World Library  
Flag as Inappropriate
Email this Article


Article Id: WHEBN0003835052
Reproduction Date:

Title: Tetracentraceae  
Author: World Heritage Encyclopedia
Language: English
Subject: Xylem, Dicotyledon, Cronquist system, Vessel element, Eudicots, Tetracentron, Trochodendraceae, Dahlgren system, APG system, APG II system
Publisher: World Heritage Encyclopedia


Trochodendron aralioides

Trochodendraceae is the only family of flowering plants in the order Trochodendrales. It comprises two living genera with two species found in south east Asia. The two living species both have secondary xylem without vessels, which is quite rare in angiosperms. As the vessel-free wood suggests primitiveness, these two species have attracted much taxonomic attention.


  • Deciduous or evergreen trees, up to 20-30 m, sometimes with umbrella-shaped branches (Trochodendron). Covering hair, scales etc. absent.
  • 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 stipules fused with the petiole (Tetracentron) or absent (Trochodendron). Idioblasts present, large, branched, sclerenchymatous in Trochodendron and secretory in Tetracentron. Stomata laterocytic or cyclocytic, hypostomatic.
  • Stems without xylematic vessels, with tracheids, heterogeneous xylem, uni- and multi-seriate, branches clearly differentiated in unifoliate brachyblasts and macroblasts with distichous phyllotaxis (Tetracentron), with nodes (1-)3(-multi)-lacunar, with (1)3(-7) leaf stems.
  • Hermaphroditic or androdioecious plants.
  • 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). Bracts and bracteoles present or absent.
  • Perfect flowers, actinomorphic or dissymmetric, yellowish. Short, sub-conical, or hollow receptacle. Hypogynous disk absent. Reduced, very thin perianth, of 4 tepals in 2 decussate whorls (Tetracentron), or at most in a recognizable preantheric state (Trochodendron). Androecium of 4 decussate stamens in pairs of 40-70 in a spiral, non-versatile, basifixed, tetrasporangial, latrorso, apiculate anthers, dehiscence along 2 longitudinal valves in the theca. Gynoecium superior (Tetracentron) to slightly semi-inferior (Trochodendron), of 4-11(-17) carpels, 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 styles (stylodious), dry, papillose, decurrent ventral stigmas, 5-30 anatropous, apotropous, bitegmicous, crassinucelate, pendulous ovules per carpel, placentation marginal in 2 series or apicoaxial.
  • Fruit in ventricidal or slightly loculicidal capsule or an aggregate of dorsally and ventrally dehiscent semicarpical follicles, with basal and external styles.
  • Small, flattened, tapered seeds, 3-4 mm in length, with lateral, apical, chalazal wings, with thin testa, with abundant, oily and proteinaceous endosperm, small embryo, with 2 cotyledons.
  • 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.
  • Chromosomal number: 2n = 48 in Tetracentron and 2n = 38, 40 in Trochodendron.


Pollination is probably myiophyllous, even though Tetracentron shows a clear anemophilous syndrome. The pulverulent seeds are dispersed by the wind (anemochory). Trochodendron is present in both protandrous and protogynous forms that are self-compatible.

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.


Flavonoids (quercetin and kaempferol) and proanthocyanidins (cyanidin and delphinidin) are present. Epicuticular waxes are basically composed of nonacosan-10-ol. Tetracentron contains chalcones or dihydrochalcones. Trochodendron contains myricetin. Ellagic acid is absent.


Trochodendron aralioides has limited use as an ornamental tree.


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 that currently.

Systematic position

The trocodendraceae are a group of flowering plants that include the clade AP-website).


The current classification of Trochodendraceae is the APG III system published in October 2009. Unlike the APG and APG II systems, this system places the family as the only family in the order Trochodendrales. It also includes Tetracentron, synonymizing Tetracentraceae fully with Trochodenraceae.[1]

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 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.

This segregation would lead to two families with one species each: Tetracentraceae with Tetracentron sinense and Trochodendraceae with Trochodendron aralioides.

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.

Taxa included

Theoretical introduction to Taxonomy

The family includes two genera with very different morphological characteristics:

  • Palmate leaves, with stipules, deciduous. Perianth of 4 tepals. Stamens 4. Carpels 4. Ovules 5-6 per carpel. Axillary inflorescence in amentoid spike.
Tetracentron Oliv., 1889. North-east India, Nepal, Bhutan, Burma, western and central China, Vietnam.
  • Pinnate leaves, without stipules, evergreen. Perianth absent. Stamens 40-70. Carpels (4-)6-11(-17). Ovules 15-30 per carpel. Terminal racemiform inflorescence , erect.
Trochodendron Siebold & Zucc., 1839. Japan, Taiwan, Korea.


External links

  • NCBI Taxonomy Browser
  • links at CSDL
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.