Polymer-based Preparation of Soil Inoculants: Applications to Arbuscular Mycorrhizal Fungi

Arbuscular mycorrhizal fungi is an important group of soil microorganisms which form beneficial symbiotic associations with roots with a wide range of plants thus improving plant growth, nutrition and health. This paper reviews the current status of preparation and formulation of mycorrhizal inoculum applying polymer materials with determined characteristics. The most widely used methods are based on the entrapment of fungal materials in natural polysaccharide gels. The potential of such inoculant preparations is illustrated by various studies which include immobilization of mycorrhized root pieces, vesicles and spores, in some cases co-entrapped with other plant beneficial microorganisms. Suggestions for further research in this field are also discussed.     

新疆3种甘草根际土壤丛枝菌根真菌群落的多样性分析

为探究新疆地区药用甘草根际土壤丛枝菌根真菌的群落结构受宿主植物种类、土壤深度和土壤理化性质的影响,该实验采集了新疆地区乌拉尔甘草、胀果甘草、光果甘草根际0～20 cm、20～40 cm、40～60 cm 3个土层的土壤样品,基于Illumina Miseq高通量测序平台测定AM真菌群落结构和多样性,结合土壤理化性质,分...     

Arbuscular Mycorrhizal Fungi, Bacillus cereus, and Candida parapsilosis from a Multicontaminated Soil Alleviate Metal Toxicity in Plants

We investigated if the limited development of Trifolium repens growing in a heavy metal (HM) multicontaminated soil was increased by selected native microorganisms, bacteria (Bacillus cereus (Bc)), yeast (Candida parapsilosis (Cp)), or arbuscular mycorrhizal fungi (AMF), used either as single or dual inoculants. These microbial inoculants were assayed to ascertain whether the selection of HM-tolerant microorganisms can benefit plant growth and nutrient uptake and depress HM acquisition. The inoculated microorganisms, particularly in dual associations, increased plant biomass by 148% (Bc), 162%, (Cp), and 204% (AMF), concomitantly producing the highest symbiotic (AMF colonisation and nodulation) rates. The lack of AMF colonisation and nodulation in plants growing in this natural, polluted soil was compensated by adapted microbial inoculants. The metal bioaccumulation abilities of the inoculated microorganisms and particularly the microbial effect on decreasing metal concentrations in shoot biomass seem to be involved in such effects. Regarding microbial HM tolerance, the activities of antioxidant enzymes known to play an important role in cell protection by alleviating cellular oxidative damage, such as superoxide dismutase, catalase, glutathione reductase, and ascorbate peroxidase, were here considered as an index of microbial metal tolerance. Enzymatic mechanisms slightly changed in the HM-adapted B. cereus or C. parapsilosis in the presence of metals. Antioxidants seem to be directly involved in the adaptative microbial response and survival in HM-polluted sites. Microbial inoculations showed a bioremediation potential and helped plants to develop in the multicontaminated soil. Thus, they could be used as a biotechnological tool to improve plant development in HM-contaminated environments.     

Global Distributions of Arbuscular Mycorrhizal Fungi

We examined potential large-scale controls over the distribution of arbuscular mycorrhizal (AM) fungi and their host plants. Specifically, we tested the hypothesis that AM fungi should be more prevalent in biomes where nutrients are primarily present in mineral, and not organic, forms. Values of percentage root length colonized (%RLC) by AM fungi, AM abundance, and host plant availability were compiled or calculated from published studies to determine biome-level means. Altogether, 151 geographic locations and nine biomes were represented. Percent RLC differed marginally significantly among biomes and was greatest in savannas. AM abundance (defined as total standing root length colonized by AM fungi) varied 63-fold, with lowest values in boreal forests and highest values in temperate grasslands. Biomes did not differ significantly in the percentage of plant species that host AM fungi, averaging 75%. Contrary to the hypothesis, %RLC, AM abundance, and host plant availability were not related to the size, influx, or turnover rate of soil organic matter pools. Instead, AM abundance was positively correlated with standing stocks of fine roots. The global pool of AM biomass within roots might approach 1.4 Pg dry weight. We note that regions harboring the largest stocks of AM fungi are also particularly vulnerable to anthropogenic nitrogen deposition, which could potentially alter global distributions of AM fungi in the near future.     

The Ecology of Arbuscular Mycorrhizal Fungi

Arbuscular mycorrhiza is a mutually beneficial biological association between species in the fungal phylum Glomeromycota and higher plants roots. The symbiosis is thought to have afforded green plants the opportunity to invade dry land ca 450 Ma ago and the vast majority of extant terrestrial plants retain this association. Arbuscular mycorrhizal (AM) fungi perform various ecological functions in exchange for host photosynthetic carbon that almost always contribute to the fitness of hosts from an individual to community level. Recent AM fungal research, increasingly delving into the ‘Black Box’, suggests that species in this phylum may play a key facilitative role in below-ground micro- and meso-organism community dynamics, even more perhaps, that of a bioengineer. The ubiquitous nature of the symbiosis in extant flora and the fact that variations from the AM symbiosis are recent events suggest that Glomeromycota and plant roots coevolved. This review considers aspects of AM fungal ecology emphasizing past and present importance of the phylum in niche to global ecosystem function. Nutrient exchange, evolution, taxonomy, phenology, below-ground microbial interaction, propagule dissemination, invasive plants interactions, the potential role in phytoremediation and some of the factors affecting AM fungal biology are discussed. We conclude that it is essential to include AM association in any study of higher plants in natural environments in order to provide an holistic understanding of ecosystems.     

Interaction between Earthworms and Arbuscular Mycorrhizal Fungi in Plants: A Review

Different kinds of soil animals and microorganisms inhabit the plant rhizosphere, which function closely to plant roots. Of them, arbuscular mycorrhizal fungi (AMF) and earthworms play a critical role in sustaining the soil-plant health. Earthworms and AMF belong to the soil community and are soil beneficial organisms at different trophic levels. Both of them improve soil fertility and structural development, collectively promoting plant growth and nutrient acquisition capacity. Earthworm activities redistribute mycorrhizal fungi spores and give diversified effects on root mycorrhizal fungal colonization. Dual inoculation with both earthworms and AMF strongly magnifies the response on plant growth through increased soil enzyme activities and changes in soil nutrient availability, collectively mitigating the negative effects of heavy metal pollution in plants and soils. This thus enhances phytoremediation and plant disease resistance. This review simply outlines the effects of earthworms and AMF on the soil-plant relationship. The effects of earthworms on root AMF colonization and activities are also analyzed. This paper also summarizes the interaction between earthworms and AMF on plants along with suggested future research.     

丛枝菌根共生关系的信号机制研究进展

在植物与微生物的共生体中,最广泛的互惠共生体就是丛枝菌根.真菌在植物根系形成菌根后,菌丝通过根的皮层细胞获取植物提供的碳源,同时将矿物营养和水从土壤转运到皮层细胞,这种共生过程的研究在生物多样性的保护、陆生植物的起源与演化、退化生态系统的修复与重建以及农业、林业和园艺业的应用具有重要的意义.近年来丛枝菌根真菌与植物根系建立共生关系的信号传导途径和作用机制备受关注,也取得了突破性的进展.本文对丛枝菌根真菌与植物根系在共生关系形成、营养交换以及防御方面的分子信号和细胞方面的研究进展进行综述,并对发展前景作以展望.     

丛枝菌根真菌对羊草生物量和氮磷吸收及土壤碳的影响

采用大田试验的方法在内蒙古锡林格勒草原进行牧草接种试验,通过灭菌和未灭菌两种土壤研究接种丛枝菌根真菌Glomus mosseae和Glomus claroidium对内蒙古典型草原优势种羊草生长的影响.结果显示,接种丛枝菌根真菌对羊草的地上部干重未产生显著影响,但向未灭菌土壤中接种能显著增加羊草根系量,同时接种G.mosseae显著增加了地上部的N、P含量及吸收量,有效地改善了植株N、P营养,提高了牧草品质;2种菌对根系的营养吸收影响不同,接种G.mosseae在灭菌土壤和未灭菌土壤中均能显著增加根系的N、P吸收量,而接种G.claroidium仅在土壤未灭菌状态下增加根系N、P吸收量;接种对土壤中的菌丝密度未产生显著影响,但接种后土壤中微生物量碳有增加的趋势,短期内难以观察到接种对土壤有机碳的影响.研究表明,丛枝菌根真菌能够提高牧草对N、P吸收,促进牧草的生长,改善牧草品质,增强牧草根际微生物量碳.     

丛枝菌根真菌在外来植物入侵演替中的作用与机制

外来植物入侵不仅是环境、经济和社会问题,也是一个生理学和生态学问题,尤其是入侵植物与本地植物、入侵植物和本地土壤生物之间的相互作用决定外来植物入侵程度。丛枝菌根真菌（AMF）作为土壤中一类极为重要的功能生物,在外来植物入侵演替过程中发挥多种不同作用。文章系统总结了AMF对入侵植物个体和群体的影响,入侵植物与本地植物竞争中AMF发挥的促进和抑制作用;探讨了AMF与入侵植物的相互作用关系,以及环境因子对AMF一入侵植物关系的影响：对AMF在外来植物入侵演替中的作用机制进行了讨论。旨在为探索控制生物入侵的新途径、为我国开展外来植物入侵研究与防控实践提供新思路。     

云南部分地区湿地植物的丛枝菌根初报

用碱解离、酸性品红染色法对昆明、澄江、建水、通海、石屏、东川和禄劝等地的15个科32种湿地植物的丛枝菌根状况进行了调查,共发现有11种植物形成丛枝菌根,占34％。从湿地植物根际土壤中分离、鉴定出分属于4个属的丛枝菌根真菌共16种,无梗囊霉属（Acaulospora）和球囊霉属（Glomus）是湿地土壤中的优势类群（94％）。摩西球囊霉（G．mosseae）占孢子总数的88％,是湿地土壤中的优势种。     

甘肃盐碱土植物VA菌根真菌侵染研究

对甘肃盐碱土中植物的VA菌根真菌共生状况进行研究,结果表明：在10科17种植物中,除碱蓬（Suaeda glauca Beg.）外均被菌根真菌侵染,占94.1%;盐碱土中孢子密度较高,表明甘肃盐碱土生态系统中植物对菌根真菌具有较高的依赖性,菌根真菌在盐碱土中产孢能力较强;所调查植物的VA菌根结构类型Arum型占68.75%,Pris型占31.25%;菌根结构类型与宿主植物类型有关,禾本科（Poaceae）和鸢尾科（Iridaceae）植物为P型菌根,百合科（Liliaceae）、胡颓子科（Elaeagnaceae）等其它科植物均为A型菌根;土壤类型影响了宿主植物的菌根侵染率和根际土的孢子密度,相同宿主植物在不同类型土壤中的菌根侵染率和孢子密度具有很大的差异.     

Arbuscular Mycorrhizal Fungi Enhance Zinc and Nickel Uptake from Contaminated Soil by Soybean and Lentil

Generally, soils in Pakistan are deficient in P and N. Due to intensive cropping and irrigation, Pakistani soils have also become deficient in micronutrients such as Zn, Fe, Cu, and Mn. Arbuscular mycorrhizal fungi, which form symbiotic associations with roots of most land plants, are known to enhance uptake of P and trace elements such as Cu, Ni, Pb, and Zn. The present study was conducted to investigate the role of arbuscular mycorrhizae (AM) in uptake of nickel (Ni) and zinc (Zn) by crops viz. soybean (Glycine max (L.) Merrill) and lentil (Lens culinaris Medic). Zn and Ni were applied as ZnSO₄ 7H₂O and NiCl₂ respectively, in four concentrations (0.0, 1.0, 3.0, and 5.0 g kg^-1 soil). AM inoculum consisted of sand containing sporocarps, spores, and AMF infected root pieces from a pot culture of Glomus mosseae. Control plants received pot culture filtrate containing soil microflora minus AM fungal propagules. A significant difference (p < 0.05) was observed in the dry weights of roots and shoots of the mycorrhizal (M) and nonmycorrhizal (NM) cereal plants. The sievate-amended treatments did not stimulate plant growth to the same extent as the AM fungal amended treatments. Trace metals inhibited the extent of mycorrhizal colonization of the cereal roots. The concentrations of the trace metals in the plant tissues of 12-week old cereal plants were found significantly (p < 0.05) higher in M than NM plants. These results indicate that mycorrhize can be used as effective tools to supply sufficient Zn in generally Zn-deficient Pakistani soils and to ameliorate the toxicity of trace metals in polluted soils. The contents of Ni in mycorrhizal soybean plant tissues were higher than those in the mycorrhizal lentil plant tissues. The implications of these results in mycorrhizo remediation of agricultural soils are discussed.     

丛枝菌根真菌对植物生长影响的研究

菌根是自然界中一种极为普遍和重要的共生现象,其中分布最为广泛的菌根类型就是丛枝菌根,可以增强植物从土壤中获取水分的能力,改善植物根系对磷、镉等矿质元素及养分的吸收,从而促进植物的生长。本文综述了丛枝菌根真菌对植物生长影响的概况。有关丛枝菌根真菌对植物水分和矿质营养的利用,尤其是磷素营养的研究较为深入,而对植物光合特性的研究较少,这些研究工作为深入理解菌根真菌与植物的相互关系提供基础资料。     

丛枝菌根真菌诱导植物产生酚类物质的研究进展

酚类物质是植物体内重要的次生代谢产物,对病原微生物的侵袭有很好的防御作用。AM真菌能够诱导植物的酚类物质合成,而且这种诱导既是原位的、也是系统的,相关研究已有大量报道。本文对AM真菌原位和系统诱导酚类物质进行了论述,并对系统诱导过程中可能的信号分子(SA、H2O2)进行了评述,最后提出了AM真菌系统诱导酚类物质产生的可能作用机理,进一步明确后续工作中的研究方向。     

Role of Arbuscular Mycorrhizal Fungi in Uptake of Phosphorus and Nitrogen From Soil

Abstract

Colonization of plant roots by arbuscular mycorrhizal fungi can greatly increase the plant uptake of phosphorus and nitrogen. The most prominent contribution of arbuscular mycorrhizal fungi to plant growth is due to uptake of nutrients by extraradical mycorrhizal hyphae. Quantification of hyphal nutrient uptake has become possible by the use of soil boxes with separated growing zones for roots and hyphae. Many (but not all) tested fungal isolates increased phosphorus and nitrogen uptake of the plant by absorbing phosphate, ammonium, and nitrate from soil. However, compared with the nutrient demand of the plant for growth, the contribution of arbuscular mycorrhizal fungi to plant phosphorus uptake is usually much larger than the contribution to plant nitrogen uptake. The utilization of soil nutrients may depend more on efficient uptake of phosphate, nitrate, and ammonium from the soil solution even at low supply concentrations than on mobilization processes in the hyphosphere. In contrast to ectomycorrhizal fungi, nonsoluble nutrient sources in soil are used only to a limited extent by hyphae of arbuscular mycorrhizal fungi. Side effects of mycorrhizal colonization on, for example, plant health or root activity may also influence plant nutrient uptake.     

湿地植物与丛枝菌根真菌(AMF)相互关系的研究进展

丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)是湿地植物主要共生菌之一,在湿地生态系统中具有重要的作用.本文就近年来AMF对湿地植物的营养物质吸收、生长发育、抗逆境胁迫和抗污染能力等的作用,湿地植物、水分、季节、土壤理化性质因素对根际AMF的多样性、侵染能力、空间分布、生长发育、孢子密度的影响,以及植物与AMF之间相互作用关系的研究进展进行综述.     

柑橘园土壤中丛枝菌根真菌土著菌株的促生效应研究

柑橘对丛枝菌根(AM)真菌具有较高的依赖性,从柑橘园土壤中分离筛选的高效促生AM真菌菌株具有重要的应用价值。本研究从广东增城柑橘园(酸橘砧‘红江橙’)土壤中分离的4个AM真菌土著菌株对‘红江橙’幼苗的促生效应。结果表明,4个土著菌株分别是Scutellospora属和Glomus属菌株,根系侵染率为12.7%～29.3%;与不接种对照相比,4个土著菌株不同程度地促进‘红江橙’幼苗的株高、生物量和N、P、K养分含量,菌根依赖性达9.4%～37.1%;主成分分析表明,土著菌株ZCSP-D的促生效应达到常用优良菌株Rhizophagus irregularis的水平。