共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
Diversity and species distribution of ectomycorrhizal fungi along productivity gradients of a southern boreal forest 总被引:2,自引:0,他引:2
Coniferous forests with diverse ectomycorrhizal fungus (EMF) communities are associated with nutrient-poor, acidic soils but
there is some debate whether EMF can be equally adapted to more productive, nitrogen-rich sites. We compared EMF species distribution
and diversity along a replicated productivity gradient in a southern boreal forest of British Columbia (Canada). Roots from
subalpine fir (Abies lasiocarpa) saplings of the understory were sampled and EMF species were identified by morphotypes supplemented with ITS rDNA analysis.
There were significant changes in the distribution and abundance of 74 EMF species along the productivity gradient, with as
little as 24% community similarity among contrasting sites. Species richness per plot increased asymptotically with foliar
nitrogen concentrations of subalpine fir, demonstrating that many EMF species were well suited to soils with high rates of
nitrogen mineralization. EMF species abundance in relation to site productivity included parabolic, negative linear, and positive
exponential curves. Both multi-site and more narrowly distributed EMF were documented, and a diverse mix of mantle exploration
types was present across the entire productivity gradient. The results demonstrate strong associations of EMF fungal species
with edaphic characteristics, especially nitrogen availability, and a specialization in EMF communities that may contribute
to the successful exploitation of such contrasting extremes in soil fertility by a single tree host. 相似文献
3.
Mitsuo Nunome Gohta Kinoshita Morihiko Tomozawa Harumi Torii Rikyu Matsuki Fumio Yamada Yoichi Matsuda Hitoshi Suzuki 《Biological journal of the Linnean Society. Linnean Society of London》2014,111(4):761-776
Seasonal changes in fur colour in some mammalian species have long attracted the attention of biologists, especially in species showing population variation in these seasonal changes. Genetic differences among populations that show differences in seasonal changes in coat colour have been poorly studied. Because the Japanese hare (Lepus brachyurus) has two allopatric morphotypes that show remarkably different coat colours in winter, we examined the population genetic structure of the species using partial sequences of the SRY gene and six autosomal genes: three coat colour‐related genes (ASIP, TYR, and MC1R) and three putatively neutral genes (TSHB, APOB, and SPTBN1). The phylogenetic tree of SRY sequences exhibited two distinct lineages that diverged approsimately 1 Mya. Although the two lineages exhibited a clear allopatric distribution, it was not consistent with the distribution of morphotypes. In addition, six nuclear gene sequences failed to reveal genetic differences between morphotypes. Population network trees for 11 expedient populations divided the populations into four groups. Genetic structure analysis revealed an admixture of four genetic clusters in L. brachyurus, two of which showed large genetic differences. Our results suggest ancient vicariance in L. brachyurus, and we detected no genetic differences between the two morphotypes. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 761–776. 相似文献
4.
Communities of arbuscular mycorrhizal fungi in grassland: Seasonal variability and effects of environment and host plants 总被引:1,自引:0,他引:1
Petr Šmilauer 《Folia Geobotanica》2001,36(3):243-263
The seasonal dynamics of a community of endomycorrhizal fungal morphotypes in the roots of three grassland species (Achillea millefolium, Poa angustifolia, Plantago lanceolata) was evaluated, together with the effects of experimental treatment (mowing and phosphorus application) and the host plant properties. Strong seasonal variability was found in the fungal community, where clear seasonal patterns can be distinguished for several fungal morphotypes. The sampling date explained 20 to 30% of the total compositional variability for all three host species. ThePlantago roots host the highest number of arbuscular mycorrhizal (AM) fungal populations. There are two co-dominant fungal morphotypes inAchillea roots (assigned to the generaScutellospora andGlomus) and only one strongly dominant morphotype (assigned toGlomus), in thePoa roots. All three host species have a comparable pattern of richness of AM morphotypes with a single peak in the summer, possibly aligned with the flowering time of the host. 相似文献
5.
The anterior half of the mitochondrial DNA control region (mtCR) sequence (ca. 400 base pairs) was compared between two color morphotypes (A, B) of Parapercis sexfasciata from Tosa Bay, southern Japan, using 16 and 21 specimens, respectively. Intramorphotypic mtCR divergences were only 0.0–0.5% and 1.0–2.5% for morphotypes A and B, respectively. In contrast, intermorphotypic mtCR divergence was much greater, 12.7–14.0%. Furthermore, phylogenetic analysis using a neighbor-joining algorithm, with P. multifasciata as an outgroup, showed that each morphotype was reciprocally monophyletic. These results and the distinct coloration and overlapping distribution indicate that the two color morphotypes of P. sexfasciata represent two distinct species. Mismatch distribution analysis suggested that both morphotypes had undergone population expansion; however, estimates of initial population sizes and mutational timescales suggested that morphotype B comprises historically larger and older populations than morphotype A. 相似文献
6.
The spatial distribution and morphological diversity of virioplankton were determined in Lake Donghu which contains three trophic regions: hypertrophic, eutrophic and mesotrophic region. Virioplankton abundance measured by transmission electron microscope (TEM) ranged from 7.7 × 108 to 3.0 × 109 ml–1, being among the highest observed in any natural aquatic system examined so far. The spatial distribution of virioplankton was correlated significantly with chlorophyll a concentration (r = 0.847; P < 0.01) at the sampling sites in Lake Donghu. 76 morphotypes were observed. Most morphotypes have tails, belonging to Siphoviridae, Myoviridae and Podoviridae. The majority of tailed phages in the lake were Myoviridae. Morphotypes which were rarely reported, such as prolate-headed virus-like particles, lemon-shaped virus-like particle, and viruses resembling Tectiviridae and Corticoviridae were all observed in the lake. It is concluded that the high viral abundance might be associated with high density of phytoplankton including algae and cyanobacteria. There was high viral diversity in this eutrophic shallow lake. In addition, cyanophage represented an important fraction of the virioplankton community in Lake Donghu. 相似文献
7.
Electromagnetic sensibility refers to the ability to perceive the electromagnetic field (EMF) without necessarily developing health symptoms attributed to EMF exposure. A large sample of young healthy adults (n = 84) performed two forced‐choice tasks on the perception of the GSM mobile phone EMF (902 MHz pulsed at 217 Hz), “Was the field on?” and “Did the field change?” (3 conditions × 100 trials for each task, n = 600 trials in total). A monetary prize was announced for good performance (correct response rate ≥75%, n = 600 trials). The performance was no better than expected by chance, and thus none of the participants won the prize. Two participants showed extraordinary performance in one of the task conditions (“Was the field on?”, n = 100 trials), with correct response rates of 97% (P = 1.28 × 10?25) and 94% (P = 9.40 × 10?22), but they failed to replicate the result in the retest of six blocks of the same condition 1 month later. Six participants had reported being able to perceive the mobile phone EMF in the preliminary inquiry, but they performed no better than the others. This study provides empirical evidence against the existence of electromagnetic sensibility to the mobile phone EMF, demonstrating the necessity for replication in EMF studies. Bioelectromagnetics 29:154–159, 2008. © 2007 Wiley‐Liss, Inc. 相似文献
8.
《Fungal Ecology》2023
Investigating the dynamics of ectomycorrhizal fungal (EMF) communities in seasonally dry tropical forests is essential for sustainable management and for understanding the resilience of this forest type in future climate change scenarios. EMF communities in secondary forest fragments with Shorea siamensis as a single host tree species in central Thailand were sampled seasonally for 2.5 y. Ten EMF taxa were identified from ectomycorrhizal morphotypes, with/tomentella-thelephora and/russula-lactarius as the dominant taxa. Seasonal differences in EMF diversity were not detected; the dominant morphotypes were present in both seasons and their abundance varied. Most EMF taxa exhibited wide environmental ranges and only a few taxa were correlated with soil moisture. Seasonal dynamics of ectomycorrhizal colonization was likely influenced by climatic factors and the phenology of host species. Together, these results suggested that climatic variation may have a long-term and subtle influence on the composition of ectomycorrhizal communities. 相似文献
9.
Seven species of dwarf lemurs (Cheirogaleus spp.) are currently recognized after a recent revision of the genus. During a field study in southeastern Madagascar, we observed 3 distinct morphotypes of Cheirogaleus resembling Cheirogaleus medius, C. major and C. crossleyi. In particular, for Cheirogaleus crossleyi southeastern Madagascar was far away from the known distribution range of the species when referring to the recent revision of the genus. In order to clarify the taxonomic status of the 3 morphotypes, we compared field samples from southeastern Madagascar to museum specimens from several locations in Madagascar and to field samples from Kirindy/CFPF, western Madagascar by genetic analyses using the mitochondrial cytochrome b gene. Genetic data yield strong support for 2 of the 3 morphotypes to represent Cheirogaleus medius and C. major. The third morphotype is genetically closely related to Cheirogaleus crossleyi, albeit more distantly than the other 2 morphotypes to the respective reference samples. The genetic distance is related to a considerable geographic distance between the location of our field study and the origin of the respective reference specimen, because Cheirogaleus crossleyi had been reported only from northern Madagascar. Our field observations indicate an isolated population in southeastern Madagascar. We propose to identify them as Cheirogaleus crossleyi and discuss the population genetic and biogeographic considerations supporting this conclusion. 相似文献
10.
Ectomycorrhizal fungi associated with two species of Kobresia in an alpine meadow in the eastern Himalaya 总被引:2,自引:0,他引:2
The diversity of ectomycorrhizal fungi (EMF) on Kobresia filicina and Kobresia capillifolia in an alpine meadow in China’s southwestern mountains, one of the word’s hotspots of biodiversity, was estimated based on
internal transcribed spacer rDNA sequence analysis of root tips. Seventy EMF operational taxonomical units (OTUs) were found
in the two plant species. Dauciform roots with EMF were detected in species of Kobresia for the first time. OTU richness of EMF was high in Tomentella/Thelophora and Inocybe, followed by Cortinarius, Sebacina, the Cenococcum geophilum complex, and Russula. Tomentella/Thelophora and Inocybe were general and dominant mycobiont genera of the two sedges. Besides the C. geophilum complex, the ascomycete components Hymenoscyphus and Lachnum were also detected on the two plants. Alpine plants in different geographical regions share similar main genera and/or families
of EMF while harboring predominantly different mycobiont species; most of the members detected by us have not been found elsewhere.
Significant differences in the profile of EMF occurrences were not found between the two plant species and among the three
sampling seasons in our sample size. 相似文献
11.
The objective of this study was to determine patterns of ectomycorrhizas (ECM) and arbuscular mycorrhizas (AM) colonization associated with Alnus acuminata (Andean alder), in relation to soil parameters (electrical conductivity, field H2O holding capacity, pH, available P, organic matter, and total N) at two different seasons (autumn and spring). The study was conducted in natural forests of A. acuminata situated in Calilegua National Park (Jujuy, Argentina). Nine ECM morphotypes were found on A. acuminata roots. The ECM colonization was affected by seasonality and associated positively with field H2O holding capacity, pH, and total N and negatively associated with organic matter. Two morphotypes (Russula alnijorullensis and Tomentella sp. 3) showed significant differences between seasons. Positive and negative correlations were found between five morphotypes (Alnirhiza silkacea, Lactarius omphaliformis, Tomentella sp. 1, Tomentella sp. 3, and Lactarius sp.) and soil parameters (total N, pH, and P). A significant negative correlation was found between field H2O holding capacity and organic matter with AM colonization. Results of this study provide evidence that ECM and AM colonization of A. acuminata can be affected by some soil chemical edaphic parameters and indicate that some ECM morphotypes are sensitive to changes in seasonality and soil parameters. 相似文献
12.
Previous studies have indicated that there is no consensus on the effects of extremely low‐frequency electromagnetic (ELF‐EMF) exposure on the cardiovascular system. This study aimed to explore the short‐term effect of ELF‐EMF exposure on heart rate (HR) and HR variability (HRV). The sample consisted of 34 healthy males aged 18–27 years. The participants were randomly assigned to the EMF (n = 17) or the Sham group (n = 17). We employed a double‐blind repeated‐measures design consisting of three 5 min experimental periods. The chest region of each individual in the EMF group was exposed to 50 Hz, 28 μT, linear polarized, continuous EMF during the EMF exposure period. HR and HRV data were recorded continuously by using a photoplethysmography sensor. Within‐subject statistical analysis indicated a significant HR deceleration in both the EMF and Sham groups. However, the standard deviation of the NN intervals (SDNN), root mean square of successive differences (RMSSD), low‐frequency (LF), and high‐frequency (HF) powers increased only in the EMF group and remained stable in the Sham group. We also compared the same HRV indices measured during the EMF and Sham periods between the two experimental groups. The between‐subject analysis results demonstrated significantly higher SDNN, RMSSD, LF, and HF values in the EMF group than in the Sham group. The LF/HF ratio did not change significantly within and between groups. On the basis of these results, we concluded that short‐term exposure of the chest region to ELF‐EMF could potentially enhance parasympathetic predominance during the resting condition. Bioelectromagnetics. 2021;42:60–75. © 2020 Bioelectromagnetics Society. 相似文献
13.
《Electromagnetic biology and medicine》2013,32(2):80-85
The aim of this study was to test if an extremely weak 1 GHz electromagnetic field (EMF), known to be in resonance with clusters of water molecules, has biological effects on human fibroblasts. We demonstrated that in an in vitro model of wound healing, this EMF can activate fibroblast migration. [3H]thymidine incorporation experiments demonstrated that the EMF could also activate fibroblast proliferation. Activation of the expression of human fibroblast growth factor 1 (HFGF1) after EMF exposure showed that molecular wound healing pathways are activated in response to this water-resonant EMF. 相似文献
14.
The effects of prenatal exposure to a 900-MHz electromagnetic field on the 21-day-old male rat heart
《Electromagnetic biology and medicine》2013,32(4):390-397
AbstractThe growing spread of mobile phone use is raising concerns about the effect on human health of the electromagnetic field (EMF) these devices emit. The purpose of this study was to investigate the effects on rat pup heart tissue of prenatal exposure to a 900 megahertz (MHz) EMF. For this purpose, pregnant rats were divided into experimental and control groups. Experimental group rats were exposed to a 900?MHz EMF (1?h/d) on days 13–21 of pregnancy. Measurements were performed with rats inside the exposure box in order to determine the distribution of EMF intensity. Our measurements showed that pregnant experimental group rats were exposed to a mean electrical field intensity of 13.77?V/m inside the box (0.50?W/m2). This study continued with male rat pups obtained from both groups. Pups were sacrificed on postnatal day 21, and the heart tissues were extracted. Malondialdehyde, superoxide dismutase and catalase values were significantly higher in the experimental group rats, while glutathione values were lower. Light microscopy revealed irregularities in heart muscle fibers and apoptotic changes in the experimental group. Electron microscopy revealed crista loss and swelling in the mitochondria, degeneration in myofibrils and structural impairments in Z bands. Our study results suggest that exposure to EMF in the prenatal period causes oxidative stress and histopathological changes in male rat pup heart tissue. 相似文献
15.
《Redox report : communications in free radical research》2013,18(5):299-301
AbstractIn an attempt to determine whether electromagnetic field (EMF) exposure might lead to DNA damage, we exposed SnCl2-treated pBR322 plasmids to EMF and analysed the resulting conformational changes using agarose gel electrophoresis. An EMF-dependent potentiation of DNA scission (i.e. the appearance of relaxed plasmids) was observed. In confirmation of this, plasmids pre-exposed to EMF also were less capable of transforming Escherichia coli. The results indicate that EMF, in the presence of a transition metal, is capable of causing DNA damage. These observations support the idea that EMF, probably through secondary generation of reactive oxygen species, can be clastogenic and provide a possible explanation for the observed correlation between EMF exposure and the frequency of certain types of cancers in humans. 相似文献
16.
The relative numbers of fourteen microbial morphotypes in transmission electron micrographs of the hindgut of a cockroach, Eublaberus posticus, were counted and their distribution was analyzed statistically. The microbiota of three wall-associated regions (the anterior paunch, the posterior paunch, and the black band region) was clearly different from that of the gut lumen. The three wall fractions were also significantly different from each other. Only one of the fourteen types, prosthecate bacteria, appeared to be distributed randomly in the four fractions. The five main wall-associated morphotypes individually constituted up to 41% of the microbes in some micrographs. They included one type with the characteristic morphology of Methanospirillum. Six morphotypes rarely made up over 2% of the population, but were consistently present. The numbers of the remaining three morphotypes were quite variable between micrographs and between individual insects, but when present often made up 5–10% of the population. 相似文献
17.
Sunk IG Trattnig S Graninger WB Amoyo L Tuerk B Steiner CW Smolen JS Bobacz K 《Arthritis research & therapy》2006,8(4):R106-11
The influence of magnetic resonance imaging (MRI) devices at high field strengths on living tissues is unknown. We investigated
the effects of a 3-tesla electromagnetic field (EMF) on the biosynthetic activity of bovine articular cartilage. Bovine articular
cartilage was obtained from juvenile and adult animals. Whole joints or cartilage explants were subjected to a pulsed 3-tesla
EMF; controls were left unexposed. Synthesis of sulfated glycosaminoglycans (sGAGs) was measured by using [35S]sulfate incorporation; mRNA encoding the cartilage markers aggrecan and type II collagen, as well as IL-1β, were analyzed
by RT–PCR. Furthermore, effects of the 3-tesla EMF were determined over the course of time directly after exposure (day 0)
and at days 3 and 6. In addition, the influence of a 1.5-tesla EMF on cartilage sGAG synthesis was evaluated. Chondrocyte
cell death was assessed by staining with Annexin V and TdT-mediated dUTP nick end labelling (TUNEL). Exposure to the EMF resulted
in a significant decrease in cartilage macromolecule synthesis. Gene expression of both aggrecan and IL-1β, but not of collagen
type II, was reduced in comparison with controls. Staining with Annexin V and TUNEL revealed no evidence of cell death. Interestingly,
chondrocytes regained their biosynthetic activity within 3 days after exposure, as shown by proteoglycan synthesis rate and
mRNA expression levels. Cartilage samples exposed to a 1.5-tesla EMF remained unaffected. Although MRI devices with a field
strength of more than 1.5 T provide a better signal-to-noise ratio and thereby higher spatial resolution, their high field
strength impairs the biosynthetic activity of articular chondrocytes in vitro. Although this decrease in biosynthetic activity seems to be transient, articular cartilage exposed to high-energy EMF may
become vulnerable to damage. 相似文献
18.
Trocha LK Kałucka I Stasińska M Nowak W Dabert M Leski T Rudawska M Oleksyn J 《Mycorrhiza》2012,22(2):121-134
Non-native tree species have been widely planted or have become naturalized in most forested landscapes. It is not clear if
native trees species collectively differ in ectomycorrhizal fungal (EMF) diversity and communities from that of non-native
tree species. Alternatively, EMF species community similarity may be more determined by host plant phylogeny than by whether
the plant is native or non-native. We examined these unknowns by comparing two genera, native and non-native Quercus robur and Quercus rubra and native and non-native Pinus sylvestris and Pinus nigra in a 35-year-old common garden in Poland. Using molecular and morphological approaches, we identified EMF species from ectomycorrhizal
root tips and sporocarps collected in the monoculture tree plots. A total of 69 EMF species were found, with 38 species collected
only as sporocarps, 18 only as ectomycorrhizas, and 13 both as ectomycorrhizas and sporocarps. The EMF species observed were
all native and commonly associated with a Holarctic range in distribution. We found that native Q. robur had ca. 120% higher total EMF species richness than the non-native Q. rubra, while native P. sylvestris had ca. 25% lower total EMF species richness than non-native P. nigra. Thus, across genera, there was no evidence that native species have higher EMF species diversity than exotic species. In
addition, we found a higher similarity in EMF communities between the two Pinus species than between the two Quercus species. These results support the naturalization of non-native trees by means of mutualistic associations with cosmopolitan
and novel fungi. 相似文献
19.
Zafer Akan Burak Aksu Aysin Tulunay Serpil Bilsel Ayse Inhan‐Garip 《Bioelectromagnetics》2010,31(8):603-612
This study aimed to determine the effect of extremely low‐frequency electromagnetic fields (ELF‐EMF) on the physiological response of phagocytes to an infectious agent. THP‐1 cells (human monocytic leukemia cell line) were cultured and 50 Hz, 1 mT EMF was applied for 4–6 h to cells induced with Staphylococcus aureus or interferon gamma/lipopolysaccharide (IFγ/LPS). Alterations in nitric oxide (NO), inducible nitric oxide synthase (iNOS) levels, heat shock protein 70 levels (hsp70), cGMP levels, caspase‐9 activation, and the growth rate of S. aureus were determined. The growth curve of exposed bacteria was lower than the control. Field application increased NO levels. The increase was more prominent for S. aureus‐induced cells and appeared earlier than the increase in cells without field application. However, a slight decrease was observed in iNOS levels. Increased cGMP levels in response to field application were closely correlated with increased NO levels. ELF‐EMF alone caused increased hsp70 levels in a time‐dependent manner. When cells were induced with S. aureus or IFγ/LPS, field application produced higher levels of hsp70. ELF‐EMF suppressed caspase‐9 activation by a small extent. These data confirm that ELF‐EMF affects bacterial growth and the response of the immune system to bacterial challenges, suggesting that ELF‐EMF could be exploited for beneficial uses. Bioelectromagnetics 31:603–612, 2010. © 2010 Wiley‐Liss, Inc. 相似文献
20.
Species–area curve and distance–decay relationships indicate habitat thresholds of ectomycorrhizal fungi in an old‐growth Pseudotsuga menziesii landscape
下载免费PDF全文
![点击此处可从《Diversity & distributions》网站下载免费的PDF全文](/ch/ext_images/free.gif)
J. M. Kranabetter S. M. Berch J. A. MacKinnon O. Ceska D. E. Dunn P. K. Ott 《Diversity & distributions》2018,24(6):755-764