Arbuscular Mycorrhizal Mediated Nutrition in Plants

ABSTRACT

Arbuscular mycorrhizae (AM) are the symbiotic fungi that predominate in the roots and soils of agricultural crop plants. The most recognized beneficial effect of these fungi is to enhance host plant uptake of relatively immobile nutrients, in particular phosphorus (P), and several micronutrients. The AM fungi absorb inorganic P either from the soluble P pools in the soil, or from insoluble forms such as rock phosphates as well as from insoluble organic sources. Recent studies show that mycorrhizal fungi would have access to rock phosphate through localized alterations of pH and/or by the production of organic acid anions that may act as chelating agents. The AM colonization also improves plant N nutrition. Generally mycorrhizal symbiosis more influences on nitrogen (N) uptake and translocation if ammonium (NH₄ ⁺) rather than nitrate (NO₃ ^?) is the nitrogen source. However, under drought stress the role of mycorrhizae in NO₃ ^? transport to the root surface may be significant as the NO₃ ^? mobility is severely restricted due to its low concentration and diffusion rate under such circumstances. However, as yet little is known about the mechanism of N uptake by the AM fungi. Uptake of micronutrients is also influenced by mycorrhizal colonization.     

BUFFERING EFFECT OF ELEMENTAL SULFUR ON MYCORRHIZAL INFECTION OF LEEK

The effect of elemental sulfur (S) on the mycorrhizal infection and yield enhancement in leek was investigated. Plants were grown on a calcareous Karaburun soil (sub-group typic xerorthent) from a farm of the University of Cukurova, Adana, Turkey. Sterilized soil with and without the addition of elemental sulfur resulted in significant biomass increase of both root and shoot dry matter. The buffering effect of the elemental sulfur against the decreasing effect of phosphorus for the inoculation percent was also observed. This new finding about the efficiency of the mycorrhizae with the optimum inoculation rate resulting from the addition of 100 ppm elemental sulfur to the application inoculated with mycorrhizae indicates that it is of major scientific interest for ecologic agriculture.     

DO MAIZE AND PEPPER PLANTS DEPEND ON MYCORRHIZAE IN TERMS OF PHOSPHORUS AND ZINC UPTAKE?

Nutrient deficiency, especially zinc (Zn) and phosphorus (P), is a common nutritional problem for the production of some crops in Turkey. This problem results in the application of increasing amounts of several fertilizers. Mycorrhizal inoculation or the indigenous potential of mycorrhizae in the soil is a critical factor in crop production under low supply of Zn and P. The effects of selected mycorrhizal inoculation on growth and Zn and P uptake of maize and green pepper were investigated in Zn- and P-deficient calcareous soils from Central Anatolia. Soils were sterilized by autoclaving and plants were grown for 7 weeks in pots under greenhouse conditions with inoculation of two selected arbuscular mycorrhizal (AM) species (Glommus moseea and G. etunicatum) at three rates of P (0, 25, 125 mg P kg^?1 soil) and two rates of Zn (0 and 5 mg Zn kg^?1soil). Without mycorrhizal inoculation, shoot and root dry matter production were severely affected by P and Zn deficiencies, and supply of adequate amounts of P and Zn significantly enhanced plant growth. When the soil was inoculated with mycorrhizal inoculation, the increasing effects of P and Zn fertilization on plant growth remained less pronounced. In accordance with growth data, mycorrhizae inoculation enhanced P and Zn concentration of plants, especially under low supply of P and Zn. The results obtained indicate that maize and green pepper are highly mycorrizal–dependent (MD) plant species under both low P and Zn supply and mycorrhizae play an essential role in P and Zn nutrition of plants in P and Zn-deficient soils. Although addition of P and Zn increased plant growth and plants are mycorrhizal dependent on P and Zn nutrition however dependence is much more dependent on P nutrition.     

EXPLOITATION OF PHOSPHORUS PATCHES WITH DIFFERENT PHOSPHORUS ENRICHMENT BY THREE ARBUSCULAR MYCORRHIZAL FUNGI

The effect of three arbuscular mycorrhizal (AM) fungi on phosphorus (P) nutrient activation and acquisition by maize from spatially heterogeneous sand was investigated using dual-mesh packages enriched with different P concentrations and compared with non-mycorrhizal cotrols. As would be expected the AM fungi significantly enhanced leaf photosynthetic rate and the biomass and P concentrations in shoots and roots. All three fungi (Glomus intraradices, Glomus mosseae and Glomus etunicatum) displayed the capacity to dissolve inorganic P and promoted P nutrient availability in the packages (P patches). G. etunicatum showed the largest effect comparing with Glomus intraradices and Glomus mosseae, particularly in packages with high concentrations of P. Possible mechanisms involved include the acidification of the P patches by the AM fungi, promotion of the dissolution of the P, and more marked effects of the three fungal isolates with increasing enrichment of P in the patches. Inoculation with G. etunicatum resulted in greater acidification compared to the other two fungi. We conclude that AM fungi can promote P availability by acidifying the soil and consequently exploiting the P in nutrient patches and by facilitating the growth and development of the host plants.     

丛枝菌根真菌最新分类系统与物种多样性研究概况

丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)是自然界分布最广泛的一类植物共生真菌,能够与大部分高等植物的根系形成共生关系.由于它们在农林、环境等领域的巨大应用潜力,国内外关于AMF物种多样性的研究一直受到较高的关注.然而,AMF专性共生的特征以及研究方法不够理想等因素长期阻碍了AMF物种多样性的研究进展.近年来,研究方法的改进与新技术的应用为AMF物种多样性的研究提供了极好的机遇.简述了AMF的最新分类系统及全球物种数量、AMF物种多样性影响因素以及AMF物种多样性研究方法三个方面的研究进展,并分析了今后在AMF物种多样性相关领域值得关注的研究方向.     

Nature Farming with Vesicular-Arbuscular Mycorrhizae in Bangladesh

Summary

Systematic research on the effect of vesicular-arbuscular mycorrhizal fungi with different agricultural crops, sand dune plants and plantation crops has been carried out in Bangladesh for last few years. Large numbers of VA-mycorrhizal fungi have been detected in different soil types for identification and inoculum production and for use in nurseries and the field as an alternative to chemical fertilizers and pesticides and to progress towards nature farming. The VAM fungi not only absorb and translocate immobile nutrients like phosphorus, zinc and copper (especially phosphorus) through external hyphae, but also play important roles in inter- and intra-specific transfer of carbon, phosphorus, and nitrogen from plant to plant. VAM fungi may also protect plants from certain root-infecting pathogens, improve plant-water relations, enhance the establishment and growth of micro-propagated plants, and increase plant tolerance to salinity. VAM fungi can improve the ecological and environmental conditions of the country and its agriculture by reducing the farmer's dependence and expenditure on chemical fertilizers and pesticides. Effective mycorrhizal inoculum can be introduced directly to the field or indirectly through the production of VAM-infected seedlings from nurseries. The gap of knowledge on the occurrence of VAM fungi in association with different agricultural and forest crops is still immense in Bangladesh. This article has been prepared to draw attention of agricultural scientists, plant physiologist, forest managers, policy-makers and different government and non-government officials towards nature farming systems utilizing VAM and possibility of utilizing VAM in production system.     

Effects of Organic and Chemical Fertilizers and Arbuscular Mycorrhizal Inoculation on Growth and Quality of Cucumber and Lettuce

Summary

Arbuscular mycorrhizae were inoculated into phosphorus-deficient soil fertilized with either organic or chemical fertilizer with cucumber (Cucumis sativus L.) as the first crop and lettuce (Lactu-ca sativa L.) as the second crop but without additional fertilization and AM inoculation. AM increased dry matter and fruit yield of cucumber significantly in the unfertilized, organic-fertilized and P-deficient plants compared with the fully chemical-fertilized plants. AM inoculation increased the available phosphorus in plant and soil by around 30% for all treatments except for those chemically-fertilized. The rate of AM infection did not differ significantly among the fertilization treatments, but the infection intensity was higher in unfertilized, organic-fertilized and phosphorus-deficient treatments than chemical-fertilized treatment. The residual effects of AM-inoculated to cucumber were evident for lettuce in all pre-treatments that were unfertilized and un-inoculated for the second cropping. Without P-fertilization, neither crop could grow optimally even when the soil was inoculated with AM, suggesting that AM could not serve as a substitute for phosphorus fertilizer. However, the other beneficial effects of AM on crop growth and yield could not be fulfilled with phosphorus fertilizer.     

低温胁迫下AMF对景天三七生长和生理特性的影响

以景天三七(Sedum aizoon)为试材,接种丛枝菌根真菌(AMF)后,再进行低温处理(0℃、5℃、10℃,以25℃为对照),在低温处理2、4、6、8和10d后对生长指标和相对电导率、丙二醛(MDA)含量、抗氧化酶活性、脯氨酸(Pro)含量、可溶性蛋白含量、叶绿素含量和叶绿素荧光参数进行测定,旨在探讨低温胁迫下接种AMF对景天三七生长和生理特性的影响。结果表明,低温胁迫抑制了AMF(Glomus mosseae)对景天三七根系的侵染能力和菌根的相对依赖性。与未接种对照相比,接种AMF的景天三七在株高、根长、干鲜重等方面有明显增加,0℃低温下增长效应更明显,总干重比未接种对照增加了75.38%;低温胁迫下景天三七相对电导率、MDA含量和Pro含量随胁迫温度的下降和胁迫时间的延长而增加;超氧化物歧化酶(SOD)活性、过氧化物酶(POD)活性、过氧化氢酶(CAT)活性和可溶性蛋白含量则呈先上升后下降的趋势;叶绿素含量和PSⅡ原初光能转化效率(Fv/Fm)呈下降趋势。与未接种对照相比,接种AMF能显著抑制低温下景天三七细胞膜透性和MDA含量的升高,显著提高景天三七体内SOD、POD和CAT的活性,诱导产生更多的可溶性蛋白和脯氨酸;提高植株体内叶绿素含量和Fv/Fm,明显缓解低温胁迫对景天三七的伤害,增强景天三七对低温胁迫的耐受性。     

橡胶树AM菌根研究进展

橡胶是四大工业原料之一 ,在交通、军用工业中尤为重要。其中天然橡胶的主要来源是巴西橡胶树 (H evea brasiliensis Muell. Arg.) ,它在我国南方热带地区广为栽培 ,是重要的经济树种和用材树种 ,因而是工业与民用的重要资源。已有研究证实 :橡胶树根系可以形成 AM菌根 (arbuscular mycorrhiza)。AM菌根是广泛分布的一类内生菌根 ,能够促进宿主植物吸收土壤中的养分 ,增强宿主的抗逆性 ,有利于植物生长。近 30 a来 ,国外一些学者对橡胶树菌根真菌的资源与分布 ,菌根真菌对苗木营养和生长效应以及提高苗木抗逆性方面进行了研究。而国内尚…     

Effect of inoculation with ecto- and arbuscular mycorrhizae and Rhizobium on the growth and nitrogen fixation by black locust,Robinia pseudoacacia

Experiments were made to determine the effect of inoculation withRhizobium, the ectomycorrhizal fungus Hebelomamesophasem and the arbuscular mycorrhizal fungus Glomuscaledonium on the growth and nitrogen fixation of black locust(Robinia pseudoacacia Linn.) seedlings grown invitro and in pot culture. The results showed that both mycorrhizalfungi and Rhizobium stimulated the growth and nitrogenfixing ability of inoculated seedlings. Inoculation with all three microbestogether produced the most beneficial effects on nitrogen fixation, mycorrhizaldevelopment and seedling growth.