Russula virescens
Encyclopedia
Russula virescens is a basidiomycete mushroom
of the genus
Russula
, and is commonly known as the green-cracking Russula, the quilted green Russula, or the green brittlegill. It can be recognized by its distinctive pale green cap
covered with darker green patches, its crowded white gills, and its white stem. A popular edible
fungus with a mild or nutty taste, its distribution encompasses Britain, Europe, and Asia, where it occurs solitary or scattered on the ground in both deciduous
and mixed forests, forming mycorrhizhal
associations with hardwood
trees like oak
and European beech. Its distribution in North America has not been clarified, due to confusion with the similar species Russula parvovirescens and Russula crustosa. The ribonuclease
enzyme of R. virescens has been studied and shown to have a unique biochemistry
compared to other edible mushrooms.
in 1836. It is the type species
of subsection Virescentinae in the Russula, a grouping of mushrooms characterized by a cap surface that breaks into patches of bran-like (furfuraceous) particles.
The specific epithet virescens is Latin
for "becoming green". The characteristic pattern of the cap surface has earned the species common name
s such as green-cracking Russula, the quilted green Russula, and the green brittlegill. In the mid-Atlantic United States, it is also known locally as the moldy Russula.
is at first dome or barrel-shaped, becoming convex and flattened with age with a diameter of up to 15 cm (5.9 in). The cuticle
of the cap is green, most profoundly in the center, with patches of the same color dispersed radially around the center; the distinct pattern is called areolate.
The green color of the cuticle is often of variable shade, ranging from gray to verdigris
to grass-green. The extent of the patching of the cuticle is also variable, giving specimens with limited patches a resemblance to other green-capped species of Russula, such as Russula aeruginea
. The green patches of the cap lie on a white to pale green background. The cap, while frequently round, may also exhibit irregular lobes and cracks. The cap cuticle is thin, and can be readily peeled off the surface to a distance of about halfway towards the cap center.
The gills are white to cream colored, and fairly crowded together; most of the gill is fused to the stem, a so-called adnate attachment. The gills are interconnected at their bases by veins. The stem
is cylindrical, white and of variable height, up to 8 cm (3.1 in) tall and 4 cm (1.6 in) wide; it is roughly the same thickness at both the top and the base. Then top portion of the stem may be farinose—covered with a white, mealy powder. It may turn slightly brown with age, or when it is injured or bruised from handling. Like other species in the Russulales
order of mushrooms, the flesh
is brittle, owing to the sphaerocyst cytoarchitecture—cylindrical cells that contrast with the typical fibrous, filamentous hypha
e present in other orders of the basidiomycota
.
of R. virescens are elliptical or ellipsoid with warts, translucent (hyaline
), and in deposit produce a white, pale or pale yellow spore print
; the spore dimensions are 6–9 by 5–7 µm
. The spore-bearing cells, the basidia, are club-shaped and with dimensions of 24–33 by 6–7.5 µm; they are colorless, and each hold from two to four spores. The pleurocystidia (cystidia located on the face of a gill) are 40–85 by 6–8 µm and end abruptly in a sharp point.
considered to be one of the best of the genus Russula, and is a popular edible in Europe. Its smell is not distinctive, but its taste has been described as mild, or nutty. When collecting Russula virescens for consumption, caution is of vital importance to avoid confusion with the dangerously poisonous Amanita phalloides (known as the death cap
), a mushroom that can be most easily identified by its volva
and ring
.
, but this species may be distinguished from R. virescens by its smaller size and smooth cap. Russula crustosa, like R. virescens also has an areolate cap, but the cap becomes sticky (viscid) when moist, and its color is more variable, as it may be reddish, yellowish, or brown. Also, the spore print of R. crustosa is a darker yellow than R. virescens. R. redolens has a cap that is "drab-green to blue-green", but unlike R. virescens, is smooth. Russula redolens also has an unpleasant taste and smells of parsley
.
Russula virescens can be found fruiting on soil in both deciduous forests
and mixed forests, forming ectomycorrhizal symbiotic
relationships with a variety of trees, including oaks (Quercus) and European beech (Fagus sylvatica). Fruiting bodies may appear singly or in groups, reappear in the same spots year after year, and are not common. In Britain and Europe, fruiting occurs mainly during the months of summer to early autumn. A Mexican study of the seasonal occurrence of several common mushroom species in subtropical forests in Xalapa
showed that the fruiting period of R. virescens occurred in April, before the onset of the rainy season
.
The distribution of R. virescens in North America is subject to debate, where a number of similar species such as R. parvovirescens and R. crustosa are also recognized. One author suggests that R. virescens "is strictly a European species", citing Buyck and collaborators (2006), who say "the virescens-crustosa group is much more complex than suspected and embraces at least a dozen taxa in the eastern US". In addition to Britain and Europe, Russula virescens has also been collected from Malaysia, Korea, and China.
s (or RNases) are enzyme
s that catalyze
the hydrolysis
of ribonucleic acid (RNA), and collectively they play a critical role in many biological processes. A RNase from R. virescens was shown to be biochemically unique amongst seven edible mushroom species in several ways: it has a co-specificity towards cleaving RNA at poly A
and poly C
, compared to the monospecific RNases of the others; it can be adsorbed
on chromatography
columns containing DEAE–cellulose as the adsorbent; it has a pH
optimum of 4.5, lower than all other species; and, it has a "distinctly different" N-terminal amino acid sequence.
Mushroom
A mushroom is the fleshy, spore-bearing fruiting body of a fungus, typically produced above ground on soil or on its food source. The standard for the name "mushroom" is the cultivated white button mushroom, Agaricus bisporus; hence the word "mushroom" is most often applied to those fungi that...
of the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Russula
Russula
Around 750 worldwide species of mycorrhizal mushrooms compose the genus Russula. They are typically common, fairly large, and brightly colored - making them one of the most recognizable genera among mycologists and mushroom collectors...
, and is commonly known as the green-cracking Russula, the quilted green Russula, or the green brittlegill. It can be recognized by its distinctive pale green cap
Pileus (mycology)
The pileus is the technical name for the cap, or cap-like part, of a basidiocarp or ascocarp that supports a spore-bearing surface, the hymenium. The hymenium may consist of lamellae, tubes, or teeth, on the underside of the pileus...
covered with darker green patches, its crowded white gills, and its white stem. A popular edible
Edible mushroom
Edible mushrooms are the fleshy and edible fruiting bodies of several species of fungi. Mushrooms belong to the macrofungi, because their fruiting structures are large enough to be seen with the naked eye. They can appear either below ground or above ground where they may be picked by hand...
fungus with a mild or nutty taste, its distribution encompasses Britain, Europe, and Asia, where it occurs solitary or scattered on the ground in both deciduous
Deciduous
Deciduous means "falling off at maturity" or "tending to fall off", and is typically used in reference to trees or shrubs that lose their leaves seasonally, and to the shedding of other plant structures such as petals after flowering or fruit when ripe...
and mixed forests, forming mycorrhizhal
Mycorrhiza
A mycorrhiza is a symbiotic association between a fungus and the roots of a vascular plant....
associations with hardwood
Hardwood
Hardwood is wood from angiosperm trees . It may also be used for those trees themselves: these are usually broad-leaved; in temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen.Hardwood contrasts with softwood...
trees like oak
Oak
An oak is a tree or shrub in the genus Quercus , of which about 600 species exist. "Oak" may also appear in the names of species in related genera, notably Lithocarpus...
and European beech. Its distribution in North America has not been clarified, due to confusion with the similar species Russula parvovirescens and Russula crustosa. The ribonuclease
Ribonuclease
Ribonuclease is a type of nuclease that catalyzes the degradation of RNA into smaller components. Ribonucleases can be divided into endoribonucleases and exoribonucleases, and comprise several sub-classes within the EC 2.7 and 3.1 classes of enzymes.-Function:All organisms studied contain...
enzyme of R. virescens has been studied and shown to have a unique biochemistry
Biochemistry
Biochemistry, sometimes called biological chemistry, is the study of chemical processes in living organisms, including, but not limited to, living matter. Biochemistry governs all living organisms and living processes...
compared to other edible mushrooms.
Taxonomy
Russula virescens was first described by Jacob Christian Schaeffer in 1774 as Agaricus virescens. Subsequently the taxon was transferred to the genus Russula by Elias FriesElias Magnus Fries
-External links:*, Authors of fungal names, Mushroom, the Journal of Wild Mushrooming.*...
in 1836. It is the type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
of subsection Virescentinae in the Russula, a grouping of mushrooms characterized by a cap surface that breaks into patches of bran-like (furfuraceous) particles.
The specific epithet virescens is Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
for "becoming green". The characteristic pattern of the cap surface has earned the species common name
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
s such as green-cracking Russula, the quilted green Russula, and the green brittlegill. In the mid-Atlantic United States, it is also known locally as the moldy Russula.
Description
The capPileus (mycology)
The pileus is the technical name for the cap, or cap-like part, of a basidiocarp or ascocarp that supports a spore-bearing surface, the hymenium. The hymenium may consist of lamellae, tubes, or teeth, on the underside of the pileus...
is at first dome or barrel-shaped, becoming convex and flattened with age with a diameter of up to 15 cm (5.9 in). The cuticle
Pileipellis
thumb|300px||right|The cuticle of some mushrooms, such as [[Russula mustelina]] shown here, can be peeled from the cap, and may be useful as an identification feature....
of the cap is green, most profoundly in the center, with patches of the same color dispersed radially around the center; the distinct pattern is called areolate.
Verdigris
Verdigris is the common name for a green pigment obtained through the application of acetic acid to copper plates or the natural patina formed when copper, brass or bronze is weathered and exposed to air or seawater over a period of time. It is usually a basic copper carbonate, but near the sea...
to grass-green. The extent of the patching of the cuticle is also variable, giving specimens with limited patches a resemblance to other green-capped species of Russula, such as Russula aeruginea
Russula aeruginea
Russula aeruginea otherwise knows as the Grass-green Russula, is an inedible russula mushroom, found only under birch, mostly in pine forests; not rare.-Description:...
. The green patches of the cap lie on a white to pale green background. The cap, while frequently round, may also exhibit irregular lobes and cracks. The cap cuticle is thin, and can be readily peeled off the surface to a distance of about halfway towards the cap center.
The gills are white to cream colored, and fairly crowded together; most of the gill is fused to the stem, a so-called adnate attachment. The gills are interconnected at their bases by veins. The stem
Stipe (mycology)
thumb|150px|right|Diagram of a [[basidiomycete]] stipe with an [[annulus |annulus]] and [[volva |volva]]In mycology a stipe refers to the stem or stalk-like feature supporting the cap of a mushroom. Like all tissues of the mushroom other than the hymenium, the stipe is composed of sterile hyphal...
is cylindrical, white and of variable height, up to 8 cm (3.1 in) tall and 4 cm (1.6 in) wide; it is roughly the same thickness at both the top and the base. Then top portion of the stem may be farinose—covered with a white, mealy powder. It may turn slightly brown with age, or when it is injured or bruised from handling. Like other species in the Russulales
Russulales
The Russulales are an order of the Agaricomycetes,...
order of mushrooms, the flesh
Trama (mycology)
In mycology trama is a term for the inner, fleshy portion of a mushroom's basidiocarp, or fruit body. It is distinct from the outer layer of tissue, known as the pileipellis or cuticle, and from the spore-bearing tissue layer known as the hymenium....
is brittle, owing to the sphaerocyst cytoarchitecture—cylindrical cells that contrast with the typical fibrous, filamentous hypha
Hypha
A hypha is a long, branching filamentous structure of a fungus, and also of unrelated Actinobacteria. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium; yeasts are unicellular fungi that do not grow as hyphae.-Structure:A hypha consists of one or...
e present in other orders of the basidiomycota
Basidiomycota
Basidiomycota is one of two large phyla that, together with the Ascomycota, comprise the subkingdom Dikarya within the Kingdom Fungi...
.
Microscopic characteristics
The sporesBasidiospore
A basidiospore is a reproductive spore produced by Basidiomycete fungi. Basidiospores typically each contain one haploid nucleus that is the product of meiosis, and they are produced by specialized fungal cells called basidia. In grills under a cap of one common species in the phylum of...
of R. virescens are elliptical or ellipsoid with warts, translucent (hyaline
Hyaline
The term hyaline denotes a substance with a glass-like appearance.-Histopathology:In histopathological medical usage, a hyaline substance appears glassy and pink after being stained with haematoxylin and eosin — usually it is an acellular, proteinaceous material...
), and in deposit produce a white, pale or pale yellow spore print
Spore print
thumb|300px|right|Making a spore print of the mushroom Volvariella volvacea shown in composite: mushroom cap laid on white and dark paper; cap removed after 24 hours showing pinkish-tan spore print...
; the spore dimensions are 6–9 by 5–7 µm
Micrometre
A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...
. The spore-bearing cells, the basidia, are club-shaped and with dimensions of 24–33 by 6–7.5 µm; they are colorless, and each hold from two to four spores. The pleurocystidia (cystidia located on the face of a gill) are 40–85 by 6–8 µm and end abruptly in a sharp point.
Edibility
Russula virescens is an edible mushroomEdible mushroom
Edible mushrooms are the fleshy and edible fruiting bodies of several species of fungi. Mushrooms belong to the macrofungi, because their fruiting structures are large enough to be seen with the naked eye. They can appear either below ground or above ground where they may be picked by hand...
considered to be one of the best of the genus Russula, and is a popular edible in Europe. Its smell is not distinctive, but its taste has been described as mild, or nutty. When collecting Russula virescens for consumption, caution is of vital importance to avoid confusion with the dangerously poisonous Amanita phalloides (known as the death cap
Death cap
Amanita phalloides , commonly known as the death cap, is a deadly poisonous basidiomycete fungus, one of many in the genus Amanita. Widely distributed across Europe, A. phalloides forms ectomycorrhizas with various broadleaved trees. In some cases, death cap has been introduced to new regions with...
), a mushroom that can be most easily identified by its volva
Volva (mycology)
The volva is a mycological term to describe a cup-like structure at the base of a mushroom that is a remnant of the universal veil. This macrofeature is important in wild mushroom identification due to it being an easily observed, taxonomically significant feature which frequently signifies a...
and ring
Annulus (mycology)
An annulus is the ring like structure sometimes found on the stipe of some species of mushrooms. The annulus represents the remaining part of the partial veil, after it has ruptured to expose the gills or other spore-producing surface. An annulus may be thick and membranous, or it may be cobweb-like...
.
Similar species
Another green-capped Russula is R. aerugineaRussula aeruginea
Russula aeruginea otherwise knows as the Grass-green Russula, is an inedible russula mushroom, found only under birch, mostly in pine forests; not rare.-Description:...
, but this species may be distinguished from R. virescens by its smaller size and smooth cap. Russula crustosa, like R. virescens also has an areolate cap, but the cap becomes sticky (viscid) when moist, and its color is more variable, as it may be reddish, yellowish, or brown. Also, the spore print of R. crustosa is a darker yellow than R. virescens. R. redolens has a cap that is "drab-green to blue-green", but unlike R. virescens, is smooth. Russula redolens also has an unpleasant taste and smells of parsley
Parsley
Parsley is a species of Petroselinum in the family Apiaceae, native to the central Mediterranean region , naturalized elsewhere in Europe, and widely cultivated as an herb, a spice and a vegetable.- Description :Garden parsley is a bright green hairless biennial herbaceous plant in temperate...
.
Habitat and distribution
Temperate deciduous forest
A temperate deciduous forest, more precisely termed temperate broadleaf forest or temperate broadleaved forest, is a biome found in North America, southern South America, Europe, and Asia. A temperate deciduous forest consists of trees that lose their leaves every year...
and mixed forests, forming ectomycorrhizal symbiotic
Symbiosis
Symbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...
relationships with a variety of trees, including oaks (Quercus) and European beech (Fagus sylvatica). Fruiting bodies may appear singly or in groups, reappear in the same spots year after year, and are not common. In Britain and Europe, fruiting occurs mainly during the months of summer to early autumn. A Mexican study of the seasonal occurrence of several common mushroom species in subtropical forests in Xalapa
Xalapa
Xalapa-Enríquez, commonly Xalapa or Jalapa, is the capital city of the Mexican state of Veracruz and the name of the surrounding municipality. In the year 2005 census the city reported a population of 387,879 and the municipality of which it serves as municipal seat reported a population of...
showed that the fruiting period of R. virescens occurred in April, before the onset of the rainy season
Wet season
The the wet season, or rainy season, is the time of year, covering one or more months, when most of the average annual rainfall in a region occurs. The term green season is also sometimes used as a euphemism by tourist authorities. Areas with wet seasons are dispersed across portions of the...
.
The distribution of R. virescens in North America is subject to debate, where a number of similar species such as R. parvovirescens and R. crustosa are also recognized. One author suggests that R. virescens "is strictly a European species", citing Buyck and collaborators (2006), who say "the virescens-crustosa group is much more complex than suspected and embraces at least a dozen taxa in the eastern US". In addition to Britain and Europe, Russula virescens has also been collected from Malaysia, Korea, and China.
Ribonuclease biochemistry
RibonucleaseRibonuclease
Ribonuclease is a type of nuclease that catalyzes the degradation of RNA into smaller components. Ribonucleases can be divided into endoribonucleases and exoribonucleases, and comprise several sub-classes within the EC 2.7 and 3.1 classes of enzymes.-Function:All organisms studied contain...
s (or RNases) are enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
s that catalyze
Enzyme catalysis
Enzyme catalysis is the catalysis of chemical reactions by specialized proteins known as enzymes. Catalysis of biochemical reactions in the cell is vital due to the very low reaction rates of the uncatalysed reactions....
the hydrolysis
Hydrolysis
Hydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...
of ribonucleic acid (RNA), and collectively they play a critical role in many biological processes. A RNase from R. virescens was shown to be biochemically unique amongst seven edible mushroom species in several ways: it has a co-specificity towards cleaving RNA at poly A
Adenine
Adenine is a nucleobase with a variety of roles in biochemistry including cellular respiration, in the form of both the energy-rich adenosine triphosphate and the cofactors nicotinamide adenine dinucleotide and flavin adenine dinucleotide , and protein synthesis, as a chemical component of DNA...
and poly C
Cytosine
Cytosine is one of the four main bases found in DNA and RNA, along with adenine, guanine, and thymine . It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached . The nucleoside of cytosine is cytidine...
, compared to the monospecific RNases of the others; it can be adsorbed
Adsorption
Adsorption is the adhesion of atoms, ions, biomolecules or molecules of gas, liquid, or dissolved solids to a surface. This process creates a film of the adsorbate on the surface of the adsorbent. It differs from absorption, in which a fluid permeates or is dissolved by a liquid or solid...
on chromatography
Column chromatography
Column chromatography in chemistry is a method used to purify individual chemical compounds from mixtures of compounds. It is often used for preparative applications on scales from micrograms up to kilograms.The main advantage of column chromatography is the relatively low cost and disposability...
columns containing DEAE–cellulose as the adsorbent; it has a pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
optimum of 4.5, lower than all other species; and, it has a "distinctly different" N-terminal amino acid sequence.
External links
- Healing-mushrooms.net Description and medicinal properties
- Morelmushroomhunting.com Several photos