砷污染土壤中接种丛枝菌根真菌和蚯蚓对土壤线虫群落和植物砷吸收的影响

The influences of arbuscular mycorrhizal fungi (MF, Acaulospora spp. and Glomus spp.), rice straw and earthworms (RE, Eisenia foetida) on nematode communities and arsenic (As) uptake by maize (Zea mays L.) in As-contaminated soils were examined in a field experiment conducted in Wujiang, Jiangsu Province, China. The experiment was designed as a 2 × 2 factorial with the factors of MF (inoculated or uninoculated) and RE (added or not added). The results demonstrated that MF inoculation led to significantly higher root colonization of MF and root dry weight. Plants inoculated with both MF and RE had the highest As concentrations in root. The number of total nematodes increased with MF inoculation when RE was absent, and decreased with RE addition when MF was inoculated. The improved abundance of nematodes with the MF treatment implied that the tested MF acted as food sources for fungivores. The abundances of omnivores-predators and plant parasites were reduced by earthworm activity. Twenty-seven genera of nematodes were identified, with Filenchus dominant in all treatments. Trophic diversity (TD), Shannon-Weaver diversity (H′), Simpson dominance index (λ), and species richness (SR) indicated higher species diversity, more proportionate species composition, evenly distributed species, and more food sources in the MF, RE, and their interaction treatments. Maturity index (MI) showed a moderately disturbed environment due to As pollution. Besides enhancing plant uptake of contaminants, MF and RE amendments could also improve soil health by restoring the structure of soil communities, as reflected by more stable nematode community structure.     

Interactions between mycorrhizal fungi and Collembola: effects on root structure of competing plant species

Mycorrhizal fungi influence plant nutrition and therefore likely modify competition between plants. By affecting mycorrhiza formation and nutrient availability of plants, Collembola may influence competitive interactions of plant roots. We investigated the effect of Collembola (Protaphorura fimata Gisin), a mycorrhizal fungus (Glomus intraradices Schenck and Smith), and their interaction on plant growth and root structure of two plant species, Lolium perenne L. (perennial ryegrass) and Trifolium repens L. (white clover). In a laboratory experiment, two individuals of each plant species were grown either in monoculture or in competition to the respective other plant species. Overall, L. perenne built up more biomass than T. repens. The clover competed poorly with grass, whereas the L. perenne grew less in presence of conspecifics. In particular, presence of conspecifics in the grass and presence of grass in clover reduced shoot and root biomass, root length, number of root tips, and root volume. Collembola reduced shoot biomass in L. perenne, enhanced root length and number of root tips, but reduced root diameter and volume. The effects of Collembola on T. repens were less pronounced, but Collembola enhanced root length and number of root tips. In contrast to our hypothesis, changes in plant biomass and root structure in the presence of Collembola were not associated with a reduction in mycorrhizal formation. Presumably, Collembola affected root structure via changes in the amount of nutrients available and their spatial distribution.     

接种丛枝菌根真菌(AMF)对施磷石膏云烟87的生长以及砷污染的影响

【目的】丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)能够促进作物养分的吸收及生长,且对土壤砷污染有一定的抗性。磷石膏(phosphogypsum,PG)因含有丰富的磷、硫等养分可以为作物生长提供必要的养分,同时也可能带来砷污染的风险。【方法】为了探讨接种AMF对云烟87生长的影响以及磷石膏农用可能引起的砷污染风险,通过盆栽模拟试验研究了不同PG添加量(0和40 g/kg以PG0、PG40表示)和接种不同AMF[不接种None mycorrhizal(NM)、接种G.mosseae丛枝菌根真菌(GM)、接种G.aggregatum丛枝菌根真菌(GA)]对云烟87苗期生长及其磷、硫、砷吸收的影响。【结果】试验结果表明:无论接种与否,PG40处理的云烟87植株磷含量、吸收量及吸收效率均显著增加,其地上部硫含量及吸收量也显著增加;除NM处理外,添加PG均显著增加了云烟87根系的硫含量、硫吸收量及吸收效率,并显著增加了其植株的生物量。相同PG添加水平下,与NM处理相比,接种GM显著增加了云烟87根系的磷、硫吸收效率和植株的磷、硫含量及吸收量,另外,GM处理显著降低了其地上部砷含量及吸收量但显著增加了其植株的磷砷吸收比。在PG0处理下,接种GA显著增加了云烟87植株的磷含量及吸收量,并显著增加了其地上部硫含量及吸收量。在PG40处理下,接种GA显著增加了云烟87根系的硫含量和吸收量以及植株的生物量。无论是否添加PG,接种GA不同程度地降低了云烟87地上部砷含量和吸收量从而增加了其地上部的磷砷吸收比。【结论】在所有复合处理中,以添加磷石膏40 g/kg和接种GM对云烟87生长的促进效果较好,对施用磷石膏造成的砷污染有一定程度的抵御作用。     

Earthworm-mycorrhiza interaction on Cd uptake and growth of ryegrass

The effects of inoculation of earthworms and arbuscular mycorrhiza separately, and in combination, on Cd uptake and growth of ryegrass were studied in soils contaminated with 0, 5, 10, 20 mg of Cd kg⁻¹ soil. Both earthworms and mycorrhiza were able to survive in all the treatments with added Cd. Earthworm activity significantly increased mycorrhizal infection rate of root and ryegrass shoot biomass. Earthworm activity decreased soil pH by about 0.2 units, and enhanced root Cd concentration and ryegrass Cd uptake. Mycorrhiza inoculation increased shoot and root Cd concentration substantially, and at the highest dosage of 20 mg Cd kg⁻¹ decreased biomass of ryegrass. Inoculation of both earthworms and mycorrhiza increased ryegrass shoot Cd uptake at low Cd concentrations (5 and 10 mg Cd kg⁻¹ soil), when compared with inoculation of earthworms or mycorrhiza alone. In conclusion, earthworm, mycorrhiza and their interaction may have a potential role in elevating phytoextraction efficiency in low to medium level metal contaminated soil.     

Arbuscular mycorrhizal fungi and nematodes are involved in negative feedback on a dual culture of alfalfa and Russian wildrye

The complex biological interactions taking place in soil–plant systems may sometimes alter the functioning of an ecosystem. We examined the relationship between arbuscular mycorrhizal (AM) root colonization, nematode populations, and plant competition in an 8-year-old field experiment comparing alfalfa monoculture to dual culture of alfalfa (Medicago sativa L.) and Russian wildrye (Psathyostachys juncea Fisch. Nevski) (RWR) grown under different soil P fertility levels, in a Brown Chernozemic soil in Saskatchewan. The experiment included three P rates: 0, 20 and 40 kg P₂O₅ ha⁻¹ (0P, 20P and 40P) applied annually and was sampled three times during the cropping season: 30 June, 1 September and 30 September. Higher AM symbiotic development compensated for reduced soil P fertility in alfalfa stands without RWR and forage dry matter yield was not affected by P rates. But in the presence of RWR, reduced soil P fertility at 0P and 20P led to forage yield reduction. Fertilization treatments modified the soil microbial community structure only in the presence of RWR, as revealed by discriminant analysis of the profiles of microbial phospholipids fatty acid in soil lipid extracts and functional nematode groups. Arbuscular mycorrhizal root colonization level was reduced with P fertilizer both in the presence and absence of RWR. In the presence of RWR, lower plant AM root colonization was concurrent with higher abundance of total, fungivorous and omnivorous nematodes. Our results are consistent with a model of negative feedback from the plant-associated soil microflora where the presence of RWR increased the population of fungivorous nematodes and grazing of AM hyphae. Negative impacts were larger in low P fertility soils promoting AM symbiotic development. The unexpected decrease in alfalfa–RWR dual culture yield under 0P and 20P fertilization levels was attributed to a carbon drain created by enhanced nematode feeding on AM fungi in the presence of RWR.     

Interaction between earthworms and arbuscular mycorrhizal fungi on the degradation of oxytetracycline in soils

The interactive impact of earthworms (Eisenia fetida) and arbuscular mycorrhizal fungi (Rhizophagus intraradices, AM fungi) on the degradation of oxytetracycline (OTC) in soils was studied under greenhouse conditions. Treatments included maize plants inoculated vs. not inoculated with AM fungi and treated with or without earthworms at low (1 mg kg⁻¹ soil DM) or high (100 mg kg⁻¹ soil DM) OTC rates. The root colonization rate, the hyphal density of mycorrhizae, the residual OTC concentration in soils, catalase, dehydrogenase, urease, soil microbial biomass C, Shannon–Wiener index (H) for microbial communities from T-RFLP profiles were measured at harvest. The results indicated that earthworms and AM fungi would individually or interactively enhance OTC decomposition and significantly decreased the residual OTC concentration at both high and low OTC rates. Both earthworms and AM fungi could promote the degradation of OTC by increasing soil microbial biomass C at both high and low OTC rates. The effect of soil enzyme activity and soil microbial diversity on OTC decomposition was different between high and low OTC rates. Hyphomicrobium and Bacillus cereus were dominant bacteria, and Thielavia and Chaetomium were dominant phyla of fungi at all occasions. Earthworm activity stimulated the growth of Hyphomicrobium and Thielavia, while AM fungi may stimulate B. cereus, Thielavia and Chaetomium, resulting in greater OTC decomposition. The interaction between earthworms and AM fungi in affecting the degradation of OTC may be attributed to different mechanisms, depending on soil microbial biomass, function (enzyme activity) and communities (the abundance of Hyphomicrobium, B. cereus, Thielavia and Chaetomium) in the soil.     

AM真菌对烟苗生长及某些生理指标的影响

在低浓度营养液条件下,利用漂浮育苗技术培育烟苗,于播种期、小十字期、生根期分别接种不同的AM真菌,研究了它们对烟苗生长、营养和某些生理指标的影响。结果表明,越早接种AM真菌,其侵染率越高;播种期接种,侵染率达到39.2%～59.6%。AM真菌的菌根效应因菌种(株)不同而异,接种球囊霉真菌（BEG-141）后,显著增加烟苗干重、磷含量、氮磷钾吸收量、叶绿素含量,以及根系硝酸还原酶、超氧化物歧化酶和几丁质酶活性。表明在漂浮育苗技术中,播种期接种适宜的AM真菌是培育壮苗的有效措施。     

丛枝菌根真菌对镉污染土壤中黑麦草幼苗生长的影响

通过不同浓度的镉污染土壤接种丛枝菌根真菌的黑麦草盆栽试验,研究了丛枝菌根真菌对镉污染条件下黑麦草幼苗生长的影响。结果表明:重度镉污染(Cd2+:180 mg/kg)条件下,Glomus mosseae对黑麦草根系的侵染率仍达到30.23%,对黑麦草的生长有较好的促进作用;丛枝菌根在一定程度上缓解了镉污染对黑麦草株高、根长和生物量积累的抑制;镉污染显著降低黑麦草叶片的叶绿素含量,叶绿素a在重度镉污染时下降幅度最大,不接种丛枝菌根真菌的黑麦草较对照下降37.9%,而接种的黑麦草下降26.7%,接种菌根真菌在中重度镉污染条件下显著提高了黑麦草叶片的叶绿素含量;重度镉污染下接种和不接种的黑麦草根系活力都开始显著下降,但接种植株根系活力下降的幅度小于不接种植株。     

Peach seedling growth in replant and non-replant soils after inoculation with arbuscular mycorrhizal fungi

The effect of pre-inoculation with arbuscular mycorrhizal fungi (AMF) on post-transplant growth of peach seedlings in replant and non-replant soils was studied for two successive seasons. Seedlings raised in sterile media and pre-inoculated with soil-based Gigaspora margarita inoculum were transplanted in replant and non-replant field soils alongside non-inoculated controls. Pre-inoculated seedlings transplanted in non-replant soils showed greater initial growth in the first year. Plant height, and lateral shoot length and number was highest in non-replant soils irrespective of mycorrhizal pre-inoculation. Similarly, biomass yield was significantly higher in seedlings in non-replant soils, though there were no significant differences in shoot/root ratios, and in tissue mineral content between and within treatments. Seedling infection by indigenous AMF was high in both replant and non-replant soils, and even non-inoculated seedlings recorded high infection levels after the first season. Generally, mycorrhizal activity was lower, and spore populations higher in replant soils, while the opposite was true in non-replant soils. It seems that soil sickness has a negative impact on plant metabolism and limits the capacity of the plant host to support the mycorrhizal symbiosis.     

Community structure of arbuscular mycorrhizal fungi associated with Robinia pseudoacacia in uncontaminated and heavy metal contaminated soils

The significance of arbuscular mycorrhizal fungi (AMF) in soil remediation has been widely recognized because of their ability to promote plant growth and increase phytoremediation efficiency in heavy metal (HM) polluted soils by improving plant nutrient absorption and by influencing the fate of the metals in the plant and soil. However, the symbiotic functions of AMF in remediation of polluted soils depend on plant–fungus–soil combinations and are greatly influenced by environmental conditions. To better understand the adaptation of plants and the related mycorrhizae to extreme environmental conditions, AMF colonization, spore density and community structure were analyzed in roots or rhizosphere soils of Robinia pseudoacacia. Mycorrhization was compared between uncontaminated soil and heavy metal contaminated soil from a lead–zinc mining region of northwest China. Samples were analyzed by restriction fragment length polymorphism (RFLP) screening with AMF-specific primers (NS31 and AM1), and sequencing of rRNA small subunit (SSU). The phylogenetic analysis revealed 28 AMF group types, including six AMF families: Glomeraceae, Claroideoglomeraceae, Diversisporaceae, Acaulosporaceae, Pacisporaceae, and Gigasporaceae. Of all AMF group types, six (21%) were detected based on spore samples alone, four (14%) based on root samples alone, and five (18%) based on samples from root, soil and spore. Glo9 (Rhizophagus intraradices), Glo17 (Funneliformis mosseae) and Acau3 (Acaulospora sp.) were the three most abundant AMF group types in the current study. Soil Pb and Zn concentrations, pH, organic matter content, and phosphorus levels all showed significant correlations with the AMF species compositions in root and soil samples. Overall, the uncontaminated sites had higher species diversity than sites with heavy metal contamination. The study highlights the effects of different soil chemical parameters on AMF colonization, spore density and community structure in contaminated and uncontaminated sites. The tolerant AMF species isolated and identified from this study have potential for application in phytoremediation of heavy metal contaminated areas.     

Facilitation of seedling growth and nutrient uptake by indigenous arbuscular mycorrhizal fungi in intensive agroecosytems

A modified in-growth core technique was employed to determine the contribution of indigenous arbuscular mycorrhizal fungi (AMF) to plant growth and nutrient uptake in intensive agroecosystems at two Experimental field sites at Shangzhuang (Experiment I) and Quzhou (Experiment II) in North China. The growth cores (26.5 cm depth, 5 cm diameter for maize plants, and 4 cm for alfalfa and tomato plants) were covered with 40-μm nylon mesh (restriction of hyphal growth) and buried in the soil. They either remained static (static mesh) or were regularly rotated (rotated mesh) to disrupt hyphal penetration into the cores. A non-rotated 0.45-μm mesh (block mesh, inhibition of hyphal growth) treatment which remained static was also included to compare with the rotated mesh treatment (Experiment I). Growth cores from the two experimental sites had different soil types and two contrasting low P levels. The soil in the growth cores was sieved and sterilized before being placed into the growth core. Three plant species, namely maize, tomato and alfalfa were selected. The growth periods for maize plants were 35 days (Experiment I) and 39 days (Experiment II), respectively, and the corresponding growth periods for tomato and alfalfa were 67 days (Experiment I) and 53 days (Experiment II). At harvest the AMF species inside and outside the in-growth cores were identified by polymerase chain reaction (PCR), cloning and sequencing. Irrespective of plant species or genotype (maize), root colonization rates and hyphal length density (Experiment I) were generally suppressed in the rotated mesh treatment. The inhibition of hyphal growth by block mesh was comparable to that by the rotated mesh treatment. The growth of all three plant species in static mesh at the two Experimental sites, at both low (Experiment I) and sub-optimal soil P supply levels (Experiment II), was significantly higher than in the rotated (or block mesh) treatment. Root colonization rates of three maize genotypes were positively correlated with plant P concentration (Experiment II). Uptake efficiencies of P and N were significantly higher in static mesh than in the rotated (or block) treatment. AMF species detected (Experiment I) were all Glomerales, including the genera Glomus and Rhizophagus. One identified species of Rhizophagus intraradices and one Glomus viscosum-like phylotype were the dominant species. We conclude that the indigenous AM are crucial for early seedling growth, particularly for plants with small seeds and low P reserves and when seedlings exhibit P deficiency. The facilitation effect is highly relevant to enhanced root P (and possibly N) uptake and P delivery by the fungal mycelium. Our results have implications for the importance of maintenance of intact hyphal networks in intensive agroecosystems.     

不同施肥量条件下AM真菌对烟苗生长及营养状况的影响

试验设置不同施肥量,于播种期分别接种根内球囊霉菌(Glomus intraradices Smith和Schenck,BEG193)和幼套球囊霉菌(Glomuse etunicatum Becker和Gerdemann,BEG168),探索了利用烤烟漂浮育苗技术生产菌根化烟苗和培育壮苗的可能性。结果表明:随着养分供应量的减少,AM真菌的侵染率提高,BEG193的侵染率高于BEG168。减施肥料总体上抑制烟苗生长,使烟苗生物量降低;但接种AM真菌显著促进烟苗生长,烟苗平均生物量比不接种的处理增加了74.38%(BEG168)和48.32%(BEG193)。接种BEG168使烟苗氮、磷、钾含量显著增加;接种BEG193主要是提高了烟苗含磷量。在施肥量减少75%辅以少量追肥的情况下,接种BEG168之后,烟苗生长状况和磷、钾含量超过或与常规施肥的非菌根苗相似。因此,在集约化烤烟漂浮育苗过程中,可采用接种AM真菌BEG168的方式培育壮苗,同时降低施肥量,减轻废弃营养液产生的环境污染。此外,接种AM真菌显著提高基质中的酸性磷酸酶活性,菌根苗基质中的磷酸酶活性随施肥量的降低而逐渐升高。因此,接种AM真菌有益于基质中有机磷的吸收利用,这可能是菌根烟苗含磷量提高的重要原因之一。     

The impact of arbuscular mycorrhizal fungi on strawberry tolerance to root damage and drought stress

Individually, arbuscular mycorrhizal fungi (AMF), drought stress, and root damage can alter terrestrial plant performance but the joint effects of these three factors have not been explored. Because AMF can improve water relations, colonization by these root symbionts may increase the host’s tolerance of drought especially when roots have been compromised by herbivory. This full factorial study examined effects of AMF, water deficit, and artificial root herbivory in three genotypes of wild strawberry, Fragaria virginiana Duchesne that originated from the same restored tallgrass prairie as the AMF inoculum. Drought stress and root damage altered allocation to roots vs. shoots but the effects were not additive and the interaction did not depend on AMF treatment. Effects of AMF were absent with one exception: root damage significantly reduced belowground mass only in plants inoculated with AMF. Although drought stress did not interact with the AMF treatment, both drought stress and root damage reduced the abundance of arbuscules, and especially vesicles, and colonization varied among genotypes. Failure to detect strong effects of AMF on host growth could be due to variable responses of individual AMF species summing to no net effects. Functionally, AMF were primarily commensals of strawberry in this study.     

丛枝菌根真菌对玉米生长生态效应的影响

1996～1998年试验研究了大田不施肥条件下3种泡囊丛枝菌根真菌Arbuscular mycorrhizal fungi (AMF),即 Glomus mosseae(G.m)、Glomus versifome(G.v)、Sclerocystis sinousa(S.s)对玉米生长的生态效应.结果表明,AMF处理的玉米根系活力为对照的2.32～3.05倍,玉米N素吸收比对照增加24.14%～56.65%,玉米P素吸收比对照增加41.14%～78.29%,促进玉米生长发育显著;在灭菌条件下G.m、G.v、S.s处理分别比对照增产17.63%、22.91%和10.80%;而不灭菌条件下3个处理分别比对照增产10.35%、20.56%和4.53%,同时显著提高玉米的水分供应状况.     

Fermentation of sugar beet waste by Aspergillus niger facilitates growth and P uptake of external mycelium of mixed populations of arbuscular mycorrhizal fungi

Sugar beet waste has potential value as a soil amendment and this work studied whether fermentation of the waste by Aspergillus niger would influence the growth and P uptake of arbuscular mycorrhizal (AM) fungi. Plants were grown in compartmentalised growth units, each with a root compartment (RC) and two lateral root-free compartments (RFC). One RFC contained untreated soil while the other RFC contained soil, which was uniformly mixed with sugar beet waste, either untreated (SB) or degraded by A. niger (ASB) in a rock phosphate (RP)-supplied medium. The soil in each pair of RFC was labelled with ³³P and ³²P in order to measure P uptake by the AM fungal mycelium, of which length density was also measured. Whole cell fatty acid (WCFA) signatures were used as biomarkers of the AM fungal mycelium and other soil microorganisms. The amount of biomarkers of saprotrophic fungi and both Gram-positive and Gram-negative bacteria was higher in SB than in ASB treatments. Whilst ASB increased growth and activity of AM mycelium, SB had the opposite effect. Moreover, shoot P content was increased by the addition of ASB, and by inoculation with AM fungi. Modification of soil microbial structure and production of exudates by A. niger, as a consequence of fermentation process of sugar beet waste, could possibly explain the increase of AM growth in ASB treatments. On the other hand, the highest P uptake was a result of the solubilisation of rock phosphate by A. niger during the fermentation.     

三种土壤上六种丛枝菌根真菌生长特征和接种效应

以分离于华北、华中和华南3个生态区及法国引进的丛枝菌根真菌为试验菌株,采用三室根箱培养的方法,研究了它们在华北、华中和华南3种典型土壤褐土、棕壤和红壤上的菌根形成、接种效应、磷吸收贡献和根外菌物量情况。结果表明,6种菌株在上述指标上存在显著的种间或生态型差异,土壤与菌株间存在显著的交互作用。6种菌株在3种土壤上都能与玉米形成菌根,在褐土和棕壤上大多数菌株在分离地所在地区土壤类型上的菌根侵染率较高,说明其对该土壤条件的适应性较强;在红壤强酸性土壤条件抑制了菌根真菌的侵染。菌株BEG168、BEG167、BEG151、BEG221和BEG141在褐土上,BEG151和BEG221在棕壤上,BEG168和BEG150在红壤上显著提高了玉米的生物量。在褐土和棕壤上,除BEG150外,BEG168、BEG167、BEG151、BEG221和BEG141能显著促进宿主吸磷;而在红壤上,BEG168和BEG141显著促进了宿主吸磷。若以真菌的根外菌物量作为衡量AM真菌菌株土壤生态适应性的指标,BEG141和BEG167是生态适应性强的菌株,为广幅生态型菌株;菌株BEG168和BEG151次之,前者在棕壤上适应性高,后者在红壤上适应性高。BEG150和BEG221生态适应性较窄,仅适应红壤或褐土,为窄幅生态型菌株。Glomus.etunicatum的两个生态型BEG168和BEG221在土壤生态适应性上差异很大,前者在两种土壤上收集到菌物量,而后者只在褐土上收集到菌物量。土壤条件可以决定丛枝菌根真菌的生长状况和功能。     

Improved growth and Cu tolerance of Cu excess-stressed white clover after inoculation with arbuscular mycorrhizal fungi

The effects of arbuscular mycorrhizal (AM) fungus, Glomus intraradices, on growth and copper (Cu) tolerance of white clover (Trifolium repens) were investigated in soils with different Cu amounts. The AM inoculation increased plant biomass and the total or bound Cu concentrations in shoots and roots but decreased the total Cu in soils and the exchangeable Cu in shoots, roots and soils at all Cu levels. Mycorrhizal plants had higher levels of root phosphorus and shoot zinc (Zn) at lower Cu levels and more nitrogen and Zn in roots and potassium, calcium and magnesium in shoots and roots at all Cu addition levels. Additionally, AM inoculation enhanced urease, acid phosphatase and catalase activities in rhizosphere soils and mycorrhizal roots showed higher levels of peroxidase, catalase, proline and soluble sugar at all Cu addition levels. These results indicate that mycorrhizal white clover is potentially suitable for Cu phytoremediation based on greenhouse studies.     

Effects of arbuscular mycorrhizal fungi on zinc uptake, translocation and accumulation in winter wheat during whole plant growth stages

Although arbuscular mycorrhizal fungi (AMF) could play important roles in zinc (Zn) uptake in host plants, the effects of AMF on Zn uptake and transport in winter wheat during the whole growth stages remain unclear. A pot experiment was conducted to investigate the effects of Funneliformis mosseae (Fm) and Claroideoglomus etunicatum (Ce) on Zn absorption, transport, and accumulation in winter wheat growing in soils spiked with different Zn levels (0, 2.5, and 25 mg kg^-1). The results showed that there was a significant correlation between mycorrhizal colonization rate and Zn absorption efficiency in winter wheat roots during the post-anthesis period, but there was no significant correlation during the pre-anthesis period. Arbuscular mycorrhizal fungi significantly increased Zn concentrations (0.56-1.58 times) in wheat grains under 0 mg kg^-1 Zn level, but decreased Zn concentrations in wheat grains under 25 mg kg^-1 Zn level. Additionally, at the filling and maturity stages, AMF increased Zn absorption rate and the contribution of root Zn uptake to grain Zn by 3-14 and 0.36-0.64 times, respectively, under 0 mg kg^-1 Zn level and 0.21-1.02 and 0.27-0.37 times, respectively, under 2.5 mg kg^-1 Zn level. However, AMF decreased root Zn absorption rate (0.32-0.61 times) and increased the contribution of Zn remobilization in vegetative tissues to grain Zn (1.69-2.01 times) under 25 mg kg^-1 Zn level. This study would complement the mechanisms and effects of AMF on Zn absorption and transport in winter wheat and provide a potential method for the application of AMF to enrich wheat grain Zn.     

Growth and interactions of arbuscular mycorrhizal fungi in soils from limestone and acid rock habitats

Arbuscular mycorrhizal (AM) development in different soil types, and the influence of AM fungal hyphae on their original soil were investigated. Plantago lanceolata, which can grow in soils of a very wide pH range, was grown in two closely related limestone soils and an acid soil from rock habitats. Plants were colonised by the indigenous AM fungal community. The use of compartmented systems allowed us to compare soil with and without mycorrhizal hyphae. Root colonisation of P. lanceolata was markedly higher in the limestone soils (30-60%) than in the acid soil (5-20%), both in the original habitat and in the experimental study. Growth of extraradical AM fungal hyphae was detected in the limestone soils, but not in the acid soil, using the signature fatty acid 16:1ω5 as biomass indicator. Analysis of signature fatty acids demonstrated an increased microbial biomass in the presence of AM fungal hyphae as judged for example from an increased amount of NLFA 16:0 with 30 nmol g⁻¹ in one of the limestone soils. Bacterial activity, but not soil phosphatase activity, was increased by around 25% in the presence of mycorrhizal hyphae in the first harvest of limestone soils. AM fungal hyphae can thus stimulate microorganisms. However, no effect of AM hyphae was observed on the soil pH or organic matter content in the limestone soils and the available P was not depleted.