Gnetophyta

Gnetophyta is a division of plants, grouped within the Gymnosperms which includes three extant families of woody plants, namely Ephedraceae, Gnetaceae, and Welwitschiaceae. These plants are unique among gymnosperms in having vessels in their xylem, and variations in the pattern of vessel distribution have been described.

Taxonomy

The division Gnetophyta consists of three orders, each containing a single family and genus. The three genera are Ephedra, Gnetum, and Welwitschia.

• Ephedra is a genus of gymnosperm shrubs, the species of which are known as joint-pines, jointfir, or Mormon-tea.
• Gnetum is a genus of gymnosperms, the sole genus in the family Gnetaceae and order Gnetales.
• Welwitschia is a monotypic gymnosperm genus, comprising solely the distinctive Welwitschia mirabilis.

Characteristics

Gnetophytes are woody plants that produce vessel elements, a type of water-conducting cell that most flowering plants also produce. This is in contrast to other gymnosperms, which lack vessels in their wood.

Distribution and Habitat

Gnetophytes are found in tropical rain forests, deserts, and temperate woodland. The three families are each highly specialized to very different habitats.

Uses

Some species in the Ephedra genus have traditional medicinal uses. For instance, Ephedra sinica, known in Chinese as ma huang, has been used in traditional Chinese medicine for 5,000 years for the treatment of asthma and hay fever, as well as for the common cold.

See Also

• Gymnosperms
• Ephedraceae
• Gnetaceae
• Welwitschiaceae

References

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  Welwitschia mirabilis
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  Ephedra distachya (male flowers)
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  Ephedra distachya (female plant in bloom)
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  Gnetum gnemon (male)
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  Gnetum gnemon
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  Female Ephedra californica cone