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Arbuscular mycorrhizal fungi (AMF) are integral functioning parts of plant root systems and are widely recognized for enhancing contaminants uptake and metabolism on severely disturbed sites. However, the patterns of their influence on the phytoremediation of iron–cyanide (Fe–CN) complexes are unknown. Fe–CN complexes are of great common interest, as iron is one of the most abundant element in soil and water. Effect of ryegrass (Lolium perenne L.) roots inoculation, using mycorrhizal fungi (Rhizophagus irregularis and a mixture of R. irregularis, Funneliformis mosseae, Rhizophagus aggregatus, and Claroideoglomus etunicatum), on iron–cyanide sorption was studied. Results indicated significantly higher colonization of R. irregularis than the mixture of AMF species on ryegrass roots. Series of batch experiments using potassium hexacyanoferrate (II) solutions, in varying concentrations revealed significantly higher reduction of total CN and free CN content in the mycorrhizal roots, indicating greater cyanide decrease in the treatment inoculated with R. irregularis. Our study is a first indication of the possible positive contribution of AM fungi on the phytoremediation of iron–cyanide complexes.
Soil pollutants such as hydrocarbons can induce toxic effects in plants and associated arbuscular mycorrhizal fungi (AMF). This study was conducted to evaluate if the legume Lotus corniculatus and the grass Elymus trachycaulus and arbuscular mycorrhizal fungi could growin two oil sands processing by-products after bitumen extraction fromthe oil sands in northern Alberta, Canada. Substrate treatmentswere coarse tailings sand (CTS), a mix of dry mature fine tailings (MFT) with CTS (1:1) and Pleistocene sandy soil (hydrocarbon free); microbial treatments were without AMF, with AMF and AMF plus soil bacteria isolated from oil sands reclamation sites. Plant biomass, root morphology, leaf water content, shoot tissue phosphorus content and mycorrhizal colonization were evaluated. Both plant species had reduced growth in CTS and tailings mix relative to sandy soil. AMF frequency and intensity in roots of E. trachycaulus was not influenced by soil hydrocarbons; however, it decreased significantly over time in roots of L. corniculatus without bacteria in CTS. Mycorrhizal inoculation alone did not significantly improve plant growth in CTS and tailings mix; however, inoculation with mycorrhizae plus bacteria led to a significantly positive response of both plant species in CTS. Thus, combined inoculationwith selected mycorrhizae and bacteria led to synergistic effects. Such combinations may be used in future to improve plant growth in reclamation of CTS and tailings mix.
Phosphogypsum (PG) is a by-product of phosphate fertilizer production. This study is the first to investigate Bromis inermis and Festuca ovina root morphology and colonization with arbuscular mycorrhizal fungi and dark septate endophytes (DSE) in pure PG and PG with a soil cap (soil). Root length density was significantly lower for plants on PG than on soil and both plant species were colonized with AMF and DSE, with lower frequency and intensity in PG. Phosphorus (20 times), calcium (35 times) and sulphur (50 times) were significantly higher in PG than in soil; resulting higher root tissue concentrations were significantly negatively correlated with mycorrhizal colonization for Festuca but not Bromus. Higher fungal colonization of Bromus, especially with DSE known to be prevalent in extreme environments, may be responsible for its better performance on PG relative to Festuca.
Plant growth can be highly dependent on symbiotic partners, such as arbuscular mycorrhizal fungi (AMF) that improve the plant's nutrient uptake. However, less is known about whether AMF can beneficially influence spatial root distribution, especially in soils with patchy nutrient concentrations. This study was conducted to evaluate root distribution and plant response of Lotus corniculatus and Calamagrostis epigeios in a heterogeneous nutrient poor soil under different mycorrhizal conditions.
Heterogeneous soil conditions of a reclamation site in the Lusation mining district, consisting of a nutrient poor sandy soil with embedded large silt-clay fragments, were used for this rhizotron experiment. Treatments were non-mycorrhizal and mycorrhizal L. corniculatus and C. epigeios in sterile soil and in sterile soil with a fungal free soil solution and mycorrhizal plants in a non-sterile soil. Mycorrhizal fungi were exogenous (Funneliformis mosseae and Rhizophagus irregularis) in sterile soil and indigenous mycorrhizal fungi in non-sterile soil. Plants were grown in rhizotrons, with clay-silt fragments in a sandy soil matrix. Treatment response variables were root density, root and shoot biomass, shoot tissue nutrient concentrations, and percentage of roots in clay-silt fragments relative to total root biomass, mycorrhizal colonization and intraradical fungal alkaline phosphatase (ALP) activity.
Exogenous mycorrhizal L. corniculatus plants had higher root mass density in clay-silt fragments than indigenous mycorrhizal and non-mycorrhizal plants while C. epigeios had only higher root mass density in clay-silt fragments relative to sandy soil only in exogenous mycorrhizal plants in sterile soil with soil solution. Nonmycorrhizal C. epigeios shoot biomass in sterile soil did not significantly differ from that of exogenous mycorrhizal treatments. The greatest shoot biomass for both plant species, was with the highest percentage of roots in clay-silt fragments relative to the total root system. Exogenous mycorrhizal plants of both species had highest shoot phosphorus concentrations in sterile soil with soil solution. However, intraradical fungal ALP activity was highest in indigenous mycorrhizal plants. The results indicate that mycorrhizal conditions can have a strong influence on spatial root development. The consequences are that conditions, which promote root growth, lead to more roots in nutrient rich clay-silt fragments and thus enhance plant exploitation of heterogeneously distributed soil nutrients.
In 2005, a 7-ha artificial watershed (Chicken Creek) was built on a post mined landscape in Lusatia, Germany from sandy substrates of Pleistocene origin, commonly used in reclamation. The watershed was developed to investigate the initial phase of soil and ecosystem development under natural conditions. At this early stage, mineral nitrogen in young sandy soils is primarily limited and nitrogen fixing legumes become key components of natural succession. Local abundant pioneering legumes Lotus corniculatus and Trifolium arvense and one pioneer grass species Calamagrostis epigeios were investigated 5 years after watershed construction. In this study, we investigated the influence of spatial root and nodule distribution of these species on soil nitrogen accumulation. Soil, including roots, was sampled from field monoliths covered with the aforementioned plant species. Root systems of both legumes were mainly restricted to the upper 20 cm of soil, whereas roots of C. epigeios also developed strongly at greater depths. A positive relationship was found, with higher plant densities associated with higher root densities which were associated with higher nodule densities for legumes and which were all associated with significantly higher soil nitrogen content relative to non-vegetated areas. This research provides rare information on the role root systems of pioneer legumes play in soil nitrogen input in the early stage of soil and ecosystem development during revegetation by natural succession.
ln 2005, a 7-ha artificial watershed (Hühnerwasser) was built an a post mined Iandscape in Lusatia, Germany from sandy Substrates of Pleistocene origin, commonly used in reclamation. The watershed was developed to investigate the initial phase of soil and ecosystem development under natural conditions. At this early stage, nutrients in young sandy soils are limited and pioneer plants become key components of natural succession. Local abundant pioneering legumes Lotus corniculatus and Trifolium arvense and one pioneer grass species Calamagrostis epigeios were investigated 5 years after watershed construction. ln the present study, we investigated the influence of spatial root distribution of these species an soil nitrogen accumulation and on nutrient redistribution. Soil, including roots, was sampled from field monoliths covered with the aforementioned plant species. Root systems of both legumes were mainly restricted to the upper 20 cm of soil, whereas roots of C. epigeios also developed strongly at greater depths. A positive relationship was found, with higher plant densities associated with higher root densities, which were related with higher nodule densities for legumes and which were all associated with significantly higher soil nitrogen concentration relative to non-vegetated areas.
This research provides rare information on the role root systems of pioneer legumes play in soil nitrogen input and development of nutrient patterns in the early stage of soil and ecosystem development during revegetation by natural succession.
Extremes in soil water, temperature, pH and inorganic nutrient availability can highly influence mycorrhizal formation and nutrient acquisition. However, the influence of soil heterogeneity and seasonal soil changes on fungal alkaline phosphatase (ALP) activity in mycorrhizal roots is unknown. Whether the activity of intraradical fungal ALP is influenced by soil texture heterogeneity, soil depth, nutrient concentrations and root density during the growing season were addressed in this research. The root system of Lotus corniculatus grown on a reclamation site was analyzed for intraradical mycorrhizal ALP activity in 0–10, 10–20 and 20–30 cm depth increments of sandy soil and in clay–silt fragments (mostly localized in 10–20 cm) from May to September. Root length density and water soluble nutrient contents in sandy soil and clay–silt fragments were determined for each sample. Soil water content and soil temperature data of a nearby site were used for climate conditions on sampling dates. Fungal ALP activity in roots growing in clay–silt fragments was higher than in those growing in sandy soil, independent of sampling date. Fungal ALP activity in sandy soil increased with soil depth which is related to decreasing root densities and lower nutrient concentrations. However, nutrient dense clay–silt fragments significantly positively influenced local mycorrhizal ALP activity in L. corniculatus roots, suggesting that the ability of mycorrhizae to selectively take up phosphorus and other nutrients from those nutrient hot spots is enhanced and could play a significant role in successful establishment of pioneer plant species on infertile reclamation sites.