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| − | '''Trochodendraceae''' is the only [[family (biology)|family]] of [[flowering plants]] in the order '''Trochodendrales'''. It comprises two extant [[Genus|genera]], each with a single [[species]]<ref name="Christenhusz-Byng2016">{{cite journal |author1=Christenhusz, M. J. M. |author2=Byng, J. W. |lastauthoramp=yes | year = 2016 | title = The number of known plants species in the world and its annual increase | journal = Phytotaxa | volume = 261 | pages = 201–217 | url = http://biotaxa.org/Phytotaxa/article/download/phytotaxa.261.3.1/20598 | doi = 10.11646/phytotaxa.261.3.1 | issue = 3 | publisher = Magnolia Press }}</ref> found in south east Asia. The two living species (''Tetracentron sinense'' and ''Trochodendron aralioides'') both have secondary xylem without [[vessel element]]s, which is quite rare in angiosperms. As the vessel-free wood suggests primitiveness, these two species have attracted much taxonomic attention.
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| − | == Description ==
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| − | * Deciduous or evergreen [[tree]]s, up to 20–30 m, sometimes with umbrella-shaped branches (''[[Trochodendron]]''). Covering hair, scales etc. absent.
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| − | * [[Leaf|Leaves]] in spirals at the end of the branches (umbrella-like appearance, ''[[Trochodendron]]'') or separate (''[[Tetracentron]]''), simple, serrulate or crenulate, with clorantoid teeth, palmately or pinnately divided, brochidodromous or actinodromous, ovate or [[obovate]], with a cordate to cuneate base and acuminate apex, stalked, with thin [[stipule]]s fused with the petiole (''[[Tetracentron]]'') or absent (''[[Trochodendron]]''). Idioblasts present, large, branched, sclerenchymatous in ''[[Trochodendron]]'' and secretory in ''[[Tetracentron]]''. [[Stoma]]ta laterocytic or cyclocytic, hypostomatic.
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| − | * [[Plant stem|Stem]]s without xylematic vessels, with tracheids, heterogeneous [[xylem]], uni- and multi-seriate, branches clearly differentiated in unifoliate brachyblasts and macroblasts with distichous [[phyllotaxis]] (''[[Tetracentron]]''), with [[burl|nodes]] (1-)3(-multi)-lacunar, with (1)3(-7) leaf stems.
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| − | * Hermaphroditic or androdioecious [[plant]]s.
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| − | * Terminal [[Inflorescence]] in erect, aggregated racemiforms (botryoid or small panicles) (''[[Trochodendron]]'') or defined, axillary, multi-floral amentoid spikes with the flower in whorls of 4 (''[[Tetracentron]]''). [[Bract]]s and bracteoles present or absent.
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| − | * Perfect [[flower]]s, actinomorphic or dissymmetric, yellowish. Short, sub-conical, or hollow [[Receptacle (botany)|receptacle]]. Hypogynous disk absent. Reduced, very thin [[perianth]], of 4 [[tepal]]s in 2 decussate whorls (''[[Tetracentron]]''), or at most in a recognizable preantheric state (''[[Trochodendron]]''). [[Androecium]] of 4 decussate [[stamen]]s in pairs of 40-70 in a spiral, non-versatile, basifixed, tetrasporangial, latrorso, apiculate [[anther]]s, [[Dehiscence (botany)|dehiscence]] along 2 longitudinal valves in the theca. [[Gynoecium]] superior (''[[Tetracentron]]'') to slightly semi-inferior (''[[Trochodendron]]''), of 4-11(-17) [[carpel]]s, syncarpous (alternating with the stamens in ''[[Tetracentron]]'') to semicarpous, the dorsal part of the ovary expanded horizontally in the anthesis, abaxially nectariferous, with sunken stomata, free [[Style (botany)|styles]] (stylodious), dry, papillose, decurrent ventral [[Stigma (botany)|stigmas]], 5-30 anatropous, apotropous, bitegmicous, crassinucelate, pendulous [[ovule]]s per carpel, [[placentation]] marginal in 2 series or apicoaxial.
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| − | * [[Fruit]] in ventricidal or slightly loculicidal [[Capsule (botany)|capsule]] or an aggregate of dorsally and ventrally dehiscent semicarpical [[Follicle (fruit)|follicles]], with basal and external styles.
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| − | * Small, flattened, tapered [[seed]]s, 3–4 mm in length, with lateral, apical, chalazal wings, with thin [[Testa (botany)|testa]], with abundant, oily and proteinaceous [[endosperm]], small [[Embryo#Plant embryos|embryo]], with 2 cotyledons.
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| − | * [[Pollen]] in small, granular, spheroidal, tricolpate, tectated-columelliform monads (10-20 μm in diameter), the surface with interwoven bars parallel to the edges of the colpus, which are granular.
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| − | * [[Chromosome|Chromosomal number]]: ''2n'' = 48 in ''[[Tetracentron]]'' and ''2n'' = 38, 40 in ''[[Trochodendron]]''.
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| − | == Ecology ==
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| − | [[Pollination]] is probably myiophyllous, even though ''[[Tetracentron]]'' shows a clear anemophilous syndrome. The pulverulent seeds are dispersed by the wind ([[Seed dispersal#Types of dispersal|anemochory]]). ''[[Trochodendron]]'' is present in both protandrous and protogynous forms that are self-compatible.
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| − | The plants are found in wooded formations, ''[[Trochodendron]]'' between 300 m and 2.700 m above sea level and ''[[Tetracentron]]'' between 1.100 m and 3.600 m above sea level.
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| − | == Phytochemistry ==
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| − | [[Flavonoid]]s (quercetin and kaempferol) and [[proanthocyanidin]]s ([[cyanidin]] and [[delphinidin]]) are present. [[Epicuticular wax]]es are basically composed of nonacosan-10-ol. ''[[Tetracentron]]'' contains [[chalcone]]s or [[dihydrochalcone]]s. ''[[Trochodendron]]'' contains [[myricetin]]. [[Ellagic acid]] is absent.
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| − | == Fossils ==
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| − | ''[[Trochodendron]]'' and the fossil genus ''Nordenskioldia'' (to which the leaf fossils called ''Zizyphoides'' are also attributed) was present in the Lower Middle [[Eocene]] (49-50 Ma), it has been found in the Republic formation of Washington State (USA), demonstrating that the family had a wider distribution than currently.
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| − | == Systematic position ==
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| − | The trocodendraceae are a group of flowering plants that include the clade [[Eudicots|Eudicotyledoneae]]. In previous systems they have been related with the [[Cercidiphyllaceae]] and the [[Eupteleaceae]], with which they share some characteristics that can be considered symplesiomorphic or convergent and that have been excluded from the order Trochodendrales because of molecular data leaving the trocodendraceae isolated. Based on molecular and morphological data, the APW (Angiosperm Phylogeny Website) considers that it constitutes the only family in the Order Trochodendrales (cf. [http://www.mobot.org/MOBOT/Research/APweb/welcome.html AP-website]).
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| − | ==Classification==
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| − | The current classification of Trochodendraceae is the [[APG IV system]] published in 2016, which maintains the circumscription of Trochodendraceae used in the [[[APG III system]] published in October 2009. Unlike the [[APG system|APG]] and [[APG II system]]s, the later systems place the family as the only family in the order Trochodendrales. They also includes ''[[Tetracentron]]'', synonymizing Tetracentraceae fully with Trochodenraceae.<ref>Angiosperm Phylogeny Group (2009). [http://www3.interscience.wiley.com/journal/122630309/abstract An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG III]. ''Botanical Journal of the Linnean Society'' '''161''': 105-121.</ref><ref name=APGIV>{{Cite journal|authors=Angiosperm Phylogeny Group|authorlink=Angiosperm Phylogeny Group|year=2016|title=An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG IV|journal=[[Botanical Journal of the Linnean Society]]|volume=181|issue=1|pages=1–20|url=http://onlinelibrary.wiley.com/doi/10.1111/boj.12385/epdf|format=PDF|issn=00244074|doi=10.1111/boj.12385}}</ref>
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| − | The [[APG II system]], of 2003 retained the classification used in the 1998 [[APG system]] recognizing Trochodendraceae as a family. APG and APG II did not place the family in an [[Taxonomy (biology)|order]], leaving it among the basal lineages of the [[eudicots]]. Both APG systems accepts this as a family of two modern species, but it does allow the option of separating out the family [[Tetracentraceae]].
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| − | This segregation would lead to two families with one species each: Tetracentraceae with ''[[Tetracentron sinense]]'' and Trochodendraceae with ''[[Trochodendron aralioides]]''.
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| − | The [[Cronquist system]], of 1981, accepted both Trochodendraceae and Tetracentraceae as families and placed these in the order Trochodendrales, in subclass [[Hamamelidae]], in class [[Magnoliopsida]].
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| − | == Taxa included ==
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| − | :''Theoretical introduction to [[Taxonomy (biology)|Taxonomy]]''
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| − | The family includes two genera with very different morphological characteristics:
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| − | * Palmate leaves, with stipules, deciduous. Perianth of 4 tepals. Stamens 4. Carpels 4. Ovules 5-6 per carpel. Axillary inflorescence in amentoid spike.
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| − | :''[[Tetracentron]]'' [[Daniel Oliver|Oliv.]], 1889. North-east India, Nepal, Bhutan, Burma, western and central China, Vietnam.
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| − | * Pinnate leaves, without stipules, evergreen. Perianth absent. Stamens 40-70. Carpels (4-)6-11(-17). Ovules 15-30 per carpel. Terminal racemiform inflorescence, erect.
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| − | :''[[Trochodendron]]'' [[Philipp Franz von Siebold|Siebold]] & [[Joseph Gerhard Zuccarini|Zucc.]], 1839. Japan, Taiwan, Korea.
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| − | ==References==
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| − | {{reflist}}
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| − | * {{cite book
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| − | | author = Endress, P.K.
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| − | | chapter = Trochodendraceae.
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| − | | title = Kubitzki, K., Rohwer, J.G. & Bittrich, V. (Editores). The Families and Genera of Vascular Plants. II. Flowering Plants - Dicotyledons.
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| − | | year = 1993
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| − | | publisher = Springer-Verlag: Berlín
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| − | | isbn = 3-540-55509-9
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| − | }}
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| − | *{{Cite web|surname= Watson, L., and Dallwitz, M.J.
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| − | |title= The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 29th July 2006.
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| − | |year= 1992 onwards
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| − | |url= http://delta-intkey.com
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| − | |accessdate= 31 January 2007
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| − | }}
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| − | ==External links==
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| − | {{commons category|Trochodendraceae}}
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| − | *[http://www.mobot.org/MOBOT/Research/APweb/maps/trochodendaceaemap.gif Mapa (en verde, ''[[Tetracentron]]'', en rojo, ''[[Trochodendron]]'']
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| − | *[http://www.ubcbotanicalgarden.org/potd/trochodendron_aralioides.jpg Flowers of ''Trochodendron aralioides'']
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| − | *[http://www.ramsbotham.nl/kk_tetracentron_sinense_2__4.1.jpg General view of ''Tetracentron sinense'']
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| − | *[http://www.ruhr-uni-bochum.de/boga/html/Tetracentron.sinense.ja.jpg Part of a foliar macroblast from ''Tetracentron sinense'']
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| − | *[http://delta-intkey.com/angio/www/Trochode.htm Trochodendraceae] in L. Watson and M.J. Dallwitz (1992 onwards). ''[http://delta-intkey.com/angio/ The families of flowering plants]: descriptions, illustrations, identification, information retrieval.'' Version: 3 May 2006. http://delta-intkey.com.
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| − | *[http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=10918 Trochodendraceae in the ''Flora of China'']
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| − | *[http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=4405&lvl=3&p=mapview&p=has_linkout&p=blast_url&p=genome_blast&lin=f&keep=1&srchmode=1&unlock NCBI Taxonomy Browser]
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| − | *[http://www.csdl.tamu.edu/FLORA/cgi/gateway_family?fam=Trochodendraceae links at CSDL]
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| | {{Ack-Wikipedia}} | | {{Ack-Wikipedia}} |
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| − | [[Category:Trochodendrales]] | + | [[Category:Eudicots]] |
