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.     

Plugging into the network: belowground connections between germlings and extraradical mycelium of arbuscular mycorrhizal fungi

Arbuscular mycorrhizal fungi (AMF) are obligate biotrophs; nevertheless their spores can germinate in the absence of host plants. Such inconsistent behavior is balanced by diverse survival strategies. The ability of AM fungal hyphae to fuse might represent a fundamental survival strategy because germlings could plug into compatible mycorrhizal networks, thus gaining access to plant-derived carbon before asymbiotic growth arrest. An in vivo experimental system was used to grow extraradical mycelium produced by Glomus mosseae colonizing three different plant species and germlings of the same isolate. After symbiotic and asymbiotic mycelia came into contact we showed that germling hyphae fused with symbiotic network hyphae and established protoplasm connections with nuclei occurring in fusion bridges. The frequency of anastomoses between germling and symbiotic hyphae was 4.9-23.9%. Prefusion and postfusion incompatible responses, with protoplasm withdrawal in interacting hyphae, were evident in some hyphal contacts. Given the multigenomic nature of AMF, the mingling of germling nuclei with those of the mycorrhizal network through perfect fusions might represent a means for the maintenance of genetic diversity in the absence of sexual recombination.     

植物磷营养状况对丛枝菌根真菌生长及代谢活性的调控*

采用四室隔网培养装置,以玉米为宿主植物,通过在植物生长室设0、50、250和500 mgPkg-1 4个施磷水平,研究了植株体内的磷营养状况对AM真菌Glomus sinuosum和Glomus intraradices生长及活性的影响。研究发现在不施磷条件下,接种AM真菌G. intraradices显著促进了植物生长和磷的吸收;低磷条件(50 mgPkg-1)下,接种菌根真菌显著促进了植物对磷的吸收,但对植物生长没有明显的影响;而在高磷条件(250 mgPkg-1 和500 mgPkg-1)下,接种菌根真菌不但没有促进植物的生长和磷的吸收,反而对其有抑制作用。随着施磷水平的提高, AM真菌根内菌丝的碱性磷酸酶活性显著下降;与不施磷相比,低量(50 mgPkg-1)供磷增加了AM真菌土壤中根外菌丝的密度,高磷(250 mgPkg-1 和500 mgPkg-1)降低了土壤中根外菌丝的密度。上述结果说明:⑴ 给宿主植物施用磷肥引起的植物磷营养状况的改变,对AM真菌生长和代谢活性具有一定的调控作用;⑵ G. sinuosum和G. intraradices两种AM真菌的生长和代谢活性对施磷水平的响应程度无显著性差异;⑶ 高磷抑制AM真菌生长和代谢活性,使真菌吸磷量减少,可能是造成菌根效应降低的原因之一     

The diversity of arbuscular mycorrhizas of selected Australian Fabaceae

Abstract

Members of the Australian native perennial Fabaceae have been little explored with regard to their root biology and the role played by arbuscular mycorrhizal (AM) fungi in their establishment, nutrition and long-term health. The ultimate goal of our research is to determine the dependency of native perennial legumes on their co-evolved AM fungi and conversely, the impact of AM fungal species in agricultural fields on the productivity of sown native perennial legume pastures. In this paper we investigate the colonisation morphology in roots and the AMF, identified by spores extracted from rhizosphere soil, from three replicate plots of each of the native legumes, Cullen australasicum, C. tenax and Lotus australis and the exotic legumes L. pedunculatus and Medicago sativa. The plants were grown in an agricultural field. The level and density of colonisation by AM fungi, and the frequency of intraradical and extraradical hyphae, arbuscules, intraradical spores and hyphal coils all differed between host plants and did not consistently differ between native and exotic species. However, there were strong similarities between species in the same genus. The three dominant species of AM fungi in rhizosphere soil also differed with host plant, but one fungus (Glomus mosseae) was always the most dominant. Sub-dominant AM species were the same between species in the same genus. No consistent differences in dominant spores were observed between the exotic and native Fabaceae species. Our results suggest that plant host influences the mycorrhizal community in the rhizosphere soil and that structural and functional differences in the symbiosis may occur at the plant genus level, not the species level or due to provenance.     

Litter N retention over winter for a low and a high phenolic species in the alpine tundra

Mycorrhizal fungus colonization of roots may modify plant metal acquisition and tolerance. In the present study, the contribution of the extraradical mycelium of an arbuscular mycorrhizal (AM) fungus, Glomus mosseae (BEG 107), to the uptake of metal cations (Cu, Zn, Cd and Ni) by cucumber (Cucumis sativus) plants was determined. The influence of the amount of P supplied to the hyphae on the acquisition and partitioning of metal cations in the mycorrhizal plants was also investigated. Pots with three compartments were used to separate root and root-free hyphal growing zones. The shoot concentration of Cd and Ni was decreased in mycorrhizal plants compared to non-mycorrhizal plants. In contrast, shoot Zn and Cu concentrations were increased in mycorrhizal plants. High P supply to hyphae resulted in decreased root Cu concentrations and shoot Cd and Ni concentrations in mycorrhizal plants. These results confirm that some elements required for plant growth (P, Zn, Cu) are taken up by mycorrhizal hyphae and are then transported to the plants. Conversely, Cd and Ni were transported in much smaller amounts by hyphae to the plant, so that arbuscular mycorrhizal fungus colonization could partly protect plants from toxic effects of these elements. Selective uptake and transport of plant essential elements over non-essential elements by AM hyphae, increased growth of mycorrhizal plants, and metal accumulation in the root may all contribute to the successful growth of mycorrhizal plants on metal-rich substrates. These effects are stimulated when hyphae can access sufficient P in soil.     

Transport of radiocaesium by arbuscular mycorrhizal fungi to Medicago truncatula under in vitro conditions

The capacity of arbuscular mycorrhizal (AM) fungi to take up and translocate radiocaesium (Cs) to their host has been shown using the root-organ culture (ROC) system. However, the absence of photosynthetic tissues, lack of a normal root hormonal balance and incomplete source-sink relationships may bias the bidirectional transfer of elements at the symbiotic interface and complicate transport studies. Accordingly, we developed a novel culture system [i.e. the Arbuscular Mycorrhizal-Plant (AM-P) in vitro culture system], where AM fungi and an autotrophic host plant develop under strict in vitro conditions. With this system, we unambiguously demonstrated the capacity of AM fungi to transport Cs. The extraradical fungal hyphae took up 21.0% of the initial supply of 134Cs. Translocation to the plant represented 83.6% of the 134Cs taken up. Distribution of 134Cs in the host plant was 89.8% in the mycorrhizal roots and 10.2% in the shoot. These results confirm that AM fungi can take up, translocate and accumulate Cs. They further demonstrate unambiguously and for the first time that Cs can be transferred from AM fungi to host tissues. These results suggest a potential involvement of AM fungi in Cs biogeochemical cycle and in plant Cs accumulation.     

The role of different arbuscular mycorrhizal fungi in the growth of Calamagrostis villosa and Deschampsia flexuosa, in experiments with simulated acid rain

A series of microcosm experiments was established to investigate the effects of simulated acid rain on the capacity of three arbuscular mycorrhizal fungi (AMF) to germinate and colonize two grasses, Calamagrostis villosa and Deschampsia flexuosa. These two grasses are normally found in degraded Norway spruce forests in the Northern Czech Republic where acid rain pollution exists and C. villosa initially outcompetes D. flexuosa for the same niche. An AM fungus isolated from acid soils (Acaulospora tuberculata BEG41) was more tolerant of acidification than two species of Glomus (isolated from agricultural soils of neutral pH) in microcosm studies. Different effects of simulated acid rain (SAR) were found at all stages of the development of three AMF studied in model systems, including spore germination, colonization of host roots, and alkaline phosphatase (ALP) and NADH diaphorase activity of the extraradical mycelium. No ALP activity was found in hyphae germinating from the spores without plants whereas it was detected in all hyphae linked to a functioning intraradical mycelium.Simulated acid rain also affected the mycorrhizal growth response and belowground competition of the two grasses. Disturbance of the ERM between the two plant species significantly reduced the growth of C. villosa but not D. flexuosa. Disturbance also decreased root colonization by AMF of both plants, the total length of ERM and the total length of extraradical hyphae with ALP and NADH diaphorase activity adjacent to both plants. D. flexuosa appeared less dependent on the mycorrhizal state, for shoot and root growth, than C. villosa under the experimental conditions. The ability, therefore, of C. villosa to thrive in forest stands suffering from acid rain pollution may be related to this dependence on its mycorrhizal hyphal links to D. flexuosa under the environmental conditions produced by the pollution including higher light levels.     

Arbuscular mycorrhizal fungi reduce growth and infect roots of the non‐host plant Arabidopsis thaliana

The arbuscular mycorrhizal (AM) symbiosis is widespread throughout the plant kingdom and important for plant nutrition and ecosystem functioning. Nonetheless, most terrestrial ecosystems also contain a considerable number of non‐mycorrhizal plants. The interaction of such non‐host plants with AM fungi (AMF) is still poorly understood. Here, in three complementary experiments, we investigated whether the non‐mycorrhizal plant Arabidopsis thaliana, the model organism for plant molecular biology and genetics, interacts with AMF. We grew A. thaliana alone or together with a mycorrhizal host species (either Trifolium pratense or Lolium multiflorum) in the presence or absence of the AMF Rhizophagus irregularis. Plants were grown in a dual‐compartment system with a hyphal mesh separating roots of A. thaliana from roots of the host species, avoiding direct root competition. The host plants in the system ensured the presence of an active AM fungal network. AM fungal networks caused growth depressions in A. thaliana of more than 50% which were not observed in the absence of host plants. Microscopy analyses revealed that R. irregularis supported by a host plant was capable of infecting A. thaliana root tissues (up to 43% of root length colonized), but no arbuscules were observed. The results reveal high susceptibility of A. thaliana to R. irregularis, suggesting that A. thaliana is a suitable model plant to study non‐host/AMF interactions and the biological basis of AM incompatibility.     

Extraradical mycelium of the arbuscular mycorrhizal fungus Glomus lamellosum can take up,accumulate and translocate radiocaesium under root-organ culture conditions

Radiocaesium enters the food chain when plants absorb it from soil, in a process that is strongly dependent on soil properties and plant and microbial species. Among the microbial species, arbuscular mycorrhizal (AM) fungi are obligate symbionts that colonize the root cortex of many plants and develop an extraradical mycelial (ERM) network that ramifies in the soil. Despite the well-known involvement of this ERM network in mineral nutrition and uptake of some heavy metals, only limited data are available on its role in radiocaesium transport in plants. We used root-organ culture to demonstrate that the ERM of the AM fungus Glomus lamellosum can take up, possibly accumulate and unambiguously translocate radiocaesium from a 137Cs-labelled synthetic root-free compartment to a root compartment and within the roots. The accumulation of 137Cs by hyphae in the root-free compartment may be explained by sequestration in the hyphae or by a bottleneck effect resulting from a limited number of hyphae crossing the partition between the two compartments. Uptake and translocation resulted from the incorporation of 137Cs into the fungal hyphae, as no 137Cs was detected in mycorrhizal roots treated with formaldehyde. The importance of the translocation process was indicated by the correlation between 137Cs measured in the roots and the total hyphal length connecting the roots with the labelled compartment. 137Cs may be translocated via a tubular vacuolar system or by cytoplasmic streaming per se.     

Phosphorus and carbon availability regulate structural composition and complexity of AM fungal mycelium

The regulation of the structural composition and complexity of the mycelium of arbuscular mycorrhizal (AM) fungi is not well understood due to their obligate biotrophic nature. The aim of this study was to investigate the structure of extraradical mycelium at high and low availability of carbon (C) to the roots and phosphorus (P) to the fungus. We used monoxenic cultures of the AM fungus Rhizophagus irregularis (formerly Glomus intraradices) with transformed carrot roots as the host in a cultivation system including a root-free compartment into which the extraradical mycelium could grow. We found that high C availability increased hyphal length and spore production and anastomosis formation within individual mycelia. High P availability increased the formation of branched absorbing structures and reduced spore production and the overall length of runner hyphae. The complexity of the mycelium, as indicated by its fractal dimensions, increased with both high C and P availability. The results indicate that low P availability induces a growth pattern that reflects foraging for both P and C. Low C availability to AM roots could still support the explorative development of the mycelium when P availability was low. These findings help us to better understand the development of AM fungi in ecosystems with high P input and/or when plants are subjected to shading, grazing or any management practice that reduces the photosynthetic ability of the plant.     

In situ analysis of anastomosis in representative genera of arbuscular mycorrhizal fungi

Arbuscular mycorrhizal fungi (AMF) form obligate symbiotic associations with plants. As a result, the role of hyphal interactions in the establishment and maintenance of common mycorrhizal networks is poorly understood because of constraints on methods for in situ analysis. We designed a rhizohyphatron that allows the examination of intact mycelia growing from whole mycorrhizal plants. Plants preinoculated with spores were cultivated in a compartment with a connecting tube from which hyphae extend through a fine nylon mesh onto agar-coated slides. Species selected from each of the five AMF genera were used to assess and characterize the anastomosis behavior in the rhizohyphatron. Hyphal networks of Paraglomus occultum, Ambispora leptoticha, Scutellospora heterogama, and Gigaspora gigantea growing on the agar-coated slides showed no evidence of hyphal fusion. In contrast, anastomosis occurred in the hyphal networks of Glomus clarum and Glomus intraradices at an average frequency of less than 15% for both species. The rhizohyphatron developed in this study will provide knowledge of the biology and genetics of self/non-self recognition in AMF and help to better understand Glomeromycotan life history strategies.     

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.     

Meeting a non-host: the behaviour of AM fungi

 Arbuscular mycorrhizal (AM) fungi are obligately biotrophic organisms that live symbiotically with the roots of most plants. The establishment of a functional symbiosis between AM fungi and host plants involves a sequence of recognition events leading to the morphological and physiological integration of the two symbionts. The developmental switches in the fungi are triggered by host signals which induce changes in gene expression and a process leading to unequivocal recognition between the two partners of the symbiosis. It has been calculated that about 80% of plant families from all phyla of land plants are hosts of AM fungi. The remaining plant species are either non-mycorrhizal or hosts of mycorrhizas other than the arbuscular type. Non-host plants have been used to obtain information on the factors regulating the development of a functional symbiosis. The aim of this present review is to highlight present-day knowledge of the fungal developmental switches involved in the process of host/non-host discrimination. The following stages of the life cycle of AM fungi are analysed in detail: spore germination, presymbiotic mycelial growth, differential branching pattern and chemotropism, appressorium formation, root colonization. Accepted: 17 June 1998     

Branched absorbing structures (BAS): a feature of the extraradical mycelium of symbiotic arbuscular mycorrhizal fungi

The present work describes the morphogenesis and cytological characteristics of 'branched absorbing structures' (BAS, formely named arbuscule-like structures, ALS), small groups of dichotomous hyphae formed by the extraradical mycelium of arbuscular mycorrhizal (AM) fungi. Monoxenic cultures of the AM fungus Glomus intraradices Smith & Schenck and tomato ( Lycopersicum esculentum Mill.) roots allowed the continuous, non-destructive study of BAS development. These structures were not observed in axenic cultures of the fungus under different nutritional conditions or in unsuccessful (asymbiotic) monoxenic cultures. However, extraradical mycelium of G. intraradices formed BAS immediately after fungal penetration of the host root and establishment of the symbiosis. The average BAS development time was 7 d under our culture conditions, after which they degenerated, becoming empty septate structures. Certain BAS were closely associated with spore formation, appearing at the spore's substending hypha. Branches of these spore-associated BAS (spore-BAS) usually formed spores. Electron microscopy studies revealed that BAS and arbuscules show several ultrastructural similarities. The possible role of BAS in nutrient uptake by the mycorrhizal plant is discussed.     

Common mycorrhizal networks provide a potential pathway for the transfer of hydraulically lifted water between plants

Plant roots may be linked by shared or common mycorrhizal networks (CMNs) that constitute pathways for the transfer of resources among plants. The potential for water transfer by such networks was examined by manipulating CMNs independently of plant roots in order to isolate the role(s) of ectomycorrhizal (EM) and arbuscular mycorrhizal fungal (AMF) networks in the plant water balance during drought (soil water potential -5.9 MPa). Fluorescent tracer dyes and deuterium-enriched water were used to follow the pathways of water transfer from coastal live oak seedlings (Quercus agrifolia Nee; colonized by EM and AMF) conducting hydraulic lift (HL) into the roots of water-stressed seedlings connected only by EM (Q. agrifolia) or AMF networks (Q. agrifolia, Eriogonum fasciculatum Benth., Salvia mellifera Greene, Keckiella antirrhinoides Benth). When connected to donor plants by hyphal linkages, deuterium was detected in the transpiration flux of receiver oak plants, and dye-labelled extraradical hyphae, rhizomorphs, mantles, and Hartig nets were observed in receiver EM oak roots, and in AMF hyphae of Salvia. Hyphal labelling was scarce in Eriogonum and Keckiella since these species are less dependent on AMF. The observed patterns of dye distribution also indicated that only a small percentage of mycorrhizal roots and extraradical hyphae were involved with water transfer among plants. Our results suggest that the movement of water by CMNs is potentially important to plant survival during drought, and that the functional ecophysiological traits of individual mycorrhizal fungi may be a component of this mechanism.     

Endo- and ectomycorrhizas in Quercus agrifolia Nee. (Fagaceae): patterns of root colonization and effects on seedling growth

We documented the patterns of root occupancy by Glomalean and ectomycorrhizal (EM) fungi in Quercus agrifolia, and host plant responses to inoculation with each mycorrhizal type alone or in combination. Glomalean hyphae, coils and vesicles, and EM root tips were recorded. Colonization patterns conformed to a succession from Glomalean and EM fungi in 1-year-old seedlings to predominantly EM in saplings (>11 years old); both mycorrhizal types were rarely detected within the same root segment. Inoculation of Q. agrifolia seedlings with EM or Glomalean fungi (AM) alone or in combination (EM+AM) altered the cost:benefit relationship of mycorrhizas to the host plant. Seedling survival, plant biomass, foliar nitrogen (N), and phosphorus (P) status were greatest in EM- or AM-only inoculated seedlings. Seedlings inoculated with both mycorrhizal types (AM+EM) exhibited the lowest survival rates, biomass, foliar N, and P levels. Roots of these plants were highly colonized by both EM (38% root length colonized) and Glomalean fungi (34%). Because these levels of colonization were similar to those detected in 1-year-old field seedlings, the presence of both mycorrhizal types may be a carbon cost and, in turn, less beneficial to oaks during establishment in the field. However, the shift to EM colonization in older plants suggests that mycorrhizal effects may become positive with time.     

菌根真菌的碳氮循环功能研究进展

菌根(Mycorrhiza)是土壤真菌与植物根系形成的共生体(Symbiont),真菌一方面从植物获取碳水化合物,同时帮助植物吸收氮等矿质养分,因此,菌根真菌在生态系统的碳氮循环过程中发挥重要的作用.研究结果表明,菌根真菌可利用约4％-26％的植物净光合固定的碳水化合物,而其生物量和分泌物(如球囊霉素)具有重要的土壤碳汇功能;同时菌根真菌可参与土壤复杂有机质的降解过程.在菌根共生体系中,氮从根外菌丝到根内菌丝的传输经历了一个“无机-有机-无机”的转变过程.本文重点总结分析了菌根真菌在碳氮代谢功能与机理等方面的国内外最新研究进展,以及目前存在的主要问题与未来的研究重点.     

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.     

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.     

植酸钠对菌根真菌根内菌丝碱性磷酸酶活性及根外菌丝生长的影响

采用三室隔网培养装置,以玉米为宿主植物,接种丛枝菌根真菌(AM)(Glomus intraradices),研究了不同用量的植酸钠对AM真菌生长和代谢活性的影响．研究发现,接种AM真菌的植株地上部和根系的P浓度和吸P量,比非菌根植物的提高了1～2倍．外源植酸钠的存在,显著降低了AM真菌根内菌丝的碱性磷酸酶活性,增加了AM真菌在土壤中的菌丝密度．结果表明,外源植酸钠对根内AM真菌碱性磷酸酶活性和真菌根外菌丝的生长具有调控(增减)作用,并且AM真菌提高了植物对土壤固有养分和外源植酸钠中P的吸收和利用．