Editing Natural rubber (section)

== Varieties ==

=== Amazonian rubber tree (''Hevea brasiliensis'') ===
The major commercial source of natural rubber latex is the Amazonian rubber tree (''[[Hevea brasiliensis]]''),<ref name=EB1911/> a member of the [[spurge]] [[family (biology)|family]], ''[[Euphorbiaceae]]''. Once native to Brazil, the species is now pan-tropical. This species is preferred because it grows well under cultivation. A properly managed tree responds to wounding by producing more latex for several years.<ref>{{Cite journal |last1=Peres |first1=João Bosco R. |last2=Pastore |first2=Floriano |date=2019-03-01 |title=Amazon Rubber, A Potential Yet to be Rediscovered |url=https://link.springer.com/article/10.1007/s10924-019-01381-7 |journal=Journal of Polymers and the Environment |language=en |volume=27 |issue=3 |pages=652–658 |doi=10.1007/s10924-019-01381-7 |bibcode=2019JPEnv..27..652P |issn=1572-8919}}</ref>

=== Congo rubber (''Landolphia owariensis'' and ''L.'' spp.) ===
[[Congo rubber]], formerly a major source of rubber, which motivated the [[atrocities in the Congo Free State]], came from vines in the genus ''[[Landolphia]]'' (''[[Landolphia kirkii|L. kirkii]]'', ''L. heudelotis'', and ''L. owariensis'').<ref>{{cite web |url=http://www.faculty.ucr.edu/~legneref/botany/rubber.htm |title=Rubber and Other Latex Products |first=Erich Fred |last=Legner |publisher=University of California, Riverside}}</ref>

=== Dandelion ===
[[Dandelion]] milk contains latex. The latex exhibits the same quality as the natural rubber from [[rubber trees]]. In the wild types of dandelion, latex content is low and varies greatly. In [[Nazi Germany]], research projects tried to use dandelions as a base for rubber production, but failed.<ref name="Heim2002">{{cite book |url={{google books |plainurl=y |id=1DqS5a5A8JkC}} |title=Autarkie und Ostexpansion: Pflanzenzucht und Agrarforschung im Nationalsozialismus |last=Heim |first=Susanne |publisher=Wallstein Verlag |year=2002 |isbn=978-3-89244-496-1 |author-link=Susanne Heim}}</ref> In 2013, by inhibiting one key enzyme and using modern cultivation methods and optimization techniques, scientists in the [[Fraunhofer Institute for Molecular Biology and Applied Ecology]] (IME) in [[Germany]] developed a cultivar of the Kazakh dandelion (''[[Taraxacum kok-saghyz]]'') that seems suitable for commercial production of natural rubber. In collaboration with [[Continental Tire]]s, IME began a pilot facility.

=== Other ===
Many other plants produce forms of latex rich in isoprene polymers, though not all produce usable forms of polymer as easily as the Pará.<ref>{{cite web |url=https://digitalcommons.humboldt.edu/cgi/viewcontent.cgi?article=1008&context=botany_jps |title=Plants & Civilization: An Introduction to the Interrelationships of Plants and People. Section 8.4, Latex Plants |last=Smith |first=James P. Jr/ |date=2006 |website=Humboldt State University Botanical Studies Open Educational Resources and Data, Humboldt State University Digital Commons |pages=137–141 |access-date=2019-06-08}}</ref> Some of them require more elaborate processing to produce anything like usable rubber, and most are more difficult to tap. Some produce other desirable materials, for example [[gutta-percha]] (''[[Palaquium gutta]]'')<ref>{{cite web |url=http://www.atlantic-cable.com/Article/GuttaPercha/ |title=The Gutta Percha Company |first=Bill |last=Burns |work=History of the Atlantic Cable & Undersea Communications |access-date=14 February 2009}}</ref> and [[chicle]] from ''[[Manilkara]]'' species. Others that have been commercially exploited, or at least showed promise as rubber sources, include the rubber fig (''[[Ficus elastica]]''), Panama rubber tree (''[[Castilla elastica]]''), various spurges (''[[Euphorbia]]'' spp.), [[lettuce]] (''[[Lactuca]]'' species), the related ''[[Scorzonera tau-saghyz]]'', various ''[[Taraxacum]]'' species, including common dandelion (''[[Taraxacum officinale]]'') and Kazakh dandelion, and, perhaps most importantly for its hypoallergenic properties, [[guayule]] (''Parthenium argentatum''). The term '''gum rubber''' is sometimes applied to the tree-obtained version of natural rubber in order to distinguish it from the synthetic version.<ref name="Ullmann">Heinz-Hermann Greve "Rubber, 2. Natural" in ''Ullmann's Encyclopedia of Industrial Chemistry'', 2000, Wiley-VCH, Weinheim. {{doi|10.1002/14356007.a23_225}}</ref>