Gnetum is one of three genera in the gymnosperm group of seed plants known as Gnetales, whose relationship to other plants has long been a subject of controversy among botanists and evolutionary biologists. Gnetum consists of fewer than three dozen species, mainly large woody climbers (two are trees). Ten species occur in tropical South America, one in West Africa, and the remainder in tropical and subtropical Asia. The seeds and foliage of some species are eaten by humans.
(Won and Renner 2006)
Gnetum is a genus of gymnosperms, the sole genus in the family Gnetaceae within the Gnetophyta. They are tropical evergreen trees, shrubs and lianas. Unlike other gymnosperms, they possess vessel elements in the xylem. Some species have been proposed to have been the first plants to be insect-pollinated as their fossils occur in association with extinct pollinating scorpionflies.[2] Molecular phylogenies based on nuclear and plastid sequences from most of the species indicate hybridization among some of the Southeast Asian species. Fossil-calibrated molecular-clocks suggest that the Gnetum lineages now found in Africa, South America and Southeast Asia are the result of ancient long-distance dispersal across seawater.[3][4]
Their leaves are rich in bioactive compounds such as flavonoids and stilbenes. Of the species studied so far, Gnetum have photosynthetic and transpiration capacities which are considerably lower than those of other seed plants, due to the absence of multiple chloroplast genes essential for photosynthesis, a trait they seem to share with the other living members of Gnetophyta, Ephedra and Welwitschia, as well as conifers.[5] There are over 50 different species of Gnetum.
subsection Araeognemones
subsection Micrognemones
section Gnetum
section Scandentiasubsection Gnemonoides
subsection Stipitati
subsection Sessiles
Phylogeny of Gnetum[7][8] sectionG. buchholzianum Engler
MicrognemonesG. africanum (de Loureiro) Welwitsch
section subsectionG. costatum Schum.
G. gnemon von Linné
Gnetum subsectionG. raya Markgraf
G. gnemonoides Brongniart
Gnemonoides subsectionG. leyboldii Tulasne
G. nodiflorum Brongniart
G. schwackeanum Taubert & Schenck ex Taubert & Markgraf
G. paniculatum Spruce ex Bentham
G. camporum (Markgraf) Stevenson & Zanoni
G. urens (Aublet) Blume
Araeognemones Gnetum sectionG. microcarpum Blume
G. diminutum Markgraf
G. klossii Merrill ex Markgraf
subsectionG. parvifolium (Warburg) Cheng
G. luofuense Cheng
G. indicum (de Loureiro) Merrill
G. hainanense Cheng ex Fu, Yu & Gilbert
G. montanum Markgraf
Stipitati subsectionG. macrostachyum Hooker
G. latifolium Blume
G. edule (Willdenow) Blume
G. neglectum Blume
G. leptostachyum Blume
G. ula Brongniart
G. tenuifolium Ridley
G. cuspidatum Blume
Sessiles ScandentiaThere are over 50 different species of Gnetum.
Many Gnetum species are edible, with the seeds being roasted, and the foliage used as a leaf vegetable.[9] The plant is harvested and yields a useful fiber. There is no sense of danger in consuming the fruit or the seeds.[10]
There is also a study done on the plant to see if it has any medicinal properties, finding some anti-coagulation effects due to its stilbenoid content. The family Gnetaceae is well known as a rich source of plant-derived stilbenoids as well as Cyperaceae, Dipterocarpaceae, Fabaceae, and Vitaceae.[11]
Some species of Gnetum are in danger of dying out. The habitats are being removed with the trees being cut down to create industry. The tropical rainforest are being destroyed so many of the species are going extinct such as Gnetum oxycarpum. The rainforests are being torn down and being turned into farmland. Gnetum live in only a small part of the rainforest.
.jpg)
Gnetum gnemon carpellate/female cones
Gnetum latifolium staminate/male cones
.jpg)
Gathered leaves of Gnetum africanum
Gnetum gnemon seeds
{{cite journal}}: Cite journal requires |journal= (help) Gnetum is a genus of gymnosperms, the sole genus in the family Gnetaceae within the Gnetophyta. They are tropical evergreen trees, shrubs and lianas. Unlike other gymnosperms, they possess vessel elements in the xylem. Some species have been proposed to have been the first plants to be insect-pollinated as their fossils occur in association with extinct pollinating scorpionflies. Molecular phylogenies based on nuclear and plastid sequences from most of the species indicate hybridization among some of the Southeast Asian species. Fossil-calibrated molecular-clocks suggest that the Gnetum lineages now found in Africa, South America and Southeast Asia are the result of ancient long-distance dispersal across seawater.
Their leaves are rich in bioactive compounds such as flavonoids and stilbenes. Of the species studied so far, Gnetum have photosynthetic and transpiration capacities which are considerably lower than those of other seed plants, due to the absence of multiple chloroplast genes essential for photosynthesis, a trait they seem to share with the other living members of Gnetophyta, Ephedra and Welwitschia, as well as conifers. There are over 50 different species of Gnetum.
