A purple acid phosphatase,GmPAP33, participates in arbuscule degeneration during arbuscular mycorrhizal symbiosis in soybean

Arbuscules are the central structures of the symbiotic association between terrestrial plants and arbuscular mycorrhizal (AM) fungi. However, arbuscules are also ephemeral structures, and following development, these structures are soon digested and ultimately disappear. Currently, little is known regarding the mechanism underlying the digestion of senescent arbuscules. Here, biochemical and functional analyses were integrated to test the hypothesis that a purple acid phosphatase, GmPAP33, controls the hydrolysis of phospholipids during arbuscule degeneration. The expression of GmPAP33 was enhanced by AM fungal inoculation independent of the P conditions in soybean roots. Promoter‐β‐glucuronidase (GUS) reporter assays revealed that the expression of GmPAP33 was mainly localized to arbuscule‐containing cells during symbiosis. The recombinant GmPAP33 exhibited high hydrolytic activity towards phospholipids, phosphatidylcholine, and phosphatidic acid. Furthermore, soybean plants overexpressing GmPAP33 exhibited increased percentages of large arbuscules and improved yield and P content compared with wild‐type plants when inoculated with AM fungi. Mycorrhizal RNAi plants had high phospholipid levels and a large percentage of small arbuscules. These results in combination with the subcellular localization of GmPAP33 at the plasma membrane indicate that GmPAP33 participates in arbuscule degeneration during AM symbiosis via involvement in phospholipid hydrolysis.     

Vesicular arbuscular mycorrhizae in floating wetland mat communities dominated by Typha

Low levels of vesicular arbuscular mycorrhizae were present in floating mats dominated by clones of Typha angustifolia L., T. x glauca Godr., and T. latifolia L. Floating mats composed of rhizomes (underwater-ground stems with high starch accumulation), roots, decaying organic matter, and wind deposited soil, easily supported human activities. The majority of roots isolated from the root cores were connected to Typha rhizomes. Tests employing the gridline intersect method, intensity, spore counts and most probable number (MPN) were used to define the level of colonization. Mycorrhizal colonization from the T. angustifolia and T. x glauca clones averaged 4 to 5%, while the T. latifolia clone averaged 13%. When colonization was encountered, intensities varied from a high of 3.0 to a low of 0.4 on a sclae of 0 to 4. Although arbuscules were not found, abundant hyphae, vesicles and spores indicated that presumed facultative associations occurred between the vesicular arbuscular fungi and the indicated that presumed facultative associations plant communities found on floating mats. The mycorrhizal fungi identified from these communities in cluded Glomus albidum Walker & Rhodes, G. caledonium (Nicol. & Gerd.) Trappe & Gerdemann, G. etunicatum Becker & Gerdemann, and G. microcarpum Tul. & Tul. Spore counts ranged from 16 to 76 spores per gram dried organic soil. The recolonization ability of VAM propagules by way of a most probable number bioassay with maize yielded numbers that ranged from zero to 96 propagules per gram soil, with G. etunicatum the only species recovered.     

Tryptophan dimer produced by water-stressed bahia grass is an attractant for <Emphasis Type="Italic">Gigaspora margarita</Emphasis> and <Emphasis Type="Italic">Glomus caledonium</Emphasis>

We isolated and elucidated the structure of several stimulants for arbuscular mycorrhizal fungi (AMF) in water-stressed bahia grass roots. We could isolate some compounds that promoted the growth of Gigaspora margarita Becker and Hall and Glomus caledonium (Nicol. and Gerd.) Trappe and Gerd. In these compounds, tryptophan dimer (Trp–Trp) was elucidated the structure. Trp–Trp was abundantly produced in water-stressed bahia grass roots and exuded to the soil, although it was scarcely detected in non-stressed root exudates. Interestingly, this peptide strongly attracted the hyphae of Gi. margarita and G. caledonium and promoted their hyphal growth in vitro (1.8 × longer than the control). Tryptophan, however, had no effect on hyphal growth and attraction. Thus, Trp–Trp exuded from water-stressed roots would play an important role as a major signal for AMF. An erratum to this article can be found at     

Interactions between Lotus japonicus genotypes and arbuscular mycorrhizal fungi

Abstract

Interactions between three genotypes (Ljsym 71-1, Ljsym 71-2 and Ljsym 72) of Lotus japoicus and one isolate from each of four species of arbuscular mycorrhizal fungi (Glomus sp. R-10, Glomus intraradices, Glomus etunicatum, and Gigaspora margarita) were investigated and compared with the wild-type ‘Gifu’ B-129. All the three genotypes showed no or defective internal colonization after inoculation with these AM fungi. In Ljsym72 mutant, the AM fungi produced deformed appressoria on the root surface, but failed to form any internal structures (internal hyphae, arbuscules and vesicles) except only in Glomus intraradices. The Ljsym71-1 and Ljsym71-2 mutants had more deformed appressoria and occasionally formed internal hyphae, arbuscules and vesicles, depending on AM fungi used. Wild-type ‘Gifu’ (nod⁺myc⁺) plants had typical colonization. The colonization of mutants by several fungi varied and provides a basis for studying recognition and compatibility between plants and mycorrhizal fungal species. These mutants also will be useful in studies of the genetics of the symbiosis between plant species and AM fungi.     

Characterization of Mycorrhizas Formed by Glomus sp. on Roots of Hypernodulating Mutants of Lotus japonicus

Lotus japonicus hypernodulating mutants, Ljsym78-1 and Ljsym78-2, by the arbuscular mycorrhizal fungus Glomus sp. was characterized. The mutants are defective in systemic autoregulation of nodulation and nitrate inhibition, and form an excess of nodules and lateral roots. The percent root length colonized by the arbuscular mycorrhizal fungi was significantly higher for the mutant than wild-type roots. Detailed assessment of the colonization indicated that the percentage of colonization by arbuscules was increased, but that by external hyphae, internal hyphae and vesicles was decreased, in the mutant roots compared with the wild-type. The succinate dehydrogenase activity of arbuscules, external hyphae and internal hyphae showed similar trends. In addition, the majority of individual arbuscules that formed on the mutant roots had a well-developed and seemingly tough morphology. The results suggest that mutation at the Ljsym78 locus positively stimulates the growth and activity of arbuscules, but leads to reduced growth and activity of hyphae. We report the first identification of Lotus japonicus mutants that show significantly increased arbuscule formation and termed these mutants Arb⁺⁺. Received 8 August 2000/ Accepted in revised form 19 October 2000     

The effect of soil phosphorus on the external mycelium growth of arbuscular mycorrhizal fungi during the early stages of mycorrhiza formation

The effects of soil P amendments and time of application on the formation of external mycelium by different arbuscular mycorrhizal (AM) fungi were studied. In the first experiment the external mycelium produced in the soil by the AM fungus Glomus etunicatum Beck. and Gerd., during the early stages of root colonization (7 and 14 days after inoculation), was quantified by the soil-agar film technique. A Brazilian Oxisol was used with three different phosphate levels, varying from deficient to supra-optimal for the plant. Significant differences were observed in the phosphate and inoculation treatments for plant dry weight, P content in the tissue, root length and root colonization, at fourteen days after planting. At 7 days, mycelium growth, root colonization and their relationship were reduced at supra-optimal P concentrations. Applications of P one week after planting reduced mycelium growth and root colonization more than when applied to the soil before planting. In a second experiment the arbuscular mycorrhizal (AM) fungi, Scutellospora heterogama (Nicol. and Gerd.) Walker and Sanders and E3 were tested and compared with Glomus etunicatum. For the species studied, the length of external hyphae per unit of colonized root length was affected by small P additions but no further significant differences were observed at high P levels. The three AM endophytes showed marked differences in their response to P in the soil: Scutellospora heterogama, although producing external mycelium more profusely than the Glomus spp., showed a higher sensitivity to soil P supply.     

Effect of Arbuscular Mycorrhizae and Induced Drought Stress on Antioxidant Enzyme and Nitrate Reductase Activities in Juniperus oxycedrus L. Grown in a Composted Sewage Sludge-amended Semi-arid Soil

We studied the influence of inoculation with a mixture of three exotic arbuscular mycorrhizal (AM) fungi, Glomus intraradices Schenck & Smith, Glomus deserticola Trappe, Bloss. & Menge and Glomus mosseae (Nicol & Gerd.) Gerd. & Trappe, and the addition of composted sewage sludge (SS) on the activities of the antioxidant enzymes superoxide dismutase (SOD, EC 1.15.1.1) and total peroxidase (POX) and of shoot and root nitrate reductase (NR, EC 1.6.6.1) in Juniperus oxycedrus L. seedlings, an evergreen shrub, grown in a non-sterile soil under well-watered and drought-stress conditions. Both the inoculation with exotic AM fungi and the addition of composted SS stimulated significantly growth and the N and P contents in shoot tissues of J. oxycedrus with respect to the plants neither inoculated nor treated with composted SS that were either well-watered or droughted. Under drought-stress conditions, only inoculation with exotic AM fungi increased shoot and root NR activity (about 188% and 38%, respectively, with respect to the plants neither inoculated nor treated with composted SS). Drought increased the POX and SOD activities in both shoots of J. oxycedrus seedlings inoculated with exotic AM fungi and grown with composted SS, but the increase was less than in the plants neither inoculated nor treated with SS. Both the plants inoculated with exotic AM fungi and the plants grown with composted SS developed additional mechanisms to avoid oxidative damage produced under water-shortage conditions.     

Mycorrhizae in Adenostoma fasciculatum Hook. & Arn.: a combination of unusual ecto- and endo-forms

 The mycorrhizal status of Adenostoma fasciculatum, the dominant shrub in California chaparral, has been unclear. In two typical, nearly monospecificstands, A. fasciculatum was found to have arbuscules and intercellular hyphae. Antisera detected hyphae of the arbuscular mycorrhizal (AM) fungal genera Acaulospora, Glomus, and Scutellospora, although we found only spores of Glomus. Some roots had partial sheaths and inter- and intracellular septate fungi without indications of root necrosis. Ectomycorrhizal root tips were also found, including Cenococcum and other unknown taxa. Sporocarps of EM fungi including species of Rhizopogon, Pisolithus, Balsamia, Laccaria, Hygrophorus, and Cortinarius were found in the stand, with no other EM or arbutoid mycorrhizal plants nearby. These observations indicate that A. fasciculatum forms mycorrhizae with AM, septate, and EM fungi, but often fails to form easily recognizable mycorrhizal structures. Accepted: 5 September 1998     

Comparative study of mycorrhizal susceptibility and anatomy of four palm species

A morphological and anatomical study of the root systems of the palm species Brahea armata S. Watson, Chamaerops humilis L., Phoenix canariensis Chabaud and Phoenix dactylifera L. has been carried out to determine possible mycorrhizal colonization sites. Furthermore, the arbuscular mycorrhizal (AM) anatomical types formed by the four palm species in association with Glomus mosseae (Nicol. & Gerd.) Gerdemann & Trappe have been examined. The presence of a continuous sclerenchymatic ring in the outer cortex and aerenchyma in the inner cortex that are anatomical indicators of mycorrhizal nonsusceptibility in all four palm species is observed. The root systems of B. armata and C. humilis present only one group of third-order roots, while the third-order roots of P. canariensis and P. dactylifera may be divided into five different groups: short thick roots, mycorrhizal thickened roots, fine short roots, fine long roots, and pneumatorhizas. Third-order and some second-order roots of B. armata and C. humilis are susceptible to colonization by AM fungi, while only the mycorrhizal thickened roots form mycorrhizas with arbuscules in the Phoenix species. The root system of the Phoenix species also presents AM colonization in fine roots with only intraradical hyphae and spores, but without arbuscules, and pseudomantles of spores anchored in the pneumatorings of the second-order roots, which are described for the first time. The mycorrhizas formed by the four palm species are of an intermediate type, between the Arum and the Paris types, and are characterized by intercalary arbusculate coils and not only by intracellular but also by intercellular fungal growth. Our study suggests that a different degree of adaptation may exist among palm mycorrhizas toward the slow growth of palms and low spore numbers in the soil where they grow.     

The Glycine–Glomus–Rhizobium symbiosis. IV. Interactions between the mycorrhizal and nitrogen-fixing endophytes

Abstract Soybean (Glycine max (L.) Men) plants were grown under controlled conditions in an experiment designed as a 4 × 4 factorial. The factors were N or P nutrition, with different strains of Rhizobium japonicum or N-fertilization as levels of the first factor and different species of vesicular-arbuscular mycorrhizal (VAM) fungi or P fertilization as levels of the other. Organisms used were R. japonicum strains USDA 110, USDA 136, and 61A118, and the VAM fungi Glomus versiforme (Karst.) Berch, Glomus fasciculatum (Thaxt. sensu Gerd.) Gerd. and Trappe, and Glomus mosseae (Nicol. & Gerd.) Gerd. and Trappe. There were 16 treatments: nine Rhizobium + Glomus combinations, three Rhizobium + V and three Glomus+ N combinations, and one non-symbiotic set of plants supplied with N + P. The tripartite symbioses were evaluated by analysis of variance against the Rhizobium + P and Glomus + N comparison treatments for effects on root and leaf dry mass, root N and P content, nodule mass and activity, and VAM colinization. Significant to highly significant main effects and interactions were found in virtually all evaluations due to both Rhizobium strain and VAM–fungal species. We conclude that different endophyte isolates affect not only the host plant, but also the development and function of their co-endophytes. These findings establish the existence of inter-endophyte compatibility, an important consideration when selecting or engineering for desirable endophyte traits.     

Cytokinin activity inCitrus jambhiri Lush. seedlings colonized by vesicular-arbuscular mycorrhizal fungi

Summary The influence of vesicular-arbuscular mycorrhizal symbiosis on cytokinin activity in Citrus jambhiri Lush, seedlings was investigated. C. jambhiri inoculated with cultures of Glomus caledonium (Nicol. and Gerd.), G. epigaeum (Dan. and Trappe), G. etunicatum (Becker and Gerd.), G. fasciculatum Thaxt. (Gerd, and Trappe) or G. mosseae (Nicol and Gerd.) was grown from seed for 105 days in a glasshouse. Cytokinin activity in roots and leaves of seedlings was analyzed using high-performance liquid chromatography, mass spectrometry and a bioassay. Seedling leaf tissue had greater cytokinin activity than root tissue. Zeatin, zeatin riboside, and their dihydro- and glucoside derivatives were isolated from leaves of 105-day-old seedlings inoculated with G. fasciculatum and G. mosseae. Cytokinin activity in roots and leaves was associated with differences in seedling total dry weight and vesicular-arbuscular mycorrhizal colonization. The ribose moiety and the saturated side chain apparently influence cytokinin transport and physiological activity in Citrus seedlings.     

龙胆VA菌根真菌的分离和鉴定

采用湿筛法和单孢接种技术,从东北龙胆根际土壤中分离到能在东北龙胆组培苗上形成VA菌根的真菌孢子和孢子果呆,依其显微形态特征对部分菌株进行鉴定,大多属于球囊霉属（Glomus）中的漏斗孢球囊霉（Glomusmosseae）和地球囊霉（G．geosporum）     

我国北部的七种VA菌根真菌

从北京和新疆地区某些栽培及野生植物根际分离出7种VA真菌:丽孢无梗囊霉Acaulospora elegans Trappe & Gerd.,地表球囊霉Glomus versiforme (karsten) Berch,隐球囊霉G.occultum Walker,透光球囊霉G.diaphanum Morton & Walker,摩西球囊霉G.mosseae(Nicol.& Gerd.)Gerd.& Trappe,缩球囊霉G.constrictum Trappe,和苏格兰球囊霉G.caledonium(Nicol.& Gerd.)Trappe & Gerd.。其中,地表球囊霉为我国新记录种。本文除描述其形态特征外,还介绍了孢壁组织化学反应及生境条件。     

Succinate dehydrogenase activity of external and internal hyphae of a vesicular-arbuscular mycorrhizal fungus,Glomus mosseae (Nicol. & Gerd.) Gerdmann and Trappe,during mycorrhizal colonization of roots of leek (Allium porrum L.), as revealed by in situ histochemical staining

The succinate dehydrogenase (SDH) activity of hyphae of the vesicular-arbuscular (VA) mycorrhizal fungus Glomus mosseae (Nicol. & Gerd.) Gerdmann and Trappe, in symbiotic association with leek (Allium porrum L.) roots, was investigated by histochemical staining in situ. Leek seedlings were transplanted to sand culture and inoculated with spores of G. mosseae placed just below the base of the stem. At intervals (14, 25, 35 and 60 days) after transplanting, the growth medium of seedlings was flooded with nitro blue tetrazolium chloride solution, thereby displacing the nutrient solution. This allowed sites of SDH activity of external and internal fungal structures of the mycorrhizas to be stained without physically disturbing the symbiotic system. After counterstaining harvested roots and mycelium with acid fuchsin, it was possible to differentiate clearly metabolically active and inactive regions of the fungus. The lengths of external hyphae and infected root both increased nearly exponentially, and were in constant proportion (1.4 m hyphae per cm of infected root) for up to 60 days. The percentage length of external hyphae with SDH activity remained almost constant (80%). In each infected length of root there was a gradation of SDH activity from inactive distal (older) hyphae to uniformly active proximal (younger) hyphae. These findings are discussed in relation to the symbiotic activity of the mycobiont.Deceased     

Extension of the phosphorus depletion zone in VA-mycorrhizal white clover in a calcareous soil

To examine the influence of vesicular-arbuscular (VA) mycorrhizal fungi on phosphorus (P) depletion in the rhizosphere, mycorrhizal and non-mycorrhizal white clover (Trifolium repens L.) were grown for seven weeks in a sterilized calcareous soil in pots with three compartments, a central one for root growth and two outer ones for hyphae growth. Compartmentation was accomplished by a 30-μm nylon net. The root compartment received a uniform level of P (50 mg kg⁻¹ soil) in combination with low or high levels of P (50 or 150 mg kg⁻¹ soil) in the hyphal compartments. Plants were inoculated withGlomus mosseae (Nicol. & Gerd.) Gerd. & Trappe or remained uninfected. Mycorrhizal inoculation doubled P concentration in shoot and root, and increased dry weight, especially of the shoot, irrespective of P levels. Mycorrhizal contribution accounted for 76% of total P uptake at the low P level and 79% at the high P level, and almost all of this P was delivered by the hyphae from the outer compartment. In the non-mycorrhizal plants, the depletion of NaHCO₃-extractable P (Olsen-P) extended about 1 cm into the outer compartment, but in the mycorrhizal plants a uniform P depletion zone extended up to 11.7 cm (the length of the hyphal compartment) from the root surface. In the outer compartment, the mycorrhizal hyphae length density was high (2.5–7 m cm⁻³ soil) at the various distances (0–11.7 cm) from the root surface. Uptake rate of P by mycorrhizal hyphae was in the range of 3.3–4.3×10⁻¹⁵ mol s⁻¹ cm⁻¹.     

有机碳和无机碳对3种真菌胞外酸性磷酸酶和蛋白酶活性的影响

多数研究表明外生菌根真菌能够促进植物养分吸收并提高植物生长,但是对其发生的原因研究较少。本文在室内控制条件下,研究了真菌菌丝分泌N、P相关胞外酶及其受土壤有机碳（胡敏酸）和无机碳（碳酸钙）添加的影响,结果表明：1）3种真菌——松乳菇(Lactarius deliciosus)、变色红菇（Russula integra）、铆钉菇（Gomphidius viscidus）菌丝均能够分泌酸性磷酸酶和蛋白酶,而且多数情况下,MMN培养基培养14 d时,各个酶活性较高,而不同菌的胞外酶活性存在较大的差异,平均值来看铆钉菇酸性磷酸酶活性最低而蛋白酶活性最高,其它2个真菌菌丝的胞外酶活性差异不大;2）添加胡敏酸后,3种菌丝的酸性磷酸酶活性都是随着胡敏酸添加量的增加而逐渐增加;但蛋白酶活性存在差异：松乳菇的蛋白酶活性随着胡敏酸添加量的增加而逐渐增加;变色红菇的蛋白酶活性对胡敏酸不敏感,受其影响不大;铆钉菇的蛋白酶活力在少量的胡敏酸作用下最强,但浓度过高反而抑制其蛋白酶的活性。3）添加碳酸钙后,总体来看,3种菌丝胞外酸性磷酸酶和蛋白酶活性都是添加少量碳酸钙时酶活性最强,随着浓度的增加(如0.1 g),其酶活性开始受到抑制。综上所述,真菌菌丝能够分泌酸性磷酸酶和蛋白酶,这可能是因为这些外生菌根真菌能够促进植物养分吸收和快速生长的原因;有机碳和无机碳的加入可以直接影响真菌菌丝胞外酶的分泌,进而影响土壤内有机磷和有机氮化合物的分解,显示其在土壤碳循环中的作用。     

Measurement of the viability of arbuscular-mycorrhizal fungi using three different stains; relation to growth and metabolic activities of soybean plants

Histochemical staining of alkaline phosphatase (ALP) and succinate dehydrogenase (SDH) activities in four arbuscular mycorrhizal fungi (Glomus intraradices, G. fasciculatum, G. monosporum and G. mosseae) and their relation to growth and metabolic activities of soybean plants were investigated in a greenhouse experiment. In general, mycorrhizal inoculation significantly increased the growth responses, phosphorus and nitrogen contents, acid and alkaline phosphatases as well as total soluble protein of soybean compared to non-mycorrhizal plants. Stimulation was related to the viability of each mycorrhizal fungus. The localization of succinate dehydrogenase (as a vital stain of metabolically active fungus) and alkaline phosphatase activity (as a potential marker of efficiency of the symbiosis) in the arbuscular mycorrhizal fungi were variable. The activity appeared in young arbuscles and intercellular hyphae, whereas the collapsed arbuscules were inactive. The histochemical staining results demonstrated that the activity of alkaline phosphatase fungi was lower than succinate dehydrogenase. The use of nitroblue tetrazolium chloride as a vital stain for SDH activity showed that all mycorrhizal infection revealed by trypan blue staining was not physiologically active. Thus, the possible utilization of these enzymes to assess the activity of mycorrhizal fungi and its relation with effectively for plant growth and mineral contents is discussed.     

Acid phosphatase and invertase activities of <Emphasis Type="Italic">Aspergillus niger</Emphasis>

Aspergillus niger is widely used as an enzyme source in industries. Considering its enzymic potential, A. niger was studied for its acid phosphatase (EC 3.1.3.2, orthophosphoric monoester phosphohydrolase), and invertase (EC 3.2.1.26, β-fructofuranoside fructohydrolase) activity in defined media supplemented with 1%, 3%, or 5% sucrose concentrations. Both these enzymes play a key role in phosphate and carbon metabolism in plants, animals, and microorganisms and hence are interesting from the standpoint of biotechnological applications. Ontogenic changes in extracellular, cytoplasmic, and wall-bound enzyme activities of A. niger were studied. Growth in terms of fresh weight showed inverse correlation with pH. At higher pH values, both enzyme activities were higher in the medium supplemented with low sucrose concentration. It was observed that the more the fresh weight of fungi decreased, the greater was the enzyme activity observed. It is suggested that these enzymes may participate in autolysis of fungi and, on the other hand, could prove to be a potential source of industrial application and exploitation.     

Effect of VAM inoculum carry-over on the successive cropping of maize and mungbean

A field study to determine the endomycorrhizal inoculum carry-over effect of the first crop [maize inoculated with Glomus mosseae (Nicol. and Gerd.) Gerd. and Trappe] on the succeeding crop (mungbean) was carried out in fumigated and nonfumigated acidic soil (pH 5.3) with moderate extractable P (Olsen 23 ppm). G. mosseae inoculation increased maize dry matter and grain yield over the uninoculated control in the nonfumigated soil. The maize inoculation failed to carry the effective inoculum over to the mungbean crop planted immediately after maize harvest and thus did not increase root colonization and grain yield of the succeeding crop. Fresh inoculation of the mungbean with G. mosseae increased grain yield over the uninoculated control.     

A comparison of arbuscular and ectomycorrhizal Eucalyptus coccifera: growth response, phosphorus uptake efficiency and external hyphal production

Eucalyptus coccifera Hook., a plant capable of forming both arbuscular mycorrhizas and ectomycorrhizas, was used to compare the effects of the two mycorrhizal types on phosphorus uptake and C allocation. Seedlings were grown in a P-deficient soil/sand mixture inoculated with peat/vermiculite spawn of Laccaria bicolor (Maire) Orton or Thelephora terrestris (Ehrh.) Fr.; or with 250-μm sievings from leek colonized by Glomus caledonium (Nicol. & Gerd.) Trappe & Gerde., Glomus sp. type E3 or Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe or with autoclaved spawn (non-mycorrhizal control). Before the 89-d harvest, a subset of the harvested plants was labelled with ¹⁴C (45–60-min pulse, 202-h chase). Growth promotion and the increase in seedling P content was largest in the two ectomycorrhizal treatments. Production of fluorescein diacetate-stained external hyphae was three to seven times higher by ectomycorrhizal (ECM) fungi compared with arbuscular mycorrhizal (AM) fungi and was highly correlated with P uptake and shoot weight. Phosphorus inflow rates of ECM and AM seedlings were 3·8 times, and 2·0–2·7 times those of non-mycorrhizal seedlings. Phosphorus acquisition efficiencies were similar (11·2 and 10·0 μmol P mmol⁻¹C for T. terrestris and Glomus E3 plants, respectively) for the two mycorrhizal types, and appeared to be greater than in uninoculated plants (7.2 μmol P mmol⁻¹C) grown at the same P level.