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1.
This study evaluated the interactive effect of arbuscular mycorrhizal fungi (AMF) inoculation and exogenous phosphorus supply on soil phosphotases, plant growth, and nutrient uptake of Kandelia obovata (Sheue, Liu & Yong). We aimed to explore the ecophysiological function of AMF in mangrove wetland ecosystems, and to clarify the possible survival mechanism of mangrove species against nutrient deficiency. K. obovata seedlings with or without AMF inoculation (mixed mangrove AMF), were cultivated for six months in autoclaved sediment medium which was supplemented with KH2PO4 (0, 15, 30, 60, 120 mg kg−1). Then the plant growth, nitrogen and phosphorus content, root vitality, AMF colonization and soil phosphatase activity were analyzed. The inoculated AMF successfully infected K. obovata roots, developed intercellular hyphae, arbuscular (Arum-type), and vesicle structures. Arbuscular mycorrhizal fungi colonization ranged from 9.04 to 24.48%, with the highest value observed under 30 and 60 mg kg−1 P treatments. Soil P supply, in the form of KH2PO4, significantly promoted the height and biomass of K. obovata, enhanced root vitality and P uptake, while partially inhibiting soil acid (ACP) and alkaline phosphotase (ALP) activities. Without enhancing plant height, the biomass, root vitality and P uptake were further increased when inoculated with AMF, and the reduction on ACP and ALP activities were alleviated. Phosphorus supply resulted in the decrease of leaf N–P ratio in K. obovata, and AMF inoculation strengthened the reduction, thus alleviating P limitation in plant growth. Arbuscular mycorrhizal fungi inoculation and adequate P supply (30 mg kg−1 KH2PO4) enhanced root vitality, maintained soil ACP and ALP activities, increased plant N and P uptake, and resulted in greater biomass of K. obovata. Mutualistic symbiosis with AMF could explain the survival strategies of mangrove plants under a stressed environment (waterlogging and nutrient limitation) from a new perspective. 相似文献
2.
Glyphosate is a systemic non-selective herbicide, the most widely used in the world. Alongside with its use in agricultural and forestry systems, this herbicide is used in grasslands in late summer with the aim of promoting winter species with the consequent increase in stocking rate. However, its effects on non-target organisms, such as arbuscular mycorrhizal fungi (AMF), are unclear. Arbuscular mycorrhizal fungi (AMF) colonize the root of more than 80% of terrestrial plants, improving their growth and survival, and therefore playing a key role in ecosystem structure and function. The aim of this work was to investigate the possible pathways through which glyphosate application affects AMF spores viability and root colonization in grassland communities. Our hypothesis is that glyphosate application can damage AMF directly (through contact with spores and external hyphae) or indirectly through the changes it generates on host plants. The experiment had a factorial array with three factors: (1) plant species, at two levels (Paspalum dilatatum and Lotus tenuis), (2) doses of glyphosate, at three levels (0 l ha−1, 0.8 l ha−1 and 3 l ha −1), and (3) application site, at two levels: soil (direct pathway) and plant foliage (indirect pathway). Spore viability was reduced even under the lowest glyphosate rate, but only when it was applied on the soil. Total root colonization for both species was similarly decreased when glyphosate was applied to plant foliage or on soil, with no difference between 0.8 and 3 l ha−1. The number of arbuscules was 20% lower when glyphosate was applied on plant foliage, than when it was applied on the soil. Our findings illustrate that glyphosate application negatively affects AMF functionality in grasslands, due to different causes depending on the herbicide application site. While, under field conditions, the occurrence of direct and/or indirect pathways will depend on the plant cover at the time of glyphosate application, the consequences of this practice on the plant community structure will vary with the mycorrhizal dependence of the species composition regardless of the pathway involved. 相似文献
3.
《Applied soil ecology》2007,35(1):163-173
Two pot experiments were conducted to investigate the effect of inoculation with the arbuscular mycorrhizal (AM) fungus Glomus intraradices on Pb uptake by two clones of Nicotiana tabacum plants. Non-transgenic tobacco plants, variety Wisconsin 38, were compared in terms of Pb uptake with transgenic plants of the same variety with inserted gene coding for polyhistidine anchor in fusion with yeast metallothionein. Bioavailability of Pb in experimentally contaminated soil was enhanced by the application of a biodegradable chelate ethylenediaminedissuccinate (EDDS).EDDS addition (2.5 and 5.0 mmol kg−1 substrate) increased Pb uptake from the substrate and enhanced Pb translocation from the roots to the shoots, with shoot Pb concentrations reaching up to 800 mg kg−1 at the higher chelate dose. Application of a single dose of 5 mmol kg−1 proved to be more efficient at increasing shoot Pb concentrations than two successive doses of 2.5 mmol kg−1, in spite of a marked negative effect on plant growth and phytotoxicity symptoms. Pb amendment (1.4 g kg−1 substrate) connected with either dose of EDDS decreased significantly plant biomass as well as reduced the development of AM fungi. AM inoculation promoted the growth of tobacco plants and partly alleviated the negative effect of Pb contamination, mainly in the case of root biomass.No consistent difference in Pb uptake was found between transgenic and non-transgenic tobacco plants. The effect of AM inoculation on Pb concentrations in plant biomass varied between experiments, with no effect observed in the first experiment and significantly higher root Pb concentrations and increased root–shoot ratio of Pb concentrations in the biomass of inoculated plants in the second experiment. Due to probable retention of Pb in fungal mycelium, the potential of AM for phytoremediation resides rather in Pb stabilisation than in phytoextraction. 相似文献
4.
《European Journal of Soil Biology》2008,44(4):381-391
In order to study the variations in spore abundance and root colonization parameters of arbuscular mycorrhizal (AM) fungi in a naturally heavy metals polluted site and their relationships with soil properties, 35 plots in the Anguran Zn and Pb mining region were selected along a transect from the mine to 4500 m away. Within each plot, a composite sample of root and rhizospheric soil from a dominant indigenous plant was collected. The soil samples were analyzed for their physico-chemical characteristics. Spores were extracted, counted and identified at genus level. The roots were examined for colonization, arbuscular abundance, mycorrhizal frequency and intensity. Along the transect, the total and available (DTPA-extractable) concentration of Zn decreased from 6472 to 45 mg kg−1 and 75 to 5 mg kg−1, respectively. For Pb the values varied from 5203 to 0 mg kg−1 and 32 to 0 mg kg−1, respectively. In parallel, root colonization rate in the dominant native plants (except Alyssum sp.) varied from 35% to 85% and the spore numbers from 80 to 1306 per 200 g dry soil along the transect. Spores of Glomus were abundantly found in all plots as dominant, while Acaulospora spores were observed only in some moderately polluted and in control plots. AM fungal propagules never disappeared completely even in soils with the highest rates of both heavy metals. Spore numbers were more affected by Zn and Pb concentrations than root colonization. The variations of AM fungi propagules were better related to available than to total concentration of both metals. Spore numbers were positively correlated with mycorrhizal colonization parameters, particularly with arbuscular abundance. 相似文献
5.
Metal(loid) accumulation and arbuscular mycorrhizal (AM) status of the dominant plant species, Cynodon dactylon, growing at four multi-metal(loid)s-contaminated sites and an uncontaminated site of China were investigated. Up to 94.7 As mg kg?1, 417 Pb mg kg?1, 498 Zn mg kg?1, 5.8 Cd mg kg?1 and 27.7 Cu mg kg?1 in shoots of C. dactylon were recorded. The plant was colonized consistently by AM fungi (33.0–65.5%) at both uncontaminated site and metal-contaminated sites. Based on morphological characteristics, fourteen species of AM fungi were identified in the rhizosphere of C. dactylon, with one belonging to the genus of Acaulospora and the other thirteen belonging to the genus of Glomus. Glomus etunicatum was the most common species associated with C. dactylon growing at metal-contaminated sites. Spore abundance in the rhizosphere of C. dactylon growing at the metal-contaminated soils (22–82 spores per 25 g soil) was significantly lower than that of the uncontaminated soils (371 spores per 25 g soil). However, AM fungal species diversity in the metal-contaminated soils was significantly higher than that in the uncontaminated soils. This is the first report of AM status in the rhizosphere of C. dactylon, the dominant plant survival in metal-contaminated soils. The investigation also suggests that phytorestoration of metal-contaminated sites might be facilitated using the appropriate plant with the aid of tolerant AM fungi. 相似文献
6.
The forest–savanna transition zone is widely distributed on nutrient-poor oxisols in Central Africa. To reveal and compare the nutrient cycle in relation to soil microbes for forest and savanna vegetation in this area, we evaluated seasonal fluctuations in microbial biomass carbon (MBC), nitrogen (MBN), and phosphorus (MBP) for 13 months as well as soil moisture, temperature, soil pH levels, and nutrients for both vegetation types in eastern Cameroon. Soil pH was significantly lower in forest (4.3) than in savanna (5.6), and soil N availability was greater in forest (87.1 mg N kg−1 soil) than in savanna (32.9 mg N kg−1 soil). We found a significant positive correlation between soil moisture and MBP in forest, indicating the importance of organic P mineralization for MBP, whereas in savanna, we found a significant positive correlation between soil N availability and MBP, indicating N limitation for MBP. These results suggest that for soil microbes, forest is an N-saturated and P-limited ecosystem, whereas savanna is an N-limited ecosystem. Additionally, we observed a significantly lower MBN and larger MB C:N ratio in forest (50.7 mg N kg−1 soil and 8.6, respectively) than in savanna (60.0 mg N kg−1 soil and 6.5, respectively) during the experimental period, despite the rich soil N condition in forest. This may be due to the significantly lower soil pH in forest, which influences the different soil microbial communities (fungi-to-bacteria ratio) in forest versus savanna, and therefore, our results indicate that, in terms of microbial N dynamics, soil pH rather than soil substrate conditions controls the soil microbial communities in this area. Further studies should be focused on soil microbial community, such as PLFA, which was not evaluated in the present study. 相似文献
7.
《Soil biology & biochemistry》2012,44(12):2441-2449
High rates of atmospheric nitrogen (N) deposition have raised questions about shifting patterns of nutrient limitation in northern hardwood forests. Of particular interest is the idea that increased supply of N may induce phosphorus (P) limitation of plant and microbial processes, especially in acid soils where P sorption by Al is high. In this study, we established field plots and plant-free laboratory mesocosms with P and Ca additions to test the hypotheses that 1) microbial biomass and activity are limited by P in the northern hardwood forest soils at the Hubbard Brook Experimental Forest in NH USA; 2) elevated Ca increases inherent P availability and therefore reduces any effects of added P and 3) P effects are more marked in the more carbon (C) rich Oie compared to the Oa horizon. Treatments included P addition (50 kg P ha−1), Ca addition (850 kg Ca ha−1) and Ca + P addition (850 kg Ca ha−1 and 50 kg P ha−1). The P treatments increased resin-available P levels and reduced phosphatase activity, but had no effect on microbial biomass C, microbial respiration, C metabolizing enzymes, potential net N mineralization and nitrification in the Oie or Oa horizon of either field plots or plant free mesocosms, in either the presence or absence of Ca. Total, prokaryote, and eukaryote PLFA were reduced by P addition, possibly due to reductions in mycorrhizal fungal biomass. These results suggest that increased N deposition and acidification have not created P limitation of microbial biomass and activity in these soils. 相似文献
8.
《Soil biology & biochemistry》2001,33(4-5):503-509
The distribution of vegetation types in Venezuelan Guyana (in the ‘Canaima’ National Park) represents a transitional stage in a long term process of savannization, a process considered to be conditioned by a combined chemical and intermittent drought stress. All types of woody vegetation in this environment accumulate large amounts of litter and soil organic carbon (SOC). We hypothesized that this accumulation is caused by low microbial activity. During 1 year we measured microbial biomass carbon (Cmic), microbial respiration and soil respiration of stony Oxisols (Acrohumox) at a tall, a medium and a low forest and with three chemical modifications of site conditions by the addition of NO3−, Ca2+ and PO43− as possible limiting elements. Due to high SOC contents, mean Cmic was 1 mg g soil−1 in the mineral topsoil and 3 mg g soil−1 in the forest floor. Mean microbial respiration in the mineral topsoil and the forest floor were 165 and 192 μg CO2-C g soil−1 d−1, respectively. We calculated high mean metabolic quotients (qCO2) of 200 mg CO2-C g Cmic−1 d−1 in the litter layer and 166 mg CO2-C g Cmic−1 d−1 in the mineral topsoil, while the Cmic-to-SOC ratios were as low as 1.0% in the litter layer and 0.8% in the mineral topsoil. Annual soil respiration was 9, 12 and 10 Mg CO2-C ha−1 yr−1 in the tall, medium and low forest, respectively. CO2 production was significantly increased by CaHPO4 fertilization, but no consistent effects were caused by Ca2+ and NO3−, fertilization. Our findings indicate that Cmic and microbial respiration are reduced by low nutrient concentrations and low litter and SOC quality. Reduced microbial decomposition may have contributed to SOC accumulation in these forests. 相似文献
9.
Future rates of atmospheric N deposition have the potential to slow litter decay and increase the accumulation of soil organic matter by repressing the activity of lignolytic soil microorganisms. We investigated the relationship between soil biochemical characteristics and enzymatic responses in a series of sugar maple (Acer saccharum)-dominated forests that have been subjected to 16 yrs of chronic N deposition (ambient + 3 g NO3−–N m−2 yr−1), in which litter decay has slowed and soil organic matter has accumulated in sandy spodosols. Cupric-oxide-extractable lignin-derived phenols were quantified to determine the presence, source, and relative oxidation state of lignin-like compounds under ambient and experimental N deposition. Pools of respired C and mineralized N, along with rate constants for these processes, were used to quantify biochemically labile substrate pools during a 16-week laboratory incubation. Extracellular enzymes mediating cellulose and lignin metabolism also were measured under ambient and experimental N deposition, and these values were compared with proxies for the relative oxidation of lignin in forest floor and surface mineral soil. Chronic N deposition had no influence on the pools or rate constants for respired C and mineralized N. Moreover, neither the total amount of extractable lignin (forest floor, P = 0.260; mineral soil, P = 0.479), nor the relative degree of lignin oxidation in the forest floor or mineral soil (forest floor P = 0.680; mineral soil P = 0.934) was influenced by experimental N deposition. Given their biochemical attributes, lignin-derived molecules in forest floor and mineral soil appear to originate from fine roots, rather than leaf litter. Under none of the studied circumstances was the presence or relative oxidation of lignin correlated with the activity of cellulolytic and lignolytic extracellular enzymes. Although chronic atmospheric N deposition has slowed litter decay and increased organic matter in our experiment, it had little effect on biochemical composition of lignin-derived molecules in forest floor and surface mineral soil suggesting organic matter has accumulated by other means. Moreover, the specific dynamics of lignin phenol decay is decoupled from short-term organic matter accumulation under chronic N deposition in this ecosystem. 相似文献
10.
《Applied soil ecology》1999,11(2-3):261-269
Different fungal ecotypes were isolated from soils which had received long-term applications of metal-contaminated sewage sludge with the aim of studying the degree of tolerance and adaptation to heavy metals of arbuscular mycorrhizal (AM) fungi. The development and structural aspects of AM colonization produced by the different fungal isolates were studied using two host plants, Allium porrum and Sorghum bicolor, which were grown in either contaminated or non-contaminated soils. Four different AM fungi were successfully isolated from the experimental field plots: (i) Glomus claroideum, isolated from plots receiving only inorganic fertilizer; (ii) another apparently similar ecotype of Glomus claroideum, but isolated from plots with 300 m3 ha−1 year−1 of contaminated sludge added, (iii) an unidentified Glomus sp., present only in the less contaminated plots (100 m3 ha−1 year−1 of unamended sludge) and (iv) Glomus mosseae, isolated from plots receiving 100 or 300 m3 ha−1 year−1 of amended or unamended sludge (intermediate rates of contamination). There were consistent differences in behaviour among the four AM fungi tested with regard to the colonization levels they produced in non-contaminated and contaminated soils. Both total and arbuscular colonization were affected by heavy metal contamination. The main conclusions of this study are that Glomus sp. and G. mosseae isolates are strongly inhibited by heavy metals, which acted mainly by interfering with the growth of the external mycelium, and also by limiting the production of arbuscules. Our results suggest that G. claroideum isolates, particularly the ecotype which was isolated from the plots receiving the highest dose of metal-contaminated sludge, shows a potential adaptation to increased metal concentration in soil. 相似文献
11.
Arbuscular mycorrhizal fungi (AMF) community composition and species richness are affected by several factors including soil attributes and plant host. In this paper we tested the hypothesis that conversion of tropical Amazon forest to pasture changes taxonomic composition of AMF community but not community species abundance and richness. Soil samples were obtained in 300 m × 300 m plots from forest (n = 11) and pasture (n = 13) and fungal spores extracted, counted and identified. A total of 36 species were recovered from both systems, with 83% of them pertaining to Acaulosporaceae and Glomeraceae. Only 12 species were shared between systems and spore abundance of the majority of fungal species did not differ between pasture and forest. Spore abundance was significantly higher in pasture compared to forest but both systems did not differ on mean species richness, Shannon diversity and Pielou equitability. Species abundance distribution depicted by species rank log abundance plots was not statistically different between both systems. We concluded that conversion of pristine tropical forest to pasture influences the taxonomic composition of AMF communities while not affecting species richness and abundance distribution. 相似文献
12.
《Soil & Tillage Research》2005,80(1-2):201-213
Minimum tillage practices are known for increasing soil organic carbon (SOC). However, not all environmental situations may manifest this potential change. The SOC and N stocks were assessed on a Mollisol in central Ohio in an 8-year-old tillage experiment as well as under two relatively undisturbed land uses; a secondary forest and a pasture on the same soil type. Cropped systems had 51±4 (equiv. mass) Mg ha−1 lower SOC and lower 3.5±0.3 (equiv. mass) Mg ha−1 N in the top 30 cm soil layer than under forest. Being a secondary forest, the loss in SOC and N stocks by cultivation may have been even more than these reported herein. No differences among systems were detected below this depth. The SOC stock in the pasture treatment was 29±3 Mg ha−1 greater in the top 10 cm layer than in cultivated soils, but was similar to those under forest and no-till (NT). Among tillage practices (plow, chisel and NT) only the 0–5 cm soil layer under NT exhibited higher SOC and N concentrations. An analysis of the literature of NT effect on SOC stocks, using meta-analysis, suggested that NT would have an overall positive effect on SOC sequestration rate but with a greater variability of what was previously reported. The average sequestration rate of NT was 330 kg SOC ha−1 year−1 with a 95% confidence interval ranging from 47 to 620 kg SOC ha−1 year−1. There was no effect of soil texture or crop rotation on the SOC sequestration rate that could explain this variability. The conversion factor for SOC stock changes from plow to NT was equal to 1.04. This suggests that the complex mechanisms and pathways of SOC accrual warrant a cautious approach when generalizing the beneficial changes of NT on SOC stocks. 相似文献
13.
《Applied soil ecology》2007,35(2-3):258-265
We examined the relationship between soil respiration rate and environmental determinants in three types of tropical forest ecosystem—primary forest, secondary forest, and an oil palm plantation in the Pasoh Forest Reserve on the Malaysian Peninsula. In August 2000, the soil respiration rate and environmental factors (soil temperature, soil water content, soil C and N contents, biomass of fine roots, and microbes) were measured at 12–16 points in research quadrats. Soil respiration rates were 831 ± 480, 1104 ± 995, 838 ± 143, 576 ± 374, and 966 ± 578 (mean ± S.D.) mg CO2 m−2 h−1 in the primary forest canopy and gap site, secondary forest canopy and gap site, and oil palm plantation, respectively. Although the mean soil respiration rates in the three forest ecosystems did not differ significantly, differences were evident in the environmental factors affecting the soil respiration. The major causes of spatial variation in soil respiration were fine root biomass, soil water content, and soil C content in the primary and secondary forests and oil palm plantation, respectively. 相似文献
14.
《Applied soil ecology》2011,47(3):450-456
Biochar holds promise as an amendment for soil quality improvement and sequestration of atmospheric carbon dioxide. However, knowledge of how biochar influences soil properties, especially soil microorganisms, is limited. Three separate studies were conducted, with two studies using Plantago lanceolata as the AMF hosting plant, and a third being conducted in the field. Each of the three studies employed a different soil type. Furthermore, a total of five different biochars, and ten different biochar application rates, were used across the three experiments. All experiments had the goal to examine biochar influences on arbuscular mycorrhizal fungal (AMF) abundance in roots and AMF abundance (hyphal lengths) in soils. AMF abundance was either decreased or remained unchanged across all biochar treatments. When AMF abundances decreased, significant changes in soil properties, primarily in soil P availability, were observed. Application of large quantities (2.0% and 4.0%, w/w) of a lodgepole pine biochar, led to significant declines in AMF abundance in roots of 58% and 73% respectively, but not in soils. These declines in AMF abundance were accompanied by significant declines (28% and 34%) in soil P availability. After addition of a peanut shell biochar produced at 360 °C, P increased by 101% while AMF root colonization and extraradical hyphal lengths deceased by 74% and 95% respectively. Field application of mango wood biochar at rates of 23.2 and 116.1 t C ha−1 increased P availabilities by 163% and 208% respectively and decreased AMF abundances in soils by 43% and 77%. These findings may have implications for soil management where the goal is to increase the services provided by AMF. 相似文献
15.
《Applied soil ecology》2003,22(3):241-253
Root distribution and mycorrhizal associations were compared in primary, secondary and limestone forests in Xishuangbanna, southwest China. Soil cores to a depth of 20 cm were collected at random points from four 50 m2 quadrats in each forest type. Arbuscular mycorrhizal (AM) associations were the only form of mycorrhiza found in all forest types. The primary forest was characterized by high root mass, root lengths and AM colonization levels higher than other forest types. In contrast, secondary forests had greater AM fungal spore numbers and specific root length, indicating that plant species in secondary forests achieved a greater degree of soil exploration with less biomass allocation to roots. Root density, AM colonization and AM fungal spore numbers decreased with soil depth in all forest types. Although the correlation between AM colonization levels and spore numbers was insignificant when all forest types were considered together, significant relationships emerged when each forest type was considered individually. AM colonization and spore numbers were correlated with several root variables. 相似文献
16.
《Pedobiologia》2014,57(4-6):197-203
Functional relationships between belowground detritivores and/or symbionts and aboveground primary producers and their herbivores are not well studied. In a factorial greenhouse experiment we studied interactions between earthworms (addition/no addition of Lumbricus terrestris; Clitellata: Lumbricidae) and arbuscular-mycorrhizal fungi (AMF; with/without inoculation of Glomus mosseae; Glomerales: Glomeraceae) on the leguminous herb Trifolium repens (Fabales: Fabaceae) and associated plant aphids (Aphis gossypii, A. craccivora; Hemiptera: Aphidoidea). In order to be able to trace organismic interactions, earthworms were dual-labelled with stable isotopes (15N-ammonium nitrate and 13C-glucose). We specifically wanted to investigate whether (i) isotopic signals can be traced from the labelled earthworms via surface castings, plant roots and leaves to plant aphids and (ii) these compartments differ in their incorporation of stable isotopes. Our results show that the tested organismic compartments differed significantly in their 15N isotope enrichments measured seven days after the introduction of earthworms. 15N isotope incorporation was highest in casts followed by earthworm tissue, roots and leaves, with lowest 15N signature in aphids. The 13C signal in roots, leaves and aphids was similar across all treatments and is for this reason not recommendable for tracing short-term interactions over multitrophic levels. AMF symbiosis affected stable isotope incorporation differently in different subsystems: the 15N isotope signature was higher below ground (in roots) but lower above ground (leaves and aphids) in AMF-inoculated mesocosms compared to AMF-free mesocosms (significant subsystem × AMF interaction). Aphid infestation was unaffected by AMF and/or earthworms. Generally, these results demonstrate that plants utilize nutrients excreted by earthworms and incorporate these nutrients into their roots, leaf tissue and phloem sap from where aphids suck. Hence, these results show that earthworms and plant aphids are functionally interlinked. Further, 15N-labelling earthworms may represent a promising tool to investigate nutrient uptake by plants and consequences for belowground-aboveground multitrophic interactions. 相似文献
17.
《Applied soil ecology》2003,22(2):139-148
A glasshouse pot experiment investigated the uptake by arbuscular mycorrhizal (AM) fungi associated with red clover of three organic sources of P added to a sterilized calcareous soil of low P availability. Each pot was separated into a central compartment for plant growth and two outer compartments for external mycelium using 30-μm nylon mesh to restrict the roots but allow hyphal penetration. Plants in the central compartments were inoculated with the AM fungus Glomus versiforme and uninoculated controls were included. Plants were harvested on three occasions: 5, 7 and 10 weeks after sowing. Application of each of the three organic P sources (lecithin, RNA and sodium phytate) or inorganic P (KH2PO4) at 50 mg P kg−1 to the outer compartments of mycorrhizal and uninoculated pots increased the yield, P concentration and total P uptake of red clover compared with pots to which no P was applied, with no differences among P sources in non-mycorrhizal plants but differences observed in mycorrhizal plants both 7 and 10 weeks after sowing suggesting differences in availability of the four P sources to AM mycelium. The contribution of external mycelium to plant uptake of applied P increased with time. The three organic P sources made smaller contributions to plant P nutrition than KH2PO4 at the first and second harvests. At the third harvest, the contribution from KH2PO4 was 23%, while those from lecithin, RNA and sodium phytate were 23, 17 and 31%, respectively. This suggests that with the mediation of AM fungi, soil organic P sources can make a contribution to host plant P nutrition comparable to that of soluble orthophosphate. 相似文献
18.
According to the economy theory, plants should preferentially allocate photosynthate to acquire below-ground resources under elevated atmospheric carbon dioxide (eCO2) but decrease below-ground C allocation when nitrogen (N) is sufficient for plant growth. Arbuscular mycorrhizae (AM) represent a critical mechanism of below-ground nutrient acquisition for plants. The dynamics of arbuscular mycorrhizal fungi (AMF) could therefore reflect the response of plant C allocation under eCO2 and N addition. We examined the responses of glomalin-related soil protein (GRSP) to eCO2 (approximately 700 μmol mol−1 CO2) and/or N addition (100 kg N ha−1 yr−1 as NH4NO3) in a modeled subtropical forest to better understand its potential influence on soil C storage. We hypothesized that GRSP would increase under eCO2 and decrease under N addition. Furthermore, the positive effects of eCO2 on GRSP would be offset by extra N addition, and GRSP would remain unchanged under combined eCO2 and N addition. Our results showed that the mean concentrations of easily extractable GRSP (EE-GRSP) and total GRSP (T-GRSP) were 0.35 ± 0.05 and 0.72 ± 0.13 mg C cm−3, respectively, which accounted for 2.76 ± 0.53% and 5.67 ± 0.92% of soil organic carbon (SOC) in the 0–10 cm soil layer. Elevated CO2 significantly increased T-GRSP by 35.02% but decreased EE-GRSP by 5.09% in the top 10 cm soil layer. The opposite responses of T-GRSP and EE-GRSP to eCO2 might result from an unchanged photosynthate investment to AMF with possible changes in their decomposition rates. The effect of N on GRSP was contrary to our hypothesis, i.e., there was a 1.72%–48.49% increase in T-GRSP and a slightly increase in EE-GRSP. Both EE-GRSP and T-GRSP concentrations increased under the combination of eCO2 and N addition, which was inconsistent with our hypothesis. The significant increase of EE-GRSP under the combination of eCO2 and N addition was partly caused by more rapid plant growth and reduced microbial diversity, and the marginal increase of T-GRSP indicated that the interaction between eCO2 and N addition offset their independent effects. In addition, the relatively higher accumulation ratios of GRSP (22.6 ± 13.6%) compared with SOC (15.9 ± 9.4%) indicated that more rapid GRSP deposition in the soil might accelerate SOC accumulation under eCO2 and N addition. Our results will improve the understanding of the functioning of GRSP in soil C sequestration under global environmental change scenarios. 相似文献
19.
Arbuscular mycorrhizal (AM) fungi colonize most plant species in the savannah/oak woodland ecosystem of the California Sierra Foothills. These fungi may form belowground linkages between plant root systems, potentially altering nutrient transfers. In a laboratory experiment with two-chambered pots where only AM fungal hyphae connected the chambers, we examined nutrient transfer between native plant species of grasses and forbs. Two separate chambers with plants were separated by a set of two stainless steel screens (25 μm mesh) separated by a 1 cm air gap. These screens successfully restricted root growth but allowed hyphal coverage (15–100% of the area) of the screens. Nutrient transfers were monitored by applying nitrogen (15N), arsenic (P analog), strontium (Ca analog), and cesium and rubidium (K analogs). The analogs and 15N were applied to leaves of donor plants for 48 h. We observed transfer of 15N, As, Cs, and Rb from donor shoots to receiver shoots. Element transfers were not correlated with receiver biomass or donor concentrations. Transfers varied among the elements and plant combinations. Both Rb and Cs (K analogs) had the same pattern of transfer. Nitrogen was transferred in greatest amounts and between forbs and grasses, and grasses acted as a stronger sink for N. Forbs were generally the stronger sink for As. Fungal hyphae facilitated transfer among forbs and grasses, suggesting that they have a key role in nutrient transfer in California oak woodlands. 相似文献
20.
Soil contamination with Cd is of primary concern and beneficial soil restoration strategies urge. The aim of this work is to evaluate the response of two different genotypes of Pinus pinaster (wild and selected) to Cd contamination and to assess how inoculation with ectomycorrhizal fungi, Suillus bovinus and Rhizopogon roseolus, influenced each genotype. Seedlings were exposed to soil contaminated at 15 and 30 mg Cd kg−1. Plant growth, mycorrhizal traits and Cd accumulation in different tissues of the plant were determined at harvest. The fungal community was assessed by denaturing gradient gel electrophoresis. At 15 mg Cd kg−1 S. bovinus increased aboveground development in both genotypes. At 30 mg Cd kg−1 non-inoculated wild genotype accumulated more Cd in the shoots (1.7-fold) than the selected genotype; inoculation with R. roseolus decreased Cd concentration in the roots of the selected genotype whereas the opposite occurred in the wild genotype. Cd concentration in the root system was the parameter most influenced by the interaction between the three studied variables. The fungal community established was affected by the Cd concentration in the soil. Results show that different genotypes of P. pinaster react differently to Cd exposure depending on the mycorrhizal association. The importance of considering the combination between plant genotype and its symbiotic partners when aiming at the forestation of degraded land is highlighted. 相似文献