the gymnosperms

The GymnospermsThe Gymnosperms

• Coniferophyta

• Cycadophyta

• Ginkgophyta

•Gnetophyta

Ref: http://www.geocities.com/Heartland/Plains/6761/ecycads.htm

Learning Objectives:Learning Objectives:

To describe the general features of the gymnosperms

To tell among the four divisions of gymnosperms

To discuss the life cycle of representative species of each division of gymnosperms.

To point out the human and ecological importance of gymnosperms.

IntroductionIntroductionare a group of vascular plants whose seeds are not

enclosed by a ripened ovary (fruit).

The seeds of many gymnosperms (literally, "naked seed") are borne in cones and are not visible.

Currently, about 60-70 genera are recognized, with a total of 700-800 species.

Gymnosperms are distributed throughout the world, with extensive latitudinal and longitudinal ranges.

General Features:General Features:

Diversity in size and structureCycads resemble palm trees, with fleshy stems and leathery, featherlike leaves. The tallest cycads reach 19 meters (62 feet). Zamia pygmaea, a cycad native to Cuba, has a trunk less than 10 centimetres (four inches) in height. Of the gnetophytes, Ephedra (joint fir) is a shrub and some species of Gnetum are vines, while the unusual Welwitschia has a massive, squat stem that rises a short distance above the ground. The apex is about 60 centimetres in diameter. From the edge of the disk-shaped stem apex arise two leathery, straplike leaves that grow from the base and survive for the life of the plant. Most gymnosperms, however, are trees. Of the conifers, the redwoods (Sequoia) exceed 100 meters in height and, while Sequoiadendron (giant redwood) is not as tall, the trunk is more massive.

Distribution and AbundanceDistribution and Abundance

Conifer forests, for example, cover vast regions of northern temperate lands in North America and Eurasia.

Vascular plants that occur at the highest altitudes are the gnetophyte Ephedra.

Land in the Southern Hemisphere is rich in conifer forests, which tend to be more abundant at higher altitudes

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Gymnosperms that occupy areas of the world with severe climatic conditions are adapted to conserving water; leaves are covered with a heavy, waxy cuticle, and pores (stomata) are sunken below the leaf surface to decrease the rate of evaporation.

Cycads are distributed throughout the world but are concentrated in equatorial regions. As a natural population, Ginkgo originally appeared to have been confined to mountains of southeastern China; extensive artificial propagation has altered this natural distribution. Distribution of gymnosperms in the distant past was much more extensive than at present. In fact, gymnosperms were dominant in the Mesozoic era (245 to 66.4 million years ago), during which time some of the modern families originated (Pinaceae, Araucariaceae, Taxodiaceae).

Importance to Human EcologyImportance to Human Ecology

Gymnosperm plants are widely used as ornamentals. Conifers are often featured in formal gardens and are used for bonsai. Yews and junipers are often low-growing plants cultivated for ground cover.

Conifers are effective windbreaks, especially those that are evergreen. Cycads are used as garden plants in warmer latitudes, and some may even thrive indoors.


Their leathery green foliage and sometimes colorful cones are striking.

Ginkgo is a hardy tree, and although it once approached extinction, it is now cultivated extensively and survives such challenging habitats as the streets of New York City

Most of the commercial lumber in the Northern Hemisphere is derived from the trunks of conifers such as pine, Douglas fir, spruce, fir, and hemlock. Araucaria, kauri, and Podocarpus are important conifers of the Southern Hemisphere used for lumber.


The wood is straight-grained, light for its strength, and easily worked.

Wood of gymnosperms is often called softwood to differentiate it from the hardwood angiosperms.

In addition to its use in building construction, gymnosperm wood is used for utility poles and railroad ties.


Aromatic wood of cedar is frequently used in the construction of closets or clothes chests and apparently repels cloth-eating moths.

Most plywood is gymnosperm. Fibers of conifers make up paper pulp and may occasionally be used for creating artificial silk or other textiles.

Conifers are frequently planted in reforestation projects. Conifer bark is often the source of compounds involved in the leather tanning industry. Bark is also used extensively as garden mulch.


From conifer resins are derived turpentine and rosin

A hardened form of resin from a kauri (Agathis australis), called copal, is used in the manufacture of paints and varnishes.

Some resins, such as balsam (from hemlock) and dammar (from Agathis) are used in the preparation of mounting media for microscope slides.


Resins may also have medicinal uses. Many types of amber are derived from fossilized resin of conifers.

Commercially useful oils are derived from such conifers as junipers, pines, hemlock, fir, spruces, and aborvitae. These oils serve as air fresheners, disinfectants, and scents in soaps and cosmetics.

Seeds are often food sources. Pine seeds are a delicacy eaten plain or used as a garnish on bakery products. Seeds of Ginkgo and cycads may be poisonous unless detoxified. "Berries" (in reality the fleshy cones) of juniper are used to flavor gin.

CycadophytesCycadophytes

Cycadales (cycads), is today represented by 10 or 11 living genera and some 130-160 species.


The living cycads are for the most part palm like, cone-bearing plants, generally of low stature (Figure 6).

Their reproduction is very primitive in that they rely on flagellated, motile male gametes (spermatozoids), a feature linking them with other plants fertilized by motile flagellated sperm (zooidogamous), such as ferns, club mosses, and other vascular cryptogams.

the gymnosperms

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