Pinopsida

Pinophyta is one of 13 or 14 division level taxa within the Kingdom Plantae. The Division Pinophyta includes all of the conifers (and in some classification schemes the ginkgo tree). In a broader sense, the Pinophyta would be equivalent to the gymnosperms, although such a grouping is clearly polyphyletic, with the latter including distinct groups like the Cycadales that are excluded from the Pinophyta. In the more modern, narrower sense, Pinophyta is equivalent to the former Coniferales: 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.

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.

Leaves (needles) of a
Norway Spruce (Picea abies)

The world's tallest, heaviest, and thickest trees are pinophytes, and all are found in the Family Cupressaceae. The tallest tree is a Coast redwood, with a height of 112 metres (367 feet). The heaviest tree is a Giant sequoia. The thickest, or tree with the greatest trunk diameter, is a Montezuma bald cypress.

Large cone of a pinophyte (Picea abies)

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 woody 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. As they mature the scales spread open allowing the seeds to fall out (or in some genera, scales disintegrate, or seeds are dispersed by birds). Ripe cones may remain on the plant for a varied amount of time before falling to the ground.

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 mitosis 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 tree. Some pinophytes have male and female cones on the same plant (monoecious species); others have them on different plants (dioecious species).

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

1. To fertilize the ovum, the male cone releases pollen that is carried on the wind to the female cone.
2. A fertilized female gamete (called a zygote) develops into a seed.
3. Mature seed drops out of cone onto the ground.
4. Seed germinates and seedling grows into a mature plant.
5. When mature, the adult plant produces cones.

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