Arbuscular Mycorrhizal Fungi (AMF) and Biosolids Enhance the Growth of a Native Australian Grass on Sulphidic Gold Mine Tailings

We tested the effect of the addition of biosolids combined with a native mycorrhizal inoculum (Arbuscular Mycorrhizal Fungi [AMF]) on growth of a native Australian grass, and on trace element stabilization of sulphidic gold mine tailings. A glasshouse trial was established on four substrates: tailings (T); tailings with a layer of 5 cm topsoil (TS); tailings amended with 100 dry t ha^?1 biosolids (LB), and tailings amended with 500 dry t ha^?1 biosolids (HB). Pots of 1.2 L of capacity were established; some were inoculated with a mixture of Glomus sp. (WUM51–9227), Scutelospora aurigloba (WUM51–53), and Acaulospora levis (WUM46) culture mix, and others were uninoculated controls. Seeds of the native Australian grass, Bothriochloa macra were sown in the pots. Root infection, plant biomass production, nutrients and trace element concentrations in shoots were investigated. Addition of biosolids significantly increased AMF infection of roots compared to unamended substrates. No clear qualitative differences in colonization were detected. Addition of biosolids and AMF together clearly improved the establishment and growth of the native grass. Similar trends in nutritional status were shown for biosolids and inoculation with AMF treatments. Mycorrhizal inoculation increased plant biomass production and the effectiveness of nutrient uptake. The combined use of biosolids and mycorrhizal inoculation could be a reliable method for phytostabilization purposes in polluted substrates.     

The influences of arbuscular mycorrhizal fungus on phytostabilization of lead/zinc tailings using four plant species

A greenhouse experiment was conducted to investigate the effects of the arbuscular mycorrhizal fungus Funneliformis mosseae on three parameters: Pb, Zn, Cu and Cd accumulation, translocation and plant growth in perennial ryegrass (Lolium perenne), tall fescue (Festuca arundinacea), showy stonecrop (Hylotelephium spectabile) and Purple Heart (Tradescantia pallida). The purpose of this work is to enhance site-specific phytostabilization of lead/zinc mine tailings using native plant species. The results showed that mycorrhizal fungi inoculation significantly increased plant biomass of F. arundinacea, H. spectabile and T. pallida. The Pb, Zn, Cu and Cd concentrations in roots were higher than those in shoots both with and without mycorrhizae, with the exception of the Zn concentration in H. spectabile. Mycorrhizae generally increased metal concentrations in roots and decreased metal concentrations in shoots of L. perenne and F. arundinacea. In addition, it was found that the majority of the bioconcentration and translocation factors were lower than 1 and mycorrhizal fungi inoculation further reduced these values. These results suggest that appropriate plant species inoculated with mycorrhiza might be a potential approach to revegetating mine tailing sites and that H. spectabile is an appropriate plant for phytostabilization of Pb/Zn tailings in northern China due to its higher biomass production and lower metal accumulation in shoots.     

Phosphorus (P) efficiencies and mycorrhizal responsiveness of old and modern wheat cultivars

A pot experiment was carried out in a growth chamber to investigate P efficiencies and mycorrhizal responsiveness of modern (Krichauff and Excalibur) and old (Khapstein, Bobin, Comeback and Purple Straw) wheat cultivars (Triticum aestivum). The arbuscular mycorrhizal fungus (AMF) used in this study was Glomus intraradices. The growth medium was a soil/sand mixture with NaHCO₃-extractable P of 9.4 mg P kg^–1 and no extra P was added. Plant P efficiencies (uptake, utilisation and agronomic) were found to differ significantly between cultivars, but no general trends of changes with the year of release of the cultivar were found. AMF colonisation was found to decrease plant growth under our experimental conditions with low light intensity. Mycorrhizal responsiveness (MR) was measured in terms of the improvement in plant P nutrition (shoot P concentrations). MR was found to be generally lower in modern cultivars than in old cultivars, indicating that modern breeding programs may have reduced the responsiveness of modern wheat cultivars to arbuscular mycorrhizal fungi. MR was also found to decrease in general with increased plant P utilisation efficiency.     

Evaluating effect of arbuscular mycorrhizal fungal consortia and Azotobacter chroococcum in improving biomass yield of Jatropha curcas

This study was conducted to study the long-term impact of bioinoculants, Azotobacter chroococcum and arbuscular mycorrhizal fungi (AMF) on growth and biomass yield of Jatropha curcas grown in nursery and in field conditions. The experiment was set up in a randomized block design, and the following treatments was designed (T₁ = control, T₂ = Azotobacter, T₃ = inoculation with AMF, and T₄ = inoculation with Azotobacter + AMF). Data on various growth attributes (shoot height and shoot diameter) and biochemical parameters [leaf relative water content (LRWC), sugars, protein, and photosynthetic pigments] were recorded up to 6 months in the nursery and in the field (18 months). Results pertaining to morpho-physiological traits showed Azotobacter and AMF consortia increase shoot height, shoot diameter, LRWC, sugars, proteins, and photosynthetic pigments over control under nursery conditions. Besides enhancing the plant growth, these bioinoculants helped in better establishment of Jatropha plants under field conditions. A significant improvement in the shoot height, shoot diameter, fruit yield/plant, and seed yield (g)/plant was evident in 18-month-old Jatropha plants under field conditions when Azotobacter and AMF were co-inoculated. This work supports the application of bioinoculants for establishment of Jatropha curcas in semi-arid regions.     

Combined application of arbuscular mycorrhizal fungi and steel slag improves plant growth and reduces Cd,Pb accumulation in Zea mays

Abstract

Little attention has been paid to the combined use of arbuscular mycorrhizal fungus (AMF) and steel slag (SS) for ameliorating heavy metal polluted soils. A greenhouse pot experiment was conducted to study the effects of SS and AMF?Funneliformis mosseae (Fm), Glomus versiforme (Gv) and Rhizophagus intraradices (Ri) on plant growth and Cd, Pb uptake by maize grown in soils added with 5?mg Cd kg^?1 and 300?mg Pb kg^?1 soil. The combined usage of AMF and SS (AMF?+?SS) promoted maize growth, and Gv?+?SS had the most obvious effect. Meanwhile, single SS addition and AMF?+?SS decreased Cd, Pb concentrations in maize, and the greater reductions were found in combined utilization, and the lowest Cd, Pb concentrations of maize appeared in Gv?+?SS. Single SS amendment and AMF?+?SS enhanced soil pH and decreased soil diethylenetriaminepentaacetic acid (DTPA)-extractable Cd, Pb concentrations. Furthermore, alone and combined usage of AMF and SS increased contents of soil total glomalin. Our research indicated a synergistic effect between AMF and SS on enhancing plant growth and reducing Cd, Pb accumulation in maize, and Gv?+?SS exerted the most pronounced effect. This work suggests that AMF inoculation in combination with SS addition may be a potential method for not only phytostabilization of Pb-Cd-contaminated soil but maize safety production.     

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

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

Differential benefits of arbuscular mycorrhizal and ectomycorrhizal infection of Salix repens

 The functional significance of arbuscular mycorrhiza (AM) and ectomycorrhiza (EcM) for Salix repens, a dual mycorrhizal plant, was investigated over three harvest periods (12, 20 and 30 weeks). Cuttings of S. repens were collected in December (low shoot P) and March (high shoot P). Glomus mosseae (an arbuscular mycorrhizal fungus, AMF) resulted in low AM colonization (<5%), but showed large short-term (<12 weeks) effects on shoot growth and root length. Hebeloma leucosarx (an ectomycorrhizal fungus, EcMF) resulted in high EcM colonization (70%), but benefits occurred over a longer term (>12 weeks). Furthermore, G. mosseae colonization resulted in higher shoot P uptake, shoot growth, root growth and response duration for S. repens collected in December than for those collected in March, whereas with H. leucosarx and the non-mycorrhizal treatment there were no differences between cuttings collected on different dates. Low AMF colonization was effective in the short term for cuttings at both collecting dates. Low AMF colonization of S. repens occurred irrespective of the amount of AMF inoculum used. The intensities and relative amounts of AMF structures in S. repens and Trifolium repens were compared over three harvest periods (12, 20 and 30 weeks) to assess plant species effects on AM colonization patterns. Accepted: 13 October 2000     

Establishment and effectiveness of inoculated arbuscular mycorrhizal fungi in agricultural soils

Arbuscular mycorrhizal fungi (AMF) are promoted as biofertilizers for sustainable agriculture. So far, most researchers have investigated the effects of AMF on plant growth under highly controlled conditions with sterilized soil, soil substrates or soils with low available P or low inoculum potential. However, it is still poorly documented whether inoculated AMF can successfully establish in field soils with native AMF communities and enhance plant growth. We inoculated grassland microcosms planted with a grass–clover mixture (Lolium multiflorum and Trifolium pratense) with the arbuscular mycorrhizal fungus Rhizoglomus irregulare. The microcosms were filled with eight different unsterilized field soils that varied greatly in soil type and chemical characteristics and indigenous AMF communities. We tested whether inoculation with AMF enhanced plant biomass and R. irregulare abundance using a species specific qPCR. Inoculation increased the abundance of R. irregulare in all soils, irrespective of soil P availability, the initial abundance of R. irregulare or the abundance of native AM fungal communities. AMF inoculation had no effect on the grass but significantly enhanced clover yield in five out of eight field soils. The results demonstrate that AMF inoculation can be successful, even when soil P availability is high and native AMF communities are abundant.     

Differential growth response to arbuscular mycorrhizal fungi and plant density in two wild plants belonging to contrasting functional types

The effect of arbuscular mycorrhizal fungi (AMF) on plant growth was examined in two wild plant species belonging to contrasting functional types: an annual forb (Bidens pilosa, Asteraceae) and a deciduous shrub (Acacia caven, Fabaceae) at three contrasting plant densities (one, two, and three individuals per pot). AMF had a slightly negative effect on B. pilosa when the species grew in isolation while they positively affected A. caven. Positive effects of AMF on shoot mass of A. caven decreased at higher plant densities, while shoot mass of individuals of B. pilosa showed less marked differences between plant densities. When considering total biomass per pot, AMF positively affected A. caven growth while negatively affecting B. pilosa, at all three plant densities. Root/shoot ratio per pot was negatively affected by AMF but not plant density in both species. These findings highlight the importance of including plants belonging to different life forms and/or traits in research regarding the interaction between AMF and intraspecific plant competition.     

Differential Effects of a <Emphasis Type="Italic">Bacillus megaterium</Emphasis> Strain on <Emphasis Type="Italic">Lactuca sativa</Emphasis> Plant Growth Depending on the Origin of the Arbuscular Mycorrhizal Fungus Coinoculated: Physiologic and Biochemical Traits

Coinoculation with plant growth–promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF) has been proposed as an efficient method to increase plant growth. In this article we investigate how the interaction between three different AMF isolates (Glomus constrictum autochthonous, GcA; G. constrictum from collection, GcC; and commercial Glomus intraradices, Gi) and a Bacillus megaterium strain isolated from a Mediterranean calcareous soil affects Lactuca sativa L. plant growth. Inoculation with B. megaterium increased plant growth when in combination with two of the AMF isolates (GcA and Gi), but decreased it when in combination with GcC. At the same time, plants inoculated with the GcC fungus alone or in combination with B. megaterium (GcC+Bm) showed leaf symptoms of stress injury by accumulating proline and reducing the amount of photosynthetic pigments, whereas the opposite occurred in plants coinoculated with Gi fungus and B. megaterium (Gi+Bm). GcC+Bm leaves also presented the highest glucose-6-phosphate dehydrogenase (G6PDH) and the lowest glutamine synthetase (GS) enzymatic activities, whereas Gi+Bm leaves showed the highest GS activity. Results on these enzymatic activities are further discussed in relation to plant growth and performance.     

Development of mycorrhized vitroplants of Jatropha curcas L. at different rooting stages

In this work, we attempted to assess the effects of inoculation of arbuscular mycorrhizal fungus (AMF), Glomus clarum, on the survival and development of micropropagated Jatropha curcas plantlets at different rooting stages. Elongated shoots (average 3?cm) of J. curcas, maintained for 0, 14, or 21?days on rooting medium in the presence or absence of 1?mg?L^?1 indole-3-butyric acid (IBA), were transferred to a sand:soil:vermiculite (1:1/2:1) (v:v:v) substrate. At the time of transplantation, the plantlets were either inoculated or not inoculated with G. clarum that had been monoaxenically produced in Ri-transformed carrot roots. After a 2-week acclimatization period, 100?% of the plants kept for 0 or 14?days in rooting medium survived. However, those that remained for 21?days in rooting medium displayed post-acclimatization survival rates of 93 and 89?% for plants inoculated and non-inoculated with G. clarum, respectively. Colonization rates ranged from 70 to 93?%, and the stimulatory effects of AMF were evidenced by increased phosphorus uptake by plants and increases in all evaluated growth parameters, except plant height. Plants that were not subjected to the rooting stage showed growth similar to or higher than those subjected to the rooting stage, regardless of the addition of IBA. It can be concluded that stimulatory effects of mycorrhizal fungi were observed, and that the inoculation of J. curcas proved effective during the initial period of the acclimatization phase.     

Arbuscular mycorrhizal fungi native from a Mediterranean saline area enhance maize tolerance to salinity through improved ion homeostasis

Soil salinity restricts plant growth and productivity. Na⁺ represents the major ion causing toxicity because it competes with K⁺ for binding sites at the plasma membrane. Inoculation with arbuscular mycorrhizal fungi (AMF) can alleviate salt stress in the host plant through several mechanisms. These may include ion selection during the fungal uptake of nutrients from the soil or during transfer to the host plant. AM benefits could be enhanced when native AMF isolates are used. Thus, we investigated whether native AMF isolated from an area with problems of salinity and desertification can help maize plants to overcome the negative effects of salinity stress better than non‐AM plants or plants inoculated with non‐native AMF. Results showed that plants inoculated with two out the three native AMF had the highest shoot dry biomass at all salinity levels. Plants inoculated with the three native AMF showed significant increase of K⁺ and reduced Na⁺ accumulation as compared to non‐mycorrhizal plants, concomitantly with higher K⁺/Na⁺ ratios in their tissues. For the first time, these effects have been correlated with regulation of ZmAKT2, ZmSOS1 and ZmSKOR genes expression in the roots of maize, contributing to K⁺ and Na⁺ homeostasis in plants colonized by native AMF.     

Mechanistic understanding of interspecific interaction between a C4 grass and a C3 legume via arbuscular mycorrhizal fungi,as influenced by soil phosphorus availability using a 13C and 15N dual-labelled organic patch

Arbuscular mycorrhizal fungi (AMF) can improve plant nutrient acquisition, either by directly supplying nutrients to plants or by promoting soil organic matter mineralization, thereby affecting interspecific plant relationships in natural communities. We examined the mechanism by which the addition of P affects interspecific interactions between a C4 grass (Bothriochloa ischaemum, a dominant species in natural grasslands) and a C3 legume (Lespedeza davurica, a subordinate species in natural grasslands) via AMF and plant growth, by continuous ¹³C and ¹⁵N labelling, combined with soil enzyme analyses. The results of ¹⁵N labelling revealed that P addition affected the shoot uptake of N via AMF by B. ischaemum and L. davurica differently. Specifically, the addition of P significantly increased the shoot uptake of N via AMF by B. ischaemum but significantly decreased that by L. davurica. Interspecific plant interactions via AMF significantly facilitated the plant N uptake via AMF by B. ischaemum but significantly inhibited that by L. davurica under P-limited soil conditions, whereas the opposite effect was observed in the case of excess P. This was consistent with the impact of interspecific plant interaction via AMF on arbuscular mycorrhizal (AM) benefit for plant growth. Our data indicate that the capability of plant N uptake via AMF is an important mechanism that influences interspecific relationships between C4 grasses and C3 legumes. Moreover, the effect of AMF on the activities of the soil enzymes responsible for N and P mineralization substantially contributed to the consequence of interspecific plant interaction via AMF for plant growth.     

Interactions between Pseudomonas putida UW4 and Gigaspora rosea BEG9 and their consequences for the growth of cucumber under salt-stress conditions

Aims: After the determination of the toxic but nonlethal concentration of NaCl for cucumber, we examined the interaction between an ACC (1‐aminocyclopropane‐1‐carboxylate) deaminase producing bacterial strain and an arbuscular mycorrhizal fungus (AMF) and their effects on cucumber growth under salinity. Methods and Results: In the first experiment, cucumber seedlings were exposed to 0·1, 50, 100 or 200 mmol l^?1 NaCl, and plant biomass and leaf area were measured. While seeds exposed to 200 mmol l^?1 NaCl did not germinate, plant growth and leaf size were reduced by 50 or 100 mmol l^?1 salt. The latter salt cancentration caused plant death in 1 month. In the second experiment, seeds were inoculated with the ACC deaminase‐producing strain Pseudomonas putida UW4 (AcdS⁺), its mutant unable to produce the enzyme (AcdS^?), or the AMF Gigaspora rosea BEG9, individually or in combination and exposed to 75 mmol l^?1 salt. Plant morphometric and root architectural parameters, mycorrhizal and bacterial colonization and the influence of each micro‐organism on the photosynthetic efficiency were evaluated. The AcdS⁺ strain or the AMF, inoculated alone, increased plant growth, affected root architecture and improved photosynthetic activity. Mycorrhizal colonization was inhibited by each bacterial strain. Conclusions: Salinity negatively affects cucumber growth and health, but root colonization by ACC deaminase‐producing bacteria or arbuscular mycorrhizal fungi can improve plant tolerance to such stressful condition. Significance and Impact of the Study: Arbuscular mycorrhizal fungus and bacterial ACC deaminase may ameliorate plant growth under stressful conditions. It was previously shown that, under optimal growth conditions, Ps. putida UW4 AcdS⁺ increases root colonization by Gi. rosea resulting in synergistic effects on cucumber growth. These results suggest that while in optimal conditions ACC deaminase is mainly involved in the bacteria/fungus interactions, while under stressful conditions this enzyme plays a role in plant/bacterium interactions. This finding is relevant from an ecological and an applicative point of view.     

Effect of<Emphasis Type="Italic">Glomus intraradices</Emphasis> isolated from Pb-contaminated soil on Pb uptake by<Emphasis Type="Italic">Agrostis capillaris</Emphasis> is changed by its cultivation in a metal-free substrate

Development and heavy metal tolerance of two cultivation lineages of the indigenous isolate of arbuscular mycorrhizal fungus (AMF)Glomus intraradices PH5 were compared in a pot experiment in soil from lead (Pb) smelter waste deposits. One lineage was sub-cultured in original Pb-contaminated soil; the second one was maintained for 13 months in an inert substrate (river sand) without Pb stress. The contribution of these cultivation lineages to the Pb uptake and accumulation by the host plantAgrostis capillaris was investigated. The experiment was conducted in a compartmented system where the lateral compartments withAgrostis seedlings were separated from the central pot containing 4-week olderAgrostis plants by a nylon mesh for allowing out-growing of extraradical mycelium (ERM) from the pot. No differences in mycorrhizal colonization, ERM length and viability were observed between the two lineages ofG. intraradices PH5 in the soil of the isolate origin. However, the ability to support plant growth and Pb uptake differed between the lineages and also between the plants in the central pots and the lateral compartments. The growth of the plants in the central pots was positively affected by AMF inoculation. The plants inoculated with the lineage maintained in original soil showed larger shoot biomass and higher shoot P content as compared to the other inoculation treatments. The shoot Pb concentration of these plants was lower when compared to the plants inoculated with the lineage sub-cultured in the inert substrate. However the concentration did not differ from non-mycorrhizal control or from the reference isolateG. intraradices BEG75 from non-contaminated soil. Also shoot Pb contents were similar for all inoculation treatments. The development ofG. intraradices BEG75 in the contaminated soil was very poor; this isolate was not able to initiate colonization of seedlings in lateral compartments. In lateral compartments, growth of seedlings in contaminated soil was inhibited by theG. intraradices PH5 lineage maintained in the inert substrate. Pb translocation from the seedling roots to shoots was increased for plants inoculated with either lineage as compared to the non-mycorrhizal control; however, the increase for the lineage cultivated in the inert substrate was significantly higher in comparison with that maintained in the original soil. After 13 months of cultivation in a metal free substrate, theG. intraradices isolate from Pb contaminated soil did not lose its tolerance to Pb as regards colonization of plant roots and growth of ERM in the soil of its origin. However, its ability to support plant growth and to prevent Pb translocation from the roots to the shoots was decreased.     

Cadmium accumulation in sunflower plants influenced by arbuscular mycorrhiza

In order to investigate the cadmium (Cd) accumulation patterns and possible alleviation of Cd stress by mycorrhization, sunflower plants (Helianthus annuus L.) were grown in the presence or absence of Cd (20 micromol L(-1)) and inoculated or not inoculated with the arbuscular mycorrhizal fungus (AMF) Glomus intraradices. No visual symptoms of Cd phytotoxicity were observed; nevertheless, in non-mycorrhizal plants the presence of Cd decreased plant growth. The addition of Cd had no significant effect on either mycorrhizal colonization or the amount of extra-radical mycelia that was produced by the AMF. Cd accumulated mainly in roots; only 22% of the total Cd absorbed was translocated to the shoots, where it accumulated to an average of 228 mg Cd kg(-1). Although the shoot-to-root ratio of Cd was similar in both the AMF inoculated and non-inoculated plants, the total absorbed Cd was 23% higher in mycorrhizal plants. Cd concentration in AMF extra-radical mycelium was 728 microg g(-1) dry weight. Despite the greater absorption of Cd, mycorrhizal plants showed higher photosynthetic pigment concentrations and shoot P contents. Cd also influenced mineral nutrition, leading to decreased Ca and Cu shoot concentrations; N, Fe and Cu shoot contents; and increased S and K shoot concentrations. Cd induced guaiacol peroxidase activity in roots in both mycorrhizal and non-mycorrhizal plants, but this increase was much more accentuated in non-mycorrhizal roots. In conclusion, sunflower plants associated with G. intraradices were less sensitive to Cd stress than non-mycorrhizal plants. Mycorrhizal sunflowers showed enhanced Cd accumulation and some tolerance to excessive Cd concentrations in plant tissues.     

Mechanism of application nursery cultivation arbuscular mycorrhizal seedling in watermelon in the field

Arbuscular mycorrhizal fungi (AMF) colonisation of plant root facilitates the absorption of nutrients such as phosphorus (P) and enhances plant biotic and abiotic resistance generally. However, arbuscular mycorrhiza (AM) colonisation decreases with application of chemical fertiliser. Here, we investigated whether AMF inoculation in nurseries would facilitate AM colonisation and take physiological and ecological functions in watermelon (Citrullus lanatus) in the field. Pot experiments were carried out to study the change of AMF colonised seedling on physiology and gene expression in nursery site. Field experiments were performed to investigate the effect of nursery AMF inoculation on yield, quality and disease resistance of watermelon in the field. The results showed that nursery‐inoculated seedlings produced more dry matter and root surface area than non‐inoculated seedlings. Expression of the secretory purple acid phosphatase (PAP) genes ClaPAP10 and ClaPAP26 was up‐regulated following AMF colonisation. Accordingly, acid phosphatase activities at the root surface and P concentrations in seedling were enhanced. After transplantation to the field, the shoot dry matter and P concentration in old stem were higher in the nursery AMF inoculated seedlings than that in non‐AMF inoculated seedling. AMF inoculation also induced increase of yields and decrease of wilt disease indexes and soluble sugar content. In addition, acid phosphatase activities and AMF spore densities were increased by nursery‐inoculation in watermelon rhizosphere soil in the field. In conclusion, nursery colonisation AMF seedling enhanced watermelon growth and yield by improving the root growth and P acquisition in nursery cultivating stage, as well as optimised soil properties in the field. Nursery cultivation of watermelon seedling with AMF was an effective technique to reduce wilt disease in continuous cropped management in watermelon.     

Impact of two fluorescent pseudomonads and an arbuscular mycorrhizal fungus on tomato plant growth,root architecture and P acquisition

The ability of fluorescent pseudomonads and arbuscular mycorrhizal fungi (AMF) to promote plant growth is well documented but knowledge of the impact of pseudomonad-mycorrhiza mixed inocula on root architecture is scanty. In the present work, growth and root architecture of tomato plants (Lycopersicon esculentum Mill. cv. Guadalete), inoculated or not with Pseudomonas fluorescens 92rk and P190r and/or the AMF Glomus mosseae BEG12, were evaluated by measuring shoot and root fresh weight and by analysing morphometric parameters of the root system. The influence of the microorganisms on phosphorus (P) acquisition was assayed as total P accumulated in leaves of plants inoculated or not with the three microorganisms. The two bacterial strains and the AMF, alone or in combination, promoted plant growth. P. fluorescens 92rk and G. mosseae BEG12 when co-inoculated had a synergistic effect on root fresh weight. Moreover, co-inoculation of the three microorganisms synergistically increased plant growth compared with singly inoculated plants. Both the fluorescent pseudomonads and the myco-symbiont, depending on the inoculum combination, strongly affected root architecture. P. fluorescens 92rk increased mycorrhizal colonization, suggesting that this strain is a mycorrhization helper bacterium. Finally, the bacterial strains and the AMF, alone or in combination, improved plant mineral nutrition by increasing leaf P content. These results support the potential use of fluorescent pseudomonads and AMF as mixed inoculants for tomato and suggest that improved tomato growth could be related to the increase in P acquisition.     

不同强度盐胁迫下AM真菌对羊草生长的影响

不同浓度NaCl盐处理下,AM真菌对羊草(Leymus chinensis)的侵染能力和对植物生长的影响,从植物形态和离子含量角度探讨了AM真菌提高羊草耐盐性的作用机理。结果表明,在高盐胁迫下,AM真菌显著降低了盐胁迫效应,提高了羊草生物量,菌根效应明显。菌根化羊草的根茎比显著增加,并且N、P浓度较高,Na~+和Cl~-离子浓度较低,表明AM真菌即促进羊草对营养元素的吸收,又减少了离子毒害。菌根化羊草的Ca~(2+)和K~+离子浓度,以及P/Na~+和K~+/Na~+比高于非菌根化羊草,表明AM真菌可通过调节渗透势以避免或减缓盐胁迫造成的生理缺水。随着盐胁迫的增加,菌根化羊草对磷的依赖性逐渐转换为对钾的依赖性。研究结果有助于揭示AM真菌提高植物耐盐能力的作用机理,并对应用菌根技术修复盐化草地具有理论指导意义。     

西南桦幼苗接种丛枝菌根真菌的生长与光合生理响应

为了解丛枝菌根真菌(arbuscular mycorrhiza,AMF)对西南桦幼苗生长和光合生理的影响,对西南桦(Betula alnoides)优良无性系接种AMF菌株后的生长、光合参数、叶绿素含量和荧光参数进行了研究。结果表明,6个AMF菌株均能与西南桦无性系幼苗形成共生体,接种根内球囊霉(Glomus intraradices)菌株(AMF5)和摩西球囊霉(G.mosseae)HUN03B菌株(AMF3)显著提高了幼苗生长量、净光合速率、水分利用效率、叶绿素含量和荧光参数(P0.05),显示出AMF5、AMF3与幼苗的亲和力明显优于其他菌株。西南桦4个无性系间的菌根侵染率差异不显著(P0.05),但AMF对无性系FB4、BY1的促生效应显著优于FB4+和A5。因此,适合与西南桦共生的优良菌株为AMF5和AMF3,这为西南桦菌根化育苗提供理论依据。