhizophagus clarus and R. irregularis were grown in a two-compartment in vitro culture system of Linum usitatissimum roots on solid modified Strullu-Romand medium in combination with two P levels (3µM (P3) and 30µM (P30)). Hyphal exudates were collected from the hyphal compartment at 118days after inoculation (DAI). The metabolite composition of the hyphal exudates was determined by capillary electrophoresis/time-of-flight mass spectrometry, resulting in the identification of a total of 141 metabolites at 118 DAI. In the hyphal exudates of R. clarus, the concentrations of 18 metabolites, including sugars, amino acids, and organic acids, were significantly higher (p<0.05) under P3 than under P30 conditions. In contrast, the concentrations of 10 metabolites, including sugar and amino acids, in the hyphal exudates of R. irregularis were significantly lower (p<0.05) under P3 than under P30 conditions. These findings suggest that the extraradical hyphae of AM fungi exude diverse metabolites of which concentrations are affected by P conditions and differ between AM fungal species.

Arbuscular mycorrhizal fungi enhance mineralisation of organic phosphorus by carrying bacteria along their extraradical hyphae.

Arbuscular mycorrhizal (AM) fungi gain access to nutrient patches outside the rhizosphere by producing an extensive network of fine hyphae. Here, we focused on establishing the mechanism by which AM fungal hyphae reach discrete organic patches with a cohort of functional bacteria transported in a biofilm on their surface. We investigated the mechanisms and impact of the translocation of phosphate solubilising bacteria (PSB) along AM fungal hyphae in bespoke microcosms. An in vitro culture experiment was also conducted to determine the direct impact of hyphal exudates of AM fungi upon the growth of PSB. The extraradical hyphae of AM fungi can transport PSB to organic phosphorus (P) patches and enhance organic P mineralisation both under in vitro culture and soil conditions. Bacteria move in a thick water film formed around fungal hyphae. However, the bacteria cannot be transferred to the organic P patch without an energy source in the form of hyphal exudates. Our results could be harnessed to better manage plant-microbe interactions and improve the ability of biological inocula involving AM fungi and bacteria to enhance the sustainability of agricultural crops in P limited conditions.

Secretion of acid phosphatase from extraradical hyphae of the arbuscular mycorrhizal fungus Rhizophagus clarus is regulated in response to phosphate availability.

Arbuscular mycorrhizal (AM) fungi increase phosphate (P) uptake by plants. Organic phosphate comprises 30-80% of total P in most agricultural soils. Some plants can utilize organic phosphate by secreting acid phosphatase (ACP) from their roots, especially under low P conditions. Although secretion of ACP from extraradical hyphae of AM fungi has been reported, the specific factors that affect the secretion of ACP are unknown. The objective of the present study was to investigate whether secretion of ACP from extraradical hyphae is induced by low P conditions. First, specimens of Allium fistulosum were either inoculated with the AM fungus Rhizophagus clarus strain CK001 or remained uninoculated and were grown in soil with 0.5 g P2O5 kg-1 soil or without P fertilization using two-compartment pots. Soil solution was collected using mullite ceramic tubes 45 days after sowing. The soil solution was analyzed for ACP activity by using p-nitrophenylphosphate. Second, Ri T-DNA transformed roots (i.e., hairy roots) of Linum usitatissimum inoculated with R. clarus were grown on solid minimal media with two P levels applied (3 and 30 μM P) using two-compartment Petri dishes under in vitro conditions. Hyphal exudates, extraradical hyphae, and hairy roots were collected and analyzed for ACP activity. ACP activity in the soil solution of the hyphal compartment in the A. fistulosum inoculation treatment was higher without P fertilization than with P fertilization. AM colonization also was higher without P fertilization than with P fertilization. In the in vitro two-compartment culture, ACP activity of hyphal exudates and extraradical hyphae were higher under the 3-μM treatment than under the 30-μM treatment. These findings suggest that the secretion of ACP from the extraradical hyphae of R. clarus into the hyphosphere is promoted under low P conditions.

Tall Fescue and E. coenophiala Genetics Influence Root-Associated Soil Fungi in a Temperate Grassland.

A constitutive, host-specific symbiosis exists between the aboveground fungal endophyte Epichloë coenophiala (Morgan-Jones & W. Gams) and the cool-season grass tall fescue (Lolium arundinaceum (Schreb.) Darbysh.), which is a common forage grass in the United States, Australia, New Zealand, and temperate European grasslands. New cultivars of tall fescue are continually developed to improve pasture productivity and animal health by manipulating both grass and E. coenophiala genetics, yet how these selected grass-endophyte combinations impact other microbial symbionts such as mycorrhizal and dark septate fungi remains unclear. Without better characterizing how genetically distinct grass-endophyte combinations interact with belowground microorganisms, we cannot determine how adoption of new E. coenophiala-symbiotic cultivars in pasture systems will influence long-term soil characteristics and ecosystem function. Here, we examined how E. coenophiala presence and host × endophyte genetic combinations control root colonization by belowground symbiotic fungi and associated plant nutrient concentrations and soil properties in a 2-year manipulative field experiment. We used four vegetative clone pairs of tall fescue that consisted of one endophyte-free (E−) and one E. coenophiala-symbiotic (E+) clone each, where E+ clones within each pair contained one of four endophyte genotypes: CTE14, CTE45, NTE16, or NTE19. After 2 years of growth in field plots, we measured root colonization of arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE), extraradical AMF hyphae in soil, total C, N, and P in root and shoot samples, as well as C and N in associated soils. Although we observed no effects of E. coenophiala presence or symbiotic genotype on total AMF or DSE colonization rates in roots, different grass-endophyte combinations altered AMF arbuscule presence and extraradical hyphal length in soil. The CTE45 genotype hosted the fewest AMF arbuscules regardless of endophyte presence, and E+ clones within NTE19 supported significantly greater soil extraradical hyphae compared to E− clones. Because AMF are often associated with improved soil physical characteristics and C sequestration, our results suggest that development and use of unique grass-endophyte combinations may cause divergent effects on long-term ecosystem properties.

Little Cross-Feeding of the Mycorrhizal Networks Shared Between C3-Panicum bisulcatum and C4-Panicum maximum Under Different Temperature Regimes.

Common mycorrhizal networks (CMNs) formed by arbuscular mycorrhizal fungi (AMF) interconnect plants of the same and/or different species, redistributing nutrients and draining carbon (C) from the different plant partners at different rates. Here, we conducted a plant co-existence (intercropping) experiment testing the role of AMF in resource sharing and exploitation by simplified plant communities composed of two congeneric grass species (Panicum spp.) with different photosynthetic metabolism types (C3 or C4). The grasses had spatially separated rooting zones, conjoined through a root-free (but AMF-accessible) zone added with 15N-labeled plant (clover) residues. The plants were grown under two different temperature regimes: high temperature (36/32°C day/night) or ambient temperature (25/21°C day/night) applied over 49 days after an initial period of 26 days at ambient temperature. We made use of the distinct C-isotopic composition of the two plant species sharing the same CMN (composed of a synthetic AMF community of five fungal genera) to estimate if the CMN was or was not fed preferentially under the specific environmental conditions by one or the other plant species. Using the C-isotopic composition of AMF-specific fatty acid (C16:1ω5) in roots and in the potting substrate harboring the extraradical AMF hyphae, we found that the C3-Panicum continued feeding the CMN at both temperatures with a significant and invariable share of C resources. This was surprising because the growth of the C3 plants was more susceptible to high temperature than that of the C4 plants and the C3-Panicum alone suppressed abundance of the AMF (particularly Funneliformis sp.) in its roots due to the elevated temperature. Moreover, elevated temperature induced a shift in competition for nitrogen between the two plant species in favor of the C4-Panicum, as demonstrated by significantly lower 15N yields of the C3-Panicum but higher 15N yields of the C4-Panicum at elevated as compared to ambient temperature. Although the development of CMN (particularly of the dominant Rhizophagus and Funneliformis spp.) was somewhat reduced under high temperature, plant P uptake benefits due to AMF inoculation remained well visible under both temperature regimes, though without imminent impact on plant biomass production that actually decreased due to inoculation with AMF.

Aboveground Epichloë coenophiala-Grass Associations Do Not Affect Belowground Fungal Symbionts or Associated Plant, Soil Parameters.

Cool season grasses host multiple fungal symbionts, such as aboveground Epichloë endophytes and belowground arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSEs). Asexual Epichloë endophytes can influence root colonization by AMF, but the type of interaction-whether antagonistic or beneficial-varies. In Schedonorus arundinaceus (tall fescue), Epichloë coenophiala can negatively affect AMF, which may impact soil properties and ecosystem function. Within field plots of S. arundinaceus that were either E. coenophiala-free (E-), infected with the common, mammal-toxic E. coenophiala strain (CTE+), or infected with one of two novel, non-toxic strains (AR542 NTE+ and AR584 NTE+), we hypothesized that (1) CTE+ would decrease AMF and DSE colonization rates and reduce soil extraradical AMF hyphae compared to E- or NTE+, and (2) this would lead to E- and NTE+ plots having greater water stable soil aggregates and C than CTE+. E. coenophiala presence and strain did not significantly alter AMF or DSE colonization, nor did it affect extraradical AMF hypha length, soil aggregates, or aggregate-associated C and N. Soil extraradical AMF hypha length negatively correlated with root AMF colonization. Our results contrast with previous demonstrations that E. coenophiala symbiosis inhibits belowground AMF communities. In our mesic, relatively nutrient-rich grassland, E. coenophiala symbiosis did not antagonize belowground symbionts, regardless of strain. Manipulating E. coenophiala strains within S. arundinaceus may not significantly alter AMF communities and nutrient cycling, yet we must further explore these relationships under different soils and environmental conditions given that symbiont interactions can be important in determining ecosystem response to global change.

Species specific responses of common grassland plants to a generalist root herbivore (Agriotes spp. larvae)

Insect root herbivores can alter plant community structure by affecting the competitive ability of single plants. Our study aims at increasing knowledge on the impact of click beetle larvae (Elateridae, genus Agriotes) on grassland plant communities, by determining biomass responses as well as responses of the arbuscular mycorrhizal fungi (AMF) symbiosis to this widespread generalist root herbivore for eight common grassland plant species (Festuca rubra, Holcus lanatus, Poa pratensis, Achillea millefolium, Plantago lanceolata, Veronica arvensis, Medicago lupulina, Trifolium repens), belonging to three functional groups (grasses, herbs, legumes).The presence of larvae in the rhizosphere of individual plants had an overall negative effect on root biomass, which varied in degree between plant species, with more root biomass being removed from larger root systems. The effect of larvae on shoot biomass, total plant biomass and shoot/root ratio also differed in strength between plant species. Relative changes in root and total plant biomass ranged from a 71% and 55% loss, respectively, in V. arvensis to an 11% and 1% increase in T. repens, but were not related to root- or plant size. Root colonization by AMF and the length of extraradical AMF hyphae were not affected by larvae. The plant's functional group did not determine the response of the plant to feeding by larvae. Growth of larvae was positively correlated with root biomass, but did not depend on plant species or group identity.The results confirm the generalist nature of Agriotes spp. larvae, which depend on sufficient root quantity and are likely to feed most on those plant species whose roots are most abundant in their habitat. Their effect on the plant community may be generated through the ability of the respective plant species to cope with the herbivore damage, with tolerances being plant species rather than plant group specific.

Direct and indirect influences of 8 yr of nitrogen and phosphorus fertilization on Glomeromycota in an alpine meadow ecosystem

We measured the influences of soil fertility and plant community composition on Glomeromycota, and tested the prediction of the functional equilibrium hypothesis that increased availability of soil resources will reduce the abundance of arbuscular mycorrhizal (AM) fungi. Communities of plants and AM fungi were measured in mixed roots and in Elymus nutans roots across an experimental fertilization gradient in an alpine meadow on the Tibetan Plateau. As predicted, fertilization reduced the abundance of Glomeromycota as well as the species richness of plants and AM fungi. The response of the glomeromycotan community was strongly linked to the plant community shift towards dominance by Elymus nutans. A reduction in the extraradical hyphae of AM fungi was associated with both the changes in soil factors and shifts in the plant community composition that were caused by fertilization. Our findings highlight the importance of soil fertility in regulating both plant and glomeromycotan communities, and emphasize that high fertilizer inputs can reduce the biodiversity of plants and AM fungi, and influence the sustainability of ecosystems.

Characterisation of microbial communities colonising the hyphal surfaces of arbuscular mycorrhizal fungi

Arbuscular mycorrhizal fungi (AMF) are symbiotic soil fungi that are intimately associated with the roots of the majority of land plants. They colonise the interior of the roots and the hyphae extend into the soil. It is well known that bacterial colonisation of the rhizosphere can be crucial for many pathogenic as well as symbiotic plant-microbe interactions. However, although bacteria colonising the extraradical AMF hyphae (the hyphosphere) might be equally important for AMF symbiosis, little is known regarding which bacterial species would colonise AMF hyphae. In this study, we investigated which bacterial communities might be associated with AMF hyphae. As bacterial-hyphal attachment is extremely difficult to study in situ, we designed a system to grow AMF hyphae of Glomus intraradices and Glomus proliferum and studied which bacteria separated from an agricultural soil specifically attach to the hyphae. Characterisation of attached and non-attached bacterial communities was performed using terminal restriction fragment length polymorphism and clone library sequencing of 16S ribosomal RNA (rRNA) gene fragments. For all experiments, the composition of hyphal attached bacterial communities was different from the non-attached communities, and was also different from bacterial communities that had attached to glass wool (a non-living substratum). Analysis of amplified 16S rRNA genes indicated that in particular bacteria from the family of Oxalobacteraceae were highly abundant on AMF hyphae, suggesting that they may have developed specific interactions with the fungi.

Effects of the mycorrhizal fungus Glomus intraradices on uranium uptake and accumulation by Medicago truncatula L. from uranium-contaminated soil

Phytostabilization strategies may be suitable to reduce the dispersion of uranium (U) and the overall environmental risks of U-contaminated soils. The role of Glomus intraradices, an arbuscular mycorrhizal (AM) fungus, in such phytostabilization of U was investigated with a compartmented plant cultivation system facilitating the specific measurement of U uptake by roots, AM roots and extraradical hyphae of AM fungi and the measurement of U partitioning between root and shoot. A soil-filled plastic pot constituted the main root compartment (CA) which contained a plastic vial filled with U-contaminated soil amended with 0, 50 or 200 mg KH2PO4−P kg–1soil (CB). The vial was sealed by coarse or fine nylon mesh, permitting the penetration of both roots and hyphae or of just hyphae. Medicago truncatula plants grown in CA were inoculated with G. intraradices or remained uninoculated. Dry weight of shoots and roots in CA was significantly increased by G. intraradices, but was unaffected by mesh size or by P application in CB. The P amendments decreased root colonization in CB, and increased P content and dry weight of those roots. Glomus intraradices increased root U concentration and content in CA, but decreased shoot U concentrations. Root U concentrations and contents were significantly higher when only hyphae could access U inside CB than when roots could also directly access this U pool. The proportion of plant U content partitioned to shoots was decreased by root exclusion from CB and by mycorrhizas (M) in the order: no M, roots in CB > no M, no roots in CB > M, roots in CB > M, no roots in CB. Such mycorrhiza-induced retention of U in plant roots may contribute to the phytostabilization of U contaminated environments.

Phytoremediation of zinc and cadmium: A study of arbuscular mycorrhizal hyphae

Arbuscular mycorrhizal fungi (AMF) are microscopic fungi naturally occurring in soil that form a symbiosis with plant roots, producing a highly elaborated hyphal mycelium network in soil.In vitro lab experiments were conducted to determine whether extraradical mycorrhizal hyphae are directly involved in sequestration and uptake of essential zinc and nonessential cadmium by plant roots under toxic concentrations. The research is a continuation of an initial study presented in the Spring 2005 issue of Remediation that focused on the specific role of AMF in the speciation of heavy metals. Thus, this article presents a more expanded view. Results show that zinc and cadmium heavy metals are sequestered and translocated to plant roots via extraradical AMF hyphae. Root/growth media accumulation factors reached 5:1 and 18:1 for zinc and cadmium, respectively. Phytoremediation of heavy metal–contaminated soils can be enhanced by mycorrhizal inoculation. © 2005 Wiley Periodicals, Inc.

Zn Acquisition by Extraradical Hyphae in Arbuscular Mycorrhizal Plant Depending on Zn Nutritional Status of Cucumber(Cucumis sativus cv. Baekdadagi)

The contribution of plant nutrition status in arbuscular mycorrhizal (AM) plant to the nutrient acquisition by extraradical hyphae of AM fungi was investigated using cucumber colonized with Glomus intraradicies (BEG 110) focusing on the Zn. Compartmentalized pots with separated Bones for hyphal growth were used to determine the contribution of extraradical AM hyphae to Zn uptake from hyphal zones. <TEX>$0.5\;{\mu}M$</TEX> Zn was supplied into the hyphal zones as nutrient solution (10 mL/day) with a form of <TEX>$ZnSO_4$</TEX>. Zn foliar application was made two times for one week before harvest (8 mL/plant). The colonization rate by AM were high in all of Zn treatments. The dry weight of cucumber increased by AM colonization compared to those of non-mycorrhizal counterpart. However: Zn foliar application resulted in no significant difference in dry weight between mycorrhizal- and non-mycorrhizal plant. In addition, the enhancement of Zn content in cucumber shoot by AM colonization were also reduced by Zn foliar application. These results indicate that the interaction between host plant and AM fungus for nutrient uptake might be related to plant nutritional status and nutrient contents. In consequence, higher Zn contents in host plant by foliar application of Zn could restrict the role of extraradical hyphae of AM fungus on the Zn acquisition and transfer from fungus to host plant.

P uptake by arbuscular mycorrhizal hyphae: effect of soil temperature and atmospheric CO2 enrichment

AbstractMycorrhizas are ubiquitous symbioses that may have an important role in the movement of C from air to soil. Studies on the effects of climate change factors on mycorrhizas have been concentrated on the effects of atmospheric [CO2] whereas temperature effects have been neglected. Based on previous results showing no effect of varying atmospheric [CO2] on the development and P uptake of the arbuscular mycorrhizal fungi (AMF) colonizing plants growing in controlled conditions, we hypothesized that soil temperature would have a higher impact on AMF development and nutrient uptake than the effects of [CO2] on the host plant. Pea plants were grown in association with either a single isolate of Glomus caledonium or AMF from field soil in factorial combination with the corresponding current (10 °C) or elevated (15 °C) soil temperatures at current (350 p.p.m) or elevated (700 p.p.m) atmospheric [CO2]. 33P uptake by extraradical AMF hyphae was measured independently from root P uptake in a root exclusion compartment. Intraradical colonization developed well at both soil temperatures and almost duplicated from 10 to 15 °C. Extraradical mycelium developed only at 15 °C in the root exclusion compartment and hyphal P uptake could therefore be studied at 15 °C only. Hyphal P uptake differed markedly between inoculum types, but was not altered by growing the host plants at two atmospheric [CO2] levels. No significant [CO2] × soil temperature interactions were observed. The results suggested that, in the system tested, AMF development and function is likely more influenced by the temperature component of climate change than by its [CO2] component. We suggest that much more attention should be paid to temperature effects in future studies.