低温胁迫下丛枝菌根真菌对玉米光合特性的影响

利用盆栽试验,在15 ℃和5 ℃低温胁迫下研究了丛枝菌根（AM）真菌对玉米生长、叶绿素含量、叶绿素荧光和光合作用的影响.结果表明：低温胁迫抑制了AM真菌的侵染;接种AM真菌的玉米地上部和地下部干物质量、相对叶绿素含量高于不接种植株.与非菌根玉米相比,菌根玉米具有较高的最大荧光（F_m）、可变荧光（F_v）、最大光化学效率（F_v/F_m）和潜在光化学效率（F_v/F_o）及较低的初始荧光（F_o）,并且在5 ℃处理中差异显著.接种AM真菌使玉米叶片的净光合速率（P_n）和蒸腾速率（T_r）显著增强;低温胁迫下,菌根植株的气孔导度（G_s）显著高于非菌根植株;而胞间CO₂浓度（C_i）显著低于非菌根植株.表明AM真菌可通过提高叶绿素含量及改善叶片叶绿素荧光和光合作用来减轻低温胁迫对玉米植株造成的伤害,提高玉米耐受低温的能力,进而提高玉米的生物量,促进玉米生长.     

铜胁迫对丛枝菌根真菌群落功能的影响

过去20年来,对不同来源丛枝菌根真菌(AMF)的功能开展了大量研究,但多数基于对单个AMF功能的比较,群落水平的研究较少,且很多研究混淆了AMF来源和群落结构对其功能的影响,忽略了宿主的重要作用.本研究通过两个短期温室盆栽试验,分析了铜胁迫对AMF群落结构的影响,比较了不同AMF群落的功能差异.结果表明:铜胁迫显著改变了AMF群落的孢子丰度和组成.以根内球囊霉和幼套球囊霉为优势种的AMF群落有效减缓了铜胁迫对玉米生长和部分生理特性的抑制作用.     

丛枝菌根真菌提高盐胁迫植物抗氧化机制的研究进展

土地盐渍化是在自然环境和人为活动的双重作用下形成的全球性的重要生态问题,其会对植物造成渗透失衡、离子胁迫、氧化损伤等危害,导致植物生长缓慢、生物量减少甚至是绝产。丛枝菌根真菌(AMF)是一种普遍存在于土壤中的有益微生物,能够与大多数植物根系形成共生关系,其共生关系在多种逆境生态系统中均具有重要生态意义。AMF-植物共生体具有高效抗氧化系统,能够提高植物在盐胁迫下的抗氧化反应进而增强耐盐性。本文从氧化损伤、渗透调节、抗氧化机制和生物活性分子等角度,系统地阐述了丛枝菌根真菌提高植物抗氧化机制的研究进展,并提出了研究展望,以期为利用菌根生物技术提高植物耐盐性提供理论参考。     

龙脑香科植物对丛枝菌根真菌的影响

在天然林地和温室盆栽条件下,比较研究了龙脑香科植物对丛枝菌根(Arbuscular mycorrhizas,AM)真菌孢子密度、相对多度、频度、属的组成、丰度和侵染状况等方面的影响.结果表明,用坡垒作盆栽寄主加富培养后,菌根侵染率、泡囊、丛枝和侵入点都低于原采样植物,以原坡垒土壤中栽植苗木的侵染率为最高,可达20.3%;而以望天树根围土壤栽植的苗木为最低,仅为10.6%;坡垒还不同程度地改变了原采样植物根围土壤中AM真菌孢子的密度、相对多度、频度、属的组成、丰度等.在4种土壤中,栽植坡垒苗木后,AM真菌的孢子密度都有不同程度的增长.采用与原采样相同种类的植物作为AM真菌加富培养的寄主更有利于促进AM真菌的生长发育、保持AM的多样性.     

Alleviation of salt stress in citrus seedlings inoculated with arbuscular mycorrhizal fungi depends on the rootstock salt tolerance

Seedlings of Cleopatra mandarin (Citrus reshni Hort. ex Tan.) and Alemow (Citrus macrophylla Wester) were inoculated with a mixture of AM fungi (Rhizophagus irregularis and Funneliformis mosseae) (+AM), or left non-inoculated (−AM). From forty-five days after fungal inoculation onwards, half of +AM or −AM plants were irrigated with nutrient solution containing 50 mM NaCl. Three months later, AM significantly increased plant growth in both Cleopatra mandarin and Alemow rootstocks. Plant growth was higher in salinized +AM plants than in non-salinized −AM plants, demonstrating that AM compensates the growth limitations imposed by salinity. Whereas AM-inoculated Cleopatra mandarin seedlings had a very good response under saline treatment, inoculation in Alemow did not alleviate the negative effect of salinity. The beneficial effect of mycorrhization is unrelated with protection against the uptake of Na or Cl and the effect of AM on these ions did not explain the different response of rootstocks. This response was related with the nutritional status since our findings confirm that AM fungi can alter host responses to salinity stress, improving more the P, K, Fe and Cu plant nutrition in Cleopatra mandarin than in Alemow plants. AM inoculation under saline treatments also increased root Mg concentration but it was higher in Cleopatra mandarin than in Alemow. This could explain why AM fungus did not completely recovered chlorophyll concentrations in Alemow and consequently it had lower photosynthesis rate than control plants. AM fungi play an essential role in citrus rootstock growth and biomass production although the intensity of this response depends on the rootstock salinity tolerance.     

A meta-analysis of arbuscular mycorrhizal effects on plants grown under salt stress

Salt stress limits crop yield and sustainable agriculture in most arid and semiarid regions of the world. Arbuscular mycorrhizal fungi (AMF) are considered bio-ameliorators of soil salinity tolerance in plants. In evaluating AMF as significant predictors of mycorrhizal ecology, precise quantifiable changes in plant biomass and nutrient uptake under salt stress are crucial factors. Therefore, the objective of the present study was to analyze the magnitude of the effects of AMF inoculation on growth and nutrient uptake of plants under salt stress through meta-analyses. For this, data were compared in the context of mycorrhizal host plant species, plant family and functional group, herbaceous vs. woody plants, annual vs. perennial plants, and the level of salinity across 43 studies. Results indicate that, under saline conditions, AMF inoculation significantly increased total, shoot, and root biomass as well as phosphorous (P), nitrogen (N), and potassium (K) uptake. Activities of the antioxidant enzymes superoxide dismutase, catalase, peroxidase, and ascorbate peroxidase also increased significantly in mycorrhizal compared to nonmycorrhizal plants growing under salt stress. In addition, sodium (Na) uptake decreased significantly in mycorrhizal plants, while changes in proline accumulation were not significant. Across most subsets of the data analysis, identities of AMF (Glomus fasciculatum) and host plants (Acacia nilotica, herbs, woody and perennial) were found to be essential in understanding plant responses to salinity stress. For the analyzed dataset, it is concluded that under salt stress, mycorrhizal plants have extensive root traits and mycorrhizal morphological traits which help the uptake of more P and K, together with the enhanced production of antioxidant enzymes resulting in salt stress alleviation and increased plant biomass.     

Comparing symbiotic performance and physiological responses of two soybean cultivars to arbuscular mycorrhizal fungi under salt stress

The presented experiments evaluated the symbiotic performance of soybean genotypes with contrasting salt stress tolerance to arbuscular mycorrhizal fungi (AMF) inoculation. In addition, the physiological stress tolerance mechanisms in plants derived from mutualistic interactions between AMF and the host plants were evaluated. Plant growth, nodulation, nitrogenase activity and levels of endogenous growth hormones, such as indole acetic acid and indole butyric acid, of salt-tolerant and salt-sensitive soybean genotypes significantly decreased at 200 mM NaCl. The inoculation of soybean with AMF improved the symbiotic performance of both soybean genotypes by improving nodule formation, leghemoglobin content, nitrogenase activity and auxin synthesis. AMF colonization also protected soybean genotypes from salt-induced membrane damage and reduced the production of hydrogen peroxide, subsequently reducing the production of TBARS and reducing lipid peroxidation. In conclusion, the results of the present investigation indicate that AMF improve the symbiotic performance of soybean genotypes regardless of their salt stress tolerance ability by mitigating the negative effect of salt stress and stimulating endogenous level of auxins that contribute to an improved root system and nutrient acquisition under salt stress.     

The differential behavior of arbuscular mycorrhizal fungi in interaction with Astragalus sinicus L. under salt stress

Three arbuscular mycorrhizal (AM) fungi (Glomus mosseae, Glomus claroideum, and Glomus intraradices) were compared for their root colonizing ability and activity in the root of Astragalus sinicus L. under salt-stressed soil conditions. Mycorrhizal formation, activity of fungal succinate dehydrogenase, and alkaline phosphatase, as well as plant biomass, were evaluated after 7 weeks of plant growth. Increasing the concentration of NaCl in soil generally decreased the dry weight of shoots and roots. Inoculation with AM fungi significantly alleviated inhibitory effect of salt stress. G. intraradices was the most efficient AM fungus compared with the other two fungi in terms of root colonization and enzyme activity. Nested PCR revealed that in root system of plants inoculated with a mix of the three AM fungi and grown under salt stress, the majority of mycorrhizal root fragments were colonized by one or two AM fungi, and some roots were colonized by all the three. Compared to inoculation alone, the frequency of G. mosseae in roots increased in the presence of the other two fungal species and highest level of NaCl, suggesting a synergistic interaction between these fungi under salt stress.     

Effects of arbuscular mycorrhizal fungi alkaline phosphatase activities on Hippophae rhamnoides drought-resistance under water stress conditions

The effects of arbuscular mycorrhizal fungi alkaline phosphatase (ALP) activities on the drought-resistance of Hippophae rhamnoides under water stress have been studied using histochemical techniques. The result shows in the mycorrhizae that total hyphae and functional hyphae form the base for the active hyphae, and amounts follow the order total hyphae>functional hyphae>active hyphae. Active hyphae play an important role in the biomass accumulation of the hosts; the hyphae with phosphatase activity (ALP) have a positive and strong effect on H. rhamnoides growth and its drought-resistance, and the rise of ALP is related to an increase in the fresh weight of the host trees, and a reduction of wilting. The direct participation of ALP in the P nutrient exchange host trees can improve the nutrient and water conditions, and raise their drought-resistance. Received: 17 August 1998 / Accepted: 18 March 1999     

水分胁迫下丛枝菌根真菌对红橘叶片活性氧代谢的影响

研究了水分胁迫下接种地表球囊霉（Glomus versiforme (Karsten) Berch）对红橘(Citrus tangerine Hort. ex Tanaka)叶片活性氧代谢的影响.结果表明：水分胁迫显著抑制了地表球囊霉对红橘根系的侵染,抑制率为33％.在正常供水和水分胁迫下,接种地表球囊霉处理的红橘叶片磷含量显著增加,与未接种处理相比,分别增加了45％和27%,丙二醛（MDA）和H₂O₂含量分别降低了25％、21％和16％、16％.正常供水和水分胁迫下接种地表球囊霉增强了叶片超氧化物岐化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)活性;提高了可溶性蛋白质、还原型抗坏血酸（ASC）和总抗坏血酸(TASC)含量.水分胁迫下接种处理显著降低了叶片超氧阴离子自由基（O₂^-_·）含量,与正常供水相比降低了31％.表明菌根化红橘植株的抗旱性增强.     

干旱胁迫下AMF对云南蓝果树叶片解剖结构的影响

苯菌灵为杀真菌剂,在土壤含水量为32.32％、29.63％、25.86％、19.39％、12.93％和6.46％的条件下,分别添加苯菌灵和不添加苯菌灵,形成“低AMF”和“高AMF”处理。该研究以云南蓝果树幼苗叶片为材料,利用盆栽试验研究了干旱胁迫下丛枝菌根真菌( AMF)对云南蓝果树幼苗叶片解剖结构及抗旱性的影响。结果表明：添加苯菌灵处理显著降低了不同水分处理条件下AMF侵染率,随着干旱胁迫程度加剧,云南蓝果树幼苗根部的AMF侵染率显著降低。轻度胁迫条件下(土壤含水量为29.63％),叶片解剖结构参数未发生显著变化;土壤含水量低于25.86％,云南蓝果树幼苗表现出较高的抗旱性,苯菌灵处理可以显著影响叶片角质层厚度、栅栏组织厚度和上表皮厚度等7个叶片结构指标,证明了高AMF可以增强代表云南蓝果树幼苗叶片抗旱性的结构性状。土壤含水量为25.86％、19.39％和12.93％时苯菌灵处理的效果较土壤含水量为6.46％时更显著,这是因为6.46％的土壤含水量严重抑制AMF的侵染,说明AMF侵染程度会影响云南蓝果树幼苗的抗旱性。进一步用隶属函数值法对10个叶片性状进行综合评价,发现高AMF处理可增强云南蓝果树幼苗的抗旱性。该研究结果为AMF在濒危物种云南蓝果树保护过程中的合理利用提供了理论依据。     

培养容器容积对AM真菌生长发育的影响

研究宿主植物栽培容器对丛枝菌根(Arbuscularmycorrhizae,AM)真菌Glomusmosseae生长发育的影响。结果表明:小容积容器的根系密度相对较大,在菌根共生体建立初期,菌根真菌繁殖体与根接触的机会增大,对于菌根真菌的迅速侵染及共生体的迅速建立非常有利,同时还增大了根外菌丝二次侵染的机会,从而使菌根真菌生长发育形成了一个良性循环,最终有利于根外孢子的形成。容器对共生体的影响决不是简单的盆的体积问题,而与其面积和体积之比有关,也和种植密度有密切关系。     

来源对丛枝菌根真菌功能的影响

丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)是一种具有重要生态功能的根际微生物。影响AMF功能的因素主要包括AMF、宿主,以及其它生物与非生物环境。近年来,大量研究表明不同来源的AMF功能存在显著差异。结合该领域的最新研究成果,从基因变异和表型可塑性两方面分析了来源影响AMF功能的原因和维持机制,并对其生态学意义进行了探讨。认为应从群落水平上研究不同来源的AMF在生态系统中的功能,重视宿主的作用,保持研究对象的对等性,并区分AMF群落结构和来源对功能的不同影响。对未来的研究重点和方向进行了讨论和展望,试图为更加清晰、全面地认识AMF在生态系统中的功能,以及AMF适应特定土壤环境与宿主的机制提供参考。     

Quantification of arbuscular mycorrhizal fungi activity by the glomalin concentration on hyphal traps

 Strips of horticultural film (16–32 cm²) were used to trap extraradical hyphae emanating from roots of sudangrass [Sorghum sudanense (Piper) Staph] enclosed in 40-μm mesh bags and colonized by Gigaspora rosea FL 224-1, Glomus intraradices EY 113/114, or Glomus caledonium UK 301-1. Strips of film were placed at opposite sides of 17–21 replicate sand culture pots for each isolate and were removed after 12–14 weeks of plant growth. To extract glomalin, a strip was cut into small pieces and submerged in 2 ml of 20 mM citrate, pH 7.0 and then autoclaved for 60 min. A quantitative enzyme-linked immunosorbent assay (ELISA) detected 0.005–0.04 μg glomalin in the volume of extract tested. The Bradford protein assay detected 1.25–5 μg of protein in the volume of extract tested. Both assays gave results ranging from 5–40 μg glomalin/cm² of film. Protein assay values were correlated with ELISA values (r=0.6091, P≤0.001, n=118). Analysis of variance indicated that isolates differed in Bradford protein values (P=0.001), but not ELISA values (P=0.154). Spatial variability of glomalin deposition ca. 7 cm from roots on opposite sides of pots was indicated by significant paired T tests (P<0.05) for protein values for each of the three isolates and ELISA for two isolates. These results indicate that hyphal traps, Bradford protein assay and ELISA are useful to assess hyphal activity over a growing season. Accepted: 11 October 1998     

Heavy-metal stress and developmental patterns of arbuscular mycorrhizal fungi

The rate of global deposition of Cd, Pb, and Zn has decreased over the past few decades, but heavy metals already in the soil may be mobilized by local and global changes in soil conditions and exert toxic effects on soil microorganisms. We examined in vitro effects of Cd, Pb, and Zn on critical life stages in metal-sensitive ecotypes of arbuscular mycorrhizal (AM) fungi, including spore germination, presymbiotic hyphal extension, presymbiotic sporulation, symbiotic extraradical mycelium expansion, and symbiotic sporulation. Despite long-term culturing under the same low-metal conditions, two species, Glomus etunicatum and Glomus intraradices, had different levels of sensitivity to metal stress. G. etunicatum was more sensitive to all three metals than was G. intraradices. A unique response of increased presymbiotic hyphal extension occurred in G. intraradices exposed to Cd and Pb. Presymbiotic hyphae of G. intraradices formed presymbiotic spores, whose initiation was more affected by heavy metals than was presymbiotic hyphal extension. In G. intraradices grown in compartmentalized habitats with only a portion of the extraradical mycelium exposed to metal stress, inhibitory effects of elevated metal concentrations on symbiotic mycelial expansion and symbiotic sporulation were limited to the metal-enriched compartment. Symbiotic sporulation was more sensitive to metal exposure than symbiotic mycelium expansion. Patterns exhibited by G. intraradices spore germination, presymbiotic hyphal extension, symbiotic extraradical mycelium expansion, and sporulation under elevated metal concentrations suggest that AM fungi may be able to survive in heavy metal-contaminated environments by using a metal avoidance strategy.     

盐碱胁迫下AM真菌对羊草生长及生理代谢的影响

利用盆栽控制试验研究了盐碱胁迫下AM真菌对羊草生长及生理代谢的影响。结果表明,盐碱胁迫显著降低了AM真菌的侵染率与侵染强度,且具有高pH的碱胁迫的抑制效应更强。接种AM真菌一定程度上提高了胁迫下羊草幼苗的生物量及光合色素(Chl a,Chl b和Car)含量。随着盐碱胁迫浓度的增加,羊草幼苗积累了大量的Na~+,并抑制了其对K~+的吸收,接种AM真菌一定程度上降低了Na~+的积累,并缓解了胁迫下K~+含量的降低,提高NO_3~-含量从而改善羊草幼苗的离子平衡。在碱胁迫下,柠檬酸、苹果酸含量均显著提高,在盐胁迫下,仅苹果酸含量显著提高,而接种AM真菌使盐碱胁迫下有机酸含量一定程度降低。在盐碱胁迫条件下,接种AM使羊草体内超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)的活性明显提高,增强宿主植物体内氧自由基的清除能力。接种AM真菌明显提高羊草幼苗抗盐碱能力,因胁迫类型不同,抗逆机理有所差异。研究结果为利用羊草进行生物改良退化盐碱草地以及菌肥的应用提供了科学依据,也为探求羊草-丛枝菌根共生体对盐碱胁迫的响应和反馈提供了数据支持。     

丛枝菌根真菌影响作物非生物胁迫耐受性的研究进展

土壤中存在着大量不同种类的微生物资源,土壤微生物能够与自然界中的大多数植物密切合作,其中丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)起着十分重要的作用。近年来,对于AMF的研究越来越多。AMF是存在于土壤中的重要真菌之一,是土壤中的菌根真菌菌丝与高等植物营养根系形成的一种联合体。AMF可以与陆地上90%左右的植物根系形成共生体,通过在植物根系形成重要的“丛枝菌根”结构而为植物提供更多的养分。为了了解接种AMF对作物生长过程中耐受一些非生物胁迫(如干旱、极端温度、重金属污染、盐分、不利的土壤pH变化等)性能方面的影响,基于之前接种AMF对养分胁迫下玉米生长影响的研究,在扩大作物品种的基础上,通过查阅大量文献,结合试验研究及对前人和近年来关于AMF的一些最新研究进展,获得了具有实践性意义的新发现：AMF与植物共生有助于植物生长,可以改善植物的营养状况,并且可以保护植物免受各种非生物环境胁迫的影响。由此可以得出结论：AMF通过各种机制改善植物生长状况,提高作物抗逆性,为作物增产、农民增收创造了福利,并且避免了由于肥料过量施用导致的一些污染环境问题。本文主要综述了接种AMF在各种非生物环境胁迫(干旱、极端温度、重金属污染、盐分、不利的土壤pH变化等)条件下对植株生长和发育的有利影响,并对目前存在的不足和今后研究的重点提出几点建议。     

盐胁迫下外源褪黑素和从枝菌根真菌对月季幼苗生理特性及光合荧光参数的影响

本试验旨在探究100mol/L盐胁迫下根际施用褪黑素(MT)、接种近明球囊霉属AMF幼套近明球囊霉(Claroideoglomus etunicatum)及其复合处理对月季幼苗生长、叶绿素荧光参数、激素代谢及抗氧化系统的影响,以探明两者缓解月季盐胁迫的机制。结果发现,盐胁迫下月季幼苗生长受到抑制,株高、茎粗以及生物量等显著下降;施用MT可以促进AMF侵染,提高侵染率、丛枝着生率、泡囊数和侵入点数。100mol/L盐处理下,与对照(CK)处理相比,AMF+MT处理的叶绿素总量、叶绿素a/b分别增加46.2%和67.2%;叶绿素荧光参数中PSⅡ最大光化学效率(Fv/Fm)、PSⅡ潜在活性(Fv/Fo)、PSⅡ实际光化学效率(φPSⅡ)、PSII有效光化学量子效率(Fv’/ Fm’)、光化学猝灭系数(qP)分别增加4.9%、51.0%、175.0%、168.7%和92.5%,NPQ的下降幅度为42.7%;此外,盐胁迫下,月季叶片中玉米素核苷(ZR)、赤霉素(GA)、生长素(IAA)含量下降,而脱落酸含量(ABA)增加,AMF+MT处理后ZR、GA、IAA分别增加146.9%、116.9%、35.7%,ABA下降21.1%;同时AMF+MT处理能够激活抗氧化酶SOD、CAT活性,降低超氧阴离子(O2-)产生速率和H2O2累积。结论认为,接种AMF、添加MT或者AMF+MT处理均可以提高叶绿素含量,保护叶绿素荧光系统,维持植物内源激素的平衡,激活SOD、CAT等抗氧化酶活性以及降低脂质过氧化和H2O2累积,以减轻盐胁迫对月季幼苗的伤害,促进月季生长,其中以AMF+MT处理下月季幼苗的抗盐性效果更佳。