Tetracentron
Encyclopedia
Tetracentron is a genus of flowering plant
, the sole living species being Tetracentron sinense. It was formerly considered the sole genus in the family Tetracentraceae, though modern botanists include it in the family Trochodendraceae
together with the genus Trochodendron
.
It is native to southern China
and the eastern Himalaya, where it grows at altitudes of 1100–3500 m in a temperate climate; it has no widely used common name in English, though is sometimes called "spur-leaf".
It is a tree
growing to 20–40 m tall. The leaves
are deciduous
(the Flora of China
reporting it as evergreen is an error), borne singly at the apex of short spur shoots, each leaf dark green, broad heart-shaped, 5–13 cm long and 4–10 cm broad, with a rugose surface and a serrated margin. The spur shoots bear a one leaf each year, slowly lengthening with each subsequent year.
The flower
s are inconspicuous, yellowish green, without petals, produced on slender catkin
s 10–15 cm long; each flower is 1–2 mm diameter. The fruit
is a follicle
2–5 mm diameter, containing 4-6 seed
s.
Tetracentron shares with Trochodendron the feature, very unusual in angiosperms
, of lacking vessel element
s in its wood
. This has long been considered a very primitive character, resulting in the classification of these two genera in a basal position in the angiosperms; however, research in Molecular phylogenetics by the Angiosperm Phylogeny Group
and others has shown that these two genera are not basal angiosperms
, but basal eudicots. This suggests that the absence of vessel elements is a secondarily evolved character, not a primitive one.
, shows a much wider distribution then modern times. Fossils of this genus have been found in British Columbia
, Canada,; Alaska
, Washington State, USA; and Iceland
,. The Miocene
Tetracentron atlanticum, described in 2008, is the first confirmed record of the genus in Europe. This species was described from pollen, fruits, and leafs found in Iceland.
Specimens from British Columbia and Washington state are found in a series of Eocene Lakes in the Okanagan Highland
s region in association with several extinct Trochodendron species. The Paleogene
species Tetracentron piperoides from Alaska is currently regarded as suspect due to the lack of associated fruits.
Flowering plant
The flowering plants , also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Angiosperms are seed-producing plants like the gymnosperms and can be distinguished from the gymnosperms by a series of synapomorphies...
, the sole living species being Tetracentron sinense. It was formerly considered the sole genus in the family Tetracentraceae, though modern botanists include it in the family Trochodendraceae
Trochodendraceae
Trochodendraceae is a family of flowering plants with two living genera found in southeast Asia. The two living species share the feature of secondary xylem without vessels, which is quite rare in angiosperms...
together with the genus Trochodendron
Trochodendron
Trochodendron is a genus of flowering plants with one living species, Trochodendron aralioides, and six extinct species known from the fossil record...
.
It is native to southern China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
and the eastern Himalaya, where it grows at altitudes of 1100–3500 m in a temperate climate; it has no widely used common name in English, though is sometimes called "spur-leaf".
It is a tree
Tree
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...
growing to 20–40 m tall. The leaves
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....
are deciduous
Deciduous
Deciduous means "falling off at maturity" or "tending to fall off", and is typically used in reference to trees or shrubs that lose their leaves seasonally, and to the shedding of other plant structures such as petals after flowering or fruit when ripe...
(the Flora of China
Flora of China (journal)
Flora of China is a scientific publication aimed at describing the plants native to China.The is a collaborative scientific effort to publish the first modern English-language account of the approximately 31,000 species of vascular plants of China...
reporting it as evergreen is an error), borne singly at the apex of short spur shoots, each leaf dark green, broad heart-shaped, 5–13 cm long and 4–10 cm broad, with a rugose surface and a serrated margin. The spur shoots bear a one leaf each year, slowly lengthening with each subsequent year.
The flower
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...
s are inconspicuous, yellowish green, without petals, produced on slender catkin
Catkin
A catkin or ament is a slim, cylindrical flower cluster, with inconspicuous or no petals, usually wind-pollinated but sometimes insect pollinated . They contain many, usually unisexual flowers, arranged closely along a central stem which is often drooping...
s 10–15 cm long; each flower is 1–2 mm diameter. The fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...
is a follicle
Follicle (fruit)
In botany, a follicle is a dry unilocular many-seeded fruit formed from one carpel and dehiscing by the ventral suture in order to release seeds, such as in larkspur, magnolia, banksia, peony and milkweed....
2–5 mm diameter, containing 4-6 seed
Seed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...
s.
Tetracentron shares with Trochodendron the feature, very unusual in angiosperms
Flowering plant
The flowering plants , also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Angiosperms are seed-producing plants like the gymnosperms and can be distinguished from the gymnosperms by a series of synapomorphies...
, of lacking vessel element
Vessel element
A vessel element is one of the cell types found in xylem, the water conducting tissue of plants. Vessel elements are typically found in the angiosperms but absent from most gymnosperms such as the conifers....
s in its wood
Wood
Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...
. This has long been considered a very primitive character, resulting in the classification of these two genera in a basal position in the angiosperms; however, research in Molecular phylogenetics by the Angiosperm Phylogeny Group
Angiosperm Phylogeny Group
The Angiosperm Phylogeny Group, or APG, refers to an informal international group of systematic botanists who came together to try to establish a consensus on the taxonomy of flowering plants that would reflect new knowledge about plant relationships discovered through phylogenetic studies., three...
and others has shown that these two genera are not basal angiosperms
Basal angiosperms
The basal angiosperms are the first flowering plants to diverge from the ancestral angiosperm. In particular, the most basal angiosperms are the so-called ANITA grade which is made up of Amborella , Nymphaeales and Austrobaileyales...
, but basal eudicots. This suggests that the absence of vessel elements is a secondarily evolved character, not a primitive one.
Fossil record
The fossil record, extending back to the EoceneEocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
, shows a much wider distribution then modern times. Fossils of this genus have been found in British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
, Canada,; Alaska
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
, Washington State, USA; and Iceland
Iceland
Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...
,. The Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
Tetracentron atlanticum, described in 2008, is the first confirmed record of the genus in Europe. This species was described from pollen, fruits, and leafs found in Iceland.
Specimens from British Columbia and Washington state are found in a series of Eocene Lakes in the Okanagan Highland
Okanagan Highland
The Okanagan Highland is a plateau-like hilly area in British Columbia, Canada, and the U.S. state of Washington . It lies between the Okanagan Valley on its west and the Kettle River on its east, and geologically is more or less an extension of the Thompson Plateau, which lies west of the Okanagan...
s region in association with several extinct Trochodendron species. The Paleogene
Paleogene
The Paleogene is a geologic period and system that began 65.5 ± 0.3 and ended 23.03 ± 0.05 million years ago and comprises the first part of the Cenozoic Era...
species Tetracentron piperoides from Alaska is currently regarded as suspect due to the lack of associated fruits.
External links
- Flora of China: Tetracentron and Tetracentraceae
- Tetracentraceae in L. Watson and M.J. Dallwitz (1992 onwards). The families of flowering plants.
- Plant Kaleidoscope: Tetracentron
- Ruhr-Universität Bochum: Tetracentron photos
- Phylogeny of basal eudicots
- Phylogenetic Tree in 5-gene, 567-taxon analysis