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Pinophyta
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{{Taxobox
| color = lightgreen
| name = Pinophyta
| image = Closeuppineneedlessm.jpg
| image_width = 250px
| image_caption = Close-up of pinophyte leaves (needles):
Norway Spruce (''Picea abies'')
| regnum =
Plantae
| divisio = '''Pinophyta'''
| classis = '''Pinopsida'''
| subdivision_ranks = Orders & Families
| subdivision =
Cordaitales †
Pinales
Pinaceae - Pine family
Araucariaceae - Araucaria family
Podocarpaceae - Yellow-wood family
Sciadopitys Sciadopityaceae - Umbrella-pine family
Cupressaceae - Cypress family
Cephalotaxaceae - Plum-yew family
Taxaceae - Yew family
Vojnovskyales †
Voltziales †
}}
The '''conifers''', division '''Pinophyta''', are one of 13 or 14 division level
taxon taxa within the
Plant Kingdom Plantae. They are
Conifer cone cone-bearing seed
plants with
Vascular plant vascular tissue; all extant conifers are
woody plants, the great majority being
trees with just a few being
shrubs. Typical examples of conifers include
cedars,
Cupressaceae cypresses,
douglas-firs,
firs,
junipers,
Agathis kauris,
larches,
pines,
redwoods,
spruces, and
Taxaceae yews. Species of conifers can be found growing naturally in almost all parts of the world, and are frequently dominant plants in their
habitat (ecology) habitats, as in e.g. the
taiga. Conifers are of immense economic value, primarily for
timber and
paper production; the wood of conifers is known as
softwood.
Taxonomy and naming
The division name Pinophyta conforms with the rules of the ''
ICBN'', which state (Art 16.1) that the names of higher
taxon taxa in plants (above the rank of family) are either formed from the name of an included family, in this case
Pinaceae (the
pine 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.
Commonly but erroneously, conifers are considered equivalent to the
Gymnosperms, as in areas with a temperate climate conifers are often the only commonly occurring gymnosperms. However, these are two quite different groupings; conifers are the largest and economically most important component group of the gymnosperms, but nevertheless only one of the four component groups. It is not clear if gymnosperms are a natural group; it may well be
polyphyletic as the component groups like the
cycads and
ginkgos are quite distinct plants (see diagram below), though some recent research does indicate they may be monophyletic.
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 (Taxaceae only) and
Pinales (the rest), but recent research into
molecular biology DNA sequences suggests that this interpretation leaves the Pinales without Taxales as
paraphyletic, 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.
Image:Pinophyta.png cladistic.html" title="Meaning of left left|thumb|380px|Phylogeny of the Pinophyta based on [[cladistic analysis of
molecular biology molecular data. Derived from papers by A. Farjon and C. J. Quinn & R. A. Price in the Proceedings of the Fourth International Conifer Conference, ''Acta Horticulturae'' 615 (2003).html" title="Meaning of thumb|380px|Phylogeny of the Pinophyta based on [[cladistic">left|thumb|380px|Phylogeny of the Pinophyta based on [[cladistic analysis of
molecular biology molecular data. Derived from papers by A. Farjon and C. J. Quinn & R. A. Price in the Proceedings of the Fourth International Conifer Conference, ''Acta Horticulturae'' 615 (2003)">thumb|380px|Phylogeny of the Pinophyta based on [[cladistic">left|thumb|380px|Phylogeny of the Pinophyta based on [[cladistic analysis of
molecular biology molecular data. Derived from papers by A. Farjon and C. J. Quinn & R. A. Price in the Proceedings of the Fourth International Conifer Conference, ''Acta Horticulturae'' 615 (2003)
The conifers are now accepted as comprising six to eight families, with a total of 65-70 genera and 600-650 species. 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 recognise
Phyllocladus Phyllocladaceae as distinct from Podocarpaceae (in which it is included here). The family
Taxodiaceae is here included in family Cupressaceae, but was widely recognised 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 recognisable 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). The size of mature conifers varies from less than one metre, to over 100 metres. The world's tallest, largest, thickest and oldest living things are all conifers. The tallest is a
Sequoia Coast Redwood (''Sequoia sempervirens''), with a height of
1 E2 m 112.83 metres. The largest is a
Giant Sequoia (''Sequoiadendron giganteum''), with a volume 1486.9 cubic metres. The thickest, or tree with the greatest trunk diameter, is a
Taxodium mucronatum Montezuma Cypress (''Taxodium mucronatum''), 11.42 metres in diameter. The oldest is a
Great Basin Bristlecone Pine (''Pinus longaeva''), 4,700 years old.
Foliage
Image:Douglas_fir_leaves_and_bud.jpg Pinaceae.html"_title="Meaning of left left|thumb|[[Pinaceae:_needle leaves and bud of
Coast Douglas-fir (''Pseudotsuga menziesii'').html" title="Meaning of thumb|[[Pinaceae">left|thumb|[[Pinaceae: needle leaves and bud of
Coast Douglas-fir (''Pseudotsuga menziesii'')">thumb|[[Pinaceae">left|thumb|[[Pinaceae: needle leaves and bud of
Coast Douglas-fir (''Pseudotsuga menziesii'')
Image:C lawsoniana Lge.jpg Cupressaceae.html"_title="Meaning of right right|thumb|[[Cupressaceae:_scale leaves of
Chamaecyparis lawsoniana Lawson's Cypress (''Chamaecyparis lawsoniana''); scale in mm.html" title="Meaning of thumb|[[Cupressaceae">right|thumb|[[Cupressaceae: scale leaves of
Chamaecyparis lawsoniana Lawson's Cypress (''Chamaecyparis lawsoniana''); scale in mm">thumb|[[Cupressaceae">right|thumb|[[Cupressaceae: scale leaves of
Chamaecyparis lawsoniana Lawson's Cypress (''Chamaecyparis lawsoniana''); scale in mm
The
leaf leaves of many conifers are long, thin and needle-like, 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. 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 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 (''
larch Larix'', ''
Pseudolarix'', ''
Glyptostrobus'', ''
Metasequoia'' and ''
Taxodium'') are
deciduous, 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
image:largepinecone.jpg Norway Spruce.html" title="Meaning of right right|thumb|Pinaceae: cone of a [[Norway Spruce (''Picea abies'').html" title="Meaning of thumb|Pinaceae: cone of a [[Norway Spruce">right|thumb|Pinaceae: cone of a [[Norway Spruce (''Picea abies'')">thumb|Pinaceae: cone of a [[Norway Spruce">right|thumb|Pinaceae: cone of a [[Norway Spruce (''Picea abies'')
''See
Conifer cone conifer cones for a more detailed discussion.''
Most conifers are
Plant sexuality monoecious, but some are
Plant sexuality subdioecious or
Plant sexuality dioecious; all are
wind-
pollination pollinated. Conifer seeds develop inside a protective cone called a ''strobilus'' (or, very loosely, "pine cones", which technically occur only on pines, not other conifers!). The cones take from four months to three years to reach maturity, and vary in size from 2 mm to 600 mm long.
In
Pinaceae,
Araucariaceae,
Sciadopityaceae and most
Cupressaceae, the cones are
woody, and when mature the scales usually spread open allowing the seeds to fall out and be dispersed by the
wind. In some (e.g.
firs and
cedars), the cones disintegrate to release the seeds, and in others (e.g. the
pines that produce
pine nuts) the nut-like seeds are dispersed by
birds (mainly
nutcrackers and
jays) 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.
Image:TXbaccata.jpg Taxus_baccata left|thumb|Taxaceae: the fleshy aril which surrounds each seed in the [[Taxus_baccata|European Yew (''Taxus baccata'') is a highly modified seed cone scale.html" title="Meaning of European Yew.html" title="Meaning of left|thumb|Taxaceae: the fleshy aril which surrounds each seed in the [[Taxus_baccata|European Yew">left|thumb|Taxaceae: the fleshy aril which surrounds each seed in the [[Taxus_baccata|European Yew (''Taxus baccata'') is a highly modified seed cone scale">European Yew.html" title="Meaning of left|thumb|Taxaceae: the fleshy aril which surrounds each seed in the [[Taxus_baccata|European Yew">left|thumb|Taxaceae: the fleshy aril which surrounds each seed in the [[Taxus_baccata|European Yew (''Taxus baccata'') is a highly modified seed cone scale
In the families
Podocarpaceae,
Cephalotaxaceae,
Taxaceae, and one
Cupressaceae genus (''
Juniperus''), the scales are soft, fleshy, sweet and brightly coloured, and are eaten by fruit-eating birds, which then pass the seeds in their droppings. These fleshy scales are (except in ''Juniperus'') known as
arils. 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
sporangium microsporangia which produce yellowish
pollen. 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
pollen grain lands near a female
gametophyte, it undergoes
meiosis and fertilizes the female gametophyte. The resulting
zygote develops into an
embryo, which along with its surrounding integument, becomes a
seed. Eventually the seed may fall to the ground and, if conditions permit, grows into a new plant.
In
forestry, the terminology of
flowering plants 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).
Life cycle
# To fertilize the ovum, the male cone releases
pollen that is carried on the wind to the female cone.
# A fertilized female gamete (called a
zygote) develops into an
embryo.
# Along with integument cells surrounding the embryo, a
seed develops containing the embryo.
# Mature seed drops out of cone onto the ground.
# Seed germinates and seedling grows into a mature plant.
# When mature, the adult plant produces cones.
Other facts
image:Young_pine_trees_sm.jpg Longleaf Pine.html" title="Meaning of left left|thumb|Young [[Longleaf Pine trees.html" title="Meaning of thumb|Young [[Longleaf Pine">left|thumb|Young [[Longleaf Pine trees">thumb|Young [[Longleaf Pine">left|thumb|Young [[Longleaf Pine trees
Although the total number of species is relatively small, conifers are of immense
ecology ecological importance. They are the dominant plants over huge areas of land, most notably the
boreal forests of the
northern hemisphere, but also in similar cool climates in mountains further south.
Many conifers have distinctly scented
resin, secreted to protect the tree against
insect infestation and
fungus fungal infection of wounds. Fossilised resin hardens into
amber.
External links
-
ToLweb: Conifers
Category:Conifers
cs:Nahosemenné
cy:Conwydden
da:Kategori:Nåletræer (Coniferophyta)
de:Nadelholzgewächse
es:ConÃfera
eo:Pinofitoj
et:Paljasseemnetaimed
fr:Pinopsida
ko:구과�물
it:Pinophyta
he:×ž×—×˜× ×?×™×?
lv:Kailsēkļi
nl:Coniferen
ja:�果�物門
no:Bartrær
pl:Iglaste
pt:ConÃfera
{| style="margin:0 auto;" align=center width=45% class="toccolours"
|align=center style="background:#ccccff"|
'''Links to other
Pinophyta families'''
|-
|align=center|
Pinaceae .html">Araucariaceae
_Podocarpaceae |
Sciadopitys Sciadopityaceae |
Cupressaceae .html">Cephalotaxaceae
_Taxaceae
|-
|}
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