Scientific name: GnetopsidaEnglish name: Vietnamese name: Gắm, Rau bépOther name:
The plant class Gnetoptsida 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 (Bowe et al. 2000, Chaw et al. 2000, Soltis et al. 2002), and the conflict between morphological and molecular data has not yet been resolved. Interestingly, gnetophyte-like vessel elements have been found in the enigmatic Late Permian gigantopterids (Zi-Qiang 1999).
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; GnetumWelwitschiales: Welwitschiaceae; WelwitschiaEphedrales: Ephedraceae; Ephedra
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. Its seeds are used to produce a crispy krupuk snack known as emping or krupuk belinjo.
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 has been traditionally used as a stimulant, but is a controlled substance today in many juristictions because of the risk of harmful or even fatal overdosing.