Mycorrhiza

enUK

mycorrhiza

[‚mīk·ə′rīz·ə] (botany) A mutual association in which the mycelium of a fungus invades the roots of a seed plant.

Mycorrhiza

the symbiotic association of the mycelium of a fungus with the roots of a higher plant. The association is referred to as ectotrophic (external) in those cases in which the fungus entwines the ground tissue of the ends of young roots and penetrates the intercellular spaces of the outer layers of bark. Endotrophic (internal) mycorrhiza is characterized by the implantation of mycelium (the hyphae of the fungus) inside the cells of a plant. Ectotrophic mycorrhiza characterizes many trees (oak, spruce, pine, birch) and shrubs (willow), as well as some low shrubs (Dryas) and herbaceous plants (viviparous bistort). The young roots usually branch and their ends thicken; the growing parts of the roots are enveloped by the thick, solid fungal sheath, from which emanate the fungal hyphae. The hyphae penetrate the soil and the intercellular spaces of the root through one or more layers of bark, forming the Hartig’s network. As a result, the root hairs atrophy (euectotrophic mycorrhiza). In the low shrub Arctous alpina and the herb Pyrola rotundifolia, the fungal hyphae penetrate not only the intercellular spaces but the cells of the bark as well (ectoendotrophic mycorrhiza). Ectotrophic mycorrhizae are formed most often by hymeomycetes (Boletus, Lactarius, Russula, Amanita) or, less frequently, by gasteromycetes. More than one species of fungus may participate in the formation of the mycorrhizae on the roots of a single plant. However, as a rule, in plant communities only certain mycorrhizal fungi are symbionts of given species of plants.

Endotrophic mycorrhizae do not cause a change in the shape of the roots, and the root hairs generally do not atrophy; the fungal sheath and Hartig’s network do not form, and the fungal hyphae penetrate the cells of the cortical parenchyma. In plants of the families Ericaceae, Pyrolaceae, Vacciniaceae, and Empetraceae, the fungal hyphae form nodules in the cells, and these nodules are digested later by the plant (ericoid mycorrhiza). Phycomycetes of the genera Endogone and Pythium participate in the formation of ericoid mycorrhizae. In plants of the family Orchidaceae, the fungal hyphae from the soil penetrate the seed and form nodules, which are then digested by cells of the seed. This type of mycorrhiza is characteristic of imperfect fungi (genus Rhizoctonia) and, less frequently, basidial fungi (genus Armillaria).

The phycomycetous type of mycorrhiza, in which the fungal hyphae permeate the epidermal cells of the root and localize in the intercellular spaces and in the cells of the middle layers of the cortical parenchyma, is the most widespread. It occurs in many annual and perennial herbs, shrubs, and trees of the most diverse families.

Mycorrhizal associations are beneficial to plants. The developed mycelium increases the absorptive surface of the root and intensifies the entry of water and nutrients into the plant. Mycorrhizal fungi probably decompose certain organic compounds of the soil that are not accessible to the plant and manufacture vitamin-like substances and growth activators. The fungi, on the other hand, use certain substances (possibly carbohydrates) that they extract from the roots of the plant. When forests are planted on soils that do not contain mycorrhizal fungi, small quantities of forest soils are applied; for example, when planting acorns, soil from an old oak grove should be added.

REFERENCES

Kursanov, L. I. Mikologiia, 2nd ed. Moscow, 1940.
Shemakhanova, N. M. Mikotrofiia drevesnykh porod. Moscow, 1962.
Lobanov, N. V. Mikotrofnost’ drevesnykh rastenii, 2nd ed. Moscow, 1971.
Katenin, A. E. Mikoriza rastenii Severn- Vostoka Evropeiskoi chasti SSSR. Leningrad, 1972.

B. P. VASIL’KOV

mycorrhiza

enUK

mycorrhiza

mycorhiza

(mī′kə-rī′zə)n. pl. mycorrhi·zae (-zē) or mycorrhi·zas The symbiotic association of the mycelium of a fungus with the roots of a plant, as is found in the majority of vascular plants.

my′cor·rhi′zal adj.

mycorrhiza

(Greek myco- fungus, rhiza root) an association between a FUNGUS and the roots of a higher plant. In some cases the fungus breaks down PROTEINS or AMINO ACIDS that are soluble and can be absorbed by the higher plant. In most cases, only nitrogen and phosphorus compounds result from fungal activity. Carbohydrates synthesized by the higher plants are absorbed by the fungus, so the relationship is a form of SYMBIOSIS. Some plants which lack chlorophyll, such as the bird's nest orchid, rely on mycorrhizas for carbohydrates in addition to protein.

There are two types of mycorrhiza: ectomycorrhiza and endomycorrhiza. In an ectomycorrhiza the infecting fungus occurs on the surface of the root and possibly between the cells of the root cortex, but does not penetrate such cells. The root becomes covered by a sheath of fungal tissue and looks different from an uninfected root. It is thicker, has no root hairs or root cap and may be a different colour. Ectomycorrhizae are found mainly on trees, such as oak and pine. In an endomycorrhiza the fungus develops within the cells of the root cortex. Subsequently the root cells digest the fungus leaving only knots of fungal material in the cells. There is usually little difference in the morphology of the root and a sheath of fungal tissue is not normally formed.

单词	mycorrhiza
释义	mycorrhiza enUK my·cor·rhi·za or my·co·rhi·za (mī′kə-rī′zə)n. pl. my·cor·rhi·zae (-zē) or my·cor·rhi·zas or my·co·rhi·zae or my·co·rhi·zas The symbiotic association of the mycelium of a fungus with the roots of a plant, as is found in the majority of vascular plants. [myco- + Greek rhiza, root; see wrād- in Indo-European roots.] my′cor·rhi′zal adj. mycorrhiza (ˌmaɪkəˈraɪzə) or mycorhiza n, pl -zae (-ziː) or -zas (Botany) an association of a fungus and a plant in which the fungus lives within or on the outside of the plant's roots forming a symbiotic or parasitic relationship. See ectotrophic mycorrhiza, endotrophic mycorrhiza[C19: from myco- + Greek rhiza root] ˌmycorˈrhizal, ˌmycoˈrhizal adj my•cor•rhi•za (ˌmaɪ kəˈraɪ zə) n., pl. -zae (-zē), -zas. a symbiotic association of the mycelium of a fungus, esp. a basidiomycete, with the roots of certain plants, in which the hyphae form a closely woven mass around the rootlets or penetrate the cells of the root. [1890–95] my`cor•rhi′zal, my`co•rhi′zal, adj. Translations Mycorrhiza enUK mycorrhiza [‚mīk·ə′rīz·ə] (botany) A mutual association in which the mycelium of a fungus invades the roots of a seed plant. Mycorrhiza the symbiotic association of the mycelium of a fungus with the roots of a higher plant. The association is referred to as ectotrophic (external) in those cases in which the fungus entwines the ground tissue of the ends of young roots and penetrates the intercellular spaces of the outer layers of bark. Endotrophic (internal) mycorrhiza is characterized by the implantation of mycelium (the hyphae of the fungus) inside the cells of a plant. Ectotrophic mycorrhiza characterizes many trees (oak, spruce, pine, birch) and shrubs (willow), as well as some low shrubs (Dryas) and herbaceous plants (viviparous bistort). The young roots usually branch and their ends thicken; the growing parts of the roots are enveloped by the thick, solid fungal sheath, from which emanate the fungal hyphae. The hyphae penetrate the soil and the intercellular spaces of the root through one or more layers of bark, forming the Hartig’s network. As a result, the root hairs atrophy (euectotrophic mycorrhiza). In the low shrub Arctous alpina and the herb Pyrola rotundifolia, the fungal hyphae penetrate not only the intercellular spaces but the cells of the bark as well (ectoendotrophic mycorrhiza). Ectotrophic mycorrhizae are formed most often by hymeomycetes (Boletus, Lactarius, Russula, Amanita) or, less frequently, by gasteromycetes. More than one species of fungus may participate in the formation of the mycorrhizae on the roots of a single plant. However, as a rule, in plant communities only certain mycorrhizal fungi are symbionts of given species of plants. Endotrophic mycorrhizae do not cause a change in the shape of the roots, and the root hairs generally do not atrophy; the fungal sheath and Hartig’s network do not form, and the fungal hyphae penetrate the cells of the cortical parenchyma. In plants of the families Ericaceae, Pyrolaceae, Vacciniaceae, and Empetraceae, the fungal hyphae form nodules in the cells, and these nodules are digested later by the plant (ericoid mycorrhiza). Phycomycetes of the genera Endogone and Pythium participate in the formation of ericoid mycorrhizae. In plants of the family Orchidaceae, the fungal hyphae from the soil penetrate the seed and form nodules, which are then digested by cells of the seed. This type of mycorrhiza is characteristic of imperfect fungi (genus Rhizoctonia) and, less frequently, basidial fungi (genus Armillaria). The phycomycetous type of mycorrhiza, in which the fungal hyphae permeate the epidermal cells of the root and localize in the intercellular spaces and in the cells of the middle layers of the cortical parenchyma, is the most widespread. It occurs in many annual and perennial herbs, shrubs, and trees of the most diverse families. Mycorrhizal associations are beneficial to plants. The developed mycelium increases the absorptive surface of the root and intensifies the entry of water and nutrients into the plant. Mycorrhizal fungi probably decompose certain organic compounds of the soil that are not accessible to the plant and manufacture vitamin-like substances and growth activators. The fungi, on the other hand, use certain substances (possibly carbohydrates) that they extract from the roots of the plant. When forests are planted on soils that do not contain mycorrhizal fungi, small quantities of forest soils are applied; for example, when planting acorns, soil from an old oak grove should be added. REFERENCES Kursanov, L. I. Mikologiia, 2nd ed. Moscow, 1940. Shemakhanova, N. M. Mikotrofiia drevesnykh porod. Moscow, 1962. Lobanov, N. V. Mikotrofnost’ drevesnykh rastenii, 2nd ed. Moscow, 1971. Katenin, A. E. Mikoriza rastenii Severn- Vostoka Evropeiskoi chasti SSSR. Leningrad, 1972. B. P. VASIL’KOV mycorrhiza enUK mycorrhiza or mycorhiza (mī′kə-rī′zə)n. pl. mycorrhi·zae (-zē) or mycorrhi·zas The symbiotic association of the mycelium of a fungus with the roots of a plant, as is found in the majority of vascular plants. my′cor·rhi′zal adj. mycorrhiza (Greek myco- fungus, rhiza root) an association between a FUNGUS and the roots of a higher plant. In some cases the fungus breaks down PROTEINS or AMINO ACIDS that are soluble and can be absorbed by the higher plant. In most cases, only nitrogen and phosphorus compounds result from fungal activity. Carbohydrates synthesized by the higher plants are absorbed by the fungus, so the relationship is a form of SYMBIOSIS. Some plants which lack chlorophyll, such as the bird's nest orchid, rely on mycorrhizas for carbohydrates in addition to protein. There are two types of mycorrhiza: ectomycorrhiza and endomycorrhiza. In an ectomycorrhiza the infecting fungus occurs on the surface of the root and possibly between the cells of the root cortex, but does not penetrate such cells. The root becomes covered by a sheath of fungal tissue and looks different from an uninfected root. It is thicker, has no root hairs or root cap and may be a different colour. Ectomycorrhizae are found mainly on trees, such as oak and pine. In an endomycorrhiza the fungus develops within the cells of the root cortex. Subsequently the root cells digest the fungus leaving only knots of fungal material in the cells. There is usually little difference in the morphology of the root and a sheath of fungal tissue is not normally formed.
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mycorrhiza

my·cor·rhi·za

mycorrhiza

mycorhiza

my•cor•rhi•za

Mycorrhiza

mycorrhiza

Mycorrhiza

REFERENCES

mycorrhiza

mycorrhiza

mycorhiza

mycorrhiza