Barbara Kieliszewska-Rokicka

The production and turnover of extramatrical mycelium of ectomycorrhizal fungi in forest soils: role in carbon cycling

There is growing evidence of the importance of extramatrical mycelium (EMM) of mycorrhizal fungi in carbon (C) cycling in ecosystems. However, our understanding has until recently been mainly based on laboratory experiments, and knowledge of such basic parameters as variations in mycelial production, standing biomass and turnover as well as the regulatory mechanisms behind such variations in forest soils is limited. Presently, the production of EMM by ectomycorrhizal (EM) fungi has been estimated at ~140 different forest sites to be up to several hundreds of kg per ha per year, but the published data are biased towards Picea abies in Scandinavia. Little is known about the standing biomass and turnover of EMM in other systems, and its influence on the C stored or lost from soils. Here, focussing on ectomycorrhizas, we discuss the factors that regulate the production and turnover of EMM and its role in soil C dynamics, identifying important gaps in this knowledge. C availability seems to be the key factor determining EMM production and possibly its standing biomass in forests but direct effects of mineral nutrient availability on the EMM can be important. There is great uncertainty about the rate of turnover of EMM. There is increasing evidence that residues of EM fungi play a major role in the formation of stable N and C in SOM, which highlights the need to include mycorrhizal effects in models of global soil C stores.

Relationship between genotype and soil environment during colonization of poplar roots by mycorrhizal and endophytic fungi

Poplars are among the few tree genera that can develop both ectomycorrhizal (ECM) and arbuscular (AM) associations; however, variable ratios of ECM/AM in dual mycorrhizal colonizations were observed in the roots of a variety of poplar species and hybrids. The objective of our study was to analyze the effect of internal and external factors on growth and dual AM and ECM colonization of poplar roots in three 12–15-year-old common gardens in Poland. We also analyzed the abundance of nonmycorrhizal fungal endophytes in the poplar roots. The Populus clones comprised black poplars (Populus deltoides and P. deltoides × Populus nigra), balsam poplars (Populus maximowiczii × Populus trichocarpa), and a hybrid of black and balsam poplars (P. deltoides × P. trichocarpa). Of the three sites that we studied, one was located in the vicinity of a copper smelter, where soil was contaminated with copper and lead. Poplar root tip abundance, mycorrhizal colonization, and soil fungi biomass were lower at this heavily polluted site. The total mycorrhizal colonization and the ratio of ECM and AM colonization differed among the study sites and according to soil depth. The influence of Populus genotype was significantly pronounced only within the individual study sites. The contribution of nonmycorrhizal fungal endophytes differed among the poplar clones and was higher at the polluted site than at the sites free of pollution. Our results indicate that poplar fine root abundance and AM and ECM symbiosis are influenced by environmental conditions. Further studies of different site conditions are required to characterize the utility of poplars for purposes such as the phytoremediation of polluted sites.

Effect of nitrogen level on acid phosphatase activity of eight isolates of ectomycorrhizal fungus Paxillus involutus cultured in vitro

The higher levels of nitrogen in ammonium form stimulated the growth of mycelia and increased the accessible as well as the total acid phosphatase activity of Paxillus involutus (Batsch) Fr. isolates grown in pure culture. Rates of mycelia growth and acid phosphatase activities varied widely from one isolate to another. Scots pine (Pinus sylvestris L.) seedlings were inoculated with different P. involutus isolates in axenic conditions. Shoots of pine seedlings with mycorrhizae contained more phosphorus than shoots of non-mycorrhizal seedlings. The relations between growth and phosphatase activity of P. involutus isolates and their efficiency in supplying the host plant with phosphate are discussed.

Mycorrhizal status of a Scots pine (Pinus sylvestris L.) plantation affected by pollution from a phosphate fertilizer plant

Ectomycorrhizas are an integral, functioning part of many conifer tree species root systems and often considered a link in the causal chain leading to forest decline. In our experiment 12-year-old Scots pine trees grown for 10 years on a polluted acid soil with high aluminium content were compared to a control stand in western Poland. Soil at the polluted site had lower pH than the control site, increased aluminium availability and very low microbial activity. Roots analysed over two years showed lower number of mycorrhizal tips at the polluted site, but only when calculated per soil volume. Differences between sites were not significant when number of mycorrhizal tips was expressed per root mass. There was no significant reduction in the occurrence of any mycorrhizal morphotype. The number of mycorrhizas on trees from the polluted stand was negatively correlated with aluminium content in the needles. Our results showed no clear pollution effect on mycorrhizas in a young stand of Scots pine.

Effect of low pH and aluminium on growth of pinus sylvestris L. Seedlings mycorrhizal with Suillus luteus (L.ex Fr.) S.F. gray

Mycorrhizal syntheses of pine seedlings were conducted with the strain of Suillus luteus No 14 characterized by high tolerance to At 3+ ions. The experiment was performed as a semi-sterile culture in peat-perlite medium with At 3 + ion concentration of 4.0 mM. Three mycorrhizal morphotypes were distinguished on the pine roots : single, dichotomously branched and coralloid. The coralloid mycorrhizas were rare on plants treated with Al. Mycorrhizal abundance was similar in At treated and untreated plants. However mycorrhizas from seedlings treated with At revealed a thinner mantle and a lack of the Hartig net as compared with the untreated control. There was no growth reduction of tested seedlings by the Al 3+ concentration used. Mycorrhiza fonnation with the selected S. luteus strain caused lower Al 3+ translocation to the upper part of the tested seedlings compared with the nonmycorrhizal control. It may be concluded that Al 3+ ion concentrations that appear in the moderately polluted fine-root layers of forest soil may in certain condition negatively influence mycorrhiza formation of young Scots pine trees.

Mycorrhizal status of selected herbaceous plants in Molinia meadows of Folusz, near Szubin (Poland)

This preliminary study examined the arbuscular mycorrhizal (AM) status of native plant species in the Molinia meadows of Folusz in the Kujawy region, Poland. Root samples from ten plant species characteristic of Molinia meadows ( Betonica officinalis , Dianthus superbus , Galium boreale , Inula salicina , Ostericum palustre , Sanguisorba officinalis , Selinum carvifolia , Serratula tinctoria , Silaum silaus , and Succisa pratensis ) were collected in August 2014. Root colonization by AM fungi was considered an indicator of symbiosis development. AM was found in all plant species examined. The frequency of mycorrhizal structures ranged between 68% and 99%. The intensity of mycorrhizal colonization in roots varied with the plant species, ranging between 3.9% ( O. palustre ) and 40.1% ( B. officinalis ). To our knowledge, this is the first study to examine the mycorrhizal status of three species: D. superbus , O. palustre , S. carvifolia . Because AM colonization depends on plant genotype and environmental factors, further studies should examine seasonal variability in plant root colonization and the compositions of AM fungal communities, which may serve as indicators of site conditions