''Hevea brasiliensis'', the Pará rubber tree, ''sharinga'' tree, seringueira, or most commonly, rubber tree or rubber plant, is a

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...

belonging to the

spurge ''Euphorbia'' is a very large and diverse genus of flowering plants, commonly called spurge, in the family Euphorbiaceae. "Euphorbia" is sometimes used in ordinary English to collectively refer to all members of Euphorbiaceae (in deference to t ...

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Euphorbiaceae Euphorbiaceae, the spurge family, is a large family of flowering plants. In English, they are also commonly called euphorbias, which is also the name of a genus in the family. Most spurges, such as ''Euphorbia paralias'', are herbs, but some, e ...

originally native to the

Amazon basin The Amazon basin is the part of South America drained by the Amazon River and its tributaries. The Amazon drainage basin covers an area of about , or about 35.5 percent of the South American continent. It is located in the countries of Bolivi ...

, but is now

pantropical A pantropical ("all tropics") distribution is one which covers Tropics, tropical regions of both hemispheres. Examples of species include caecilians, modern sirenians and the plant genera ''Acacia'' and ''Bacopa''. ''Neotropical'' is a zoogeogra ...

in distribution due to introductions. It is the most economically important member of the genus ''

Hevea ''Hevea'' is a genus of flowering plants in the spurge family, Euphorbiaceae, with about ten members. It is also one of many names used commercially for the wood of the most economically important rubber tree, '' H. brasiliensis''. The genus is n ...

'' because the milky

latex Latex is an emulsion (stable dispersion) of polymer microparticles in water. Latexes are found in nature, but synthetic latexes are common as well. In nature, latex is found as a milky fluid found in 10% of all flowering plants (angiosperms ...

extracted from the tree is the primary source of

natural rubber Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Thailand, Malaysia, and ...

Description

''H. brasiliensis'' is a tall

deciduous In the fields of horticulture and Botany, the term ''deciduous'' () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed leaves, usually in the autumn; to the shedding of petals, aft ...

tree growing to a height of up to in the wild, but cultivated trees are usually much smaller because drawing off the latex restricts the growth of the tree. The trunk is cylindrical and may have a swollen, bottle-shaped base. The bark is some shade of brown, and the inner bark oozes

when damaged. The leaves have three leaflets and are spirally arranged. The

inflorescence An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants where flowers are formed o ...

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.

Rubber tree plantation

In the wild, the tree can reach a height of up to . The white or yellow latex occurs in latex vessels in the bark, mostly outside the

phloem Phloem (, ) is the living biological tissue, tissue in vascular plants that transports the soluble organic compounds made during photosynthesis and known as ''photosynthates'', in particular the sugar sucrose, to the rest of the plant. This tran ...

. These vessels spiral up the tree in a right-handed

helix A helix () is a shape like a corkscrew or spiral staircase. It is a type of smooth space curve with tangent lines at a constant angle to a fixed axis. Helices are important in biology, as the DNA molecule is formed as two intertwined helices, ...

which forms an

angle In Euclidean geometry, an angle is the figure formed by two Ray (geometry), rays, called the ''Side (plane geometry), sides'' of the angle, sharing a common endpoint, called the ''vertex (geometry), vertex'' of the angle. Angles formed by two ...

of about 30 degrees with the horizontal, and can grow as high as . 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 a

tropical The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referred to ...

subtropical climate The subtropical zones or subtropics are geographical and climate zones to the north and south of the tropics. Geographically part of the temperate zones of both hemispheres, they cover the middle latitudes from to approximately 35° north and ...

with a minimum of about per year of rainfall, and no frost. 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.

Latex tapping

150px, Latex being collected from an incised rubber tree and a bucket of collected latex The natural rubber tree takes between seven and ten years to deliver the first harvest. 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 as

rubber tapping Rubber tapping is the process by which latex is collected from a rubber tree. The latex is harvested by slicing a groove into the bark of the tree at a depth of with a hooked knife and peeling back the bark. Trees must be approximately six years ...

. Latex production is highly variable from tree to tree and across clone types.

Wood harvesting

As latex production declines with age, rubber trees are generally felled 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 for furniture making.

History

The South American rubber tree grew only in the

Amazon rainforest The Amazon rainforest, Amazon jungle or ; es, Selva amazónica, , or usually ; french: Forêt amazonienne; nl, Amazoneregenwoud. In English, the names are sometimes capitalized further, as Amazon Rainforest, Amazon Forest, or Amazon Jungle. ...

, and increasing demand and the discovery of the

vulcanization Vulcanization (British: Vulcanisation) is a range of processes for hardening rubbers. The term originally referred exclusively to the treatment of natural rubber with sulfur, which remains the most common practice. It has also grown to include ...

procedure in 1839 led to the rubber boom in that region, enriching the cities of

Belém Belém (; Portuguese for Bethlehem; initially called Nossa Senhora de Belém do Grão-Pará, in English Our Lady of Bethlehem of Great Pará) often called Belém of Pará, is a Brazilian city, capital and largest city of the state of Pará in t ...

, Santarém, and

Manaus Manaus () is the capital and largest city of the Brazilian state of Amazonas. It is the seventh-largest city in Brazil, with an estimated 2020 population of 2,219,580 distributed over a land area of about . Located at the east center of the s ...

in Brazil and

Iquitos Iquitos (; ) is the capital city of Peru's Maynas Province and Loreto Region. It is the largest metropolis in the Peruvian Amazon, east of the Andes, as well as the ninth-most populous city of Peru. Iquitos is the largest city in the world th ...

, 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 of Grão-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. The

Olmec The Olmecs () were the earliest known major Mesoamerican civilization. Following a progressive development in Soconusco, they occupied the tropical lowlands of the modern-day Mexican states of Veracruz and Tabasco. It has been speculated that t ...

people of

Mesoamerica Mesoamerica is a historical region and cultural area in southern North America and most of Central America. It extends from approximately central Mexico through Belize, Guatemala, El Salvador, Honduras, Nicaragua, and northern Costa Rica. W ...

extracted and produced similar forms of primitive rubber from analogous latex-producing trees such as ''

Castilla elastica ''Castilla elastica'', the Panama rubber tree, is a tree native to the tropical areas of Mexico, Central America, and northern South America. It was the principal source of latex among the Mesoamerican peoples in pre-Columbian times. The latex g ...

'' as early as 3,600 years ago. The rubber was used, among other things, to make the balls used in the

Mesoamerican ballgame The Mesoamerican ballgame ( nah, ōllamalīztli, , myn, pitz) was a sport with ritual associations played since at least 1650 BC by the pre-Columbian people of Mesoamerica, Ancient Mesoamerica. The sport had different versions in different pl ...

. Early attempts were made in 1873 to grow ''H. brasilensis'' outside

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

. After some effort, 12 seedlings were germinated at the

Royal Botanic Gardens, Kew Royal Botanic Gardens, Kew is a non-departmental public body in the United Kingdom sponsored by the Department for Environment, Food and Rural Affairs. An internationally important botanical research and education institution, it employs 1,100 ...

. These were sent to

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...

for cultivation, but died. A second attempt was then made, some 70,000 seeds being smuggled to Kew in 1875, by Henry Wickham, in the service of the British Empire."The Brazilian Armed Forces: Current changes, new challenges", ''Dreifuss, R. Armand''. InJOHN OLSLICK ELDER STREET THIEF KKALAJOA554977 ternational Seminar Research Committee Armed Forces and Society, Romania, 2002. Retrieved August 19, 2009 from "Amazon - The Animation", ''Greepeace Digital''. Artificial Environments, n/d. Retrieved August 19, 2009 from "Acre: História e etnologia", ''Marco António Gonçalves (Org.)''. Núcleo de Etnologia Indígena Laboratório de Pesquisa Social/IFCS - UFRJ, n/d. Retrieved August 19, 2009 from http://eduardoeginacarli.blogspot.com/2007_07_01_archive.html About four percent of these germinated, and in 1876, about 2,000 seedlings were sent, in

Wardian case The Wardian case was an early type of terrarium, a sealed protective container for plants. It found great use in the 19th century in protecting foreign plants imported to Europe from overseas, the great majority of which had previously died from ...

s, to

Ceylon Sri Lanka (, ; si, ශ්‍රී ලංකා, Śrī Laṅkā, translit-std=ISO (); ta, இலங்கை, Ilaṅkai, translit-std=ISO ()), formerly known as Ceylon and officially the Democratic Socialist Republic of Sri Lanka, is an ...

(modern day Sri Lanka) and 22 were sent to the botanic gardens in

Singapore Singapore (), officially the Republic of Singapore, is a sovereign island country and city-state in maritime Southeast Asia. It lies about one degree of latitude () north of the equator, off the southern tip of the Malay Peninsula, borde ...

. Once established outside its native country, rubber was extensively propagated in the British colonies. Rubber trees were brought to the botanical gardens at

Buitenzorg Bogor ( su, , nl, Buitenzorg) is a city in the West Java province, Indonesia. Located around south of the national capital of Jakarta, Bogor is the 6th largest city in the Jakarta metropolitan area and the 14th overall nationwide. By 1898, a rubber plantation had been established in Malaya, with imported Chinese field workers being the dominant work force in rubber production in the early 20th-century. The cultivation of the tree in South America (Amazon) ended early in the 20th century because of indigenous

blight Blight refers to a specific symptom affecting plants in response to infection by a pathogenic organism. Description Blight is a rapid and complete chlorosis, browning, then death of plant tissues such as leaves, branches, twigs, or floral org ...

s that targeted the rubber tree."Elastomer-The rubber tree", ''Encyclopædia Britannica'', 2008 The blight, called South American leaf blight, is caused by the

ascomycete Ascomycota is a phylum of the kingdom Fungi that, together with the Basidiomycota, forms the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. It is the largest phylum of Fungi, with over 64,000 species. The defi ...

Pseudocercospora ''Pseudocercospora'' is a genus of ascomycete fungi. An anamorphic version of the genus ''Mycosphaerella'', ''Pseudocercospora'' species are plant pathogens, including the causal agent of the so-called South American leaf blight of the rubber tr ...

ulei'', also called ''Microcyclus ulei'', or ''Dothidella ulei''. Rubber production then moved to parts of the world where it is not indigenous, and therefore not affected by local plant diseases. Today, most rubber tree plantations are in

South South is one of the cardinal directions or Points of the compass, compass points. The direction is the opposite of north and is perpendicular to both east and west. Etymology The word ''south'' comes from Old English ''sūþ'', from earlier Pro ...

and

Southeast Asia Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia, South-eastern Asia or SEA, is the geographical United Nations geoscheme for Asia#South-eastern Asia, south-eastern region of Asia, consistin ...

, the top rubber producing countries in 2011 being Thailand, Indonesia, Malaysia, India and Vietnam.

Environmental concerns

The toxicity of arsenic to

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pairs ...

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

, and

fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...

has led to the heavy use of

arsenic trioxide Arsenic trioxide, sold under the brand name Trisenox among others, is an inorganic compound and medication. As an industrial chemical, whose major uses include in the manufacture of wood preservatives, pesticides, and glass. As a medication, i ...

on rubber plantations, especially in

Malaysia Malaysia ( ; ) is a country in Southeast Asia. The federation, federal constitutional monarchy consists of States and federal territories of Malaysia, thirteen states and three federal territories, separated by the South China Sea into two r ...

. 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.

Secondary metabolites

''H. brasiliensis'' produces

cyanogenic glycosides In chemistry, a glycoside is a molecule in which a sugar is bound to another functional group via a glycosidic bond. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosi ...

(CGs) as a defense, concentrated in the seeds. (Although effective against other attackers, CGs are not very effective against fungal pathogens. In rare cases, they are even detrimental. This is the case for ''H. b.'', which actually suffers ''worse'' from ''Pseudocercospora ulei'' if the rubber tree produces more CGs. This may be because cyanide inhibits the production of other defensive metabolites. This results in significantly divergent subpopulations with selection for or against CGs, 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. The α-hydroxynitrilases are likely contained in the

cytoplasm In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. The ...

Linamarin Linamarin is a cyanogenic glucoside found in the leaves and roots of plants such as cassava, lima beans, and flax. It is a glucoside of acetone cyanohydrin. Upon exposure to enzymes and gut flora in the human intestine, linamarin and its methylat ...

hydrolyzed Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile. Biological hydrolysis ...

by an accompanying

linamarase Linamarase, or beta-D-glucosidase (), is an enzyme found in many plants including cassava and the Phaseolus lunatus, butter bean. In cassava it is found in the cell walls. When the plant is chewed or ground, it exposes the enzyme to compounds like ...

, a β-glycosidase. ''H. b.'' linamarase ''does'' act upon linamarin because it is a

monoglucoside A glucoside is a glycoside that is derived from glucose. Glucosides are common in plants, but rare in animals. Glucose is produced when a glucoside is hydrolysed by purely chemical means, or decomposed by fermentation or enzymes. The name was o ...

, while it does ''not'' for linustatin because it is a diglucoside - in fact, the production of linustatin inhibits linamarase cleavage of linamarin. This allows intra-plant, post-synthesis transport of linustatin without risking premature cleavage.

Notes

References

* 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.

External links

* {{Taxonbar, from=Q156538 Crops originating from South America Crotonoideae Rubber Trees of Brazil Trees of Peru Trees of the Amazon