功能内生菌强化超积累植物修复重金属污染土壤的研究进展

土壤重金属污染已成为威胁人类健康和经济可持续发展的重大环境问题。内生菌-超积累植物联合修复是近年来发展起来的一种重金属污染土壤的生物修复技术,不仅能促进植物生长、提高其重金属抗性,同时,还可以改变重金属的形态和迁移率,提高植物修复的效率,具有广阔的应用前景。现概述植物内生菌(plant growth promoting endophyte, PGPE)的特征、种类以及促进超积累植物生长的作用机理,综述近年来国内外有关功能内生菌协同超积累植物修复重金属污染土壤的应用现状和研究进展,同时展望内生菌协同超积累植物修复土壤重金属的研究思路,旨在为今后土壤重金属污染治理提供新的思路和理论依据。     

植物超积累重金属的生理机制研究进展

土壤重金属污染已经成为一个全球性问题。重金属超积累植物在修复土壤重金属污染中具有重要的应用前景。重金属超积累植物通常具备三个基本特征,即：根系具有从土壤中吸收重金属的强大能力、能从根到地上部分高效转运重金属、在叶片中能解毒和隔离大量重金属。本文总结了重金属超积累植物吸收、转运、隔离和解毒重金属的生理机制研究进展,以期为进一步阐明植物超积累重金属的机制及其在植物修复中的应用提供参考。     

植物内生细菌在植物修复重金属污染土壤中的应用

土壤重金属污染是威胁人群健康和经济可持续发展的重要环境问题。植物修复具有经济、环保等特点,已成为治理重金属污染土壤的重要技术。如何提高植物对重金属的抗性、促进植物生长是影响植物修复效率的关键之一。内生菌群-植物共生关系在此方面具有独特优势。其中,植物内生细菌可改善植物营养、降低植物病菌感染、影响酶活性,以及分泌激素、含铁载体和有机配位体等,进而提高超积累植物对重金属的吸收作用。本文综述了近年来国内外关于抗重金属植物内生细菌筛选与应用的研究进展,分析了内生细菌促进植物生长、增强植物对重金属抗性、促进重金属向茎叶转移的机理,阐述了植物内生细菌在重金属污染土壤修复中的应用前景与研究重点。     

丛枝菌根对有机污染土壤的修复作用及机理

丛枝菌根(AM)是丛枝菌根真菌(AMF)与植物根系相互作用的互惠共生体,能改良土壤结构,增强植物抗性.自然界中已知的AMF有170多种,分布广泛,且可与大多数植物共生.利用AM修复有机污染土壤正成为一个崭新的研究方向.本文综述了AM对多环芳烃、酞酸脂、石油和农药等一些典型有机污染物污染土壤的修复作用.AM修复有机污染土壤的机理主要包括:AMF代谢有机污染物;AM分泌酶,降解污染物;AM影响根系分泌作用,并促进根际微生物对有机污染物的降解;AMF宿主植物吸收积累污染物.AM修复研究中,高效AMF的筛选、复合菌种效应、土壤老化、AM作用下植物对有机污染物的吸收积累等几方面仍有待于深入研究.     

植物内生细菌修复重金属污染土壤作用机制研究进展

内生细菌生活在植物组织内部,长期以来与宿主植物形成了紧密的共生关系。内生细菌在重金属吸收、耐受和解毒方面具有优良的特性,为修复重金属污染土壤提供了有效的新方案。综述了内生细菌强化植物修复重金属污染土壤的作用机制,包括内生细菌通过产生植物生长调节激素,分泌ACC脱氨酶和几丁质酶等,促进宿主植物在重金属胁迫条件下的生长;通过改变重金属的生物有效性/毒性,减轻植物重金属毒害;通过与植物形成联合修复体,加强植物抗重金属毒性的能力。分析了近几年超富集植物内生细菌多样性及其影响因素,探讨了联合修复过程中影响内生细菌强化修复效果的主要因素,包括内生细菌的来源、活性和环境胁迫等各种生物因素和非生物因素,并对内生细菌与植物联合修复的研究方向进行展望,涉及内生细菌自身存活原因和如何耐受重金属的机制研究,植物内生细菌的行为动力学和代谢,以及内生细菌、植物及土壤之间的生态互作效应等,以期推动内生细菌大规模应用于植物修复重金属污染土壤。     

植物吸收、转运和积累镉的机理研究进展

重金属镉(Cd)虽然不是植物生长的必需矿质元素,但依然能被植物吸收。且部分植物具有富集镉的特点,从而导致农产品镉含量超标,并通过食物链危害人类健康。研究植物吸收、转运和积累Cd的机理,对于培育低镉作物品种、降低农产品镉含量,以及选育超富集镉植物,修复镉污染土壤具有重要意义。从影响植物吸收Cd的因子,植物吸收、转运和积累Cd的机理以及植物拒Cd和富集Cd的分子机制等方面进行综述,以期为低镉作物的研究以及Cd污染土壤的综合治理提供一些参考。     

重金属污染土壤超积累植物修复关键技术的发展

我国土壤重金属污染问题日益突出,严重影响食品安全和人类健康,同时也制约了社会经济的可持续发展。在众多土壤重金属修复技术中,超富集植物修复技术以廉价高效、操作简单、安全可靠、环境友好等优点,被认为是最具发展潜力的绿色修复技术之一。本文回顾了该技术在国内外的发展历程,并对超积累植物的筛选鉴定、对重金属的吸收转运机制、强化修复措施及植物安全处置与利用等几个关键技术进行了阐述,对该技术今后的发展方向和突破点进行了展望。     

超积累植物吸收重金属的根际效应研究进展

阐述近年来国内外在超积累植物吸收重金属的根际微生态效应这一领域的最新研究成果 ,介绍了根际微生态效应在植物修复中的应用 ,并对当前超积累植物在根际微生态效应研究中的不足之处和需要进一步深入研究的方向进行讨论。     

重金属污染土壤植物修复中的微生物功能研究进展

综述了国内外在重金属污染土壤植物-微生物联合修复领域的研究报道,总结了近5年的研究实例。植物-微生物联合修复体系具有生物固定与生物去除土壤重金属的两种功能,根际微生物可以菌根、内生菌等方式与根系形成联合体,通过增强植物抗性和优化根际环境,促进根系发展,增强植物吸收和向上转运重金属的能力。建立植物-微生物联合修复体系,可充分发挥植物与微生物作用功能的优势,提高污染土壤的修复效率。增强植物修复体系中微生物功能的重点是深入研究根际微生物、根系和介质载体三者之间复合功能,结合污染土壤类型与植物群落配置的特点筛选扩繁高效菌种与菌群。     

我国土壤重金属污染植物吸取修复研究进展

我国从上世纪90年代中后期开始土壤重金属（含类金属砷）污染的植物吸取修复研究及技术探索,先后发现了一批具有较高研究价值和应用前景的铜、砷、镉、锰等重金属的积累或超积累植物,并从重金属耐性和超积累生理机制、植物吸取修复的根际过程与机制、吸取修复强化措施和修复植物处置与资源化利用等方面进行了研究,同时开展了植物吸取修复技术的示范与应用,已有一些较成功的植物修复工程应用案例,使我国重金属污染土壤植物修复技术,尤其是植物吸取修复技术在国际上产生了较强的影响力。本文就近年来我国土壤重金属污染植物吸取修复研究进展进行了综述,并对今后的发展趋势进行了展望。     

Vacuolar compartmentalization as indispensable component of heavy metal detoxification in plants

Plant cells orchestrate an array of molecular mechanisms for maintaining plasmatic concentrations of essential heavy metal (HM) ions, for example, iron, zinc and copper, within the optimal functional range. In parallel, concentrations of non‐essential HMs and metalloids, for example, cadmium, mercury and arsenic, should be kept below their toxicity threshold levels. Vacuolar compartmentalization is central to HM homeostasis. It depends on two vacuolar pumps (V‐ATPase and V‐PPase) and a set of tonoplast transporters, which are directly driven by proton motive force, and primary ATP‐dependent pumps. While HM non‐hyperaccumulator plants largely sequester toxic HMs in root vacuoles, HM hyperaccumulators usually sequester them in leaf cell vacuoles following efficient long‐distance translocation. The distinct strategies evolved as a consequence of organ‐specific differences particularly in vacuolar transporters and in addition to distinct features in long‐distance transport. Recent molecular and functional characterization of tonoplast HM transporters has advanced our understanding of their contribution to HM homeostasis, tolerance and hyperaccumulation. Another important part of the dynamic vacuolar sequestration syndrome involves enhanced vacuolation. It involves vesicular trafficking in HM detoxification. The present review provides an updated account of molecular aspects that contribute to the vacuolar compartmentalization of HMs.     

微生物胞外多糖的合成及其在重金属修复中的作用机制与应用

重金属的生物不可降解性使其在环境中长期存在,导致严重的环境污染,对人类健康和生态系统构成威胁。与传统的物化修复技术相比,微生物修复具有成本低廉、环境友好和高效等特点。在面对重金属胁迫或营养不均衡时,微生物会被激发以分泌合成胞外多糖(exopolysaccharides, EPS)。由此可见,EPS的产生是微生物对抗重金属胁迫的重要策略之一。EPS不仅能保护微生物在低温、高温、高盐等极端环境或受毒性化合物胁迫的条件下存活,并且在细胞内外进行信息和物质的交流与传递,既作为保护屏障限制重金属离子进入细胞,又作为介质进行交流。EPS结构中含有多个带负电荷的官能团,能够与重金属离子发生络合、离子交换、氧化还原等反应,从而降低重金属的生物有效性并减轻其毒性。微生物EPS在重金属胁迫环境中的修复具有重要意义。然而,目前缺乏关于微生物EPS合成过程、与重金属互作机制及其在重金属胁迫环境中应用现状的系统综述。本文概述了微生物EPS及其分类,详细阐述了细菌EPS胞内及胞外的生物合成机制,并探讨了微生物EPS与重金属互作机制,以及微生物EPS修复水、土环境中重金属污染方面的研究进展。最后,展望了EPS合成及其在重金属修复中的作用机制研究,可为微生物EPS进一步应用于环境重金属污染修复提供支持。     

Mycorrhizal inoculations and silicon fortifications improve rhizobial symbiosis,antioxidant defense,trehalose turnover in pigeon pea genotypes under cadmium and zinc stress

Cadmium (Cd) is a non-essential and highly toxic element for plant growth while zinc (Zn) becomes toxic at elevated levels. Presence of these heavy metals (HMs) in soils has negative impact on rhizobial symbiosis in legumes leading to reduced agricultural productivity. Role of silicon (Si) amendment and Rhizophagus irregularis in mitigating HM stress has gained importance in recent years. Present study evaluated the individual and cumulative effects of Si and/or AM on Cd (25, 50 mg/kg) or Zn (600, 1000 mg/kg) induced responses in terms of nitrogen fixing efficiency, trehalose biosynthesis, antioxidant defense and phytochelatin (PC) synthesis in pigeon pea genotypes (Tolerant-Pusa 2002, Sensitive-Pusa 991). Results indicated that although mycorrhizal colonization (MC) declined with increase in metal concentration in both genotypes, Pusa 2002 was able to form significant colonization even under stress. Cadmium and zinc stress negatively affected plant biomass and rhizobial symbiosis, with Cd more toxic than Zn. The decline in nodulation potential under both HMs was much more significant in Pusa 991 than Pusa 2002 which could be correlated with proportionately reduced MC, nutrient uptake and ultimate N accumulation. Individual application of AM was much more effective in improving nitrogen fixing efficiency by increasing trehalose biosynthesis, PC production and strengthening antioxidant defense than Si. Restoration of rhizobial symbiosis under combined applications of Si and AM could be correlated with enhanced Si uptake through mycorrhization. Thus, study suggested use of AM as a tool in enhancing benefits of Si nutrition in terms of restoration of nodule senescence and N-fixing competence in pigeon pea under HMs stress.     

Thermal Characteristics of Hyperaccumulator and Fate of Heavy Metals during Thermal Treatment of Sedum plumbizincicola

Thermal treatment is one of the most promising disposal techniques for heavy metal- (HM)-enriched hyperaccumulators. However, the thermal characteristics and fate of HMs during thermal treatment of hyperaccumulator biomass need to be known in detail. A horizontal tube furnace was used to analyze the disposal process of hyperaccumulator biomass derived from a phyto-extracted field in which the soil was moderately contaminated with heavy metals. Different operational conditions regarding temperature and gas composition were tested. A thermo-dynamic analysis by advanced system for process engineering was performed to predict HM speciation during thermal disposal and SEM-EDS, XRD and sequential chemical extraction were used to characterize the heavy metals. The recovery of Zn, Pb and Cd in bottom ash decreased with increasing temperature but recovery increased in the fly ash. Recovery of Zn, Pb and Cd fluctuated with increasing air flow rate and the metal recovery rates were higher in the fly ash than the bottom ash. Most Cl, S, Fe, Al and SiO₂ were found as alkali oxides, SO₂, Fe₂(SO₄)₃, iron oxide, Ca₃Al₂O₆, K₂SiO₃ and SiO₂ instead of reacting with HMs. Thus, the HMs were found to occur as the pure metals and their oxides during the combustion process and as the sulfides during the reducing process.     

Phytoextraction of initial cutting of Salix matsudana for Cd and Cu

Salix species are widely used as vegetation filters because of their flourishing root system and fast growth rate. However, studies have yet to determine whether the root system functions in vegetable filters with mixed heavy metal (HM) pollution or whether initial cutting participates in the phytoextraction of HMs. This study aims to determine the function of the root system and initial cutting as vegetation filters in the absorption and accumulation of Cd and Cu. Thick (>1?cm in diameter) and fine (<1?cm in diameter) initial cuttings of Salix matsudana were planted in a nutrient solution with single and mixed (Cd?+?Cu) treatments. The roots of several initial cuttings were removed daily to eradicate rhizofiltration. Results revealed that the existence of the root system altered distribution and interaction of Cd and Cu in plant organs and enhanced tolerance and phytoextraction capacity of plants. The initial cuttings could also absorb and accumulate HMs in the early growth stages of willow without roots. Cu inhibited the plant absorption and accumulation of Cd and promoted Cd transport to shoots. Cd inhibited the Cu absorption of the root system. Our study provided essential data regarding woody species as vegetation filters of HM pollution.     

Zinc nutrition and arbuscular mycorrhizal symbiosis effects on maize (Zea mays L.) growth and productivity

Zinc (Zn) is an essential micronutrient required to enhance crop growth and yield. In the arid – semiarid region, Zn deficiency is expected due to alkaline calcareous soil. Contrarily, Zn toxicity is also becoming an environmental concern due to increasing anthropogenic activities (metal smelting, copper industry, etc.). Therefore, balanced Zn application is necessary to save resources and achieve optimum crop growth and yield. Most scientists suggest biological approaches to overcome the problem of Zn toxicity and deficiency. These biological approaches are mostly environment-friendly and cost-effective. In these biological approaches, the use of arbuscular mycorrhizae fungi (AMF) symbiosis is becoming popular. It can provide tolerance to the host plant against Zn-induced stress. Inoculation of AMF helps in balance uptake of Zn and enhances the growth and yield of crops. On the other hand, maize (Zea mays L.) is an important cereal crop due to its multifarious uses. As maize is an effective host for mycorrhizae symbiosis, that’s why this review was written to elaborate on the beneficial role of arbuscular mycorrhizal fungi (AMF). The review aimed to glance at the recent advances in the use of AMF to enhance nutrient uptake, especially Zn. It was also aimed to discuss the mechanism of AMF to overcome the toxic effect of Zn. We have also discussed the detailed mechanism and physiological improvement in the maize plant. In conclusion, AMF can play an imperative role in improving maize growth, yield, and balance uptake of Zn by alleviating Zn stress and mitigating its toxicity.     

Physiological and molecular mechanisms of heavy metal accumulation in nonmycorrhizal versus mycorrhizal plants

Uptake, translocation, detoxification, and sequestration of heavy metals (HMs) are key processes in plants to deal with excess amounts of HM. Under natural conditions, plant roots often establish ecto‐ and/or arbuscular‐mycorrhizae with their fungal partners, thereby altering HM accumulation in host plants. This review considers the progress in understanding the physiological and molecular mechanisms involved in HM accumulation in nonmycorrhizal versus mycorrhizal plants. In nonmycorrhizal plants, HM ions in the cells can be detoxified with the aid of several chelators. Furthermore, HMs can be sequestered in cell walls, vacuoles, and the Golgi apparatus of plants. The uptake and translocation of HMs are mediated by members of ZIPs, NRAMPs, and HMAs, and HM detoxification and sequestration are mainly modulated by members of ABCs and MTPs in nonmycorrhizal plants. Mycorrhizal‐induced changes in HM accumulation in plants are mainly due to HM sequestration by fungal partners and improvements in the nutritional and antioxidative status of host plants. Furthermore, mycorrhizal fungi can trigger the differential expression of genes involved in HM accumulation in both partners. Understanding the molecular mechanisms that underlie HM accumulation in mycorrhizal plants is crucial for the utilization of fungi and their host plants to remediate HM‐contaminated soils.     

镍污染土壤植物采矿技术关键过程及其研究进展

植物采矿是利用超积累植物高量吸收土壤中的重金属,并从中提取、冶炼金属产品,在修复污染土壤的同时实现金属的资源化。全世界广泛分布着自然风化的镍污染土壤,植物采矿因其重要的环境、生态及资源价值,被作为一种环境友好且具备经济效益的土壤修复技术,在此类地区具有广阔的应用前景。该植物采矿技术关键过程主要包括超积累植物镍高选择性根际环境响应、植物镍高效吸收转运以及生物质中镍高附加值资源化等过程。近30年,污染土壤中镍的植物采矿已经在美国、阿尔巴尼亚、马来西亚等多个国家进行了野外实践,取得了良好效果。然而,相关技术在我国的研究与应用仍然处于起步阶段。文中通过综述植物采矿技术的关键过程的研究进展,发现其中的瓶颈,为接下来植物采矿的科学研究和技术在全世界推广提供理论基础和技术指导。     

Mycorrhiza in floriculture: difficulties and opportunities

Arbuscular mycorrhizal fungi (AMF) establish symbiotic relationships with the roots of about 80% of plant species. The arbuscular mycorrhizal (AM) symbiosis benefits the growth and development of plants, among them a variety of ornamental horticulture (floriculture) plants. AMF have been shown to benefit plants that suffer from stunted growth, including that stemming from abiotic stress. Many floriculture crops are grown in the semi-arid environment of the Mediterranean region, and therefore AMF application may be implemented in floriculture practices to significantly promote crop growth and yield. However, for successful commercial utilization of the AM symbiosis and its introduction into ornamental floriculture practices, several considerations must be taken into account. These are highlighted and examined in the present review. They include the prerequisite of availability of high quantities of good-quality AMF inocula, the need to use different types and dosages of AMF inocula, at different times of inoculation, and the agricultural crop growth practices that are best-suited for integration with AMF inoculation. The difficulties and opportunities in AMF usage in floriculture are discussed and suggestions on different ways to solve the encountered difficulties are made, to promote cost-effective use of AMF in floriculture.