Gnetum

Gnetum is a genus of gymnosperms, the sole genus in the family Gnetaceae and order Gnetales. 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]

Gnetum
Gnetum macrostachyum in Thailand
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Division: Gnetophyta
Class: Gnetopsida
Order: Gnetales
T.M.Fries
Family: Gnetaceae
Lindleyx
Genus: Gnetum
L.
Distribution
Synonyms[1]
  • Gnemon Rumph. ex Kuntze
  • Thoa Aubl.
  • Abutua Lour.
  • Arthostema Neck.

Their leaves are rich in bioactive compounds, like flavonoids and stilbenes, which have "remarkable medical effects". Of the species studies 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 Ephedra and Welwitschia.[5]

Species
  • Gnetum sect. Cylindrostachys
      • Gnetum arboreum
      • Gnetum catasphaericum
      • Gnetum contractum
      • Gnetum costatum
      • Gnetum cuspidatum
      • Gnetum diminutum
      • Gnetum giganteum
      • Gnetum gnemonoides
      • Gnetum gracilipes
      • Gnetum hainanense
      • Gnetum klossii
      • Gnetum latifolium
      • Gnetum leptostachyum
      • Gnetum loerzingii
      • Gnetum luofuense
      • Gnetum macrostachyum
      • Gnetum microcarpum
      • Gnetum montanum
      • Gnetum neglectum
      • Gnetum oxycarpum
      • Gnetum parvifolium
      • Gnetum pendulum
      • Gnetum ridleyi
      • Gnetum tenuifolium
      • Gnetum ula

Uses

Many Gnetum species are edible, with the seeds being roasted, and the foliage used as a leaf vegetable.[6]

References
  1. Kew World Checklist of Selected Plant Families
  2. 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
  3. 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
  4. 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
  5. Significance of Photosynthetic Characters in the Evolution of Asian Gnetum (Gnetales)
  6. 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
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