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74-454: Subg. Chronosemium subg. Trifolium Clovers , also called trefoils , are plants of the genus Trifolium (from Latin tres  'three' and folium  'leaf'), consisting of about 300 species of flowering plants in the legume family Fabaceae originating in Europe. The genus has a cosmopolitan distribution with the highest diversity in

148-460: A cyanobiont (cyanobacteria such as Nostoc ) which fix nitrogen for them: Some symbiotic relationships involving agriculturally-important plants are: A method for nitrogen fixation was first described by Henry Cavendish in 1784 using electric arcs reacting nitrogen and oxygen in air. This method was implemented in the Birkeland–Eyde process of 1903. The fixation of nitrogen by lightning

222-399: A nitrogenase enzyme. The overall reaction for BNF is: N 2 + 16ATP + 16H 2 O + 8e + 8H → 2NH 3 +H 2 + 16ADP + 16P i The process is coupled to the hydrolysis of 16 equivalents of ATP and is accompanied by the co-formation of one equivalent of H 2 . The conversion of N 2 into ammonia occurs at a metal cluster called FeMoco , an abbreviation for

296-557: A species : see Botanical name and Specific name (zoology) . The rules for the scientific names of organisms are laid down in the nomenclature codes , which allow each species a single unique name that, for animals (including protists ), plants (also including algae and fungi ) and prokaryotes ( bacteria and archaea ), is Latin and binomial in form; this contrasts with common or vernacular names , which are non-standardized, can be non-unique, and typically also vary by country and language of usage. Except for viruses ,

370-543: A critical threshold. The specialized heterocyst cell is necessary for the performance of nitrogenase as a result of its sensitivity to ambient oxygen. Nitrogenase consist of two proteins, a catalytic iron-dependent protein, commonly referred to as MoFe protein and a reducing iron-only protein (Fe protein). There are three different iron dependent proteins, molybdenum -dependent, vanadium -dependent, and iron -only, with all three nitrogenase protein variations containing an iron protein component. Molybdenum-dependent nitrogenase

444-666: A crop, with negative effects on pollinators, but in the 1990s and 2010s, the cost of industrially-fixed nitrogen rose substantially, approximately doubling, and reviving interest in forage mixes that include clover. As the fixation process in energy-intensive, prices are closely tied to energy prices. The 21st century also took interest in clover as a countermeasure to fight the global pollinator decline . Several species of clover are extensively cultivated as fodder plants . The most widely cultivated clovers are white clover , Trifolium repens , and red clover , Trifolium pratense . Clover, either sown alone or in mixture with ryegrass , has for

518-651: A later homonym of a validly published name is a nomen illegitimum or nom. illeg. ; for a full list refer to the International Code of Nomenclature for algae, fungi, and plants and the work cited above by Hawksworth, 2010. In place of the "valid taxon" in zoology, the nearest equivalent in botany is " correct name " or "current name" which can, again, differ or change with alternative taxonomic treatments or new information that results in previously accepted genera being combined or split. Prokaryote and virus codes of nomenclature also exist which serve as

592-628: A long time and redescribed as new by a range of subsequent workers, or if a range of genera previously considered separate taxa have subsequently been consolidated into one. For example, the World Register of Marine Species presently lists 8 genus-level synonyms for the sperm whale genus Physeter Linnaeus, 1758, and 13 for the bivalve genus Pecten O.F. Müller, 1776. Within the same kingdom, one generic name can apply to one genus only. However, many names have been assigned (usually unintentionally) to two or more different genera. For example,

666-497: A long time formed a staple crop for silaging, for several reasons: it grows freely, shooting up again after repeated mowings; it produces an abundant crop; it is palatable to and nutritious for livestock ; it fixes nitrogen using symbiotic bacteria in its root nodules , reducing the need for synthetic fertilizers ; it grows in a great range of soils and climates ; and it is appropriate for either pasturage or green composting . In many areas, particularly on acidic soil , clover

740-447: A low nitrogen content, has been shown to host a diazotrophic community. The bacteria enrich the wood substrate with nitrogen through fixation, thus enabling deadwood decomposition by fungi. Nitrogenases are rapidly degraded by oxygen. For this reason, many bacteria cease production of the enzyme in the presence of oxygen. Many nitrogen-fixing organisms exist only in anaerobic conditions, respiring to draw down oxygen levels, or binding

814-424: A new era of soil science ." In 1901, Beijerinck showed that Azotobacter chroococcum was able to fix atmospheric nitrogen. This was the first species of the azotobacter genus, so-named by him. It is also the first known diazotroph , species that use diatomic nitrogen as a step in the complete nitrogen cycle . Biological nitrogen fixation (BNF) occurs when atmospheric nitrogen is converted to ammonia by

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888-409: A reference for designating currently accepted genus names as opposed to others which may be either reduced to synonymy, or, in the case of prokaryotes, relegated to a status of "names without standing in prokaryotic nomenclature". An available (zoological) or validly published (botanical) name that has been historically applied to a genus but is not regarded as the accepted (current/valid) name for

962-459: A soft hairy plant with minute white or pale pink flowers and feathery sepals; Trifolium fragiferum , strawberry clover, with globose, rose-purple heads and swollen calyxes; Trifolium campestre , hop trefoil, on dry pastures and roadsides, the heads of pale yellow flowers suggesting miniature hops; and the somewhat similar Trifolium dubium , common in pastures and roadsides, with smaller heads and small yellow flowers turning dark brown. Clover

1036-427: A taxon; however, the names published in suppressed works are made unavailable via the relevant Opinion dealing with the work in question. In botany, similar concepts exist but with different labels. The botanical equivalent of zoology's "available name" is a validly published name . An invalidly published name is a nomen invalidum or nom. inval. ; a rejected name is a nomen rejiciendum or nom. rej. ;

1110-455: A total of c. 520,000 published names (including synonyms) as at end 2019, increasing at some 2,500 published generic names per year. "Official" registers of taxon names at all ranks, including genera, exist for a few groups only such as viruses and prokaryotes, while for others there are compendia with no "official" standing such as Index Fungorum for fungi, Index Nominum Algarum and AlgaeBase for algae, Index Nominum Genericorum and

1184-659: Is catalyzed by enzymes called nitrogenases . These enzyme complexes are encoded by the Nif genes (or Nif homologs ) and contain iron , often with a second metal (usually molybdenum , but sometimes vanadium ). Some nitrogen-fixing bacteria have symbiotic relationships with plants , especially legumes , mosses and aquatic ferns such as Azolla . Looser non-symbiotic relationships between diazotrophs and plants are often referred to as associative, as seen in nitrogen fixation on rice roots. Nitrogen fixation occurs between some termites and fungi . It occurs naturally in

1258-697: Is 63, set on August 2, 2023, by Yoshiharu Watanabe in Japan. The previous record holder, Shigeo Obara, had discovered an 18-leaf clover in 2002, a 21-leaf clover in 2008 and a 56-leaf clover in 2009, also in Japan. The first extensive classification of Trifolium had been done by Michael Zohary and David Heller, and it was subsequently released in 1984. They divided the genus into eight sections: Lotoidea, Paramesus, Mistyllus, Vesicamridula, Chronosemium, Trifolium, Trichoecephalum, and Involucrarium, with Lotoidea placed most basally . Within this classification system, Trifolium repens falls within section Lotoidea ,

1332-408: Is a required precursor to fertilizers , explosives , and other products. The Haber process requires high pressures (around 200 atm) and high temperatures (at least 400 °C), which are routine conditions for industrial catalysis. This process uses natural gas as a hydrogen source and air as a nitrogen source. The ammonia product has resulted in an intensification of nitrogen fertilizer globally and

1406-532: Is a very similar natural occurring process. The possibility that atmospheric nitrogen reacts with certain chemicals was first observed by Desfosses in 1828. He observed that mixtures of alkali metal oxides and carbon react with nitrogen at high temperatures. With the use of barium carbonate as starting material, the first commercial process became available in the 1860s, developed by Margueritte and Sourdeval. The resulting barium cyanide reacts with steam, yielding ammonia. In 1898 Frank and Caro developed what

1480-566: Is credited with supporting the expansion of the human population from around 2 billion in the early 20th century to roughly 8 billion people now. Much research has been conducted on the discovery of catalysts for nitrogen fixation, often with the goal of lowering energy requirements. However, such research has thus far failed to approach the efficiency and ease of the Haber process. Many compounds react with atmospheric nitrogen to give dinitrogen complexes . The first dinitrogen complex to be reported

1554-442: Is dependent on many factors, including the legume and air and soil conditions. For example, nitrogen fixation by red clover can range from 50 to 200 lb/acre (56 to 224 kg/ha). The ability to fix nitrogen in nodules is present in actinorhizal plants such as alder and bayberry , with the help of Frankia bacteria. They are found in 25 genera in the orders Cucurbitales , Fagales and Rosales , which together with

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1628-612: Is discouraged by both the International Code of Zoological Nomenclature and the International Code of Nomenclature for algae, fungi, and plants , there are some five thousand such names in use in more than one kingdom. For instance, A list of generic homonyms (with their authorities), including both available (validly published) and selected unavailable names, has been compiled by the Interim Register of Marine and Nonmarine Genera (IRMNG). The type genus forms

1702-437: Is foraged for by wildlife such as bears, game animals, and birds. Clover is edible by humans, although red clover should be avoided by pregnant women. The plant is a traditional Native American food, which is eaten both raw and after drying and smoking the roots. The seeds from the blossoms are used to make bread. It is also possible to make tea from the blossoms. Shamrock , the traditional Irish symbol, which according to legend

1776-408: Is genetically regulated, and the activity of the protein complex is dependent on ambient oxygen concentrations, and intra- and extracellular concentrations of ammonia and oxidized nitrogen species (nitrate and nitrite). Additionally, the combined concentrations of both ammonium and nitrate are thought to inhibit N Fix , specifically when intracellular concentrations of 2- oxoglutarate (2-OG) exceed

1850-571: Is known as the Frank–Caro process to fix nitrogen in the form of calcium cyanamide . The process was eclipsed by the Haber process , which was discovered in 1909. The dominant industrial method for producing ammonia is the Haber process also known as the Haber-Bosch process. Fertilizer production is now the largest source of human-produced fixed nitrogen in the terrestrial ecosystem . Ammonia

1924-796: Is no conclusive agreement on which form of nitrogenase arose first. Diazotrophs are widespread within domain Bacteria including cyanobacteria (e.g. the highly significant Trichodesmium and Cyanothece ), green sulfur bacteria , purple sulfur bacteria , Azotobacteraceae , rhizobia and Frankia . Several obligately anaerobic bacteria fix nitrogen including many (but not all) Clostridium spp. Some archaea such as Methanosarcina acetivorans also fix nitrogen, and several other methanogenic taxa , are significant contributors to nitrogen fixation in oxygen-deficient soils. Cyanobacteria , commonly known as blue-green algae, inhabit nearly all illuminated environments on Earth and play key roles in

1998-522: Is short-lived because of a combination of insect pests, diseases and nutrient balance; this is known as "clover sickness". When crop rotations are managed so that clover does not recur at intervals shorter than eight years, it grows with much of its pristine vigor. Clovers are most efficiently pollinated by bumblebees , which have declined as a result of agricultural intensification. Honeybees can also pollinate clover, and beekeepers are often in heavy demand from farmers with clover pastures. Farmers reap

2072-460: Is somewhat arbitrary. Although all species within a genus are supposed to be "similar", there are no objective criteria for grouping species into genera. There is much debate among zoologists about whether enormous, species-rich genera should be maintained, as it is extremely difficult to come up with identification keys or even character sets that distinguish all species. Hence, many taxonomists argue in favor of breaking down large genera. For instance,

2146-474: Is the type species , and the generic name is permanently associated with the type specimen of its type species. Should the specimen turn out to be assignable to another genus, the generic name linked to it becomes a junior synonym and the remaining taxa in the former genus need to be reassessed. In zoological usage, taxonomic names, including those of genera, are classified as "available" or "unavailable". Available names are those published in accordance with

2220-590: Is the most commonly present nitrogenase. The different types of nitrogenase can be determined by the specific iron protein component. Nitrogenase is highly conserved. Gene expression through DNA sequencing can distinguish which protein complex is present in the microorganism and potentially being expressed. Most frequently, the nif H gene is used to identify the presence of molybdenum-dependent nitrogenase, followed by closely related nitrogenase reductases (component II) vnf H and anf H representing vanadium-dependent and iron-only nitrogenase, respectively. In studying

2294-485: The Fabales form a nitrogen-fixing clade of eurosids . The ability to fix nitrogen is not universally present in these families. For example, of 122 Rosaceae genera, only four fix nitrogen. Fabales were the first lineage to branch off this nitrogen-fixing clade; thus, the ability to fix nitrogen may be plesiomorphic and subsequently lost in most descendants of the original nitrogen-fixing plant; however, it may be that

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2368-621: The International Code of Zoological Nomenclature ; the earliest such name for any taxon (for example, a genus) should then be selected as the " valid " (i.e., current or accepted) name for the taxon in question. Consequently, there will be more available names than valid names at any point in time; which names are currently in use depending on the judgement of taxonomists in either combining taxa described under multiple names, or splitting taxa which may bring available names previously treated as synonyms back into use. "Unavailable" names in zoology comprise names that either were not published according to

2442-824: The International Plant Names Index for plants in general, and ferns through angiosperms, respectively, and Nomenclator Zoologicus and the Index to Organism Names for zoological names. Totals for both "all names" and estimates for "accepted names" as held in the Interim Register of Marine and Nonmarine Genera (IRMNG) are broken down further in the publication by Rees et al., 2020 cited above. The accepted names estimates are as follows, broken down by kingdom: The cited ranges of uncertainty arise because IRMNG lists "uncertain" names (not researched therein) in addition to known "accepted" names;

2516-404: The platypus belongs to the genus Ornithorhynchus although George Shaw named it Platypus in 1799 (these two names are thus synonyms ) . However, the name Platypus had already been given to a group of ambrosia beetles by Johann Friedrich Wilhelm Herbst in 1793. A name that means two different things is a homonym . Since beetles and platypuses are both members of the kingdom Animalia,

2590-473: The French botanist Joseph Pitton de Tournefort (1656–1708) is considered "the founder of the modern concept of genera". The scientific name (or the scientific epithet) of a genus is also called the generic name ; in modern style guides and science, it is always capitalised. It plays a fundamental role in binomial nomenclature , the system of naming organisms , where it is combined with the scientific name of

2664-414: The air by means of NO x production by lightning . Nitrogen fixation is essential to life on Earth because fixed inorganic nitrogen compounds are required for the biosynthesis of all nitrogen-containing organic compounds such as amino acids , polypeptides and proteins , nucleoside triphosphates and nucleic acids . As part of the nitrogen cycle , it is essential for soil fertility and

2738-697: The amount of nitrogen fixed in the ocean is at least as much as that on land. The colonial marine cyanobacterium Trichodesmium is thought to fix nitrogen on such a scale that it accounts for almost half of the nitrogen fixation in marine systems globally. Marine surface lichens and non-photosynthetic bacteria belonging in Proteobacteria and Planctomycetes fixate significant atmospheric nitrogen. Species of nitrogen fixing cyanobacteria in fresh waters include: Aphanizomenon and Dolichospermum (previously Anabaena). Such species have specialized cells called heterocytes , in which nitrogen fixation occurs via

2812-522: The basal position of Lotoidea , because they were ancestral. Aside from considering this section basal, they did not propose relationships between other sections. Since then, molecular data has both questioned and confirmed the proposed phylogeny from Zohary and Heller. A genus-wide molecular study has since proposed a new classification system, made up of two subgenera, Chronosemium and Trifolium. This recent reclassification further divides subgenus Trifolium into eight sections. The molecular data supports

2886-442: The base for higher taxonomic ranks, such as the family name Canidae ("Canids") based on Canis . However, this does not typically ascend more than one or two levels: the order to which dogs and wolves belong is Carnivora ("Carnivores"). The numbers of either accepted, or all published genus names is not known precisely; Rees et al., 2020 estimate that approximately 310,000 accepted names (valid taxa) may exist, out of

2960-409: The basic genetic and physiological requirements were present in an incipient state in the most recent common ancestors of all these plants, but only evolved to full function in some of them. In addition, Trema ( Parasponia ), a tropical genus in the family Cannabaceae , is unusually able to interact with rhizobia and form nitrogen-fixing nodules. Some other plants live in association with

3034-400: The benefits of increased reseeding that occurs with increased bee activity, which means that future clover yields remain abundant. Beekeepers benefit from the clover bloom, as clover is one of the main nectar sources for honeybees . Trifolium repens , white or Dutch clover, is a perennial abundant in meadows and good pastures. The flowers are white or pinkish, becoming brown and deflexed as

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3108-561: The carbon and nitrogen cycle of the biosphere . In general, cyanobacteria can use various inorganic and organic sources of combined nitrogen, such as nitrate , nitrite , ammonium , urea , or some amino acids . Several cyanobacteria strains are also capable of diazotrophic growth, an ability that may have been present in their last common ancestor in the Archean eon. Nitrogen fixation not only naturally occurs in soils but also aquatic systems, including both freshwater and marine. Indeed,

3182-602: The corolla fades. Trifolium hybridum , alsike or Swedish clover, is a perennial which was introduced early in the 19th century and has now become naturalized in Britain. The flowers are white or rosy, and resemble those of Trifolium repens . Trifolium medium , meadow or zigzag clover, a perennial with straggling flexuous stems and rose-purple flowers, has potential for interbreeding with T. pratense to produce perennial crop plants. Other species are: Trifolium arvense , hare's-foot trefoil; found in fields and dry pastures,

3256-498: The ecology and evolution of nitrogen-fixing bacteria , the nifH gene is the biomarker most widely used. nif H has two similar genes anf H and vnfH that also encode for the nitrogenase reductase component of the nitrogenase complex. Nitrogenase is thought to have evolved sometime between 1.5-2.2 billion years ago (Ga), although some isotopic support showing nitrogenase evolution as early as around 3.2 Ga. Nitrogenase appears to have evolved from maturase -like proteins, although

3330-446: The form "author, year" in zoology, and "standard abbreviated author name" in botany. Thus in the examples above, the genus Canis would be cited in full as " Canis Linnaeus, 1758" (zoological usage), while Hibiscus , also first established by Linnaeus but in 1753, is simply " Hibiscus L." (botanical usage). Each genus should have a designated type , although in practice there is a backlog of older names without one. In zoology, this

3404-410: The function of the preceding protein is currently unknown. Nitrogenase has three different forms ( Nif, Anf, and Vnf ) that correspond with the metal found in the active site of the protein (Molybdenum, Iron, and Vanadium respectively). Marine metal abundances over Earth’s geologic timeline are thought to have driven the relative abundance of which form of nitrogenase was most common. Currently, there

3478-737: The generic name (or its abbreviated form) still forms the leading portion of the scientific name, for example, Canis lupus lupus for the Eurasian wolf subspecies, or as a botanical example, Hibiscus arnottianus ssp. immaculatus . Also, as visible in the above examples, the Latinised portions of the scientific names of genera and their included species (and infraspecies, where applicable) are, by convention, written in italics . The scientific names of virus species are descriptive, not binomial in form, and may or may not incorporate an indication of their containing genus; for example,

3552-406: The growth of terrestrial and semiaquatic vegetations , upon which all consumers of those ecosystems rely for biomass . Nitrogen fixation is thus crucial to the food security of human societies in sustaining agricultural yields (especially staple crops ), livestock feeds ( forage or fodder ) and fishery (both wild and farmed ) harvests . It is also indirectly relevant to

3626-432: The idea that a newly defined genus should fulfill these three criteria to be descriptively useful: Moreover, genera should be composed of phylogenetic units of the same kind as other (analogous) genera. The term "genus" comes from Latin genus , a noun form cognate with gignere ('to bear; to give birth to'). The Swedish taxonomist Carl Linnaeus popularized its use in his 1753 Species Plantarum , but

3700-548: The iron- molybdenum cofactor. The mechanism proceeds via a series of protonation and reduction steps wherein the FeMoco active site hydrogenates the N 2 substrate. In free-living diazotrophs , nitrogenase-generated ammonia is assimilated into glutamate through the glutamine synthetase /glutamate synthase pathway. The microbial nif genes required for nitrogen fixation are widely distributed in diverse environments. For example, decomposing wood, which generally has

3774-419: The largest and least heterogeneous section. Lotoidea contains species from America, Africa, and Eurasia, considered a clade because of their inflorescence shape, floral structure, and legume that protrudes from the calyx. However, these traits are not unique to the section, and are shared with many other species in other sections. Zohary and Heller argued that the presence of these traits in other sections proved

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3848-633: The largest component, with 23,236 ± 5,379 accepted genus names, of which 20,845 ± 4,494 are angiosperms (superclass Angiospermae). By comparison, the 2018 annual edition of the Catalogue of Life (estimated >90% complete, for extant species in the main) contains currently 175,363 "accepted" genus names for 1,744,204 living and 59,284 extinct species, also including genus names only (no species) for some groups. The number of species in genera varies considerably among taxonomic groups. For instance, among (non-avian) reptiles , which have about 1180 genera,

3922-457: The lizard genus Anolis has been suggested to be broken down into 8 or so different genera which would bring its ~400 species to smaller, more manageable subsets. Nitrogen fixation Nitrogen fixation is a chemical process by which molecular dinitrogen ( N 2 ) is converted into ammonia ( NH 3 ). It occurs both biologically and abiologically in chemical industries . Biological nitrogen fixation or diazotrophy

3996-492: The manufacture of all nitrogenous industrial products , which include fertilizers , pharmaceuticals , textiles , dyes and explosives . Biological nitrogen fixation was discovered by Jean-Baptiste Boussingault in 1838. Later, in 1880, the process by which it happens was discovered by German agronomist Hermann Hellriegel and Hermann Wilfarth  [ de ] and was fully described by Dutch microbiologist Martinus Beijerinck . "The protracted investigations of

4070-632: The monophyletic nature of three sections proposed by Zohary and Heller ( Tripholium, Paramesus, and Trichoecepalum ), but not of Lotoidea (members of this section have since been reclassified into five other sections). Other molecular studies, although smaller, support the need to reorganize Lotoidea. 291 species of Trifolium are accepted: Genus The composition of a genus is determined by taxonomists . The standards for genus classification are not strictly codified, so different authorities often produce different classifications for genera. There are some general practices used, however, including

4144-403: The most (>300) have only 1 species, ~360 have between 2 and 4 species, 260 have 5–10 species, ~200 have 11–50 species, and only 27 genera have more than 50 species. However, some insect genera such as the bee genera Lasioglossum and Andrena have over 1000 species each. The largest flowering plant genus, Astragalus , contains over 3,000 species. Which species are assigned to a genus

4218-428: The name could not be used for both. Johann Friedrich Blumenbach published the replacement name Ornithorhynchus in 1800. However, a genus in one kingdom is allowed to bear a scientific name that is in use as a generic name (or the name of a taxon in another rank) in a kingdom that is governed by a different nomenclature code. Names with the same form but applying to different taxa are called "homonyms". Although this

4292-473: The nitrogenase enzyme. One type of organelle can turn nitrogen gas into a biologically available form. This nitroplast was discovered in algae . Plants that contribute to nitrogen fixation include those of the legume family — Fabaceae — with taxa such as kudzu , clover , soybean , alfalfa , lupin , peanut and rooibos . They contain symbiotic rhizobia bacteria within nodules in their root systems , producing nitrogen compounds that help

4366-409: The oxygen with a protein such as leghemoglobin . Atmospheric nitrogen is inaccessible to most organisms, because its triple covalent bond is very strong. Most take up fixed nitrogen from various sources. For every 100 atoms of carbon, roughly 2 to 20 atoms of nitrogen are assimilated. The atomic ratio of carbon (C) : nitrogen (N) : phosphorus (P) observed on average in planktonic biomass

4440-475: The plant to grow and compete with other plants. When the plant dies, the fixed nitrogen is released, making it available to other plants; this helps to fertilize the soil . The great majority of legumes have this association, but a few genera (e.g., Styphnolobium ) do not. In many traditional farming practices, fields are rotated through various types of crops, which usually include one consisting mainly or entirely of clover . Fixation efficiency in soil

4514-541: The provisions of the ICZN Code, e.g., incorrect original or subsequent spellings, names published only in a thesis, and generic names published after 1930 with no type species indicated. According to "Glossary" section of the zoological Code, suppressed names (per published "Opinions" of the International Commission of Zoological Nomenclature) remain available but cannot be used as the valid name for

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4588-686: The rarer it is; see four-leaf clover ), with stipules adnate to the leaf-stalk, and heads or dense spikes of small red, purple, white, or yellow flowers; the small, few-seeded pods are enclosed in the calyx . Other closely related genera often called clovers include Melilotus (sweet clover) and Medicago ( alfalfa or Calvary clover ). As legumes , clovers fix nitrogen using symbiotic bacteria in their root nodules , and are used as an alternative or supplement to synthetic nitrogen fertilizers . They are also valuable food source for grazing livestock and bees. The domestication of clover caused substantial increases in agricultural productivity. Clover

4662-462: The relation of plants to the acquisition of nitrogen begun by de Saussure , Ville , Lawes , Gilbert and others, and culminated in the discovery of symbiotic fixation by Hellriegel and Wilfarth in 1887." "Experiments by Bossingault in 1855 and Pugh, Gilbert & Lawes in 1887 had shown that nitrogen did not enter the plant directly. The discovery of the role of nitrogen fixing bacteria by Herman Hellriegel and Herman Wilfarth in 1886-1888 would open

4736-507: The rural landscape; adding clover made livestock feed more nutritious. Honey production also rose drastically, and clover remained the main nectar source for bees until the mid-twentieth century. Clover was carried around the world as a crop by European colonists , and some clover species became invasive in some areas. Imports of guano and the development of the Haber-Bosch process in the 20th century substantially displaced clover as

4810-497: The specific name particular to the wolf. A botanical example would be Hibiscus arnottianus , a particular species of the genus Hibiscus native to Hawaii. The specific name is written in lower-case and may be followed by subspecies names in zoology or a variety of infraspecific names in botany . When the generic name is already known from context, it may be shortened to its initial letter, for example, C. lupus in place of Canis lupus . Where species are further subdivided,

4884-412: The standard format for a species name comprises the generic name, indicating the genus to which the species belongs, followed by the specific epithet, which (within that genus) is unique to the species. For example, the gray wolf 's scientific name is Canis lupus , with Canis ( Latin for 'dog') being the generic name shared by the wolf's close relatives and lupus (Latin for 'wolf') being

4958-403: The taxon is termed a synonym ; some authors also include unavailable names in lists of synonyms as well as available names, such as misspellings, names previously published without fulfilling all of the requirements of the relevant nomenclatural code, and rejected or suppressed names. A particular genus name may have zero to many synonyms, the latter case generally if the genus has been known for

5032-462: The temperate Northern Hemisphere , but many species also occur in South America and Africa , including at high altitudes on mountains in the tropics. They are small annual , biennial , or short-lived perennial herbaceous plants, typically growing up to 30 cm (12 in) tall. The leaves are trifoliate (rarely, they have four or more leaflets; the more leaflets the leaf has,

5106-576: The values quoted are the mean of "accepted" names alone (all "uncertain" names treated as unaccepted) and "accepted + uncertain" names (all "uncertain" names treated as accepted), with the associated range of uncertainty indicating these two extremes. Within Animalia, the largest phylum is Arthropoda , with 151,697 ± 33,160 accepted genus names, of which 114,387 ± 27,654 are insects (class Insecta). Within Plantae, Tracheophyta (vascular plants) make up

5180-429: The virus species " Salmonid herpesvirus 1 ", " Salmonid herpesvirus 2 " and " Salmonid herpesvirus 3 " are all within the genus Salmonivirus ; however, the genus to which the species with the formal names " Everglades virus " and " Ross River virus " are assigned is Alphavirus . As with scientific names at other ranks, in all groups other than viruses, names of genera may be cited with their authorities, typically in

5254-767: Was Ru(NH 3 ) 5 ( N 2 ) . Some soluble complexes do catalyze nitrogen fixation. Nitrogen can be fixed by lightning converting nitrogen gas ( N 2 ) and oxygen gas ( O 2 ) in the atmosphere into NO x ( nitrogen oxides ). The N 2 molecule is highly stable and nonreactive due to the triple bond between the nitrogen atoms. Lightning produces enough energy and heat to break this bond allowing nitrogen atoms to react with oxygen, forming NO x . These compounds cannot be used by plants, but as this molecule cools, it reacts with oxygen to form NO 2 , which in turn reacts with water to produce HNO 2 ( nitrous acid ) or HNO 3 ( nitric acid ). When these acids seep into

5328-579: Was coined by Saint Patrick for the Holy Trinity , is commonly associated with clover, although alternatively sometimes with the various species within the genus Oxalis , which are also trifoliate. Clovers occasionally have four leaflets, instead of the usual three. These four-leaf clovers , like other rarities, are considered lucky. Clovers can also have five, six, or more leaflets, but these are rarer still. The clover's outer leaf structure varies in physical orientation. The record for most leaflets

5402-524: Was first domesticated in Spain in around the year 1000. During European urbanization, crop rotations involving clover became essential for replacing the fixed nitrogen exported to cities as food. Increased soil nitrogen levels from the spreading use of clover were one of the main reasons why European agricultural production in 1880 was about 275% of the production in 1750. Fields of clover, used as forage and newly-invented silage , became an important part of

5476-422: Was originally described by Alfred Redfield, who determined the stoichiometric relationship between C:N:P atoms, The Redfield Ratio, to be 106:16:1. The protein complex nitrogenase is responsible for catalyzing the reduction of nitrogen gas (N 2 ) to ammonia (NH 3 ). In cyanobacteria , this enzyme system is housed in a specialized cell called the heterocyst . The production of the nitrogenase complex

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