Arbuscular Mycorrhizal Fungi
Arbuscular mycorrhizal fungi are a type of symbiotic fungi that form mutualistic relationships with the roots of most plant species. They facilitate the exchange of nutrients between plants and soil, particularly phosphorus and nitrogen, enhancing the plants' ability to absorb these essential elements. These fungi are characterized by their arbuscules, which are tree-like structures within the plant roots where nutrient exchange occurs.
7 Key excerpts on "Arbuscular Mycorrhizal Fungi"
eBook - ePubA Handbook of Tropical Soil Biology
Sampling and Characterization of Below-ground Biodiversity
- Fatima M. S. Moreira, E. Jeroen Huising, David E. Bignell(Authors)
- 2012(Publication Date)
- Routledge(Publisher)
...Chapter 7 Arbuscular Mycorrhizal Fungi (AMF) Joseph D. Bagyaraj and Sidney L. Stürmer INTRODUCTION It is now very well documented that Arbuscular Mycorrhizal Fungi (AMF) improve fitness and growth of plants that are important in agriculture, horticulture and forestry. The soil hyphal network produced by AMF during association with the plant host provides a greater absorptive surface than root hairs alone and thus increases significantly the absorption of relatively immobile ions such as phosphate, copper and zinc. In most tropical soils, available phosphorus is very low and thereby limiting for plant development. In addition, mycorrhizally infected plants have been shown to have greater tolerance to toxic metals, to root pathogens, to drought, to high soil temperature, to saline soils, to adverse soil pH and to transplant shock than non-mycorrhizal plants (Mosse et al. 1981; Bagyaraj, 1990; Bagyaraj and Varma, 1995). AMF have been reported from natural ecosystems such as deserts, sand dunes, tropical forests, salt marshes and managed systems such as pastures, orchards and field crops (Brundrett, 1991). In the tropics, agriculture is practised in areas previously occupied by two main plant species-rich natural ecosystems: tropical forests and savannah woodlands. The conversion of these two ecosystems into agro-ecosystems, whether related to subsistence agriculture, production of cash crops or industrial forest plantations, provokes changes in the chemical, physical and biological characteristics of the edaphic environment. Sites are usually cleared of multispecies, uneven-aged vegetation and normally planted with a single species of one age-class. For AMF, conversion of natural ecosystems into distinct land use systems influences spore abundance and species composition. Jasper et al (1987) observed a drop in spore numbers and a shift in species composition after disturbance in some Australian sites...
- B. D. Kaushik, Deepak Kumar, Md. Shamim, B. D. Kaushik, Deepak Kumar, Md. Shamim(Authors)
- 2019(Publication Date)
- Apple Academic Press(Publisher)
...In AM, hypha enters the cortical cells of the roots. They can either produce diverse shapes of balloon-like, membrane-bound organelles, which may be outside or inside the cortical cells. These are called vesicles or may constitute arbuscules, which are finely divided dichotomously branched hyphal invaginations (Fig. 15.2). FIGURE 15.2 (See color insert.) Transfer mechanism of nutrient by the AM fungi. This type of bidirectional interaction is meant for the exchange of resources. In this symbiotic association, the mycorrhizal symbiont provides mineral nutrients, such as phosphate and nitrogen to the host plant, and also helps to impart abiotic stress tolerance against salinity, drought, heavy metal, and biotic stress from various soil-borne root pathogens, and in return to this, the host plant offers about 4–20% of its photosynthates, that is, carbon compounds to the mycorrhizal symbiont (Wright et al., 1998). Fossil studies indicate that mycorrhizal association plays a significant role in the ancient colonization of land-plants (Smith and Read, 2008). Ectotrophic and arbuscular mycorrhizal associations, which are mutually beneficial, have great ecological and economic importance (Marschner and Dell, 1994). Arbuscular Mycorrhizal Fungi is a “biofertilizer and bioprotector” in sustainable agriculture. AMF helps in phytoremediation and also revegetation purposes (Bücking, 2011; Giri et al., 2005). AM fungi belong to the class azygosporous Zygomycetes covering six genera. The establishment of AMF in the root leads to changes in the rhizospheric microflora (Meyer and Linderman, 1986; Marschner et al., 2001) exaggerating plant tolerance to a wide range of abiotic and biotic stresses (Auge et al., 2004; Whipps, 2004; Jansa et al., 2009)...
eBook - ePub- Sarah C. Watkinson, Lynne Boddy, Nicholas Money(Authors)
- 2015(Publication Date)
- Academic Press(Publisher)
...The results point to the potential of AMF inoculation in crop nutrition and protection. AMF in Ecosystems In natural and semi-natural ecosystems, AMF fungi play vital, but still poorly-understood parts in plant productivity and community diversity (Figure 7.5) as well as making essential contributions to soil structure and carbon sequestration. The ability to connect to an AMF network can affect nutrient capture by roots. Plants colonised by AMF may be more efficient at extracting soil phosphate and/or nitrogen than plants grown in sterile soil. Roots typically form mycorrhizal associations under nutrient limitation. Plant roots containing abundant phosphate inhibit the formation of AMF arbuscules, the plant thereby avoiding an unnecessary drain on its carbon resources. Soil minerals accumulated by the extraradical hyphae are partitioned between the fungus and the plant. Figure 7.5 The effect of AMF species-richness on plant and fungal growth. Sets of replicate trays of sterilised soil, placed out of doors in a field site, were inoculated with soil containing 1, 2, 4, 8, or 14 different strains of species of AMF. The inoculated trays were then sown with 100 seeds from a mixture of 15 plant species. After one growing season, the plants growing in each tray were assessed for diversity of species (a), shoot and root biomass (b and c, respectively) and the total length of hyphae of mycorrhizal fungi in the soil (d). The levels of phosphate were also measured in the soil (e) and in plants (f). Plants grew better, and the plant community was more diverse, when 8 or 14 different AMF were present. There were accompanying increases in hyphal growth and phosphate uptake from soil to plants. Source: van der Heijden et al. (1998). AMF hyphae translocate nutrients not only from soil to root, but also between roots of adjacent plants...
- Zed Rengel, Ivica Djalovic, Zed Rengel, Ivica Djalovic(Authors)
- 2021(Publication Date)
- Wiley-Blackwell(Publisher)
...et al. (2020b). Arbuscular mycorrhizal symbiosis increases phosphorus uptake and productivity of mixtures of maize varieties compared to monocultures. Journal of Applied Ecology 57: 2203–2211. Wang, X.X., Wang, X., Sun, Y. et al. (2018). Arbuscular Mycorrhizal Fungi negatively affect nitrogen acquisition and grain yield of maize in a N‐deficient soil. Frontiers in Microbiology 9: 418. Weemstra, M., Mommer, L., Visser, E.J.W. et al. (2016). Towards a multidimensional root trait framework: a tree root review. New Phytologist 211: 1159–1169. Werner, G.D.A., Cornelissen, J.H.C., Cornwell, W.K. et al. (2018). Symbiont switching and alternative resource acquisition strategies drive mutualism breakdown. Proceedings of the National Academy of Sciences of the United States of America 115: 5229–5234. Yang, Y.R., Tang, M., Sulpice, R. et al. (2014). Arbuscular Mycorrhizal Fungi alter fractal dimensions characteristics of Robinia pseudoacacia L. seedlings through regulating plant growth, leaf water status, photosynthesis, and nutrient concentration under drought stress. Journal of Plant Growth Regulation 33: 612–625. Yang, H., Zhang, Q., Koide, R.T. et al. (2017). Taxonomic resolution is a determinant of biodiversity effects in arbuscular mycorrhizal fungal communities. Journal of Ecology 105: 219–228. Yooyongwech, S., Samphumphuang, T., Tisarum, R. et al. (2016). Arbuscular Mycorrhizal Fungi (AMF) improved water deficit tolerance in two different sweet potato genotypes involves osmotic adjustments via soluble sugar and free proline. Scientia Horticulturae 198: 107–117. Zhang, B.B., Zhang, H., Wang, H. et al. (2018). Effect of phosphorus additions and arbuscular mycorrhizal fungal inoculation on the growth, physiology, and phosphorus uptake of wheat under two water regimes. Communications in Soil Science and Plant Analysis 49: 862–874....
eBook - ePub- Darlene Southworth, Darlene Southworth(Authors)
- 2011(Publication Date)
- Wiley-Blackwell(Publisher)
...2001). These fungi may form arbuscules, vesicles, and hyphae in the cortex of plant roots and extensive networks of extraradical hyphae that extend from the roots into the soil matrix (Figure 3.1). Mycorrhizal fungi transport mineral nutrients absorbed by their hyphae to the arbuscules where they receive photosynthate (Fitter 2006; Parniske 2008). The amount of biomass accounted for by Glomeromycotan fungal hyphae in soils can be substantial (Miller et al. 1995; Olsson et al. 1999). In addition to their importance in plant nutrition, these fungi play a critical role in grasslands as carbon sinks and in structuring soils (Miller and Jastrow 2000; Zhu and Miller 2003; Wilson et al. 2009). Figure 3.1 Arbuscular mycorrhizal (AM) fungi inside (intraradical) and outside (extraradical) plant roots. Intraradical arbuscules (A) and vesicles (B) are magnified 100× and are stained with trypan blue. Extraradical hyphae (C) and spores (D) are magnified 20×. (Courtesy of Julie Wolf and Anita Antoninka.) (For a color version of this figure, see the color plate section.) Few grassland ecosystems remain that are not impacted by human activities; mesic grasslands have been converted to production agriculture, and semiarid and arid grasslands are used for grazing domestic animals. Despite anthropogenic disturbances, AM fungi remain and form symbioses with crops and pasture plants, although the biomass and species composition of Glomeromycotan communities may change when natural grasslands are converted into managed grasslands (Helgason et al. 1998; Oehl et al. 2003; Jansa et al. 2009). If these grasslands are managed properly, the fungi can recover, at least in hyphal and spore biomass, to levels observed in native grasslands (Allison et al. 2005; Fitzsimons et al. 2008)...
eBook - ePub- Andrew Lack, David Evans(Authors)
- 2021(Publication Date)
- Taylor & Francis(Publisher)
...When working to mutual benefit, sugars generated by photosynthesis in the plant are transported to the roots and taken up by the fungi, and nutrients, most importantly nitrogen and phosphorus, are absorbed by the fungal hyphae in the soil and conducted to the plant. Many plants with AM can survive without them, particularly on nutrient-rich soils, but those with EM and the specialist groups are normally obligately associated at least at some stage in their life cycle. There are usually at least 20 species of mycorrhizal fungi in a plant community. Some fungi only infect one species or genus of plants, whereas others, especially AM fungi, can infect many species. Most plants can be infected by many species of fungi, so there will be a complex web of interactions. The growth form of the fungi in the soil varies greatly, with some producing a mass of hyphae close to the roots, others spreading more widely and thinly. AM grow out from a root to form an expanding fan and normally do not fuse with other neighboring fungi though may penetrate another plant. EM start growing similarly but when they meet hyphae from other EMs these can fuse, or anastomose, and the mycorrhizae form a network of interconnecting hyphae in the soil. Effects of the fungi on plants The main effect of the fungi is absorbing nutrients from the soil. Roots infected with AM retain root hairs and are able to absorb nutrients, but plants with EM and the specialist types generally lose all their root hairs and rely solely on the fungus. All mycorrhizal fungi have an extensive hyphal network in the soil. Nitrogen and/or phosphorus are vital plant nutrients that are frequently limited in supply and the fungal hyphae absorb these more efficiently and over a much larger soil area than roots alone, leading to enhanced growth of the plant, experimentally up to 200% greater...
eBook - ePub- Rattan Lal(Author)
- 2017(Publication Date)
- CRC Press(Publisher)
...Mycorrhiza of Forest Ecosystesm Ian A. Dickie School of Forest Resources, University of Minnesota, St. Paul, Minnesota, U.S.A. Abstract Mycorrhiza are involved in every aspect of forest soil ecology—they are central to plant nutrient uptake, they can short-circuit the nitrogen cycle, they participate in primary weathering of soil nutrients, and they provide a major input of carbon into the soil ecosystem. In addition, a lack of mycorrhizal fungi may limit the ability of forest tree species to establish slowing forest succession on disturbed sites. At least a basic understanding of mycorrhiza is therefore critical to understanding both soil and plant ecology. INTRODUCTION Most land plants (>80% of angiosperms and almost all gymnosperms) form mycorrhiza: symbiotic associations between plant roots and fungi that increase plant nutrient uptake. [ 1, 2 ] Mycorrhizal fungi are an important component of the soil ecosystem, with ca. 200 m of mycorrhizal hyphae per gram of forest soil. [ 1 ] Several types of mycorrhiza occur, including arbuscular mycorrhiza (dominants of grasslands, many tropical, and some temperate forests), ectomycorrhiza (dominants of boreal, most temperate, and some tropical forests), and ericoid mycorrhiza (common in temperate and boreal forests and heathlands). Mycorrhiza plays a critical role in plant nutrient uptake, particularly of phosphorus (P), NH 4 +, and organic nutrients. In return for increased nutrient acquisition, plants direct 10–30% of total fixed carbon (C) to supporting mycorrhizas. This represents an important flow of C to the soil ecosystem, creating “mycorrhizosphere” communities in association with fungal hyphae. Mycorrhizal Types Arbuscular mycorrhizas are the ancestral state of all land plants, and approximately 67% of all angiosperms and nearly all non-Pinaceae gymnosperms retain this association. [ 2 ] Arbuscular mycorrhizas are formed by most tropical and many temperate forest trees, as well as many forest understory plants...
