Pinophyta
| Pinophyta: conifers | ||||||||
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| Families | ||||||||
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Pinaceae, pines Araucariaceae, araucarias Podocarpaceae, yellow-woods Phyllocladaceae Sciadopityaceae, umbrella-pine Cupressaceae, cypresses Cephalotaxaceae, plum-yews Taxaceae, yews |
Pinophyta is one of 13 or 14 division level taxa within the Kingdom Plantae. The Division Pinophyta as currently treated includes all of the conifers. They are cone-bearing seed plants with vascular tissue, typified by trees such as firs and most pines, or shrubs such as many junipers and a few pines.
In the older, broader sense, the Pinophyta would be equivalent to the gymnosperms, although this grouping is polyphyletic, including distinct plants like the Cycads and Ginkgo that are excluded from the Pinophyta.
The division contains but one class of living plants, Class Pinopsida; once split into the two orders, Pinales and Taxales, recent genetic evidence has shown that the Pinales and Taxales are monophyletic, and the latter order is no longer regarded as distinct.
The leaves of many pinophytes are long thin needles, but some others, including most of the Cupressaceae and some of the Podocarpaceae have scale-like leaves instead of needles. The stomata are in lines or patches on the needles, and can be closed when it is very dry or cold. The leaves are often dark in colour which may help absorb a maximum of heat from weak sunshine at high latitudes. In most genera the leaves are evergreen, usually remaining on the plant for several years before falling, but a few genera are deciduous, shedding the leaves in autumn and leafless through the winter.
Pinophyte seeds develop inside protective cones 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 2mm to 600mm 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, or in some genera, the cones disintegrate to release the seeds (e.g. Firs), or the nut-like seeds are dispersed by birds (e.g. pine nuts). 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.
In the families Podocarpaceae, Phyllocladaceae, Cephalotaxaceae, Taxaceae, and one Cupressaceae genus (Juniperus), the scales are fleshy, sweet and brightly coloured, and are eaten by birds which pass the seeds in their droppings. In some of these, the cone is reduced to just one single scale.
The fleshy aril which surrounds each seed in the yew is a highly modified seed cone scale
Male cones have structures called sporangia which produce yellowish pollen. Pollen is released and carried by the wind to female cones. When a pollen grain lands near a female gametophyte, it undergoes meiosis and fertilizes the female gametophyte. The resulting zygote develops into a seed; eventually the seed reaches the ground and, if conditions permit, grows into a new plant. Some pinophytes have male and female cones on the same plant (monoecious species); others have them on different plants (dioecious species).
The world's tallest, largest, thickest and oldest living things are all pinophytes. The tallest is a Coast redwood, with a height of 112.34m. The largest is a Giant sequoia, volume 1486.9 m3. The thickest, or tree with the greatest trunk diameter, is a Montezuma cypress, 11.42m in diameter. The oldest is a Great Basin Bristlecone pine, 4,700 years old.
Many pinophytes have distinctly scented resinous sap, secreted to protect the tree against insect infestation. The resin hardens into amber.
Young pine trees
Life cycle