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1.
Aims
This work addresses the relevant effects that one single compound, used as model herbicide, provokes on the activity/survival of a suitable herbicide degrading model bacterium and on a plant that hosts this bacterium and its bacterial rhizospheric community.Methods
The effects of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D), on Acacia caven hosting the 2,4-D degrading bacterium Cupriavidus pinatubonensis JMP134, and its rhizospheric microbiota, were simultaneously addressed in plant soil microcosms, and followed by culture dependent and independent procedures, herbicide removal tests, bioprotection assays and use of encapsulated bacterial cells.Results
The herbicide provokes deleterious effects on the plant, which are significantly diminished by the presence of the plant associated C. pinatubonensis, especially with encapsulated cells. This improvement correlated with increased 2,4-D degradation rates. The herbicide significantly changes the structure of the A. caven bacterial rhizospheric community; and it also diminishes the preference of C. pinatubonensis for the A. caven rhizosphere compared with the surrounding bulk soil.Conclusions
The addition of an herbicide to soil triggers a complex, although more or less predictable, suite of effects on rhizobacterial communities, herbicide degrading bacteria and their plant hosts that should be taken into account in fundamental studies and design of bio(phyto)remediation procedures. 相似文献2.
Ma del Carmen Orozco-Mosqueda Crisanto Velázquez-Becerra Lourdes I. Macías-Rodríguez Gustavo Santoyo Idolina Flores-Cortez Ruth Alfaro-Cuevas Eduardo Valencia-Cantero 《Plant and Soil》2013,362(1-2):51-66
Background and aims
Iron is an essential nutrient for plant growth. Although abundant in soil, iron is poorly available. Therefore, plants have evolved mechanisms for iron mobilization and uptake from the rhizospheric environment. In this study, we examined the physiological responses to iron deficiency in Medicago truncatula plants exposed to volatile organic compounds (VOCs) produced by Arthrobacter agilis UMCV2.Methods
The VOC profiles of the plant and bacterium were determined separately and during interaction assays using gas chromatography. M. truncatula plants exposed to A. agilis VOCs and pure dimethylhexadecylamine were transferred to conditions of iron deficiency, and parameters associated with iron nutritional status were measured.Results
The relative abundance of the bacterial VOC dimethylhexadecylamine increased 12-fold when in co-cultures of A. agilis and M. truncatula, compared to axenic cultures. Plants exposed to bacterial VOCs or dimethylhexadecylamine exhibited a higher rhizosphere acidification capacity, enhanced ferric reductase activity, higher biomass generation, and elevated chlorophyll and iron content relative to controls.Conclusions
The VOCs emitted by A. agilis UMCV2 induce iron acquisition mechanisms in vitro in the Strategy I plant M. truncatula. Dimethylhexadecylamine is the signal molecule responsible for producing the beneficial effects. 相似文献3.
Physiological and genetic characterization of rice nitrogen fixer PGPR isolated from rhizosphere soils of different crops 总被引:1,自引:0,他引:1
Safiullah Habibi Salem Djedidi Kunlayakorn Prongjunthuek Md Firoz Mortuza Naoko Ohkama-Ohtsu Hitoshi Sekimoto Tadashi Yokoyoma 《Plant and Soil》2014,379(1-2):51-66
Aims
We aimed to identify plant growth-promoting rhizobacteria that could be used to develop a biofertilizer for rice.Methods
To obtain plant growth-promoting rhizobacteria, rhizosphere soils from different crops (rice, wheat, oats, crabgrass, maize, ryegrass, and sweet potato) were inoculated to rice plants. In total, 166 different bacteria were isolated and their plant growth-promoting traits were evaluated in terms of colony morphology, indole-3-acetic acid production, acetylene reduction activity, and phosphate solubilization activity. Moreover, genetic analysis was carried out to evaluate their phylogenetic relationships based on 16S rRNA sequence data.Results
Strains of Bacillus altitudinis, Pseudomonas monteilii, and Pseudomonas mandelii formed associations with rice plants and fixed nitrogen. A strain of Rhizobium daejeonense showed nitrogen fixation activity in an in vitro assay and in vivo. Strains of B. altitudinis and R. daejeonense derived from rice rhizosphere soil, strains of P. monteilii and Enterobacter cloacae derived from wheat rhizosphere soil, and a strain of Bacillus pumilus derived from maize rhizosphere soil significantly promoted rice plant growth.Conclusions
These methods are effective to identify candidate species that could be developed as biofertilizers for target crops. 相似文献4.
Aims
In the present study, we analysed the diversity of indigenous arbuscular mycorrhizal fungi (AMF) colonising both the roots and rhizosphere soil of an annual herbaceous species, Bromus rubens, and a perennial herbaceous species, Brachypodium retusum, co-occurring in the same Mediterranean, semiarid degraded area. The intention was to study whether these two species promoted the diversity of AM fungi in their rhizospheres differently and to ascertain whether the AMF community harboured by an annual plant species differed from that harboured by a perennial species when both grew in the same place.Methods
The AMF large subunit ribosomal RNA genes (LSU) were subjected to nested PCR, cloning, sequencing and phylogenetic analysis.Results
Twenty AMF sequence types belonging to Glomus group A, Glomus group B and Diversispora were identified. The two plant species differed in the AMF community composition in their roots, B. rubens showing a higher diversity of AMF than B. retusum. However the composition of the AMF communities associated with the two rhizosphere soils was similar.Conclusions
These results suggest that the management of these Mediterranean, semiarid degraded areas should include the promotion of annual herbaceous plant communities in order to maintain the sustainability and productivity of these ecosystems. 相似文献5.
Stefania Cocco Alberto Agnelli George R. Gobran Giuseppe Corti 《Plant and Soil》2013,368(1-2):297-313
Background and aims
We report on the modifications induced by the roots of Erica arborea L. on a soil derived from alkaline and fine-textured marine sediments.Methods
Physical, chemical, mineralogical and biochemical properties of bulk soil and of the rhizosphere of Erica were characterised to evaluate its role on soil development.Results
Once the upper horizons had been decarbonated because of geomorphic and pedogenic processes, Erica colonised the soil and progressively modified it through the activity of roots. In the upper horizons, there was no difference between rhizosphere and bulk soil for pH, organic C and exchangeable Al and H. At depth, pH, organic C and exchangeable Al and H differed between rhizosphere and bulk soil. The weathering reactions induced by the Erica roots caused a relative quartz enrichment in the rhizosphere compared with the bulk soil. In the E, EB and Bw horizons, the microbial community of the rhizosphere appeared better adapted than in the underlying 2Bw horizons, where the rhizospheric microorganisms were poorly adapted as these horizons represented the boundary between acid and sub-alkaline soil environments.Conclusions
The activity of Erica roots modified soil properties so to produce more favourable conditions for itself and the rhizosphere microflora. 相似文献6.
Indirect effects of polycyclic aromatic hydrocarbon contamination on microbial communities in legume and grass rhizospheres 总被引:1,自引:0,他引:1
Background and aims
Biodegradation of polycyclic aromatic hydrocarbons (PAHs) is accelerated in the presence of plants, due to the stimulation of rhizosphere microbes by plant exudates (nonspecific enhancement). However, plants may also recruit specific microbial groups in response to PAH stress (specific enhancement). In this study, plant effects on the development of rhizosphere microbial communities in heterogeneously contaminated soils were assessed for three grasses (ryegrass, red fescue and Yorkshire fog) and four legumes (white clover, chickpea, subterranean clover and red lentil).Methods
Plants were cultivated using a split-root model with their roots divided between two independent pots containing either uncontaminated soil or PAH-contaminated soil (pyrene or phenanthrene). Microbial community development in the two halves of the rhizosphere was assessed by T-RFLP (bacterial and fungal community) or DGGE (bacterial community), and by 16S rRNA gene tag-pyrosequencing.Results
In legume rhizospheres, the microbial community structure in the uncontaminated part of the split-root model was significantly influenced by the presence of PAH-contamination in the other part of the root system (indirect effect), but this effect was not seen for grasses. In the contaminated rhizospheres, Verrucomicrobia and Actinobacteria showed increased populations, and there was a dramatic increase in Denitratisoma numbers, suggesting that this genus may be important in rhizoremediation processes.Conclusion
Our results show that Trifolium and other legumes respond to PAH-contamination stress in a systemic manner, to influence the microbial diversity in their rhizospheres. 相似文献7.
8.
Aluminum tolerance of wheat does not induce changes in dominant bacterial community composition or abundance in an acidic soil 总被引:1,自引:0,他引:1
Chao Wang Xue Qiang Zhao Rong Fu Chen Hai Yan Chu Ren Fang Shen 《Plant and Soil》2013,367(1-2):275-284
Aims
Aluminum-tolerant wheat plants often produce more root exudates such as malate and phosphate than aluminum-sensitive ones under aluminum (Al) stress, which provides environmental differences for microorganism growth in their rhizosphere soils. This study investigated whether soil bacterial community composition and abundance can be affected by wheat plants with different Al tolerance.Methods
Two wheat varieties, Atlas 66 (Al-tolerant) and Scout 66 (Al-sensitive), were grown for 60 days in acidic soils amended with or without CaCO3. Plant growth, soil pH, exchangeable Al content, bacterial community composition and abundance were investigated.Results
Atlas 66 showed better growth and lower rhizosphere soil pH than Scout 66 irrespective of CaCO3 amendment or not, while there was no significant difference in the exchangeable Al content of rhizosphere soil between the two wheat lines. The dominant bacterial community composition and abundance in rhizosphere soils did not differ between Atlas 66 and Scout 66, although the bacterial abundance in rhizosphere soil of both wheat lines was significantly higher than that in bulk soil. Sphingobacteriales, Clostridiales, Burkholderiales and Acidobacteriales were the dominant bacteria phylotypes.Conclusions
The difference in wheat Al tolerance does not induce the changes in the dominant bacterial community composition or abundance in the rhizosphere soils. 相似文献9.
G. Torres-Cortés V. Millán A. J. Fernández-González J. F. Aguirre-Garrido H. C. Ramírez-Saad M. Fernández-López N. Toro F. Martínez-Abarca 《Plant and Soil》2012,357(1-2):275-288
Background and aims
The Tehuacán-Cuitcatlán reserve is an area of unique plant biodiversity mostly in the form of xerophytes, with exceptionally high numbers of rare and endemic species. This endemism results partly from the characteristics of the climate of this area, with two distinct seasons: rainy and dry seasons. Although rhizosphere communities must be critical in the function of this ecosystem, understanding the structure of these communities is currently limited. This is the first molecular study of the microbial diversity present in the rhizosphere of Mamillaria carnea.Methods
Total DNA was obtained from soil and rhizosphere samples at three locations in the Tehuacán Cuicatlán Reserve, during dry and rainy seasons. Temperature gradient gel electrophoresisis (TGGE) fingerprinting, 16S rRNA gene libraries and pyrosequencing were used to investigate bacterial diversity in the rhizosphere of Mammillaria carnea and changes in the microbial community between seasons.Results
Deep sequencing data reveal a higher level of biodiversity in the dry season. Statistical analyses based on these data indicates that the composition of the bacterial community differed between both seasons affecting to members of the phyla Acidobacteria, Cyanobacteria, Gemmatimonadetes, Plantomycetes, Actinobacteria and Firmicutes. In addition, the depth of sequencing performed (>24,000 reads) enables detection of changes in the relative abundance of lower bacterial taxa (novel bacterial phylotypes) indicative of the increase of specific bacterial populations due to the season.Conclusions
This study states the basis of the bacterial diversity in the rhizosphere of cacti in semi-arid environments and it is a sequence-based demonstration of community shifts in different seasons. 相似文献10.
Lina Zhen Gaowen Yang Haijun Yang Yongliang Chen Nan Liu Yingjun Zhang 《Plant and Soil》2014,375(1-2):127-136
Background and aims
Nitrogen (N) deposition usually alters plant community structure and reduces plant biodiversity in grasslands. Seedling recruitment is essential for maintaining species richness and determines plant community composition. Arbuscular mycorrhizal fungi (AMF) are widespread symbiotic fungi and could facilitate seedling establishment. Here we conducted an experiment to address whether the influence of AMF on seedling recruitment depends on N addition and plant species.Methods
Leymus chinensis were cultivated for 5 months in the microcosms that were inoculated with or without AMF at five N addition rates. Seeds of three main species (two C3 grasses and one non-N2-fixing forb) of the Eurasian steppe were sown to the 5-month-old microcosms. Seedling establishment was estimated by shoot biomass, N and P contents 7 weeks after seedling germination.Results
AMF promoted seedlings recruitment of two C3 grasses at addition rates above 0.5 g N m?2. In contrast, seedling recruitment of the non-N2-fixing forb was increased by AMF at addition rates below 0.5 g N m?2 but was decreased above 2.5 g N m?2.Conclusions
These results partly explain why N addition favored the dominance of grasses over forbs in perennial grassland communities. Our study indicates that AMF have the potential to influence plant community composition by mediating revegetation in the face of N deposition. 相似文献11.
Aims
We investigated how rhizosphere factors (total rhizosphere, roots, arbuscular mycorrhizal fungal hyphae [AMF], and soil solution) and water availability affect interactions between neighboring Medicago sativa plants.Methods
A three-compartment mesocosm was used to test the effects of rhizosphere factors on plant–plant interactions. A relative interaction index (RII) was calculated to indicate whether effects of neighbor plant on target plant were positive or negative (facilitative or competitive). Isotope tracers were used to test whether AMF hyphae mediated competition for nitrogen (N) between target and neighbor plants.Results
The effects of rhizosphere factors on the interactions between neighboring M. sativa plants depended on water availability. The effects of total rhizosphere shifted RII from negative to positive as water availability increased. Interaction with the roots and rhizosphere soil solution of neighbor plants shifted RII from negative to positive as water availability increased but the opposite was true for AMF hyphae. AMF hyphae helped neighbor plants compete for 15N when water was available but not when water was limiting.Conclusions
The effect of total rhizosphere on plant–plant interaction of M. sativa shifted from competitive to facilitative as water availability increased. Competition was reduced by neighboring soil solution and roots but was increased by AMF hyphae. 相似文献12.
Effects of condensed tannins in conifer leaves on the composition and activity of the soil microbial community in a tropical montane forest 总被引:1,自引:0,他引:1
Background and aims
Condensed tannins, a dominant class of plant secondary metabolites, play potentially important roles in plant-soil feedbacks by influencing the soil microbial community. Effects of condensed tannins on the soil microbial community and activity were examined by a short-term tannin-addition experiment under field and laboratory conditions.Methods
Condensed tannins were extracted from the leaves of a dominant conifer (Dacrydium gracilis) in a tropical montane forest on Mt. Kinabalu, Borneo. The extracted tannins were added to soils beneath the conifer and a dominant broadleaf (Lithocarpus clementianus) to evaluate the dependence of the response to tannin addition on the initial composition of the soil microbial community.Results
Enzyme activities in the field tannin-addition treatment were lower than in the deionized-water treatment. Carbon and nitrogen mineralization were also inhibited by tannin-addition. The fungi-to-bacteria ratio after tannin-addition was higher compared with the distilled-water treatment in the laboratory experiment.Conclusions
Based on our results, we suggest that the higher concentration of condensed tannins in the leaf tissues of Dacrydium than in those of Lithocarpus is a factor influencing the microbial community and activity. This may have influences on subsequent plant performance, which induces plant-soil feedback processes that can control dynamics of the tropical montane forest ecosystem. 相似文献13.
Background and aims
Vineyards harbour a variety of weeds, which are usually controlled since they compete with grapevines for water and nutrients. However, weed plants may host groups of fungi and bacteria exerting important functions.Methods
We grew three different common vineyard weeds (Taraxacum officinalis, Trifolium repens and Poa trivialis) in four different soils to investigate the effects of weeds and soil type on bacterial and fungal communities colonising bulk soil, rhizosphere and root compartments. Measurements were made using the cultivation-independent technique Automated Ribosomal Intergenic Spacer Analysis (ARISA).Results
Weeds have a substantial effect on roots but less impact on the rhizosphere and bulk soil, while soil type affects all three compartments, in particular the bulk soil community. The fungal, but not the bacterial, bulk soil community structure was affected by the plants at the late experimental stage. Root communities contained a smaller number of Operational Taxonomic Units (OTUs) and different bacterial and fungal structures compared with rhizosphere and bulk soil communities.Conclusions
Weed effect is localised to the rhizosphere and does not extend to bulk soil in the case of bacteria, although the structure of fungal communities in the bulk soil may be influenced by some weed plants. 相似文献14.
15.
Aims
Rice fields are an important source for the greenhouse gas methane. Plants play an essential role in carbon supply for soil microbiota, but the influence of the microbial community on carbon cycling is not well understood.Methods
Microcosms were prepared using sand-vermiculite amended with different soils and sediments, and planted with rice. The microcosms at different growth stages were pulse-labeled with 13CO2 followed by tracing 13C in plant, soil and atmospheric carbon pools and quantifying the abundance of methanogenic archaea in rhizosphere soil.Results
Overall,?>85 % of the freshly assimilated carbon was allocated in aboveground plant biomass, approximately 10 % was translocated into the roots and?2 % was recovered in soil organic matter, independently from soil type. Only about 0.3 % was transformed to CH4, but emission of 13C-labeled CH4 started immediately and 13C enrichment revealed that plant-derived carbon was an important source for methanogenesis. The results further demonstrated that carbon assimilation and translocation processes, microbial abundance and gas emission were not only affected by the plant growth stage, but also by the content and type of soil in which the rice plants grew.Conclusions
The study illustrates the close ties between plant physiology, soil properties and microbial communities for carbon turnover and ecosystem functioning. 相似文献16.
Background and aims
Phosphorus and nitrogen availability and forms are affected by soil properties as well as by plant species and further modulated by soil microbes. Additionally, close contact of the roots of two plant species may affect concentrations and forms of N and P. The aim of this study was to assess properties related to N and P cycling in the rhizosphere of wheat and legumes grown in monoculture or in wheat/legume mixtures in three soils differing in pH.Methods
Faba bean, white lupin and wheat were grown in three soils differing in pH (4.8, 7.5 and 8.8) in monoculture or in mixed culture of wheat and legumes. Rhizosphere soil was collected at flowering and analyzed for P pools by sequential fractionation, available N as well as community structure of bacteria, fungi, ammonia oxidizers, N2-fixers and P mobilizers by polymerase chain reaction (PCR)—denaturing gradient gel electrophoresis (DGGE).Results
Soil type was the major factor determining plant growth, rhizosphere nutrient dynamics and microbial community structure. Among the crop species, only faba bean had a significant effect on nitrification potential activity (PNA) in all three soils with lower activity compared to the unplanted soil. Soil type and plant spieces affected the community composition of ammonia-oxidizing archaea (AOB), ammonia-oxidizing archaea (AOA), N2-fixers (nifH), P mobilizers (ALP gene) and fungi, but not that of bacteria. Among the microbial groups, the AOA and nifH community composition were most strongly affected by crop species, cropping system and soil type, suggesting that these groups are quite sensitive to environmental conditions. All plants depleted some labile as well as non-labile P pools whereas the less labile organic P pools (NaOH extractable P pools, acid extractable P pools) accumulated in the rhizosphere of legumes. The pattern of depletion and accumulation of some P pools differed between monoculture and mixed culture as well as among soils.Conclusions
Plant growth and rhizosphere properties were mainly affected by soil type, but also by crop species whereas cropping system had the least effect. Wheat and the legumes depleted less labile inorganic P pools in some soils whereas less labile organic P pools (NaOH extractable P, acid extractable P) accumulated in the rhizosphere of legumes. 相似文献17.
Background and Aims
Rhizosphere processes affect the mobility, phytoavailability and toxicity of solutes in soil. To study reactions in the rhizosphere under quasi in situ conditions, we recently developed the “micro push-pull test” (μPPT) method, combining micro-suction cups with the principle of the “push-pull test” method known from groundwater applications. Here we report the application of μPPT to investigate rhizosphere reactions in situ, i.e. degradation of deuterated citrate (citrate-d4) in the rhizosphere of Lupinus albus grown in sand-filled rhizoboxes.Methods
In a μPPT, a solution containing reactive (citrate-d4) and non-reactive solutes (bromide) is injected into a porous medium and shortly thereafter, the pore water solution is re-extracted from the same location. Concentration (“breakthrough”) curves of extracted reactants can be compared to those of the non-reactive solute, allowing the determination of reaction rates. We applied the μPPT in rhizoboxes with Lupinus albus and sampled different types of micro-habitats: bulk soil, rhizosphere of normal roots and rhizosphere of cluster roots of different ages.Results
Breakthrough curves of citrate-d4 varied considerably between tests adjacent to cluster roots and normal roots, and in bulk soil. Degradation of citrate-d4 in bulk soil and adjacent to normal roots was below detection, while we found strong degradation of citrate-d4 adjacent to 4 to 5-days old cluster roots. In situ degradation rate constants for citrate-d4 around cluster roots were found to be in the range from 0.38 to 0.71 h?1.Conclusions
We successfully applied the μPPT to the rhizosphere. The μPPT is useful to investigate local processes in microcosms and to monitor processes also over time (e.g., during cluster-root development) due to its non-destructive nature. 相似文献18.
Context
In acidic forest soils, aluminium can alter tree health due to its potential toxicity. Aluminium phytotoxicity is mainly influenced by its chemical form and its availability.Methods
As physical-chemical indicators of Al toxicity in soil, Al speciation in soil solutions and in the exchange complex was measured in the rhizosphere and the bulk soil of two tree species (Norway spruce (Picea abies (L.) Karst.) and European Beech (Fagus sylvatica L.) in an acidic soil and in 4 months (November, February, May and August) representing the four seasons in a year.Results
In the bulk soil, Al toxicity was generally higher under Norway spruce than under beech. Furthermore, temporal changes in Al behaviour were identified under Norway spruce but not under beech. The monomeric Al in the soil solutions and the exchangeable Al in the solid soil increased significantly in February under Norway spruce and were positively correlated with nitrate concentration, suggesting that nitrate influence Al speciation and mobility under Norway spruce. In the rhizosphere, Al toxicity was restricted through Al complexation by organic compounds and by nutrient contents independently from the season. The ecological importance of the rhizosphere in Al detoxification is discussed.Conclusions
This study suggests that plant specific differences as well as seasonal changes in plant physiology, microbial activity and microclimatology influence aluminum toxicity in acid forest soils. 相似文献19.
Background and aims
Rhizosphere influences the dynamics of nutrients and contaminants through increased microbial activity, release of root exudates and alteration of pH. The objective of this study was to evaluate the rhizosphere-induced reduction (i.e. rhizoreduction) and redistribution of arsenate [As(V)] and chromate [Cr(VI)] in Australian native vegetation in relation to their bioavailability.Methods
The reduction of As(V) and Cr(VI) was examined using rhizosphere soils from a number of Australian native vegetation (Acacia pubescens, Eucalyptus camaldulensis, Enchylaena tomentosa, Templetonia retusa, Dichantheum sericeum and Austrodanthonia richardsonii). Naturally contaminated As and Cr soils were used to examine the effect of Dichantheum sericeum on the redistribution and bioavailability of these metal(loid)s.Results
The rhizosphere soil contained higher levels of microbial activity, dissolved organic carbon and organic acid content than the non-rhizosphere soil. The rhizosphere soil caused up to 2.4 and 5.1 fold increases in the rate of reduction of As(V) and Cr(VI), respectively. There was a significant relationship between rhizosphere-induced increases in microbial activity (Δ basal respiration) and As(V) and Cr(VI) reduction (Δ rate of reduction), indicating the role of increased microbial activity in rhizosphere soil on metal(loid) reduction. In the plant growth experiment, Dichantheum sericeum enhanced the reduction of metal(loid)s in the naturally contaminated soils, thereby increasing the bioavailability of As but decreasing that of Cr.Conclusions
Depending on the nature of metal(loid)s present in soil, the rhizosphere-induced reduction by plant species such as Dichantheum sericeum and Templetonia retusa has implications to both their bioavailability to higher plants and microorganisms, and remediation of contaminated soils. While rhizoreduction decreases Cr bioavailability it increases that of As. 相似文献20.
Root-induced changes in radial oxygen loss, rhizosphere oxygen profile, and nitrification of two rice cultivars in Chinese red soil regions 总被引:4,自引:0,他引:4