Growth Of Arbuscular Mycorrhizal Fungi Research Articles

Glyphosate decreases mycorrhizal colonization and affects plant-soil feedback

Our aim was to study the effects of glyphosate, tilling practice and cultivation history on mycorrhizal colonization and growth of target (weeds) and non-target (crops) plants. Glyphosate, the world's most widely used pesticide, inhibits an enzyme found in plants but also in microbes. We examined the effects of glyphosate treatment applied in the preceding fall on growth of a perennial weed, Elymus repens (target plant) and a forage grass, Festuca pratensis (non-target plant) and their arbuscular mycorrhizal fungal (AMF) root colonization in a field pot experiment. Non-target plants were sown in the following spring. Furthermore, we tested if glyphosate effects depend on tillage or soil properties modulated by long cultivation history of endophyte symbiotic grass (E+ grass). AMF root colonization, plant establishment and growth, glyphosate residues in plants, and soil chemistry were measured. Glyphosate reduced the mycorrhizal colonization and growth of both target and non-target grasses. The magnitude of reduction depended on tillage and soil properties due to cultivation history of E+ grass. We detected glyphosate residues in weeds and crop plants in the growing season following the glyphosate treatment. Residues were higher in plants growing in no-till pots compared to conspecifics in tilled pots. These results demonstrate negative effects of glyphosate on non-target organisms in agricultural environments and grassland ecosystems.

Long-term grazing exclusion influences arbuscular mycorrhizal fungi and their association with vegetation in typical steppe of Inner Mongolia, China

It is not certain that long-term grazing exclusion influences arbuscular mycorrhizal (AM) fungi and their association with steppe vegetation. In this study, soil and plant samples were collected from two sites of grazing exclusion since 1983 (E83) and 1996 (E96), and one site of free-grazing (FG) in the typical steppe of Xilinguole League, Inner Mongolia, China, and assayed for soil basic physicochemical properties, AM fungal parameters, aboveground biomass and shoot phosphorus (P) uptake as well. The results showed that long-term grazing exclusion of E83 and E96 led to less drastic seasonal changes and significant increases in spore density, hyphal length density and root colonization intensity of AM fungi and even soil alkaline phosphatase activity, by up to 300, 168, 110 and 102%, respectively, compared with those of FG site. In addition, the total aboveground biomass and shoot P uptake of E83 and E96 were 75–992% and 58–645%, respectively, higher than those of FG. Generally, the root colonization intensity, spore density, and hyphal length density of AM fungi were all positively correlated with the aboveground biomass and even shoot P uptake of plant. These results may imply that grazing exclusion play a critical role in increasing the growth of AM fungi, and subsequently, may increase plant P uptake and aboveground biomass production. Moreover, the spore density could sensitively reflect the impacts of long-term grazing exclusion on AM fungi since survival strategy of spores in soil.

Effects of Arbuscular Mycorrhizal Fungi on Accumulation of Heavy Metals in Rhizosphere Soil

<p><em>The rhizosphere soil arbuscular mycorrhizal fungi will affect the absorption of heavy metal substances by the host plants. The effects of the arbuscular mycorrhizal fungi are inhibitory and conversion effects. The type and quantity of AMF fungi are different, and there are also differences in the absorption of arbuscular mycorrhizal fungi in the rhizosphere soil. Changes in the accumulation of heavy metals will affect the growth of arbuscular mycorrhizal fungi in the rhizosphere soil. In this paper, a preliminary investigation is made as to whether the AMF fungus number will affect the absorption of heavy metal Cd. Experiments show that with the increase of soil spores, the available cadmium content of soil also tends to increase.</em></p>

Effects of glyphosate application and nitrogen fertilization on the soil and the consequences on aboveground and belowground interactions

The application of nitrogen (N) and herbicides are commonly used to fertilize crops and protect them against weed development, but are also considered as soil and environment pollutants. Even so, the individual and combined non-target effects of N fertilizers and herbicides on multitrophic interactions within agrosystems are not well known. From soil samples collected in the field, we examined the effects of the direct application of glyphosate and/or N fertilization on microbial activities and soil nutrient status. In addition, we investigated the increase in biomass and, nutrient acquisition of the bean (Phaseolus vulgaris) and the consequences of the applications of N and glyphosate on the performance of the herbivore aphid (Aphis fabae). From soils that did (N+) or did not receive (N0) synthetic N fertilization over a 6-year period, we assessed the effects of glyphosate (CK, without glyphosate; FR, field rate of glyphosate) and N fertilization (N+, with N fertilization; N0, without N fertilization) applications in a mesocosm experiment for 75-days. Following the 75 day treatment, the biological and physiological consequences, both belowground and aboveground were determined. The growth of arbuscular mycorrhizal fungi (AMF) and dehydrogenase activity, were negatively affected following N+ fertilization and the application of the FR of glyphosate, while in the absence of glyphosate, alkaline phosphatase (AIP) activity was reduced. Functional microbial responses were unaffected by both N and glyphosate, even when applied in combination. Conversely, the N fertilization significantly increased the nitrate content (NO3−) in the CK soils and the total N in the FR soils, compared to CK/N0 and FR/N0 soils. The combined effects of glyphosate and nitrogen fertilization (FR/N+) significantly decreased the soil C:N ratio, but significantly increased nitrification compared to CK/N0 and FR/N0 soils. The FR/N+ treatments positively affected plant performance, improving the total chlorophyll, sucrose, ammonium, amino acid content, and pod biomass, compared to the CK/N0 and FR/N0 soils. Unlike glyphosate, which did not appear to exert an effect when applied alone or in combination, N fertilization significantly increased aphid nymph survival. The non-metric multidimensional scale allowed us to establish belowground and aboveground interactions with glyphosate and N fertilization. We conclude that glyphosate and N fertilization have negative effects on soil microflora and potential pests, but do not necessarily affect belowground and aboveground interactions, and may offer equal or superior benefits to crop productivity.

The effects of arbuscular mycorrhizal fungi on glomalin-related soil protein distribution, aggregate stability and their relationships with soil properties at different soil depths in lead-zinc contaminated area.

Glomalin-related soil protein (GRSP), a widespread glycoprotein produced by arbuscular mycorrhizal fungi (AMF), is crucial for ecosystem functioning and ecological restoration. In the present study, an investigation was conducted to comprehensively analyze the effects of heavy metal (HM) contamination on AMF status, soil properties, aggregate distribution and stability, and their correlations at different soil depths (0–10, 10–20, 20–30, 30–40 cm). Our results showed that the mycorrhizal colonization (MC), hyphal length density (HLD), GRSP, soil organic matter (SOM) and soil organic carbon (SOC) were significantly inhibited by Pb compared to Zn at 0–20 cm soil depth, indicating that HM had significant inhibitory effects on AMF growth and soil properties, and that Pb exhibited greater toxicity than Zn at shallow layer of soil. Both the proportion of soil large macroaggregates (>2000 μm) and mean weight diameter (MWD) were positively correlated with GRSP, SOM and SOC at 0–20 cm soil depth (P < 0.05), proving the important contributions of GRSP, SOM and SOC for binding soil particles together into large macroaggregates and improving aggregate stability. Furthermore, MC and HLD had significantly positive correlation with GRSP, SOM and SOC, suggesting that AMF played an essential role in GRSP, SOM and SOC accumulation and subsequently influencing aggregate formation and particle-size distribution in HM polluted soils. Our study highlighted that the introduction of indigenous plant associated with AMF might be a successful biotechnological tool to assist the recovery of HM polluted soils, and that proper management practices should be developed to guarantee maximum benefits from plant-AMF symbiosis during ecological restoration.

Silver nanoparticles deteriorate the mutual interaction between maize (Zea mays L.) and arbuscular mycorrhizal fungi: a soil microcosm study

The effects of silver nanoparticles (AgNPs) on plants and soil microbial communities have been widely documented. However, the influence of AgNPs on plant growth and rhizospheric microbial communities, especially the important symbiotic microbes, such as arbuscular mycorrhizal (AM) fungi, remains under debate. In this study, a greenhouse pot experiment was established to investigate the responses of maize (Zea mays L.) growth and rhizospheric AM fungal assemblages to different application levels (0.025, 0.25 and 2.5mgkg−1) of AgNPs or bulk Ag. The results indicated that 2.5mgkg−1 of AgNPs significantly decreased (p<0.05) plant biomass and dissolved organic carbon (DOC) content in rhizospheric soils compared to the control and bulk Ag conditions. Growth inhibition was associated with increased Ag accumulation in plant tissues and increased antioxidant enzyme activity. A similar toxicity for the AM fungal community was observed as a significant decrease (p<0.05) in their diversity and remarkable variations in their structure, which were closely correlated with plant root biomass, soil soluble Ag and DOC content. Consequently, AgNPs caused a reduction in AM fungal growth and ecological function, characterized by a significantly decreased (p<0.05) root mycorrhizal colonization rate, soil alkaline phosphatase activity, available phosphorus (P) content and P nutrition in plants. These results suggest that high concentrations of AgNPs can deteriorate the mutual interaction between plants and AM fungi and negatively influence the rhizospheric soil P cycling, both of which go against plant growth and soil fertility.

Combined Application of Biofertilizers and Inorganic Nutrients Improves Sweet Potato Yields.

Sweet potato [Ipomoea batatas (L) Lam] yields currently stand at 4.5 t ha−1 on smallholder farms in Uganda, despite the attainable yield (45–48 t ha−1) of NASPOT 11 cultivar comparable to the potential yield (45 t ha−1) in sub-Saharan Africa (SSA). On-farm field experiments were conducted for two seasons in the Mt Elgon High Farmlands and Lake Victoria Crescent agro-ecological zones in Uganda to determine the potential of biofertilizers, specifically arbuscular mycorrhizal fungi (AMF), to increase sweet potato yields (NASPOT 11 cultivar). Two kinds of biofertilizers were compared to different rates of phosphorus (P) fertilizer when applied with or without nitrogen (N) and potassium (K). The sweet potato response to treatments was variable across sites (soil types) and seasons, and significant tuber yield increase (p < 0.05) was promoted by biofertilizer and NPK treatments during the short-rain season in the Ferralsol. Tuber yields ranged from 12.8 to 20.1 t ha−1 in the Rhodic Nitisol (sandy-clay) compared to 7.6 to 14.9 t ha−1 in the Ferralsol (sandy-loam) during the same season. Root colonization was greater in the short-rain season compared to the long-rain season. Biofertilizers combined with N and K realized higher biomass and tuber yield than biofertilizers alone during the short-rain season indicating the need for starter nutrients for hyphal growth and root colonization of AMF. In this study, N0.25PK (34.6 t ha−1) and N0.5PK (32.9 t ha−1) resulted in the highest yield during the long and the short-rain season, respectively, but there was still a yield gap of 11.9 and 13.6 t ha−1 for the cultivar. Therefore, a combination of 90 kg N ha−1 and 100 kg K ha−1 with either 15 or 30 kg P ha−1 can increase sweet potato yield from 4.5 to >30 t ha−1. The results also show that to realize significance of AMF in nutrient depleted soils, starter nutrients should be included.

Effect of Quercetin and Pectinase on Spore Germination and Hyphal Growth of Arbuscular Mycorrhizal Fungi and Biomass Production of Nicotiana tabacum L. and Calopogonium mucunoides desv

Effect of Quercetin and Pectinase on Spore Germination and Hyphal Growth of Arbuscular Mycorrhizal Fungi and Biomass Production of Nicotiana tabacum L. and Calopogonium mucunoides desv

Bacteria with Phosphate Solubilizing Capacity Alter Mycorrhizal Fungal Growth Both Inside and Outside the Root and in the Presence of Native Microbial Communities.

Arbuscular mycorrhizal fungi (AMF) and phosphate solubilizing Pseudomonas bacteria (PSB) could potentially interact synergistically because PSB solubilize phosphate into a form that AMF can absorb and transport to the plant. However, very little is known about the interactions between these two groups of microorganisms and how they influence the growth of each other. We tested whether different strains of bacteria, that have the capacity to solubilize phosphate, are able to grow along AMF hyphae and differentially influence the growth of AMF both outside the roots of carrot in in vitro conditions and inside the roots of potato in the presence of a microbial community. We found strong effects of AMF on the growth of the different bacterial strains. Different bacterial strains also had very strong effects on the growth of AMF extraradical hyphae outside the roots of carrot and on colonization of potato roots by AMF. The differential effects on colonization occurred in the presence of a microbial community. Our results show that these two important groups of rhizosphere microorganisms indeed interact with each other. Such interactions could potentially lead to synergistic effects between the two groups but this could depend on whether the bacteria truly solubilize phosphate in the rhizosphere in the presence of microbial communities.

Functional compatibility in cucumber mycorrhizas in terms of plant growth performance and foliar nutrient composition.

Functional compatibility in cucumber mycorrhizas in terms of plant and fungal growth, and foliar nutrient composition from all possible combinations of six cucumber varieties and three species of arbuscular mycorrhizal (AM) fungi was evaluated. Measurements of foliar nutrient composition included N, P, K, Mg, Ca, Na, Fe, Zn, Mn and Cu. Growth of AM fungi was measured in terms of root colonisation, as examined with microscopy and the AM fungus biomarker fatty acid 16:1ω5 from both phospholipids and neutral lipids. Different responses of plant growth and foliar nutrient profiles were observed for the different AM symbioses examined. The AM fungus Claroideoglomus claroideum caused growth depression in association with four out of six cucumber varieties; Rhizophagus irregularis caused growth promotion in one of six cucumber varieties; whereas Funneliformis mosseae had no effect on the growth performance of any of the cucumber varieties examined. All three AM fungi markedly altered host plant shoot nutrient composition, with the strongest contrast observed between cucumber-R.irregularis symbioses and non-mycorrhizal cucumber plants, independent of cucumber variety. On the other hand, AM fungal growth in roots differed between the three AM fungi, but was unaffected by host genotype. Strong build-up of storage lipids was observed for R.irregularis, which was more moderate in the two other AM fungi. In conclusion, strong differential responses of cucumber varieties to inoculation with different AM fungi in terms of growth and shoot nutrient composition revealed high functional diversity in AM symbioses in cucumber plants.

L-System model for the growth of arbuscular mycorrhizal fungi, both within and outside of their host roots.

Development of arbuscular mycorrhizal fungal colonization of roots and the surrounding soil is the central process of mycorrhizal symbiosis, important for ecosystem functioning and commercial inoculum applications. To improve mechanistic understanding of this highly spatially and temporarily dynamic process, we developed a three-dimensional model taking into account growth of the roots and hyphae. It is for the first time that infection within the root system is simulated dynamically and in a spatially resolved way. Comparison between data measured in a calibration experiment and simulated results showed a good fit. Our simulations showed that the position of the fungal inoculum affects the sensitivity of hyphal growth parameters. Variation in speed of secondary infection and hyphal lifetime had a different effect on root infection and hyphal length, respectively, depending on whether the inoculum was concentrated or dispersed. For other parameters (branching rate, distance between entry points), the relative effect was the same independent of inoculum placement. The model also indicated that maximum root colonization levels well below 100%, often observed experimentally, may be a result of differential spread of roots and hyphae, besides intrinsic plant control, particularly upon localized placement of inoculum and slow secondary infection.

Arbuscule Frequency in Grapevine Roots Is More Responsive to Reduction in Photosynthetic Capacity Than to Increased Levels of Shoot Phosphorus

An interplay between carbon and phosphorus is known to regulate root colonization by arbuscular mycorrhizal fungi (AMF); however, it is unclear whether plant C or plant P status plays a bigger role in controlling the abundance of arbuscules (the primary site of nutrient exchange in AMF symbiosis) in roots. In this study, ‘Pinot noir’ grapevine (Vitis vinifera) was grown in an unsterilized vineyard soil and colonized by indigenous AMF in two experiments, where photosynthetic capacity (defoliation or shading) and shoot nutrition (foliar fertilizer) were manipulated. Temporal changes in root colonization by AMF and plant growth and nutrition were determined. Foliar fertilizer application increased P and K uptake, but reduced Cu uptake in both experiments. Decreasing the photosynthetic capacity of shoots due to defoliation or shading rapidly reduced arbuscules in fine roots (within 7 to 14 days). In contrast a 3-fold increase in shoot P status from foliar fertilizer only reduced arbuscules after a more prolonged time (28 to 56 days). The combination of shading (15% of full sun) and foliar P application reduced arbuscules more than shading alone within the first month, whereas foliar P use in full sun had no influence on arbuscules within a month. Returning plants to full sun after 28 days in shade resulted in a resurgence of arbuscules in roots regardless of plant P status. Arbuscules in grapevine roots are regulated by the interaction between plant C and P status, such that high shoot P reduces arbuscule formation or maintenance more when combined with reduced plant photosynthesis. This indicates that grapevines do not reduce AMF nutrient transfer as an immediate response to elevated shoot P as long as plants are maintained in a high light environment.

Can biochar increase the bioavailability of phosphorus?

A large proportion of phosphate (P) fertilizer applied to Andosols reacts with reactive aluminum (Al) and iron (Fe) to become unavailable for plant uptake. We investigated whether biochar could enhance plant growth by (i) mobilizing soil P through changing soil pH or facilitating the growth of arbuscular mycorrhizal fungi (AMF), and/or (ii) introducing additional P. We grew Lotus pedunculatus cv barsille in two Andosols of contrasting P status amended with three biochars (with distinct porosity, nutrient and liming properties) at a dose of 10 t ha-1 for 32 weeks. The growth medium was divided into a root and a hyphal zone through a nylon mesh and a tephra layer that allowed the P in the hyphal zone to be transferred only by AMF hyphae. The addition of a relative nutrient-rich biochar (e.g. made from willow woodchips) with liming properties to the root zone of the P-deficient soil increased plant growth by 59% and P uptake by 73%. Pine-based biochar provided no extra nutrient acquisition and no plant-growth stimulation when added to the root zone of the P-deficient soil. However,when hyphae of those plants had access to a P-rich soil patch, the presence of pine biochar in the soil patch greatly enhanced P uptake and plant growth (e.g., by 76% and 40% when using biochar produced at 450oC compared to the absence of it). None of the tested biochars conferred advantages in the root zone of a high-P soil. We concluded that the benefits from biochar addition to nutrient uptake and plant growth are biochar- and soil-specific. Thus, biochars need to be tailored-made for certain soils by optimizing feedstock and pyrolysis conditions before application.

Arbuscular Mycorrhizal Association for Growth and Nutrients Assimilation of Pharagmites japonica and Polygonum cuspidatum Plants Growing on River Bank Soil

ABSTRACTEffects of arbuscular mycorrhizal fungi (AMF) on the growth, nutrient absorption, and inoculation effectiveness of AMF on pioneer plants Pharagmites japonica (C4) and Polygonum cuspidatum (C3) were evaluated by performing a pot experiment in a greenhouse at Saitama University, Japan. AMF spores were collected from the commercial product, Serakinkon. The average colonization levels of P. japonica and P. cuspidatum were 24–33% and 0.2–0.5% respectively and no colonization was found in sterilized soil treatment. AMF colonization increased the plant dry mass, phosphorus (P), and nitrogen (N) concentrations of P. japonica’s roots, stems, and leaves when AMF applied with natural and sterilized soil compared with only sterilized and natural soil. This was a significant effect for N-loss minimization from soil. Maximum value showed when P. japonica was grown with natural soil in combination with AMF whereas P. cuspidatum showed very less or a negative response to AMF colonization in all cases.

The molecular characteristics of compost affect plant growth, arbuscular mycorrhizal fungi, and soil microbial community composition

Compost amendment to agricultural soils influences plant growth and soil quality by affecting activity of arbuscular mycorrhizal fungi (AMF) and composition of microbial community. We related the molecular composition of compost of different maturity added to soils to their effects on maize growth, N and P uptake, AMF root colonization and growth, and composition of soil microbial community. The characteristics of compost after different days of maturation (C60, C90, C120) were provided by 13C-solid state NMR spectroscopy, while neutral (NLFA) and phospholipid (PLFA) fatty acid analyses were used to evaluate the effects of compost on the composition of soil microbial communities. Multivariate elaboration was used to determine the relationships between microbial groups, as identified by PLFA analysis, and molecular properties of composts. Although compost amendments increased soil total C and N, and available P, soil addition of both C60 and C120 compost samples was detrimental to plant and AMF growth. Compost amendments modified the composition of soil microbial communities. The high content of biolabile compounds in C60 and C120 compost samples decreased the C16:1ω5 NLFA that was related to AMF and Gram(+)/Gram(−) and AMF/saprotrophic fungi ratios. A linear correlation was found between the molecular indexes in compost and the microbial groups in soil, thereby suggesting that the molecular composition of compost strictly controls the development and abundance of soil microbial communities. These findings highlight the importance of controlling the molecular quality of recycled biomass added to soil, in order to predict the effect on crop yields and biotic composition of soil.

Do native and invasive plants differ in their interactions with arbuscular mycorrhizal fungi? A meta‐analysis

Summary Divergent hypotheses have been proposed that suggest plant invasions either enhance or degrade the mutualism between plants and arbuscular mycorrhizal (AM) fungi, but their relative support remains unknown. We conducted a meta‐analysis using 67 publications, involving 70 native and 55 invasive plant species to assess support for the enhanced mutualism hypothesis, the degraded mutualism hypothesis and an alternative hypothesis that factors other than invasive status (such as plant functional group) better predict AM function following invasion. We used multiple measurements to test these hypotheses: AM fungal colonization, growth responses to AM fungi and AM fungal‐mediated shifts in competitive interactions among native and invasive plants. Additionally, we assessed whether invasive plants alter AM associations in native plants and whether native and invasive plants host different AM fungal abundances and communities. Arbuscular mycorrhizal fungal colonization (%) and average growth responses did not differ between native and invasive plants. However, growth responses (±) were dampened among invasive plants, and the positive correlation between AM fungal colonization and growth response in native plants was absent in invasive plants. Rather than plant invasive status, plant functional group was a significant explanatory factor; forbs were generally more colonized and exhibited positive growth responses (when grown alone and in competition), whereas grass responses were neutral to negative. Arbuscular mycorrhizal fungal abundance (measured by percentage colonization, extraradical hyphal and spore densities, as well as neutral lipid fatty acid and glomalin concentrations) did not differ between native and invasive plants, but invasive plants hosted different AM fungal communities in 78% of studies. AM fungal colonization of native plants was lower when grown with, or after, invasive plants, likely due to the prevalence of non‐mycorrhizal plants in studies of neighbour and legacy effects. Synthesis. Neither the degraded nor the enhanced mutualism hypothesis was supported, suggesting that invasions do not select for directional shifts in AM associations. Instead, our results indicate that AM fungi are most likely to influence invasion trajectories when native and invasive plants belong to different functional groups.

Arbuscular mycorrhizal influences on growth, nutrient uptake, and use efficiency of Miscanthus sacchariflorus growing on nutrient-deficient river bank soil

The potential effects of arbuscular mycorrhizal fungi (AMF) on growth, nutrient assimilation, and inoculation effectiveness of AMF on the pioneer plant Miscanthus sacchariflorus which is dominant in river banks were evaluated. A pot experiment was performed in a greenhouse at Saitama University, Japan. Spores of AMF strains were collected from the commercial product ‘Serakinkon’. The average colonization level of M. sacchariflorus was 23–28%, whereas no colonization was found in sterilized soil. AMF colonization increased the chlorophyll content, plant dry mass, N, P, K, Mg, Fe, Cu, and Zn concentration of the M. sacchariflorus plant’s roots, stems, and leaves when it was applied with natural and sterilized soil. In all cases, maximum values were measured when the M. sacchariflorus plant was applied with natural soil in combination with AMF, but Ca concentration decreased as colonization level increased. Mn concentration decreased in roots and stems but increased in leaves in natural soil, and AMF with natural soil treatment. N loss minimization from the soil was significant when colonization level was high. Therefore, AMF have some potential effects for growth of the C4 grass Miscanthus sacchariflorus and nitrogen retention in aquatic–terrestrial inter-faces (river banks).

The relative importance of host vigor and hormonal response to pathogens in controlling the development of arbuscular mycorrhizal fungi

Plants are routinely colonized by both beneficial and detrimental microorganisms. These two microbial guilds may indirectly interact with each other via their host, either by modifying its vigor, or by altering its hormonal/defense status. Here, we studied indirect interactions between arbuscular mycorrhizal (AM) fungi and three plant pathogens. We show that AM fungal sporulation was only triggered by the least aggressive fungal pathogen, which is known to induce a jasmonate-based hormonal response by the host without affecting its vegetative growth and vigor. Conversely, the most aggressive fungal pathogen considerably reduced host vigor but did not alter AM fungal growth and sporulation. Our results thus suggest that the plant hormonal system is an important component of indirect interactions between AM fungi and plant pathogens.

Long-term fertilizer application effects on the soil, root arbuscular mycorrhizal fungi and community composition in rotation agriculture

Arbuscular mycorrhizal fungi (AMF) play key roles in plant growth, ecosystem sustainability and stability. However, it is still unclear how the soil, root AMF growth and community composition are affected by fertilizer application in subtropical wheat–rice rotation agro-ecosystems. We investigated the impact of different organic and/or inorganic fertilizers on AMF growth and community composition in a long-term experiment field in Zhejiang Province, east China. AMF biomass was determined using 16:1ω5 phospholipid fatty acids (PLFAs) and neutral lipid fatty acids (NLFAs) content. Soil and root AMF community compositions were determined by DGGE analysis, cloning, sequencing and phylogenetic analyses. The root colonization rate was not significantly affected by different fertilizer regimes. Manure amendment significantly enhanced both AMF hyphal (i.e., 16:1ω5 PLFA) and spore (i.e., 16:1ω5 NLFA) biomass content, while inorganic fertilizer only increased the AMF spore biomass. A total of 10 and 11 Glomeromycota phylotypes were detected in soil and root samples, respectively. Glomus was the dominant genus in both soil and root samples, while Acaulospora genus occurred in roots only. Although the different fertilizers altered soil AMF communities, the root AMF community structure was not significantly altered. Soil pH (F=5.695, P<0.01) and available K (F=4.888, P<0.01) contributed to both soil and root AMF community composition, while the C/P ratio (F=3.893, P<0.01) only contributed to soil AMF community. The data suggests that high soil organic C content benefits AMF growth, while soil pH and available K concentration strongly influence AMF community. The root AMF community was much more resilient to the changes caused by long-term fertilizer application than the soil community.

Using AMF inoculum to improve the nutritional status of Prunella vulgaris plants in green roof substrate during establishment

Arbuscular mycorrhizal fungi (AMF) have been shown to improve the growth, health, nutrient uptake, flowering and drought tolerance of many terrestrial plant species. Green roofs are generally deficient in nutrients, organic matter and water, and therefore AMF could be extremely beneficial in improving green roof plant performance. Despite this there is a lack of empirical research into artificially introducing AMF into green roof substrates.In this study, a commercial AMF inoculum was applied to Prunella vulgaris green roof plugs grown in small modules on a flat roof in Sheffield, UK. The modules were filled with commercial green roof substrate (80% small particle sized crushed brick, 20% green waste compost) to a depth of 100mm. AMF inoculum was applied as four treatments: (i) directly with plug, (ii) mixed evenly into surrounding substrate, (iii) split between plug and substrate, (iv) control treatment with no inoculum added.Significantly greater levels of AMF colonisation of P. vulgaris roots was detected in all AMF treatments compared to the control. Low levels of AMF colonisation of P. vulgaris roots were also observed in the control treatment, confirming that low levels of AMF inoculum were present in this commercial substrate. Shoot phosphorous (P) concentration was improved in all AMF treatments, however there was no significant effect of any AMF treatment on P. vulgaris growth rate or biomass production. The highest AMF colonisation of P. vulgaris roots was observed when AMF inoculum was directly added to just the plug. Promisingly, P. vulgaris flowering time at the end of the first growing season was also extended in the plug AMF treatment only.This study has confirmed that commercial AMF inoculum can be used to successfully colonise plants and introduce AMF networks into green roof substrate. Although AMF inoculum was naturally present in the substrate used in this study, levels were extremely low, and unlikely to have any significant effect on plants. This study indicates that care should be taken in the use of AMF inoculum on green roofs, as the growth and health benefits of AMF are not always immediately apparent for green roof plants. In addition much more research is required in order to fully assess the extent of the benefits of AMF on green roof plants and to determine if their use can be financially viable.