Gnetophyta
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The plant division Gnetophyta or gnetophytes comprise three related families of woody plants grouped in the gymnosperms. The gnetophytes differ from other gymnosperms in having vessel elements as in the flowering plants (Angiosperms or Magnoliophytes), and on the basis of morphological data it has been suggested that Gnetophytes may be the group of spermatophytes most closely related to the flowering plants. Molecular data have suggested a closer relationship to other gymnosperms than to angiosperms, and the conflict between morphological and molecular data has not yet been resolved.
Gnetophyta contains only one class of living plants, class Gnetopsida. The class includes three extant genera, which in some classifications are placed in a single order (Gnetales) but in others distributed among three orders, each containing a single family and genus:
- Gnetales: Gnetaceae; Gnetum
- Welwitschiales: Welwitschiaceae; Welwitschia
- Ephedrales: Ephedraceae; Ephedra
The Gnetales consist of a single genus, Gnetum, which are mostly woody climbers in tropical forests. However, the most well-known member of this group, Gnetum gnemon, is a tree. The seeds produced are used to produce a crispy snack known as 'Keropok Belinjau' in Malaysia and Indonesia. The Malay name for this plant is 'belinjau'.
The Welwitschiales comprise only one species, Welwitschia mirabilis. It grows only in the deserts of Namibia and Angola. The plant is strange in having only two large strap-like leaves for all its life. These grow continuously from the base, and are usually tattered at the ends by flapping in the winds.
The Ephedrales consist of a single genus Ephedra, and are known as the jointfirs because they have long slender branches which bear tiny scale-like leaves at their nodes. Ephedra is reputed to have medicinal properties, but has some legal controls over it in some juristictions due to potentially harmful and deadly side effects that result from consuming large amounts in a single dose.
[edit] References
- Bowe, L. Michelle, Gwénaële Coat, and Claude W. dePamphilis. 2000. Phylogeny of seed plants based on all three genomic compartments: Extant gymnosperms are monophyletic and Gnetales' closest relatives are conifers. Proceedings of the National Academy of Sciences 97: 4092-4097.
- Soltis, Douglas E., Pamela S. Soltis and Michael J. Zanis. 2002. Phylogeny of seed plants based on evidence from eight genes. American Journal of Botany 89: 1670-1681 (abstract here).
- Chaw, Shu-Miaw, Christopher L. Parkinson, Yuchang Cheng, Thomas M. Vincent, and Jeffrey D. Palmer. 2000. Seed plant phylogeny inferred from all three plant genomes: Monophyly of extant gymnosperms and origin of Gnetales from conifers. Proceedings of the National Academy of Sciences 97: 4086-4091 (abstract here).
