Influence of arbuscular mycorrhiza on lipid peroxidation and antioxidant enzyme activity of maize plants under temperature stress

The influence of the arbuscular mycorrhizal (AM) fungus, Glomus etunicatum, on characteristics of growth, membrane lipid peroxidation, osmotic adjustment, and activity of antioxidant enzymes in leaves and roots of maize (Zea mays L.) plants was studied in pot culture under temperature stress. The maize plants were placed in a sand and soil mixture under normal temperature for 6 weeks and then exposed to five different temperature treatments (5oC, 15oC, 25oC, 35oC, and 40oC) for 1 week. AM symbiosis decreased membrane relative permeability and malondialdehyde content in leaves and roots. The contents of soluble sugar content and proline in roots were higher, but leaf proline content was lower in mycorrhizal than nonmycorrhizal plants. AM colonization increased the activities of superoxide dismutase, catalase, and peroxidase in leaves and roots. The results indicate that the AM fungus is capable of alleviating the damage caused by temperature stress on maize plants by reducing membrane lipid peroxidation and membrane permeability and increasing the accumulation of osmotic adjustment compounds and antioxidant enzyme activity. Consequently, arbuscular mycorrhiza formation highly enhanced the extreme temperature tolerance of maize plant, which increased host biomass and promoted plant growth.     

Influence of arbuscular mycorrhiza on organic solutes in maize leaves under salt stress

A pot experiment was conducted to examine the effect of the arbuscular mycorrhizal (AM) fungus, Glomus mosseae, on plant biomass and organic solute accumulation in maize leaves. Maize plants were grown in sand and soil mixture with three NaCl levels (0, 0.5, and 1.0 g kg⁻¹ dry substrate) for 55 days, after 15 days of establishment under non-saline conditions. At all salinity levels, mycorrhizal plants had higher biomass and higher accumulation of organic solutes in leaves, which were dominated by soluble sugars, reducing sugars, soluble protein, and organic acids in both mycorrhizal and non-mycorrhizal plants. The relative abundance of free amino acids and proline in total organic solutes was lower in mycorrhizal than in non-mycorrhizal plants, while that of reducing sugars was higher. In addition, the AM symbiosis raised the concentrations of soluble sugars, reducing sugars, soluble protein, total organic acids, oxalic acid, fumaric acid, acetic acid, malic acid, and citric acid and decreased the concentrations of total free amino acids, proline, formic acid, and succinic acid in maize leaves. In mycorrhizal plants, the dominant organic acid was oxalic acid, while in non-mycorrhizal plants, the dominant organic acid was succinic acid. All the results presented here indicate that the accumulation of organic solutes in leaves is a specific physiological response of maize plants to the AM symbiosis, which could mitigate the negative impact of soil salinity on plant productivity.     

Influence of arbuscular mycorrhiza on growth and reproductive response of plants under water deficit: a meta-analysis

Despite a large body of literature that describes the effects of arbuscular mycorrhizal colonization on plant response to water deficit, reviews of these works have been mainly in narrative form, and it is therefore difficult to quantify the magnitude of the effect. We performed a meta-analysis to examine the effect of mycorrhizal colonization on growth and yield of plants exposed to water deficit stress. Data were compared in the context of annual vs. perennial plants, herbaceous vs. woody plants, field vs. greenhouse conditions, degree of stress, functional group, regions of plant growth, and mycorrhizal and host species. We found that, in terms of biomass measurements, mycorrhizal plants have better growth and reproductive response under water stress compared to non-mycorrhizal plants. When variables such as habit, life cycle, or water stress level are considered, differences in mycorrhizal effect on plant growth between variables are observed. While growth of both annual and perennial plants is improved by symbiosis, perennials respond more favorably to colonization than annuals. Overall, our meta-analysis reveals a quantifiable corroboration of the commonly held view that, under water-deficit conditions, plants colonized by mycorrhizal fungi have better growth and reproductive response than those that are not.     

丛枝菌根对植物根际逆境的生态学意义

近年来,我国在菌根分子生物学、菌根营养学、菌根分类学和菌根生态学等方面取得了令人瞩目的研究成果,其中对丛枝菌根真菌(AMF)的研究居多。AMF能与大部分陆地植物根系形成共生关系,促进植物生长发育,提高植物抗逆性,在保持生态平衡、保护生态环境等方面发挥重要作用。本文主要从非生物胁迫(干旱胁迫、重金属污染、盐碱胁迫)和生物胁迫(致病菌和线虫侵染)方面介绍了AMF在植物根际逆境中发挥的生态功能及作用机制,提出了该研究领域尚存的不足之处和研究前景,为AMF后续研究提供参考。     

Some physiological responses of chickpea cultivars to arbuscular mycorrhiza under drought stress

A factorial experiment based on RCB design with three replicates was conducted to investigate changes in some physiological responses of two chickpea (Cicer arietinum L.) cultivars (Pirouz from Desi type and ILC482 from Kabuli type) to arbuscular mycorrhiza (Glomus etunicatum Becker and Gerdman) under different irrigation treatments. The experiment was carried out in the greenhouse of the Agricultural Faculty of Kurdistan University from April to August 2009. The results showed that leaf chlorophyll content of chickpea cultivars was significantly increased by arbuscular mycorrhiza (AM) under both well and limited irrigation conditions. Proline accumulation in chickpea leaves under moderate and severe drought stresses was significantly stronger than that under optimum irrigation. Inoculation of chickpea with mycorrhizal fungi caused an increase in the activities of polyphenol oxidase and peroxidase, but a decrease in the activity of catalase. Comparisons among different irrigation levels showed that chickpea plants under drought stress had the most active lipid peroxidation. Non-AM plants showed stronger lipid peroxidation under moderate and severe water stresses than AM plants. Lipid peroxidation was more active in Pirouz leaves than in ILC₄₈₂ leaves. It seems that Kabuli-type cultivar responded better to mycorrhizal symbiosis under drought stress than Desitype cultivar.     

丛枝菌根真菌对盐胁迫下黄瓜植株生长、果实产量和品质的影响

采用有机基质栽培,选用盐敏感黄瓜品种‘津春2号’为试验材料,研究了丛枝菌根真菌(AMF)对盐胁迫下黄瓜植株生长、矿质营养吸收、果实品质和产量的影响.结果表明：接种AMF可以有效促进黄瓜植株生长和对矿质营养的吸收,提高果实产量和改善蔬菜营养品质;盐胁迫下,黄瓜生长受到抑制,植株体内N、P、K、Cu、Zn含量减少和K⁺/Na⁺降低,果实产量和可溶性蛋白、总糖、Vc、硝酸盐含量下降;接种AMF可缓解盐胁迫对黄瓜生长的抑制作用,使植株体内N、P、K、Cu和Zn含量分别比对照提高7.3%、11.7%、28.2%、13.5%和9.9%,K⁺/Na⁺、果实产量、可溶性蛋白、总糖、Vc含量明显提高,果实硝酸盐含量显著降低.表明AMF可通过促进盐胁迫下黄瓜植株对矿质营养的吸收,促进植株生长,增强植株对盐胁迫的耐性,进而提高其产量和改善营养品质.     

Occurrence of arbuscular mycorrhiza and ectomycorrhiza on

Leptospermum is one of only three New Zealand genera that are colonised by ectomycorrhizal (EM) fungi, and L. scoparium is one of the very few New Zealand species that can be colonised by both arbuscular mycorrhizal (AM) and EM fungi. This study examined AM and EM colonisation on L. scoparium growing within AM grassland ecosystems or adjoining Nothofagus forest in the Rakaia catchment, Canterbury. Very low AM colonisation was found (<4%) in all samples, while EM colonisation ranged from 7 to 55% of root length colonised. These results contradict an earlier report that L. scoparium is mostly colonised by AM fungi. We suggest the montane environment of the study sites would favour EM rather than AM colonisation. EM colonisation was higher in mature plants than in saplings. Lowest EM colonisation (7–15%) was recorded on root samples that were from either young or mature plants occurring as separate individuals in grassland distant from other indigenous EM species, while highest colonisation (49–55%) was recorded on samples from mature closed canopy L. scoparium stands, irrespective of distance from other indigenous EM sources.     

Influence of arbuscular mycorrhizae on the metabolism of maize under drought stress

A greenhouse experiment was carried out to investigate the influence of the arbuscular mycorrhizal (AM) fungus (Glomus intraradices Schenck & Smith) on metabolic changes in tropical maize (Zea mays L.) under drought. Two cultivars, Tuxpeno sequia CO (drought sensitive) and C8 (drought resistant), were subjected for 3 weeks to water stress following tasselling (75–95 days after sowing). Fully expanded 7th or 8th leaves were sampled and assessed for levels of chlorophyll, sugars, proteins, and amino acids. Chlorophyll content was not altered either by water stress or the presence of mycorrhizae. Mycorrhizal plants (M+) had higher total and reducing sugars than nonmycorrhizal plants (M-) at the end of 3 weeks of the drought cycle. An increase in protein content was observed with drought stress in M + plants of the cultivar C0. Most of the amino acids showed a linear increase during the period of water stress in M+ and M- plants for both cultivars. Total amino acids increased by 40.6% and 43.7% in M- plants of C0 and C8, respectively. With the presence of AM fungus, amino acid levels increased by only 10.7% and 19.2% of leaf dry mass in C0 and C8, respectively. Alanine, asparagine, glutamine, and glycine accounted for 70% of the amino acid pool. Under drought, AM inoculation enabled the plants to retain considerable amounts of sugars and proteins, especially in the drought-sensitive cultivar C0. This may be of physiological importance in helping the plant to withstand moderate drought.     

Microbial ecology of the arbuscular mycorrhiza

Arbuscular mycorrhizal (AM) fungi interact with a wide variety of organisms during all stages of their life. Some of these interactions such as grazing of the external mycelium are detrimental, while others including interactions with plant growth promoting rhizobacteria (PG PR) promote mycorrhizal functioning. Following mycorrhizal colonisation the functions of the root become modified, with consequences for the rhizosphere community which is extended into the mycorrhizosphere due to the presence of the AM external mycelium. However, we still know relatively little of the ecology of AM fungi and, in particular, the mycelium network under natural conditions. This area merits attention in the future with emphasis on the fungal partner in the association rather than the plant which has been the focus in the past.     

The effects of salt stress and arbuscular mycorrhiza on plant neighbour effects and self-thinning

Abiotic and biotic factors can alter the nature and strength of plant–plant interactions and therefore self-thinning (density-dependent mortality), but few studies have looked at how such factors interact. We investigated how salt stress and arbuscular mycorrhizal fungi (AMF) influence plant neighbour effects and self-thinning in experimental populations of Medicago sativa. We obtained two mycorrhizal levels by applying the fungicide benomyl (low AMF) or not (high AMF) at three salinity levels (0.05%, 0.2% and 0.5%). In experiment 1, we investigated how salinity and AMF interact to influence plant interaction intensity using a neighbour removal treatment. In experiment 2, we investigated how self-thinning dynamics vary under salinity conditions and different AMF levels at two initial plant densities (6000 and 17,500 seeds m^?2). Shoot biomass and plant density were measured 30, 60 and 90 days after sowing. Standardized major axis regression was used to estimate self-thinning parameters. In experiment 1, AMF increased competitive plant neighbour effects when there was no salinity stress, but this enhancement was not significant with increasing salinity. In experiment 2, there were effects of salinity and AMF on the self-thinning trajectory. The slope of the log (mean shoot biomass per unit area) vs. log density relationship was significantly steeper for the high AMF treatment than for the low AMF treatment without salinity, but the effect of AMF level on the self-thinning exponent was not significant under the two higher salinity levels. The effect of AMF treatments on the intercept of the self-thinning line was not significant at 0.2% salinity but was significant at 0.5% salinity, higher elevation for high AMF treatment. In self-thinning populations, AMF decreased the survival rate without salinity, but increased the survival rate at the highest salinity level. Our results support the hypothesis that salinity and AMF interact to influence plant neighbour effects and self-thinning. Under no-salinity conditions, AMF increased competition, steepened the self-thinning line and decreased survival rate, but these effects of AMF were not significant in the presence of salinity.     

Occurrence of arbuscular mycorrhiza on aged Eucalyptus

Eucalyptus despite the fact that Eucalyptus seedlings do form both endomycorrhiza and ectomycorrhiza early during their developement. In the present study, all the structures of arbuscular mycorrhiza were observed within roots of four Eucalyptus species of 15, 17 and more than 50 years old at three different sites in northern Algeria. Arbuscular mycorrhiza frequency was assessed in roots of 15-years old Eucalyptus camaldulensis species, during two periods in 2 consecutive years (July and November of 1996 and 1997). Intensity of root colonization was dependent on the time of sampling and attained 42% in July 1997. Accepted: 17 September 1999     

A history of research on arbuscular mycorrhiza

This is not a review paper in the traditional sense, of which there are many. Three of the most influential reviews that summarized well some of the older literature include those by Nicolson (1967), Gerdemann (1968) and Mosse (1973). Instead, in this brief and incomplete work, we attempt to show the historical development of research on arbuscular mycorrhizas. We owe much to those who have written other historical accounts, including Rayner (1926–1927), Trappe and Berch (1985), Mosse (1985), Schenck (1985), Harley (1991) and Allen (1996), but the contents of this work naturally reflect our own ignorance, interests and biases. It was often difficult to distinguish between the historical and the contemporary, and we did not use any specific cutoff date in making this distinction. The degree to which we include contemporary literature was determined by our own assessment of its connectedness to older literature. In any case, we hope this will be of some interest to those of you who study the arbuscular mycorrhiza, and that it will serve the purpose of providing what we consider to be an important historical context for current researchers. We wish you good fortune in your research.Taken from a paper presented at the COST 8.38 meeting AM Research in Europe (Pisa, Italy): The Dawning of a New Millenium     

Influence of salt stress on growth,lipid peroxidation and antioxidative enzyme activity in borage (Borago officinalis L.)

Abstract

The effects of increasing salt concentrations on the growth, electrolyte leakage, lipid peroxidation, and major antioxidant enzyme activities (superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase) of borage plants were investigated. Plants were grown in half strength of Hoagland nutrient solution added with 0, 25, 50, and 75 mM of NaCl. Most measured parameters were affected by salinity. Increasing salt levels caused a significant reduction in leaf area, stem length, stem diameter, flower number, and dry masses of different organs. Growth of borage plants, in terms of dry weight, was affected. As a consequence of salinity stress, lipid peroxidation and membrane permeability was increased. Antioxidant activity showed an increase in the activity of superoxide dismutase, a non-induced activity of catalase and ascorbate peroxidase, and a slight increase in glutathione reductase activity. The results indicate that borage plants appear to be sensitive to salt stress, since enzymes related to antioxidant enzymatic defense system in treated leaves should be highly active.     

Effect of short-term heat stress on growth, physiology and antioxidative defence system in wheat seedlings

An experiment was conducted to find out the effect of short-term heat stress on morpho-physiological characters and antioxidants in 10 diverse wheat genotypes. Seed were aseptically grown in test tubes containing filter paper whose lower half was dipped in one-fourth MS media. Heat stress conditions were created by exposing the seedlings at 45 °C for 2 h after 7 days of their germination. Measurements were taken after 3 days of treatment. Heat stress significantly reduced the shoot dry mass, root dry mass, shoot length and root length in all the genotypes. The chlorophyll content and membrane stability index decreased, whereas proline content increased in heat-treated plants. There was significant increase in the activity of catalase, guaiacol peroxidase and superoxide dismutase under stress conditions. The genotypic variations were also significant. On the basis of a coordinated simulation of all these parameters, wheat genotypes Raj 4037 and PBW 373 were identified as tolerant to high temperature stress. The study provides evidence that the tolerant genotypes were equipped with better management of physiological processes along with an efficient antioxidative defence system, sensitivity of which can be evaluated to a sufficient level of certainty at seedling stage.     

Photon-harvesting efficiency and arbuscular mycorrhiza in amphibious plants

The amphibious plant species of intermittent aquatic habitats thrive both submerged and emerged. In order to outline the adaptive characters of these two life forms photochemical efficiency of photosystem 2, leaf contents of chlorophyll (Chl) a and b, carotenoids (Car), anthocyanins (Ant), and UV-B absorbing compounds (UV-B abs), and root aerenchyma and arbuscular mycorrhizal (AM) colonisation were studied in Glyceria fluitans, Gratiola officinalis, Ranunculus lingua, Teucrium scordium, Sium latifolium, Sparganium emersum, and Veronica anagallis-aquatica. Water level fluctuations did not exert a severe effect on photon harvesting efficiency. Submerged specimens had higher contents of Car and Ant whereas higher contents of UV-B abs were found in emerged specimens indicating efficient protection against the harmful effects of solar radiation. Roots of all species studied had extensive aerenchyma and were colonised by AM fungi, which were significantly more abundant in emerged specimens. This is the first report on AM symbiosis in S. latifolium and S. emersum.     

Influence of arbuscular mycorrhizae on photosynthesis and water status of maize plants under salt stress

The influence of arbuscular mycorrhizal (AM) fungus Glomus mosseae on characteristics of the growth, water status, chlorophyll concentration, gas exchange, and chlorophyll fluorescence of maize plants under salt stress was studied in the greenhouse. Maize plants were grown in sand and soil mixture with five NaCl levels (0, 0.5, 1.0, 1.5, and 2.0 g/kg dry substrate) for 55 days, following 15 days of non-saline pretreatment. Under salt stress, mycorrhizal maize plants had higher dry weight of shoot and root, higher relative chlorophyll content, better water status (decreased water saturation deficit, increased water use efficiency, and relative water content), higher gas exchange capacity (increased photosynthetic rate, stomatal conductance and transpiration rate, and decreased intercellular CO(2) concentration), higher non-photochemistry efficiency [increased non-photochemical quenching values (NPQ)], and higher photochemistry efficiency [increased the maximum quantum yield in the dark-adapted state (Fv/Fm), the maximum quantum yield in the light-adapted sate (Fv'/Fm'), the actual quantum yield in the light-adapted steady state (varphiPSII) and the photochemical quenching values (qP)], compared with non-mycorrhizal maize plants. In addition, AM symbiosis could trigger the regulation of the energy biturcation between photochemical and non-photochemical events reflected in the deexcitation rate constants (kN, kN', kP, and kP'). All the results show that G. mosseae alleviates the deleterious effect of salt stress on plant growth, through improving plant water status, chlorophyll concentration, and photosynthetic capacity, while the influence of AM symbiosis on photosynthetic capacity of maize plants can be indirectly affected by soil salinity and mycorrhizae-mediated enhancement of water status, but not by the mycorrhizae-mediated enhancement of chlorophyll concentration and plant biomass.     

丛枝菌根利用氮素研究进展

氮素是植物需求量最大的元素,丛枝菌根真菌与植物形成共生体后能从土壤中获取无机氮、简单的氨基酸,还能利用一些复杂的有机态氮.考虑到NH+4在土壤中的移动性低及丛枝菌根真菌的专性共生菌的特点,丛枝菌根真菌吸收NH+4对植物的贡献较大.近年来的研究发现丛枝菌根真菌内存在与氮素代谢有关的鸟氨酸循环,而精氨酸则是菌丝内氮素转移的主要形式.综述最近的AMF对氮素的吸收、转运、同化、交换等方面的文献,旨在揭示丛枝菌根真菌氮素利用特点,阐明丛枝菌根真菌在氮循环系统中的重要作用.     

植物激素调控丛枝菌根发育的作用机制研究进展

丛枝菌根（arbuscular mycorrhiza,AM）是土壤中AM真菌和绝大多数维管植物根系长期进化过程中相互识别、相互作用形成的互利共生体。AM的发育与功能效应依赖AM真菌-寄主植物之间精准的“分子对话”,同时受到环境条件特别是土壤养分水平、干旱和盐渍化的制约。植物激素作为低浓度的小分子有机物,是参与调控AM共生过程的重要信号分子。其中,主要有9种植物激素参与AM发育过程且分工各有不同：独脚金内酯（strigolactones,SLs）参与AM真菌-寄主植物之间最初的共生识别,脱落酸（abscisic acid,ABA）和油菜素内酯（brassinosteroid,BR）促进前期的菌丝入侵,但水杨酸（salicylic acid,SA）和乙烯（ethylene,ET）抑制前期的菌丝入侵,生长素（auxin,Aux）、ABA和BR促进随后的丛枝形成而ET和赤霉素（gibberellin,GA）的作用则相反,茉莉酸（jasmonic acid,JA）对菌丝入侵与丛枝形成均可能存在正调控或负调控作用。目前细胞分裂素（cytokinin,CTK）在AM发育中的作用尚不明确。更为复杂的是,通常植物激素信号之间的交叉互作决定AM的发育进程。本文针对AM发育过程总结了不同植物激素的调控作用特点和不同植物激素信号之间的互作（协同或拮抗）,以及胁迫条件下不同植物激素信号的可能调控机制。深入研究和系统阐明植物激素调控AM真菌-寄主植物共生的生理/分子机制,将有助于促进生物共生学理论研究及菌根技术的应用。     

环境污染物对丛枝菌根(AM)形成及功能的影响

丛枝菌根(AM)具有植物和微生物的双重特性,在污染土壤修复中受到越来越多的重视.AM在修复污染土壤的同时,也深受污染物毒害的影响,从而降低AM在污染土壤修复中的作用.如何减少环境污染物对AM的不利影响,是AM应用中需要考虑的问题.从有机和无机污染物角度, 综述了不同污染物对AM形成及功能的影响,并分析了可能的影响机理.大量研究表明,无论是有机污染物还是无机污染物,都会对AM的结构、形成和功能产生破坏性影响,主要表现在孢子萌发、侵染率、菌丝伸长受抑制等.有机污染物可能通过影响光合产物向AM真菌的分配, 间接影响AM真菌的活性,而重金属则通过抑制AM真菌活性, 直接对其产生影响.