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1.
《European Journal of Soil Biology》2008,44(1):122-128
In a controlled potted experiment, citrus (Poncirus trifoliata) seedlings were inoculated with three species of arbuscular mycorrhizal (AM) fungi, Glomus mosseae, G. versiforme or G. diaphanum. Two soil-water levels (ample water, −0.10 MPa; drought stress, −0.44 MPa) were applied to the pots 4 months after transplantation. Eighty days after water treatments, the soils and the citrus seedlings were well colonized by the three AM fungi. Mycorrhizal fungus inoculation improved plant biomass regardless of soil-water status but decreased the concentrations of hot water-extractable and hydrolyzable carbohydrates of soils. Mycorrhizal soils exhibited higher Bradford-reactive soil protein concentrations than non-mycorrhizal soils. Mycorrhizas enhanced >2 mm, 1–2 mm and >0.25 mm water-stable aggregate fractions but reduced 0.25–0.5 mm water-stable aggregates. Peroxidase activity was higher in AM than in non-AM soils whether drought stressed or not, whereas catalase activity was lower in AM than non-AM soils. Drought stress and AM fungus inoculation did not affect polyphenol oxidase activity of soils. A positive correlation between the Bradford-reactive soil protein concentrations, soil hyphal length densities, and water-stable aggregates (only >2 mm, 1–2 mm and >0.25 mm) suggests beneficial effects of the AM symbiosis on soil structure. It concluded that AM fungus colonization enhanced plant growth under drought stress indirectly through affecting the soil moisture retention via glomalin's effect on soil water-stable aggregates, although direct mineral nutritional effects could not be excluded. 相似文献
2.
《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
3.
《Applied soil ecology》2007,35(2):261-271
Arbuscular mycorrhizal (AM) fungi are known to exist in wetlands, but little is known about their function in these environments. We conducted greenhouse experiments to study the effects of AM fungal assemblages—collected from different vegetation communities in a Florida wetland-under free-drained and flooded conditions, and at three phosphorus (P) levels on growth and P nutrition of Typha latifolia L. and Panicum hemitomon Schult. We also studied the effects of flooding on the spread of extraradical hyphae from P. hemitomon roots. For both plants no AM fungal assemblage had a consistent effect on plant growth and P nutrition. For T. latifolia, flooding nearly eliminated AM fungal colonization and, in the free-drained treatments, P amendment suppressed colonization. Furthermore, colonization by some mycorrhizal assemblages increased shoot- and root-P concentrations, but there were no significant plant growth responses. For P. hemitomon, the mycorrhizal association was suppressed by flooding and P amendment but, among the fungal assemblages, there were differences in root colonization. Mycorrhizal colonization improved some plant-growth and P-nutrition parameters at lower P levels relative to nonmycorrhizal controls, but generally conferred no benefit or was detrimental at higher P levels. Extraradical hyphae of most assemblages were restricted by flooding to 2.5 cm, though differences among AM fungal assemblages occurred with a maximum observed extension of 16.5 cm. We conclude that the impact of the mycorrhizal association on these wetland plants was a function of the complex interactions among the AM fungal assemblages, plant species, water condition, and P level. Future studies should focus on understanding the species composition of the assemblages, and potential adaptation to wetland conditions among these fungal species. 相似文献
4.
《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
5.
The sweet herb of Paraguay, Stevia rebaudiana (Bertoni), is becoming more important worldwide in herbal care for diabetes, as it produces the zero-calorie sweeteners steviol glycosides (SGs)—stevioside and rebaudioside-A. While arbuscular mycorrhizal fungi (AMF) have been shown to enhance production of secondary metabolites in many plant species, their effect on S. rebaudiana has not been studied. Moreover, relatively little is known about the mechanisms that may be involved in the increased accumulation of phytochemicals in mycorrhizal plants. Therefore, this study was performed to test the ability of Rhizophagus fasciculatus (Thaxt.) C. Walker & A. Schüßler to improve the yield of SGs in S. rebaudiana and to relate this with some AMF-induced physiological changes in addition to improved phosphorus (P) uptake. The performance of plants inoculated with R. fasciculatus was compared with that of non-mycorrhizal plants with similar P concentrations. Mycorrhizal (M) and non-mycorrhizal plants with P-supplementation (NM + P) produced higher concentrations of SGs compared with control plants. However, M plants had more SGs than did NM + P plants. The higher content of SGs in M plants is due to increased concentrations of SGs and to the enhanced biomass of the shoots. The increase in biomass is directly due to the improved uptake of nutrients (N, K, Mg, Cu, Fe, Mn and Zn), and chlorophyll and carbohydrate concentrations in M plants. Higher concentrations of total carbohydrates and jasmonic acid in M plants than in NM + P plants contribute to more biosynthesis of SGs via the methyl erythritol phosphate pathway. This study suggests that AMF-mediated increases in SGs involve both nutritionally and non-nutritionally linked mechanisms. 相似文献
6.
《Applied soil ecology》2006,33(3):350-365
The aim of this paper was to investigate the effects of soil conditions and distance from a host plant on the ability of hyphae of arbuscular mycorrhizal (AM) fungi to grow and colonise a new host. Two glasshouse experiments were conducted using compartmented pots. The first investigated the effects of distance between a colonised and uncolonised host plant (Trifolium subterraneum L.) and average pore size of the growth substrate (100 μm, 38 μm) on the ability of two AM fungi, G. intraradices and G. mosseae, to colonise a new host plant. The second experiment determined if the pore size of the substrate (100 μm, 38 μm) affected the growth of AM fungi in the absence of a new host. In Experiment 1, both G. mosseae and G. intraradices grew successfully through the two sand substrates and colonised new host plants. Both fungi reached and colonised new hosts fastest when hosts were separated by the shortest distance (2.5 cm), with largest pore size substrate (100 μm). G. mosseae produced more external hyphae per unit of colonised root and colonised new host plants more rapidly than G. intraradices. However, receiver plants colonised by G. mosseae exhibited a negative mycorrhizal growth response following colonisation. Experiment 2 showed that G. mosseae grew further from its host than G. intraradices. The results support the theory that some AM fungal species may produce large amounts of external hyphae primarily to increase the probability of locating and colonising a new host plant. 相似文献
7.
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
8.
《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
9.
《Applied soil ecology》2006,31(1-2):110-119
A pot culture experiment was carried out to study the effects of arbuscular mycorrhizal (AM) inoculation on the growth of Elsholtzia splendens and Zea mays and the activities of phosphatase and urease in a soil contaminated with Cu, Zn, Pb and Cd. Two AM fungal inocula, MI containing Glomus caledonium and MII containing Gigaspora margarita,Gigaspora decipens, Scutellospora gilmori, Acaulospora spp. and Glomus spp., were applied to the soil. The plants of E. splendens and Z. mays were harvested after 24 and 10 weeks of growth, respectively. Both plant species had a similar trend in mycorrhizal colonization rates, MI > MII > control. Shoot and root biomass of Z. mays was increased by MI, while not affected significantly by MII. Although both MI and MII increased plant dry weight of E. splendens, MII was more effective. Mycorrhizal dependency (MD) with MI and MII was 14.8 and 33.5, respectively for E. splendens, and 11.0 and 0.9, respectively for Z. mays. Both inocula increased the activities of phosphatase and urease in the soils of E. splendens and Z. mays, but MI was more effective than MII for urease, while MII more effective than MI for phosphatase. Although the mechanisms involved in these responses are not clear, AM fungal inoculum may be important and used for the phytoremediation of heavy metal contaminated soils, but both inoculum type and host species must be considered. 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.
A greenhouse pot experiment was conducted to study cadmium (Cd) and phosphorous (P) acquisition of upland kangkong (Ipomoea aquatica Forsk.) intercropped with Alfred stonecrop (Sedum alfredii Hance) in a Cd-contaminated soil inoculated with arbuscular mycorrhizal (AM) fungi. There were four treatments, including monoculture of kangkong (control), intercropping with stonecrop (IS), and intercropping with stonecrop plus inoculation with Glomus caledonium (IS + Gc) or Glomus versiforme (IS + Gv). Both kangkong and stonecrop plants were harvested at week 8 after seeding or cutting. Compared with the control, IS tended to decrease Cd and P acquisition by neighboring kangkong via competition for phytoavailable Cd and P. The inoculation of Gc, but not Gv, significantly elevated Cd acquisition by stonecrop, and hence resulted in significantly lower Cd acquisition by kangkong and the subsequent Cd concentrations in both roots and shoots of kangkong. Both Gc and Gv significantly increased mycorrhizal colonization rates in stonecrop roots, as well as acid phosphatase activities and available P concentrations in the soil. However, only Gc significantly elevated P acquisition and shoot biomass of the host plant (stonecrop), while Gv significantly increased P acquisition and shoot biomass of neighboring kangkong rather than of stonecrop, causing a significant dilution effect on kangkong shoot Cd concentration. In addition, both Gc and Gv inoculation significantly decreased soil DTPA-extractable (phytoavailable) Cd concentrations by elevating soil pH. The results showed that Gc and Gv played totally different roles in the intercropping system for vegetable production and phytoremediation of Cd-contaminated soils. 相似文献
12.
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
13.
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
14.
《Applied soil ecology》2005,28(1):23-36
This study assessed the effect of mycorrhizal colonization by Glomus intraradices (Gi) and G. versiforme (Gv) on the bacterial community composition in the rhizosphere of canola, clover and two tomato genotypes (wild type (76R) and its mutant with reduced mycorrhizal colonization (rmc)). Additionally, the effect of light intensity on the rhizosphere bacterial community composition of the tomato genotypes was studied. The bacterial community composition was assessed by denaturing gradient gel electrophoresis (DGGE). In canola, which is considered to be a non-mycorrhizal species, inoculation with Gi increased the shoot dw compared to Gv and the non-mycorrhizal control plants and also induced changes in the bacterial community composition in the rhizosphere. These fungal effects were observed although less than 8% of the root length of canola was colonized. On the other hand, about 50% of the root length of clover was colonized and inoculation with Gv resulted in a higher shoot dw compared to Gi or the control plants but the rhizosphere bacterial community composition was not affected by inoculation. Plant growth, mycorrhizal colonization and bacterial community composition of the two tomato genotypes were affected by a complex interaction between tomato genotype, AM fungal species and light intensity. Low light intensity (photosynthetic photon flux 200–250 μmol m−2 s−1) increased the shoot–root ratio in both genotypes and reduced colonization in the wild type. The differences in bacterial community composition between the two genotypes were more pronounced at low than at high light intensity (550–650 μmol m−2 s−1). 相似文献
15.
Arbuscular mycorrhizal fungus (AMF) can enhance plant growth and resistance to toxicity produced by heavy metals (HMs), affect the bioavailability of HMs in soil and the uptake of HMs by plants, and thus has been emerged as the most prominent symbiotic fungus for contribution to phytoremediation. A greenhouse pot experiment was conducted to assess the effect of Glomus versiforme BGC GD01C (Gv) on the growth and Cd accumulation of Cd-hyperaccumulator Solanum nigrum in different Cd-added soils (0, 25, 50, 100 mg Cd kg−1 soil). Mycorrhizal colonization rates were generally high (from 71% to 82%) in Gv-inoculated treatments at all Cd levels. Gv colonization enhanced soil acid phosphatase activity, and hence elevated P acquisition and growth of S. nigrum at all Cd levels. Moreover, the presence of Gv significantly increased DTPA-extractable (phytoavailable) Cd concentrations in 25 and 50 mg Cd kg−1 soils, but did not affect phytoavailable Cd in 100 mg Cd kg−1 soil. Similarly, inoculation with Gv significantly increased Cd concentrations of S. nigrum in 25 and 50 mg Cd kg−1 soils, but decreased Cd concentrations of the plants in 100 mg Cd kg−1 soil. Overall, inoculation with Gv greatly improved the total Cd uptakes in all plant tissues at all Cd levels. The present results indicated that S. nigrum associated with Gv effectively improved the Cd uptake by plant and would be a new strategy in microbe-assisted phytoremediation for Cd-contaminated soils. 相似文献
16.
《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
17.
《Pedobiologia》2014,57(4-6):223-233
Mycorrhizal fungi and earthworms can individually or interactively influence plant growth and heavy metal uptake. The influence of earthworms and arbuscular mycorrhizal (AM) fungi either alone or in combination on maize (Zea mays L.) growth and cadmium (Cd) uptake was investigated in a calcareous soil artificially spiked with Cd. Soils were contaminated with Cd (10 and 20 mg Cd kg−1), inoculated or un-inoculated with the epigeic earthworm Lumbricus rubellus and two AM fungal species (Rhizophagus irregularis and Funneliformis mosseae) for two months of growth under greenhouse conditions. Generally, earthworms alone increased both shoot P uptake and biomass but decreased shoot Cd concentration and root Cd uptake. AM fungi individually often increased total maize P uptake, declined shoot Cd concentration, and consequently produced higher total biomass. However, R. irregularis enhanced shoot Cd uptake at low Cd level and root Cd uptake at high Cd level. In plants inoculated with F. mosseae species, earthworms increased shoot biomass and Cd uptake, decreased root biomass and Cd uptake at all Cd levels, and increased shoot Cd concentration at low Cd level. In plants colonized by R. irregularis species, however, earthworm addition decreased maize biomass only at high Cd level and root Cd concentration and total maize Cd uptake at both Cd levels. Earthworm activity decreased Cd transfer from the soil to maize roots at low Cd level, but this was counterbalanced in the presence of F. mosseae. Mycorrhizal symbiosis significantly reduced the transfer of Cd from roots to shoots, independence of earthworm effect. Overall, it is concluded that L. rubellus and AM fungi, in particular F. mosseae isolate, improved maize tolerance to Cd toxicity both individually and interactively by increasing plant growth and P nutrition, and restricting Cd transfer to the aboveground biomass. Consequently, the single and interactive effects of the two soil organisms might potentially be important not only in protecting maize plants against Cd toxicity, but also in Cd phytostabilization in soils polluted by this highly toxic metal. 相似文献
18.
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
19.
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
20.
Fabricio Cassán Santiago Maiale Oscar Masciarelli Alfonso Vidal Virginia Luna Oscar Ruiz 《European Journal of Soil Biology》2009,45(1):12-19
Polyamines are considered as plant growth regulating compounds; among them, cadaverine has been correlated with root growth promotion or osmotic stress mitigation in some plant species. The purpose of this study was to evaluate the capacity of bacterial Azospirillum brasilense Az39 strain to produce cadaverine in chemically defined medium and inoculated plants, and to correlate this capacity with root growth promotion or osmotic stress mitigation in hydroponics conditions. To evaluate cadaverine production in chemically defined medium A. brasilense Az39 was cultivated aerobically at 30 °C and 80 rpm in NFb medium or NFb-l supplemented with the precursor l-lysine. To evaluate the bacterial cadaverine production and growth promotion in plants, rice (Oryza sativa L.) cv. El Paso 144 seedlings were inoculated and hydroponically cultured under optimal conditions in growth chamber. In both, cadaverine was identified and quantified by dansyl-derivative method using a fluorescence-HPLC system, and lysine decarboxylase (LDC) activity was determined by 14CO2 production in a closed tube system fed with [14C]-lysine. To evaluate the possible role of bacterial cadaverine in osmotic stress conditions, abscisic acid (ABA) production was analyzed in rice seedlings hydroponically cultured under 0 (no stress), ?0.47 (stress) or ?0.82 (severe stress) MPa osmotic potential generated by mannitol, with the addition of 1 nM or 1 μM cadaverine or A. brasilense Az39 inoculation. Our results indicate that A. brasilense Az39 promoted root growth and helped mitigate osmotic stress in rice seedlings, due in part to cadaverine production. 相似文献