植物提取影响因素研究进展

Hyperaccumulators concentrate trace metals and heavy metals in their shoots when grown in metal-contaminated soils and these trace metal-loaded plants may be removed by harvesting the fields. Studies exploring the beneficial role of these hyperaccumulators to clean up the environment have led to the development of phytoextraction. The success of phytoextraction depends upon the high biomass of plant species and bioavailability of metals for plant uptake. The phytoavailability of metals is influenced by soil-associated factors, such as pH, redox potential, cation exchange capacity, soil type, and soil texture, and by plant-associated factors, such as root exudates and root rhizosphere processes (microorganisms). Efficiency of phytoextraction can be improved by advanced agronomic practices including soil and crop management by application of genetic engineering to enhance the metal tolerance, shoot translocation, accumulation, and sequestration and by application of chelate treatments to enhance metal bioavailability. Application of microorganisms including bacteria and mycorrhiza may facilitate the phytoextraction application at commercially large scale.     

沼泽红假单胞菌与枯草芽孢杆菌混施对水稻根域细菌多样性与功能的影响

[目的]微生物菌肥作为一种绿色环保的生物肥料,可以改善土壤质量,促进作物生长.以水稻根际和根表微生物为对象,探究不同微生物菌肥单施和混施对其群落多样性和功能的影响.[方法]采用盆栽试验,设单施沼泽红假单胞菌(Rhodopseudomonas palustris)、单施枯草芽孢杆菌(Bacillus subtilis)及...     

Effects of interactions between arbuscular mycorrhizal fungi and bacteria on the growth of Lotus corniculatus L.: From the perspective of regulating rhizosphere fungal community

Arbuscular mycorrhizal fungi (AMF) provide essential nutrients to crops and are affected by fertilizers. Phosphate-solubilizing bacteria (PSB), nitrogen-fixing bacteria (NFB), and AMF have mutually beneficial relationships with plants, but the effects of their interactions on plant growth by regulating rhizosphere fungal community have not been sufficiently studied. In this study, a greenhouse pot experiment was conducted to investigate the interactions between AMF and bacteria (PSB and NFB) on the growth of Lotus corniculatus L. Specifically, the role of rhizosphere fungal community in the growth of Lotus corniculatus L. was explored using Illumina MiSeq high-throughput sequencing. The results showed that combined inoculation of AMF with PSB and NFB increased plant biomass, plant height, and fungal colonization rate. The richness, complexity, and stability of rhizosphere fungal community also increased after combined inoculation of AMF with PSB and/or NFB, particularly with PSB. In addition, combined inoculation of AMF with PSB and NFB enriched the abundance of beneficial microorganisms, with Chaetomium and Humicola showing the greatest alterations. The structural equation model showed that the interactions of AMF with PSB and NFB promoted plant growth by affecting fungal network structure and soil enzyme activities involved in carbon, nitrogen, and phosphorus cycling. These findings provide evidence for the effects of interactions of AMF with PSB and NFB on rhizosphere fungal community and plant growth.     

植物提取影响因素研究进展（英文）

Hyperaccumulators concentrate trace metals and heavy metals in their shoots when grown in metal-contaminated soils and these trace metal-loaded plants may be removed by harvesting the fields.Studies exploring the beneficial role of these hyperaccumulators to clean up the environment have led to the development of phytoextraction.The success of phytoextraction depends upon the high biomass of plant species and bioavailability of metals for plant uptake.The phytoavailability of metals is influenced by soilassociated factors,such as pH,redox potential,cation exchange capacity,soil type,and soil texture,and by plant-associated factors,such as root exudates and root rhizosphere processes(microorganisms).Efficiency of phytoextraction can be improved by advanced agronomic practices including soil and crop management by application of genetic engineering to enhance the metal tolerance,shoot translocation,accumulation,and sequestration and by application of chelate treatments to enhance metal bioavailability.Application of microorganisms including bacteria and mycorrhiza may facilitate the phytoextraction application at commercially large scale.     

Soil protozoa and forest tree growth: non-nutritional effects and interaction with mycorrhizae

Mycorrhizal (Lactarius rufus Fr.) and non-mycorrhizal Norway spruce seedlings (Picea abies Karst.) were grown in a sand culture and inoculated with protozoa (naked amoebae and flagellates) extracted from native forest soil or with protozoa grown on agar cultures. A soil suspension from which the protozoa were eliminated by filtration or chloroform fumigation was used as a control. After 19 weeks of growth in a climate chamber at 20–22°C, the seedlings were harvested. Protozoa reduced the number of bacterial colony-forming units extracted from the rhizoplane of both non-mycorrhizal and mycorrhizal seedlings and significantly increased seedling growth. However, concentrations of mineral nutrients in needles were not increased in seedlings with protozoan treatment. It is concluded that the increased growth of seedling was not caused by nutrients released during amoebal grazing on rhizosphere micro-organisms. The protozoa presumably affected plant physiological processes, either directly, via production of phytohormones, or indirectly, via modification of the structure and performance of the rhizosphere microflora and their impact on plant growth. Mycorrhizal colonization significantly increased the abundance of naked amoebae at the rhizoplane. Our observations indicate that protozoa in the rhizosphere interact significantly with mycorrhizae.     

N2-fixing bacteria in the rhizosphere: Quantification and hormonal effects on root development

The paper summarizes the results of a series of experiments on enumeration of N₂-fixing bacteria (diazotrophs) and hormonal effects of Azospirillum on root development. Numbers of N₂-fixing and N-heterotrophic bacteria were determined on the root (rhizoplane plus “inner” root surface) and in the rhizosphere soil (0–3 mm from the root surface) of Arrhenatherum elatius, other forage grasses and some herbaceous plant species. Pot experiments involved freshly collected soil from an unfertilized grassland area containing its natural population of N₂-fixing bacteria. The MPN (most probable number) of diazotrophs in relation to the MPN of the total bacterial population was always lower on the root than in the rhizosphere soil, suggesting that diazotrophs were not selectively advantaged at the root surface. Supply of mineral nitrogen (NH₄NO₃) decreased the proportion of N₂-fixing bacteria at the rhizoplane as well as in the rhizosphere soil. Similar results were obtained when N was supplied via the leaves. The data suggest that N₂-fixing bacteria in the rhizosphere are poor competitors once they loose their competitive advantage of binding dinitrogen. Correspondingly, the increase in the MPN of the diazotrophs found during plant development was interpreted as a result of decreased available combined N in the rhizosphere. The proportion of N₂-fixing bacteria relative to the total number of bacteria was generally below 1%. Considering the potential amount of substrate released from the roots and the substrate requirement of the bacterial population, N₂-fixation was considered insignificant for plant growth under the given conditions. For the investigations on possible beneficial effects on plant development by bacterial hormones, Azospirillum brasilense was chosen because evidence suggests that amongst the soil bacteria releasing hormones, especially IAA, certain strains of this species are more important than other bacteria. Application of A. brasilense Cd (ATCC 29710) onto the roots of young wheat plants grown in soil increased the number of lateral roots, the total root length and the number of root hairs. Similar results were obtained after application of IAA. This suggests that IAA is an important factor responsible for the effects observed after inoculation with A. brasilense. The increase in root surface may improve acquisition of nutrients and enhance growth of plants. Another hormonal effect of A. brasilense was an increase in nodulation of Medicago sativa grown on agar. Again pure IAA resulted in a similar increase in nodule number. Increases in nodule number were only in part associated with a change in root morphology. Therefore an effect of IAA on the plant immanent regulation system for nodulation is likely.     

Resistance of bacterial communities in the potato rhizosphere to disturbance and its application to agroecology

Soil bacteria have the ability to increase agricultural sustainability through the production of biopesticides and biofertilizers. Application of bacteria to field crops often results in sporadic colonization and unpredictable crop performance. This research sought to understand the colonization of the potato (Solanum tuberosum L.) rhizosphere using reciprocal transplants. Plants were grown in a forest or an agricultural soil and then transplanted into either the same soil or the opposite soil. Bacterial communities were profiled using terminal restriction fragment length polymorphism (TRFLP) and analyzed using pairwise comparisons. The results revealed that the bacterial community that colonized the rhizosphere in the first soil remained mostly intact for 30 days after the plants were transplanted into another soil in which the soil bacteria community differed from that found in the original soil. The concept that it may be possible to establish a functional microbiota and to deliver it to an agricultural environment was tested. A nitrogen-fixing bacterial community was established on plants grown under tissue culture conditions and the plants were transplanted into a field soil. Plants inoculated with eight separate nitrogen-fixing communities showed an average fivefold increase in dry biomass when compared to mock-inoculated plants and the microbial profiles remained distinct at 30 days after transplantation. These results demonstrate that the plant rhizosphere is a resistant community and that the first bacterial community that becomes established on the root remains with the plant even when the plant is placed into soil with a vastly different microbiota.     

抗病性不同大豆品种根面及根际微生物区系的变化 Ⅰ.非连作大豆(正茬)根面及根际微生物区系的变化

采用平板计数法测定了3个抗病性不同的大豆品种在生育期内根面和根际微生物区系的变化情况,并应用荧光计数法直接测定了根际细菌和真菌的生物量。结果表明,土体的微生物种类最丰富、根际的次之、根面的较单一。播种后从三叶期到鼓粒初期,根面和根际的可培养细菌总数随生育期逐渐增加,鼓粒初期达最大值,而成熟期则有明显的下降;大豆根际细菌生物量也存在相同的变化规律。抗病性不同的大豆品种其根面、根际可培养细菌总数存在差异;抗病品种大豆的根瘤重明显高于感病品种。种植一季后感病品种根际积累的病原生物(镰孢霉Fusarium.sp.和大豆胞囊线虫Heterodera.glycines的胞囊数)明显高于抗病品种。说明大豆根系分泌物对微生物具有选择性的促进或抑制作用,不同大豆品种以及同一大豆品种在不同生育时期根系分泌物的组成和数量不同,从而使大豆根面及根际形成了特定的微生物区系组成。     

土传病原细菌的生存与致病权衡

土传病原细菌严重威胁土壤-植物系统健康和农业可持续发展。在接触和入侵寄主植物根系之前,病原细菌会经受土壤pH、含氧量、营养物质种类和数量等非生物因素骤变以及其他土壤微生物的竞争、寄生和捕食等生物胁迫。病原细菌的生物膜形成、代谢、运动、毒力、DNA修复以及对噬菌体、抗生素或环境压力的抵抗能力等特性对其在土壤环境中生存和侵染寄主非常重要。为适应复杂且多变的土壤生物和非生物环境,病原细菌必须动态权衡其生存和致病力之间的关系,维持其生存、传播、增殖和侵染致病间的平衡,以最大化其在土壤环境中的适应性。系统理解土传病原细菌应对胁迫和侵染寄主植物的过程及权衡机制是建立精准、高效生态防控手段的关键。为此,以土传病原细菌为代表,总结了土传病原细菌生存与致病的权衡规律和典型现象及土壤中的生物和非生物影响因素,阐述了土传病原细菌入侵植物根际过程中的生存与致病权衡机制,并提出一些与土传病原细菌生存与致病权衡相关的科学问题,呼吁建立基于生存-致病权衡理论的土传病害生态防控策略,为绿色农业可持续发展提供理论参考。     

抗病性不同大豆品种根面及根际微生物区系的变化 Ⅱ.连作大豆(重茬)根面及根际微生物区系的变化

采用平板计数法测定了两个抗根腐病连作大豆品种生育期间根面和根际微生物区系动态变化。结果表明,两个品种大豆根面细菌随生育期增加呈递减趋势,品种间无差异。合丰25(H25)的根际细菌数量随生育期呈递减趋势,绥农10号(S10)根际细菌数量从三叶期到鼓粒初期不断增加,到成熟期又急剧减少。感病品种H25根瘤重明显低于抗病品种S10。H25根面真菌和镰孢霉总数在三叶期和成熟期均高于S10,苗期是根腐病的主要发病期。总之,在连作条件下,无论抗病品种还是感病品种大豆成熟期其根面和根际细菌减少,真菌和主要病原菌(镰孢霉Fusarium)都会大量富集,表明根系分泌物对根面和根际的微生物种群有选择性地促进或抑制作用。     

土传病原细菌的生存与致病权衡

土传病原细菌严重威胁土壤-植物系统健康和农业可持续发展。在接触和入侵寄主植物根系之前,病原细菌会经受土壤pH、含氧量、营养物质种类和数量等非生物因素骤变以及其他土壤微生物的竞争、寄生和捕食等生物胁迫。病原细菌的生物膜形成、代谢、运动、毒力、DNA修复以及对噬菌体、抗生素或环境压力的抵抗能力等特性对其在土壤环境中生存和侵染寄主非常重要。为适应复杂且多变的土壤生物和非生物环境,病原细菌必须动态权衡其生存和致病力之间的关系,维持其生存、传播、增殖和侵染致病间的平衡,以最大化其在土壤环境中的适应性。系统理解土传病原细菌应对胁迫和侵染寄主植物的过程及权衡机制是建立精准、高效生态防控手段的关键。为此,以土传病原细菌为代表,总结了土传病原细菌生存与致病的权衡规律和典型现象及土壤中的生物和非生物影响因素,阐述了土传病原细菌入侵植物根际过程中的生存与致病权衡机制,并提出一些与土传病原细菌生存与致病权衡相关的科学问题,呼吁建立基于生存-致病权衡理论的土传病害生态防控策略,为绿色农业可持续发展提供理论参考。     

Bacteria and fungi on roots of different barley varieties (Hordeum vulgare L.)

Summary We investigated the abundance of bacteria and fungi on roots of different barley varieties grown in soil and in a nutrient solution. Measurements were made on the rhizoplane and, for soil-grown plants, also in the rhizosphere soil. Further, the influence of plant age was investigated. Barley variety, had a significant influence both for plants grown in soil and in the nutrient solution, and the effects were most pronounced on the rhizoplane. There were no significant differences among varieties in fungal hyphal lengths on the roots. Bacterial abundance on the rhizoplane was significantly decreased with increasing plant age. Varietal differences were maintained over different plant ages.     

植物化感作用类型及其在农业中的应用

本文总结前人研究成果的基础上,对不同植物化感作用类型及其作用机制和在农业中的应用进行了探讨。植物化感作用包括化感偏害作用、自毒作用、自促作用和互惠作用。植物化感偏害作用是由植物根系分泌物介导下的植物与特异微生物共同作用的结果。利用植物化感偏害作用控制田间杂草是一项环境友好型的可持续农业技术,并已在水稻化感抑草研究方面取得了较突出的成果。植物化感自毒作用(作物连作障碍)是造成作物产量降低、生长状况变差、品质变差、病虫害频发的现象。药用植物,特别是以根部入药的药用植物中,连作障碍表现更为突出。近年来研究结果认为根系分泌物生态效应的间接作用及土壤微生物区系功能紊乱是导致植物连作障碍的主要因素。因此,改善土壤生长环境,恢复和修复根际土壤微生物结构平衡,增强生态系统机能是克服作物连作障碍的关键。植物化感自促作用(连作促进作用)是在植物根系分泌物促进下,根际土壤微生物之间此消彼长,有益微生物之间互利协作,土壤肥力和营养补给能力明显改善,从而增强植物根系抗性,促进植物生长发育,提高产量和品质的结果。牛膝的连作促进作用明显,有学者试图通过牛膝与其他不耐连作药用植物间作套种或轮作,实现药用植物生产的可持续发展。植物间的正相互作用(互惠作用)是作物间套种系统超产和养分等资源高效利用的重要机制,根系分泌物在介导根际微生物与植物的有利互作中起到重要作用。最后作者强调指出,存在于根际土壤的微生物群落的宏基因组组成是决定植物能否健康生长的关键。深入研究存在于土壤生态系统中的植物体外基因组的组成与演化机制,将成为借用现代合成生物学原理与技术,定向控制植物根际生物学过程,促进作物生产可持续发展的优先研究领域。     

Use of chrome azurol S reagents to evaluate siderophore production by rhizosphere bacteria

Summary Siderophores produced by rhizosphere bacteria may enhance plant growth by increasing the availability of Fe near the root or by inhibiting the colonization of roots by plant pathogens or other harmful bacteria. To examine the populations of siderophore-producing bacteria colonizing the roots of two grass species that differed in their susceptibility to Fe deficiency, we inoculated serial dilutions of root samples onto chrome azurol S (CAS) agar and several other selective and non-selective culture meida. CAS agar effectively differentiated bacteria that were capable of excreting large amounts of siderophore, but the composition of the medium limited its usefulness for ecological studies. A large proportion (71–79%) of the bacterial population that grew on a non-selective medium (tryptic soy agar) failed to grow on CAS agar, and several isolates that showed no sign of siderophore production on CAS agar produced siderophore in liquid culture. Similar populations of siderophore-producing bacteria were observed on roots of St. Augustine grass, which frequently exhibits Fe chlorosis, and bermuda grass, which does not. Roots of both grasses were colonized by bacteria that produced siderophore in vitro at concentrations ranging from 100 to 230 M. The CAS assay solution was also used to compare siderophore production by Pseudomonas fluorescens Q6, an isolate from bermuda grass, and by P. putida B 10, a plant growth-promoting pseudomonad. P. fluorescens Q6 produced 2.4 times more siderophore in vitro than P. putida B 10.     

Vitamin production in relation to phosphate solubilization by soil bacteria

Studies were conducted to determine the relationship of vitamin production and ability to dissolve bicalcium phosphate in bacteria isolated from rhizosphere, rhizoplane and control soil. Production of vitamin B₁₂, riboflavin, niacin, pantothenate and biotin was determined using a bioassay procedure that may be useful for large-scale screening of bacteria for vitamin production.Among isolates producing one or more vitamins, 76.4, 37.5 and 57.5% of control, rhizosphere and rhizoplane isolates, respectively, solubilized phosphate. However, phosphate-solubilizing isolates from rhizosphere and rhizoplane were more active vitamin producers than solubilizing isolates from control soil, and non-solubilizing isolates from any of the three regions.Production of vitamin B₁₂, riboflavin and niacin by rhizosphere isolates and of riboflavin by rhizoplane isolates was also correlated with ability to solubilize phosphate, but similar relationships were not observed for control isolates.     

水稻根际反硝化细菌生态分布的研究

本文报道了三种土壤中水稻根际反硝化细菌的生态分布及两种作物对根际反硝化细菌的影响.结果表明:水稻各生育期菌数均以根面大于根际,又大于根外,R/S值为10-100以上.水稻与大麦的根面及根际反硝化细菌与细菌总数均以抽穗期最多,成熟期菌数明显下降,但水稻不同生育期菌数高于大麦相应时期的菌数.其优势种根面比根际者单纯;同一土壤中不同作物根面反硝化细菌优势种有明显差异;不同土壤中同一作物根面、根际反硝化细菌优势种差异不明显.     

Proteomic studies of plant-bacterial interactions

Plants and bacteria can interact with one another in a variety of different ways. The interaction may be beneficial, harmful or neutral for the plant, and sometimes the impact of a bacterium may vary as the soil conditions change. While a number of different soil bacteria are phytopathogenic, the majority of the more agronomically important plant disease-causing soil microorganisms are fungi. On the other hand, plant growth-promoting bacteria are typically of three general types: those that form a symbiotic relationship with the plant, those that are endophytic and colonize the inner tissues of the plant, and those of soil bacteria, which have competitive abilities to colonize efficiently the rhizosphere and the surface of plant roots.While there have been significant advances in elucidating the mechanistic details of plant-bacterial interactions in recent years, many fundamental questions about these processes remain. Unfortunately, studies that focus on only a single biochemical pathway or mechanism often miss the multiplicity of effects that plants and bacteria have on one another, motivating the employment of broader proteome-wide approaches. On the other hand, using proteomics technology including high-resolution two-dimensional gel electrophoresis (2-DE) and high-sensitivity mass spectrometry (MS), it is possible to gain greater insight into the detailed impact that plants and soil bacteria have on one another.In this regard, of all of the proteomic studies of plant-bacterial interactions, the symbiotic interaction between nitrogen-fixing bacteria and legumes has been studied in the greatest detail. Studies of the proteome of plant-pathogen interactions have also received considerable attention. However, there are currently very few proteomic studies of endophytic and rhizosphere associated plant growth promoting bacteria.Here, some fundamental proteomic tools are introduced and the applications of one of these approaches (i.e., 2-DE coupled to MS) to the study of plant-bacterial interactions are discussed. This review specifically addresses the questions: what are the impacts of plants on the bacterial proteomes, and vice versa?     

Effect of seed inoculation with the rhizopseudomonad strain 7NSK2 on the root microbiota of maize (Zea mays) and barley (Hordeum vulgare)

Summary The addition of sugars or amino acids to the soil gave rise to the development of different groups of microorganisms. The increase in the number of different groups of microorganisms in the soil had an influence on the microbiota in the rhizoplane and endorhizosphere of maize and barley grown in that soil. Furthermore, growth of maize and barley decreased with increasing microbial activity and density in soil. This effect could be counteracted effectively by the rhizopseudomonad strain 7NSK2. The beneficial effect of the strain 7NSK2 correlated inversely with the microbial activity, as measured by soil respiration, in the bulk-pretreated soil.The effect of seed inoculation with the rhizopseudomonad strain 7NSK2 on the root microbiota of maize and barley was evaluated. The strain 7NSK2 was capable of colonizing the rhizoplane and endorhizosphere of the maize cultivar Beaupré and barley cultivar Than very effectively and of considerably altering their composition. The number of total bacteria, fungi, pseudomonads and coliform bacteria in the rhizoplane and endorhizosphere of both plants was strongly reduced by inoculating the seeds with the strain 7NSK2.     

Significance of timing and level of inoculation with rhizosphere bacteria on wheat plants

The importance of time of inoculation and bacterial concentration in the inoculum on the response of wheat plants was evaluated, using eight strains of rhizosphere bacteria. The optimal bacterial concentration, for all strains, was 10⁵–10⁶ colony forming units ml⁻¹. Plant response was highest when seeds had been inoculated but was less when seedlings were inoculated. Successive inoculations somewhat increased plant response. Early inoculations resulted in an increased colonization of plant roots at later stages of growth. It was concluded that time of inoculation and the concentration of bacteria in the inoculum were of significant importance in plant response to inoculation and they may govern the inconsistency found in inoculation experiments using beneficial bacteria.     

Use of aliette,a basipetally translocated antimicrobial compound,to enhance rhizophere colonization and nodulation by root-nodule bacteria

Summary A method was developed to improve the colonizing ability of inoculated strains of root-nodule bacteria using aliette (aluminum tris-O-ethyl phosphonate), a basipetally translocated fungicide. Aliette applied to seeds of alfalfa inoculated with an aliette-resistant strain of Rhizobium meliloti increased the numbers of R. meliloti in the rhizosphere after 3 but not 37 days, increased the number of nodules, and with some seed treatments, increased the growth of alfalfa. The enhanced colonization by R. meliloti as a result of seed treatment with aliette lasted for at least 31 days for alfalfa, although plant weights did not increase, Colonization by R. meliloti was further enhanced if seeds and foliage were treated with the fungicide. Coating seeds or sparaying the foliage with aliette also increased the number and weight of nodules and nitrogenase activity in soybeans inoculated with an aliette-resistant strain of Bradyrhizobium japonicum. The stimulation of B. japonicum in the rhizosphere and of nodulation was evident with successive plantings of soybeans if the seeds for each planting were treated with the chemical, but aliette did not increase the yield of inoculated soybeans in the subsequent plantings. With only the seeds of the first planting of inoculated soybeans treated with aliette, the numbers of B. japonicum in the rhizosphere of subsequent plantings were only occasionally greater and the numbers of nodules on the later plantings were not increased. We suggest that root colonization, nodulation, and N₂ fixation by Rhizobium and Bradyrhizobium may be enhanced by the use of basipetally translocated antimicrobial compounds together with root-nodule bacteria that are resistant to those compounds.