Equisetum Temporal range: | |
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"Candocks" of Equisetum telmateia subsp. telmateia (great horsetail), showing whorls of branches and the tiny dark-tipped leaves | |
Scientific classification | |
Kingdom: | Plantae |
Clade: | Tracheophytes |
Division: | Polypodiophyta |
Class: | Polypodiopsida |
Subclass: | Equisetidae |
Order: | Equisetales |
Family: | Equisetaceae |
Genus: | Equisetum L. |
Type species | |
Equisetum arvense | |
Species | |
See text | |
Synonyms [1] | |
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Equisetum ( /ˌɛkwɪˈsiːtəm/ ; horsetail, marestail, snake grass, puzzlegrass) is the only living genus in Equisetaceae, a family of vascular plants that reproduce by spores rather than seeds. [2]
Equisetum is a "living fossil", the only living genus of the entire subclass Equisetidae, which for over 100 million years was much more diverse and dominated the understorey of late Paleozoic forests. Some equisetids were large trees reaching to 30 m (98 ft) tall. [3] The genus Calamites of the family Calamitaceae, for example, is abundant in coal deposits from the Carboniferous period. The pattern of spacing of nodes in horsetails, wherein those toward the apex of the shoot are increasingly close together, is said to have inspired John Napier to invent logarithms. [4] Modern horsetails first appeared during the Jurassic period.
A superficially similar but entirely unrelated flowering plant genus, mare's tail ( Hippuris ), is occasionally referred to as "horsetail", and adding to confusion, the name "mare's tail" is sometimes applied to Equisetum. [5]
Despite centuries of use in traditional medicine, there is no evidence that Equisetum has any medicinal properties.
This section needs additional citations for verification .(August 2018) |
The name "horsetail", often used for the entire group, arose because the branched species somewhat resemble a horse's tail. Similarly, the scientific name Equisetum is derived from the Latin equus ('horse') + seta ('bristle'). [6]
Other names include candock for branching species, and snake grass or scouring-rush for unbranched or sparsely branched species. The latter name refers to the rush-like appearance of the plants and to the fact that the stems are coated with abrasive silicates, making them useful for scouring (cleaning) metal items such as cooking pots or drinking mugs, particularly those made of tin. Equisetum hyemale , rough horsetail, is still boiled and then dried in Japan to be used for the final polishing process on woodcraft to produce a smooth finish. [7] In German, the corresponding name is Zinnkraut ('tin-herb'). In Spanish-speaking countries, these plants are known as cola de caballo ('horsetail').
Equisetum leaves are greatly reduced and usually non-photosynthetic. They contain a single, non-branching vascular trace, which is the defining feature of microphylls. However, it has recently been recognised that horsetail microphylls are probably not ancestral as in lycophytes (clubmosses and relatives), but rather derived adaptations, evolved by reduction of megaphylls. [8]
The leaves of horsetails are arranged in whorls fused into nodal sheaths. The stems are usually green and photosynthetic, and are distinctive in being hollow, jointed and ridged (with sometimes 3 but usually 6–40 ridges). There may or may not be whorls of branches at the nodes.[ citation needed ] Unusually, the branches often emerge below the leaves in an internode, and grow from buds between their bases.
The spores are borne under sporangiophores in strobili, cone-like structures at the tips of some of the stems. In many species the cone-bearing shoots are unbranched, and in some (e.g. E. arvense , field horsetail) they are non-photosynthetic, produced early in spring. In some other species (e.g. E. palustre , marsh horsetail) they are very similar to sterile shoots, photosynthetic and with whorls of branches. [9] : 12–15
Horsetails are mostly homosporous, though in the field horsetail, smaller spores give rise to male prothalli. The spores have four elaters that act as moisture-sensitive springs, assisting spore dispersal through crawling and hopping motions after the sporangia have split open longitudinally. [10] They are photosynthetic and have a lifespan that is usually two weeks at most, but will germinate immediately under humid conditions and develop into a gametophyte. [11]
The crude cell extracts of all Equisetum species tested contain mixed-linkage glucan : xyloglucan endotransglucosylase (MXE) activity. [12] This is a novel enzyme and is not known to occur in any other plants. In addition, the cell walls of all Equisetum species tested contain mixed-linkage glucan (MLG), a polysaccharide which, until recently, was thought to be confined to the Poales. [13] [14] The evolutionary distance between Equisetum and the Poales suggests that each evolved MLG independently. The presence of MXE activity in Equisetum suggests that they have evolved MLG along with some mechanism of cell wall modification. Non-Equisetum land plants tested lack detectable MXE activity. An observed negative correlation between XET activity and cell age led to the suggestion that XET is catalysing endotransglycosylation in controlled wall-loosening during cell expansion. [15] The lack of MXE in the Poales suggests that there it must play some other, currently unknown, role. Due to the correlation between MXE activity and cell age, MXE has been proposed to promote the cessation of cell expansion.[ citation needed ]
The living members of the genus Equisetum are divided into three distinct lineages, which are usually treated as subgenera. The name of the type subgenus, Equisetum, means "horse hair" in Latin, while the name of the other large subgenus, Hippochaete, means "horse hair" in Greek. Hybrids are common, but hybridization has only been recorded between members of the same subgenus. [16] While plants of subgenus Equisetum are usually referred to as horsetails, those of subgenus Hippochaete are often called scouring rushes, especially when unbranched.[ citation needed ]
Two Equisetum plants are sold commercially under the names Equisetum japonicum (barred horsetail) and Equisetum camtschatcense (Kamchatka horsetail). These are both types of E. hyemale var. hyemale, although they may also be listed as separate varieties of E. hyemale. [17] [ citation needed ]
The oldest remains of modern horsetails of the genus Equisetum first appear in the Early Jurassic, represented by Equisetum dimorphum from the Early Jurassic of Patagonia [18] and Equisetum laterale from the Early-Middle Jurassic of Australia. [19] [20] Silicified remains of Equisetum thermale from the Late Jurassic of Argentina exhibit all the morphological characters of modern members of the genus. [21] The estimated split between Equisetum bogotense and all other living Equisetum is estimated to have occurred no later than the Early Jurassic. [20]
Christenhusz et al. 2019 [22] | Nitta et al. 2022 [23] and Fern Tree of life [24] | ||||||||||||||||||||||||||||||
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The genus Equisetum as a whole, while concentrated in the non-tropical northern hemisphere, is near-cosmopolitan, being absent only from Antarctica, though they are not known to be native to Australia, New Zealand nor the islands of the Pacific. They are most common in northern North America (Canada and the northernmost United States), where the genus is represented by nine species (E. arvense, E. fluviatile, E. hyemale, E. laevigatum, E. palustre, E. pratense, E. scirpoides, E. sylvaticum', and E. variegatum). Only four (E. bogotense, E. giganteum, E. myriochaetum, and E. ramosissimum) of the fifteen species are known to be native south of the Equator. They are perennial plants, herbaceous and dying back in winter as most temperate species, or evergreen as most tropical species and the temperate species E. hyemale (rough horsetail), E. ramosissimum (branched horsetail), E. scirpoides (dwarf horsetail) and E. variegatum (variegated horsetail). They typically grow 20 cm–1.5 m (8 in–5 ft) tall, though the "giant horsetails" are recorded to grow as high as 2.5 m (8 ft) ( E. telmateia , northern giant horsetail), 5 m (16 ft) ( E. giganteum , southern giant horsetail) or 8 m (26 ft) ( E. myriochaetum , Mexican giant horsetail), and allegedly even more. [25]
One species, Equisetum fluviatile , is an emergent aquatic, rooted in water with shoots growing into the air. The stalks arise from rhizomes that are deep underground and difficult to dig out. Field horsetail ( E. arvense ) can be a nuisance weed, readily regrowing from the rhizome after being pulled out. It is unaffected by many herbicides designed to kill seed plants. [26] [ citation needed ] Since the stems have a waxy coat, the plant is resistant to contact weedkillers like glyphosate. [27] However, as E. arvense prefers an acid soil, lime may be used to assist in eradication efforts to bring the soil pH to 7 or 8. [28] Members of the genus have been declared noxious weeds in Australia and in the US state of Oregon. [29] [30]
All the Equisetum are classed as "unwanted organisms" in New Zealand and are listed on the National Pest Plant Accord. [31]
People have regularly consumed horsetails. For example, the fertile stems bearing strobili of some species are cooked and eaten like asparagus [32] (a dish called tsukushi (土筆) in Japan [33] [ failed verification ]). Indigenous nations across Cascadia consume and use horsetails in a variety of ways, with the Squamish calling them sx̱ém'x̱em and the Lushootseed using gʷəɫik, or horsetail roots, for cedar root baskets. [34] [35] [36] The young plants are eaten cooked or raw, but considerable care must be taken. [37]
If eaten over a long enough period of time, some species of horsetail can be poisonous to grazing animals, including horses. [38] The toxicity appears to be due to thiaminase, which can cause thiamin (vitamin B1) deficiency. [37] [39] [40] [41]
Equisetum species may have been a common food for herbivorous dinosaurs. With studies showing that horsetails are nutritionally of high quality, it is assumed that horsetails were an important component of herbivorous dinosaur diets. [42] Analysis of the scratch marks on hadrosaur teeth is consistent with grazing on hard plants like horsetails. [43]
Extracts and other preparations of E. arvense have served as herbal remedies, with records dating over centuries. [37] [39] [44] In 2009, the European Food Safety Authority concluded there was no evidence for the supposed health effects of E. arvense, such as for invigoration, weight control, skincare, hair health or bone health. [45] As of 2018 [update] , there is insufficient scientific evidence for its effectiveness as a medicine to treat any human condition. [37] [44] [45]
E. arvense contains thiaminase, which metabolizes the B vitamin, thiamine, potentially causing thiamine deficiency and associated liver damage, if taken chronically. [37] [39] Horsetail might produce a diuretic effect. [37] [39] Further, its safety for oral consumption has not been sufficiently evaluated and it may be toxic, especially to children and pregnant women. [37]
Equisetum fluviatile, the water horsetail or swamp horsetail, is a vascular plant. It is a perennial herbaceous pteridophyte.
Equisetidae is one of the four subclasses of Polypodiopsida (ferns), a group of vascular plants with a fossil record going back to the Devonian. They are commonly known as horsetails. They typically grow in wet areas, with whorls of needle-like branches radiating at regular intervals from a single vertical stem.
Equisetum sylvaticum, the wood horsetail, is a horsetail native to the Northern Hemisphere, occurring in North America and Eurasia. Because of its lacy appearance, it is considered among the most attractive of the horsetails.
Equisetum arvense, the field horsetail or common horsetail, is an herbaceous perennial plant in the Equisetidae (horsetails) sub-class, native throughout the arctic and temperate regions of the Northern Hemisphere. It has separate sterile non-reproductive and fertile spore-bearing stems growing from a perennial underground rhizomatous stem system. The fertile stems are produced in early spring and are non-photosynthetic, while the green sterile stems start to grow after the fertile stems have wilted and persist through the summer until the first autumn frosts. It is sometimes confused with mare's tail, Hippuris vulgaris.
Equisetum palustre, the marsh horsetail, is a perennial herbaceous pteridophyte belonging to the division of horsetails (Equisetopsida). It is widespread in cooler regions of North America and Eurasia.
Equisetum telmateia, the great horsetail or northern giant horsetail, is a species of Equisetum (puzzlegrass) with an unusual distribution, with one subspecies native to Europe, western Asia and northwest Africa, and a second subspecies native to western North America. The North American subspecies is often simply but ambiguously called "giant horsetail", but that name may just as well refer to the Latin American Equisetum giganteum and Equisetum myriochaetum.
Equisetum hyemale is an evergreen perennial herbaceous pteridophyte in the horsetail family Equisetaceae. It is a native plant throughout the Holarctic Kingdom, found in North America, Europe, and northern Asia.
Giant horsetails are usually living species of horsetail that grow to very large sizes, more than 1.5 metres.
Mixed-linkage glucan : xyloglucan endotransglucosylase (MXE) is a plant cell wall-modifying enzyme found in plants of the genus Equisetum. The enzyme is proposed, in vivo, to catalyse the endotransglucosylation of two different hemicellulose polysaccharides, mixed-linkage glucan and xyloglucan, effectively 'stitching' them together. However only the 'stitching' of a mixed-linkage glucan polysaccharide to a xyloglucan oligosaccharide has actually been witnessed to date.
Mixed-linkage glucan (MLG), sometimes incorrectly referred to as beta-glucan, is a hemicellulosic polysaccharide consisting of β-D(1-3) and β-D(1-4) linked glucosyl residues. MLG is highly prevalent within the Poales, where it has important properties in the diet. In addition, although thought to be confined to the Poales, MLG has been found to be highly prevalent in plants of the distantly related genus Equisetum.
Equisetum scirpoides Michx., Fl. Bor.-Amer. 2: 281 (1803). 2 n = 216.The smallest of the currently occurring representatives of the genus Equisetum (horsetail).
Equisetum thermale is an extinct horsetail species in the family Equisetaceae described from a group of whole plant fossils including rhizomes, stems, and leaves. The species is known from Middle to Late Jurassic sediments exposed in the province of Santa Cruz, Argentina. It is one of several extinct species placed in the living genus Equisetum.
Equisetum ramosissimumDesf., known as branched horsetail, is a species of evergreen horsetail.
Equisetum ramosissimum var. huegelii, with synonyms including Equisetum debile and Equisetum huegelii, is a variety of Equisetum ramosissimum, a plant in the family Equisetaceae, found in parts of tropical Asia and China.
Equisetum dimorphum is an extinct horsetail species of the family Equisetaceae, and one of the oldest records of the genus Equisetum. It was found in rocks from the Lower Jurassic of Chubut, Argentina, among other plants as ferns, conifers and pteridosperms. Their remains consist of stems, leaves, strobili, and pagoda structures, which are preserved as impressions and casts. The combination of fine grained sediment, and the probable silica deposits in the epidermis of the plant, have managed to conserve not only its gross morphology, but also epidermal details not often present in this kind of preservation. This species was described in 2015 in Ameghiniana by a team led by Andres Elgorriaga, that included investigators of the Museum of Paleontology Egidio Feruglio, the Swedish Museum of Natural History, and the Buenos Aires University.
Grypus equiseti, known by the common name horsetail weevil, is a species of weevil native to Europe. It feeds on Equisetum arvense and Equisetum palustre plants. It has been introduced to New Zealand to control Equisetum arvense, which is an invasive species there.
Equisetites is an extinct genus of vascular plants within Equisetaceae, a family of vascular plants that reproduce by spores rather than seeds. The genus was named by Sternberg (1833) and contains at least 40 named species and two unnamed species, with the earliest known species being E. hemingwayi from the Westphalian of Yorkshire, England, though the affinity of this genus to modern Equistaceae is uncertain.
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