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   » » Wiki: Pinophyta
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Conifer is a Latin word, a compound word of conus and ferre (to bear), meaning the one that bears (a) cone(s).

The conifers, division Pinophyta, also known as division Coniferophyta or Coniferae, are one of 13 or 14 level within the . Pinophytes are . They are seed with tissue; all extant conifers are , the great majority being with just a few being . Typical examples of conifers include , , , , , , , , , , , and .Campbell, Reece, "Phylum Coniferophyta". Biology. 7th. 2005. Print. P.595 The division contains approximately eight families, 68 genera, and 630 living species. Database Catalogue of Life: 2007 Annual checklist - Conifer databaseLott, J., Liu, J., Pennell, K., Lesage, A., & West, M. (2002, September). Iron-rich particles and globoids in embryos of seeds from phyla Coniferophyta, Cycadophyta, Gnetophyta, and Ginkgophyta: characteristics of early seed plants. Canadian Journal of Botany, 80(9), 954–961. Retrieved July 17, 2009, from Academic Search Premier database.

Although the total number of species is relatively small, conifers are of immense importance. They are the dominant plants over huge areas of land, most notably the of the , but also in similar cool climates in mountains further south. Boreal conifers have many wintertime adaptations. 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 have more and turnover, the immense conifer forests of the world represent the largest terrestrial , i.e. where from is bound as organic compounds.

They are also of great economic value, primarily for and production; the wood of conifers is known as .


Evolution
The earliest conifers in the fossil record date to the late () period (about 300 million years ago),Henry, R.J.(2005) Plant Diversity and evolution. London: CABI. possibly arising from , a seed-bearing plant with cone-like fertile structures. This plant resembled the modern . Pinophyta, , and all developed at this time. An important adaptation of these gymnosperms was allowing plants to live without being so dependent on water. Other adaptations are pollen (so fertilization can occur without water) and the seed, which lets the embryo be transported and developed elsewhere.

Conifers appear to be one of the taxa that benefited from the .


Taxonomy and naming
The division name Pinophyta conforms to the rules of the , which state (Article 16.1) that the names of higher 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 (the 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 it is possible to use a name formed by replacing the termination -aceae in the name of an included family, in this case preferably , by the appropriate termination, in the case of this division -ophyta. Alternatively, "" may also be used at any above family. Both are allowed.

This means that if conifers are considered a division, they may be called Pinophyta or Coniferae (as a class they may be called Pinopsida or Coniferae; as an order they may be called Pinales or Coniferae (but see also )).

Commonly, conifers are considered equivalent to the , 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, (Taxaceae only) and (the rest), but recent research into suggests that this interpretation leaves the Pinales without Taxales as , and the latter order is no longer considered 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 .

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). 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 as distinct from Podocarpaceae (in which it is included here). The family is here included in family Cupressaceae, but was widely recognized in the past and can still be found in many field guides. A new classification and linear sequence based on molecular data can be found in an article by Christenhusz et al.Christenhusz, M.J.M., Reveal, J., Farjon, A., Gardner, M.F., Mill, R.R. & Chase, M.W. (2011) A new classification and linear sequence of extant gymnosperms. Phytotaxa 19: 55–70.

The conifers are an ancient group, with a record extending back about 300 million years to the in the late 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 eras. Fossil conifers included many diverse forms, the most dramatically distinct from modern conifers being some conifers with no woody stems. Major fossil orders of conifers or conifer-like plants include the , , and perhaps also the (possibly more closely related to the ).


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 . Many conifers have distinctly scented , secreted to protect the tree against infestation and infection of wounds. Fossilized resin hardens into . The size of mature conifers varies from less than one meter, to over 100 meters.Enright, Neal J. and Robert S. Hill. 1990. Ecology of the southern conifers. Washington, DC: Smithsonian. 342pp. The world's tallest, thickest, and oldest living trees are all conifers. The tallest is a ( Sequoia sempervirens), with a height of 115.55 meters (although one Victorian mountain ash, , allegedly grew to a height of 140 meters, although the exact dimensions were not confirmed). The thickest, or tree with the greatest trunk diameter, is a ( Taxodium mucronatum), 11.42 meters in diameter. The smallest is the ( Lepidothamnus laxifolius) of New Zealand, which is seldom taller than 30cm tall when mature. The oldest is a ( Pinus longaeva), 4,700 years old.Dallimore, William, Albert Bruce Jackson, and S.G. Harrison. 1967. A handbook of Coniferae and Ginkgoaceae, 4th ed. New York: St. Martin's Press. xix, 729 p. Conflicting sources claim that the largest tree by 3 dimensional volume is either: a ( Sequoiadendron giganteum), with a volume 1486.9 cubic meters Vidakovic, Mirko. 1991. Conifers: morphology and variation. Translated from Croatian by Maja Soljan. Croatia: Graficki Zavod Hrvatske or a named with volume unspecified.Peter Matthews; Michelle Dunkley McCarthy; Mark (CON) Young (October 1993). The Guinness Book of Records 1994. Facts on File. ISBN 978-0-8160-2645-6. Retrieved 5 June 2012.


Foliage
Since most conifers are evergreens, the of many conifers are long, thin and have a needle-like appearance, but others, including most of the and some of the , have flat, triangular scale-like leaves. Some, notably in Araucariaceae and in Podocarpaceae, have broad, flat strap-shaped leaves. Others such as 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 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. Pinus engelmannii). The 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 or under forest canopy shade. Conifers from hotter areas with high sunlight levels (e.g. Pinus brutia) often have yellower-green leaves, while others (e.g. Picea pungens) have a very strong glaucous wax bloom to reflect . In the great majority of genera the leaves are , usually remaining on the plant for several (2-40) years before falling, but five genera ( , , , and ) are , shedding the leaves in autumn and leafless through the winter. 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.


Reproduction
Most conifers are , but some are or ; all are -. Conifer seeds develop inside a protective cone called a . The cones take from four months to three years to reach maturity, and vary in size from 2 mm to 600 mm long.

In , , and most , the cones are , and when mature the scales usually spread open allowing the seeds to fall out and be dispersed by the . In some (e.g. and ), the cones disintegrate to release the seeds, and in others (e.g. the that produce ) the nut-like seeds are dispersed by (mainly , and ), which break up the specially adapted softer cones. Ripe cones may remain on the plant for a varied amount of time before falling to the ground; in some fire-adapted pines, the seeds may be stored in closed cones for up to 60–80 years, being released only when a fire kills the parent tree.

In the families , , , and one genus ( ), the scales are soft, fleshy, sweet and brightly colored, and are eaten by fruit-eating birds, which then pass the seeds in their droppings. These fleshy scales are (except in Juniperus) known as . In some of these conifers (e.g. most Podocarpaceae), the cone consists of several fused scales, while in others (e.g. Taxaceae), the cone is reduced to just one seed scale or (e.g. Cephalotaxaceae) the several scales of a cone develop into individual arils, giving the appearance of a cluster of berries.

The male cones have structures called that produce yellowish pollen through meiosis. Pollen is released and carried by the wind to female cones. Pollen grains from living pinophyte species produce pollen tubes, much like those of angiosperms. When a grain lands near a female , it undergoes fertilization of the female gametophyte. Alternatively, the male gametophytes are carried by wind to a female cone and are drawn into a tiny opening on the ovule called the . It is within the ovule that germination occurs. From here, a pollen tube seeks out the female gametophyte and if successful, fertilization occurs. In both cases, the resulting develops into an , which along with its surrounding integument, becomes a . Eventually the seed may fall to the ground and, if conditions permit, grows into a new plant.

In , the terminology of has commonly though inaccurately been applied to cone-bearing trees as well. The male cone and unfertilized female cone are called male flower and female flower, respectively. After fertilization, the female cone is termed fruit, which undergoes ripening (maturation).

Picea abies cone USFWS.jpg|Pinaceae: cone of a ( Picea abies) Taxus baccata MHNT.jpg|Taxaceae: the fleshy aril that surrounds each seed in the ( Taxus baccata) is a highly modified seed cone scale Immature fir cone.jpg|Pinaceae: pollen cone of a ( Larix kaempferi)


Life cycle
  1. To fertilize the ovum, the male cone releases that is carried on the wind to the female cone. (Male and female cones can be found on the same plant)
  2. The pollen fertilizes the female gamete (located in the female cone).*
  3. A fertilized female gamete (called a ) develops into an .
  4. Along with integument cells surrounding the embryo, a develops containing the embryo. This is an evolutionary characteristic of the gymnosperms.
  5. Mature seed drops out of cone onto the ground.
  6. Seed germinates and seedling grows into a mature plant.
  7. When the plant is mature, the adult plant produces cones and the cycle continues.


Invasive species
A number of conifers have become in parts of , while , and have become in parts of . These "wilding conifers" are a serious environmental issue causing problems for pastoral farming and for .


Cultivation
Conifers - notably (Fir), (Cedar), (Lawson's cypress), (Cypress), , (Spruce), (Pine), (Yew), - have been the subject of extensive cultivation and hybridisation for ornamental purposes. A multitude of different forms, sizes, and colours are commonly seen in parks and gardens throughout the world. ξ1


External links


References
    ^ (2019). 9789004177185, Brill Academic Publishers.

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