Gnetum is a genus of
gymnosperms, the sole genus in the family Gnetaceae within the
Gnetophyta. They are
tropicalevergreentrees,
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]
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.[clarification needed] 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]
Conservation
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.
^Ren D, Labandeira CC, Santiago-Blay JA, Rasnitsyn A, Shih CK, Bashkuev A, Logan MA, Hotton CL, Dilcher D. (2009). Probable Pollination Mode Before Angiosperms: Eurasian, Long-Proboscid Scorpionflies. Science, 326 (5954), 840-847.
doi:
10.1126/science.1178338
^Won H, Renner SS: The internal transcribed spacer of nuclear ribosomal DNA in the gymnosperm Gnetum. Molecular Phylogenetics and Evolution 2005, 36:581-597.
doi:
10.1016/j.ympev.2005.03.011
^Won, H., and S. S. Renner. 2006. Dating dispersal and radiation in the gymnosperm Gnetum (Gnetales) – clock calibration when outgroup relationships are uncertain. Systematic Biology 55(4): 610-622.
doi:
10.1080/10635150600812619
^Hoe, V.B. and Siong, K.H., "The Nutritional Value of Indigenous Fruits and Vegetables in Sarawak,"Asia-Pacific Journal of Clinical Nutrition, Vol. 8, no. 1, 1998, pp 24-31