Studying the relationship between rhizosphere microorganisms and root exudates is of great significance for the interaction between rhizosphere microorganisms and plants, and the prevention and control of soil-borne d...Studying the relationship between rhizosphere microorganisms and root exudates is of great significance for the interaction between rhizosphere microorganisms and plants, and the prevention and control of soil-borne diseases. This article analyzed the effects of different microorganisms on tobacco root exudates and rhizosphere microorganisms. It was found that the bacterial wilt pathogen can greatly increase acids and amines, while the probiotic <i>B. amyloliquefaciens</i> ZM9 can eliminate some acids and amines. The results of the study show that the root exudates of pathogenic bacteria may contain a variety of allelochemicals that cause soil-borne diseases.展开更多
In order to explore the differences of amino acids in root exudates and plant tissues,we selected four flue-cured tobacco varieties [Yunyan 87(Ⅰ),K326( Ⅱ),NC102( Ⅲ),Hongda( Ⅳ) ]as the test materials and studied th...In order to explore the differences of amino acids in root exudates and plant tissues,we selected four flue-cured tobacco varieties [Yunyan 87(Ⅰ),K326( Ⅱ),NC102( Ⅲ),Hongda( Ⅳ) ]as the test materials and studied the components and mass fractions of amino acids in rhizosphere soil,non rhizosphere soil,roots and leaves via high performance capillary zone electrophoresis. Ten amino acids were detected out from four varieties,including histidine,lysine,tryptophan,phenylalanine,valine,threonine,proline,serine,alanine and glycine. The mass fractions of amino acids in leaves and roots were higher than those in rhizosphere soil and non rhizosphere soil. In rhizosphere soil and non-rhizosphere soil,the mass fractions of lysine,phenylalanine,threonine,proline and glycine in susceptible varieties( Ⅲ,Ⅳ) were higher than those in resistant varieties(Ⅰ,Ⅱ). In rhizosphere soil,the total amino acids successively were Ⅳ > Ⅲ >Ⅰ> Ⅱ,and in non rhizosphere soil were Ⅲ > Ⅳ >Ⅰ> Ⅱ. The total amino acids in roots of variety Ⅳ was the highest,up to 6 359. 195 μg / g. In leaves,the total amino acids in varietiesⅠand Ⅱ were higher than those in varieties Ⅲ and Ⅳ. The results indicated that amino acids could secrete to rhizosphere via root secretion,and the compositions and mass fractions of amino acids varied with flue-cured tobacco varieties,thus the secretion amount of susceptible varieties was higher than that of resistant varieties.展开更多
Terrestrial plants can affect the growth and health of adjacent plants via interspecific interaction.Here,we studied the mechanism by which plant root exudates affect the recruitment of the rhizosphere microbiome in a...Terrestrial plants can affect the growth and health of adjacent plants via interspecific interaction.Here,we studied the mechanism by which plant root exudates affect the recruitment of the rhizosphere microbiome in adjacent plants—with implications for plant protection—using a tomato(Solanum lycopersicum)–potatoonion(Allium cepa var.agrogatum)intercropping system.First,we showed that the intercropping system results in a disease-suppressive rhizosphere microbiome that protects tomato plants against Verticillium wilt disease caused by the soilborne pathogen Verticillium dahliae.Second,16S rRNA gene sequencing revealed that intercropping with potatoonion altered the composition of the tomato rhizosphere microbiome by promoting the colonization of specific Bacillus sp.This taxon was isolated and shown to inhibit V.dahliae growth and induce systemic resistance in tomato plants.Third,a belowground segregation experiment found that root exudates mediated the interspecific interaction between potatoonion and tomato.Moreover,experiments using split-root tomato plants found that root exudates from potatoonion,especially taxifolin—a flavonoid compound—stimulate tomato plants to recruit plant-beneficial bacteria,such as Bacillus sp.Lastly,ultra-high-pressure liquid chromatography–mass spectrometry analysis found that taxifolin alters tomato root exudate chemistry;thus,this compound acts indirectly in modulating root colonization by Bacillus sp.Our results revealed that this intercropping system can improve tomato plant fitness by changing rhizosphere microbiome recruitment via the use of signaling chemicals released by root exudates of potatoonion.This study revealed a novel mechanism by which interspecific plant interaction modulates the establishment of a disease-suppressive microbiome,thus opening up new avenues of research for precision plant microbiome manipulations.展开更多
Root exudates are crucial for plants returning organic matter to soils,which is assumed to be a major source of carbon for the soil microbial community.This study investigated the influence of root exudates on the fat...Root exudates are crucial for plants returning organic matter to soils,which is assumed to be a major source of carbon for the soil microbial community.This study investigated the influence of root exudates on the fate of arsenic(As)with a lab simulation experiment.Our findings suggested that root exudates had a dose effect on the soil physicochemical properties,As speciation transformation and the microbial community structure at different concentrations.The addition of root exudates increased the soil pH while decreased the soil redox potential(Eh).These changes in the soil pH and Eh increased As and ferrous(Fe(Ⅱ))concentrations in soil porewater.Results showed that 40 mg/L exudates addition significantly increased arsenite(As(Ⅲ))and arsenate(As(Ⅴ))by 541 and 10 times respectively within 30 days in soil porewater.The relative abundance of Fe(Ⅲ)-reducing bacteria Geobacter and Anaeromyxobacter increased with the addition of root exudates,which enhanced microbial Fe reduction.Together these results suggest that investigating how root exudates affect the mobility and transformation of As in paddy soils is helpful to systematically understand the biogeochemical cycle of As in soil-rice system,which is of great significance for reducing the health risk of soil As contamination.展开更多
The release of root exudates(REs) provides an important source of soil organic carbon. This work revealed the molecular composition of REs of different plant species including alfalfa( Medicago sativa L.), bean( Phase...The release of root exudates(REs) provides an important source of soil organic carbon. This work revealed the molecular composition of REs of different plant species including alfalfa( Medicago sativa L.), bean( Phaseolus vulgaris L.), barley( Hordeum vulgare L.), maize( Zea mays), wheat( Triticum aestivum L.), ryegrass( Lolium perenne L.) and pumpkin( Cucurbita maxima) using electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry(ESI FT-ICR MS). The combination of positive ion mode( + ESI) and negative ion mode(-ESI) increased the number of the molecules detected by ESI FT-ICR MS, and a total of 8758 molecules were identified across all the samples. In detail, lipids and proteins and unsaturated hydrocarbons were more easily detected in + ESI mode, while aromatic compounds with high O/C were readily ionized in-ESI mode, and only 38% of the total assigned formulas were shared by -ESI and + ESI modes. Multivariate statistical analysis of the formulas indicated that the close related plants species secreted REs with similar molecular components. Moreover, the unsaturation degree and nitrogen content were the two key parameters able to distinguish the similarities and differences of molecular components of REs between plant species. The results provided a feasible analysis method for characterization of the molecular components of REs and for the first time characterized the molecular components of REs of a variety of plant species using ESI FT-ICR MS.展开更多
Plants are capable of releasing specific root exudates to recruit beneficial rhizosphere microbes upon foliar pathogen invasion attack,including long-chain fatty acids,amino acids,short-chain organic acids and sugars....Plants are capable of releasing specific root exudates to recruit beneficial rhizosphere microbes upon foliar pathogen invasion attack,including long-chain fatty acids,amino acids,short-chain organic acids and sugars.Although long-chain fatty acids and amino acids application have been linked to soil legacy effects that improve future plant performance in the presence of the pathogen,the precise mechanisms involved are to a large extent still unknown.Here,we conditioned soils with long-chain fatty acids and amino acids application(L+A)or short-chain organic acids and sugars(S+S)to examine the direct role of such exudates on soil microbiome structure and function.The L+A treatment recruited higher abundances of Proteobacteria which were further identified as members of the genera Sphingomonas,Pseudomonas,Roseiflexus,and Flavitalea.We then isolated the enriched bacterial strains from these groups,identifying ten Pseudomonas strains that were able to help host plant to resist foliar pathogen infection.Further investigation showed that the L+A treatment resulted in growth promotion of these Pseudomonas strains.Collectively,our data suggest that long-chain fatty acids and amino acids stimulated by foliar pathogen infection can recruit specific Pseudomonas populations that can help protect the host plant or future plant generations.展开更多
The effect of zinc(Zn) deficiency and excessive bicarbonate on the allocation and exudation of organic acids in plant organs(root, stem, and leaf) and root exudates of two Moraceae plants(Broussonetia papyrifera and M...The effect of zinc(Zn) deficiency and excessive bicarbonate on the allocation and exudation of organic acids in plant organs(root, stem, and leaf) and root exudates of two Moraceae plants(Broussonetia papyrifera and Morus alba) were investigated. Two Moraceae plants were hydroponically grown and cultured in nutrient solution in four different treatments with 0.02 mM Zn or no Zn,combined with no or 10 mM bicarbonate. The variations of organic acids in different plant organs were similar to those of root exudates in the four treatments except B. papyrifera, which was in a treatment that was a combination of 0.02 mM Zn and no bicarbonate. The response characteristics in the production, translocation, and allocation of organic acids in the plant organs and root exudates varied with species and treatments. Organic acids in plant organs and root exudates increased under Zn-deficient conditions,excessive bicarbonate, or both. An increase of organic acids in the leaves resulted in an increase of root-exuded organic acids. B. papyrifera translocated more oxalate and citrate from the roots to the rhizosphere than M. alba under the dual influence of 10 mM bicarbonate and Zn deficiency. Organic acids of leaves may be derived from dark respiration and photorespiration. By comparison, organic acids in stems, roots, and root exudates may be derived from dark respiration and organic acid translocation from the leaves. These results provide evidence for the selective adaptation of plants to environments with low Zn levels or high bicarbonate levels such as a karst ecosystem.展开更多
Rhizosphere microbial communities play important roles in facilitating or inhibiting the establishment of exotic species.Since some invasive plants interact with soil microbial communities such as rhizosphere bacteria...Rhizosphere microbial communities play important roles in facilitating or inhibiting the establishment of exotic species.Since some invasive plants interact with soil microbial communities such as rhizosphere bacteria,changes triggered by rhizosphere bacteria may alter competitive interactions between exotic and native plants.This study compared the Bacillus cereus content in soils with different degrees of Ageratina adenophora invasion,and investigated the effects of A.adenophora allelochemicals on B.cereus growth and soil characteristics and the feedback effects of B.cereus on A.adenophora growth.Bacillus cereus content in the rhizosphere of A.adenophora increased with intensification of the invasion process,and newly invaded soil contained almost twice as much bacteria as noninvaded soil.When rhizosphere soil was added to the root exudates of A.adenophora,the contents of B.cereus were twice as much as the control,except on the first day.Certain soil parameters increased significantly,such as ammonium nitrogen(NH_(4)^(+)-N)and available phosphorus(AP),which were increased by 41 and 27%,respectively.Soil treatment with B.cereus promoted the degradation of two allelochemicals from the rhizosphere of A.adenophora,amorpha-4,7(11)-dien-8-one and 6-hydroxy-5-isopropy1-3,8-dimethyl-4 a,5,6,7,8,8 ahexahydraphthalen-2(1 H)-one,to varying degrees;and increased the germination rate by 50%,root length by 117%,shoot length by 48%and fresh weight by 81%for A.adenophora compared to those of untreated soil.Our results confirmed that the invasion of A.adenophora will promote an increase of B.cereus,a beneficial rhizosphere bacterium,which in turn induces a positive feedback effect on A.adenophora.展开更多
Pseudomonas stutzeriA1501, associative and endophytic nitrogen-fixing bacterium showed the capacity of colonization in the rice roots and considered as the good colonizer in the rice plant. The experiment was conducte...Pseudomonas stutzeriA1501, associative and endophytic nitrogen-fixing bacterium showed the capacity of colonization in the rice roots and considered as the good colonizer in the rice plant. The experiment was conducted to study the expression of genes potentiality relevant to the association of nitrogen fixing Pseudomonas stutzeri with host rice and reveal the molecular mechanism by which underlying interaction between bacteria and host rice. The bacteria were shown to be uniformly distributed on the rhizoplane of the root and the density of bacteria was found at the intercellular junction and micro colony developed on the surface of the epidermal cells and on the cellular junctions. Root exudates of rice were the major components of carbon and energy sources for bacteria. RT-PCR analyses of pilK, metE, rpoN and fdhE genes expression of P. stutzeri A1501 were performed at positive and negative (control) conditions. After 1 h, it was found that pilK, metE and rpoN transcription were increased 5.7, 6.4 and 3.4-fold, respectively, whereas in the fdhE gene has no expression. Consequently, after 4 h pilk, fdhE, metE and rpoN were decreased -1.9, -4.4, -0.2 and -0.8-fold, respectively. The gene pilK, expression was up-regulation after 1 h and down-regulation after 4 h that has twitching motility to convey the bacterial cell to point of attachment in to host plant. The gene expressions of the bacteria, pilK, metE, rpoN and fdhE were up- and down-regulated during the influence of root exudates which regulated the colonization of bacteria during plant-microbe interaction.展开更多
The RIPENING-INHIBITOR(RIN)transcriptional factor is a key regulator governing fruit ripening.While RIN also affects other physiological processes,its potential roles in triggering interactions with the rhizosphere mi...The RIPENING-INHIBITOR(RIN)transcriptional factor is a key regulator governing fruit ripening.While RIN also affects other physiological processes,its potential roles in triggering interactions with the rhizosphere microbiome and plant health are unknown.Here we show that RIN affects microbiome-mediated disease resistance via root exudation,leading to recruitment of microbiota that suppress the soil-borne,phytopathogenic Ralstonia solanacearum bacterium.Compared with the wild-type(WT)plant,RIN mutants had different root exudate profiles,which were associated with distinct changes in microbiome composition and diversity.Specifically,the relative abundances of antibiosis-associated genes and pathogensuppressing Actinobacteria(Streptomyces)were clearly lower in the rhizosphere of rin mutants.The composition,diversity,and suppressiveness of rin plant microbiomes could be restored by the application of 3-hydroxyflavone and riboflavin,which were exuded in much lower concentrations by the rin mutant.Interestingly,RIN-mediated effects on root exudates,Actinobacteria,and disease suppression were evident from the seedling stage,indicating that RIN plays a dual role in the early assembly of diseasesuppressive microbiota and late fruit development.Collectively,our work suggests that,while plant disease resistance is a complex trait driven by interactions between the plant,rhizosphere microbiome,and the pathogen,it can be indirectly manipulated using"prebiotic"compounds that promote the recruitment of disease-suppressive microbiota.展开更多
Rice paddy-field microbial fuel cells (RPF-MFCs) are devices that exploit rhizosphere bacteria to generate electricity from soil organic matter, including those excreted from roots. Previous studies have examined fact...Rice paddy-field microbial fuel cells (RPF-MFCs) are devices that exploit rhizosphere bacteria to generate electricity from soil organic matter, including those excreted from roots. Previous studies have examined factors affecting electric outputs from RPF-MFCs and demonstrated that RPFMFC was able to generate electricity up to 80 mW·m<sup>-2</sup> (based on the projected area of anode). The present study operated RPF-MFCs with different sizes of anodes and cathodes and examined how electrode sizes affected electricity generation. We show that anodes are the limiting factor for electricity generation immediately after commencing the operation, while cathodes become the limiting factor after anode performances are sufficiently increased. RPF-MFC achieved the maximum power density of 140 mW·m<sup>-2</sup> (based on the projected area of anode), when the cathode is sufficiently larger than the anode. Results suggest that the cathode needs to be improved for eliciting the maximum capacity of rhizosphere bacteria for electricity generation in RPF-MFC.展开更多
As a special form of allelopathy,autotoxicity is common in cucurbits,and it is one of main factors inducing continuous cropping obstacles.Therefore,the autotoxicity research has both theoretical and practical signific...As a special form of allelopathy,autotoxicity is common in cucurbits,and it is one of main factors inducing continuous cropping obstacles.Therefore,the autotoxicity research has both theoretical and practical significance on overcoming continuous cropping obstacles.In this review,commencing on the concept of autotoxicity,research results of autotoxicity in watermelon in recent years were summarized.The significance of researches on autotoxicity in watermelon,watermelon root exudate and its autotoxicity,and the autotoxicity of watermelon stubble and the mechanisms were explained.Meanwhile,some questions needed to be further studied.展开更多
Climate change,urbanization,and population increase limit food availability.To sustain human existence,there is the need to increase food and agricultural production to mitigate the impact of these factors.Scientists ...Climate change,urbanization,and population increase limit food availability.To sustain human existence,there is the need to increase food and agricultural production to mitigate the impact of these factors.Scientists have been working for years on ways to increase food production.From plant breeding techniques to soil science,scientists have made tremendous progress.The rhizobiome has been proven to be important to crop production,and the impact of the rhizobiome on plant health cannot be overemphasized.Being rich in diverse complex microbial interactions,the rhizosphere has become a major force in recent plant growth promotion studies.The upsurge in next-generation sequencing applications with the various“omics”technologies is helping to unearth information relating to rhizosphere impact on plant growth.Explaining the complex interactions between and across microbial species present in the rhizosphere is important to further enhance our understanding of their mechanistic and mutualistic functions.Knowledge from this can be used in rhizosphere biome engineering for improved plant growth and yield in the face of the various biotic and abiotic challenges.展开更多
The present experiment was conducted to evaluate the influence of </span><i><span style="font-family:Verdana;">Lamiaceae </span></i><span style="font-family:Verdana;&quo...The present experiment was conducted to evaluate the influence of </span><i><span style="font-family:Verdana;">Lamiaceae </span></i><span style="font-family:Verdana;">herbs companion planting on growth and secondary metabolites changes in tomato plants. Furthermore, the free amino acid changes in tomato due to companion planting w</span></span><span style="font-family:Verdana;">ere</span><span style="font-family:Verdana;"> also evaluated using tomato-basil companionship as a model. Four-week-old seedlings of tomato were grown in a pot containing autoclaved commercial soil with basil, peppermint and hyssop as a companion plant separately in different density. Four weeks after companion planting, tomato plants under 1:1 companionship with the herbs showed significant increase in dry weights of shoots compared to control. Higher density of the herbs on the other hand expressed a growth suppression on tomato possibly due to nutrient competition. By the LC-MS analysis, shikimic acid and apigenin were identified as the major secondary compounds found in tomato plants and 1:1 companionship with basil seemed to have a positive influence on their content in tomato shoots. On the other hand, in case of peppermint and hyssop, the increase was observed in all parts of tomato plants. In addition, promotion in several free amino acid contents w</span><span style="font-family:Verdana;">as</span><span style="font-family:Verdana;"> also observed in tomato plants with basil companion planting compared to control. Thus, tomato plants grown with herb companion planting in 1:1 ratio seems to have a positive impact on growth of tomato. This positive influence might be related to the increase in some secondary metabolites and changes in the free amino acids observed in this study.展开更多
There is increasing evidence of plant communication and behavior. We examine how two Lactuca species, L. sativa andL. serriola, communicate with themselves and one another via root exudates. We exp...There is increasing evidence of plant communication and behavior. We examine how two Lactuca species, L. sativa andL. serriola, communicate with themselves and one another via root exudates. We exposed both species to their own, to the same species, and to the other species root exudates. We then measured the length of their primary root as a proxy for competitive effort. L. serriola produced longer roots when exposed to its own exudates relative to when exposed to L. sativa’s. In contrast, L. sativa produced shorter roots when exposed to its own root exudates. These results indicate kin recognition in these species. Further, the results show that L. sativa, a domesticated species, shares resources well with conspecifics. In contrast, L. serriola, a sparsely distributed species, is more competitive with conspecifics than with other species. We argue that artificial selection and domestication of L. sativa, from its progenitor L. serriola, modify how the species interprets and respond to exudate cues from neighboring plants.展开更多
Plant roots are one of the major mediators that allocate carbon captured from the atmosphere to soils as rhizodeposits,including root exudates.Although rhizodeposition regulates both microbial activity and the biogeoc...Plant roots are one of the major mediators that allocate carbon captured from the atmosphere to soils as rhizodeposits,including root exudates.Although rhizodeposition regulates both microbial activity and the biogeochemical cycling of nutrients,the effects of particular exudate species on soil carbon fluxes and key rhizosphere microorganisms remain unclear.By combining high-throughput sequencing,q-PCR,and NanoSIMS analyses,we characterized the bacterial community structure,quantified total bacteria depending on root exudate chemistry,and analyzed the consequences on the mobility of mineral-protected carbon.Using well-controlled incubation experiments,we showed that the three most abundant groups of root exudates(amino acids,carboxylic acids,and sugars)have contrasting effects on the release of dissolved organic carbon(DOC)and bioavailable Fe in an Ultisol through the disruption of organo-mineral associations and the alteration of bacterial communities,thus priming organic matter decomposition in the rhizosphere.High resolution(down to 50 nm)NanoSIMS images of mineral particles indicated that iron and silicon colocalized significantly more organic carbon following amino acid inputs than treatments without exudates or with carboxylic acids.The application of sugar strongly reduced microbial diversity without impacting soil carbon mobilization.Carboxylic acids increased the prevalence of Actinobacteria and facilitated carbon mobilization,whereas amino acid addition increased the abundances of Proteobacteria that prevented DOC release.In summary,root exudate functions are defined by their chemical composition that regulates bacterial community composition and,consequently,the biogeochemical cycling of carbon in the rhizosphere.展开更多
Sugars are frequently and abundantly found in root exudates,but influence of specific sugars on the fate of soil-borne pathogens,microbiome structure,and particularly microbial interactions are not well understood.A 4...Sugars are frequently and abundantly found in root exudates,but influence of specific sugars on the fate of soil-borne pathogens,microbiome structure,and particularly microbial interactions are not well understood.A 42-day of microcosm incubation was conducted with two soils:a natural watermelon Fusarium wilt pathogen(i.e.,Fusarium oxysporum f.sp.niveum(FON))-infested soil(Low-FON soil)and the soil further receiving the wilt pathogen inocula(High-FON soil).Both soils were supplemented with four simple sugars before incubation.The results show that,in both soils,FON was enriched by all sugars although co-living with tremendously diverse microbes;and bacterial richness,evenness,and diversity were decreased and bacterial community structure was changed by all sugars.Bacterial richness and evenness were negatively correlated with FON quantity in both Low-FON and High-FON soils,indicating that FON may tend to live in soil with low alpha-diversity.In both Low-FON and High-FON soils,the sugar-spiked networks had more links,higher density,larger modules,and shorter harmonic geodesic distance,suggesting greater potentials for microbial interaction and niche-sharing.The positive links between some of the keystone taxa and FON indicates that these keystone taxa may have promoted FON.This may be one of reasons why FON could proliferate vigorously after sugar supplementation.展开更多
Aboveground litter inputs and root exudates provide basal resources for soil communities,however,their relative contributions to soil food web are still not well understood.Here,we conducted a field manipulative exper...Aboveground litter inputs and root exudates provide basal resources for soil communities,however,their relative contributions to soil food web are still not well understood.Here,we conducted a field manipulative experiment to differentiate the effects of litter inputs and living root on nematode community composition of surface and subsoils in a young Acacia crassicapa plantation in southern China.Our results showed that both litter addition and root presence significantly enhanced soil nematode abundance by 17.3%and 35.3%,respectively.Litter addition altered nematode trophic group composition,decreased fungivore to bacterivore ratio,and enhanced maturity index and structure index,which led to a bacterial-based energy channel and a more complex food web structure.However,root presence had a limited impact on the nematode community composition and ecological indices.Despite nematodes surface assembly,soil depth did not affect nematode trophic group composition or ecological index.Our findings highlight the importance of litter inputs in shaping soil nematode community structure and regulating soil energy channel.展开更多
Rhizospheres can promote self-transmissible plasmid transfer,however,the corresponding mechanism has not received much attention.Plant-microbe remediation is an effective way to promote pollutant biodegradation;howeve...Rhizospheres can promote self-transmissible plasmid transfer,however,the corresponding mechanism has not received much attention.Plant-microbe remediation is an effective way to promote pollutant biodegradation;however,some pollutants,such as naphthalene,are harmful to plants and result in inefficient plant-microbe remediation.In this study,trans-fer of a TOL-like plasmid,a self-transmissible plasmid loaded with genetic determinants for pollutant degradation,among different bacteria was examined in bulk and rhizosphere soils as well as addition of maize root exudate and its artificial root exudate(ARE).The results showed that the numbers of transconjugants and recipients as well as bacterial metabolic activities,such as xylE mRNA expression levels and catechol 2,3-dioxygenase(C23O)activ-ities of bacteria,remained high in rhizosphere soils,when compared with bulk soils.The number of transconjugants and bacterial metabolic activities increased with the increasing exudate and ARE concentrations,whereas the populations of donor and recipient bacteria were substantially unaltered at all concentrations.All the experiments consistently showed that a certain number of bacteria is required for self-transmissible plasmid transfer,and that the increased plasmid transfer might predominantly be owing to bacterial metabolic activ-ity stimulated by root exudates and ARE.Furthermore,ARE addition increased naphthalene degradation by transconjugants in both culture medium and soil.Thus,the combined action of a wide variety of components in ARE might contribute to the increased plasmid transfer and naphthalene degradation.These findings suggest that ARE could be an effectively al-ternative for plant-microbe remediation of pollutants in environments where plants cannot survive.展开更多
Plant species have different traits for mobilizing sparingly soluble phosphorus (P) resources,which could potentially lead to overyielding in P uptake by plant species mixtures compared to monocultures due to higher P...Plant species have different traits for mobilizing sparingly soluble phosphorus (P) resources,which could potentially lead to overyielding in P uptake by plant species mixtures compared to monocultures due to higher P uptake as a result of resource (P) partitioning and facilitation.However,there is circumstantial evidence at best for overyielding as a result of these mechanisms.Overyielding (the outcome) is easily confused with underlying mechanisms because of unclear definitions.We aimed to define a conceptual framework to separate outcome from underlying mechanisms and test it for facilitation and complementarity with respect to P acquisition by three plant species combinations grown on four soils.Our conceptual framework describes both mechanisms of complementarity and facilitation and outcomes (overyielding of mixtures or no overyielding) depending on the competitive ability of the species to uptake the mobilized P.Millet/chickpea mixtures were grown in pots on two calcareous soils mixed with calcium-bound P (CaP) and phytate P (PhyP).Cabbage/faba bean mixtures were grown on both acid and neutral soils mixed with P-coated iron (hydr)oxide (FeP) and PhyP.Wheat/maize mixtures were grown on all four soils.Rhizosphere carboxylate concentration and acid phosphatase activity (mechanisms) as well as plant P uptake and biomass (outcome) were determined for monocultures rhizosphere and species mixtures.Facilitation of P uptake occurred in millet/chickpea mixtures on one calcareous soil.We found no indications for P acquisition from different P sources,neither in millet/chickpea,nor in cabbage/faba bean mixtures.Cabbage and faba bean on the neutral soil differed in rhizosphere acid phosphatase activity and carboxylate concentration,but showed no overyielding.Wheat and maize,with similar root exudates,showed overyielding (the observed P uptake being 22%higher than the expected P uptake) on one calcareous soil.We concluded that although differences in plant physiological traits (root exudates) provide necessary conditions for complementarity and facilitation with respect to P uptake from different P sources,they do not necessarily result in increased P uptake by species mixtures,because of the relative competitive ability of the mixed species.展开更多
文摘Studying the relationship between rhizosphere microorganisms and root exudates is of great significance for the interaction between rhizosphere microorganisms and plants, and the prevention and control of soil-borne diseases. This article analyzed the effects of different microorganisms on tobacco root exudates and rhizosphere microorganisms. It was found that the bacterial wilt pathogen can greatly increase acids and amines, while the probiotic <i>B. amyloliquefaciens</i> ZM9 can eliminate some acids and amines. The results of the study show that the root exudates of pathogenic bacteria may contain a variety of allelochemicals that cause soil-borne diseases.
基金Supported by Project of Yunnan Hongyun Honghe Tobacco(Group)Co.,Ltd.(KX140906)
文摘In order to explore the differences of amino acids in root exudates and plant tissues,we selected four flue-cured tobacco varieties [Yunyan 87(Ⅰ),K326( Ⅱ),NC102( Ⅲ),Hongda( Ⅳ) ]as the test materials and studied the components and mass fractions of amino acids in rhizosphere soil,non rhizosphere soil,roots and leaves via high performance capillary zone electrophoresis. Ten amino acids were detected out from four varieties,including histidine,lysine,tryptophan,phenylalanine,valine,threonine,proline,serine,alanine and glycine. The mass fractions of amino acids in leaves and roots were higher than those in rhizosphere soil and non rhizosphere soil. In rhizosphere soil and non-rhizosphere soil,the mass fractions of lysine,phenylalanine,threonine,proline and glycine in susceptible varieties( Ⅲ,Ⅳ) were higher than those in resistant varieties(Ⅰ,Ⅱ). In rhizosphere soil,the total amino acids successively were Ⅳ > Ⅲ >Ⅰ> Ⅱ,and in non rhizosphere soil were Ⅲ > Ⅳ >Ⅰ> Ⅱ. The total amino acids in roots of variety Ⅳ was the highest,up to 6 359. 195 μg / g. In leaves,the total amino acids in varietiesⅠand Ⅱ were higher than those in varieties Ⅲ and Ⅳ. The results indicated that amino acids could secrete to rhizosphere via root secretion,and the compositions and mass fractions of amino acids varied with flue-cured tobacco varieties,thus the secretion amount of susceptible varieties was higher than that of resistant varieties.
基金supported by the National Key Research and Development Program(2021YFD1900100,2018YFD1000800)the National Natural Science Foundation of China(32072655,32172652)the China Agriculture Research System of MOF and MARA(CARS-23-B-10).
文摘Terrestrial plants can affect the growth and health of adjacent plants via interspecific interaction.Here,we studied the mechanism by which plant root exudates affect the recruitment of the rhizosphere microbiome in adjacent plants—with implications for plant protection—using a tomato(Solanum lycopersicum)–potatoonion(Allium cepa var.agrogatum)intercropping system.First,we showed that the intercropping system results in a disease-suppressive rhizosphere microbiome that protects tomato plants against Verticillium wilt disease caused by the soilborne pathogen Verticillium dahliae.Second,16S rRNA gene sequencing revealed that intercropping with potatoonion altered the composition of the tomato rhizosphere microbiome by promoting the colonization of specific Bacillus sp.This taxon was isolated and shown to inhibit V.dahliae growth and induce systemic resistance in tomato plants.Third,a belowground segregation experiment found that root exudates mediated the interspecific interaction between potatoonion and tomato.Moreover,experiments using split-root tomato plants found that root exudates from potatoonion,especially taxifolin—a flavonoid compound—stimulate tomato plants to recruit plant-beneficial bacteria,such as Bacillus sp.Lastly,ultra-high-pressure liquid chromatography–mass spectrometry analysis found that taxifolin alters tomato root exudate chemistry;thus,this compound acts indirectly in modulating root colonization by Bacillus sp.Our results revealed that this intercropping system can improve tomato plant fitness by changing rhizosphere microbiome recruitment via the use of signaling chemicals released by root exudates of potatoonion.This study revealed a novel mechanism by which interspecific plant interaction modulates the establishment of a disease-suppressive microbiome,thus opening up new avenues of research for precision plant microbiome manipulations.
基金supported by the National Natural Science Foundation of China(Nos.41991332,42122048 and 41907101).
文摘Root exudates are crucial for plants returning organic matter to soils,which is assumed to be a major source of carbon for the soil microbial community.This study investigated the influence of root exudates on the fate of arsenic(As)with a lab simulation experiment.Our findings suggested that root exudates had a dose effect on the soil physicochemical properties,As speciation transformation and the microbial community structure at different concentrations.The addition of root exudates increased the soil pH while decreased the soil redox potential(Eh).These changes in the soil pH and Eh increased As and ferrous(Fe(Ⅱ))concentrations in soil porewater.Results showed that 40 mg/L exudates addition significantly increased arsenite(As(Ⅲ))and arsenate(As(Ⅴ))by 541 and 10 times respectively within 30 days in soil porewater.The relative abundance of Fe(Ⅲ)-reducing bacteria Geobacter and Anaeromyxobacter increased with the addition of root exudates,which enhanced microbial Fe reduction.Together these results suggest that investigating how root exudates affect the mobility and transformation of As in paddy soils is helpful to systematically understand the biogeochemical cycle of As in soil-rice system,which is of great significance for reducing the health risk of soil As contamination.
基金supported by the National Key Research and Development Program of China (No. 2018YFC1800701)the National Natural Science Foundation of China (Nos. 21537005,21621064 and 21876187)。
文摘The release of root exudates(REs) provides an important source of soil organic carbon. This work revealed the molecular composition of REs of different plant species including alfalfa( Medicago sativa L.), bean( Phaseolus vulgaris L.), barley( Hordeum vulgare L.), maize( Zea mays), wheat( Triticum aestivum L.), ryegrass( Lolium perenne L.) and pumpkin( Cucurbita maxima) using electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry(ESI FT-ICR MS). The combination of positive ion mode( + ESI) and negative ion mode(-ESI) increased the number of the molecules detected by ESI FT-ICR MS, and a total of 8758 molecules were identified across all the samples. In detail, lipids and proteins and unsaturated hydrocarbons were more easily detected in + ESI mode, while aromatic compounds with high O/C were readily ionized in-ESI mode, and only 38% of the total assigned formulas were shared by -ESI and + ESI modes. Multivariate statistical analysis of the formulas indicated that the close related plants species secreted REs with similar molecular components. Moreover, the unsaturation degree and nitrogen content were the two key parameters able to distinguish the similarities and differences of molecular components of REs between plant species. The results provided a feasible analysis method for characterization of the molecular components of REs and for the first time characterized the molecular components of REs of a variety of plant species using ESI FT-ICR MS.
基金the National Natural Science Foundation of China(31902107)Natural Science Foundation of Jiangsu Province(BK20170724)National Postdoctoral Program for Innovative Talents(BX201600075).
文摘Plants are capable of releasing specific root exudates to recruit beneficial rhizosphere microbes upon foliar pathogen invasion attack,including long-chain fatty acids,amino acids,short-chain organic acids and sugars.Although long-chain fatty acids and amino acids application have been linked to soil legacy effects that improve future plant performance in the presence of the pathogen,the precise mechanisms involved are to a large extent still unknown.Here,we conditioned soils with long-chain fatty acids and amino acids application(L+A)or short-chain organic acids and sugars(S+S)to examine the direct role of such exudates on soil microbiome structure and function.The L+A treatment recruited higher abundances of Proteobacteria which were further identified as members of the genera Sphingomonas,Pseudomonas,Roseiflexus,and Flavitalea.We then isolated the enriched bacterial strains from these groups,identifying ten Pseudomonas strains that were able to help host plant to resist foliar pathogen infection.Further investigation showed that the L+A treatment resulted in growth promotion of these Pseudomonas strains.Collectively,our data suggest that long-chain fatty acids and amino acids stimulated by foliar pathogen infection can recruit specific Pseudomonas populations that can help protect the host plant or future plant generations.
基金funded by the National Key Basic Research Program of China under Grant No. 2013CB956701the National Natural Science Foundation of China under Grant No. 31070365Funded by talents introduction of Anqing Normal University (No. 14000100032)
文摘The effect of zinc(Zn) deficiency and excessive bicarbonate on the allocation and exudation of organic acids in plant organs(root, stem, and leaf) and root exudates of two Moraceae plants(Broussonetia papyrifera and Morus alba) were investigated. Two Moraceae plants were hydroponically grown and cultured in nutrient solution in four different treatments with 0.02 mM Zn or no Zn,combined with no or 10 mM bicarbonate. The variations of organic acids in different plant organs were similar to those of root exudates in the four treatments except B. papyrifera, which was in a treatment that was a combination of 0.02 mM Zn and no bicarbonate. The response characteristics in the production, translocation, and allocation of organic acids in the plant organs and root exudates varied with species and treatments. Organic acids in plant organs and root exudates increased under Zn-deficient conditions,excessive bicarbonate, or both. An increase of organic acids in the leaves resulted in an increase of root-exuded organic acids. B. papyrifera translocated more oxalate and citrate from the roots to the rhizosphere than M. alba under the dual influence of 10 mM bicarbonate and Zn deficiency. Organic acids of leaves may be derived from dark respiration and photorespiration. By comparison, organic acids in stems, roots, and root exudates may be derived from dark respiration and organic acid translocation from the leaves. These results provide evidence for the selective adaptation of plants to environments with low Zn levels or high bicarbonate levels such as a karst ecosystem.
基金the National Natural Science Foundations of China(31772229 and 31660546)。
文摘Rhizosphere microbial communities play important roles in facilitating or inhibiting the establishment of exotic species.Since some invasive plants interact with soil microbial communities such as rhizosphere bacteria,changes triggered by rhizosphere bacteria may alter competitive interactions between exotic and native plants.This study compared the Bacillus cereus content in soils with different degrees of Ageratina adenophora invasion,and investigated the effects of A.adenophora allelochemicals on B.cereus growth and soil characteristics and the feedback effects of B.cereus on A.adenophora growth.Bacillus cereus content in the rhizosphere of A.adenophora increased with intensification of the invasion process,and newly invaded soil contained almost twice as much bacteria as noninvaded soil.When rhizosphere soil was added to the root exudates of A.adenophora,the contents of B.cereus were twice as much as the control,except on the first day.Certain soil parameters increased significantly,such as ammonium nitrogen(NH_(4)^(+)-N)and available phosphorus(AP),which were increased by 41 and 27%,respectively.Soil treatment with B.cereus promoted the degradation of two allelochemicals from the rhizosphere of A.adenophora,amorpha-4,7(11)-dien-8-one and 6-hydroxy-5-isopropy1-3,8-dimethyl-4 a,5,6,7,8,8 ahexahydraphthalen-2(1 H)-one,to varying degrees;and increased the germination rate by 50%,root length by 117%,shoot length by 48%and fresh weight by 81%for A.adenophora compared to those of untreated soil.Our results confirmed that the invasion of A.adenophora will promote an increase of B.cereus,a beneficial rhizosphere bacterium,which in turn induces a positive feedback effect on A.adenophora.
文摘Pseudomonas stutzeriA1501, associative and endophytic nitrogen-fixing bacterium showed the capacity of colonization in the rice roots and considered as the good colonizer in the rice plant. The experiment was conducted to study the expression of genes potentiality relevant to the association of nitrogen fixing Pseudomonas stutzeri with host rice and reveal the molecular mechanism by which underlying interaction between bacteria and host rice. The bacteria were shown to be uniformly distributed on the rhizoplane of the root and the density of bacteria was found at the intercellular junction and micro colony developed on the surface of the epidermal cells and on the cellular junctions. Root exudates of rice were the major components of carbon and energy sources for bacteria. RT-PCR analyses of pilK, metE, rpoN and fdhE genes expression of P. stutzeri A1501 were performed at positive and negative (control) conditions. After 1 h, it was found that pilK, metE and rpoN transcription were increased 5.7, 6.4 and 3.4-fold, respectively, whereas in the fdhE gene has no expression. Consequently, after 4 h pilk, fdhE, metE and rpoN were decreased -1.9, -4.4, -0.2 and -0.8-fold, respectively. The gene pilK, expression was up-regulation after 1 h and down-regulation after 4 h that has twitching motility to convey the bacterial cell to point of attachment in to host plant. The gene expressions of the bacteria, pilK, metE, rpoN and fdhE were up- and down-regulated during the influence of root exudates which regulated the colonization of bacteria during plant-microbe interaction.
基金the National Key Research and Development Program of China(2021YFD1900100,2022YFD1500202,and 2022YFF1001804)the Fundamental Research Funds for the Central Universities(KYT2023001)+1 种基金the National Natural Science Foundation of China(42325704,41922053,31972504,and 42377118)V.P.F.is funded by the Royal Society(RSG\R1\180213 and CHL\R1\180031)and jointly by a grant from UKRI,Defra,and the Scottish Government,under the Strategic Priorities Fund Plant Bacterial Diseases program(BB/T010606/1)at the University of York.
文摘The RIPENING-INHIBITOR(RIN)transcriptional factor is a key regulator governing fruit ripening.While RIN also affects other physiological processes,its potential roles in triggering interactions with the rhizosphere microbiome and plant health are unknown.Here we show that RIN affects microbiome-mediated disease resistance via root exudation,leading to recruitment of microbiota that suppress the soil-borne,phytopathogenic Ralstonia solanacearum bacterium.Compared with the wild-type(WT)plant,RIN mutants had different root exudate profiles,which were associated with distinct changes in microbiome composition and diversity.Specifically,the relative abundances of antibiosis-associated genes and pathogensuppressing Actinobacteria(Streptomyces)were clearly lower in the rhizosphere of rin mutants.The composition,diversity,and suppressiveness of rin plant microbiomes could be restored by the application of 3-hydroxyflavone and riboflavin,which were exuded in much lower concentrations by the rin mutant.Interestingly,RIN-mediated effects on root exudates,Actinobacteria,and disease suppression were evident from the seedling stage,indicating that RIN plays a dual role in the early assembly of diseasesuppressive microbiota and late fruit development.Collectively,our work suggests that,while plant disease resistance is a complex trait driven by interactions between the plant,rhizosphere microbiome,and the pathogen,it can be indirectly manipulated using"prebiotic"compounds that promote the recruitment of disease-suppressive microbiota.
文摘Rice paddy-field microbial fuel cells (RPF-MFCs) are devices that exploit rhizosphere bacteria to generate electricity from soil organic matter, including those excreted from roots. Previous studies have examined factors affecting electric outputs from RPF-MFCs and demonstrated that RPFMFC was able to generate electricity up to 80 mW·m<sup>-2</sup> (based on the projected area of anode). The present study operated RPF-MFCs with different sizes of anodes and cathodes and examined how electrode sizes affected electricity generation. We show that anodes are the limiting factor for electricity generation immediately after commencing the operation, while cathodes become the limiting factor after anode performances are sufficiently increased. RPF-MFC achieved the maximum power density of 140 mW·m<sup>-2</sup> (based on the projected area of anode), when the cathode is sufficiently larger than the anode. Results suggest that the cathode needs to be improved for eliciting the maximum capacity of rhizosphere bacteria for electricity generation in RPF-MFC.
文摘As a special form of allelopathy,autotoxicity is common in cucurbits,and it is one of main factors inducing continuous cropping obstacles.Therefore,the autotoxicity research has both theoretical and practical significance on overcoming continuous cropping obstacles.In this review,commencing on the concept of autotoxicity,research results of autotoxicity in watermelon in recent years were summarized.The significance of researches on autotoxicity in watermelon,watermelon root exudate and its autotoxicity,and the autotoxicity of watermelon stubble and the mechanisms were explained.Meanwhile,some questions needed to be further studied.
基金funded by the National Research Foundation(NRF)of South Africa(UID123634 and UID132595)which was granted to Olubukola O.Babalola。
文摘Climate change,urbanization,and population increase limit food availability.To sustain human existence,there is the need to increase food and agricultural production to mitigate the impact of these factors.Scientists have been working for years on ways to increase food production.From plant breeding techniques to soil science,scientists have made tremendous progress.The rhizobiome has been proven to be important to crop production,and the impact of the rhizobiome on plant health cannot be overemphasized.Being rich in diverse complex microbial interactions,the rhizosphere has become a major force in recent plant growth promotion studies.The upsurge in next-generation sequencing applications with the various“omics”technologies is helping to unearth information relating to rhizosphere impact on plant growth.Explaining the complex interactions between and across microbial species present in the rhizosphere is important to further enhance our understanding of their mechanistic and mutualistic functions.Knowledge from this can be used in rhizosphere biome engineering for improved plant growth and yield in the face of the various biotic and abiotic challenges.
文摘The present experiment was conducted to evaluate the influence of </span><i><span style="font-family:Verdana;">Lamiaceae </span></i><span style="font-family:Verdana;">herbs companion planting on growth and secondary metabolites changes in tomato plants. Furthermore, the free amino acid changes in tomato due to companion planting w</span></span><span style="font-family:Verdana;">ere</span><span style="font-family:Verdana;"> also evaluated using tomato-basil companionship as a model. Four-week-old seedlings of tomato were grown in a pot containing autoclaved commercial soil with basil, peppermint and hyssop as a companion plant separately in different density. Four weeks after companion planting, tomato plants under 1:1 companionship with the herbs showed significant increase in dry weights of shoots compared to control. Higher density of the herbs on the other hand expressed a growth suppression on tomato possibly due to nutrient competition. By the LC-MS analysis, shikimic acid and apigenin were identified as the major secondary compounds found in tomato plants and 1:1 companionship with basil seemed to have a positive influence on their content in tomato shoots. On the other hand, in case of peppermint and hyssop, the increase was observed in all parts of tomato plants. In addition, promotion in several free amino acid contents w</span><span style="font-family:Verdana;">as</span><span style="font-family:Verdana;"> also observed in tomato plants with basil companion planting compared to control. Thus, tomato plants grown with herb companion planting in 1:1 ratio seems to have a positive impact on growth of tomato. This positive influence might be related to the increase in some secondary metabolites and changes in the free amino acids observed in this study.
文摘There is increasing evidence of plant communication and behavior. We examine how two Lactuca species, L. sativa andL. serriola, communicate with themselves and one another via root exudates. We exposed both species to their own, to the same species, and to the other species root exudates. We then measured the length of their primary root as a proxy for competitive effort. L. serriola produced longer roots when exposed to its own exudates relative to when exposed to L. sativa’s. In contrast, L. sativa produced shorter roots when exposed to its own root exudates. These results indicate kin recognition in these species. Further, the results show that L. sativa, a domesticated species, shares resources well with conspecifics. In contrast, L. serriola, a sparsely distributed species, is more competitive with conspecifics than with other species. We argue that artificial selection and domestication of L. sativa, from its progenitor L. serriola, modify how the species interprets and respond to exudate cues from neighboring plants.
基金supported by National Natural Science Foundation of China(Grants No.31902107 and 41977271)Natural Science Foundation of Jiangsu Province(Grant No.BK20211577)+3 种基金the Innovative Research Team Development Plan of the Ministry of Education of China(Grant No.IRT_17R56)supported by Qing Lan Project of Jiangsu Provincethe support by the RUDN University Strategic Academic Leadership Programthe WeChat subscription ID“meta-Genome”and“Micro-Bioinformatics and microflora”for the analysis methods.
文摘Plant roots are one of the major mediators that allocate carbon captured from the atmosphere to soils as rhizodeposits,including root exudates.Although rhizodeposition regulates both microbial activity and the biogeochemical cycling of nutrients,the effects of particular exudate species on soil carbon fluxes and key rhizosphere microorganisms remain unclear.By combining high-throughput sequencing,q-PCR,and NanoSIMS analyses,we characterized the bacterial community structure,quantified total bacteria depending on root exudate chemistry,and analyzed the consequences on the mobility of mineral-protected carbon.Using well-controlled incubation experiments,we showed that the three most abundant groups of root exudates(amino acids,carboxylic acids,and sugars)have contrasting effects on the release of dissolved organic carbon(DOC)and bioavailable Fe in an Ultisol through the disruption of organo-mineral associations and the alteration of bacterial communities,thus priming organic matter decomposition in the rhizosphere.High resolution(down to 50 nm)NanoSIMS images of mineral particles indicated that iron and silicon colocalized significantly more organic carbon following amino acid inputs than treatments without exudates or with carboxylic acids.The application of sugar strongly reduced microbial diversity without impacting soil carbon mobilization.Carboxylic acids increased the prevalence of Actinobacteria and facilitated carbon mobilization,whereas amino acid addition increased the abundances of Proteobacteria that prevented DOC release.In summary,root exudate functions are defined by their chemical composition that regulates bacterial community composition and,consequently,the biogeochemical cycling of carbon in the rhizosphere.
基金supported by the National Science Foundation for Young Scientists of China(41601266)the Natural Science Foundation of Jiangsu Province(SBK2020023002)the Special Fund for Basic Scientific Research by Jiangsu Academy of Agricultural Sciences(ZX(2020)3011).
文摘Sugars are frequently and abundantly found in root exudates,but influence of specific sugars on the fate of soil-borne pathogens,microbiome structure,and particularly microbial interactions are not well understood.A 42-day of microcosm incubation was conducted with two soils:a natural watermelon Fusarium wilt pathogen(i.e.,Fusarium oxysporum f.sp.niveum(FON))-infested soil(Low-FON soil)and the soil further receiving the wilt pathogen inocula(High-FON soil).Both soils were supplemented with four simple sugars before incubation.The results show that,in both soils,FON was enriched by all sugars although co-living with tremendously diverse microbes;and bacterial richness,evenness,and diversity were decreased and bacterial community structure was changed by all sugars.Bacterial richness and evenness were negatively correlated with FON quantity in both Low-FON and High-FON soils,indicating that FON may tend to live in soil with low alpha-diversity.In both Low-FON and High-FON soils,the sugar-spiked networks had more links,higher density,larger modules,and shorter harmonic geodesic distance,suggesting greater potentials for microbial interaction and niche-sharing.The positive links between some of the keystone taxa and FON indicates that these keystone taxa may have promoted FON.This may be one of reasons why FON could proliferate vigorously after sugar supplementation.
基金the NSFC-Henan Joint Fund(U1804101,U1904204)Henan Key Scientific and Technological Project(192102110160)+1 种基金the National Natural Science Foundation of China(31800405)Innovation Scientists and Technicians Troop Construction Projects of Henan Province.
文摘Aboveground litter inputs and root exudates provide basal resources for soil communities,however,their relative contributions to soil food web are still not well understood.Here,we conducted a field manipulative experiment to differentiate the effects of litter inputs and living root on nematode community composition of surface and subsoils in a young Acacia crassicapa plantation in southern China.Our results showed that both litter addition and root presence significantly enhanced soil nematode abundance by 17.3%and 35.3%,respectively.Litter addition altered nematode trophic group composition,decreased fungivore to bacterivore ratio,and enhanced maturity index and structure index,which led to a bacterial-based energy channel and a more complex food web structure.However,root presence had a limited impact on the nematode community composition and ecological indices.Despite nematodes surface assembly,soil depth did not affect nematode trophic group composition or ecological index.Our findings highlight the importance of litter inputs in shaping soil nematode community structure and regulating soil energy channel.
基金This work was supported by the Shanghai Municipal Science and Technology Commission(No.16391902100)the Shanghai Construction Group(No.19JCSF-12)the Ministry of Agriculture,P.R.China and Shanghai Engineering Research Center of Plant Germplasm Resources(No.17DZ2252700).
文摘Rhizospheres can promote self-transmissible plasmid transfer,however,the corresponding mechanism has not received much attention.Plant-microbe remediation is an effective way to promote pollutant biodegradation;however,some pollutants,such as naphthalene,are harmful to plants and result in inefficient plant-microbe remediation.In this study,trans-fer of a TOL-like plasmid,a self-transmissible plasmid loaded with genetic determinants for pollutant degradation,among different bacteria was examined in bulk and rhizosphere soils as well as addition of maize root exudate and its artificial root exudate(ARE).The results showed that the numbers of transconjugants and recipients as well as bacterial metabolic activities,such as xylE mRNA expression levels and catechol 2,3-dioxygenase(C23O)activ-ities of bacteria,remained high in rhizosphere soils,when compared with bulk soils.The number of transconjugants and bacterial metabolic activities increased with the increasing exudate and ARE concentrations,whereas the populations of donor and recipient bacteria were substantially unaltered at all concentrations.All the experiments consistently showed that a certain number of bacteria is required for self-transmissible plasmid transfer,and that the increased plasmid transfer might predominantly be owing to bacterial metabolic activ-ity stimulated by root exudates and ARE.Furthermore,ARE addition increased naphthalene degradation by transconjugants in both culture medium and soil.Thus,the combined action of a wide variety of components in ARE might contribute to the increased plasmid transfer and naphthalene degradation.These findings suggest that ARE could be an effectively al-ternative for plant-microbe remediation of pollutants in environments where plants cannot survive.
基金supported by the National Key R & D Program of China (Nos. 2017YFD0200200 and 2017YFD0200202)Projects of International Cooperation and Exchanges NSFC (No. 31210103906)Wageningen University Sandwich Ph.D. Fellowship (The Netherlands)。
文摘Plant species have different traits for mobilizing sparingly soluble phosphorus (P) resources,which could potentially lead to overyielding in P uptake by plant species mixtures compared to monocultures due to higher P uptake as a result of resource (P) partitioning and facilitation.However,there is circumstantial evidence at best for overyielding as a result of these mechanisms.Overyielding (the outcome) is easily confused with underlying mechanisms because of unclear definitions.We aimed to define a conceptual framework to separate outcome from underlying mechanisms and test it for facilitation and complementarity with respect to P acquisition by three plant species combinations grown on four soils.Our conceptual framework describes both mechanisms of complementarity and facilitation and outcomes (overyielding of mixtures or no overyielding) depending on the competitive ability of the species to uptake the mobilized P.Millet/chickpea mixtures were grown in pots on two calcareous soils mixed with calcium-bound P (CaP) and phytate P (PhyP).Cabbage/faba bean mixtures were grown on both acid and neutral soils mixed with P-coated iron (hydr)oxide (FeP) and PhyP.Wheat/maize mixtures were grown on all four soils.Rhizosphere carboxylate concentration and acid phosphatase activity (mechanisms) as well as plant P uptake and biomass (outcome) were determined for monocultures rhizosphere and species mixtures.Facilitation of P uptake occurred in millet/chickpea mixtures on one calcareous soil.We found no indications for P acquisition from different P sources,neither in millet/chickpea,nor in cabbage/faba bean mixtures.Cabbage and faba bean on the neutral soil differed in rhizosphere acid phosphatase activity and carboxylate concentration,but showed no overyielding.Wheat and maize,with similar root exudates,showed overyielding (the observed P uptake being 22%higher than the expected P uptake) on one calcareous soil.We concluded that although differences in plant physiological traits (root exudates) provide necessary conditions for complementarity and facilitation with respect to P uptake from different P sources,they do not necessarily result in increased P uptake by species mixtures,because of the relative competitive ability of the mixed species.
