Uptake of Arsenic by Maize Inoculated with Three Different Arbuscular Mycorrhizal Fungi

Effects of inoculation with three different arbuscular mycorrhizal (AM) fungi (Glomus etunicatum, Glomus constrictum, and Glomus mosseae) on arsenic (As) accumulation by maize were investigated by using soil spiked with As at rates of 0, 25, 50, and 100 mg kg^?1. The root colonization rates by the three fungi were significantly different (G. mosseae > G. etunicatum > G. constrictum) and decreased markedly with increasing As concentration in the soil. Inoculation with G. etunicatum or G. mosseae increased maize biomass and phosphorus (P) accumulation (G. mosseae > G. etunicatum) and reduced As accumulation in shoots (G. mosseae ≈ G. etunicatum), whereas inoculation with G. constrictum had little effect on these parameters. Inoculation with G. mosseae produced greater biomass and P uptake and less shoot As accumulation, and therefore it may be a promising approach to reduce As translocation from contaminated soils to plants.     

分室法研究不同磷况下两种接种丛枝菌根玉米

A modified glass bead compartment cultivation system was used to compare some chemical and biolog-ical properties of the two arbuscular mycorrhizal (AM) fungi Glomus mosseae and Glomus versiforme usingmaize (Zea mays) as the host plant with four added levels of available phosphorus (P). The proportion of host plant root length infected was determined at harvest. Shoot and root yields and nutrient concentra-tions were determined, together with the nutrient concentrations in the AM fungal external mycelium. Themorphology of various mycorrhizal structures of the two AM fungi was also compared by microscopic obser-vation. Inoculation with G. mosseae gave higher plant yields than that with G. versghrme, and the two fungiresponded differently in infection rate to areilable phosphorus level. Root infection rate of mycorrhizal maizecolonized by G. mosseae decreased markedly with increasing P level, and there was very poor development of the extraradical mpcelium at the highest rate of P addition. In contrast, G. versiforme showed greater tolerance to increasing P level. Elemental analysis showed that phosphorus, copper and zinc concentrations in the external mycelium differed between the two fungi and were much higher than those in the host plant. Differences in the morphology of the two fungi were also observed.     

Effect of salinity and arbuscular mycorrhizal fungi on growth and some physiological parameters of Citrus jambheri

Arbuscular mycorrhizal (AM) fungi alleviate the unfavorable effects of salinity stress on plant growth. A pot study was conducted to determine the effects of AM fungi and salt on growth and some physiological parameters of Citrus jambheri rootstock. Four levels of salinity (2, 4, 6, and 8 dS m^?1 as NaCl) and three mycorrhizal treatments (Glomus etunicatum, Glomus intraradices and non-mycorrhizal (NM) control) were used. As salinity increased, all measured characteristics of plants after 4.5-month growth except Na uptake, proline content, and electrolyte leakage decreased. Shoot dry weight and K uptake were significantly higher in G. intraradices-colonized seedlings than NM controls at all salinity levels. Root dry weight and shoot P uptake were significantly higher in G. etunicatum-colonized seedlings than NM controls at all salinity levels. G. intraradices-colonized seedlings had significantly higher proline content than NM controls and G. etunicatum-colonized seedlings at salinity levels of 4, 6 and 8 dS m^?1. The electrolyte leakage percentage was significantly lower in G. intraradices-colonized seedlings than NM controls at all salinity levels. The data demonstrated that mycorrhizal citrus seedlings exhibited greater tolerance to salt stress than NM seedlings and the enhanced proline content seems to be one of the mechanisms involved.     

Response of nitrogen-transforming microorganisms to arbuscular mycorrhizal fungi

 We studied fluctuations in the numbers of autotrophic ammonium oxidizers, ammonifying microorganisms and denitrifying microorganisms in pot cultures of mycorrhizal and non-mycorrhizal maize. The populations were enumerated after 0, 15, 30, 45 and 60 days of plant growth. Two arbuscular mycorrhizal (AM) fungi belonging to different Glomus species were investigated. Pot cultures with AM-infected maize had significant quantitative and qualitative changes in the root-associated population of N-transforming bacteria compared with the non-mycorrhizal controls. The occurrence of autotrophic ammonium oxidizers in pot cultures of the AM fungi Glomus mosseae and G. fasciculatum was significantly higher than in non-mycorrhizal cultures throughout maize growth. The occurrence of these bacteria was delayed by 15 days in non-mycorrhizal as opposed to Glomus-colonized soil. Ammonifying and denitrifying bacterial populations were significantly decreased in the pot cultures of AM plants compared with the control. The distribution patterns of the physiological groups of bacteria tested were similar for both AM treatments but different from that of the non-mycorrhizal controls. Activity measurements expressed on a per cell basis showed changes with respect to the form of N in the mycorrhizal soil. G. fasciculatum was more active than G. mosseae during the earlier stages of plant growth. Received: 8 July 1997     

AM真菌对田间山银花生长、矿质营养及绿原酸含量的影响

Lonicera confusa, a traditional Chinese medicine herb for treating cold, flu, acute fever, and so forth, is often grown artificially in acidic soils and suffers from phosphorus (P) deficiency. A five-year field experiment was carried out to study the colonization rate, growth, nutrition, and chlorogenic acid content of Lonicera confusa seedlings inoculated with arbuscular mycorrhizal (AM) fungi, Glomus etunicatum and Glomus intraradices. Before transplanting into a field, both AM-inoculated and uninoculated control plants were cultured in nursery beds. In the plants inoculated with the AM fungi, the colonization rate decreased linearly with time and a greater decrease was observed in the plants inoculated with G. intraradices than with G. etunicatum, while the AM colonization increased from 0% to 12.1% in the uninoculated control plants 5 years after transplanting. Plant height, crown diameter, number of new branches, and flower yield increased significantly by AM inoculation as compared to the uninoculated control. Phosphorus concentrations in leaves and flowers increased, and plant uptake of nutrients, e.g., nitrogen (N), P, and potassium (K), was also enhanced significantly by AM inoculation. The Lonicera confusa seedlings had a better response to inoculation of G. intraradices than G. etunicatum in both growth and chlorogenic acid content in flowers. In contrast, both plant P uptake and P concentrations in leaves and flowers were similar between two fungal inoculations. The positive responses of Lonicera confusa to AM inoculation in growth, nutrient uptake, flowering, and chlorogenic acid content in flowers suggested that AM inoculation in nursery beds could promote the plant growth and increase chlorogenic acid content in flowers of Lonicera confusa when grown on acidic and P-deficient soils.     

Interaction between Alternaria alternata or Fusarium equiseti and Glomus mosseae and its effects on plant growth

The effect of inoculation with the saprophytic fungi Alternaria alternata or Fusarium equiseti on maize (Zea mays) and lettuce (Lactuca sativa) with or without arbuscular mycorrhizal (AM) colonization by Glomus mosseae was studied in a greenhouse trial. Plant dry weights of non-AM-inoculated maize and lettuce were unaffected by the presence of A. alternata and F. equiseti. In contrast, A. alternata and F. equiseti decreased plant dry weights and mycorrhization when inoculated to the rhizosphere before G. mosseae. The saprophytic fungi inoculated 2 weeks after G. mosseae did not affect the percentage of root length colonized by the AM endophyte, but did affect its metabolic activity assessed as succinate dehydrogenase activity. Although F. equiseti inoculated at the same time as G. mosseae did not affect mycorrhization of maize roots, its effect on AM colonization of lettuce roots was similar to that with A. alternata. In the rhizosphere of both plants, the population of saprophytic fungi decreased significantly, but was not affected by the presence of G. mosseae. Our results suggest that there may have been a direct effect of the saprophytic fungi on the mycorrhizal fungi in the extramatrical phase of the latter, and when the AM fungus was established in the root the AM fungus was less affected by the saprophytic fungi. Received: 16 January 1996     

Mycorrhizae,biocides, and biocontrol. 4. Response of a mixed culture of arbuscular mycorrhizal fungi and host plant to three fungicides

The effects of three commonly used fungicides on the colonization and sporulation by a mixture of three arbuscular mycorrhizal (AM) fungi consisting of Glomus etunicatum (Becker & Gerd.), Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe, and Gigaspora rosea (Nicol. & Schenck) in symbiosis with pea plants and the resulting response of the host-plant were examined. Benomyl, PCNB, and captan were applied as soil drenches at a rate of 20 mg active ingredient kg^-1 soil 2 weeks after transplanting pea seedlings in a silty clay-loam soil containing the mixed inocula of AM fungi (AM plants). Effects of fungicides were compared to untreated plants that were inoculated with fungi (AM control). The effect of mycorrhizal inoculation on plant growth was also examined by including nonmycorrhizal, non-fungicide-treated plants (non-AM control). Fungicides or inoculation with AM fungi had only a small effect on the final shoot weights of pea plants, but had greater effects on root length and seed yield. AM control plants had higher seed yields and lower root lengths than the corresponding non-AM plants, and the fungicide-treated AM plants had intermediate yields and root lengths. Seed N and P contents were likewise highest in AM control plants, lowest in non-AM plants, and intermediate in fungicide-treated AM plants. All three fungicides depressed the proportion (%) of root length colonized by AM fungi, but these differences did not translate to reductions in the total root length that was colonized, since roots were longer in the fungicide-treated AM plants. Pea plants apparently compensated for the reduction in AM-fungal metabolism due to fungicides by increasing root growth. Fungicides affected the population of the three fungi as determined by sporulation at the final harvest. Captan significantly reduced the number, relative abundance, and relative volume of G. rosea spores in the final population relative to the controls. The relative volume of G. etunicatum spores was greater in all the fungicide-treated soils, while G. mosseae relative volumes were only greater in the captan-treated soil. These findings show that fungicides can alter the species composition of an AM-fungal community. The results also show that AM fungi can increase seed yield without enhancing the vegetative shoot growth of host plants.     

EXPLOITATION OF PHOSPHORUS PATCHES WITH DIFFERENT PHOSPHORUS ENRICHMENT BY THREE ARBUSCULAR MYCORRHIZAL FUNGI

The effect of three arbuscular mycorrhizal (AM) fungi on phosphorus (P) nutrient activation and acquisition by maize from spatially heterogeneous sand was investigated using dual-mesh packages enriched with different P concentrations and compared with non-mycorrhizal cotrols. As would be expected the AM fungi significantly enhanced leaf photosynthetic rate and the biomass and P concentrations in shoots and roots. All three fungi (Glomus intraradices, Glomus mosseae and Glomus etunicatum) displayed the capacity to dissolve inorganic P and promoted P nutrient availability in the packages (P patches). G. etunicatum showed the largest effect comparing with Glomus intraradices and Glomus mosseae, particularly in packages with high concentrations of P. Possible mechanisms involved include the acidification of the P patches by the AM fungi, promotion of the dissolution of the P, and more marked effects of the three fungal isolates with increasing enrichment of P in the patches. Inoculation with G. etunicatum resulted in greater acidification compared to the other two fungi. We conclude that AM fungi can promote P availability by acidifying the soil and consequently exploiting the P in nutrient patches and by facilitating the growth and development of the host plants.     

渭北旱塬葡萄园土著AM真菌对赤霞珠葡萄促生效应研究

以筛选自渭北旱塬葡萄园的3种土著AM真菌菌株Glomus mosseae(GM)、Glomus intraradices(GI)和Glomus versiforme(GV)为试材,在盆栽条件下研究了3种AM真菌单独接种及混合接种对酿酒葡萄赤霞珠(Cabernet Sauvignon)扦插苗营养生长指标的影响。结果表明,不同接种处理的葡萄幼苗AM真菌侵染程度不同,混合接种显著高于单接种;混合接种GI+GVGM+GVGM+GI,单接种GVGIGM。接种AM真菌促进葡萄幼苗的生长,显著提高植株高度和地上、地下干重,并提高葡萄叶片净光合速率、气孔导度、胞间二氧化碳浓度和蒸腾速率,从而提高葡萄叶片的光合作用;葡萄叶片中叶绿素含量、可溶性糖含量、可溶性蛋白含量均高于未接种对照,且混合接种优于单接种。     

Interactive effects of co-inoculation of Bradyrhizobium japonicum strains and mycorrhiza species on soybean growth and nutrient contents in plant

The main objective of this study was to investigate the effects of co-inoculation with different strains of Bradyrhizobium japonicum (i.e. Helinitro, Rizoking, and Nitragin) and arbuscular mycorrhizal fungi (AMF) species (i.e. Glomus fasciculatum, Glomus versiforme, Glomus intraradices, Glomus mosseae, and Glomus etunicatum) on soybean growth, fungal root colonization, and nutrient uptake of nitrogen (N), phosphorus (P), zinc (Zn), iron (Fe), and copper (Cu). Co-inoculation with various AMF species and rhizobia significantly (p<0.01) increased the soybean biomass production as compared to the non-inoculated controls. Furthermore, AMF colonization of roots of soybean plants increased by 79, 70.1, 67, 63, 57.5, and 50.1% in the presence of G. fasciculatum (GF), G. versiforme (GV), G. intraradices (GI), G. mosseae (GM), and G. etunicatum (GE), and Gmix (a mixed culture of fungi), respectively. Higher nutrient contents were observed in plants co-inoculated with Helinitro and GF. More insight into these results will enable optimization of the effective use of AM fungi in combination with their bacterial partners as a tool for increasing soybean yields in Iran; however, its general analytical framework could be applied to other parts of the world.     

红三叶草丛枝菌根对有机磷的吸收

The capacities of two arbuscular mycorrhizal (AM) fungi, Glomus mosseae and Glomus versderme, tomineralize added organic P were studied in a sterilized calcareous soil. Mycorrhizal (inoculated with either of the AM fungi) and non-mycorrhizal red clover (Trghlium pmtense L.) plants were grown for eight weeksin pots with upper root, central hyphal and lower soil compartments. The hyphal and soil compartmentsreceived either organic P (as Na-phytate) or inorganic P (as KH₂PO₄) at tbe rate of 50 mg P kg^-1. No P wasadded to the root compartments. Control pots received no added P. Yields were higher in mycorrhizal than innon-mycorrhizal clover. Mycorrhizal inoculation doubled shoot P concentration and more than doubled total P uptake of plaflts in P-amended soil, irrespective of the form of applied P. The mycorrhizal contributionto inorganic P uptake was 80% or 76% in plants inoculated with G. mosseae or G. verefforme, respectively. Corresponding values were 74% and 82% when Na-phytate was applied. In the root compartments of the mycorrhizal treatments, the proportion of root length infected, hyphal length density and phosphatase activity were all higher when organic P was applied than when inorganic P was added.     

32P Isotope to Determine the Efficiency of Mycorrhizal Wheat Symbiosis Subjected to Saline Water

Phosphorus (P) behavior and its efficiency in mycorrhizal plants are of great importance. The objective was to evaluate the behavior of soil labeled P absorbed by different mycorrhizal wheat genotypes subjected to saline water. Three wheat genotypes including cultivar Kavir, the local cultivar Roshan, and the mutated line Tabasi T-65-7-1 were inoculated with different species of arbuscular mycorrhiza (AM) including Glomus etunicatum, G. mosseae, and G. intraradices. Plants were irrigated using saline water (electrical conductivity of 13.87 dS m^?1). The experiment was a factorial with 12 treatments and three replications under greenhouse conditions. Wheat genotypes and AM species significantly affected plant dry weight, specific activity, and total plant activity (P?=?0.01). A maximum of 1.49-fold increase in specific activity or P uptake per gram of plant dry matter and 3.53-fold increase in plant activity or plant total P uptake resulted by G. etunicatum as compared with control.     

Arbuscular mycorrhizal fungi associated with wild forage plants in typical steppe of eastern Inner Mongolia

A preliminary investigation was conducted on the arbuscular mycorrhizal (AM) status of the dominant and common wild forage plants in typical steppe of eastern Inner Mongolia, a major semi-arid grassland region in China. Fifty-four wild forage plant species were collected and examined, and 27 of these were colonized by AM fungi. Some plants belonging to families that are presumed to lack mycorrhizas (Cyperaceae, Caryophyllaceae and Chenopodiaceae) were also found to be mycorrhizal. Higher proportions of arbuscular mycorrhizal plants were found in perennial (56.1%) and monocotyledonous (64.7%) forage species. However, neither percentage of root length colonized nor spore density varied significantly between the two life forms or cotyledon types. Twenty-seven species belonging to 7 genera of AM fungi were identified in total according to the morphological characteristics of the spores from field soil and trap cultures, and the results indicate that Glomus was the dominant AM genus and Glomus geosporum (Nicolson & Gerdemann) Walker and Glomus mosseae (Nicolson & Gerdemann) Gerdemann & Trappe were the dominant species in field soil and trap cultures, respectively. Glomus intraradices Schenck & Smith, Glomus etunicatum Becher & Gerdemann, Glomus claroideum Schenk & Smith emend Walker & Vestberg, Glomus clarum Nicolson & Schenck and Scutellospora callospora (Nicolson & Gerdemann) Walker & Sanders also occurred with high frequencies.     

The influence of use of different rates of mycorrhizal inoculum on root infection,plant growth,and phosphorus uptake

Abstract

Sorghum and leek plants were used as hosts in order to test the effectiveness and infectiveness of four mycorrhizal species on spore production, plant growth and phosphorus (P) uptake. When sorghum was used as a test plant, Glomus mosseae, Glomus etunicatum, and Glomus caledonium, respectively, gave the highest number of spores, while on leek, G. etunicatum, G. mosseae, and G. caledonium, respectively, resulted in higher spore production. Glomus intraradices produced the least amount of inoculum among the four species. Based on relative spore production and root infection, G. mosseae and G. etunicatum were determined to be the two best fungi as sources of inoculum for further use in the experiment. It is very important to know the minimum amount of inoculum in order to reach the maximum percentage of infection. Thus different amounts of inoculum were applied to determine optimum rates of inoculation. Sorghum and leek plants were infected with 0, 6, 12, 18, and 24 g G. mosseae and G. etunicatum of mycorrhizal inoculum per pot in a low P content and natural soil. As the inoculum rate increased, plant parameters and the percent of infection gradually increased with increasing rate to 18 g. Higher inoculum rates did not stimulate growth on infection percentage.     

Colonization of nonmycorrhizal plants by mycorrhizal neighbours as influenced by the collembolan, Folsomia candida

 Soil microarthropods have been shown to stimulate or be detrimental to arbuscular mycorrhizal function by their grazing actions, but their role as dispersal agents has not been assessed. The ability of three species of arbuscular mycorrhizal (AM) fungi (Glomus etunicatum, Acaulospora denticulata, Scutellospora calospora) infecting Plantago lanceolata roots to further colonize neighbouring plants was measured in response to the distance between root systems and the presence of the collembolan, Folsomia candida. In the absence of collembola, all three fungal species infected neighbouring plants in two weeks or less (at short distances), but were not successful when neighbouring plants were placed 45 cm away or further. Colonization by G. etunicatum was the quickest at short distances, but S. calospora showed greatest ability to colonize at increasing distance,whereas A. denticulata was intermediate. In the presence of the collembolan, G. etunicatum took longer to colonize neighbouring plants, but was able to infect at least 30 cm further, illustrating the arthropod's ability to disperse the AM inoculum. A. denticulata increased its range by 10 cm in the presence of F. candida, but unlike G. etunicatum, there was no delay in the colonization. In contrast, colonization of neighbouring plants by S. calospora was negatively affected both in terms of overall distance and time. These data support the hypothesis that soil arthropods can act as dispersal agents for AM inoculum, but the extent of this is fungal species-specific. Received: 1 July 1998     

磷胁迫下AMF对玉米生长的影响

研究在低磷的南方酸性红壤中,3种磷水平(20、40、60 m g/kg)下,接种丛枝菌根真菌G.m osseae和G lom us versif orm e对玉米营养生长的影响。结果表明,菌根的形成可使玉米的株高、鲜重增加,促进玉米的营养生长;在低磷水平下,菌根侵染率最高,玉米的株高、鲜重增加也最显著,其中接种G.m osseae的处理其株高和茎叶鲜重的增加达到极显著水平。     

Mycorrhizae, biocides, and biocontrol 3. Effects of three different fungicides on developmental stages of three AM fungi

The effects of biocide use on nontarget organisms, such as arbuscular mycorrhizal (AM) fungi, are of interest to agriculture, since inhibition of beneficial organisms may counteract benefits derived from pest and disease control. Benomyl, pentachloronitrobenzene (PCNB) and captan were tested for their effects on the germination and early hyphal growth of the AM fungiGlomus etunicatum (Becker & Gerd.),Glomus mosseae (Nicol. & Gerd.). Gerd. and Trappe andGigaspora rosea (Nicol & Schenck) in a silty-clay loam soil placed in petri plates. Application of fungicides at 20 mg active ingredient (a.i) kg^–1 soil inhibited spore germination by all three AM-fungal isolates incubated on unsterilized soil for 2 weeks. However, fungicides applied at 10 mg a.i. kg^–1 soil had variable effects on AM-fungal isolates. Fungicide effects on germination and hyphal growth of G.etunicatum were modified by soil pasteurization and CO₂ concentration in petri plates and also by placing spores below the soil surface followed by fungicide drenches. Effects of fungicides on mycorrhiza formation and sporulation of AM fungi, and the resulting host-plant response, were evaluated in the same soil in associated pea (Pisum sativum L.) plants. Fungicides applied at 20 mg a.i. kg^–1 soil did not affect the root length colonized byG. etunicatum, but both benomyl and PCNB reduced sporulation by this fungus. Benomyl and PCNB reduced the root length colonized byG. rosea at 48 and 82 days after transplanting. PCNB also reducedG. mosseae-colonized root length at 48 and 82 days, but benomyl only affected root length colonized byG. mosseae at the earlier time point. Only PCNB reduced sporulation byG. mosseae, consistent with its effect on root length colonized by this fungus. captan reduced the root length colonized by G. rosea at 48 days, but not at 82 days, and reduced colonization byG. mosseae at 82 days, but not at 48 days. Captan did not affect sporulation by any of the fungi.G. rosea spore production was highly variable, but benomyl appeared to reduce sporulation by this fungus. Overall,G. etunicatum was the most tolerant to fungicides in association with pea plants in this soil, andG. rosea the most sensitive. Benomyl and PCNB were overall more toxic to these fungi than captan. Interactions of AM fungi and fungicides were highly variable and biological responses depended on fungus-fungicide combinations and on environmental conditions.     

Response of Two Maize Inbred Lines with Contrasting Phosphorus Efficiency and Root Morphology to Mycorrhizal Colonization at Different Soil Phosphorus Supply Levels

ABSTRACT

A pot experiment investigated the response of two maize inbred lines with contrasting root morphology and phosphorus (P) efficiency to inoculation with Glomus mosseae or Glomus etunicatum compared with non-mycorrhizal controls. Soil phosphorus was supplied at rates of 10, 50, and 100 mg P kg ^?1 soil. Root length, specific root length, and specific phosphorus uptake of maize line 178 (P-efficient) were significantly higher than of line Hc (P-inefficient). Percentage of root length colonized showed the opposite trend regardless of soil P supply level. The two maize lines did not differ significantly in growth response to mycorrhizal colonization. Root colonization rate decreased with increasing soil phosphorus supply. The beneficial effect of the two AM fungi on plant growth and P uptake was greatest at low soil P level and the responses were negative at high P supply. Mycorrhizal responsiveness also decreased with increasing P supply and differed between the two mycorrhizal fungal isolates.     

Variations in nitrogen,zinc, and sugar concentrations in Chinese fir seedlings grown on shrubland and plowed soils in response to arbuscular mycorrhizae-mediated process

One-year-old seedlings of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) are not colonized with ectomycorrhizal (EM) fungi, but often colonized with arbuscular mycorrhizal (AM) fungi. The AM fungi could be important for nutrient acquisition in Chinese fir seedlings. Previous studies show that feedbacks between aboveground and belowground plant tissues play a fundamental role in controlling the interaction between plants and AM fungi. Our results indicate significant feedback in seedlings grown on shrubland soils, but not on plowed soils. The amounts of sugar in fir leaves in the shrubland soils were significantly lower than those in plowed soils. Leaf zinc (Zn) and nitrogen (N) concentrations were significantly higher in seedlings in shrubland soils than in plowed soils. In mycorrhizal seedlings growing in shrubland soils, leaf N:P ratios were significantly higher than those in plowed soils, likely because of enhanced N absorption through AM-mediated process. Leaf N:P ratios in seedlings grown on plowed soils were below the threshold levels, because of low metabolic activity of feedback in AM-mediated process. The results suggested that the presence of feedback between Chinese fir seedlings and AM fungi should be benefit in transplanting Chinese fir seedlings.     

Solubilization of Insoluble Inorganic Phosphate by Hyphal Exudates of Arbuscular Mycorrhizal Fungi

Increased phosphate (P) uptake in plants by arbuscular mycorrhizal (AM) fungi is thought to depend mainly on the extension of external hyphae into soil. On the other hand, it is known that the hyphae of some kinds of ectomycorrhizal fungi release organic acids into soil and that they dissolve the insoluble inorganic P. This study collected hyphal exudates of AM fungi within compartmentalized pot culture and clarified their ability to solubilize insoluble inorganic P. Sterilized Andisol was packed in pots that were separated into root and hyphal compartments with a nylon net of 30 μm pore size. Seedlings of Allium cepa inoculated with AM fungi, Gigaspora margarita, or Glomus etunicatum were grown. Control pots were not inoculated. Mullite ceramic tubes were buried in the soil of each compartment and soil solution was collected. The anionic fraction of the soil solution was incubated with iron phosphate (4 mg FePO₄ in 1 mL of 0.4 acetate buffer). Solubilized P was measured. The AM colonization of plants inoculated with G. margarita and G. etunicatum was 86% and 54%, respectively. Adhesion of external hyphae was observed on the surface of the mullite ceramic tubes buried in soil of the hyphal compartment. Colonization of both fungi increased shoot P uptake and growth. Soil solution collected from the hyphal compartments of both fungi solubilized more P than did that from uninoculated plants. It is suggested that hyphal exudates can contribute to increased P uptake of colonized plants.