Gnetaceae and Gnetum descriptions

Species
Separate descriptions are available for the following species:
G. camporum
G. gnemon
G. leyboldii
G. nodiflorum
G. paniculatum
G. urens

There are very few data on the following species, treated in the "Range" and "Remarks" sections, below:
G. arboreum
G. buchholzianum
G. africanum
G. contractum
G. costatum
G. cuspidatum
G. diminutum
G. gnemonoides
G. hainanense
G. klossii
G. latifolium
G. leptostachyum
G. loerzingii
G. macrostachyum
G. microcarpum
G. montanum
G. neglectum
G. oblongum
G. oxycarpum
G. ridleyi
G. schwackeanum
G. tenuifolium
G. ula
G. venosum

Gnetaceae Lindley

Common Names

[Chinese].

Taxonomic Notes

About 30 species in one genus, Gnetum Linnaeus.

The genus has been subdivided by Markgraf (1930, in Carlquist 1996b) as follows:

Section	Subsection	Species
Gnetum	Gnetum	G. gnemon and one other Indomalesian tree species
	Micrognemones	Two species of African lianas
	Araeognemones	Nine species of Neotropical lianas
Cylindrostachys		About 19 species of Asian and Indomalesian lianas, incl. G. arboreum, G. contractum, G. cuspidatum, G. diminutum, G. gnemonoides, G.hainanense, G. klossii, G. latifolium, G. leptostachyum, G. loerzingii, G.macrostachyum, G. microcarpum, G. montanum, G. neglectum, G. oxycarpum, G.ridleyi, G. ula, and two other species.

Description

Monoecious or dioecious plants, mostly woody climbers, rarely shrubs or trees. Leaves elliptic, with netted veins and drip tips at their ends. Flowers monosexual, in catkin-like formations; male flower consists of a stamen and perianth, and female flower of an ovule with 2 integuments and perianth (Vidakovic 1991, Carlquist 1996b).

Range

Indomalaysia, tropical parts of West Africa, Fiji and the northern regions of South America (Schultes and Raffauf 1990).

The following species are found in Malesia or SE Asia (Carlquist 1996b): Gnetum costatum, G. gnemonoides Brongniart, G. klossii Merrill, G. latifolium Blume, G. leptostachyum Blume, G. loerzingii Markgraf, G. macrostachyum Hooker f., G. microcarpum Blume, Gnetum montanum Markgraf, and Gnetum ula Brongniart.

Gnetum arboreum Foxworthy is restricted to a small portion of Luzon, Philippines (Markgraf 1930, in Carlquist 1996b).

Gnetum contractum Markgraf is found in Travancore, India (Markgraf 1930, in Carlquist 1996b).

Gnetum diminutum Markgraf is restricted to a small portion of Sarawak, Malaysia (Markgraf 1930,in Carlquist 1996b).

Gnetum hainanense Cheng is found in China: Hainan.

Gnetum neglectum Blume is restricted to a small area in E Borneo (Markgraf 1930, in Carlquist 1996b).

Gnetum oxycarpum Ridley is restricted to the Mentawi Islands near Sumatra (Markgraf 1930, in Carlquist 1996b).

Gnetum ridleyi Gamble is restricted to a small area in Pahang, Malaysia (Markgraf 1930, in Carlquist 1996b).

Big Tree

Oldest

Dendrochronology

There is no record of any work being done with G. gnemon, and as the remaining species of the genus are all woody vines, they are presumably not usable in dendrochronology.

Ethnobotany

Ethnopharmacological studies have found C-glycosyl-flavones; and a group of complex stilbenes and stilbene-substituted benzofurans. Gnetol, a hydroxylated stilbene, occurs in G. ula. "Lignans are of the guaiacyl-syringyl-type; the antiasthmatic properties for which G. parviflorum is used in Chinese medicine have been ascribed to the presence of demethylcoclaurine hydrochloride" (Schultes and Raffauf 1990).

Observations

Remarks

"[L]ocating and collecting tropical lianoid Gnetum species is difficult because the fertile portions necessary to identify them as species of Gnetum often occur in the high forest canopy, whereas the more easily accessible stems visible at ground level cannot be identified for certain as stems of Gnetum rather than as any of numerous other lianas" (Carlquist 1996b).

Gnetum leptostachyum Blume and Gnetum montanum Markgraf are listed as threatened in Viet Nam by the World Conservation Monitoring Centre.

Gnetum africanum Welwitsch: See Shiembo et al. 1996.

Gnetum ula Brongniart: See Augustine and D'Souza (1997).

"At Mt. Bosavi a protected area is proposed, occupying and sharing areas of the Southern [Highlands], Western and Gulf Provinces [of Papua New Guinea]. The mountain is an isolated volcano south of the Central Divide. The area has locally endemic plant species, e.g. the only known site of an endemic Gnetum species. There are also many bird species. The area should extend down to lowland forest to preserve areas dominated by Vatica massak and other lowland species typical for this region" (Filer 1991).

For the following species, I know nothing but their name: Gnetum buchholzianum, Gnetum cuspidatum Blume, Gnetum oblongum, Gnetum schwackeanum, Gnetum tenuifolium, Gnetum venosum.

Citations

Augustine, A. C. and L. D'Souza. 1997. Somatic embryogenesis in Gnetum ula Brongn. (Gnetum edule) (Willd) Blume. Plant cell reports 16(5): 354.

Shiembo, P.N., A.C. Newton and R.R.B. Leakey. 1996. Vegetative propagation of Gnetum africanum Welw., a leafy vegetable from West Africa. The journal of horticultural science 71(1):149.