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

ovule In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the '' integument'', forming its outer layer, the ''nucellus'' (or remnant of the megasporangium), and the f ...

s in their unfertilized state). The non-encased condition of their seeds contrasts with the seeds and ovules of flowering plants (

angiosperms Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. They include all forbs (flowering plants without a woody stem), grasses and grass-like plants, a vast majority of br ...

), 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 ''Torreya'' is a genus of conifers comprising six or seven species placed in the family Taxaceae, though sometimes formerly placed in Cephalotaxaceae. Four species are native to eastern Asia; the other two are native to North America. They ...

'', '' Ginkgo''. Gymnosperm lifecycles involve alternation of generations. They have a dominant

diploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respecti ...

sporophyte phase and a reduced haploid

gametophyte A gametophyte () is one of the two alternation of generations, alternating multicellular organism, multicellular phases in the life cycles of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has on ...

phase which is dependent on the sporophytic phase. The term "gymnosperm" is often used in

paleobotany Paleobotany, which is also spelled as palaeobotany, is the branch of botany dealing with the recovery and identification of plant remains from geological contexts, and their use for the biological reconstruction of past environments (paleogeog ...

to refer to all non-angiosperm seed plants. In that case, to specify the modern

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic ...

group of gymnosperms, the term Acrogymnospermae is sometimes used. The gymnosperms and

together comprise the spermatophytes or seed plants. The gymnosperms are subdivided into five Divisions, four of which, the Cycadophyta, Ginkgophyta,

Gnetophyta Gnetophyta () is a division of plants (alternatively considered the subclass Gnetidae or order Gnetales), grouped within the gymnosperms (which also includes conifers, cycads, and ginkgos), that consists of some 70 species across the three Reli ...

, 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'', '' 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 Dioecy (; ; adj. dioecious , ) is a characteristic of a species, meaning that it has distinct individual organisms (unisexual) that produce male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproducti ...

, 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 period, replacing the lycopsid rainforests of the tropical region, but more recent phylogenetic evidence indicates that they diverged from the ancestors of

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 * Early ...

. The radiation of gymnosperms during the late Carboniferous appears to have resulted from a whole genome duplication 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 A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular mouthparts used for feeding and sucking. In vertebrates, a proboscis is an elonga ...

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) resembled the modern butterflies that arose far later. Zamia integrifolia02

All gymnosperms are perennial 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 Herbaceous plants are vascular plants that have no persistent woody stems above ground. This broad category of plants includes many perennials, and nearly all annuals and biennials. Definitions of "herb" and "herbaceous" The fourth edition ...

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 (fo ...

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 discove ...

), epiphytes ( Zamia pseudoparasitica) and rheophytes ( Retrophyllum minus).

Conifer Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single extant class, Pinopsida. All ex ...

s 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, 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 In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

. The fossil record of gymnosperms includes many distinctive

taxa In biology, a taxon ( back-formation from '' taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular n ...

that do not belong to the four modern groups, including seed-bearing trees that have a somewhat

fern A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes except ...

-like vegetative morphology (the so-called "seed ferns" or pteridosperms). 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'' **Family Zamiaceae: '' Dioon'', '' Bowenia'', '' Macrozamia'', '' Lepidozamia'', '' Encephalartos'', '' Stangeria'', '' Ceratozamia'', '' 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 Ginkgoidae 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 contains the single extant genus ''Ginkg ...

*Order Ginkgoales **Family Ginkgoaceae: '' Ginkgo'' Subclass

Gnetidae Gnetophyta () is a division of plants (alternatively considered the subclass Gnetidae or order Gnetales), grouped within the gymnosperms (which also includes conifers, cycads, and ginkgos), that consists of some 70 species across the three ...

*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) ...

**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) ...

: '' Welwitschia'' *Order Gnetales **Family Gnetaceae: '' Gnetum'' *Order

Ephedrales Ephedraceae is a family of gymnosperms belonging to Gnetophyta, it contains only a single extant genus, ''Ephedra'', as well as a number of extinct genera from the Early Cretaceous. Taxonomy File:Eamesia chinensis.png, '' Eamesia'' File:Chengia ...

**Family Ephedraceae: '' Ephedra'' Subclass Pinidae *Order

Pinales The order Pinales in the division Pinophyta, class Pinopsida, comprises all the extant conifers. The distinguishing characteristic is the reproductive structure known as a cone produced by all Pinales. All of the extant conifers, such as ce ...

**Family

Pinaceae The Pinaceae, or pine family, are conifer trees or shrubs, including many of the well-known conifers of commercial importance such as cedars, firs, hemlocks, larches, pines and spruces. The family is included in the order Pinales, formerly know ...

: ''

Cedrus ''Cedrus'', common English name cedar, is a genus of coniferous trees in the plant family Pinaceae (subfamily Abietoideae). They are native to the mountains of the western Himalayas and the Mediterranean region, occurring at altitudes of 1,500� ...

'', ''

Pinus A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. The World Flora Online created by the Royal Botanic Gardens, Kew and Missouri Botanical Garden a ...

'', ''

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 ''Larch, Larix''. A second species, ' ...

'', '' 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 furth ...

'', '' Pseudolarix'', ''

Tsuga ''Tsuga'' (, from Japanese (), the name of ''Tsuga sieboldii'') is a genus of conifers in the subfamily Abietoideae of Pinaceae, the pine family. The common name hemlock is derived from a perceived similarity in the smell of its crushed foliage ...

'', '' Nothotsuga'', '' Keteleeria'', '' Abies'' *Order Araucariales **Family Araucariaceae: '' Araucaria'', '' Wollemia'', '' Agathis'' **Family Podocarpaceae: '' 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 discove ...

'', ''

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 (Pinac ...

'', '' Manoao'', '' Saxegothaea'', ''

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 ...

'', ''

Pherosphaera ''Pherosphaera'' is a genus of conifers belonging to the family Podocarpaceae. Its native range is Southeastern Australia. Both species are evergreen shrubs. They are dioecious, with male and female flowers on separate plants. Species Specie ...

'', '' Acmopyle'', '' Dacrycarpus'', '' Dacrydium'', ''

Falcatifolium ''Falcatifolium'' is a genus of conifers of the family Podocarpaceae. The genus includes evergreen dioecious shrubs and large trees of up to . Five species are presently recognized. The genus was first described by de Laubenfels in 1969, and ...

'', '' Retrophyllum'', '' Nageia'', '' Afrocarpus'', '' Podocarpus'' *Order Cupressales **Family Sciadopityaceae: '' Sciadopitys'' **Family Cupressaceae: '' Cunninghamia'', '' Taiwania'', '' Athrotaxis'', '' Metasequoia'', '' Sequoia'', '' Sequoiadendron'', ''

Cryptomeria ''Cryptomeria'' (literally "hidden parts") is a monotypic genus of conifer in the cypress family Cupressaceae, formerly belonging to the family Taxodiaceae. It includes only one species, ''Cryptomeria japonica'' (syn. ''Cupressus japonica'' ...

'', '' 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'', '' Libocedrus'', '' Pilgerodendron'', '' Widdringtonia'', '' Diselma'', '' Fitzroya'', '' Callitris'', '' Actinostrobus'', '' Neocallitropsis'', '' Thujopsis'', '' Thuja'', '' Fokienia'', '' Chamaecyparis'', '' Cupressus'', '' Juniperus'', '' Calocedrus'', ''

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'', '' Pseudotaxus'', '' Taxus'', '' Cephalotaxus'', '' Amentotaxus'', ''

Extinct groupings

* Division Pteridospermatophyta * Order Bennettitales ** Family Cycadeoidaceae ** Family Williamsoniaceae * Order

Erdtmanithecales Erdtmanithecales is an extinct order of gymnosperm plants known from the Mesozoic era. Known remains include pollen organs, seed cones and seeds associated with '' Eucommiidites'' pollen, which is considered diagnostic for the order. The order was ...

*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

(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 (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

, 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 ''Picea abies'', the Norway spruce or European spruce, is a species of spruce native to Northern, Central and Eastern Europe. It has branchlets that typically hang downwards, and the largest cones of any spruce, 9–17 cm long. It is very clo ...

'' 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 used ...

varnish Varnish is a clear transparent hard protective coating or film. It is not a stain. It usually has a yellowish shade from the manufacturing process and materials used, but it may also be pigmented as desired, and is sold commercially in vario ...

, nail polish, food, gum, and perfumes.

References

General bibliography

External links

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