HOME

TheInfoList



OR:

The gymnosperms ( lit. revealed seeds) are a group of seed-producing plants that includes conifers, cycads, '' Ginkgo'', and gnetophytes, forming the clade Gymnospermae. The term ''gymnosperm'' comes from the composite word in el, γυμνόσπερμος ( el, γυμνός, translit=gymnos, lit=naked, label=none and el, σπέρμα, translit=sperma, lit=seed, label=none), literally meaning 'naked seeds'. The name is based on the unenclosed condition of their seeds (called ovules in their unfertilized state). The non-encased condition of their seeds contrasts with the seeds and ovules of flowering plants ( angiosperms), which are enclosed within an ovary. Gymnosperm seeds develop either on the surface of scales or leaves, which are often modified to form cones, or solitary as in
yew Yew is a common name given to various species of trees. It is most prominently given to any of various coniferous trees and shrubs in the genus ''Taxus'': * European yew or common yew (''Taxus baccata'') * Pacific yew or western yew (''Taxus br ...
, '' Torreya'', '' Ginkgo''. Gymnosperm lifecycles involve alternation of generations. They have a dominant diploid sporophyte phase and a reduced haploid gametophyte phase which is dependent on the sporophytic phase. The term "gymnosperm" is often used in paleobotany to refer to all non-angiosperm seed plants. In that case, to specify the modern monophyletic group of gymnosperms, the term Acrogymnospermae is sometimes used. The gymnosperms and angiosperms together comprise the spermatophytes or seed plants. The gymnosperms are subdivided into five Divisions, four of which, the Cycadophyta, Ginkgophyta, Gnetophyta, and Pinophyta (also known as Coniferophyta) are still in existence while the Pteridospermatophyta are now extinct. Newer classification place the gnetophytes among the conifers. By far the largest group of living gymnosperms are the conifers (pines, cypresses, and relatives), followed by cycads, gnetophytes (''
Gnetum ''Gnetum'' is a genus of gymnosperms, the sole genus in the family Gnetaceae within the Gnetophyta. They are tropical evergreen trees, shrubs and lianas. Unlike other gymnosperms, they possess vessel elements in the xylem. Some species have been ...
'', '' Ephedra'' and '' Welwitschia''), and ''
Ginkgo biloba ''Ginkgo biloba'', commonly known as ginkgo or gingko ( ), also known as the maidenhair tree, is a species of tree native to China. It is the last living species in the order Ginkgoales, which first appeared over 290 million years ago. Fossils ...
'' (a single living species). About 65% of gymnosperms are dioecious, but conifers are almost all monoecious. Some genera have mycorrhiza, fungal associations with roots (''Pinus''), while in some others (''Cycas'') small specialised roots called coralloid roots are associated with nitrogen-fixing cyanobacteria.


Diversity and origin

Over 1000 living species of gymnosperm exist. It was previously widely accepted that the gymnosperms originated in the
Late Carboniferous Late may refer to: * LATE, an acronym which could stand for: ** Limbic-predominant age-related TDP-43 encephalopathy, a proposed form of dementia ** Local-authority trading enterprise, a New Zealand business law ** Local average treatment effe ...
period, replacing the lycopsid rainforests of the tropical region, but more recent phylogenetic evidence indicates that they diverged from the ancestors of angiosperms during the
Early Carboniferous Early may refer to: History * The beginning or oldest part of a defined historical period, as opposed to middle or late periods, e.g.: ** Early Christianity ** Early modern Europe Places in the United States * Early, Iowa * Early, Texas * Ear ...
. The radiation of gymnosperms during the late Carboniferous appears to have resulted from a whole
genome duplication Polyploidy is a condition in which the cells of an organism have more than one pair of ( homologous) chromosomes. Most species whose cells have nuclei (eukaryotes) are diploid, meaning they have two sets of chromosomes, where each set contains ...
event around . Early characteristics of seed plants are evident in fossil progymnosperms of the late Devonian period around 383 million years ago. It has been suggested that during the mid-Mesozoic era, pollination of some extinct groups of gymnosperms was by extinct species of scorpionflies that had specialized proboscis for feeding on pollination drops. The scorpionflies likely engaged in pollination mutualisms with gymnosperms, long before the similar and independent coevolution of nectar-feeding insects on angiosperms. Evidence has also been found that mid-Mesozoic gymnosperms were pollinated by Kalligrammatid lacewings, a now-extinct family with members which (in an example of
convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...
) resembled the modern butterflies that arose far later. All gymnosperms are
perennial A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is often used to differentiate a plant from shorter-lived annuals and biennials. The term is also widel ...
woody plants, apart from the cycads. The soft and highly parenchymatous wood in cycads is poorly lignified, and their main structural support comes from an armor of sclerenchymatous leaf bases covering the stem, with the exception of species with underground stems. There are no herbaceous gymnosperms and compared to angiosperms they occupy fewer
ecological niche In ecology, a niche is the match of a species to a specific environmental condition. Three variants of ecological niche are described by It describes how an organism or population responds to the distribution of resources and competitors (for ...
s, but have evolved both parasites (
parasitaxus ''Parasitaxus usta'' is a rare species of conifer of the family Podocarpaceae, and the sole species of the genus ''Parasitaxus''. It is a woody shrub up to 1.8 m found only in the remote, densely forested areas of New Caledonia, first discov ...
), epiphytes ( Zamia pseudoparasitica) and rheophytes ( Retrophyllum minus). Conifers are by far the most abundant extant group of gymnosperms with six to eight families, with a total of 65–70 genera and 600–630 species (696 accepted names).Catalogue of Life: 2007 Annual checklist – Conifer database
Most conifers are evergreens. The leaves of many conifers are long, thin and needle-like, other species, including most Cupressaceae and some
Podocarpaceae Podocarpaceae is a large family of mainly Southern Hemisphere conifers, known in English as podocarps, comprising about 156 species of evergreen trees and shrubs.James E. Eckenwalder. 2009. ''Conifers of the World''. Portland, Oregon: Timber P ...
, have flat, triangular scale-like leaves. '' Agathis'' in Araucariaceae and '' Nageia'' in Podocarpaceae have broad, flat strap-shaped leaves. Cycads are the next most abundant group of gymnosperms, with two or three families, 11 genera, and approximately 338 species. A majority of cycads are native to tropical climates and are most abundantly found in regions near the equator. The other extant groups are the 95–100 species of Gnetales and one species of Ginkgo. Today gymnosperms are the most threatened of all plant groups.


Classification

A formal classification of the living gymnosperms is the "Acrogymnospermae", which form a monophyletic group within the spermatophytes. The wider "Gymnospermae" group includes extinct gymnosperms and is thought to be paraphyletic. The fossil record of gymnosperms includes many distinctive taxa that do not belong to the four modern groups, including seed-bearing trees that have a somewhat fern-like vegetative morphology (the so-called "seed ferns" or
pteridosperm The term Pteridospermatophyta (or "seed ferns" or "Pteridospermatopsida") is a polyphyletic group of extinct seed-bearing plants (spermatophytes). The earliest fossil evidence for plants of this type is the genus ''Elkinsia'' of the late Devonian ...
s). When fossil gymnosperms such as these and the Bennettitales, glossopterids, and ''
Caytonia ''Caytonia'' is an extinct genus of seed ferns. Description ''Caytonia'' has berry like cupules with numerous small seeds arrayed along axes Whole plant reconstructions Different organs attributed to the same original plant can ...
'' are considered, it is clear that angiosperms are nested within a larger gymnospermae clade, although which group of gymnosperms is their closest relative remains unclear. The extant gymnosperms include 12 main families and 83 genera which contain more than 1000 known species. Subclass Cycadidae *Order Cycadales **Family
Cycadaceae ''Cycas'' is a genus of plants belonging to a very ancient lineage, the Cycadophyta, which are not closely related to palms, ferns, trees or any other modern group of plants. They are evergreen perennials which achieved their maximum diversity i ...
: '' Cycas'' **Family
Zamiaceae The Zamiaceae are a family of cycads that are superficially palm or fern-like. They are divided into two subfamilies with eight genera and about 150 species in the tropical and subtropical regions of Africa, Australia and North and South Americ ...
: '' Dioon'', ''
Bowenia The genus ''Bowenia'' includes two living and two fossil species of cycads in the family Stangeriaceae, sometimes placed in their own family Boweniaceae. They are entirely restricted to Australia. The two living species occur in Queensland. '' ...
'', ''
Macrozamia ''Macrozamia'' is a genus of around forty species of cycads, family Zamiaceae, all of which are endemic to Australia. Many parts of the plant have been utilised for food and material, most of which is toxic if not processed correctly. Descrip ...
'', '' Lepidozamia'', '' Encephalartos'', '' Stangeria'', ''
Ceratozamia ''Ceratozamia'' is a genus of New World cycads in the family Zamiaceae. The genus contains 27 known currently living species and one or two fossil species. Most species are endemic to mountainous areas of Mexico, while few species extend into the ...
'', '' Microcycas'', ''
Zamia ''Zamia'' is a genus of cycad of the family Zamiaceae, native to North America from the United States (in Georgia and Florida) throughout the West Indies, Central America, and South America as far south as Bolivia. The genus is considered to be ...
'' Subclass Ginkgoidae *Order Ginkgoales **Family Ginkgoaceae: '' Ginkgo'' Subclass Gnetidae *Order
Welwitschiales Welwitschiaceae is a family of plants of the order Gnetales with one living species, '' Welwitschia mirabilis'', found in southwestern Africa. Three fossil genera have been recovered from the Crato Formation – late Aptian (Lower Cretaceous) st ...
**Family
Welwitschiaceae Welwitschiaceae is a family of plants of the order Gnetales with one living species, ''Welwitschia mirabilis'', found in southwestern Africa. Three fossil genera have been recovered from the Crato Formation – late Aptian (Lower Cretaceous) str ...
: '' Welwitschia'' *Order Gnetales **Family Gnetaceae: ''
Gnetum ''Gnetum'' is a genus of gymnosperms, the sole genus in the family Gnetaceae within the Gnetophyta. They are tropical evergreen trees, shrubs and lianas. Unlike other gymnosperms, they possess vessel elements in the xylem. Some species have been ...
'' *Order Ephedrales **Family Ephedraceae: '' Ephedra'' Subclass
Pinidae Pinidae is a subclass of Equisetopsida in the sense used by Mark W. Chase and James L. Reveal in their 2009 article "A phylogenetic classification of the land plants to accompany APG III." This subclass comprises the conifers. The Pinidae subcl ...
*Order Pinales **Family Pinaceae: '' Cedrus'', '' Pinus'', ''
Cathaya ''Cathaya'' is a genus in the pine family, Pinaceae, with one known living species, ''Cathaya argyrophylla''. ''Cathaya'' is a member of the subfamily Laricoideae, most closely related to ''Pseudotsuga'' and ''Larix''. A second species, ''C. na ...
'', '' Picea'', ''
Pseudotsuga ''Pseudotsuga'' is a genus of evergreen coniferous trees in the family Pinaceae (subfamily Laricoideae). Common names for species in the genus include Douglas fir, Douglas-fir, Douglas tree, Oregon pine and Bigcone spruce. ''Pseudotsuga menzie ...
'', ''
Larix Larches are deciduous conifers in the genus ''Larix'', of the family Pinaceae (subfamily Laricoideae). Growing from tall, they are native to much of the cooler temperate northern hemisphere, on lowlands in the north and high on mountains fu ...
'', '' Pseudolarix'', '' Tsuga'', ''
Nothotsuga ''Nothotsuga'' is a genus of coniferous trees in the family Pinaceae endemic to China. ''Nothotsuga'' contains only one species, ''Nothotsuga longibracteata'', commonly known as the bristlecone hemlock, which is found in southeastern China, in ...
'', '' Keteleeria'', ''
Abies Firs (''Abies'') are a genus of 48–56 species of evergreen coniferous trees in the family Pinaceae. They are found on mountains throughout much of North and Central America, Europe, Asia, and North Africa. The genus is most closely re ...
'' *Order
Araucariales Araucariaceae – also known as araucarians – is an extremely ancient family of coniferous trees. The family achieved its maximum diversity during the Jurassic and Cretaceous periods and the early Cenozoic, when it was distributed almost world ...
**Family Araucariaceae: '' Araucaria'', '' Wollemia'', '' Agathis'' **Family
Podocarpaceae Podocarpaceae is a large family of mainly Southern Hemisphere conifers, known in English as podocarps, comprising about 156 species of evergreen trees and shrubs.James E. Eckenwalder. 2009. ''Conifers of the World''. Portland, Oregon: Timber P ...
: '' Phyllocladus'', '' Lepidothamnus'', '' Prumnopitys'', '' Sundacarpus'', '' Halocarpus'', ''
Parasitaxus ''Parasitaxus usta'' is a rare species of conifer of the family Podocarpaceae, and the sole species of the genus ''Parasitaxus''. It is a woody shrub up to 1.8 m found only in the remote, densely forested areas of New Caledonia, first discov ...
'', ''
Lagarostrobos ''Lagarostrobos franklinii'' is a species of conifer native to the wet southwestern corner of Tasmania, Australia. It is often known as the Huon pine or Macquarie pine, although it is actually a podocarp (Podocarpaceae), not a true pine (Pinace ...
'', '' Manoao'', ''
Saxegothaea ''Saxegothaea'' is a genus comprising a single species, ''Saxegothaea conspicua''. It is a conifer in the podocarp family Podocarpaceae, native to southern South America. It grows in Chile and Argentina from 35° to 46° South latitude; in its ...
'', ''
Microcachrys ''Microcachrys tetragona'', the creeping pine or creeping strawberry pine, is a species of dioecious conifer belonging to the podocarp family (Podocarpaceae).Christopher N. Page. 1990. "Podocarpaceae" pages 332-346. In: Klaus Kubitzki (general e ...
'', '' Pherosphaera'', '' Acmopyle'', '' Dacrycarpus'', '' Dacrydium'', '' Falcatifolium'', '' Retrophyllum'', '' Nageia'', ''
Afrocarpus ''Afrocarpus'' is a genus of conifers of the family Podocarpaceae. Two to six species are recognized. They are evergreen trees native to Africa. ''Afrocarpus'' was designated a genus in 1989, when several species formerly classified in ''Podocar ...
'', '' Podocarpus'' *Order Cupressales **Family
Sciadopityaceae ''Sciadopitys verticillata'', the or Japanese umbrella-pine, is a unique conifer endemic to Japan. It is the sole member of the family Sciadopityaceae and genus ''Sciadopitys'', a living fossil with no close relatives. The oldest fossils of ...
: '' Sciadopitys'' **Family Cupressaceae: '' Cunninghamia'', ''
Taiwania ''Taiwania'', with the single living species ''Taiwania cryptomerioides'', is a large coniferous tree in the cypress family Cupressaceae. Etymology ''Taiwania'' means 'from Taiwan', while ''Cryptomerioides'' means 'resembling ''Cryptomeria''.G ...
'', '' Athrotaxis'', ''
Metasequoia ''Metasequoia'', or dawn redwoods, is a genus of fast-growing deciduous trees, one of three species of conifers known as redwoods. The living species ''Metasequoia glyptostroboides'' is native to Lichuan county in Hubei province, China. Althou ...
'', '' Sequoia'', '' Sequoiadendron'', '' Cryptomeria'', '' Glyptostrobus'', '' Taxodium'', ''
Papuacedrus ''Papuacedrus papuana'' is a species in the conifer family Cupressaceae, the sole species in the genus ''Papuacedrus''. Some botanists do not consider this species as forming a distinct genus, but include it in the related genus ''Libocedrus''. I ...
'', ''
Austrocedrus ''Austrocedrus'' is a genus of conifer belonging to the cypress family (Cupressaceae). It has only one species, ''Austrocedrus chilensis'', native to the Valdivian temperate rain forests and the adjacent drier steppe-forests of central-southern ...
'', '' Libocedrus'', '' Pilgerodendron'', '' Widdringtonia'', '' Diselma'', ''
Fitzroya ''Fitzroya'' is a monotypic genus in the cypress family. The single living species, ''Fitzroya cupressoides'', is a tall, long-lived conifer native to the Andes mountains and coastal of southern Chile, and only to the Andes mountains Argentina, ...
'', '' Callitris'', '' Actinostrobus'', ''
Neocallitropsis ''Callitris pancheri'' is a plant species of the family Cupressaceae. It is endemic to New Caledonia, where it occurs in small, scattered population along rivers. It used to be placed in its own genus ''Neocallitropsis'' but molecular phyloge ...
'', '' Thujopsis'', '' Thuja'', '' Fokienia'', ''
Chamaecyparis ''Chamaecyparis'', common names cypress or false cypress (to distinguish it from related cypresses), is a genus of conifers in the cypress family Cupressaceae, native to eastern Asia (Japan and Taiwan) and to the western and eastern margins of t ...
'', '' Cupressus'', '' Juniperus'', ''
Calocedrus ''Calocedrus'', the incense cedar (alternatively spelled incense-cedar), is a genus of coniferous trees in the cypress family Cupressaceae first described as a genus in 1873. It is native to eastern Asia and western North America. The generic n ...
'', ''
Tetraclinis ''Tetraclinis'' (also called arar, araar or Sictus tree) is a genus of evergreen coniferous trees in the cypress family Cupressaceae, containing only one species, ''Tetraclinis articulata'', also known as Thuja articulata,Platycladus'', '' Microbiota'' **Family Taxaceae: ''
Austrotaxus ''Austrotaxus spicata'', the New Caledonia yew or southern yew, is a species of yew, the sole species in the genus ''Austrotaxus''. It is related to the other yews in the genera '' Taxus'' and '' Pseudotaxus''. It is endemic to New Caledonia, ...
'', ''
Pseudotaxus ''Pseudotaxus chienii'', the whiteberry yewThomas, P. & Yang, Y. 2013''Pseudotaxus chienii''.The IUCN Red List of Threatened Species. Version 2015.2. Downloaded on 04 September 2015. (), is a species of plant in the yew family, Taxaceae. It is t ...
'', '' Taxus'', ''
Cephalotaxus ''Cephalotaxus'', commonly called plum yew or cowtail pine, is a genus of conifers comprising 11 species, treated in either the Cephalotaxaceae, or in the Taxaceae when that family is considered in a broad sense. The genus is endemic to easter ...
'', ''
Amentotaxus ''Amentotaxus'' is a genus of conifers (catkin-yews) comprising five species, treated in either the Cephalotaxaceae, or in the Taxaceae when that family is considered in a broad sense. The genus is endemic to subtropical Southeast Asia, from ...
'', '' Torreya''


Extinct groupings

* Division Pteridospermatophyta * Order Bennettitales ** Family
Cycadeoidaceae Cycadeoidaceae is a family of bennettitalean plants which flourished in the Mesozoic era. Two genera, '' Cycadeoidea'' and '' Monanthesia'', are currently recognised though most species are poorly known. They had a similar morphology to cycads ...
** Family
Williamsoniaceae ''Williamsoniaceae'' is a family within the Bennettitales, an extinct group of seed plants within the Cycadophyta subdivision. Members of this family are believed to have been around two meters tall and with widely serrate leaves along a central ...
* Order Erdtmanithecales *Order Pentoxylales *Order
Czekanowskiales Czekanowskiales, also known as Leptostrobales, are an extinct group of seed plants. Members of the family are distinguished by persistent leaves borne on deciduous short shoots, subtended by scale-like leaves. The leaves are highly dissected (div ...


Life cycle

Gymnosperms, like all vascular plants, have a sporophyte-dominant life cycle, which means they spend most of their life cycle with diploid cells, while the gametophyte (gamete-bearing phase) is relatively short-lived. Like all seed plants, they are heterosporous, having two spore types, microspores (male) and megaspores (female) that are typically produced in pollen cones or ovulate cones, respectively. The exception is the females in the cycad genus Cycas, which form a loose structure called megasporophylls instead of cones. As with all heterosporous plants, the gametophytes develop within the spore wall. Pollen grains (microgametophytes) mature from microspores, and ultimately produce sperm cells. Megagametophytes develop from megaspores and are retained within the ovule. Gymnosperms produce multiple archegonia, which produce the female gamete. During pollination, pollen grains are physically transferred between plants from the pollen cone to the ovule. Pollen is usually moved by wind or insects. Whole grains enter each ovule through a microscopic gap in the ovule coat ( integument) called the micropyle. The pollen grains mature further inside the ovule and produce sperm cells. Two main modes of fertilization are found in gymnosperms. Cycads and '' Ginkgo'' have flagellated motile sperm that swim directly to the egg inside the ovule, whereas conifers and gnetophytes have sperm with no flagella that are moved along a pollen tube to the egg. After
syngamy Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a new individual organism or offspring and initiate its development. Pro ...
(joining of the sperm and egg cell), the zygote develops into an embryo (young sporophyte). More than one embryo is usually initiated in each gymnosperm seed. The mature seed comprises the embryo and the remains of the female gametophyte, which serves as a food supply, and the seed coat.


Genetics

The first published sequenced genome for any gymnosperm was the genome of '' Picea abies'' in 2013.


Uses

Gymnosperms have major economic uses. Pine, fir, spruce, and cedar are all examples of conifers that are used for
lumber Lumber is wood that has been processed into dimensional lumber, including beams and planks or boards, a stage in the process of wood production. Lumber is mainly used for construction framing, as well as finishing (floors, wall panels, w ...
, paper production, and resin. Some other common uses for gymnosperms are
soap Soap is a salt of a fatty acid used in a variety of cleansing and lubricating products. In a domestic setting, soaps are surfactants usually used for washing, bathing, and other types of housekeeping. In industrial settings, soaps are us ...
, varnish, nail polish, food, gum, and
perfume Perfume (, ; french: parfum) is a mixture of fragrant essential oils or aroma compounds (fragrances), fixatives and solvents, usually in liquid form, used to give the human body, animals, food, objects, and living-spaces an agreeable scent ...
s.


References


General bibliography

*


External links


Gymnosperm DatabaseGymnosperms on the Tree of Life
* {{Authority control 01 Extant Late Devonian first appearances