Mineral acquisition by arbuscular mycorrhizal plants

Arbuscular mycorrhizal fungi (AMF) benefit plants by allowing them to grow and produce in relatively harsh mineral stress environments. This has been attributed extensively to ability of AMF to expand the volume of soil for which mineral nutrients are made available to plants compared to what roots themselves would contact. This article reviews the effects of AMF on enhancing/reducing acquisition of phosphorus (P), nitrogen (N), sulfur (S), boron (B), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), zinc (Zn), copper (Cu), manganese (Mn), iron (Fe), aluminum (Al), silicon (Si), and some trace elements in plants. The nutrients enhanced most in host plants grown in many soils (e.g., high and low soil pH) are P, N, Zn, and Cu, but K, Ca, and Mg are enhanced when plants are grown in acidic soils. Many AMF have also the ability to ameliorate Al and Mn toxicities for plants are grown in acidic soil.     

Alleviation of salt stress by arbuscular mycorrhizal in zucchini plants grown at low and high phosphorus concentration

With the aim of determining whether the arbuscular mycorrhizal (AM) inoculation would give an advantage to overcome salinity problems and if the phosphorus (P) concentration can profoundly influence zucchini (Cucurbita pepo L.) plant responses to AM, a greenhouse experiment was carried out with AM (+AM) and non-AM (−AM). Plants were grown in sand culture with two levels of salinity (1 and 35 mM NaCl, giving electrical conductivity values of 1.8 and 5.0 dS m⁻¹) and P (0.3 and 1 mM P) concentrations. The percentages of marketable yield and shoot biomass reduction caused by salinity were significantly lower in the plants grown at 0.3 mM P, compared to those grown at 1 mM P. However, even at high P concentration, the absolute value of yield and shoot biomass of +AM zucchini plants grown under saline conditions was higher than those grown at low P concentration. The +AM plants under saline conditions had higher leaf chlorophyll content and relative water content than −AM. Mycorrhizal zucchini plants grown under saline conditions had a higher concentration of K and lower Na concentration in leaf tissue compared to −AM plants. The P content of zucchini leaf tissue was similar for +AM and −AM treatments at both low and high P concentrations in the saline nutrient solution. The beneficial effects of AM on zucchini plants could be due to an improvement in water and nutritional status (high K and low Na accumulation).     

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.     

Adaptation of plants and arbuscular mycorrhizal fungi to coal tailings in Indiana

We tested the potential for arbuscular mycorrhizal fungi to mediate plant adaptation to mine soil conditions utilizing a full factorial experiment involving two fungal communities, two ecotypes of plants and two soil types. We found that plants grew larger with fungal communities derived from mine soil regardless of the soil type in which they were grown. There was no evidence that the plants suffered from aluminum toxicity; however, plants grown in coal tailings produced far less biomass than those grown in low-nutrient clay soil. Andropogon virginicus L. grown from seeds collected from a coal mine had increased allocation to roots in sterile soil. Plantago lanceolata L. grown from seeds collected from a coal mine also showed an increased allocation to roots. We concluded that harsh edaphic conditions may help reinforce the symbiotic relationship between plants and AM fungi, resulting in more beneficial symbionts.     

Specific activity of phosphorus in mycorrhizal and non-mycorrhizal plants in relation to the availability of phosphorus to plants

Phosphate was allowed to react with a soil to which iron hydroxide had been added. The P was then labelled by a subsequent addition of ³²P. Soil P was extracted by 10 mm CaCl₂, 0.5 m NaHCO₃, and acid NH₄F solutions and the specific activity of P in the extracts was measured. Subterranean clover plants were grown both with and without a mycorrhizal fungus. Phosphorus contents and the specific activities of P in the plant shoots were determined.For mycorrhizal plants, adding iron hydroxide had no effect on the amount of P taken up, but for non-mycorrhizal plants it decreased the uptake. However there was no effect of iron hydroxide or of mycorrhizal infection on the specific activity of P in the plants. Adding iron hydroxide had no effect on the amount of P extracted by acid NH₄F, but decreased the P extracted by 10mm CaCl₂ and by 0.5 m NaHCO₃. The specific activity of P in the extracts was not affected by the addition of iron hydroxide and was the same for the three extractants. Further, the specific activity of P in all extractants was similar to that of P in both mycorrhizal and non-mycorrhizal plants. Thus differences in the availability of soil P to mycorrhizal and non-mycorrhizal plants and to the extractants were not reflected by differences in labelling. It therefore follows that lack of difference in specific activity between mycorrhizal and non-mycorrhizal plants does not eliminate the possibility that mycorrhizal plants can obtain P that was unavailable to non-mycorrhizal plants.     

氮、磷供给水平对丛枝菌根真菌生长发育的影响

为了研究营养元素氮、磷对丛枝菌根真菌（arbuscular mycorrhizal fungus）生长发育的影响,以黄瓜、番茄为宿主植物,采用半液培的方式,在LAN营养液的基础上,设置不同氮、磷供给水平的处理。结果显示,同一N、P处理水平条件下,接种处理对黄瓜植株地上部和根系的生物量未产生显著影响。不同N、P供应水平对菌根生长发育显著影响。提高供氮水平显著增加了菌根结构的数量,同时降低了植株地上部的磷含量;而磷处理对侵染结构的影响因不同供氮水平而有所差异,供N 0.3 mmol/L时,提高磷供给水平显著降低了侵染结构的数量,而当把供氮水平提高到N 3 mmol/L时,随着供磷水平的增加,菌根侵染结构数量显著增加。在此条件下,基于氮对菌根真菌和植株磷营养状况的影响的一致性,氮对菌根结构的作用可能源于氮、磷之间的交互作用。     

Effects of phosphorus application and vesicular arbuscular mycorrhizal inoculation on the growth and phosphorus nutrition of maize

The growth and nutrition of maize (Zea mays L.) grown with and without the soil application of phosphorus (P) fertilizer and/or mycorrhizal inoculum was studied in pots placed under field environments. Inoculation enhanced the growth of maize significantly (up to 81.8%) during the early stages but response gradually disappeared during the later stages of growth. Addition of phosphate increased plant growth, but suppressed mycorrhizal infection. In the first half of the season, the stimulation in plant growth was related to higher rates of P uptake by the inoculated plants, but later a decline of growth in these treatments was most probably due to fungal parasitism as a result of high root densities.     

菌根植物适应低磷胁迫的分子机制

丛枝菌根 (AM) 真菌能够和绝大多数陆生植物建立共生体系,对于植物适应低磷胁迫具有重要作用。已有很多研究从不同角度揭示了宿主植物和AM真菌协同适应低磷胁迫的生理机制,并已深入到分子和信号水平。本文归纳了近年来相关研究成果,从磷胁迫信号感知、有机酸分泌、磷酸酶与激素合成相关基因、磷酸盐转运蛋白基因、转录因子与小分子物质miRNA等若干方面讨论了菌根共生体系响应和适应磷胁迫的分子机理,重点介绍了1) 环境磷浓度作为营养信号诱发菌根植物的生理响应过程及其在共生体系建立中的关键作用;2) AM真菌调节植物激素平衡进而影响植物生长发育和根系构型的生理机制;3) 丛枝菌根涉及的植物、真菌以及菌根特异诱导植物产生的磷酸盐转运蛋白基因在磷酸盐摄取中的特殊作用及可能调控机制;4) 转录因子作为感知磷胁迫信号和调控转录表达水平的枢纽,在增强植物适应磷胁迫能力方面的重要贡献。这些因素既单独作用又相互关联,共同构成菌根植物适应磷胁迫的分子调控网络。未来需要着重加强菌根共生界面的磷转运机制、菌根植物适应低磷胁迫的转录因子调节,以及各调控因子相互作用研究,从而全面揭示菌根植物适应低磷胁迫的分子调控网络,为发展和应用菌根技术调控植物磷营养奠定理论基础。     

供磷水平对玉米丛枝菌根侵染及其对异质养分吸收的影响

【目的】 探究酸性土壤玉米丛枝菌根侵染对植物磷素吸收的促进作用,以加深理解根外菌丝对局部磷养分的获取如何受丛枝真菌侵染和环境磷养分的影响。 【方法】 以玉米为宿主植物,进行盆栽试验。在低磷酸性土壤上设置供P 0、50、500 mg/kg 3个水平 (P0、P50、P500),供试磷肥为磷酸二氢钾。每个处理再设置局部养分处理,即在每个重复中埋置两个各装有120 g灭菌土 (提前加 P 50 mg/kg) 的塑料小管,分别用孔径为0.45 μm(根系、菌丝均不能进入,以“–H”表示处理) 和50 μm(根系不能进入,菌丝可以进入,以“+H”表示处理) 的尼龙膜封住管口。测定了玉米的生长与磷吸收、土著丛枝菌根真菌的侵染和根外菌丝密度以及菌丝对局部磷养分的获取。 【结果】 1) 玉米株高、叶片SPAD值、全株干重、磷浓度及吸收量都随供磷水平升高而增加,以P50处理的根系干重最高,根冠比随供磷水平上升而降低。3个供磷水平下玉米根系均有不同程度的丛枝菌根真菌侵染。以P50处理的丛枝菌根侵染率、丛枝和孢囊结构发育最好;P0处理的丛枝菌根侵染率、丛枝丰度与P50处理没有显著差异,但孢囊丰度明显下降;P500处理虽然87.2%的根系具有侵染点,但整个根系形成的真菌结构、丛枝和孢囊比例远低于P0和P50处理,丛枝菌根的发育受到严重抑制。2) 土体土 (除塑料管之外的土) 菌丝密度随供磷水平升高而降低,但P0和P50处理差异不显著。–H处理塑料管中的菌丝密度在3个供磷水平下基本不变,保持在极低水平,而+H处理塑料管中的菌丝密度随供磷水平升高而下降。在相同供磷水平下,土体土的菌丝密度最高,其次是+H处理,–H处理的菌丝密度最低。根外菌丝从+H处理塑料管中获取的磷随环境供磷水平的升高而减少。 【结论】 酸性土壤条件下,适当地供磷可以促进玉米根系生长和丛枝菌根真菌的侵染。根外菌丝对局部磷养分的获取受环境磷养分的调控,在环境磷养分较低而局部磷养分高于环境磷养分时,较多的菌丝会进入局部区域获取磷。      

多样化培肥模式调控丛枝菌根真菌促进玉米磷素吸收

利用丛枝菌根真菌（Arbuscular mycorrhizal fungi，AMF）从农田生态系统获取养分，是红壤作物吸收土壤磷（P）素的有效途径。针对我国南方红壤生物功能退化、P素生物有效性低、作物产量低等问题，如何调控作物根际AMF群落，优化其与宿主的互惠共生关系，是打破红壤区作物P摄取瓶颈的关键。本研究结合红壤旱地生态间作与有机（秸秆、猪粪、生物肥）无机肥料配施的4种多样化培肥措施，基于作物产量和红壤磷素活化水平，筛选最优培肥模式。进一步利用扩增子高通量测序和显微观察等技术，解析红壤旱地最优培肥措施调控AMF群落组成，揭示优化的AMF群落激发宿主玉米P素摄取机理。结果表明，花生/玉米间作结合秸秆/生物肥的有机无机配施（In+NPKSB）相较于其他培肥方式使红壤旱地全磷（TP）提高29.07%、有效磷（AP）提升1.35倍，且增强了玉米根内AMF群落科水平间的联系。该措施AMF定殖率是传统培肥措施的2.24倍，提高玉米根际酸/碱性磷酸酶（ACP/ALP）活性32.18%和41.66%，玉米生物量提高34.98%，产量提高67.27%。本研究证实红壤旱地花生/玉米生态间作结合秸秆/生物肥有机无机配施的培肥措施可通过优化玉米根内AMF群落组成，促进土壤P素活化，为在红壤旱地因地制宜推广可持续农业发展的集成应用提供理论依据。     

Patterns of effects of arbuscular mycorrhizal fungi on plants grown in contaminated soil

Arbuscular mycorrhizal fungi (AMF) are integral functioning parts of plant root systems and are widely recognized for enhancing plant growth on severely disturbed sites, including those contaminated with heavy metals. However, the generality of detailed patterns observed for their influence on various metals and oxidative‐stress parameters in multiple plant species is not clarified. The goal of this study was to investigate the patterns of metal‐stress alleviation by AMF in four plant species. For this purpose, clover, sunflower, mustard, and phacelia were inoculated with Glomus intraradices and compared to noninoculated plants grown under heavy metal–stressed conditions. The study focused on the effect of AMF inoculation on plant biomass, assimilating pigments, total protein, superoxide dismutase and peroxidase activity, lipid peroxidation and As, Cd, Co, Cu, Fe, Mn, P, Pb, U, and Zn contents. As a result of inoculation very different patterns of variation were obtained for concentrations of elements and for biochemical parameters in plants. The particular effect of AMF inoculation on plants was species‐ and metal‐specific, although there was a general enhancement of plant growth.     

丛枝菌根真菌对玉米锌、磷拮抗作用的影响

【目的】 利用丛枝菌根 (arbuscular mycorrhizal fungi,AM) 真菌与作物互利共生的关系来提高作物对锌的吸收是缓解锌、磷拮抗作用的途径之一,本试验在不同锌、磷浓度条件下,研究了接种AM真菌对玉米侵染和锌、磷吸收的影响,以期为揭示AM真菌影响锌、磷拮抗作用的机理提供理论依据。 【方法】 采用盆栽试验,设置三个施磷水平 (0、200 、400 mg/kg),两个施锌水平 (0、5 mg/kg),2个接菌水平[接菌 (+AM)和不接菌 (–AM)],共12个处理,每个处理4次重复。利用生物镝灯补充光照,在人工光照植物培养室内植株生长50天后,地上部与根部分别收获,测定其生物量、锌磷的含量和吸收量。 【结果】 施磷和接种AM真菌都显著提高了玉米植株生物量,不施锌条件下,施磷从0 mg/kg增加到400 mg/kg,玉米植株地下部和地上部生物量分别提高6.67倍、9.30倍。接种处理对玉米植株生物量的影响也有相同的趋势。在锌水平为5 mg/kg、磷水平为200 mg/kg的条件下,接种AM真菌玉米植株地下部磷的吸收量和含量分别增加了110%、55%;在同一锌、磷供给条件下,接种AM真菌显著提高了玉米对锌的吸收量,地下部和地上部分别是未接种处理的1.71倍和1.68倍。随着施磷水平的不断提高,玉米植株的锌含量会逐渐下降。不施锌条件下,施磷从0 mg/kg增加到200 mg/kg,玉米植株地上部锌含量降低36%,与之相反,接种AM真菌后地上部锌含量增加35%。但在高磷条件 (400 mg/kg) 下,接种AM真菌对玉米植株锌磷含量和吸收量影响均不显著。 【结论】 在本试验条件下,施磷抑制玉米对锌的吸收,接种AM真菌可提高玉米锌磷的含量和吸收量,有效缓解玉米锌磷拮抗作用,改善玉米的锌营养状况。      

External phosphorus requirement of mycorrhizal and non-mycorrhizal barley and soybean plants

An experiment was conducted under greenhouse conditions to evaluate the effects of vesicular arbuscular mycorrhizal (VAM) fungi on the external P requirements of barley and soybeans. The plants were grown in pots containing a P-deficient soil. A range of 10 P levels was obtained by adding 0, 20, 30, 40, 50, 60, 70, 110, 160, or 310 mg P kg^-1 as NaH₂PO₄ 2H₂O. Half of the pots were inoculated with the VAM fungus Glomus intraradices. The P concentration in the soil solution was determined using an adsorption isotherm and plotted against the relative yield. Barley did not respond to mycorrhizal inoculation and we concluded that P nutrition was not the limiting factor on the growth of this lowmycotrophic plant. In contrast, mycorrhizal inoculation stimulated the growth of soybeans. The external P requirements were 0.110 g ml^-1 for mycorrhizal and 0.148 g ml^-1 for non-mycorrhizal soybeans to obtain 80% of the maximum yield. In terms of P fertilization this corresponds to a saving of 222 kg P₂O₅ ha^-1. The mycorrhizal dependency of the soybean was highly correlated with the P concentration in the soil solution and it is proposed that both values should be displayed together.     

丛枝菌根真菌介导的土壤有机碳稳定机制研究进展

土壤有机碳(SOC)的稳定是陆地生态系统碳循环的关键过程之一,对维持土壤肥力和减少温室气体排放具有重要意义。以往认为植物残体中难降解性物质的物理保护和腐殖质影响土壤中有机碳库的稳定性。最近的研究结果表明,微生物介导的碳循环过程在土壤有机碳稳定中发挥着重要作用。丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)作为土壤中一类重要的共生微生物,参与植物光合碳向土壤的转运和分配,是陆地生态系统碳循环的重要一环,但其在土壤有机碳稳定中的作用潜力还未得到充分挖掘。基于此,本文估算了植物光合碳在AMF根外菌丝的分配量;总结了AMF介导的土壤有机碳稳定机制,主要包括AMF活体菌丝对碳的截留,分泌物及残体的分子结构抗性和土壤矿物吸附,提高植物源碳的质量和数量,菌丝分泌物及残体的激发效应和稳定土壤团聚体;探讨了影响AMF介导的稳定性有机碳形成的非生物(气候因子、土壤养分和土壤矿物)和生物因子(植物和AMF种类);提出了AMF与土壤有机碳周转互作机理进一步的研究方向,包括探究菌根植物光合碳转化为稳定性SOC的机制,解析不同生态系统中AMF对稳定性SOC的贡献及影响因素,并厘清...     

毛乌素沙地典型克隆植物根际AM真菌多样性研究

为阐明毛乌素沙地3种典型克隆植物沙鞭[Psammochloa villosa(Trin.)Bor.]、羊柴(Hedysarum leaveMaxim)和油蒿(Artemisia ordosica Krasch.)根际AM真菌多样性,2006年的5月、7月、10月从毛乌素沙地选取东北缘的中国科学院植物研究所鄂尔多斯沙地草地生态研究站和西南缘的陕西榆林珍稀沙生植物保护基地两个样地,按0~10 cm、10~20 cm、20~30 cm、30~40 cm、40~50 cm 5个土层采集3种克隆植物根际土壤样品,研究了其根际AM真菌物种多样性和生态分布。在分离出的4属23种AM真菌中,球囊霉属(Glomus)15种,无梗囊霉属(Acaulospora)5种,巨孢囊霉属(Gigaspora)2种,盾巨孢囊霉属(Scutellospora)1种。摩西球囊霉(G.mosseae)是沙鞭根际的优势种,黑球囊霉(G.melanosporum)是3种克隆植物共同的常见种;不同属种的AM真菌生态分布亦存在差异。AM真菌孢子密度、种的丰度和物种多样性指数均表现为在研究站样地的羊柴根际最高。该研究结果表明,毛乌素沙地的3种典型克隆植物与AM真菌之间形成良好的共生关系,这对开发漠境AM真菌资源和利用菌根生物技术维护沙地生态系统结构的完整性具有重要意义。     

Inter- and intraspecific functional variability of tropical arbuscular mycorrhizal fungi isolates colonizing corn plants

For a single plant species under the same environmental conditions, the interaction with arbuscular mycorrhizal fungi (AMF) and their contribution to plant growth varies among AMF isolates, with both inter and intraspecific variability. The present study evaluated the functional variability of 41 isolates of 20 species and eight genera of AMF for root colonization, growth promotion, and P uptake of corn and observed the relationship of this functional variability with the isolates genetic variability revealed by PCR-RFLP analysis. All the isolates abundantly colonized the corn roots, but only 23 promoted higher shoot dry mass and P leaf content. The cluster analysis based on functional variability data separated the isolates Acaulospora morrowiae (Am2), Acaulospora sp. (Aca), A. colombiana (Ac3, Ac4, and Ac5), Gigaspora albida (Gia1), Gi. margarita (Gim4 and Gim5), Gi. rosea (Gir), Rhizophagus clarus (Rc2, Rc3, Rc4, Rc5, and Rc6), Claroideoglomus etunicatum (Ce4), R. manihotis (Rm), Scutellospora calospora (Sc), S. heterogama (Sh2, Sh3, Sh4, and Sh5) and S. pellucida (Sp3) from the others at the distance of 80% functional similarity. These were considered efficient in promoting functional symbiosis in corn while the other isolates were considered inefficient. The cluster analysis obtained by the PCR-RFLP technique was partly coherent with the species classification based on spore morphology. The isolates of R. clarus fell into one cluster and the isolates of the Gigaspora and Scutellospora genera (Gigasporaceae family) were clustered in a second cluster, without the ability to separate the species of these genera.     

低磷环境下接种丛枝菌根真菌促进紫花苜蓿生长和磷素吸收的机理

[目的]磷极易被土壤吸附和固定,导致土壤中磷有效性较低.研究接种丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)和低磷处理两者交互对紫花苜蓿生长和磷吸收的影响,为提高碱性土壤中磷肥利用率提供理论依据.[方法]以黄绵土和紫花苜蓿(Medicago sativa)为试验材料进行盆栽试验.在施...     

Altered amino acid profile of arbuscular mycorrhizal maize plants under low temperature stress

We investigated the effect of arbuscular mycorrhiza (AM) on amino acid concentration and composition of maize plants under low‐temperature stress. The AM plants had higher amino acid concentrations than the non‐AM pants. The concentrations of Thr, Lys, Gly, Ala, His, and Ile of the AM plants were higher than non‐AM plants. The results show that low‐temperature stress decreased the concentrations of amino acids and altered their composition.     

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.     

辣椒丛枝菌根真菌吸磷机制研究

A pot experiment was conducted to investigate the action mechanisms of arbuscular mycorrhizal (AM) fungi in phosphorus (P) uptake of Capsicum annuum L.in a sterilized fossil Oxisol.Three P levels of 0,10 and 200 mg kg-1 soil (P0,P10 and P200,respectively) without and with AM fungal inoculation were applied as Ca(H2PO4)2·H2O.Shoot dry matter yields and shoot P uptake increased significantly (P > 0.05) by the inoculation of AM fungi at P0 and P10.Root length and P concentration in soil solution increased with the inoculation of AM fungi but the root:shoot ratio decreased or remained constant.Around 50% roots of inoculated plants were infected by AM and the external hyphae amounted to 20 m g-1 soil at P10 and P200.The hyphae surface area of the infected root cylinder amounted to 11 and 2 cm-2 cm-2 root at P0 and P10,respectively.The increased P uptake of inoculated plants was mainly because of an up to 5 times higher P influx of the infected root.Model calculations showed that the root alone could not have achieved the measured P influx in both infected and non-infected roots.But the P influx for hyphae calculated by the model was even much higher than the measured one.The P uptake capacity of hyphae introduced in the model was too high.Model calculations further showed that the depletion zone around roots or hyphae was very narrow.In the case of the root only 7% of the soil volume would contribute P to the plant,while in the case of hyphae it would be 100%.The results together with the model calculations showed that the increased P uptake of AM inoculated plants could be explained partly by the increased P concentration in the soil solution and by the increased P absorbing surface area coming from the external hyphae.