Gnetum

Gnetum
Gnetum luofuense in China
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Gymnospermae
Division:	Gnetophyta
Order:	Gnetales Mart
Family:	Gnetaceae Blume
Genus:	Gnetum L.
Type species
Gnetum gnemon L.
Distribution
Synonyms[1]
Gnemon Rumph. ex Kuntze Thoa Aubl. Abutua Lour. Arthostema Neck.

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 phytochemicals 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.^{[citation needed]}