|Gnetum macrostachyum in Thailand|
Gnetum is the only genus in the plant family Gnetaceae. They are gymnosperms: their seeds are naked, whereas the seeds of flowering plants are covered.
Plants in Gnetum are evergreen. Most of them are woody vines, but some are big enough to be trees. They grow in warmer, tropical regions of the world. There are over 50 species living. Although some are endangered, the group as a whole are not threatened. Some species are in danger of dying out because they only live in small areas, and the forest where they grow is being turned into land for farming.
Gnetum may have been one of the first plants to be pollinated by insects, with other members of this group such as Ephedra and Welwitschia.
Gnetophyte fossils have been found that date from the Permian and the Triassic. Fossils dating back to the Jurassic have been found, though whether or not they belong to the gnetophytes is uncertain. Overall, the fossil record is richest in the early Cretaceous: fossils of plants, seeds, and pollen have been found which are clearly gnetophytes.
References[change | change source]
- ↑ Kew World Checklist of Selected Plant Families
- ↑ 2.0 2.1 2.2 "Gnetaceae and Gnetum (gnetophytes) description". The Gymnosperm Database. 23 November 2012. Retrieved 11 July 2017.
- ↑ "Gnetum oxycarpum". The IUCN Red List of Threatened Species. Retrieved 11 July 2017.
- ↑ Zi-Qiang Wang (2004). "A new Permian Gnetalean cone as fossil evidence for supporting current molecular phylogeny". Annals of Botany. 94 (2): 281–288. doi:10.1093/aob/mch138. PMC 4242163. PMID 15229124.
- ↑ 5.0 5.1 Catarina Rydin; Kaj Raunsgaard Pedersen; Peter R. Crane; Else Marie Friis (2006). "Former diversity of Ephedra (Gnetales): evidence from early Cretaceous seeds from Portugal and North America". Annals of Botany. 98 (1): 123–140. doi:10.1093/aob/mcl078. PMC 2803531. PMID 16675607.