Mycelium Of Ectomycorrhizal Fungi Research Articles

Biomass of external mycelium of ectomycorrhizal fungi in Norway spruce stands in Poland

<p>Biomass of extramatrical mycorrhizal mycelium (EMM) was examined under canopies of mature Norway spruce trees grown in different forest stands in Poland. Two mountain forest sites (Brenna and Salmopol), one upland site (Zwierzyniec) and one lowland site (Mirachowo) have been investigated, using sand-filled mesh-bags method. The in-grow mesh-bags were buried in the soil for 12 months (since October up to the next October) or for 4 months (since June up to October) at four depths at each site: 5, 15, 30 and 45 cm (Brenna and Salmopol) or 60 cm (Zwierzyniec and Mirachowo). The mycelium biomass was estimated from the ergosterol content determined in the mesh-bags. The results indicated significant differences in EMM production and their vertical distribution between the mountain and the upland and lowland forest sites. The lowest EMM biomass was found at the experimental plot in the mountainious site Brenna. Considerable decrease of EMM biomass with the soil depth was recorded after 12 months of the mesh-bags incubation in soil in the upland and lowland sites, while in the mountain forests decrease of the EMM biomass in the lower soil depths diminished more gradually EMM biomass determined in the mesh-bags placed in soil at the upper 5 and 15 cm tended to be higher after 4 months than after 12 months of incubation period. Such results suggest that the time necessary for evaluation of EMM biomass in soil may be limited to the summer–autumn months, when the production of EMM is the highest. Variable stress factors can influence decreased ectomycorrhizal mycelium production and/or their destruction. Further research in different forest types and regions are needed for better understanding factors determining EMM biomass production and surviving in soil.</p>

Influence of ectomycorrhizal inoculation on Pinus wallichiana and Cedrus deodara seedlings under nursery conditions

A study was undertaken to examine the extent of root colonization by four locally isolated ectomycorrhizal (ECM) fungi (Hebeloma theobrominum, Boletus dryophilus, Scleroderma citrinum and Suillus luteus) and their effects on seedling growth in Pinus wallichiana and Cedrus deodara under nursery conditions. Seedlings of the two conifers were inoculated with mycelium of ECM fungi and were grown in pots containing sterilized forest soil for six months. The percentage of ECM colonization of roots was 38%–52% in Pinus wallichiana and 33%–48% in Cedrus deodara. ECM colonization increased shoot height, needle number, shoot and root biomass and survival of inoculated seedlings. Among the four ECM fungi Hebeloma theobrominum was more effective with Pinus wallichiana and Scleroderma citrinum with Cedrus deodara in promoting seedling survival and overall growth. All the four ECM fungi used enhanced growth of inoculated seedlings and thus can be used in afforestation and regeneration programmes in degraded forests ecosystems.

Changes in hyphal morphology and activity of phenoloxidases during interactions between selected ectomycorrhizal fungi and two species of Trichoderma

Patterns of phenoloxidase activity can be used to characterize fungi of different life styles, and changes in phenoloxidase synthesis were suspected to play a role in the interaction between ectomycorrhizal and two species of Trichoderma. Confrontation between the ectomycorrhizal fungi Amanita muscaria and Laccaria laccata with species of Trichoderma resulted in induction of laccase synthesis, and the laccase enzyme was bound to mycelia of ectomycorrhizal fungi. Tyrosinase release was noted only during interaction of L. laccata strains with Trichoderma harzianum and T. virens. Ectomycorrhizal fungi, especially strains of Suillus bovinus and S. luteus, inhibited growth of Trichoderma species and caused morphological changes in its colonies in the zone of interaction. In contrast, hyphal changes occurred less often in the ectomycorrhizal fungi tested. Species of Suillus are suggested to present a different mechanism in their interaction with other fungi than A. muscaria and L. laccata.

Expression of the nitrate transporter nrt2 gene from the symbiotic basidiomycete Hebeloma cylindrosporum is affected by host plant and carbon sources

Although the function of the extramatrical mycelium of ectomycorrhizal fungi is considered essential for the acquisition of nitrogen by forest trees, gene regulation in this fungal compartment is poorly characterized. In this study, the expression of the nitrate transporter gene nrt2 from the ectomycorrhizal basidiomycete Hebeloma cylindrosporum was shown to be regulated by plant host and carbon sources. In the presence of a low fructose concentration, nrt2 expression could not be detected in the free-living mycelium but was high in the extramatrical symbiotic mycelium associated to the host plant Pinus pinaster. In the absence of nitrogen or in the presence of nitrate, high sugar concentrations in the medium were able to enhance nrt2 expression. Nevertheless, in the presence of high fructose concentration, high ammonium concentration still completely repressed nrt2 expression indicating that the nitrogen repression overrides sugar stimulation. This is the first report revealing an effect of host plant and of carbon sources on the expression of a fungal nitrate transporter-encoding gene.

Oxalate and ferricrocin exudation by the extramatrical mycelium of an ectomycorrhizal fungus in symbiosis with Pinus sylvestris

Accurate estimates of mycelial exudation in time and space are crucial for the assessment of ectomycorrhizal involvement in biogeochemical processes. Knowledge of exudation from mycelia of ectomycorrhizal fungi is still limited, especially for fungi in symbiosis with a host. Pinus sylvestris seedlings colonized by Hebeloma crustuliniforme were grown in aseptic multicompartment dishes. This novel system enabled identification of exudates originating only from extramatrical mycelium. At harvest, hyphal density and numbers were estimated using microscopic imaging. A fractal geometric approach was adopted for calculation of exudation rates. The main compounds identified were oxalate and ferricrocin. The exudation rate for oxalate was 19 +/- 3 fmol per hyphal tip h(-1) (mean +/- standard error of the mean) or 488 +/- 95 fmol hyphal mm(-2) h(-1). Ferricrocin rates were approx. 10 000 times lower. The fractal dimension (D) of the mycelia was 1.4 +/- 0.1, suggesting an explorative growth. Potassium nutrition was a significant regulatory factor for ferricrocin but not oxalate. The results suggest that hyphal exudation may alter the chemical conditions of soil microsites and affect mineral dissolution. Calculations also indicated that oxalate exudation may be a significant carbon sink.

Development of ectomycorrhizas in model beech–spruce ecosystems on siliceous and calcareous soil: a 4-year experiment with atmospheric CO2 enrichment and nitrogen fertilization

To study responses of forests to global change, model ecosystems consisting of beech and spruce trees were established in open top chambers. The ecosystems were exposed to four conditions for 4 years, each replicated four times: ambient and elevated CO2, and low and high nitrogen input. At the end of the trial, the trees were 6–8 years old. Each chamber contained two separate compartments with siliceous and calcareous soil. Here, we focus on the development of ectomycorrhizas in the topsoil layer. Ectomycorrhizal fungal biomass associated with the fine roots, estimated by using ergosterol content as a marker, was much higher in the siliceous compared to the richer calcareous soil. Also, in root-free soil samples, the level of ergosterol, indicative of the extraradical mycelium of ectomycorrhizal fungi as well as the mycelium of other fungi, was about six times higher in the siliceous than in the calcareous soil. Conditions of elevated atmospheric CO2 primarily affected ectomycorrhizas in the calcareous soil. Fungal biomass, calculated per soil volume of the top soil layer, increased significantly, as did the metabolic activity of the ectomycorrhizal fungi, measured as uptake of glucose and synthesis of trehalose. Conditions of nitrogen fertilization affected ectomycorrhizas in the siliceous, nutrient poor soil.

Demonstration of aluminium in polyphosphate of Laccaria amethystea (Bolt. ex Hooker) Murr. by means of electron energy‐loss spectroscopy

SummaryToxic aluminium species in acidified soil damage the rootlets of trees. The symbiotic association with ectomycorrhizal fungi may, however, protect the rootlets by sequestration of aluminium in polyphosphates. Electron energy‐loss imaging and spectroscopy was used to identify the relative amount of aluminium in the polyphosphate of the mycelium of the ectomycorrhizal fungus Laccaria amethystea. A three‐window method at the L2,3 edge yielded results which were in agreement with the spectra obtained at the aluminium K edge. The aluminium net distribution images were recorded at 85 eV, the backgrounds at 70 eV and 60 eV, setting the energy selecting slit to 5 eV and the beam current to 15 μA. The method can be used to study the sequestration of aluminium in mycelia of ectomycorrhizal fungi under different stress situations.

The use of granulated ectomycorrhizal inoculum for reforestation of deteriorated regions

A modified method has been developed for laboratory preparation of granulated mycorrhizal inoculum. Mycelia of ectomycorrhizal fungi are immobilized in alginate gel in a mixture with a silicate carrier-perlite. This inoculum is applied at sowing in forest nurseries to obtain resistant plants for afforestation of areas exposed to man-made stresses. Under both sterile and nonsterile conditions, the growth of seedlings and mycorrhiza development were increased by inoculation with a strain Laccaria laccata. This strain may be a good perspective symbiont for Picea abies and Pinus sylvestris, particularly when high levels of inoculum are used.