El
árbol del caucho,
siringa o
seringueira (en portugués) es un
árbol de la familia de las
euforbiáceas, de 20 a 30 m de altura. El tronco es recto y cilíndrico de 30 a 60 cm de diámetro, de madera blanca y liviana. Sus hojas son compuestas trifoliadas, alternas, de 16 cm de longitud, por 6 a 7 cm de ancho; deja caer parcialmente las hojas durante la estación seca, antes de lo cual las hojas de la copa del árbol se tornan de color rojizo. Las flores son pequeñas y reunidas en amplias
panículas.
Frutos: produce desde los 4 años, cada uno de los cuales es una gran cápsula de 4 cm de diámetro que se abre en valvas, con
semillas ricas en aceite.
Su
látex es blanco o amarillento y abundante hasta los 25 años de edad del árbol. De él se fabrica el
caucho, luego de "sangrar" el tronco mediante incisiones angulares en V. Este látex contiene 30 a 36% de
hidrocarburo del caucho, 0,5% de cenizas, 1,5% de proteínas, 2% de resina y 0,5% de quebrachitol. El caucho también puede obtenerse del látex de otros árboles del género
Hevea (v.g.
H. guianensis y
H. pauciflora).
Este árbol es originario de la
cuenca hidrográfica del
río Amazonas, donde existía en abundancia y con exclusividad, características que generaron el auge o
fiebre del caucho, periodo de la historia sudamericana de mucha riqueza y pujanza para empresarios que se asentaron en la región
amazónica y a la vez de desastre para la población indígena, hasta que los
ingleses se apoderaron del lucrativo negocio, al sacar el botánico
Henry A. Wickham ilegalmente de
Brasil semillas de este árbol, en 1876, para establecer plantaciones en
Malasia,
Birmania,
Ceilán y
África subsahariana. Para 1914 la cantidad de caucho obtenido de plantaciones ya superaba la extraída de árboles silvestres.
The Pará rubber tree (Hevea brasiliensis), often simply called rubber tree, is a tree belonging to the family Euphorbiaceae and the most economically important member of the genus Hevea. It is of major economic importance because its sap-like extract (known as latex) can be collected and is the primary source of natural rubber.
In the wilderness, the tree can reach a height of up to 144 feet (44 m). The white or yellow latex occurs in latex vessels in the bark, mostly outside the phloem. These vessels spiral up the tree in a right-handed helix which forms an angle of about 30 degrees with the horizontal, and can grow as high as 45 ft.
In plantations, the trees are kept smaller, up to 78 feet (24 m) tall, so as to use most of the available carbon dioxide for latex production.[1]
The tree requires a climate with heavy rainfall and without frost.
History
The Pará rubber tree initially grew only in the Amazon Rainforest. Increasing demand and the discovery of the vulcanization procedure in 1839 led to the rubber boom in that region, enriching the cities of Belém and Manaus. The name of the tree derives from Pará, the second largest Brazilian state, whose capital is Belém.
These trees were used to obtain rubber by the Olmec people of Mesoamerica as early as 3600 years ago. The rubber was used, among other things, to make the balls used in the Mesoamerican ballgame. There had been an attempt made, in 1873, to grow rubber outside Brazil. After some effort, twelve seedlings were germinated at the Royal Botanic Gardens, Kew. These were sent to India for cultivation, but died. A second attempt was then made, some 70,000 seeds being smuggled to Kew in 1875, by Henry Wickman, at the service of the British Empire [2][3][4][5]. About 4% of these germinated, and in 1876 about 2000 seedlings were sent, in Wardian cases, to Ceylon, and 22 sent to the Botanic Gardens in Singapore. Once established outside its native country, rubber was extensively propagated in the British colonies. Rubber trees were brought to the botanical gardens at Buitenzorg, Java in 1883.[6] By 1898, a rubber plantation had been established in Malaya, and today most rubber tree plantations are in South and Southeast Asia and some also in tropical West Africa. Efforts to cultivate the tree in South America were unsatisfactory, because of blight.[1]
