The conifers, division Pinophyta, also known as division Coniferophyta or Coniferae, are one of 13 or 14 division In biology, a phylum [note 1] is a taxonomic rank below Kingdom and above Class. "Phylum" is equivalent to the botanical term division level taxa A taxon is a group of (one or more) organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement. Defining what belongs or does not belong to such a taxonomic group is done by a taxonomist. It is not uncommon for one taxonomist to disagree with another on what exactly belongs to within the Kingdom Plantae Plants are living organisms belonging to the kingdom Plantae. They include familiar organisms such as trees, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The scientific study of plants, known as botany, has identified about 350,000 extant species of plants, defined as seed plants, bryophytes, ferns and fern allies. As of 2004,. Pinophytes are gymnosperms Once an authoritative and major classification level in the plant kingdom, the gymnosperms form today a rather heterogeneous group of seed-bearing plants that includes conifers, cycads, Ginkgo and Gnetales. The term "gymnosperm" comes from the Greek word gymnospermos , meaning "naked seeds", after the unenclosed condition of. They are cone-bearing A cone is an organ on plants in the division Pinophyta (conifers) that contains the reproductive structures. The familiar woody cone is the female cone, which produces seeds. The male cones, which produce pollen, are usually herbaceous and much less conspicuous even at full maturity. The name "cone" derives from the fact that the shape seed plants Plants are living organisms belonging to the kingdom Plantae. They include familiar organisms such as trees, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The scientific study of plants, known as botany, has identified about 350,000 extant species of plants, defined as seed plants, bryophytes, ferns and fern allies. As of 2004, with vascular Vascular plants are those plants that have lignified tissues for conducting water, minerals, and photosynthetic products through the plant. Vascular plants include the ferns, clubmosses, flowering plants, conifers and other gymnosperms. Scientific names for the group include Tracheophyta and Tracheobionta, but neither name is very widely used.[ tissue; all extant conifers are woody plants A woody plant is a plant that uses wood as its structural tissue. They are typically perennial plants that have their stems and larger roots reinforced with wood produced adjacent to the vascular tissues: typically the main stem and larger branches and roots are covered by a layer of thickened bark. Woody plants are usually either trees, shrubs,, the great majority being trees 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 6 m; some authors set a minimum of 10 cm trunk diameter with just a few being shrubs A shrub or bush is distinguished from a tree by its multiple stems and lower height, usually less than 5–6 m tall. A large number of plants can be either shrubs or trees, depending on the growing conditions they experience. Small, low shrubs such as lavender, periwinkle and thyme are often termed subshrubs. Typical examples of conifers include cedars Cedrus, is a genus of coniferous trees in the plant family Pinaceae. They are native to the mountains of the western Himalaya and the Mediterranean region, occurring at altitudes of 1,500–3,200 m in the Himalaya and 1,000–2,200 m in the Mediterranean, Douglas-firs Douglas-fir is the English name applied in common to evergreen coniferous trees of the genus Pseudotsuga in the family Pinaceae. There are five species, two in western North America, one in Mexico, and two in eastern Asia. Nineteenth-century botanists had problems in classifying Douglas-firs, due to the species' similarity to various other, cypresses The Cupressaceae or cypress family is a conifer family with worldwide distribution. The family includes 27 to 30 genera with about 130-140 species. They are monoecious, subdioecious or (rarely) dioecious trees and shrubs from 1-116 m (3-379 ft) tall. The bark of mature trees is commonly orange- to red- brown and of stringy texture, often flaking, firs Firs are a genus of 48–55 species of evergreen conifers in the family Pinaceae. They are found through much of North and Central America, Europe, Asia, and North Africa, occurring in mountains over most of the range. Firs are most closely related to the cedars (Cedrus); Douglas-firs are not true firs, being of the genus Pseudotsuga, junipers Junipers are coniferous plants in the genus Juniperus of the cypress family Cupressaceae. Depending on taxonomic viewpoint, there are between 50-67 species of juniper, widely distributed throughout the northern hemisphere, from the Arctic, south to tropical Africa in the Old World, and to the mountains of Central America, kauris The genus Agathis, commonly known as kauri or dammar, is a relatively small genus of 21 species of evergreen tree. The genus is part of the ancient Araucariaceae family of conifers, a group once widespread during the Jurassic period, but now largely restricted to the Southern Hemisphere except for a number of extant Malesian Agathis, larches Larches are conifers in the genus Larix, in the family Pinaceae. Growing from 15-50m tall, they are native to much of the cooler temperate northern hemisphere, on lowlands in the far north, and high on mountains further south. Larch are among the dominant plants in the immense boreal forests of Russia and Canada, pines See Pinus classification for complete taxonomy to species level. See list of pines by region for list of species by geographical distribution, hemlocks There are between eight and ten species within the genus , with four species occurring in North America and four to six in eastern Asia, redwoods Sequoia sempervirens is the sole living species of the genus Sequoia in the cypress family Cupressaceae (formerly treated in Taxodiaceae). Common names include coast redwood, giant redwood and California redwood (it is one of three species of trees known as redwoods, but redwood per se normally refers to this species). It is an evergreen, long-, spruces A spruce is a tree of the genus Picea , a genus of about 35 species of coniferous evergreen trees in the Family Pinaceae, found in the northern temperate and boreal (taiga) regions of the earth. Spruces are large trees, from 20–60 metres (66–200 ft) tall when mature, and can be distinguished by their whorled branches and conical form. The, and yews The family Taxaceae, commonly called the yew family, includes three genera and about 7 to 12 species of coniferous plants, or in other interpretations , six genera and about 30 species.^[1] The division contains approximately eight families, 68 genera, and 630 living species.^[2][3] Although the total number of species is relatively small, conifers are of immense ecological Ecology is the scientific study of the distributions, abundance and relations of organisms and their interactions with the environment. Ecology includes the study of plant and animal populations, plant and animal communities and ecosystems. Ecosystems describe the web or network of relations among organisms at different scales of organization importance. They are the dominant plants over huge areas of land,^[4] most notably the boreal forests Taiga , also known as the boreal forest, is a biome characterized by coniferous forests of the northern hemisphere The Northern Hemisphere is the half of a planet that is north of equator—the word hemisphere literally means 'half sphere'. It is also that half of the celestial sphere north of the celestial equator. Earth's northern hemisphere contains most of its land area and most of its human population,^[1] but also in similar cool climates in mountains further south. Boreal conifers have many winter time adaptions. The narrow conical shape of northern conifers, and their downward-drooping limbs help them shed snow, many of them seasonally alter their biochemistry to make them more resistant to freezing, called "hardening". While tropical rain forests have more biodiversity and turnover, the immense conifer forests of the world represent the largest terrestrial carbon sink, i.e. where carbon is bound as organic compounds. They are also of great economic value, primarily for timber Lumber or timber is wood that is used in any of its stages from felling through readiness for use as structural material for construction, or wood pulp for paper production and paper Paper is a thin material mainly used for writing upon, printing upon or for packaging. It is produced by pressing together moist fibers, typically cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets production;^[1][4] the wood of conifers is known as softwood The term softwood is used to describe wood from conifers. It may also be used to describe these trees, which tend to be evergreen, notable exceptions being bald cypress and the larches.

Evolution

The earliest conifers in the fossil record date to the late Carboniferous The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Ma , to the beginning of the Permian Period, about 299.0 ± 0.8 Ma (ICS, 2004, (Pennsylvanian The Pennsylvanian is in the ICS geologic timescale the youngest subperiod or upper subsystem of the Carboniferous Period. It lasted from roughly 318.1± 1.3 to 299± 0.8 Ma . As with most other geochronologic units, the rock beds that define the Pennsylvanian are well identified, but the exact date of the start and end are uncertain by a few) period, (about 300 million years ago),^[5] possibly arising from Cordaites Cordaites is an important genus of extinct gymnosperms which grew on wet ground similar to the Everglades in Florida. Brackish water mussels and crustacea are found frequently between the roots of these trees. The fossils are found in rock sections from the Upper Carboniferous of the Dutch - Belgian - German coal area. A number of many noteworthy, a seed-bearing plant with cone-like fertile structures. This plant resembled the modern Araucaria Araucaria is a genus of evergreen coniferous trees in the family Araucariaceae. There are 19 species in the genus, with a highly disjunct distribution in New Caledonia , Norfolk Island, eastern Australia, New Guinea, Argentina, Chile, and southern Brazil. Pinophyta, Cycadophyta, and Ginkgophyta all developed at this time.^[5] An important adaptation of these gymnosperms was allowing plants to live without being so dependent on water. Other adaptations are pollen (allowing fertilization to occur without water) and the seed, which allows the embryo to be transported and developed elsewhere.^[5]

Conifers appear to be one of the taxa that benefitted from the Permo-Triassic extinction event.

Taxonomy and naming

The division name Pinophyta conforms to the rules of the ICBN The International Code of Botanical Nomenclature is the set of rules and recommendations dealing with the formal botanical names that are given to plants. Its intent is that each taxonomic group ("taxon", plural "taxa") of plants has only one correct name that is accepted worldwide. The value of a scientific name is that it is, which state (Article 16.1) that the names of higher taxa A taxon is a group of (one or more) organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement. Defining what belongs or does not belong to such a taxonomic group is done by a taxonomist. It is not uncommon for one taxonomist to disagree with another on what exactly belongs to in plants (above the rank of family) are either formed from the name of an included family (usually the most common and/or representative), in this case Pinaceae The family Pinaceae , is in the order Pinales, formerly known as the Coniferales, and includes many of the well-known conifers of commercial importance such as cedars, firs, hemlocks, larches, pines and spruces. It is supported as monophyletic by its protein-type sieve cell plastids, pattern of proembryogeny, and lack of bioflavonoid. It is the (the pine See Pinus classification for complete taxonomy to species level. See list of pines by region for list of species by geographical distribution family), or are descriptive. In the latter case the name for the conifers (at whatever rank is chosen) is Coniferae (Art 16 Ex 2), which is also in widespread use. Older scientific names (no longer allowed) are Coniferophyta and Coniferales.

According to the ICBN The International Code of Botanical Nomenclature is the set of rules and recommendations dealing with the formal botanical names that are given to plants. Its intent is that each taxonomic group ("taxon", plural "taxa") of plants has only one correct name that is accepted worldwide. The value of a scientific name is that it is it is possible to use a name formed by replacing the termination -aceae in the name of an included family, in this case preferably Pinaceae The family Pinaceae , is in the order Pinales, formerly known as the Coniferales, and includes many of the well-known conifers of commercial importance such as cedars, firs, hemlocks, larches, pines and spruces. It is supported as monophyletic by its protein-type sieve cell plastids, pattern of proembryogeny, and lack of bioflavonoid. It is the, by the appropriate termination, in the case of this division -ophyta. Alternatively, "descriptive botanical names Descriptive botanical names are names that are governed by Article 16 of the International Code of Botanical Nomenclature , which rules that a name above the rank of family may be either descriptive or formed from the name of an included family. The latter leads to names such as Magnoliophyta and Magnoliopsida" may also be used at any rank In biological classification, rank is the level in a taxonomic hierarchy. The most basic rank is that of species, the next most important is genus, and then family. Sometimes (but only rarely) the term "taxonomic category" is used instead of "rank" above family. Both are allowed.

This means that if the conifers are regarded to be a division they may be called Pinophyta or Coniferae (if regarded as a class they may be called Pinopsida or Coniferae; if regarded as an order they may be called Pinales or Coniferae (but see also Coniferales The Order Pinales in the Division Pinophyta, Class Pinopsida comprises all the extant conifers. This order was formerly known as the Coniferales)).

Commonly the conifers are considered equivalent to the Gymnosperms Once an authoritative and major classification level in the plant kingdom, the gymnosperms form today a rather heterogeneous group of seed-bearing plants that includes conifers, cycads, Ginkgo and Gnetales. The term "gymnosperm" comes from the Greek word gymnospermos , meaning "naked seeds", after the unenclosed condition of,^[4] particularly in areas with a temperate climate where they may be the only commonly occurring gymnosperms. However, these are two different levels of grouping: conifers are the largest and economically most important component group of the gymnosperms, but nevertheless they comprise only one of the four groups. The division Pinophyta consists of just one class, Pinopsida, which includes both living and fossil taxa. Subdivision of the living conifers into two or more orders has been proposed from time to time. The most commonly seen in the past was a split into two orders, Taxales The plant order Taxales was until recently treated as a distinct order in the division Pinophyta, class Pinopsida, and included only those species in the family Taxaceae, known commonly as yews. Under this interpretation, all other conifers were classified separately in the order Pinales. Recent genetic and micromorphological studies have however (Taxaceae only) and Pinales The Order Pinales in the Division Pinophyta, Class Pinopsida comprises all the extant conifers. This order was formerly known as the Coniferales (the rest), but recent research into DNA sequences Molecular biology is the study of biology at a molecular level. The field overlaps with other areas of biology and chemistry, particularly genetics and biochemistry. Molecular biology chiefly concerns itself with understanding the interactions between the various systems of a cell, including the interactions between DNA, RNA and protein suggests that this interpretation leaves the Pinales without Taxales as paraphyletic A group of taxa is said to be paraphyletic if the group contains its last common ancestor but does not contain all the descendants of that ancestor. This term is used in both phylogenetics[note 1] and linguistics, and the latter order is no longer regarded as distinct. A more accurate subdivision would be to split the class into three orders, Pinales containing only Pinaceae, Araucariales containing Araucariaceae and Podocarpaceae, and Cupressales containing the remaining families (including Taxaceae), but there has not been any significant support for such a split, with the majority of opinion preferring retention of all the families within a single order Pinales, despite their antiquity and diverse morphology In biology "morphology" is the study of the form, structure and configuration of an organism. This includes aspects of the outward appearance [citation needed] as well as the form and structure of the internal parts like bones and organs. This is in contrast to physiology, which deals primarily with function.

The conifers are now accepted as comprising six to eight families, with a total of 65-70 genera and 600-630 species (696 accepted names).^[2] The seven most distinct families are linked in the box above right and phylogenetic diagram left. In other interpretations, the Cephalotaxaceae may be better included within the Taxaceae, and some authors additionally recognize Phyllocladaceae Phyllocladus is a small genus of conifers, now treated in the Family Podocarpaceae. They are morphologically very distinct from the other genera in that family, and some botanists treat them in a family of their own, the Phyllocladaceae. However, genetic analysis shows that they fall within the Podocarpaceae; their removal from this family leaves as distinct from Podocarpaceae (in which it is included here). The family Taxodiaceae is here included in family Cupressaceae, but was widely recognized in the past and can still be found in many field guides.

The conifers are an ancient group, with a fossil record extending back about 300 million years to the Paleozoic in the late Carboniferous period; even many of the modern genera are recognizable from fossils 60-120 million years old. Other classes and orders, now long extinct, also occur as fossils, particularly from the late Paleozoic and Mesozoic eras. Fossil conifers included many diverse forms, the most dramatically distinct from modern conifers being some herbaceous conifers with no woody stems. Major fossil orders of conifers or conifer-like plants include the Cordaitales, Vojnovskyales, Voltziales and perhaps also the Czekanowskiales (possibly more closely related to the Ginkgophyta).

Morphology

All living conifers are woody plants, and most are trees, the majority having monopodial growth form (a single, straight trunk with side branches) with strong apical dominance. Many conifers have distinctly scented resin, secreted to protect the tree against insect infestation and fungal infection of wounds. Fossilized resin hardens into amber. The size of mature conifers varies from less than one meter, to over 100 meters ^[7] The world's tallest, largest, thickest and oldest living things are all conifers. The tallest is a Coast Redwood (Sequoia sempervirens), with a height of 115.55 meters. The largest is a Giant Sequoia (Sequoiadendron giganteum), with a volume 1486.9 cubic meters .^[8] The thickest, or tree with the greatest trunk diameter, is a Montezuma Cypress (Taxodium mucronatum), 11.42 meters in diameter. The oldest is a Great Basin Bristlecone Pine (Pinus longaeva), 4,700 years old.^[9]

Foliage

Since most conifers are evergreens,^[1] the leaves of many conifers are long, thin and have a needle-like appearance, but others, including most of the Cupressaceae and some of the Podocarpaceae, have flat, triangular scale-like leaves. Some, notably Agathis in Araucariaceae and Nageia in Podocarpaceae, have broad, flat strap-shaped leaves. Others such as Araucaria columnaris have leaves that are awl-shaped. In the majority of conifers, the leaves are arranged spirally, exceptions being most of Cupressaceae and one genus in Podocarpaceae, where they are arranged in decussate opposite pairs or whorls of 3 (-4). In many species with spirally arranged leaves, the leaf bases are twisted to present the leaves in a very flat plane for maximum light capture (see e.g. photo of Grand Fir Abies grandis). Leaf size varies from 2 mm in many scale-leaved species, up to 400 mm long in the needles of some pines (e.g. Apache Pine Pinus engelmannii). The stomata are in lines or patches on the leaves, and can be closed when it is very dry or cold. The leaves are often dark green in colour which may help absorb a maximum of energy from weak sunshine at high latitudes or under forest canopy shade. Conifers from hotter areas with high sunlight levels (e.g. Turkish Pine Pinus brutia) often have yellower-green leaves, while others (e.g. Blue Spruce Picea pungens) have a very strong glaucous wax bloom to reflect ultraviolet light. In the great majority of genera the leaves are evergreen, usually remaining on the plant for several (2-40) years before falling, but five genera (Larix, Pseudolarix, Glyptostrobus, Metasequoia and Taxodium) are deciduous, shedding the leaves in autumn and leafless through the winter.^[1] The seedlings of many conifers, including most of the Cupressaceae, and Pinus in Pinaceae, have a distinct juvenile foliage period where the leaves are different, often markedly so, from the typical adult leaves.

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