| Platanaceae | |
|---|---|
 | |
| Inflorescence ofPlatanus × hispanica | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Order: | Proteales |
| Family: | Platanaceae T. Lestib.[2] |
| Type genus | |
| PlatanusL., 1753 | |
| Other genera | |
| |
Platanaceae, theplane family, is afamily of flowering plants in the orderProteales. The family consists of only a singleextant genusPlatanus, with twelve known species.[4] The plants are tall trees, native to temperate and subtropical regions of the Northern Hemisphere. The hybridLondon plane is widely planted in cities worldwide.
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Pollination isanemophilous; flowering begins at the start of spring when the new leaves are sprouting. The heads that sustain the fruit normally shed the year after they have matured, during the autumn.Dispersion of the individual fruiting bodies, with their thistledown, is anemochorous (they are sometimes dispersed by water as a secondary mechanism).
The plants grow in cool situations in temperate climates and are frequently found on the banks of rivers and streams. They are totally absent from dry or excessively cold areas.
They containcyanogenic glycosides derived fromtyrosine,flavonoids belonging to theproanthocyanidins group (e.g.prodelphinidin) andflavonols (kaempferol,quercetin,myricetin), in addition totriterpenols (includingbetulinic acid). They lackellagic acid,saponins, andsapogenins.
The main use for a number of the species is to provide shade in pedestrian areas in temperate regions, particularly the London plane (Platanus × hispanica), which is widely distributed throughout Europe and North America. It is highly resistant, probably due to so-calledhybrid vigour, although its use requires caution due to their allergy-producing thistledown. The parent species are also grown for the same effect, but with poorer results as they are less resistant to contamination, among other reasons. The wood is used in cabinetmaking, paneling, and other interior work, and is also prized for its long burn time.
A large number of fossils of this family have been recorded from the LowerCretaceous (98-113 million years ago,Platanocarpus). The examples from that time had very small pollen (8-10 μm) and a developed perianth and they lacked hairs at the base of the nucule. It is thought to have hadentomophilous pollination. During the mid Cretaceous, the fossilized forms with platanoid leaves became mixed with pinnate leaves (Sapindopsis) or pedatisect leaves (Debeya,Dewalquea), and these forms lasted until theEocene. The leaves with typical stipules belonging to the sub-genusPlatanus are very common inPalaeocene formations (60 M years ago). It is thought that the only modern genus,Platanus, is arelict that can be considered aliving fossil. It must have beenpolyploid during its evolution judging by the size of its stomata.
TheAPG II system (2003) allows the option of including it in the familyProteaceae, or treating it as distinct as a segregate family. In as far as APG II accepts the family, it is placed in the orderProteales, in the cladeeudicots. This represents a slight change from theAPG system of 1998, which did accept this family. TheCronquist system of 1981 recognized the family and placed it in orderHamamelidales, in subclassHamamelidae [sic] in classMagnoliopsida (dicotyledons). TheDahlgren system andThorne system (1992) also recognized this family and placed it in the order Hamamelidales in superorder Rosanae in subclass Magnoliidaesensu Dahlgren and Thorne (dicotyledons). TheEngler system, in its 1964 update, also recognized the family and placed it in the orderRosales in subclass Archichlamydeae of classDicotyledoneae. TheWettstein system, last revised in 1935, also recognized the family and placed it in the order Hamamelidales in the Monochlamydeae in subclass Choripetalae of the class Dicotyledones. Based on molecular and morphological data the APW (Angiosperm Phylogeny Website) places the family in the order Proteales as a sister family to theProteaceae, making them the Northern Hemisphere version of this family (cf.AP-website).
The only extant genus,PlatanusL., 1753, has the type speciesPlatanus orientalisL., 1753. It is divided into two subgenera: the subgenusCastaneophyllumJ.-F. Leroy, 1982, with elliptical, penninerved leaves with small scarious, stipules, that only includesPlatanus kerriiGagnep., 1939, an isolated relict species that represents the genus’ evolutionary basal branch and which is the sister group of the other species, which comprise the subgenusPlatanus.
The London plane or hybrid plane has long been considered a hybrid derived from the cross betweenP. occidentalis andP. orientalis, despite this its origin is not clear. Some experts think it originated in London and others in Spain or even in natural or cultivated hybrid form (or not) in Turkey. The question has not been investigated with modern molecular methods. As a consequence, even its nomenclature is hotly debated, to the extent that until recently, some anglophone authors denied the priority of the name used byOtto von Münchhausen (following Maria da Luz de Oliveira Tavares Monteiro da Rocha Afonso, 1990, see References). The plant is not found in the wild, though it appears in anaturalised form along the banks of rivers and streams.
HybridPlatanus × hispanicaMill. exMünchh., 1770 (=P. orientalis var.acerifoliaAiton, 1789;P. hybridaBrot., 1804;P. vulgarisSpach, 1841,nom. illeg.;P. × acerifolia.
Other names proposed for hybrids that are probably synonymous with the above, which is the only name in English, and which represent smaller minorities are:
The references consulted do not agree as to whether the fruit is a nucule orachene, the difference between the two ultimately depends on the size of the pericarp and the extent of its lignification. The fruit is dry, indehiscent, monocarpelar and monospermatic.
Media related toPlatanaceae at Wikimedia Commons
Data related toPlatanaceae at Wikispecies
