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1.
Twenty isolates of ectomycorrhizal fungi – 3 from Picea
glehnii, 12 from other coniferous trees, and 5 from decidous trees – were tested for the ability to form mycorrhizae with P.
glehnii, using an in vitro synthesis technique. Macroscopically, mycorrhizal formation was observed 3 months after inoculation, when
the lateral roots began to grow. Mycelial growth was observed in all inoculated treatments, generally around and along the
roots. Six months after inoculation, seedlings were harvested and the mycorrhizae were observed microscopically. Fourteen
of the 20 isolates formed ectomycorrhizae with a dense sheath and a deep Hartig net; 1 formed ectendomycorrhizae with a rudimentary
mantle, a well-developed Hartig net and intracellular hyphae; 3 formed pseudomycorrhizae with a mantle but without the Hartig
net; and only 2 of the fungi tested, Chalciporus
pipeparatus 5/92 and Lyophyllum sp. 61/92, did not form mycorrhizae at all. P.
glehnii was a good host species since it had low specificity to ectomycorrhizal fungi isolated from trees other than P. glehnii.
Accepted: 6 May 1996 相似文献
2.
Nutrient uptake in mycorrhizal symbiosis 总被引:44,自引:2,他引:44
The role of mycorrhizal fungi in acquisition of mineral nutrients by host plants is examined for three groups of mycorrhizas.
These are; the ectomycorrhizas (ECM), the ericoid mycorrhizas (EM), and the vesicular-arbuscular mycorrhizas (VAM). Mycorrhizal
infection may affect the mineral nutrition of the host plant directly by enhancing plant growth through nutrient acquisition
by the fungus, or indirectly by modifying transpiration rates and the composition of rhizosphere microflora.
A capacity for the external hyphae to take up and deliver nutrients to the plant has been demonstrated for the following nutrients
and mycorrhizas; P (VAM, EM, ECM), NH4
+ (VAM, EM, ECM), NO3
- (ECM), K (VAM, ECM), Ca (VAM, EM), SO4
2- (VAM), Cu (VAM), Zn (VAM) and Fe (EM). In experimental chambers, the external hyphae of VAM can deliver up to 80% of plant
P, 25% of plant N, 10% of plant K, 25% of plant Zn and 60% of plant Cu. Knowledge of the role of mycorrhiza in the uptake
of nutrients other than P and N is limited because definitive studies are few, especially for the ECM. Although further quantification
is required, it is feasible that the external hyphae may provide a significant delivery system for N, K, Cu and Zn in addition
to P in many soils. Proposals that ECM and VAM fungi contribute substantially to the Mg, B and Fe nutrition of the host plant
have not been substantiated.
ECM and EM fungi produce ectoenzymes which provide host plants with the potential to access organic N and P forms that are
normally unavailable to VAM fungi or to non mycorrhizal roots. The relative contribution of these nutrient sources requires
quantification in the field.
Further basic research, including the quantification of nutrient uptake and transport by fungal hyphae in soil and regulation
at the fungal-plant interface, is essential to support the selection and utilization of mycorrhizal fungi on a commercial
scale. 相似文献
3.
The microscale spatial distribution patterns of ectomycorrhizal (ECM) morphotypes of red oak (Quercus rubra L.) were analyzed over a 600 × 6 × 3 cm (length x width x depth) soil monolith. For this purpose, the soil monolith was divided
into 2 × 2 × 1 cm cuboids. Each cuboid was assigned to an organic sublayer, namely the F- or H-layer. A new classification
method was used to combine morphotypes with similar distribution patterns into five different groups. For identification of
the ECM fungi, internal transcribed spacer (ITS) regions from nuclear rDNA were sequenced and compared with sequences from
the international GenBank. Twenty-eight ECM types were identified in the soil monolith. Using this new classification method,
it was found that the majority of morphotypes (16) appeared in a scattered horizontal distribution and that only 5 morphotypes
formed clusters. In addition, it was found that many morphotypes had a clear preference for a specific organic sublayer: 14
morphotypes preferred the F-layer, 5 the H-layer, and only 4 morphotypes showed no preference for a given layer. Analysis
of the distribution patterns showed that ECM fungi either exclude each other or occur together. The most frequent morphotypes,
Cenococcum geophilum and Tomentella spec. 01, were associated with the whole ECM community. In contrast, the frequent morphotype Tomentella terrestris showed the lowest degree of association among the identified morphotypes. 相似文献
4.
Hugues B. Massicotte Lewis H. Melville R. Larry Peterson Linda E. Tackaberry Daniel L. Luoma 《Mycorrhiza》2010,20(6):391-397
All members of the Monotropoideae (Ericaceae), including the species, Allotropa virgata and Pleuricospora fimbriolata, are mycoheterotrophs dependent on associated symbiotic fungi and autotrophic plants for their carbon needs. Although the
fungal symbionts have been identified for A. virgata and P. fimbriolata, structural details of the fungal–root interactions are lacking. The objective of this study was, therefore, to determine
the structural features of these plant root–fungus associations. Root systems of these two species did not develop dense clusters
of mycorrhizal roots typical of some monotropoid species, but rather, the underground system was composed of elongated rhizomes
with first- and second-order mycorrhizal adventitious roots. Both species developed mantle features typical of monotropoid
mycorrhizas, although for A. virgata, mantle development was intermittent along the length of each root. Hartig net hyphae were restricted to the host epidermal
cell layer, and fungal pegs formed either along the tangential walls (P. fimbriolata) or radial walls (A. virgata) of epidermal cells. Plant-derived wall ingrowths were associated with each fungal peg, and these resembled transfer cells
found in other systems. Although the diffuse nature of the roots of these two plants differs from some members in the Monotropoideae,
the structural features place them along with other members of the Monotropoideae in the “monotropoid” category of mycorrhizas. 相似文献
5.
We examined the influence of phosphorus source and availability on host plant (Pinus rigida) response to ectomycorrhizal diversity under contrasting P conditions. An ectomycorrhizal richness gradient was established with equimolar P supplied as either inorganic phosphate or organic inositol hexaphosphate. We measured growth and N and P uptake of individual P. rigida seedlings inoculated with one, two, or four species of ectomycorrhizal fungi simultaneously and without mycorrhizas in axenic culture. Whereas colonization of P. rigida by individual species of ectomycorrhizal fungi decreased with increasing fungal richness, colonization of all species combined increased. Plant biomass and N content increased across the ectomycorrhizal richness gradient in the organic but not the inorganic P treatment. Plants grown under organic P conditions had higher N concentration than those grown under inorganic P conditions, but there was no effect of richness. Phosphorus content of plants grown in the organic P treatment increased with increasing ectomycorrhizal richness, but there was no response in the inorganic P treatment. Phosphorus concentration was higher in plants grown at the four-species richness level in the organic P treatment, but there was no effect of diversity under inorganic P conditions. Overall, few ectomycorrhizal composition effects were found on plant growth or nutrient status. Phosphatase activities of individual ectomycorrhizal fungi differed under organic P conditions, but there was no difference in total root system phosphatase expression between the inorganic or organic P treatments or across richness levels. Our results provide evidence that plant response to ectomycorrhizal diversity is dependent on the source and availability of P. 相似文献
6.
Babette Münzenberger Ben Bubner Jens Wöllecke Thomas N. Sieber Robert Bauer Matthias Fladung Reinhard F. Hüttl 《Mycorrhiza》2009,19(7):481-492
Relatively few ectomycorrhizal fungal species are known to form sclerotia. Usually, sclerotia are initiated at the extraradical
mycelium. In this study, we present anatomical and ultrastructural evidence for the formation of sclerotia directly in the
hyphal mantle of the mycorrhizal morphotype Pinirhiza sclerotia. A dark-pigmented fungal strain was isolated from Pinirhiza sclerotia and identified by molecular tools as Acephala macrosclerotiorum sp. nov., a close relative of Phialocephala fortinii s.l. As dark septate fungi are known to be mostly endophytic, resyntheses with Pinus sylvestris and A. macrosclerotiorum as well as Populus tremula × Populus tremuloides and A. macrosclerotiorum or P. fortinii s.l. were performed under axenic conditions. No mycorrhizas were found when hybrid aspen was inoculated with A. macrosclerotiorum or P. fortinii. However, A. macrosclerotiorum formed true ectomycorrhizas in vitro with P. sylvestris. Anatomical and ultrastructural features of this ectomycorrhiza are presented. The natural and synthesized ectomycorrhizal
morphotypes were identical and characterized by a thin hyphal mantle that bore sclerotia in a later ontogenetic stage. The
Hartig net was well-developed and grew up to the endodermis. To our knowledge, this is the first evidence at the anatomical
and ultrastructural level that a close relative of P. fortinii s.l. forms true ectomycorrhizas with a coniferous host. 相似文献
7.
The rates and controls of ectomycorrhizal fungal production were assessed in a 22-year-old longleaf pine (Pinus palustris Mill.) plantation using a complete factorial design that included two foliar scorching (control and 95% plus needle scorch)
and two nitrogen (N) fertilization (control and 5 g N m−2 year−1) treatments during an annual assessment. Ectomycorrhizal fungi production comprised of extramatrical mycelia, Hartig nets
and mantles on fine root tips, and sporocarps was estimated to be 49 g m−2 year−1 in the control treatment plots. Extramatrical mycelia accounted for approximately 95% of the total mycorrhizal production
estimate. Mycorrhizal production rates did not vary significantly among sample periods throughout the annual assessment (p = 0.1366). In addition, reduction in foliar leaf area via experimental scorching treatments did not influence mycorrhizal
production (p = 0.9374), suggesting that stored carbon (C) may decouple the linkage between current photosynthate production and ectomycorrhizal
fungi dynamics in this forest type. Nitrogen fertilization had a negative effect, whereas precipitation had a positive effect
on mycorrhizal fungi production (p = 0.0292; r
2 = 0.42). These results support the widely speculated but poorly documented supposition that mycorrhizal fungi are a large
and dynamic component of C flow and nutrient cycling dynamics in forest ecosystems. 相似文献
8.
Structures present within field-collected Tricholoma matsutake/Pinus densiflora ectomycorrhizas and in vitro infections of P. densiflora roots by T. matsutake were observed by clearing, bleaching and staining whole lateral roots and mycorrhizas. Field mycorrhizas were characterized
by a lack of root hairs, by the presence of a sparse discontinuous mantle composed of irregularly darkly staining hyphae over
the root surface, primarily behind the root cap, and by the presence of Hartig net mycelium within the root cortex. Hartig
net 'palmettis' were classified into three basic structures, each with distinctive morphologies. Aerial hyphae, bearing terminal
swellings, were observed emanating from the mantle. Cleared, bleached and stained in vitro-infected roots possessed multibranched
hyphal structures within the host root cortex and aerial hyphae bearing terminal swellings were observed arising from the
mycelium colonizing the root surface. T. matsutake on P. densiflora conforms to the accepted morphology of an ectomycorrhiza. This staining protocol is particularly suited to the study of Matsutake
mycorrhizal roots and gives rapid, clear, high-contrast images using standard light microscopy while conserving spatial relationships
between hyphal elements and host tissues.
Accepted: 26 August 1999 相似文献
9.
Seedlings of Lotus glaberMill., were grown in a native saline-sodic soil in a greenhouse for 50 days and then subjected to waterlogging for an additional
period of 40 days. The effect of soil waterlogging was evaluated by measuring plant growth allocation, mineral nutrition and
soil chemical properties. Rhizobiumnodules and mycorrhizal colonisation in L. glaberroots were measured before and after waterlogging. Compared to control plants, waterlogged plants had decreased root/shoot
ratio, lower number of stems per plant, lower specific root length and less allocation of P and N to roots. Waterlogged plants
showed increased N and P concentrations in plant tissues, larger root crown diameter and longer internodes. Available N and
P and organic P, pH and amorphous iron increased in waterlogged soil, but total N, EC and exchangeable sodium were not changed.
Soil waterlogging decreased root length colonised by arbuscular mycorrhizal (AM) fungi, arbuscular colonisation and number
of entry points per unit of root length colonised. Waterlogging also increased vesicle colonisation and Rhizobium nodules on roots. AM fungal spore density was lower at the end of the experiment in non-waterlogged soil but was not reduced
under waterlogging. The results indicate that L. glaber can grow, become nodulated by Rhizobium and colonised by mycorrhizas under waterlogged condition. The responses of L. glaber may be related its ability to form aerenchyma. 相似文献
10.
Tytti Sarjala 《Mycorrhiza》1999,8(5):277-281
The abilities of three ectomycorrhizal fungi, Paxillus involutus, Suillus
variegatus and Lactarius rufus, to utilize organic and inorganic nitrogen sources were determined by measuring the growth and endogenous free polyamines
(putrescine, spermidine and spermine) of pure culture mycelium. Differences were found in the utilization of the nitrogen
sources and in the polyamine concentrations between the fungal species and between isolates of L. rufus. All the fungi grew well on ammonium and on several amino acids. Endogenous polyamine levels varied with the nitrogen source.
Spermidine was commonly the most abundant polyamine; however, more putrescine than spermidine was found in P. involutus growing on inorganic nitrogen or arginine. Low amounts of spermine were found in S. variegatus and some samples of L. rufus. None or only a trace of spermine was found in P. involutus mycelium. In all fungi, putrescine concentrations were higher with ammonium than with the nitrate treatment. The total nitrogen
content of peat did not determine the ability of L. rufus strains isolated from peatland forest sites to utilize organic nitrogen.
Accepted: 27 November 1998 相似文献
11.
We studied the tolerance of ectomycorrhizal (ECM) fungi to sodium chloride (NaCl) to find the best fungus to aid growth of
Pinus thunbergii. Four ECM fungi, Cenococcum geophilum, Pisolithus tinctorius, Rhizopogon rubescens, and Suillus luteus, were grown in liquid MMN media with five different concentrations of NaCl for 30 days, and their mycelial weights were determined.
Mycelial weights of P. tinctorius and R. rubescens were not significantly different between 0 mM and 200 mM, whereas those of C. geophilum and S. luteus decreased with increasing NaCl concentration, indicating that the former two species were more tolerant to higher NaCl concentrations
than the latter species. We further studied the intraspecific differences in NaCl tolerance of nine P. tinctorius isolates. They were grown on MMN agar media with six different concentrations of NaCl for 21 days, and their radial growth
was measured. In total, the hyphal growth at 25 mM NaCl was significantly higher than those at the other NaCl concentrations,
and EC50 values were confirmed at between 50 mM and 200 mM. Among the isolates, Pt03 and Pt21 showed measurable growth at 200 mM;
the growth of Pt03 was not significantly different between 0 mM and 200 mM. The results indicate that there are intraspecific
variations in NaCl tolerance of Pisolithus species. 相似文献
12.
13.
Ectomycorrhizas were synthesized in pots and growth pouches betweenQuercus serrata, Q. acutissima, and two ectomycorrhizal fungi,Pisolithus tinctorius andHebeloma cylindrosporum. Root morphology and the structure of the mantle and Hartig net were compared using light, fluorescence, scanning and transmission
electron microscopy.P. tinctorius initially colonized root cap cells, and eventually produced a highly branched lateral root system with a complete mantle,
whereasH. cylindrosporum promoted root elongation with few hyphae on the root apex surface indicating that interaction between roots differs with
fungal species. Hartig net structure and hyphal inclusions varied between all the combinations tested. There were structural
differences between mycorrhizas ofH. cylindrosporum/Q. acutissima grown in soil and growth pouches, which indicate that the growth pouch environment can induce artefacts in roots. Fruit bodies
ofH. cylindrosporum developed in pots withQ. acutissima. AlthoughP. tinctorius has been used to inoculate oak seedlings in the nursery, results of this study indicate thatH. cylindrosporum may also be an effective ectomycorrhizal fungus forQ. serrata andQ. acutissima. 相似文献
14.
Xiaomin Zhu Hans Lambers Wanji Guo Dongdong Chen Zhanfeng Liu Ziliang Zhang Huajun Yin 《Global Change Biology》2023,29(16):4605-4619
Ectomycorrhizal (ECM) functional traits related to nutrient acquisition are impacted by nitrogen (N) deposition. However, less is known about whether these nutrient-acquisition traits associated with roots and hyphae differentially respond to increased N deposition in ECM-dominated forests with different initial N status. We conducted a chronic N addition experiment (25 kg N ha−1 year−1) in two ECM-dominated forests with contrasting initial N status, that is, a Pinus armandii forest (with relatively low N availability) and a Picea asperata forest (with relatively high N availability), to assess nutrient-mining and nutrient-foraging strategies associated with roots and hyphae under N addition. We show that nutrient-acquisition strategies of roots and hyphae differently respond to increased N addition. Root nutrient-acquisition strategies showed a consistent response to N addition, regardless of initial forest nutrient status, shifting from organic N mining toward inorganic N foraging. In contrast, the hyphal nutrient-acquisition strategy showed diverse responses to N addition depending on initial forest N status. In the Pinus armandii forest, trees increased belowground carbon (C) allocation to ECM fungi thus enhancing hyphal N-mining capacity under increased N availability. By comparison, in the Picea asperata forest, ECM fungi enhanced both capacities of P foraging and P mining in response to N-induced P limitation. In conclusion, our results demonstrate that ECM fungal hyphae exhibit greater plasticity in nutrient-mining and nutrient-foraging strategies than roots do in response to changes of nutrient status induced by N deposition. This study highlights the importance of ECM associations in tree acclimation and forest function stability under changing environments. 相似文献
15.
16.
对菌根共生机制的研究是对其进行应用的前提,到目前为止,绝大多数外生菌根(ectomycorrhiza,ECM)的建立过程尚不明晰,在一定程度上限制了这些ECM真菌在林业中的应用。本研究以我国南方地区主栽树种之一——马尾松Pinus massoniana和其林下优势ECM真菌——粘盖乳牛肝菌Suillus bovinus为材料,在无菌条件下研究两者菌根共生体形成过程的形态学特征。结果表明马尾松与粘盖乳牛肝菌的共生过程分为2个阶段:(1)预共生阶段,即物理接触之前,粘盖乳牛肝菌可通过释放挥发物和分泌物促进马尾松根系伸长和分枝;(2)共生阶段,又可分为3个时期。接种后第4天,粘盖乳牛肝菌菌丝体开始与马尾松根系接触并形成附着胞进入接触期;第7天菌丝开始侵入根系内部,侵入期开始;第28天菌套和哈氏网形成,即菌套和哈氏网形成期,该时期菌根化根尖开始膨大,随后继续发育至二叉分枝状菌根形成。在发育顺序方面,哈氏网与菌套同步发育,但哈氏网成形早于菌套。以上结果可对后续ECM共生机制的深入研究及马尾松高效菌根化育苗技术的开发提供参考。 相似文献
17.
Nitrogen deposition and intentional forest fertilisation with nitrogen are known to affect the species composition of ectomycorrhizal
fungal communities. To learn more about the mechanisms responsible for these effects, the relations between fungal growth,
nitrogen uptake and nitrogen availability were studied in ectomycorrhizal fungi in axenic cultures and in symbiosis with pine
seedlings. Effects of different levels of inorganic nitrogen (NH4) on the mycelial growth of four isolates of Paxillus involutus and two isolates of Suillus bovinus were assessed. With pine seedlings, fungal uptake of
15N-labelled NH4 was studied in short-term incubation experiments (72 h) in microcosms and in long-term incubation experiments (3 months)
in pot cultures. For P. involutus growing in symbiosis with pine seedlings, isolates with higher NH4 uptake were affected more negatively at high levels of nitrogen availability than isolates with lower uptake. More NH4 was allocated to shoots of seedlings colonised by a high-uptake isolate, indicating transfer of a larger fraction of assimilated
NH4 to the host than with isolates showing lower NH4 uptake rates. Thus low rates of N uptake and N transfer to the host may enable EM fungi avoid stress induced by elevated
levels of nitrogen. Seedlings colonised by S. bovinus transferred a larger fraction of the 15N label to the shoots than seedlings colonised by P. involutus. Seedling shoot growth probably constituted a greater carbon sink in pot cultures than in microcosms, since the mycelial growth
of P. involutus was more sensitive to high NH4 in pots. There was no homology in mycelial growth rate between pure culture and growth in symbiosis, but N uptake in pure
culture corresponded to that during growth in symbiosis. No relationship was found between deposition of antropogenic nitrogen
at the sites of origin of the P. involutus isolates and their mycelial growth or uptake of inorganic nitrogen.
Accepted: 18 September 1998 相似文献
18.
Nygren CM Eberhardt U Karlsson M Parrent JL Lindahl BD Taylor AF 《The New phytologist》2008,180(4):875-889
Ectomycorrhizal (ECM) fungi are often considered to be most prevalent under conditions where organic sources of N predominate. However, ECM fungi are increasingly exposed to nitrate from anthropogenic sources. Currently, the ability of ECM fungi to metabolize this nitrate is poorly understood. Here, growth was examined among 106 isolates, representing 68 species, of ECM fungi on nitrate as the sole N source. In addition, the occurrence of genes coding for the nitrate reductase enzyme (nar gene) in a broad range of ectomycorrhizal fungi was investigated. All isolates grew on nitrate, but there was a strong taxonomic signature in the biomass production, with the Russulaceae and Amanita showing the lowest growth. Thirty-five partial nar sequences were obtained from 43 tested strains comprising 31 species and 10 genera. These taxa represent three out of the four clades of the Agaricales within which ECM fungi occur. No nar sequences were recovered from the Russulaceae and Amanita, but Southern hybridization showed that the genes were present. The results demonstrate that the ability to utilize nitrate as an N source is widespread in ECM fungi, even in those fungi from boreal forests where the supply of nitrate may be very low. 相似文献
19.
Anatomical aspects of field ectomycorrhizas on Polygonum viviparum (Polygonaceae) and Kobresia bellardii (Cyperaceae) 总被引:3,自引:3,他引:0
Root systems of the herbaceous species Polygonum viviparum and Kobresia bellardii were excavated from an alpine site in the Rocky Mountains, Colorado, and processed for microscopic examination. Several ectomycorrhizal
morphotypes were present on root systems of both species;K. bellardii often had complex clusters of mycorrhizal roots present. A mantle and Hartig net were present on all mycorrhizal root tips
processed. The Hartig net was confined to the epidermis, and the parenchyma cells of this layer were radially elongated, vacuolated
and contained densely staining inclusions. Intracellular hyphae and structures typical for vesicular-arbuscular mycorrhizas
were never observed. Both herbaceous species, therefore, had ectomycorrhizal associations comparable to those described for
woody angiosperm species.
Accepted: 14 February 1998 相似文献
20.
In this study we show that the natural abundance of the nitrogen isotope 15, δ15N, of plants in heath tundra and at the tundra-forest ecocline is closely correlated with the presence and type of mycorrhizal
association in the plant roots. A total of 56 vascular plant species, 7 moss species, 2 lichens and 6 species of fungi from
four heath and forest tundra sites in Greenland, Siberia and Sweden were analysed for δ15N and N concentration. Roots of vascular plants were examined for mycorrhizal colonization, and the soil organic matter was
analysed for δ15N, N concentration and soil inorganic, dissolved organic and microbial N. No arbuscular mycorrhizal (AM) colonizations were
found although potential host plants were present in all sites. The dominant species were either ectomycorrhizal (ECM) or
ericoid mycorrhizal (ERI). The δ15N of ECM or ERI plants was 3.5–7.7‰ lower than that of non-mycorrhizal (NON) species in three of the four sites. This corresponds
to the results in our earlier study of mycorrhiza and plant δ15N which was limited to one heath and one fellfield in N Sweden. Hence, our data suggest that the δ15N pattern: NON/AM plants > ECM plants ≥ ERI plants is a general phenomenon in ecosystems with nutrient-deficient organogenic
soils. In the fourth site, a␣birch forest with a lush herb/shrub understorey, the differences between functional groups were
considerably smaller, and only the ERI species differed (by 1.1‰) from the NON species. Plants of all functional groups from
this site had nearly twice the leaf N concentration as that found in the same species at the other three sites. It is likely
that low inorganic N availability is a prerequisite for strong δ15N separation among functional groups. Both ECM roots and fruitbodies were 15N enriched compared to leaves which suggests that the difference in δ15N between plants with different kinds of mycorrhiza could be due to isotopic fractionation at the␣fungal-plant interface.
However, differences in δ15N between soil N forms absorbed by the plants could also contribute to the wide differences in plant δ15N found in most heath and forest tundra ecosystems. We hypothesize that during microbial immobilization of soil ammonium the
microbial N pool could become 15N-depleted and the remaining, plant-available soil ammonium 15N-enriched. The latter could be a main source of N for NON/AM plants which usually have high δ15N. In contrast, amino acids and other soil organic N compounds presumably are 15N-depleted, similar to plant litter, and ECM and ERI plants with high uptake of these N forms hence have low leaf δ15N. Further indications come from the δ15N of mosses and lichens which was similar to that of ECM plants. Tundra cryptogams (and ECM and ERI plants) have previously
been shown to have higher uptake of amino acid than ammonium N; their low δ15N might therefore reflect the δ15N of free amino acids in the soil. The concentration of dissolved organic N was 3–16 times higher than that of inorganic N
in the sites. Organic nitrogen could be an important N source for ECM and, in particular, ERI plants in heath and forest tundra
ecosystems with low release rate of inorganic N from the soil organic matter.
Received: 8 June 1997 / Accepted: 28 February 1998 相似文献