"Rubber tree" and "para rubber" redirect here. For the ornamental plant also known as "rubber tree", seeFicus elastica. For the New Zealand brand Para Rubber, seeSkellerup.
Hevea brasiliensis, thePará rubber tree,sharinga tree, seringueira, or most commonly,rubber tree orrubber plant, is aflowering plant belonging to the spurge family,Euphorbiaceae, originally native to theAmazon basin, but is nowpantropical in distribution due tointroductions. It is the most economically important member of the genusHevea because the milkylatex extracted from the tree is the primary source ofnatural rubber.
Hevea brasiliensis is a talldeciduous tree growing to a height of up to 43 m (141 ft) in the wild. Cultivated trees are usually much smaller because drawing off the latex restricts their growth. The trunk is cylindrical and may have a swollen, bottle-shaped base. The bark is some shade of brown, and the inner bark oozeslatex when damaged. The leaves have threeleaflets and are spirally arranged. Theinflorescences include separate male and female flowers. The flowers are pungent, creamy-yellow and have no petals. The fruit is a capsule that contains three large seeds; it opens explosively when ripe.[2]
SeedsA sprouting seed in a house backyard inMalaysia
In the wild the tree can reach a height of up to 43 metres (141 ft). The white or yellow latex occurs in latex vessels in thebark, mostly outside thephloem. These vessels spiral up the tree in a right-handedhelix which forms anangle of about 30 degrees with the horizontal, and can grow as high as 15 metres (49 ft).[3]
In plantations the trees are generally smaller for two reasons: 1) trees grow more slowly when they are tapped for latex, and 2) trees are generally cut down after only 30 years, because latex production declines as trees age, and they are no longer economically productive. The tree requires atropical orsubtropical climate with a minimum of about 1,200 mm (50 in) per year of rainfall, and no frost.[4] If frost does occur, the results can be disastrous for production. One frost can cause the rubber from an entire plantation to become brittle and break once it has been refined.[5]
Trunk crosssectionLatex being collected from an incised rubber tree and a bucket of collected latex"Spiral tapping ofHevea brasiliensis." Photograph circa 1911, taken in Brazil.
The rubber tree takes between seven and ten years to deliver the first harvest.[6]Harvesters make incisions across the latex vessels, just deep enough to tap the vessels without harming the tree's growth, and the latex is collected in small buckets. This process is known asrubber tapping. Latex production is highly variable from tree to tree and across clone types.[3]
As latex production declines with age, rubber trees are generallyfelled when they reach the age of 25 to 30 years. The earlier practice was to burn the trees, but in recent decades, the wood has been harvested forfurniture making.[3]
The South American rubber tree grew only in theAmazon rainforest, and increasing demand and the discovery of thevulcanization procedure in 1839 led to the rubber boom in that region, enriching the cities ofBelém,Santarém, andManaus in Brazil andIquitos, Peru, from 1840 to 1913. In Brazil, before the name was changed to 'Seringueira' the initial name of the plant was 'pará rubber tree', derived from the name of the province ofGrão-Pará. In Peru, the tree was called 'árbol del caucho', and the latex extracted from it was called 'caucho'. The tree was used to obtain rubber by the natives who inhabited its geographical distribution. TheOlmec people ofMesoamerica extracted and produced similar forms of primitive rubber from analogous latex-producing trees such asCastilla elastica as early as 3,600 years ago. The rubber was used, among other things, to make the balls used in theMesoamerican ballgame.[7] Early attempts were made in 1873 to growH. brasiliensis outsideBrazil. After some effort, 12 seedlings were germinated at theRoyal Botanic Gardens, Kew. These were sent toIndia for cultivation, but died. A second attempt was then made, some 70,000 seeds being smuggled to Kew in 1875, byHenry Wickham, in the service of the British Empire.[8]: 55 [9][10] About four percent of these germinated, and in 1876, about 2,000 seedlings were sent, inWardian cases, toCeylon (modern day Sri Lanka) and 22 were sent to the botanic gardens inSingapore.
“Henry Wickham, who in 1876 directed an operation smuggling 70,000 rubber tree seeds”
Once established outside its native country, rubber was extensively propagated in the British colonies. Rubber trees were brought to the botanical gardens atBuitenzorg, Java, in 1883.[11] By 1898, a rubber plantation had been established inMalaya, with imported Chinese field workers being the dominant work force in rubber production in the early 20th-century.[12]
The cultivation of the tree in South America (Amazon) ended early in the 20th century because of indigenousblights that targeted the rubber tree.[4] The blight, called South American leaf blight, is caused by theascomycetePseudocercosporaulei,[13][14][15] also calledMicrocyclus ulei,[16] orDothidella ulei, which is endemic to the Amazon Basin. The blight was considered one of the five most aggressive diseases in commercial crops in South America.[17]Rubber production then moved to parts of the world where it is not indigenous, and therefore not affected by local plant diseases.[18] Today, most rubber tree plantations are inSouth andSoutheast Asia, the top rubber producing countries in 2011 being Thailand, Indonesia, Malaysia, India and Vietnam.[19]
The majority of the rubber trees in Southeast Asia are clones of varieties highly susceptible to the South American leaf blight—Pseudocercospora ulei. For these reasons, environmental historian Charles C. Mann, in his 2011 book,1493: Uncovering the New World Columbus Created, predicted that the Southeast Asian rubber plantations will be ravaged by the blight in the not-too-distant future, thus creating a potential calamity for international industry.[21]
Hevea brasiliensis producescyanogenic glycosides (CGs) as a defense, concentrated in the seeds. (Although effective against other attackers, cyanogenic glycosides are not very effective againstfungal pathogens. In rare cases, they are even detrimental. This is the case for the rubber tree, which actually suffersworse fromPseudocercospora ulei when it produces more cyanogenic glycosides. This may be because cyanide inhibits the production of other defensive metabolites. This results in significantly divergent subpopulations with selection for or against cyanogenic glycosides, depending on local likelihoods of fungal or non-fungal pest pressure.) The carbon and nitrogen in CGs are recycled for growth and latex production if needed, and the ease of doing so makes them an attractive nitrogen store - especially if the plant is light-deprived and storage in photosynthesis proteins would thus be unhelpful. Theα-hydroxynitriles are likely contained in thecytoplasm.Linamarin ishydrolyzed by an accompanyinglinamarase, aβ-glycosidase.Hevea brasiliensis linamarasedoes act upon linamarin because it is amonoglucoside, while it doesnot forlinustatin because it is a diglucoside - in fact, the production of lovastatin inhibits linamarase cleavage of linamarin. This allows intra-plant, post-synthesis transport of linustatin without risking premature cleavage.[22]
^"The Brazilian Armed Forces: Current changes, new challenges",Dreifuss, R. Armand. International Seminar Research Committee Armed Forces and Society, Romania, 2002. Retrieved August 19, 2009 from"Archived copy"(PDF). Archived fromthe original(PDF) on 2009-07-31. Retrieved2009-08-19.{{cite web}}: CS1 maint: archived copy as title (link)
^"Amazon - The Animation",Greepeace Digital. Artificial Environments, n/d. Retrieved August 19, 2009 from"The Animation". Archived fromthe original on 2011-07-07. Retrieved2009-08-19.
^Harold A. Crouch,Economic Change, Social Structure, and the Political System in Southeast Asia, Institute of Southeast Asian Studies: Singapore 1985, pp. 16–17ISBN9971-988-23-2
Zhang, J., Huss, V.A.R., Sun, X., Chang, K. and Pan, D. 2008. Morphology and phylogenetic position of a trebouxiophycean green algae (Chlorophyta) growing on the rubber tree,Hevea brasiliensis, with the description of a new genus and species.Eur. J. Phycol.43(2): 185–193.
Charles C. Mann 2011. 1493. Uncovering the New World Columbus Created. Ch.7 Black Gold.
