Equisetum
Template:Short description Template:Redirect Template:Automatic taxobox
Equisetum (Template:IPAc-en; horsetail) is the only living genus in Equisetaceae, a family of vascular plants that reproduce by spores rather than seeds.<ref>Template:Cite book</ref>
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 Template:Cvt tall.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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.<ref>Template:Cite magazine</ref> 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.<ref>Template:Cite OED</ref>
EtymologyEdit
Template:More citations needed 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 {{#invoke:Lang|lang}} ('horse') + {{#invoke:Lang|lang}} ('bristle').<ref>Template:Cite book</ref>
Other names include candock for branching species, puzzlegrass, 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.<ref name=Husby>Template:Cite journal</ref> In German, the corresponding name is {{#invoke:Lang|lang}} ('tin-herb'). In Spanish-speaking countries, these plants are known as {{#invoke:Lang|lang}} ('horsetail').
DescriptionEdit
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.<ref>Template:Cite journal</ref>
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.<ref name = Streeter>Streeter D, Hart-Davies C, Hardcastle A, Cole F, Harper L. 2009. Collins Flower Guide. Harper Collins Template:ISBN</ref> Unusually, the branches often emerge below the leaves in an internode, and grow from buds between their bases.
B = branch in whorl
I = internode
L = leaves
N = node
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The small white protuberances are accumulated silicates on cells.
SporesEdit
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.<ref name=Stace>Template:Cite book</ref>Template:Rp
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.<ref>Template:Cite news</ref> 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.<ref>Template:Cite journal</ref>
Cell wallsEdit
The crude cell extracts of all Equisetum species tested contain mixed-linkage glucan : xyloglucan endotransglucosylase (MXE) activity.<ref>Template:Cite journal</ref> 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.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> 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.<ref>Template:Cite journal</ref> 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.Template:Citation needed
TaxonomyEdit
SpeciesEdit
Currently, 18 species of Equisetum are accepted by Plants of the World Online.<ref name=powo/> The living members 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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Two Equisetum plants are sold 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.<ref>Template:Cite book</ref>Template:Citation needed
Evolutionary historyEdit
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<ref>Template:Cite journal</ref> and Equisetum laterale from the Early-Middle Jurassic of Australia.<ref>Gould, R. E. 1968. Morphology of Equisetum laterale Phillips, 1829, and E. bryanii sp. nov. from the Mesozoic of south‐eastern Queensland. Australian Journal of Botany 16: 153–176.</ref><ref name="Elgorriaga-2018">Template:Cite journal</ref> Silicified remains of Equisetum thermale from the Late Jurassic of Argentina exhibit all the morphological characters of modern members of the genus.<ref>Template:Cite journal</ref> The estimated split between Equisetum bogotense and all other living Equisetum is estimated to have occurred no later than the Early Jurassic.<ref name="Elgorriaga-2018" />
Subgenus ParamochaeteEdit
- Template:Txil – Andean horsetail; upland South America up to Costa Rica; includes E. rinihuense, sometimes treated as a separate species. Previously included in subg. Equisetum, but Christenhusz et al. (2019)<ref name="Christenhusz2019" /> transfer this here, as E. bogotense appears to be sister to all the remaining species in the genus.
Subgenus EquisetumEdit
- Template:Txil – field horsetail or common horsetail; circumboreal down through temperate zones
- Template:Txil – northern giant horsetail, syn. E. telmateia subsp. braunii (Milde) Hauke.; west coast of North America
- Template:Txil – Himalayan horsetail; Himalayan India and China and adjacent nations above about Template:Convert
- Template:Txil – water horsetail; circumboreal down through temperate zones
- Template:Txil – marsh horsetail; circumboreal down through temperate zones
- Template:Txil – shady horsetail, meadow horsetail, shade horsetail; circumboreal except for tundra down through cool temperate zones
- Template:Txil – wood horsetail; circumboreal down through cool temperate zones, more restricted in east Asia
- Template:Txil – great horsetail; Europe to Asia Minor and north Africa. The former North American subspecies Equisetum telmateia subsp. braunii (Milde) Hauke is now treated as a separate species Template:Tx<ref name="Christenhusz2019" /><ref name=powo/>
Subgenus HippochaeteEdit
- Template:Txil – southern giant horsetail or giant horsetail; temperate to tropical South America and Central America north to southern Mexico
- Template:Txil – rough horsetail; most of non-tropical Old World. The former North American subspecies Equisetum hyemale subsp. affine (Engelm.) A.A.Eat. is now treated as a separate species Template:Tx<ref name="Christenhusz2019" /><ref name=powo/>
- Template:Txil – smooth horsetail, smooth scouringrush; western 3/4 of North America down into northwestern Mexico; also sometimes known as Equisetum kansanum
- Template:Txil – Mexican giant horsetail; from central Mexico south to Peru
- Template:Txil – scouringrush horsetail, syn. E. hyemale subsp. affine (Engelm.) A.A.Eat.; temperate North America
- Template:Txil (including E. debile) – branched horsetail; Asia, Europe, Africa, southwest Pacific islands
- Template:Txil – dwarf horsetail, dwarf scouringrush; northern (cool temperate) zones worldwide
- Template:Txil – variegated horsetail, variegated scouringrush; northern (cool temperate) zones worldwide, except for northeasternmost Asia
- Template:Txil – Atacama Desert giant horsetail; southern Peru, northern Chile
Unplaced to subgenusEdit
- Template:ExtinctEquisetum dimorphum – Early Jurassic, Argentina
- Template:ExtinctEquisetum laterale – Early to Middle Jurassic, Australia
- Template:ExtinctEquisetum thermale – Middle to Late Jurassic, Argentina
- Template:ExtinctEquisetum similkamense – Ypresian, British Columbia
Named hybridsEdit
Hybrids between species in subgenus EquisetumEdit
- Equisetum × bowmanii Template:Small (Equisetum sylvaticum × Equisetum telmateia)
- Equisetum × dycei Template:Small (Equisetum fluviatile × Equisetum palustre)
- Equisetum × font-queri Template:Small (Equisetum palustre × Equisetum telmateia)
- Equisetum × litorale Template:Small (Equisetum arvense × Equisetum fluviatile)
- Equisetum × mchaffieae Template:Small (Equisetum fluviatile × Equisetum pratense)
- Equisetum × mildeanum Template:Small (Equisetum pratense × Equisetum sylvaticum)
- Equisetum × robertsii Template:Small (Equisetum arvense × Equisetum telmateia)
- Equisetum × rothmaleri Template:Small (Equisetum arvense × Equisetum palustre)
- Equisetum × willmotii Template:Small (Equisetum fluviatile × Equisetum telmateia)
Hybrids between species in subgenus HippochaeteEdit
- Equisetum × ferrissii Template:Small (Equisetum hyemale × Equisetum laevigatum)
- Equisetum × moorei Template:Small (Equisetum hyemale × Equisetum ramosissimum)
- Equisetum × nelsonii Template:Small (Equisetum laevigatum × Equisetum variegatum)
- Equisetum × schaffneri Template:Small (Equisetum giganteum × Equisetum myriochaetum)
- Equisetum × trachyodon Template:Small (Equisetum hyemale × Equisetum variegatum)
PhylogenyEdit
| Christenhusz et al. 2019<ref name="Christenhusz2019">Template:Cite journal</ref> | Nitta et al. 2022<ref>Template:Cite journal</ref> and Fern Tree of life<ref>{{#invoke:citation/CS1|citation | CitationClass=web
}}</ref> |
|---|---|---|
Distribution and ecologyEdit
The genus Equisetum as a whole, while concentrated in the non-tropical northern hemisphere, is near-cosmopolitan, being absent naturally only from Antarctica, Australia, New Zealand, and the islands of the Pacific Ocean. They are most common in northern Europe, with ten species (E. arvense, E. fluviatile, E. hyemale, E. palustre, E. pratense, E. ramosissimum, E. scirpoides, E. sylvaticum, E. telmateia, and E. variegatum); Great Britain has nine of these species, missing only E. scirpoides of the European list.<ref name="Fitter">Template:Cite book</ref><ref name = Streeter/> Northern North America (Canada and the northernmost United States), also has nine species (E. arvense, E. fluviatile, E. laevigatum, E. palustre, E. praealtum, E. pratense, E. scirpoides, E. sylvaticum, and E. variegatum). Only five (E. bogotense, E. giganteum, E. myriochaetum, E. ramosissimum, and E. xylochaetum) of the eighteen species are known to be native south of the Equator.
They are perennial plants, herbaceous and dying back in winter in 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 subtropical "giant horsetails" are recorded to grow as high as Template:Cvt (E. giganteum, southern giant horsetail) or Template:Cvt (E. myriochaetum, Mexican giant horsetail), and allegedly even more.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>Template:Citation needed Since the stems have a waxy coat, the plant is resistant to contact weedkillers like glyphosate.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Members of the genus have been declared noxious weeds in Australia and in the US state of Oregon.<ref name=aus>Template:Cite book</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
All the Equisetum are classed as "unwanted organisms" in New Zealand and are listed on the National Pest Plant Accord.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
ConsumptionEdit
People have regularly consumed horsetails. The fertile stems bearing strobili of some species can be cooked and eaten like asparagus<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> (a dish called Template:Nihongo in Japan<ref>Template:Cite book</ref>Template: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.<ref>Template:Cite book</ref><ref>Template:Cite book</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The young plants are eaten cooked or raw, but considerable care must be taken.<ref name=drugs/>
If eaten over a long enough period of time, some species of horsetail can be poisonous to grazing animals, including horses.<ref>Template:Cite book</ref> The toxicity appears to be due to thiaminase, which can cause thiamin (vitamin B1) deficiency.<ref name="drugs">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name=NIH/><ref name=Henderson>Template:Cite journal</ref><ref name=Fabre>Template:Cite journal</ref>
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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Analysis of the scratch marks on hadrosaur teeth is consistent with grazing on hard plants like horsetails.<ref name=WillBarrPurn09>Template:Citation</ref>
Folk medicine and safety concernsEdit
Extracts and other preparations of E. arvense have served as herbal remedies, with records dating over centuries.<ref name=drugs/><ref name="NIH">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="sarris">Template:Cite journal</ref> 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.<ref name ="efsa">Template:Cite journal</ref> Template:As of, there is insufficient scientific evidence for its effectiveness as a medicine to treat any human condition.<ref name=drugs/><ref name=sarris/><ref name=efsa/>
E. arvense contains thiaminase, which metabolizes the B vitamin, thiamine, potentially causing thiamine deficiency and associated liver damage, if taken chronically.<ref name=drugs/><ref name=NIH/> Horsetail might produce a diuretic effect.<ref name=drugs/><ref name=NIH/> Further, its safety for oral consumption has not been sufficiently evaluated and it may be toxic, especially to children and pregnant women.<ref name=drugs/>
See alsoEdit
ReferencesEdit
Further readingEdit
- Template:Cite journal
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- {{#invoke:citation/CS1|citation
|CitationClass=web }}
External linksEdit
- Equisetum at the Tree of Life Web Project
- National Collection of Equisetum
- International Equisetological Association
- Template:Cite EB1911
Template:Plant classification Template:Fern classification Template:Taxonbar Template:Authority control