Gnetophytes

= Gnetophytes =


 * Gnetophytes are seed-bearing plants that can grow as shrubs, trees, or vines and share similarities with both gymnosperms (a plant that has a seed unprotected by an ovary or fruit) and angiosperms ( a plant that has flowers and produces seeds enclosed with a carpel)
 * Although fossil records of Gnetophytes is poor, it is believed that they first appeared in the late Triassic era.
 * About 70%, day species of the phylum Gnetophyta are known, placed in just 3 genera
 * They are considered as "woody plants"
 * The Gnetophyta differ from other gymnosperms because they have vessel elements (the water conducting tissue of plants) as in the flowering plants.

 Three genera of Gnetophytes: Ephedra, Gnetum, and Welwitschia


 * **Ephedra ** is an evergreen shrub of warm, arid regions that have trailing or climbing stems and tiny, scale-like leaves. Some kinds are a source of ephedrine (a crystalline alkaloid drug) and are used medically.


 * **Gnetum ** is a genus of about 30-35 species of gymnosperms. They are tropical evergreen trees, shrubs and lianas (a woody climbing plant that hangs from trees).
 * **Welwitschia ** is a gymnospermous plant of desert regions in southwestern Africa that has a dwarf massive trunk, two long strap-shaped leaves, and male and female flowers in the scales of scarlet cones. It is remarkable for its ability to extract moisture from fog. [[image:Picture3.jpg caption="Welwitschia"]][[image:Picture2.jpg width="231" height="414" align="right" caption="Gnetum"]]

The three Gnetophyte genera have largely disjunct distributions
 * Ephedra occurs mostly in semiaridand arid parts of North America, Mexico, South America (Ecuador to Patagonia and lowland Argentina), S Europe, Asia, and N Africa (including the Canary Islands).


 * <span style="font-family: Verdana,Geneva,sans-serif;">Gnetum is found in wet forests of Indo-Malaysia, tropical parts of West Africa, Fiji and the northern regions of South America


 * <span style="font-family: Verdana,Geneva,sans-serif;">Welwitschia is found in Africa: Angola and Namibia, South Eastern of the United States, South of Central America, and some parts of Europe.

<span style="background-color: #ff9800; font-family: 'Palatino Linotype','Book Antiqua',Palatino,serif; font-size: 130%;">Characteristics of the Gnetophyte
 * <span style="font-family: Verdana,Geneva,sans-serif;">An interesting feature of all gnetophytes is the presence of both tracheids (water conducting cell) and vessel elements in their xylem (vascular tissue) . Most flowering plants contain vessel elements, too, providing evidence to some botanists (scientists who study plants) that the Gnetophyta might have been ancestral to angiosperms
 * <span style="font-family: Verdana,Geneva,sans-serif;">Gnetophyta's unique fertilization feature is that a tube grows from the eggs to unite with the pollen tubes in order for fertilization to take place between the gametophytes (dominant form of the division of small, simple plants) . The sperm themselves are not motile (capable of motion), like we see in the cycads (palm-like plants).
 * <span style="font-family: Verdana,Geneva,sans-serif;">This is the only type of gymnosperm that undergoes double fertilization, however no endosperm (food storage) forms and the 2nd egg fertilized disintegrates. Also like the angiosperms, some of the species produce nectar and are visited by insects.
 * <span style="font-family: Verdana,Geneva,sans-serif;">It is thought that this group may have evolved the angiosperms, but not any of the extant species.

<span style="background-color: #d21919; font-family: 'Palatino Linotype','Book Antiqua',Palatino,serif; font-size: 130%;">Uses for the Gnetophytes <span style="font-family: Verdana,Geneva,sans-serif;">The Gnetophytes have very few uses such as the following:
 * <span style="font-family: Verdana,Geneva,sans-serif;">Decorations
 * <span style="font-family: Verdana,Geneva,sans-serif;">Snacks
 * <span style="font-family: Verdana,Geneva,sans-serif;">Medical uses such as crystalline alkaloid drug