The mycorrhizosphere is the region around a

mycorrhiza A mycorrhiza (from Greek μύκης ', "fungus", and ῥίζα ', "root"; pl. mycorrhizae, mycorrhiza or mycorrhizas) is a symbiotic association between a fungus and a plant. The term mycorrhiza refers to the role of the fungus in the plant ...

l fungus in which nutrients released from the fungus increase the microbial population and its activities. The roots of most terrestrial plants, including most

crop A crop is a plant that can be grown and harvested extensively for profit or subsistence. When the plants of the same kind are cultivated at one place on a large scale, it is called a crop. Most crops are cultivated in agriculture or hydroponic ...

plants and almost all woody plants, are colonized by mycorrhiza-forming

symbiotic Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasit ...

fungi. In this relationship, the plant roots are infected by a fungus, but the rest of the fungal

mycelium Mycelium (plural mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Fungal colonies composed of mycelium are found in and on soil and many other substrate (biology), substrates. A typical single ...

continues to grow through the soil, digesting and absorbing nutrients and water and sharing these with its plant

host A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places * Host, Pennsylvania, a village in Berks County People *Jim Host (born 1937), American businessman * Michel Host ...

. The fungus in turn benefits by receiving

photosynthetic Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in c ...

sugars from its host. The mycorrhizosphere consists of roots,

hypha A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Structure A hypha consists of one or ...

e of the directly connected mycorrhizal fungi, associated microorganisms, and the soil in their direct influence.

Organisms involved

The mycorrhizosphere involves a community of microorganisms. There are three divisions of fungi that can form mycorrhizae, the

Glomeromycota Glomeromycota (often referred to as glomeromycetes, as they include only one class, Glomeromycetes) are one of eight currently recognized divisions within the kingdom Fungi, with approximately 230 described species. Members of the Glomeromycot ...

Ascomycota Ascomycota is a phylum of the kingdom Fungi that, together with the Basidiomycota, forms the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. It is the largest phylum of Fungi, with over 64,000 species. The def ...

, and

Basidiomycota Basidiomycota () is one of two large divisions that, together with the Ascomycota, constitute the subkingdom Dikarya (often referred to as the "higher fungi") within the kingdom Fungi. Members are known as basidiomycetes. More specifically, Basi ...

. Glomeromycota can form arbuscular mycorrhizae with

angiosperm Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...

s (flowering plants),

gymnosperm The gymnosperms ( lit. revealed seeds) are a group of seed-producing plants that includes conifers, cycads, ''Ginkgo'', and gnetophytes, forming the clade Gymnospermae. The term ''gymnosperm'' comes from the composite word in el, γυμνό� ...

s (seed-producing plants),

pteridophyte A pteridophyte is a vascular plant (with xylem and phloem) that disperses spores. Because pteridophytes produce neither flowers nor seeds, they are sometimes referred to as "cryptogams", meaning that their means of reproduction is hidden. Ferns, ...

moss Mosses are small, non-vascular flowerless plants in the taxonomic division Bryophyta (, ) '' sensu stricto''. Bryophyta (''sensu lato'', Schimp. 1879) may also refer to the parent group bryophytes, which comprise liverworts, mosses, and hor ...

es,

lycopod Lycopodiopsida is a class of vascular plants known as lycopods, lycophytes or other terms including the component lyco-. Members of the class are also called clubmosses, firmosses, spikemosses and quillworts. They have dichotomously branching s ...

s, and Psilotales. Ascomycota fungi form

ericoid mycorrhiza The ericoid mycorrhiza is a mutualistic relationship formed between members of the plant family Ericaceae and several lineages of mycorrhizal fungi. This symbiosis represents an important adaptation to acidic and nutrient poor soils that specie ...

s with plants of the order

Ericales The Ericales are a large and diverse order of dicotyledons. Species in this order have considerable commercial importance including for Camellia sinensis, tea, persimmon, blueberry, kiwifruit, Brazil nuts, Argania, argan, and azalea. The order i ...

, and ectomycorrhizas with trees. Basidiomycota fungi form ecto-,

orchid Orchids are plants that belong to the family Orchidaceae (), a diverse and widespread group of flowering plants with blooms that are often colourful and fragrant. Along with the Asteraceae, they are one of the two largest families of flowering ...

, monotropoid, arbutoid, and some ericoid mycorrhizae. Fungal hyphae are thinner than plant roots, which allows them to penetrate areas in the soil with moisture and nutrient that are inaccessible to roots. In some cases, mycorrhizal fungi in the mycorrhizosphere may ward off fungal

plant pathogen Plant pathology (also phytopathology) is the scientific study of diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomyc ...

s. For example, the arbuscular mycorrhizal fungus ''

Glomus intraradices ''Rhizophagus irregularis'' (previously known as ''Glomus intraradices'') is an arbuscular mycorrhizal fungus used as a soil inoculant in agriculture and horticulture. ''Rhizophagus irregularis'' is also commonly used in scientific studies of the ...

'' reduces

germination Germination is the process by which an organism grows from a seed or spore. The term is applied to the sprouting of a seedling from a seed of an angiosperm or gymnosperm, the growth of a sporeling from a spore, such as the spores of fungi, fer ...

of the pathogen '' Fusarium oxysporum'', but stimulates germination of a non-pathogenic fungus ''

Trichoderma harzianum ''Trichoderma harzianum'' is a fungus that is also used as a fungicide. It is used for foliar application, seed treatment and soil treatment for suppression of fungal pathogens causing various fungal plant diseases. Commercial biotechnological p ...

''. Soil

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

in the mycorrhizosphere influence plant growth in several ways: by affecting the uptake of nutrients, providing protection against pathogens, contributing to

nitrogen fixation Nitrogen fixation is a chemical process by which molecular nitrogen (), with a strong triple covalent bond, in the air is converted into ammonia () or related nitrogenous compounds, typically in soil or aquatic systems but also in industry. Atmo ...

, and contributing to

mineral weathering Weathering is the deterioration of rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little or no movement), ...

Archaea Archaea ( ; singular archaeon ) is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaebac ...

are also known to exist in mycorrhizosphere. They may contribute to nitrogen fixation and produce antibiotic compounds, but the extent of their interactions with other organisms and their overall function is not well known. Soil

protozoa Protozoa (singular: protozoan or protozoon; alternative plural: protozoans) are a group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic tissues and debris. Histo ...

feed on bacteria, and, in some cases, hyphae. The type of mycorrhizae greatly influences the protozoal population in a mycorrhizosphere. For example, a ''

Paxillus involutus ''Paxillus involutus'', commonly known as the brown roll-rim, common roll-rim is a basidiomycete fungus that is widely distributed across the Northern Hemisphere. It has been inadvertently introduced to Australia, New Zealand, South Africa, ...

''–

conifer Conifers are a group of conifer cone, cone-bearing Spermatophyte, seed plants, a subset of gymnosperms. Scientifically, they make up the phylum, division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single ...

mycorrhiza seems to reduce the density of protozoa in the resulting mycorrhizosphere, but mycorrhizae formed with ''

Lactarius rufus ''Lactarius rufus'' is a common, medium-sized member of the mushroom genus ''Lactarius'', whose many members are commonly known as milkcaps. Known by the common name of the rufous milkcap, or the red hot milk cap in North America. It is dark b ...

'' and '' Suillus bovinus'' have the opposite effect. Other soil organisms that influence the mycorrhizosphere community include soil animals such as

nematode The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant-Parasitism, parasitic nematodes also known as eelworms. They are a diverse animal phylum inhab ...

mite Mites are small arachnids (eight-legged arthropods). Mites span two large orders of arachnids, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari, but genetic analysis does not show clear evid ...

s, and

earthworm An earthworm is a terrestrial invertebrate that belongs to the phylum Annelida. They exhibit a tube-within-a-tube body plan; they are externally segmented with corresponding internal segmentation; and they usually have setae on all segments. Th ...

s, which forage on roots, hyphae and their associated microorganisms.

References

{{Reflist, refs= {{cite book , vauthors=Timonen S, Marschner P , chapter=Mycorrhizosphere concept , title=Microbial Activity in the Rhizoshere , series=Soil Biology , volume=7 , year=2006 , veditors=Mukerji JG, Manoharachary C, Singh J , publisher=Springer , location=Berlin; New York , pages=155–72 , isbn=978-3-540-29182-4 Fungus ecology Soil biology Plant roots Environmental soil science